Sample records for warm enso events

  1. Coupling between strong warm ENSO events and the phase of the stratospheric QBO.

    NASA Astrophysics Data System (ADS)

    Christiansen, Bo

    2017-04-01

    Although there in general are no significant long-term correlations between the QBO and the ENSO in observations we find that the QBO and the ENSO were aligned in the 3 to 4 years after the three strong warm ENSO events in 1982, 1997, and 2015. We study this possible connection between the QBO and the ENSO with a new version of the EC-Earth model which includes non-orographic gravity waves and a well modeled QBO. We analyze the modeled QBO in ensembles consisting of 10 AMIP-type experiments with climatological SSTs and 10 experiments with observed daily SSTs. The model experiments cover the period 1982-2013. For the ENSO we use the multivariate index (MEI). As expected the coherence is strong and statistically significant in the equatorial troposphere in the ensemble with observed SSTs. Here the coherence is a measure of the alignment of the ensemble members. In the ensemble with observed SSTs we find a strong and significant alignment of the ensemble members in the equatorial stratospheric winds in the 2 to 4 years after the strong ENSO event in 1997. This alignment also includes the observed QBO. No such alignment is found in the ensemble with climatological SSTs. These results indicate that strong warm ENSO events can directly influence the phase of the QBO. An open and maybe related question is what caused the anomalous QBO in 2016. This behaviour, which is unprecedented in the 50-60 years with data, has been described as a hiccup or a death-spiral. At least it is clear that in the last 18 months the QBO has been stuck in the same corner of the phase-space spanned by its two leading principal components. The possible connection to the ENSO will be investigated.

  2. Change of ENSO characteristics in response to global warming

    NASA Astrophysics Data System (ADS)

    Sun, X.; Xia, Y.; Yan, Y.; Feng, W.; Huang, F.; Yang, X. Q.

    2017-12-01

    By using datasets of HadISST monthly SST from 1895 to 2014 and 600-year simulations of two CESM model experiments with/without doubling of CO2 concentration, ENSO characteristics are compared pre- and post- global warming. The main results are as follows. Due to global warming, the maximum climatological SST warming occurs in the tropical western Pacific (La Niña-like background warming) and the tropical eastern Pacific (El Niño-like background warming) for observations and model, respectively, resulting in opposite zonal SST gradient anomalies in the tropical Pacific. The La Niña-like background warming induces intense surface divergence in the tropical central Pacific, which enhances the easterly trade winds in the tropical central-western Pacific and shifts the strongest ocean-atmosphere coupling westward, correspondingly. On the contrary, the El Niño-like background warming causes westerly winds in the whole tropical Pacific and moves the strongest ocean-atmosphere coupling eastward. Under the La Niña-like background warming, ENSO tends to develop and mature in the tropical central Pacific, because the background easterly wind anomaly weakens the ENSO-induced westerly wind anomaly in the tropical western Pacific, leading to the so-called "Central Pacific ENSO (CP ENSO)". However, the so-called "Eastern Pacific ENSO (EP ENSO)" is likely formed due to increased westerly wind anomaly by the El Niño-like background warming. ENSO lifetime is significantly extended under both the El Niño-like and the La Niña-like background warmings, and especially, it can be prolonged by up to 3 months in the situation of El Niño-like background warming. The prolonged El Nino lifetime mainly applies to extreme El Niño events, which is caused by earlier outbreak of the westerly wind bursts, shallower climatological thermocline depth and weaker "discharge" rate of the ENSO warm signal in response to global warming. Results from both observations and the model also show that

  3. ENSO events in the northern Gulf of Alaska, and effects on selected marine fisheries

    USGS Publications Warehouse

    Bailey, K.M.; Macklin, S.A.; Reed, R.K.; Brodeur, R.D.; Ingraham, W.J.; Piatt, John F.; Shima, M.; Francis, R.C.; Anderson, P.J.; Royer, T.C.; Hollowed, A.; Somerton, D.A.; Wooster, W.S.

    1995-01-01

    The 1991-93 El Nino-Southern Oscillation (ENSO) event first appeared in the northern Gulf of Alaska in autumn 1991 with warm sea-surface temperatures. In winter 1992, there were pulses of increased sea level and anomalous circulation. El Nino conditions persisted at least through summer 1993. The effects of this ENSO event on major groundfish species and Pacific herring in the northern Gulf of Alaska were examined and compared with the effects of previous ENSO events. There is little evidence that the 1991-93 or 1982-83 ENSO events affected landings of walleye pollock, Pacific cod, Pacific halibut, or arrowtooth flounder. Some changes in distribution of groundfish species were observed in 1993, but the effect was similar to changes observed in non-ENSO warm years. In general, warm ocean conditions have a positive effect on recruitment of northern stocks, but ENSO events appear to have an inconsistent effect on year-class strength within species and among different species. For example, strong year classes of halibut and arrowtooth flounder sometimes, but not always, coincide with ENSO events; ENSO events are associated with moderate to weak year classes of cod and pollock. However, post-ENSO warm years often are associated with strong recruitment of many groundfish species. Major changes have occurred in the Gulf of Alaska ecosystem since 1977. The influence of the 1976 ENSO event in precipitating these changes and the role of the frequency or strength of subsequent El Nino events is presently unknown. Herring and other stocks of small pelagic fishes may be more affected by ENSO events. In particular, decreased catches, recruitment, and weight-at-age of herring are sometimes associated with ENSO events. Furthermore, a variety of seabirds which feed mostly on pelagic forage fishes or the pelagic juvenile stages of groundfish suffered widespread mortalities and breeding failures in the Gulf of Alaska during the ENSO years of 1983 and 1993. These effects on seabirds

  4. Increased frequency of ENSO-related hydroclimate extremes in a warming climate

    NASA Astrophysics Data System (ADS)

    Sun, Q.; Miao, C.; AghaKouchak, A.

    2017-12-01

    Global warming will likely alter surface warming in tropical Pacific regions, leading to changes in the characteristics of the El Niño Southern Oscillation (ENSO) characteristics and an incresed frequency of extreme ENSO events. The ENSO-related climatic variation and associated impacts will likely be modified in a warmer climatic state. However, little is known about the effect of changes in ENSO teleconnections with regard to future dry and wet conditions over land around the globe, especially outside tropical regions. We used the model simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) for different twenty-first-century emission scenarios (RCP 4.5 and RCP 8.5) to investigate the changes in the ENSO' teleconnection on dry/wet condition over global land. Our results show that 64.64% and 38.12% of 181 river basins studied are expected to experience an increase in the frequency of unusually wet/dry events forced by both ENSO phases under the RCP 4.5 and 8.5, respectively. The anomalous precipitation variability forced by ENSO events will be intensified through a "wet-get-wetter, dry-get-drier" mechanism over west North America, South America, central Asia, and west Asia. More than 850 million people are at risk of exposure to unusually dry/wet events. There is a potential increased risk of high-intensity dry/wet events, with an increase/decrease in the 50-year return level of SPI value for drying/wetting regions. These results have important implications for disaster evaluation and related policies and for appropriate engineering design.

  5. Salinity anomaly as a trigger for ENSO events

    PubMed Central

    Zhu, Jieshun; Huang, Bohua; Zhang, Rong-Hua; Hu, Zeng-Zhen; Kumar, Arun; Balmaseda, Magdalena A.; Marx, Lawrence; Kinter III, James L.

    2014-01-01

    According to the classical theories of ENSO, subsurface anomalies in ocean thermal structure are precursors for ENSO events and their initial specification is essential for skillful ENSO forecast. Although ocean salinity in the tropical Pacific (particularly in the western Pacific warm pool) can vary in response to El Niño events, its effect on ENSO evolution and forecasts of ENSO has been less explored. Here we present evidence that, in addition to the passive response, salinity variability may also play an active role in ENSO evolution, and thus important in forecasting El Niño events. By comparing two forecast experiments in which the interannually variability of salinity in the ocean initial states is either included or excluded, the salinity variability is shown to be essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate salinity observations with large-scale spatial coverage. PMID:25352285

  6. Salinity anomaly as a trigger for ENSO events.

    PubMed

    Zhu, Jieshun; Huang, Bohua; Zhang, Rong-Hua; Hu, Zeng-Zhen; Kumar, Arun; Balmaseda, Magdalena A; Marx, Lawrence; Kinter, James L

    2014-10-29

    According to the classical theories of ENSO, subsurface anomalies in ocean thermal structure are precursors for ENSO events and their initial specification is essential for skillful ENSO forecast. Although ocean salinity in the tropical Pacific (particularly in the western Pacific warm pool) can vary in response to El Niño events, its effect on ENSO evolution and forecasts of ENSO has been less explored. Here we present evidence that, in addition to the passive response, salinity variability may also play an active role in ENSO evolution, and thus important in forecasting El Niño events. By comparing two forecast experiments in which the interannually variability of salinity in the ocean initial states is either included or excluded, the salinity variability is shown to be essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate salinity observations with large-scale spatial coverage.

  7. ENSO Diversity Changes Due To Global Warming In CESM-LE

    NASA Astrophysics Data System (ADS)

    Carreric, A.; Dewitte, B.; Guemas, V.

    2017-12-01

    The El Niño Southern Oscillation (ENSO) is predicted to be modified due to global warming based on the CMIP3 and CMIP5 data bases. In particular the frequency of occurrence of extreme Eastern Pacific El Niño events is to double in the future in response to the increase in green-house gazes. Such forecast relies however on state-of-the-art models that still present mean state biases and do not simulate realistically key features of El Niño events such as its diversity which is related to the existence of at least two types of El Niño events, the Eastern Pacific (EP) El Nino and the Central Pacific (CP) El Niño events. Here we take advantage of the Community Earth System Model (CESM) Large Ensemble (LE) that provides 35 realizations of the climate of the 1920-2100 period with a combination of both natural and anthropogenic climate forcing factors, to explore on the one hand methods to detect changes in ENSO statistics and on the other hand to investigate changes in thermodynamical processes associated to the increase oceanic stratification owed to global warming. The CESM simulates realistically many aspects of the ENSO diversity, in particular the non-linear evolution of the phase space of the first two EOF modes of Sea Surface Temperature (SST) anomalies in the tropical Pacific. Based on indices accounting for the two ENSO regimes used in the literature, we show that, although there is no statistically significant (i.e. confidence level > 95%) changes in the occurrence of El Niño types from the present to the future climate, the estimate of the changes is sensitive to the definition of ENSO indices that is used. CESM simulates in particular an increase occurrence of extreme El Niño events that can vary by 28% from one method to the other. It is shown that the seasonal evolution of EP El Niño events is modified from the present to the future climate, with in particular a larger occurrence of events taking place in Austral summer in the warmer climate

  8. Future Changes to ENSO Temperature and Precipitation Teleconnections Under Warming

    NASA Astrophysics Data System (ADS)

    Perry, S.; McGregor, S.; Sen Gupta, A.; England, M. H.

    2016-12-01

    As the dominant mode of interannual climate variability, the El Niño-Southern Oscillation (ENSO) modulates temperature and rainfall globally, additionally contributing to weather extremes. Anthropogenic climate change has the potential to alter the strength and frequency of ENSO and may also alter ENSO-driven atmospheric teleconnections, affecting ecosystems and human activity in regions far removed from the tropical Pacific. State-of-art climate models exhibit considerable disagreement in projections of future changes in ENSO sea surface temperature variability. Despite this uncertainty, recent model studies suggest that the precipitation response to ENSO will be enhanced in the tropical Pacific under future warming, and as such the societal impacts of ENSO will increase. Here we use temperature and precipitation data from an ensemble of 41 CMIP5 models to show where ENSO teleconnections are being enhanced and dampened in a high-emission future scenario (RCP8.5) focusing on the changes that are occurring over land areas globally. Although there is some spread between the model projections, robust changes with strong ensemble agreement are found in certain locations, including amplification of teleconnections in southeast Australia, South America and the Maritime Continent. Our results suggest that in these regions future ENSO events will lead to more extreme temperature and rainfall responses.

  9. Increasing ENSO-Driven Drought and Wildfire Risks in a Warming Climate

    NASA Astrophysics Data System (ADS)

    Fasullo, J.; Otto-Bliesner, B. L.; Stevenson, S.

    2015-12-01

    ENSO-related teleconnections occurring in the transient climate states of the 20th and 21st centuries are examined using the NCAR CESM1-CAM5 Large Ensemble (LE). A focus is given to quantifying the changing nature of related variability in a warming climate, the statistical robustness of which is enhanced by the numerous members of the LE (presently ~40). It is found that while the dynamical components of ENSO's teleconnections weaken considerably in a warming world, associated variability over land is in many cases sustained by changes in the background state, such as for rainfall due to the background rise in specific humidity. In some fields, particularly those associated with associated with thermal stress (e.g. drought and wildfire), ENSO-related variance increases dramatically. This, combined with the fact that ENSO variance itself increases in a warming climate in the LE, contributes to dramatic projected increases in ENSO-driven drought and wildfire risks in a warming world.

  10. Changes in ENSO amplitude under climate warming and cooling

    NASA Astrophysics Data System (ADS)

    Wang, Yingying; Luo, Yiyong; Lu, Jian; Liu, Fukai

    2018-05-01

    The response of ENSO amplitude to climate warming and cooling is investigated using the Community Earth System Model (CESM), in which the warming and cooling scenarios are designed by adding heat fluxes of equal amplitude but opposite sign onto the ocean surface, respectively. Results show that the warming induces an increase of the ENSO amplitude but the cooling gives rise to a decrease of the ENSO amplitude, and these changes are robust in statistics. A mixed layer heat budget analysis finds that the increasing (decreasing) SST tendency under climate warming (cooling) is mainly due to an enhancement (weakening) of dynamical feedback processes over the equatorial Pacific, including zonal advective (ZA) feedback, meridional advective (MA) feedback, thermocline (TH) feedback, and Ekman (EK) feedback. As the climate warms, a wind anomaly of the same magnitude across the equatorial Pacific can induce a stronger zonal current change in the east (i.e., a stronger ZA feedback), which in turn produces a greater weakening of upwelling (i.e., a stronger EK feedback) and thus a larger thermocline change (i.e., a stronger TH feedback). In response to the climate warming, in addition, the MA feedback is also strengthened due to an enhancement of the meridional SST gradient around the equator resulting from a weakening of the subtropical cells (STCs). It should be noted that the weakened STCs itself has a negative contribution to the change of the MA feedback which, however, appears to be secondary. And vice versa for the cooling case. Bjerknes linear stability (BJ) index is also evaluated for the linear stability of ENSO, with remarkably larger (smaller) BJ index found for the warming (cooling) case.

  11. Mean-state SST Response to global warming caused by the ENSO Nonlinearity

    NASA Astrophysics Data System (ADS)

    Kohyama, T.; Hartmann, D. L.

    2017-12-01

    The majority of the models that participated in the Coupled Model Intercomparison Project phase 5 (CMIP5) exhibit El Niño-like trends under global warming. GFDL-ESM2M, however, is an exception that exhibits a La Niña-like response with strengthened trade winds. Our previous studies have shown that this La Niña-like trend could be a physically consistent warming response, and we proposed the Nonlinear ENSO Warming Suppression (NEWS) mechanism to explain this La Niña-like response to global warming. The most important necessary condition of NEWS is the ENSO skewness (El Niños are stronger than La Niñas). Most CMIP5 models do not reproduce the observed ENSO skewness, while GFDL-ESM2M exhibits the realistic ENSO skewness, which suggests that, despite being in the minority, the La Niña-like trend of GFDL-ESM2M could be a plausible equatorial Pacific response to warming. In this study, we introduce another interesting outlier, MIROC5, which reproduces the observed skewness, yet exhibits an El Niño-like response. By decomposing the source of the ENSO nonlinearity into the following three components: "SST anomalies modulate winds", "winds excite oceanic waves", and "oceanic waves modulate the subsurface temperature", we show that the large inter-model spread of the third component appears to explain the most important cause of the poor reproducibility of the ENSO nonlinearity in CMIP5 models. It is concluded that the change in the response of subsurface temperature to oceanic waves is the primary explanation for the different warming response of GFDL-ESM2M and MIROC5. Our analyses suggest that the difference of the warming response are caused by difference in the climatological thermal stratification. This study may shed new light on the fundamental question of why observed ENSO has a strong skewness and on the implications of this skewed ENSO for the mean-state sea surface temperature response to global warming.

  12. Response of Global Lightning Activity Observed by the TRMM/LIS During Warm and Cold ENSO Phases

    NASA Technical Reports Server (NTRS)

    Chronis, Themis G.; Cecil, Dan; Goodman, Steven J.; Buechler, Dennis

    2007-01-01

    This paper investigates the response of global lightning activity to the transition from the warm (January February March-JFM 1998) to the cold (JFM 1999) ENSO phase. The nine-year global lightning climatology for these months from the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) provides the observational baseline. Flash rate density is computed on a 5.0x5.0 degree lat/lon grid within the LIS coverage area (between approx.37.5 N and S) for each three month period. The flash rate density anomalies from this climatology are examined for these months in 1998 and 1999. The observed lightning anomalies spatially match the documented general circulation features that accompany the warm and cold ENSO events. During the warm ENSO phase the dominant positive lightning anomalies are located mostly over the Western Hemisphere and more specifically over Gulf of Mexico, Caribbean and Northern Mid-Atlantic. We further investigate specifically the Northern Mid-Atlantic related anomaly features since these show strong relation to the North Atlantic Oscillation (NAO). Furthermore these observed anomaly patterns show strong spatial agreement with anomalous upper level (200 mb) cold core cyclonic circulations. Positive sea surface temperature anomalies during the warm ENSO phase also affect the lightning activity, but this is mostly observed near coastal environments. Over the open tropical oceans, there is climatologically less lightning and the anomalies are less pronounced. Warm ENSO related anomalies over the Eastern Hemisphere are most prominent over the South China coast. The transition to the cold ENSO phase illustrates the detected lightning anomalies to be more pronounced over East and West Pacific. A comparison of total global lightning between warm and cold ENSO phase reveals no significant difference, although prominent regional anomalies are located over mostly oceanic environments. All three tropical "chimneys" (Maritime Continent, Central

  13. HadCM3 Simulations of ENSO behaviour during the Mid-Pliocene Warm Period

    NASA Astrophysics Data System (ADS)

    Bonham, S. G.; Haywood, A. M.; Lunt, D. J.

    2009-04-01

    It has been suggested that a permanent El Niño state existed during the mid-Pliocene (ca. 3.3 - 3.0 Ma BP), with a west-to-east temperature gradient in the tropical Pacific considerably weaker than today. This is based upon a number of palaeoceanographic studies which have examined the development of the thermocline and SST gradient in the tropical Pacific over the last five million years. This state is now being referred to as El Padre in recognition of the fact that a mean state warming in EEP SSTs does not necessarily imply the presence of a permanent El Niño. Recent results from mid-Pliocene coupled ocean-atmosphere model simulations have shown clear ENSO variability whilst maintaining the warming in the EEP. This research expands on this study, using the UK Met Office GCM (HadCM3), to examine the behaviour and characteristics of ENSO in two mid-Pliocene simulations (with an open and closed Central American Seaway, CAS) compared with a control pre-industrial run, as well as produce a detailed profile of the mean state climates. The results shown include timescales of ENSO variability across four regions in the Pacific, as well as frequency, EOF and wavelet analysis. We have also looked at the interaction of ENSO with the annual cycle and the onset of ENSO events, and the interdecadal variability in the simulations. The initial timeseries produced have shown a greater variability of ENSO during the closed CAS mid-Pliocene simulation where the system oscillates between events much more frequently than seen in the pre-industrial run. The EOF and wavelet analyses quantify this behaviour, showing that the variability is approximately 15% higher over the central and eastern equatorial Pacific, with a period of oscillation of 2-5 years compared with 4-8 years for the pre-industrial simulation. These results will be compared with those obtained from the second mid-Pliocene simulation (open CAS).

  14. How are warm and cool years in the California Current related to ENSO?

    NASA Astrophysics Data System (ADS)

    Fiedler, Paul C.; Mantua, Nathan J.

    2017-07-01

    The tropical El Niño-Southern Oscillation (ENSO) is a dominant mode of interannual variability that impacts climate throughout the Pacific. The California Current System (CCS) in the northeast Pacific warms and cools from year to year, with or without a corresponding tropical El Niño or La Niña event. We update the record of warm and cool events in the CCS for 1950-2016 and use composite sea level pressure (SLP) and surface wind anomalies to explore the atmospheric forcing mechanisms associated with tropical and CCS warm and cold events. CCS warm events are associated with negative SLP anomalies in the NE Pacific—a strong and southeastward displacement of the wintertime Aleutian Low, a weak North Pacific High, and a regional pattern of cyclonic wind anomalies that are poleward over the CCS. We use a first-order autoregressive model to show that regional North Pacific forcing is predominant in SST variations throughout most of the CCS, while remote tropical forcing is more important in the far southern portion of the CCS. In our analysis, cool events in the CCS tend to be more closely associated with tropical La Niña than are warm events in the CCS with tropical El Niño; the forcing of co-occurring cool events is analogous, but nearly opposite, to that of warm events.

  15. Air-temperature variations and ENSO effects in Indonesia, the Philippines and El Salvador. ENSO patterns and changes from 1866-1993

    NASA Astrophysics Data System (ADS)

    Harger, J. R. E.

    The major features in development of the "El Nino-Southern Oscillation" (ENSO) involve oscillation of the Pacific ocean-atmosphere in an essentially unpredictable (chaotic) fashion. The system moves between extremes of the so-called "warm events" lasting one or two years and involving movement of warm sea water from the western Pacific along the equator to impact on the west coast of the American continent and "cold-events" associated with easterly trade-wind-induced flows of colder water from the eastern Pacific towards the west. Historical data indicate that ENSO years as experienced by the Island of Java are either much warmer than non-ENSO years or only slightly, if at all, warmer than normal (non-ENSO) years. Hot-dry years within the ENSO warm event cycle are almost always followed by cooler wet years and vice versa. This pattern also extends to include the year immediately following the terminal year of an ENSO warm event set. The initial year of an ENSO warm event set may be either hot with a long dry season or relatively cool (nearer to the temperature of a non-ENSO year) and having a short dry season. In recent years, since 1950, of the 9 ENSO warm events, the initial year tends to have been hot and dry for 6 (1951, 1957, 1963, 1972, 1982, 1991) and neutral or cool and wet for 3 (1968, 1976, 1986). An area of 88,000 ha burned in 1991 (Jakarta Post 30 November 1991) largely in Kalimantan in association with the 1991-1992 ENSO event, an extensive pall of smoke developed over Kalimantan, Singapore and Malaysia during September-October of 1991. Surface vegetation-based fires continued to burn in East Kalimantan as of 29 April 1992 and extended into the 1992 dry season, in response to the ENSO conditions carrying forward from 1991. The increasing annual trend in air-temperature exhibited by the mean monthly values over the period 1866-1993, for the Jakarta and the Semarang data taken together is 1.64°C (0.0132°C per year from 25.771 to 27.409°C). The major

  16. Possible shift in the ENSO-Indian monsoon rainfall relationship under future global warming

    PubMed Central

    Azad, Sarita; Rajeevan, M.

    2016-01-01

    EI Nino-Southern Oscillation (ENSO) and Indian monsoon rainfall are known to have an inverse relationship, which we have observed in the rainfall spectrum exhibiting a spectral dip in 3–5 y period band. It is well documented that El Nino events are known to be associated with deficit rainfall. Our analysis reveals that this spectral dip (3–5 y) is likely to shift to shorter periods (2.5–3 y) in future, suggesting a possible shift in the relationship between ENSO and monsoon rainfall. Spectral analysis of future climate projections by 20 Coupled Model Intercomparison project 5 (CMIP5) models are employed in order to corroborate our findings. Change in spectral dip speculates early occurrence of drought events in future due to multiple factors of global warming. PMID:26837459

  17. Reforecasting the ENSO Events in the Past Fifty-Seven Years (1958-2014)

    NASA Astrophysics Data System (ADS)

    Huang, B.; Shin, C. S.; Shukla, J.; Marx, L.; Balmaseda, M.; Halder, S.; Dirmeyer, P.; Kinter, J. L.

    2016-12-01

    anomalies in strong El Niño events. Both facts imply that the model air-sea feedback is overly active in the eastern Pacific before ENSO termination, likely induced by the model warm bias in the eastern Pacific during boreal winter and spring.

  18. Competing Influences of Anthropogenic Warming, ENSO, and Plant Physiology on Future Terrestrial Aridity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bonfils, Céline; Anderson, Gemma; Santer, Benjamin D.

    The 2011–16 California drought illustrates that drought-prone areas do not always experience relief once a favorable phase of El Niño–Southern Oscillation (ENSO) returns. In the twenty-first century, such an expectation is unrealistic in regions where global warming induces an increase in terrestrial aridity larger than the changes in aridity driven by ENSO variability. This premise is also flawed in areas where precipitation supply cannot offset the global warming–induced increase in evaporative demand. Here, atmosphere-only experiments are analyzed to identify land regions where aridity is currently sensitive to ENSO and where projected future changes in mean aridity exceed the range causedmore » by ENSO variability. Insights into the drivers of these changes in aridity are obtained using simulations with the incremental addition of three different factors to the current climate: ocean warming, vegetation response to elevated CO 2 levels, and intensified CO 2 radiative forcing. The effect of ocean warming overwhelms the range of ENSO-driven temperature variability worldwide, increasing potential evapotranspiration (PET) in most ENSO-sensitive regions. Additionally, about 39% of the regions currently sensitive to ENSO will likely receive less precipitation in the future, independent of the ENSO phase. Consequently aridity increases in 67%–72% of the ENSO-sensitive area. When both radiative and physiological effects are considered, the area affected by arid conditions rises to 75%–79% when using PET-derived measures of aridity, but declines to 41% when an aridity indicator for total soil moisture is employed. This reduction mainly occurs because plant stomatal resistance increases under enhanced CO 2 concentrations, resulting in improved plant water-use efficiency, and hence reduced evapotranspiration and soil desiccation. Imposing CO 2-invariant stomatal resistance may overestimate future drying in PET-derived indices.« less

  19. Competing Influences of Anthropogenic Warming, ENSO, and Plant Physiology on Future Terrestrial Aridity

    DOE PAGES

    Bonfils, Céline; Anderson, Gemma; Santer, Benjamin D.; ...

    2017-07-27

    The 2011–16 California drought illustrates that drought-prone areas do not always experience relief once a favorable phase of El Niño–Southern Oscillation (ENSO) returns. In the twenty-first century, such an expectation is unrealistic in regions where global warming induces an increase in terrestrial aridity larger than the changes in aridity driven by ENSO variability. This premise is also flawed in areas where precipitation supply cannot offset the global warming–induced increase in evaporative demand. Here, atmosphere-only experiments are analyzed to identify land regions where aridity is currently sensitive to ENSO and where projected future changes in mean aridity exceed the range causedmore » by ENSO variability. Insights into the drivers of these changes in aridity are obtained using simulations with the incremental addition of three different factors to the current climate: ocean warming, vegetation response to elevated CO 2 levels, and intensified CO 2 radiative forcing. The effect of ocean warming overwhelms the range of ENSO-driven temperature variability worldwide, increasing potential evapotranspiration (PET) in most ENSO-sensitive regions. Additionally, about 39% of the regions currently sensitive to ENSO will likely receive less precipitation in the future, independent of the ENSO phase. Consequently aridity increases in 67%–72% of the ENSO-sensitive area. When both radiative and physiological effects are considered, the area affected by arid conditions rises to 75%–79% when using PET-derived measures of aridity, but declines to 41% when an aridity indicator for total soil moisture is employed. This reduction mainly occurs because plant stomatal resistance increases under enhanced CO 2 concentrations, resulting in improved plant water-use efficiency, and hence reduced evapotranspiration and soil desiccation. Imposing CO 2-invariant stomatal resistance may overestimate future drying in PET-derived indices.« less

  20. Relationships between Rwandan seasonal rainfall anomalies and ENSO events

    NASA Astrophysics Data System (ADS)

    Muhire, I.; Ahmed, F.; Abutaleb, K.

    2015-10-01

    This study aims primarily at investigating the relationships between Rwandan seasonal rainfall anomalies and El Niño-South Oscillation phenomenon (ENSO) events. The study is useful for early warning of negative effects associated with extreme rainfall anomalies across the country. It covers the period 1935-1992, using long and short rains data from 28 weather stations in Rwanda and ENSO events resourced from Glantz (2001). The mean standardized anomaly indices were calculated to investigate their associations with ENSO events. One-way analysis of variance was applied on the mean standardized anomaly index values per ENSO event to explore the spatial correlation of rainfall anomalies per ENSO event. A geographical information system was used to present spatially the variations in mean standardized anomaly indices per ENSO event. The results showed approximately three climatic periods, namely, dry period (1935-1960), semi-humid period (1961-1976) and wet period (1977-1992). Though positive and negative correlations were detected between extreme short rains anomalies and El Niño events, La Niña events were mostly linked to negative rainfall anomalies while El Niño events were associated with positive rainfall anomalies. The occurrence of El Niño and La Niña in the same year does not show any clear association with rainfall anomalies. However, the phenomenon was more linked with positive long rains anomalies and negative short rains anomalies. The normal years were largely linked with negative long rains anomalies and positive short rains anomalies, which is a pointer to the influence of other factors other than ENSO events. This makes projection of seasonal rainfall anomalies in the country by merely predicting ENSO events difficult.

  1. Role of 20th tropical precipitation on ENSO amplitude changes due to greenhouse warming in CMIP5

    NASA Astrophysics Data System (ADS)

    Ham, Yoo-Geun; Kug, Jong-Seong

    2016-04-01

    This study examines the relationship between the intermodel diversities of the present-climate climatology and those of ENSO amplitude change under global warming in the Coupled Model Intercomparison Project phase 5 (CMIP5) models. The models with increased ENSO amplitude under greenhouse warming (i.e., 'ENSO-amplified models') tend to simulate a 20th century stronger climatological ITCZ and SPCZ over the central-eastern Pacific that are located further away from the equator during boreal spring. Moisture budget analysis indicates that those climatological differences lead to stronger positive climatological precipitation change over the off-equatorial central-eastern Pacific under greenhouse warming. The stronger positive climatological precipitation change enhances the air-sea coupling strength over the central-eastern Pacific, which leads to increase the ENSO amplitude.

  2. On the role of ozone feedback in the ENSO amplitude response under global warming

    NASA Astrophysics Data System (ADS)

    Nowack, P. J.; Braesicke, P.; Abraham, N. L.; Pyle, J. A.

    2017-12-01

    The El Niño-Southern Oscillation (ENSO) in the tropical Pacific is of key importance to global climate and weather. However, climate models still disagree on the ENSO's response under climate change. Here we show that typical model representations of ozone can have a first-order impact on ENSO amplitude projections in climate sensitivity simulations (i.e. standard abrupt 4xCO2). We mainly explain this effect by the lapse rate adjustment of the tropical troposphere to ozone changes in the upper troposphere and lower stratosphere (UTLS) under 4xCO2. The ozone-induced lapse rate changes modify the Walker circulation response to the CO2 forcing and consequently tropical Pacific surface temperature gradients. Therefore, not including ozone feedbacks increases the number of extreme ENSO events in our model. In addition, we demonstrate that even if ozone changes in the tropical UTLS are included in the simulations, the neglect of the ozone response in the middle-upper stratosphere still leads to significantly larger ENSO amplitudes (compared to simulations run with a fully interactive atmospheric chemistry scheme). Climate modeling studies of the ENSO often neglect changes in ozone. Our results imply that this could affect the inter-model spread found in ENSO projections and, more generally, surface climate change simulations. We discuss the additional complexity in quantifying such ozone-related effects that arises from the apparent model dependency of chemistry-climate feedbacks and, possibly, their range of surface climate impacts. In conclusion, we highlight the need to understand better the coupling between ozone, the tropospheric circulation, and climate variability. Reference: Nowack PJ, Braesicke P, Abraham NL, and Pyle JA (2017), On the role of ozone feedback in the ENSO amplitude response under global warming, Geophys. Res. Lett. 44, 3858-3866, doi:10.1002/2016GL072418.

  3. Volcanic Tephra ejected in south eastern Asia is the sole cause of all historic ENSO events. This natural aerosol plume has been intensified by an anthropogenic plume in the same region in recent decades which has intensified some ENSO events and altered the Southern Oscillation Index characteristics

    NASA Astrophysics Data System (ADS)

    Potts, K. A.

    2017-12-01

    ENSO events are the most significant perturbation of the climate system. Previous attempts to link ENSO with volcanic eruptions typically failed because only large eruptions across the globe which eject tephra into the stratosphere were considered. I analyse all volcanic eruptions in South Eastern (SE) Asia (10ºS to 10ºN and from 90ºE to 160ºE) the most volcanically active area in the world with over 23% of all eruptions in the Global Volcanism Program database occurring here and with 5 volcanoes stated to have erupted nearly continuously for 30 years. SE Asia is also the region where the convective arm of the thermally direct Walker Circulation occurs driven by the intense equatorial solar radiation which creates the high surface temperature. The volcanic tephra plume intercepts some of the solar radiation by absorption/reflection which cools the surface and heats the atmosphere creating a temperature inversion compared to periods without the plume. This reduces convection and causes the Walker Cell and Trade Winds to weaken. This reduced wind speed causes the central Pacific Ocean to warm which creates convection there which further weakens the Walker Cell. With the reduced wind stress the western Pacific warm pool migrates east. This creates an ENSO event which continues until the tephra plume reduces, typically when the SE Asian monsoon commences, and convection is re-established over SE Asia and the Pacific warm pool migrates back to the west. Correlations of SE Asian tephra and the ENSO indices are typically over 0.80 at p < 0.01 In recent decades the anthropogenic SE Asian aerosol Plume (SEAP) has intensified the volcanic plume in some years from August to November. Using NASA satellite data from 1978 and the NASA MERRA 2 reanalysis dataset I show correlation coefficients typically over 0.70 and up to 0.97 at p < 0.01 between the aerosol optical depth or index and the ENSO indices. If two events A and B correlate 5 options are available: 1. A causes B; 2

  4. Response of the Antarctic Stratosphere to Warm Pool EI Nino Events in the GEOS CCM

    NASA Technical Reports Server (NTRS)

    Hurwitz, Margaret M.; Song, In-Sun; Oman, Luke D.; Newman, Paul A.; Molod, Andrea M.; Frith, Stacey M.; Nielsen, J. Eric

    2011-01-01

    A new type of EI Nino event has been identified in the last decade. During "warm pool" EI Nino (WPEN) events, sea surface temperatures (SSTs) in the central equatorial Pacific are warmer than average. The EI Nino signal propagates poleward and upward as large-scale atmospheric waves, causing unusual weather patterns and warming the polar stratosphere. In austral summer, observations show that the Antarctic lower stratosphere is several degrees (K) warmer during WPEN events than during the neutral phase of EI Nino/Southern Oscillation (ENSO). Furthermore, the stratospheric response to WPEN events depends of the direction of tropical stratospheric winds: the Antarctic warming is largest when WPEN events are coincident with westward winds in the tropical lower and middle stratosphere i.e., the westward phase of the quasi-biennial oscillation (QBO). Westward winds are associated with enhanced convection in the subtropics, and with increased poleward wave activity. In this paper, a new formulation of the Goddard Earth Observing System Chemistry-Climate Model, Version 2 (GEOS V2 CCM) is used to substantiate the observed stratospheric response to WPEN events. One simulation is driven by SSTs typical of a WPEN event, while another simulation is driven by ENSO neutral SSTs; both represent a present-day climate. Differences between the two simulations can be directly attributed to the anomalous WPEN SSTs. During WPEN events, relative to ENSO neutral, the model simulates the observed increase in poleward planetary wave activity in the South Pacific during austral spring, as well as the relative warming of the Antarctic lower stratosphere in austral summer. However, the modeled response to WPEN does not depend on the phase of the QBO. The modeled tropical wind oscillation does not extend far enough into the lower stratosphere and upper troposphere, likely explaining the model's insensitivity to the phase of the QBO during WPEN events.

  5. Tridacna Derived ENSO Records From The Philippines During The Last Interglacial Show Similar ENSO Activity To The Present Day

    NASA Astrophysics Data System (ADS)

    Welsh, K.; Morgan, Z.; Suzuki, A.

    2016-12-01

    Although modeled predictions for the relative strength and frequency of ENSO under mean warming conditions suggest an increase in the number and strength of ENSO event, however there are limited seasonally resolved records of ENSO variability during previous warm periods for example the last interglacial to test these models as reliable archives such as corals are not generally well preserved over these time periods. Presented here are two multi decadal Tridacna gigas derived stable isotopic time series from a coral terrace on the island of Cebu in the Philippines that formed during MIS5e based upon geomorphology and open-system corrected U/Th dating of corals. The ENSO activity observed in these time well preserved records indicate a similar level of ENSO activity during the last interglacial period as the present day based upon comparisons with recent coral derived stable isotopic records. Though these are relatively short records they provide further windows into ENSO activity from this important time period and demonstrate this area may be provide more opportunities to gather these archives.

  6. Precipitation response to the current ENSO variability in a warming world

    NASA Astrophysics Data System (ADS)

    Bonfils, C.; Santer, B. D.; Phillips, T. J.; Marvel, K.; Leung, L.

    2013-12-01

    The major triggers of past and recent droughts include large modes of variability, such as ENSO, as well as specific and persistent patterns of sea surface temperature anomalies (SSTAs; Hoerling and Kumar, 2003, Shin et al. 2010, Schubert et al. 2009). However, alternative drought initiators are also anticipated in response to increasing greenhouse gases, potentially changing the relative contribution of ocean variability as drought initiator. They include the intensification of the current zonal wet-dry patterns (the thermodynamic mechanism, Held and Soden, 2006), a latitudinal redistribution of global precipitation (the dynamical mechanism, Seager et al. 2007, Seidel et al. 2008, Scheff and Frierson 2008) and a reduction of local soil moisture and precipitation recycling (the land-atmosphere argument). Our ultimate goal is to investigate whether the relative contribution of those mechanisms change over time in response to global warming. In this study, we first perform an EOF analysis of the 1900-1999 time series of observed global SST field and identify a simple ENSO-like (ENSOL) mode of SST variability. We show that this mode is well spatially and temporally correlated with observed worldwide regional precipitation and drought variability. We then develop concise metrics to examine the fidelity with which the CMIP5 coupled global climate models (CGCMs) capture this particular ENSO-like mode in the current climate, and their ability to replicate the observed teleconnections with precipitation. Based on the CMIP5 model projections of future climate change, we finally analyze the potential temporal variations in ENSOL to be anticipated under further global warming, as well as their associated teleconnections with precipitation (pattern, amplitude, and total response). Overall, our approach allows us to determine what will be the effect of the current ENSO-like variability (i.e., as measured with instrumental observations) on precipitation in a warming world. This

  7. Influence of ENSO Modoki on Colombia Precipitation

    NASA Astrophysics Data System (ADS)

    Rojo Hernandez, J. D.; Mesa, O. J.; Gómez Ríos, S.; Martinez Pérez, K.

    2015-12-01

    In recent years, multiple observations reported contrasting effects in climate patterns around the world, due to differential warming patterns in tropical regions of Pacific Ocean during ENSO warm and cold events. Several authors have proposedthe concept that these variations are part of a new type of El Niño-Southern Oscillation (ENSO) named as "Modoki". Using the classification of periods as Canonical or Modoki ENSO proposed by Tedeschi et al. (2013) we discriminatedthe quarterly mean values of precipitation in Colombia since 1975 to 2006 in order to analyze the rainfall behavior during El Niño Modoki (ENM) and La Nina Modoki (LNM), and contrast them with Canonical El Niño and La Niña (ENC-LNC) effects. The observations show that for the precipitation in Colombia, ENSO Modoki effects are different from Canonical ENSO effects, producing in general opposite climatic conditions between ENC and ENM, as well as between LNC and LNM. In other regions, the ENSO Modoki produces anomalies with the same sign that ENC, but with lower intensity. R. G. Tedeschi, I. F. Cavalcanti, and A. M. Grimm. Influences of two types of ENSO on Southamerican precipitation. International Journal of Climatology, 33(6):1382-1400, 2013.

  8. Reforecasting the 1972-73 ENSO Event and the Monsoon Drought Over India

    NASA Astrophysics Data System (ADS)

    Shukla, J.; Huang, B.; Shin, C. S.

    2016-12-01

    This paper presents the results of reforcasting the 1972-73 ENSO event and the Indian summer monsoon drought using the National Centers for Environmental Prediction (NCEP) Climate Forecast System, version 2 (CFSv2), initialized with the Eu­ropean Centre for Medium-Range Weather Forecasts (ECMWF) global ocean reanalysis version 4, and observation-based land and atmosphere reanalyses. The results of this paper demonstrate that if the modern day climate models were available during the 1970's, even with the limited observations at that time, it should have been possible to predict the 1972-73 ENSO event and the associated monsoon drought. These results further suggest the necessity of continuing to develop realistic models of the climate system for accurate and reliable seasonal predictions. This paper also presents a comparison of the 1972-73 El Niño reforecast with the 1997-98 case. As the strongest event during 1958-78, the 1972-73 El Niño is distinguished from the 1997-98 one by its early termination. Initialized in the spring season, the forecast system predicted the onset and development of both events reasonably well, although the reforecasts underestimate the ENSO peaking magnitudes. On the other hand, the reforecasts initialized in spring and fall of 1972 persistently predicted lingering wind and SST anomalies in the eastern equatorial Pacific during the spring of 1973. Initialized in fall of 1997, the reforecast also grossly overestimates the peaking westerly wind and warm SST anomalies in the 1997-98 El Niño.In 1972-73, both the Eastern Pacific SST anomalies (for example Nino 3 Index) and the summer monsoon drought over India and the adjoining areas were predicted remarkably well. In contrast, the Eastern Pacific SST anomalies for the 1997-98 event were predicted well, but the normal summer monsoon rainfall over India of 1997 was not predicted by the model. This case study of the 1972-73 event is part of a larger, comprehensive reforecast project

  9. The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event

    NASA Astrophysics Data System (ADS)

    Chen, H. C.; Hu, Z. Z.; Huang, B.; Sui, C. H.

    2016-02-01

    In this study, we demonstrate that a sudden reversal of anomalous equatorial zonal current at the peaking ENSO phase triggers the rapid termination of an ENSO event. Throughout an ENSO cycle, the anomalous equatorial zonal current is strongly controlled by the concavity of the anomalous thermocline meridional structure near the equator. During the ENSO developing phase, the anomalous zonal current in the central and eastern Pacific generally enhances the ENSO growth through its zonal SST advection. In the mature phase of ENSO, however, the equatorial thermocline depth anomalies are reflected in the eastern Pacific and slowly propagate westward off the equator in both hemispheres. As a result, the concavity of the thermocline anomalies near the equator is reversed, i.e., the off-equatorial thermocline depth anomalies become higher than that on the equator for El Niño events and lower for La Niño events. This meridional change of thermocline structure reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, which weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal mass transport weakens the existing zonal tilting of equatorial thermocline and suppresses the thermocline feedback. Both processes are concentrated in the eastern equatorial Pacific and can be effective on subseasonal time scales. These current reversal effects are built-in to the ENSO peak phase and independent of the zonal wind effect on thermocline slope. It functions as an oceanic control on ENSO evolution during both El Niño and La Niña events.

  10. A possible explanation for the divergent projection of ENSO amplitude change under global warming

    NASA Astrophysics Data System (ADS)

    Chen, Lin; Li, Tim; Yu, Yongqiang; Behera, Swadhin K.

    2017-12-01

    The El Niño-Southern Oscillation (ENSO) is the greatest climate variability on interannual time scale, yet what controls ENSO amplitude changes under global warming (GW) is uncertain. Here we show that the fundamental factor that controls the divergent projections of ENSO amplitude change within 20 coupled general circulation models that participated in the Coupled Model Intercomparison Project phase-5 is the change of climatologic mean Pacific subtropical cell (STC), whose strength determines the meridional structure of ENSO perturbations and thus the anomalous thermocline response to the wind forcing. The change of the thermocline response is a key factor regulating the strength of Bjerknes thermocline and zonal advective feedbacks, which ultimately lead to the divergent changes in ENSO amplitude. Furthermore, by forcing an ocean general circulation mode with the change of zonal mean zonal wind stress estimated by a simple theoretical model, a weakening of the STC in future is obtained. Such a change implies that ENSO variability might strengthen under GW, which could have a profound socio-economic consequence.

  11. The Impact of Warm Pool El Nino Events on Antarctic Ozone

    NASA Technical Reports Server (NTRS)

    Hurwitz, Margaret M.; Newman, P. A.; Song, In-Sun; Frith, Stacey M.

    2011-01-01

    Warm pool El Nino (WPEN) events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific in austral spring and summer. Previous work found an enhancement in planetary wave activity in the South Pacific in austral spring, and a warming of 3-5 K in the Antarctic lower stratosphere during austral summer, in WPEN events as compared with ENSO neutral. In this presentation, we show that weakening of the Antarctic vortex during WPEN affects the structure and magnitude of high-latitude total ozone. We use total ozone data from TOMS and OMI, as well as station data from Argentina and Antarctica, to identify shifts in the longitudinal location of the springtime ozone minimum from its climatological position. In addition, we examine the sensitivity of the WPEN-related ozone response to the phase of the quasi-biennial oscillation (QBO). We then compare the observed response to WPEN events with Goddard Earth Observing System chemistry-climate model, version 2 (GEOS V2 CCM) simulations. Two, 50-year time-slice simulations are forced by annually repeating SST and sea ice climatologies, one set representing observed WPEN events and the second set representing neutral ENSO events, in a present-day climate. By comparing the two simulations, we isolate the impact of WPEN events on lower stratospheric ozone, and furthermore, examine the sensitivity of the WPEN ozone response to the phase of the QBO.

  12. ENSO amplitude changes due to greenhouse warming in CMIP5: Role of mean tropical precipitation in the 20th centur

    NASA Astrophysics Data System (ADS)

    Ham, Yoo-Geun; Kug, Jong-Seong

    2017-04-01

    The relationship between the present-climate climatology and those of ENSO amplitude change under global warming in the CMIP5 models is examined. The models with increased ENSO amplitude under greenhouse warming tend to simulate a 20th century stronger climatological ITCZ and SPCZ over the central-eastern Pacific that are located further away from the equator during boreal spring. The budget analysis using moisture equation indicates that those climatological differences lead to stronger positive climatological precipitation change over the off-equatorial central-eastern Pacific under greenhouse warming. The stronger positive climatological precipitation change enhances the air-sea coupling strength over the central-eastern Pacific, which results in the increase of the ENSO amplitude.

  13. Increasing water cycle extremes in California and in relation to ENSO cycle under global warming.

    PubMed

    Yoon, Jin-Ho; Wang, S-Y Simon; Gillies, Robert R; Kravitz, Ben; Hipps, Lawrence; Rasch, Philip J

    2015-10-21

    Since the winter of 2013-2014, California has experienced its most severe drought in recorded history, causing statewide water stress, severe economic loss and an extraordinary increase in wildfires. Identifying the effects of global warming on regional water cycle extremes, such as the ongoing drought in California, remains a challenge. Here we analyse large-ensemble and multi-model simulations that project the future of water cycle extremes in California as well as to understand those associations that pertain to changing climate oscillations under global warming. Both intense drought and excessive flooding are projected to increase by at least 50% towards the end of the twenty-first century; this projected increase in water cycle extremes is associated with a strengthened relation to El Niño and the Southern Oscillation (ENSO)--in particular, extreme El Niño and La Niña events that modulate California's climate not only through its warm and cold phases but also its precursor patterns.

  14. Increasing water cycle extremes in California and in relation to ENSO cycle under global warming

    PubMed Central

    Yoon, Jin-Ho; Wang, S-Y Simon; Gillies, Robert R.; Kravitz, Ben; Hipps, Lawrence; Rasch, Philip J.

    2015-01-01

    Since the winter of 2013–2014, California has experienced its most severe drought in recorded history, causing statewide water stress, severe economic loss and an extraordinary increase in wildfires. Identifying the effects of global warming on regional water cycle extremes, such as the ongoing drought in California, remains a challenge. Here we analyse large-ensemble and multi-model simulations that project the future of water cycle extremes in California as well as to understand those associations that pertain to changing climate oscillations under global warming. Both intense drought and excessive flooding are projected to increase by at least 50% towards the end of the twenty-first century; this projected increase in water cycle extremes is associated with a strengthened relation to El Niño and the Southern Oscillation (ENSO)—in particular, extreme El Niño and La Niña events that modulate California's climate not only through its warm and cold phases but also its precursor patterns. PMID:26487088

  15. Increasing water cycle extremes in California and in relation to ENSO cycle under global warming

    NASA Astrophysics Data System (ADS)

    Yoon, Jin-Ho; Wang, S.-Y. Simon; Gillies, Robert R.; Kravitz, Ben; Hipps, Lawrence; Rasch, Philip J.

    2015-10-01

    Since the winter of 2013-2014, California has experienced its most severe drought in recorded history, causing statewide water stress, severe economic loss and an extraordinary increase in wildfires. Identifying the effects of global warming on regional water cycle extremes, such as the ongoing drought in California, remains a challenge. Here we analyse large-ensemble and multi-model simulations that project the future of water cycle extremes in California as well as to understand those associations that pertain to changing climate oscillations under global warming. Both intense drought and excessive flooding are projected to increase by at least 50% towards the end of the twenty-first century; this projected increase in water cycle extremes is associated with a strengthened relation to El Niño and the Southern Oscillation (ENSO)--in particular, extreme El Niño and La Niña events that modulate California's climate not only through its warm and cold phases but also its precursor patterns.

  16. Tropical Pacific Mean State and ENSO Variability across Marine Isotope Stage 3

    NASA Astrophysics Data System (ADS)

    Hertzberg, J. E.; Schmidt, M. W.; Marcantonio, F.; Bianchi, T. S.

    2017-12-01

    The El Niño/Southern Oscillation (ENSO) phenomenon is the largest natural interannual signal in the Earth's climate system and has widespread effects on global climate that impact millions of people worldwide. A series of recent research studies predict an increase in the frequency of extreme El Niño and La Niña events as Earth's climate continues to warm. In order for climate scientists to forecast how ENSO will evolve in response to global warming, it is necessary to have accurate, comprehensive records of how the system has naturally changed in the past, especially across past abrupt warming events. Nevertheless, there remains significant uncertainty about past changes in tropical Pacific climate and how ENSO variability relates to the millennial-scale warming events of the last ice age. This study aims to reconstruct changes in the tropical Pacific mean state and ENSO variability across Marine Isotope Stage 3 from a sediment core recovered from the Eastern Equatorial Pacific cold tongue (MV1014-02-17JC, 0°10.8' S, 85°52.0' W, 2846 m water depth). In this region, thermocline temperatures are significantly correlated to ENSO variability - thus, we analyzed Mg/Ca ratios in the thermocline dwelling foraminifera Neogloboquadrina dutertrei as a proxy for thermocline temperatures in the past. Bulk ( 50 tests/sample) foraminifera Mg/Ca temperatures are used to reconstruct long-term variability in the mean state, while single shell ( 1 test/sample, 60 samples) Mg/Ca analyses are used to assess thermocline temperature variance. Based on our refined age model, we find that thermocline temperature increases of up to 3.5°C occur in-step with interstadial warming events recorded in Greenland ice cores. Cooler thermocline temperatures prevail during stadial intervals and Heinrich Events. This suggests that interstadials were more El-Niño like, while stadials and Heinrich Events were more La-Niña like. These temperature changes are compared to new records of dust flux

  17. Re-reading the IPCC Report: Aerosols, Droughts and ENSO Events

    NASA Astrophysics Data System (ADS)

    Potts, K. A.

    2008-12-01

    The Technical Summary of Working Group One in the IPCC Fourth Assessment Report states that "changes in aerosols may have affected precipitation and other aspects of the hydrologic cycle more strongly than other anthropogenic forcing agents" and that "Simulations also suggest that absorbing aerosols, particularly black carbon, can reduce the solar radiation reaching the surface and can warm the atmosphere at regional scales, affecting the vertical temperature profile and the large-scale atmospheric circulation". Taking these two statements at face value I first identify eight seasonal, anthropogenic, regional scale, aerosol plumes which now occur each year and then report the correlation of the aerosol optical depth (AOD) of some of these plumes with climate anomalies in the higher latitudes and with ENSO events. The eight identified aerosol plumes vary significantly in extent and AOD inter annually. They have also increased in geographic extent and AOD over recent decades as the population in the tropics, the origin of the majority of these plumes, has increased dramatically requiring increased levels of agriculture and commercial activity. I show that: the AOD of the South East Asian Plume, occurring from late July to November, correlates with four characteristics of drought in south eastern Australia; the aerosol index of the Middle East Plume correlates negatively with rainfall in Darfur; and the volume of tephra ejected by volcanoes in south east Asia correlates: negatively with rainfall and water inflows into the Murray River in south eastern Australia; and positively with ENSO events over the period 1890/91 to 2006. I conclude that aerosol plumes over south eastern Asia are the cause of drought in south eastern Australia and ENSO events and confirm the statements made in the IPCC Report with respect to these aerosol plumes. I propose a new component of surface aerosol radiative forcing, Regional Dimming, which interferes with the seasonal movement of the

  18. Modification of ENSO and ENSO-related atmospheric characteristics due to future climate change

    NASA Astrophysics Data System (ADS)

    Matveeva, Tatiana; Gushchina, Daria

    2017-04-01

    The El Niño/Southern Oscillation (ENSO) is the strongest natural climate interannual fluctuation in Tropical Pacific, it affects regional and global climate. There are two types of this phenomenon: East Pacific (EP) El Niño characterized by maximum of SST anomalies centered over the eastern tropical Pacific and Central Pacific (CP) El Niño with SST warming in the center of the Pacific Ocean [Ashok et al., 2007; Kug et al., 2009]. The ability of CMIP5 coupled ocean-atmosphere general circulation models (CGCMs) to simulate two flavors of El Niño correctly was estimated using EOF-analysis technique of SST anomalies [Takahashi et al., 2011] in the recent studies [Matveeva and Gushchina, 2016]. It was shown that only several CGCMs were able to reproduce two types of ENSO. The ENSO-related characteristics can alter due to global climate change. However, scientific community can't be sure whether ENSO activity will be enhanced or damped under global warming. In this study, we choose the 6 "best" CGCMs (BNU-ESM, CCSM4, CNRM-CM5, FIO-ESM, INM-CM4, MIROC5) which simulated spatial and temporal features of the two types of El Niño the most realistic way. To obtain a complete result we analyzed anomalies of complex ENSO-related characteristics (SST, rainfall, vertical movement, atmospheric circulation in the upper and lower troposphere) during two types of El Niño events. We compared the spatial distribution of these anomalies depending future climate scenarios (we took two scenarios with significant differences - RCP 2.6 and RCP 8.5 [Taylor et al., 2012]). It was shown the large difference in model's estimates ENSO-related anomalies' changes for future climate. The main aspect of this study is the analysis of the ENSO characteristics' modification (frequency, amplitude, the ratio between EP and CP El Niño) under different scenarios of warming. We didn't expect any significant change of frequency for two types of El Nino. It was shown that there was no well

  19. The preconditioning role of Tropical Atlantic Variability in the development of the ENSO teleconnection: implications for the prediction of Nordeste rainfall

    NASA Astrophysics Data System (ADS)

    Giannini, A.; Saravanan, R.; Chang, P.

    A comparison of rainfall variability in the semi-arid Brazilian Nordeste in observations and in two sets of model simulations leads to the conclusion that the evolving interaction between Tropical Atlantic Variability (TAV) and the El Niño-Southern Oscillation (ENSO) phenomenon can explain two puzzling features of ENSO's impact on the Nordeste: (1) the event-to-event unpredictability of ENSO's impact; (2) the greater impact of cold rather than warm ENSO events during the past 50 years. The explanation is in the `preconditioning' role of Tropical Atlantic Variability. When, in seasons prior to the mature phase of ENSO, the tropical Atlantic happens to be evolving consistently with the development expected of the ENSO teleconnection, ENSO and TAV add up to force large anomalies in Nordeste rainfall. When it happens to be evolving in opposition to the canonical development of ENSO, then the net outcome is less obvious, but also less anomalous. The more frequent occurrence of tropical Atlantic conditions consistent with those that develop during a cold ENSO event, i.e. of a negative meridional sea surface temperature gradient, explains the weaker warm ENSO and stronger cold ENSO anomalies in Nordeste rainfall of the latter part of the twentieth century. Close monitoring of the evolution of the tropical Atlantic in seasons prior to the mature phase of ENSO should lead to an enhanced forecast potential.

  20. Can the GEOS CCM Simulate the Temperature Response to Warm Pool El Nino Events in the Antarctic Stratosphere?

    NASA Technical Reports Server (NTRS)

    Hurwitz, M. M.; Song, I.-S.; Oman, L. D.; Newman, P. A.; Molod, A. M.; Frith, S. M.; Nielsen, J. E.

    2010-01-01

    "Warm pool" (WP) El Nino events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific. During austral spring. WP El Nino events are associated with an enhancement of convective activity in the South Pacific Convergence Zone, provoking a tropospheric planetary wave response and thus increasing planetary wave driving of the Southern Hemisphere stratosphere. These conditions lead to higher polar stratospheric temperatures and to a weaker polar jet during austral summer, as compared with neutral ENSO years. Furthermore, this response is sensitive to the phase of the quasi-biennial oscillation (QBO): a stronger warming is seen in WP El Nino events coincident with the easterly phase of the quasi-biennial oscillation (QBO) as compared with WP El Nino events coincident with a westerly or neutral QBO. The Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) is used to further explore the atmospheric response to ENSO. Time-slice simulations are forced by composited SSTs from observed WP El Nino and neutral ENSO events. The modeled eddy heat flux, temperature and wind responses to WP El Nino events are compared with observations. A new gravity wave drag scheme has been implemented in the GEOS CCM, enabling the model to produce a realistic, internally generated QBO. By repeating the above time-slice simulations with this new model version, the sensitivity of the WP El Nino response to the phase of the quasi-biennial oscillation QBO is estimated.

  1. Can the GEOS CCM Simulate the Temperature Response to Warm Pool El Nino Events in the Antarctic Stratosphere?

    NASA Technical Reports Server (NTRS)

    Hurwitz, M. M.; Song, I.-S.; Oman, L. D.; Newman, P. A.; Molod, A. M.; Frith, S. M.; Nielsen, J. E.

    2011-01-01

    "Warm pool" (WP) El Nino events are characterized by positive sea surface temperature (SST) anomalies in the central equatorial Pacific. During austral spring, WP El Nino events are associated with an enhancement of convective activity in the South Pacific Convergence Zone, provoking a tropospheric planetary wave response and thus increasing planetary wave driving of the Southern Hemisphere stratosphere. These conditions lead to higher polar stratospheric temperatures and to a weaker polar jet during austral summer, as compared with neutral ENSO years. Furthermore, this response is sensitive to the phase of the quasi-biennial oscillation (QBO): a stronger warming is seen in WP El Nino events coincident with the easterly phase of the quasi-biennial oscillation (QBO) as compared with WP El Nino events coincident with a westerly or neutral QBO. The Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) is used to further explore the atmospheric response to ENSO. Time-slice simulations are forced by composited SSTs from observed NP El Nino and neutral ENSO events. The modeled eddy heat flux, temperature and wind responses to WP El Nino events are compared with observations. A new gravity wave drag scheme has been implemented in the GEOS CCM, enabling the model to produce e realistic, internally generated QBO. By repeating the above time-slice simulations with this new model version, the sensitivity of the WP El Nino response to the phase of the quasi-biennial oscillation QBO is estimated.

  2. Global Precipitation Patterns Associated with ENSO and Tropical Circulations

    NASA Technical Reports Server (NTRS)

    Curtis, Scott; Adler, Robert; Huffman, George; Bolvin, David; Nelkin, Eric

    1999-01-01

    Tropical precipitation and the accompanying latent heat release is the engine that drives the global circulation. An increase or decrease in rainfall in the tropics not only leads to the local effects of flooding or drought, but contributes to changes in the large scale circulation and global climate system. Rainfall in the tropics is highly variable, both seasonally (monsoons) and interannually (ENSO). Two experimental observational data sets, developed under the auspices of the Global Precipitation Climatology Project (GPCP), are used in this study to examine the relationships between global precipitation and ENSO and extreme monsoon events over the past 20 years. The V2x79 monthly product is a globally complete, 2.5 deg x 2.5 deg, satellite-gauge merged data set that covers the period 1979 to the present. Indices based on patterns of satellite-derived rainfall anomalies in the Pacific are used to analyze the teleconnections between ENSO and global precipitation, with emphasis on the monsoon systems. It has been well documented that dry (wet) Asian monsoons accompany warm (cold) ENSO events. However, during the summer seasons of the 1997/98 ENSO the precipitation anomalies were mostly positive over India and the Bay of Bengal, which may be related to an epoch-scale variability in the Asian monsoon circulation. The North American monsoon may be less well linked to ENSO, but a positive precipitation anomaly was observed over Mexico around the September following the 1997/98 event. For the twenty-year record, precipitation and SST patterns in the tropics are analyzed during wet and dry monsoons. For the Asian summer monsoon, positive rainfall anomalies accompany two distinct patterns of tropical precipitation and a warm Indian Ocean. Negative anomalies coincide with a wet Maritime Continent.

  3. Sensitivity of ENSO teleconnections to a warming background state.

    NASA Astrophysics Data System (ADS)

    Drouard, Marie; Cassou, Christophe

    2016-04-01

    The sensitivity of ENSO teleconnections to the background state is investigated using two ensembles of coupled model experiments, one representative of the pre-industrial climate and the other one expected of the end of the 21st century based on the high emission RCP85 scenario. A 30-year period of representative ENSO events bearing resemblance to observed ones is a priori selected from a 850-year pre-industrial simulation of the CNRM-CM5 model. Following the so-called pacemaker protocol, new coupled experiments are carried with the model SST being restored in the eastern tropical Pacific towards the selected anomalies, the rest of the globe being fully coupled. In the first set of experiments, the anomalous restoring is applied on top of pre-industrial mean ocean state and in the second, on top of RCP85 mean state. Two sets of 10-member of 30-year long integrations are then generated. By construction, they share the exact same ENSO and thus make it possible to strictly isolate the dependence of the ENSO teleconnections to a warmer background state. Results confirm the eastward shift of the ENSO-induced deepening Aleutian low as documented in the literature for the winter season. They also show changes in the wintertime teleconnection over the North Atlantic. Several diagnostic tools (such as E-vectors) are used to investigate the dynamics of the teleconnection between the tropical Pacific, the North Pacific and dowstream towards the North Atlantic along the jet wave guide. A more indirect route based on the change in the Walker cell and associated signals in the tropical Atlantic leading to the excitation of forced Rossby wave is also analysed.

  4. The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño

    NASA Astrophysics Data System (ADS)

    Santoso, Agus; Mcphaden, Michael J.; Cai, Wenju

    2017-12-01

    The year 2015 was special for climate scientists, particularly for the El Niño Southern Oscillation (ENSO) research community, as a major El Niño finally materialized after a long pause since the 1997/1998 extreme El Niño. It was scientifically exciting since, due to the short observational record, our knowledge of an extreme El Niño has been based only on the 1982/1983 and 1997/1998 events. The 2015/2016 El Niño was marked by many environmental disasters that are consistent with what is expected for an extreme El Niño. Considering the dramatic impacts of extreme El Niño, and the risk of a potential increase in frequency of ENSO extremes under greenhouse warming, it is timely to evaluate how the recent event fits into our understanding of ENSO extremes. Here we provide a review of ENSO, its nature and dynamics, and through analysis of various observed key variables, we outline the processes that characterize its extremes. The 2015/2016 El Niño brings a useful perspective into the state of understanding of these events and highlights areas for future research. While the 2015/2016 El Niño is characteristically distinct from the 1982/1983 and 1997/1998 events, it still can be considered as the first extreme El Niño of the 21st century. Its extremity can be attributed in part to unusually warm condition in 2014 and to long-term background warming. In effect, this study provides a list of physically meaningful indices that are straightforward to compute for identifying and tracking extreme ENSO events in observations and climate models.

  5. The role of South Pacific atmospheric variability in the development of different types of ENSO

    NASA Astrophysics Data System (ADS)

    You, Yujia; Furtado, Jason C.

    2017-07-01

    Recent advances in tropical Pacific climate variability have focused on understanding the development of El Niño-Southern Oscillation (ENSO) events, specifically the types or "flavors" of ENSO (i.e., central versus eastern Pacific events). While precursors to ENSO events exist, distinguishing the particular flavor of the expected ENSO event remains unresolved. This study offers a new look at ENSO predictability using South Pacific atmospheric variability during austral winter as an indicator. The positive phase of the leading mode of South Pacific sea level pressure variability, which we term the South Pacific Oscillation (SPO), exhibits a meridional dipole with with a(n) (anti)cyclonic anomaly dominating the subtropics (extratropics/high latitudes). Once energized, the cyclonic anomalies in the subtropical node of the SPO weaken the southeasterly trade winds and promote the charging of the eastern equatorial Pacific Ocean, giving rise to eastern Pacific ENSO events. Indeed, the type of ENSO event can be determined accurately using only the magnitude and phase of the SPO during austral winter as a predictor (17 out of 23 cases). The SPO may also play a role in explaining the asymmetry of warm and cold events. Collectively, our findings present a new perspective on ENSO-South Pacific interactions that can advance overall understanding of the ENSO system and enhance its predictability across multiple timescales.

  6. Evaporation/SST Sensitivity Over the Tropical Oceans During ENSO Events as Estimated from the da Silva, Young, Levitus Surface Marine Data Set

    NASA Technical Reports Server (NTRS)

    Robertson, F. R.; Fitzjarrald, D. E.; Sohn, B.-J.; Arnold, James E. (Technical Monitor)

    2001-01-01

    The da Silva, Young and Levitus Surface Marine Atlas, based on observations from the Comprehensive Ocean Atmosphere Data Set (COADS) Release 1, has been used to investigate the relationship between evaporation and sea-surface temperature (SST) over the global oceans. For the period 1950 to 1987 SST, surface latent heat flux, and other related variables have been filtered to minimize data uncertainties and to focus upon interannual variations associated with warm (El Nino) and cold (La Nina) ENSO events. Compositing procedures have enabled identification of systematic variations in latent heat fluxes accompanying these events and the relationship to spatial anomalies in ocean surface wind speed and humidity. The evaporation response associated with ENSO sea surface temperature (SST) variability is systematic in nature and composed of offsetting contributions from the surface wind and humidity variations. During warm events exceeding 1.0 S.D. delta SST, increases in the surface humidity deficit, delta(qs-qa), between the surface and 2m height dominate regions of positive SST anomalies and lead to increases in evaporation of almost 2 Wm (exp -2) at deltaSST = 0.23 K. Despite the increases in specific humidity, relative humidity decreases slightly in regions of elevated SSTs. For the most part, variations in wind speed are consistent with previous investigations. Weakening of the equatorial easterlies (and generation of westerlies) between 160 degrees E and 140 degrees W dominates during the early phases of warm events. Elevated wind speeds in adjacent subtropical regions and in the eastern equatorial Pacific subsequently develop too. The net contribution of these winds, which reflect adjustments in Hadley and Walker circulation components is toward reduced evaporation. Results for cold periods are approximately similar, but opposite in sign to warm events, though evidence of different temporal evolution is noted.

  7. Using multi-resolution proxies to assess ENSO impacts on the mean state of the tropical Pacific.

    NASA Astrophysics Data System (ADS)

    Karamperidou, C.; Conroy, J. L.

    2016-12-01

    Observations and model simulations indicate that the relationship between ENSO and the mean state of the tropical Pacific is a two-way interaction. On one hand, a strong zonal SST gradient (dSST) in the Pacific (colder cold tongue) increases the potential intensity of upcoming ENSO events and may lead to increased ENSO variance. On the other hand, in a period of increased ENSO activity, large events can warm the cold tongue at decadal scales via residual heating, and thus lead to reduced zonal SST gradient (ENSO rectification mechanism). The short length of the observational record hinders our ability to confidently evaluate which mechanism dominates in each period, and whether it is sensitive to external climate forcing. This question is effectively a question of interaction between two timescales: interannual and decadal. Paleoclimate proxies of different resolutions can help elucidate this question, since they can be independent records of variability in these separate timescales. Here, we use coral proxies of ENSO variability from across the Pacific and multi-proxy records of dSST at longer timescales. Proxies, models, and observations indicate that in periods of increased ENSO activity, dSST is negatively correlated with ENSO variance at decadal timescales, indicating that strong ENSO events may affect the decadal mean state via warming the cold tongue. Using climate model simulations we attribute this effect to residual nonlinear dynamical heating, thus supporting the ENSO rectification mechanism. On the contrary, in periods without strong events, ENSO variance and dSST are positively correlated, which indicates that the primary mechanism at work is the effect of the mean state on ENSO. Our analysis also quantitatively identifies the regions where paleoclimate proxies are needed in order to reduce the existing uncertainties in ENSO-mean state interactions. Hence, this study is a synthesis of observations, model simulations and paleoclimate proxy evidence

  8. Is ENSO part of an Indo-Pacific phenomenon?

    NASA Astrophysics Data System (ADS)

    Wieners, Claudia; de Ruijter, Wilhelmus; Dijkstra, Henk

    2015-04-01

    The Seychelles Dome (SD) - a thermocline ridge in the West Indian Ocean - is a dynamically active region with a strong Sea Surface Temperature (SST)-atmosphere coupling and located at the origin of the Madden-Julian Oscillation. Analysis of observational data suggests that it might influence El Niño occurrence and evolution at a lead time of 1.5 years. We find a negative correlation between SD SST in boreal summer and Nino3.4 SST about 18 months later. Such a correlation might be a mere side-effect of the fact that ENSO has influence on the SD - El Niño (La Niña) is followed by a warm (cool) SD after about 3-6 months - and of the cyclicity of ENSO with a preferred period of about 4 years. However, we find the correlation to be significantly stronger than one would expect in that case, implying that the SD contains information linearly independent from ENSO. A Multi-channel Singular Spectrum analysis (MSSA) on tropical SST, zonal wind and zonal wind variability reveals three significant oscillations. All of these show ENSO-like behaviour in the Pacific Ocean, with East Pacific SST anomalies being followed by anomalies of the same sign in the SD region after 3-5 months. Wind patterns propagate from the Indian to the Pacific Ocean. These findings suggest that the Indian and Pacific Oceans act as a unified system. The slower two oscillations, with periods around 4 years, have the strongest ENSO signal in the East Pacific (like a `Cold Tongue El Niño'). Compared to them, the fastest oscillation, with a period of 2.5 years, has a stronger signal in the Central Pacific (more resembling a `Warm Pool El Niño'). Because of the short period of the fastest mode, the time elapsed between an SD anomaly and the following ENSO anomaly (of opposite sign) is only 11 months - much less than the 18 months lag at which the correlation between SD and ENSO is minimal. This suggests that while the Cold Tongue El Niño's tend to be preceded by a cool SD event at a lead time suitable

  9. Influence of El Niño–Southern Oscillation (ENSO) events on the evolution of central California's shoreline

    USGS Publications Warehouse

    Storlazzi, Curt D.; Griggs, Gary B.

    2000-01-01

    Significant sea-cliff erosion and storm damage occurred along the central coast of California during the 1982–1983 and 1997–1998 El Niño winters. This generated interest among scientists and land-use planners in how historic El Niño–Southern Oscillation (ENSO) winters have affected the coastal climate of central California. A relative ENSO intensity index based on oceanographic and meteorologic data defines the timing and magnitude of ENSO events over the past century. The index suggests that five higher intensity (relative values 4–6) and 17 lower intensity (relative values 1–3) ENSO events took place between 1910 and 1995. The ENSO intensity index correlates with fluctuations in the time series of cyclone activity, precipitation, detrended sea level, wave height, sea-surface temperature, and sea-level barometric pressure. Wave height, sea level, and precipitation, which are the primary external forcing parameters in sea-cliff erosion, increase nonlinearly with increasing relative ENSO event intensity. The number of storms that caused coastal erosion or storm damage and the historic occurrence of large-scale sea-cliff erosion along the central coast also increase nonlinearly with increasing relative event intensity. These correlations and the frequency distribution of relative ENSO event intensities indicate that moderate- to high-intensity ENSO events cause the most sea-cliff erosion and shoreline recession over the course of a century.

  10. Asian Summer Monsoon Rainfall associated with ENSO and its Predictability

    NASA Astrophysics Data System (ADS)

    Shin, C. S.; Huang, B.; Zhu, J.; Marx, L.; Kinter, J. L.; Shukla, J.

    2015-12-01

    The leading modes of the Asian summer monsoon (ASM) rainfall variability and their seasonal predictability are investigated using the CFSv2 hindcasts initialized from multiple ocean analyses over the period of 1979-2008 and observation-based analyses. It is shown that the two leading empirical orthogonal function (EOF) modes of the observed ASM rainfall anomalies, which together account for about 34% of total variance, largely correspond to the ASM responses to the ENSO influences during the summers of the developing and decaying years of a Pacific anomalous event, respectively. These two ASM modes are then designated as the contemporary and delayed ENSO responses, respectively. It is demonstrated that the CFSv2 is capable of predicting these two dominant ASM modes up to the lead of 5 months. More importantly, the predictability of the ASM rainfall are much higher with respect to the delayed ENSO mode than the contemporary one, with the predicted principal component time series of the former maintaining high correlation skill and small ensemble spread with all lead months whereas the latter shows significant degradation in both measures with lead-time. A composite analysis for the ASM rainfall anomalies of all warm ENSO events in this period substantiates the finding that the ASM is more predictable following an ENSO event. The enhanced predictability mainly comes from the evolution of the warm SST anomalies over the Indian Ocean in the spring of the ENSO maturing phases and the persistence of the anomalous high sea surface pressure over the western Pacific in the subsequent summer, which the hindcasts are able to capture reasonably well. The results also show that the ensemble initialization with multiple ocean analyses improves the CFSv2's prediction skill of both ENSO and ASM rainfall. In fact, the skills of the ensemble mean hindcasts initialized from the four different ocean analyses are always equivalent to the best ones initialized from any individual ocean

  11. Changes in Sea Salt Emissions Enhance ENSO Variability

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Yang; Russell, Lynn M.; Lou, Sijia

    Two 150-year pre-industrial simulations with and without interactive sea salt emissions from the Community Earth System Model (CESM) are performed to quantify the interactions between sea salt emissions and El Niño–Southern Oscillation (ENSO). Variations in sea salt emissions over the tropical Pacific Ocean are affected by changing wind speed associated with ENSO variability. ENSO-induced interannual variations in sea salt emissions result in decreasing (increasing) aerosol optical depth (AOD) by 0.03 over the equatorial central-eastern (western) Pacific Ocean during El Niño events compared to those during La Niña events. These changes in AOD further increase (decrease) radiative fluxes into the atmospheremore » by +0.2 W m -2 (-0.4 W m -2) over the tropical eastern (western) Pacific. Thereby, sea surface temperature increases (decreases) by 0.2–0.4 K over the tropical eastern (western) Pacific Ocean during El Niño compared to La Niña events and enhances ENSO variability by 10%. The increase in ENSO amplitude is a result of systematic heating (cooling) during the warm (cold) phase, of ENSO in the eastern Pacific. Interannual variations in sea salt emissions then produce the anomalous ascent (subsidence) over the equatorial eastern (western) Pacific between El Niño and La Niña events, which is a result of heating anomalies. Due to variations in sea salt emissions, the convective precipitation is enhanced by 0.6–1.2 mm day -1 over the tropical central-eastern Pacific Ocean and weakened by 0.9–1.5 mm day -1 over the Maritime Continent during El Niño compared to La Niña events, enhancing the precipitation variability over the tropical Pacific.« less

  12. A Further Extension of the Tahiti-Darwin SOI, Early ENSO Events and Darwin Pressure.

    NASA Astrophysics Data System (ADS)

    Allan, Robert J.; Nicholls, Neville; Jones, Phil D.; Butterworth, Ian J.

    1991-07-01

    An extension of the Tahiti minus Darwin Southern Oscillation Index (SOI) from 1882 back to 1876 is reported following the recovery of early Darwin mean sea-level pressure data spanning the period 1865-81. As a result, we are able to compare, for the first time, the major 1877-78 and 1982-83 ENSO events on the basis of this commonly used index. Early Darwin and Jakarta data are also examined in terms of a measure of the Australian response to documented El Niño and/or ENSO events in 1866, 1868, 1871, 1873, 1874 and 1875.The SOI during the 1877-78 ENSO event has a similar temporal response to that in 1982-83, but the index is slightly weaker than in the recent event. Examination of documentary evidence confirms the severity of the drought conditions that affected the Australian continent during the 1877-78 ENSO, and shows that this response is in line with the wider Indo-Pacific impacts reported in the literature. Earlier El Niño phases in 1868 and 1873 are not resolved distinctly in either the Darwin or Jakarta pressure data. This appears to illustrate that El Niño event histories do not always indicate wider ENSO influences in the Indo-Pacific basin, particularly during weak to moderate phases.

  13. Two Distinct Roles of Atlantic SSTs in ENSO Variability: North Tropical Atlantic SST and Atlantic Nino

    NASA Technical Reports Server (NTRS)

    Ham, Yoo-Geun; Kug, Jong-Seong; Park, Jong-Yeon

    2013-01-01

    Two distinct roles of the Atlantic sea surface temperatures (SSTs), namely, the North Tropical Atlantic (NTA) SST and the Atlantic Nino, on the El Nino-Southern Oscillation (ENSO) variability are investigated using the observational data from 1980 to 2010 and coupled model experiments. It appears that the NTA SST and the Atlantic Nino can be used as two independent predictors for predicting the development of ENSO events in the following season. Furthermore, they are likely to be linked to different types of El Nino events. Specifically, the NTA SST cooling during February, March, and April contributes to the central Pacific warming at the subsequent winter season, while the negative Atlantic Nino event during June, July, and August contributes to enhancing the eastern Pacific warming. The coupled model experiments support these results. With the aid of a lagged inverse relationship, the statistical forecast using two Atlantic indices can successfully predict various ENSO indices.

  14. ENSO Dynamics and Trends, AN Alternate View

    NASA Astrophysics Data System (ADS)

    Rojo Hernandez, J. D.; Lall, U.; Mesa, O. J.

    2017-12-01

    El Niño - Southern Oscillation (ENSO) is the most important inter-annual climate fluctuation on a planetary level with great effects on the hydrological cycle, agriculture, ecosystems, health and society. This work demonstrates the use of the Non-Homogeneus hidden Markov Models (NHMM) to characterize ENSO using a set of discrete states with variable transition probabilities matrix using the data of sea surface temperature anomalies (SSTA) of the Kaplan Extended SST v2 between 120E -90W, 15N-15S from Jan-1856 to Dec-2016. ENSO spatial patterns, their temporal distribution, the transition probabilities between patterns and their temporal evolution are the main results of the NHHMM applied to ENSO. The five "hidden" states found appear to represent the different "Flavors" described in the literature: the Canonical El Niño, Central El Niño, a Neutral state, Central La Niña and the Canonical Niña. Using the whole record length of the SSTA it was possible to identify trends in the dynamic system, with a decrease in the probability of occurrence of the cold events and a significant increase of the warm events, in particular of Central El Niño events whose probability of occurrence has increased Dramatically since 1960 coupled with increases in global temperature.

  15. A reduction in the asymmetry of ENSO amplitude due to global warming: The role of atmospheric feedback

    NASA Astrophysics Data System (ADS)

    Ham, Yoo-Geun

    2017-08-01

    This study analyzes a reduction in the asymmetry of El Niño Southern-Oscillation (ENSO) amplitude due to global warming in Coupled Model Intercomparison Project Phase 5 models. The multimodel-averaged Niño3 skewness during December-February season decreased approximately 40% in the RCP4.5 scenario compared to that in the historical simulation. The change in the nonlinear relationship between sea surface temperature (SST) and precipitation is a key factor for understanding the reduction in ENSO asymmetry due to global warming. In the historical simulations, the background SST leading to the greatest precipitation sensitivity (SST for Maximum Precipitation Sensitivity, SST_MPS) occurs when the positive SST anomaly is located over the equatorial central Pacific. Therefore, an increase in climatological SST due to global warming weakens the atmospheric response during El Niño over the central Pacific. However, the climatological SST over this region in the historical simulation is still lower than the SST_MPS for the negative SST anomaly; therefore, a background SST increase due to global warming can further increase precipitation sensitivity. The atmospheric feedbacks during La Niña are enhanced and increase the La Niña amplitude due to global warming.

  16. Increasing water cycle extremes in California and relation to ENSO cycle under global warming

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yoon, Jin -Ho; Wang, S. -Y. Simon; Gillies, Robert R.

    California has experienced its most severe drought in recorded history since the winter of 2013-2014. The long duration of drought has stressed statewide water resources and the economy, while fueling an extraordinary increase in wildfires. The effects of global warming on the regional climate include a hotter and drier climate, as well as earlier snowmelt, both of which exacerbate drought conditions. However, connections between a changing climate and how climate oscillations modulate regional water cycle extremes are not well understood. Here we analyze large-ensemble simulations of future climate change in California using the Community Earth System Model version 1 (CESM1)more » and multiple climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Both intense drought and excessive flooding are projected to increase by at least 50% toward the end of the 21st century. Furthermore, the projected increase in water cycle extremes is associated with tighter relation to El Niño and Southern Oscillation (ENSO), particularly extreme El Niño and La Niña events, which modulates California’s climate not only through its warm and cold phases, but also ENSO’s precursor patterns.« less

  17. Increasing water cycle extremes in California and relation to ENSO cycle under global warming

    DOE PAGES

    Yoon, Jin -Ho; Wang, S. -Y. Simon; Gillies, Robert R.; ...

    2015-10-21

    California has experienced its most severe drought in recorded history since the winter of 2013-2014. The long duration of drought has stressed statewide water resources and the economy, while fueling an extraordinary increase in wildfires. The effects of global warming on the regional climate include a hotter and drier climate, as well as earlier snowmelt, both of which exacerbate drought conditions. However, connections between a changing climate and how climate oscillations modulate regional water cycle extremes are not well understood. Here we analyze large-ensemble simulations of future climate change in California using the Community Earth System Model version 1 (CESM1)more » and multiple climate models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Both intense drought and excessive flooding are projected to increase by at least 50% toward the end of the 21st century. Furthermore, the projected increase in water cycle extremes is associated with tighter relation to El Niño and Southern Oscillation (ENSO), particularly extreme El Niño and La Niña events, which modulates California’s climate not only through its warm and cold phases, but also ENSO’s precursor patterns.« less

  18. ENSO in a warming world: interannual climate variability in the early Miocene Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Fox, Bethany; Wilson, Gary; Lee, Daphne

    2016-04-01

    The El Niño - Southern Oscillation (ENSO) is the dominant source of interannual variability in the modern-day climate system. ENSO is a quasi-periodic cycle with a recurrence interval of 2-8 years. A major question in modern climatology is how ENSO will respond to increased climatic warmth. ENSO-like (2-8 year) cycles have been detected in many palaeoclimate records for the Holocene. However, the temporal resolution of pre-Quaternary palaeoclimate archives is generally too coarse to investigate ENSO-scale variability. We present a 100-kyr record of ENSO-like variability during the second half of the Oligocene/Miocene Mi-1 event, a period of increasing global temperatures and Antarctic deglaciation (~23.032-2.93 Ma). This record is drawn from an annually laminated lacustrine diatomite from southern New Zealand, a region strongly affected by ENSO in the present day. The diatomite consists of seasonal alternations of light (diatom bloom) and dark (low diatom productivity) layers. Each light-dark couplet represents one year's sedimentation. Light-dark couplet thickness is characterised by ENSO-scale variability. We use high-resolution (sub-annual) measurements of colour spectra to detect couplet thickness variability. Wavelet analysis indicates that absolute values are modulated by orbital cycles. However, when orbital effects are taken into account, ENSO-like variability occurs throughout the entire depositional period, with no clear increase or reduction in relation to Antarctic deglaciation and increasing global warmth.

  19. On the role of ozone feedback in the ENSO amplitude response under global warming.

    PubMed

    Nowack, Peer J; Braesicke, Peter; Luke Abraham, N; Pyle, John A

    2017-04-28

    The El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean is of key importance to global climate and weather. However, state-of-the-art climate models still disagree on the ENSO's response under climate change. The potential role of atmospheric ozone changes in this context has not been explored before. Here we show that differences between typical model representations of ozone can have a first-order impact on ENSO amplitude projections in climate sensitivity simulations. The vertical temperature gradient of the tropical middle-to-upper troposphere adjusts to ozone changes in the upper troposphere and lower stratosphere, modifying the Walker circulation and consequently tropical Pacific surface temperature gradients. We show that neglecting ozone changes thus results in a significant increase in the number of extreme ENSO events in our model. Climate modeling studies of the ENSO often neglect changes in ozone. We therefore highlight the need to understand better the coupling between ozone, the tropospheric circulation, and climate variability.

  20. Response of ENSO amplitude to global warming in CESM large ensemble: uncertainty due to internal variability

    NASA Astrophysics Data System (ADS)

    Zheng, Xiao-Tong; Hui, Chang; Yeh, Sang-Wook

    2018-06-01

    El Niño-Southern Oscillation (ENSO) is the dominant mode of variability in the coupled ocean-atmospheric system. Future projections of ENSO change under global warming are highly uncertain among models. In this study, the effect of internal variability on ENSO amplitude change in future climate projections is investigated based on a 40-member ensemble from the Community Earth System Model Large Ensemble (CESM-LE) project. A large uncertainty is identified among ensemble members due to internal variability. The inter-member diversity is associated with a zonal dipole pattern of sea surface temperature (SST) change in the mean along the equator, which is similar to the second empirical orthogonal function (EOF) mode of tropical Pacific decadal variability (TPDV) in the unforced control simulation. The uncertainty in CESM-LE is comparable in magnitude to that among models of the Coupled Model Intercomparison Project phase 5 (CMIP5), suggesting the contribution of internal variability to the intermodel uncertainty in ENSO amplitude change. However, the causations between changes in ENSO amplitude and the mean state are distinct between CESM-LE and CMIP5 ensemble. The CESM-LE results indicate that a large ensemble of 15 members is needed to separate the relative contributions to ENSO amplitude change over the twenty-first century between forced response and internal variability.

  1. Effects of ENSO-induced extremes on terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Xu, M.; Hoffman, F. M.

    2017-12-01

    The El Niño Southern Oscillation (ENSO) with its warm (El Niño) and cold phase (La Niña) has well-known global impacts on the Earth system through the mechanism of teleconnections. Not only the global mean temperature and precipitation distributions will be changed but also the climate extremes will be enhanced during ENSO events. In this study, the advanced Earth System Model ACME version 0.3 was used to simulate terrestrial biogeochemistry and global climate from 1982 to 2020 with prescribed Sea Surface Temperature (SST) from data fusions of the NOAA high resolution daily Optimum Interpolation SST (OISST), CFS v2 9-month seasonal forecast and data reconstructions. We investigated how ENSO-induced climate extremes affect land carbon dynamics both regionally and globally and the implications for the functioning of different vegetated ecosystems under the influence of climate extremes. The results show that the ENSO-induced climate extremes, especially drought and heat waves, have significant impacts on the terrestrial carbon cycle. The responses to ENSO-induced climate extremes are divergent among different vegetation types.

  2. ENSO relationship to Summer Rainfall Variability and its Potential Predictability over Arabian Peninsula Region

    NASA Astrophysics Data System (ADS)

    Adnan Abid, Mohammad; Almazroui, Mansour; Kucharski, Fred

    2017-04-01

    Summer seasonal rainfall falls mainly over the south and southwestern parts of the Arabian Peninsula (AP). The relationship between this mean summer seasonal rainfall pattern and El Niño Southern Oscillation (ENSO) is analyzed with the aid of a 15-member ensemble of simulations using the King Abdulaziz University (KAU) Atmospheric Global Climate Model (AGCM). Each simulation is forced with Hadley Sea Surface Temperature (SST) for the period 1980-2015. The southwestern peninsula rainfall is linked towith the SST anomalies in the central-eastern pacific region. This relation is established through an atmospheric teleconnection which shows an upper-level convergence (divergence) anomalies over the southern Arabian Peninsula compensating the central-eastern Pacific region upper-level divergence (convergence) anomalies for the warm (cold) El Niño Southern Oscillaton (ENSO) phase. The upper-level convergence (divergence) over the southern Arabian Peninsula leads to sinking (rising) motion, low-level divergence (convergence) and consequently to reduced (enhanced) rainfall. The correlation coefficient between the observed area-averged Niño3.4 index and athe South Arabian Rainfall Index (SARI) is -0.54. This indicates that AP receives less rainfall during the warm (El Niño) phase, while the opposite happens in the cold (La Niña) El Niño Southern Oscillaton (ENSO) phase. The lower tropospheric cyclonic circulation anomalies strongly modulate the ENSO-related rainfall in the region. Overall, the model shows a 43% potential predictability (PP) for the Southern Arabian Peninsula Rainfall Index (SARI). Further, the predictability during the warm ENSO (El Niño) events is higher than during cold ENSO (La Niña) events. This is not only because of a stronger signal, but also noise reduction contributes to the increase of the regional PP in El Niño compared to that of La Niña years.

  3. ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing

    NASA Astrophysics Data System (ADS)

    Yeh, Sang-Wook; Cai, Wenju; Min, Seung-Ki; McPhaden, Michael J.; Dommenget, Dietmar; Dewitte, Boris; Collins, Matthew; Ashok, Karumuri; An, Soon-Il; Yim, Bo-Young; Kug, Jong-Seong

    2018-03-01

    El Niño and Southern Oscillation (ENSO) is the most prominent year-to-year climate fluctuation on Earth, alternating between anomalously warm (El Niño) and cold (La Niña) sea surface temperature (SST) conditions in the tropical Pacific. ENSO exerts its impacts on remote regions of the globe through atmospheric teleconnections, affecting extreme weather events worldwide. However, these teleconnections are inherently nonlinear and sensitive to ENSO SST anomaly patterns and amplitudes. In addition, teleconnections are modulated by variability in the oceanic and atmopsheric mean state outside the tropics and by land and sea ice extent. The character of ENSO as well as the ocean mean state have changed since the 1990s, which might be due to either natural variability or anthropogenic forcing, or their combined influences. This has resulted in changes in ENSO atmospheric teleconnections in terms of precipitation and temperature in various parts of the globe. In addition, changes in ENSO teleconnection patterns have affected their predictability and the statistics of extreme events. However, the short observational record does not allow us to clearly distinguish which changes are robust and which are not. Climate models suggest that ENSO teleconnections will change because the mean atmospheric circulation will change due to anthropogenic forcing in the 21st century, which is independent of whether ENSO properties change or not. However, future ENSO teleconnection changes do not currently show strong intermodel agreement from region to region, highlighting the importance of identifying factors that affect uncertainty in future model projections.

  4. Impact of ENSO longitudinal position on teleconnections to the NAO

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjun; Wang, Ziqi; Stuecker, Malte F.; Turner, Andrew G.; Jin, Fei-Fei; Geng, Xin

    2018-02-01

    While significant improvements have been made in understanding how the El Niño-Southern Oscillation (ENSO) impacts both North American and Asian climate, its relationship with the North Atlantic Oscillation (NAO) remains less clear. Observations indicate that ENSO exhibits a highly complex relationship with the NAO-associated atmospheric circulation. One critical contribution to this ambiguous ENSO/NAO relationship originates from ENSO's diversity in its spatial structure. In general, both eastern (EP) and central Pacific (CP) El Niño events tend to be accompanied by a negative NAO-like atmospheric response. However, for two different types of La Niña the NAO response is almost opposite. Thus, the NAO responses for the CP ENSO are mostly linear, while nonlinear NAO responses dominate for the EP ENSO. These contrasting extra-tropical atmospheric responses are mainly attributed to nonlinear air-sea interactions in the tropical eastern Pacific. The local atmospheric response to the CP ENSO sea surface temperature (SST) anomalies is highly linear since the air-sea action center is located within the Pacific warm pool, characterized by relatively high climatological SSTs. In contrast, the EP ENSO SST anomalies are located in an area of relatively low climatological SSTs in the eastern equatorial Pacific. Here only sufficiently high positive SST anomalies during EP El Niño events are able to overcome the SST threshold for deep convection, while hardly any anomalous convection is associated with EP La Niña SSTs that are below this threshold. This ENSO/NAO relationship has important implications for NAO seasonal prediction and places a higher requirement on models in reproducing the full diversity of ENSO.

  5. The Evolution of Tropical Precipitation Patterns During ENSO Events Using 21+ Years of GPCP Merged Data

    NASA Technical Reports Server (NTRS)

    Curtis, Scott; Adler, Robert

    2000-01-01

    The ENSO phenomenon is characterized by fluctuations in the climate system of the tropical Pacific. Quantifying changes in the precipitation component of this system is important in understanding the distribution of heating in the atmosphere which drives the large-scale circulation and affects the weather patterns in the mid-latitudes. Monitoring precipitation anomalies in the Pacific is also an important component for tracking the evolution of ENSO. The most timely and complete observations of the earth come from satellite instruments. In this study, the state of the art satellite-gauge merged monthly precipitation data set from the Global Precipitation Climatology Project (GPCP) is used to depict tropical rainfall patterns during ENSO events over the past two decades and quantify these patterns using indices. This analysis will be complemented by daily precipitation data which can resolve the Madden-Julian Oscillation and westerly wind burst events. The 1997-98 El Nino and 1998-2000 La Nina were the best observed ENSO cycle in the historic record. Prior to the El Nino (in terms of anomalous warming of the east Pacific) dry anomalies over the Maritime Continent were observed in February 1997 as a westerly wind burst advected convection to the east. The largest SST anomalies occurred around November-December 1997, which were followed by the largest precipitation anomalies in the beginning of 1998. The largest precipitation departures from normal were not colocated with the SST anomalies, but were further west, In the spring of 1998 negative precipitation anomalies to the north of the equator intensified, signaling the mature phase of the El Nino. A rapid increase in the precipitation-based La Nina index from December-January 1998 to March-April 1998 signaled the coming La Nina. The 1982-1983 El Nino was comparable in strength (according to several indices) and the precipitation patterns evolved in a similar fashion. For the 1998-2000 La Nina, the coldest anomalies

  6. Global Terrestrial Water Storage Changes and Connections to ENSO Events

    NASA Astrophysics Data System (ADS)

    Ni, Shengnan; Chen, Jianli; Wilson, Clark R.; Li, Jin; Hu, Xiaogong; Fu, Rong

    2018-01-01

    Improved data quality of extended record of the Gravity Recovery and Climate Experiment (GRACE) satellite gravity solutions enables better understanding of terrestrial water storage (TWS) variations. Connections of TWS and climate change are critical to investigate regional and global water cycles. In this study, we provide a comprehensive analysis of global connections between interannual TWS changes and El Niño Southern Oscillation (ENSO) events, using multiple sources of data, including GRACE measurements, land surface model (LSM) predictions and precipitation observations. We use cross-correlation and coherence spectrum analysis to examine global connections between interannual TWS changes and the Niño 3.4 index, and select four river basins (Amazon, Orinoco, Colorado, and Lena) for more detailed analysis. The results indicate that interannual TWS changes are strongly correlated with ENSO over much of the globe, with maximum cross-correlation coefficients up to 0.70, well above the 95% significance level ( 0.29) derived by the Monte Carlo experiments. The strongest correlations are found in tropical and subtropical regions, especially in the Amazon, Orinoco, and La Plata basins. While both GRACE and LSM TWS estimates show reasonably good correlations with ENSO and generally consistent spatial correlation patterns, notably higher correlations are found between GRACE TWS and ENSO. The existence of significant correlations in middle-high latitudes shows the large-scale impact of ENSO on the global water cycle.

  7. Tracking the delayed response of the northern winter stratosphere to ENSO using multi reanalyses and model simulations

    NASA Astrophysics Data System (ADS)

    Ren, Rongcai; Rao, Jian; Wu, Guoxiong; Cai, Ming

    2017-05-01

    The concurrent effects of the El Niño-Southern Oscillation (ENSO) on the northern winter stratosphere have been widely recognized; however, the delayed effects of ENSO in the next winter after mature ENSO have yet to be confirmed in multi reanalyses and model simulations. This study uses three reanalysis datasets, a long-term fully coupled model simulation, and a high-top general circulation model to examine ENSO's delayed effects in the stratosphere. The warm-minus-cold composite analyses consistently showed that, except those quick-decaying quasi-biennial ENSO events that reverse signs during July-August-September (JAS) in their decay years, ENSO events particularly those quasi-quadrennial (QQ) that persist through JAS, always have a significant effect on the extratropical stratosphere in both the concurrent winter and the next winter following mature ENSO. During the concurrent winter, the QQ ENSO-induced Pacific-North American (PNA) pattern corresponds to an anomalous wavenumber-1 from the upper troposphere to the stratosphere, which acts to intensify/weaken the climatological wave pattern during warm/cold ENSO. Associated with the zonally quasi-homogeneous tropical forcing in spring of the QQ ENSO decay years, there appear persistent and zonally quasi-homogeneous temperature anomalies in the midlatitudes from the upper troposphere to the lower stratosphere until summer. With the reduction in ENSO forcing and the PNA responses in the following winter, an anomalous wavenumber-2 prevails in the extratropics. Although the anomalous wave flux divergence in the upper stratospheric layer is still dominated by wavenumber-1, it is mainly caused by wavenumber-2 in the lower stratosphere. However, the wavenumber-2 activity in the next winter is always underestimated in the model simulations, and wavenumber-1 activity dominates in both winters.

  8. Joint impact of North and South Pacific extratropical atmospheric variability on the onset of ENSO events

    NASA Astrophysics Data System (ADS)

    Ding, Ruiqiang; Li, Jianping; Tseng, Yu-heng; Sun, Cheng; Xie, Fei

    2017-01-01

    Previous studies have indicated that boreal winter subtropical and extratropical sea surface pressure (SLP) anomalies over both the North and South Pacific are significantly related to the El Niño-Southern Oscillation (ENSO) state in the following boreal winter. Here we use observational data and model simulations to show that the ability of the boreal winter North Pacific SLP anomalies to initiate ENSO events a year later may strongly depend on the state of the simultaneous South Pacific SLP anomalies and vice versa. When the boreal winter North Pacific SLP anomalies are of the opposite sign to the simultaneous South Pacific anomalies, the correlation of the North or South Pacific anomalies with the following ENSO state becomes much weaker, and the strength of the ENSO events also tends to be weaker. One possible reason for this is that when the boreal winter North and South Pacific SLP anomalies have the opposite sign, the westerly anomalies over the western-central equatorial Pacific during the following boreal summer are greatly reduced by the interference between the antecedent North and South Pacific SLP anomalies, thereby not favoring the development of ENSO events. Further analysis indicates that a combination of North and South Pacific precursor signals may serve to enhance the ENSO prediction skill.

  9. ENSO's non-stationary and non-Gaussian character: the role of climate shifts

    NASA Astrophysics Data System (ADS)

    Boucharel, J.; Dewitte, B.; Garel, B.; Du Penhoat, Y.

    2009-07-01

    El Niño Southern Oscillation (ENSO) is the dominant mode of climate variability in the Pacific, having socio-economic impacts on surrounding regions. ENSO exhibits significant modulation on decadal to inter-decadal time scales which is related to changes in its characteristics (onset, amplitude, frequency, propagation, and predictability). Some of these characteristics tend to be overlooked in ENSO studies, such as its asymmetry (the number and amplitude of warm and cold events are not equal) and the deviation of its statistics from those of the Gaussian distribution. These properties could be related to the ability of the current generation of coupled models to predict ENSO and its modulation. Here, ENSO's non-Gaussian nature and asymmetry are diagnosed from in situ data and a variety of models (from intermediate complexity models to full-physics coupled general circulation models (CGCMs)) using robust statistical tools initially designed for financial mathematics studies. In particular α-stable laws are used as theoretical background material to measure (and quantify) the non-Gaussian character of ENSO time series and to estimate the skill of ``naïve'' statistical models in producing deviation from Gaussian laws and asymmetry. The former are based on non-stationary processes dominated by abrupt changes in mean state and empirical variance. It is shown that the α-stable character of ENSO may result from the presence of climate shifts in the time series. Also, cool (warm) periods are associated with ENSO statistics having a stronger (weaker) tendency towards Gaussianity and lower (greater) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through nonlinear processes. The relationship between changes in mean state and nonlinearity (skewness) is further investigated both in the Zebiak and Cane (1987)'s model and the models of the Intergovernmental Panel for Climate Change (IPCC). Whereas there is a clear relationship in all

  10. Variability of Extreme Precipitation Events in Tijuana, Mexico During ENSO Years

    NASA Astrophysics Data System (ADS)

    Cavazos, T.; Rivas, D.

    2007-05-01

    We present the variability of daily precipitation extremes (top 10 percecnt) in Tijuana, Mexico during 1950-2000. Interannual rainfall variability is significantly modulated by El Nino/Southern Oscillation. The interannual precipitation variability exhibits a large change with a relatively wet period and more variability during 1976- 2000. The wettest years and the largest frequency of daily extremes occurred after 1976-1977, with 6 out of 8 wet years characterized by El Nino episodes and 2 by neutral conditions. However, more than half of the daily extremes during 1950-2000 occurred in non-ENSO years, evidencing that neutral conditions also contribute significantly to extreme climatic variability in the region. Extreme events that occur in neutral (strong El Nino) conditions are associated with a pineapple express and a neutral PNA (negative TNH) teleconnection pattern that links an anomalous tropical convective forcing west (east) of the date line with a strong subtropical jet over the study area. At regional scale, both types of extremes are characterized by a trough in the subtropical jet over California/Baja California, which is further intensified by thermal interaction with an anomalous warm California Current off Baja California, low-level moisture advection from the subtropical warm sea-surface region, intense convective activity over the study area and extreme rainfall from southern California to Baja California.

  11. Mean state dependence of ENSO diversity resulting from an intermediate coupled model

    NASA Astrophysics Data System (ADS)

    Xie, Ruihuang; Jin, Fei-Fei; Mu, Mu

    2016-04-01

    ENSO diversity is referred to the event-to-event differences in the amplitude, longitudinal location of maximum sea surface temperature (SST) anomalies and evolutional mechanisms, as manifested in both observation data and climate model simulations. Previous studies argued that westerly wind burst (WWB) has strong influence on ENSO diversity. Here, we bring evidences, from a modified intermediate complexity Zebiak-Cane (ZC) coupled model, to illustrate that the ENSO diversity is also determined by the mean states. Stabilities of the linearized ZC model reveal that the mean state with weak (strong) wind stress and deep (shallow) thermocline prefers ENSO variation in the equitorial eastern (central) Pacific with a four-year (two-year) period. Weak wind stress and deep thermocline make the thermocline (TH) feedback the dominant contribution to the growth of ENSO SST anomalies, whereas the opposite mean state favors the zonal advective (ZA) feedback. Different leading dynamical SST-controller makes ENSO display its diversity. In a mean state that resembles the recent climate in the tropical Pacific, the four-year and two-year ENSO variations coexist with similar growth rate. Even without WWB forcing, the nonlinear integration results with adjusted parameters in this special mean state also present at least two types of El Niño, in which the maximum warming rates are contributed by either TH or ZA feedback. The consistency between linear and nonlinear model results indicates that the ENSO diversity is dependent on the mean states.

  12. Earth rotation and ENSO events: combined excitation of interannual LOD variations by multiscale atmospheric oscillations

    NASA Astrophysics Data System (ADS)

    Zheng, Dawei; Ding, Xiaoli; Zhou, Yonghong; Chen, Yongqi

    2003-03-01

    Time series of the length of day characterizing the rate of Earth rotation, the atmospheric angular momentum and the Southern Oscillation Index from 1962 to 2000 are used to reexamine the relationships between the ENSO events and the changes in the length of day, as well as the global atmospheric angular momentum. Particular attention is given to the different effects of the 1982-1983 and 1997-1998 ENSO events on the variations of Earth rotation. The combined effects of multiscale atmospheric oscillations (seasonal, quasi-biennial and ENSO time scales) on the anomalous variations of the interannual rates of Earth rotation are revealed in this paper by studying the wavelet spectra of the data series.

  13. Shifting patterns of ENSO variability from a 492-year South Pacific coral core

    NASA Astrophysics Data System (ADS)

    Tangri, N.; Linsley, B. K.; Mucciarone, D.; Dunbar, R. B.

    2017-12-01

    Anticipating the impacts of ENSO in a changing climate requires detailed reconstructions of changes in its timing, amplitude, and spatial pattern, as well as attempts to attribute those changes to external forcing or internal variability. A continuous coral δ18O record from American Samoa, in the tropical South Pacific, sheds light on almost five centuries of these changes. We find evidence of internally-driven 50-100 year cycles with broad peaks of high variability punctuated by short transitions of low variability. We see a long, slow trend towards more frequent ENSO events, punctuated by sharp decreases in frequency; the 20th century in particular shows a strong trend towards higher-frequency ENSO. Due to the unique location of American Samoa with respect to ENSO sea surface temperature (SST) anomalies, we infer changes in the spatial pattern of ENSO. American Samoa currently lies on the ENSO 3.4 nodal line - the boomerang shape that separates waters warmed by El Niño from those that cool. Closer examination reveals that SST around American Samoa displays opposing responses to Eastern and Central Pacific ENSO events. However, this has not always been the case; in the late 19th and early 20th century, SST responded similarly to both flavors of ENSO. We interpret this to mean a geographic narrowing towards the equator of the eastern Pacific El Niño SST anomaly pattern in the first half of the 20th century.

  14. MJO influence on ENSO effects in precipitation and temperature over South America

    NASA Astrophysics Data System (ADS)

    Shimizu, M. H.; Bombardi, R. J.; Ambrizzi, T.

    2013-12-01

    Researches on the effects of the El Niño Southern Oscillation (ENSO) over precipitation and temperature, such as drought, flood, and anomalous high or cold temperatures, have great importance because of the impact of ENSO on the environment, society, and economy. Several studies have reported the influences of ENSO over South American precipitation and temperature climatological patterns, such as drier than normal conditions over northeast Brazil during the warm phase (El Niño) and wetter than normal conditions over northeast Brazil in the cold phase (La Niña). However, some recent studies focusing on the Northern Hemisphere have indicated that the basic response of ENSO is dependent on the phase of the Madden-Julian Oscillation (MJO). The MJO is characterized by the eastward propagation of the convection from Indian to Central Pacific Ocean and is related to variations in the position and intensity of the South Atlantic Convergence Zone (SACZ). The present work investigates the combined response of the phases of these two distinct phenomena, ENSO and MJO, over South America. Our goal is to explore the relative importance of the MJO to precipitation and temperature anomalies during ENSO events. MJO events were defined using the MJO index created by Jones and Carvalho (2012) based on empirical orthogonal functions analysis. ENSO phases were defined according to the Oceanic Niño Index provided by the National Oceanic and Atmospheric Administration (NOAA). A composite analysis with each combination of the phases of ENSO and MJO was performed to obtain the mean patterns of temperature and precipitation over South America for the months of November to March (austral summer). The results showed that the precipitation and temperature anomalies patterns observed during ENSO events, without the concurrent occurrence of the MJO, can be strengthened or weakened during events where ENSO and MJO occur simultaneously. Moreover, the effect on the anomalies patterns in these

  15. Sensitivity of Water Scarcity Events to ENSO-Driven Climate Variability at the Global Scale

    NASA Technical Reports Server (NTRS)

    Veldkamp, T. I. E.; Eisner, S.; Wada, Y.; Aerts, J. C. J. H.; Ward, P. J.

    2015-01-01

    Globally, freshwater shortage is one of the most dangerous risks for society. Changing hydro-climatic and socioeconomic conditions have aggravated water scarcity over the past decades. A wide range of studies show that water scarcity will intensify in the future, as a result of both increased consumptive water use and, in some regions, climate change. Although it is well-known that El Niño- Southern Oscillation (ENSO) affects patterns of precipitation and drought at global and regional scales, little attention has yet been paid to the impacts of climate variability on water scarcity conditions, despite its importance for adaptation planning. Therefore, we present the first global-scale sensitivity assessment of water scarcity to ENSO, the most dominant signal of climate variability. We show that over the time period 1961-2010, both water availability and water scarcity conditions are significantly correlated with ENSO-driven climate variability over a large proportion of the global land area (> 28.1 %); an area inhabited by more than 31.4% of the global population. We also found, however, that climate variability alone is often not enough to trigger the actual incidence of water scarcity events. The sensitivity of a region to water scarcity events, expressed in terms of land area or population exposed, is determined by both hydro-climatic and socioeconomic conditions. Currently, the population actually impacted by water scarcity events consists of 39.6% (CTA: consumption-to-availability ratio) and 41.1% (WCI: water crowding index) of the global population, whilst only 11.4% (CTA) and 15.9% (WCI) of the global population is at the same time living in areas sensitive to ENSO-driven climate variability. These results are contrasted, however, by differences in growth rates found under changing socioeconomic conditions, which are relatively high in regions exposed to water scarcity events. Given the correlations found between ENSO and water availability and scarcity

  16. Are population dynamics of shorebirds affected by El Niño/Southern Oscillation (ENSO) while on their non-breeding grounds in Ecuador?

    NASA Astrophysics Data System (ADS)

    O'Hara, Patrick D.; Haase, Ben J. M.; Elner, Robert W.; Smith, Barry D.; Kenyon, Jamie K.

    2007-08-01

    Declines in avian populations are a global concern, particularly for species that migrate between Arctic-temperate and tropical locations. Long-term population studies offer opportunities to detect and document ecological effects attributable to long-term climatic cycles such as the El Niño/Southern Oscillation (ENSO). In this study, we report possible population-level effects of such climatic cycles on shorebird species that use two non-breeding season sites in Ecuador (Santa Elena peninsula area, near La Libertad). During our 9-year study period (1991/1992-1999/2000), there was a particularly strong ENSO warm phase event during 1997/1998. Population trend data for three species of shorebird, Western Sandpipers ( Calidris mauri), Semipalmated Sandpipers ( C. pusilla), and Least Sandpipers ( C. minutilla), indicated abundances generally declined during the 1990s, but there was an increase in the proportion of first-year birds and their abundance in the years following the 1997/1998 ENSO warm phase. There was some support for variation in apparent survivorship associated with the onset of the ENSO warm phase event in our population models, based on capture-mark-recapture data. Following the 1997/1998 ENSO event onset, individuals for all three species were significantly lighter during the non-breeding season ( F1,3789 = 6.6, p = 0.01). Least-squares mean mass (controlling for size, sex and day of capture) for first-year birds dropped significantly more than for adults following ENSO (first-year mass loss = 0.69 ± 0.12 g; adult mass loss = 0.34 ± 0.11 g, F1,3789 = 5.31, p = 0.021), and least-squares mean mass dropped most during the period when sandpipers prepare for northward migration by gaining mass and moulting into breeding plumage. Least Sandpipers may have declined the most in mean mass following ENSO (0.76 ± 0.19 g), whereas Semipalmated Sandpipers were 0.52 ± 0.12 g lighter, and Western Sandpipers 0.40 ± 0.13 g lighter, but overall variation among

  17. Probable Causes of the Abnormal Ridge Accompanying the 2013-2014 California Drought: ENSO Precursor and Anthropogenic Warming Footprint

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, S-Y; Hipps, Lawrence; Gillies, Robert R.

    2014-05-16

    The 2013-14 California drought was accompanied by an anomalous high-amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer, and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either ENSO or Pacific Decadal Oscillation; instead it is correlated with a typemore » of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased GHG loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013-14, the associated drought and its intensity.« less

  18. Probable causes of the abnormal ridge accompanying the 2013-2014 California drought: ENSO precursor and anthropogenic warming footprint

    NASA Astrophysics Data System (ADS)

    Wang, S.-Y.; Hipps, Lawrence; Gillies, Robert R.; Yoon, Jin-Ho

    2014-05-01

    The 2013-2014 California drought was initiated by an anomalous high-amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either El Niño-Southern Oscillation (ENSO) or Pacific Decadal Oscillation; instead, it is correlated with a type of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased greenhouse gas loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013-2014 and the associated drought.

  19. The ENSO Effect on the Temporal and Spatial Distribution of Global Lightning Activity

    NASA Technical Reports Server (NTRS)

    Chronis, Themis G.; Goodman, Steven J.; Cecil, Dan; Buechler, Dennis; Pittman, Jasna; Robertson, Franklin R.; Blakeslee, Richard J.

    2007-01-01

    The recently reprocessed (1997-2006) OTD/LIS database is used to investigate the global lightning climatology in response to the ENSO cycle. A linear correlation map between lightning anomalies and ENSO (NINO3.4) identifies areas that generally follow patterns similar to precipitation anomalies. We also observed areas where significant lightning/ENSO correlations are found and are not accompanied of significant precipitation/ENSO correlations. An extreme case of the strong decoupling between lightning and precipitation is observed over the Indonesian peninsula (Sumatra) where positive lightning/NINO3.4 correlations are collocated with negative precipitation/NINO3.4 correlations. Evidence of linear relationships between the spatial extent of thunderstorm distribution and the respective NINO3.4 magnitude are presented for different regions on the Earth. Strong coupling is found over areas remote to the main ENSO axis of influence and both during warm and cold ENSO phases. Most of the resulted relationships agree with the tendencies of precipitation related to ENSO empirical maps or documented teleconnection patterns. Over the Australian continent, opposite behavior in terms of thunderstorm activity is noted for warm ENSO phases with NINO3.4 magnitudes with NINO3.4>+l.08 and 0warm/cold (El Nino/La Nina) ENSO episodes of the past decade. The observed patterns show no spatial overlapping and identify areas that in their majority are in agreement with empirical precipitation/ENSO maps. The areas that appear during the warm ENSO phase are found over regions that have been identified as anomalous Hadley circulation ENSO-related patterns. The areas that appear during the cold ENSO phase are found predominantly around the west hemisphere equatorial belt and are in their majority identified by anomalous Walker circulation.

  20. Recent climate extremes associated with the West Pacific Warming Mode

    USGS Publications Warehouse

    Funk, Chris; Hoell, Andrew

    2017-01-01

    Here we analyze empirical orthogonal functions (EOFs) of observations and a 30 member ensemble of Community Earth System Model version 1 (CESM1) simulations, and suggest that precipitation declines in the Greater Horn of Africa (GHA) and the northern Middle East/Southwestern Asia (NME/SWE: Iran, Iraq, Kuwait, Syria, Saudi Arabia north of 25°N, Israel, Jordan, and Lebanon) may be interpreted as an interaction between La Niña-like decadal variability and the West Pacific Warming Mode (WPWM). While they exhibit different SST patterns, warming of the Pacific cold tongue (ENSO) and warming of the western Pacific (WPWM) produce similar warm pool diabatic forcing, Walker circulation anomalies, and terrestrial teleconnections. CESM1 SST EOFs indicate that both La Niña-like WPWM warming and El Niño-like east Pacific warming will be produced by climate change. The temporal frequency of these changes, however, are distinct. WPWM varies decadally, while ENSO is dominated by interannual variability. Future WPWM and ENSO warming may manifest as a tendency toward warm West Pacific SST, punctuated by extreme warm East Pacific events. WPWM EOFs from Global Precipitation Climatology Project (GPCP) precipitation also identify dramatic WPWM-related declines in the Greater Horn of Africa and NME/SWE.

  1. Holocene ITCZ and ENSO-driven climate variability from the Panama isthmus

    NASA Astrophysics Data System (ADS)

    Urrego, D. H.; Aronson, R. B.; Bush, M. B.

    2009-12-01

    Holocene climate has previously been considered relatively stable compared to Pleistocene fluctuations. Recent paleoclimatic reconstructions have shown, however, that Holocene climatic variability is large and that the key to understanding and predicting responses to current climate change could lie in Holocene climatic history. In tropical regions, one of the most important oceanic-atmospheric systems regulating present and past interannual climatic fluctuations is the InterTropical Convergence Zone (ITCZ). Several hypotheses have been postulated to explain Holocene climate oscillations and their impacts in Northern South America. One of these hypotheses is that reduced precipitation during the mid-Holocene in the Caribbean and off the coast of Venezuela resulted from a southward migration of the ITCZ’s mean annual position (1, 2). In turn, this southward movement was associated with changes in the location of warm pools and insolation maxima regions in the tropical Atlantic. However, oscillations in Pacific warm pools should be expected to influence the annual ITCZ cycle as well. The latitudinal positions of these warm pools in the Pacific are directly influenced by ENSO (El Niño Southern Oscillation), and are predicted to move south during El Niño (warm-ENSO) years. A mid-Holocene increase in the frequency of warm ENSO events is reported in the eastern Pacific after 6 ka (3, 4), and although this change occurred more than a thousand years earlier than the southward migrations of the ITCZ reconstructed from tropical Atlantic systems, we hypothesize that there must be a link between these two apparently separate events. Reconciling the roles of Atlantic versus Pacific ocean-atmosphere interactions, and the effect of Pacific phenomena like ENSO on the annual position of the ITCZ are therefore crucial to understand climatic variability in tropical America. Lago La Yeguada is located in the Isthmus of Panama and its climate is determined mainly by the ITCZ, ENSO

  2. ENSO-driven nutrient variability recorded by central equatorial Pacific corals

    NASA Astrophysics Data System (ADS)

    LaVigne, M.; Nurhati, I. S.; Cobb, K. M.; McGregor, H. V.; Sinclair, D. J.; Sherrell, R. M.

    2012-12-01

    Recent evidence for shifts in global ocean primary productivity suggests that surface ocean nutrient availability is a key link between global climate and ocean carbon cycling. Time-series records from satellite, in situ buoy sensors, and bottle sampling have documented the impact of the El Niño Southern Oscillation (ENSO) on equatorial Pacific hydrography and broad changes in biogeochemistry since the late 1990's, however, data are sparse prior to this. Here we use a new paleoceanographic nutrient proxy, coral P/Ca, to explore the impact of ENSO on nutrient availability in the central equatorial Pacific at higher-resolution than available from in situ nutrient data. Corals from Christmas (157°W 2°N) and Fanning (159°W 4°N) Islands recorded a well-documented decrease in equatorial upwelling as a ~40% decrease in P/Ca during the 1997-98 ENSO cycle, validating the application of this proxy to Pacific Porites corals. We compare the biogeochemical shifts observed through the 1997-98 event with two pre-TOGA-TAO ENSO cycles (1982-83 and 1986-87) reconstructed from a longer Christmas Island core. All three corals revealed ~30-40% P/Ca depletions during ENSO warming as a result of decreased regional wind stress, thermocline depth, and equatorial upwelling velocity. However, at the termination of each El Niño event, surface nutrients did not return to pre-ENSO levels for ~4-12 months after, SST as a result of increased biological draw down of surface nutrients. These records demonstrate the utility of high-resolution coral nutrient archives for understanding the impact of tropical Pacific climate on the nutrient and carbon cycling of this key region.

  3. Spatiotemporal Variance of Global Horizontal Moisture Transport and the Influence of Strong ENSO Events Using ERA-Interim Reanalysis

    NASA Astrophysics Data System (ADS)

    Kutta, E. J.; Hubbart, J. A.; Svoma, B. M.; Eichler, T. P.; Lupo, A. R.

    2016-12-01

    El Nino-Southern Oscillation (ENSO) is well documented as a leading source of seasonal to inter-annual variations in global weather and climate. Strong ENSO events have been shown to alter the location and magnitude of Hadley and Walker circulations that maintain equilibrium at tropical latitudes and regulate moisture transport into mid-latitude storm tracks. Broad impacts associated with ENSO events include anomalous regional precipitation (ARP) and temperature patterns and subsequent impacts to socioeconomic and human health systems. Potential socioeconomic and human health impacts range from regional changes in water resources and agricultural productivity to local storm water management, particularly in rapidly urbanizing watersheds. Evidence is mounting to suggest that anthropogenic climate change will increase the frequency of heavy precipitation events, which compounds impacts of ARP patterns associated with strong El Nino events. Therefore, the need exists to identify common regional patterns of spatiotemporal variance of horizontal moisture flux (HMF) during months (Oct-Feb) associated with the peak intensity (Oceanic Nino Index [ONI]) of the three strongest El Nino (ONI > µ + 2σ) and La Nina (ONI < µ - σ) events occurring between January 1979 and June 2016. ERA-Interim reanalysis output on model levels was used to quantify spatial and temporal covariance of HMF at 6-hourly resolution before taking the density weighted vertical average. Long term means (LTM; 1979-2015) were quantified and the influence of strong ENSO events was assessed by quantifying deviations from the LTM for each respective covariance property during months associated with the selected ENSO events. Results reveal regions of statistically significant (CI = 0.05) differences from the LTM for the vertically integrated HMF and each covariance quantity. Broader implications of this work include potential for improved seasonal precipitation forecasts at regional scales and subsequent

  4. Future Projections of ENSO and Drought (Invited)

    NASA Astrophysics Data System (ADS)

    Cane, M. A.

    2009-12-01

    Jule Charney, who was my advisor, worked very broadly - and profoundly - on climate dynamics. In this discussion of the present state of knowledge I will focus on two aspects of climate that I view as legacies of his work: our ability to project climate variability in the tropics and to project drought. (I have in mind his work with Shukla on predictability of monsoons, and Charney 1975, Dynamics of deserts and drought in the Sahel., Q. J. Roy. Meteor. Soc., 101, 193-202). First, I will consider the projections of ENSO (El Niño and Southern Oscillation) in a warming world. (My own interest in ENSO was piqued in discussions with Charney and others during the ENSO-influenced blocking events in the late 1970s; in good measure, the approach I took to understanding and modeling ENSO was based in my thesis work.) Current IPCC models differ markedly in their projections of the mean state of the equatorial Pacific, some favoring a more “El Niño- like”, some the opposite. Possible reasons for these disagreements will be considered in the light of our understanding of ENSO and tropical climate more generally. Observational data for the past century and a half will figure prominently. Droughts in the US Southwest have a strong ENSO signal, but IPCC models are fairly consistent in projecting enhanced drought there. The reasons for this will be discussed. Models are less consistent in their predictions of the future Sahel. I will discuss what is understood about causes of drought in the Sahel, which appear to point toward sea surface temperature as the controlling influence, in contrast to Charney’s albedo hypothesis.

  5. Accelerated increase in the Arctic tropospheric warming events surpassing stratospheric warming events during winter

    NASA Astrophysics Data System (ADS)

    Wang, S.-Y. Simon; Lin, Yen-Heng; Lee, Ming-Ying; Yoon, Jin-Ho; Meyer, Jonathan D. D.; Rasch, Philip J.

    2017-04-01

    In January 2016, a robust reversal of the Arctic Oscillation took place associated with a rapid tropospheric warming in the Arctic region; this was followed by the occurrence of a classic sudden stratospheric warming in March. The succession of these two distinct Arctic warming events provides a stimulating opportunity to examine their characteristics in terms of similarities and differences. Historical cases of these two types of Arctic warming were identified and validated based upon tropical linkages with the Madden-Julian Oscillation and El Niño as documented in previous studies. The analysis indicates a recent and seemingly accelerated increase in the tropospheric warming type versus a flat trend in stratospheric warming type. The shorter duration and more rapid transition of tropospheric warming events may connect to the documented increase in midlatitude weather extremes, more so than the route of stratospheric warming type. Forced simulations with an atmospheric general circulation model suggest that the reduced Arctic sea ice contributes to the observed increase in the tropospheric warming events and associated remarkable strengthening of the cold Siberian high manifest in 2016.

  6. Tropical warming and the dynamics of endangered primates.

    PubMed

    Wiederholt, Ruscena; Post, Eric

    2010-04-23

    Many primate species are severely threatened, but little is known about the effects of global warming and the associated intensification of El Niño events on primate populations. Here, we document the influences of the El Niño southern oscillation (ENSO) and hemispheric climatic variability on the population dynamics of four genera of ateline (neotropical, large-bodied) primates. All ateline genera experienced either an immediate or a lagged negative effect of El Niño events. ENSO events were also found to influence primate resource levels through neotropical arboreal phenology. Furthermore, frugivorous primates showed a high degree of interspecific population synchrony over large scales across Central and South America attributable to the recent trends in large-scale climate. These results highlight the role of large-scale climatic variation and trends in ateline primate population dynamics, and emphasize that global warming could pose additional threats to the persistence of multiple species of endangered primates.

  7. Interactions between marine biota and ENSO: a conceptual model analysis

    NASA Astrophysics Data System (ADS)

    Heinemann, M.; Timmermann, A.; Feudel, U.

    2011-01-01

    We develop a conceptual coupled atmosphere-ocean-ecosystem model for the tropical Pacific to investigate the interaction between marine biota and the El Niño-Southern Oscillation (ENSO). Ocean and atmosphere are represented by a two-box model for the equatorial Pacific cold tongue and the warm pool, including a simplified mixed layer scheme. Marine biota are represented by a three-component (nutrient, phytoplankton, and zooplankton) ecosystem model. The atmosphere-ocean model exhibits an oscillatory state which qualitatively captures the main physics of ENSO. During an ENSO cycle, the variation of nutrient upwelling, and, to a small extent, the variation of photosynthetically available radiation force an ecosystem oscillation. The simplified ecosystem in turn, due to the effect of phytoplankton on the absorption of shortwave radiation in the water column, leads to (1) a warming of the tropical Pacific, (2) a reduction of the ENSO amplitude, and (3) a prolongation of the ENSO period. We qualitatively investigate these bio-physical coupling mechanisms using continuation methods. It is demonstrated that bio-physical coupling may play a considerable role in modulating ENSO variability.

  8. Accelerated Increase in the Arctic Tropospheric Warming Events Surpassing StratosphericWarming Events During Winter

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Simon; Lin, Yen-Heng; Lee, Ming-Ying

    2017-04-22

    In January 2016, a robust reversal of the Arctic Oscillation (AO) took place associated with a rapid tropospheric warming in the Arctic region; this was followed by the occurrence of a classic sudden stratospheric warming in March-April. The succession of these two distinct Arctic warming events provides a stimulating opportunity to examine their characteristics in terms of similarities and differences. Historical cases of these two types of Arctic warming were identified and validated based upon tropical linkages with the Madden-Julian Oscillation and El Niño as well as those documented in previous studies. Our results indicate a recent and accelerated increasemore » in the tropospheric warming type versus a flat trend in stratospheric warming type. Given that tropospheric warming events occur twice as fast than the stratospheric warming type, the noted increase in the former implies further intensification in midlatitude winter weather extremes similar to those experienced in early 2016. Forced simulations with an atmospheric general circulation model suggest that the reduced Arctic sea ice contributes to the observed increase in the tropospheric warming events and associated impact on the anomalously cold Siberia.« less

  9. Different impacts of mega-ENSO and conventional ENSO on the Indian summer rainfall: developing phase

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Wu, Zhiwei; Zhou, Yefan

    2016-04-01

    Mega-El Niño-Southern Oscillation (ENSO), a boarder version of conventional ENSO, is found to be a main driving force of Northern Hemisphere summer monsoon rainfall including the Indian summer rainfall (ISR). The simultaneous impacts of "pure" mega-ENSO and "pure" conventional ENSO events on the ISR in its developing summer remains unclear. This study examines the different linkages between mega-ENSO-ISR and conventional ENSO-ISR. During the developing summer of mega-El Niño, negative rainfall anomalies are seen over the northeastern Indian subcontinent, while the anomalous rainfall pattern is almost the opposite for mega-La Niña; as for the conventional ENSO, the approximate "linear opposite" phenomenon vanishes. Furthermore, the global zonal wave trains anomalous are found at mid-latitude zones, with a local triple circulation pattern over the central-east Eurasia during mega-ENSO events, which might be an explanation of corresponding rainfall response over the Indian Peninsula. Among 106-year historical run (1900-2005) of 9 state-of-the-art models from the Coupled Model Inter-comparison Project Phase 5 (CMIP5), HadGEM2-ES performs a promising skill in simulating the anomalous circulation pattern over mid-latitude and central-east Eurasia while CanESM2 cannot. Probably, it is the models' ability of capturing the mega-ENSO-ISR linkage and the characteristic of mega-ENSO that make the difference.

  10. Accelerated increase in the Arctic tropospheric warming events surpassing stratospheric warming events during winter: Accelerated Increase in Arctic Warming

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, S. -Y. Simon; Lin, Yen-Heng; Lee, Ming-Ying

    In January 2016, a robust reversal of the Arctic Oscillation (AO) took place associated with a rapid tropospheric warming in the Arctic region; this was followed by the occurrence of a classic sudden stratospheric warming in March-April. The succession of these two distinct Arctic warming events provides a stimulating opportunity to examine their characteristics in terms of similarities and differences. Historical cases of these two types of Arctic warming were identified and validated based upon tropical linkages with the Madden-Julian Oscillation and El Niño as well as those documented in previous studies. Our results indicate a recent and accelerated increasemore » in the tropospheric warming type versus a flat trend in stratospheric warming type. Given that tropospheric warming events occur twice as fast than the stratospheric warming type, the noted increase in the former implies further intensification in midlatitude winter weather extremes similar to those experienced in early 2016. Forced simulations with an atmospheric general circulation model suggest that the reduced Arctic sea ice contributes to the observed increase in the tropospheric warming events and associated impact on the anomalously cold Siberia.« less

  11. ENSO and its modulations on annual and multidecadal timescales revealed by Nonlinear Laplacian Spectral Analysis

    NASA Astrophysics Data System (ADS)

    Giannakis, D.; Slawinska, J. M.

    2016-12-01

    The variability of the Indo-Pacific Ocean on interannual to multidecadal timescales is investigated in a millennial control run of CCSM4 and in observations using a recently introduced technique called Nonlinear Laplacian Spectral Analysis (NLSA). Through this technique, drawbacks associated with ad hoc pre-filtering of the input data are avoided, enabling recovery of low-frequency and intermittent modes not accessible previously via classical approaches. Here, a multiscale hierarchy of modes is identified for Indo-Pacific SST and numerous linkages between these patterns are revealed. On interannual timescales, a mode with spatiotemporal pattern corresponding to the fundamental component of ENSO emerges, along with modulations of the annual cycle by ENSO in agreement with ENSO combination mode theory. In spatiotemporal reconstructions, these patterns capture the seasonal southward migration of SST and zonal wind anomalies associated with termination of El Niño and La Niña events. Notably, this family of modes explains a significant portion of SST variance in Eastern Indian Ocean regions employed in the definition of Indian Ocean dipole (IOD) indices, suggesting that it should be useful for understanding the linkage of these indices with ENSO and the interaction of the Indian and Pacific Oceans. In model data, we find that the ENSO and ENSO combination modes are modulated on multidecadal timescales by a mode predominantly active in the western tropical Pacific - we call this mode West Pacific Multidecadal Oscillation (WPMO). Despite the relatively low variance explained by this mode, its dynamical role appears to be significant as it has clear sign-dependent modulating relationships with the interannual modes carrying most of the variance. In particular, cold WPMO events are associated with anomalous Central Pacific westerlies favoring stronger ENSO events, while warm WPMO events suppress ENSO activity. Moreover, the WPMO has significant climatic impacts as

  12. Calibrating a Method for Reconstructing ENSO Variance in the Eastern Tropical Pacific Using Mg/Ca in Individual Planktic Foraminifera

    NASA Astrophysics Data System (ADS)

    Rongstad, B.; Marchitto, T. M., Jr.; Koutavas, A.; Mekik, F.

    2017-12-01

    El Niño Southern Oscillation (ENSO) is Earth's dominant mode of interannual climate variability, and is responsible for widespread climatic, ecological and societal impacts, such as reduced upwelling and fishery collapse in the eastern equatorial Pacific during El Niño events. While corals offer high resolution records of paleo-ENSO, continuous and gap-free records for the tropical Pacific are rare. Individual foraminifera analyses provide an opportunity to create continuous down-core records of ENSO through the construction and comparison of species-specific sea surface temperature (SST) distributions at different time periods; however, there has been little focus on calibrating this technique to modern ENSO conditions. Here, we present data from a core-top calibration of individual Mg/Ca measurements in planktic foraminifera in the eastern tropical Pacific, using surface dweller G. ruber and thermocline dweller N. dutertrei. We convert the individual Mg/Ca measurements to inferred temperature distributions for each species, and then compare the distributions to modern day temperature characteristics including vertical structure, annual mean, seasonality, and interannual variability. ENSO variance is theoretically inferred from the tails of the distributions: El Niño events affect the warm tail and La Niña events affect the cool tail. Finally, we discuss the utility of individual measurements of Mg/Ca in planktic foraminifera to reconstruct ENSO in down-core sections.

  13. Modulation of the SSTA decadal variation on ENSO events and relationships of SSTA With LOD,SOI, etc

    NASA Astrophysics Data System (ADS)

    Liao, D. C.; Zhou, Y. H.; Liao, X. H.

    2007-01-01

    Interannual and decadal components of the length of day (LOD), Southern Oscillation Index (SOI) and Sea Surface Temperature anomaly (SSTA) in Nino regions are extracted by band-pass filtering, and used for research of the modulation of the SSTA on the ENSO events. Results show that besides the interannual components, the decadal components in SSTA have strong impacts on monitoring and representing of the ENSO events. When the ENSO events are strong, the modulation of the decadal components of the SSTA tends to prolong the life-time of the events and enlarge the extreme anomalies of the SST, while the ENSO events, which are so weak that they can not be detected by the interannual components of the SSTA, can also be detected with the help of the modulation of the SSTA decadal components. The study further draws attention to the relationships of the SSTA interannual and decadal components with those of LOD, SOI, both of the sea level pressure anomalies (SLPA) and the trade wind anomalies (TWA) in tropic Pacific, and also with those of the axial components of the atmospheric angular momentum (AAM) and oceanic angular momentum (OAM). Results of the squared coherence and coherent phases among them reveal close connections with the SSTA and almost all of the parameters mentioned above on the interannual time scales, while on the decadal time scale significant connections are among the SSTA and SOI, SLPA, TWA, ?3w and ?3w+v as well, and slight weaker connections between the SSTA and LOD, ?3pib and ?3bp

  14. Influence of ENSO events on the freshwater discharge pattern at Patos Lagoon, Rio Grande do Sul, Brazil

    NASA Astrophysics Data System (ADS)

    Barros, G. P.; Marques, W. C.

    2013-05-01

    The aim of this study is to investigate the influence and importance of ENSO events on the control of the freshwater discharge pattern at Patos Lagoon, in timescales longer than one year. For this study it was used freshwater discharge, water levels and South Oscillation Index (SOI) data sets. The Southern Oscillation Index, or SOI, gives an indication of the development and intensity of El Niño or La Niña events in the Pacific Ocean. Sustained negative values of the SOI greater than -8 often indicate El Niño episodes. Sustained positive values of the SOI greater than +8 are typical of a La Niña episode. Cross wavelet technique is applied to examine the coherence and phase between interannual time-series (South Oscillation Index, freshwater discharge and water levels). Over synoptic time scales, wind action is the most effective forcing in Patos Lagoon's circulation. However, at longer time scales (over one year), freshwater discharge becomes the most important forcing, controling the water levels, circulation and other processes. At longer time scales, South America is affected by ENSO's influence. El Niño is the South Oscillation phase where the trade winds are weak, the pressure is low over the eastern Tropical Pacific and high on the west side. The south region of Brazil shows precipitation anomalies associated with the ENSO occurrence. The most significant ENSO events show a high temporal variability, which may occur in near biannual scales (1.5 - 3 years) or in lower frequencies (3 years - 7 years). The freshwater discharge of the main tributaries and water levels in Patos Lagoon are influenced by ENSO on interannual scales (cycles between 3.8 and 6 years). Therefore, El Niño events are associated with high mean values of freshwater discharge and water levels above the mean. On the other hand, La Niña events are associated with low mean values of freshwater discharge and water levels below the mean. These results are consistent with analysis related to

  15. Tropical Intraseasonal Air-Sea Exchanges during the 1997 Pacific Warming

    NASA Technical Reports Server (NTRS)

    Sui, C.-H.; Lau, K.-M.; Chou, S.-H.; Wang, Zihou

    1999-01-01

    The Madden Julian Oscillations (MJO) and associated westerly wind (WW) events account for much of the tropical intraseasonal variability (TISV). The TISV has been suggested as an important stochastic forcing that may be one of the underlying causes for the observed irregularities of the El Nino-Southern Oscillation (ENSO). Recent observational studies and theories of interannual to interdecadal-scale variability suggest that ENSO may arise from different mechanisms depending on the basic states. The Pacific warming event of 1997, being associated with a period of strong MJO and WW events, serves as a natural experiment for studying the possible role of TISV in triggering an ENSO event. We have performed a combined statistical and composite analysis of surface WW events based on the assimilated surface wind and sea level pressure for the period of 1980-1993, the SSM/I wind for the period of 1988-1997, and OLR. Results indicates that extratropical forcing contribute significantly to the evolution of MJO and establishment of WW events over the Pacific warm pool. Following the major WW events, there appeared an eastward extension of equatorial warm SST anomalies from the western Pacific warm pool. Such tropical-extratropical interaction is particularly clear in the winter of 96-97 that leads to the recent warming event in 1997/98. From the above discussion, our current study on this subject is based on the hypothesis that 1) there is an enhanced air-sea interaction associated with TISV and the northerly surges from the extratropics in the initial phase of the 97/98 warming event, and 2) the relevant mechanisms are functions of the basic state of the coupled system (in terms of SST distribution and atmospheric mean circulation) that varies at the interannual and interdecadal time scale. We are analyzing the space-time structure of the northerly surges, their association with air-sea fluxes and upper ocean responses during the period of September 1996 to June 1997. The

  16. The increasing control of the Atlantic Ocean on ENSO after the early 1990s

    NASA Astrophysics Data System (ADS)

    Yu, J. Y.; Paek, H.; Wang, L.; Lyu, K.

    2016-12-01

    The El Niño-Southern Oscillation (ENSO) is the most powerful interannual variability in Earth's climate system. Previous studies have emphasized processes within the tropical Pacific or Indian Oceans for the generation of ENSO. Recent studies have increasingly suggested that the Atlantic Ocean may play an active role in forcing ENSO variability. In this talk, we will present evidence from observational analyses and modeling experiments to show that the Atlantic Ocean became more capable of influencing ENSO properties after the Atlantic Multidecadal Oscillation (AMO) changed to its positive phase in the early-1990s. A wave source mechanism is proposed to explain how the positive phase of the AMO can intensify the North Pacific Subtropical High (NPSH) to change the ENSO from the Eastern Pacific (EP) type to the Central Pacific (CP) type. A sequence of processes are identified to suggest that the AMO can displace the Pacific Walker circulation, induce a wave source in the tropical central Pacific, and excite a barotropic wave train toward higher-latitudes to enhance the NPSH, which then triggers subtropical Pacific atmospheric forcing and atmosphere-ocean coupling to increase the occurrence of the CP ENSO. An Atlantic capacitor mechanism is also proposed to explain how the positive phase of the AMO can intensify the quasi-biennial (QB) component of ENSO resulting in a more frequent occurrence of ENSO events. We will show that the capacitor mechanism works only after the AMO warmed up the Atlantic sea surface temperatures after the early-1990s. The increased feedback from the Atlantic to the Pacific has enabled the Atlantic capacitor mechanism to intensify the biennial variability in the Pacific during the past two decades. Our suggestion is very different from the previous prevailing views that have emphasized the Indo-Pacific Oceans as the pacemaker for the biennial variability in ENSO. The increasing control of the Atlantic has enabled the CP ENSO dynamics to

  17. Mesoscale Convective Complexes (MCCs) over the Indonesian Maritime Continent during the ENSO events

    NASA Astrophysics Data System (ADS)

    Trismidianto; Satyawardhana, H.

    2018-05-01

    This study analyzed the mesoscale convective complexes (MCCs) over the Indonesian Maritime Continent (IMC) during the El Niño/Southern Oscillation (ENSO) events for the the15-year period from 2001 to 2015. The MCCs identified by infrared satellite imagery that obtained from the Himawari generation satellite data. This study has reported that the frequencies of the MCC occurrences at the El Niño and La Niña were higher than that of neutral conditions during DJF. Peak of MCC occurrences during DJF at La Niña and neutral condition is in February, while El Niño is in January. ENSO strongly affects the occurrence of MCC during the DJF season. The existences of the MCC were also accompanied by increased rainfall intensity at the locations of the MCC occurrences for all ENSO events. During JJA seasons, the MCC occurrences are always found during neutral conditions, El Niño and La Niña in Indian Ocean. MCC occurring during the JJA season on El Niño and neutral conditions averaged much longer than during the DJF season. In contrast, MCCs occurring in La Niña conditions during the JJA season are more rapidly extinct than during the DJF. It indicates that the influence of MCC during La Niña during the DJF season is stronger than during the JJA season.

  18. Impacts of ENSO events on cloud radiative effects in preindustrial conditions: Changes in cloud fraction and their dependence on interactive aerosol emissions and concentrations: IMPACT OF ENSO ON CLOUD RADIATIVE EFFECT

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yang, Yang; Russell, Lynn M.; Xu, Li

    The impacts of the El Niño–Southern Oscillation (ENSO) events on shortwave and longwave cloud radiative effects (CRESW and CRELW) and the underlying changes in cloud fraction as well as aerosol emissions, wet scavenging and transport are quantified using three 150-year simulations in preindustrial conditions by the CESM model. Compared to recent observations from Clouds and the Earth’s Radiant Energy System (CERES), the model simulation successfully reproduced larger variations of CRESW over the tropical western and central Pacific, Indonesian regions, and the eastern Pacific Ocean, as well as large variations of CRELW located mainly within the tropics. The ENSO cycle ismore » found to dominate interannual variations of cloud radiative effects, especially over the tropics. Relative to those during La Niña events, simulated cooling (warming) effects from CRESW (CRELW) during El Niño events are stronger over the tropical western and central Pacific Ocean, with the largest difference exceeding 40 Wm–2 (30 Wm–2), with weaker effects of 10–30 Wm–2 over Indonesian regions and the subtropical Pacific Ocean. Sensitivity tests show that variations of cloud radiative effects are mainly driven by ENSO-related changes in cloud fraction. The variations in medium and high cloud fractions each account for about 20–50% of the interannual variations of CRESW over the tropics and almost all of the variations of CRELW between 60°S and 60°N. The variation of low cloud fraction contributes most interannual variations of CRESW over the mid-latitude oceans. Variations in natural aerosol concentrations considering emissions, wet scavenging and transport explained 10–30% of the interannual variations of both CRESW and CRELW over the tropical Pacific, Indonesian regions and the tropical Indian Ocean. Changes in wet scavenging of natural aerosol modulate the variations of cloud radiative effects. Because of increased (decreased) precipitation over the tropical western

  19. Response of the Antarctic Stratosphere to Two Types of El Nino Events

    NASA Technical Reports Server (NTRS)

    Hurwitz, M. M.; Newman, P. A.; Oman, L. D.; Molod, A. M.

    2010-01-01

    This study is the first to identify a robust El Nino/Southern Oscillation (ENSO) signal in the Antarctic stratosphere. El Nino events are classified as either conventional "cold tongue" events (positive SST anomalies in the Nino 3 region) or "warm pool" events (positive SST anomalies in the Nino 4 region). The ERA-40, NCEP and MERRA meteorological reanalyses are used to show that the Southern Hemisphere stratosphere responds differently to these two types of El Nino events. Consistent with previous studies, "cold tongue" events do not impact temperatures in the Antarctic stratosphere. During "warm pool" El Nino events, the poleward extension and increased strength of the South Pacific Convergence Zone (SPCZ) favor an enhancement of planetary wave activity during the SON season. On average, these conditions lead to higher polar stratospheric temperatures and a weakening of the Antarctic polar jet in November and December, as compared with neutral ENSO years. The phase of the quasi-biennial oscillation (QBO) modulates the stratospheric response to "warm pool" El Nino events: the strongest planetary wave driving events are coincident with the easterly phase of the QBO.

  20. Potential role of salinity in ENSO and MJO predictions

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Kumar, A.; Murtugudde, R. G.; Xie, P.

    2017-12-01

    Studies have suggested that ocean salinity can vary in response to ENSO and MJO. For example, during an El Niño event, sea surface salinity decreases in the western and central equatorial Pacific, as a result of zonal advection of low salinity water by anomalous eastward surface currents, and to a lesser extent as a result of a rainfall excess associated with atmospheric convection and warm water displacements. However, the effect of salinity on ENSO and MJO evolutions and their forecasts has been less explored. In this analysis, we explored the potential role of salinity in ENSO and MJO predictions by conducting sensitivity experiments with NCEP CFSv2. Firstly, two forecasts experiments are conducted to explore its effect on ENSO predictions, in which the interannual variability of salinity in the ocean initial states is either included or excluded. Comparisons suggested that the salinity variability is essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate sustained salinity observations having large-scale spatial coverage. We also assessed the potential role of salinity in MJO by evaluating a long coupled free run that has a relatively realistic MJO simulation and a set of predictability experiment, both based on CFSv2. Diagnostics of the free run suggest that, while the intraseasonal SST variations lead convections by a quarter cycle, they are almost in phase only with changes in barrier layer thickness, thereby suggesting an active role of salinity on SST. Its effect on MJO predictions is further explored by controlling the surface salinity

  1. Characterization of extreme flood and drought events in Singapore and investigation of their relationships with ENSO

    NASA Astrophysics Data System (ADS)

    Li, Xin; Babovic, Vladan

    2016-04-01

    Flood and drought are hydrologic extreme events that have significant impact on human and natural systems. Characterization of flood and drought in terms of their start, duration and strength, and investigation of the impact of natural climate variability (i.e., ENSO) and anthropogenic climate change on them can help decision makers to facilitate adaptions to mitigate potential enormous economic costs. To date, numerous studies in this area have been conducted, however, they are primarily focused on extra-tropical regions. Therefore, this study presented a detailed framework to characterize flood and drought events in a tropical urban city-state (i.e., Singapore), based on daily data from 26 precipitation stations. Flood and drought events are extracted from standardized precipitation anomalies from monthly to seasonal time scales. Frequency, duration and magnitude of flood and drought at all the stations are analyzed based on crossing theory. In addition, spatial variation of flood and drought characteristics in Singapore is investigated using ordinary kriging method. Lastly, the impact of ENSO condition on flood and drought characteristics is analyzed using regional regression method. The results show that Singapore can be prone to extreme flood and drought events at both monthly and seasonal time scales. ENSO has significant influence on flood and drought characteristics in Singapore, but mainly during the South West Monsoon season. During the El Niño phase, drought can become more extreme. The results have implications for water management practices in Singapore.

  2. Decadal modulation of the ENSO-East Asian winter monsoon relationship by the Atlantic Multidecadal Oscillation

    NASA Astrophysics Data System (ADS)

    Geng, Xin; Zhang, Wenjun; Stuecker, Malte F.; Liu, Peng; Jin, Fei-Fei; Tan, Guirong

    2017-10-01

    This work investigates the decadal modulation of the El Niño-Southern Oscillation (ENSO)-East Asian winter monsoon (EAWM) relationship by the Atlantic Multidecadal Oscillation (AMO). A stable ENSO-EAWM relationship is found during the positive AMO phase but not during the negative phase. While the impact of El Niño events on the EAWM does not depend on the AMO phase, a different picture is observed for La Niña events. The La Niña boreal winter season coincides with a strengthened EAWM during a positive AMO phase and a weakened EAWM during a negative AMO phase. We suggest that the AMO's modulating effect mainly comprises two pathways that influence ENSO's impact on the EAWM. On one hand, when La Niña coincides with a positive AMO, the warm SST anomalies over the western North Pacific (WNP) are amplified both in intensity and spatial extent, which favors strengthened WNP cyclonic anomalies and an enhanced EAWM. During La Niña with a negative AMO, only very weak SST anomalies occur over the WNP with reduced WNP cyclonic anomalies that are confined to the tropics, thus having little effect on the EAWM. On the other hand, an eastward-propagating Rossby wavetrain across the mid-high latitudes of Eurasia during a warm AMO phase strengthens the Siberian high and thus leads to a strengthened EAWM, while during a cold AMO phase the Siberian high is weakened, leading to a reduced EAWM. In contrast, El Niño and its associated atmospheric responses are relatively strong and stable, independent of the AMO phase. These results carry important implications to the seasonal-to-interannual predictability associated with ENSO.

  3. The role of Indonesian convection in the interaction between the Indian Ocean and ENSO

    NASA Astrophysics Data System (ADS)

    Wieners, Claudia; Dijkstra, Henk; de Ruijter, Will

    2017-04-01

    In recent years it has been discussed whether a cool West Indian Ocean (WIO) or negative Indian Ocean Dipole (IOD) in boreal autumn favours El Niño at a lead time of 15 months (Izumo et al, 2010; Wieners et al, 2016). Observational evidence suggests that a cool WIO or negative IOD might be accompanied by easterlies over the West Pacific, though it is hard to disentangle influences of the Indian Ocean and ENSO through data analysis. Such easterlies can enhance the West Pacific Warm Water Volume, thus favouring El Niño development from the following boreal spring onward. However, the Gill response to a cool WIO (negative IOD) forcing would lead to westerly (nearly zero) winds over the WPO. We hypothesise that a cool WIO or negative IOD leads to low-level air convergence and hence enhanced convectional heating over the Maritime Continent (MC), which in turn amplifies the wind convergence such as to cause easterly winds over the West Pacific. This hypothesis is tested by adding a simplified Indian Ocean and a simple convective feedback over the MC to a Zebiak-Cane model. We confirm that for a sufficiently strong convection feedback a cool WIO or negative IOD indeed leads to easterlies over the WPO. The response IO cooling over the whole zonal width of the basin (negative Indian Ocean Basinwide warming / IOB) is still westerly, with the direct Gill response dominating over convection-induced winds. Positive (negative) IOB events typically occur a few months after El Niño (La Niña) - observed correlations are about 0.9 - and cause easterlies (westerlies) over the Pacific, facilitating the switch to the opposite ENSO phase, hence IOB variability dampens the ENSO mode and reduces its period. The IOD, on the other hand, tends to be positive (negative) a few months prior to El Niño (La Niña) and trigger westerlies (easterlies) favouring ENSO development. However, the observed correlation between IOD and ENSO is only about 0.6, i.e. the IOD is less closely liked to the

  4. Coral based-ENSO/IOD related climate variability in Indonesia: a review

    NASA Astrophysics Data System (ADS)

    Yudawati Cahyarini, Sri; Henrizan, Marfasran

    2018-02-01

    Indonesia is located in the prominent site to study climate variability as it lies between Pacific and Indian Ocean. It has consequences to the regional climate in Indonesia that its climate variability is influenced by the climate events in the Pacific oceans (e.g. ENSO) and in the Indian ocean (e.g. IOD), and monsoon as well as Indonesian Throughflow (ITF). Northwestern monsoon causes rainfall in the region of Indonesia, while reversely Southwestern monsoon causes dry season around Indonesia. The ENSO warm phase called El Nino causes several droughts in Indonesian region, reversely the La Nina causes flooding in some regions in Indonesia. However, the impact of ENSO in Indonesia is different from one place to the others. Having better understanding on the climate phenomenon and its impact to the region requires long time series climate data. Paleoclimate study which provides climate data back into hundreds to thousands even to million years overcome this requirement. Coral Sr/Ca can provide information on past sea surface temperature (SST) and paired Sr/Ca and δ18O may be used to reconstruct variations in the precipitation balance (salinity) at monthly to annual interannual resolution. Several climate studies based on coral geochemical records in Indonesia show that coral Sr/Ca and δ18O from Indonesian records SST and salinity respectively. Coral Sr/Ca from inshore Seribu islands complex shows more air temperature rather than SST. Modern coral from Timor shows the impact of ENSO and IOD to the saliniy and SST is different at Timor sea. This result should be taken into account when interpreting Paleoclimate records over Indonesia. Timor coral also shows more pronounced low frequency SST variability compared to the SST reanalysis (model). The longer data of low frequency variability will improve the understanding of warming trend in this climatically important region.

  5. Linkages between ENSO/PDO signals and precipitation, streamflow in China during the last 100 years

    NASA Astrophysics Data System (ADS)

    Ouyang, R.; Liu, W.; Fu, G.; Liu, C.; Hu, L.; Wang, H.

    2014-09-01

    This paper investigates the single and combined impacts of El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) on precipitation and streamflow in China over the last century. Results indicate that the precipitation and streamflow overall decrease during El Niño/PDO warm phase periods and increase during La Niña/PDO cool phase periods in the majority of China, although there are regional and seasonal differences. Precipitation and streamflow in the Yellow River basin, Yangtze River basin and Pearl River basin are more significantly influenced by El Niño and La Niña events than is precipitation and streamflow in the Songhua River basin, especially in October and November. Moreover, significant influence of ENSO on streamflow in the Yangtze River mainly occurs in summer and autumn while in the Pearl River influence primarily occurs in the winter and spring. The precipitation and streamflow are relatively greater in the warm PDO phase in the Songhua River basin and several parts of the Yellow River basin and relatively less in the Pearl River basin and most parts of Northwest China compared to those in the cool PDO phase, though there is little significance detected by Wilcoxon signed-rank test. When considering the combined influence of ENSO and PDO, the responses of precipitation/streamflow are shown to be opposite in northern China and southern China, with ENSO-related precipitation/streamflow enhanced in northern China and decreased in southern China during the warm PDO phases, and enhanced in southern China and decreased in northern China during the cool PDO phases. It is hoped that this study will be beneficial for understanding the precipitation/streamflow responses to the changing climate and will correspondingly provide valuable reference for water resources prediction and management across China.

  6. Numerical Study on Interdecadal Modulations of ENSO-related Spring Rainfall over South China by the Pacific Decadal Oscillation

    NASA Astrophysics Data System (ADS)

    MAO, J.; WU, X.

    2017-12-01

    The spatio-temporal variations of eastern China spring rainfall are identified via empirical orthogonal function (EOF) analysis of rain-gauge (gridded) precipitation datasets for the period 1958-2013 (1920-2013). The interannual variations of the first two leading EOF modes are linked with the El Niño-Southern Oscillation (ENSO), with this linkage being modulated by the Pacific Decadal Oscillation (PDO). The EOF1 mode, characterized by predominant rainfall anomalies from the Yangtze River to North China (YNC), is more likely associated with out-of-phase PDO-ENSO events [i.e., El Niño during cold PDO (EN_CPDO) and La Niña during warm PDO (LN_WPDO)]. The sea surface temperature anomaly (SSTA) distributions of EN_CPDO (LN_WPDO) events induce a significant anomalous anticyclone (cyclone) over the western North Pacific stretching northwards to the Korean Peninsula and southern Japan, resulting in anomalous southwesterlies (northeasterlies) prevailing over eastern China and above-normal (below-normal) rainfall over YNC. In contrast, EOF2 exhibits a dipole pattern with predominantly positive rainfall anomalies over southern China along with negative anomalies over YNC, which is more likely connected to in-phase PDO-ENSO events [i.e., El Niño during warm PDO (EN_WPDO) and La Niña during cold PDO (LN_CPDO)]. EN_WPDO (LN_CPDO) events force a southwest-northeast oriented dipole-like circulation pattern leading to significant anomalous southwesterlies (northeasterlies) and above-normal (below-normal) rainfall over southern China. Numerical experiments with the CAM5 model forced by the SSTA patterns of EN_WPDO and EN_CPDO events reproduce reasonably well the corresponding anomalous atmospheric circulation patterns and spring rainfall modes over eastern China, validating the related mechanisms.

  7. ENSO shifts and their link to Southern Africa surface air temperature in summer

    NASA Astrophysics Data System (ADS)

    Manatsa, D.; Mukwada, G.; Makaba, L.

    2018-05-01

    ENSO has been known to influence the trends of summer warming over Southern Africa. In this work, we used observational and reanalysis data to analyze the relationship between ENSO and maximum surface air temperature (SATmax) trends during the three epochs created by the ENSO phase shifts around 1977 and 1997 for the period 1960 to 2014. We observed that while ENSO and cloud cover remains the dominant factor controlling SATmax variability, the first two epochs had the predominant La Niña (El Niño)-like events connected to robust positive (negative) trends in cloud fraction. However, this established relationship reversed in the post-1997 La Niña-like dominated epoch which coincided with a falling cloud cover trend. It is established that this deviation from the previously established link within the previous epochs could be due to the post-1998 era in which SATmin was suppressed while SATmax was enhanced. The resulting increase in diurnal temperature range (DTR) could have discouraged the formation of low-level clouds which have relatively more extensive areal coverage and hence allowing more solar energy to reach the surface to boost daytime SATmax. It is noted that these relationships are more pronounced from December to March.

  8. Reconstruction of the West Pacific ENSO precipitation anomaly using the compound-specific hydrogen isotopic record of marine lake sediments of Palau

    NASA Astrophysics Data System (ADS)

    Smittenberg, R. H.; Sachs, J. P.; Dawson, M. N.

    2004-12-01

    There is still much uncertainty whether the El Niño Southern Oscillation (ENSO) will become stronger or more frequent in a warming global climate. A principal reason for this uncertainty stems from a glaring lack of paleoclimate data in the equatorial Pacific, which hampers model validation. To partly resolve this data deficiency, sediments of three marine anoxic lakes were cored in Palau, an island group that lies in the heart of the West Pacific Warm Pool. The lakes contain seawater that seeps through fissures in the surrounding karst, and they are permanently stratified due to fresh water input provided by the year-round wet climate (map 1970-2000 = 3.7m). During ENSO events, however, the islands suffer from drought. The surface water hydrogen isotopic compositions in the lakes are sensitive to the relative proportions of D-depleted rainwater and D-enriched seawater, and are therefore sensitive to ENSO events. The lake surface water H/D values are recorded by algal and bacterial biomarkers that are preserved well in the highly organic and anoxic sediments, which accumulate relatively fast (mean 1 mm/yr). Ongoing down core measurement will eventually result in a precipitation proxy record of the islands. To obtain endmember D/H values, a comprehensive set of water samples from sea, lakes and rain water was obtained, as well as suspended particulate matter. Higher plant biomarker D/H values derived from the jungle vegetation surrounding the lakes may render supporting climatic proxy data, being influenced by evapotranspiration. Some lakes are inhabited by millions of jellyfish (Mastigias) that live in symbiosis with zooxanthellae. The jellyfish of one of the investigated lakes disappeared completely after the last large ENSO event in 1998 (returning in 2000-01), and a correlation is suggested. To reconstruct the history of jellyfish occurrence, jellyfish and sedimentary lipids were extracted and compared. In addition to a possible ENSO proxy record, this

  9. Coral Cd/Ca and Mn/Ca records of ENSO variability in the Gulf of California

    NASA Astrophysics Data System (ADS)

    Carriquiry, J. D.; Villaescusa, J. A.

    2010-06-01

    We analyzed the trace element ratios Cd/Ca and Mn/Ca in three coral colonies (Porites panamensis (1967-1989), Pavona clivosa (1967-1989) and Pavona gigantea (1979-1989)) from Cabo Pulmo reef, Southern Gulf of California, Mexico, to assess the oceanographic changes caused by El Niño - Southern Oscillation (ENSO) events in the Eastern Tropical North Pacific (ETNP). Interannual variations in the coral Cd/Ca and Mn/Ca ratios showed clear evidence that incorporation of Cd and Mn in the coral skeleton was influenced by ENSO conditions, but the response for each metal was controlled by different processes. The Mn/Ca ratios were significantly higher during ENSO years (p<0.05) relative to non-ENSO years for the three species of coral. In contrast, the Cd/Ca was systematically lower during ENSO years, but the difference was significant (p<0.05) only in Pavona gigantea. A decrease in the incorporation of Cd and a marked increase in Mn indicated strongly reduced vertical mixing in the Gulf of California during the mature phase of El Niño. The oceanic warming during El Niño events produces a relaxation of upwelling and a stabilization of the thermocline, which may act as a physical barrier limiting the transport of Cd from deeper waters into the surface layer. In turn, this oceanic condition can increase the residence time of particulate-Mn in surface waters, allowing an increase in the photo-reduction of particulate-Mn and the release of available Mn into the dissolved phase. These results support the use of Mn/Ca and Cd/Ca ratios in biogenic carbonates as tracers of increases in ocean stratification and trade wind weakening and/or collapse in the ETNP during ENSO episodes.

  10. ENSO influences the onset of violent conflicts

    NASA Astrophysics Data System (ADS)

    Meng, K. C.; Hsiang, S. M.

    2009-12-01

    Climatic changes are frequently cited as a possible external driver of violent conflict in human societies. Qualitative studies suggest that climatic shifts may stress populations and be conducive to violent conflict. Statistical evidence has shown that anomalous local rainfall is correlated with the onset of conflict. This study finds that in addition to idiosyncratic weather events, climatic states also play a role in triggering violent conflict. El Niño Southern Oscillation (ENSO), the semi-periodic, oceanic Kelvin wave in the tropical Pacific, induces remote temperatures in the tropical free troposphere to rise. This ``ENSO teleconnection'' is not globally uniform and is felt most strongly in the tropical regions during the boreal winter. To determine the degree in which country-level climatic conditions are affected by ENSO, an absolute correlation measure between surface temperature and two ENSO indices was calculated for every country for the period 1949-2009. Countries with high levels of correlation are labeled “ENSO affected,” while countries with low correlation are labeled “ENSO unaffected”. Thus, historical variation in ENSO serves as a ``natural experiment'': if the state of ENSO influences conflict onset, it should be apparent for ENSO affected countries but not for unaffected countries. Using the UCDP/PRIO Armed Conflict Dataset, we find evidence of a large and statistically significant influence of ENSO on the onset of violent conflict. Between 1949-2009, the average probability of a conflict beginning in any country was 0.03. For the ENSO affected countries, we find that a 1°C rise in either NINO12 or NINO34 is associated with an increased probability of conflict onset by 0.015 (or 50% of the global country average). A relationship was not detected for the ENSO unaffected group of countries. This result is robust to a range of statistical models. Nonparametric methods (see figure) also indicate a marked difference in the response of ENSO

  11. Repetitive mammalian dwarfing during ancient greenhouse warming events

    PubMed Central

    D’Ambrosia, Abigail R.; Clyde, William C.; Fricke, Henry C.; Gingerich, Philip D.; Abels, Hemmo A.

    2017-01-01

    Abrupt perturbations of the global carbon cycle during the early Eocene are associated with rapid global warming events, which are analogous in many ways to present greenhouse warming. Mammal dwarfing has been observed, along with other changes in community structure, during the largest of these ancient global warming events, known as the Paleocene-Eocene Thermal Maximum [PETM; ~56 million years ago (Ma)]. We show that mammalian dwarfing accompanied the subsequent, smaller-magnitude warming event known as Eocene Thermal Maximum 2 [ETM2 (~53 Ma)]. Statistically significant decrease in body size during ETM2 is observed in two of four taxonomic groups analyzed in this study and is most clearly observed in early equids (horses). During ETM2, the best-sampled lineage of equids decreased in size by ~14%, as opposed to ~30% during the PETM. Thus, dwarfing appears to be a common evolutionary response of some mammals during past global warming events, and the extent of dwarfing seems related to the magnitude of the event. PMID:28345031

  12. ENSO Weather and Coral Bleaching on the Great Barrier Reef, Australia

    NASA Astrophysics Data System (ADS)

    McGowan, Hamish; Theobald, Alison

    2017-10-01

    The most devastating mass coral bleaching has occurred during El Niño events, with bleaching reported to be a direct result of increased sea surface temperatures (SSTs). However, El Niño itself does not cause SSTs to rise in all regions that experience bleaching. Nor is the upper ocean warming trend of 0.11°C per decade since 1971, attributed to global warming, sufficient alone to exceed the thermal tolerance of corals. Here we show that weather patterns during El Niño that result in reduced cloud cover, higher than average air temperatures and higher than average atmospheric pressures, play a crucial role in determining the extent and location of coral bleaching on the world's largest coral reef system, the World Heritage Great Barrier Reef (GBR), Australia. Accordingly, synoptic-scale weather patterns and local atmosphere-ocean feedbacks related to El Niño-Southern Oscillation (ENSO) and not large-scale SST warming due to El Niño alone and/or global warming are often the cause of coral bleaching on the GBR.

  13. Greening of the Sahara suppressed ENSO activity during the mid-Holocene.

    PubMed

    Pausata, Francesco S R; Zhang, Qiong; Muschitiello, Francesco; Lu, Zhengyao; Chafik, Léon; Niedermeyer, Eva M; Stager, J Curt; Cobb, Kim M; Liu, Zhengyu

    2017-07-07

    The evolution of the El Niño-Southern Oscillation (ENSO) during the Holocene remains uncertain. In particular, a host of new paleoclimate records suggest that ENSO internal variability or other external forcings may have dwarfed the fairly modest ENSO response to precessional insolation changes simulated in climate models. Here, using fully coupled ocean-atmosphere model simulations, we show that accounting for a vegetated and less dusty Sahara during the mid-Holocene relative to preindustrial climate can reduce ENSO variability by 25%, more than twice the decrease obtained using orbital forcing alone. We identify changes in tropical Atlantic mean state and variability caused by the momentous strengthening of the West Africa Monsoon (WAM) as critical factors in amplifying ENSO's response to insolation forcing through changes in the Walker circulation. Our results thus suggest that potential changes in the WAM due to anthropogenic warming may influence ENSO variability in the future as well.

  14. Assessing the effect of the relative atmospheric angular momentum (AAM) on length-of-day (LOD) variations under climate warming

    NASA Astrophysics Data System (ADS)

    Lehmann, E.; Hansen, F.; Ulbrich, U.; Nevir, P.; Leckebusch, G. C.

    2009-04-01

    While most studies on model-projected future climate warming discuss climatological quantities, this study investigates the response of the relative atmospheric angular momentum (AAM) to climate warming for the 21th century and discusses its possible effects on future length-of-day variations. Following the derivation of the dynamic relation between atmosphere and solid earth by Barnes et al. (Proc. Roy. Soc., 1985) this study relates the axial atmospheric excitation function X3 to changes in length-of-day that are proportional to variations in zonal winds. On interannual time scales changes in the relative AAM (ERA40 reanalyses) are well correlated with observed length-of-day (LOD, IERS EOP CO4) variability (r=0.75). The El Niño-Southern Oscillation (ENSO) is a prominent coupled ocean-atmosphere phenomenon to cause global climate variability on interannual time scales. Correspondingly, changes in observed LOD relate to ENSO due to observed strong wind anomalies. This study investigates the varying effect of AAM anomalies on observed LOD by relating AAM to variations to ENSO teleconnections (sea surface temperatures, SSTs) and the Pacific North America (PNA) oscillation for the 20th and 21st century. The differently strong effect of strong El Niño events (explained variance 71%-98%) on present time (1962-2000) observed LOD-AAM relation can be associated to variations in location and strength of jet streams in the upper troposphere. Correspondingly, the relation between AAM and SSTs in the NIÑO 3.4 region also varies between explained variances of 15% to 73%. Recent coupled ocean-atmosphere projections on future climate warming suggest changes in frequency and amplitude of ENSO events. Since changes in the relative AAM indicate shifts in large-scale atmospheric circulation patterns due to climate change, AAM - ENSO relations are assessed in coupled atmosphere-ocean (ECHAM5-OM1) climate warming projections (A1B) for the 21st century. A strong rise (+31%) in

  15. Suppression of ENSO in a coupled model without water vapor feedback

    NASA Astrophysics Data System (ADS)

    Hall, A.; Manabe, S.

    We examine 800-year time series of internally generated variability in both a coupled ocean-atmosphere model where water vapor anomalies are not allowed to interact with longwave radiation and one where they are. The ENSO-like phenomenon in the experiment without water vapor feedback is drastically suppressed both in amplitude and geographic extent relative to the experiment with water vapor feedback. Surprisingly, the reduced amplitude of ENSO-related sea surface temperature anomalies in the model without water vapor feedback cannot be attributed to greater longwave damping of sea surface temperature. (Differences between the two experiments in radiative feedback due to clouds counterbalance almost perfectly the differences in radiative feedback due to water vapor.) Rather, the interaction between water vapor anomalies and longwave radiation affects the ENSO-like phenomenon through its influence on the vertical structure of radiative heating: Because of the changes in water vapor associated with it, a given warm equatorial Pacific sea surface temperature anomaly is associated with a radiative heating profile that is much more gravitationally unstable when water vapor feedback is present. The warm sea surface temperature anomaly therefore results in more convection in the experiment with water vapor feedback. The increased convection, in turn, is related to a larger westerly wind-stress anomaly, which creates a larger decrease in upwelling of cold water, thereby enhancing the magnitude of the original warm sea surface temperature anomaly. In this manner, the interaction between water vapor anomalies and longwave radiation magnifies the air-sea interactions at the heart of the ENSO phenomenon; without this interaction, the coupling between sea surface temperature and wind stress is effectively reduced, resulting in smaller amplitude ENSO episodes with a more limited geographical extent.

  16. Last Millennium ENSO-Mean State Interactions in the Tropical Pacific

    NASA Astrophysics Data System (ADS)

    Wyman, D. A.; Conroy, J. L.; Karamperidou, C.

    2017-12-01

    The nature and degree of interaction between the mean state of the tropical Pacific and ENSO remains an open question. Here we use high temporal resolution, tropical Pacific sea surface temperature (SST) records from the last millennium to investigate the relationship between ENSO and the tropical Pacific zonal sea surface temperature gradient (hereafter dSST). A dSST time series was created by standardizing, interpolating, and compositing 7 SST records from the western and 3 SST records from the eastern tropical Pacific. Propagating the age uncertainty of each of these records was accomplished through a Monte Carlo Empirical Orthogonal Function analysis. We find last millennium dSST is strong from 700 to 1300 CE, begins to weaken at approximately 1300 CE, and decreases more rapidly at 1700 CE. dSST was compared to 14 different ENSO reconstructions, independent of the records used to create dSST, to assess the nature of the ENSO-mean state relationship. dSST correlations with 50-year standard deviations of ENSO reconstructions are consistently negative, suggesting that more frequent, strong El Niño events on this timescale reduces dSST. To further assess the strength and direction of the ENSO-dSST relationship, moving 100-year standard deviations of ENSO reconstructions were compared to moving 100-year averages of dSST using Cohen's Kappa statistic, which measures categorical agreement. The Li et al. (2011) and Li et al. (2013) Nino 3.4 ENSO reconstructions had the highest agreement with dSST (k=0.80 and 0.70, respectively), with greater ENSO standard deviation coincident with periods of weak dSST. Other ENSO reconstructions showed weaker agreement with dSST, which may be partly due to low sample size. The consistent directional agreement of dSST with ENSO, coupled with the inability of strong ENSO events to develop under a weak SST gradient, suggests periods of more frequent strong El Niño events reduced tropical Pacific dSST on centennial timescales over the

  17. The seasonality and geographic dependence of ENSO impacts on U.S. surface ozone variability

    NASA Astrophysics Data System (ADS)

    Xu, Li; Yu, Jin-Yi; Schnell, Jordan L.; Prather, Michael J.

    2017-04-01

    We examine the impact of El Niño-Southern Oscillation (ENSO) on surface ozone abundance observed over the continental United States (U.S.) during 1993-2013. The monthly ozone decreases (increases) during El Niño (La Niña) years with amplitude up to 1.8 ppb per standard deviation of Niño 3.4 index. The largest ENSO influences occur over two southern U.S. regions during fall when the ENSO develops and over two western U.S. regions during the winter to spring after the ENSO decays. ENSO affects surface ozone via chemical processes during warm seasons in southern regions, where favorable meteorological conditions occur, but via dynamic transport during cold seasons in western regions, where the ENSO-induced circulation variations are large. The geographic dependence and seasonality of the ENSO impacts imply that regulations regarding air quality and its exceedance need to be adjusted for different seasons and U.S. regions to account for the ENSO-driven patterns in surface ozone.

  18. The impact of the 2015-2016 El Niño-Southern Oscillation (ENSO) event on greenhouse gas exchange and surface energy budget in an Indonesian oil palm plantation

    NASA Astrophysics Data System (ADS)

    Stiegler, Christian; Meijide, Ana; June, Tania; Knohl, Alexander

    2017-04-01

    The 2015-2016 El Niño-Southern Oscillation (ENSO) event was one of the strongest observed in the last 20 years. Oil palm plantations cover a large fraction of tropical lowlands in Southeast Asia but despite their growing areal extent, measurements and observations of greenhouse gas exchange and surface energy balance are still scarce. In addition, the effects of extreme events such as ENSO on carbon sequestration and the partitioning of surface energy balance components are widely unknown. In this study, we use micrometeorological measurements located in commercial oil palm plantations in the Jambi province (Sumatra, Indonesia) to assess the impact of the 2015-2016 ENSO event and severe forest fires on greenhouse gas exchange and surface energy budget. Continuous measurements are in operation since July 2013 and we assess turbulent fluxes of carbon dioxide (CO2), water vapour and sensible heat using the eddy covariance technique before, during and after the 2015-2016 ENSO event. In the beginning of the ENSO event, the area experienced a strong drought with decreasing soil moisture, increasing air and surface temperatures, and strong atmospheric vapour pressure deficit. During the peak of the drought from August to October 2015, hundreds of forest fires in the area resulted in strong smoke production, decreasing incoming solar radiation by 35% compared to pre-ENSO values and diffuse radiation became almost the sole shortwave radiation flux. During the beginning of the drought, carbon uptake of the oil palm plantation was around 2.1 gC m-2 d-1 and initially increased by 50% due to clear-sky conditions and high incoming photosynthetically active radiation (PAR) but increasing density of smoke turned the oil palm plantation into a source of carbon. The turbulent heat fluxes experienced an increase in sensible heat fluxes due to drought conditions at the cost of latent heat fluxes resulting in an increase in the midday Bowen-ratio from 0.17 to 0.40. Strong smoke

  19. South Asian Summer Monsoon and Its Relationship with ENSO in the IPCC AR4 Simulations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Annamalai, H; Hamilton, K; Sperber, K R

    In this paper we use the extensive integrations produced for the IPCC Fourth Assessment Report (AR4) to examine the relationship between ENSO and the monsoon at interannual and decadal timescales. We begin with an analysis of the monsoon simulation in the 20th century integrations. Six of the 18 models were found to have a reasonably realistic representation of monsoon precipitation climatology. For each of these six models SST and anomalous precipitation evolution along the equatorial Pacific during El Nino events display considerable differences when compared to observations. Out of these six models only four (GFDL{_}CM{_}2.0, GFDL{_}CM{_}2.1, MRI, and MPI{_}ECHAM5) exhibitmore » a robust ENSO-monsoon contemporaneous teleconnection, including the known inverse relationship between ENSO and rainfall variations over India. Lagged correlations between the all-India rainfall (AIR) index and Nino3.4 SST reveal that three models represent the timing of the teleconnection, including the spring predictability barrier which is manifested as the transition from positive to negative correlations prior to the monsoon onset. Furthermore, only one of these three models (GFDL{_}CM{_}2.1) captures the observed phase lag with the strongest anticorrelation of SST peaking 2-3 months after the summer monsoon, which is partially attributable to the intensity of simulated El Nino itself. We find that the models that best capture the ENSO-monsoon teleconnection are those that correctly simulate the timing and location of SST and diabatic heating anomalies in the equatorial Pacific, and the associated changes to the equatorial Walker Circulation during El Nino events. The strength of the AIR-Nino3.4 SST correlation in the model runs waxes and wanes to some degree on decadal timescales. The overall magnitude and timescale for this decadal modulation in most of the models is similar to that seen in observations. However, there is little consistency in the phase among the realizations

  20. Greening of the Sahara suppressed ENSO activity during the mid-Holocene

    PubMed Central

    Pausata, Francesco S. R.; Zhang, Qiong; Muschitiello, Francesco; Lu, Zhengyao; Chafik, Léon; Niedermeyer, Eva M.; Stager, J. Curt; Cobb, Kim M.; Liu, Zhengyu

    2017-01-01

    The evolution of the El Niño-Southern Oscillation (ENSO) during the Holocene remains uncertain. In particular, a host of new paleoclimate records suggest that ENSO internal variability or other external forcings may have dwarfed the fairly modest ENSO response to precessional insolation changes simulated in climate models. Here, using fully coupled ocean-atmosphere model simulations, we show that accounting for a vegetated and less dusty Sahara during the mid-Holocene relative to preindustrial climate can reduce ENSO variability by 25%, more than twice the decrease obtained using orbital forcing alone. We identify changes in tropical Atlantic mean state and variability caused by the momentous strengthening of the West Africa Monsoon (WAM) as critical factors in amplifying ENSO’s response to insolation forcing through changes in the Walker circulation. Our results thus suggest that potential changes in the WAM due to anthropogenic warming may influence ENSO variability in the future as well. PMID:28685758

  1. Interdecadal variations of ENSO around 1999/2000

    NASA Astrophysics Data System (ADS)

    Hu, Zeng-Zhen; Kumar, Arun; Huang, Bohua; Zhu, Jieshun; Ren, Hong-Li

    2017-02-01

    This paper discusses the interdecadal changes of the climate in the tropical Pacific with a focus on the corresponding changes in the characteristics of the El Niño-Southern Oscillation (ENSO). Compared with 1979-1999, the whole tropical Pacific climate system, including both the ocean and atmosphere, shifted to a lower variability regime after 1999/2000. Meanwhile, the frequency of ENSO became less regular and was closer to a white noise process. The lead time of the equatorial Pacific's subsurface ocean heat content in preceding ENSO decreased remarkably, in addition to a reduction in the maximum correlation between them. The weakening of the correlation and the shortening of the lead time pose more challenges for ENSO prediction, and is the likely reason behind the decrease in skill with respect to ENSO prediction after 2000. Coincident with the changes in tropical Pacific climate variability, the mean states of the atmospheric and oceanic components also experienced physically coherent changes. The warm anomaly of SST in the western Pacific and cold anomaly in the eastern Pacific resulted in an increased zonal SST gradient, linked to an enhancement in surface wind stress and strengthening of the Walker circulation, as well as an increase in the slope of the thermocline. These changes were consistent with an increase (a decrease) in precipitation and an enhancement (a suppression) of the deep convection in the western (eastern) equatorial Pacific. Possible connections between the mean state and ENSO variability and frequency changes in the tropical Pacific are also discussed.

  2. The impact of the 2015-2016 El Niño-Southern Oscillation (ENSO) event on greenhouse gas exchange and surface energy budget in an Indonesian oil palm plantation

    NASA Astrophysics Data System (ADS)

    Stiegler, C.; Meijide, A.; June, T.; Knohl, A.

    2016-12-01

    Oil palm plantations cover a large fraction of tropical lowlands in Southeast Asia. However, despite their growing areal extent, measurements and observations of greenhouse gas exchange and surface energy balance are still scarce. In addition, the effects of extreme events such as El Niño-Southern Oscillation (ENSO) on carbon sequestration and the partitioning of surface energy balance components are widely unknown. In this study, we use micrometeorological measurements located in commercial oil palm plantations in the Jambi province (Sumatra, Indonesia) to assess the impact of the 2015-2016 ENSO event on greenhouse gas exchange and surface energy budget. Measurements are in operation since July 2013 and we assess continuously turbulent fluxes of carbon dioxide (CO2), water vapour and sensible heat using the eddy covariance technique before, during and after the 2015-2016 ENSO event. The full surface energy budget is completed by measurements of radiative components, ground heat fluxes, and soil thermal and hydrological properties. The study is part of a large interdisciplinary project focussing on the ecological and socioeconomic functions of lowland rainforest transformation systems (EFForTS). During the ENSO event, the area experienced a strong drought with decreasing soil moisture and increasing air and surface temperatures. During the peak in September and October 2015, hundreds of fires in the area resulted in strong smoke production decreasing incoming solar radiation and increasing the diffuse fraction. Compared to regular years, the carbon uptake of the oil palm plantation decreased during the ENSO event. The turbulent heat fluxes experienced an increase in sensible heat fluxes due to drought conditions at the cost of latent heat fluxes resulting in an increase in the Bowen-ratio. Overall, the ENSO event resulted in a major anomaly of exchange processes between the oil palm plantation and the atmosphere.

  3. Improved predictability of droughts over southern Africa using the standardized precipitation evapotranspiration index and ENSO

    NASA Astrophysics Data System (ADS)

    Manatsa, Desmond; Mushore, Terrence; Lenouo, Andre

    2017-01-01

    The provision of timely and reliable climate information on which to base management decisions remains a critical component in drought planning for southern Africa. In this observational study, we have not only proposed a forecasting scheme which caters for timeliness and reliability but improved relevance of the climate information by using a novel drought index called the standardised precipitation evapotranspiration index (SPEI), instead of the traditional precipitation only based index, the standardised precipitation index (SPI). The SPEI which includes temperature and other climatic factors in its construction has a more robust connection to ENSO than the SPI. Consequently, the developed ENSO-SPEI prediction scheme can provide quantitative information about the spatial extent and severity of predicted drought conditions in a way that reflects more closely the level of risk in the global warming context of the sub region. However, it is established that the ENSO significant regional impact is restricted only to the period December-March, implying a revisit to the traditional ENSO-based forecast scheme which essentially divides the rainfall season into the two periods, October to December and January to March. Although the prediction of ENSO events has increased with the refinement of numerical models, this work has demonstrated that the prediction of drought impacts related to ENSO is also a reality based only on observations. A large temporal lag is observed between the development of ENSO phenomena (typically in May of the previous year) and the identification of regional SPEI defined drought conditions. It has been shown that using the Southern Africa Regional Climate Outlook Forum's (SARCOF) traditional 3-month averaged Nino 3.4 SST index (June to August) as a predictor does not have an added advantage over using only the May SST index values. In this regard, the extended lead time and improved skill demonstrated in this study could immensely benefit

  4. The IOD-ENSO precursory teleconnection over the tropical Indo-Pacific Ocean: dynamics and long-term trends under global warming

    NASA Astrophysics Data System (ADS)

    Yuan, Dongliang; Hu, Xiaoyue; Xu, Peng; Zhao, Xia; Masumoto, Yukio; Han, Weiqing

    2018-01-01

    The dynamics of the teleconnection between the Indian Ocean Dipole (IOD) in the tropical Indian Ocean and El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%-15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.

  5. Fires, Floods, and Hurricanes: Is ENSO to Blame?

    ERIC Educational Resources Information Center

    Mjelde, James W.; Litzenberg, Kerry K.; Hoyle, Julie E.; Holochwost, Sharon R.; Funkhouser, Sarah

    2007-01-01

    Scientists have associated the El Nino/Southern Oscillation (ENSO) phenomenon with extreme climate events such as flooding in California, droughts in Australia, fires in Indonesia, and increased hurricane activity in the Atlantic Ocean. The popular media is constantly attributing individual storms to the ENSO phenomenon. The reality is that a…

  6. Increasing frequency and duration of Arctic winter warming events

    NASA Astrophysics Data System (ADS)

    Graham, R. M.; Cohen, L.; Petty, A.; Boisvert, L.; Rinke, A.; Hudson, S. R.; Nicolaus, M.; Granskog, M. A.

    2017-12-01

    Record low Arctic sea ice extents were observed during the last three winter seasons (March). During each of these winters, near-surface air temperatures close to 0°C were observed, in situ, over sea ice in the central Arctic. Recent media reports and scientific studies suggest that such winter warming events were unprecedented for the Arctic. Here we use in situ winter (December-March) temperature observations, such as those from Soviet North Pole drifting stations and ocean buoys, to determine how common Arctic winter warming events are. The earliest record we find of a winter warming event was in March 1896, where a temperature of -3.7˚C was observed at 84˚N during the Fram expedition. Observations of winter warming events exist over most of the Arctic Basin. Despite a limited observational network, temperatures exceeding -5°C were measured in situ during more than 30% of winters from 1954 to 2010, by either North Pole drifting stations or ocean buoys. Correlation coefficients between the atmospheric reanalysis, ERA-Interim, and these in-situ temperature records are shown to be on the order of 0.90. This suggests that ERA-Interim is a suitable tool for studying Arctic winter warming events. Using the ERA-Interim record (1979-2016), we show that the North Pole (NP) region typically experiences 10 warming events (T2m > -10°C) per winter, compared with only five in the Pacific Central Arctic (PCA). We find a positive trend in the overall duration of winter warming events for both the NP region (4.25 days/decade) and PCA (1.16 days/decade), due to an increased number of events of longer duration.

  7. ENSO Related Interannual Lightning Variability from the Full TRMM LIS Lightning Climatology

    NASA Technical Reports Server (NTRS)

    Clark, Austin; Cecil, Daniel J.

    2018-01-01

    It has been shown that the El Nino/Southern Oscillation (ENSO) contributes to inter-annual variability of lightning production in the tropics and subtropics more than any other atmospheric oscillation. This study further investigated how ENSO phase affects lightning production in the tropics and subtropics. Using the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) and the Oceanic Nino Index (ONI) for ENSO phase, lightning data were averaged into corresponding mean annual warm, cold, and neutral 'years' for analysis of the different phases. An examination of the regional sensitivities and preliminary analysis of three locations was conducted using model reanalysis data to determine the leading convective mechanisms in these areas and how they might respond to the ENSO phases. These processes were then studied for inter-annual variance and subsequent correlation to ENSO during the study period to best describe the observed lightning deviations from year to year at each location.

  8. Evaluation of the impact of ENSO on precipitation extremes in southern Brazil considering the ODP phases

    NASA Astrophysics Data System (ADS)

    Firpo, M. A.; Sansigolo, C. A.

    2011-12-01

    extreme events in El Niño (La Niña) conditions. The impact of El Niño in the increase of rainfall quantities is higher than the impact of La Niña in its reduction. Furthermore, the El Niño impacts are more persistent. For La Niña analyses, the period of DJF (summer austral) showed bigger lag on this impact; for El Niño the impact starts simultaneously in all seasons and lasted more in JJA. Considering PDO phases, in warm (cold) phase there were more El Niño (La Niña) events. When PDO is positive, the impact of El Niño is stronger over the precipitation increase than in negative phase. The same occurs with La Niña, and the decrease of precipitation in the negative phase of PDO, but only for the DJF period. The Cross-Wavelets showed that PDO and ENSO interacts in both time scales, with ENSO leading PDO in the scale of 4-7 years, and PDO leading ENSO in 16-28 years. Both PDO and ENSO are coherent with the precipitation index in the scale of 2-7 years, but this coherence only appears in the periods of positive phase of PDO. Thus, only ENOS do not explain the climate variability in this region, and it is important to consider the PDO phases in studies of impacts of ENSO in the precipitation extremes in Southern Brazil.

  9. Relative contributions of mean-state shifts and ENSO-driven variability to precipitation changes in a warming climate

    DOE PAGES

    Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; ...

    2015-12-18

    The El Niño–Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with coupled general circulation models (CGCMs) to investigate how regional precipitation in the twenty-first century may be affected by changes in both ENSO-driven precipitation variability and slowly evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of twentieth-century climate change.more » Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in twenty-first-century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with twentieth-century observations and more stationary during the twenty-first century. Finally, the model-predicted twenty-first-century rainfall response to cENSO is decomposed into the sum of three terms: 1) the twenty-first-century change in the mean state of precipitation, 2) the historical precipitation response to the cENSO pattern, and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. Lastly, by examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.« less

  10. Relative Contributions of Mean-State Shifts and ENSO-Driven Variability to Precipitation Changes in a Warming Climate

    NASA Technical Reports Server (NTRS)

    Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, L. Ruby; Doutriaux, Charles; Capotondi, Antonietta

    2015-01-01

    El Niño-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with coupled general circulation models (CGCMs) to investigate how regional precipitation in the twenty-first century may be affected by changes in both ENSO-driven precipitation variability and slowly evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of twentieth-century climate change. Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in twenty-first-century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with twentieth-century observations and more stationary during the twenty-first century. Finally, the model-predicted twenty-first-century rainfall response to cENSO is decomposed into the sum of three terms: 1) the twenty-first-century change in the mean state of precipitation, 2) the historical precipitation response to the cENSO pattern, and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. By examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.

  11. Relative Contributions of Mean-State Shifts and ENSO-Driven Variability to Precipitation Changes in a Warming Climate

    NASA Technical Reports Server (NTRS)

    Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, L. Ruby; Doutriaux, Charles; Capotondi, Antonietta

    2015-01-01

    The El Nino-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with Coupled General Circulation Models (CGCMs) to investigate how regional precipitation in the 21st century may be affected by changes in both ENSO-driven precipitation variability and slowly-evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of 20th century climate change. Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in 21st century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with 20th century observations and more stationary during the 21st century. Finally, the model-predicted 21st century rainfall response to cENSO is decomposed into the sum of three terms: 1) the 21st century change in the mean state of precipitation; 2) the historical precipitation response to the cENSO pattern; and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. By examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.

  12. Amplification of ENSO Effects on Indian Summer Monsoon by Absorbing Aerosols

    NASA Technical Reports Server (NTRS)

    Kim, Maeng-Ki; Lau, William K. M.; Kim, Kyu-Myong; Sang, Jeong; Kim, Yeon-Hee; Lee, Woo-Seop

    2015-01-01

    In this study, we present observational evidence, based on satellite aerosol measurements and MERRA reanalysis data for the period 1979-2011, indicating that absorbing aerosols can have strong influence on seasonal-to-interannual variability of the Indian summer monsoon rainfall, including amplification of ENSO effects. We find a significant correlation between ENSO (El Nino Southern Oscillation) and aerosol loading in April-May, with La Nina (El Nino) conditions favoring increased (decreased) aerosol accumulation over northern India, with maximum aerosol optical depth (AOD) over the Arabian Sea and Northwestern India, indicative of strong concentration of dust aerosols transported from West Asia and Middle East deserts. Composite analyses based on a normalized aerosol index (NAI) show that high concentration of aerosol over northern India in April-May is associated with increased moisture transport, enhanced dynamically induced warming of the upper troposphere over the Tibetan Plateau, and enhanced rainfall over northern India and the Himalayan foothills during May-June, followed by a subsequent suppressed monsoon rainfall over all India,consistent with the Elevated Heat Pump (EHP) hypothesis (Lau et al. 2006). Further analyses from sub-sampling of ENSO years, with normal (less than 1 sigma), and abnormal (greater than 1 sigma)) NAI over northern India respectively show that the EHP may lead to an amplification of the Indian summer monsoon response to ENSO forcing, particularly with respect to the increased rainfall over the Himalayan foothills, and the warming of the upper troposphere over the Tibetan Plateau. Our results suggest that absorbing aerosol, particular desert dusts can strongly modulate ENSO influence, and possibly play important roles as a feedback agent in climate change in Asian monsoon regions.

  13. Inter-annual Variability of Temperature and Extreme Heat Events during the Nairobi Warm Season

    NASA Astrophysics Data System (ADS)

    Scott, A.; Misiani, H. O.; Zaitchik, B. F.; Ouma, G. O.; Anyah, R. O.; Jordan, A.

    2016-12-01

    Extreme heat events significantly stress all organisms in the ecosystem, and are likely to be amplified in peri-urban and urban areas. Understanding the variability and drivers behind these events is key to generating early warnings, yet in Equatorial East Africa, this information is currently unavailable. This study uses daily maximum and minimum temperature records from weather stations within Nairobi and its surroundings to characterize variability in daily minimum temperatures and the number of extreme heat events. ERA-Interim reanalysis is applied to assess the drivers of these events at event and seasonal time scales. At seasonal time scales, high temperatures in Nairobi are a function of large scale climate variability associated with the Atlantic Multi-decadal Oscillation (AMO) and Global Mean Sea Surface Temperature (GMSST). Extreme heat events, however, are more strongly associated with the El Nino Southern Oscillation (ENSO). For instance, the persistence of AMO and ENSO, in particular, provide a basis for seasonal prediction of extreme heat events/days in Nairobi. It is also apparent that the temporal signal from extreme heat events in tropics differs from classic heat wave definitions developed in the mid-latitudes, which suggests that a new approach for defining these events is necessary for tropical regions.

  14. ENSO Related Inter-Annual Lightning Variability from the Full TRMM LIS Lightning Climatology

    NASA Technical Reports Server (NTRS)

    Clark, Austin; Cecil, Daniel

    2018-01-01

    The El Nino/Southern Oscillation (ENSO) contributes to inter-annual variability of lightning production more than any other atmospheric oscillation. This study further investigated how ENSO phase affects lightning production in the tropics and subtropics using the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS). Lightning data were averaged into mean annual warm, cold, and neutral 'years' for analysis of the different phases and compared to model reanalysis data. An examination of the regional sensitivities and preliminary analysis of three locations was conducted using model reanalysis data to determine the leading convective mechanisms in these areas and how they might respond to the ENSO phases

  15. ENSO/PDO-Like Variability of Tropical Ocean Surface Energy Fluxes Over the Satellite Era

    NASA Technical Reports Server (NTRS)

    Robertson, F. R.; Miller, Tim L.

    2008-01-01

    Recent variations of tropical climate on interannual to near-decadal scales have provided a useful target for studying the nature of climate feedback processes. A strong warm / cold ENSO couplet (e.g. 1997-2000) along with several subsequent weaker events are prominent interannual signals that are part of an apparent longer term strengthening of the Walker circulation during the mid to late 1990's with some weakening thereafter. Decadal scale changes in tropical SST structure during the 1990s are accompanied by focusing of precipitation over the Indo-Pacific warm pool and an increase in tropical ocean evaporation of order 1.0 % /decade. Associated with ENSO and PDO-like tropical SST changes are surface freshwater and radiative fluxes which have important implications for heat and energy transport variations. In this study we examine how surface fluxes attending interannual to decadal SST fluctuations, e.g. precipitation (GPCP, TRMM), turbulent fluxes (OAFlux), and radiative fluxes (ERBE/CERES, SRB) are coupled. Using these data we analyze vertically-integrated divergence of moist static energy, divMSE, and its dry static energy and latent energy components. We examine consistency between these data sets and explore relationships between SST variations, flux changes and modulation of tropical Walker and Hadley circulations. Strong signatures ofMSE flux transport linking ascending and descending regions of tropical circulations are found. Relative strengths of these fluxes and transports are interpreted as a measure of efficiency in the overall process of tropical heat balance during episodes of warm or cold tropical SST.

  16. El Nino/Southern Oscillation response to global warming.

    PubMed

    Latif, M; Keenlyside, N S

    2009-12-08

    The El Niño/Southern Oscillation (ENSO) phenomenon, originating in the Tropical Pacific, is the strongest natural interannual climate signal and has widespread effects on the global climate system and the ecology of the Tropical Pacific. Any strong change in ENSO statistics will therefore have serious climatic and ecological consequences. Most global climate models do simulate ENSO, although large biases exist with respect to its characteristics. The ENSO response to global warming differs strongly from model to model and is thus highly uncertain. Some models simulate an increase in ENSO amplitude, others a decrease, and others virtually no change. Extremely strong changes constituting tipping point behavior are not simulated by any of the models. Nevertheless, some interesting changes in ENSO dynamics can be inferred from observations and model integrations. Although no tipping point behavior is envisaged in the physical climate system, smooth transitions in it may give rise to tipping point behavior in the biological, chemical, and even socioeconomic systems. For example, the simulated weakening of the Pacific zonal sea surface temperature gradient in the Hadley Centre model (with dynamic vegetation included) caused rapid Amazon forest die-back in the mid-twenty-first century, which in turn drove a nonlinear increase in atmospheric CO(2), accelerating global warming.

  17. Trans-Pacific ENSO teleconnections pose a correlated risk to global agriculture

    NASA Astrophysics Data System (ADS)

    Anderson, W. B.; Seager, R.; Cane, M. A.; Baethgen, W.

    2017-12-01

    The El Niño Southern Oscillation (ENSO) is a major source of interannual climate variability, particularly in the Pacific Basin. ENSO life-cycles tend to evolve over multiple years, as do the associated trans-Pacific ENSO teleconnections. This analysis, however, represents the first attempt to characterize the structure of the risk posed by ENSO to wheat, maize and soybean production across the Pacific Basin. Our results indicate that most ENSO teleconnections relevant for crop flowering seasons are the result of a single trans-Pacific circulation anomaly that develops in boreal summer and persists through the spring. During the late summer and early fall of a developing ENSO event, the tropical Pacific forces an atmospheric anomaly in the midlatitudes that spans the Pacific Basin. This teleconnection directly links the soybean and maize growing seasons of the US, Mexico and China. It also connects the wheat growing seasons of Argentina, southern Brazil and Australia. The ENSO event peaks in boreal winter, when the atmospheric circulation anomalies intensify and affect maize and soybeans in southeast South America. As the event decays, the ENSO-induced circulation anomalies persist through the wheat flowering seasons in China and the US. While the prospect of ENSO forcing simultaneous droughts in major food producing regions seems disastrous, there may be a silver lining from the perspective of global food security: trans-Pacific ENSO teleconnections to yields are often offsetting between major producing regions in the eastern and western portions of the Pacific Basin. El Niños tend to create good maize and soybean growing conditions in the US and southeast South America, but poor growing conditions in China, Mexico and northeast Brazil. The opposite is true during La Niña. Wheat growing conditions in southeast South America generally have the opposite sign of those in Australia. Finally, we investigate how trade networks interact with this structure of ENSO

  18. Indo-Pacific ENSO modes in a double-basin Zebiak-Cane model

    NASA Astrophysics Data System (ADS)

    Wieners, Claudia; de Ruijter, Will; Dijkstra, Henk

    2016-04-01

    We study Indo-Pacific interactions on ENSO timescales in a double-basin version of the Zebiak-Cane ENSO model, employing both time integrations and bifurcation analysis (continuation methods). The model contains two oceans (the Indian and Pacific Ocean) separated by a meridional wall. Interaction between the basins is possible via the atmosphere overlaying both basins. We focus on the effect of the Indian Ocean (both its mean state and its variability) on ENSO stability. In addition, inspired by analysis of observational data (Wieners et al, Coherent tropical Indo-Pacific interannual climate variability, in review), we investigate the effect of state-dependent atmospheric noise. Preliminary results include the following: 1) The background state of the Indian Ocean stabilises the Pacific ENSO (i.e. the Hopf bifurcation is shifted to higher values of the SST-atmosphere coupling), 2) the West Pacific cooling (warming) co-occurring with El Niño (La Niña) is essential to simulate the phase relations between Pacific and Indian SST anomalies, 3) a non-linear atmosphere is needed to simulate the effect of the Indian Ocean variability onto the Pacific ENSO that is suggested by observations.

  19. Warm-season severe wind events in Germany

    NASA Astrophysics Data System (ADS)

    Gatzen, Christoph

    2013-04-01

    A 15-year data set of wind measurements was analyzed with regard to warm season severe wind gusts in Germany. For April to September of the years 1997 to 2011, 1035 wind measurements of 26 m/s or greater were found. These wind reports were associated with 268 wind events. In total, 252 convective wind events contributed to 837 (81%) of the wind reports, 16 non-convective synoptic-scale wind events contributed to 198 reports (19%). Severe wind events were found with synoptic situations characterized by rather strong mid-level flow and advancing mid-level troughs. Severe convective wind events were analyzed using radar images and classified with respect to the observed radar structure. The most important convective mode was squall lines that were associated with one third of all severe wind gusts, followed by groups, bow echo complexes, and bow echoes. Supercells and cells were not associated with many wind reports. The low contribution of isolated cells indicates that rather large-scale forcing by synoptic-scale features like fronts is important for German severe wind events. Bow echoes were found to be present for 58% of all wind reports. The movement speed of bow echoes indicated a large variation with a maximum speed of 33 m/s. Extreme wind events as well as events with more than 15 wind reports were found to be related to higher movement speeds. Concentrating on the most intense events, derechos seem to be very important to the warm season wind threat in Germany. Convective events with a path length of more than 400 km contributed to 36% of all warm-season wind gusts in this data set. Furthermore, eight of nine extreme gusts exceeding 40 m/s were recorded with derecho events.

  20. ENSO and cholera: a nonstationary link related to climate change?

    PubMed

    Rodo, Xavier; Pascual, Mercedes; Fuchs, George; Faruque, A S G

    2002-10-01

    We present here quantitative evidence for an increased role of interannual climate variability on the temporal dynamics of an infectious disease. The evidence is based on time-series analyses of the relationship between El Niño/Southern Oscillation (ENSO) and cholera prevalence in Bangladesh (formerly Bengal) during two different time periods. A strong and consistent signature of ENSO is apparent in the last two decades (1980-2001), while it is weaker and eventually uncorrelated during the first parts of the last century (1893-1920 and 1920-1940, respectively). Concomitant with these changes, the Southern Oscillation Index (SOI) undergoes shifts in its frequency spectrum. These changes include an intensification of the approximately 4-yr cycle during the recent interval as a response to the well documented Pacific basin regime shift of 1976. This change in remote ENSO modulation alone can only partially serve to substantiate the differences observed in cholera. Regional or basin-wide changes possibly linked to global warming must be invoked that seem to facilitate ENSO transmission. For the recent cholera series and during specific time intervals corresponding to local maxima in ENSO, this climate phenomenon accounts for over 70% of disease variance. This strong association is discontinuous in time and can only be captured with a technique designed to isolate transient couplings.

  1. Mapping the Historical Probability of Increased Flood Hazard During ENSO Events Using a New 20th Century River Flow Reanalysis

    NASA Astrophysics Data System (ADS)

    Emerton, R.; Cloke, H. L.; Stephens, L.; Woolnough, S. J.; Zsoter, E.; Pappenberger, F.

    2016-12-01

    El Niño Southern Oscillation (ENSO), a mode of variability which sees fluctuations between anomalously high or low sea surface temperatures in the Pacific, is known to influence river flow and flooding at the global scale. The anticipation and forecasting of floods is crucial for flood preparedness, and this link, alongside the predictive skill of ENSO up to seasons ahead, may provide an early indication of upcoming severe flood events. Information is readily available indicating the likely impacts of El Niño and La Niña on precipitation across the globe, which is often used as a proxy for flood hazard. However, the nonlinearity between precipitation and flood magnitude and frequency means that it is important to assess the impact of ENSO events not only on precipitation, but also on river flow and flooding. Historical probabilities provide key information regarding the likely impacts of ENSO events. We estimate, for the first time, the historical probability of increased flood hazard during El Niño and La Niña through a global hydrological analysis, using a new 20thCentury ensemble river flow reanalysis for the global river network. This dataset was produced by running the ECMWF ERA-20CM atmospheric reanalysis through a research set-up of the Global Flood Awareness System (GloFAS) using the CaMa-Flood hydrodynamic model, to produce a 110-year global reanalysis of river flow. We further evaluate the added benefit of the hydrological analysis over the use of precipitation as a proxy for flood hazard. For example, providing information regarding regions that are likely to experience a lagged influence on river flow compared to the influence on precipitation. Our results map, at the global scale, the probability of abnormally high river flow during any given month during an El Niño or La Niña; information such as this is key for organisations that work at the global scale, such as humanitarian aid organisations, providing a seasons-ahead indicator of potential

  2. The nonstationary impact of local temperature changes and ENSO on extreme precipitation at the global scale

    NASA Astrophysics Data System (ADS)

    Sun, Qiaohong; Miao, Chiyuan; Qiao, Yuanyuan; Duan, Qingyun

    2017-12-01

    The El Niño-Southern Oscillation (ENSO) and local temperature are important drivers of extreme precipitation. Understanding the impact of ENSO and temperature on the risk of extreme precipitation over global land will provide a foundation for risk assessment and climate-adaptive design of infrastructure in a changing climate. In this study, nonstationary generalized extreme value distributions were used to model extreme precipitation over global land for the period 1979-2015, with ENSO indicator and temperature as covariates. Risk factors were estimated to quantify the contrast between the influence of different ENSO phases and temperature. The results show that extreme precipitation is dominated by ENSO over 22% of global land and by temperature over 26% of global land. With a warming climate, the risk of high-intensity daily extreme precipitation increases at high latitudes but decreases in tropical regions. For ENSO, large parts of North America, southern South America, and southeastern and northeastern China are shown to suffer greater risk in El Niño years, with more than double the chance of intense extreme precipitation in El Niño years compared with La Niña years. Moreover, regions with more intense precipitation are more sensitive to ENSO. Global climate models were used to investigate the changing relationship between extreme precipitation and the covariates. The risk of extreme, high-intensity precipitation increases across high latitudes of the Northern Hemisphere but decreases in middle and lower latitudes under a warming climate scenario, and will likely trigger increases in severe flooding and droughts across the globe. However, there is some uncertainties associated with the influence of ENSO on predictions of future extreme precipitation, with the spatial extent and risk varying among the different models.

  3. On the relationship between ENSO and tropical cyclones in the western North Pacific during the boreal summer

    NASA Astrophysics Data System (ADS)

    Zhao, Haikun; Wang, Chunzai

    2018-02-01

    The present paper uses the satellite era data from 1979 to 2015 to examine the relationship between El Niño-Southern Oscillation (ENSO) and tropical cyclones (TCs) in the western North Pacific (WNP) during the boreal summer from June to August. It is found that WNP TC variability is characterized by two major feature changes: (1) a significant reduction of the TC number since 1998 and (2) a stronger interannual relationship between ENSO and TCs since 1998. Results suggested that such changes are largely due to the synergy effects of a shifting ENSO and the Pacific climate regime shift. Since 1998 with a cool Pacific decadal oscillation phase switching from a warm phase, more La Niña and central Pacific (CP) El Niño events occur. The decreased low-level relative vorticity and increased vertical wind shear during 1998-2015 compared to 1979-1997 are responsible for the TC reduction. The stronger interannual relationship between ENSO and TCs since 1998 is closely associated the change of CP sea surface temperature. It enhances the associations of environmental factors including vertical wind shear and mid-level relative humidity with TCs and thus increases the interannual relationship between ENSO and TCs. These two feature changes also manifest in the mean TC genesis location, with a northwestward shift of the TC genesis location during 1998-2015 and an increased relation to El Niño Modoki index since 1998. This study has an important implication for TC outlooks in the WNP based on climate predictions and projections.

  4. Can solar cycle modulate the ENSO effect on the Pacific/North American pattern?

    NASA Astrophysics Data System (ADS)

    Li, Delin; Xiao, Ziniu

    2018-01-01

    The ENSO effect on the Pacific/North American pattern (PNA) is well-known robust. Recent studies from observations and model simulations have reported that some important atmospheric circulation systems of extratropics are markedly modulated by the 11-year solar cycle. But less effort has been devoted to revealing the solar influence on the PNA. We thus hypothesize that the instability and uncertainty in the relationship between solar activity and PNA could be due to the ENSO impacts. In this study, solar cycle modulation of the ENSO effect on the PNA has been statistically examined by the observations from NOAA and NCEP/NCAR for the period of 1950-2014. Results indicate that during the high solar activity (HS) years, the PNA has stronger relevance to the ENSO, and the response of tropospheric geopotential height to ENSO variability is broadly similar to the typical positive PNA pattern. However, in the case of low solar activity (LS) years, the correlation between ENSO and PNA decreases relatively and the response has some resemblance to the negative phase of Arctic Oscillation (AO). Also, we find the impacts of solar activity on the middle troposphere are asymmetric during the different solar cycle phases, and the weak PNA-like response to solar activity only presents in the HS years. Closer inspection suggests that the higher solar activity has a much more remarkable modulation on the PNA-like response to the warm ENSO (WE) than that to the cold ENSO (CE), particularly over the Northeast Pacific region. The possible cause of the different responses might be the solar influence on the subtropical westerlies of upper troposphere. When the sea surface temperature (SST) of east-central tropical Pacific is anomalously warm, the upper tropospheric westerlies are significantly modulated by the higher solar activity, resulting in the acceleration and eastward shift of the North Pacific subtropical jet, which favors the propagation of WE signal from the tropical Pacific

  5. Changes in El Nino - Southern Oscillation (ENSO) conditions during the Younger Dryas revealed by New Zealand tree-rings.

    NASA Astrophysics Data System (ADS)

    Palmer, Jonathan; Turney, Chris; Cook, Edward; Fenwick, Pavla; Thomas, Zoë; Helle, Gerhard; Jones, Richard; Clement, Amy; Hogg, Alan; Southon, John; Bronk Ramsey, Christopher; Staff, Richard; Muscheler, Raimund; Corrège, Thierry; Hua, Quan

    2017-04-01

    The warming trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remains uncertain. Whilst the wider Atlantic region has a network of high-resolution proxy records spanning the YD, the Pacific Ocean suffers from a scarcity of sub-decadally resolved sequences. Here we report the results from an investigation into a tree-ring chronology from northern New Zealand aimed at addressing the paucity of data. The conifer tree species kauri (Agathis australis) is known from contemporary studies to be sensitive to regional climate changes. An analysis of a 'historic' 452-year kauri chronology confirms a tropical-Pacific teleconnection via the El Niño - Southern Oscillation (ENSO). We then focus our study to a 1010-year subfossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring-width downturn between 12,500 to 12,380 cal BP within the YD. Wavelet analysis shows a marked increase in ENSO-like periodicities occurring after the downturn event. Comparison to low- and mid-latitude Pacific records suggests a coherency in the changes to ENSO and Southern Hemisphere westerly airflow during this period. The drivers for this climate event remain unclear but may be related to solar changes that subsequently led to establishment and/or increased expression of ENSO across the mid-latitudes of the Pacific, seemingly independent of the Atlantic and polar regions.

  6. Mechanism of ENSO influence on the South Asian monsoon rainfall in global model simulations

    NASA Astrophysics Data System (ADS)

    Joshi, Sneh; Kar, Sarat C.

    2018-02-01

    Coupled ocean atmosphere global climate models are increasingly being used for seasonal scale simulation of the South Asian monsoon. In these models, sea surface temperatures (SSTs) evolve as coupled air-sea interaction process. However, sensitivity experiments with various SST forcing can only be done in an atmosphere-only model. In this study, the Global Forecast System (GFS) model at T126 horizontal resolution has been used to examine the mechanism of El Niño-Southern Oscillation (ENSO) forcing on the monsoon circulation and rainfall. The model has been integrated (ensemble) with observed, climatological and ENSO SST forcing to document the mechanism on how the South Asian monsoon responds to basin-wide SST variations in the Indian and Pacific Oceans. The model simulations indicate that the internal variability gets modulated by the SSTs with warming in the Pacific enhancing the ensemble spread over the monsoon region as compared to cooling conditions. Anomalous easterly wind anomalies cover the Indian region both at 850 and 200 hPa levels during El Niño years. The locations and intensity of Walker and Hadley circulations are altered due to ENSO SST forcing. These lead to reduction of monsoon rainfall over most parts of India during El Niño events compared to La Niña conditions. However, internally generated variability is a major source of uncertainty in the model-simulated climate.

  7. A Teleconnection between the West Siberian Plain and the ENSO Region

    NASA Astrophysics Data System (ADS)

    Liess, S.; Agrawal, S.; Chatterjee, S.; Kumar, V.

    2017-12-01

    This study presents a mechanism that links the El Niño/Southern Oscillation (ENSO) to extratropical waves that are deflected from the Northern Hemisphere polar regions and travel southeastward over Central Asia toward the west Pacific warm pool during northern winter. The initial wave pattern resembles the well-known East Atlantic-West Russia pattern. Here we show its influence on the ENSO region. We identify a tripole pattern between the West Siberian Plain and the two centers of action of ENSO with a graph-based approach. It indicates that the background state of ENSO with respect to global sea level pressure (SLP) has a significant negative correlation to the West Siberian Plain. The correlation with the background state, which is defined by the sum of the two centers of action of ENSO, is higher than each of the pairwise correlations with either of the ENSO centers alone. We define the centers with a clustering algorithm that detects regions with similar characteristics. The normalized monthly SLP time series for the two centers of ENSO (around Darwin, Australia and Tahiti) are area-averaged and the sum of both regions is considered as the background state of ENSO. This wave train can be detected throughout the troposphere and the lower stratosphere. Its origins can be traced back to atmospheric wave activity triggered by convection over the subtropical North Atlantic that emanates wave activity toward the West Siberian Plain. The same wave train also propagates to the central Pacific Ocean around Tahiti and can be used to predict the background state over the ENSO region. This background state also modifies the subtropical bridge between the tropical east Pacific and the subtropical North Atlantic, thus leading to a circumglobal wave train.

  8. Carbon Isotopes in Pinus elliotti from Big Pine Key, Florida: Indicators of Seasonal Precipitation, ENSO and Disturbance Events

    NASA Astrophysics Data System (ADS)

    Rebenack, C.; Willoughby, H. E.; Anderson, W. T.; Cherubini, P.

    2013-12-01

    The South Florida coastal ecosystem is among the world's subtropical coastlines which are threatened by the potential effects of climate change. A well-developed localized paleohistory is essential in the understanding of the role climate variability/change has on both hydrological dynamics and disturbance event frequency and intensity; this understanding can then aid in the development of better predictive models. High resolution paleoclimate proxies, such as those developed from tree-ring archives, may be useful tools for extrapolating actual climate trends over time from the overlapping long-term and short-term climate cycles, such as the Atlantic Multidecadal Oscillation (AMO) and the El Niño-Southern Oscillation (ENSO). In South Florida, both the AMO and ENSO strongly influence seasonal precipitation, and a more complete grasp of how these cycles have affected the region in the past could be applied to future freshwater management practices. Dendrochronology records for the terrestrial subtropics, including South Florida, are sparse because seasonality for this region is precipitation driven; this is in contrast to the drastic temperature changes experienced in the temperate latitudes. Subtropical seasonality may lead to the complete lack of visible rings or to the formation of ring structures that may or may not represent annual growth. Fortunately, it has recently been demonstrated that Pinus elliottii trees in South Florida produce distinct annual growth rings; however ring width was not found to significantly correlate with either the AMO or ENSO. Dendrochronology studies may be taken a step beyond the physical tree-ring proxies by using the carbon isotope ratios to infer information about physiological controls and environmental factors that affect the distribution of isotopes within the plant. It has been well established that the stable isotope composition of cellulose can be related to precipitation, drought, large-scale ocean/atmospheric oscillations

  9. Late-Holocene vegetation and climate change in Jeju Island, Korea and its implications for ENSO influences

    NASA Astrophysics Data System (ADS)

    Park, Jungjae; Shin, Young Ho; Byrne, Roger

    2016-12-01

    Several recent studies suggest the hypothesis that the El Niño-Southern Oscillation (ENSO) is an important factor controlling the Holocene East Asian Monsoon (EAM). However, the mechanism underlying this influence remains unclear due to the lack of high-resolution paleoclimate records from the coast of East Asia. Here, we provide a new record of late Holocene climate change in coastal East Asia based on multi-proxy evidence (pollen, organic content, magnetic susceptibility, grain size) obtained from a sediment core from Jeju Island, South Korea. As Jeju Island is strongly influenced by the Kuroshio flow, our sediment proxy records contain ENSO signals from the tropical Pacific. The study area was affected by dry/cool conditions in the western tropical Pacific (WTP) between 4350 and 1920 cal yr BP when El Niños were frequent, and by rapid warming/wetting and forestation since 1920 cal yr BP when La Niñas were more common. Jeju Island was relatively dry/cool between 2100 and 1600, 1300-1200, 1100-1000, 800-650, and 300-50 cal yr BP, as opposed to the Galápagos Islands, which were relatively wet/warm, reflecting the ENSO-related negative correlation between eastern and western margins of Pacific. Wet conditions may have prevailed during the early Little Ice Age (LIA) (620-280 cal yr BP) despite consistent cooling. This period of high precipitation may have been associated with the increased landfall of typhoons and with warmer Kuroshio currents under La Niña-like conditions. According to our results, EAM on the East Asian coastal margin was predominantly driven by ENSO activity, rather than by the precession effect. Paleoclimatic data from Jeju Island, with its insular position and closeness to warm Kuroshio currents, provide clear evidence of these ENSO influences.

  10. Decadal-scale progression of Dansgaard-Oeschger warming events - Are warmings at the end of Heinrich-Stadials different from others?

    NASA Astrophysics Data System (ADS)

    Erhardt, T.; Capron, E.; Rasmussen, S.; Schuepbach, S.; Bigler, M.; Fischer, H.

    2017-12-01

    During the last glacial period proxy records throughout the Northern Hemisphere document a succession of rapid millennial-scale warming events, called Dansgaard Oeschger (DO) events. Marine proxy records from the Atlantic also reveal, that some of the warming events where preceded by large ice rafting events, referred to as Heinrich events. Different mechanisms have been proposed, that can produce DO-like warming in model experiments, however the progression and plausible trigger of the events and their possible interplay with the Heinrich events is still unknown. Because of their fast nature, the progression is challenging to reconstruct from paleoclimate data due to the temporal resolution achievable in many archives and cross-dating uncertainties between records. We use new high-resolution multi-proxy records of sea-salt and terrestrial aerosol concentrations over the period 10-60 ka from two Greenland deep ice cores in conjunction with local precipitation and temperature proxy records from one of the cores to investigate the progression of environmental changes at the onset of the individual warming events. The timing differences are then used to explore whether the DO warming events that terminate Heinrich-Stadials progressed differently in comparison to those after Non-Heinrich-Stadials. Our analysis indicates no difference in the progression of the warming terminating Heinrich-Stadials and Non-Heinrich-Stadials. Combining the evidence from all warming events in the period, our analysis shows a consistent lead of the changes in both local precipitation and terrestrial dust aerosol concentrations over the change in sea-salt aerosol concentrations and local temperature by approximately one decade. This implies that both the moisture transport to Greenland and the intensity of the Asian winter monsoon changed before the sea-ice cover in the North Atlantic was reduced, rendering a collapse of the sea-ice cover as a trigger for the DO events unlikely.

  11. ENSO and cholera: A nonstationary link related to climate change?

    PubMed Central

    Rodó, Xavier; Pascual, Mercedes; Fuchs, George; Faruque, A. S. G.

    2002-01-01

    We present here quantitative evidence for an increased role of interannual climate variability on the temporal dynamics of an infectious disease. The evidence is based on time-series analyses of the relationship between El Niño/Southern Oscillation (ENSO) and cholera prevalence in Bangladesh (formerly Bengal) during two different time periods. A strong and consistent signature of ENSO is apparent in the last two decades (1980–2001), while it is weaker and eventually uncorrelated during the first parts of the last century (1893–1920 and 1920–1940, respectively). Concomitant with these changes, the Southern Oscillation Index (SOI) undergoes shifts in its frequency spectrum. These changes include an intensification of the approximately 4-yr cycle during the recent interval as a response to the well documented Pacific basin regime shift of 1976. This change in remote ENSO modulation alone can only partially serve to substantiate the differences observed in cholera. Regional or basin-wide changes possibly linked to global warming must be invoked that seem to facilitate ENSO transmission. For the recent cholera series and during specific time intervals corresponding to local maxima in ENSO, this climate phenomenon accounts for over 70% of disease variance. This strong association is discontinuous in time and can only be captured with a technique designed to isolate transient couplings. PMID:12228724

  12. DMS role in ENSO cycle in the tropics: DMS Role in ENSO Cycle in Tropics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Xu, Li; Cameron-Smith, Philip; Russell, Lynn M.

    We examined the multiyear mean and variability of dimethyl sulfide (DMS) and its relationship to sulfate aerosols, as well as cloud microphysical and radiative properties. We conducted a 150 year simulation using preindustrial conditions produced by the Community Earth System Model embedded with a dynamic DMS module. The model simulated the mean spatial distribution of DMS emissions and burden, as well as sulfur budgets associated with DMS, SO2, H2SO4, and sulfate that were generally similar to available observations and inventories for a variety of regions. Changes in simulated sea-to-air DMS emissions and associated atmospheric abundance, along with associated aerosols andmore » cloud and radiative properties, were consistently dominated by El Niño–Southern Oscillation (ENSO) cycle in the tropical Pacific region. Simulated DMS, aerosols, and clouds showed a weak positive feedback on sea surface temperature. This feedback suggests a link among DMS, aerosols, clouds, and climate on interannual timescales. The variability of DMS emissions associated with ENSO was primarily caused by a higher variation in wind speed during La Niña events. The simulation results also suggest that variations in DMS emissions increase the frequency of La Niña events but do not alter ENSO variability in terms of the standard deviation of the Niño 3 sea surface temperature anomalies.« less

  13. Weather-forced variations of Central and East Pacific ENSO events

    NASA Astrophysics Data System (ADS)

    Alexander, M. A.; Newman, M.; Shin, S.

    2010-12-01

    It has been suggested that a possible outcome of climate change is an increase in the occurrence of “Modoki” or central Pacific El Nino events relative to canonical eastern Pacific El Nino events, and that this change may already be occurring. Such a determination, however, is complicated by possible natural variations of the two types of events. How large a change in the relative occurrence can be expected from purely internal variability? To explore this question, a “patterns-based” red noise null hypothesis is constructed from 40 years of observed seasonally-averaged SST, 20 deg C thermocline depth, and surface zonal wind stress anomalies. Patterns-based (or multivariate) red noise differs from “local” (or univariate) red noise since it allows for non-local advective processes; for example, weather noise driving surface wind stress in one location to produce an ocean response in a different location. It is shown that natural random variations of the central Pacific to east Pacific El Nino occurrence ratio are large enough that they could account for all past observed differences as well as all differences found in the SRESA1B runs of all AR4 climate models. Additionally, the correlation between Nino3 and Nino4 SST indices over 30-yr periods can range between 0.7 and 0.9 simply due to such variations in noise, with apparent multidecadal “trends” during which the value increases or decreases. Further analysis shows the different spatial patterns of “noise” (i.e., random weather forcing) that can lead to the development of central vs. eastern Pacific ENSO events or various combinations thereof.

  14. ENSO and PDO-related climate variability impacts on Midwestern United States crop yields.

    PubMed

    Henson, Chasity; Market, Patrick; Lupo, Anthony; Guinan, Patrick

    2017-05-01

    An analysis of crop yields for the state of Missouri was completed to determine if an interannual or multidecadal variability existed as a result of the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Corn and soybean yields were recorded in kilograms per hectare for each of the six climate regions of Missouri. An analysis using the Mokhov "method of cycles" demonstrated interannual, interdecadal, and multidecadal variations in crop yields. Cross-spectral analysis was used to determine which region was most impacted by ENSO and PDO influenced seasonal (April-September) temperature and precipitation. Interannual (multidecadal) variations found in the spectral analysis represent a relationship to ENSO (PDO) phase, while interdecadal variations represent a possible interaction between ENSO and PDO. Average crop yields were then calculated for each combination of ENSO and PDO phase, displaying a pronounced increase in corn and soybean yields when ENSO is warm and PDO is positive. Climate regions 1, 2, 4, and 6 displayed significant differences (p value of 0.10 or less) in yields between El Niño and La Niña years, representing 55-70 % of Missouri soybean and corn productivity, respectively. Final results give the opportunity to produce seasonal predictions of corn and soybean yields, specific to each climate region in Missouri, based on the combination of ENSO and PDO phases.

  15. El Niño/Southern Oscillation response to global warming

    PubMed Central

    Latif, M.; Keenlyside, N. S.

    2009-01-01

    The El Niño/Southern Oscillation (ENSO) phenomenon, originating in the Tropical Pacific, is the strongest natural interannual climate signal and has widespread effects on the global climate system and the ecology of the Tropical Pacific. Any strong change in ENSO statistics will therefore have serious climatic and ecological consequences. Most global climate models do simulate ENSO, although large biases exist with respect to its characteristics. The ENSO response to global warming differs strongly from model to model and is thus highly uncertain. Some models simulate an increase in ENSO amplitude, others a decrease, and others virtually no change. Extremely strong changes constituting tipping point behavior are not simulated by any of the models. Nevertheless, some interesting changes in ENSO dynamics can be inferred from observations and model integrations. Although no tipping point behavior is envisaged in the physical climate system, smooth transitions in it may give rise to tipping point behavior in the biological, chemical, and even socioeconomic systems. For example, the simulated weakening of the Pacific zonal sea surface temperature gradient in the Hadley Centre model (with dynamic vegetation included) caused rapid Amazon forest die-back in the mid-twenty-first century, which in turn drove a nonlinear increase in atmospheric CO2, accelerating global warming. PMID:19060210

  16. ENSO Transition Asymmetry: Internal and External Causes and Intermodel Diversity

    NASA Astrophysics Data System (ADS)

    An, Soon-Il; Kim, Ji-Won

    2018-05-01

    El Niño is frequently followed by La Niña, but the opposite case rarely happens. Here we explore a mechanism for such an asymmetrical transition and its future changes. Internally, the asymmetrical response of upper ocean waves against surface wind stress anomaly exerts a primary cause of El Niño-Southern Oscillation (ENSO) transition asymmetry. Externally, the asymmetrical capacitor effects of both Indian and Atlantic Oceans play some roles in driving the ENSO transition asymmetry via the interbasin interactions. The historical runs of Coupled Model Intercomparison Project Phase 5 show that the intermodel transition asymmetry is significantly correlated with the intermodel asymmetry in ocean wave response to surface wind forcing but not with that in the interbasin interactions. In addition, the El Niño-to-La Niña transition tendency was weaker in moderate global warming scenario runs (Representative Concentration Pathway 4.5) while slightly enhanced in strong warming scenario runs (Representative Concentration Pathway 8.5). Similar changes also appeared in the asymmetrical response of ocean waves against the surface wind forcing.

  17. The El Nino-Southern Oscillation in the second Hadley Centre coupled model and its response to greenhouse warming

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Collins, M.

    This paper describes El Nino-Southern Oscillation (ENSO) interannual variability simulated in the second Handley Centre coupled model under control and greenhouse warming scenarios. The model produces a very reasonable simulation of ENSO in the control experiment--reproducing the amplitude, spectral characteristics, and phase locking to the annual cycle that are observed in nature. The mechanism for the model ENSO is shown to be a mixed SST-ocean dynamics mode that can be interpreted in terms of the ocean recharge paradigm of Jin. In experiments with increased levels of greenhouse gases, no statistically significant changes in ENSO are seen until these levels approachmore » four times preindustrial values. In these experiments, the model ENSO has an approximately 20% larger amplitude, a frequency that is approximately double that of the current ENSO (implying more frequent El Ninos and La Ninas), and phase locks to the annual cycle at a different time of year. It is shown that the increase in the vertical gradient of temperature in the thermocline region, associated with the model's response to increased greenhouse gases, is responsible for the increase in the amplitude of ENSO, while the increase in meridional temperature gradients on either side of the equator, again associated with the models response to increasing greenhouse gases, is responsible for the increased frequency of ENSO events.« less

  18. Characteristics of the East Asian Winter Climate Associated with the Westerly Jet Stream and ENSO

    NASA Technical Reports Server (NTRS)

    Yang, Song; Lau, K.-M.; Kim, K.-M.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    In this study, the influences of the East Asian jet stream (EAJS) and El Nino/Southern Oscillation (ENSO) on the interannual variability of the East Asian winter climate are examined with a focus on the relative climate impacts of the two phenomena. Although the variations of the East Asian winter monsoon and the temperature and precipitation of China, Japan, and Korea are emphasized, the associated changes in the broad-scale atmospheric circulation patterns over Asia and the Pacific and in the extratropical North Pacific sea surface temperature (SST) are also investigated. It is demonstrated that there is no apparent relationship between ENSO and the interannual variability of EAJS core. The EAJS and ENSO are associated with distinctly different patterns of atmospheric circulation and SST in the Asian-Pacific regions. While ENSO causes major climate signals in the Tropics and over the North Pacific east of the dateline, the EAJS produces significant changes in the atmospheric circulation over East Asia and western Pacific. In particular, the EAJS explains larger variance of the interannual signals of the East Asian trough, the Asian continental high, the Aleutian low, and the East Asian winter monsoon. When the EAJS is strong, all these atmospheric systems intensify significantly. The response of surface temperature and precipitation to EAJS variability and ENSO is more complex. In general, the East Asian winter climate is cold (warm) and dry (wet) when the EAJS is strong (weak) and it is warm during El Nino years. However, different climate signals are found during different La Nina years. In terms of linear correlation, both the temperature and precipitation of northern China, Korea, and central Japan are more significantly associated with the EAJS than with ENSO.

  19. More extreme swings of the South Pacific convergence zone due to greenhouse warming.

    PubMed

    Cai, Wenju; Lengaigne, Matthieu; Borlace, Simon; Collins, Matthew; Cowan, Tim; McPhaden, Michael J; Timmermann, Axel; Power, Scott; Brown, Josephine; Menkes, Christophe; Ngari, Arona; Vincent, Emmanuel M; Widlansky, Matthew J

    2012-08-16

    The South Pacific convergence zone (SPCZ) is the Southern Hemisphere's most expansive and persistent rain band, extending from the equatorial western Pacific Ocean southeastward towards French Polynesia. Owing to its strong rainfall gradient, a small displacement in the position of the SPCZ causes drastic changes to hydroclimatic conditions and the frequency of extreme weather events--such as droughts, floods and tropical cyclones--experienced by vulnerable island countries in the region. The SPCZ position varies from its climatological mean location with the El Niño/Southern Oscillation (ENSO), moving a few degrees northward during moderate El Niño events and southward during La Niña events. During strong El Niño events, however, the SPCZ undergoes an extreme swing--by up to ten degrees of latitude toward the Equator--and collapses to a more zonally oriented structure with commensurately severe weather impacts. Understanding changes in the characteristics of the SPCZ in a changing climate is therefore of broad scientific and socioeconomic interest. Here we present climate modelling evidence for a near doubling in the occurrences of zonal SPCZ events between the periods 1891-1990 and 1991-2090 in response to greenhouse warming, even in the absence of a consensus on how ENSO will change. We estimate the increase in zonal SPCZ events from an aggregation of the climate models in the Coupled Model Intercomparison Project phases 3 and 5 (CMIP3 and CMIP5) multi-model database that are able to simulate such events. The change is caused by a projected enhanced equatorial warming in the Pacific and may lead to more frequent occurrences of extreme events across the Pacific island nations most affected by zonal SPCZ events.

  20. Changes in Indonesian Outflow in relation to East Asian Monsoon and ENSO Activities since the Last Glacial

    NASA Astrophysics Data System (ADS)

    Xu, J.

    2013-12-01

    mechanisms in controlling changes of the ITF outflow after the ITF recovered during ~16-11.5ka. It is speculated that intensified precipitation due to prevailed East Asian summer monsoon and possible ENSO-like cold phase during the early Holocene (11.5-6ka) significantly freshened surface waters over the Indonesian Seas, impeding ITF surface flow and in turn enhanced thermocline flow. Continuous cooling of ITF thermocline waters and shoaling of thermocline depth in the TS after 6ka were partially related to impedance of ITF surface flow, which is however very likely caused by fresh surface water plug driven by winter monsoon, as it operates today (Gordon, 2005). More frequent ENSO-like events during the mid-to-late Holocene may play an additional role, as eastward movement of the warm pool is concomitant with shoaling and cooling of thermocline in the WPWP during modern ENSO events.

  1. Impacts of ENSO on global hydrology

    NASA Astrophysics Data System (ADS)

    Ward, P. J.; Eisner, S.; Flörke, M.; Kummu, M.

    2012-04-01

    The economic consequences of flooding are huge, as exemplified by recent major floods in Thailand, Pakistan, and Australia. Moreover, research shows that economic losses due to flooding have increased dramatically in recent decades. Whilst much research is being carried out to assess how this may be related to socioeconomic development (increased exposure to floods) or climate change (increased hazard), the role of interannual climate variability is poorly understood at the global scale. We provide the first global assessment of the sensitivity of extreme global river discharge to the El Niño Southern Oscillation (ENSO). Past studies have either: (a) assessed this at the local scale; or (b) assessed only global correlations between ENSO and mean river discharge. Firstly, we used a daily observed discharge dataset for 622 gauging stations (from the GRDC database), and assessed and mapped correlations and sensitivities between these time-series and several indices of ENSO. We found that, on average, for the stations studied ENSO has a greater impact on annual high-flow events than on mean annual discharge, especially in the extra-tropics. However, the geographical coverage of the dataset is poor in some regions, and is highly skewed towards certain areas (e.g. North America, Europe, and eastern Australia). This renders a truly global assessment of ENSO impacts impossible based on these observed time-series. Hence, we are also using a modelling approach to estimate correlations and sensitivities in all basins, gauged and ungauged. For this, we are using a gridded time-series of modelled daily discharge from the EU-WATCH project, and analysing relationships between these time-series (per grid-cell) and indices of ENSO. This allows for the first truly global assessment of the impact of ENSO variability on river discharge; these analyses are ongoing. Of course, this approach entails its own problems; the use of global hydrological models to derive daily discharge time

  2. Evolution of Tropical and Extratropical Precipitation Anomalies During the 1997 to 1999 ENSO Cycle

    NASA Technical Reports Server (NTRS)

    Curtis, Scott; Adler, Robert; Huffman, George; Nelkin, Eric; Bolvin, David; Einaudi, Franco (Technical Monitor)

    2000-01-01

    The 1997-1999 ENSO period was very powerful, but also well observed. Multiple satellite rainfall estimates combined with gauge observations allow for a quantitative analysis of precipitation anomalies in the tropics and elsewhere accompanying the 1997-99 ENSO cycle. An examination of the evolution of the El Nino and accompanying precipitation anomalies revealed that a dry Maritime Continent preceded the formation of positive SST anomalies in the eastern Pacific Ocean. 30-60 day oscillations in the winter of 1996/97 may have contributed to this lag relationship. Furthermore, westerly wind burst events may have maintained the drought over the Maritime Continent. The warming of the equatorial Pacific was then followed by an increase in convection. A rapid transition from El Nino to La Nina occurred in May 1998, but as early as October-November 1997 precipitation indices captured substantial changes in Pacific rainfall anomalies. The global precipitation patterns for this event were in good agreement with the strong consistent ENSO-related precipitation signals identified in earlier studies. Differences included a shift in precipitation anomalies over Africa during the 1997-98 El Nino and unusually wet conditions over northeast Australia during the later stages of the El Nino. Also, the typically wet region in the north tropical Pacific was mostly dry during the 1998-99 La Nina. Reanalysis precipitation was compared to observations during this time period and substantial differences were noted. In particular, the model had a bias towards positive precipitation anomalies and the magnitudes of the anomalies in the equatorial Pacific were small compared to the observations. Also, the evolution of the precipitation field, including the drying of the Maritime Continent and eastward progression of rainfall in the equatorial Pacific was less pronounced for the model compared to the observations.

  3. Influence of Mean State Changes on the Structure of ENSO in a Tropical Coupled GCM.

    NASA Astrophysics Data System (ADS)

    Codron, Francis; Vintzileos, Augustin; Sadourny, Robert

    2001-03-01

    This study examines the response of the climate simulated by the Institut Pierre Simon Laplace tropical Pacific coupled general circulation model to two changes in parameterization: an improved coupling scheme at the coast, and the introduction of a saturation mixing ratio limiter in the water vapor advection scheme, which improves the rainfall distribution over and around orography. The main effect of these modifications is the suppression of spurious upwelling off the South American coast in Northern Hemisphere summer. Coupled feedbacks then extend this warming over the whole basin in an El Niño-like structure, with a maximum at the equator and in the eastern part of the basin. The mean precipitation pattern widens and moves equatorward as the trade winds weaken.This warmer mean state leads to a doubling of the standard deviation of interannual SST anomalies, and to a longer ENSO period. The structure of the ENSO cycle also shifts from westward propagation in the original simulation to a standing oscillation. The simulation of El Niño thus improves when compared to recent observed events. The study of ENSO spatial structure and lagged correlations shows that these changes of El Niño characteristics are caused by both the increase of amplitude and the modification of the spatial structure of the wind stress response to SST anomalies.These results show that both the mean state and variability of the tropical ocean can be very sensitive to biases or forcings, even geographically localized. They may also give some insight into the mechanisms responsible for the changes in ENSO characteristics due to decadal variability or climate change.

  4. Summer monsoon circulation and precipitation over the tropical Indian Ocean during ENSO in the NCEP climate forecast system

    NASA Astrophysics Data System (ADS)

    Chowdary, J. S.; Chaudhari, H. S.; Gnanaseelan, C.; Parekh, Anant; Suryachandra Rao, A.; Sreenivas, P.; Pokhrel, S.; Singh, P.

    2014-04-01

    This study investigates the El Niño Southern Oscillation (ENSO) teleconnections to tropical Indian Ocean (TIO) and their relationship with the Indian summer monsoon in the coupled general circulation model climate forecast system (CFS). The model shows good skill in simulating the impact of El Niño over the Indian Oceanic rim during its decay phase (the summer following peak phase of El Niño). Summer surface circulation patterns during the developing phase of El Niño are more influenced by local Sea Surface Temperature (SST) anomalies in the model unlike in observations. Eastern TIO cooling similar to that of Indian Ocean Dipole (IOD) is a dominant model feature in summer. This anomalous SST pattern therefore is attributed to the tendency of the model to simulate more frequent IOD events. On the other hand, in the model baroclinic response to the diabatic heating anomalies induced by the El Niño related warm SSTs is weak, resulting in reduced zonal extension of the Rossby wave response. This is mostly due to weak eastern Pacific summer time SST anomalies in the model during the developing phase of El Niño as compared to observations. Both eastern TIO cooling and weak SST warming in El Niño region combined together undermine the ENSO teleconnections to the TIO and south Asia regions. The model is able to capture the spatial patterns of SST, circulation and precipitation well during the decay phase of El Niño over the Indo-western Pacific including the typical spring asymmetric mode and summer basin-wide warming in TIO. The model simulated El Niño decay one or two seasons later, resulting long persistent warm SST and circulation anomalies mainly over the southwest TIO. In response to the late decay of El Niño, Ekman pumping shows two maxima over the southern TIO. In conjunction with this unrealistic Ekman pumping, westward propagating Rossby waves display two peaks, which play key role in the long-persistence of the TIO warming in the model (for more than a

  5. Oceanic Channel of the IOD-ENSO teleconnection over the Indo-Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Yuan, Dongliang; Wang, Jing; Zhao, Xia; Zhou, Hui; Xu, Tengfei; Xu, Peng

    2017-04-01

    The lag correlations of observations and model simulated data that participate the Coupled Model Intercomparison Project phase-5 (CMIP5) are used to study the precursory teleconnection between the Indian Ocean Dipole (IOD) and the Pacific ENSO one year later through the Indonesian seas. The results suggest that Indonesian Throughflow (ITF) play an important role in the IOD-ENSO teleconnection. Numerical simulations using a hierarchy of ocean models and climate coupled models have shown that the interannual sea level depressions in the southeastern Indian Ocean during IOD force enhanced ITF to transport warm water of the Pacific warm pool to the Indian Ocean, producing cold subsurface temperature anomalies, which propagate to the eastern equatorial Pacific and induce significant coupled ocean-atmosphere evolution. The teleconnection is found to have decadal variability. Similar decadal variability has also been identified in the historical simulations of the CMIP5 models. The dynamics of the inter-basin teleconnection during the positive phases of the decadal variability are diagnosed to be the interannual variations of the ITF associated with the Indian Ocean Dipole (IOD). During the negative phases, the thermocline in the eastern equatorial Pacific is anomalously deeper so that the sea surface temperature anomalies in the cold tongue are not sensitive to the thermocline depth changes. The IOD-ENSO teleconnection is found not affected significantly by the anthropogenic forcing.

  6. Impact of Temperature Anomalies Associated with El Niño-Southern Oscillation and Indian Ocean Dipole Events on Wine Grape Maturity in Australia

    NASA Astrophysics Data System (ADS)

    Jarvis, C.; Barlow, E.; Darbyshire, R.; Eckard, R.; Goodwin, I.

    2016-12-01

    Annual grapevine growth and development are intimately linked with growing season weather conditions. Shifts in circulation patterns resulting from atmospheric teleconnections to changes in sea surface temperature (SST) anomalies associated with El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events can alter seasonal weather across Australia. Both ENSO and IOD events tend to peak in austral spring, when vine and berry development is especially critical and susceptible to damage. To investigate the impacts of ENSO and IOD events on the Australian wine grape growing sector, historical gridded climate data and annual vineyard grape maturity data from a variety of wine growing regions was collected and analysed. The greatest impacts on grape maturity were found when La Niña and IOD positive events occurred in tandem. During these events, significantly dry and hot conditions persist throughout the wine grape growing season, suggesting that the IOD overrides the ENSO signal. These conditions lead to a rapid, compressed growing season, which can cause logistical complications during harvest and impact grape and wine quality. Warming of equatorial SSTs in the Indian Ocean are likely to enhance the amplitude of IOD positive events, which has serious implications for wine grape production in Australia, highlighting the importance of this research.

  7. ENSO and hydrologic extremes in the western United States

    USGS Publications Warehouse

    Cayan, D.R.; Redmond, K.T.; Riddle, L.G.

    1999-01-01

    Frequency distributions of daily precipitation in winter and daily stream flow from late winter to early summer, at several hundred sites in the western United States, exhibit strong and systematic responses to the two phases of ENSO. Most of the stream flows considered are driven by snowmelt. The Southern Oscillation index (SOI) is used as the ENSO phase indicator. Both modest (median) and larger (90th percentile) events were considered. In years with negative SOI values (El Nino), days with high daily precipitation and stream flow are more frequent than average over the Southwest and less frequent over the Northwest. During years with positive SOI values (La Nina), a nearly opposite pattern is seen. A more pronounced increase is seen in the number of days exceeding climatological 90th percentile values than in the number exceeding climatological 50th percentile values, for both precipitation and stream flow. Stream flow responses to ENSO extremes are accentuated over precipitation responses. Evidence suggests that the mechanism for this amplification involves ENSO-phase differences in the persistence and duration of wet episodes, affecting the efficiency of the process by which precipitation is converted to runoff. The SOI leads the precipitation events by several months, and hydrologic lags (mostly through snowmelt) dealy the stream flow response by several more months. The combined 6-12 month predictive aspect of this relationship should be of significant benefit in responding to flood (or drought) risk and in improving overall water management in the western states.Frequency distributions of daily precipitation in winter and daily stream flow from late winter to early summer, at several hundred sites in the western United States, exhibit strong and systematic responses to the two phases of ENSO. Most of the stream flows considered are driven by snowmelt. The Southern Oscillation index (SOI) is used as the ENSO phase indicator. Both modest (median) and larger

  8. Distinguishing Southern Africa precipitation response by strength of El Niño events

    NASA Astrophysics Data System (ADS)

    Pomposi, C.; Funk, C. C.; Shukla, S.; Magadzire, T.

    2017-12-01

    The El Niño Southern Oscillation (ENSO) is a leading mode of interannual precipitation variability and the main source of skill for seasonal climate predictions. Interannual precipitation variability linked to ENSO can have drastic impacts on agricultural systems and food resources in the semi-arid tropics, highlighting the need for increased information regarding ENSO's links to sub-seasonal to seasonal precipitation variations. The present work describes a case study on recent precipitation variability during warm ENSO events (i.e. El Niño) for the austral summer rainy season (December-February) in Southern Africa. Using a blending of observational and model data, it is found that the probability distribution of precipitation varies according to the strength of El Niño events. Strong El Niño events show a much clearer tendency for drying than moderate or weak events, which have smaller absolute magnitude anomalies and larger spatial heterogeneity in the precipitation response. A dynamical exploration of the various precipitation responses is also completed. The techniques utilized can be easily expanded to study likelihood of drought during El Niño for a variety of other regions and also provides information about El Niño strength and its influence on regional teleconnections. Finally, this presentation will describe the channels by which seasonal forecasting information is disseminated in the region and utilized by the Famine Early Warning Systems Network to help mitigate the impacts of potential food insecurity crises.

  9. Significant influences of global mean temperature and ENSO on extreme rainfall over Southeast Asia

    NASA Astrophysics Data System (ADS)

    Villafuerte, Marcelino, II; Matsumoto, Jun

    2014-05-01

    Along with the increasing concerns on the consequences of global warming, and the accumulating records of disaster related to heavy rainfall events in Southeast Asia, this study investigates whether a direct link can be detected between the rising global mean temperature, as well as the El Niño-Southern Oscillation (ENSO), and extreme rainfall over the region. The maximum likelihood modeling that allows incorporating covariates on the location parameter of the generalized extreme value (GEV) distribution is employed. The GEV model is fitted to annual and seasonal rainfall extremes, which were taken from a high-resolution gauge-based gridded daily precipitation data covering a span of 57 years (1951-2007). Nonstationarities in extreme rainfall are detected over the central parts of Indochina Peninsula, eastern coasts of central Vietnam, northwest of the Sumatra Island, inland portions of Borneo Island, and on the northeastern and southwestern coasts of the Philippines. These nonstationarities in extreme rainfall are directly linked to near-surface global mean temperature and ENSO. In particular, the study reveals that a kelvin increase in global mean temperature anomaly can lead to an increase of 30% to even greater than 45% in annual maximum 1-day rainfall, which were observed pronouncedly over central Vietnam, southern coast of Myanmar, northwestern sections of Thailand, northwestern tip of Sumatra, central portions of Malaysia, and the Visayas island in central Philippines. Furthermore, a pronounced ENSO influence manifested on the seasonal maximum 1-day rainfall; a northward progression of 10%-15% drier condition over Southeast Asia as the El Niño develops from summer to winter is revealed. It is important therefore, to consider the results obtained here for water resources management as well as for adaptation planning to minimize the potential adverse impact of global warming, particularly on extreme rainfall and its associated flood risk over the region

  10. ENSO-based probabilistic forecasts of March-May U.S. tornado and hail activity

    NASA Astrophysics Data System (ADS)

    Lepore, Chiara; Tippett, Michael K.; Allen, John T.

    2017-09-01

    Extended logistic regression is used to predict March-May severe convective storm (SCS) activity based on the preceding December-February (DJF) El Niño-Southern Oscillation (ENSO) state. The spatially resolved probabilistic forecasts are verified against U.S. tornado counts, hail events, and two environmental indices for severe convection. The cross-validated skill is positive for roughly a quarter of the U.S. Overall, indices are predicted with more skill than are storm reports, and hail events are predicted with more skill than tornado counts. Skill is higher in the cool phase of ENSO (La Niña like) when overall SCS activity is higher. SCS forecasts based on the predicted DJF ENSO state from coupled dynamical models initialized in October of the previous year extend the lead time with only a modest reduction in skill compared to forecasts based on the observed DJF ENSO state.

  11. A metric for quantifying El Niño pattern diversity with implications for ENSO-mean state interaction

    NASA Astrophysics Data System (ADS)

    Lemmon, Danielle E.; Karnauskas, Kristopher B.

    2018-04-01

    Recent research on the El Niño-Southern Oscillation (ENSO) phenomenon increasingly reveals the highly complex and diverse nature of ENSO variability. A method of quantifying ENSO spatial pattern uniqueness and diversity is presented, which enables (1) formally distinguishing between unique and "canonical" El Niño events, (2) testing whether historical model simulations aptly capture ENSO diversity by comparing with instrumental observations, (3) projecting future ENSO diversity using future model simulations, (4) understanding the dynamics that give rise to ENSO diversity, and (5) analyzing the associated diversity of ENSO-related atmospheric teleconnection patterns. Here we develop a framework for measuring El Niño spatial SST pattern uniqueness and diversity for a given set of El Niño events using two indices, the El Niño Pattern Uniqueness (EPU) index and El Niño Pattern Diversity (EPD) index, respectively. By applying this framework to instrumental records, we independently confirm a recent regime shift in El Niño pattern diversity with an increase in unique El Niño event sea surface temperature patterns. However, the same regime shift is not observed in historical CMIP5 model simulations; moreover, a comparison between historical and future CMIP5 model scenarios shows no robust change in future ENSO diversity. Finally, we support recent work that asserts a link between the background cooling of the eastern tropical Pacific and changes in ENSO diversity. This robust link between an eastern Pacific cooling mode and ENSO diversity is observed not only in instrumental reconstructions and reanalysis, but also in historical and future CMIP5 model simulations.

  12. Intensified ENSO-Driven Precipitation Teleconnections in the Future

    NASA Astrophysics Data System (ADS)

    Bonfils, C.; Santer, B. D.; Phillips, T. J.; Marvel, K.; Leung, L. R.; Doutriaux, C.

    2014-12-01

    The El Niño-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. Most climate models project an increase in the frequency of extreme El Niño events under increased greenhouse-gas (GHG) forcing. However, it is unclear how other aspects of ENSO and ENSO-driven teleconnections will evolve in the future. Here, we identify in 20th century sea-surface temperature (SST) observations a time-invariant ENSO-like (ENSOL) pattern that is largely uncontaminated by GHG forcing. We use this pattern to investigate the future precipitation (P) response to ENSO-like SST anomalies. Models that better capture observed ENSOL characteristics produce P teleconnection patterns that are in better accord with observations and more stationary in the 21st century. We decompose the future P response to ENSOL into the sum of three terms: (1) the change in P mean state, (2) the historical P response to ENSOL, and (3) a future enhancement in the P response to ENSOL. In many regions, this last term can aggravate the P extremes associated with ENSO variability. This simple decomposition allows us to identify regions likely to experience ENSOL-induced P changes that are without precedent in the current climate. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  13. Record-breaking warming and extreme drought in the Amazon rainforest during the course of El Niño 2015-2016

    NASA Astrophysics Data System (ADS)

    Jiménez-Muñoz, Juan C.; Mattar, Cristian; Barichivich, Jonathan; Santamaría-Artigas, Andrés; Takahashi, Ken; Malhi, Yadvinder; Sobrino, José A.; Schrier, Gerard Van Der

    2016-09-01

    The El Niño-Southern Oscillation (ENSO) is the main driver of interannual climate extremes in Amazonia and other tropical regions. The current 2015/2016 EN event was expected to be as strong as the EN of the century in 1997/98, with extreme heat and drought over most of Amazonian rainforests. Here we show that this protracted EN event, combined with the regional warming trend, was associated with unprecedented warming and a larger extent of extreme drought in Amazonia compared to the earlier strong EN events in 1982/83 and 1997/98. Typical EN-like drought conditions were observed only in eastern Amazonia, whilst in western Amazonia there was an unusual wetting. We attribute this wet-dry dipole to the location of the maximum sea surface warming on the Central equatorial Pacific. The impacts of this climate extreme on the rainforest ecosystems remain to be documented and are likely to be different to previous strong EN events.

  14. Record-breaking warming and extreme drought in the Amazon rainforest during the course of El Niño 2015-2016.

    PubMed

    Jiménez-Muñoz, Juan C; Mattar, Cristian; Barichivich, Jonathan; Santamaría-Artigas, Andrés; Takahashi, Ken; Malhi, Yadvinder; Sobrino, José A; Schrier, Gerard van der

    2016-09-08

    The El Niño-Southern Oscillation (ENSO) is the main driver of interannual climate extremes in Amazonia and other tropical regions. The current 2015/2016 EN event was expected to be as strong as the EN of the century in 1997/98, with extreme heat and drought over most of Amazonian rainforests. Here we show that this protracted EN event, combined with the regional warming trend, was associated with unprecedented warming and a larger extent of extreme drought in Amazonia compared to the earlier strong EN events in 1982/83 and 1997/98. Typical EN-like drought conditions were observed only in eastern Amazonia, whilst in western Amazonia there was an unusual wetting. We attribute this wet-dry dipole to the location of the maximum sea surface warming on the Central equatorial Pacific. The impacts of this climate extreme on the rainforest ecosystems remain to be documented and are likely to be different to previous strong EN events.

  15. The natural oscillation of two types of ENSO events based on analyses of CMIP5 model control runs

    NASA Astrophysics Data System (ADS)

    Xu, Kang; Su, Jingzhi; Zhu, Congwen

    2014-07-01

    The eastern- and central-Pacific El Niño-Southern Oscillation (EP- and CP-ENSO) have been found to be dominant in the tropical Pacific Ocean, and are characterized by interannual and decadal oscillation, respectively. In the present study, we defined the EP- and CP-ENSO modes by singular value decomposition (SVD) between SST and sea level pressure (SLP) anomalous fields. We evaluated the natural features of these two types of ENSO modes as simulated by the pre-industrial control runs of 20 models involved in phase five of the Coupled Model Intercomparison Project (CMIP5). The results suggested that all the models show good skill in simulating the SST and SLP anomaly dipolar structures for the EP-ENSO mode, but only 12 exhibit good performance in simulating the tripolar CP-ENSO modes. Wavelet analysis suggested that the ensemble principal components in these 12 models exhibit an interannual and multi-decadal oscillation related to the EP- and CP-ENSO, respectively. Since there are no changes in external forcing in the pre-industrial control runs, such a result implies that the decadal oscillation of CP-ENSO is possibly a result of natural climate variability rather than external forcing.

  16. Heartbeat of the Southern Oscillation explains ENSO climatic resonances

    NASA Astrophysics Data System (ADS)

    Bruun, John T.; Allen, J. Icarus; Smyth, Timothy J.

    2017-08-01

    The El Niño-Southern Oscillation (ENSO) nonlinear oscillator phenomenon has a far reaching influence on the climate and human activities. The up to 10 year quasi-period cycle of the El Niño and subsequent La Niña is known to be dominated in the tropics by nonlinear physical interaction of wind with the equatorial waveguide in the Pacific. Long-term cyclic phenomena do not feature in the current theory of the ENSO process. We update the theory by assessing low (>10 years) and high (<10 years) frequency coupling using evidence across tropical, extratropical, and Pacific basin scales. We analyze observations and model simulations with a highly accurate method called Dominant Frequency State Analysis (DFSA) to provide evidence of stable ENSO features. The observational data sets of the Southern Oscillation Index (SOI), North Pacific Index Anomaly, and ENSO Sea Surface Temperature Anomaly, as well as a theoretical model all confirm the existence of long-term and short-term climatic cycles of the ENSO process with resonance frequencies of {2.5, 3.8, 5, 12-14, 61-75, 180} years. This fundamental result shows long-term and short-term signal coupling with mode locking across the dominant ENSO dynamics. These dominant oscillation frequency dynamics, defined as ENSO frequency states, contain a stable attractor with three frequencies in resonance allowing us to coin the term Heartbeat of the Southern Oscillation due to its characteristic shape. We predict future ENSO states based on a stable hysteresis scenario of short-term and long-term ENSO oscillations over the next century.Plain Language SummaryThe Pacific El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) nonlinear oscillator phenomenon has a far reaching influence on the climate and our human activities. This work can help predict both long-term and short-term future <span class="hlt">ENSO</span> <span class="hlt">events</span> and to assess the risk of future climate hysteresis changes: is the elastic band that regulates the <span class="hlt">ENSO</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/481955','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/481955"><span>Proxy Records of the Indonesian Low and the El Ni{tilde n}o-Southern Oscillation (<span class="hlt">ENSO</span>) from Stable Isotope Measurements of Indonesian Reef Corals</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Moore, M.D.</p> <p>1995-12-31</p> <p>The Earth`s largest atmospheric convective center is the Indonesian Low. It generates the Australasian monsoon, drives the zonal tropospheric Walker Circulation, and is implicated in the genesis of the El Nino-Southern Oscillation (<span class="hlt">ENSO</span>). The long-term variability of the Indonesian Low is poorly characterized, yet such information is crucial for evaluating whether changes in the strength and frequency of <span class="hlt">ENSO</span> <span class="hlt">events</span> are a possible manifestation of global <span class="hlt">warming</span>. Stable oxygen isotope ratios ({delta}{sup 18}O) in shallow-water reef coral skeletons track topical convective activity over hundreds of years because the input of isotopically-depleted rainwater dilutes seawater {delta}{sup 18}O. Corals also impose amore » temperature-dependent fractionation on {delta}{sup 18}O, but where annual rainfall is high and sea surface temperature (SST) variability is low the freshwater flux effect dominates.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2381G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2381G"><span>Decadal modulation of the relationship between intraseasonal tropical variability and <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gushchina, Daria; Dewitte, Boris</p> <p>2018-05-01</p> <p>The El Niño Southern Oscillation (<span class="hlt">ENSO</span>) amplitude is modulated at decadal timescales, which, over the last decades, has been related to the low-frequency changes in the frequency of occurrence of the two types of El Niño <span class="hlt">events</span>, that is the Eastern Pacific (EP) and Central Pacific (CP) El Niños. Meanwhile <span class="hlt">ENSO</span> is tightly linked to the intraseasonal tropical variability (ITV) that is generally enhanced prior to El Niño development and can act as a trigger of the <span class="hlt">event</span>. Here we revisit the ITV/<span class="hlt">ENSO</span> relationship taking into account changes in <span class="hlt">ENSO</span> properties over the last six decades. The focus is on two main components of ITV, the Madden-Julian Oscillation (MJO) and convectively coupled equatorial Rossby waves (ER). We show that the ITV/<span class="hlt">ENSO</span> relationship exhibits a decadal modulation that is not related in a straight-forward manner to the change in occurrence of El Niño types and Pacific decadal modes. While enhanced MJO activity associated to EP El Niño development mostly took place over the period 1985-2000, the ER activity is enhanced prior to El Niño development over the whole period with a tendency to relate more to CP El Niño than to EP El Niño. In particular the relationship between ER activity and <span class="hlt">ENSO</span> was particularly strong for the period 2000-2015, which results in a significant positive long-term trend of the predictive value of ER activity. The statistics of the MJO and ER activity is consistent with the hypothesis that they can be considered a state-dependent noise for <span class="hlt">ENSO</span> linked to distinct lower frequency climate modes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5015046','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5015046"><span>Record-breaking <span class="hlt">warming</span> and extreme drought in the Amazon rainforest during the course of El Niño 2015–2016</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jiménez-Muñoz, Juan C.; Mattar, Cristian; Barichivich, Jonathan; Santamaría-Artigas, Andrés; Takahashi, Ken; Malhi, Yadvinder; Sobrino, José A.; Schrier, Gerard van der</p> <p>2016-01-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is the main driver of interannual climate extremes in Amazonia and other tropical regions. The current 2015/2016 EN <span class="hlt">event</span> was expected to be as strong as the EN of the century in 1997/98, with extreme heat and drought over most of Amazonian rainforests. Here we show that this protracted EN <span class="hlt">event</span>, combined with the regional <span class="hlt">warming</span> trend, was associated with unprecedented <span class="hlt">warming</span> and a larger extent of extreme drought in Amazonia compared to the earlier strong EN <span class="hlt">events</span> in 1982/83 and 1997/98. Typical EN-like drought conditions were observed only in eastern Amazonia, whilst in western Amazonia there was an unusual wetting. We attribute this wet-dry dipole to the location of the maximum sea surface <span class="hlt">warming</span> on the Central equatorial Pacific. The impacts of this climate extreme on the rainforest ecosystems remain to be documented and are likely to be different to previous strong EN <span class="hlt">events</span>. PMID:27604976</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171263','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171263"><span>Contrasting Indian Ocean SST Variability With and Without <span class="hlt">ENSO</span> Influence: A Coupled Atmosphere-Ocean GCM Study</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yu, Jin-Yi; Lau, K. M.</p> <p>2004-01-01</p> <p>In this study, we perform experiments with a coupled atmosphere-ocean general circulation model (CGCM) to examine <span class="hlt">ENSO</span>'s influence on the interannual sea surface temperature (SST) variability of the tropical Indian Ocean. The control experiment includes both the Indian and Pacific Oceans in the ocean model component of the CGCM (the Indo-Pacific Run). The anomaly experiment excludes <span class="hlt">ENSOs</span> influence by including only the Indian Ocean while prescribing monthly-varying climatological SSTs for the Pacific Ocean (the Indian-Ocean Run). In the Indo-Pacific Run, an oscillatory mode of the Indian Ocean SST variability is identified by a multi-channel singular spectral analysis (MSSA). The oscillatory mode comprises two patterns that can be identified with the Indian Ocean Zonal Mode (IOZM) and a basin-wide <span class="hlt">warming</span>/cooling mode respectively. In the model, the IOZM peaks about 3-5 months after <span class="hlt">ENSO</span> reaches its maximum intensity. The basin mode peaks 8 months after the IOZM. The timing and associated SST patterns suggests that the IOZM is related to <span class="hlt">ENSO</span>, and the basin- wide <span class="hlt">warming</span>/cooling develops as a result of the decay of the IOZM spreading SST anomalies from western Indian Ocean to the eastern Indian Ocean. In contrast, in the Indian-Ocean Run, no oscillatory modes can be identified by the MSSA, even though the Indian Ocean SST variability is characterized by east-west SST contrast patterns similar to the IOZM. In both control and anomaly runs, IOZM-like SST variability appears to be associated with forcings from fluctuations of the Indian monsoon. Our modeling results suggest that the oscillatory feature of the IOZM is primarily forced by <span class="hlt">ENSO</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active"><span>9</span></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_9 --> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AtmEn.167..426W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AtmEn.167..426W"><span><span class="hlt">ENSO</span>-related PM10 variability on the Korean Peninsula</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wie, Jieun; Moon, Byung-Kwon</p> <p>2017-10-01</p> <p>Particulate matter, defined as particles of less than 10 μm in diameter (PM10), was analyzed over the Korean Peninsula from 2001 to 2015 to examine the influence of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) on subseasonal PM10 variability. The PM10 data were obtained from 151 air quality monitoring stations provided by the Korea Environment Corporation (KECO). Lead-lag correlation analysis, which was performed to investigate the connection between NDJF (November-February) NINO3 index and seasonal mean PM10 data, did not yield any statistically significant correlations. However, using five-pentad moving-averaged PM10 data, statistically significant correlations between NDJF NINO3 index and PM10 variability were found in four subseasonal periods, with alternating positive and negative correlations. In the periods during which PM10 levels on the Korean Peninsula were positively (negatively) correlated with the <span class="hlt">ENSO</span> index, the positive PM10 anomalies are associated with El Niño (La Niña) years, which implies that the occurrence of high-PM10 <span class="hlt">events</span> could be modulated by the <span class="hlt">ENSO</span> phase. In addition, this <span class="hlt">ENSO</span>-related PM10 variation is negatively correlated with <span class="hlt">ENSO</span>-related precipitation in the Korean Peninsula, indicating that more (less) wet deposition leads to lower (higher) PM10 level. Therefore, we conclude that the <span class="hlt">ENSO</span>-induced precipitation anomalies over the Korean Peninsula are mainly responsible for <span class="hlt">ENSO</span>-related PM10 variations. This study will be helpful for further identifying detailed chemistry-climate processes that control PM10 concentrations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP33A1316P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP33A1316P"><span>Fossil Coral Records of <span class="hlt">ENSO</span> during the Last Glacial Period</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Partin, J. W.; Taylor, F. W.; Shen, C. C.; Edwards, R. L.; Quinn, T. M.; DiNezro, P.</p> <p>2017-12-01</p> <p> to climate model simulations in order to elucidate the mechanisms driving the changes in <span class="hlt">ENSO</span>. The proposed research activities will shed light on the sensitivity of <span class="hlt">ENSO</span> to external forcings, a highly critical issue given that climate model projections used for future climate projection do not agree if <span class="hlt">ENSO</span> will strengthen or weaken as the Earth <span class="hlt">warms</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004GeoRL..3115207B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004GeoRL..3115207B"><span>El Niño suppresses Antarctic <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bertler, Nancy A. N.; Barrett, Peter J.; Mayewski, Paul A.; Fogt, Ryan L.; Kreutz, Karl J.; Shulmeister, James</p> <p>2004-08-01</p> <p>Here we present new isotope records derived from snow samples from the McMurdo Dry Valleys, Antarctica and re-analysis data of the European Centre for Medium-Range Weather Forecasts (ERA-40) to explain the connection between the <span class="hlt">warming</span> of the Pacific sector of the Southern Ocean [Jacka and Budd, 1998; Jacobs et al., 2002] and the current cooling of the terrestrial Ross Sea region [Doran et al., 2002a]. Our analysis confirms previous findings that the <span class="hlt">warming</span> is linked to the El Niño Southern Oscillation (<span class="hlt">ENSO</span>) [Kwok and Comiso, 2002a, 2002b; Carleton, 2003; Ribera and Mann, 2003; Turner, 2004], and provides new evidence that the terrestrial cooling is caused by a simultaneous <span class="hlt">ENSO</span> driven change in atmospheric circulation, sourced in the Amundsen Sea and West Antarctica.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1330473-distinct-persistence-barriers-two-types-enso-persistence-barriers-two-enso-types','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1330473-distinct-persistence-barriers-two-types-enso-persistence-barriers-two-enso-types"><span>Distinct persistence barriers in two types of <span class="hlt">ENSO</span>: PERSISTENCE BARRIERS OF TWO <span class="hlt">ENSO</span> TYPES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Ren, Hong-Li; Jin, Fei-Fei; Tian, Ben</p> <p></p> <p>El Niño–Southern Oscillation (<span class="hlt">ENSO</span>) is usually subject to a persistence barrier (PB) in boreal spring. This study quantifies the PB and then reveals its distinct features in the two types of <span class="hlt">ENSO</span>, the eastern Pacific (EP) and central Pacific (CP) types. We suggest that the PB of <span class="hlt">ENSO</span> can be measured by the maximum rate of autocorrelation decline of Niño sea surface temperature anomaly (SSTA) indices. Results show that the PB of <span class="hlt">ENSO</span> generally occurs in boreal late spring to early summer in terms of Niño3.4 index, and the EP <span class="hlt">ENSO</span> has the PB in late spring, while the CPmore » type has the PB in summer. By defining an index to quantify PB intensity of <span class="hlt">ENSO</span>, we find that the CP <span class="hlt">ENSO</span> type features a much weaker PB, compared to the EP type, and the PB intensity of equatorial SSTAs is larger over the EP than the western Pacific and the far EP.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1330473-distinct-persistence-barriers-two-types-enso-persistence-barriers-two-enso-types','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1330473-distinct-persistence-barriers-two-types-enso-persistence-barriers-two-enso-types"><span>Distinct persistence barriers in two types of <span class="hlt">ENSO</span>: PERSISTENCE BARRIERS OF TWO <span class="hlt">ENSO</span> TYPES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Ren, Hong-Li; Jin, Fei-Fei; Tian, Ben; ...</p> <p>2016-10-30</p> <p>El Niño–Southern Oscillation (<span class="hlt">ENSO</span>) is usually subject to a persistence barrier (PB) in boreal spring. This study quantifies the PB and then reveals its distinct features in the two types of <span class="hlt">ENSO</span>, the eastern Pacific (EP) and central Pacific (CP) types. We suggest that the PB of <span class="hlt">ENSO</span> can be measured by the maximum rate of autocorrelation decline of Niño sea surface temperature anomaly (SSTA) indices. Results show that the PB of <span class="hlt">ENSO</span> generally occurs in boreal late spring to early summer in terms of Niño3.4 index, and the EP <span class="hlt">ENSO</span> has the PB in late spring, while the CPmore » type has the PB in summer. By defining an index to quantify PB intensity of <span class="hlt">ENSO</span>, we find that the CP <span class="hlt">ENSO</span> type features a much weaker PB, compared to the EP type, and the PB intensity of equatorial SSTAs is larger over the EP than the western Pacific and the far EP.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS34A..08C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS34A..08C"><span>Biological consequences of <span class="hlt">ENSO</span>: What have we learned recently?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chavez, F.; Messié, M.</p> <p>2013-12-01</p> <p>A comprehensive theory regarding the biological response to El Niño was developed from observations during the 1982-83 <span class="hlt">event</span>. The theory has withstood the test of time but additional information from remote sensing and growing in situ databases has allowed for a more comprehensive evaluation of the biological consequences of the full <span class="hlt">ENSO</span> cycle on global scales and in relation to other climatic variability and change. Here we review the major developments over the past few decades that include a greater appreciation for the cool or La Niña phase and the relation of <span class="hlt">ENSO</span> to other climatic variability including the Pacific Decadal Oscillation and the North Pacific Gyre Oscillation. The use of <span class="hlt">ENSO</span> as an analog for biological consequences of a warmer world is also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A51O0297X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A51O0297X"><span>Is <span class="hlt">ENSO</span> related to 2015 Easter Star Capsized on the Yangtze River of China?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xie, P.</p> <p>2015-12-01</p> <p>Natural disasters have profound effects on community security and economic damage of China's Hubei province. In June 1st, 2015, a cruise ship, Easter Star, capsized on Yangtze River in Hubei province with 442 died. What reason gives rise to such strong convection causing ship sunk? Based on the wind disasters of Hubei province happened in 1963-2015, this study analyzes their features bytime-series regression, and correlates them to global El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span>. The compared results demonstrated that the wind disasters shown an increasing tendency. There are two peaks corresponding to the strongest <span class="hlt">ENSO</span> peaks during the past 50 years; each peak lasts two-three years. The facts demonstrated an essential linear relation between the <span class="hlt">ENSO</span> phenomena and wind disasters in Hubei province. 2015 Easter Star capsized happened at current El Niño <span class="hlt">event</span> in 2014-2015. We also observed that the historical wind disasters appeared in seasonal variation. Over 90% <span class="hlt">events</span> concentrated in spring and summer; very few <span class="hlt">events</span> happened in autumn and winter. Moreover, the disasters depend on the geographic conditions. Most disasters concentrated in four zones, named as Xingshan-Baokang, Xuanen, Wufeng-Yichang, Jingzhou-Gongan, in which Xingshan and Changyang are the two most density of zones. Yangtze River provides an air flowing conduct for strong convective winds. It can be concluded that the strong convection causing 2015 Easter Star capsized is related to current global <span class="hlt">ENSO</span> phenomenon.Keywords: <span class="hlt">ENSO</span>, wind disaster, time-series regression analysis, Easter Star, Yangtze River, Hubei Province,</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ClDy...46.2155P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ClDy...46.2155P"><span>Modulation of equatorial Pacific westerly/easterly wind <span class="hlt">events</span> by the Madden-Julian oscillation and convectively-coupled Rossby waves</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Puy, Martin; Vialard, J.; Lengaigne, M.; Guilyardi, E.</p> <p>2016-04-01</p> <p>Synoptic wind <span class="hlt">events</span> in the equatorial Pacific strongly influence the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) evolution. This paper characterizes the spatio-temporal distribution of Easterly (EWEs) and Westerly Wind <span class="hlt">Events</span> (WWEs) and quantifies their relationship with intraseasonal and interannual large-scale climate variability. We unambiguously demonstrate that the Madden-Julian Oscillation (MJO) and Convectively-coupled Rossby Waves (CRW) modulate both WWEs and EWEs occurrence probability. 86 % of WWEs occur within convective MJO and/or CRW phases and 83 % of EWEs occur within the suppressed phase of MJO and/or CRW. 41 % of WWEs and 26 % of EWEs are in particular associated with the combined occurrence of a CRW/MJO, far more than what would be expected from a random distribution (3 %). Wind <span class="hlt">events</span> embedded within MJO phases also have a stronger impact on the ocean, due to a tendency to have a larger amplitude, zonal extent and longer duration. These findings are robust irrespective of the wind <span class="hlt">events</span> and MJO/CRW detection methods. While WWEs and EWEs behave rather symmetrically with respect to MJO/CRW activity, the impact of <span class="hlt">ENSO</span> on wind <span class="hlt">events</span> is asymmetrical. The WWEs occurrence probability indeed increases when the <span class="hlt">warm</span> pool is displaced eastward during El Niño <span class="hlt">events</span>, an increase that can partly be related to interannual modulation of the MJO/CRW activity in the western Pacific. On the other hand, the EWEs modulation by <span class="hlt">ENSO</span> is less robust, and strongly depends on the wind <span class="hlt">event</span> detection method. The consequences of these results for <span class="hlt">ENSO</span> predictability are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1913121L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1913121L"><span><span class="hlt">ENSO</span> activity during the last climate cycle using IFA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leduc, Guillaume; Vidal, Laurence; Thirumalai, Kaustubh</p> <p>2017-04-01</p> <p>The El Niño / Southern Oscillation (<span class="hlt">ENSO</span>) is the principal mode of interannual climate variability and affects key climate parameters such as low-latitude rainfall variability. Anticipating future <span class="hlt">ENSO</span> variability under anthropogenic forcing is vital due to its profound socioeconomic impact. Fossil corals suggest that 20th century <span class="hlt">ENSO</span> variance is particularly high as compared to other time periods of the Holocene (Cobb et al., 2013, Science), the Last Glacial Maximum (Ford et al., 2015, Science) and the last glacial period (Tudhope et al., 2001, Science). Yet, recent climate modeling experiments suggest an increase in the frequency of both El Niño (Cai et al., 2014, Nature Climate Change) and La Niña (Cai et al., 2015, Nature Climate Change) <span class="hlt">events</span>. We have expanded an Individual Foraminifera Analysis (IFA) dataset using the thermocline-dwelling N. dutertrei on a marine core collected in the Panama Basin (Leduc et al., 2009, Paleoceanography), that has proven to be a skillful way to reconstruct the <span class="hlt">ENSO</span> (Thirumalai et al., 2013, Paleoceanography). Our new IFA dataset comprehensively covers the Holocene, the last deglaciation and Termination II (MIS5/6) time windows. We will also use previously published data from the Marine Isotope Stage 3 (MIS3). Our dataset confirms variable <span class="hlt">ENSO</span> intensity during the Holocene and weaker activity during LGM than during the Holocene. As a next step, <span class="hlt">ENSO</span> activity will be discussed with respect to the contrasting climatic background of the analysed time windows (millenial-scale variability, Terminations).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JHyd..530...51S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JHyd..530...51S"><span>A global analysis of the asymmetric effect of <span class="hlt">ENSO</span> on extreme precipitation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Xun; Renard, Benjamin; Thyer, Mark; Westra, Seth; Lang, Michel</p> <p>2015-11-01</p> <p>The global and regional influence of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon on extreme precipitation was analyzed using a global database comprising over 7000 high quality observation sites. To better quantify possible changes in relatively rare design-relevant precipitation quantiles (e.g. the 1 in 10 year <span class="hlt">event</span>), a Bayesian regional extreme value model was used, which employed the Southern Oscillation Index (SOI) - a measure of <span class="hlt">ENSO</span> - as a covariate. Regions found to be influenced by <span class="hlt">ENSO</span> include parts of North and South America, southern and eastern Asia, South Africa, Australia and Europe. The season experiencing the greatest <span class="hlt">ENSO</span> effect varies regionally, but in most of the <span class="hlt">ENSO</span>-affected regions the strongest effect happens in boreal winter, during which time the 10-year precipitation for |SOI| = 20 (corresponding to either a strong El Niño or La Niña episode) can be up to 50% higher or lower than for SOI = 0 (a neutral phase). Importantly, the effect of <span class="hlt">ENSO</span> on extreme precipitation is asymmetric, with most parts of the world experiencing a significant effect only for a single <span class="hlt">ENSO</span> phase. This finding has important implications on the current understanding of how <span class="hlt">ENSO</span> influences extreme precipitation, and will enable a more rigorous theoretical foundation for providing quantitative extreme precipitation intensity predictions at seasonal timescales. We anticipate that incorporating asymmetric impacts of <span class="hlt">ENSO</span> on extreme precipitation will help lead to better-informed climate-adaptive design of flood-sensitive infrastructure.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QSRv..153..139P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QSRv..153..139P"><span>Changes in El Niño - Southern Oscillation (<span class="hlt">ENSO</span>) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palmer, Jonathan G.; Turney, Chris S. M.; Cook, Edward R.; Fenwick, Pavla; Thomas, Zoë; Helle, Gerhard; Jones, Richard; Clement, Amy; Hogg, Alan; Southon, John; Bronk Ramsey, Christopher; Staff, Richard; Muscheler, Raimund; Corrège, Thierry; Hua, Quan</p> <p>2016-12-01</p> <p>The <span class="hlt">warming</span> trend at the end of the last glacial was disrupted by rapid cooling clearly identified in Greenland (Greenland Stadial 1 or GS-1) and Europe (Younger Dryas Stadial or YD). This reversal to glacial-like conditions is one of the best known examples of abrupt change but the exact timing and global spatial extent remain uncertain. Whilst the wider Atlantic region has a network of high-resolution proxy records spanning GS-1, the Pacific Ocean suffers from a scarcity of sub-decadally resolved sequences. Here we report the results from an investigation into a tree-ring chronology from northern New Zealand aimed at addressing the paucity of data. The conifer tree species kauri (Agathis australis) is known from contemporary studies to be sensitive to regional climate changes. An analysis of a 'historic' 452-year kauri chronology confirms a tropical-Pacific teleconnection via the El Niño - Southern Oscillation (<span class="hlt">ENSO</span>). We then focus our study on a 1010-year sub-fossil kauri chronology that has been precisely dated by comprehensive radiocarbon dating and contains a striking ring-width downturn between ∼12,500 and 12,380 cal BP within GS-1. Wavelet analysis shows a marked increase in <span class="hlt">ENSO</span>-like periodicities occurring after the downturn <span class="hlt">event</span>. Comparison to low- and mid-latitude Pacific records suggests a coherency with <span class="hlt">ENSO</span> and Southern Hemisphere atmospheric circulation change during this period. The driver(s) for this climate <span class="hlt">event</span> remain unclear but may be related to solar changes that subsequently led to establishment and/or increased expression of <span class="hlt">ENSO</span> across the mid-latitudes of the Pacific, seemingly independent of the Atlantic and polar regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.1577N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.1577N"><span>Understanding the <span class="hlt">Warm</span> Water Volume Precursor of <span class="hlt">ENSO</span> <span class="hlt">Events</span> and its Interdecadal Variation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neske, S.; McGregor, S.</p> <p>2018-02-01</p> <p>A wind forced ocean model is used to decompose the equatorial Pacific <span class="hlt">warm</span> water volume (WWV) between 1980 and 2016 into two components: the (i) adjusted wind response, which is found by letting the model evolve unforced for three months, and (ii) instantaneous wind response, which are the instantaneous WWV changes due to Ekman transports. Our results suggest that roughly half of WWV variability is only as predictable as the winds that drive the instantaneous change. Separate examinations of pre-2000 and post-2000 periods reveal (i) nearly equal importance of instantaneous and adjusted responses for the pre-2000 period and (ii) dominance of the instantaneous response during the post-2000 period, which is most apparent during the recharged phase. This increasing instantaneous contribution prominence explains the post-2000 reduction in WWV/El Niño-Southern Oscillation sea surface temperature lead times (from six to nine months pre-2000 down to three months post-2000) and is consistent with the reduction in post-2000 El Niño-Southern Oscillation prediction skill.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1918230T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1918230T"><span>The role of sea surface salinity in <span class="hlt">ENSO</span> related water cycle anomaly</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tang, Wenqing; Yueh, Simon</p> <p>2017-04-01</p> <p>This study investigates the role of sea surface salinity (SSS) in the water cycle anomaly associated with El Niño Southern Oscillation (<span class="hlt">ENSO</span>). The 2015-16 El Niño, one of the strongest <span class="hlt">ENSO</span> <span class="hlt">events</span> observed in centuries, coincident with unprecedented coverage of spacebased remote sensing of SSS over global oceans. We analyze three SSS data sets: from the NASA's missions of SMAP and Aquarius, and the ESA's Soil Moisture and Ocean Salinity (SMOS). One typical characteristics of an <span class="hlt">ENSO</span> <span class="hlt">event</span> is the zonal displacement of the Western equatorial Pacific Fresh Pool (WPFP). The edge of the pool extends eastward during El Niño, retreats westward during La Niña. For super El Niño, the eastern edge of WPFP extends much more east across the equatorial Pacific. Indeed, SSS from SMAP reveals much stronger eastward migration of WPFP starting in April 2015. The eastern edge of WPFP reached 140°W in March 2016, about 40° more eastward extension than Aquarius observed in previous years. In the following months from March to June 2016, WPFP retreated westward, coincident with the ending of this strong El Niño <span class="hlt">event</span> [WMO, El Nino/La Nina update, 2016]. SMOS data shows similar feature, confirming that there is no systematic biases between SMAP and Aquarius retrievals. We examine the linkage between the observed SSS variation and <span class="hlt">ENSO</span> related water cycle anomaly by integrated analysis of SSS data sets in conjunction with other satellite and in situ measurements on rain, wind, evaporation and ocean currents. Based on the governing equation of the mixed layer salt budget, the freshwater exchange between air-sea interfaces is estimated as residual of the mixed-layer salinity (MLS) temporal change and advection (Focean), as an alternative to evaporation minus precipitation (FE-P). We analyzed the spatial and temporal variation of Focean and FE-P to explore the anomalous signature in the oceanic and atmospheric branches of the water cycle associated with 2015/16 <span class="hlt">ENSO</span>. The maximum</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSAH13A..07B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSAH13A..07B"><span>Spatial and Temporal Changes in Coral Community Responses to Ocean <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Barkley, H.; Cohen, A. L.</p> <p>2016-02-01</p> <p>Tropical Pacific sea surface temperature is projected to rise 2-3°C by the end of this century, fueling efforts to identify thermally-tolerant reef communities that have the best chance of surviving future climate change. We used skeletal indicators of thermal stress in massive Porites corals collected across the Palau archipelago to document spatial and temporal changes in community-scale tolerance to anomalous <span class="hlt">warm</span> <span class="hlt">events</span> associated with the 1998 and 2010 Pacific <span class="hlt">ENSOs</span>. Within communities where bleaching was documented by visual surveys, we find a strong correlation between percent bleaching and the proportion of surviving Porites colonies exhibiting skeletal density anomalies or "stress bands". Using this relationship, we reconstructed the intensity and spatial patterns of bleaching during the 1998 <span class="hlt">ENSO</span> <span class="hlt">event</span> when survey data are limited. On exposed barrier reefs and inshore fringing reefs, the proportion of corals with 1998 stress bands (60% and 40% respectively) was consistent with that expected from DHW predictions and post-bleaching surveys. Conversely, in the Rock Island bays, where ambient temperatures were highest, no 1998 stress bands were recorded. However, these corals did respond to the 2010 thermal anomaly with the appearance of stress bands and an abrupt decline in calcification. The reasons for this apparent shift in thermal tolerance in response to the relatively weak 2010 <span class="hlt">warming</span> are not yet clear. While the interplay of temperature with other environmental variables including light and flow cannot yet be ruled out, stressors associated with an increase in human activities, including tourism, on Palau are also considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PrOce.140....1D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PrOce.140....1D"><span><span class="hlt">ENSO</span> and anthropogenic impacts on phytoplankton diversity in tropical coastal waters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doan-Nhu, Hai; Nguyen-Ngoc, Lam; Nguyen, Chi-Thoi</p> <p>2016-01-01</p> <p>16-year phytoplankton data were analysed to assess <span class="hlt">ENSO</span> and anthropogenic impacts on biodiversity and community structure at 3 locations (Nha-Trang and Phan-Thiet Bays and near Phu-Qui Island) in South Centre Viet Nam to understand (1) the primary scales of change in phytoplankton community structure, and traditional and taxonomic diversity indices; (2) the significance of environmental changes and/or climate variability on phytoplankton diversity; and (3) the usefulness of these long-term data for analysing future impacts of anthropogenic and climate changes. Traditional and taxonomic diversity indices were compared and tested in linkage with environmental conditions and <span class="hlt">ENSO</span>. Nutrient data indicated stronger environmental impacts in Phan-Thiet Bay, milder in Nha-Trang Bay and less noticeable near Phu-Qui Island. There were measurable impacts of both anthropogenic and <span class="hlt">ENSO</span> on phytoplankton at different locations in various parameters, e.g. species number, diversity and community structures. The lowest diversity was recorded in the most anthropogenically impacted site, Phan-Thiet Bay. Although a stronger impact on phytoplankton was recorded in <span class="hlt">ENSO</span> year in Phan Thiet Bay, quantitative separation between anthropogenic and <span class="hlt">ENSO</span> impacts using phytoplankton biodiversity indices was impossible. In the waters with less anthropogenic impacts, <span class="hlt">ENSO</span> effects on taxonomic diversity was better indicated by negative phytoplankton responses to the ONI index (Nha-Trang Bay) and recovery of phytoplankton after the <span class="hlt">ENSO</span> <span class="hlt">events</span> (near Phu-Qui Island). Among the diversity indices, the taxonomic diversity indices (e.g. Δ+ and Λ+) better described impacts of <span class="hlt">ENSO</span> than the traditional ones.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.6073P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.6073P"><span>Interhemispheric temperature difference as a predictor of boreal winter <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piskozub, Jacek; Gutowska, Dorota</p> <p>2013-04-01</p> <p>We use statistical analysis to show statistically significant relationship between the boreal winter MEI index of <span class="hlt">ENSO</span> and HadCRUT3 temperature difference between Northern and Southern hemispheres (NH - SH) during the preceding summer. Correlation values increase (in absolute terms) if the correlated time periods are increased from month to seasonal length. For example December and January (DJ) MEI values anticorrelate stronger with the preceding MJJA period than with any of the four months taken separately. We believe this is further evidence that the correlation is caused by a real physical process as increase of the averaging period tends to reduce statistical noise. The motivation for looking for such a relationship comes from review of literature on paleoclimatic <span class="hlt">ENSO</span> behavior. We have noticed that in many cases relatively cold NH coincided with "strong <span class="hlt">ENSO</span>" (frequent El Niños), for example the Ice Age periods and Little Ice Age. On the other hand periods of relatively <span class="hlt">warm</span> NH (the Holocene climate optimum or Medieval Climate Anomaly) are coincident with frequent or even "permanent" La Niñas. This relationship suggest the influence of the position of Intertropical Convergence Zone (ITCZ) on the frequency of El Niños. The simplest physical mechanism of the relationship is that the positive (negative) NH-SH temperature difference causes a north (south) shift of ITCZ with a parallel shift of trade wind zones. The North-South orographic difference between the Panama Isthmus and the South America may cause stronger (weaker) trade winds in Eastern Tropical Pacific increasing (decreasing) the thermochemical tilt which, in turn, causes a more negative (positive) <span class="hlt">ENSO</span> values. Of course this may be only a first approximation of the real mechanism of this "teleconnection". The correlations we have found are not strong even if statistically significant. For example, the MJJA NH-SH temperature vs. DJ MEI correlation has r = -0.28 implying it explains only 8% of boreal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26PSL.442...61C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26PSL.442...61C"><span>A high-resolution speleothem record of western equatorial Pacific rainfall: Implications for Holocene <span class="hlt">ENSO</span> evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Sang; Hoffmann, Sharon S.; Lund, David C.; Cobb, Kim M.; Emile-Geay, Julien; Adkins, Jess F.</p> <p>2016-05-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is the primary driver of interannual climate variability in the tropics and subtropics. Despite substantial progress in understanding ocean-atmosphere feedbacks that drive <span class="hlt">ENSO</span> today, relatively little is known about its behavior on centennial and longer timescales. Paleoclimate records from lakes, corals, molluscs and deep-sea sediments generally suggest that <span class="hlt">ENSO</span> variability was weaker during the mid-Holocene (4-6 kyr BP) than the late Holocene (0-4 kyr BP). However, discrepancies amongst the records preclude a clear timeline of Holocene <span class="hlt">ENSO</span> evolution and therefore the attribution of <span class="hlt">ENSO</span> variability to specific climate forcing mechanisms. Here we present δ18 O results from a U-Th dated speleothem in Malaysian Borneo sampled at sub-annual resolution. The δ18 O of Borneo rainfall is a robust proxy of regional convective intensity and precipitation amount, both of which are directly influenced by <span class="hlt">ENSO</span> activity. Our estimates of stalagmite δ18 O variance at <span class="hlt">ENSO</span> periods (2-7 yr) show a significant reduction in interannual variability during the mid-Holocene (3240-3380 and 5160-5230 yr BP) relative to both the late Holocene (2390-2590 yr BP) and early Holocene (6590-6730 yr BP). The Borneo results are therefore inconsistent with lacustrine records of <span class="hlt">ENSO</span> from the eastern equatorial Pacific that show little or no <span class="hlt">ENSO</span> variance during the early Holocene. Instead, our results support coral, mollusc and foraminiferal records from the central and eastern equatorial Pacific that show a mid-Holocene minimum in <span class="hlt">ENSO</span> variance. Reduced mid-Holocene interannual δ18 O variability in Borneo coincides with an overall minimum in mean δ18 O from 3.5 to 5.5 kyr BP. Persistent <span class="hlt">warm</span> pool convection would tend to enhance the Walker circulation during the mid-Holocene, which likely contributed to reduced <span class="hlt">ENSO</span> variance during this period. This finding implies that both convective intensity and interannual variability in Borneo are driven by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP23D..04Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP23D..04Z"><span>Reduced <span class="hlt">ENSO</span> Variability at the LGM Revealed by an Isotope-enabled Earth System Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, J.; Liu, Z.; Otto-Bliesner, B. L.; Brady, E. C.; Noone, D.; Zhang, J.; Tomas, R. A.; Jahn, A.; Nusbaumer, J. M.; Wong, T. E.</p> <p>2016-12-01</p> <p>El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) is the most important climate variability at interannual timescale, greatly affecting the weather and climate worldwide. Studying the <span class="hlt">ENSO</span> at the Last Glacial Maximum (LGM, 21 kyrs before present) can help us better understand its dynamics and improve its projections under anthropogenic global <span class="hlt">warming</span>. However, both numerical simulations and paleoclimate reconstructions show contradicting results among themselves, e.g., using the Individual Foraminifera Analysis (IFA) approach, some paleo-records suggest an amplified <span class="hlt">ENSO</span> at the LGM relative to present day; while others indicate a weakened <span class="hlt">ENSO</span>. These contradictions are hard to explore using traditional climate models due to the indirect nature of model-data comparison: numerical models usually simulate variations in climate state variables (e.g., temperature); while reconstructions can only use proxies (e.g., water isotopes) to infer changes in these state variables. Here we employ the recently developed isotope-enabled Community Earth System Model (iCESM) to study the <span class="hlt">ENSO</span> strength at the LGM and attempt to provide a consistent picture between climate model and different reconstructions. We find that <span class="hlt">ENSO</span> at the LGM is about 30% weaker than that of the preindustrial in iCESM, primarily attributable to the weakened atmosphere-ocean coupled feedbacks in a colder climate with a deeper thermocline. With the capability of simulating water isotopes, our model demonstrates that total variance recorded by the IFA water-isotope records in the eastern equatorial Pacific (e.g., Core CD21-30) could actually increase because of an intensified annual cycle, instead of an amplified <span class="hlt">ENSO</span>. Furthermore, our isotope-enabled simulations suggest that caution should be applied when interpreting the subsurface IFA water-isotope records (e.g., Cores CD38-17P and MD02-2529) due to the wide spread of habitat depth of thermocline-dwelling foraminifera and their possible migration with temporally varying</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26394551','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26394551"><span>Distinctive ocean interior changes during the recent <span class="hlt">warming</span> slowdown.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cheng, Lijing; Zheng, Fei; Zhu, Jiang</p> <p>2015-09-23</p> <p>The earth system experiences continuous heat input, but a "climate hiatus" of upper ocean waters has been observed in this century. This leads to a question: where is the extra heat going? Using four in situ observation datasets, we explore the ocean subsurface temperature changes from 2004 to 2013. The observations all show that the ocean has continued to gain heat in this century, which is indicative of anthropogenic global <span class="hlt">warming</span>. However, a distinctive pattern of change in the interior ocean is observed. The sea surface (1-100 m) temperature has decreased in this century, accompanied by <span class="hlt">warming</span> in the 101-300 m layer. This pattern is due to the changes in the frequency of El Niño and La Niña <span class="hlt">events</span> (<span class="hlt">ENSO</span> characteristics), according to both observations and CMIP5 model simulations. In addition, we show for the first time that the ocean subsurface within 301-700 m experienced a net cooling, indicative of another instance of variability in the natural ocean. Furthermore, the ocean layer of 701-1500 m has experienced significant <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSAH13A..05M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSAH13A..05M"><span>Galápagos coral reef persistence after <span class="hlt">ENSO</span> <span class="hlt">warming</span> across an acidification gradient</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Manzello, D.; Enochs, I.; Bruckner, A.; Renaud, P.; Kolodziej, G.; Budd, D. A.; Carlton, R.; Glynn, P.</p> <p>2016-02-01</p> <p>Anthropogenic CO2 is causing <span class="hlt">warming</span> and ocean acidification. Coral reefs are being severely impacted, yet confusion lingers regarding how reefs will respond to these stressors over this century. Since the 1982-1983 El Niño-Southern Oscillation <span class="hlt">warming</span> <span class="hlt">event</span>, the persistence of reefs around the Galápagos Islands has differed across an acidification gradient. Reefs disappeared where pH < 8.0 and aragonite saturation state (Ωarag) ≤ 3 and have not recovered, whereas one reef has persisted where pH > 8.0 and Ωarag > 3. Where upwelling is greatest, calcification by massive Porites is higher than predicted by a published relationship with temperature despite high CO2, possibly due to elevated nutrients. However, skeletal P/Ca, a proxy for phosphate exposure, negatively correlates with density (R = - 0.822, p < 0.0001). We propose that elevated nutrients have the potential to exacerbate acidification by depressing coral skeletal densities and further increasing bioerosion already accelerated by low pH.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active"><span>10</span></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_10 --> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.476..100W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.476..100W"><span>Rapid drawdown of Antarctica's Wordie Ice Shelf glaciers in response to <span class="hlt">ENSO</span>/Southern Annular Mode-driven <span class="hlt">warming</span> in the Southern Ocean</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walker, C. C.; Gardner, A. S.</p> <p>2017-10-01</p> <p>Here we investigate the largest acceleration in ice flow across all of Antarctica between ∼2008 InSAR and 2014 Landsat velocity mappings. This occurred in glaciers that used to feed into the Wordie Ice Shelf on the west Antarctic Peninsula, which rapidly disintegrated in ∼1989. Between 2008 and 2014, these glaciers experienced at least a threefold increase in surface elevation drawdown relative to the 2002-2008 time period. After ∼20 yrs of relative stability, it is unlikely that the ice shelf collapse played a role in the large response. Instead, we find that the rapid acceleration and surface drawdown is linked to enhanced melting at the ice-ocean boundary, attributable to changes in winds driven by global atmospheric circulation patterns, namely the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and Southern Annular Mode (SAM), linking changes in grounded ice to atmospheric-driven ocean <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.1157K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.1157K"><span><span class="hlt">ENSO</span> and East Asian winter monsoon relationship modulation associated with the anomalous northwest Pacific anticyclone</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Ji-Won; An, Soon-Il; Jun, Sang-Yoon; Park, Hey-Jin; Yeh, Sang-Wook</p> <p>2017-08-01</p> <p>Using observational datasets and numerical model experiments, the mechanism on the slowly varying change in the relationship between the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and the East Asian winter monsoon (EAWM) is investigated. The decadal-window (11-, 15-, and 21-year) moving correlations show a significant change in the boreal wintertime <span class="hlt">ENSO</span>-EAWM relationship between two sub-periods of 1976‒1992 and 1997‒2013. Such recent change in <span class="hlt">ENSO</span>-EAWM relationship is mainly attributed to the changes in the intensity and zonal location of the anomalous lower-tropospheric northwest Pacific anticyclone (NWP-AC). NWP-AC commonly develops near the region of the Philippine Sea during the <span class="hlt">ENSO</span>'s peak phase and plays an important role of bridging the tropical convection and mid-latitude teleconnection. On one hand, the intensity of the NWP-AC is influenced by the interdecadal variation in a linkage between <span class="hlt">ENSO</span> and the Indian Ocean sea surface temperature (SST) variability, referring that a strong connection between the Pacific and Indian Oceans results in the strengthening of NWP-AC response to <span class="hlt">ENSO</span>. On the other hand, the zonal displacement of the NWP-AC is associated with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). That is, the tropical Pacific mean state (i.e., zonal SST gradient between climatologically <span class="hlt">warm</span> western Pacific and cold eastern Pacific)—strengthened by either the negative PDO phase or the positive AMO phase—drives the anomalous <span class="hlt">ENSO</span>-induced convection to be shifted to the west. With this westward shift, the zonal center of the NWP-AC also migrates westward over the Philippine Islands and exerts stronger connection between <span class="hlt">ENSO</span> and EAWM. In contrast, the relaxed zonal SST contrast associated with either the positive PDO phase or the negative AMO phase tends to exhibit weaker <span class="hlt">ENSO</span>-EAWM relationship via both of eastward shifted zonal centers of the anomalous <span class="hlt">ENSO</span>-induced convection and the NWP-AC. Finally, a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/576797-forecasting-enso-events-neural-network-extended-eof-approach','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/576797-forecasting-enso-events-neural-network-extended-eof-approach"><span>Forecasting <span class="hlt">ENSO</span> <span class="hlt">events</span>: A neural network-extended EOF approach</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Tangang, F.T.; Tang, B.; Monahan, A.H.</p> <p></p> <p>The authors constructed neural network models to forecast the sea surface temperature anomalies (SSTA) for three regions: Nino 4. Nino 3.5, and Nino 3, representing the western-central, the central, and the eastern-central parts of the equatorial Pacific Ocean, respectively. The inputs were the extended empirical orthogonal functions (EEOF) of the sea level pressure (SLP) field that covered the tropical Indian and Pacific Oceans and evolved for a duration of 1 yr. The EEOFs greatly reduced the size of the neural networks from those of the authors` earlier papers using EOFs. The Nino 4 region appeared to be the best forecastedmore » region, with useful skills up to a year lead time for the 1982-93 forecast period. By network pruning analysis and spectral analysis, four important inputs were identified: modes 1, 2, and 6 of the SLP EEOFs and the SSTA persistence. Mode 1 characterized the low-frequency oscillation (LFO, with 4-5-yr period), and was seen as the typical <span class="hlt">ENSO</span> signal, while mode 2, with a period of 2-5 yr, characterized the quasi-biennial oscillation (QBO) plus the LFO. Mode 6 was dominated by decadal and interdecadal variations. Thus, forecasting <span class="hlt">ENSO</span> required information from the QBO, and the decadal-interdecadal oscillations. The nonlinearity of the networks tended to increase with lead time and to become stronger for the eastern regions of the equatorial Pacific Ocean. 35 refs., 14 figs., 4 tabs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26634438','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26634438"><span>Dynamical excitation of the tropical Pacific Ocean and <span class="hlt">ENSO</span> variability by Little Ice Age cooling.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Rustic, Gerald T; Koutavas, Athanasios; Marchitto, Thomas M; Linsley, Braddock K</p> <p>2015-12-18</p> <p>Tropical Pacific Ocean dynamics during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are poorly characterized due to a lack of evidence from the eastern equatorial Pacific. We reconstructed sea surface temperature, El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) activity, and the tropical Pacific zonal gradient for the past millennium from Galápagos ocean sediments. We document a mid-millennium shift (MMS) in ocean-atmosphere circulation around 1500-1650 CE, from a state with dampened <span class="hlt">ENSO</span> and strong zonal gradient to one with amplified <span class="hlt">ENSO</span> and weak gradient. The MMS coincided with the deepest LIA cooling and was probably caused by a southward shift of the intertropical convergence zone. The peak of the MCA (900-1150 CE) was a <span class="hlt">warm</span> period in the eastern Pacific, contradicting the paradigm of a persistent La Niña pattern. Copyright © 2015, American Association for the Advancement of Science.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5157030','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5157030"><span>The December 2015 North Pole <span class="hlt">Warming</span> <span class="hlt">Event</span> and the Increasing Occurrence of Such <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Moore, G. W. K.</p> <p>2016-01-01</p> <p>In late December 2015, widespread media interest revolved around forecasts that the surface air temperature at the North Pole would rise above freezing. Although there has been significant interest in the enhanced <span class="hlt">warming</span> that is occurring at high northern latitudes, a process known as arctic amplification, remarkably little is known about these midwinter <span class="hlt">warming</span> <span class="hlt">events</span> at the pole including their frequency, duration and magnitude as well as the environmental conditions responsible for their occurrence. Here we use buoy and radiosonde data along with operational weather forecasts and atmospheric reanalyses to show that such <span class="hlt">events</span> are associated with surface cyclones near the pole as well as a highly perturbed polar vortex. They occur once or twice each decade with the earliest identified <span class="hlt">event</span> taking place in 1959. In addition, the warmest midwinter temperatures at the North Pole have been increasing at a rate that is twice as large as that for mean midwinter temperatures at the pole. It is argued that this enhanced trend is consistent with the loss of winter sea ice from the Nordic Seas that moves the reservoir of <span class="hlt">warm</span> air over this region northwards making it easier for weather systems to transport this heat polewards. PMID:27976745</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017E%26PSL.475...25C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017E%26PSL.475...25C"><span><span class="hlt">ENSO</span> variability reflected in precipitation oxygen isotopes across the Asian Summer Monsoon region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Zhongyin; Tian, Lide; Bowen, Gabriel J.</p> <p>2017-10-01</p> <p>Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation <span class="hlt">events</span> indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (<span class="hlt">ENSO</span>) response (e.g., high values corresponding to <span class="hlt">warm</span> phases), which we interpret as a response to changes in regional convection. We show that the isotope-<span class="hlt">ENSO</span> response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-<span class="hlt">ENSO</span> activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018E%26ES..139a2020D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018E%26ES..139a2020D"><span>The impact of <span class="hlt">ENSO</span> on regional chlorophyll-a anomaly in the Arafura Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dewi, D. M. P. R.; Fatmasari, D.; Kurniawan, A.; Munandar, M. A.</p> <p>2018-03-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is a naturally occurring phenomenon that involves fluctuating ocean temperature in the equatorial Pacific. <span class="hlt">ENSO</span> influences ocean climate variability in Indonesia including the Arafura Sea. The relationship between oceanic chlorophyll-a and <span class="hlt">ENSO</span> has been the focus of study over the past decade. Here we examine the impact of <span class="hlt">ENSO</span> on regional chlorophyll-a anomaly in the Papua waters using 14 years of chlorophyll-a and sea surface temperature (SST) data from AQUA MODIS and sea level anomaly data from AVISO. It is found that when El Niño <span class="hlt">events</span> occur the negative SST anomaly in the Papua waters as well as the enhanced upwelling cause the increase of chlorophyll-a concentration. The highest chlorophyll-a concentration (> 1 mg–cm-3) occured during El Niño and observed around the Aru archipelago. In contrast during La Niña <span class="hlt">event</span>, the positive SST anomaly in Papua waters and the suppressed upwelling cause the decrease of chlorophyll-a concentration. Our results suggest that during El Niño (La Niña), the enhanced (suppressed) upwelling related to the significant decreasing (increasing) of sea level anomaly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP54B..01K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP54B..01K"><span>High-Resolution Modeling of <span class="hlt">ENSO</span>-Induced Precipitation in the Tropical Andes: Implications for Proxy Interpretation.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kiefer, J.; Karamperidou, C.</p> <p>2017-12-01</p> <p>Clastic sediment flux into high-elevation Andean lakes is controlled by glacial processes and soil erosion caused by high precipitation <span class="hlt">events</span>, making these lakes suitable archives of past climate. To wit, sediment records from Laguna Pallcacocha in Ecuador have been interpreted as proxies of <span class="hlt">ENSO</span> variability, owing to increased precipitation in the greater region during El Niño <span class="hlt">events</span>. However, the location of the lake's watershed, the presence of glaciers, and the different impacts of <span class="hlt">ENSO</span> on precipitation in the eastern vs western Andes have challenged the suitability of the Pallcacocha record as an <span class="hlt">ENSO</span> proxy. Here, we employ WRF, a high-resolution regional mesoscale weather prediction model, to investigate the circulation dynamics, sources of moisture, and resulting precipitation response in the L. Pallcacocha region during different flavors of El Niño and La Niña <span class="hlt">events</span>, and in the presence or absence of ice caps. In patricular, we investigate Eastern Pacific (EP), Central Pacific (CP), coastal El Niño, and La Niña <span class="hlt">events</span>. We validate the model simulations against spatially interpolated station measurements and reanalysis data. We find that during EP <span class="hlt">events</span>, moisture is primarily advected from the Pacific, whereas during CP <span class="hlt">events</span>, moisture primarily originates from the Atlantic. More moisture is available during EP <span class="hlt">events</span>, which implies higher precipitation rates. Furthermore, we find that precipitation during EP <span class="hlt">events</span> is mostly non-convective in contrast to primarily convective precipitation during CP <span class="hlt">events</span>. Finally, a synthesis of the sedimentary record and the EP:CP ratio of accumulated precipitation and specific humidity in the L. Pallcacocha region allows us to assess whether past changes in the relative frequency of the two <span class="hlt">ENSO</span> flavors may have been recorded in paleoclimate archives in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.pices.int/publications/scientific_reports/Report10/default.aspx','USGSPUBS'); return false;" href="http://www.pices.int/publications/scientific_reports/Report10/default.aspx"><span>Biological effects of the 1997/98 <span class="hlt">ENSO</span> in Cook Inlet, Alaska</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Piatt, John F.; Drew, Gary S.; van Pelt, Thomas I.; Abookire, Alisa A.; Nielsen, April; Shultz, Michael T.; Kitaysky, Alexander S.</p> <p>1999-01-01</p> <p>We have been conducting detailed studies of the biology of seabirds in relation to oceanography and forage fish ecology in lower Cook Inlet, Alaska, since 1995. This fortuitously allowed us to document biological effects of the 1997/98 <span class="hlt">ENSO</span> in this region. Anomalously <span class="hlt">warm</span> sea surface temperatures (SSTs) were observed in the Gulf of Alaska (GOA) beginning in June of 1997, but not in Cook Inlet until September, 1997. <span class="hlt">Warm</span> temperature anomalies at the surface and at depth persisted until May of 1998, when temperatures returned to average in the GOA and Cook Inlet. Thus, temperature anomalies occurred outside the core window of productivity (June–August) for forage fish and seabirds in both 1997 and 1998. Abundance or production of phytoplankton, zooplankton, fish, and seabirds in lower Cook Inlet varied among years, and overall appeared to be depressed in 1998. We observed a few biological anomalies that might be attributed to <span class="hlt">ENSO</span> effects: (1) a significant die-off of Common Murres occurred in March–May of 1998, (2) murres and Black-legged Kittiwakes were physiologically stressed during the 1998 breeding season, (3) murres failed to reproduce at one colony in 1998, (4) kittiwake breeding success was lower than usual at colonies in 1998, and (5) phenology of breeding was later in 1998 for both murres and kittiwakes. We presume that seabird die-offs, reduced productivity and delayed phenology were linked to a reduction or delay in food availability, but the mechanism by which anomalously <span class="hlt">warm</span> water temperatures in winter reduce forage fish availability during the summer breeding season for seabirds is not known.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020049829&hterms=climate+change+anthropogenic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dclimate%2Bchange%2Banthropogenic','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020049829&hterms=climate+change+anthropogenic&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dclimate%2Bchange%2Banthropogenic"><span>Sensitivity of the Tropical Atmospheric Energy Balance to <span class="hlt">ENSO</span>-Related SST Changes: Comparison of Climate Model Simulations to Observed Responses</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robertson, Franklin R.; Fitzjarrald, Dan; Marshall, Susan; Oglesby, Robert; Roads, John; Arnold, James E. (Technical Monitor)</p> <p>2001-01-01</p> <p>This paper focuses on how fresh water and radiative fluxes over the tropical oceans change during <span class="hlt">ENSO</span> <span class="hlt">warm</span> and cold <span class="hlt">events</span> and how these changes affect the tropical energy balance. At present, <span class="hlt">ENSO</span> remains the most prominent known mode of natural variability at interannual time scales. While this natural perturbation to climate is quite distinct from possible anthropogenic changes in climate, adjustments in the tropical water and energy budgets during <span class="hlt">ENSO</span> may give insight into feedback processes involving water vapor and cloud feedbacks. Although great advances have been made in understanding this phenomenon and realizing prediction skill over the past decade, our ability to document the coupled water and energy changes observationally and to represent them in climate models seems far from settled (Soden, 2000 J Climate). In a companion paper we have presented observational analyses, based principally on space-based measurements which document systematic changes in rainfall, evaporation, and surface and top-of-atmosphere (TOA) radiative fluxes. Here we analyze several contemporary climate models run with observed SSTs over recent decades and compare SST-induced changes in radiation, precipitation, evaporation, and energy transport to observational results. Among these are the NASA / NCAR Finite Volume Model, the NCAR Community Climate Model, the NCEP Global Spectral Model, and the NASA NSIPP Model. Key disagreements between model and observational results noted in the recent literature are shown to be due predominantly to observational shortcomings. A reexamination of the Langley 8-Year Surface Radiation Budget data reveals errors in the SST surface longwave emission due to biased SSTs. Subsequent correction allows use of this data set along with ERBE TOA fluxes to infer net atmospheric radiative heating. Further analysis of recent rainfall algorithms provides new estimates for precipitation variability in line with interannual evaporation changes inferred from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP41C1371Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP41C1371Y"><span><span class="hlt">ENSO</span>-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.</p> <p>2014-12-01</p> <p>The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global <span class="hlt">warming</span> may increase the frequency of extreme <span class="hlt">ENSO</span> <span class="hlt">events</span>. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that <span class="hlt">ENSO</span>-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern <span class="hlt">ENSO</span> cycles and solar cycles, as well as</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50..375C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50..375C"><span>Impacts of winter NPO on subsequent winter <span class="hlt">ENSO</span>: sensitivity to the definition of NPO index</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Shangfeng; Wu, Renguang</p> <p>2018-01-01</p> <p>This study investigates the linkage between boreal winter North Pacific Oscillation (NPO) and subsequent winter El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) based on seven different NPO indices. Results show that the influence of winter NPO on the subsequent winter El Niño is sensitive to how the NPO is defined. A significant NPO-El Niño connection is obtained when the NPO-related anomalous cyclone over the subtropical North Pacific extends to near-equatorial regions. The anomalous cyclone induces <span class="hlt">warm</span> sea surface temperature (SST) anomalies through modulating surface heat fluxes. These <span class="hlt">warm</span> SST anomalies are able to maintain into the following spring and summer through an air-sea coupled process and in turn induce significant westerly wind anomalies over the tropical western Pacific. In contrast, the NPO-El Niño relationship is unclear when the NPO-related anomalous cyclone over the subtropical North Pacific is confined to off-equatorial regions and cannot induce significant <span class="hlt">warm</span> SST anomalies over the subtropical North Pacific. The present study suggests that definitions of NPO should be taken into account when using NPO to predict <span class="hlt">ENSO</span>. In particular, we recommend defining the NPO index based on the empirical orthogonal function technique over appropriate region that does not extend too far north.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMGC31D1206W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMGC31D1206W"><span>Mapping <span class="hlt">ENSO</span>: Precipitation for the U.S. Affiliated Pacific Islands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wright, E.; Price, J.; Kruk, M. C.; Luchetti, N.; Marra, J. J.</p> <p>2015-12-01</p> <p>The United States Affiliated Pacific Islands (USAPI) are highly susceptible to extreme precipitation <span class="hlt">events</span> such as drought and flooding, which directly affect their freshwater availability. Precipitation distribution differs by sub-region, and is predominantly influenced by phases of the El Niño Southern Oscillation (<span class="hlt">ENSO</span>). Forecasters currently rely on <span class="hlt">ENSO</span> climatologies from sparse in situ station data to inform their precipitation outlooks. This project provided an updated <span class="hlt">ENSO</span>-based climatology of long-term precipitation patterns for each USAPI Exclusive Economic Zone (EEZ) using the NOAA PERSIANN Climate Data Record (CDR). This data provided a 30-year record (1984-2015) of daily precipitation at 0.25° resolution, which was used to calculate monthly, seasonal, and yearly precipitation. Results indicated that while the PERSIANN precipitation accurately described the monthly, seasonal, and annual trends, it under-predicted the precipitation on the islands. Additionally, maps showing percent departure from normal (30 year average) were made for each three month season based on the Oceanic Niño Index (ONI) for five <span class="hlt">ENSO</span> phases (moderate-strong El Niño and La Niña, weak El Niño and La Niña, and neutral). Local weather service offices plan on using these results and maps to better understand how the different <span class="hlt">ENSO</span> phases influence precipitation patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20497369','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20497369"><span>Impacts of extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> on plant physiology in a sub-Arctic heath community.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bokhorst, Stef; Bjerke, Jarle W; Davey, Matthew P; Taulavuori, Kari; Taulavuori, Erja; Laine, Kari; Callaghan, Terry V; Phoenix, Gareth K</p> <p>2010-10-01</p> <p>Insulation provided by snow cover and tolerance of freezing by physiological acclimation allows Arctic plants to survive cold winter temperatures. However, both the protection mechanisms may be lost with winter climate change, especially during extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> where loss of snow cover from snow melt results in exposure of plants to <span class="hlt">warm</span> temperatures and then returning extreme cold in the absence of insulating snow. These <span class="hlt">events</span> cause considerable damage to Arctic plants, but physiological responses behind such damage remain unknown. Here, we report simulations of extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> using infrared heating lamps and soil <span class="hlt">warming</span> cables in a sub-Arctic heathland. During these <span class="hlt">events</span>, we measured maximum quantum yield of photosystem II (PSII), photosynthesis, respiration, bud swelling and associated bud carbohydrate changes and lipid peroxidation to identify physiological responses during and after the winter <span class="hlt">warming</span> <span class="hlt">events</span> in three dwarf shrub species: Empetrum hermaphroditum, Vaccinium vitis-idaea and Vaccinium myrtillus. Winter <span class="hlt">warming</span> increased maximum quantum yield of PSII, and photosynthesis was initiated for E. hermaphroditum and V. vitis-idaea. Bud swelling, bud carbohydrate decreases and lipid peroxidation were largest for E. hermaphroditum, whereas V. myrtillus and V. vitis-idaea showed no or less strong responses. Increased physiological activity and bud swelling suggest that sub-Arctic plants can initiate spring-like development in response to a short winter <span class="hlt">warming</span> <span class="hlt">event</span>. Lipid peroxidation suggests that plants experience increased winter stress. The observed differences between species in physiological responses are broadly consistent with interspecific differences in damage seen in previous studies, with E. hermaphroditum and V. myrtillus tending to be most sensitive. This suggests that initiation of spring-like development may be a major driver in the damage caused by winter <span class="hlt">warming</span> <span class="hlt">events</span> that are predicted to become more</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.A11G..04C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.A11G..04C"><span>Where was <span class="hlt">ENSO</span> strongest?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cane, M. A.; Chen, D.; Kaplan, A.</p> <p>2008-12-01</p> <p>Mark A. Cane, Dake Chen, Alexey Kaplan The description of this session begins: "Historical SST records suggest that for the past three decades, <span class="hlt">ENSO</span> has been anomalously strong" and goes on to ask why. In this talk we dispute this interpretation of the historical record from within the historical record. In particular, we suggest that the most "anomalously strong" period in the historical <span class="hlt">ENSO</span> record is the late nineteenth century. This claim requires a discussion of how we measure "<span class="hlt">ENSO</span> strength". We also speculate on possible reasons for the strength of <span class="hlt">ENSO</span> in this earlier period. Finally, we consult the models, and in reiteration of the collective conclusion of all speakers at this session, find that the riddles the models provide are inelegant and disobliging, lacking the cryptic wisdom of the classical oracles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PApGe.171..323M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PApGe.171..323M"><span>Verification of an <span class="hlt">ENSO</span>-Based Long-Range Prediction of Anomalous Weather Conditions During the Vancouver 2010 Olympics and Paralympics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mo, Ruping; Joe, Paul I.; Doyle, Chris; Whitfield, Paul H.</p> <p>2014-01-01</p> <p>A brief review of the anomalous weather conditions during the Vancouver 2010 Winter Olympic and Paralympic Games and the efforts to predict these anomalies based on some preceding El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) signals are presented. It is shown that the Olympic Games were held under extraordinarily <span class="hlt">warm</span> conditions in February 2010, with monthly mean temperature anomalies of +2.2 °C in Vancouver and +2.8 °C in Whistler, ranking respectively as the highest and the second highest in the past 30 years (1981-2010). The <span class="hlt">warm</span> conditions continued, but became less anomalous, in March 2010 for the Paralympic Games. While the precipitation amounts in the area remained near normal through this winter, the lack of snow due to <span class="hlt">warm</span> conditions created numerous media headlines and practical problems for the alpine competitions. A statistical model was developed on the premise that February and March temperatures in the Vancouver area could be predicted using an <span class="hlt">ENSO</span> signal with considerable lead time. This model successfully predicted the warmer-than-normal, lower-snowfall conditions for the Vancouver 2010 Winter Olympics and Paralympics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020049983&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbalance%2Bgeneral','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020049983&hterms=balance+general&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbalance%2Bgeneral"><span>Sensitivity of the Tropical Atmosphere Energy Balance to <span class="hlt">ENSO</span>-Related SST Changes: How Well Can We Quantify Hydrologic and Radiative Responses?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robertson, Franklin R.; Fitzjarrald, Dan; Sohn, Byung-Ju; Arnold, James E. (Technical Monitor)</p> <p>2001-01-01</p> <p>The continuing debate over feedback mechanisms governing tropical sea surface temperatures (SSTs) and tropical climate in general has highlighted the diversity of potential checks and balances within the climate system. Competing feedbacks due to changes in surface evaporation, water vapor, and cloud long- and shortwave radiative properties each may serve critical roles in stabilizing or destabilizing the climate system. It is also intriguing that even those climate variations having origins internal to the climate system-- changes in ocean heat transport for example, apparently require complementary equilibrating effects by changes in atmospheric energy fluxes. Perhaps the best observational evidence of this is the relatively invariant nature of tropically averaged net radiation exiting the top-of-atmosphere (TOA) as measured by broadband satellite sensors over the past two decades. Thus, analyzing how these feedback mechanisms are operating within the context of current interannual variability may offer considerable insight for anticipating future climate change. In this paper we focus on how fresh water and radiative fluxes over the tropical oceans change during <span class="hlt">ENSO</span> <span class="hlt">warm</span> and cold <span class="hlt">events</span> and how these changes affect the tropical energy balance. At present, <span class="hlt">ENSO</span> remains the most prominent known mode of natural variability at interannual time scales. Although great advances have been made in understanding this phenomenon and realizing prediction skill over the past decade, our ability to document the coupled water and energy changes observationally and to represent them in climate models seems far from settled (Soden, 2000 J Climate). Our analysis makes use a number of data bases, principally those derived from space-based measurements, to explore systematic changes in rainfall, evaporation, and surface and top-of-atmosphere (TOA) radiative fluxes, A reexamination of the Langley 8-Year Surface Radiation Budget data set reveals errors in the surface longwave</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140017640','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140017640"><span>Comparison of Forced <span class="hlt">ENSO</span>-Like Hydrological Expressions in Simulations of the Preindustrial and Mid-Holocene</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lewis, Sophie C.; LeGrande, Allegra N.; Schmidt, Gavin A.; Kelley, Maxwell</p> <p>2014-01-01</p> <p>Using the water isotope- and vapor source distribution (VSD) tracer-enabled Goddard Institute for Space Studies ModelE-R, we examine changing El Nino-Southern Oscillation (<span class="hlt">ENSO</span>)-like expressions in the hydrological cycle in a suite of model experiments. We apply strong surface temperature anomalies associated with composite observed El Nino and La Nina <span class="hlt">events</span> as surface boundary conditions to preindustrial and mid-Holocene model experiments in order to investigate <span class="hlt">ENSO</span>-like expressions in the hydrological cycle under varying boundary conditions. We find distinct simulated hydrological anomalies associated with El Nino-like ("ENSOWARM") and La Nina-like ("ENSOCOOL") conditions, and the region-specific VSD tracers show hydrological differences across the Pacific basin between El Nino-like and La Nina-like <span class="hlt">events</span>. The application of ENSOCOOL forcings does not produce climatological anomalies that represent the equal but opposite impacts of the ENSOWARM experiment, as the isotopic anomalies associated with ENSOWARM conditions are generally stronger than with ENSOCOOL and the spatial patterns of change distinct. Also, when the same <span class="hlt">ENSO</span>-like surface temperature anomalies are imposed on the mid-Holocene, the hydrological response is muted, relative to the preindustrial. Mid-Holocene changes in moisture sources to the analyzed regions across the Pacific reveal potentially complex relationships between <span class="hlt">ENSO</span>-like conditions and boundary conditions. Given the complex impacts of <span class="hlt">ENSO</span>-like conditions on various aspects of the hydrological cycle, we suggest that proxy record insights into paleo-<span class="hlt">ENSO</span> variability are most likely to be robust when synthesized from a network of many spatially diverse archives, which can account for the potential nonstationarity of <span class="hlt">ENSO</span> teleconnections under different boundary conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMPP31D2324C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMPP31D2324C"><span>Connection between <span class="hlt">ENSO</span> and Asian Summer Monsoon Precipitation Oxygen Isotope</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Z.; Tian, L.</p> <p>2016-12-01</p> <p>In an effort to understand the connection between El Niño Southern Oscillation (<span class="hlt">ENSO</span>) and Asian Summer Monsoon (ASM) precipitation oxygen isotope, this study investigates the spatial and interannual patterns in summer (JJAS) monsoon precipitation δ18O and satellite water vapor isotope retrievals, especially those patterns associated with convection and vapor transport. Both precipitation and vapor isotope values exhibit a "V" shaped longitudinal pattern in their spatial variations, reflecting the gradual rainout and increase in convective intensity along vapor transport routes. In order to understand interannual variations, an ASM precipitation δ18O index (ASMOI) is introduced to measure the temporal variations in regional precipitation δ18O; and these variations are consistent with central Indo-Pacific convection and cloud-top height. The counter variations in the ASMOI in El Niño and La Niña years confirm the existence of a positive isotope- <span class="hlt">ENSO</span> response (e.g., high values corresponding to <span class="hlt">warm</span> phases) over the eastern Indian Ocean and southeastern Asia (80°E-120°E/10°S-30°N) as a response to changes in convection. However, JJAS vapor δD over the western Pacific (roughly east of 120oE) varies in opposition, due to the influence of water vapor transport. This opposite variation does not support the interpretation of precipitation isotope-<span class="hlt">ENSO</span> relationship as changing proportion of vapor transported from different regions, but rather condensation processes associated with convection. These findings are important for studying past ASM and <span class="hlt">ENSO</span> activity from various isotopic archives and have implications for the study of the atmospheric water cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000118278','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000118278"><span>Monsoon-<span class="hlt">Enso</span> Relationships: A New Paradigm</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, K. M.; Einaudi, Franco (Technical Monitor)</p> <p>2000-01-01</p> <p>This article is partly a review and partly a new research paper on monsoon-<span class="hlt">ENSO</span> relationship. The paper begins with a discussion of the basic relationship between the Indian monsoon and <span class="hlt">ENSO</span> dating back to the work of Sir Gilbert Walker up to research results in more recent years. Various factors that may affect the monsoon-<span class="hlt">ENSO</span>, relationship, including regional coupled ocean-atmosphere processes, Eurasian snow cover, land-atmosphere hydrologic feedback, intraseasonal oscillation, biennial variability and inter-decadal variations, are discussed. The extreme complex and highly nonlinear nature of the monsoon-<span class="hlt">ENSO</span> relationship is stressed. We find that for regional impacts on the monsoon, El Nino and La Nina are far from simply mirror images of each other. These two polarities of <span class="hlt">ENSO</span> can have strong or no impacts on monsoon anomalies depending on the strength of the intraseasonal oscillations and the phases of the inter-decadal variations. For the Asian-Australian monsoon (AAM) as a whole, the <span class="hlt">ENSO</span> impact is effected through a east-west shift in the Walker Circulation. For rainfall anomalies over specific monsoon areas, regional processes play important roles in addition to the shift in the Walker Circulation. One of the key regional processes identified for the boreal summer monsoon is the anomalous West Pacific Anticyclone (WPA). This regional feature has similar signatures in interannual and intraseasonal time scales and appears to determine whether the monsoon-<span class="hlt">ENSO</span> relationship is strong or weak in a given year. Another important regional feature includes a rainfall and SST dipole across the Indian Ocean, which may have strong impact on the austral summer monsoon. Results are shown indicating that monsoon surface wind forcings may induce a strong biennial signal in <span class="hlt">ENSO</span> and that strong monsoon-<span class="hlt">ENSO</span> coupling may translate into pronounced biennial variability in <span class="hlt">ENSO</span>. Finally, a new paradigm is proposed for the study of monsoon variability. This paradigm provides</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active"><span>11</span></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_11 --> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4585812','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4585812"><span>Distinctive ocean interior changes during the recent <span class="hlt">warming</span> slowdown</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cheng, Lijing; Zheng, Fei; Zhu, Jiang</p> <p>2015-01-01</p> <p>The earth system experiences continuous heat input, but a “climate hiatus” of upper ocean waters has been observed in this century. This leads to a question: where is the extra heat going? Using four in situ observation datasets, we explore the ocean subsurface temperature changes from 2004 to 2013. The observations all show that the ocean has continued to gain heat in this century, which is indicative of anthropogenic global <span class="hlt">warming</span>. However, a distinctive pattern of change in the interior ocean is observed. The sea surface (1–100 m) temperature has decreased in this century, accompanied by <span class="hlt">warming</span> in the 101–300 m layer. This pattern is due to the changes in the frequency of El Niño and La Niña <span class="hlt">events</span> (<span class="hlt">ENSO</span> characteristics), according to both observations and CMIP5 model simulations. In addition, we show for the first time that the ocean subsurface within 301–700 m experienced a net cooling, indicative of another instance of variability in the natural ocean. Furthermore, the ocean layer of 701–1500 m has experienced significant <span class="hlt">warming</span>. PMID:26394551</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...815531T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...815531T"><span>Extreme temperatures in Southeast Asia caused by El Niño and worsened by global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thirumalai, Kaustubh; Dinezio, Pedro N.; Okumura, Yuko; Deser, Clara</p> <p>2017-06-01</p> <p>In April 2016, southeast Asia experienced surface air temperatures (SATs) that surpassed national records, exacerbated energy consumption, disrupted agriculture and caused severe human discomfort. Here we show using observations and an ensemble of global <span class="hlt">warming</span> simulations the combined impact of the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon and long-term <span class="hlt">warming</span> on regional SAT extremes. We find a robust relationship between <span class="hlt">ENSO</span> and southeast Asian SATs wherein virtually all April extremes occur during El Niño years. We then quantify the relative contributions of long-term <span class="hlt">warming</span> and the 2015-16 El Niño to the extreme April 2016 SATs. The results indicate that global <span class="hlt">warming</span> increases the likelihood of record-breaking April extremes where we estimate that 29% of the 2016 anomaly was caused by <span class="hlt">warming</span> and 49% by El Niño. These post-Niño Aprils can potentially be anticipated a few months in advance, and thus, help societies prepare for the projected continued increases in extremes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28585927','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28585927"><span>Extreme temperatures in Southeast Asia caused by El Niño and worsened by global <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thirumalai, Kaustubh; DiNezio, Pedro N; Okumura, Yuko; Deser, Clara</p> <p>2017-06-06</p> <p>In April 2016, southeast Asia experienced surface air temperatures (SATs) that surpassed national records, exacerbated energy consumption, disrupted agriculture and caused severe human discomfort. Here we show using observations and an ensemble of global <span class="hlt">warming</span> simulations the combined impact of the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon and long-term <span class="hlt">warming</span> on regional SAT extremes. We find a robust relationship between <span class="hlt">ENSO</span> and southeast Asian SATs wherein virtually all April extremes occur during El Niño years. We then quantify the relative contributions of long-term <span class="hlt">warming</span> and the 2015-16 El Niño to the extreme April 2016 SATs. The results indicate that global <span class="hlt">warming</span> increases the likelihood of record-breaking April extremes where we estimate that 29% of the 2016 anomaly was caused by <span class="hlt">warming</span> and 49% by El Niño. These post-Niño Aprils can potentially be anticipated a few months in advance, and thus, help societies prepare for the projected continued increases in extremes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2707B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2707B"><span>On the relative role of meridional convergence and downwelling motion during the heat buildup leading to El Niño <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ballester, Joan; Bordoni, Simona; Petrova, Desislava; Rodó, Xavier</p> <p>2015-04-01</p> <p>Despite steady progress in the understanding of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) in the past decades, questions remain on the exact mechanisms leading to the onset of El Niño (EN) <span class="hlt">events</span>. Several authors have highlighted how the subsurface heat buildup in the western tropical Pacific and the recharged phase in equatorial heat content are intrinsic elements of <span class="hlt">ENSO</span> variability, leading to those changes in zonal wind stress, sea surface temperature and thermocline tilt that characterize the growing and mature phases of EN. Here we use an ensemble of ocean and atmosphere assimilation products to identify the mechanisms contributing to the heat buildup that precedes EN <span class="hlt">events</span> by about 18-24 months on average. Anomalous equatorward subsurface mass convergence due to meridional Sverdrup transport is found to be an important mechanism of thermocline deepening near and to the east of the dateline. In the <span class="hlt">warm</span> pool, instead, surface horizontal convergence and downwelling motion have a leading role in subsurface <span class="hlt">warming</span>, since equatorward mass convergence is weaker and counterbalanced by subsurface zonal divergence. The picture emerging from our results highlights the complexity of the three dimensional dynamic and thermodynamic structure of the tropical Pacific during the heat buildup leading to EN <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP53B1127C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP53B1127C"><span>Precipitation and ice core isotopes from the Asian Summer Monsoon region reflect coherent <span class="hlt">ENSO</span> variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cai, Z.; Tian, L.; Bowen, G. J.</p> <p>2017-12-01</p> <p>Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation <span class="hlt">events</span> indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (<span class="hlt">ENSO</span>) response (e.g., high values corresponding to <span class="hlt">warm</span> phases), which we interpret as a response to changes in regional convection. We show that the isotope-<span class="hlt">ENSO</span> response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-<span class="hlt">ENSO</span> activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712849P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712849P"><span>Ocean-state dependency of the equatorial Pacific response to Westerly Wind <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Puy, martin; Lengaigne, matthieu; Madec, gurvan; Vialard, jerome; Guilyardi, eric</p> <p>2015-04-01</p> <p>Short-lived wind <span class="hlt">events</span> in the equatorial Pacific strongly influence the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) evolution. In the first part of this study, we found in observations that both westerly wind <span class="hlt">events</span> (WWEs) and their easterly wind <span class="hlt">events</span> (EWEs) counterpart are unambiguously associated with increased Madden Julian oscillation and atmospheric equatorial Rossby waves activity, i.e. that the atmospheric state influences the occurrence probability of WWEs. In the second part, we investigate how the oceanic state modulates the response to these WWEs by applying the same WWE forcing over a interannually-varying ocean state in an OGCM simulation. We find that the amplitude of the SST response, both at the <span class="hlt">warm</span> pool eastern edge and in the eastern Pacific, can vary by a factor of up to two depending on the ocean state. The sea level and current response are also clearly modulated, with varying contributions of the second and third baroclinic modes depending on the oceanic stratification. We will discuss the mechanisms by which the oceanic state modulates the response to the WWE, and how this could contribute to their impact on <span class="hlt">ENSO</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70025104','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70025104"><span>Effects of <span class="hlt">ENSO</span> on weather-type frequencies and properties at New Orleans, Louisiana, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McCabe, G.J.; Muller, R.A.</p> <p>2002-01-01</p> <p>Examination of historical climate records indicates a significant relation between the El Nin??o/Southern Oscillation (<span class="hlt">ENSO</span>) and seasonal temperature and precipitation in Louisiana. In this study, a 40 yr record of twice daily (06:00 and 15:00 h local time) weather types are used to study the effects of <span class="hlt">ENSO</span> variability on the local climate at New Orleans, Louisiana. Tropical Pacific sea-surface temperatures (SSTs) for the NINO3.4 region are used to define <span class="hlt">ENSO</span> <span class="hlt">events</span> (i.e. El Nin??o and La Nin??a <span class="hlt">events</span>), and daily precipitation and temperature data for New Orleans are used to define weather-type precipitation and temperature properties. Data for winters (December through February) 1962-2000 are analyzed. The 39 winters are divided into 3 categories; winters with NINO3.4 SST anomalies 1??C (El Nin??o <span class="hlt">events</span>), and neutral conditions (all other years). For each category, weather-type frequencies and properties (i.e. precipitation and temperature) are determined and analyzed. Results indicate that El Nin??o <span class="hlt">events</span> primarily affect precipitation characteristics of weather types at New Orleans, whereas the effects of La Nin??a <span class="hlt">events</span> are most apparent in weather-type frequencies. During El Nin??o <span class="hlt">events</span>, precipitation for some of the weather types is greater than during neutral and La Nin??a conditions and is related to increased water vapor transport from the Tropics to the Gulf of Mexico. The changes in weather-type frequencies during La Nin??a <span class="hlt">events</span> are indicative of a northward shift in storm tracks and/or a decrease in storm frequency in southern Louisiana.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JESS..126...30D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JESS..126...30D"><span>Study of the global and regional climatic impacts of <span class="hlt">ENSO</span> magnitude using SPEEDY AGCM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dogar, Muhammad Mubashar; Kucharski, Fred; Azharuddin, Syed</p> <p>2017-03-01</p> <p><span class="hlt">ENSO</span> is considered as a strong atmospheric teleconnection that has pronounced global and regional circulation effects. It modifies global monsoon system, especially, Asian and African monsoons. Previous studies suggest that both the frequency and magnitude of <span class="hlt">ENSO</span> <span class="hlt">events</span> have increased over the last few decades resulting in a need to study climatic impacts of <span class="hlt">ENSO</span> magnitude both at global and regional scales. Hence, to better understand the impact of <span class="hlt">ENSO</span> amplitude over the tropical and extratropical regions focussing on the Asian and African domains, <span class="hlt">ENSO</span> sensitivity experiments are conducted using ICTPAGCM (`SPEEDY'). It is anticipated that the tropical Pacific SST forcing will be enough to produce <span class="hlt">ENSO</span>-induced teleconnection patterns; therefore, the model is forced using NINO3.4 regressed SST anomalies over the tropical Pacific only. SPEEDY reproduces the impact of <span class="hlt">ENSO</span> over the Pacific, North and South America and African regions very well. However, it underestimates <span class="hlt">ENSO</span> teleconnection patterns and associated changes over South Asia, particularly in the Indian region, which suggests that the tropical Pacific SST forcing is not sufficient to represent <span class="hlt">ENSO</span>-induced teleconnection patterns over South Asia. Therefore, SST forcing over the tropical Indian Ocean together with air-sea coupling is also required for better representation of <span class="hlt">ENSO</span>-induced changes in these regions. Moreover, results obtained by this pacemaker experiment show that <span class="hlt">ENSO</span> impacts are relatively stronger over the Inter-Tropical Convergence Zone (ITCZ) compared to extratropics and high latitude regions. The positive phase of <span class="hlt">ENSO</span> causes weakening in rainfall activity over African tropical rain belt, parts of South and Southeast Asia, whereas, the La Niña phase produces more rain over these regions during the summer season. Model results further reveal that <span class="hlt">ENSO</span> magnitude has a stronger impact over African Sahel and South Asia, especially over the Indian region because of its significant impact</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP23D..06L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP23D..06L"><span><span class="hlt">ENSO</span> activity during the last climate cycle using Individual Foraminifera Analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Leduc, G.; Vidal, L.; Thirumalai, K.</p> <p>2017-12-01</p> <p>The El Niño / Southern Oscillation (<span class="hlt">ENSO</span>) is the principal mode of interannual climate variability and affects key climate parameters such as low-latitude rainfall variability. Recent climate modeling experiments tend to suggest an increase in the frequency of both El Niño and La Niña <span class="hlt">events</span> in the future, but these results remain model-dependent and require to be validated by paleodata-model comparisons. Fossil corals indicate that the <span class="hlt">ENSO</span> variance during the 20th century is particularly high as compared to other time periods of the Holocene. Beyond the Holocene, however, little is known on past <span class="hlt">ENSO</span> changes, which makes difficult to test paleoclimate model simulations that are used to study the <span class="hlt">ENSO</span> sensitivity to various types of forcings. We have expanded an Individual Foraminifera Analysis (IFA) dataset using the thermocline-dwelling N. dutertrei on a marine core collected in the Panama Basin (Leduc et al., 2009), that has proven to be a skillful way to reconstruct the <span class="hlt">ENSO</span> (Thirumalai et al., 2013). Our new IFA dataset comprehensively covers the Holocene, allowing to verify how the IFA method compares with <span class="hlt">ENSO</span> reconstructions using corals. The dataset then extends back in time to Marine Isotope Stage 6 (MIS), with a special focus the last deglaciation and Termination II (MIS5/6) time windows, as well as key time periods to tests the sensitivity of <span class="hlt">ENSO</span> to ice volume and orbital parameters. The new dataset confirms variable <span class="hlt">ENSO</span> activity during the Holocene and weaker activity during LGM than during the Holocene, as a recent isotope-enabled climate model simulations of the LGM suggests (Zhu et al., 2017). Such pattern is reproduced for the Termination II. Leduc, G., L. Vidal, O. Cartapanis, and E. Bard (2009), Modes of eastern equatorial Pacific thermocline variability: Implications for <span class="hlt">ENSO</span> dynamics over the last glacial period, Paleoceanography, 24, PA3202, doi:10.1029/2008PA001701. Thirumalai, K., J. W. Partin, C. S. Jackson, and T. M. Quinn (2013</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B31G0554B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B31G0554B"><span>Effects of the 2015/16 <span class="hlt">ENSO</span> <span class="hlt">event</span> on tropical trees in regrowing secondary forests in Central Panama</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bretfeld, M.; Ewers, B. E.; Hall, J. S.; Ogden, F. L.</p> <p>2016-12-01</p> <p>The 2015/16 El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">event</span> ranks amongst the driest and hottest periods on record in Panama, with severe drought conditions reported for over 90% of the country. A predicted long-term transition into a drier climatic period makes this <span class="hlt">event</span> an ideal opportunity to study the effects of drought on tropical tree species in secondary forests of central Panama. These forests are associated with desirable hydrological ecosystem services, characterized by reduced peak runoff during high precipitation <span class="hlt">events</span> in the rainy season and increased base flow during the dry season ("sponge-effect"), making these forest invaluable for water provisioning for the Panama Canal's $2 billion business and Panama's thriving capital city. Starting in February 2015, we installed heat-ratio sap flow sensors in 76 trees (representing 42 different species) in secondary forests of three different ages (8, 25, and 80+ years) in the 15 km2 Agua Salud study area, located in the Panama Canal Watershed. Within each site, trees were selected to represent local tree size distribution. Additional sensors were installed on the roots of a subset of trees. Sap flow data were logged every 30 minutes and soil moisture was measured every 3 minutes at 10, 30, 50, and 100 cm depth. Pre-dawn, mid-day, and pre-dusk leaf water potentials were measured during the dry season (March 2016) and rainy season (July 2016). Meteorological data were taken from a nearby met-station ("Celestino"). Primary drivers of transpiration were vapor pressure deficit and solar radiation. Trees of the 25 and 80+ year old forests appear not water limited during the dry season following <span class="hlt">ENSO</span> while reduced sap flow rates of trees in the 8 year old forest are indicative of a regulatory response to the drought. Younger understory trees in the 80+ year old forest showed no signs of a drought response. Throughout most of the dry season, volumetric water content at 30 and 50 cm depths was 8% lower in the 8 year old</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMGC41I..01T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMGC41I..01T"><span>Climate, <span class="hlt">ENSO</span> and 'Black Swans' over the Last Millennium</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, L. G.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.</p> <p>2014-12-01</p> <p>Tropical rainfall patterns influence the lives of billions of people both north and south of the Equator. Evidence of major <span class="hlt">ENSO</span> <span class="hlt">events</span> such as droughts is often recorded in the oxygen isotopic ratios and aerosol concentrations in tropical ice cores. Here we examine unusual <span class="hlt">events</span> recorded in three ice cores, two (Quelccaya and Coropuna) in the Southern Hemisphere on the Peruvian Altiplano and the third (Dasuopu) located 22,000 km away on the southern edge of the Tibetan Plateau at the top of the Himalayas. These records suggest that the unique lower and middle tropospheric air flow over chloride (Cl-) and fluoride (F-) enriched areas upwind of the sites during <span class="hlt">ENSO</span> <span class="hlt">events</span> leads to enhanced deposition of these species on these glaciers. Linkages are demonstrated between ice-core chemistry and drought indicators, changes in lake levels, and <span class="hlt">ENSO</span> and monsoon indices. Two unusual <span class="hlt">events</span>, in the late 18th and mid-14th Centuries, are marked by abnormally high concentrations of F- and Cl- in at least two of the ice core records. All three records document a drought from 1789 to 1800 CE in which increases in these anionic concentrations reflect the abundance of continental atmospheric dust derived from arid regions upwind of the core sites. The earlier <span class="hlt">event</span>, apparent only in the Quelccaya and Dasuopu ice cores, begins abruptly in 1343 and tapers off by 1375. The interaction between high frequency El Niños and low frequency shifts in the inter-tropical convergence zone may have resulted in these unusually severe and extended droughts. These "Black Swan" <span class="hlt">events</span> correspond to historically documented, devastating population disruptions that were in part climate related. The 1789 to 1800 CE <span class="hlt">event</span> was concurrent with the Doji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive climate disruptions are documented in Central and South America. The mid-14th Century drought is concomitant with major monsoon</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H13O..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H13O..04M"><span>Influence of <span class="hlt">ENSO</span> on coastal flood hazard and exposure at the global-scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muis, S.; Haigh, I. D.; Guimarães Nobre, G.; Aerts, J.; Ward, P.</p> <p>2017-12-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is the dominant signal of interannual climate variability. The unusually <span class="hlt">warm</span> (El Niño) and cold (La Niña) oceanic and atmospheric conditions in the tropical Pacific drives interannual variability in both mean and extreme sea levels, which in turn may influence the probabilities and impacts of coastal flooding. We assess the influence of <span class="hlt">ENSO</span> on coastal flood hazard and exposure using daily timeseries from the Global Time and Surge Reanalysis (GTSR) dataset (Muis et al., 2016). As the GTSR timeseries do not include steric effects (i.e. density differences), we improve the GTSR timeseries by adding steric sea levels. Evaluation against observed sea levels shows that the including steric sea levels leads to a much better representation of the seasonal and interannual variability. We show that sea level anomalies occur during <span class="hlt">ENSO</span> years with higher sea levels during La Niña in the South-Atlantic, Indian Ocean and the West Pacific, whereas sea levels are lower in the east Pacific. The pattern is generally inversed for El Niño. We also find an effect of <span class="hlt">ENSO</span> in the number of people exposed to coastal flooding. Although the effect is minor at the global-scale, it may be important for flood risk management to consider at the national or sub national levels. Previous studies at the global-scale have used tide gauge observation to assess the influence of <span class="hlt">ENSO</span> on extreme sea levels. The advantage of our approach over observations is that GTSR provides a consistent dataset with a full global coverage for the period 1979-2014. This allows us to assess <span class="hlt">ENSO</span>'s influence on sea level extremes anywhere in the world. Furthermore, it enables us to also calculate the impacts of extreme sea levels in terms of coastal flooding and exposed population. ReferencesMuis et al (2016) A global reanalysis of storm surges and extreme sea levels. Nature Communications.7:11969. doi:10.1038/ncomms11969.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611667P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611667P"><span>Role of tropical Indian and Atlantic Oceans variability on <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Prodhomme, Chloé; Terray, Pascal; Masson, Sebastien; Boschat, Ghyslaine</p> <p>2014-05-01</p> <p>There are strong evidences of an interaction between tropical Indian, Atlantic and Pacific Oceans. Nevertheless, these interactions remain deeply controversial. While some authors claim the tropical Indian and Atlantic oceans only play a passive role with respect to <span class="hlt">ENSO</span>, others suggest a driving role for these two basins on <span class="hlt">ENSO</span>. The mecanisms underlying these relations are not fully understood and, in the Indian Ocean, the possible role of both modes of tropical variability (the Indian Ocean Dipole (IOD) and the Indian Ocean Basin mode (IOB)) remain unclear. To better quantify and understand how the variability of the tropical Indian and Atlantic Oceans impact <span class="hlt">ENSO</span> variability, we performed two sensitivity experiments using the SINTEX-F2 coupled model. For each experiment, we suppressed the variability of SST and the air-sea coupling in either the tropical Indian Ocean or tropical Atlantic Ocean by applying a strong nudging of the SST to the observed SST climatology. In both experiments, the <span class="hlt">ENSO</span> periodicity increases. In the Atlantic experiment, our understanding of this increased periodicity is drastically limited by the strongly biased mean state in this region. Conversely, in the Indian Ocean experiment, the increase of <span class="hlt">ENSO</span> periodicity is related to the absence of the IOB following the El Niño peak, which leads to a decrease of westerly winds in the western Pacific during late winter and spring after the peak. These weaker westerlies hinders the transition to a La Niña phase and thus increase the duration and periodicity of the <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171391','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171391"><span><span class="hlt">ENSO</span> Bred Vectors in Coupled Ocean-Atmosphere General Circulation Models</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yang, S. C.; Cai, Ming; Kalnay, E.; Rienecker, M.; Yuan, G.; Toth, ZA.</p> <p>2004-01-01</p> <p>The breeding method has been implemented in the NASA Seasonal-to-Interannual Prediction Project (NSIPP) Coupled General Circulation Model (CGCM) with the goal of improving operational seasonal to interannual climate predictions through ensemble forecasting and data assimilation. The coupled instability as cap'tured by the breeding method is the first attempt to isolate the evolving <span class="hlt">ENSO</span> instability and its corresponding global atmospheric response in a fully coupled ocean-atmosphere GCM. Our results show that the growth rate of the coupled bred vectors (BV) peaks at about 3 months before a background <span class="hlt">ENSO</span> <span class="hlt">event</span>. The dominant growing BV modes are reminiscent of the background <span class="hlt">ENSO</span> anomalies and show a strong tropical response with wind/SST/thermocline interrelated in a manner similar to the background <span class="hlt">ENSO</span> mode. They exhibit larger amplitudes in the eastern tropical Pacific, reflecting the natural dynamical sensitivity associated with the presence of the shallow thermocline. Moreover, the extratropical perturbations associated with these coupled BV modes reveal the variations related to the atmospheric teleconnection patterns associated with background <span class="hlt">ENSO</span> variability, e.g. over the North Pacific and North America. A similar experiment was carried out with the NCEP/CFS03 CGCM. Comparisons between bred vectors from the NSIPP CGCM and NCEP/CFS03 CGCM demonstrate the robustness of the results. Our results strongly suggest that the breeding method can serve as a natural filter to identify the slowly varying, coupled instabilities in a coupled GCM, which can be used to construct ensemble perturbations for ensemble forecasts and to estimate the coupled background error covariance for coupled data assimilation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GPC...112...33C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GPC...112...33C"><span>Inter-decadal modulation of <span class="hlt">ENSO</span> teleconnections to the Indian Ocean in a coupled model: Special emphasis on decay phase of El Niño</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chowdary, J. S.; Parekh, Anant; Gnanaseelan, C.; Sreenivas, P.</p> <p>2014-01-01</p> <p>Inter-decadal modulation of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) teleconnections to tropical Indian Ocean (TIO) is investigated in the coupled general circulation model Climate Forecast System (CFS) using a hundred year integration. The model is able to capture the periodicity of El Niño variability, which is similar to that of the observations. The maximum TIO/north Indian Ocean (NIO) SST <span class="hlt">warming</span> (during spring following the decay phase of El Niño) associated with El Niño is well captured by the model. Detailed analysis reveals that the surface heat flux variations mainly contribute to the El Niño forced TIO SST variations both in observations and model. However, spring <span class="hlt">warming</span> is nearly stationary throughout the model integration period, indicating poor inter-decadal El Niño teleconnections. The observations on the other hand displayed maximum SST <span class="hlt">warming</span> with strong seasonality from epoch to epoch. The model El Niño decay delayed by more than two seasons, results in persistent TIO/NIO SST <span class="hlt">warming</span> through the following December unlike in the observations. The ocean wave adjustments and persistent westerly wind anomalies over the equatorial Pacific are responsible for late decay of El Niño in the model. Consistent late decay of El Niño, throughout the model integration period (low variance), is mainly responsible for the poor inter-decadal <span class="hlt">ENSO</span> teleconnections to TIO/NIO. This study deciphers that the model needs to produce El Niño decay phase variability correctly to obtain decadal-modulations in <span class="hlt">ENSO</span> teleconnection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6834435-analysis-enso-episode-comparison','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6834435-analysis-enso-episode-comparison"><span>Analysis of the 1877-78 <span class="hlt">ENSO</span> episode and comparison with 1982-83</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kiladis, G.N.; Diaz, H.F.</p> <p></p> <p>A comparison of the 1877-78 and 1982-83 El Nino/Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span> was made using monthly and seasonal values of sea surface temperature (SST) and station pressure in the tropics, sea level pressure (SLP) in North America and the North Atlantic, temperature in North America and precipitation in several key areas around the globe. SST anomalies in the eastern tropical Pacific, heavy rains in coastal Peru and extreme pressure anomalies across the Pacific and Indian Oceans during 1877-78 indicate an <span class="hlt">ENSO</span> <span class="hlt">event</span> of comparable magnitude to that during 1982-83. Both <span class="hlt">events</span> were also associated with drought conditions in the Indonesianmore » region, India, South Africa, northeastern Brazil and Hawaii. Wintertime teleconnections in the midlatitudes of the Northern Hemisphere were similar in terms of SLP from the North Pacific to Europe, resulting in significantly higher than normal temperatures over most of the US and extreme rains in California.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.1989W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.1989W"><span>What Controls <span class="hlt">ENSO</span>-Amplitude Diversity in Climate Models?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wengel, C.; Dommenget, D.; Latif, M.; Bayr, T.; Vijayeta, A.</p> <p>2018-02-01</p> <p>Climate models depict large diversity in the strength of the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) (<span class="hlt">ENSO</span> amplitude). Here we investigate <span class="hlt">ENSO</span>-amplitude diversity in the Coupled Model Intercomparison Project Phase 5 (CMIP5) by means of the linear recharge oscillator model, which reduces <span class="hlt">ENSO</span> dynamics to a two-dimensional problem in terms of eastern equatorial Pacific sea surface temperature anomalies (T) and equatorial Pacific upper ocean heat content anomalies (h). We find that a large contribution to <span class="hlt">ENSO</span>-amplitude diversity originates from stochastic forcing. Further, significant interactions exist between the stochastic forcing and the growth rates of T and h with competing effects on <span class="hlt">ENSO</span> amplitude. The joint consideration of stochastic forcing and growth rates explains more than 80% of the <span class="hlt">ENSO</span>-amplitude variance within CMIP5. Our results can readily explain the lack of correlation between the Bjerknes Stability index, a measure of the growth rate of T, and <span class="hlt">ENSO</span> amplitude in a multimodel ensemble.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoRL..40.2284B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoRL..40.2284B"><span>Kawasaki disease and <span class="hlt">ENSO</span>-driven wind circulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ballester, Joan; Burns, Jane C.; Cayan, Dan; Nakamura, Yosikazu; Uehara, Ritei; Rodó, Xavier</p> <p>2013-05-01</p> <p>disease (KD) is the most common cause of acquired heart disease in children worldwide. Recently, a climatological study suggested that KD may be triggered by a windborne agent traveling across the north Pacific through the westerly wind flow prevailing at midlatitudes. Here we use KD records to describe the association between enhanced disease activity on opposite sides of the basin and different phases of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon, via the linkage to these tropospheric winds. Results show that years with higher-than-normal KD cases in Japan preferentially occur during either El Niño Modoki or La Niña conditions, while in San Diego during the mature phase of El Niño or La Niña <span class="hlt">events</span>. Given that <span class="hlt">ENSO</span> offers a degree of predictability at lead times of 6 months, these modulations suggest that seasonal predictions of KD could be used to alert clinicians to periods of increased disease activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMOS33D..03R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMOS33D..03R"><span>Understanding multidecadal variability in <span class="hlt">ENSO</span> amplitude</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Russell, A.; Gnanadesikan, A.</p> <p>2013-12-01</p> <p>Sea surface temperatures (SSTs) in the tropical Pacific vary as a result of the coupling between the ocean and atmosphere driven largely by the El Niño - Southern Oscillation (<span class="hlt">ENSO</span>). <span class="hlt">ENSO</span> has a large impact on the local climate and hydrology of the tropical Pacific, as well as broad-reaching effects on global climate. <span class="hlt">ENSO</span> amplitude is known to vary on long timescales, which makes it very difficult to quantify its response to climate change and constrain the physical processes that drive it. In order to assess the extent of unforced multidecadal changes in <span class="hlt">ENSO</span> variability, a linear regression of local SST changes is applied to the GFDL CM2.1 model 4000-yr pre-industrial control run. The resulting regression coefficient strengths, which represent the sensitivity of SST changes to thermocline depth and zonal wind stress, vary by up to a factor of 2 on multi-decadal time scales. This long-term modulation in ocean-atmosphere coupling is highly correlated with <span class="hlt">ENSO</span> variability, but do not explain the reasons for such variability. Variation in the relationship between SST changes and wind stress points to a role for changing stratification in the central equatorial Pacific in modulating <span class="hlt">ENSO</span> amplitudes with stronger stratification reducing the response to winds. The main driving mechanism we have identified for higher <span class="hlt">ENSO</span> variance are changes in the response of zonal winds to SST anomalies. The shifting convection and precipitation patterns associated with the changing state of the atmosphere also contribute to the variability of the regression coefficients. These mechanisms drive much of the variability in <span class="hlt">ENSO</span> amplitude and hence ocean-atmosphere coupling in the tropical Pacific.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS51A2024S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS51A2024S"><span>Contrasting <span class="hlt">ENSO</span> types with novel satellite derived ocean phytoplankton biomass</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sharma, P.; Singh, A. M.; Marinov, I.; Kostadinov, T. S.</p> <p>2016-12-01</p> <p>Observed variations in community structure and biogeochemical processes in the tropics and the North Atlantic have been linked, in the first order, to the El Niño Southern Oscillation phenomenon (e.g., Bates, 2001; Karl et al., 2001; Di Lorenzo et al., 2010; Di Lorenzo et al., 2013). Current significant technical advances have allowed for the retrieval of biological data from the optical properties of the water via satellite ocean color remote sensing, providing an opportunity for quantifying the relationships between biological and climate indices. Studies have focused in-depth on contrasting flavors of the <span class="hlt">ENSO</span> types with various physical (e.g., Singh et al. 2011; Turk et al. 2011) and biological (e.g., Radenac et al. 2012) indices. Here, we analyze the impact of different <span class="hlt">ENSO</span> types on biology via analysis of recently-derived backscattering-based biomass separated into size-groups (Kostadinov et al. 2010, 2016) over the 17-year (1997-2013). We further contrast the responses of biomass with those of chlorophyll (Chl) and particulate inorganic carbon (PIC). We analyze the complex spatial differences in both physical (SST, mixed layer depth, winds) and biological (Chl, total and size-partitioned biomass) variability across the Pacific <span class="hlt">warm</span> pool and equatorial tongue via simple EOF, combined regression-EOF and Agglomerative Hierarchical Clustering (AHC) analysis. The interannual variability in the physical and biological fields show clear signatures of the Niño cold-tongue (NCT) and Niño <span class="hlt">warm</span> pool (NWP). Possible mechanisms responsible for these signatures are discussed.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active"><span>12</span></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_12 --> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUSMPP21A..04S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUSMPP21A..04S"><span>Paleoclimate Records from New Zealand Maar Lakes, Insights into <span class="hlt">ENSO</span> Teleconnections and Climatic <span class="hlt">Events</span> in the South (West) Pacific.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shulmeister, J.; Nobes, D. C.; Striewski, B.</p> <p>2008-05-01</p> <p>The maar craters of the New Zealand Auckland Volcanic Field (36.5°S, 174.5°E) contain some of the highest resolution late-Quaternary paleoclimate records in the Southern Hemisphere. Here we integrate laminae count results from recent drilling in the Hopua Crater with existing records from the nearby Onepoto Crater (Pepper et al., 2004). In total these records cover many thousands of years between the onset of the last glaciation maximum and the early mid-Holocene. The cores are strongly laminated. Individual laminae in both craters are very fine (sub-mm to mm scale) and form couplets which comprise a darker mineralogenic rich layer and a lighter diatomaceous layer. In places these couplets are annual, and may reflect seasonal algal blooms, but in other sections of the record, notably through the late-Glacial and Holocene, the couplets are deposited at inter-annual time scales. Spectral analyses of couplet thickness counts using a fast Fourier transform (FFT) with 64 to 256-year running windows, and a 50 per cent overlap indicate strong spectral power during the LGM and markedly weaker power during both the deglaciation and early Holocene. In fact there is no spectral strength for most of these periods. Three brief (centennial duration) <span class="hlt">events</span> punctuate this extended period of low spectral power. These occur at c. 16 ka, c. 14.8 ka and during the early Holocene. They display spectral power in the 5-7yr <span class="hlt">ENSO</span> window and also at longer time intervals that may be consistent with the Pacific Decadal Oscillation. We infer the local switching on (or up) of <span class="hlt">ENSO</span> and PDO teleconnections and suspect these are embedded in circum-polar circulation changes. In addition to these spectral power episodes, there is a general increase in the number of couplet cycles per century between the deglaciation and the early mid-Holocene. This matches observations from Equador and Peru and suggests that trans-Pacific <span class="hlt">ENSO</span> responses are in phase between western tropical South America and New</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53E2304P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53E2304P"><span>Subtropical tropospheric wave forcing of planetary wave 2 in the prephase of the Stratospheric Sudden <span class="hlt">Warming</span> <span class="hlt">Event</span> in January 2009</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peters, D. H. W.; Schneidereit, A.; Grams, C. M.; Quinting, J. F.; Keller, J. H.; Wolf, G. A.; Teubler, F.; Riemer, M.; Romppainen-Martius, O.</p> <p>2017-12-01</p> <p>Tropospheric forcing of planetary wavenumber 2 is examined in the prephase of the major stratospheric sudden <span class="hlt">warming</span> <span class="hlt">event</span> in January 2009 (MSSW 2009). Because of a huge increase in Eliassen-Palm fluxes induced mainly by wavenumber 2, easterly angular momentum is transported into the Arctic stratosphere, deposited, and then decelerates the polar night jet. In agreement with earlier studies, the results reveal that the strongest eddy heat fluxes, associated with wavenumber 2, occur at 100hPa during the prephase of MSSW 2009 in ERA-Interim. In addition, moderate conditions of the cold phase of <span class="hlt">ENSO</span> (La Niña) contribute to the eddy heat flux anomaly. It is shown that enhanced tropospheric wave forcing over Alaska and Scandinavia is caused by tropical processes in two ways. First, in a climatological sense, La Niña contributes to an enhanced anticyclonic flow over both regions. Second, the Madden-Julian oscillation (MJO) has an indirect influence on the Alaskan ridge by enhancing eddy activity over the North Pacific. This is manifested in an increase in cyclone frequency and associated <span class="hlt">warm</span> conveyor belt outflow, which contribute to the maintenance and amplification of the Alaskan anticyclone. The Scandinavian ridge is maintained by wave trains emanating from the Alaskan ridge propagating eastward, including an enhanced transport of eddy kinetic energy. The MSSW2009 is an extraordinary case of how a beneficial phasing of La Niña and MJO conditions together with multi scale interactions enhances tropospheric forcing for wavenumber 2-induced zonal mean eddy heat flux in the lower stratosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdAtS..34.1358Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdAtS..34.1358Z"><span>Influence of the preceding austral summer Southern Hemisphere annular mode on the amplitude of <span class="hlt">ENSO</span> decay</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Fei; Li, Jianping; Ding, Ruiqiang</p> <p>2017-11-01</p> <p>There is increasing evidence of the possible role of extratropical forcing in the evolution of <span class="hlt">ENSO</span>. The Southern Hemisphere Annular Mode (SAM) is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics. This study shows that the austral summer (December-January-February; DJF) SAM may also influence the amplitude of <span class="hlt">ENSO</span> decay during austral autumn (March-April-May; MAM). The mechanisms associated with this SAM-<span class="hlt">ENSO</span> relationship can be briefly summarized as follows: The SAM is positively (negatively) correlated with SST in the Southern Hemisphere middle (high) latitudes. This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole (SOD). The DJF SOD, caused by the DJF SAM, could persist until MAM and then influence atmospheric circulation, including trade winds, over the Niño3.4 area. Anomalous trade winds and SST anomalies over the Niño3.4 area related to the DJF SAM are further developed through the Bjerkness feedback, which eventually results in a cooling (<span class="hlt">warming</span>) over the Niño3.4 area followed by the positive (negative) DJF SAM.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5467164','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5467164"><span>Extreme temperatures in Southeast Asia caused by El Niño and worsened by global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Thirumalai, Kaustubh; DiNezio, Pedro N.; Okumura, Yuko; Deser, Clara</p> <p>2017-01-01</p> <p>In April 2016, southeast Asia experienced surface air temperatures (SATs) that surpassed national records, exacerbated energy consumption, disrupted agriculture and caused severe human discomfort. Here we show using observations and an ensemble of global <span class="hlt">warming</span> simulations the combined impact of the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon and long-term <span class="hlt">warming</span> on regional SAT extremes. We find a robust relationship between <span class="hlt">ENSO</span> and southeast Asian SATs wherein virtually all April extremes occur during El Niño years. We then quantify the relative contributions of long-term <span class="hlt">warming</span> and the 2015–16 El Niño to the extreme April 2016 SATs. The results indicate that global <span class="hlt">warming</span> increases the likelihood of record-breaking April extremes where we estimate that 29% of the 2016 anomaly was caused by <span class="hlt">warming</span> and 49% by El Niño. These post-Niño Aprils can potentially be anticipated a few months in advance, and thus, help societies prepare for the projected continued increases in extremes. PMID:28585927</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122.5539L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122.5539L"><span><span class="hlt">ENSO</span> effects on MLT diurnal tides: A 21 year reanalysis data-driven GAIA model simulation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Huixin; Sun, Yang-Yi; Miyoshi, Yasunobu; Jin, Hidekatsu</p> <p>2017-05-01</p> <p>Tidal responses to El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) in the mesosphere and lower thermosphere (MLT) are investigated for the first time using reanalysis data-driven simulations covering 21 years. The simulation is carried out with the Ground-to-topside Atmosphere-Ionosphere model for Aeronomy (GAIA) during 1996-2016, which covers nine <span class="hlt">ENSO</span> <span class="hlt">events</span>. <span class="hlt">ENSO</span> impacts on diurnal tides at 100 km altitude are analyzed and cross-compared among temperature (T), zonal wind (U), and meridional wind (V), which reveals the following salient features: (1) Tidal response can differ significantly among T, U, and V in terms of magnitude and latitudinal structure, making detection of <span class="hlt">ENSO</span> effects sensitive to the parameter used and the location of a ground station; (2) the nonmigrating DE3 tide in T and U shows a prominent hemisphere asymmetric response to La Niña, with an increase between 0° and 30°N and a decrease between 30° and 0°S. In contrast, DE3 in V exhibits no significant response; (3) the migrating DW1 enhances during El Niño in equatorial regions for T and U but in off-equatorial regions for V. As the first <span class="hlt">ENSO</span> study based on reanalysis-driven simulations, GAIA's full set of tidal responses in T, U, and V provides us with a necessary global context to better understand and cross-compare observations during <span class="hlt">ENSO</span> <span class="hlt">events</span>. Comparisons with observations during the 1997-98 El Niño and 2010-11 La Niña reveal good agreement in both magnitude and timing. Comparisons with "free-run" WACCM simulations (T) show consistent results in nonmigrating tides DE2 and DE3 but differences in the migrating DW1 tide.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A43I..03L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A43I..03L"><span>Influence of <span class="hlt">ENSO</span> on Gulf Stream cyclogenesis and the North Atlantic storm track</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, C.; Schemm, S.; Ciasto, L.; Kvamsto, N. G.</p> <p>2015-12-01</p> <p>There is emerging evidence that climate in the North Atlantic-European sector is sensitive to vacillations of tropical Pacific sea surface temperatures, in particular, the central Pacific flavour of the El Nino Southern Oscillation (<span class="hlt">ENSO</span>) and concomitant trends in atmospheric heating. The frequency of central Pacific <span class="hlt">ENSOs</span> appears to have increased over the last decades and some studies suggest it may continue increasing in the future, but the precise mechanisms by which these <span class="hlt">events</span> affect the North Atlantic synoptic scale circulation are poorly understood. Here, we show that central Pacific <span class="hlt">ENSOs</span> influence where midlatitude cyclogenesis occurs over the Gulf Stream, producing more cyclogenesis in the jet exit region rather than in the climatologically preferred jet entrance region. The cyclones forming over the Gulf Stream in central Pacific <span class="hlt">ENSO</span> seasons tend to veer north, penetrating deeper into the Arctic rather than into continental Europe. The shift in cyclogenesis is linked to changes in the large scale circulation, namely, the upper-level trough formed in the lee of the Rocky Mountains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70193647','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70193647"><span>North Pacific deglacial hypoxic <span class="hlt">events</span> linked to abrupt ocean <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Praetorius, Summer K; Mix, Alan C.; Davies, Maureen H.; Wolhowe, Matthew D; Addison, Jason A.; Prahl, Frederick G</p> <p>2015-01-01</p> <p>Marine sediments from the North Pacific document two episodes of expansion and strengthening of the subsurface oxygen minimum zone (OMZ) accompanied by seafloor hypoxia during the last deglacial transition1, 2, 3, 4. The mechanisms driving this hypoxia remain under debate1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. We present a new high-resolution alkenone palaeotemperature reconstruction from the Gulf of Alaska that reveals two abrupt <span class="hlt">warming</span> <span class="hlt">events</span> of 4–5 degrees Celsius at the onset of the Bølling and Holocene intervals that coincide with sudden shifts to hypoxia at intermediate depths. The presence of diatomaceous laminations and hypoxia-tolerant benthic foraminiferal species, peaks in redox-sensitive trace metals12, 13, and enhanced 15N/14N ratio of organic matter13, collectively suggest association with high export production. A decrease in 18O/16O values of benthic foraminifera accompanying the most severe deoxygenation <span class="hlt">event</span> indicates subsurface <span class="hlt">warming</span> of up to about 2 degrees Celsius. We infer that abrupt <span class="hlt">warming</span> triggered expansion of the North Pacific OMZ through reduced oxygen solubility and increased marine productivity via physiological effects; following initiation of hypoxia, remobilization of iron from hypoxic sediments could have provided a positive feedback on ocean deoxygenation through increased nutrient utilization and carbon export. Such a biogeochemical amplification process implies high sensitivity of OMZ expansion to <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A22E..04Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A22E..04Z"><span>An MJO-Mediated Mechanism to Explain <span class="hlt">ENSO</span> and IOD Impacts on East African Short Rains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaitchik, B. F.; Berhane, F.; Gnanadesikan, A.</p> <p>2015-12-01</p> <p>Previous studies have found that the El Nino Southern Oscillation (<span class="hlt">ENSO</span>) and the Indian Ocean Dipole (IOD) have significant impacts on rainfall over East Africa (EA) during the short rains (Oct-Dec). However, not all <span class="hlt">ENSO</span> and IOD <span class="hlt">events</span> are associated with significant precipitation anomalies over EA. Our analysis shows that the IOD and <span class="hlt">ENSO</span> influence EA rainfall by modifying the MJO. Composite analysis of rainfall and outgoing longwave radiation data show that the MJO over the Indian Ocean (phases 2 and 3 of the Wheeler and Hendon index) is associated with significant increase in precipitation over EA during El Niño. In La Niña and non-<span class="hlt">ENSO</span> years, the MJO over the Indian Ocean has very weak impacts on EA convection and precipitation. Although previous studies have found that El Niño / La Niña <span class="hlt">events</span> are associated with anomalous wetness/dryness over EA, the associations are not evident in the absence of the MJO. Similarly, the IOD exhibits strong associations with EA precipitation when there is MJO activity over the Indian Ocean. During the positive phase of the IOD, the MJO over the Indian Ocean has impacts that extend to EA. In the absence of the MJO, however, the IOD shows weak associations with EA precipitation. Furthermore, there are more MJO days in the Indian Ocean during El Niño and positive IOD <span class="hlt">events</span>, which implies stronger impacts on EA. During La Niña <span class="hlt">events</span> more MJO days are observed in the Pacific Ocean, favoring subsidence over the western Indian Ocean and dry anomalies over EA. These observations suggest two critical MJO-related questions that must be addressed in order to explain EA short rain variability typically attributed to <span class="hlt">ENSO</span> or IOD: first, how do <span class="hlt">ENSO</span> and IOD modify background conditions in a way that causes Indian Ocean MJO activity to be more strongly connected to EA under El Niño and IOD positive conditions, and second, why is it that El Niño and IOD positive states slow MJO propagation over the Indian Ocean and speed it over</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.C21A0703P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.C21A0703P"><span>Interannual Variability in Amundsen Sea Ice-Shelf Height Change Linked to <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paolo, F. S.; Fricker, H. A.; Padman, L.</p> <p>2015-12-01</p> <p>Atmospheric and sea-ice conditions around Antarctica, particularly in the Amundsen and Bellingshausen seas, respond to climate dynamics in the tropical Pacific Ocean on interannual time scales including the El Nino-Southern Oscillation (<span class="hlt">ENSO</span>). It has been hypothesized that the mass balance of the Antarctic Ice Sheet, including its floating ice shelves, also responds to this climate signal; however, this has not yet been unambiguously demonstrated. We apply multivariate singular spectrum analysis (MSSA) to our 18-year (1994-2012) time series of ice-shelf height in the Amundsen Sea (AS) region. This advanced spectral method distinguishes between regular deterministic behavior ("cycles") at sub-decadal time scale and irregular behavior ("noise") at shorter time scales. Although the long-term trends of AS ice-shelf height changes are much larger than the range of interannual variability, the short-term rate of change dh/dt can vary about the trend by more than 50%. The mode of interannual variability in the AS ice-shelf height is strongly correlated with the low-frequency mode of <span class="hlt">ENSO</span> (periodicity of ~4.5 years) as represented by the Southern Oscillation Index. The ice-shelf height in the AS is expected to respond to changes in precipitation and inflows of <span class="hlt">warm</span> subsurface Circumpolar Deep Water (CDW) into the ocean cavities under the ice shelves, altering basal melt rates. Since both of these processes affecting ice-shelf mass balance respond to changes in wind fields for different <span class="hlt">ENSO</span> states, we expect some correlation between them. We will describe the spatial structure of AS ice-shelf height response to <span class="hlt">ENSO</span>, and attempt to distinguish the precipitation signal from basal mass balance due to changing CDW inflows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA......310C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA......310C"><span>The <span class="hlt">enso</span> signal in the lower stratosphere: propagation via rossby waves.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calvo, N.; Garcia Herrera, R.; Garcia, R.; Gallego, D.; Gimeno, L.; Hernandez, E.; Ribera, P.</p> <p>2003-04-01</p> <p>The <span class="hlt">ENSO</span> signal on the lower stratosphere has been analyzed through the study of the relationship between SST in the Tropical Pacific and lower stratospheric temperatures from the Microwave Sounding Unit (MSU) using the t4 channel, which is sensitive to lower stratospheric temperature. Lagged point correlations have been calculated between the Niño3.4 index and MSU t4 monthly anomaly series at each grid point for the whole globe from January 1979 through December 2000. Correlation values are very similar in both tropics and extratropics, but their signs are opposite: positive in extratropical regions and negative in the tropics. Moreover, the significant correlation signal is longer lasting at middle latitudes, from lag 9 to lag 6, and much shorter in the Tropics, where it is significant only at lags 0 and 3. In the extratropical area, four regions are significant: Eurasia, the Southern Indian Ocean, and the North and South Pacific Oceans. The signal in Eurasia is the first to be observed (at lag 9) and it could be considered as a predictor of extreme <span class="hlt">ENSO</span> <span class="hlt">events</span>. The Pacific Ocean shows the PNA and PSA patterns. There, the signal appears earlier in the Southern Hemisphere (lag 6) because wind conditions at boreal summer (usually lag 6) do not favour the propagation of Rossby waves into the stratosphere. Further, the shape of the correlation patterns suggests that only planetary waves are able to propagate the <span class="hlt">ENSO</span> signal into the stratosphere. In the tropics, the <span class="hlt">ENSO</span> signal takes the form of a pair of Rossby gyres, observed in the Pacific Ocean at lags 0 and 3 as two regions of significant correlation located symmetricaly north and south of the Equator. The same analysis has been carried out for a period without any extreme <span class="hlt">events</span> (SST anomalies in the Niño3.4 region smaller than 1 standard desviation), in which case no signal is observed in the lower stratosphere. This suggests that only strong <span class="hlt">ENSO</span> (defined by anomalies larger than 1 standard desviation in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1613044P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1613044P"><span>Easterly and westerly wind <span class="hlt">events</span> in the equatorial Pacific ocean and their oceanic response</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Puy, martin; Lengaigne, matthieu; Vialard, jerome; Guilyardi, eric</p> <p>2014-05-01</p> <p>Intraseasonal wind variability is known to influence the onset and evolution of the El Niño Southern Oscillation (<span class="hlt">ENSO</span>), in particular through the occurrence of Westerly Wind <span class="hlt">Events</span> (WWEs) in the western Equatorial Pacific. For predictability purposes, it is important to identify the large scale atmospheric controls of the occurrences of those WWEs. We hence carefully assess the link between equatorial WWEs and large-scale atmospheric waves. We find that WWEs preferably occur during convectively active phases associated to equatorial atmospheric Rossby waves (74% against 15% if the distribution was random) and to the MJO (60% against 15%). We also find that WWEs that occur in relation with those atmospheric waves tend to be stronger. The results also show that WWEs that occur in relation with the MJO tend to be longer than others, and tend to have a larger impact on SST, both on the eastern edge of the <span class="hlt">warm</span> pool and in the eastern Pacific. We further show that the central and eastern equatorial Pacific is home to frequent easterly wind <span class="hlt">events</span> (EWEs). These EWEs are further shown to be influenced by atmospheric Rossby waves and the MJO, but to a lesser extent than WWEs. We will discuss the potential influence of EWEs on the <span class="hlt">ENSO</span> cycle, and propose a modeling strategy to test the influence of these EWEs / WWEs on the <span class="hlt">ENSO</span> evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4310891M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4310891M"><span><span class="hlt">ENSO</span> controls interannual fire activity in southeast Australia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mariani, M.; Fletcher, M.-S.; Holz, A.; Nyman, P.</p> <p>2016-10-01</p> <p>El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is the main mode controlling the variability in the ocean-atmosphere system in the South Pacific. While the <span class="hlt">ENSO</span> influence on rainfall regimes in the South Pacific is well documented, its role in driving spatiotemporal trends in fire activity in this region has not been rigorously investigated. This is particularly the case for the highly flammable and densely populated southeast Australian sector, where <span class="hlt">ENSO</span> is a major control over climatic variability. Here we conduct the first region-wide analysis of how <span class="hlt">ENSO</span> controls fire activity in southeast Australia. We identify a significant relationship between <span class="hlt">ENSO</span> and both fire frequency and area burnt. Critically, wavelet analyses reveal that despite substantial temporal variability in the <span class="hlt">ENSO</span> system, <span class="hlt">ENSO</span> exerts a persistent and significant influence on southeast Australian fire activity. Our analysis has direct application for developing robust predictive capacity for the increasingly important efforts at fire management.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.3513C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.3513C"><span>A comparison of sea surface salinity in the equatorial Pacific Ocean during the 1997-1998, 2012-2013, and 2014-2015 <span class="hlt">ENSO</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Corbett, Caroline M.; Subrahmanyam, Bulusu; Giese, Benjamin S.</p> <p>2017-11-01</p> <p>Sea surface salinity (SSS) variability during the 1997-1998 El Niño <span class="hlt">event</span> and the failed 2012-2013 and 2014-2015 El Niño <span class="hlt">events</span> is explored using a combination of observations and ocean reanalyses. Previously, studies have mainly focused on the sea surface temperature (SST) and sea surface height (SSH) variability. This analysis utilizes salinity data from Argo and the Simple Ocean Data Assimilation (SODA) reanalysis to examine the SSS variability. Advective processes and evaporation minus precipitation (E-P) variability is understood to influence SSS variability. Using surface wind, surface current, evaporation, and precipitation data, we analyze the causes for the observed SSS variability during each <span class="hlt">event</span>. Barrier layer thickness and upper level salt content are also examined in connection to subsurface salinity variability. Both advective processes and E-P variability are important during the generation and onset of a successful El Niño, while a lack of one or both of these processes leads to a failed <span class="hlt">ENSO</span> <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.C33G..08B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.C33G..08B"><span>Characterizing the Chemical and Physical Signature of the 2015-16 El Niño in the Quelccaya Ice Cap Snow and Ice to Calibrate Past <span class="hlt">ENSO</span> Reconstructions.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beaudon, E.; Barker, J. D.; Kenny, D. V.; Thompson, L. G.</p> <p>2017-12-01</p> <p>Pacific Sea Surface Temperature (SST) anomalies have reached +3°C in the Niño 3.4 region in November 2015 making this one of the strongest El Niños in 100 years. This <span class="hlt">warm</span> phase of the El Niño - Southern Oscillation (<span class="hlt">ENSO</span>) has pronounced differential impacts across the tropical Pacific as well as in South America. Peru statistically experienced flooding in the northern and central regions and drought conditions in the south on the Altiplano. However, the 2015-16 El Nino <span class="hlt">event</span> led to drought throughout the Peruvian Andes. El Niño is a <span class="hlt">warm</span> and dry episode, phase locked with the accumulation season on the Quelccaya Ice Cap (QIC) so that this strong <span class="hlt">event</span> create conditions favorable for enhanced surface ablation and dry deposition of soluble and insoluble aerosols. Here we present new glaciochemical (major and organic ions, dust, black carbon, oxygen isotopes) results from two consecutive snow and ice sampling campaign on QIC framing the climax of the 2015/2016 El Niño episode in Peru. We allocate the ionic and black carbon sources and describe the biogenic and evaporitic contributions to Quelccaya snow chemistry under El Niño atmospheric conditions. Elution factors and ionic budgets are compared to those of the snow and ice samples collected prior to the El Niño initiation and thereby assess the magnitude of the impact of El Niño-induced post-depositional processes. Our results provide the database needed to verify that: 1) melt and percolation induced by El Niño is identifiable in the prior year's snow layer and thus might be calibrated to the El Niño's strength; and 2) the concentration and co-association of biogenic (e.g., NH4, black carbon) and evaporitic (salts) species is enhanced and detectable deeper in the ice and thereby might serve as a proxy for documenting past El Niño frequency. By capturing the chemical signature of a modern El Niño <span class="hlt">event</span> occurring in a <span class="hlt">warming</span> world, these results shed light on past <span class="hlt">ENSO</span> variability preserved in ice core</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThApC.129.1059D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThApC.129.1059D"><span>Predicting monthly precipitation along coastal Ecuador: <span class="hlt">ENSO</span> and transfer function models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>de Guenni, Lelys B.; García, Mariangel; Muñoz, Ángel G.; Santos, José L.; Cedeño, Alexandra; Perugachi, Carlos; Castillo, José</p> <p>2017-08-01</p> <p>It is well known that El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) modifies precipitation patterns in several parts of the world. One of the most impacted areas is the western coast of South America, where Ecuador is located. El Niño <span class="hlt">events</span> that occurred in 1982-1983, 1987-1988, 1991-1992, and 1997-1998 produced important positive rainfall anomalies in the coastal zone of Ecuador, bringing considerable damage to livelihoods, agriculture, and infrastructure. Operational climate forecasts in the region provide only seasonal scale (e.g., 3-month averages) information, but during <span class="hlt">ENSO</span> <span class="hlt">events</span> it is key for decision-makers to use reliable sub-seasonal scale forecasts, which at the present time are still non-existent in most parts of the world. This study analyzes the potential predictability of coastal Ecuador rainfall at monthly scale. Instead of the discrete approach that considers training models using only particular seasons, continuous (i.e., all available months are used) transfer function models are built using standard <span class="hlt">ENSO</span> indices to explore rainfall forecast skill along the Ecuadorian coast and Galápagos Islands. The modeling approach considers a large-scale contribution, represented by the role of a sea-surface temperature index, and a local-scale contribution represented here via the use of previous precipitation observed in the same station. The study found that the Niño3 index is the best <span class="hlt">ENSO</span> predictor of monthly coastal rainfall, with a lagged response varying from 0 months (simultaneous) for Galápagos up to 3 months for the continental locations considered. Model validation indicates that the skill is similar to the one obtained using principal component regression models for the same kind of experiments. It is suggested that the proposed approach could provide skillful rainfall forecasts at monthly scale for up to a few months in advance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170004582','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170004582"><span>The Impact of <span class="hlt">ENSO</span> on Trace Gas Composition in the Upper Troposphere to Lower Stratosphere</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oman, Luke; Douglass, Anne; Ziemke, Jerry; Waugh, Darryn Warwick</p> <p>2016-01-01</p> <p>The El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) is the dominant mode of interannual variability in the tropical troposphere and its effects extend well into the stratosphere. Its impact on atmospheric dynamics and chemistry cause important changes to trace gas constituent distributions. A comprehensive suite of satellite observations, reanalyses, and chemistry climate model simulations are illuminating our understanding of processes like <span class="hlt">ENSO</span>. Analyses of more than a decade of observations from NASAs Aura and Aqua satellites, combined with simulations from the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM) and other Chemistry Climate Modeling Initiative (CCMI) models, and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis have provided key insights into the response of atmospheric composition to <span class="hlt">ENSO</span>. While we will primarily focus on ozone and water vapor responses in the upper troposphere to lower stratosphere, the effects of <span class="hlt">ENSO</span> ripple through many important trace gas species throughout the atmosphere. The very large 2015-2016 El Nino <span class="hlt">event</span> provides an opportunity to closely examine these impacts with unprecedented observational breadth. An improved quantification of natural climate variations, like those from <span class="hlt">ENSO</span>, is needed to detect and quantify anthropogenic climate changes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000044331','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000044331"><span>On The Bimodality of <span class="hlt">ENSO</span> Cycle Extremes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, Robert M.</p> <p>2000-01-01</p> <p>On the basis of sea surface temperature in the El Nino 3.4 region (5N.-5S., 120-170W.) during the interval of 1950-1997, Kevin Trenberth previously has identified some 16 El Nino and 10 La Nina, these 26 <span class="hlt">events</span> representing the extremes of the quasi-periodic El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) cycle. Runs testing shows that the duration, recurrence period, and sequencing of these extremes vary randomly. Hence, the decade of the 1990's, especially for El Nino, is not significantly different from that of previous decadal epochs, at least, on the basis of the frequency of onsets of <span class="hlt">ENSO</span> extremes. Additionally, the distribution of duration for both El Nino and La Nina looks strikingly bimodal, each consisting of two preferred modes, about 8- and 16-months long for El Nino and about 9- and 18-months long for La Nina, as does the distribution of the recurrence period for El Nino, consisting of two preferred modes about 21- and 50- mo long. Scatterplots of the recurrence period versus duration for El Nino are found to be statistically important, displaying preferential associations that link shorter (longer) duration with shorter (longer) recurrence periods. Because the last onset of El Nino occurred in April 1997 and the <span class="hlt">event</span> was of longer than average duration, onset of the next anticipated El Nino is not expected until February 2000 or later.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004CSR....24.2343A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004CSR....24.2343A"><span>Geochemistry of coral from Papua New Guinea as a proxy for <span class="hlt">ENSO</span> ocean-atmosphere interactions in the Pacific <span class="hlt">Warm</span> Pool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ayliffe, Linda K.; Bird, Michael I.; Gagan, Michael K.; Isdale, Peter J.; Scott-Gagan, Heather; Parker, Bruce; Griffin, David; Nongkas, Michael; McCulloch, Malcolm T.</p> <p>2004-12-01</p> <p>A Porites sp. coral growing offshore from the Sepik and Ramu Rivers in equatorial northern Papua New Guinea has yielded an accurate 20-year history (1977-1996) of sea surface temperature (SST), river discharge, and wind-induced mixing of the upper water column. Depressions in average SSTs of about 0.5-1.0 °C (indicated by coral Sr/Ca) and markedly diminished freshwater runoff to the coastal ocean (indicated by coral δ18O, δ13C and UV fluorescence) are evident during the El Niño - Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span> of 1982-1983, 1987 and 1991-1993. The perturbations recorded by the coral are in good agreement with changes in instrumental SST and river discharge/precipitation records, which are known to be diagnostic of the response of the Pacific <span class="hlt">Warm</span> Pool ocean-atmosphere system to El Niño. Consideration of coastal ocean dynamics indicates that the establishment of northwest monsoon winds promotes mixing of near-surface waters to greater depths in the first quarter of most years, making the coral record sensitive to changes in the Asian-Australian monsoon cycle. Sudden cooling of SSTs by ˜1°C following westerly wind episodes, as indicated by the coral Sr/Ca, is consistent with greater mixing in the upper water column at these times. Furthermore, the coral UV fluorescence and oxygen isotope data indicate minimal contribution of river runoff to surface ocean waters at the beginning of most years, during the time of maximum discharge. This abrupt shift in flood-plume behaviour appears to reflect the duration and magnitude of northwest monsoon winds, which tend to disperse flood plume waters to a greater extent in the water column when wind-mixing is enhanced. Our results suggest that a multi-proxy geochemical approach to the production of long coral records should provide comprehensive reconstructions of tropical paleoclimate processes operating on interannual timescales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2384E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2384E"><span>Future changes in rainfall associated with <span class="hlt">ENSO</span>, IOD and changes in the mean state over Eastern Africa</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Endris, Hussen Seid; Lennard, Christopher; Hewitson, Bruce; Dosio, Alessandro; Nikulin, Grigory; Artan, Guleid A.</p> <p>2018-05-01</p> <p>This study examines the projected changes in the characteristics of the El Niño Southern Oscillation (<span class="hlt">ENSO</span>) and Indian Ocean Dipole (IOD) in terms of mean state, intensity and frequency, and associated rainfall anomalies over eastern Africa. Two regional climate models driven by the same four global climate models (GCMs) and the corresponding GCM simulations are used to investigate projected changes in teleconnection patterns and East African rainfall. The period 1976-2005 is taken as the reference for present climate and the far-future climate (2070-2099) under Representative Concentration Pathway 8.5 (RCP8.5) is analyzed for projected change. Analyses of projections based on GCMs indicate an El Niño-like (positive IOD-like) <span class="hlt">warming</span> pattern over the tropical Pacific (Indian) Ocean. However, large uncertainties remain in the projected future changes in <span class="hlt">ENSO</span>/IOD frequency and intensity with some GCMs show increase of <span class="hlt">ENSO</span>/IOD frequency and intensity, and others a decrease or no/small change. Projected changes in mean rainfall over eastern Africa based on the GCM and RCM data indicate a decrease in rainfall over most parts of the region during JJAS and MAM seasons, and an increase in rainfall over equatorial and southern part of the region during OND, with the greatest changes in equatorial region. During <span class="hlt">ENSO</span> and IOD years, important changes in the strength of the teleconnections are found. During JJAS, when <span class="hlt">ENSO</span> is an important driver of rainfall variability over the region, both GCM and RCM projections show an enhanced La Niña-related rainfall anomaly compared to the present period. Although the long rains (MAM) have little association with <span class="hlt">ENSO</span> in the reference period, both GCMs and RCMs project stronger <span class="hlt">ENSO</span> teleconnections in the future. On the other hand, during the short rains (OND), a dipole future change in rainfall teleconnection associated with <span class="hlt">ENSO</span> and IOD is found, with a stronger <span class="hlt">ENSO</span>/IOD related rainfall anomaly over the eastern part of the domain</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006EOSTr..87..165B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006EOSTr..87..165B"><span>Eocene Hyperthermal <span class="hlt">Event</span> Offers Insight Into Greenhouse <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bowen, Gabriel J.; Bralower, Timothy J.; Delaney, Margaret L.; Dickens, Gerald R.; Kelly, Daniel C.; Koch, Paul L.; Kump, Lee R.; Meng, Jin; Sloan, Lisa C.; Thomas, Ellen; Wing, Scott L.; Zachos, James C.</p> <p>2006-04-01</p> <p>What happens to the Earth's climate, environment, and biota when thousands of gigatons of greenhouse gases are rapidly added to the atmosphere? Modern anthropogenic forcing of atmospheric chemistry promises to provide an experiment in such change that has not been matched since the early Paleogene, more than 50 million years ago (Ma),when catastrophic release of carbon to the atmosphere drove abrupt, transient, hyperthermal <span class="hlt">events</span>. Research on the Paleocene-Eocene Thermal Maximum (PETM)-the best documented of these <span class="hlt">events</span>, which occurred about 55 Ma-has advanced significantly since its discovery 15 years ago. During the PETM, carbon addition to the oceans and atmosphere was of a magnitude similar to that which is anticipated through the 21st century. This <span class="hlt">event</span> initiated global <span class="hlt">warming</span>, biotic extinction and migration, and fundamental changes in the carbon and hydrological cycles that transformed the early Paleogene world.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active"><span>13</span></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_13 --> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4265694','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4265694"><span>Characteristics of Lake Chad Level Variability and Links to <span class="hlt">ENSO</span>, Precipitation, and River Discharge</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Demoz, Belay; Gebremariam, Sium</p> <p>2014-01-01</p> <p>This study used trend, correlation, and wavelet analysis to characterize Lake Chad (LC) level fluctuations, river discharge, El Niño Southern Oscillation (<span class="hlt">ENSO</span>), and precipitation regimes and their interrelationships. Linear correlation results indicate a negative association between <span class="hlt">ENSO</span> and LC level, river discharge and precipitation. Trend analysis shows increasing precipitation in the Lake Chad Basin (LCB) but decreasing LC level. The mode of interannual variability in LC level, rainfall, and <span class="hlt">ENSO</span> analyzed using wavelet analysis is dominated by 3-4-year periods. Results show that variability in <span class="hlt">ENSO</span> could explain only 31% and 13% of variations in LC level at Kindjeria and precipitation in the northern LCB, respectively. The wavelet transform coherency (WTC) between LC level of the southern pool at Kalom and <span class="hlt">ENSO</span> is statistically significant at the 95% confidence level and phase-locked, implying a cause-and-effect association. These strong coherencies coincide with the La Niña years with the exception of 1997-1998 El Niño <span class="hlt">events</span>. The WTC shows strong covariance between increasing precipitation and LC level in the northern pool at a 2- to 4-year band and 3- to 4-year band localized from 1996 to 2010. Implications for water resource planning and management are discussed. PMID:25538946</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950040891&hterms=Global+warming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DGlobal%2Bwarming','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950040891&hterms=Global+warming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DGlobal%2Bwarming"><span>Global variations of zonal mean ozone during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Randel, William J.</p> <p>1993-01-01</p> <p>Eight years of Solar Backscatter Ultraviolet (SBUV) ozone data are examined to study zonal mean variations associated with stratospheric planetary wave (<span class="hlt">warming</span>) <span class="hlt">events</span>. These fluctuations are found to be nearly global in extent, with relatively large variations in the tropics, and coherent signatures reaching up to 50 deg in the opposite (summer) hemisphere. These ozone variations are a manifestation of the global circulation cells associated with stratospheric <span class="hlt">warming</span> <span class="hlt">events</span>; the ozone responds dynamically in the lower stratosphere to transport, and photochemically in the upper stratosphere to the circulation-induced temperature changes. The observed ozone variations in the tropics are of particular interest because transport is dominated by zonal-mean vertical motions (eddy flux divergences and mean meridional transports are negligible), and hence, substantial simplifications to the governing equations occur. The response of the atmosphere to these impulsive circulation changes provides a situation for robust estimates of the ozone-temperature sensitivity in the upper stratosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990079379&hterms=pacific+ocean+phytoplankton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpacific%2Bocean%2Bphytoplankton','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990079379&hterms=pacific+ocean+phytoplankton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dpacific%2Bocean%2Bphytoplankton"><span>Ocean Thermal and Color Evolution During the 1997/1998 <span class="hlt">ENSO</span> <span class="hlt">Event</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Rienecker, Michele</p> <p>1998-01-01</p> <p>A reduced gravity primitive equation modeling and assimilation system is used to study the evolution of the tropical Pacific during the 1997/1998 <span class="hlt">ENSO</span> cycle. The modeling/assimilation scheme ingests satellite altimeter data and TAO temperature profiles and uses SSM/I satellite derived winds as surface boundary forcing. The four-dimensional structure of the upper ocean circulation structure will be compared against available in situ observations across the Pacific basin. In particular, variability near the Galapagos Islands will be highlighted during the spring of 1998 when phytoplankton concentrations were observed to increase a hundred-fold over a two week period.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC24G..05P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC24G..05P"><span>PDO and <span class="hlt">ENSO</span> Sea Surface Temperature Anomalies Control Grassland Plant Production across the United States Great Plains</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parton, W. J.; Del Grosso, S. J.; Smith, W. K.; Chen, M.</p> <p>2017-12-01</p> <p>The El Nino Southern Oscillation (<span class="hlt">ENSO</span>) and Pacific Decadal Oscillation (PDO) are multi-annual to multi-decadal climate patterns defined by ocean temperature anomalies that can strongly modulate climate variability. Here we evaluated the impacts of PDO and <span class="hlt">ENSO</span> sea surface temperature (SST) anomalies on observed grassland above ground plant production (ANPP; 1940 to 2015), spring (April to July) cumulative actual evapotranspiration (iAET; 1900 to 2015) , and satellite-derived growing season (April to October) cumulative normalized difference vegetation index (iNDVI 1982 to 2015) across the United States Great Plains. The results showed that grassland ANPP is well correlated to iAET (r2=0.69) and iNDVI (r2=0.50 to 0.70) for the Cheyenne Wyoming and Northeastern Colorado long-term ANPP sites. At the site scale, during the negative phase of the PDO, we find ANPP is much lower (25%) and that variability of iAET, iNDVI, and ANPP are much higher (2 to 3 times) compared to the <span class="hlt">warm</span> phase PDO. Further, we find there is a high frequency of below normal iAET when PDO and <span class="hlt">ENSO</span> SST's are both negative, while there is a high frequency of above normal iAET when PDO and <span class="hlt">ENSO</span> values are positive. At the regional scale, iAET, iNDVI, and modeled ANPP data sets show that plant production and iAET values are high in the southern Great Plains and low in the northern Great Plains when spring PDO and <span class="hlt">ENSO</span> are both in the positive phase, while the opposite pattern is observed when both PDO and <span class="hlt">ENSO</span> are both in the negative phase. Variability of iAET, iNDVI, and modeled ANPP are much higher in the central Great Plains during the negative phase PDO. We demonstrate clearly that the PDO and <span class="hlt">ENSO</span> SST anomalies have large impacts on mean and variability of grassland plant production across the Great Plains.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20403836','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20403836"><span>Recent and future <span class="hlt">warm</span> extreme <span class="hlt">events</span> and high-mountain slope stability.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huggel, C; Salzmann, N; Allen, S; Caplan-Auerbach, J; Fischer, L; Haeberli, W; Larsen, C; Schneider, D; Wessels, R</p> <p>2010-05-28</p> <p>The number of large slope failures in some high-mountain regions such as the European Alps has increased during the past two to three decades. There is concern that recent climate change is driving this increase in slope failures, thus possibly further exacerbating the hazard in the future. Although the effects of a gradual temperature rise on glaciers and permafrost have been extensively studied, the impacts of short-term, unusually <span class="hlt">warm</span> temperature increases on slope stability in high mountains remain largely unexplored. We describe several large slope failures in rock and ice in recent years in Alaska, New Zealand and the European Alps, and analyse weather patterns in the days and weeks before the failures. Although we did not find one general temperature pattern, all the failures were preceded by unusually <span class="hlt">warm</span> periods; some happened immediately after temperatures suddenly dropped to freezing. We assessed the frequency of <span class="hlt">warm</span> extremes in the future by analysing eight regional climate models from the recently completed European Union programme ENSEMBLES for the central Swiss Alps. The models show an increase in the higher frequency of high-temperature <span class="hlt">events</span> for the period 2001-2050 compared with a 1951-2000 reference period. <span class="hlt">Warm</span> <span class="hlt">events</span> lasting 5, 10 and 30 days are projected to increase by about 1.5-4 times by 2050 and in some models by up to 10 times. <span class="hlt">Warm</span> extremes can trigger large landslides in temperature-sensitive high mountains by enhancing the production of water by melt of snow and ice, and by rapid thaw. Although these processes reduce slope strength, they must be considered within the local geological, glaciological and topographic context of a slope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018OcSci..14...69T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018OcSci..14...69T"><span>Response of O2 and pH to <span class="hlt">ENSO</span> in the California Current System in a high-resolution global climate model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Turi, Giuliana; Alexander, Michael; Lovenduski, Nicole S.; Capotondi, Antonietta; Scott, James; Stock, Charles; Dunne, John; John, Jasmin; Jacox, Michael</p> <p>2018-02-01</p> <p>Coastal upwelling systems, such as the California Current System (CalCS), naturally experience a wide range of O2 concentrations and pH values due to the seasonality of upwelling. Nonetheless, changes in the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) have been shown to measurably affect the biogeochemical and physical properties of coastal upwelling regions. In this study, we use a novel, high-resolution global climate model (GFDL-ESM2.6) to investigate the influence of <span class="hlt">warm</span> and cold <span class="hlt">ENSO</span> <span class="hlt">events</span> on variations in the O2 concentration and the pH of the CalCS coastal waters. An assessment of the CalCS response to six El Niño and seven La Niña <span class="hlt">events</span> in ESM2.6 reveals significant variations in the response between <span class="hlt">events</span>. However, these variations overlay a consistent physical and biogeochemical (O2 and pH) response in the composite mean. Focusing on the mean response, our results demonstrate that O2 and pH are affected rather differently in the euphotic zone above ˜ 100 m. The strongest O2 response reaches up to several hundreds of kilometers offshore, whereas the pH signal occurs only within a ˜ 100 km wide band along the coast. By splitting the changes in O2 and pH into individual physical and biogeochemical components that are affected by <span class="hlt">ENSO</span> variability, we found that O2 variability in the surface ocean is primarily driven by changes in surface temperature that affect the O2 solubility. In contrast, surface pH changes are predominantly driven by changes in dissolved inorganic carbon (DIC), which in turn is affected by upwelling, explaining the confined nature of the pH signal close to the coast. Below ˜ 100 m, we find conditions with anomalously low O2 and pH, and by extension also anomalously low aragonite saturation, during La Niña. This result is consistent with findings from previous studies and highlights the stress that the CalCS ecosystem could periodically undergo in addition to impacts due to climate change.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5441735','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5441735"><span>Quantifying the influence of global <span class="hlt">warming</span> on unprecedented extreme climate <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Singh, Deepti; Horton, Daniel E.; Swain, Daniel L.; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; Rajaratnam, Bala</p> <p>2017-01-01</p> <p>Efforts to understand the influence of historical global <span class="hlt">warming</span> on individual extreme climate <span class="hlt">events</span> have increased over the past decade. However, despite substantial progress, <span class="hlt">events</span> that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global <span class="hlt">warming</span> on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical <span class="hlt">warming</span> has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry <span class="hlt">events</span>, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent. PMID:28439005</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28439005','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28439005"><span>Quantifying the influence of global <span class="hlt">warming</span> on unprecedented extreme climate <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diffenbaugh, Noah S; Singh, Deepti; Mankin, Justin S; Horton, Daniel E; Swain, Daniel L; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; Rajaratnam, Bala</p> <p>2017-05-09</p> <p>Efforts to understand the influence of historical global <span class="hlt">warming</span> on individual extreme climate <span class="hlt">events</span> have increased over the past decade. However, despite substantial progress, <span class="hlt">events</span> that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global <span class="hlt">warming</span> on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical <span class="hlt">warming</span> has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry <span class="hlt">events</span>, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20180000172&hterms=Global+warming&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DGlobal%2Bwarming','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20180000172&hterms=Global+warming&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DGlobal%2Bwarming"><span>Quantifying the Influence of Global <span class="hlt">Warming</span> on Unprecedented Extreme Climate <span class="hlt">Events</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Diffenbaugh, Noah S.; Singh, Deepti; Mankin, Justin S.; Horton, Daniel E.; Swain, Daniel L.; Touma, Danielle; Charland, Allison; Liu, Yunjie; Haugen, Matz; Tsiang, Michael; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20180000172'); toggleEditAbsImage('author_20180000172_show'); toggleEditAbsImage('author_20180000172_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20180000172_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20180000172_hide"></p> <p>2017-01-01</p> <p>Efforts to understand the influence of historical global <span class="hlt">warming</span> on individual extreme climate <span class="hlt">events</span> have increased over the past decade. However, despite substantial progress, <span class="hlt">events</span> that are unprecedented in the local observational record remain a persistent challenge. Leveraging observations and a large climate model ensemble, we quantify uncertainty in the influence of global <span class="hlt">warming</span> on the severity and probability of the historically hottest month, hottest day, driest year, and wettest 5-d period for different areas of the globe. We find that historical <span class="hlt">warming</span> has increased the severity and probability of the hottest month and hottest day of the year at >80% of the available observational area. Our framework also suggests that the historical climate forcing has increased the probability of the driest year and wettest 5-d period at 57% and 41% of the observed area, respectively, although we note important caveats. For the most protracted hot and dry <span class="hlt">events</span>, the strongest and most widespread contributions of anthropogenic climate forcing occur in the tropics, including increases in probability of at least a factor of 4 for the hottest month and at least a factor of 2 for the driest year. We also demonstrate the ability of our framework to systematically evaluate the role of dynamic and thermodynamic factors such as atmospheric circulation patterns and atmospheric water vapor, and find extremely high statistical confidence that anthropogenic forcing increased the probability of record-low Arctic sea ice extent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC32B..08K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC32B..08K"><span>A hierarchy of models for <span class="hlt">ENSO</span> flavors in past climates.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Karamperidou, C.; Xie, R.; Di Nezio, P. N.</p> <p>2017-12-01</p> <p>The existence of two distinct <span class="hlt">ENSO</span> flavors versus an <span class="hlt">ENSO</span> continuum remains an open question. Investigating the response of <span class="hlt">ENSO</span> diversity to past climate forcings provides a framework to approach this question. Previous work using GCMs has shown that <span class="hlt">ENSO</span> flavors may respond differentially to mid-Holocene orbital forcing, with a significant suppression of Eastern Pacific <span class="hlt">ENSO</span> as opposed to insensitivity of Central Pacific <span class="hlt">ENSO</span>. Here, we employ a hierarchy of models to explore the robustness of <span class="hlt">ENSO</span>-flavor response to orbital forcing. First, we use a modified version of the Zebiak-Cane model which simulates two <span class="hlt">ENSO</span> modes reminiscent of <span class="hlt">ENSO</span> flavors. We find a quasi-linear response of these two modes to orbital forcing corresponding to 6ka, 111ka, and 121ka BP in terms of growth rates, frequency and spatial pattern of SST anomalies. We then employ an Earth System Model subject only to orbital forcing to show the corresponding response in the three past climates. This investigation indicates that no extratropical influences may be required to produce such quasi-linear <span class="hlt">ENSO</span>-flavor response to orbital forcing. Aided by paleoclimate proxies, the hierarchy of models employed here presents a paleoclimate perspective to the fundamental and elusive question of the nature and origins of <span class="hlt">ENSO</span> diversity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJBm...59...89P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJBm...59...89P"><span>Tree growth response to <span class="hlt">ENSO</span> in Durango, Mexico</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pompa-García, Marin; Miranda-Aragón, Liliana; Aguirre-Salado, Carlos Arturo</p> <p>2015-01-01</p> <p>The dynamics of forest ecosystems worldwide have been driven largely by climatic teleconnections. El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is the strongest interannual variation of the Earth's climate, affecting the regional climatic regime. These teleconnections may impact plant phenology, growth rate, forest extent, and other gradual changes in forest ecosystems. The objective of this study was to investigate how Pinus cooperi populations face the influence of <span class="hlt">ENSO</span> and regional microclimates in five ecozones in northwestern Mexico. Using standard dendrochronological techniques, tree-ring chronologies (TRI) were generated. TRI, <span class="hlt">ENSO</span>, and climate relationships were correlated from 1950-2010. Additionally, multiple regressions were conducted in order to detect those <span class="hlt">ENSO</span> months with direct relations in TRI ( p < 0.1). The five chronologies showed similar trends during the period they overlapped, indicating that the P. cooperi populations shared an interannual growth variation. In general, <span class="hlt">ENSO</span> index showed correspondences with tree-ring growth in synchronous periods. We concluded that <span class="hlt">ENSO</span> had connectivity with regional climate in northern Mexico and radial growth of P. cooperi populations has been driven largely by positive <span class="hlt">ENSO</span> values (El Niño episodes).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24728555','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24728555"><span>Tree growth response to <span class="hlt">ENSO</span> in Durango, Mexico.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pompa-García, Marin; Miranda-Aragón, Liliana; Aguirre-Salado, Carlos Arturo</p> <p>2015-01-01</p> <p>The dynamics of forest ecosystems worldwide have been driven largely by climatic teleconnections. El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is the strongest interannual variation of the Earth's climate, affecting the regional climatic regime. These teleconnections may impact plant phenology, growth rate, forest extent, and other gradual changes in forest ecosystems. The objective of this study was to investigate how Pinus cooperi populations face the influence of <span class="hlt">ENSO</span> and regional microclimates in five ecozones in northwestern Mexico. Using standard dendrochronological techniques, tree-ring chronologies (TRI) were generated. TRI, <span class="hlt">ENSO</span>, and climate relationships were correlated from 1950-2010. Additionally, multiple regressions were conducted in order to detect those <span class="hlt">ENSO</span> months with direct relations in TRI (p < 0.1). The five chronologies showed similar trends during the period they overlapped, indicating that the P. cooperi populations shared an interannual growth variation. In general, <span class="hlt">ENSO</span> index showed correspondences with tree-ring growth in synchronous periods. We concluded that <span class="hlt">ENSO</span> had connectivity with regional climate in northern Mexico and radial growth of P. cooperi populations has been driven largely by positive <span class="hlt">ENSO</span> values (El Niño episodes).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H51I1393S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H51I1393S"><span>Analysis of the Effects of <span class="hlt">ENSO</span> and Atmospheric Rivers on Precipitation in Los Angeles County</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santacruz, A.; Lamb, K.</p> <p>2017-12-01</p> <p>The Winter 2016-2017 season in California was marked by substantial amounts of precipitation; this resulted in critically-low reservoirs filling up and the removal of most of California from drought status. The year prior was characterized by one of the strongest El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span>, though it did not produce nearly enough precipitation as the 2016-2017 season. The major contributors to the increased rainfall during the 2016-2017 season were climactic phenomenon known as atmospheric rivers (ARs), which transport water vapor through the atmosphere in narrow bands, and are known to produce extreme rain <span class="hlt">events</span>. Determining the exact timing, landfall areas, and total precipitation amounts of ARs is currently of great interest; a recent study showed that extreme weather <span class="hlt">events</span> are likely to increase in California in the coming years, which motivates research into how phenomenon such as <span class="hlt">ENSO</span> and ARs play a role. Using long-term daily rain gauge data provided by the Los Angeles County Department of Public Works, we compute the precipitation volume and storm count for various locations in Los Angeles County and identify anomalies. These data will then be compared with the occurrence and intensity of AR and <span class="hlt">ENSO</span> <span class="hlt">events</span> by using NOAA's NOI and ESRL AR data. The results can be used to provide a better grasp of extreme climactic patterns and their effects on the amount of precipitation in the region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/535479-seasonal-interannual-variability-atmospheric-heat-sources-moisture-sinks-determined-from-ncep-ncar-reanalysis-part-ii-variability-associated-enso','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/535479-seasonal-interannual-variability-atmospheric-heat-sources-moisture-sinks-determined-from-ncep-ncar-reanalysis-part-ii-variability-associated-enso"><span>Seasonal and interannual variability of atmospheric heat sources and moisture sinks as determined from NCEP/NCAR reanalysis: Part II variability associated with <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Tomita, Tomohiko; Yanai, Michio</p> <p></p> <p>The link between the Asian monsoon and the El Nino/Southern Oscillation (<span class="hlt">ENSO</span>) has been demonstrated by a number of studies. This study examines two <span class="hlt">ENSO</span> withdrawal periods and discusses if the Asian monsoon played a role in the differences between them. The 1986 <span class="hlt">event</span> occurred in the later half of 1986 and retreated in 1988. The 1951 and 1991 <span class="hlt">events</span> were similar to each other and seemed to continue to the second year after onset and not to have the clear La Nina phase after the <span class="hlt">events</span>. In the central and eastern Pacific, three variables progress in phase as themore » <span class="hlt">ENSO</span> cycle: sea surface temperature (SST), heat source (Q1), and divergence. Correlation coefficients were calculated and examined with the mean SST on the equator and with the standard deviation of the interannual components of SST. In the central and eastern Pacific, the standard deviation is large and three correlation coefficients are large (over 0.6). Strong air-sea interaction associated with <span class="hlt">ENSO</span> cycle is deduced. In the Indian Ocean and the western Pacific, the correlation coefficients with SST become small rapidly, while the correlation coefficient between Q1 and the divergence is still large. The interannual variability of SSt may not be crucial for those of Q1 and of the divergence in this region because of the potential to generate well organized convection through the high mean SST. This suggests that various factors, such as effects from mid-latitudes, may modify the interannual variability in the region. To examine the effects of the Asian winter monsoon, the anomalous wind field at 850 hPa was investigated. The conditions of the Asian winter monsoon were quite different between the withdrawal periods in the 1986 and 1991 <span class="hlt">ENSO</span> <span class="hlt">events</span>. The Asian winter monsoon seems to be a factor to modify the <span class="hlt">ENSO</span> cycle, especially in the retreat periods. In addition, the SST from the tropical Indian Ocean to western Pacific may be important for the modulation of the <span class="hlt">ENSO</span>/monsoon system. 9 refs., 10</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.2244B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.2244B"><span><span class="hlt">ENSO</span> effects on stratospheric ozone: A nudged model perspective</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braesicke, Peter; Kirner, Oliver; Versick, Stefan; Joeckel, Patrick</p> <p>2015-04-01</p> <p>The El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon is an important pacemaker for interannual variability in the Earth's atmosphere. <span class="hlt">ENSO</span> impacts on ozone have been observed and modelled for the stratosphere and the troposphere. It is well recognized that attribution of <span class="hlt">ENSO</span> variability is important for trend detection. <span class="hlt">ENSO</span> impacts in low latitudes are easier to detect, because the response emerges close (temporally and spatially) to the forcing. Moving from low to high latitudes it becomes increasingly difficult to isolate <span class="hlt">ENSO</span> driven variability, due to time-lags involved and many other modes of variability playing a role as well. Here, we use a nudged version of the EMAC chemistry-climate model to evaluate <span class="hlt">ENSO</span> impacts on ozone over the last 35 years. In the nudged mode configuration EMAC is not entirely free running. The tropospheric meteorology is constrained using ERA-Interim data. Only the upper stratosphere and the composition (including ozone) are calculated without additional observational constraints. Using lagged correlations and supported by additional idealised modelling, we describe the <span class="hlt">ENSO</span> impact on tropospheric and stratospheric ozone in the EMAC system. We trace the <span class="hlt">ENSO</span> signal from the tropical lower troposphere to the polar lower and middle stratosphere. Instead of distinguishing tropospheric and stratospheric responses, we present a coherent approach detecting the <span class="hlt">ENSO</span> signal as a function of altitude, latitude and time, and demonstrate how a concise characterisation of the <span class="hlt">ENSO</span> impact aids improved trend detection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.tmp..141B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.tmp..141B"><span>Interannual hydroclimatic variability and the 2009-2011 extreme <span class="hlt">ENSO</span> phases in Colombia: from Andean glaciers to Caribbean lowlands</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bedoya-Soto, Juan Mauricio; Poveda, Germán; Trenberth, Kevin E.; Vélez-Upegui, Jorge Julián</p> <p>2018-03-01</p> <p>During 2009-2011, Colombia experienced extreme hydroclimatic <span class="hlt">events</span> associated with the extreme phases of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). Here, we study the dynamics of diverse land-atmosphere phenomena involved in such anomalous <span class="hlt">events</span> at continental, regional, and local scales. Standardized anomalies of precipitation, 2-m temperature, total column water (TCW), volumetric soil water (VSW), temperature at 925 hPa, surface sensible heat (SSH), latent heat (SLH), evaporation (EVP), and liquid water equivalent thickness (LWET) are analyzed to assess atmosphere-land controls and relationships over tropical South America (TropSA) during 1986-2013 (long term) and 2009-2011 (<span class="hlt">ENSO</span> extreme phases). An assessment of the interannual covariability between precipitation and 2-m temperature is performed using singular value decomposition (SVD) to identify the dominant spatiotemporal modes of hydroclimatic variability over the region's largest river basins (Amazon, Orinoco, Tocantins, Magdalena-Cauca, and Essequibo). <span class="hlt">ENSO</span>, its evolution in time, and strong and consistent spatial structures emerge as the dominant mode of variability. In situ anomalies during both extreme phases of <span class="hlt">ENSO</span> 2009-2011 over the Magdalena-Cauca River basins are linked at the continental scale. The <span class="hlt">ENSO</span>-driven hydroclimatic effects extend from the diurnal cycle to interannual timescales, as reflected in temperature data from tropical glaciers and the rain-snow boundary in the highest peaks of the Central Andes of Colombia to river levels along the Caribbean lowlands of the Magdalena-Cauca River basin.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1912639W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1912639W"><span>Differential imprints of different <span class="hlt">ENSO</span> flavors in global patterns of seasonal precipitation extremes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wiedermann, Marc; Siegmund, Jonatan F.; Donges, Jonathan F.; Donner, Reik V.</p> <p>2017-04-01</p> <p>The El Nino Southern Oscillation (<span class="hlt">ENSO</span>) with its positive (El Nino) and negative (La Nina) phases is known to trigger climatic responses in various parts of the Earth, an effect commonly attributed to teleconnectivity. A series of studies has demonstrated that El Nino periods exhibits a relatively broad variety of spatial patterns, which can be classified into two main flavors termed East Pacific (EP, canonical) and Central Pacific (CP, Modoki) El Nino, and that both subtypes can trigger distinct climatic responses like droughts vs. precipitation increases at the regional level. More recently, a similar discrimination of La Nina periods into two different flavors has been reported, and it is reasonable to assume that these different expressions are equally accompanied by differential responses of regional climate variability in particularly affected regions. In this work, we study in great detail the imprints of both types of El Nino and La Nina periods in extremal seasonal precipitation sums during fall (SON), winter (DJF) and spring (MAM) around the peak time of the corresponding <span class="hlt">ENSO</span> phase. For this purpose, we employ a recently developed objective classification of El Nino and La Nina periods into their two respective flavors based on global teleconnectivity patterns in daily surface air temperature anomalies as captured by the associated climate network representations (Wiedermann et al., 2016). In order to study the statistical relevance of the timing of different El Nino and La Nina types on that of seasonal precipitation extremes around the globe (according to the GPCC data set as a reference), we utilize <span class="hlt">event</span> coincidence analysis (Donges et al., 2016), a new powerful yet conceptually simple and intuitive statistical tool that allows quantifying the degree of simultaneity of distinct <span class="hlt">events</span> in pairs of time series. Our results provide a comprehensive overview on <span class="hlt">ENSO</span> related imprints in regional seasonal precipitation extremes. We demonstrate that key</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A43C0238T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A43C0238T"><span>Extreme April 2016 temperatures in Mainland Southeast Asia caused by El Niño and exacerbated by global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thirumalai, K.; Di Nezio, P. N.; Okumura, Y.; Deser, C.</p> <p>2016-12-01</p> <p>In April 2016, Mainland Southeast Asia (MSA) experienced monthly mean surface air temperatures (SATs) that surpassed national records, caused widespread discomfort, and greatly exacerbated energy consumption. First, we reveal a robust relationship between the El Niño Southern Oscillation (<span class="hlt">ENSO</span>) and April SATs in the region, demonstrating that virtually all extreme, hot Aprils occur during El Niño years. Next, we show that MSA has experienced continuous <span class="hlt">warming</span> since the early 20th century. To quantify the relative contributions of this long-term <span class="hlt">warming</span> trend and the 2015 El Niño to the extreme April 2016 SATs, we use observations and a large ensemble of global <span class="hlt">warming</span> simulations, performed with a model that realistically simulates this El-Niño-MSA link. We find robust evidence that the "post-Niño" hot Aprils are being exacerbated by global <span class="hlt">warming</span>, with this effect being pronounced for the 2016 <span class="hlt">event</span>, where we estimate 24% was caused by <span class="hlt">warming</span> and 49% by El Niño. Despite an increased likelihood of hot Aprils during El Niño years in the future, our findings suggest that these extremes can potentially be anticipated a few months in advance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012GeoRL..3911704K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012GeoRL..3911704K"><span>The two types of <span class="hlt">ENSO</span> in CMIP5 models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Seon Tae; Yu, Jin-Yi</p> <p>2012-06-01</p> <p>In this study, we evaluate the intensity of the Central-Pacific (CP) and Eastern-Pacific (EP) types of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) simulated in the pre-industrial, historical, and the Representative Concentration Pathways (RCP) 4.5 experiments of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Compared to the CMIP3 models, the pre-industrial simulations of the CMIP5 models are found to (1) better simulate the observed spatial patterns of the two types of <span class="hlt">ENSO</span> and (2) have a significantly smaller inter-model diversity in <span class="hlt">ENSO</span> intensities. The decrease in the CMIP5 model discrepancies is particularly obvious in the simulation of the EP <span class="hlt">ENSO</span> intensity, although it is still more difficult for the models to reproduce the observed EP <span class="hlt">ENSO</span> intensity than the observed CP <span class="hlt">ENSO</span> intensity. Ensemble means of the CMIP5 models indicate that the intensity of the CP <span class="hlt">ENSO</span> increases steadily from the pre-industrial to the historical and the RCP4.5 simulations, but the intensity of the EP <span class="hlt">ENSO</span> increases from the pre-industrial to the historical simulations and then decreases in the RCP4.5 projections. The CP-to-EP <span class="hlt">ENSO</span> intensity ratio, as a result, is almost the same in the pre-industrial and historical simulations but increases in the RCP4.5 simulation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000032525','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000032525"><span>On the Bimodality of <span class="hlt">ENSO</span> Cycle Extremes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, Robert M.</p> <p>2000-01-01</p> <p>On the basis of sea surface temperature in the El Nino 3.4 region (5 deg. N.,-5 deg. S., 120-170 deg. W.) during the interval of 1950-1997, Kevin Trenberth previously has identified some 16 El Nino and 10 La Nina, these 26 <span class="hlt">events</span> representing the extremes of the quasi-periodic El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) cycle. Runs testing shows that the duration, recurrence period, and sequencing of these extremes vary randomly. Hence, the decade of the 1990's, especially for El Nino, is not significantly different from that of previous decadal epochs, at least, on the basis of the frequency of onsets of <span class="hlt">ENSO</span> extremes. Additionally, the distribution of duration for both El Nino and La Nina looks strikingly bimodal, each consisting of two preferred modes, about 8- and 16-mo long for El Nino and about 9- and 18-mo long for La Nina, as does the distribution of the recurrence period for El Nino, consisting of two preferred modes about 21- and 50-mo long. Scatterplots of the recurrence period versus duration for El Nino are found to be statistically important, displaying preferential associations that link shorter (longer) duration with shorter (longer) recurrence periods. Because the last onset of El Nino occurred in April 1997 and the <span class="hlt">event</span> was of longer than average duration, onset of the next anticipated El Nino is not expected until February 2000 or later.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMPP53A..05A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMPP53A..05A"><span>A Millennial Record of Rainfall And <span class="hlt">ENSO</span> Variability in Stalagmites From a Mid-Ocean Island in the South Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aharon, P.; Rasbury, M. S.; Lambert, W. J.; Ghaleb, B.; Lambert, L.</p> <p>2005-12-01</p> <p>Improved understanding of ocean-atmosphere interactions that control interdecadal <span class="hlt">ENSO</span> variability prompted recently a renewed interest in the acquisition of highly resolved proxy <span class="hlt">ENSO</span> records. Corals possessing annual growth increments have extended the <span class="hlt">ENSO</span> archive several centuries beyond the existing instrumental data but much longer records are needed to constrain the interdecadal periodicities and unravel their underlying causes. To this end, paleoclimate proxies archived in stalagmites from tropical Pacific settings have not been harnessed to the task of <span class="hlt">ENSO</span> paleo-reconstructions although stalagmites elsewhere have offered valuable paleoclimate insights. Here we report the results of an investigation of stalagmites from a water-table cave on Niue Island in the South Pacific (19o 00' S; 169o 50' W) located at the epicenter of oceanic <span class="hlt">ENSO</span>. Century-long instrumental records on Niue provide a frame of reference and indicate that the interannual and interdecadal air temperature variability is negligible but the rainfall is fully engaged in the wheels of <span class="hlt">ENSO</span> such that El-Niño and La-Niña <span class="hlt">events</span> correspond with droughts and abundant rainfall, respectively. Seasonal monsoon and trade rainfalls exhibit a marked contrast in their oxygen isotope compositions. Rainfall amount governs microbial soil activities resulting in convergent 18O and 13C depletions and enrichments in the drips that are transferred to the calcite stalagmites in the Niuean caves. A detailed study of four actively growing stalagmites whose chronology overlaps with the instrumental records confirms that interannual and decadal-scale <span class="hlt">ENSO</span> variability is clearly expressed in the annual couplets widths and stable oxygen and carbon isotope time-series records of continuous layered stalagmites. Acquisition of a chronology for USM1 stalagmite posed radiometric dating challenges. The U concentration, in the range of 44.2 to 97.5 ppb, is relatively low by comparison with typical stalagmite values</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5805265','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5805265"><span>Large-scale climatic phenomena drive fluctuations in macroinvertebrate assemblages in lowland tropical streams, Costa Rica: The importance of <span class="hlt">ENSO</span> <span class="hlt">events</span> in determining long-term (15y) patterns</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Ramírez, Alonso; Pringle, Catherine M.</p> <p>2018-01-01</p> <p>Understanding how environmental variables influence the distribution and density of organisms over relatively long temporal scales is a central question in ecology given increased climatic variability (e.g., precipitation, <span class="hlt">ENSO</span> <span class="hlt">events</span>). The primary goal of our study was to evaluate long-term (15y time span) patterns of climate, as well as environmental parameters in two Neotropical streams in lowland Costa Rica, to assess potential effects on aquatic macroinvertebrates. We also examined the relative effects of an 8y whole-stream P-enrichment experiment on macroinvertebrate assemblages against the backdrop of this long-term study. Climate, environmental variables and macroinvertebrate samples were measured monthly for 7y and then quarterly for an additional 8y in each stream. Temporal patterns in climatic and environmental variables showed high variability over time, without clear inter-annual or intra-annual patterns. Macroinvertebrate richness and abundance decreased with increasing discharge and was positively related to the number of days since the last high discharge <span class="hlt">event</span>. Findings show that fluctuations in stream physicochemistry and macroinvertebrate assemblage structure are ultimately the result of large-scale climatic phenomena, such as <span class="hlt">ENSO</span> <span class="hlt">events</span>, while the 8y P-enrichment did not appear to affect macroinvertebrates. Our study demonstrates that Neotropical lowland streams are highly dynamic and not as stable as is commonly presumed, with high intra- and inter-annual variability in environmental parameters that change the structure and composition of freshwater macroinvertebrate assemblages. PMID:29420548</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018CSR...156...11B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018CSR...156...11B"><span>Mechanism for the recent ocean <span class="hlt">warming</span> <span class="hlt">events</span> on the Scotian Shelf of eastern Canada</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brickman, D.; Hebert, D.; Wang, Z.</p> <p>2018-03-01</p> <p>In 2012, 2014, and 2015 anomalous <span class="hlt">warm</span> <span class="hlt">events</span> were observed in the subsurface waters in the Scotian Shelf region of eastern Canada. Monthly output from a high resolution numerical ocean model simulation of the North Atlantic ocean for the period 1990-2015 is used to investigate this phenomenon. It is found that the model shows skill in simulating the anomaly fields derived from various sources of data, and the observed <span class="hlt">warming</span> trend over the last decade. From analysis of the model run it is found that the anomalies originate from the interaction between the Gulf Stream and the Labrador Current at the tail of the Grand Banks (south of Newfoundland). This interaction results in the creation of anomalous <span class="hlt">warm</span>/salty (or cold/fresh) eddies that travel east-to-west along the shelfbreak. These anomalies penetrate into the Gulf of St. Lawrence, onto the Scotian Shelf, and into the Gulf of Maine via deep channels along the shelfbreak. The observed <span class="hlt">warming</span> trend can be attributed to an increase in the frequency of creation of <span class="hlt">warm</span> anomalies during the last decade. Strong anomalous <span class="hlt">events</span> are commonly observed in the data and model, and thus should be considered as part of the natural variability of the coupled atmosphere-ocean system.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2365C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2365C"><span>The Angola Low: relationship with southern African rainfall and <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crétat, Julien; Pohl, Benjamin; Dieppois, Bastien; Berthou, Ségolène; Pergaud, Julien</p> <p>2018-05-01</p> <p> major 1982/83 and 1997/98 El Niño <span class="hlt">events</span> suggests that the weak rainfall anomalies and strong seasonal AL in 1997/98 may result from counteracting effects between <span class="hlt">ENSO</span> and Indian Ocean coupled modes of variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SGeo...38..277R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SGeo...38..277R"><span>Phenological Responses to <span class="hlt">ENSO</span> in the Global Oceans</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Racault, M.-F.; Sathyendranath, S.; Menon, N.; Platt, T.</p> <p>2017-01-01</p> <p>Phenology relates to the study of timing of periodic <span class="hlt">events</span> in the life cycle of plants or animals as influenced by environmental conditions and climatic forcing. Phenological metrics provide information essential to quantify variations in the life cycle of these organisms. The metrics also allow us to estimate the speed at which living organisms respond to environmental changes. At the surface of the oceans, microscopic plant cells, so-called phytoplankton, grow and sometimes form blooms, with concentrations reaching up to 100 million cells per litre and extending over many square kilometres. These blooms can have a huge collective impact on ocean colour, because they contain chlorophyll and other auxiliary pigments, making them visible from space. Phytoplankton populations have a high turnover rate and can respond within hours to days to environmental perturbations. This makes them ideal indicators to study the first-level biological response to environmental changes. In the Earth's climate system, the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) dominates large-scale inter-annual variations in environmental conditions. It serves as a natural experiment to study and understand how phytoplankton in the ocean (and hence the organisms at higher trophic levels) respond to climate variability. Here, the <span class="hlt">ENSO</span> influence on phytoplankton is estimated through variations in chlorophyll concentration, primary production and timings of initiation, peak, termination and duration of the growing period. The phenological variabilities are used to characterise phytoplankton responses to changes in some physical variables: sea surface temperature, sea surface height and wind. It is reported that in oceanic regions experiencing high annual variations in the solar cycle, such as in high latitudes, the influence of <span class="hlt">ENSO</span> may be readily measured using annual mean anomalies of physical variables. In contrast, in oceanic regions where <span class="hlt">ENSO</span> modulates a climate system characterised by a seasonal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70192182','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70192182"><span>Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Zhu, Qiuan; Peng, Changhui; Ciais, Philippe; Jiang, Hong; Liu, Jinxun; Bousquet, Philippe; Li, Shiqin; Chang, Jie; Fang, Xiuqin; Zhou, Xiaolu; Chen, Huai; Liu, Shirong; Lin, Guanghui; Gong, Peng; Wang, Meng; Wang, Han; Xiang, Wenhua; Chen, Jing</p> <p>2017-01-01</p> <p>Methane (CH4) emissions from tropical wetlands contribute 60%–80% of global natural wetland CH4 emissions. Decreased wetland CH4 emissions can act as a negative feedback mechanism for future climate <span class="hlt">warming</span> and vice versa. The impact of the El Niño–Southern Oscillation (<span class="hlt">ENSO</span>) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño <span class="hlt">events</span> are expected to become more severe based on climate models’ projections. We use a process-based model of global wetland CH4 emissions to investigate the impacts of the <span class="hlt">ENSO</span> on CH4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH4 emissions from tropical wetlands respond strongly to repeated <span class="hlt">ENSO</span> <span class="hlt">events</span>, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8-month time lag was detected between tropical wetland CH4 emissions and <span class="hlt">ENSO</span> <span class="hlt">events</span>, which was caused by the combined time lag effects of <span class="hlt">ENSO</span> <span class="hlt">events</span> on precipitation and temperature over tropical wetlands. The <span class="hlt">ENSO</span> can explain 49% of interannual variations for tropical wetland CH4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH4 emissions than the changes in precipitation during <span class="hlt">ENSO</span> periods. The occurrence of several El Niño <span class="hlt">events</span> contributed to a lower decadal mean growth rate in atmospheric CH4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH4 concentrations from 1999 to 2006, resulting in negative feedback to global <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28418083','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28418083"><span>Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhu, Qiuan; Peng, Changhui; Ciais, Philippe; Jiang, Hong; Liu, Jinxun; Bousquet, Philippe; Li, Shiqin; Chang, Jie; Fang, Xiuqin; Zhou, Xiaolu; Chen, Huai; Liu, Shirong; Lin, Guanghui; Gong, Peng; Wang, Meng; Wang, Han; Xiang, Wenhua; Chen, Jing</p> <p>2017-11-01</p> <p>Methane (CH 4 ) emissions from tropical wetlands contribute 60%-80% of global natural wetland CH 4 emissions. Decreased wetland CH 4 emissions can act as a negative feedback mechanism for future climate <span class="hlt">warming</span> and vice versa. The impact of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) on CH 4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño <span class="hlt">events</span> are expected to become more severe based on climate models' projections. We use a process-based model of global wetland CH 4 emissions to investigate the impacts of the <span class="hlt">ENSO</span> on CH 4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH 4 emissions from tropical wetlands respond strongly to repeated <span class="hlt">ENSO</span> <span class="hlt">events</span>, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8-month time lag was detected between tropical wetland CH 4 emissions and <span class="hlt">ENSO</span> <span class="hlt">events</span>, which was caused by the combined time lag effects of <span class="hlt">ENSO</span> <span class="hlt">events</span> on precipitation and temperature over tropical wetlands. The <span class="hlt">ENSO</span> can explain 49% of interannual variations for tropical wetland CH 4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH 4 emissions than the changes in precipitation during <span class="hlt">ENSO</span> periods. The occurrence of several El Niño <span class="hlt">events</span> contributed to a lower decadal mean growth rate in atmospheric CH 4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH 4 concentrations from 1999 to 2006, resulting in negative feedback to global <span class="hlt">warming</span>. © 2017 John Wiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFMPP33A2068T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFMPP33A2068T"><span>A High-Resolution <span class="hlt">ENSO</span>-Driven Rainfall Record Derived From an Exceptionally Fast Growing Stalagmite From Niue Island (South Pacific)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Troy, S.; Aharon, P.; Lambert, W. J.</p> <p>2012-12-01</p> <p>El Niño-Southern Oscillation's (<span class="hlt">ENSO</span>) dominant control over the present global climate and its unpredictable response to a global <span class="hlt">warming</span> makes the study of paleo-<span class="hlt">ENSO</span> important. So far corals, spanning the Tropical Pacific Ocean, are the most commonly used geological archives of paleo-<span class="hlt">ENSO</span>. This is because corals typically exhibit high growth rates (>1 cm/yr), and reproduce reliably surface water temperatures at sub-annual resolution. However there are limitations to coral archives because their time span is relatively brief (in the order of centuries), thus far making a long and continuous <span class="hlt">ENSO</span> record difficult to achieve. On the other hand stalagmites from island settings can offer long and continuous records of <span class="hlt">ENSO</span>-driven rainfall. Niue Island caves offer an unusual opportunity to investigate <span class="hlt">ENSO</span>-driven paleo-rainfall because the island is isolated from other large land masses, making it untainted by continental climate artifacts, and its geographical location is within the Tropical Pacific "rain pool" (South Pacific Convergence Zone; SPCZ) that makes the rainfall variability particularly sensitive to the <span class="hlt">ENSO</span> phase switches. We present here a δ18O and δ13C time series from a stalagmite sampled on Niue Island (19°00' S, 169°50' W) that exhibits exceptionally high growth rates (~1.2 mm/yr) thus affording a resolution comparable to corals but for much longer time spans. A precise chronology, dating back to several millennia, was achieved by U/Th dating of the stalagmite. The stalagmite was sampled using a Computer Automated Mill (CAM) at 300 μm increments in order to receive sub-annual resolution (every 3 months) and calcite powders of 50-100 μg weight were analyzed for δ18O and δ13C using a Continuous Flow Isotope Ratio Mass Spectrometer (CF-IRMS). The isotope time series contains variable shifts at seasonal, inter-annual, and inter-decadal periodicities. The δ13C and δ18O yield ranges of -3.0 to -13.0 (‰ VPDB) and -3.2 to -6.2 (‰ VPDB</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.2487W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.2487W"><span>Disentangling Global <span class="hlt">Warming</span>, Multidecadal Variability, and El Niño in Pacific Temperatures</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wills, Robert C.; Schneider, Tapio; Wallace, John M.; Battisti, David S.; Hartmann, Dennis L.</p> <p>2018-03-01</p> <p>A key challenge in climate science is to separate observed temperature changes into components due to internal variability and responses to external forcing. Extended integrations of forced and unforced climate models are often used for this purpose. Here we demonstrate a novel method to separate modes of internal variability from global <span class="hlt">warming</span> based on differences in time scale and spatial pattern, without relying on climate models. We identify uncorrelated components of Pacific sea surface temperature variability due to global <span class="hlt">warming</span>, the Pacific Decadal Oscillation (PDO), and the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). Our results give statistical representations of PDO and <span class="hlt">ENSO</span> that are consistent with their being separate processes, operating on different time scales, but are otherwise consistent with canonical definitions. We isolate the multidecadal variability of the PDO and find that it is confined to midlatitudes; tropical sea surface temperatures and their teleconnections mix in higher-frequency variability. This implies that midlatitude PDO anomalies are more persistent than previously thought.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatSR...742281Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatSR...742281Z"><span><span class="hlt">ENSO</span> elicits opposing responses of semi-arid vegetation between Hemispheres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Anzhi; Jia, Gensuo; Epstein, Howard E.; Xia, Jiangjiang</p> <p>2017-02-01</p> <p>Semi-arid ecosystems are key contributors to the global carbon cycle and may even dominate the inter-annual variability (IAV) and trends of the land carbon sink, driven largely by the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). The linkages between dynamics of semi-arid ecosystems and climate at the hemispheric scale however are not well known. Here, we use satellite data and climate observations from 2000 to 2014 to explore the impacts of <span class="hlt">ENSO</span> on variability of semi-arid ecosystems, using the Ensemble Empirical Mode Decomposition method. We show that the responses of semi-arid vegetation to <span class="hlt">ENSO</span> occur in opposite directions, resulting from opposing controls of <span class="hlt">ENSO</span> on precipitation between the Northern Hemisphere (positively correlated to <span class="hlt">ENSO</span>) and the Southern Hemisphere (negatively correlated to <span class="hlt">ENSO</span>). Also, the Southern Hemisphere, with a robust negative coupling of temperature and precipitation anomalies, exhibits stronger and faster responses of semi-arid ecosystems to <span class="hlt">ENSO</span> than the Northern Hemisphere. Our findings suggest that natural coherent variability in semi-arid ecosystem productivity responded to <span class="hlt">ENSO</span> in opposite ways between two hemispheres, which may imply potential prediction of global semi-arid ecosystem variability, particularly based on variability in tropical Pacific Sea Surface Temperatures.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70022697','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70022697"><span>Predicting and downscaling <span class="hlt">ENSO</span> impacts on intraseasonal precipitation statistics in California: The 1997/98 <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Gershunov, A.; Barnett, T.P.; Cayan, D.R.; Tubbs, T.; Goddard, L.</p> <p>2000-01-01</p> <p>Three long-range forecasting methods have been evaluated for prediction and downscaling of seasonal and intraseasonal precipitation statistics in California. Full-statistical, hybrid-dynamical - statistical and full-dynamical approaches have been used to forecast El Nin??o - Southern Oscillation (<span class="hlt">ENSO</span>) - related total precipitation, daily precipitation frequency, and average intensity anomalies during the January - March season. For El Nin??o winters, the hybrid approach emerges as the best performer, while La Nin??a forecasting skill is poor. The full-statistical forecasting method features reasonable forecasting skill for both La Nin??a and El Nin??o winters. The performance of the full-dynamical approach could not be evaluated as rigorously as that of the other two forecasting schemes. Although the full-dynamical forecasting approach is expected to outperform simpler forecasting schemes in the long run, evidence is presented to conclude that, at present, the full-dynamical forecasting approach is the least viable of the three, at least in California. The authors suggest that operational forecasting of any intraseasonal temperature, precipitation, or streamflow statistic derivable from the available records is possible now for <span class="hlt">ENSO</span>-extreme years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=269692','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=269692"><span>Effect of <span class="hlt">ENSO</span> on Corn Aflatoxin in South Georgia</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>The El Niño Southern Oscillation (<span class="hlt">ENSO</span>) is associated with climate variability around the world, and is known to adversely affect food production systems. In the Southeastern US, research has shown that <span class="hlt">ENSO</span> influences crop production. Two multivariate <span class="hlt">ENSO</span> Indices, MEI and Niño 3.4, are typical...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009EGUGA..11.6597Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009EGUGA..11.6597Z"><span>A delay differential model of <span class="hlt">ENSO</span> variability: Extreme values and stability analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaliapin, I.; Ghil, M.</p> <p>2009-04-01</p> <p>.e., thermocline depth), period, and extreme annual values, for purely periodic, seasonal forcing. The model reproduces the Devils bleachers characterizing other <span class="hlt">ENSO</span> models, such as nonlinear, coupled systems of partial differential equations; some of the features of this behavior have been documented in general circulation models, as well as in observations. We analyze the values of annual extremes and their location within an annual cycle and report the phase-locking phenomenon, which is connected to the occurrence of El-Niño <span class="hlt">events</span> during the boreal (Northern Hemisphere) winter. We report existence of multiple solutions and study their basins of attraction in a space of initial conditions. We also present a model-based justification for the observed quasi-biennial oscillation in Tropical Pacific SSTs. We expect similar behavior in much more detailed and realistic models, where it is harder to describe its causes as completely. The basic mechanisms used in our model (delayed feedback and forcing) may be relevant to other natural systems in which internal instabilities interact with external forcing and give rise to extreme <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.1393X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.1393X"><span>PDO modulation of the <span class="hlt">ENSO</span> impact on the summer South Asian high</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xue, Xu; Chen, Wen; Chen, Shangfeng; Feng, Juan</p> <p>2018-02-01</p> <p>This study investigates modulation effects of the Pacific decadal oscillation (PDO) on the impact of boreal winter El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) on the South Asian high (SAH) variability in the following summer. In the El Niño together with positive PDO (EL/+PDO) or the La Niña together with negative PDO (LA/-PDO) years, boreal winter <span class="hlt">ENSO</span> can influence the following summer SAH activity significantly. The SAH tends to be obviously strengthened (weakened) and located further south (north) during EL/+PDO (LA/-PDO). However, in the El Niño together with negative PDO (EL/-PDO) or the La Niña together with positive PDO (LA/+PDO) years, the influence of <span class="hlt">ENSO</span> on the SAH tends to be weak. The strength and location of SAH are close to those in the climatology of 1950-2011 during the EL/-PDO or the LA/+PDO. Further analysis indicates that the PDO could exert pronounced influence on the <span class="hlt">ENSO</span>-SAH connection via modulating the anomalous Walker circulation and charge effect over the tropical Indian Ocean (TIO). During the EL/+PDO or LA/-PDO, the anomalous Walker circulation associated with El Niño or La Niña is stronger and lasts for a longer time than those during the EL/-PDO or LA/+PDO. This leads to stronger descending (ascending) motion over the Maritime Continent and easterly (westerly) wind anomalies over the eastern Indian Ocean in the EL/+PDO (LA/-PDO), which further exert larger effects on the surface heat fluxes and subsurface ocean dynamical heating process over the Indian Ocean. As such, the induced <span class="hlt">warm</span> (cold) sea surface temperature anomalies over the Indian Ocean are more significant and larger in the EL/+PDO (LA/-PDO). These larger sea surface temperature anomalies over the TIO could exert a more significant influence on the tropospheric temperature via moisture adjustment, which subsequently results in stronger SAH variability in the EL/+PDO or the LA/-PDO.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/7552109','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7552109"><span>The association between El Niño/Southern Oscillation <span class="hlt">events</span> and typhoons in the Marshall Islands.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Spennemann, D H; Marschner, I C</p> <p>1995-09-01</p> <p>An analysis of the historic record of typhoons in the Marshall Islands has identified a significant association between the occurrence of the El Niño/Southern Oscillation phenomenon (<span class="hlt">ENSO</span>) and the occurrence of typhoons in the Marshall Islands. Whilst typhoons normally occur further to the east, the <span class="hlt">warming</span> of the ocean waters around the Marshall Islands, as part of the <span class="hlt">ENSO</span> phenomenon, generates typhoons further to the west. The results suggest that typhoons are 2.6 times more likely to occur during <span class="hlt">ENSO</span> years, with a 71 per cent chance of a typhoon striking during an <span class="hlt">ENSO</span> year, and only a 26 per cent chance of one happening during a non-<span class="hlt">ENSO</span> year. This has implications for planning and public safety, which the relevant authorities may wish to take note of.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1801g0001H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1801g0001H"><span>Seasonal <span class="hlt">ENSO</span> forecasting: Where does a simple model stand amongst other operational <span class="hlt">ENSO</span> models?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Halide, Halmar</p> <p>2017-01-01</p> <p>We apply a simple linear multiple regression model called IndOzy for predicting <span class="hlt">ENSO</span> up to 7 seasonal lead times. The model still used 5 (five) predictors of the past seasonal Niño 3.4 <span class="hlt">ENSO</span> indices derived from chaos theory and it was rolling-validated to give a one-step ahead forecast. The model skill was evaluated against data from the season of May-June-July (MJJ) 2003 to November-December-January (NDJ) 2015/2016. There were three skill measures such as: Pearson correlation, RMSE, and Euclidean distance were used for forecast verification. The skill of this simple model was than compared to those of combined Statistical and Dynamical models compiled at the IRI (International Research Institute) website. It was found that the simple model was only capable of producing a useful <span class="hlt">ENSO</span> prediction only up to 3 seasonal leads, while the IRI statistical and Dynamical model skill were still useful up to 4 and 6 seasonal leads, respectively. Even with its short-range seasonal prediction skills, however, the simple model still has a potential to give <span class="hlt">ENSO</span>-derived tailored products such as probabilistic measures of precipitation and air temperature. Both meteorological conditions affect the presence of wild-land fire hot-spots in Sumatera and Kalimantan. It is suggested that to improve its long-range skill, the simple INDOZY model needs to incorporate a nonlinear model such as an artificial neural network technique.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/enso_cycle.shtml','SCIGOVWS'); return false;" href="http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensocycle/enso_cycle.shtml"><span>Climate Prediction Center - The <span class="hlt">ENSO</span> Cycle</span></a></p> <p><a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a></p> <p></p> <p></p> <p>Weather Service NWS logo - Click to go to the NWS home page <em>Climate</em> Prediction Center Home Site Map News Web resources and services. HOME > El Niño/La Niña > The <span class="hlt">ENSO</span> Cycle <span class="hlt">ENSO</span> Cycle Banner <em>Climate</em> for Weather and <em>Climate</em> Prediction <em>Climate</em> Prediction Center 5830 University Research Court College</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PEPS....4....5B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PEPS....4....5B"><span>A 2700-year record of <span class="hlt">ENSO</span> and PDO variability from the Californian margin based on coccolithophore assemblages and calcification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beaufort, Luc; Grelaud, Michaël</p> <p>2017-12-01</p> <p>The El Niño Southern Oscillation (<span class="hlt">ENSO</span>) and the Pacific Decadal Oscillation (PDO) account for a large part of modern climate variability. Over the last decades, understanding of these modes of climate variability has increased but prediction in the context of global <span class="hlt">warming</span> has proven difficult because of the lack of pertinent and reproducible paleodata. Here, we infer the dynamics of these oscillations from fossil assemblage and calcification state of coccolithophore in the Californian margin because El Niño has a strong impact on phytoplankton ecology and PDO on the upwelling intensity and hence on the ocean chemistry. Intense Californian upwelling brings water rich in CO2 and poor in carbonate ions and coccolithophores secrete lower calcified coccoliths. Seasonally laminated sediments of the Santa Barbara Basin are used to document <span class="hlt">ENSO</span> variability and PDO index for the last 2700 years at a temporal resolution of 3 years. The records present the same characteristics as other PDO or <span class="hlt">ENSO</span> records from the same area spanning the last centuries. We are therefore confident on the value produced here for the last 2.7 millennia. The records show important centennial variability that is equivalent to solar cycles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JOUC...11..137H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JOUC...11..137H"><span>Spatial-temporal variations of dominant drought/flood modes and the associated atmospheric circulation and ocean <span class="hlt">events</span> in rainy season over the east of China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Shaoni; Huang, Fei</p> <p>2012-06-01</p> <p>By using Season-reliant Empirical Orthogonal Function (S-EOF) analysis, three dominant modes of the spatial-temporal evolution of the drought/flood patterns in the rainy season over the east of China are revealed for the period of 1960-2004. The first two leading modes occur during the turnabout phase of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) decaying year, but the drought/flood patterns in the rainy season over the east of China are different due to the role of the Indian Ocean (IO). The first leading mode appears closely correlated with the <span class="hlt">ENSO</span> <span class="hlt">events</span>. In the decaying year of El Niño, the associated western North Pacific (WNP) anticyclone located over the Philippine Sea persists from the previous winter to the next early summer, transports <span class="hlt">warm</span> and moist air toward the southern Yangtze River in China, and leads to wet conditions over this entire region. Therefore, the precipitation anomaly in summer exhibits a `Southern Flood and Northern Drought' pattern over East China. On the other hand, the basin-wide Indian Ocean sea surface temperature anomaly (SSTA) plays a crucial role in prolonging the impact of <span class="hlt">ENSO</span> on the second mode during the <span class="hlt">ENSO</span> decaying summer. The Indian Ocean basin mode (IOBM) <span class="hlt">warming</span> persists through summer and unleashes its influence, which forces a Matsuno-Gill pattern in the upper troposphere. Over the subtropical western North Pacific, an anomalous anticyclone forms in the lower troposphere. The southerlies on the northwest flank of this anticyclone increase the moisture transport onto central China, leading to abundant rainfall over the middle and lower reaches of the Yangtze River and Huaihe River valleys. The anomalous anticyclone causes dry conditions over South China and the South China Sea (SCS). The precipitation anomaly in summer exhibits a `Northern Flood and Southern Drought' pattern over East China. Therefore, besides the <span class="hlt">ENSO</span> <span class="hlt">event</span> the IOBM is an important factor to influence the drought/flood patterns in the rainy season over</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2661091','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2661091"><span>The role of <span class="hlt">ENSO</span> in understanding changes in Colombia's annual malaria burden by region, 1960–2006</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Mantilla, Gilma; Oliveros, Hugo; Barnston, Anthony G</p> <p>2009-01-01</p> <p>Background Malaria remains a serious problem in Colombia. The number of malaria cases is governed by multiple climatic and non-climatic factors. Malaria control policies, and climate controls such as rainfall and temperature variations associated with the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>), have been associated with malaria case numbers. Using historical climate data and annual malaria case number data from 1960 to 2006, statistical models are developed to isolate the effects of climate in each of Colombia's five contrasting geographical regions. Methods Because year to year climate variability associated with <span class="hlt">ENSO</span> causes interannual variability in malaria case numbers, while changes in population and institutional control policy result in more gradual trends, the chosen predictors in the models are annual indices of the <span class="hlt">ENSO</span> state (sea surface temperature [SST] in the tropical Pacific Ocean) and time reference indices keyed to two major malaria trends during the study period. Two models were used: a Poisson and a Negative Binomial regression model. Two <span class="hlt">ENSO</span> indices, two time reference indices, and one dummy variable are chosen as candidate predictors. The analysis was conducted using the five geographical regions to match the similar aggregation used by the National Institute of Health for its official reports. Results The Negative Binomial regression model is found better suited to the malaria cases in Colombia. Both the trend variables and the <span class="hlt">ENSO</span> measures are significant predictors of malaria case numbers in Colombia as a whole, and in two of the five regions. A one degree Celsius change in SST (indicating a weak to moderate <span class="hlt">ENSO</span> <span class="hlt">event</span>) is seen to translate to an approximate 20% increase in malaria cases, holding other variables constant. Conclusion Regional differentiation in the role of <span class="hlt">ENSO</span> in understanding changes in Colombia's annual malaria burden during 1960–2006 was found, constituting a new approach to use <span class="hlt">ENSO</span> as a significant predictor of the</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMGC51A0457K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMGC51A0457K"><span><span class="hlt">ENSO</span>-Based Index Insurance: Approach and Peru Flood Risk Management Application</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khalil, A. F.; Kwon, H.; Lall, U.; Miranda, M. J.; Skees, J. R.</p> <p>2006-12-01</p> <p>Index insurance has recently been advocated as a useful risk transfer tool for disaster management situations where rapid fiscal relief is desirable, and where estimating insured losses may be difficult, time consuming, or subject to manipulation and falsification. For climate related hazards, a rainfall or temperature index may be proposed. However, rainfall may be highly spatially variable relative to the gauge network, and in many locations data are inadequate to develop an index due to short time-series and the spatial dispersion of stations. In such cases, it may be helpful to consider a climate proxy index as a regional rainfall index. This is particularly useful if a long record is available for the climate index through an independent source and it is well correlated with the regional rainfall hazard. Here, <span class="hlt">ENSO</span> related climate indices are explored for use as a proxy to extreme rainfall in one of the departments of Peru -- Piura. The <span class="hlt">ENSO</span> index insurance product may be purchased by banks or microfinance institutions (MFIs) to aid agricultural damage relief in Peru. Crop losses in the region are highly correlated with floods, but are difficult to assess directly. Beyond agriculture, many other sectors suffer as well. Basic infrastructure is destroyed during the most severe <span class="hlt">events</span>. This disrupts trade for many micro-enterprises. The reliability and quality of the local rainfall data is variable. Averaging the financial risk across the region is desirable. Some issues with the implementation of the proxy <span class="hlt">ENSO</span> index are identified and discussed. Specifically, we explore (a) the reliability of the index at different levels of probability of exceedance of maximum seasonal rainfall; (b) the potential for clustering of payoffs; (c) the potential that the index could be predicted with some lead time prior to the flood season; and (d) evidence for climate change or non-stationarity in the flood exceedance probability from the long <span class="hlt">ENSO</span> record. Finally, prospects for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24919920','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24919920"><span>Increased frequency of extreme Indian Ocean Dipole <span class="hlt">events</span> due to greenhouse <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cai, Wenju; Santoso, Agus; Wang, Guojian; Weller, Evan; Wu, Lixin; Ashok, Karumuri; Masumoto, Yukio; Yamagata, Toshio</p> <p>2014-06-12</p> <p>The Indian Ocean dipole is a prominent mode of coupled ocean-atmosphere variability, affecting the lives of millions of people in Indian Ocean rim countries. In its positive phase, sea surface temperatures are lower than normal off the Sumatra-Java coast, but higher in the western tropical Indian Ocean. During the extreme positive-IOD (pIOD) <span class="hlt">events</span> of 1961, 1994 and 1997, the eastern cooling strengthened and extended westward along the equatorial Indian Ocean through strong reversal of both the mean westerly winds and the associated eastward-flowing upper ocean currents. This created anomalously dry conditions from the eastern to the central Indian Ocean along the Equator and atmospheric convergence farther west, leading to catastrophic floods in eastern tropical African countries but devastating droughts in eastern Indian Ocean rim countries. Despite these serious consequences, the response of pIOD <span class="hlt">events</span> to greenhouse <span class="hlt">warming</span> is unknown. Here, using an ensemble of climate models forced by a scenario of high greenhouse gas emissions (Representative Concentration Pathway 8.5), we project that the frequency of extreme pIOD <span class="hlt">events</span> will increase by almost a factor of three, from one <span class="hlt">event</span> every 17.3 years over the twentieth century to one <span class="hlt">event</span> every 6.3 years over the twenty-first century. We find that a mean state change--with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster <span class="hlt">warming</span> in the western than the eastern equatorial Indian Ocean--facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent extreme pIOD <span class="hlt">events</span>, suggesting an increasing frequency of extreme climate and weather <span class="hlt">events</span> in regions affected by the pIOD.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003JCli...16....3L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003JCli...16....3L"><span>Atmosphere-Ocean Variations in the Indo-Pacific Sector during <span class="hlt">ENSO</span> Episodes.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lau, Ngar-Cheung; Nath, Mary Jo</p> <p>2003-01-01</p> <p>The influences of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span> on air-sea interaction in the Indian-western Pacific (IWP) Oceans have been investigated using a general circulation model. Observed monthly sea surface temperature (SST) variations in the deep tropical eastern/central Pacific (DTEP) have been inserted in the lower boundary of this model through the 1950-99 period. At all maritime grid points outside of DTEP, the model atmosphere has been coupled with an oceanic mixed layer model with variable depth. Altogether 16 independent model runs have been conducted.Composite analysis of selected <span class="hlt">ENSO</span> episodes illustrates that the prescribed SST anomalies in DTEP affect the surface atmospheric circulation and precipitation patterns in IWP through displacements of the near-equatorial Walker circulation and generation of Rossby wave modes in the subtropics. Such atmospheric responses modulate the surface fluxes as well as the oceanic mixed layer depth, and thereby establish a well-defined SST anomaly pattern in the IWP sector several months after the peak in <span class="hlt">ENSO</span> forcing in DTEP. In most parts of the IWP region, the net SST tendency induced by atmospheric changes has the same polarity as the local composite SST anomaly, thus indicating that the atmospheric forcing acts to reinforce the underlying SST signal.By analyzing the output from a suite of auxiliary experiments, it is demonstrated that the SST perturbations in IWP (which are primarily generated by <span class="hlt">ENSO</span>-related atmospheric changes) can, in turn, exert notable influences on the atmospheric conditions over that region. This feedback mechanism also plays an important role in the eastward migration of the subtropical anticyclones over the western Pacific in both hemispheres.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49..391C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49..391C"><span><span class="hlt">ENSO</span> related SST anomalies and relation with surface heat fluxes over south Pacific and Atlantic</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chatterjee, S.; Nuncio, M.; Satheesan, K.</p> <p>2017-07-01</p> <p>The role of surface heat fluxes in Southern Pacific and Atlantic Ocean SST anomalies associated with El Nino Southern Oscillation (<span class="hlt">ENSO</span>) is studied using observation and ocean reanalysis products. A prominent dipole structure in SST anomaly is found with a positive (negative) anomaly center over south Pacific (65S-45S, 120W-70W) and negative (positive) one over south Atlantic (50S-30S, 30W-0E) during austral summer (DJF) of El Nino (LaNina). During late austral spring-early summer (OND) of El Nino (LaNina), anomalous northerly (southerly) meridional moisture transport and a positive (negative) sea level pressure anomaly induces a suppressed (enhanced) latent heat flux from the ocean surface over south Pacific. This in turn results in a shallower than normal mixed layer depth which further helps in development of the SST anomaly. Mixed layer thins further due to anomalous shortwave radiation during summer and a well developed SST anomaly evolves. The south Atlantic pole exhibits exactly opposite characteristics at the same time. The contribution from the surface heat fluxes to mixed layer temperature change is found to be dominant over the advective processes over both the basins. Net surface heat fluxes anomaly is also found to be maximum during late austral spring-early summer period, with latent heat flux having a major contribution to it. The anomalous latent heat fluxes between atmosphere and ocean surface play important role in the growth of observed summertime SST anomaly. Sea-surface height also shows similar out-of-phase signatures over the two basins and are well correlated with the <span class="hlt">ENSO</span> related SST anomalies. It is also observed that the magnitude of <span class="hlt">ENSO</span> related anomalies over the southern ocean are weaker in LaNina years than in El Nino years, suggesting an intensified tropics-high latitude tele-connection during <span class="hlt">warm</span> phases of <span class="hlt">ENSO</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28096384','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28096384"><span>Holocene <span class="hlt">ENSO</span>-related cyclic storms recorded by magnetic minerals in speleothems of central China.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhu, Zongmin; Feinberg, Joshua M; Xie, Shucheng; Bourne, Mark D; Huang, Chunju; Hu, Chaoyong; Cheng, Hai</p> <p>2017-01-31</p> <p>Extreme hydrologic <span class="hlt">events</span> such as storms and floods have the potential to severely impact modern human society. However, the frequency of storms and their underlying mechanisms are limited by a paucity of suitable proxies, especially in inland areas. Here we present a record of speleothem magnetic minerals to reconstruct paleoprecipitation, including storms, in the eastern Asian monsoon area over the last 8.6 ky. The geophysical parameter IRM soft-flux represents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRM soft-flux exhibits relatively higher values before 6.7 ky and after 3.4 ky and lower values in the intervening period, consistent with regional hydrological changes observed in independent records. Abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) patterns, documenting the occurrence of <span class="hlt">ENSO</span>-related storms in the Holocene. Spectral power analyses reveal that the storms occur on a significant 500-y cycle, coincident with periodic solar activity and <span class="hlt">ENSO</span> variance, showing that reinforced (subdued) storms in central China correspond to reduced (increased) solar activity and amplified (damped) <span class="hlt">ENSO</span>. Thus, the magnetic minerals in speleothem HS4 preserve a record of the cyclic storms controlled by the coupled atmosphere-oceanic circulation driven by solar activity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1425660-enso-driven-energy-budget-perturbations-observations-cmip-models','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1425660-enso-driven-energy-budget-perturbations-observations-cmip-models"><span><span class="hlt">ENSO</span>-driven energy budget perturbations in observations and CMIP models</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Mayer, Michael; Fasullo, John T.; Trenberth, Kevin E.; ...</p> <p>2016-03-19</p> <p>Various observation-based datasets are employed to robustly quantify changes in ocean heat content (OHC), anomalous ocean–atmosphere energy exchanges and atmospheric energy transports during El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). These results are used as a benchmark to evaluate the energy pathways during <span class="hlt">ENSO</span> as simulated by coupled climate model runs from the CMIP3 and CMIP5 archives. The models are able to qualitatively reproduce observed patterns of <span class="hlt">ENSO</span>-related energy budget variability to some degree, but key aspects are seriously biased. Area-averaged tropical Pacific OHC variability associated with <span class="hlt">ENSO</span> is greatly underestimated by all models because of strongly biased responses of net radiation atmore » top-of-the-atmosphere to <span class="hlt">ENSO</span>. The latter are related to biases of mean convective activity in the models and project on surface energy fluxes in the eastern Pacific Intertropical Convergence Zone region. Moreover, models underestimate horizontal and vertical OHC redistribution in association with the generally too weak Bjerknes feedback, leading to a modeled <span class="hlt">ENSO</span> affecting a too shallow layer of the Pacific. Vertical links between SST and OHC variability are too weak even in models driven with observed winds, indicating shortcomings of the ocean models. Furthermore, modeled teleconnections as measured by tropical Atlantic OHC variability are too weak and the tropical zonal mean <span class="hlt">ENSO</span> signal is strongly underestimated or even completely missing in most of the considered models. In conclusion, results suggest that attempts to infer insight about climate sensitivity from <span class="hlt">ENSO</span>-related variability are likely to be hampered by biases in <span class="hlt">ENSO</span> in CMIP simulations that do not bear a clear link to future changes.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018APJAS..54...63S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018APJAS..54...63S"><span>Interdecadal Change in the Relationship Between the North Pacific Oscillation and the Pacific Meridional Mode and Its Impact on <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shin, So-Jung; An, Soon-Il</p> <p>2018-02-01</p> <p>Two leading but independent modes of Northern Pacific atmospheric circulation: the North Pacific Oscillation (NPO) and the Pacific Meridional Mode (PMM), are known external triggers of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) by the sequential migration of sea surface temperature (SST) anomalies into the tropics possibly by means of wind-evaporation-SST (WES) feedbacks. Because of the similar roles of NPO and PMM, most previous studies have explored them with no separation. Here, we investigate their independent and combined effects in triggering <span class="hlt">ENSO</span>, and find that when the NPO and PMM occur simultaneously during spring, <span class="hlt">ENSO</span> or <span class="hlt">ENSO</span>-like SST anomalies are generated during the following winter; whereas when either the NPO or PMM occur alone, <span class="hlt">ENSO</span> <span class="hlt">events</span> rarely occur. Furthermore, the relationship between NPO and PMM shows noticeable interdecadal variability, which is related to decadal changes in the mean upper-level jet stream over the North Pacific. Changes in the upper-level jet stream modify the location of the center of the Aleutian Low, which plays a role in bridging the NPO and PMM processes, especially when it migrates to the southwest. The period when NPO and PMM are well correlated coincides somewhat with the active <span class="hlt">ENSO</span> period, and vice versa, indicating that a more efficient trigger due to combined NPO-PMM processes results in a higher variation of <span class="hlt">ENSO</span>. Finally, analysis of the coupled model control simulations strongly supports our observational analysis results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48..893I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48..893I"><span>Simulation of different types of <span class="hlt">ENSO</span> impacts on South Asian Monsoon in CCSM4</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Islam, Siraj ul; Tang, Youmin</p> <p>2017-02-01</p> <p>It has been found in observation that there are different types of influences of El Nino Southern Oscillation (<span class="hlt">ENSO</span>) on the South Asian Monsoon (SAM). A correct description and representation of these teleconnections is critical for climate models to simulate and predict SAM. In this study, we examine these teleconnections in NCAR CAM4 and CCSM4 models, including the strength and weakness of these models in preserving different types of <span class="hlt">ENSO</span>-SAM relationships. By using observational and simulation dataset, the composite analysis, based on specific selection criteria, is performed for both SAM rainfall and the eastern equatorial Pacific sea surface temperature (SST) anomalies. Anomalous SAM rainfall is characterized in three different types i.e. the indirect influence of the SST anomalies of preceding winter (DJF-only), direct influence of the SST anomalies of concurrent summer (JJAS-only) and the combined influence of both preceding winter and concurrent summer (DJF&JJAS). The analysis reveals that CAM4 uncoupled simulation can reasonably well reproduce the anomalous SAM rainfall in DJF-only and DJF&JJAS types whereas the model fails to simulate the anomalous rainfall in the JJAS-only type. The better performance of CAM4, particularly in DJF&JJAS type, comes from its realistic simulation of moisture content and thermal contrast. Its failure to preserve the <span class="hlt">ENSO</span>-SAM relationship of JJAS-only type is due to the absence of <span class="hlt">ENSO</span> induced <span class="hlt">warming</span> in Northern Indian Ocean via atmospheric circulation which is indirectly linked to the lack of air-sea coupling. The role of Indian Ocean in controlling the <span class="hlt">ENSO</span>-SAM teleconnections of the DJF&JJAS type is further investigated using CAM4 sensitivity experiments. It is found that in absence of Indian Ocean SST, the anomalous SAM summer rainfall suppresses in the DJF&JJAS type, suggesting the important modulation by Indian Ocean SST probably through the preceding winter equatorial Pacific SST forcing and the atmospheric</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.4272A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.4272A"><span>Feedback process responsible for intermodel diversity of <span class="hlt">ENSO</span> variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>An, Soon-Il; Heo, Eun Sook; Kim, Seon Tae</p> <p>2017-05-01</p> <p>The origin of the intermodel diversity of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) variability is investigated by applying a singular value decomposition (SVD) analysis between the intermodel tropical Pacific sea surface temperature anomalies (SSTA) variance and the intermodel <span class="hlt">ENSO</span> stability index (BJ index). The first SVD mode features an <span class="hlt">ENSO</span>-like pattern for the intermodel SSTA variance (74% of total variance) and the dominant thermocline feedback (TH) for the BJ index (51%). Intermodel TH is mainly modified by the intermodel sensitivity of the zonal thermocline gradient response to zonal winds over the equatorial Pacific (βh), and the intermodel βh is correlated higher with the intermodel off-equatorial wind stress curl anomalies than the equatorial zonal wind stress anomalies. Finally, the intermodel off-equatorial wind stress curl is associated with the meridional shape and intensity of <span class="hlt">ENSO</span>-related wind patterns, which may cause a model-to-model difference in <span class="hlt">ENSO</span> variability by influencing the off-equatorial oceanic Rossby wave response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100031161','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100031161"><span>The Impact of Ocean Data Assimilation on Seasonal-to-Interannual Forecasts: A Case Study of the 2006 El Nino <span class="hlt">Event</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yang, Shu-Chih; Rienecker, Michele; Keppenne, Christian</p> <p>2010-01-01</p> <p>This study investigates the impact of four different ocean analyses on coupled forecasts of the 2006 El Nino <span class="hlt">event</span>. Forecasts initialized in June 2006 using ocean analyses from an assimilation that uses flow-dependent background error covariances are compared with those using static error covariances that are not flow dependent. The flow-dependent error covariances reflect the error structures related to the background <span class="hlt">ENSO</span> instability and are generated by the coupled breeding method. The ocean analyses used in this study result from the assimilation of temperature and salinity, with the salinity data available from Argo floats. Of the analyses, the one using information from the coupled bred vectors (BV) replicates the observed equatorial long wave propagation best and exhibits more <span class="hlt">warming</span> features leading to the 2006 El Nino <span class="hlt">event</span>. The forecasts initialized from the BV-based analysis agree best with the observations in terms of the growth of the <span class="hlt">warm</span> anomaly through two <span class="hlt">warming</span> phases. This better performance is related to the impact of the salinity analysis on the state evolution in the equatorial thermocline. The early <span class="hlt">warming</span> is traced back to salinity differences in the upper ocean of the equatorial central Pacific, while the second <span class="hlt">warming</span>, corresponding to the mature phase, is associated with the effect of the salinity assimilation on the depth of the thermocline in the western equatorial Pacific. The series of forecast experiments conducted here show that the structure of the salinity in the initial conditions is important to the forecasts of the extension of the <span class="hlt">warm</span> pool and the evolution of the 2006 El Ni o <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1237098','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1237098"><span>Changes in Intense Precipitation <span class="hlt">Events</span> in West Africa and the central U.S. under Global <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Cook, Kerry H.; Vizy, Edward</p> <p></p> <p>The purpose of the proposed project is to improve our understanding of the physical processes and large-scale connectivity of changes in intense precipitation <span class="hlt">events</span> (high rainfall rates) under global <span class="hlt">warming</span> in West Africa and the central U.S., including relationships with low-frequency modes of variability. This is in response to the requested subject area #2 “simulation of climate extremes under a changing climate … to better quantify the frequency, duration, and intensity of extreme <span class="hlt">events</span> under climate change and elucidate the role of low frequency climate variability in modulating extremes.” We will use a regional climate model and emphasize an understandingmore » of the physical processes that lead to an intensification of rainfall. The project objectives are as follows: 1. Understand the processes responsible for simulated changes in <span class="hlt">warm</span>-season rainfall intensity and frequency over West Africa and the Central U.S. associated with greenhouse gas-induced global <span class="hlt">warming</span> 2. Understand the relationship between changes in <span class="hlt">warm</span>-season rainfall intensity and frequency, which generally occur on regional space scales, and the larger-scale global <span class="hlt">warming</span> signal by considering modifications of low-frequency modes of variability. 3. Relate changes simulated on regional space scales to global-scale theories of how and why atmospheric moisture levels and rainfall should change as climate <span class="hlt">warms</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B33E2116A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B33E2116A"><span>2015-16 <span class="hlt">ENSO</span> Drove Tropical Soil Moisture Dynamics and Methane Fluxes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aronson, E. L.; Dierick, D.; Botthoff, J.; Swanson, A. C.; Johnson, R. F.; Allen, M. F.</p> <p>2017-12-01</p> <p>The El Niño/Southern Oscillation <span class="hlt">Event</span> (<span class="hlt">ENSO</span>) cycle drives large-scale climatic trends globally. Within the new world tropics, El Niño brings dryer weather than the counterpart La Niña. Atmospheric methane growth rates have shown extreme variability over the past three decades. One proposed driver is the proportion of tropical land surface saturated, affecting methane production or consumption. We measured methane flux bimonthly through the transition of 2015-16 <span class="hlt">ENSO</span>. The date of measurement, across El Niño and La Niña within the typical "rainy" and "dry" seasons, to be the most significant driver of methane flux. Soil moisture varied across this time period, and regulated methane flux. During the strong El Niño, extreme dry soil conditions occurred in a typical "rainy" season month reducing soil moisture. Wetter than usual soil conditions appeared during the "rainy" season month of the moderate La Niña. The dry El Niño soils corresponded to greater methane consumption by tropical forest soils, and a reduced local atmospheric column methane concentration. Conversely, the wet La Niña soils had lower methane consumption and higher local atmospheric column methane concentrations. The <span class="hlt">ENSO</span> cycle is a strong driver of tropical terrestrial and wetland soil moisture conditions, and can regulate global atmospheric methane dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2867B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2867B"><span>The Chennai extreme rainfall <span class="hlt">event</span> in 2015: The Bay of Bengal connection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boyaj, Alugula; Ashok, Karumuri; Ghosh, Subimal; Devanand, Anjana; Dandu, Govardhan</p> <p>2018-04-01</p> <p>Southeast India experienced a heavy rainfall during 30 Nov-2 Dec 2015. Particularly, the Chennai city, the fourth major metropolitan city in India with a population of 5 million, experienced extreme flooding and causalities. Using various observed/reanalysed datasets, we find that the concurrent southern Bay of Bengal (BoB) sea surface temperatures (SST) were anomalously <span class="hlt">warm</span>. Our analysis shows that BoB sea surface temperature anomalies (SSTA) are indeed positively, and significantly, correlated with the northeastern Indian monsoonal rainfall during this season. Our sensitivity experiments carried out with the Weather Research and Forecasting (WRF) model at 25 km resolution suggest that, while the strong concurrent El Niño conditions contributed to about 21.5% of the intensity of the extreme Chennai rainfall through its signals in the local SST mentioned above, the <span class="hlt">warming</span> trend in BoB SST also contributed equally to the extremity of the <span class="hlt">event</span>. Further, the El Niño southern oscillation (<span class="hlt">ENSO</span>) impacts on the intensity of the synoptic <span class="hlt">events</span> in the BoB during the northeast monsoon are manifested largely through the local SST in the BoB as compared through its signature in the atmospheric circulations over the BoB.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..917D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..917D"><span>Diversity of moderate El Niño <span class="hlt">events</span> evolution: role of air-sea interactions in the eastern tropical Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dewitte, Boris; Takahashi, Ken</p> <p>2017-12-01</p> <p>In this paper we investigate the evolution of moderate El Niño <span class="hlt">events</span> during their developing phase with the objective to understand why some of them did not evolve as extreme <span class="hlt">events</span> despite favourable conditions for the non-linear amplification of the Bjerknes feedback (i.e. <span class="hlt">warm</span> SST in Austral winter in the eastern equatorial Pacific). Among the moderate <span class="hlt">events</span>, two classes are considered consisting in the Eastern Pacific (EP) El Niño <span class="hlt">events</span> and Central Pacific (CP) <span class="hlt">events</span>. We first show that the observed SST variability across moderate El Niño <span class="hlt">events</span> (i.e. inter-<span class="hlt">event</span> variability) is largest in the far eastern Pacific (east of 130°W) in the Austral winter prior to their peak, which is associated to either significant <span class="hlt">warm</span> anomaly (moderate EP El Niño) or an anomaly between weak <span class="hlt">warm</span> and cold (moderate CP El Niño) as reveals by the EOF analysis of the SST anomaly evolution during the development phase of El Niño across the El Niño years. Singular value decomposition (SVD) analysis of SST and wind stress anomalies across the El Niño years further indicates that the inter-<span class="hlt">event</span> SST variability is associated with an air-sea mode explaining 31% of the covariance between SST and wind stress. The associated SST pattern consists in SST anomalies developing along the coast of Ecuador in Austral fall and expanding westward as far as 130°W in Austral winter. The associated wind stress pattern features westerlies (easterlies) west of 130°W along the equator peaking around June-August for EP (CP) El Niño <span class="hlt">events</span>. This air-sea mode is interpreted as resulting from a developing seasonal Bjerknes feedback for EP El Niño <span class="hlt">events</span> since it is shown to be associated to a Kelvin wave response at its peak phase. However equatorial easterlies east of 130°W emerge in September that counters the growing SST anomalies associated to the air-sea mode. These have been particularly active during both the 1972 and the 2015 El Niño <span class="hlt">events</span>. It is shown that the easterlies are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70016220','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70016220"><span>Expression of seasonal and <span class="hlt">ENSO</span> forcing in climatic variability at lower than <span class="hlt">ENSO</span> frequencies: evidence from Pleistocene marine varves off California</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Anderson, R.Y.; Linsley, B.K.; Gardner, J.V.</p> <p>1990-01-01</p> <p>Upper Pleistocene marine sediments along the upper continental slope off northern and central California contain alternations of varved and bioturbated sediments and associated changes in biota and sediment composition. These alternations can be related to conditions that accompany El Nin??o and anti-El Nin??o (<span class="hlt">ENSO</span>) circulation. Anti-El Nin??o conditions are characterized by increased upwelling and productivity and by low concentrations of dissolved oxygen in the oxygen minimum zone that resulted in varve preservation. El Nin??o conditions are characterized by little or no upwelling, low productivity, and higher concentrations of dissolved oxygen that resulted in zones of bioturbation. Alternations of varves and zones of bioturbation, that range from decades to millennia, occur through the upper Pleistocene section. The inferred long-term alternations in El Nin??o and anti-El Nin??o conditions appear to be a re-expression of <span class="hlt">ENSO</span>'s primary 3-7 year cycle. Decadal to millennial cycles of productivity associated with El Nin??o and anti-El Nin??o conditions may have served as a "carbon pump" and transferred atmospheric CO2 to the marine reservoir. Changes in sediment composition and organisms associated with El Nin??o or anti-El Nin??o conditions can be related to both seasonal and <span class="hlt">ENSO</span> phenomena. Expression of these changes at lower-than-<span class="hlt">ENSO</span> frequencies may be partly explained by adding the effects of seasonal variability to effects produced by a self-oscillating <span class="hlt">ENSO</span> system. However, deterministic mechanisms, including solar modulation of <span class="hlt">ENSO</span>, may also contribute to long-term alternations of El Nin??o and anti-El Nin??o conditions. ?? 1990.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMOS21C..02W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMOS21C..02W"><span>The Tropical Western Hemisphere <span class="hlt">Warm</span> Pool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, C.; Enfield, D. B.</p> <p>2002-12-01</p> <p>The paper describes and examines variability of the tropical Western Hemisphere <span class="hlt">warm</span> pool (WHWP) of water warmer than 28.5oC. The WHWP is the second-largest tropical <span class="hlt">warm</span> pool on Earth. Unlike the Eastern Hemisphere <span class="hlt">warm</span> pool in the western Pacific, which straddles the equator, the WHWP is entirely north of the equator. At various stages of development the WHWP extends over parts of the eastern North Pacific, the Gulf of Mexico, the Caribbean, and the western tropical North Atlantic. It has a large seasonal cycle and its interannual fluctuations of area and intensity are significant. Surface heat fluxes <span class="hlt">warm</span> the WHWP through the boreal spring to an annual maximum of SST and WHWP area in the late summer/early fall, associated with eastern North Pacific and Atlantic hurricane activities and rainfall from northern South America to the southern tier of the United States. Observations suggest that a positive ocean-atmosphere feedback operating through longwave radiation and associated cloudiness seems to operate in the WHWP. During winter preceding large <span class="hlt">warm</span> pool, there is an alteration of the Walker and Hadley circulation cells that serves as a "tropospheric bridge" for transferring Pacific <span class="hlt">ENSO</span> effects to the Atlantic sector and inducing initial <span class="hlt">warming</span> of <span class="hlt">warm</span> pool. Associated with the <span class="hlt">warm</span> SST anomalies is a decrease in sea level pressure anomalies and an anomalous increase in atmospheric convection and cloudiness. The increase in convective activity and cloudiness results in less net longwave radiation loss from the sea surface, which then reinforces SST anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP31A1107F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP31A1107F"><span>Equatorial Precession Drove Mid-Latitude Changes in <span class="hlt">ENSO</span>-Scale Variation in the Earliest Miocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.</p> <p>2014-12-01</p> <p>Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation <span class="hlt">event</span>. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant <span class="hlt">ENSO</span>-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that <span class="hlt">ENSO</span>-band variation is modulated by the 11-kyr cycle, with power in the <span class="hlt">ENSO</span> band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on <span class="hlt">ENSO</span>-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4312560Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4312560Z"><span>Modulation of Bjerknes feedback on the decadal variations in <span class="hlt">ENSO</span> predictability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Fei; Fang, Xiang-Hui; Zhu, Jiang; Yu, Jin-Yi; Li, Xi-Chen</p> <p>2016-12-01</p> <p>Clear decadal variations exist in the predictability of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>), with the most recent decade having the lowest <span class="hlt">ENSO</span> predictability in the past six decades. The Bjerknes Feedback (BF) intensity, which dominates the development of <span class="hlt">ENSO</span>, has been proposed to determine <span class="hlt">ENSO</span> predictability. Here we demonstrate that decadal variations in BF intensity are largely a result of the sensitivity of the zonal winds to the zonal sea level pressure (SLP) gradient in the equatorial Pacific. Furthermore, the results show that during low-<span class="hlt">ENSO</span> predictability decades, zonal wind anomalies over the equatorial Pacific are more linked to SLP variations in the off-equatorial Pacific, which can then transfer this information into surface temperature and precipitation fields through the BF, suggesting a weakening in the ocean-atmosphere coupling in the tropical Pacific. This result indicates that more attention should be paid to off-equatorial processes in the prediction of <span class="hlt">ENSO</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2361H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2361H"><span>Contribution of tropical instability waves to <span class="hlt">ENSO</span> irregularity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Holmes, Ryan M.; McGregor, Shayne; Santoso, Agus; England, Matthew H.</p> <p>2018-05-01</p> <p>Tropical instability waves (TIWs) are a major source of internally-generated oceanic variability in the equatorial Pacific Ocean. These non-linear phenomena play an important role in the sea surface temperature (SST) budget in a region critical for low-frequency modes of variability such as the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). However, the direct contribution of TIW-driven stochastic variability to <span class="hlt">ENSO</span> has received little attention. Here, we investigate the influence of TIWs on <span class="hlt">ENSO</span> using a 1/4° ocean model coupled to a simple atmosphere. The use of a simple atmosphere removes complex intrinsic atmospheric variability while allowing the dominant mode of air-sea coupling to be represented as a statistical relationship between SST and wind stress anomalies. Using this hybrid coupled model, we perform a suite of coupled ensemble forecast experiments initiated with wind bursts in the western Pacific, where individual ensemble members differ only due to internal oceanic variability. We find that TIWs can induce a spread in the forecast amplitude of the Niño 3 SST anomaly 6-months after a given sequence of WWBs of approximately ± 45% the size of the ensemble mean anomaly. Further, when various estimates of stochastic atmospheric forcing are added, oceanic internal variability is found to contribute between about 20% and 70% of the ensemble forecast spread, with the remainder attributable to the atmospheric variability. While the oceanic contribution to <span class="hlt">ENSO</span> stochastic forcing requires further quantification beyond the idealized approach used here, our results nevertheless suggest that TIWs may impact <span class="hlt">ENSO</span> irregularity and predictability. This has implications for <span class="hlt">ENSO</span> representation in low-resolution coupled models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150022193','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150022193"><span>Stability of <span class="hlt">ENSO</span> and Its Tropical Pacific Teleconnections over the Last Millennium</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lewis, Sophie; Legrande, A. N.</p> <p>2015-01-01</p> <p>Determining past changes in the amplitude, frequency and teleconnections of the El Nio Southern Oscillation (<span class="hlt">ENSO</span>) is important for understanding its potential sensitivity to future anthropogenic climate change. Palaeo-reconstructions from proxy records provide long-term information of <span class="hlt">ENSO</span> interactions with the background climatic state through time. However, it remains unclear how <span class="hlt">ENSO</span> characteristics have changed through time, and precisely which signals proxies record. Proxy interpretations are underpinned by the assumption of stationarity in relationships between local and remote climates, and often utilise archives from single locations located in the Pacific Ocean to reconstruct <span class="hlt">ENSO</span> histories. Here, we investigate the stationarity of <span class="hlt">ENSO</span> teleconnections using the Last Millennium experiment of CMIP5 (Coupled Model Intercomparison Project phase 5) (Taylor et al., 2012). We show that modelled <span class="hlt">ENSO</span> characteristics vary on decadal- to centennial-scales, resulting from internal variability and external forcings, such as tropical volcanic eruptions. Furthermore, the relationship between <span class="hlt">ENSO</span> conditions and local climates across the Pacific basin varies throughout the Last Millennium. Results show the stability of teleconnections is regionally dependent and proxies may reveal complex changes in teleconnected patterns, rather than large-scale changes in base <span class="hlt">ENSO</span> characteristics. As such, proxy insights into <span class="hlt">ENSO</span> likely require evidence to be synthesised over large spatial areas in order to deconvolve changes occurring in the NINO3.4 region from those pertaining to proxy-relevant local climatic variables. To obtain robust histories of the <span class="hlt">ENSO</span> and its remote impacts, we recommend interpretations of proxy records should be considered in conjunction with palaeo-reconstructions from within the Central Pacific</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PalOc..30.1425P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PalOc..30.1425P"><span>Tropical North Atlantic subsurface <span class="hlt">warming</span> <span class="hlt">events</span> as a fingerprint for AMOC variability during Marine Isotope Stage 3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, Andrew O.; Schmidt, Matthew W.; Chang, Ping</p> <p>2015-11-01</p> <p>The role of Atlantic Meridional Overturning Circulation (AMOC) as the driver of Dansgaard-Oeschger (DO) variability that characterized Marine Isotope Stage 3 (MIS 3) has long been hypothesized. Although there is ample proxy evidence suggesting that DO <span class="hlt">events</span> were robust features of glacial climate, there is little data supporting a link with AMOC. Recently, modeling studies and subsurface temperature reconstructions have suggested that subsurface <span class="hlt">warming</span> across the tropical North Atlantic can be used to fingerprint a weakened AMOC during the deglacial because a reduction in the strength of the western boundary current allows <span class="hlt">warm</span> salinity maximum water of the subtropical gyre to enter the deep tropics. To determine if AMOC variability played a role during the DO cycles of MIS 3, we present new, high-resolution Mg/Ca and δ18O records spanning 24-52 kyr from the near-surface dwelling planktonic foraminifera Globigerinoides ruber and the lower thermocline dwelling planktonic foraminifera Globorotalia truncatulinoides in Southern Caribbean core VM12-107 (11.33°N, 66.63°W, 1079 m depth). Our subsurface Mg/Ca record reveals abrupt increases in Mg/Ca ratios (the largest equal to a 4°C <span class="hlt">warming</span>) during the interstadial-stadial transition of most DO <span class="hlt">events</span> during this period. This change is consistent with reconstructions of subsurface <span class="hlt">warming</span> <span class="hlt">events</span> associated with cold <span class="hlt">events</span> across the deglacial using the same core. Additionally, our data support the conclusion reached by a recently published study from the Florida Straits that AMOC did not undergo significant reductions during Heinrich <span class="hlt">events</span> 2 and 3. This record presents some of the first high-resolution marine sediment derived evidence for variable AMOC during MIS 3.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130014807','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130014807"><span>Assessment of the APCC Coupled MME Suite in Predicting the Distinctive Climate Impacts of Two Flavors of <span class="hlt">ENSO</span> during Boreal Winter</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jeong, Hye-In; Lee, Doo Young; Karumuri, Ashok; Ahn, Joong-Bae; Lee, June-Yi; Luo, Jing-Jia; Schemm, Jae-Kyung E.; Hendon, Harry H.; Braganza, Karl; Ham, Yoo-Geun</p> <p>2012-01-01</p> <p>Forecast skill of the APEC Climate Center (APCC) Multi-Model Ensemble (MME) seasonal forecast system in predicting two main types of El Nino-Southern Oscillation (<span class="hlt">ENSO</span>), namely canonical (or cold tongue) and Modoki <span class="hlt">ENSO</span>, and their regional climate impacts is assessed for boreal winter. The APCC MME is constructed by simple composite of ensemble forecasts from five independent coupled ocean-atmosphere climate models. Based on a hindcast set targeting boreal winter prediction for the period 19822004, we show that the MME can predict and discern the important differences in the patterns of tropical Pacific sea surface temperature anomaly between the canonical and Modoki <span class="hlt">ENSO</span> one and four month ahead. Importantly, the four month lead MME beats the persistent forecast. The MME reasonably predicts the distinct impacts of the canonical <span class="hlt">ENSO</span>, including the strong winter monsoon rainfall over East Asia, the below normal rainfall and above normal temperature over Australia, the anomalously wet conditions across the south and cold conditions over the whole area of USA, and the anomalously dry conditions over South America. However, there are some limitations in capturing its regional impacts, especially, over Australasia and tropical South America at a lead time of one and four months. Nonetheless, forecast skills for rainfall and temperature over East Asia and North America during <span class="hlt">ENSO</span> Modoki are comparable to or slightly higher than those during canonical <span class="hlt">ENSO</span> <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ClDy...42.3061B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ClDy...42.3061B"><span>Zonal structure and variability of the Western Pacific dynamic <span class="hlt">warm</span> pool edge in CMIP5</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Jaclyn N.; Langlais, Clothilde; Maes, Christophe</p> <p>2014-06-01</p> <p>The equatorial edge of the Western Pacific <span class="hlt">Warm</span> Pool is operationally identified by one isotherm ranging between 28° and 29 °C, chosen to align with the interannual variability of strong zonal salinity gradients and the convergence of zonal ocean currents. The simulation of this edge is examined in 19 models from the World Climate Research Program Coupled Model Intercomparison Project Phase 5 (CMIP5), over the historical period from 1950 to 2000. The dynamic <span class="hlt">warm</span> pool edge (DWPE), where the zonal currents converge, is difficult to determine from limited observations and biased models. A new analysis technique is introduced where a proxy for DWPE is determined by the isotherm that most closely correlates with the movements of the strong salinity gradient. It can therefore be a different isotherm in each model. The DWPE is simulated much closer to observations than if a direct temperature-only comparison is made. Aspects of the DWPE remain difficult for coupled models to simulate including the mean longitude, the interannual excursions, and the zonal convergence of ocean currents. Some models have only very weak salinity gradients trapped to the western side of the basin making it difficult to even identify a DWPE. The model's DWPE are generally 1-2 °C cooler than observed. In line with theory, the magnitude of the zonal migrations of the DWPE are strongly related to the amplitudes of the Nino3.4 SST index. Nevertheless, a better simulation of the mean location of the DWPE does not necessarily improve the amplitude of a model's <span class="hlt">ENSO</span>. It is also found that in a few models (CSIROMk3.6, inmcm and inmcm4-esm) the <span class="hlt">warm</span> pool displacements result from a net heating or cooling rather than a zonal advection of <span class="hlt">warm</span> water. The simulation of the DWPE has implications for <span class="hlt">ENSO</span> dynamics when considering <span class="hlt">ENSO</span> paradigms such as the delayed action oscillator mechanism, the Advective-Reflective oscillator, and the zonal-advective feedback. These are also discussed in the context</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040161152&hterms=forest+trees&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dforest%2Btrees','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040161152&hterms=forest+trees&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dforest%2Btrees"><span>Forest Understory Fire in the Brazilian Amazon in <span class="hlt">ENSO</span> and Non-<span class="hlt">ENSO</span> Years: Area Burned and Committed Carbon Emissions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Alencar, A.; Nepstad, D.; Ver-Diaz, M. Del. C.</p> <p>2004-01-01</p> <p>"Understory fires" that burn the floor of standing forests are one of the most important types of forest impoverishment in the Amazon, especially during the severe droughts of El Nino Southern Oscillation (<span class="hlt">ENSO</span>) episodes. However, we are aware of no estimates of the areal extent of these fires for the Brazilian Amazon and, hence, of their contribution to Amazon carbon fluxes to the atmosphere. We calculated the area of forest understory fires for the Brazilian Amazon region during an El Nino (1998) and a non El Nino (1995) year based on forest fire scars mapped with satellite images for three locations in eastern and southern Amazon, where deforestation is concentrated. The three study sites represented a gradient of both forest types and dry season severity. The burning scar maps were used to determine how the percentage of forest that burned varied with distance from agricultural clearings. These spatial functions were then applied to similar forest/climate combinations outside of the study sites to derive an initial estimate for the Brazilian Amazon. Ninety-one percent of the forest area that burned in the study sites was within the first kilometer of a clearing for the non <span class="hlt">ENSO</span> year and within the first four kilometers for the <span class="hlt">ENSO</span> year. The area of forest burned by understory forest fire during the severe drought (<span class="hlt">ENSO</span>) year (3.9 millions of hectares) was 13 times greater than the area burned during the average rainfall year (0.2 million hectares), and twice the area of annual deforestation rate. Dense forest was, proportionally, the forest area most affected by understory fires during the El Nino year, while understory fires were concentrated in transitional forests during the year of average rainfall. Our estimate of aboveground tree biomass killed by fire ranged from 0.06 Pg to 0.38 Pg during the <span class="hlt">ENSO</span> and from 0,004 Pg to 0,024 Pg during the non <span class="hlt">ENSO</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1811455B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1811455B"><span><span class="hlt">ENSO</span> effects on stratospheric trace gases: How do we capture reality?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Braesicke, Peter; Kirner, Oliver; Versick, Stefan; Joeckel, Patrick; Stiler, Gabriele</p> <p>2016-04-01</p> <p>The El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon is an important pacemaker for interannual variability in the Earth's atmosphere. <span class="hlt">ENSO</span> impacts on trace gases have been observed and modelled for the stratosphere and the troposphere. However, unambiguous attribution is often difficult due to the limited length of homogenous observational records and thus long-term (decadal) trends are sometimes difficult to detect. Generally <span class="hlt">ENSO</span> impacts in low latitudes are easier to detect, because the response emerges close (temporally and spatially) to the forcing. Moving from low to high latitudes it becomes increasingly difficult to isolate <span class="hlt">ENSO</span> driven variability, due to time-lags involved and many other modes of variability playing a role as well. Here, we use a nudged version of the EMAC chemistry-climate model to evaluate <span class="hlt">ENSO</span> impacts on trace gases over the last 35 years (a so-called Ref-C1SD integration) and contrast the nudged model with its free running counterpart. We use water vapour and ozone observations from the MIPAS instrument on ENVISAT from 2002 to 2012 to test the model performance. Using lagged correlations for the longer model time-series we trace the <span class="hlt">ENSO</span> signal from the tropical lower troposphere to the polar lower and middle stratosphere and provide a framework for simple attribution of the <span class="hlt">ENSO</span> signal in trace gases. This concise characterisation of the <span class="hlt">ENSO</span> impact on trace gases aids improved trend detection in temporally limited time series.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APJAS..50..531Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APJAS..50..531Y"><span>Interdecadal changes in the Asian winter monsoon variability and its relationship with <span class="hlt">ENSO</span> and AO</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yun, Kyung-Sook; Seo, Ye-Won; Ha, Kyung-Ja; Lee, June-Yi; Kajikawa, Yoshiyuki</p> <p>2014-08-01</p> <p>Interdecadal changes in the Asian winter monsoon (AWM) variability are investigated using three surface air temperature datasets for the 55-year period of 1958-2012 from (1) the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis 1 (NCEP), (2) combined datasets from the European Centre for Medium-range Weather Forecasts (ECMWF) 40-yr reanalysis and interim data (ERA), and (3) Japanese 55-year reanalysis (JRA). Particular attention has been paid to the first four empirical orthogonal function (EOF) modes of the AWM temperature variability that together account for 64% of the total variance and have been previously identified as predictable modes. The four modes are characterized as follows: the first mode by a southern <span class="hlt">warming</span> over the Indo-western Pacific Ocean associated with a gradually increasing basin-wide <span class="hlt">warming</span> trend; the second mode by northern <span class="hlt">warming</span> with the interdecadal change after the late 1980s; the third and fourth modes by north-south triple pattern, which reveal a phase shift after the late 1970s. The three reanalyses agree well with each other when producing the first three modes, but show large discrepancy in capturing both spatial and temporal characteristics of the fourth mode. It is therefore considered that the first three leading modes are more reliable than the rest higher modes. Considerable interdecadal changes are found mainly in the first two modes. While the first mode shows gradually decreasing variance, the second mode exhibits larger interannual variance during the recent decade. In addition, after the late 1970s, the first mode has a weakening relationship with the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) whereas the second mode has strengthening association with the Artic Oscillation (AO). This indicates an increasing role of AO but decreasing role of <span class="hlt">ENSO</span> on the AWM variability. A better understanding of the interdecadal change in the dominant modes would contribute toward advancing in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015rtpm.book..173S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015rtpm.book..173S"><span>A New Technique to Observe <span class="hlt">ENSO</span> Activity via Ground-Based GPS Receivers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Suparta, Wayan; Iskandar, Ahmad; Singh, Mandeep Singh Jit</p> <p></p> <p>In an attempt to study the effects of global climate change in the tropics for improving global climate model, this paper aims to detect the <span class="hlt">ENSO</span> <span class="hlt">events</span>, especially El Nino phase by using ground-based GPS receivers. Precipitable water vapor (PWV) obtained from the Global Positioning System (GPS) Meteorology measurements in line with the sea surface temperature anomaly (SSTa) are used to connect their response to El Niño activity. The data gathered from four selected stations over the Southeast Asia, namely PIMO (Philippines), KUAL (Malaysia), NTUS (Singapore) and BAKO (Indonesia) for the year of 2009/2010 were processed. A strong correlation was observed for PIMO station with a correlation coefficient of -0.90, significantly at the 99 % confidence level. In general, the relationship between GPS PWV and SSTa at all stations on a weekly basis showed with a negative correlation. The negative correlation indicates that during the El Niño <span class="hlt">event</span>, the PWV variation was in decreased trend. Decreased trend of PWV value is caused by a dry season that affected the GPS signals in the ocean-atmospheric coupling. Based on these promising results, we can propose that the ground-based GPS receiver is capable used to monitor <span class="hlt">ENSO</span> activity and this is a new prospective method that previously unexplored.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150011475','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150011475"><span>Role of Tropical Atlantic SST Variability as a Modulator of El Nino Teleconnections</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ham, Yoo-Geun; Sung, Mi-Kyung; An, Soon-II; Schubert, Siegfried D.; Kug, Jong-Seong</p> <p>2014-01-01</p> <p>The present study suggests that the off-equatorial North Atlantic (NATL) SST <span class="hlt">warming</span> plays a significant role in modulating El Niño teleconnection and its impact on the North Atlantic and European regions. The El Niño <span class="hlt">events</span> accompanied by NATL SST <span class="hlt">warming</span> exhibit south-north dipole pattern over the Western Europe to Atlantic, while the <span class="hlt">ENSO</span> teleconnection pattern without NATL <span class="hlt">warming</span> exhibits a Rossby wave-like pattern confined over the North Pacific and western Atlantic. Especially, the El Niño <span class="hlt">events</span> with NATL <span class="hlt">warming</span> show positive (negative) geopotential-height anomalies over the North Atlantic (Western Europe) which resemble the negative phase of the NAO. Consistently, it is shown using a simple statistical model that NATL SSTA in addition to the tropical Pacific SSTA leads to better prediction on regional climate variation over the North Atlantic and European regions. This role of NATL SST on <span class="hlt">ENSO</span> teleconnection is also validated and discussed in a long term simulation of coupled global circulation model (CGCM).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29672529','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29672529"><span>Potential and limits for rapid genetic adaptation to <span class="hlt">warming</span> in a Great Barrier Reef coral.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Matz, Mikhail V; Treml, Eric A; Aglyamova, Galina V; Bay, Line K</p> <p>2018-04-01</p> <p>Can genetic adaptation in reef-building corals keep pace with the current rate of sea surface <span class="hlt">warming</span>? Here we combine population genomics, biophysical modeling, and evolutionary simulations to predict future adaptation of the common coral Acropora millepora on the Great Barrier Reef (GBR). Genomics-derived migration rates were high (0.1-1% of immigrants per generation across half the latitudinal range of the GBR) and closely matched the biophysical model of larval dispersal. Both genetic and biophysical models indicated the prevalence of southward migration along the GBR that would facilitate the spread of heat-tolerant alleles to higher latitudes as the climate <span class="hlt">warms</span>. We developed an individual-based metapopulation model of polygenic adaptation and parameterized it with population sizes and migration rates derived from the genomic analysis. We find that high migration rates do not disrupt local thermal adaptation, and that the resulting standing genetic variation should be sufficient to fuel rapid region-wide adaptation of A. millepora populations to gradual <span class="hlt">warming</span> over the next 20-50 coral generations (100-250 years). Further adaptation based on novel mutations might also be possible, but this depends on the currently unknown genetic parameters underlying coral thermal tolerance and the rate of <span class="hlt">warming</span> realized. Despite this capacity for adaptation, our model predicts that coral populations would become increasingly sensitive to random thermal fluctuations such as <span class="hlt">ENSO</span> cycles or heat waves, which corresponds well with the recent increase in frequency of catastrophic coral bleaching <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70148676','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70148676"><span>Relating large-scale climate variability to local species abundance: <span class="hlt">ENSO</span> forcing and shrimp in Breton Sound, Louisiana, USA</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Piazza, Bryan P.; LaPeyre, Megan K.; Keim, B.D.</p> <p>2010-01-01</p> <p>Climate creates environmental constraints (filters) that affect the abundance and distribution of species. In estuaries, these constraints often result from variability in water flow properties and environmental conditions (i.e. water flow, salinity, water temperature) and can have significant effects on the abundance and distribution of commercially important nekton species. We investigated links between large-scale climate variability and juvenile brown shrimp Farfantepenaeus aztecus abundance in Breton Sound estuary, Louisiana (USA). Our goals were to (1) determine if a teleconnection exists between local juvenile brown shrimp abundance and the El Niño Southern Oscillation (<span class="hlt">ENSO</span>) and (2) relate that linkage to environmental constraints that may affect juvenile brown shrimp recruitment to, and survival in, the estuary. Our results identified a teleconnection between winter <span class="hlt">ENSO</span> conditions and juvenile brown shrimp abundance in Breton Sound estuary the following spring. The physical connection results from the impact of <span class="hlt">ENSO</span> on winter weather conditions in Breton Sound (air pressure, temperature, and precipitation). Juvenile brown shrimp abundance effects lagged <span class="hlt">ENSO</span> by 3 mo: lower than average abundances of juvenile brown shrimp were caught in springs following winter El Niño <span class="hlt">events</span>, and higher than average abundances of brown shrimp were caught in springs following La Niña winters. Salinity was the dominant <span class="hlt">ENSO</span>-forced environmental filter for juvenile brown shrimp. Spring salinity was cumulatively forced by winter river discharge, winter wind forcing, and spring precipitation. Thus, predicting brown shrimp abundance requires incorporating climate variability into models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20120016994&hterms=atlantic+meridional+overturning+circulation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Datlantic%2Bmeridional%2Boverturning%2Bcirculation"><span><span class="hlt">Warm</span> and Saline <span class="hlt">Events</span> Embedded in the Meridional Circulation of the Northern North Atlantic</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkinen, Sirpa; Rhines, Peter B.; Worthen, Denise L.</p> <p>2011-01-01</p> <p>Ocean state estimates from 1958 to 2005 from the Simple Ocean Assimilation System (SODA) system are analyzed to understand circulation between subtropical and subpolar Atlantic and their connection with atmospheric forcing. This analysis shows three periods (1960s, around 1980, and 2000s) with enhanced <span class="hlt">warm</span>, saline waters reaching high latitudes, alternating with freshwater <span class="hlt">events</span> originating at high latitudes. It complements surface drifter and altimetry data showing the subtropical -subpolar exchange leading to a significant temperature and salinity increase in the northeast Atlantic after 2001. The <span class="hlt">warm</span> water limb of the Atlantic meridional overturning cell represented by SODA expanded in density/salinity space during these <span class="hlt">warm</span> <span class="hlt">events</span>. Tracer simulations using SODA velocities also show decadal variation of the Gulf Stream waters reaching the subpolar gyre and Nordic seas. The negative phase of the North Atlantic Oscillation index, usually invoked in such variability, fails to predict the <span class="hlt">warming</span> and salinization in the early 2000s, with salinities not seen since the 1960s. Wind stress curl variability provided a linkage to this subtropical/subpolar gyre exchange as illustrated using an idealized two ]layer circulation model. The ocean response to the modulation of the climatological wind stress curl pattern was found to be such that the northward penetration of subtropical tracers is enhanced when amplitude of the wind stress curl is weaker than normal. In this case both the subtropical and subpolar gyres weaken and the subpolar density surfaces relax; hence, the polar front moves westward, opening an enhanced northward access of the subtropical waters in the eastern boundary current.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/55476','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/55476"><span>Relationships of the symmetric and asymmetric components of <span class="hlt">ENSO</span> to US extreme precipitation</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>Lejiang Yu; Warren E. Heilman; Shiyuan Zhong; Xindi Bian</p> <p>2017-01-01</p> <p>We used 35-year (1979–2013) hourly rainfall data from theNorth American LandData Assimilation System (NLDAS-2) to examine the relationships of the symmetric and asymmetric components of two types of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) (El Niño and ElNiño Modoki) episodes with occurrences of extreme precipitation <span class="hlt">events</span> across the United States. During the cold season,...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThApC.tmp..288L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThApC.tmp..288L"><span>The dependence on atmospheric resolution of <span class="hlt">ENSO</span> and related East Asian-western North Pacific summer climate variability in a coupled model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Bo; Zhao, Guijie; Huang, Gang; Wang, Pengfei; Yan, Bangliang</p> <p>2017-08-01</p> <p>The authors present results for El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and East Asian-western North Pacific climate variability simulated in a new version high-resolution coupled model (ICM.V2) developed at the Center for Monsoon System Research of the Institute of Atmospheric Physics (CMSR, IAP), Chinese Academy of Sciences. The analyses are based on the last 100-year output of a 1000-year simulation. Results are compared to an earlier version of the same coupled model (ICM.V1), reanalysis, and observations. The two versions of ICM have similar physics but different atmospheric resolution. The simulated climatological mean states show marked improvement over many regions, especially the tropics in ICM.V2 compared to those in ICM.V1. The common bias in the cold tongue has reduced, and the <span class="hlt">warm</span> biases along the ocean boundaries have improved as well. With improved simulation of <span class="hlt">ENSO</span>, including its period and strength, the <span class="hlt">ENSO</span>-related western North Pacific summer climate variability becomes more realistic compared to the observations. The simulated East Asian summer monsoon anomalies in the El Niño decaying summer are substantially more realistic in ICM.V2, which might be related to a better simulation of the Indo-Pacific Ocean capacitor (IPOC) effect and Pacific decadal oscillation (PDO).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5148022-stable-isotope-geochemistry-corals-from-costa-rica-proxy-indicator-el-nino-southern-oscillation-enso','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5148022-stable-isotope-geochemistry-corals-from-costa-rica-proxy-indicator-el-nino-southern-oscillation-enso"><span>Stable isotope geochemistry of corals from Costa Rica as proxy indicator of the El Nino/Southern Oscillation (<span class="hlt">ENSO</span>)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Carriquiry, J.D.; Risk, M.J.; Schwarcz, H.P.</p> <p></p> <p>The authors analyzed the [delta][sup 18]O and [delta][sup 13]C time-series contained in coral skeletons collected from Isla de Cano, Costa Rica, that survived the 1982-1983 El Nino <span class="hlt">warming</span> <span class="hlt">event</span>. Coral [delta][sup 18]O give a record of thermal histories with a precision of [approximately]0.5[degrees]C. For this locality, the authors have determined that the average [Delta][delta][sub w] effect in the coral skeletons is equivalent to 33% of the skeletal [delta][sup 18]O range. Therefore, if [delta][sub w] effects are not compensated for, the annual skeletal-[delta][sup 18]O range displays a temperature range of 1[degrees]C lower than actual values. The isotopic record of Porites lobatamore » skeletons shows simultaneous depletions in [sup 18]O and [sup 13]C at skeletal levels corresponding to 1983, coincident with the El Nino/Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">event</span>. Therefore, the El Nino <span class="hlt">event</span> is not only recorded as negative [delta][sup 18]O anomalies in the skeleton, suggesting the <span class="hlt">warming</span> of ambient waters, but also in the [delta][sup 13]C signal as negative anomalies, indicating coral bleaching. Contrary to the predictions of the [open quotes][sup 13]C-insolation model[close quotes] that the annual carbon isotope variation should be attenuated with depth in proportion to the decrease in light-intensity variation with depth, the authors found a clear trend where [Delta][delta][minus][sup 13]C increases with depth. Coral bioenergetics, which depends on both coral physiology and ecology, may adequately explain the unexpected increase in [delta][sup 13]C range with depth, without contradicting the seasonal character of [delta][sup 13]C variability with the solar irradiance cycle. Although some authors have determined the presence of hiatuses in the skeletal record due to severe stress and growth cessation, in this study it has been found that skeletal growth was not seriously diminished during the El Nino year of 1983.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3930050','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3930050"><span>Snow cover and extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> control flower abundance of some, but not all species in high arctic Svalbard</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Semenchuk, Philipp R; Elberling, Bo; Cooper, Elisabeth J</p> <p>2013-01-01</p> <p>Abstract The High Arctic winter is expected to be altered through ongoing and future climate change. Winter precipitation and snow depth are projected to increase and melt out dates change accordingly. Also, snow cover and depth will play an important role in protecting plant canopy from increasingly more frequent extreme winter <span class="hlt">warming</span> <span class="hlt">events</span>. Flower production of many Arctic plants is dependent on melt out timing, since season length determines resource availability for flower preformation. We erected snow fences to increase snow depth and shorten growing season, and counted flowers of six species over 5 years, during which we experienced two extreme winter <span class="hlt">warming</span> <span class="hlt">events</span>. Most species were resistant to snow cover increase, but two species reduced flower abundance due to shortened growing seasons. Cassiope tetragona responded strongly with fewer flowers in deep snow regimes during years without extreme <span class="hlt">events</span>, while Stellaria crassipes responded partly. Snow pack thickness determined whether winter <span class="hlt">warming</span> <span class="hlt">events</span> had an effect on flower abundance of some species. <span class="hlt">Warming</span> <span class="hlt">events</span> clearly reduced flower abundance in shallow but not in deep snow regimes of Cassiope tetragona, but only marginally for Dryas octopetala. However, the affected species were resilient and individuals did not experience any long term effects. In the case of short or cold summers, a subset of species suffered reduced reproductive success, which may affect future plant composition through possible cascading competition effects. Extreme winter <span class="hlt">warming</span> <span class="hlt">events</span> were shown to expose the canopy to cold winter air. The following summer most of the overwintering flower buds could not produce flowers. Thus reproductive success is reduced if this occurs in subsequent years. We conclude that snow depth influences flower abundance by altering season length and by protecting or exposing flower buds to cold winter air, but most species studied are resistant to changes. Winter <span class="hlt">warming</span> <span class="hlt">events</span>, often</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4738287','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4738287"><span>Global <span class="hlt">Warming</span> Attenuates the Tropical Atlantic-Pacific Teleconnection</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jia, Fan; Wu, Lixin; Gan, Bolan; Cai, Wenju</p> <p>2016-01-01</p> <p>Changes in global sea surface temperature (SST) since the end of last century display a pattern of widespread <span class="hlt">warming</span> intercepted by cooling in the eastern equatorial Pacific and western coasts of the American continent. Studies have suggested that the cooling in the eastern equatorial Pacific may be partly induced by <span class="hlt">warming</span> in the North Atlantic. However, it remains unknown how stable this inter-tropical teleconnection will be under global <span class="hlt">warming</span>. Here we show that the inter-tropical teleconnection from the tropical Atlantic to Pacific weakens substantially as the CO2 concentration increases. This reduced impact is related to the El Niño-like <span class="hlt">warming</span> of the tropical Pacific mean state, which leads to limited seasonal migration of the Pacific inter-tropical convergence zone (ITCZ) and weakened ocean heat transport. A fast decay of the tropical Atlantic SST anomalies in a warmer climate also contributes to the weakened teleconnection. Our study suggests that as greenhouse <span class="hlt">warming</span> continues, the trend in the tropical Pacific as well as the development of <span class="hlt">ENSO</span> will be less frequently interrupted by the Atlantic because of this attenuation. The weakened teleconnection is also supported by CMIP5 models, although only a few of these models can capture this inter-tropical teleconnection. PMID:26838053</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26838053','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26838053"><span>Global <span class="hlt">Warming</span> Attenuates the Tropical Atlantic-Pacific Teleconnection.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jia, Fan; Wu, Lixin; Gan, Bolan; Cai, Wenju</p> <p>2016-02-03</p> <p>Changes in global sea surface temperature (SST) since the end of last century display a pattern of widespread <span class="hlt">warming</span> intercepted by cooling in the eastern equatorial Pacific and western coasts of the American continent. Studies have suggested that the cooling in the eastern equatorial Pacific may be partly induced by <span class="hlt">warming</span> in the North Atlantic. However, it remains unknown how stable this inter-tropical teleconnection will be under global <span class="hlt">warming</span>. Here we show that the inter-tropical teleconnection from the tropical Atlantic to Pacific weakens substantially as the CO2 concentration increases. This reduced impact is related to the El Niño-like <span class="hlt">warming</span> of the tropical Pacific mean state, which leads to limited seasonal migration of the Pacific inter-tropical convergence zone (ITCZ) and weakened ocean heat transport. A fast decay of the tropical Atlantic SST anomalies in a warmer climate also contributes to the weakened teleconnection. Our study suggests that as greenhouse <span class="hlt">warming</span> continues, the trend in the tropical Pacific as well as the development of <span class="hlt">ENSO</span> will be less frequently interrupted by the Atlantic because of this attenuation. The weakened teleconnection is also supported by CMIP5 models, although only a few of these models can capture this inter-tropical teleconnection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6666914-prediction-enso-episodes-using-canonical-correlation-analysis','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6666914-prediction-enso-episodes-using-canonical-correlation-analysis"><span>Prediction of <span class="hlt">ENSO</span> episodes using canonical correlation analysis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Barnston, A.G.; Ropelewski, C.F.</p> <p></p> <p>Canonical correlation analysis (CCA) is explored as a multivariate linear statistical methodology with which to forecast fluctuations of the El Nino/Southern Oscillation (<span class="hlt">ENSO</span>) in real time. CCA is capable of identifying critical sequences of predictor patterns that tend to evolve into subsequent pattern that can be used to form a forecast. The CCA model is used to forecast the 3-month mean sea surface temperature (SST) in several regions of the tropical Pacific and Indian oceans for projection times of 0 to 4 seasons beyond the immediately forthcoming season. The predictor variables, representing the climate situation in the four consecutive 3-monthmore » periods ending at the time of the forecast, are (1) quasi-global seasonal mean sea level pressure (SLP) and (2) SST in the predicted regions themselves. Forecast skill is estimated using cross-validation, and persistence is used as the primary skill control measure. Results indicate that a large region in the eastern equatorial Pacific (120[degrees]-170[degrees] W longitude) has the highest overall predictability, with excellent skill realized for winter forecasts made at the end of summer. CCA outperforms persistence in this region under most conditions, and does noticeably better with the SST included as a predictor in addition to the SLP. It is demonstrated that better forecast performance at the longer lead times would be obtained if some significantly earlier (i.e., up to 4 years) predictor data were included, because the ability to predict the lower-frequency <span class="hlt">ENSO</span> phase changes would increase. The good performance of the current system at shorter lead times appears to be based largely on the ability to predict <span class="hlt">ENSO</span> evolution for <span class="hlt">events</span> already in progress. The forecasting of the eastern tropical Pacific SST using CCA is now done routinely on a monthly basis for a O-, 1-, and 2-season lead at the Climate Analysis Center.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/15005803-simulated-impacts-el-nino-southern-oscillation-united-states-water-resources','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/15005803-simulated-impacts-el-nino-southern-oscillation-united-states-water-resources"><span>Simulated Impacts of El Nino/Southern Oscillation on United States Water Resources</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Thomson, Allison M.; Brown, Robert A.; Rosenberg, Norman J.</p> <p></p> <p>The El Nino/Southern Oscillation alters global weather patterns with consequences for fresh water quality and supply. <span class="hlt">ENSO</span> <span class="hlt">events</span> impact regions and natural resource sectors around the globe. For example, in 1997-98, a strong El Ni?o brought <span class="hlt">warm</span> ocean temperatures, flooding and record snowfall to the west coast of the US. Research on <span class="hlt">ENSO</span> <span class="hlt">events</span> and their impacts has improved long range weather predictions, potentially reducing the damage and economic cost of these anomalous weather patterns. Here, we simulate the impacts of four types of <span class="hlt">ENSO</span> states on water resources in the conterminous United States. We distinguish between Neutral, El Ni?o,more » La Ni?a and strong El Ni?o years over the period of 1960-1989. Using climate statistics that characterize these <span class="hlt">ENSO</span> states to drive the HUMUS water resources model, we examine the effects of 'pure' <span class="hlt">ENSO</span> <span class="hlt">events</span>, without complications from transition periods. Strong El Ni?o is not simply an amplification of El Ni?o; it leads to strikingly different consequences for climate and water resources.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdSpR..60.2379A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdSpR..60.2379A"><span>Variability of lightning activity over India on <span class="hlt">ENSO</span> time scales</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahmad, Adnan; Ghosh, Mili</p> <p>2017-12-01</p> <p><span class="hlt">ENSO</span>, the reliable indicator of inter-annual climate variation of the ocean-atmosphere system in the tropical Pacific region, can affect the overall lightning activity which is another atmospheric phenomenon. In the present study, the impact of the <span class="hlt">ENSO</span> on the total lightning activity over India has been studied for the period 2004-2014. During the El-Nino period (July 2004-April 2005 and July 2009-April 2010), total number of lightning flashes increased by 10% and 18% respectively and during La-Nina period (July 2010-April 2011 and August 2011 to March 2012), the total number of lightning flashes decreased approximately by 19% and 28% respectively as compared to the mean of corresponding period (2004-14) of the Non-<span class="hlt">ENSO</span>. Seasonal variation of flash density is also examined for the El-Nino and La-Nina period. The result shows that in the El-Nino period of the pre-monsoon and monsoon seasons, there is an increment in the flash density approximately by 48% and 9% respectively than the Non-<span class="hlt">ENSO</span> and the spatial variation also having high flash density along the foot of Himalayas region. In the post-monsoon season, there is a marginal change in the flash density between El-Nino and the Non-<span class="hlt">ENSO</span>. In the winter season, there is an increment in flash density in the El-Nino period approximately by 45% than the Non-<span class="hlt">ENSO</span>. In the La-Nina period of the pre-monsoon and monsoon seasons, there is the decrement in the flash density approximately by the 44% and 24% respectively than the Non-<span class="hlt">ENSO</span>. In the Post-monsoon season and winter season of La-Nina, the flash density is increased by about 24% and 33% over India. These findings can be applied to do proper planning of lightning induced hazard mitigation as lightning is of one of the major natural disasters of India.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28729610','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28729610"><span>Mean Bias in Seasonal Forecast Model and <span class="hlt">ENSO</span> Prediction Error.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kim, Seon Tae; Jeong, Hye-In; Jin, Fei-Fei</p> <p>2017-07-20</p> <p>This study uses retrospective forecasts made using an APEC Climate Center seasonal forecast model to investigate the cause of errors in predicting the amplitude of El Niño Southern Oscillation (<span class="hlt">ENSO</span>)-driven sea surface temperature variability. When utilizing Bjerknes coupled stability (BJ) index analysis, enhanced errors in <span class="hlt">ENSO</span> amplitude with forecast lead times are found to be well represented by those in the growth rate estimated by the BJ index. <span class="hlt">ENSO</span> amplitude forecast errors are most strongly associated with the errors in both the thermocline slope response and surface wind response to forcing over the tropical Pacific, leading to errors in thermocline feedback. This study concludes that upper ocean temperature bias in the equatorial Pacific, which becomes more intense with increasing lead times, is a possible cause of forecast errors in the thermocline feedback and thus in <span class="hlt">ENSO</span> amplitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A11A0079R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A11A0079R"><span>Statistical Relationships between the El Niño Southern Oscillation, the North Atlantic Oscillation, and Winter Tornado Outbreaks in the U.S</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Robinson Cook, A. D.; Schaefer, J. T.</p> <p>2009-12-01</p> <p>Winter tornado activity (January-March) between 1950 and 2003 was analyzed to determine the possible effects of the El Niño Southern Oscillation and the North Atlantic Oscillation on the frequency, location, and strength of tornado outbreaks in the United States. Outbreaks were gauged through analyses of tornadoes occurring on tornado days (a calendar day featuring six or more tornadoes within the contiguous United States) and then stratified according to <span class="hlt">warm</span> (37 tornado days), cold (51 tornado days), and neutral (74 tornado days) winter <span class="hlt">ENSO</span> phase. Tornado days were also stratified according to NAO phase (positive, negative, and neutral) as well. Although significant changes in the frequency of tornado outbreaks were not observed, spatial shifts in tornado activity are observed, primarily as a function of <span class="hlt">ENSO</span> phase. Historically, the neutral <span class="hlt">ENSO</span> phase features tornado outbreaks from central Oklahoma and Kansas eastward through the Carolinas. During cold <span class="hlt">ENSO</span> phases (La Niña), tornado outbreaks typically occur in a zone stretching from southeastern Texas northeastward into Illinois, Indiana, and Michigan. Winter tornado activity was mainly limited to areas near the Gulf Coast, including central Florida, during anomalously <span class="hlt">warm</span> phases (El Niño). Shifts in the intensity of tornado activity were also found as a function of <span class="hlt">ENSO</span> and particularly NAO phase. Stronger tornadoes with longer path lengths were observed during La Niña and Neutral <span class="hlt">ENSO</span> <span class="hlt">events</span>, as well as Positive and Neutral NAO <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4892549','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4892549"><span>Response of a Habitat-Forming Marine Plant to a Simulated <span class="hlt">Warming</span> <span class="hlt">Event</span> Is Delayed, Genotype Specific, and Varies with Phenology</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Reynolds, Laura K.; DuBois, Katherine; Abbott, Jessica M.; Williams, Susan L.; Stachowicz, John J.</p> <p>2016-01-01</p> <p>Growing evidence shows that increasing global temperature causes population declines and latitudinal shifts in geographical distribution for plants living near their thermal limits. Yet, even populations living well within established thermal limits of a species may suffer as the frequency and intensity of <span class="hlt">warming</span> <span class="hlt">events</span> increase with climate change. Adaptive response to this stress at the population level depends on the presence of genetic variation in thermal tolerance in the populations in question, yet few data exist to evaluate this. In this study, we examined the immediate effects of a moderate <span class="hlt">warming</span> <span class="hlt">event</span> of 4.5°C lasting 5 weeks and the legacy effects after a 5 week recovery on different genotypes of the marine plant Zostera marina (eelgrass). We conducted the experiment in Bodega Bay, CA USA, where average summer water temperatures are 14–15°C, but extended <span class="hlt">warming</span> periods of 17–18°C occur episodically. Experimental <span class="hlt">warming</span> increased shoot production by 14% compared to controls held at ambient temperature. However, after returning temperature to ambient levels, we found strongly negative, delayed effects of <span class="hlt">warming</span> on production: shoot production declined by 27% and total biomass decreased by 50% relative to individuals that had not been <span class="hlt">warmed</span>. While all genotypes’ production decreased in the recovery phase, genotypes that grew the most rapidly under benign thermal conditions (control) were the most susceptible to the detrimental effects of <span class="hlt">warming</span>. This suggests a potential tradeoff in relative performance at normal vs. elevated temperatures. Modest short-term increases in water temperature have potentially prolonged negative effects within the species’ thermal envelope, but genetic variation within these populations may allow for population persistence and adaptation. Further, intraspecific variation in phenology can result in maintenance of population diversity and lead to enhanced production in diverse stands given sufficient frequency of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27258011','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27258011"><span>Response of a Habitat-Forming Marine Plant to a Simulated <span class="hlt">Warming</span> <span class="hlt">Event</span> Is Delayed, Genotype Specific, and Varies with Phenology.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Reynolds, Laura K; DuBois, Katherine; Abbott, Jessica M; Williams, Susan L; Stachowicz, John J</p> <p>2016-01-01</p> <p>Growing evidence shows that increasing global temperature causes population declines and latitudinal shifts in geographical distribution for plants living near their thermal limits. Yet, even populations living well within established thermal limits of a species may suffer as the frequency and intensity of <span class="hlt">warming</span> <span class="hlt">events</span> increase with climate change. Adaptive response to this stress at the population level depends on the presence of genetic variation in thermal tolerance in the populations in question, yet few data exist to evaluate this. In this study, we examined the immediate effects of a moderate <span class="hlt">warming</span> <span class="hlt">event</span> of 4.5°C lasting 5 weeks and the legacy effects after a 5 week recovery on different genotypes of the marine plant Zostera marina (eelgrass). We conducted the experiment in Bodega Bay, CA USA, where average summer water temperatures are 14-15°C, but extended <span class="hlt">warming</span> periods of 17-18°C occur episodically. Experimental <span class="hlt">warming</span> increased shoot production by 14% compared to controls held at ambient temperature. However, after returning temperature to ambient levels, we found strongly negative, delayed effects of <span class="hlt">warming</span> on production: shoot production declined by 27% and total biomass decreased by 50% relative to individuals that had not been <span class="hlt">warmed</span>. While all genotypes' production decreased in the recovery phase, genotypes that grew the most rapidly under benign thermal conditions (control) were the most susceptible to the detrimental effects of <span class="hlt">warming</span>. This suggests a potential tradeoff in relative performance at normal vs. elevated temperatures. Modest short-term increases in water temperature have potentially prolonged negative effects within the species' thermal envelope, but genetic variation within these populations may allow for population persistence and adaptation. Further, intraspecific variation in phenology can result in maintenance of population diversity and lead to enhanced production in diverse stands given sufficient frequency of <span class="hlt">warming</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B43B0594M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B43B0594M"><span>Phenology of seed and leaves rain in response to periodic climatic variability in a seasonal wet tropical forest</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matteo, D.; Wright, S. J.; Davies, S. J.; Muller-Landau, H. C.; Wolfe, B.; Detto, M.</p> <p>2016-12-01</p> <p>Phenology, by controlling the rhythms of plants, plays a fundamental role in regulating access to resources, ecosystem processes, competition among species, interactions with consumers and feedbacks to the climate. In high biodiverse tropical forests, where phenology of flowering and leafing are complex, an adequate representation of phenology must take into account a given set of climatic, edaphic and biotic factors. Climatic factors are particularly important because plants may use them as cues for timing different phenological phases and be influenced by their intensity. Climatic variability can be periodic, if <span class="hlt">events</span> occur with regular frequency, or aperiodic. One prominent periodic large-scale pattern that causes unusual weather is <span class="hlt">ENSO</span> <span class="hlt">event</span>. In general, Central America tends to be dry and <span class="hlt">warm</span> during a mature phase of an <span class="hlt">ENSO</span> <span class="hlt">event</span>, which usually peaks between October and January with a frequency of 2-3 <span class="hlt">events</span> per decade. Because in many tropical areas the effect of <span class="hlt">ENSO</span> is highly prominent, it is plausible that plants have adapted their growth and reproduction mechanisms to synchronize <span class="hlt">ENSO</span> phases, in a similar way that plants do during the seasonal cycle. We used a long dataset (30+ years) of fruits and leaves rains of tropical trees and lianas to determine ecosystem response and species specific response of these phenological <span class="hlt">events</span> to local climate variability corresponding to the modes of <span class="hlt">ENSO</span>. Specifically, we tested the hypothesis that phenological responses to <span class="hlt">ENSO</span> are similar to response to seasonal cycles, i.e., higher litterfall before a <span class="hlt">warm</span>-dry phase and higher fruiting after such phase, with strong correlation between seeds and leaves. At sub-community level, we evaluated whether evergreen and deciduous, biotic and abiotic dispersers and free and climbing life forms, have the same response to <span class="hlt">ENSO</span> in terms of leaves and seeds rain. At species level we tested the hypothesis that species with low photosynthetic capacity leaves are more responsive</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.3560Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.3560Y"><span><span class="hlt">ENSO</span> influence on the Asian summer monsoon anticyclone as derived from the satellite observations, reanalysis and model simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yan, Xiaolu; Konopka, Paul; Ploeger, Felix; Tao, Mengchu; Bian, Jianchun; Mueller, Rolf</p> <p>2017-04-01</p> <p>El Nino and La Nina are opposite phases of El Nino-Southern Oscillation (<span class="hlt">ENSO</span>). The extremes of <span class="hlt">ENSO</span> patterns have impacts not only on ocean processes, but also on global weather and climate. The <span class="hlt">ENSO</span> activities typically show pronounced features in boreal winter time, but some prolonged <span class="hlt">events</span> may last for months or years. In this study we analyze the influence of <span class="hlt">ENSO</span> on the atmospheric composition in the tropical and extra-tropical UTLS region in the months following strong <span class="hlt">ENSO</span> <span class="hlt">events</span>. In particular, we are interested in the impact of <span class="hlt">ENSO</span> on the Asian summer monsoon (ASM) anticyclone. Using the Multivariate <span class="hlt">ENSO</span> Index (MEI), we define two composites starting from strong El Nino and La Nina winters (|MEI|>0.9) and analyze the anomalies caused by them in the following months. To quantify the differences in dynamics, the velocity potential (VP) and the stream function (SF) are calculated based on ERA-Interim reanalysis from 1979 to 2015. SF shows that during winter the horizontal flow in the tropical UTLS is dominated by two equatorially symmetric anticyclones resembling the well-known Matsuno-Gill solution. In summer, the anticyclone in the North Hemisphere is shifted to the ASM region. VP shows that the centers of the divergent part of the flow lie in the West Tropical Pacific and Central Pacific for La Nina and El Nino winters, respectively. These centers move northwestwards during spring and summer. The anticyclone, subtropical jet and the divergent part of the flow after La Nina winters are significantly stronger than after El Nino winters. Based on the MLS measurements of CO, H2O and O3 from 2004 to 2015, we also discuss the respective anomalies at the tropopause level for the El Nino/La Nina composites. EL Nino composite of CO shows higher values in the tropical region not only during winter but also during spring and summer. La Nina composite of H2O shows low anomaly over Maritime Continent which spread over the whole tropics until summer. The H2O</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017QSRv..155..159M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017QSRv..155..159M"><span>Holocene climatic variations in the Western Cordillera of Colombia: A multiproxy high-resolution record unravels the dual influence of <span class="hlt">ENSO</span> and ITCZ</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Muñoz, Paula; Gorin, Georges; Parra, Norberto; Velásquez, Cesar; Lemus, Diego; Monsalve-M., Carlos; Jojoa, Marcela</p> <p>2017-01-01</p> <p>The Páramo de Frontino (3460 m elevation) in Colombia is located approximately halfway between the Pacific and Atlantic oceans. It contains a 17 kyr long, stratigraphically continuous sedimentary sequence dated by 30 AMS 14C ages. Our study covers the last 11,500 cal yr and focuses on the biotic (pollen) and abiotic (microfluorescence-X or μXRF) components of this high mountain ecosystem. The pollen record provides a proxy for temperature and humidity with a resolution of 20-35 yr, and μXRF of Ti and Fe is a proxy for rainfall with a sub-annual (ca. 6-month) resolution. Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition from a cold (mean annual temperature (MAT) 3.5 °C lower than today) and wet Younger Dryas to a <span class="hlt">warm</span> and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT varied from ca. 2.5 °C below to 3.5° above present-day temperature. <span class="hlt">Warm</span> periods (11,410-10,700, 9700-6900, 4000-2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human impact. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late Holocene was dry. Spectral analysis of μXRF data show rainfall cyclicity at millennial scale throughout the Holocene, and at centennial down to <span class="hlt">ENSO</span> scale in more specific time intervals. The highest rainfall intervals correlate with the highest activity of <span class="hlt">ENSO</span>. Variability in solar output is possibly the main cause for this millennial to decadal cyclicity. We interpret <span class="hlt">ENSO</span> and ITCZ as the main climate change-driving mechanisms in Frontino. Comparison with high-resolution XRF data from the Caribbean Cariaco Basin (a proxy for rainfall in the coastal Venezuelian cordilleras) demonstrates that climate in Frontino was Pacific-driven (<span class="hlt">ENSO</span>-dominated) during the YD and early Holocene, whereas it was Atlantic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B51E0465X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B51E0465X"><span>Modeling biogeochemical responses of vegetation to <span class="hlt">ENSO</span>: comparison and analysis on subgrid PFT patches</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, M.; Hoffman, F. M.</p> <p>2016-12-01</p> <p>The El Niño Southern Oscillation (<span class="hlt">ENSO</span>) is an important interannual climate variability and has significant consequences and impacts on the global biosphere. The responses of vegetation to <span class="hlt">ENSO</span> are highly heterogeneous and generally depend on the biophysical and biochemical characteristics associated with model plant functional types (PFTs). The modeled biogeochemical variables from Earth System Models (ESMs) are generally grid averages consisting of several PFTs within a gridcell, which will lead to difficulties in directly comparing them with site observations and large uncertainties in studying their responses to large scale climate variability. In this study, we conducted a transient <span class="hlt">ENSO</span> simulation for the previoustwo decades from 1995 to 2020 using the DOE ACME v0.3 model. It has a comprehensive terrestrial biogeochemistry model that is fully coupled with a sophisticated atmospheric model with an advanced spectral element dynamical core. The model was driven by the NOAA optimum interpolation sea surface temperature (SST) for contemporary years and CFS v2 nine-month seasonal predicted and reconstructed SST for future years till to 2020. We saved the key biogeochemical variables in the subgrid PFT patches and compared them with site observations directly. Furthermore, we studied the biogeochemical responses of terrestrial vegetation to two largest <span class="hlt">ENSO</span> <span class="hlt">events</span> (1997-1998 and 2015-2016) for different PFTs. Our results show that it is useful and meaningful to compare and analyze model simulations in subgrid patches. The comparison and analysis not only gave us the details of responses of terrestrial ecosystem to global climate variability under changing climate, but also the insightful view on the model performance on the PFT level.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20140001093&hterms=saber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsaber','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20140001093&hterms=saber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsaber"><span>Influence of El Nino Southern Oscillation on the Mesospheric Temperature</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Tao; Calvo, Natalia; Yue, Jia; Dou, Xiankang; Russell, J. M, III; Mlynczak, M. G.; She, Chiao-Yao; Xue, Xianghui</p> <p>2013-01-01</p> <p>Using the middle atmosphere temperature data set observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite experiment between 2002 and 2012, and temperatures simulated by the Whole Atmospheric Community Climate Model version 3.5 (WACCM3.5) between 1953 and 2005, we studied the influence of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) on middle atmosphere temperature during the Northern Hemisphere (NH) wintertime. For the first time, a significant winter temperature response to <span class="hlt">ENSO</span> in the middle mesosphere has been observed, with an anomalous <span class="hlt">warming</span> of approximately 1.0 K/MEI (Multivariate <span class="hlt">ENSO</span> Index) in the tropics and an anomalous cooling of approximately 2.0 K/MEI in the NH middle latitudes. The observed temperature responses to <span class="hlt">ENSO</span> in the mesosphere are opposite to those in the stratosphere, in agreement with previous modeling studies. Temperature responses to <span class="hlt">ENSO</span> observed by SABER show similar patterns to those simulated by the WACCM3.5 model. Analysis of the WACCM3.5 residual mean meridional circulation response to <span class="hlt">ENSO</span> reveals a significant downwelling in the tropical mesosphere and upwelling in the NH middle and high latitudes during <span class="hlt">warm</span> <span class="hlt">ENSO</span> <span class="hlt">events</span>, which is mostly driven by anomalous eastward gravity wave forcing in the NH mesosphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1290364-meridional-dipole-premonsoon-bay-bengal-tropical-cyclone-activity-induced-enso-tropical-cyclones-monsoon-enso','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1290364-meridional-dipole-premonsoon-bay-bengal-tropical-cyclone-activity-induced-enso-tropical-cyclones-monsoon-enso"><span>A meridional dipole in premonsoon Bay of Bengal tropical cyclone activity induced by <span class="hlt">ENSO</span>: TROPICAL CYCLONES, MONSOON AND <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Balaguru, Karthik; Leung, L. Ruby; Lu, Jian</p> <p>2016-06-27</p> <p>Analysis of Bay of Bengal tropical cyclone (TC) track data for the month of May during 1980-2013 reveals a meridional dipole in TC intensification: TC intensification rates increased in the northern Bay and decreased in the southern Bay. The dipole was driven by an increase in low-level vorticity and atmospheric humidity in the northern Bay, making the environment more favorable for TC intensification, and enhanced vertical wind shear in the southern Bay, tending to reduce TC development. These environmental changes were associated with a strengthening of the monsoon circulation for the month of May, driven by a La Nin˜a-like shiftmore » in tropical Pacific SSTs andassociated tropical wave dynamics. Analysis of a suite of climate models fromthe CMIP5 archive for the 150-year historical period shows that most models correctly reproduce the link between <span class="hlt">ENSO</span> and Bay of Bengal TC activity through the monsoon at interannual timescales. Under the RCP 8.5 scenario the same CMIP5 models produce an El Nin˜o like <span class="hlt">warming</span> trend in the equatorial Pacific, tending to weaken the monsoon circulation. These results suggest« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AtmRe.202....1R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AtmRe.202....1R"><span>Influence of aerosol-cloud interaction on austral summer precipitation over Southern Africa during <span class="hlt">ENSO</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ruchith, R. D.; Sivakumar, V.</p> <p>2018-04-01</p> <p>In the present study, we are investigating the role of aerosols-and clouds in modulating the austral summer precipitation (December-February) during <span class="hlt">ENSO</span> <span class="hlt">events</span> over southern Africa region for the period from 2002 to2012 by using satellite and complimentary data sets. Aerosol radiative forcing (ARF) and Cloud radiative forcing (CRF) shows distinct patterns for El-Nina and La-Nina years. Further analysis were carried out by selecting the four Southern Africa regions where the precipitation shows remarkable difference during El-Nino and La-Nina years. These regions are R1 (33°S-24°S, 18°E-30°E), R2 (17°S-10°S, 24°E-32°E), R3 (19°S-9°S, 33°E-41°E) and R4 (7°S-0°S, 27°E-36°E). Aerosol Optical depth (AOD) shows considerable differences during these <span class="hlt">events</span>. In region R1, R2 and R3 AOD shows more abundance in El-Nino years as compared to La-Nina years where as in R4 the AOD shows more abundance in La-Nina years. Cloud Droplet Effective radius (CDER) shows higher values during La-Nina years over R1, R2 and R3 regions but in R4 region CDER shows higher values in El-Nino years. Aerosol indirect effect (AIE) is estimated both for fixed cloud liquid water path (CLWP) and for fixed cloud ice path (CIP) bins, ranging from 1 to 300 gm -2 at 25 gm -2 interval over all the selected regions for El-Nino and La-Nina years. The results indicate more influence of positive indirect effect (Twomey effect) over R1 and R3 region during El-Nino years as compared to La-Nina years. This analysis reveals the important role of aerosol on cloud-precipitation interaction mechanism illustrating the interlinkage between dynamics and microphysics during austral summer season over southern Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5099569','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5099569"><span>Direct and indirect <span class="hlt">ENSO</span> modulation of winter temperature over the Asian–Pacific–American region</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Leung, Marco Y. T.; Zhou, Wen</p> <p>2016-01-01</p> <p>In this study, the direct and indirect atmospheric responses over the Asian–Pacific–American region to the El Niño–Southern Oscillation (<span class="hlt">ENSO</span>) are documented. Since <span class="hlt">ENSO</span> is likely to induce the northward displacement of the East Asian trough (NDEAT), some of the influence of <span class="hlt">ENSO</span> on the Asian–Pacific–American region is possibly indirect and acts by inducing NDEAT. To separate corresponding influences of <span class="hlt">ENSO</span> and NDEAT, partial regression is utilized. It is noted that temperature variations in the East Asian–Western Pacific region are controlled mainly by NDEAT. In contrast, <span class="hlt">ENSO</span> demonstrates a weak direct relation to the temperature variation over the East Asian–Western Pacific region. This suggests that the influence of <span class="hlt">ENSO</span> on this region is indirect, through modulation of NDEAT. On the other hand, temperature variation over the tropical eastern Pacific is dominated by <span class="hlt">ENSO</span> forcing. Finally, temperature variation over the eastern North American–Western Pacific region is controlled by both <span class="hlt">ENSO</span> and NDEAT. Nevertheless, their influences on temperature and circulation over this region tend to offset each other. This implies that temperature variation is controlled by their relative strengths. PMID:27821838</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000034198','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000034198"><span>Intrinsic Coupled Ocean-Atmosphere Modes of the Asian Summer Monsoon: A Re-assessment of Monsoon-<span class="hlt">ENSO</span> Relationships</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lau, K.-M.; Wu, H. T.</p> <p>2000-01-01</p> <p>Using global rainfall and sea surface temperature (SST) data for the past two decades (1979-1998), we have investigated the intrinsic modes of Asian summer monsoon (ASM) and <span class="hlt">ENSO</span> co-variability. Three recurring ASM rainfall-SST coupled modes were identified. The first is a basin scale mode that features SST and rainfall variability over the entire tropics (including the ASM region), identifiable with those occurring during El Nino or La Nina. This mode is further characterized by a pronounced biennial variation in ASM rainfall and SST associated with fluctuations of the anomalous Walker circulation that occur during El Nino/La Nina transitions. The second mode comprises mixed regional and basin-scale rainfall and SST signals, with pronounced intraseasonal and interannual variabilities. This mode features a SST pattern associated with a developing La Nina, with a pronounced low level anticyclone in the subtropics of the western Pacific off the coast of East Asia. The third mode depicts an east-west rainfall and SST dipole across the southern equatorial Indian Ocean, most likely stemming from coupled ocean-atmosphere processes within the ASM region. This mode also possesses a decadal time scale and a linear trend, which are not associated with El Nino/La Nina variability. Possible causes of year-to-year rainfall variability over the ASM and sub-regions have been evaluated from a reconstruction of the observed rainfall from singular eigenvectors of the coupled modes. It is found that while basin-scale SST can account for portions of ASM rainfall variability during <span class="hlt">ENSO</span> <span class="hlt">events</span> (up to 60% in 1998), regional processes can accounts up to 20-25% of the rainfall variability in typical non-<span class="hlt">ENSO</span> years. Stronger monsoon-<span class="hlt">ENSO</span> relationship tends to occur in the boreal summer immediately preceding a pronounced La Nina, i.e., 1998, 1988 and 1983. Based on these results, we discuss the possible impacts of the ASM on <span class="hlt">ENSO</span> variability via the west Pacific anticyclone and articulate a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP13D1109M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP13D1109M"><span>Isotopic composition of ice core air reveals abrupt Antarctic <span class="hlt">warming</span> during and after Heinrich <span class="hlt">Event</span> 1a</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Morgan, J. D.; Bereiter, B.; Baggenstos, D.; Kawamura, K.; Shackleton, S. A.; Severinghaus, J. P.</p> <p>2017-12-01</p> <p>Antarctic temperature variations during Heinrich <span class="hlt">events</span>, as recorded by δ18O­ice­, generally show more gradual changes than the abrupt <span class="hlt">warmings</span> seen in Greenland ice. However, quantitative temperature interpretation of the water isotope temperature proxy is difficult as the relationship between δ18Oice and temperature is not constant through time. Fortunately, ice cores offer a second temperature proxy based on trapped gases. During times of surface <span class="hlt">warming</span>, thermal fractionation of gases in the column of unconsolidated snow (firn) on top of the ice sheet results in isotopically heavier nitrogen (N2) and argon (Ar) being trapped in the ice core bubbles. During times of surface cooling, isotopically lighter gases are trapped. Measurements of δ15N and δ40Ar can therefore be used, in combination with a model for the height of the column of firn, to quantitatively reconstruct surface temperatures. In the WAIS Divide Ice Core, the two temperature proxies show a brief disagreement during Heinrich Stadial 1. Despite δ18Oice recording relatively constant temperature, the nitrogen and argon isotopes imply an abrupt <span class="hlt">warming</span> between 16 and 15.8 kyr BP, manifest as an abrupt 1.25oC increase in the firn temperature gradient. To our knowledge, this would be the first evidence that such abrupt climate change has been recorded in an Antarctic climate proxy. If confirmed by more detailed studies, this <span class="hlt">event</span> may represent <span class="hlt">warming</span> due to an extreme southward shift of the Earth's thermal equator (and the southern hemisphere westerly wind belt), caused by the 16.1 ka Heinrich <span class="hlt">Event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1094946-greenhouse-gases-changing-enso-precursors-western-north-pacific','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1094946-greenhouse-gases-changing-enso-precursors-western-north-pacific"><span>Are Greenhouse Gases Changing <span class="hlt">ENSO</span> Precursors in the Western North Pacific?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Wang, S-Y; Heureux, Michelle L.; Yoon, Jin-Ho</p> <p></p> <p>Using multiple observational and modeling datasets, we document a strengthening relationship between boreal winter sea surface temperature anomalies (SSTA) in the western North Pacific (WNP) and the development of the El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) one year later. The increased WNP-<span class="hlt">ENSO</span> association emerged in the mid 20th century and has grown through the present, reaching correlation coefficients as high as ~0.70 in recent decades. Fully coupled climate experiments with the Community Earth System Model (CESM) replicate the WNP-<span class="hlt">ENSO</span> association and indicate that greenhouse gases (GHG) are largely responsible for the observed increase. We speculate that shifts in the location and amplitudesmore » of positive SST trends in the subtropical-tropical western Pacific impacts the low-level circulation so that WNP variability is increasingly influencing the development of <span class="hlt">ENSO</span> one year later. A strengthened GHG-driven relationship between the WNP and <span class="hlt">ENSO</span> provides an example of how anthropogenic climate change can potentially improve the skill of intraseasonal-to-interannual climate prediction.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001JCli...14..445T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001JCli...14..445T"><span>A Linear Stochastic Dynamical Model of <span class="hlt">ENSO</span>. Part II: Analysis.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, C. J.; Battisti, D. S.</p> <p>2001-02-01</p> <p>In this study the behavior of a linear, intermediate model of <span class="hlt">ENSO</span> is examined under stochastic forcing. The model was developed in a companion paper (Part I) and is derived from the Zebiak-Cane <span class="hlt">ENSO</span> model. Four variants of the model are used whose stabilities range from slightly damped to moderately damped. Each model is run as a simulation while being perturbed by noise that is uncorrelated (white) in space and time. The statistics of the model output show the moderately damped models to be more realistic than the slightly damped models. The moderately damped models have power spectra that are quantitatively quite similar to observations, and a seasonal pattern of variance that is qualitatively similar to observations. All models produce <span class="hlt">ENSOs</span> that are phase locked to the annual cycle, and all display the `spring barrier' characteristic in their autocorrelation patterns, though in the models this `barrier' occurs during the summer and is less intense than in the observations (inclusion of nonlinear effects is shown to partially remedy this deficiency). The more realistic models also show a decadal variability in the lagged autocorrelation pattern that is qualitatively similar to observations.Analysis of the models shows that the greatest part of the variability comes from perturbations that project onto the first singular vector, which then grow rapidly into the <span class="hlt">ENSO</span> mode. Essentially, the model output represents many instances of the <span class="hlt">ENSO</span> mode, with random phase and amplitude, stimulated by the noise through the optimal transient growth of the singular vectors.The limit of predictability for each model is calculated and it is shown that the more realistic (moderately damped) models have worse potential predictability (9-15 months) than the deterministic chaotic models that have been studied widely in the literature. The predictability limits are strongly correlated with the stability of the models' <span class="hlt">ENSO</span> mode-the more highly damped models having much shorter</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.1541L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.1541L"><span>Extreme High-Temperature <span class="hlt">Events</span> Over East Asia in 1.5°C and 2°C Warmer Futures: Analysis of NCAR CESM Low-<span class="hlt">Warming</span> Experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Donghuan; Zhou, Tianjun; Zou, Liwei; Zhang, Wenxia; Zhang, Lixia</p> <p>2018-02-01</p> <p>Extreme high-temperature <span class="hlt">events</span> have large socioeconomic and human health impacts. East Asia (EA) is a populous region, and it is crucial to assess the changes in extreme high-temperature <span class="hlt">events</span> in this region under different climate change scenarios. The Community Earth System Model low-<span class="hlt">warming</span> experiment data were applied to investigate the changes in the mean and extreme high temperatures in EA under 1.5°C and 2°C <span class="hlt">warming</span> conditions above preindustrial levels. The results show that the magnitude of <span class="hlt">warming</span> in EA is approximately 0.2°C higher than the global mean. Most populous subregions, including eastern China, the Korean Peninsula, and Japan, will see more intense, more frequent, and longer-lasting extreme temperature <span class="hlt">events</span> under 1.5°C and 2°C <span class="hlt">warming</span>. The 0.5°C lower <span class="hlt">warming</span> will help avoid 35%-46% of the increases in extreme high-temperature <span class="hlt">events</span> in terms of intensity, frequency, and duration in EA with maximal avoidance values (37%-49%) occurring in Mongolia. Thus, it is beneficial for EA to limit the <span class="hlt">warming</span> target to 1.5°C rather than 2°C.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28836593','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28836593"><span>Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt <span class="hlt">warming</span> <span class="hlt">event</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Petrenko, Vasilii V; Smith, Andrew M; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F; Severinghaus, Jeffrey P</p> <p>2017-08-23</p> <p>Methane (CH 4 ) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane ( 14 CH 4 ) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt <span class="hlt">warming</span> <span class="hlt">event</span> that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today's natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal <span class="hlt">event</span> was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal <span class="hlt">warming</span> are comparable to those of the current anthropogenic <span class="hlt">warming</span>, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Natur.548..443P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Natur.548..443P"><span>Minimal geological methane emissions during the Younger Dryas-Preboreal abrupt <span class="hlt">warming</span> <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Petrenko, Vasilii V.; Smith, Andrew M.; Schaefer, Hinrich; Riedel, Katja; Brook, Edward; Baggenstos, Daniel; Harth, Christina; Hua, Quan; Buizert, Christo; Schilt, Adrian; Fain, Xavier; Mitchell, Logan; Bauska, Thomas; Orsi, Anais; Weiss, Ray F.; Severinghaus, Jeffrey P.</p> <p>2017-08-01</p> <p>Methane (CH4) is a powerful greenhouse gas and plays a key part in global atmospheric chemistry. Natural geological emissions (fossil methane vented naturally from marine and terrestrial seeps and mud volcanoes) are thought to contribute around 52 teragrams of methane per year to the global methane source, about 10 per cent of the total, but both bottom-up methods (measuring emissions) and top-down approaches (measuring atmospheric mole fractions and isotopes) for constraining these geological emissions have been associated with large uncertainties. Here we use ice core measurements to quantify the absolute amount of radiocarbon-containing methane (14CH4) in the past atmosphere and show that geological methane emissions were no higher than 15.4 teragrams per year (95 per cent confidence), averaged over the abrupt <span class="hlt">warming</span> <span class="hlt">event</span> that occurred between the Younger Dryas and Preboreal intervals, approximately 11,600 years ago. Assuming that past geological methane emissions were no lower than today, our results indicate that current estimates of today’s natural geological methane emissions (about 52 teragrams per year) are too high and, by extension, that current estimates of anthropogenic fossil methane emissions are too low. Our results also improve on and confirm earlier findings that the rapid increase of about 50 per cent in mole fraction of atmospheric methane at the Younger Dryas-Preboreal <span class="hlt">event</span> was driven by contemporaneous methane from sources such as wetlands; our findings constrain the contribution from old carbon reservoirs (marine methane hydrates, permafrost and methane trapped under ice) to 19 per cent or less (95 per cent confidence). To the extent that the characteristics of the most recent deglaciation and the Younger Dryas-Preboreal <span class="hlt">warming</span> are comparable to those of the current anthropogenic <span class="hlt">warming</span>, our measurements suggest that large future atmospheric releases of methane from old carbon sources are unlikely to occur.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PrOce.153....1L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PrOce.153....1L"><span>Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an <span class="hlt">ENSO</span> <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Loick-Wilde, Natalie; Bombar, Deniz; Doan, Hai Nhu; Nguyen, Lam Ngoc; Nguyen-Thi, Anh Mai; Voss, Maren; Dippner, Joachim W.</p> <p>2017-04-01</p> <p>Investigating microplankton biomass and diversity under different climatological conditions is key to the understanding of cascading effects of climate change on nutrient cycles and biological productivity. Here we have used data collected during two contrasting summers along the coast of Viet Nam to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">event</span> and was characterized by weak coastal upwelling, in the second summer during July 2004, upwelling was normal. Very low silicate (SiO4) concentrations and SiO4:DIN ratios characterized the source water mass for upwelling in July 2004, and dynamic SiO4 to dissolved inorganic nitrogen ratios (SiO4:DIN) mainly below the Redfield-Brzezinski ratio and DIN to phosphate ratios (DIN:PO43-) below the Redfield ratio were a common feature off Viet Nam. Much higher particle concentrations and PSi/PC ratios during normal upwelling revealed major changes in the microplankton community structure among summers. Small dinoflagellates (10-20 μm) prevailed ubiquitously during reduced upwelling. During normal upwelling, the diatom Rhizosolenia sp. dominated the cell-carbon biomass in the silicate poor upwelling waters. Trichodesmium erythraeum dominated in the Mekong-influenced and nutrient depleted offshore waters, where it co-occurred with Rhizosolenia sp. Both species were directly associated with the much higher primary production (PP) and N2 fixation rates that were quantified in earlier studies, as well as with much higher diversities at these offshore sites. Along the coast, the correlation between Rhizosolenia sp. and PP rates was less clear and the factors regulating the biomass of Rhizosolenia sp. in the upwelling waters are discussed. The very low silicate concentrations in the source water</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PalOc..32..881T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PalOc..32..881T"><span>Modeling the stable water isotope expression of El Niño in the Pliocene: Implications for the interpretation of proxy data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tindall, Julia C.; Haywood, Alan M.; Thirumalai, Kaustubh</p> <p>2017-08-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) drives interannual climate variability; hence, its behavior over a range of climates needs to be understood. It is therefore important to verify that the paleoarchives, used for preinstrumental <span class="hlt">ENSO</span> studies, can accurately record <span class="hlt">ENSO</span> signals. Here we use the isotope enabled Hadley Centre General Circulation Model, HadCM3, to investigate <span class="hlt">ENSO</span> signals in paleoarchives from a <span class="hlt">warm</span> paleoclimate, the mid-Pliocene <span class="hlt">Warm</span> Period (mPWP: 3.3-3.0 Ma). Continuous (e.g., coral) and discrete (e.g., foraminifera) proxy data are simulated throughout the tropical Pacific, and <span class="hlt">ENSO</span> <span class="hlt">events</span> suggested by the pseudoproxy data are assessed using modeled <span class="hlt">ENSO</span> indices. HadCM3 suggests that the ability to reconstruct <span class="hlt">ENSO</span> from coral data is predominantly dependent on location. However, since modeled <span class="hlt">ENSO</span> is slightly stronger in the mPWP than the preindustrial, <span class="hlt">ENSO</span> is slightly easier to detect in mPWP aged coral. HadCM3 also suggests that using statistics from a number of individual foraminifera (individual foraminifera analysis, IFA) generally provides more accurate <span class="hlt">ENSO</span> information for the mPWP than for the preindustrial, particularly in the western and central Pacific. However, a test case from the eastern Pacific showed that for some locations, the IFA method can work well for the preindustrial but be unreliable for a different climate. The work highlights that sites used for paleo-<span class="hlt">ENSO</span> analysis should be chosen with extreme care in order to avoid unreliable results. Although a site with good skill for preindustrial <span class="hlt">ENSO</span> will usually have good skill for assessing mPWP <span class="hlt">ENSO</span>, this is not always the case.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110013371','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110013371"><span>The Response of Tropical Tropospheric Ozone to <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oman, L. D.; Ziemke, J. R.; Douglass, A. R.; Waugh, D. W.; Lang, C.; Rodriguez, J. M.; Nielsen, J. E.</p> <p>2011-01-01</p> <p>We have successfully reproduced the Ozone <span class="hlt">ENSO</span> Index (OEI) in the Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) forced by observed sea surface temperatures over a 25-year period. The vertical ozone response to <span class="hlt">ENSO</span> is consistent with changes in the Walker circulation. We derive the sensitivity of simulated ozone to <span class="hlt">ENSO</span> variations using linear regression analysis. The western Pacific and Indian Ocean region shows similar positive ozone sensitivities from the surface to the upper troposphere, in response to positive anomalies in the Nino 3.4 Index. The eastern and central Pacific region shows negative sensitivities with the largest sensitivity in the upper troposphere. This vertical response compares well with that derived from SHADOZ ozonesondes in each region. The OEI reveals a response of tropospheric ozone to circulation change that is nearly independent of changes in emissions and thus it is potentially useful in chemistry-climate model evaluation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1911292C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1911292C"><span>Analysis of the <span class="hlt">ENSO</span> temperature and specific humidity signals in the troposphere and lower stratosphere with global COSMIC GPS RO observations from June 2006 to June 2014</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Zhiping; Luo, Jia</p> <p>2017-04-01</p> <p>The specific humidity and the temperature response of El Niño-Southern Oscillation in the troposphere and lower stratosphere (TLS) over different areas i.e., Niño 3.4 (N3.4); -5˚ S-5˚ N, 180˚ W-180˚ E (G5); -30˚ S-30˚ N, 180˚ W-180˚ E (G30); -60˚ S-60˚ N, 180˚ W-180˚ E (G60); -90˚ S-90˚ N, 180˚ W-180˚ E (G90) were investigated using Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Positioning System (GPS) radio occultation (RO) data from June 2006 to June 2014. The empirical orthogonal functions (EOFs) and band-pass filtering with different filtering ranges at different altitudes were used to extract the <span class="hlt">ENSO</span>-related signals of the specific humidity and the temperature over different altitude levels in the TLS. The time series that has the maximum correlation coefficient between the <span class="hlt">ENSO</span>-related signals and the ONI were regarded as the strongest response to <span class="hlt">ENSO</span>. The results confirmed that the <span class="hlt">ENSO</span> was originated from tropical Pacific Ocean. The lag time and the phase of the maximum specific humidity or temperature response to <span class="hlt">ENSO</span> <span class="hlt">event</span> does not show a uniform patern at different altitudes in the troposphere over different areas, but the 1-2 seasons lag ONI was found and consistent with previous study results. The maximum correlation coefficient between the specific humidity and the ONI was about 0.94 at a lag time of 3 months at about 225 hpa altitude over the statistical areas while the maximum correlation coefficients (0.91) between the temperature and the ONI was found at ˜325 hpa altitude level at a lag time of 1 month in the TLS. The well agreement between the <span class="hlt">ENSO</span>-related signals in the troposphere and the ONI indicates that the specific humidity and temperature derived from COSMIC GPS RO observations are significant for monitoring the <span class="hlt">ENSO</span> <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H43I1338K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H43I1338K"><span>Integration of <span class="hlt">ENSO</span> Signal Power Through Hydrological Processes in the Little River Watershed</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Keener, V. W.; Jones, J. W.; Bosch, D. D.; Cho, J.</p> <p>2011-12-01</p> <p>The relationship of the El-Nino/Southern Oscillation (<span class="hlt">ENSO</span>) to hydrology is typically discussed in terms of the ability to separate significantly different hydrologic variable responses versus the anomaly that has taken place. Most of the work relating <span class="hlt">ENSO</span> trends to proxy variables had been done on precipitation records until the mid 1990s, at which point increasing numbers of studies started to focus on <span class="hlt">ENSO</span> relationships with streamflow as well as other environmental variables. The signals in streamflow are typically complex, representing the integration of both climatic, landscape, and anthropological responses that are able to strengthen the inherent <span class="hlt">ENSO</span> signal in chaotic regional precipitation data. There is a need to identify climate non-stationarities related to <span class="hlt">ENSO</span> and their links to watershed-scale outcomes. For risk-management in particular, inter-annual modes of climate variability and their seasonal expression are of interest. In this study, we analyze 36 years of historical monthly streamflow data from the Little River Watershed (LWR), a coastal plain ecosystem in Georgia, in conjunction with wavelet spectral analysis and modeling via the Soil & Water Assessment Tool (SWAT). Using both spectral and physical models allows us to identify the mechanism by which the <span class="hlt">ENSO</span> signal power in surface and simulated groundwater flow is strengthened as compared to precipitation. The clear increase in the power of the inter-annual climate signal is demonstrated by shared patterns in water budget and exceedance curves, as well as in high <span class="hlt">ENSO</span> related energy in the 95% significant wavelet spectra for each variable and the NINO 3.4 index. In the LRW, the power of the <span class="hlt">ENSO</span> teleconnection is increased in both the observed and simulated stream flow through the mechanisms of groundwater flow and interflow, through confinement by a geological layer, the Hawthorn Formation. This non-intuitive relationship between <span class="hlt">ENSO</span> signal strength and streamflow could prove to be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29401493','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29401493"><span>Global patterns and impacts of El Niño <span class="hlt">events</span> on coral reefs: A meta-analysis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Claar, Danielle C; Szostek, Lisa; McDevitt-Irwin, Jamie M; Schanze, Julian J; Baum, Julia K</p> <p>2018-01-01</p> <p>Impacts of global climate change on coral reefs are being amplified by pulse heat stress <span class="hlt">events</span>, including El Niño, the <span class="hlt">warm</span> phase of the El Niño Southern Oscillation (<span class="hlt">ENSO</span>). Despite reports of extensive coral bleaching and up to 97% coral mortality induced by El Niño <span class="hlt">events</span>, a quantitative synthesis of the nature, intensity, and drivers of El Niño and La Niña impacts on corals is lacking. Herein, we first present a global meta-analysis of studies quantifying the effects of El Niño/La Niña-<span class="hlt">warming</span> on corals, surveying studies from both the primary literature and International Coral Reef Symposium (ICRS) Proceedings. Overall, the strongest signal for El Niño/La Niña-associated coral bleaching was long-term mean temperature; bleaching decreased with decreasing long-term mean temperature (n = 20 studies). Additionally, coral cover losses during El Niño/La Niña were shaped by localized maximum heat stress and long-term mean temperature (n = 28 studies). Second, we present a method for quantifying coral heat stress which, for any coral reef location in the world, allows extraction of remotely-sensed degree heating weeks (DHW) for any date (since 1982), quantification of the maximum DHW, and the time lag since the maximum DHW. Using this method, we show that the 2015/16 El Niño <span class="hlt">event</span> instigated unprecedented global coral heat stress across the world's oceans. With El Niño <span class="hlt">events</span> expected to increase in frequency and severity this century, it is imperative that we gain a clear understanding of how these thermal stress anomalies impact different coral species and coral reef regions. We therefore finish with recommendations for future coral bleaching studies that will foster improved syntheses, as well as predictive and adaptive capacity to extreme <span class="hlt">warming</span> <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5798774','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5798774"><span>Global patterns and impacts of El Niño <span class="hlt">events</span> on coral reefs: A meta-analysis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Szostek, Lisa; McDevitt-Irwin, Jamie M.; Schanze, Julian J.; Baum, Julia K.</p> <p>2018-01-01</p> <p>Impacts of global climate change on coral reefs are being amplified by pulse heat stress <span class="hlt">events</span>, including El Niño, the <span class="hlt">warm</span> phase of the El Niño Southern Oscillation (<span class="hlt">ENSO</span>). Despite reports of extensive coral bleaching and up to 97% coral mortality induced by El Niño <span class="hlt">events</span>, a quantitative synthesis of the nature, intensity, and drivers of El Niño and La Niña impacts on corals is lacking. Herein, we first present a global meta-analysis of studies quantifying the effects of El Niño/La Niña-<span class="hlt">warming</span> on corals, surveying studies from both the primary literature and International Coral Reef Symposium (ICRS) Proceedings. Overall, the strongest signal for El Niño/La Niña-associated coral bleaching was long-term mean temperature; bleaching decreased with decreasing long-term mean temperature (n = 20 studies). Additionally, coral cover losses during El Niño/La Niña were shaped by localized maximum heat stress and long-term mean temperature (n = 28 studies). Second, we present a method for quantifying coral heat stress which, for any coral reef location in the world, allows extraction of remotely-sensed degree heating weeks (DHW) for any date (since 1982), quantification of the maximum DHW, and the time lag since the maximum DHW. Using this method, we show that the 2015/16 El Niño <span class="hlt">event</span> instigated unprecedented global coral heat stress across the world's oceans. With El Niño <span class="hlt">events</span> expected to increase in frequency and severity this century, it is imperative that we gain a clear understanding of how these thermal stress anomalies impact different coral species and coral reef regions. We therefore finish with recommendations for future coral bleaching studies that will foster improved syntheses, as well as predictive and adaptive capacity to extreme <span class="hlt">warming</span> <span class="hlt">events</span>. PMID:29401493</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ams.confex.com/ams/93Annual/webprogram/Paper219818.html','USGSPUBS'); return false;" href="https://ams.confex.com/ams/93Annual/webprogram/Paper219818.html"><span>The anomalous circulation associated with the <span class="hlt">ENSO</span>-related west Pacific sea surface temperature gradient</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hoell, Andrew; Funk, Christopher C.</p> <p>2013-01-01</p> <p>The temporal evolution and distribution of Pacific SST as well as the near-surface tropical Pacific zonal wind, tropical divergence and vertical velocity are considerably different during <span class="hlt">ENSO</span> <span class="hlt">events</span> partitioned according to the strength of the WPG. Modifications to the tropical circulation result in changes to the Indo-west Pacific precipitation and vertically integrated energy budgets and are linked to strong and consistent circulation and precipitation modifications throughout the Northern Hemisphere during winter.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3158189','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3158189"><span>Ice-shelf collapse from subsurface <span class="hlt">warming</span> as a trigger for Heinrich <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Marcott, Shaun A.; Clark, Peter U.; Padman, Laurie; Klinkhammer, Gary P.; Springer, Scott R.; Liu, Zhengyu; Otto-Bliesner, Bette L.; Carlson, Anders E.; Ungerer, Andy; Padman, June; He, Feng; Cheng, Jun; Schmittner, Andreas</p> <p>2011-01-01</p> <p>Episodic iceberg-discharge <span class="hlt">events</span> from the Hudson Strait Ice Stream (HSIS) of the Laurentide Ice Sheet, referred to as Heinrich <span class="hlt">events</span>, are commonly attributed to internal ice-sheet instabilities, but their systematic occurrence at the culmination of a large reduction in the Atlantic meridional overturning circulation (AMOC) indicates a climate control. We report Mg/Ca data on benthic foraminifera from an intermediate-depth site in the northwest Atlantic and results from a climate-model simulation that reveal basin-wide subsurface <span class="hlt">warming</span> at the same time as large reductions in the AMOC, with temperature increasing by approximately 2 °C over a 1–2 kyr interval prior to a Heinrich <span class="hlt">event</span>. In simulations with an ocean model coupled to a thermodynamically active ice shelf, the increase in subsurface temperature increases basal melt rate under an ice shelf fronting the HSIS by a factor of approximately 6. By analogy with recent observations in Antarctica, the resulting ice-shelf loss and attendant HSIS acceleration would produce a Heinrich <span class="hlt">event</span>. PMID:21808034</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49.1429C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49.1429C"><span>Indian Ocean and Indian summer monsoon: relationships without <span class="hlt">ENSO</span> in ocean-atmosphere coupled simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crétat, Julien; Terray, Pascal; Masson, Sébastien; Sooraj, K. P.; Roxy, Mathew Koll</p> <p>2017-08-01</p> <p>The relationship between the Indian Ocean and the Indian summer monsoon (ISM) and their respective influence over the Indo-Western North Pacific (WNP) region are examined in the absence of El Niño Southern Oscillation (<span class="hlt">ENSO</span>) in two partially decoupled global experiments. <span class="hlt">ENSO</span> is removed by nudging the tropical Pacific simulated sea surface temperature (SST) toward SST climatology from either observations or a fully coupled control run. The control reasonably captures the observed relationships between <span class="hlt">ENSO</span>, ISM and the Indian Ocean Dipole (IOD). Despite weaker amplitude, IODs do exist in the absence of <span class="hlt">ENSO</span> and are triggered by a boreal spring ocean-atmosphere coupled mode over the South-East Indian Ocean similar to that found in the presence of <span class="hlt">ENSO</span>. These pure IODs significantly affect the tropical Indian Ocean throughout boreal summer, inducing a significant modulation of both the local Walker and Hadley cells. This meridional circulation is masked in the presence of <span class="hlt">ENSO</span>. However, these pure IODs do not significantly influence the Indian subcontinent rainfall despite overestimated SST variability in the eastern equatorial Indian Ocean compared to observations. On the other hand, they promote a late summer cross-equatorial quadrupole rainfall pattern linking the tropical Indian Ocean with the WNP, inducing important zonal shifts of the Walker circulation despite the absence of <span class="hlt">ENSO</span>. Surprisingly, the interannual ISM rainfall variability is barely modified and the Indian Ocean does not force the monsoon circulation when <span class="hlt">ENSO</span> is removed. On the contrary, the monsoon circulation significantly forces the Arabian Sea and Bay of Bengal SSTs, while its connection with the western tropical Indian Ocean is clearly driven by <span class="hlt">ENSO</span> in our numerical framework. Convection and diabatic heating associated with above-normal ISM induce a strong response over the WNP, even in the absence of <span class="hlt">ENSO</span>, favoring moisture convergence over India.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A42E..05K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A42E..05K"><span>Inter-model Diversity of <span class="hlt">ENSO</span> simulation and its relation to basic states</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kug, J. S.; Ham, Y. G.</p> <p>2016-12-01</p> <p>In this study, a new methodology is developed to improve the climate simulation of state-of-the-art coupledglobal climate models (GCMs), by a postprocessing based on the intermodel diversity. Based on the closeconnection between the interannual variability and climatological states, the distinctive relation between theintermodel diversity of the interannual variability and that of the basic state is found. Based on this relation,the simulated interannual variabilities can be improved, by correcting their climatological bias. To test thismethodology, the dominant intermodel difference in precipitation responses during El Niño-SouthernOscillation (<span class="hlt">ENSO</span>) is investigated, and its relationship with climatological state. It is found that the dominantintermodel diversity of the <span class="hlt">ENSO</span> precipitation in phase 5 of the Coupled Model Intercomparison Project(CMIP5) is associated with the zonal shift of the positive precipitation center during El Niño. This dominantintermodel difference is significantly correlated with the basic states. The models with wetter (dryer) climatologythan the climatology of the multimodel ensemble (MME) over the central Pacific tend to shift positive<span class="hlt">ENSO</span> precipitation anomalies to the east (west). Based on the model's systematic errors in atmospheric<span class="hlt">ENSO</span> response and bias, the models with better climatological state tend to simulate more realistic atmospheric<span class="hlt">ENSO</span> responses.Therefore, the statistical method to correct the <span class="hlt">ENSO</span> response mostly improves the <span class="hlt">ENSO</span> response. Afterthe statistical correction, simulating quality of theMMEENSO precipitation is distinctively improved. Theseresults provide a possibility that the present methodology can be also applied to improving climate projectionand seasonal climate prediction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000085545','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000085545"><span>Dynamics of Monsoon-Induced Biennial Variability in <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kim, Kyu-Myong; Lau, K.-M.; Einaudi, Franco (Technical Monitor)</p> <p>2000-01-01</p> <p>The mechanism of the quasi-biennial tendency in El Nino Southern Oscillation (<span class="hlt">ENSO</span>)-monsoon coupled system is investigated using an intermediate coupled model. The monsoon wind forcing is prescribed as a function of Sea Surface Temperature (SST) anomalies based on the relationship between zonal wind anomalies over the western Pacific to sea level change in the equatorial eastern Pacific. The key mechanism of quasi-biennial tendency in El Nino evolution is found to be in the strong coupling of <span class="hlt">ENSO</span> to monsoon wind forcing over the western Pacific. Strong boreal summer monsoon wind forcing, which lags the maximum SST anomaly in the equatorial eastern Pacific approximately 6 months, tends to generate Kelvin waves of the opposite sign to anomalies in the eastern Pacific and initiates the turnabout in the eastern Pacific. Boreal winter monsoon forcing, which has zero lag with maximum SST in the equatorial eastern Pacific, tends to damp the <span class="hlt">ENSO</span> oscillations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A41L..04O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A41L..04O"><span>The 2015/16 El Niño <span class="hlt">Event</span> as Recorded in Central Tropical Pacific Corals: Temperature, Hydrology, and Ocean Circulation Influences</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Connor, G.; Cobb, K. M.; Sayani, H. R.; Grothe, P. R.; Atwood, A. R.; Stevenson, S.; Hitt, N. T.; Lynch-Stieglitz, J.</p> <p>2016-12-01</p> <p>The El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) of 2015/2016 was a record-breaking <span class="hlt">event</span> in the central Pacific, driving profound changes in the properties of the ocean and atmosphere. Prolonged ocean <span class="hlt">warming</span> of up to 3°C translated into a large-scale coral bleaching and mortality <span class="hlt">event</span> on Christmas Island (2°N, 157°W) that very few individuals escaped unscathed. As part of a long-term, interdisciplinary monitoring effort underway since August 2014, we present results documenting the timing and magnitude of environmental changes on the Christmas Island reefs. In particular, we present the first coral geochemical time series spanning the last several years, using cores that were drilled from rare living coral colonies during a field expedition in April 2016, at the tail end of the <span class="hlt">event</span>. These geochemical indicators are sensitive to both ocean temperature, salinity, and water mass properties and have been used to quantitatively reconstruct <span class="hlt">ENSO</span> extremes of the recent [Nurhati et al., 2011] and distant [Cobb et al., 2013] past. By analyzing multiple cores from both open ocean and lagoonal settings, we are able to undertake a quantitative comparison of this <span class="hlt">event</span> with past very strong El Niño <span class="hlt">events</span> contained in the coral archive - including the 1940/41, 1972/73, and 1997/98 <span class="hlt">events</span>. For the most recent <span class="hlt">event</span>, we compare our coral geochemistry records with a rich suite of in situ environmental data, including physical and geochemical parameters collected as part of the NOAA rapid response campaign in the central tropical Pacific. This unique dataset not only provides physical context interpreting coral geochemical records from the central tropical Pacific, but allows us to assess why the 2015/2016 El Niño <span class="hlt">event</span> was so devastating to coral reef ecosystems in this region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028573','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028573"><span>Soluble reactive phosphorus transport and retention in tropical, rainforest streams draining a volcanic and geothermally active landscape in Costa Rica.: Long-term concentration patterns, pore water environment and response to <span class="hlt">ENSO</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Triska, F.J.; Pringle, C.M.; Duff, J.H.; Avanzino, R.J.; Ramirez, A.; Ardon, M.; Jackman, A.P.</p> <p>2006-01-01</p> <p>Soluble reactive phosphorus (SRP) transport/retention was determined at four sites in three rainforest streams draining La Selva Biological Station, Costa Rica. La Selva is located at the base of the last remaining intact rainforest transect from 30 m above sea level to 3000 m along the entire Caribbean slope of Central America. Steam SRP levels can be naturally high there due to regional, geothermal groundwater discharged at ambient temperature. Monitoring since 1988 has revealed distinctive long-term differences in background SRP and total P (TP) for three streams in close proximity, and identified the impact of <span class="hlt">ENSO</span> (El Nino Southern Oscillation) <span class="hlt">events</span> on SRP-enriched reaches. Mean interannual SRP concentrations (?? standard deviation) were 89 ?? 53??g/l in the Salto (1988-1996), 21 ?? 39??g/l in the Pantano (1988-1998), and 26 ?? 35??g/l in the Sabalo (1988-1996). After January, 1997 the separate upland-lowland contributions to discharge and SRP load were determined monthly in the Salto. SRP in Upper Salto was low (19 ?? 8??g/l, 1997-2002) until enriched at the upland-lowland transition by regional groundwater. Mean SRP concentration in Lower Salto (108 ?? 104??g/l) was typically highest February-April, the driest months, and lowest July-September, the wettest. SRP concentration was positively correlated to the inverse of discharge in Lower Salto when <span class="hlt">ENSO</span> data were omitted (1992 and 1998-1999), but not in the Upper Salto, Pantano, or Sabalo. TP was positively correlated to the inverse of discharge in all three streams when <span class="hlt">ENSO</span> data were omitted. High SRP springs and seeps along the Lower Salto contributed 36% of discharge but 85% of SRP export 1997-2001. Annual SRP flux from the total Salto watershed (1997-2001) averaged 2.9 kg/ha year, but only 0.6 kg/ha year from the Upper Salto. A dye tracer injection showed that pore water environments were distinctly different between Upper and Lower Salto. Upper Salto had high surface water-pore water exchange, high</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFMPP24A..03Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFMPP24A..03Z"><span>Late Miocene - Pliocene Evolution of the Pacific <span class="hlt">Warm</span> Pool and Cold Tongue: Implications for El Niño</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Y.; Pagani, M.</p> <p>2011-12-01</p> <p>The Western Pacific <span class="hlt">Warm</span> Pool of the tropical Pacific Ocean retains the largest and warmest sea surface water body on Earth, while the eastern equatorial Pacific is characterized by strong upwelling of cold, nutrient-rich deep waters, termed the Pacific cold tongue. Evolution of the Pacific <span class="hlt">warm</span> pool and cold tongue are important because they control the circum-Pacific climate and impact the globe via El Niño - Southern Oscillation (<span class="hlt">ENSO</span>) teleconnections. Sea surface temperature (SST) reconstructions using a single site from the <span class="hlt">warm</span> pool (ODP 806) and two sites from the cold tongue (ODP 846, 847) suggest that the temperature of the <span class="hlt">warm</span> pool was "stable" throughout the Plio-Pleistocene, whereas the cold tongue was much warmer in the Pliocene and subsequently cooled. The absence of an east-west Pacific temperature gradient during the early Pliocene is the basis for the "permanent El Niño" hypothesis. However, annually-resolved fossil coral and evaporite records found 3-7 years climate variability during the Pliocene <span class="hlt">warm</span> period and late Miocene, challenging a "permanent" or invariant climate state. Here we present a multi-proxy (TEX86, UK37, Mg/Ca), multi-site reconstruction of the late Miocene - Pliocene (ca. 12 Ma - 3 Ma) SST in the Pacific <span class="hlt">warm</span> pool (ODP 806, ODP 769 in the Sulu Sea, ODP 1143 in the South China Sea) and the cold tongue (ODP 850, 849, 846). Our results show that the cold tongue was even warmer in the late Miocene than the Pliocene, and that the <span class="hlt">warm</span> pool cooled 2-3°C from the late Miocene into the Pliocene - in contrast to the invariant character previously assumed. Temperature comparison between different sites suggests that the <span class="hlt">warm</span> pool may have expanded in size in the late Miocene. Although eastern and western ends of the tropical Pacific were warmer, a persistent, but low east-west temperature gradient (~3°C) is apparent. This agrees with recent studies which have shown <span class="hlt">ENSO</span>-related frequency of climate change in the late Miocene and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFMPP51A0302E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFMPP51A0302E"><span>Tracking <span class="hlt">ENSO</span> with tropical trees: Progress in stable isotope dendroclimatology</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evans, M. N.; Poussart, P. F.; Saleska, S. R.; Schrag, D. P.</p> <p>2002-12-01</p> <p>The terrestrial tropics remain an important gap in the growing proxy network used to characterize past <span class="hlt">ENSO</span> behavior. Here we describe a strategy for development of proxy estimates of paleo-<span class="hlt">ENSO</span>, via proxy rainfall estimates derived from stable isotope (δ18O) measurements made on tropical trees. The approach applies a new model of oxygen isotopic composition of alpha-cellulose (Roden et al., 2000), a rapid method for cellulose extraction from raw wood (Brendel et al., 2000), and continuous flow isotope ratio mass spectrometry (Brand, 1996) to develop proxy chronological, rainfall and growth rate estimates from tropical trees, even those lacking annual rings. The promise and pitfalls of the approach are illustrated in pilot datasets from the US, Costa Rica, Brazil, and Peru, which show isotopic cycles of 4-6 per mil, and interannual anomalies of up to 8 per mil. Together with the mature <span class="hlt">ENSO</span> proxies (corals, extratropical tree-rings, varved sediments, and ice cores), replicated and well-dated stable isotope chronologies from tropical trees may eventually improve our understanding of <span class="hlt">ENSO</span> history over the past several hundred years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18....8S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18....8S"><span>Dynamics and spatial structure of <span class="hlt">ENSO</span> from re-analyses versus CMIP5 models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Serykh, Ilya; Sonechkin, Dmitry</p> <p>2016-04-01</p> <p>Basing on a mathematical idea about the so-called strange nonchaotic attractor (SNA) in the quasi-periodically forced dynamical systems, the currently available re-analyses data are considered. It is found that the El Niño - Southern Oscillation (<span class="hlt">ENSO</span>) is driven not only by the seasonal heating, but also by three more external periodicities (incommensurate to the annual period) associated with the ~18.6-year lunar-solar nutation of the Earth rotation axis, ~11-year sunspot activity cycle and the ~14-month Chandler wobble in the Earth's pole motion. Because of the incommensurability of their periods all four forces affect the system in inappropriate time moments. As a result, the <span class="hlt">ENSO</span> time series look to be very complex (strange in mathematical terms) but nonchaotic. The power spectra of <span class="hlt">ENSO</span> indices reveal numerous peaks located at the periods that are multiples of the above periodicities as well as at their sub- and super-harmonic. In spite of the above <span class="hlt">ENSO</span> complexity, a mutual order seems to be inherent to the <span class="hlt">ENSO</span> time series and their spectra. This order reveals itself in the existence of a scaling of the power spectrum peaks and respective rhythms in the <span class="hlt">ENSO</span> dynamics that look like the power spectrum and dynamics of the SNA. It means there are no limits to forecast <span class="hlt">ENSO</span>, in principle. In practice, it opens a possibility to forecast <span class="hlt">ENSO</span> for several years ahead. Global spatial structures of anomalies during El Niño and power spectra of <span class="hlt">ENSO</span> indices from re-analyses are compared with the respective output quantities in the CMIP5 climate models (the Historical experiment). It is found that the models reproduce global spatial structures of the near surface temperature and sea level pressure anomalies during El Niño very similar to these fields in the re-analyses considered. But the power spectra of the <span class="hlt">ENSO</span> indices from the CMIP5 models show no peaks at the same periods as the re-analyses power spectra. We suppose that it is possible to improve modeled</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2813D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2813D"><span>A <span class="hlt">warming</span> tropical central Pacific dries the lower stratosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, Qinghua; Fu, Qiang</p> <p>2018-04-01</p> <p>The amount of water vapor in the tropical lower stratosphere (TLS), which has an important influence on the radiative energy budget of the climate system, is modulated by the temperature variability of the tropical tropopause layer (TTL). The TTL temperature variability is caused by a complex combination of the stratospheric quasi-biennial oscillation (QBO), tropospheric convective processes in the tropics, and the Brewer-Dobson circulation (BDC) driven by mid-latitude and subtropical atmospheric waves. In 2000, the TLS water vapor amount exhibited a stepwise transition to a dry phase, apparently caused by a change in the BDC. In this study, we present observational and modeling evidence that the epochal change of water vapor between the periods of 1992-2000 and 2001-2005 was also partly caused by a concurrent sea surface temperature (SST) <span class="hlt">warming</span> in the tropical central Pacific. This SST <span class="hlt">warming</span> cools the TTL above by enhancing the equatorial wave-induced upward motion near the tropopause, which consequently reduces the amount of water vapor entering the stratosphere. The QBO affects the TLS water vapor primarily on inter-annual timescales, whereas a classical El Niño southern oscillation (<span class="hlt">ENSO</span>) <span class="hlt">event</span> has small effect on tropical mean TLS water vapor because its responses are longitudinally out of phase. This study suggests that the tropical central Pacific SST is another driver of TLS water vapor variability on inter-decadal timescales and the tropical SST changes could contribute to about 30% of the step-wise drop of the lower stratospheric water vapor from 1992-2000 to 2001-2005.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1612884W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1612884W"><span><span class="hlt">ENSO</span> impacts on flood risk at the global scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ward, Philip; Dettinger, Michael; Jongman, Brenden; Kummu, Matti; Winsemius, Hessel</p> <p>2014-05-01</p> <p>We present the impacts of El Niño Southern Oscillation (<span class="hlt">ENSO</span>) on society and the economy, via relationships between <span class="hlt">ENSO</span> and the hydrological cycle. We also discuss ways in which this knowledge can be used in disaster risk management and risk reduction. This contribution provides the most recent results of an ongoing 4-year collaborative research initiative to assess and map the impacts of large scale interannual climate variability on flood hazard and risk at the global scale. We have examined anomalies in flood risk between <span class="hlt">ENSO</span> phases, whereby flood risk is expressed in terms of indicators such as: annual expected damage; annual expected affected population; annual expected affected Gross Domestic Product (GDP). We show that large anomalies in flood risk occur during El Niño or La Niña years in basins covering large parts of the Earth's surface. These anomalies reach statistical significance river basins covering almost two-thirds of the Earth's surface. Particularly strong anomalies exist in southern Africa, parts of western Africa, Australia, parts of Central Eurasia (especially for El Niño), the western USA (especially La Niña anomalies), and parts of South America. We relate these anomalies to possible causal relationships between <span class="hlt">ENSO</span> and flood hazard, using both modelled and observed data on flood occurrence and extremity. The implications for flood risk management are many-fold. In those regions where disaster risk is strongly influenced by <span class="hlt">ENSO</span>, the potential predictably of <span class="hlt">ENSO</span> could be used to develop probabilistic flood risk projections with lead times up to several seasons. Such data could be used by the insurance industry in managing risk portfolios and by multinational companies for assessing the robustness of their supply chains to potential flood-related interruptions. Seasonal forecasts of <span class="hlt">ENSO</span> influence of peak flows could also allow for improved flood early warning and regulation by dam operators, which could also reduce overall risks</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP51B..01Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP51B..01Q"><span>Tales from the South (and West) Pacific in the Common Era: A Climate Proxy Perspective (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Quinn, T. M.; Taylor, F. W.; Partin, J. W.; Maupin, C. R.; Hereid, K. A.; Gorman, M. K.</p> <p>2010-12-01</p> <p>The southwest Pacific is a major source of tropical climate variability through heat and moisture exchanges associated with the Western Pacific <span class="hlt">Warm</span> Pool (WPWP) and the South Pacific Convergence Zone (SPCZ). These variations are especially significant at the annual, interannual (El Niño-Southern Oscillation, <span class="hlt">ENSO</span>), and multi-decadal timescales. Gridded SST data products are available in the pre-satellite era in this region for the past ~130 years, although data density is a significant issue for the older half of these records. Time series of salinity (SSS) and rainfall from this region are exceedingly rare. Thus, climate proxy records must be used to reconstruct SST, SSS, and rainfall variations in the Common Era (CE) in the tropical Pacific. The analytical laboratory for paleoclimate studies at UT has focused its research efforts into producing climate proxy time series from southwest tropical Pacific using modern and fossil corals, and speleothems. Our most recent results are summarized in this presentation, although much of this work is still in progress. Coral climate records have been generated from Sabine Bank, Vanuatu (16°S, 166°E) and Misima Island, Papua New Guinea (10.6°S, 152.8°E). The Vanuatu coral record of monthly resolved Sr/Ca variations extends back to the late 18th century. All strong <span class="hlt">ENSO</span> <span class="hlt">warm</span> phase <span class="hlt">events</span> of the 20th century observed in the instrumental record are also observed in the coral record. We note that several <span class="hlt">ENSO</span> <span class="hlt">warm</span> phase <span class="hlt">events</span> in the 19th century portion of the coral record are comparable in size to that recorded in response to the 1982/1983 and 1997/1998 <span class="hlt">events</span>. The Misima coral record of monthly resolved δ18O and Sr/Ca variations spans the interval ~1414-1645 CE — the heart of the Little Ice Age. Amplitude modulation of interannual variability is observed in this LIA record, much like what is observed during the relatively quiescent period of 1920-1950 in the 20th century instrumental and proxy records of <span class="hlt">ENSO</span>. However</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMPP22A..06T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMPP22A..06T"><span>Hydrological Cycle in the Western Equatorial <span class="hlt">Warm</span> Pool over the Past 220 k years</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tachikawa, K.; Cartapanis, O.; Vidal, L.; Beaufort, L.; Bard, E.</p> <p>2008-12-01</p> <p>The Western Pacific <span class="hlt">Warm</span> Pool is a major source of heat and moisture to extra-tropical regions, and its condition could have great impact on global climate response to various forcing factors. We reconstructed the rainfall pattern over Papua New Guinea (PNG) for the past 220 kyr using terrigenous elemental contents (Ti, Fe, K and Si) and calcareous productivity (Ca) recorded in a marine sediment core MD05-2920 (2°51.48S, 144°32.04E) from 100 km off the Sepik River mouth in Northern PNG. The core chronostratigraphy is established by 14C dating and benthic foraminiferal oxygen isotopes. The Sepik and Ramu river system forms one of the highest sediment discharge zones in the world because of high rainfall rates, <span class="hlt">warm</span> and humid climate, steep topography and erodible volcanic rocks in the draining basin. At present, the rainfall over this area is under the influence of both Asia-Australian monsoon and El Niño Southern Oscillation (<span class="hlt">ENSO</span>). The results obtained by an XRF core scanner indicate that for the whole record major sediment components are of terrigenous river-born nature and biogenic CaCO3. Spectral analysis reveals that dominant peaks for Ti are precession and obliquity periods whereas Ca variability is rather dominated by obliquity. The wet periods appear during maximum local insolation, which is in phase with minimum East Asian summer monsoon strength recorded by Chinese speleothems. Modeled past <span class="hlt">ENSO</span> activity cannot explain the reconstructed rainfall and productivity patterns. Taken together, the fresh water cycle over New Guinea is better explained by latitudinal shifts of the Intertropical Convergence Zone rather than <span class="hlt">ENSO</span>-type variability on orbital time scales. The variability of calcareous productivity is likely related to general changes in nutricline depth of the tropical Pacific band.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmRe.168...33S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmRe.168...33S"><span>Changes in extreme temperature and precipitation <span class="hlt">events</span> in the Loess Plateau (China) during 1960-2013 under global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sun, Wenyi; Mu, Xingmin; Song, Xiaoyan; Wu, Dan; Cheng, Aifang; Qiu, Bing</p> <p>2016-02-01</p> <p>In recent decades, extreme climatic <span class="hlt">events</span> have been a major issue worldwide. Regional assessments on various climates and geographic regions are needed for understanding uncertainties in extreme <span class="hlt">events</span>' responses to global <span class="hlt">warming</span>. The objective of this study was to assess the annual and decadal trends in 12 extreme temperature and 10 extreme precipitation indices in terms of intensity, frequency, and duration over the Loess Plateau during 1960-2013. The results indicated that the regionally averaged trends in temperature extremes were consistent with global <span class="hlt">warming</span>. The occurrence of <span class="hlt">warm</span> extremes, including summer days (SU), tropical nights (TR), <span class="hlt">warm</span> days (TX90), and nights (TN90) and a <span class="hlt">warm</span> spell duration indicator (WSDI), increased by 2.76 (P < 0.01), 1.24 (P < 0.01), 2.60 (P = 0.0003), 3.41 (P < 0.01), and 0.68 (P = 0.0041) days/decade during the period of 1960-2013, particularly, sharp increases in these indices occurred in 1985-2000. Over the same period, the occurrence of cold extremes, including frost days (FD), ice days (ID), cold days (TX10) and nights (TN10), and a cold spell duration indicator (CSDI) exhibited decreases of - 3.22 (P < 0.01), - 2.21 (P = 0.0028), - 2.71 (P = 0.0028), - 4.31 (P < 0.01), and - 0.69 (P = 0.0951) days/decade, respectively. Moreover, extreme <span class="hlt">warm</span> <span class="hlt">events</span> in most regions tended to increase while cold indices tended to decrease in the Loess Plateau, but the trend magnitudes of cold extremes were greater than those of <span class="hlt">warm</span> extremes. The growing season (GSL) in the Loess Plateau was lengthened at a rate of 3.16 days/decade (P < 0.01). Diurnal temperature range (DTR) declined at a rate of - 0.06 °C /decade (P = 0.0931). Regarding the precipitation indices, the annual total precipitation (PRCPTOT) showed no obvious trends (P = 0.7828). The regionally averaged daily rainfall intensity (SDII) exhibited significant decreases (- 0.14 mm/day/decade, P = 0.0158), whereas consecutive dry days (CDD) significantly increased (1.96 days</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....12986S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....12986S"><span>Aspects of extratropical synoptic-scale processes in opposing <span class="hlt">ENSO</span> phases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schwierz, C.; Wernli, H.; Hess, D.</p> <p>2003-04-01</p> <p>Energy and momentum provided by anomalous tropical heating/cooling affect the circulation on the global scale. Pacific Sea surface temperature anomalies strongly force local conditions in the equatorial Pacific, but are also known to change the climate in the extratropics, particularly over the American continent. The impact on more remote areas such as the Atlantic-European region is less clear. There the observed effects in both analyses and model studies show dependence on the resolution of the model/data, as well as on the time scales under consideration (Merkel and Latif, 2002; Compo et al., 2001). Most of the previous studies focus on larger-scale processes and seasonal time scales (or longer). Here we concentrate on the impact of opposing <span class="hlt">ENSO</span> phases on extratropical synoptic-scale dynamics. The investigation is undertaken for the Niño/Niña <span class="hlt">events</span> of 1972/3 and 1973/4 respectively, for 5 winter months (NDJFM) using ECMWF ERA40 data with 1o× 1o horizontal resolution and 60 vertical levels. The examination of the resulting differences in terms of standard dynamical fields (temperature, sea level pressure, precipitation, geopotential) is complemented with additional diagnostic fields (e.g. potential vorticity (PV), anti-/cyclone tracks and frequencies, PV streamers/cut-offs, blocking) in an attempt to gain more insight into aspects of extratropical synoptic-scale dynamical processes associated with <span class="hlt">ENSO</span> SST anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26916258','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26916258"><span>Summer precipitation anomalies in Asia and North America induced by Eurasian non-monsoon land heating versus <span class="hlt">ENSO</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhao, Ping; Wang, Bin; Liu, Jiping; Zhou, Xiuji; Chen, Junming; Nan, Sulan; Liu, Ge; Xiao, Dong</p> <p>2016-02-26</p> <p>When floods ravage Asian monsoon regions in summer, megadroughts often attack extratropical North America, which feature an intercontinental contrasting precipitation anomaly between Asia and North America. However, the characteristics of the contrasting Asian-North American (CANA) precipitation anomalies and associated mechanisms have not been investigated specifically. In this article, we firmly establish this summer CANA pattern, providing evidence for a significant effect of the land surface thermal forcing over Eurasian non-monsoon regions on the CANA precipitation anomalies by observations and numerical experiments. We show that the origin of the CANA precipitation anomalies and associated anomalous anticyclones over the subtropical North Pacific and Atlantic has a deeper root in Eurasian non-monsoon land surface heating than in North American land surface heating. The ocean forcing from the <span class="hlt">ENSO</span> is secondary and tends to be confined in the tropics. Our results have strong implications to interpretation of the feedback of global <span class="hlt">warming</span> on hydrological cycle over Asia and North America. Under the projected global <span class="hlt">warming</span> due to the anthropogenic forcing, the prominent surface <span class="hlt">warming</span> over Eurasian non-monsoon regions is a robust feature which, through the mechanism discussed here, would favor a precipitation increase over Asian monsoon regions and a precipitation decrease over extratropical North America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCC...7..123C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCC...7..123C"><span>Projected increase in El Niño-driven tropical cyclone frequency in the Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chand, Savin S.; Tory, Kevin J.; Ye, Hua; Walsh, Kevin J. E.</p> <p>2017-02-01</p> <p>The El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) drives substantial variability in tropical cyclone (TC) activity around the world. However, it remains uncertain how the projected future changes in <span class="hlt">ENSO</span> under greenhouse <span class="hlt">warming</span> will affect TC activity, apart from an expectation that the overall frequency of TCs is likely to decrease for most ocean basins. Here we show robust changes in <span class="hlt">ENSO</span>-driven variability in TC occurrence by the late twenty-first century. In particular, we show that TCs become more frequent (~20-40%) during future-climate El Niño <span class="hlt">events</span> compared with present-climate El Niño <span class="hlt">events</span>--and less frequent during future-climate La Niña <span class="hlt">events</span>--around a group of small island nations (for example, Fiji, Vanuatu, Marshall Islands and Hawaii) in the Pacific. We examine TCs across 20 models from the Coupled Model Intercomparison Project phase 5 database, forced under historical and greenhouse <span class="hlt">warming</span> conditions. The 12 most realistic models identified show a strong consensus on El Niño-driven changes in future-climate large-scale environmental conditions that modulate development of TCs over the off-equatorial western Pacific and the central North Pacific regions. These results have important implications for climate change and adaptation pathways for the vulnerable Pacific island nations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999BAMS...80.1117C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999BAMS...80.1117C"><span>Interactions with a Weather-Sensitive Decision Maker: A Case Study Incorporating <span class="hlt">ENSO</span> Information into a Strategy for Purchasing Natural Gas.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Changnon, David; Creech, Tamara; Marsili, Nathan; Murrell, William; Saxinger, Michael</p> <p>1999-06-01</p> <p>During the 1997/98 El Niño <span class="hlt">event</span>, a Northern Illinois University (NIU) faculty member and a group of undergraduate meteorology students interacted with the university's heating plant manager to determine whether climate information and forecast tools could assist him with NIU's natural gas purchase decisions each fall. Based on the El Niño-driven temperature forecasts and information developed by the faculty-directed student group, which indicated that northern Illinois would experience a warmer than average winter (December through March), the manager chose the option to ride the market on a continuous basis, buying incrementally to reduce total natural gas expenditures, rather than lock into a fixed price.To aid this annual decision process, winter El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) classifications, based on sea surface temperature (SST) data measured in the Niño-3 region, were analyzed to determine whether relationships existed between local mean winter temperature and the <span class="hlt">ENSO</span> phenomena during the 1951-97 period. An SST <span class="hlt">ENSO</span> model, which uses the past winter's <span class="hlt">ENSO</span> state along with the SST trends from April through September, was developed to predict the upcoming winter's temperatures (above, near, or below average). The model predicted an 83% chance of a winter experiencing average to below-average temperatures following an El Niño winter, regardless of trend. Those winters following a non-<span class="hlt">ENSO</span> winter with steady or increasing SST trends experienced average or above-average temperatures 79% of the time. These results supported the manager's natural gas decision, which in turn saved NIU approximately $500,000 and aided in the university's decision to hire a full-time applied meteorologist to provide advice on a continuing basis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3997310','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3997310"><span>Phytoplankton chlorophyte structure as related to <span class="hlt">ENSO</span> <span class="hlt">events</span> in a saline lowland river (Salado River, Buenos Aires, Argentina)</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Solari, Lía C; Gabellone, Néstor A; Claps, María C; Casco, María A; Quaíni, Karina P; Neschuk, Nancy C</p> <p>2014-01-01</p> <p>We analyzed the phytoplankton present in the lower sector of the Salado River (Buenos Aires, Argentina) for 10 years (1995–2005) and detected significant changes occurring in chlorophyte abundance and species richness during La Niña <span class="hlt">event</span> (1998–1999), which period was analyzed throughout the entire basin (main stream and tributaries). We compared the physicochemical and biologic variables between two El Niño–La Niña–Southern Oscillation (<span class="hlt">ENSO</span>) periods – El Niño (March 1997–January 1998) and La Niña (May 1998–May 1999) – to identify possible indicators of a relationship between climatic anomalies and chlorophyte performance. Chlorophyte density increased during the La Niña. Under normal or extreme hydrologic conditions, mobile (Chlamydomonas spp.) and nonmobile (Monoraphidium spp.) chlorophytes codominated. These species belonged to Reynolds's functional groups X1 and X2, those typical of nutrient-enriched environments. Comparative analyses between El Niño and La Niña periods indicated significant differences in physicochemical (K+, dissolved polyphenols, particulate reactive phosphorus, alkalinity, pH) and biologic (species diversity and richness, phytoplankton and chlorophyte total densities) variables between the two periods at all basin sites. During the La Niña condition, species richness was greater owing to interconnected shallow lakes and drainage-channel inputs, while the Shannon diversity index was lower because of the high abundance values of Monoraphidium minutum. A detailed analysis of the chlorophytes in the entire basin, indicated that changes in density and species dominance occurred on a regional scale although diverse chlorophyte assemblages were identified in the different sectors of the Salado River basin. After La Niña <span class="hlt">event</span>, the entire basin had the potential to revert to the previous density values, showing the resilience to global environmental changes and the ability to reestablish the general conditions of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24772271','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24772271"><span>Phytoplankton chlorophyte structure as related to <span class="hlt">ENSO</span> <span class="hlt">events</span> in a saline lowland river (Salado River, Buenos Aires, Argentina).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Solari, Lía C; Gabellone, Néstor A; Claps, María C; Casco, María A; Quaíni, Karina P; Neschuk, Nancy C</p> <p>2014-04-01</p> <p>We analyzed the phytoplankton present in the lower sector of the Salado River (Buenos Aires, Argentina) for 10 years (1995-2005) and detected significant changes occurring in chlorophyte abundance and species richness during La Niña <span class="hlt">event</span> (1998-1999), which period was analyzed throughout the entire basin (main stream and tributaries). We compared the physicochemical and biologic variables between two El Niño-La Niña-Southern Oscillation (<span class="hlt">ENSO</span>) periods - El Niño (March 1997-January 1998) and La Niña (May 1998-May 1999) - to identify possible indicators of a relationship between climatic anomalies and chlorophyte performance. Chlorophyte density increased during the La Niña. Under normal or extreme hydrologic conditions, mobile (Chlamydomonas spp.) and nonmobile (Monoraphidium spp.) chlorophytes codominated. These species belonged to Reynolds's functional groups X1 and X2, those typical of nutrient-enriched environments. Comparative analyses between El Niño and La Niña periods indicated significant differences in physicochemical (K(+), dissolved polyphenols, particulate reactive phosphorus, alkalinity, pH) and biologic (species diversity and richness, phytoplankton and chlorophyte total densities) variables between the two periods at all basin sites. During the La Niña condition, species richness was greater owing to interconnected shallow lakes and drainage-channel inputs, while the Shannon diversity index was lower because of the high abundance values of Monoraphidium minutum. A detailed analysis of the chlorophytes in the entire basin, indicated that changes in density and species dominance occurred on a regional scale although diverse chlorophyte assemblages were identified in the different sectors of the Salado River basin. After La Niña <span class="hlt">event</span>, the entire basin had the potential to revert to the previous density values, showing the resilience to global environmental changes and the ability to reestablish the general conditions of stability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ERL....13d4031L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ERL....13d4031L"><span>Identification of symmetric and asymmetric responses in seasonal streamflow globally to <span class="hlt">ENSO</span> phase</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, Donghoon; Ward, Philip J.; Block, Paul</p> <p>2018-04-01</p> <p>The phase of the El Niño Southern Oscillation (<span class="hlt">ENSO</span>) has large-ranging effects on streamflow and hydrologic conditions globally. While many studies have evaluated this relationship through correlation analysis between annual streamflow and <span class="hlt">ENSO</span> indices, an assessment of potential asymmetric relationships between <span class="hlt">ENSO</span> and streamflow is lacking. Here, we evaluate seasonal variations in streamflow by <span class="hlt">ENSO</span> phase to identify asymmetric (AR) and symmetric (SR) spatial pattern responses globally and further corroborate with local precipitation and hydrological condition. The AR and SR patterns between seasonal precipitation and streamflow are identified at many locations for the first time. Our results identify strong SR patterns in particular regions including northwestern and southern US, northeastern and southeastern South America, northeastern and southern Africa, southwestern Europe, and central-south Russia. The seasonally lagged anomalous streamflow patterns are also identified and attributed to snowmelt, soil moisture, and/or cumulative hydrological processes across river basins. These findings may be useful in water resources management and natural hazards planning by better characterizing the propensity of flood or drought conditions by <span class="hlt">ENSO</span> phase.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSME41B..03Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSME41B..03Z"><span>The 2014-2015 <span class="hlt">Warming</span> Anomaly in the Southern California Current System: Glider Observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaba, K. D.; Rudnick, D. L.</p> <p>2016-02-01</p> <p>During 2014-2015, basin-wide patterns of oceanic and atmospheric anomalies affected surface waters throughout the North Pacific Ocean. We present regional physical and biological effects of the <span class="hlt">warming</span>, as observed by our autonomous underwater gliders in the southern California Current System (SCCS). Established in 2006, the California Glider Network provides sustained subsurface observations for monitoring the coastal effects of large-scale climate variability. Along repeat sections that extend to 350-500 km in offshore distance and 500 m in depth, Spray gliders have continuously occupied CalCOFI lines 66.7, 80, and 90 for nearly nine years. Following a sawtooth trajectory, the gliders complete each dive in approximately 3 hours and over 3 km. Measured variables include pressure, temperature, salinity, chlorophyll fluorescence, and velocity. For each of the three lines, a comprehensive climatology has been constructed from the multiyear timeseries. The ongoing surface-intensified <span class="hlt">warming</span> anomaly, which began locally in early 2014 and persists through present, is unprecedented in the glider climatology. Reaching up to 5°C, positive temperature anomalies have been generally confined to the upper 50 m and persistent for over 20 months. The timing of the <span class="hlt">warming</span> was in phase along each glider line but out of phase with equatorial SST anomalies, suggesting a decoupling of tropical and mid-latitude dynamics. Concurrent physical oceanographic anomalies included a depressed thermocline and high stratification. An induced biological response was apparent in the deepening of the subsurface chlorophyll fluorescence maximum. Ancillary atmospheric data from the NCEP North American Mesoscale (NAM) model indicate that a combination of surface forcing anomalies, namely high downward heat flux and weak wind stress magnitude, caused the unusual <span class="hlt">warm</span>, downwelling conditions. With a strong El Niño <span class="hlt">event</span> in the forecast for winter 2015-2016, our sustained glider network will</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..889W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..889W"><span>Modulation of <span class="hlt">ENSO</span> evolution by strong tropical volcanic eruptions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Tao; Guo, Dong; Gao, Yongqi; Wang, Huijun; Zheng, Fei; Zhu, Yali; Miao, Jiapeng; Hu, Yongyun</p> <p>2017-11-01</p> <p>The simulated responses of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) to volcanic forcings are controversial, and some mechanisms of these responses are not clear. We investigate the impacts of volcanic forcing on the <span class="hlt">ENSO</span> using a long-term simulation covering 1400-1999 as simulated by the Bergen Climate Model (BCM) and a group of simulations performed with the Community Atmosphere Model version 4.0 (CAM4) and the BCM's ocean component Miami Isopycanic Coordinated Ocean Model (MICOM). The analysis of the long-term BCM simulation indicates that <span class="hlt">ENSO</span> has a negative-positive-negative response to strong tropical volcanic eruptions (SVEs), which corresponds to the different stages of volcanic forcing. In the initial forcing stage, a brief and weak La Niña-like response is caused by the cooling along the west coast of the South American continent and associated enhancement of the trade winds. In the peak forcing stage, westerly wind anomalies are excited by both reduced east-west sea level pressure gradients and weakened and equatorward shifted tropical convergence zones. These westerly wind anomalies extend to the equatorial eastern Pacific, leading to an El Niño-like response. At the same time, easterly wind anomalies west of 120°E and strong cooling effects can promote a discharged thermocline state and excite an upwelling Kelvin wave in the western Pacific. In the declining forcing stage, forced by the recovered trade winds, the upwelling Kelvin wave propagates eastward and reaches the equatorial eastern Pacific. Through the Bjerknes feedback, a strong and temporally extended La Niña-like response forms. Additional CAM4 simulations suggest a more important role of the surface cooling over the Maritime Continent and surrounding ocean in shaping the westerly wind anomalies over the equatorial central-eastern Pacific and the easterly wind anomalies west of 120° E, which are key to causing the El Niño-like responses and subsequent La Niña-like responses</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917382F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917382F"><span>Coupling Post-<span class="hlt">Event</span> and Prospective Analyses for El Niño-related Risk Reduction in Peru</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>French, Adam; Keating, Adriana; Mechler, Reinhard; Szoenyi, Michael; Cisneros, Abel; Chuquisengo, Orlando; Etienne, Emilie; Ferradas, Pedro</p> <p>2017-04-01</p> <p>Analyses in the wake of natural disasters play an important role in identifying how ex ante risk reduction and ex post hazard response activities have both succeeded and fallen short in specific contexts, thereby contributing to recommendations for improving such measures in the future. <span class="hlt">Event</span> analyses have particular relevance in settings where disasters are likely to reoccur, and especially where recurrence intervals are short. This paper applies the Post <span class="hlt">Event</span> Review Capability (PERC) methodology to the context of frequently reoccurring El Niño Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span> in the country of Peru, where over the last several decades <span class="hlt">ENSO</span> impacts have generated high levels of damage and economic loss. Rather than analyzing the impacts of a single <span class="hlt">event</span>, this study builds upon the existing PERC methodology by combining empirical <span class="hlt">event</span> analysis with a critical examination of risk reduction and adaptation measures implemented both prior to and following several <span class="hlt">ENSO</span> <span class="hlt">events</span> in the late 20th and early 21st centuries. Additionally, the paper explores linking the empirical findings regarding the uptake and outcomes of particular risk reduction and adaptation strategies to a prospective, scenario-based approach for projecting risk several decades into the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990116053&hterms=recurrence+plot&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drecurrence%2Bplot','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990116053&hterms=recurrence+plot&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drecurrence%2Bplot"><span>On the Bimodality of <span class="hlt">ENSO</span> Cycle Extremes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, Robert M.</p> <p>1999-01-01</p> <p>On the basis of sea surface temperature in the Nino 3.4 region (5 deg N-5 deg S, 120 deg- 170 deg W) during the interval of 1950-1997, Kevin Trenberth previously has identified some 16 El Nino and 10 La Nina, these 26 <span class="hlt">events</span> representing the extremes of the quasi-periodic El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) cycle. Runs testing shows that the duration and recurrence period associated with these extremes vary randomly, as does the sequencing of the extremes. Hence, the frequency of occurrence of these <span class="hlt">events</span> during the 1990s, especially, for El Nino should not be construed as being significantly different from that of previous epochs. Additionally, the distribution of duration for both El Nino and La Nina looks bimodal, consisting of two preferred modes - about 8 and 16 months in length for El Nino and about 9 and 18 months in length for La Nina. Likewise, the distribution of recurrence period, especially, for El Nino looks bimodal, consisting of two preferred modes - about 21 and 50 months in length. Scatter plots of the recurrence period versus duration for El Nino strongly suggest preferential associations between them, linking shorter (longer) duration with shorter (longer) recurrence period. Because the last known onset of El Nino occurred in April 1997 and the <span class="hlt">event</span> was of longer than average duration, one infers that the onset of the next expected El Nino will not occur until February 2000 or later.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThApC.132..465R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThApC.132..465R"><span>Diversity in the representation of large-scale circulation associated with <span class="hlt">ENSO</span>-Indian summer monsoon teleconnections in CMIP5 models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ramu, Dandi A.; Chowdary, Jasti S.; Ramakrishna, S. S. V. S.; Kumar, O. S. R. U. B.</p> <p>2018-04-01</p> <p>Realistic simulation of large-scale circulation patterns associated with El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is vital in coupled models in order to represent teleconnections to different regions of globe. The diversity in representing large-scale circulation patterns associated with <span class="hlt">ENSO</span>-Indian summer monsoon (ISM) teleconnections in 23 Coupled Model Intercomparison Project Phase 5 (CMIP5) models is examined. CMIP5 models have been classified into three groups based on the correlation between Niño3.4 sea surface temperature (SST) index and ISM rainfall anomalies, models in group 1 (G1) overestimated El Niño-ISM teleconections and group 3 (G3) models underestimated it, whereas these teleconnections are better represented in group 2 (G2) models. Results show that in G1 models, El Niño-induced Tropical Indian Ocean (TIO) SST anomalies are not well represented. Anomalous low-level anticyclonic circulation anomalies over the southeastern TIO and western subtropical northwest Pacific (WSNP) cyclonic circulation are shifted too far west to 60° E and 120° E, respectively. This bias in circulation patterns implies dry wind advection from extratropics/midlatitudes to Indian subcontinent. In addition to this, large-scale upper level convergence together with lower level divergence over ISM region corresponding to El Niño are stronger in G1 models than in observations. Thus, unrealistic shift in low-level circulation centers corroborated by upper level circulation changes are responsible for overestimation of <span class="hlt">ENSO</span>-ISM teleconnections in G1 models. <span class="hlt">Warm</span> Pacific SST anomalies associated with El Niño are shifted too far west in many G3 models unlike in the observations. Further large-scale circulation anomalies over the Pacific and ISM region are misrepresented during El Niño years in G3 models. Too strong upper-level convergence away from Indian subcontinent and too weak WSNP cyclonic circulation are prominent in most of G3 models in which <span class="hlt">ENSO</span>-ISM teleconnections are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20180000959&hterms=earth+system&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dearth%2Bsystem','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20180000959&hterms=earth+system&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dearth%2Bsystem"><span>Reduced <span class="hlt">ENSO</span> Variability at the LGM Revealed by an Isotope-Enabled Earth System Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhu, Jiang; Liu, Zhengyu; Brady, Esther; Otto-Bliesner, Bette; Zhang, Jiaxu; Noone, David; Tomas, Robert; Nusbaumer, Jesse; Wong, Tony; Jahn, Alexandra; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20180000959'); toggleEditAbsImage('author_20180000959_show'); toggleEditAbsImage('author_20180000959_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20180000959_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20180000959_hide"></p> <p>2017-01-01</p> <p>Studying the El Nino Southern Oscillation (<span class="hlt">ENSO</span>) in the past can help us better understand its dynamics and improve its future projections. However, both paleoclimate reconstructions and model simulations of <span class="hlt">ENSO</span> strength at the Last Glacial Maximum (LGM; 21 ka B.P.) have led to contradicting results. Here we perform model simulations using the recently developed water isotope-enabled Community Earth System Model (iCESM). For the first time, model-simulated oxygen isotopes are directly compared with those from <span class="hlt">ENSO</span> reconstructions using the individual foraminifera analysis (IFA). We find that the LGM <span class="hlt">ENSO</span> is most likely weaker comparing with the preindustrial. The iCESM suggests that total variance of the IFA records may only reflect changes in the annual cycle instead of <span class="hlt">ENSO</span> variability as previously assumed. Furthermore, the interpretation of subsurface IFA records can be substantially complicated by the habitat depth of thermocline-dwelling foraminifera and their vertical migration with a temporally varying thermocline.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.U53F..03S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.U53F..03S"><span>The <span class="hlt">ENSO</span>-pandemic influenza connection: coincident or causal?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shaman, J. L.; Lipsitch, M.</p> <p>2011-12-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) is a coupled ocean-atmosphere system in the tropical Pacific, which affects weather conditions, including temperatures, precipitation, winds and storm activity, across the planet. <span class="hlt">ENSO</span> has two extreme phases marked by either warmer (El Niño) or cooler (La Niña) than average sea surface temperatures in the central equatorial Pacific. We find that the 4 most recent human influenza pandemics (1918, 1957, 1968, 2009), all of which were first identified in boreal spring or summer, were preceded by La Niña conditions in the equatorial Pacific. Changes in <span class="hlt">ENSO</span> have been shown to alter the migration, stopover time, fitness and interspecies mixing of migratory birds, and consequently likely affect their mixing with domestic animals. We hypothesize that La Niña conditions bring divergent influenza subtypes together in some parts of the world and favor the reassortment of influenza through simultaneous multiple infection of individual hosts and the generation of novel pandemic strains. We propose approaches to test this hypothesis using influenza population genetics, virus prevalence in various host species, and avian migration patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.1939P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.1939P"><span>Ocean Chlorophyll as a Precursor of <span class="hlt">ENSO</span>: An Earth System Modeling Study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, Jong-Yeon; Dunne, John P.; Stock, Charles A.</p> <p>2018-02-01</p> <p>Ocean chlorophyll concentration, a proxy for phytoplankton, is strongly influenced by internal ocean dynamics such as those associated with El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). Observations show that ocean chlorophyll responses to <span class="hlt">ENSO</span> generally lead sea surface temperature (SST) responses in the equatorial Pacific. A long-term global Earth system model simulation incorporating marine biogeochemical processes also exhibits a preceding chlorophyll response. In contrast to simulated SST anomalies, which significantly lag the wind-driven subsurface heat response to <span class="hlt">ENSO</span>, chlorophyll anomalies respond rapidly. Iron was found to be the key factor connecting the simulated surface chlorophyll anomalies to the subsurface ocean response. Westerly wind bursts decrease central Pacific chlorophyll by reducing iron supply through wind-driven thermocline deepening but increase western Pacific chlorophyll by enhancing the influx of coastal iron from the maritime continent. Our results mechanistically support the potential for chlorophyll-based indices to inform seasonal <span class="hlt">ENSO</span> forecasts beyond previously identified SST-based indices.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.noaa.gov/topic-tags/el-nino-la-nina-enso','SCIGOVWS'); return false;" href="http://www.noaa.gov/topic-tags/el-nino-la-nina-enso"><span>El Nino, La Nina, <span class="hlt">ENSO</span> | National Oceanic and Atmospheric Administration</span></a></p> <p><a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a></p> <p></p> <p></p> <p>your local weather Enter your ZIP code GO Enter Search Terms El Nino, <em>La</em> Nina, <span class="hlt">ENSO</span> Content <em>La</em> Nina is gone, for now May 10, 2018 More On El Nino, <em>La</em> Nina, <span class="hlt">ENSO</span> Ocean surface temperatures in April 2018 compared to the 1981-2010 average. What's going on with <em>La</em> Niña? March 22, 2018 More On El Nino, <em>La</em> Nina</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5027414','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5027414"><span>Simple stochastic model for El Niño with westerly wind bursts</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Thual, Sulian; Majda, Andrew J.; Chen, Nan; Stechmann, Samuel N.</p> <p>2016-01-01</p> <p>Atmospheric wind bursts in the tropics play a key role in the dynamics of the El Niño Southern Oscillation (<span class="hlt">ENSO</span>). A simple modeling framework is proposed that summarizes this relationship and captures major features of the observational record while remaining physically consistent and amenable to detailed analysis. Within this simple framework, wind burst activity evolves according to a stochastic two-state Markov switching–diffusion process that depends on the strength of the western Pacific <span class="hlt">warm</span> pool, and is coupled to simple ocean–atmosphere processes that are otherwise deterministic, stable, and linear. A simple model with this parameterization and no additional nonlinearities reproduces a realistic <span class="hlt">ENSO</span> cycle with intermittent El Niño and La Niña <span class="hlt">events</span> of varying intensity and strength as well as realistic buildup and shutdown of wind burst activity in the western Pacific. The wind burst activity has a direct causal effect on the <span class="hlt">ENSO</span> variability: in particular, it intermittently triggers regular El Niño or La Niña <span class="hlt">events</span>, super El Niño <span class="hlt">events</span>, or no <span class="hlt">events</span> at all, which enables the model to capture observed <span class="hlt">ENSO</span> statistics such as the probability density function and power spectrum of eastern Pacific sea surface temperatures. The present framework provides further theoretical and practical insight on the relationship between wind burst activity and the <span class="hlt">ENSO</span>. PMID:27573821</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFMPP43B1677M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFMPP43B1677M"><span>Stable isotope records of convection variability in the West Pacific <span class="hlt">Warm</span> Pool from fast-growing stalagmites</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maupin, C. R.; Partin, J. W.; Quinn, T. M.; Shen, C.; Lin, K.; Taylor, F. W.; Sinclair, D. J.; Banner, J. L.</p> <p>2010-12-01</p> <p>The potential response of the tropical Pacific to ongoing anthropogenic global <span class="hlt">warming</span> conditions is informed by instrumental data, model predictions and climate proxy evidence. However, these distinct lines of evidence lead to opposing predictions in terms of the nature of interannual (<span class="hlt">ENSO</span>) variability in a <span class="hlt">warming</span> world. Interpreted in an <span class="hlt">ENSO</span> framework, <span class="hlt">warming</span> in the tropical Pacific may elicit a zonally asymmetrical response and lead to an intensified Walker Circulation (more ‘La Niña - like’). Alternatively, discrepancies in the increasing rates of latent heat flux and rainfall due to <span class="hlt">warming</span> conditions may in fact reduce Walker Circulation (more ‘El Niño - like’). However, in order for such a framework to be useful in the context of future climate change, some knowledge of the natural variability in the strength of Walker Circulation components is required. The extant instrumental data are not of sufficient temporal length to fully assess the spectrum of natural variability in such climate components. Oxygen isotope records from tropical speleothems have been successfully used to document the nature of precessional forcing on precipitation and atmospheric circulation patterns throughout the tropics. Typical stalagmite growth rates of 10-100 μm yr-1 allow decadally resolved records of δ18O variability on time scales of centuries to millennia and beyond. Here we present the initial results from calcite stalagmites of heretofore unprecedented growth rates (~1-4 mm yr-1) in a cave in northwest Guadalcanal, Solomon Islands (~9°S, 160°E). These stalagmites have been absolutely dated by U-Th techniques and indicate stalagmite growth spanning ~1650 to 2010 CE. The δ18O records from stalagmites provide evidence for changes in convection in the equatorial WPWP region of the SPCZ: the rising limb of the Pacific Walker Circulation, and therefore provide critical insight into changes in zonal atmospheric circulation across the Pacific.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A53E2292B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A53E2292B"><span>Vertical Wave Coupling associated with Stratospheric Sudden <span class="hlt">Warming</span> <span class="hlt">Events</span> analyzed in an Isentropic-Coordinate NWP Model.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bleck, R.; Sun, S.; Benjamin, S.; Brown, J. M.</p> <p>2017-12-01</p> <p>Two- to four-week predictions of stratospheric sudden <span class="hlt">warming</span> <span class="hlt">events</span> during the winter seasons of 1999-2014, carried out with a high-resolution icosahedral NWP model using potential temperature as vertical coordinate, are inspected for commonalities in the evolution of both minor and major <span class="hlt">warmings</span>. Emphasis is on the evolution of the potential vorticity field at different levels in the stratosphere, as well as on the sign and magnitude of the vertical component of the Eliassen-Palm flux vector suggestive of wave forcing in either direction. Material is presented shedding light on the skill of the model (FIM, developed at NOAA/ESRL) in predicting stratospheric <span class="hlt">warmings</span> generally 2 weeks in advance. With an icosahedral grid ideally suited for studying polar processes, and a vertical coordinate faithfully reproducing details in the evolution of the potential vorticity and EP flux vector fields, FIM is found to be a good tool for investigating the SSW mechanism.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1134073','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1134073"><span>Final Report for UW-Madison Portion of DE-SC0005301, "Collaborative Project: Pacific Decadal Variability and Central Pacific <span class="hlt">Warming</span> El Niño in a Changing Climate"</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Vimont, Daniel</p> <p></p> <p>This project funded two efforts at understanding the interactions between Central Pacific <span class="hlt">ENSO</span> <span class="hlt">events</span>, the mid-latitude atmosphere, and decadal variability in the Pacific. The first was an investigation of conditions that lead to Central Pacific (CP) and East Pacific (EP) <span class="hlt">ENSO</span> <span class="hlt">events</span> through the use of linear inverse modeling with defined norms. The second effort was a modeling study that combined output from the National Center for Atmospheric Research (NCAR) Community Atmospheric Model (CAM4) with the Battisti (1988) intermediate coupled model. The intent of the second activity was to investigate the relationship between the atmospheric North Pacific Oscillation (NPO), themore » Pacific Meridional Mode (PMM), and <span class="hlt">ENSO</span>. These two activities are described herein.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1376649-global-land-carbon-sink-response-temperature-precipitation-varies-enso-phase','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1376649-global-land-carbon-sink-response-temperature-precipitation-varies-enso-phase"><span>Global land carbon sink response to temperature and precipitation varies with <span class="hlt">ENSO</span> phase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.; ...</p> <p>2017-06-01</p> <p>Climate variability associated with the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and its consequent impacts on land carbon sink interannual variability have been used as a basis for investigating carbon cycle responses to climate variability more broadly, and to inform the sensitivity of the tropical carbon budget to climate change. Past studies have presented opposing views about whether temperature or precipitation is the primary factor driving the response of the land carbon sink to <span class="hlt">ENSO</span>. We show that the dominant driver varies with <span class="hlt">ENSO</span> phase. And whereas tropical temperature explains sink dynamics following El Niño conditions (r TG,P = 0.59, p <more » 0.01), the post La Niña sink is driven largely by tropical precipitation (r PG,T= -0.46, p = 0.04). This finding points to an <span class="hlt">ENSO</span>-phase-dependent interplay between water availability and temperature in controlling the carbon uptake response to climate variations in tropical ecosystems. Furthermore, we find that none of a suite of ten contemporary terrestrial biosphere models captures these <span class="hlt">ENSO</span>-phase-dependent responses, highlighting a key uncertainty in modeling climate impacts on the future of the global land carbon sink.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1406686-global-land-carbon-sink-response-temperature-precipitation-varies-enso-phase','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1406686-global-land-carbon-sink-response-temperature-precipitation-varies-enso-phase"><span>Global land carbon sink response to temperature and precipitation varies with <span class="hlt">ENSO</span> phase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.</p> <p></p> <p>Climate variability associated with the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and its consequent impacts on land carbon sink interannual variability have been used as a basis for investigating carbon cycle responses to climate variability more broadly, and to inform the sensitivity of the tropical carbon budget to climate change. Past studies have presented opposing views about whether temperature or precipitation is the primary factor driving the response of the land carbon sink to <span class="hlt">ENSO</span>. Here, we show that the dominant driver varies with <span class="hlt">ENSO</span> phase. Whereas tropical temperature explains sink dynamics following El Niño conditions (r TG,P=0.59, p<0.01), the post Lamore » Niña sink is driven largely by tropical precipitation (r PG,T=-0.46, p=0.04). This finding points to an <span class="hlt">ENSO</span>-phase-dependent interplay between water availability and temperature in controlling the carbon uptake response to climate variations in tropical ecosystems. We further find that none of a suite of ten contemporary terrestrial biosphere models captures these <span class="hlt">ENSO</span>-phase-dependent responses, highlighting a key uncertainty in modeling climate impacts on the future of the global land carbon sink.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1376649','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1376649"><span>Global land carbon sink response to temperature and precipitation varies with <span class="hlt">ENSO</span> phase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.</p> <p></p> <p>Climate variability associated with the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and its consequent impacts on land carbon sink interannual variability have been used as a basis for investigating carbon cycle responses to climate variability more broadly, and to inform the sensitivity of the tropical carbon budget to climate change. Past studies have presented opposing views about whether temperature or precipitation is the primary factor driving the response of the land carbon sink to <span class="hlt">ENSO</span>. We show that the dominant driver varies with <span class="hlt">ENSO</span> phase. And whereas tropical temperature explains sink dynamics following El Niño conditions (r TG,P = 0.59, p <more » 0.01), the post La Niña sink is driven largely by tropical precipitation (r PG,T= -0.46, p = 0.04). This finding points to an <span class="hlt">ENSO</span>-phase-dependent interplay between water availability and temperature in controlling the carbon uptake response to climate variations in tropical ecosystems. Furthermore, we find that none of a suite of ten contemporary terrestrial biosphere models captures these <span class="hlt">ENSO</span>-phase-dependent responses, highlighting a key uncertainty in modeling climate impacts on the future of the global land carbon sink.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27152990','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27152990"><span>Extreme <span class="hlt">warm</span> temperatures alter forest phenology and productivity in Europe.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Crabbe, Richard A; Dash, Jadu; Rodriguez-Galiano, Victor F; Janous, Dalibor; Pavelka, Marian; Marek, Michal V</p> <p>2016-09-01</p> <p>Recent climate <span class="hlt">warming</span> has shifted the timing of spring and autumn vegetation phenological <span class="hlt">events</span> in the temperate and boreal forest ecosystems of Europe. In many areas spring phenological <span class="hlt">events</span> start earlier and autumn <span class="hlt">events</span> switch between earlier and later onset. Consequently, the length of growing season in mid and high latitudes of European forest is extended. However, the lagged effects (i.e. the impact of a <span class="hlt">warm</span> spring or autumn on the subsequent phenological <span class="hlt">events</span>) on vegetation phenology and productivity are less explored. In this study, we have (1) characterised extreme <span class="hlt">warm</span> spring and extreme <span class="hlt">warm</span> autumn <span class="hlt">events</span> in Europe during 2003-2011, and (2) investigated if direct impact on forest phenology and productivity due to a specific <span class="hlt">warm</span> <span class="hlt">event</span> translated to a lagged effect in subsequent phenological <span class="hlt">events</span>. We found that warmer <span class="hlt">events</span> in spring occurred extensively in high latitude Europe producing a significant earlier onset of greening (OG) in broadleaf deciduous forest (BLDF) and mixed forest (MF). However, this earlier OG did not show any significant lagged effects on autumnal senescence. Needleleaf evergreen forest (NLEF), BLDF and MF showed a significantly delayed end of senescence (EOS) as a result of extreme <span class="hlt">warm</span> autumn <span class="hlt">events</span>; and in the following year's spring phenological <span class="hlt">events</span>, OG started significantly earlier. Extreme <span class="hlt">warm</span> spring <span class="hlt">events</span> directly led to significant (p=0.0189) increases in the productivity of BLDF. In order to have a complete understanding of ecosystems response to <span class="hlt">warm</span> temperature during key phenological <span class="hlt">events</span>, particularly autumn <span class="hlt">events</span>, the lagged effect on the next growing season should be considered. Copyright © 2016 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004PrOce..60..201A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004PrOce..60..201A"><span>Regime shifts in the Humboldt Current ecosystem [review article</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alheit, Jürgen; Niquen, Miguel</p> <p>2004-02-01</p> <p> main food source. Horse mackerel and mackerel, the main predators of anchovy, increase predation pressure on juvenile and adult anchovies due to extended invasion into the anchovy habitat in warmer years. In contrast to these periods of <span class="hlt">warm</span> and cold temperature anomalies on the decadal scale, <span class="hlt">ENSO</span> <span class="hlt">events</span> do not play an important role for long-term anchovy dynamics, as the anchovy can recover even from strong <span class="hlt">ENSO</span> <span class="hlt">events</span> within 1-2 years. Consequently, the strong 1972-1973 <span class="hlt">ENSO</span> <span class="hlt">event</span> (in combination with overfishing) was not the cause of the famous crash of the Peruvian anchovy fishery in the 1970s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/188464-influence-volcanic-stratospheric-aerosols-interannual-global-climate-variations-ph-thesis','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/188464-influence-volcanic-stratospheric-aerosols-interannual-global-climate-variations-ph-thesis"><span>The influence of volcanic stratospheric aerosols on interannual global climate variations. Ph.D. Thesis</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Andsager, K.M.</p> <p></p> <p>A qualitative physical mechanism has been proposed to explain the forcing of the EI Nino/Southern Oscillation (<span class="hlt">ENSO</span>) by low-latitude volcanic stratospheric aerosols. This mechanism is based on the normal global annual cycle resulting from the normal annual cycle in the distribution of incoming solar radiation. The presence of a volcanic stratospheric aerosol, which backscatters incoming solar radiation, is hypothesized to trigger the <span class="hlt">ENSO</span> through an amplification of the normal annual decrease in wind strength and corresponding increase in sea surface temperatures (SST) in the eastern tropical Pacific Ocean. The observational evidence for an association between the record of volcanic eruptionsmore » and SST and the Southern Oscillation Index (SOI, Tahiti SLP minus Darwin SLP) over the last 120 years is examined using superposed epoch analysis. Composites using as key dates low-latitude volcanic eruptions suggest that these eruptions are followed by statistically significantly <span class="hlt">warm</span> sea surface temperatures at least at the 1 percent level, if not higher, with the greatest <span class="hlt">warming</span> generally occurring in the first three seasons after the eruption. Satellite data on the distribution of recent volcanic aerosols suggests that an aerosol must only be present over the tropics (about 20 deg S to 20 deg N) to trigger an <span class="hlt">ENSO</span> <span class="hlt">event</span>. For the physical mechanism by which an <span class="hlt">ENSO</span> <span class="hlt">event</span> may be triggered by a volcanic stratospheric aerosol, these results and the results of recent computer modeling studies imply the need for a shift away from past emphasis on surface cooling and SLP anomalies and toward consideration of stratospheric <span class="hlt">warming</span> and changes in energy storage and transport.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20020023732&hterms=How+temperature+effect+rate+evaporation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHow%2Btemperature%2Beffect%2Brate%2Bevaporation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20020023732&hterms=How+temperature+effect+rate+evaporation&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHow%2Btemperature%2Beffect%2Brate%2Bevaporation"><span>Tropical Ocean Evaporation/SST Sensitivity and It's Link to Water and Energy Budget Variations During <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robertson, Franklin R.; Marshall, Susan; Oglesby, Robert; Roads, John; Sohn, Byung-Ju; Arnold, James E. (Technical Monitor)</p> <p>2001-01-01</p> <p>The continuing debate over feedback mechanisms governing tropical sea surface temperatures (SSTs) and tropical climate in general has highlighted the diversity of potential checks and balances within the climate system. Competing feedbacks due to changes in surface evaporation, water vapor, and cloud long- and shortwave radiative properties each may serve critical roles in stabilizing or destabilizing the climate system. It is also intriguing that even those climate variations having origins internal to the climate system - changes in ocean heat transport for example, apparently require complementary equilibrating effects by changes in atmospheric energy fluxes. Perhaps the best observational evidence of this is the relatively invariant nature of tropically averaged net radiation exiting the top-of-atmosphere (TOA) as measured by broadband satellite sensors over the past two decades. Thus, analyzing how these feedback mechanisms are operating within the context of current interannual variability may offer considerable insight for anticipating future climate change. In this paper we focus primarily on interannual variations of ocean evaporative fluxes and their significance for coupled water and energy cycles within the tropical climate system. In particular, we use both the da Silva estimates of surface fluxes (based on the Comprehensive Ocean Atmosphere Data Set, COADS) and numerical simulations from several global climate models to examine evaporation sensitivity to perturbations in SST associated with <span class="hlt">warm</span> and cold <span class="hlt">ENSO</span> <span class="hlt">events</span>. The specific questions we address are as follows: (1) What recurring patterns of surface wind and humidity anomalies are present during <span class="hlt">ENSO</span> and how do they combine to yield systematic evaporation anomalies?, (2) What is the resulting tropical ocean mean evaporation-SST sensitivity associated with this climate perturbation?, and (3) What role does this evaporation play in tropical heat and water balance over tropical oceanic regions? We</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015NatCo...6E7154W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015NatCo...6E7154W"><span>Rethinking Indian monsoon rainfall prediction in the context of recent global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Bin; Xiang, Baoqiang; Li, Juan; Webster, Peter J.; Rajeevan, Madhavan N.; Liu, Jian; Ha, Kyung-Ja</p> <p>2015-05-01</p> <p>Prediction of Indian summer monsoon rainfall (ISMR) is at the heart of tropical climate prediction. Despite enormous progress having been made in predicting ISMR since 1886, the operational forecasts during recent decades (1989-2012) have little skill. Here we show, with both dynamical and physical-empirical models, that this recent failure is largely due to the models' inability to capture new predictability sources emerging during recent global <span class="hlt">warming</span>, that is, the development of the central-Pacific El Nino-Southern Oscillation (CP-<span class="hlt">ENSO</span>), the rapid deepening of the Asian Low and the strengthening of North and South Pacific Highs during boreal spring. A physical-empirical model that captures these new predictors can produce an independent forecast skill of 0.51 for 1989-2012 and a 92-year retrospective forecast skill of 0.64 for 1921-2012. The recent low skills of the dynamical models are attributed to deficiencies in capturing the developing CP-<span class="hlt">ENSO</span> and anomalous Asian Low. The results reveal a considerable gap between ISMR prediction skill and predictability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26864787','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26864787"><span>Hydrological cycle effects on the aquatic community in a Neotropical stream of the Andean piedmont during the 2007-2010 <span class="hlt">ENSO</span> <span class="hlt">events</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ríos-Pulgarín, M I; Barletta, M; Mancera-Rodriguez, N J</p> <p>2016-07-01</p> <p>The seasonal and interannual changes in the fish, macroinvertebrates and phycoperiphyton assemblages of the Guarinó River were examined in relation to the physical and chemical environmental changes associated with the hydrological cycle and the El Niño-Niña/Southern Oscillation (<span class="hlt">ENSO</span>) between 2007 and 2010. Four samplings (in dry and rainy seasons) were performed per year. Environmental variables (temperature, pH, conductivity, turbidity, oxygen, total nitrogen, orthophosphate, depth and flow rate) were measured. The temporal patterns of the taxonomic compositions for the three assemblages and the functional composition of fish and macroinvertebrate assemblages with respect to environmental variables were examined through canonical discriminant analysis, multidimensional scaling and multiple correlations. The presence and abundance of fishes, macroinvertebrates and algae species were regulated by environmental variables associated with extreme hydrological <span class="hlt">events</span>, which derived from the natural torrential regimen of the basin and larger-scale phenomena, such as El Niño and La Niña. Fish abundance and richness were significantly correlated with algal density and pH, the macroinvertebrate density was negatively related to the flow rate and the richness was positively correlated with algal density. The algae richness was positively correlated with pH and negatively correlated with the flow rate and nitrogen. The algal density was positively correlated with pH and temperature and negatively correlated with river flow. The phycoperiphyton assemblage exhibited more direct responses in its density and richness to the hydrological changes (r(2) = 0·743 and 0·800, respectively). In functional terms, the El Niño phenomenon was defined by a greater abundance of omnivorous and insectivorous fishes, as well as filter feeders, scrapers and macroinvertebrate predators. During La Niña, a greater abundance of benthic fishes (both detritivorous and insectivorous) and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC32B..04S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC32B..04S"><span>An Ensemble Approach to Understanding the <span class="hlt">ENSO</span> Response to Climate Change</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stevenson, S.; Capotondi, A.; Fasullo, J.; Otto-Bliesner, B. L.</p> <p>2017-12-01</p> <p>The dynamics of the El Nino/Southern Oscillation (<span class="hlt">ENSO</span>) are known to be sensitive to changes in background climate conditions, as well as atmosphere/ocean feedbacks. However, the degree to which shifts in <span class="hlt">ENSO</span> characteristics can be robustly attributed to external climate forcings remains unknown. Efforts to assess these changes in a multi-model framework are subject to uncertainties due to both differing model physics and internal <span class="hlt">ENSO</span> variability. New community ensembles created at the National Center for Atmospheric Research and the NOAA Geophysical Fluid Dynamics Laboratory are ideally suited to addressing this problem, providing many realizations of the climate of the 850-2100 period with a combination of both natural and anthropogenic climate forcing factors. Here we analyze the impacts of external forcing on El Nino and La Nina evolution using four sets of simulations: the CESM Last Millennium Ensemble (CESM-LME), which covers the 850-2005 period and provides long-term context for forced responses; the Large Ensemble (CESM-LE), which includes 20th century and 21st century (RCP8.5) projections; the Medium Ensemble (CESM-ME), which is composed of 21st century RCP4.5 projections; and a large ensemble with the GFDL ESM2M, which includes 20th century and RCP8.5 projections. In the CESM, <span class="hlt">ENSO</span> variance increases slightly over the 20th century in all ensembles, with the effects becoming much larger during the 21st. The slower increase in variance over the 20th century is shown to arise from compensating influences from greenhouse gas (GHG) and anthropogenic aerosol emissions, which give way to GHG-dominated effects by 2100. However, the 21st century variance increase is not robust: CESM and the ESM2M differ drastically in their <span class="hlt">ENSO</span> projections. The mechanisms for these inter-model differences are discussed, as are the implications for the design of future multi-model <span class="hlt">ENSO</span> projection experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009pcms.confE.115B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009pcms.confE.115B"><span>Analysis of <span class="hlt">warm</span> convective rain <span class="hlt">events</span> in Catalonia</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ballart, D.; Figuerola, F.; Aran, M.; Rigo, T.</p> <p>2009-09-01</p> <p> steep slopes. These factors increase the number of flash floods and the risk indexes. In the present study it is showed the general characteristics of the <span class="hlt">warm</span> rain <span class="hlt">events</span> observed in Catalonia, using meteorological, pluviometric, thermodynamic, and remote sensing data. Beside this, other heavy rain <span class="hlt">events</span> with different features have been analyzed with the purpose of identify the main differences and to improve the knowledge in order to provide enough information for surveillance tasks</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70043240','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70043240"><span>A westward extension of the <span class="hlt">warm</span> pool leads to a westward extension of the Walker circulation, drying eastern Africa</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Williams, A. Park; Funk, Christopher C.</p> <p>2011-01-01</p> <p>Observations and simulations link anthropogenic greenhouse and aerosol emissions with rapidly increasing Indian Ocean sea surface temperatures (SSTs). Over the past 60 years, the Indian Ocean <span class="hlt">warmed</span> two to three times faster than the central tropical Pacific, extending the tropical <span class="hlt">warm</span> pool to the west by ~40° longitude (>4,000 km). This propensity toward rapid <span class="hlt">warming</span> in the Indian Ocean has been the dominant mode of interannual variability among SSTs throughout the tropical Indian and Pacific Oceans (55°E–140°W) since at least 1948, explaining more variance than anomalies associated with the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). In the atmosphere, the primary mode of variability has been a corresponding trend toward greatly increased convection and precipitation over the tropical Indian Ocean. The temperature and rainfall increases in this region have produced a westward extension of the western, ascending branch of the atmospheric Walker circulation. Diabatic heating due to increased mid-tropospheric water vapor condensation elicits a westward atmospheric response that sends an easterly flow of dry air aloft toward eastern Africa. In recent decades (1980–2009), this response has suppressed convection over tropical eastern Africa, decreasing precipitation during the ‘long-rains’ season of March–June. This trend toward drought contrasts with projections of increased rainfall in eastern Africa and more ‘El Niño-like’ conditions globally by the Intergovernmental Panel on Climate Change. Increased Indian Ocean SSTs appear likely to continue to strongly modulate the <span class="hlt">Warm</span> Pool circulation, reducing precipitation in eastern Africa, regardless of whether the projected trend in <span class="hlt">ENSO</span> is realized. These results have important food security implications, informing agricultural development, environmental conservation, and water resource planning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7249H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7249H"><span>Subsurface <span class="hlt">warming</span> in the subpolar North Atlantic during rapid climate <span class="hlt">events</span> in the Early and Mid-Pleistocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hernández-Almeida, Iván; Sierro, Francisco; Cacho, Isabel; Abel Flores, José</p> <p>2014-05-01</p> <p>A new high-resolution reconstruction of the temperature and salinity of the subsurface waters using paired Mg/Ca-δ18O measurements on the planktonic foraminifera Neogloboquadrina pachyderma sinistrorsa (sin.) was conducted on a deep-sea sediment core in the subpolar North Atlantic (Site U1314). This study aims to reconstruct millennial-scale subsurface hydrography variations during the Early and Mid-Pleistocene (MIS 31-19). These rapid climate <span class="hlt">events</span> are characterized by abrupt shifts between <span class="hlt">warm</span>/cold conditions, and ice-sheet oscillations, as evidenced by major ice rafting <span class="hlt">events</span> recorded in the North Atlantic sediments (Hernández-Almeida et al., 2012), similar to those found during the Last Glacial period (Marcott et al, 2011). The Mg/Ca derived paleotemperature and salinity oscillations prior and during IRD discharges at Site U1314 are related to changes in intermediate circulation. The increases in Mg/Ca paleotemperatures and salinities during the IRD <span class="hlt">event</span> are preceded by short episodes of cooling and freshening of subsurface waters. The response of the AMOC to this perturbation is an increased of <span class="hlt">warm</span> and salty water coming from the south, transported to high latitudes in the North Atlantic beneath the thermocline. This process is accompanied by a southward shift in the convection cell from the Nordic Seas to the subpolar North Atlantic and better ventilation of the North Atlantic at mid-depths. Poleward transport of <span class="hlt">warm</span> and salty subsurface subtropical waters causes intense basal melting and thinning of marine ice-shelves, that culminates in large-scale instability of the ice sheets, retreat of the grounding line and iceberg discharge. The mechanism proposed involves the coupling of the AMOC with ice-sheet dynamics, and would explain the presence of these fluctuations before the establishment of high-amplitude 100-kyr glacial cycles. Hernández-Almeida, I., Sierro, F.J., Cacho, I., Flores, J.A., 2012. Impact of suborbital climate changes in the North</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFMPP23B1394C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFMPP23B1394C"><span>Assessing the El Niño/Southern Oscillation proxy potential of the sediment record from Genovesa Crater Lake, Galápagos</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Conroy, J.; Overpeck, J. T.; Cole, J. E.; Collins, A.; Bush, M. B.; Steinitz-Kannan, M.</p> <p>2009-12-01</p> <p>Paleoclimate records from the tropical Pacific Ocean suggest significant changes in sea surface temperature (SST) and El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) variability during the Holocene, but there are still many spatial and temporal gaps in our understanding of past tropical Pacific climate change. Many of the annually-resolved records of past <span class="hlt">ENSO</span> variability are short, discontinuous, or from outside the tropical Pacific, whereas those records from the tropical Pacific often do not have the temporal resolution to accurately resolve the timing of individual El Niño <span class="hlt">events</span>. Paleoclimate records from the Galápagos Islands are ideal for reconstructing past changes in tropical Pacific climate variability, since these islands are located in the heart of the <span class="hlt">ENSO</span> phenomenon. Records from other lakes in the Galápagos have already suggested significant changes in <span class="hlt">ENSO</span> frequency and the mean state of the eastern tropical Pacific throughout the Holocene. However, these lake sediment records have interannual temporal resolution at best, hampering our understanding of past <span class="hlt">ENSO</span> dynamics. Here we present our initial findings from an additional Galápagos lake: Genovesa Crater Lake. The Genovesa sediment record is finely laminated and will likely provide a high-resolution paleoclimate record for this region of the tropical Pacific, as well as a means to test the hypotheses proposed by other <span class="hlt">ENSO</span> reconstructions. Scanning μ-XRF time series of elemental abundances in the Genovesa sediment cores indicate that peaks in Ca abundance reflect the <span class="hlt">warm</span>/wet season and El Niño <span class="hlt">events</span>. We hypothesize that during <span class="hlt">warm</span>/wet periods, a reduced sea bird population around the typically guanotropic Genovesa Crater Lake reduces the guano input into the lake, allowing layers of relatively clean carbonate to precipitate. During the cool season and La Niña <span class="hlt">events</span>, guano input dilutes the precipitated carbonate. High-resolution pollen and diatom analyses will provide additional constraints on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.1643C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.1643C"><span>The influence of <span class="hlt">ENSO</span> on an oceanic eddy pair in the South China Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chu, Xiaoqing; Dong, Changming; Qi, Yiquan</p> <p>2017-03-01</p> <p>An eddy pair off the Vietnam coast is one of the most important features of the summertime South China Sea circulation. Its variability is of interest due to its profound impact on regional climate, ecosystems, biological processes, and fisheries. This study examines the influence of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>), a basin-scale climatic mode, on the interannual variability of this regional eddy pair using satellite observational data and historical hydrographic measurements. Over the last three decades, the eddy pair strengthened in 1994 and 2002, and weakened in 2006, 2007, and 2008. It was absent in 1988, 1995, 1998, and 2010, coinciding with strong El Nino-to-La Nina transitions. Composite analyses showed that the strong transition <span class="hlt">events</span> of <span class="hlt">ENSO</span> led to radical changes in the summer monsoon, through the forcing of a unique sea surface temperature anomaly structure over the tropical Indo-Pacific basin. With weaker zonal wind, a more northward wind direction, and the disappearance of a pair of positive and negative wind stress curls, the eastward current jet turns northward along the Vietnam coast and the eddy pair disappears.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GeoRL..44.6334Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GeoRL..44.6334Z"><span>Importance of convective parameterization in <span class="hlt">ENSO</span> predictions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhu, Jieshun; Kumar, Arun; Wang, Wanqiu; Hu, Zeng-Zhen; Huang, Bohua; Balmaseda, Magdalena A.</p> <p>2017-06-01</p> <p>This letter explored the influence of atmospheric convection scheme on El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) predictions using a set of hindcast experiments. Specifically, a low-resolution version of the Climate Forecast System version 2 is used for 12 month hindcasts starting from each April during 1982-2011. The hindcast experiments are repeated with three atmospheric convection schemes. All three hindcasts apply the identical initialization with ocean initial conditions taken from the European Centre for Medium-Range Weather Forecasts and atmosphere/land initial states from the National Centers for Environmental Prediction. Assessments indicate a substantial sensitivity of the sea surface temperature prediction skill to the different convection schemes, particularly over the eastern tropical Pacific. For the Niño 3.4 index, the anomaly correlation skill can differ by 0.1-0.2 at lead times longer than 2 months. Long-term simulations are further conducted with the three convection schemes to understand the differences in prediction skill. By conducting heat budget analyses for the mixed-layer temperature anomalies, it is suggested that the convection scheme having the highest skill simulates stronger and more realistic coupled feedbacks related to <span class="hlt">ENSO</span>. Particularly, the strength of the Ekman pumping feedback is better represented, which is traced to more realistic simulation of surface wind stress. Our results imply that improving the mean state simulations in coupled (ocean-atmosphere) general circulation model (e.g., ameliorating the Intertropical Convergence Zone simulation) might further improve our <span class="hlt">ENSO</span> prediction capability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120001939','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120001939"><span>Modeling and Observations of the Response of Tropical Tropospheric Ozone to <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Waugh, D. W.; Lang, C.; Rodriquez, J. M.; Nielsen, J. E.</p> <p>2012-01-01</p> <p>The El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) is the dominant mode of tropical variability on interannual time scales. <span class="hlt">ENSO</span> appears to extend its influence into the chemical composition of the tropical troposphere, Recent results have revealed an <span class="hlt">ENSO</span> induced wave-1 anomaly in observed tropical tropospheric column ozone, This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this result using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years, An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region, We will show targeted comparisons with SHADOZ ozonesondes over these regions to provide insight into the vertical structure. Also, comparisons with NASA's Aura satellite Microwave Limb Sounder (MLS) and Tropospheric Emissions Spectrometer (TES) instruments and other appropriate data sets will be shown. In addition, the water vapor response to <span class="hlt">ENSO</span> will be compared to help illuminate its role relative to dynamics in impacting ozone concentrations. These results indicate that the tropospheric ozone response to <span class="hlt">ENSO</span> is potentially a very useful chemistry-climate diagnostic and should be considered in future modeling assessments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B41C0056M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B41C0056M"><span>Modeling the Impacts of Long-Term <span class="hlt">Warming</span> Trends on Gross Primary Productivity Across North America</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mekonnen, Z. A.; Grant, R. F.</p> <p>2014-12-01</p> <p>There is evidence of <span class="hlt">warming</span> over recent decades in most regions of North America (NA) that affects ecosystem productivity and the past decade has been the warmest since instrumental records of global surface temperatures began. In this study, we examined the spatial and temporal variability and trends of <span class="hlt">warming</span> across NA using climate data from the North America Regional Reanalysis (NARR) from 1979 to 2010 with a 3-hourly time-step and 0.250 x 0.250 spatial resolution as part of the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP). A comprehensive mathematical process model, ecosys was used to simulate impacts of this variability in <span class="hlt">warming</span> on gross primary productivity (GPP). In a test of model results, annual GPP modeled for pixels which corresponded to the locations of 25 eddy covariance towers correlated well (R2=0.76) with annual GPP derived from the flux towers in 2005. At the continental scale long-term (2000 - 2010) annual average modeled GPP for NA correlated well (geographically weighed regression R2 = 0.8) with MODIS GPP, demonstrating close similarities in spatial patterns. Results from the NARR indicated that most areas of NA, particularly high latitude regions, have experienced <span class="hlt">warming</span> but changes in precipitation vary spatially over the last three decades. GPP modeled in most areas with lower mean annual air temperature (Ta), such as those in boreal climate zones, increased due to early spring and late autumn <span class="hlt">warming</span> observed in NARR. However modeled GPP declined in most southwestern regions of NA, due to water stress from rising Ta and declining precipitation. Overall, GPP modeled across NA had a positive trend of +0.025 P g C yr-1 with a range of -1.16 to 0.87 P g C yr-1 from the long-term mean. Interannual variability of GPP was the greatest in southwest of US and part of the Great Plains, which could be as a result of frequent El Niño-Southern Oscillation' (<span class="hlt">ENSO</span>) <span class="hlt">events</span> that led to major droughts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ECSS..194..172W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ECSS..194..172W"><span>The Gulf of Carpentaria heated Torres Strait and the Northern Great Barrier Reef during the 2016 mass coral bleaching <span class="hlt">event</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wolanski, E.; Andutta, F.; Deleersnijder, E.; Li, Y.; Thomas, C. J.</p> <p>2017-07-01</p> <p>The 2015/16 <span class="hlt">ENSO</span> <span class="hlt">event</span> increased the temperature of waters surrounding northeast Australia to above 30 °C, with large patches of water reaching 32 °C, for over two months, which led to severe bleaching of corals of the Northern Great Barrier Reef (NGBR). This study provides evidence gained from remote-sensing data, oceanographic data and oceanographic modeling, that three factors caused this excessive heating, namely: 1) the shutdown of the North Queensland Coastal Current, which would otherwise have flushed and cooled the Northern Coral Sea and the NGBR through tidal mixing 2) the advection of <span class="hlt">warm</span> (>30 °C) water from the Gulf of Carpentaria eastward through Torres Strait and then southward over the NGBR continental shelf, and 3) presumably local solar heating. The eastward flux of this <span class="hlt">warm</span> water through Torres Strait was driven by a mean sea level difference on either side of the strait that in turn was controlled by the wind, which also generated the southward advection of this <span class="hlt">warm</span> water onto the NGBR shelf. On the NGBR shelf, the residence time of this <span class="hlt">warm</span> water was longer inshore than offshore, and this may explain the observed cross-shelf gradient of coral bleaching intensity. The fate of the Great Barrier Reef is thus controlled by the oceanography of surrounding seas.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A23M..08L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A23M..08L"><span>Tropical cyclone prediction skills - MJO and <span class="hlt">ENSO</span> dependence in S2S data sets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lee, C. Y.; Camargo, S.; Vitart, F.; Sobel, A. H.; Tippett, M.</p> <p>2017-12-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and the Madden-Julian Oscillation (MJO) are two important climate controls on tropical cyclone (TC) activity. The seasonal prediction skill of dynamical models is determined in large part by their accurate representations of the <span class="hlt">ENSO</span>-TC relationship. Regarding intraseasonal TC variability, observations suggest MJO to be the primary control. Given the ongoing effort to develop dynamical seasonal-to-subseasonal (S2S) TC predictions, it is important to examine whether the global models, running on S2S timescales, are able to reproduce these known <span class="hlt">ENSO</span>-TC and MJO-TC relationships, and how this ability affects forecasting skill. Results from the S2S project (from F. Vitart) suggest that global models have skill in predicting MJO phase with up to two weeks of lead time (four weeks for ECMWF). Meanwhile, our results show that, qualitatively speaking, the MJO-TC relationship in storm genesis is reasonably captured, with some models (e.g., ECMWF, BoM, NCEP, MetFr) performing better than the others. However, we also find that model skill in predicting basin-wide genesis and accumulated cyclone energy (ACE) are mainly due to the models' ability to capture the climatological seasonality. Removing the seasonality significantly reduces the models' skill; even the best model (ECMWF) in the most reliable basin (western north Pacific and Atlantic) has very little skill (close to 0.1 in Brier skill score for genesis and close to 0 in rank probability skill score for ACE). This brings up the question: do any factors contribute to intraseasonal TC prediction skill other than seasonality? Is the low skill, after removing the seasonality, due to poor MJO and <span class="hlt">ENSO</span> simulations, or to poor representation of other <span class="hlt">ENSO</span>-TC or MJO-TC relationships, such as <span class="hlt">ENSO</span>'s impact on the storm tracks? We will quantitatively discuss the dependence of the TC prediction skill on <span class="hlt">ENSO</span> and MJO, focusing on Western North Pacific and Atlantic, where we have sufficient</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMEP23B0964B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMEP23B0964B"><span><span class="hlt">ENSO</span>-Related Variability in Wave Climate Drives Greater Erosion Potential on Central Pacific Atolls</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bramante, J. F.; Ashton, A. D.; Donnelly, J. P.</p> <p>2015-12-01</p> <p>The El Nino Southern Oscillation (<span class="hlt">ENSO</span>) modulates atmospheric circulation across the equatorial Pacific over a periodic time scale of 2-7 years. Despite the importance of this climate mode in forcing storm generation and trade wind variability, its impact on the wave climate incident on central Pacific atolls has not been addressed. We used the NOAA Wavewatch III CFSR reanalysis hindcasts (1979-2007) to examine the influence of <span class="hlt">ENSO</span> on sediment mobility and transport at Kwajalein Atoll (8.8°N, 167.7°E). We found that during El Nino <span class="hlt">event</span> years, easterly trade winds incident on the atoll weakened by 4% compared to normal years and 17% relative to La Nina <span class="hlt">event</span> years. Despite this decrease in wind strength, significant wave heights incident on the atoll were 3-4% greater during El Nino <span class="hlt">event</span> years. Using machine learning to partition these waves revealed that the greater El Nino wave heights originated mainly from greater storm winds near the atoll. The southeastern shift in tropical cyclone genesis location during El Nino years forced these storm winds and contributed to the 7% and 16% increases in annual wave energy relative to normal and La Nina years, respectively. Using nested SWAN and XBeach models we determined that the additional wave energy during El Nino <span class="hlt">event</span> years significantly increased potential sediment mobility at Kwajalein Atoll and led to greater net offshore transport on its most populous island. The larger storm waves likely deplete ocean-facing beaches and reef flats of sediment, but increase the supply of sediment to the atoll lagoon across open reef platforms that are not supporting islands. We discuss further explicit modelling of storms passing over the atoll to elucidate the confounding role of storm surge on the net erosional/depositional effects of these waves. Extrapolating our results to recent Wavewatch III forecasts leads us to conclude that climate change-linked increases in wave height and storm wave energy will increase erosion on</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AtmRe.198...56K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AtmRe.198...56K"><span>Variability modes of precipitation along a Central Mediterranean area and their relations with <span class="hlt">ENSO</span>, NAO, and other climatic patterns</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kalimeris, Anastasios; Ranieri, Ezio; Founda, Dimitra; Norrant, Caroline</p> <p>2017-12-01</p> <p>This study analyses a century-long set of precipitation time series in the Central Mediterranean (encompassing the Greek Ionian and the Italian Puglia regions) and investigates the statistically significant modes of the interannual precipitation variability using efficient methods of spectral decomposition. The statistical relations and the possible physical couplings between the detected modes and the global or hemispheric patterns of climatic variability (the El Niño Southern Oscillation or <span class="hlt">ENSO</span>, the North Atlantic Oscillation or NAO, the East Atlantic or EA, the Scandinavian or SCAND, and others) were examined in the time-frequency domain and low-order synchronization <span class="hlt">events</span> were sought. Significant modes of precipitation variability were detected in the Taranto Gulf and the southern part of the Greek Ionian region at the sub-decadal scales (mostly driven by the SCAND pattern) and particularly at the decadal and quasi-decadal scales, where strong relations found with the <span class="hlt">ENSO</span> activity (under complex implications of EA and NAO) prior to the 1930s or after the early-1970s. The precipitation variations in the Adriatic stations of Puglia are dominated by significant bi-decadal modes which found to be coherent with the <span class="hlt">ENSO</span> activity and also weakly related with the Atlantic Ocean sea surface temperature intrinsic variability. Additionally, important discontinuities characterize the evolution of precipitation in certain stations of the Taranto Gulf and the Greek Ionian region during the early-1960s and particularly during the early-1970s, followed by significant reductions in the mean annual precipitation. These discontinuities seem to be associated with regional effects of NAO and SCAND, probably combined with the impact of the 1970s climatic shift in the Pacific and the <span class="hlt">ENSO</span> variability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ACP....18.6939P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ACP....18.6939P"><span>Multi-year assimilation of IASI and MLS ozone retrievals: variability of tropospheric ozone over the tropics in response to <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Peiro, Hélène; Emili, Emanuele; Cariolle, Daniel; Barret, Brice; Le Flochmoën, Eric</p> <p>2018-05-01</p> <p>The Infrared Atmospheric Sounder Instrument (IASI) allows global coverage with very high spatial resolution and its measurements are promising for long-term ozone monitoring. In this study, Microwave Limb Sounder (MLS) O3 profiles and IASI O3 partial columns (1013.25-345 hPa) are assimilated in a chemistry transport model to produce 6-hourly analyses of tropospheric ozone for 6 years (2008-2013). We have compared and evaluated the IASI-MLS analysis and the MLS analysis to assess the added value of IASI measurements. The global chemical transport model MOCAGE (MOdèle de Chimie Atmosphérique à Grande Echelle) has been used with a linear ozone chemistry scheme and meteorological forcing fields from ERA-Interim (ECMWF global reanalysis) with a horizontal resolution of 2° × 2° and 60 vertical levels. The MLS and IASI O3 retrievals have been assimilated with a 4-D variational algorithm to constrain stratospheric and tropospheric ozone respectively. The ozone analyses are validated against ozone soundings and tropospheric column ozone (TCO) from the OMI-MLS residual method. In addition, an Ozone <span class="hlt">ENSO</span> Index (OEI) is computed from the analysis to validate the TCO variability during the <span class="hlt">ENSO</span> <span class="hlt">events</span>. We show that the assimilation of IASI reproduces the variability of tropospheric ozone well during the period under study. The variability deduced from the IASI-MLS analysis and the OMI-MLS measurements are similar for the period of study. The IASI-MLS analysis can reproduce the extreme oscillation of tropospheric ozone caused by <span class="hlt">ENSO</span> <span class="hlt">events</span> over the tropical Pacific Ocean, although a correction is required to reduce a constant bias present in the IASI-MLS analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007QSRv...26.2012C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007QSRv...26.2012C"><span>Abrupt climate <span class="hlt">warming</span> in East Antarctica during the early Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Cremer, Holger; Heiri, Oliver; Wagner, Bernd; Wagner-Cremer, Friederike</p> <p>2007-08-01</p> <p>We report a centennial-scale <span class="hlt">warming</span> <span class="hlt">event</span> between 8600 and 8400 cal BP from Amery Oasis, East Antarctica, that is documented by the geochemical record in a lacustrine sediment sequence. The organic carbon content, the C/S ratio, and the sedimentation rate in this core have distinctly elevated values around 8500 y ago reflecting relatively <span class="hlt">warm</span> and ice-free conditions that led to well-ventilated conditions in the lake and considerable sedimentation of both autochthonous and allochthonous organic matter on the lake bottom. This abrupt <span class="hlt">warming</span> <span class="hlt">event</span> occurred concurrently with reported <span class="hlt">warm</span> climatic conditions in the Southern Ocean while the climate in central East Antarctic remained cold. The comparison of the spatial and temporal variability of <span class="hlt">warm</span> climatic periods documented in various terrestrial, marine, and glacial archives from East Antarctica elucidates the uniqueness of the centennial-scale <span class="hlt">warming</span> <span class="hlt">event</span> in the Amery Oasis. We also discuss a possible correlation of the Amery <span class="hlt">warming</span> <span class="hlt">event</span> with the abrupt climatic deterioration around 8200 cal BP on the Northern Hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC41B1022P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC41B1022P"><span>Biennial-Aligned Lunisolar-Forcing of <span class="hlt">ENSO</span>: Implications for Simplified Climate Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pukite, P. R.</p> <p>2017-12-01</p> <p>By solving Laplace's tidal equations along the equatorial Pacific thermocline, assuming a delayed-differential effective gravity forcing due to a combined lunar+solar (lunisolar) stimulus, we are able to precisely match <span class="hlt">ENSO</span> periodic variations over wide intervals. The underlying pattern is difficult to decode by conventional means such as spectral analysis, which is why it has remained hidden for so long, despite the excellent agreement in the time-domain. What occurs is that a non-linear seasonal modulation with monthly and fortnightly lunar impulses along with a biennially-aligned "see-saw" is enough to cause a physical aliasing and thus multiple folding in the frequency spectrum. So, instead of a conventional spectral tidal decomposition, we opted for a time-domain cross-validating approach to calibrate the amplitude and phasing of the lunisolar cycles. As the lunar forcing consists of three fundamental periods (draconic, anomalistic, synodic), we used the measured Earth's length-of-day (LOD) decomposed and resolved at a monthly time-scale [1] to align the amplitude and phase precisely. Even slight variations from the known values of the long-period tides will degrade the fit, so a high-resolution calibration is possible. Moreover, a narrow training segment from 1880-1920 using NINO34/SOI data is adequate to extrapolate the cycles of the past 100 years (see attached figure). To further understand the biennial impact of a yearly differential-delay, we were able to also decompose using difference equations the historical sea-level-height readings at Sydney harbor to clearly expose the <span class="hlt">ENSO</span> behavior. Finally, the <span class="hlt">ENSO</span> lunisolar model was validated by back-extrapolating to Unified <span class="hlt">ENSO</span> coral proxy (UEP) records dating to 1650. The quasi-biennial oscillation (QBO) behavior of equatorial stratospheric winds derives following a similar pattern to <span class="hlt">ENSO</span> via the tidal equations, but with an emphasis on draconic forcing. This improvement in <span class="hlt">ENSO</span> and QBO understanding has</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996PhDT.........7X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996PhDT.........7X"><span>Predictability of a Coupled Model of <span class="hlt">ENSO</span> Using Singular Vector Analysis: Optimal Growth and Forecast Skill.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xue, Yan</p> <p></p> <p>The optimal growth and its relationship with the forecast skill of the Zebiak and Cane model are studied using a simple statistical model best fit to the original nonlinear model and local linear tangent models about idealized climatic states (the mean background and <span class="hlt">ENSO</span> cycles in a long model run), and the actual forecast states, including two sets of runs using two different initialization procedures. The seasonally varying Markov model best fit to a suite of 3-year forecasts in a reduced EOF space (18 EOFs) fits the original nonlinear model reasonably well and has comparable or better forecast skill. The initial error growth in a linear evolution operator A is governed by the eigenvalues of A^{T}A, and the square roots of eigenvalues and eigenvectors of A^{T}A are named singular values and singular vectors. One dominant growing singular vector is found, and the optimal 6 month growth rate is largest for a (boreal) spring start and smallest for a fall start. Most of the variation in the optimal growth rate of the two forecasts is seasonal, attributable to the seasonal variations in the mean background, except that in the cold <span class="hlt">events</span> it is substantially suppressed. It is found that the mean background (zero anomaly) is the most unstable state, and the "forecast IC states" are more unstable than the "coupled model states". One dominant growing singular vector is found, characterized by north-south and east -west dipoles, convergent winds on the equator in the eastern Pacific and a deepened thermocline in the whole equatorial belt. This singular vector is insensitive to initial time and optimization time, but its final pattern is a strong function of initial states. The <span class="hlt">ENSO</span> system is inherently unpredictable for the dominant singular vector can amplify 5-fold to 24-fold in 6 months and evolve into the large scales characteristic of <span class="hlt">ENSO</span>. However, the inherent <span class="hlt">ENSO</span> predictability is only a secondary factor, while the mismatches between the model and data is a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18409426','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18409426"><span>Phenological sequences reveal aggregate life history response to climatic <span class="hlt">warming</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Post, Eric S; Pedersen, Christian; Wilmers, Christopher C; Forchhammer, Mads C</p> <p>2008-02-01</p> <p>Climatic <span class="hlt">warming</span> is associated with organisms breeding earlier in the season than is typical for their species. In some species, however, response to <span class="hlt">warming</span> is more complex than a simple advance in the timing of all life history <span class="hlt">events</span> preceding reproduction. Disparities in the extent to which different components of the reproductive phenology of organisms vary with climatic <span class="hlt">warming</span> indicate that not all life history <span class="hlt">events</span> are equally responsive to environmental variation. Here, we propose that our understanding of phenological response to climate change can be improved by considering entire sequences of <span class="hlt">events</span> comprising the aggregate life histories of organisms preceding reproduction. We present results of a two-year <span class="hlt">warming</span> experiment conducted on 33 individuals of three plant species inhabiting a low-arctic site. Analysis of phenological sequences of three key <span class="hlt">events</span> for each species revealed how the aggregate life histories preceding reproduction responded to <span class="hlt">warming</span>, and which individual <span class="hlt">events</span> exerted the greatest influence on aggregate life history variation. For alpine chickweed (Cerastium alpinum), <span class="hlt">warming</span> elicited a shortening of the duration of the emergence stage by 2.5 days on average, but the aggregate life history did not differ between <span class="hlt">warmed</span> and ambient plots. For gray willow (Salix glauca), however, all phenological <span class="hlt">events</span> monitored occurred earlier on <span class="hlt">warmed</span> than on ambient plots, and <span class="hlt">warming</span> reduced the aggregate life history of this species by 22 days on average. Similarly, in dwarf birch (Betula nana), <span class="hlt">warming</span> advanced flower bud set, blooming, and fruit set and reduced the aggregate life history by 27 days on average. Our approach provides important insight into life history responses of many organisms to climate change and other forms of environmental variation. Such insight may be compromised by considering changes in individual phenological <span class="hlt">events</span> in isolation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122.9107H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122.9107H"><span>Exploring the combined effects of the Arctic Oscillation and <span class="hlt">ENSO</span> on the wintertime climate over East Asia using self-organizing maps</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Wenyu; Chen, Ruyan; Yang, Zifan; Wang, Bin; Ma, Wenqian</p> <p>2017-09-01</p> <p>To examine the combined effects of the different spatial patterns of the Arctic Oscillation (AO)-related sea level pressure (SLP) anomalies and the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>)-related sea surface temperature (SST) anomalies on the wintertime surface temperature anomalies over East Asia, a nonlinear method based on self-organizing maps is employed. Investigation of identified regimes reveals that the AO can affect East Asian temperature anomalies when there are significant SLP anomalies over the Arctic Ocean and northern parts of Eurasian continent. Analogously, <span class="hlt">ENSO</span> is found to affect East Asian temperature anomalies when significant SST anomalies are present over the tropical central Pacific. The regimes with the warmest and coldest temperature anomalies over East Asia are both associated with the negative phase of the AO. The <span class="hlt">ENSO</span>-activated, Pacific-East Asian teleconnection pattern could affect the higher latitude continental regions when the impact of the AO is switched off. When the spatial patterns of the AO and <span class="hlt">ENSO</span> have significant, but opposite, impacts on the coastal winds, no obvious temperature anomalies can be observed over south China. Further, the circulation state with nearly the same AO and Niño3 indices may drive rather different responses in surface temperature over East Asia. The well-known continuous weakening (recovery) of the East Asian winter monsoon that occurred around 1988 (2009) can be attributed to the transitions of the spatial patterns of the SLP anomalies over the Arctic Ocean and Eurasian continent, through their modulation on the occurrences of the Ural and central Siberian blocking <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.6043P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.6043P"><span>The crucial role of the Green Sahara in damping <span class="hlt">ENSO</span> variability during the Holocene</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pausata, Francesco S. R.; Zhang, Qiong; Muschitiello, Francesco; Stager, Curt</p> <p>2016-04-01</p> <p>Several paleoclimate records show that the <span class="hlt">ENSO</span> variability may have been remarkably smaller during the mid Holocene (MH) relative to today; however, MH model simulations in which only the orbital forcing is taken into account are not able to fully capture the magnitude of this change. We use a fully coupled simulation for 6000 yr BP (MH) in which we prescribed not only the MH orbital forcing but also Saharan vegetation and reduced dust concentrations. By performing a set of idealized experiments in which each forcing is changed in turn, we show that when accounting for both vegetated Sahara and reduced dust concentrations, the amplitude of the <span class="hlt">ENSO</span> cycle and its variability are remarkably reduced (~25%) compared to case when only the orbital forcing is prescribed (only 7%). The changes in <span class="hlt">ENSO</span> behavior are accompanied by damping of the Atlantic El Niño variability (almost 50%). The simulated changes in equatorial variability are connected to the momentous strengthening of the WAM monsoon, which extents all the way to the northernmost part of the Sahara desert. Such changes in the WAM and in the atmospheric circulation over the equatorial Atlantic led to a reduction of the Atlantic El Niño variability and affect <span class="hlt">ENSO</span> behavior through the atmospheric circulation bridge between the Atlantic and the Pacific. Hence, our results suggest orbital forcing is likely not the only forcing at play behind the changes in <span class="hlt">ENSO</span> behavior and point to the changes over equatorial Atlantic connected to the Sahara greening as a crucial factor in altering the <span class="hlt">ENSO</span> spatiotemporal characteristic during the MH.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70155280','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70155280"><span>A westward extension of the <span class="hlt">warm</span> pool leads to a westward extension of the Walker circulation, drying eastern Africa</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Funk, Christopher C.; Williams, A. Park</p> <p>2011-01-01</p> <p>Observations and simulations link anthropogenic greenhouse and aerosol emissions with rapidly increasing Indian Ocean sea surface temperatures (SSTs). Over the past 60 years, the Indian Ocean <span class="hlt">warmed</span> two to three times faster than the central tropical Pacific, extending the tropical <span class="hlt">warm</span> pool to the west by ~40° longitude (>4,000 km). This propensity toward rapid <span class="hlt">warming</span> in the Indian Ocean has been the dominant mode of interannual variability among SSTs throughout the tropical Indian and Pacific Oceans (55°E–140°W) since at least 1948, explaining more variance than anomalies associated with the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). In the atmosphere, the primary mode of variability has been a corresponding trend toward greatly increased convection and precipitation over the tropical Indian Ocean. The temperature and rainfall increases in this region have produced a westward extension of the western, ascending branch of the atmospheric Walker circulation. Diabatic heating due to increased mid-tropospheric water vapor condensation elicits a westward atmospheric response that sends an easterly flow of dry air aloft toward eastern Africa. In recent decades (1980–2009), this response has suppressed convection over tropical eastern Africa, decreasing precipitation during the ‘long-rains’ season of March–June. This trend toward drought contrasts with projections of increased rainfall in eastern Africa and more ‘El Niño-like’ conditions globally by the Intergovernmental Panel on Climate Change. Increased Indian Ocean SSTs appear likely to continue to strongly modulate the <span class="hlt">Warm</span> Pool circulation, reducing precipitation in eastern Africa, regardless of whether the projected trend in <span class="hlt">ENSO</span> is realized. These results have important food security implications, informing agricultural development, environmental conservation, and water resource planning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29720617','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29720617"><span>Modulation of the relationship between spring AO and the subsequent winter <span class="hlt">ENSO</span> by the preceding November AO.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Shangfeng; Chen, Wen; Yu, Bin</p> <p>2018-05-02</p> <p>Previous studies indicated that the spring Arctic Oscillation (AO) exerts significant influences on the subsequent winter El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). This analysis suggests that the spring AO-<span class="hlt">ENSO</span> linkage is highly modulated by its preceding November AO. When November and the subsequent spring AO indices are in phase, the spring AO has a pronounced influence on <span class="hlt">ENSO</span>. However, when the November and spring AO indices are out of phase, the spring AO-<span class="hlt">ENSO</span> connection disappears. Modulation of the November AO on the spring AO-<span class="hlt">ENSO</span> connection is mainly through the constructive and destructive superposition of the November and spring AO associated sea surface temperature (SST) anomalies in the tropical central-eastern Pacific in spring and summer, as well as the SST anomalies developed further in the tropical Pacific via the positive air-sea feedback.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8316G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8316G"><span>A preliminary look at the impact of <span class="hlt">warming</span> Mediterranean Sea temperatures on some aspects of extreme thunderstorm <span class="hlt">events</span> in Italy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gallus, William; Parodi, Antonio; Miglietta, Marcello; Maugeri, Maurizio</p> <p>2017-04-01</p> <p>As the global climate has <span class="hlt">warmed</span> in recent decades, interest has grown in the impacts on extreme <span class="hlt">events</span> associated with thunderstorms such as tornadoes and intense rainfall that can cause flash flooding. Because warmer temperatures allow the atmosphere to contain larger values of water vapor, it is generally accepted that short-term rainfall may become more intense in a future warmer climate. Regarding tornadoes, it is more difficult to say what might happen since although increased temperatures and humidity in the lowest part of the troposphere should increase thermodynamic instability, allowing for stronger thunderstorm updrafts, vertical wind shear necessary for storm-scale rotation may decrease as the pole to equator temperature gradient weakens. The Mediterranean Sea is an important source for moisture that fuels thunderstorms in Italy, and it has been <span class="hlt">warming</span> faster than most water bodies in recent decades. The present study uses three methods to gain preliminary insight into the role that the <span class="hlt">warming</span> Mediterranean may have on tornadoes and thunderstorms with intense rainfall in Italy. First, a historical archive of Italian tornadoes has been updated for the 1990s, and it will be used along with other data from the European Severe Weather Database to discuss possible trends in tornado occurrence. Second, convection-allowing Weather Research and Forecasting (WRF) model simulations have been performed for three extreme <span class="hlt">events</span> to examine sensitivity to both the sea surface temperatures and other model parameters. These <span class="hlt">events</span> include a flash flood-producing storm <span class="hlt">event</span> near Milan, a non-tornadic severe hail <span class="hlt">event</span> in far northeastern Italy, and the Mira EF-4 tornado of July 2015. Sensitivities in rainfall amount, radar reflectivity and storm structure, and storm rotation will be discussed. Finally, changes in the frequency of intense mesoscale convective system <span class="hlt">events</span> in and near the Ligurian Sea, inferred from the presence of strong convergence lines in EXPRESS</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AdAtS..34..360Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AdAtS..34..360Q"><span>Relationships between the extratropical <span class="hlt">ENSO</span> precursor and leading modes of atmospheric variability in the Southern Hemisphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Qin, Jianhuang; Ding, Ruiqiang; Wu, Zhiwei; Li, Jianping; Zhao, Sen</p> <p>2017-03-01</p> <p>Previous studies suggest that the atmospheric precursor of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) in the extratropical Southern Hemisphere (SH) might trigger a quadrapole sea surface temperature anomaly (SSTA) in the South Pacific and subsequently influence the following <span class="hlt">ENSO</span>. Such a quadrapole SSTA is referred to as the South Pacific quadrapole (SPQ). The present study investigated the relationships between the atmospheric precursor signal of <span class="hlt">ENSO</span> and leading modes of atmospheric variability in the extratropical SH [including the SH annular mode (SAM), the first Pacific-South America (PSA1) mode, and the second Pacific-South America (PSA2) mode]. The results showed that the atmospheric precursor signal in the extratropical SH basically exhibits a barotropic wavenumber-3 structure over the South Pacific and is significantly correlated with the SAM and the PSA2 mode during austral summer. Nevertheless, only the PSA2 mode was found to be a precursor for the following <span class="hlt">ENSO</span>. It leads the SPQ-like SSTA by around one month, while the SAM and the PSA1 mode do not show any obvious linkage with either <span class="hlt">ENSO</span> or the SPQ. This suggests that the PSA2 mode may provide a bridge between the preceding circulation anomalies over the extratropical SH and the following <span class="hlt">ENSO</span> through the SPQ-like SSTA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H14A..04A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H14A..04A"><span>Revisiting Cholera-Climate Teleconnections in the Native Homeland: <span class="hlt">ENSO</span> and other Extremes through the Regional Hydroclimatic Drivers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akanda, A. S.; Jutla, A.; Huq, A.; Colwell, R. R.</p> <p>2014-12-01</p> <p>Cholera is a global disease, with significantly large outbreaks occurring since the 1990s, notably in Sub-Saharan Africa and South Asia and recently in Haiti, in the Caribbean. Critical knowledge gaps remain in the understanding of the annual recurrence in endemic areas and the nature of epidemic outbreaks, especially those that follow extreme hydroclimatic <span class="hlt">events</span>. Teleconnections with large-scale climate phenomena affecting regional scale hydroclimatic drivers of cholera dynamics remain largely unexplained. For centuries, the Bengal delta region has been strongly influenced by the asymmetric availability of water in the rivers Ganges and the Brahmaputra. As these two major rivers are known to have strong contrasting affects on local cholera dynamics in the region, we argue that the role of El Nino-Southern Oscillation (<span class="hlt">ENSO</span>), Indian Ocean Dipole (IOD), or other phenomena needs to be interpreted in the context of the seasonal role of individual rivers and subsequent impact on local environmental processes, not as a teleconnection having a remote and unified effect. We present a modified hypothesis that the influences of large-scale climate phenomena such as <span class="hlt">ENSO</span> and IOD on Bengal cholera can be explicitly identified and incorporated through regional scale hydroclimatic drivers. Here, we provide an analytical review of the literature addressing cholera and climate linkages and present hypotheses, based on recent evidence, and quantification on the role of regional scale hydroclimatic drivers of cholera. We argue that the seasonal changes in precipitation and temperature, and resulting river discharge in the GBM basin region during <span class="hlt">ENSO</span> and IOD <span class="hlt">events</span> have a dominant combined effect on the endemic persistence and the epidemic vulnerability to cholera outbreaks in spring and fall seasons, respectively, that is stronger than the effect of localized hydrological and socio-economic sensitivities in Bangladesh. In addition, systematic identification of underlying seasonal</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp.2396G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp.2396G"><span>Linear dynamical modes as new variables for data-driven <span class="hlt">ENSO</span> forecast</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gavrilov, Andrey; Seleznev, Aleksei; Mukhin, Dmitry; Loskutov, Evgeny; Feigin, Alexander; Kurths, Juergen</p> <p>2018-05-01</p> <p>A new data-driven model for analysis and prediction of spatially distributed time series is proposed. The model is based on a linear dynamical mode (LDM) decomposition of the observed data which is derived from a recently developed nonlinear dimensionality reduction approach. The key point of this approach is its ability to take into account simple dynamical properties of the observed system by means of revealing the system's dominant time scales. The LDMs are used as new variables for empirical construction of a nonlinear stochastic evolution operator. The method is applied to the sea surface temperature anomaly field in the tropical belt where the El Nino Southern Oscillation (<span class="hlt">ENSO</span>) is the main mode of variability. The advantage of LDMs versus traditionally used empirical orthogonal function decomposition is demonstrated for this data. Specifically, it is shown that the new model has a competitive <span class="hlt">ENSO</span> forecast skill in comparison with the other existing <span class="hlt">ENSO</span> models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.9431L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.9431L"><span>What do we need to know to predict <span class="hlt">ENSO</span>? Student-centered learning in a Master course in Climate Physics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lübbecke, Joke; Glessmer, Mirjam</p> <p>2017-04-01</p> <p>An important learning outcome of a Master of Sciences program is to empower students to understand which information they need, how they can gain the required knowledge and skills, and how to apply those to solve a given scientific problem. In designing a class on the El-Nino-Southern-Oscillation (<span class="hlt">ENSO</span>) for students in the Climate Physics program at Kiel University, Germany, we have implemented various active learning strategies to meet this goal. The course is guided by an overarching question, embedded in a short story: What would we need to know to successfully predict <span class="hlt">ENSO</span>? The students identify desired learning outcomes and collaboratively construct a concept map which then serves as a structure for the 12 weeks of the course, where each individual topic is situated in the larger context of the students' own concept map. Each learning outcome of the course is therefore directly motivated by a need to know expressed by the students themselves. During each session, students are actively involved in the learning process. They work individually or in small groups, for example testing different index definitions, analyzing data sets, setting up simple numerical models and planning and constructing hands-on experiments to demonstrate physical processes involved in the formation of El Niño <span class="hlt">events</span>. The instructor's role is to provide the necessary background information and guide the students where it is needed. Insights are shared between groups as students present their findings to each other and combine the information, for example by cooperatively constructing a world map displaying the impacts of <span class="hlt">ENSO</span> or by exchanging experts on different <span class="hlt">ENSO</span> oscillator theories between groups. Development of this course was supported by the PerLe Fonds for teaching innovations at Kiel University. A preliminary evaluation has been very positive with students in particular appreciating their active involvement in the class.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A43D0268P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A43D0268P"><span>A Spatial Perspective of Droughts and Pluvials in the Tropics and their Relationships to <span class="hlt">ENSO</span> in CMIP5 Model Simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Perez Arango, J. D.; Lintner, B. R.; Lyon, B.</p> <p>2016-12-01</p> <p>Although many aspects of the tropical response to <span class="hlt">ENSO</span> are well-known, the spatial characteristics of the rainfall response to <span class="hlt">ENSO</span> remain relatively unexplored. Moreover, in current generation climate models, the spatial signatures of the <span class="hlt">ENSO</span> tropical teleconnection are more uncertain than other aspects of <span class="hlt">ENSO</span> variability, such as the amplitude of rainfall anomalies. Following the approach of Lyon (2004) and Lyon and Barnston (2005), we analyze here integrated measures of the spatial extent of drought and pluvial conditions in the tropics and their relationship to <span class="hlt">ENSO</span> in observations as well as simulations of Phase 5 of the Coupled Model Intercomparison Project (CMIP5) with prescribed SST forcing. We compute diagnostics including the model ensemble-means and standard deviations of moderate, intermediate, and severe droughts and pluvials and the lagged correlations with respect to <span class="hlt">ENSO</span>-based SST indices like NINO3. Overall, in a tropics-wide sense, the models generally capture the areal extent of observed droughts and pluvials and their phasing with respect to <span class="hlt">ENSO</span>. However, at more local scales, e.g., tropical South America, the simulated metrics agree less strongly with observations, underscoring the role of errors in the spatial patterns of <span class="hlt">ENSO</span>-induced rainfall anomalies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4683514','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4683514"><span><span class="hlt">ENSO</span> Modulations due to Interannual Variability of Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng</p> <p>2015-01-01</p> <p>Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances <span class="hlt">ENSO</span> variability and slightly prolongs the simulated <span class="hlt">ENSO</span> period, while the interannual OBH reduces <span class="hlt">ENSO</span> variability and slightly shortens the <span class="hlt">ENSO</span> period, with their feedback effects tending to counteract each other. PMID:26678931</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.8072V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.8072V"><span>On the unstable <span class="hlt">ENSO</span>-Western North Pacific Monsoon relation during the 20th Century</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vega Martín, Inmaculada; Gallego Puyol, David; Ribera Rodriguez, Pedro; Gómez Delgado, Francisco de Paula; Peña-Ortiz, Cristina</p> <p>2017-04-01</p> <p> our extended series suggests a more complex scheme. We have found evidences of a persistently strong WNPSM during 1918-1948, a period in which the WNPSM was considerably less variable than today and a change in the <span class="hlt">ENSO</span>-WNPSM relation during the first half of the 20th Century, with a reversal in the sign of the WNPSM-<span class="hlt">ENSO</span> correlation for <span class="hlt">ENSO</span> decaying years. These changes seem related to an alteration in the timing of the <span class="hlt">ENSO</span> <span class="hlt">events</span> between the first and the second parts of the 20th century. Research funded by the Spanish Ministerio de Economía y Competitividad through the project INCITE (CGL2013-44530-P, BES-2014-069733).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018APJAS..54...77Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018APJAS..54...77Y"><span>Numerical Study of the Role of Microphysical Latent Heating and Surface Heat Fluxes in a Severe Precipitation <span class="hlt">Event</span> in the <span class="hlt">Warm</span> Sector over Southern China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yin, Jin-Fang; Wang, Dong-Hai; Liang, Zhao-Ming; Liu, Chong-Jian; Zhai, Guo-Qing; Wang, Hong</p> <p>2018-02-01</p> <p>Simulations of the severe precipitation <span class="hlt">event</span> that occurred in the <span class="hlt">warm</span> sector over southern China on 08 May 2014 are conducted using the Advanced Weather Research and Forecasting (WRF-ARWv3.5.1) model to investigate the roles of microphysical latent heating and surface heat fluxes during the severe precipitation processes. At first, observations from surface rain gauges and ground-based weather radars are used to evaluate the model outputs. Results show that the spatial distribution of 24-h accumulated precipitation is well reproduced, and the temporal and spatial distributions of the simulated radar reflectivity agree well with the observations. Then, several sensitive simulations are performed with the identical model configurations, except for different options in microphysical latent heating and surface heat fluxes. From the results, one of the significant findings is that the latent heating from <span class="hlt">warm</span> rain microphysical processes heats the atmosphere in the initial phase of the precipitation and thus convective systems start by self-triggering and self-organizing, despite the fact that the environmental conditions are not favorable to the occurrence of precipitation <span class="hlt">event</span> at the initial phase. In the case of the severe precipitation <span class="hlt">event</span> over the <span class="hlt">warm</span> sector, both <span class="hlt">warm</span> and ice microphysical processes are active with the ice microphysics processes activated almost two hours later. According to the sensitive results, there is a very weak precipitation without heavy rainfall belt when microphysical latent heating is turned off. In terms of this precipitation <span class="hlt">event</span>, the <span class="hlt">warm</span> microphysics processes play significant roles on precipitation intensity, while the ice microphysics processes have effects on the spatial distribution of precipitation. Both surface sensible and latent heating have effects on the precipitation intensity and spatial distribution. By comparison, the surface sensible heating has a strong influence on the spatial distribution of precipitation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1916970M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1916970M"><span>Mechanisms of the global electric circuit and lightning variability on the <span class="hlt">ENSO</span> time scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mareev, Evgeny; Volodin, Evgeny; Slyunyaev, Nikolay</p> <p>2017-04-01</p> <p>Many studies of lightning activity on the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) time scale show increased activity over tropical land areas during the <span class="hlt">warm</span> El Niño phase (e.g., Satori et al., 2009; Price, 2009). The mechanisms of this variability—particularly in terms of its role in the global electric circuit (GEC)—are still under debate (e.g., Williams and Mareev, 2014). In this study a general circulation model of the atmosphere and ocean INMCM4.0 (Institute of Numerical Mathematics Coupled Model) is used for modelling the GEC variability on the <span class="hlt">ENSO</span> time scale. The ionospheric potential (IP) and the lightning flash rate are calculated to study regional peculiarities and possible mechanisms of lightning variation. The IP parameterisation is used (Mareev and Volodin, 2014) which takes into account quasi-stationary currents of electrified clouds (including thunderstorms) as principal contributors into the DC global circuit. The account of conductivity variation in the IP parameterisation is suggested based on the approach realised in (Slyunyaev et al., 2014). Comparison of simulation results with the observational data on lightning activity on the <span class="hlt">ENSO</span> time scale is discussed. Numerical simulations suggest that the inter-annual IP variability is low and does not exceed 1% of the mean value, being tightly correlated with the mean sea surface temperature (SST) in the Pacific Ocean (180W-100W, 5S-5N—El Niño area). The IP maximum corresponds to the SST minimum. This result can be explained taking into account that during El Niño (positive temperature anomaly) precipitations in the equatorial part of the Pacific increase while in other tropic zones including the land areas they decrease. Comparison of simulation results with the observational data on lightning activity on the <span class="hlt">ENSO</span> time scale is discussed. During the El Niño period in the model, the mean aerosol content in the atmosphere decrease, which is caused by the weakening of the winds over Sahara and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.G24A..10Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.G24A..10Z"><span>Merging altimeter data with Argo profiles to improve observation of tropical Pacific thermocline circulation and <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, D.; Lee, T.; Wang, F.; McPhaden, M. J.; Kessler, W. S.</p> <p>2016-12-01</p> <p>Meridional thermocline currents play an important role in the recharge and discharge of tropical Pacific <span class="hlt">warm</span> water during the development and transition of <span class="hlt">ENSO</span> cycles. Previous analyses have shown large variations of the equatorward meridional thermocline convergence/divergence on <span class="hlt">ENSO</span> and decadal time scales in the interior ocean. The total convergence/divergence is however unknown due to the lack of long term observation in the western boundary currents. Numerical modelling studies suggested a tendency of compensation between the interior and western boundary currents, but the exact compensation is model dependent. While Argo floats provide reasonable data coverage in the interior ocean, few floats are in the western boundary currents. Recent multi-mission satellite altimeter data and advanced processing techniques have resulted in higher resolution sea surface height anomaly (SSHA) products with better accuracy closer to the coasts. This study utilizes the statistical relationship between Argo dynamic height profiles and altimeter SSHA to calculate geostrophic thermocline currents in both the interior ocean and the western boundary of the tropical Pacific. The derived thermocline currents in the western boundary are validated by a 3.5-year moored Acoustic Doppler Current Profiler (ADCP) measurement in the Mindanao Current and by a series of glider surveys (Davis et al. 2012) in the Solomon Sea. The meridional transport timeseries of the interior and western boundary currents in the thermocline show different lead-lag relationships to the Nino 3.4 index. Results will be discussed in the context of recent 2014-2015 El Nino development and the potential contribution to the Tropical Pacific Observing System (TPOS).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140011840','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140011840"><span><span class="hlt">ENSO</span> Effect on East Asian Tropical Cyclone Landfall via Changes in Tracks and Genesis in a Statistical Model</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yonekura, Emmi; Hall, Timothy M.</p> <p>2014-01-01</p> <p>Improvements on a statistical tropical cyclone (TC) track model in the western North Pacific Ocean are described. The goal of the model is to study the effect of El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) on East Asian TC landfall. The model is based on the International Best-Track Archive for Climate Stewardship (IBTrACS) database of TC observations for 1945-2007 and employs local regression of TC formation rates and track increments on the Nino-3.4 index and seasonally varying climate parameters. The main improvements are the inclusion of <span class="hlt">ENSO</span> dependence in the track propagation and accounting for seasonality in both genesis and tracks. A comparison of simulations of the 1945-2007 period with observations concludes that the model updates improve the skill of this model in simulating TCs. Changes in TC genesis and tracks are analyzed separately and cumulatively in simulations of stationary extreme <span class="hlt">ENSO</span> states. <span class="hlt">ENSO</span> effects on regional (100-km scale) landfall are attributed to changes in genesis and tracks. The effect of <span class="hlt">ENSO</span> on genesis is predominantly a shift in genesis location from the southeast in El Nino years to the northwest in La Nina years, resulting in higher landfall rates for the East Asian coast during La Nina. The effect of <span class="hlt">ENSO</span> on track propagation varies seasonally and spatially. In the peak activity season (July-October), there are significant changes in mean tracks with <span class="hlt">ENSO</span>. Landfall-rate changes from genesis- and track-<span class="hlt">ENSO</span> effects in the Philippines cancel out, while coastal segments of Vietnam, China, the Korean Peninsula, and Japan show enhanced La Nina-year increases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A41L..06S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A41L..06S"><span>Predictability of <span class="hlt">ENSO</span>, the QBO, and European winter 2015/16</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Scaife, A. A.; Ineson, S.; Ruth, C.; Dunstone, N. J.; Fereday, D.; Folland, C. K.; Good, E.; Gordon, M.; Hermanson, L.; Karpechko, A.; Knight, J. R.; MacLachlan, C.; Maidens, A. V.; Peterson, A.; Slingo, J.; Smith, D.; Walker, B.</p> <p>2016-12-01</p> <p>The northern winter of 2015/16 gave rise to the strongest El Niño <span class="hlt">event</span> since 1997/8. Central and eastern Pacific sea surface temperature anomalies exceeded three degrees and closely resembled the strong El Niño in winter of 1982/3. A second feature of this winter was a strong westerly phase of the Quasi-Biennial Oscillation and very strong winds in the stratospheric polar night jet. At the surface, intense extratropical circulation anomalies occurred in both the North Pacific and North Atlantic that were consistent with known teleconnections to the observed phases of <span class="hlt">ENSO</span> and the QBO. The North Atlantic Oscillation was very positive in the early winter period (Nov-Dec) and was more blocked in the late winter. Initialised climate predictions were able to capture these signals at seasonal lead times. This case study adds to the evidence that north Atlantic circulation exhibits predictability on seasonal timescales, and in this case we show that even aspects of the detailed pattern and sub-seasonal evolution were predicted, providing warning of increased risk of extreme <span class="hlt">events</span> such as the intense rainfall which caused extreme flooding in the UK in December.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMPP53B1120H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMPP53B1120H"><span>Continuous Real-time Measurements of δ-values of Precipitation during Rain <span class="hlt">Events</span>: Insights into Tropical Convection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>He, S.; Goodkin, N.; Jackisch, D.; Ong, M. R.</p> <p>2017-12-01</p> <p>Studying how the tropical convection affects stable isotopes in precipitation can help us understand the evolution of the precipitation isotopes over time and improve the interpretation of paleoclimate records in the tropical region. We have been continuously monitoring δ-values of precipitation during rain <span class="hlt">events</span> in Singapore for the past three years (2014-2017) using a diffusion sampler-cavity ring-down spectrometer (DS-CRDS) system. This period of time spans the most recent El Niño and La Niña, and thus affords us the opportunity to use our ultra-high temporal resolutsion data to examine the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) impact on the precipitation isotopes during convection and the intra-annual variability in the region. δ-values of precipitation could change significantly during a single <span class="hlt">event</span>, and mainly exhibits "V" (or "U" ) shape or "W" shape patterns. The mesoscale subsidence and rain re-evaporation are two processes that largely shape the isotopes of precipitation during <span class="hlt">events</span>. Time series of the initial, highest and lowest δ-values of individual <span class="hlt">events</span>, and absolute change in δ-values during these <span class="hlt">events</span> show clear evolution over time. <span class="hlt">Events</span> with low δ-values occurred less frequently in 2015 than the other years. Likewise, the frequency of <span class="hlt">events</span> with larger magnitude change in δ-values and low initial values are also lower in 2015. The <span class="hlt">events</span> with low averaged δ-values usually have very low initial δ-values, and are closely associated with organized regional convection, indicating that the convective activities in the upwind area can significantly influence the δ-values of precipitation. All these observations suggest lower intensity and frequency of regional organized convection in 2015. The <span class="hlt">ENSO</span> <span class="hlt">event</span> in 2015 was likely responsible for these changes. During an <span class="hlt">ENSO</span> <span class="hlt">event</span>, convection over the central and eastern Pacific is strengthened while that of the western Pacific and Southeast Asia is supressed, resulting in a weakened</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.5499K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.5499K"><span>Dynamics of the exceptional <span class="hlt">warming</span> <span class="hlt">events</span> during the Arctic winters 2003/04, 2005/06 and 2008/09</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuttippurath, Jayanarayanan; Godin-Beekmann, Sophie; Lefèvre, Franck; Nikulin, Grigory</p> <p>2010-05-01</p> <p>Sudden stratospheric <span class="hlt">warmings</span> (SSW) are common features of the Arctic meteorology. During a major SSW, polar temperature rises and the zonal mean flow weakens dramatically over a short period of time. This situation causes displacement, distortion or split of the polar vortex. The Arctic winters 2003/04, 2005/06 and 2008/09 were characterized by major midwinter <span class="hlt">warming</span> of different proportions. The major <span class="hlt">warming</span> occurred in early January in 2003/04 and in mid-January in the other winters in the lower stratosphere. The winter 2003/04 was remarkable in that a stable vortex formed again in March 2004 after two months of severe disturbance. No vortex was evident in other winters after the mid-January major <span class="hlt">warming</span>. The planetary waves 1 and 2 play a key role in <span class="hlt">warming</span> <span class="hlt">events</span> and in vortex distortions as they control the stratospheric circulation. The dominating presence and amplitude of these waves were also different in each winter. In this presentation, we characterize the winters 2003/04, 2005/06 and 2008/09 in terms of chemical and dynamical situation during the winters. In order to illustrate, we exploit the heat flux, zonal wind characteristics, Eliassen-Palm vectors and planetary wave analyzes for the winters in a comparative perspective. The dynamical parameters are derived from ECMWF analyzes and the chemical realm are discussed in terms of the measurements from MLS (Microwave Limb Sounder) and POAM (Polar Ozone and Aerosol Measurement) as well as simulations from the Mimosa-Chim global three-dimensional chemical transport model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AdAtS..31...66L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AdAtS..31...66L"><span>The interdecadal changes of south pacific sea surface temperature in the mid-1990s and their connections with <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Gang; Li, Chongyin; Tan, Yanke; Bai, Tao</p> <p>2014-01-01</p> <p>The characteristic changes of South Pacific sea surface temperature anomalies (SSTAs) for the period January 1979 to December 2011, during which the 1990s Pacific pan-decadal variability (PDV) interdecadal regime shifts occurred, were examined. Empirical Orthogonal Function (EOF) analysis was applied to the monthly mean SSTA for two sub-periods: January 1979 to December 1994 (P1) and January 1996 to December 2011 (P2). Both the spatial and temporal features of the leading EOF mode for P1 and P2 showed a remarkable difference. The spatial structure of the leading EOF changed from a tripolar pattern for P1 (EOF-P1) to a dipole-like pattern for P2 (EOF-P2). Besides, EOF-P1 (EOF-P2) had significant spectral peaks at 4.6 yr (2.7 yr). EOF-P2 not only had a closer association with El Niño-Southern Oscillation (<span class="hlt">ENSO</span>), but also showed a faster response to <span class="hlt">ENSO</span> than EOF-P1 based on their lead-lag relationships with <span class="hlt">ENSO</span>. During the development of <span class="hlt">ENSO</span>, the South Pacific SSTA associated with <span class="hlt">ENSO</span> for both P1 and P2 showed a significant eastward propagation. However, after the peak of <span class="hlt">ENSO</span>, EOF-P1 showed a stronger persistence than EOF-P2, which still showed eastward propagation. The variability of the SSTA associated with the whole process of <span class="hlt">ENSO</span> evolution during P1 and the SSTA associated with the development of <span class="hlt">ENSO</span> during P2 support the existence of ocean-to-atmosphere forcing, but the SSTA associated with the decay of <span class="hlt">ENSO</span> shows the phenomenon of atmosphere-to-ocean forcing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JASTP.171..201K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JASTP.171..201K"><span>Comparisons of planetary wave propagation to the upper atmosphere during stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> at different QBO phases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koval, Andrey V.; Gavrilov, Nikolai M.; Pogoreltsev, Alexander I.; Savenkova, Elena N.</p> <p>2018-06-01</p> <p>The dynamical coupling of the lower and upper atmosphere by planetary waves (PWs) is studied. Numerical simulations of planetary wave (PW) amplitudes during composite sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">events</span> in January-February are made using a model of general circulation of the middle and upper atmosphere with initial and boundary conditions typical for the westerly and easterly phases of quasi-biennial oscillation (QBO). The changes in PW amplitudes in the middle atmosphere before, during and after SSW <span class="hlt">event</span> for the different QBO phases are considered. Near the North Pole, the increase in the mean temperature during SSW reaches 10-30 K at altitudes 30-50 km for four pairs of the model runs with the eQBO and wQBO, which is characteristic for the sudden stratospheric <span class="hlt">warming</span> <span class="hlt">event</span>. Amplitudes of stationary PWs in the middle atmosphere of the Northern hemisphere may differ up to 30% during wQBO and eQBO before and during the SSW. After the SSW <span class="hlt">event</span> SPW amplitudes are substantially larger during wQBO phase. PW refractivity indices and Eliassen-Palm flux vectors are calculated. The largest EP-fluxes in the middle atmosphere correspond to PWs with zonal wavenumber m=1. Simulated changes in PW amplitudes correspond to inhomogeneities of the global circulation, refractivity index and EP-flux produced by the changes in QBO phases. Comparisons of differences in PW characteristics and circulation between the wQBO and eQBO show that PWs could provide effective coupling mechanism and transport dynamical changes from local regions of the lower atmosphere to distant regions of the upper atmosphere of both hemispheres.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170003686','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170003686"><span>The 2015/16 El Niño <span class="hlt">Event</span> in Context of the MERRA-2 Reanalysis: A Comparison of the Tropical Pacific with 1982/83 and 1997/98</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lim, Young-Kwon; Kovach, Robin M.; Pawson, Steven; Vernieres, Guillaume</p> <p>2017-01-01</p> <p>The 2015-2016 El Nino is analyzed using atmospheric/oceanic analysis produced using the Goddard Earth Observing System (GEOS) data assimilation systems. As well as describing the structure of the <span class="hlt">event</span>, a theme of the work is to compare and contrast it with two other strong El Ninos, in 1982/1983 and 1997/1998. These three El Nino <span class="hlt">events</span> are included in the Modern-Era Retrospective analysis for Research and Applications (MERRA) and in the more recent MERRA-2 reanalyses. MERRA-2 allows a comparison of fields derived from the underlying GEOS model, facilitating a more detailed comparison of physical forcing mechanisms in the El Nino <span class="hlt">events</span>. Various atmospheric/oceanic structures indicate that the 2015/2016 El Nino maximized in the Nino3.4 region, with the large region of <span class="hlt">warming</span> over most of the Pacific and Indian Ocean. The eastern tropical Indian Ocean, Maritime Continent, and western tropical Pacific are found to be less dry in boreal winter, compared to the earlier two strong <span class="hlt">events</span>. While the 2015/2016 El Nino had an earlier occurrence of the equatorial Pacific <span class="hlt">warming</span> and was the strongest <span class="hlt">event</span> on record in the central Pacific, the 1997/1998 <span class="hlt">event</span> exhibited a more rapid growth due to stronger westerly wind bursts and Madden-Julian Oscillation during spring, making it the strongest El Nino in the eastern Pacific. Compared to 1982/1983 and 1997/1998, the 2015/2016 <span class="hlt">event</span> has a shallower thermocline over the eastern Pacific with a weaker zonal contrast of sub-surface water temperatures along the equatorial Pacific. While the three major <span class="hlt">ENSO</span> <span class="hlt">events</span> have similarities, each are unique when looking at the atmosphere and ocean surface and sub-surface.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP33D..02M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP33D..02M"><span>Inter-annual precipitation variabiity inferred from late Holocene speleothem records from Fiji: implications for SPCZ localisation and <span class="hlt">ENSO</span> behaviour</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mattey, D.; Stephens, M.; Hoffmann, D.; Brett, M.</p> <p>2015-12-01</p> <p>The modern tropical Fiji climate is characterised by seasonal rainfall controlled by the position of the South Pacific Convergence Zone (SPCZ). Interannual rainfall is strongly modulated on decadal timescales by <span class="hlt">ENSO</span> with higher rainfall associated with La Nina <span class="hlt">events</span>. Voli Voli cave near Sigatoga (Viti Levu) is a stream passage that has been monitored since 2009. A U-Th dated laminated speleothem spans a 1500 year interval across the transition from the Medieval <span class="hlt">Warm</span> Period into the Little Ice Age marked by a fabric change from finely laminated calcite with thin clay layers, to white well-laminated calcite. The older record is characterised by rising δ13C values followed by a rapid decrease in δ13C around 1200 AD. Evidence from cave monitoring shows that cave air CO2 levels are strongly seasonal as a result of greater ventilation by winter trade winds and high resolution δ13C record shows regularly spaced peaks correlated with paired laminae and cycles in P and S which provide annual markers driven by rainfall and seasonal ventilation. δ18O values remain relatively unchanged throughout the record but micromilling at sub-annual resolution reveals systematic cycles in δ18O that span groups of paired laminae with an inferred periodicity of 3-7 years i.e. a similar frequency to modern <span class="hlt">ENSO</span>. The presence of these sub-decadal cycles in δ18O may be a result of a combination of factors. The amplitude of 2-3‰ would be equivalent to an amount-effect related change in annual precipitation of around 50% but an additional smoothing process, perhaps a result of aquifer storage, is required to attenuate interannual variance in precipitation. The Voli Voli record provides evidence of an underlying climatic change to more frequent La Niña conditions from 1200 AD and may be associated with increased conflict, shifts in settlements and changes in subsistence strategies on the island. Coeval speleothem isotope records from tropical Pacific Islands provide a provide a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1617208','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1617208"><span>Marine lake ecosystem dynamics illustrate <span class="hlt">ENSO</span> variation in the tropical western Pacific</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Martin, Laura E; Dawson, Michael N; Bell, Lori J; Colin, Patrick L</p> <p>2005-01-01</p> <p>Understanding El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) and its biological consequences is hindered by a lack of high-resolution, long-term data from the tropical western Pacific. We describe a preliminary, 6 year dataset that shows tightly coupled <span class="hlt">ENSO</span>-related bio-physical dynamics in a seawater lake in Palau, Micronesia. The lake is more strongly stratified during La Niña than El Niño conditions, temperature anomalies in the lake co-vary strongly with the Niño 3.4 climate index, and the abundance of the dominant member of the pelagic community, an endemic subspecies of zooxanthellate jellyfish, is temperature associated. These results have broad relevance because the lake: (i) illustrates an <span class="hlt">ENSO</span> signal that is partly obscured in surrounding semi-enclosed lagoon waters and, therefore, (ii) may provide a model system for studying the effects of climate change on community evolution and cnidarian–zooxanthellae symbioses, which (iii) should be traceable throughout the Holocene because the lake harbours a high quality sediment record; the sediment record should (iv) provide a sensitive and regionally unique record of Holocene climate relevant to predicting <span class="hlt">ENSO</span> responses to future global climate change and, finally, (v) seawater lake ecosystems elsewhere in the Pacific may hold similar potential for past, present, and predictive measurements of climate variation and ecosystem response. PMID:17148349</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17148349','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17148349"><span>Marine lake ecosystem dynamics illustrate <span class="hlt">ENSO</span> variation in the tropical western Pacific.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Martin, Laura E; Dawson, Michael N; Bell, Lori J; Colin, Patrick L</p> <p>2006-03-22</p> <p>Understanding El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) and its biological consequences is hindered by a lack of high-resolution, long-term data from the tropical western Pacific. We describe a preliminary, 6 year dataset that shows tightly coupled <span class="hlt">ENSO</span>-related bio-physical dynamics in a seawater lake in Palau, Micronesia. The lake is more strongly stratified during La Niña than El Niño conditions, temperature anomalies in the lake co-vary strongly with the Niño 3.4 climate index, and the abundance of the dominant member of the pelagic community, an endemic subspecies of zooxanthellate jellyfish, is temperature associated. These results have broad relevance because the lake: (i) illustrates an <span class="hlt">ENSO</span> signal that is partly obscured in surrounding semi-enclosed lagoon waters and, therefore, (ii) may provide a model system for studying the effects of climate change on community evolution and cnidarian-zooxanthellae symbioses, which (iii) should be traceable throughout the Holocene because the lake harbours a high quality sediment record; the sediment record should (iv) provide a sensitive and regionally unique record of Holocene climate relevant to predicting <span class="hlt">ENSO</span> responses to future global climate change and, finally, (v) seawater lake ecosystems elsewhere in the Pacific may hold similar potential for past, present, and predictive measurements of climate variation and ecosystem response.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016SPIE10005E..12A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016SPIE10005E..12A"><span>Monitoring of vegetation condition using the NDVI/<span class="hlt">ENSO</span> anomalies in Central Asia and their relationships with ONI (very strong) phases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aralova, Dildora; Toderich, Kristina; Jarihani, Ben; Gafurov, Dilshod; Gismatulina, Liliya</p> <p>2016-10-01</p> <p>An investigation of temporal dynamics of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and spatial patterns of dryness/wetness period over arid and semi-arid zones of Central Asia and their relationship with Normalized Difference Vegetation Index (NDVI) values (1982-2011) have explored in this article. For identifying periodical oscillations and their relationship with NDVI values have selected El Nino 3.4 index and thirty years of new generation bi-weekly NDVI 3g acquired by the Advanced Very High Resolution Radiometer (AVHRR) satellites time-series data. Based on identification ONI (Oceanic Nino Index) is a very strong El Nino (<span class="hlt">warm</span>) anomalies observed during 1982-1983, 1997-1998 and very strong La Nino (cool) period <span class="hlt">events</span> have observed 1988-1989 years. For correlation these two factors and seeking positive and negative trends it has extracted from NDVI time series data as "low productivity period" following years: 1982-1983, 1997 -1998; and as "high productivity period" following years: 1988 -1989. Linear regression observed <span class="hlt">warm</span> <span class="hlt">events</span> as moderate phase period selected between moderate El Nino (ME) and NDVI with following periods:1986-1987; 1987-1988; 1991-1992; 2002-2003; 2009-2010; and moderate La Niña (ML) periods and NDVI (1998-1999; 1999-2000; 2007-2008) which has investigated a spatial patterns of wetness conditions. The results indicated that an inverse relationship between very strong El Nino and NDVI, decreased vegetation response with larger positive ONI value; and direct relationship between very strong La Niña and NDVI, increased vegetation response with smaller negative ONI value. Results assumed that significant impact of these anomalies influenced on vegetation productivity. These results will be a beneficial for efficient rangeland/grassland management and to propose drought periods for assessment and reducing quantity of flocks' due to a lack of fodder biomass for surviving livestock flocks on upcoming years in rangelands. Also results demonstrate</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3861369','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3861369"><span>Effects of <span class="hlt">ENSO</span> and Temporal Rainfall Variation on the Dynamics of Successional Communities in Old-Field Succession of a Tropical Dry Forest</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Maza-Villalobos, Susana; Poorter, Lourens; Martínez-Ramos, Miguel</p> <p>2013-01-01</p> <p>The effects of temporal variation of rainfall on secondary succession of tropical dry ecosystems are poorly understood. We studied effects of inter-seasonal and inter-year rainfall variation on the dynamics of regenerative successional communities of a tropical dry forest in Mexico. We emphasized the effects caused by the severe El Niño Southern Oscillation (<span class="hlt">ENSO</span>) occurred in 2005. We established permanent plots in sites representing a chronosequence of Pasture (abandoned pastures, 0–1 years fallow age), Early (3–5), Intermediate (8–12), and Old-Growth Forest categories (n = 3 per category). In total, 8210 shrubs and trees 10 to 100-cm height were identified, measured, and monitored over four years. Rates of plant recruitment, growth and mortality, and gain and loss of species were quantified per season (dry vs. rainy), year, and successional category, considering whole communities and separating seedlings from sprouts and shrubs from trees. Community rates changed with rainfall variation without almost any effect of successional stage. Mortality and species loss rates peaked during the <span class="hlt">ENSO</span> year and the following year; however, after two rainy years mortality peaked in the rainy season. Such changes could result from the severe drought in the <span class="hlt">ENSO</span> year, and of the outbreak of biotic agents during the following rainy years. Growth, recruitment and species gain rates were higher in the rainy season but they were significantly reduced after the <span class="hlt">ENSO</span> year. Seedlings exhibited higher recruitment and mortality rate than sprouts, and shrubs showed higher recruitment than trees. <span class="hlt">ENSO</span> strongly impacted both the dynamics and trajectory of succession, creating transient fluctuations in the abundance and species richness of the communities. Overall, there was a net decline in plant and species density in most successional stages along the years. Therefore, strong drought <span class="hlt">events</span> have critical consequences for regeneration dynamics, delaying the successional process</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRD..123..198S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRD..123..198S"><span>Modulation of Winter Precipitation Dynamics Over the Arabian Gulf by <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sandeep, S.; Ajayamohan, R. S.</p> <p>2018-01-01</p> <p>The Arabian Gulf (Gulf) and the surrounding regions are centers of intense economic activity. The precipitating weather systems that form over the Gulf are important for this predominantly arid region. It is suggested that El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) influences the Middle East precipitation variability through an equatorward shift of the subtropical jet. Here we present compelling evidence to illustrate the role of <span class="hlt">ENSO</span> in modulating the local dynamics and moisture transport in initiating precipitation during different <span class="hlt">ENSO</span> phases using satellite and reanalysis data. It is found that the moisture transport from the Red and Arabian Seas toward the Gulf is stronger during El Niño years. The pattern and strength of moisture transport toward the Gulf is weakened during La Niña and neutral years, with most of the transport directed toward the northern Gulf. Using a 120 h back trajectory analysis, it is found that while the air parcels coming toward the Gulf from the Arabian and Red Seas side originate at lower tropospheric levels, the air parcels from the Mediterranean originate at middle and upper tropospheric levels during El Niño years. In contrast, upper tropospheric air parcels originating over the southern Arabian Sea plays a dominant role on Gulf precipitation during La Niña and neutral years. The seasonal mean transients of zonal winds show a robust <span class="hlt">ENSO</span> signature over the Gulf, indicating a favorable (less favorable) condition for the penetration of midlatitude eddies over the region during El Niño (La Niña) winters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSAH13A..04M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSAH13A..04M"><span>Changes in coral reef metabolism during the 2015 El Niño in the eastern Pacific</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>McGillis, W. R.; Manzello, D.; Smith, T. B.; Baker, A.; Fong, P.; Glynn, P.; Smith, J.; Takeshita, Y.; Martz, T. R.; Hsueh, D.; Langdon, C.; Price, N.; Mate, J.</p> <p>2016-02-01</p> <p>The likely strong 2015-2016 El Niño <span class="hlt">event</span> offers an opportunity to assess coral reef benthic metabolism under stressful high temperatures, coral bleaching, and mortality. During a period of increasing ocean temperatures caused by the 2015-2016 El Niño-Southern Oscillation (<span class="hlt">ENSO</span>), we assessed the metabolism, at hourly intervals, of eastern Pacific coral reefs using the Benthic Ecosystem and Acidification Measurement System (BEAMS). We measured coral reef net ecosystem productivity (NEP) and net ecosystem calcification (NEC) in 2014 before the start of the El Niño <span class="hlt">event</span> and in 2015 during the first anomalously high sea surface temperatures of the 2015 El Niño. Increases in ocean temperatures of 1-2°C between 2014 and 2015 caused over 30% decline in calcification at Uva Is. (Panama) and Darwin Is. (Galapagos), along with significant coral bleaching at Uva and coral paling at Darwin. <span class="hlt">Warming</span> at Saboga Island, in the seasonally upwelling Gulf of Panama, was only 0.3oC, did not result in significant bleaching, and was accompanied by a significant increase in coral reef metabolism. Additional key findings include an increase in nighttime dissolution of calcium carbonate during <span class="hlt">ENSO</span> heating. Light-NEP and light-NEC relationships were generated for each location, and showed that variations in metabolism were strongly correlated with the incident bottom solar intensity, with strong daily cycles and patterns of light-enhanced calcification also identified. The response of different coral species also provides in situ data on the varying metabolism. The metabolism of the 2015-2016 El Niño shows the possible reef function under future <span class="hlt">warming</span> and acidified conditions. These emerging results may be harbingers of significant further decreases in metabolism, and other detrimental impacts, if this region experiences additional <span class="hlt">warming</span> during the current <span class="hlt">ENSO</span> <span class="hlt">event</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8453P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8453P"><span><span class="hlt">ENSO</span> detection and use to inform the operation of large scale water systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pham, Vuong; Giuliani, Matteo; Castelletti, Andrea</p> <p>2016-04-01</p> <p>El Nino Southern Oscillation (<span class="hlt">ENSO</span>) is a large-scale, coupled ocean-atmosphere phenomenon occurring in the tropical Pacific Ocean, and is considered one of the most significant factors causing hydro-climatic anomalies throughout the world. Water systems operations could benefit from a better understanding of this global phenomenon, which has the potential for enhancing the accuracy and lead-time of long-range streamflow predictions. In turn, these are key to design interannual water transfers in large scale water systems to contrast increasingly frequent extremes induced by changing climate. Despite the <span class="hlt">ENSO</span> teleconnection is well defined in some locations such as Western USA and Australia, there is no consensus on how it can be detected and used in other river basins, particularly in Europe, Africa, and Asia. In this work, we contribute a general framework relying on Input Variable Selection techniques for detecting <span class="hlt">ENSO</span> teleconnection and using this information for improving water reservoir operations. Core of our procedure is the Iterative Input variable Selection (IIS) algorithm, which is employed to find the most relevant determinants of streamflow variability for deriving predictive models based on the selected inputs as well as to find the most valuable information for conditioning operating decisions. Our framework is applied to the multipurpose operations of the Hoa Binh reservoir in the Red River basin (Vietnam), taking into account hydropower production, water supply for irrigation, and flood mitigation during the monsoon season. Numerical results show that our framework is able to quantify the relationship between the <span class="hlt">ENSO</span> fluctuations and the Red River basin hydrology. Moreover, we demonstrate that such <span class="hlt">ENSO</span> teleconnection represents valuable information for improving the operations of Hoa Binh reservoir.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.cpc.ncep.noaa.gov/products/predictions/90day/fxhw40.html','SCIGOVWS'); return false;" href="http://www.cpc.ncep.noaa.gov/products/predictions/90day/fxhw40.html"><span>Climate Prediction Center - Seasonal Outlook</span></a></p> <p><a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a></p> <p></p> <p></p> <p>LEAST THROUGH THE NORTHERN HEMISPHERE SUMMER 2018, WITH THE POSSIBILITY OF <em>EL</em> NINO NEARING 50% BY PRECIPITATION ARE LOWERED. SOME <span class="hlt">ENSO</span> FORECAST MODELS PREDICT A <span class="hlt">WARM</span> <span class="hlt">EVENT</span> (<em>EL</em> NINO) BY THE NORTHERN HEMISPHERE WINTER 2018-19. IF CORRECT, HISTORICAL <em>EL</em> NINO COMPOSITES FAVOR INCREASED ODDS FOR DRY CONDITIONS FOR</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.2537W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.2537W"><span>Effect of AMOC collapse on <span class="hlt">ENSO</span> in a high resolution general circulation model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Williamson, Mark S.; Collins, Mat; Drijfhout, Sybren S.; Kahana, Ron; Mecking, Jennifer V.; Lenton, Timothy M.</p> <p>2018-04-01</p> <p>We look at changes in the El Niño Southern Oscillation (<span class="hlt">ENSO</span>) in a high-resolution eddy-permitting climate model experiment in which the Atlantic Meridional Circulation (AMOC) is switched off using freshwater hosing. The <span class="hlt">ENSO</span> mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased <span class="hlt">ENSO</span> period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the meridional sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in <span class="hlt">ENSO</span> amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B21G2046D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B21G2046D"><span>Tree Carbohydrate Dynamics Across a Rainfall Gradient in Panama During the 2016 <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dickman, L. T.; Xu, C.; Behar, H.; McDowell, N.</p> <p>2017-12-01</p> <p>Non-structural carbohydrates (NSC) provide a measure of the carbon supply available to support respiration, growth, and defense. Support for a role of carbon starvation - or depletion of NSC stores - in drought induced tree mortality is varied without consensus for the tropics. The 2016 <span class="hlt">ENSO</span> drought provided a unique opportunity to capture drought impacts on tropical forest carbohydrate dynamics. To quantify these impacts, we collected monthly NSC samples across a rainfall gradient in Panama for the duration of the <span class="hlt">ENSO</span>. We observed high variability in foliar NSC among species within sites. Foliage contained very little starch, indicating that total NSC dynamics are driven by soluble sugars. Foliar NSC depletion did not progress with drought duration as predicted, but showed little variation over course of the <span class="hlt">ENSO</span>. Foliar NSC did, however, increase with rainfall, suggesting NSC depletion may occur with longer-term drought. These results suggest that, while short-term droughts like the 2016 <span class="hlt">ENSO</span> may not have a significant impact on carbon dynamics, we may observe greater impacts as drought progresses over longer timescales. These results will be used to evaluate whether the current implementation of carbon starvation in climate models are capturing observed trends in tropical forest carbon allocation and mortality, and to tune model parameters for improved predictive capability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A33C2375A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A33C2375A"><span>Frequency of Tropical Ocean Deep Convection and Global <span class="hlt">Warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Aumann, H. H.; Behrangi, A.; Ruzmaikin, A.</p> <p>2017-12-01</p> <p>The average of 36 CMIP5 models predicts about 3K of <span class="hlt">warming</span> and a 4.7% increase in precipitation for the tropical oceans with a doubling of the CO2 by the end of this century. For this scenario we evaluate the increase in the frequency of Deep Convective Clouds (DCC) in the tropical oceans. We select only DCC which reach or penetrate the tropopause in the 15 km AIRS footprint. The evaluation is based on Probability Distribution Functions (PDFs) of the current temperatures of the tropical oceans, those predicted by the mean of the CMIP5 models and the PDF of the DCC process. The PDF of the DCC process is derived from the Atmospheric Infrared Sounder (AIRS) between the years 2003 and 2016. During this time the variability due <span class="hlt">Enso</span> years provided a 1 K p-p change in the mean tropical SST. The key parameter is the SST associated with the onset of the DCC process. This parameter shifts only 0.5 K for each K of <span class="hlt">warming</span> of the oceans. As a result the frequency of DCC is expected to increases by the end of this century by about 50% above the current frequency.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACPD...1523969N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACPD...1523969N"><span>Equatorial middle atmospheric chemical composition changes during sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nath, O.; Sridharan, S.</p> <p>2015-09-01</p> <p>Chemical composition data obtained from the Microwave Limb Sounder (MLS) and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instruments onboard EOS-Aura and ENVISAT satellites are used to investigate the variation of ozone (O3), water vapor (H2O) and methane (CH4) volume mixing ratios (VMRs) in the height range 20-60 km over the equatorial region during the sudden stratospheric <span class="hlt">warmings</span> (SSWs) of 2004, 2009 and 2012, the occurrence of which are identified using the ERA (European Center for Medium Range Weather Forecasting Reanalysis) Interim temperature and zonal wind data sets. It is found that the O3 VMR shows increment whereas H2O VMR shows decrement during the SSW <span class="hlt">event</span> and the possible reasons for these changes in the VMRs are investigated. In the upper stratosphere, the source of water vapor is oxidation of CH4 which takes place either by hydroxyl (OH) or by atomic oxygen (O). However, the OH VMR available for the year 2009 SSW <span class="hlt">event</span> does not show any significant variation. The decrease of zonal mean MLS temperature over the equator during the SSW suggests that the rate of the reaction of ozone production (O + O2 ⟶ O3 + M), which increases with decreasing temperature, shifts the O/O3 ratio towards O3, resulting in the decrease of CH4 oxidation and consequent decrease in water vapor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18..604S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18..604S"><span>Empirical modeling <span class="hlt">ENSO</span> dynamics with complex-valued artificial neural networks</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Seleznev, Aleksei; Gavrilov, Andrey; Mukhin, Dmitry</p> <p>2016-04-01</p> <p>The main difficulty in empirical reconstructing the distributed dynamical systems (e.g. regional climate systems, such as El-Nino-Southern Oscillation - <span class="hlt">ENSO</span>) is a huge amount of observational data comprising time-varying spatial fields of several variables. An efficient reduction of system's dimensionality thereby is essential for inferring an evolution operator (EO) for a low-dimensional subsystem that determines the key properties of the observed dynamics. In this work, to efficient reduction of observational data sets we use complex-valued (Hilbert) empirical orthogonal functions which are appropriate, by their nature, for describing propagating structures unlike traditional empirical orthogonal functions. For the approximation of the EO, a universal model in the form of complex-valued artificial neural network is suggested. The effectiveness of this approach is demonstrated by predicting both the Jin-Neelin-Ghil <span class="hlt">ENSO</span> model [1] behavior and real <span class="hlt">ENSO</span> variability from sea surface temperature anomalies data [2]. The study is supported by Government of Russian Federation (agreement #14.Z50.31.0033 with the Institute of Applied Physics of RAS). 1. Jin, F.-F., J. D. Neelin, and M. Ghil, 1996: El Ni˜no/Southern Oscillation and the annual cycle: subharmonic frequency locking and aperiodicity. Physica D, 98, 442-465. 2. http://iridl.ldeo.columbia.edu/SOURCES/.KAPLAN/.EXTENDED/.v2/.ssta/</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.2791Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.2791Z"><span>Improved ensemble-mean forecasting of <span class="hlt">ENSO</span> <span class="hlt">events</span> by a zero-mean stochastic error model of an intermediate coupled model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Fei; Zhu, Jiang</p> <p>2017-04-01</p> <p>How to design a reliable ensemble prediction strategy with considering the major uncertainties of a forecasting system is a crucial issue for performing an ensemble forecast. In this study, a new stochastic perturbation technique is developed to improve the prediction skills of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) through using an intermediate coupled model. We first estimate and analyze the model uncertainties from the ensemble Kalman filter analysis results through assimilating the observed sea surface temperatures. Then, based on the pre-analyzed properties of model errors, we develop a zero-mean stochastic model-error model to characterize the model uncertainties mainly induced by the missed physical processes of the original model (e.g., stochastic atmospheric forcing, extra-tropical effects, Indian Ocean Dipole). Finally, we perturb each member of an ensemble forecast at each step by the developed stochastic model-error model during the 12-month forecasting process, and add the zero-mean perturbations into the physical fields to mimic the presence of missing processes and high-frequency stochastic noises. The impacts of stochastic model-error perturbations on <span class="hlt">ENSO</span> deterministic predictions are examined by performing two sets of 21-yr hindcast experiments, which are initialized from the same initial conditions and differentiated by whether they consider the stochastic perturbations. The comparison results show that the stochastic perturbations have a significant effect on improving the ensemble-mean prediction skills during the entire 12-month forecasting process. This improvement occurs mainly because the nonlinear terms in the model can form a positive ensemble-mean from a series of zero-mean perturbations, which reduces the forecasting biases and then corrects the forecast through this nonlinear heating mechanism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45..327G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45..327G"><span>A New Method for Interpreting Nonstationary Running Correlations and Its Application to the <span class="hlt">ENSO</span>-EAWM Relationship</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Geng, Xin; Zhang, Wenjun; Jin, Fei-Fei; Stuecker, Malte F.</p> <p>2018-01-01</p> <p>We here propose a new statistical method to interpret nonstationary running correlations by decomposing them into a stationary part and a first-order Taylor expansion approximation for the nonstationary part. Then, this method is applied to investigate the nonstationary behavior of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>)-East Asian winter monsoon (EAWM) relationship, which exhibits prominent multidecadal variations. It is demonstrated that the first-order approximation of the nonstationary part can be expressed to a large extent by the impact of the nonlinear interaction between the Atlantic Multidecadal Oscillation (AMO) and <span class="hlt">ENSO</span> (AMO*Niño3.4) on the EAWM. Therefore, the nonstationarity in the <span class="hlt">ENSO</span>-EAWM relationship comes predominantly from the impact of an AMO modulation on the <span class="hlt">ENSO</span>-EAWM teleconnection via this key nonlinear interaction. This general method can be applied to investigate nonstationary relationships that are often observed between various different climate phenomena.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120009842','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120009842"><span>The Response of Tropospheric Ozone to <span class="hlt">ENSO</span> in Observations and a Chemistry-Climate Simulation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Waugh, D. W.; Rodriguez, J. M.; Nielsen, J. E.</p> <p>2012-01-01</p> <p>The El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) is the dominant mode of tropical variability on interannual time scales. <span class="hlt">ENSO</span> appears to extend its influence into the chemical composition of the tropical troposphere. Recent results have revealed an <span class="hlt">ENSO</span> induced wave-l anomaly in observed tropical tropospheric column ozone. This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this result using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years. An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region. We will show targeted comparisons with observations from NASA's Aura satellite Microwave Limb Sounder (MLS), and the Tropospheric Emissions Spectrometer (TES) to provide insight into the vertical structure of ozone changes. The tropospheric ozone response to <span class="hlt">ENSO</span> could be a useful chemistry-climate model evaluation tool and should be considered in future modeling assessments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ACP....18.7169M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ACP....18.7169M"><span>A comparison of the momentum budget in reanalysis datasets during sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Martineau, Patrick; Son, Seok-Woo; Taguchi, Masakazu; Butler, Amy H.</p> <p>2018-05-01</p> <p>The agreement between reanalysis datasets, in terms of the zonal-mean momentum budget, is evaluated during sudden stratospheric <span class="hlt">warming</span> (SSW) <span class="hlt">events</span>. It is revealed that there is a good agreement among datasets in the lower stratosphere and troposphere concerning zonal-mean zonal wind, but less so in the upper stratosphere. Forcing terms of the momentum equation are also relatively similar in the lower atmosphere, but their uncertainties are typically larger than uncertainties of the zonal-wind tendency. Similar to zonal-wind tendency, the agreement among forcing terms is degraded in the upper stratosphere. Discrepancies among reanalyses increase during the onset of SSW <span class="hlt">events</span>, a period characterized by unusually large fluxes of planetary-scale waves from the troposphere to the stratosphere, and decrease substantially after the onset. While the largest uncertainties in the resolved terms of the momentum budget are found in the Coriolis torque, momentum flux convergence also presents a non-negligible spread among the reanalyses. Such a spread is reduced in the latest reanalysis products, decreasing the uncertainty of the momentum budget. It is also found that the uncertainties in the Coriolis torque depend on the strength of SSW <span class="hlt">events</span>: the SSW <span class="hlt">events</span> that exhibit the most intense deceleration of zonal-mean zonal wind are subject to larger discrepancies among reanalyses. These uncertainties in stratospheric circulation, however, are not communicated to the troposphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdAtS..35..671F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdAtS..35..671F"><span>Simulating Eastern- and Central-Pacific Type <span class="hlt">ENSO</span> Using a Simple Coupled Model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fang, Xianghui; Zheng, Fei</p> <p>2018-06-01</p> <p>Severe biases exist in state-of-the-art general circulation models (GCMs) in capturing realistic central-Pacific (CP) El Niño structures. At the same time, many observational analyses have emphasized that thermocline (TH) feedback and zonal advective (ZA) feedback play dominant roles in the development of eastern-Pacific (EP) and CP El Niño-Southern Oscillation (<span class="hlt">ENSO</span>), respectively. In this work, a simple linear air-sea coupled model, which can accurately depict the strength distribution of the TH and ZA feedbacks in the equatorial Pacific, is used to investigate these two types of El Niño. The results indicate that the model can reproduce the main characteristics of CP <span class="hlt">ENSO</span> if the TH feedback is switched off and the ZA feedback is retained as the only positive feedback, confirming the dominant role played by ZA feedback in the development of CP <span class="hlt">ENSO</span>. Further experiments indicate that, through a simple nonlinear control approach, many <span class="hlt">ENSO</span> characteristics, including the existence of both CP and EP El Niño and the asymmetries between El Niño and La Niña, can be successfully captured using the simple linear air-sea coupled model. These analyses indicate that an accurate depiction of the climatological sea surface temperature distribution and the related ZA feedback, which are the subject of severe biases in GCMs, is very important in simulating a realistic CP El Niño.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...49..249H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...49..249H"><span>The weakening of the <span class="hlt">ENSO</span>-Indian Ocean Dipole (IOD) coupling strength in recent decades</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ham, Yoo-Geun; Choi, Jun-Young; Kug, Jong-Seong</p> <p>2017-07-01</p> <p>This study examines a recent weakening of the coupling between the El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) and the Indian Ocean Dipole (IOD) mode after the 2000s and 2010s compared to the previous two decades (1980s and 1990s). The correlation between the IOD during the September-November season and the Nino3.4 index during the December-February season is 0.21 for 1999-2014, while for the previous two decades (1979-1998) it is 0.64. It is found that this weakening of the <span class="hlt">ENSO</span>-IOD coupling during the 2000s and 2010s is associated with different spatial patterns in <span class="hlt">ENSO</span> evolution during the boreal spring and summer seasons. During the boreal spring season of the El Nino developing phase, positive precipitation anomalies over the northern off-equatorial western Pacific is systematically weakened during the 2000s and 2010s. This also weakens the low-level cross-equatorial southerly flow, which can cause local negative precipitation anomalies over the maritime continent through increased evaporation and cold and dry moist energy advection. The weakened negative precipitation anomalies over the maritime continent reduces the amplitude of the equatorial easterly over the IO, therefore, suppresses a <span class="hlt">ENSO</span>-related IOD variability. An analysis using climate models that participated in the Coupled Model Intercomparison Project phase 5 (CMIP5) supports this observational findings that the amplitude of the cross-equatorial southerly flow and associated suppressed convective activities over the maritime continent during the El Nino developing season are critical for determining the <span class="hlt">ENSO</span>-IOD coupling strength in climate models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy..tmp..246T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy..tmp..246T"><span>Assessing probabilistic predictions of <span class="hlt">ENSO</span> phase and intensity from the North American Multimodel Ensemble</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tippett, Michael K.; Ranganathan, Meghana; L'Heureux, Michelle; Barnston, Anthony G.; DelSole, Timothy</p> <p>2017-05-01</p> <p>Here we examine the skill of three, five, and seven-category monthly <span class="hlt">ENSO</span> probability forecasts (1982-2015) from single and multi-model ensemble integrations of the North American Multimodel Ensemble (NMME) project. Three-category forecasts are typical and provide probabilities for the <span class="hlt">ENSO</span> phase (El Niño, La Niña or neutral). Additional forecast categories indicate the likelihood of <span class="hlt">ENSO</span> conditions being weak, moderate or strong. The level of skill observed for differing numbers of forecast categories can help to determine the appropriate degree of forecast precision. However, the dependence of the skill score itself on the number of forecast categories must be taken into account. For reliable forecasts with same quality, the ranked probability skill score (RPSS) is fairly insensitive to the number of categories, while the logarithmic skill score (LSS) is an information measure and increases as categories are added. The ignorance skill score decreases to zero as forecast categories are added, regardless of skill level. For all models, forecast formats and skill scores, the northern spring predictability barrier explains much of the dependence of skill on target month and forecast lead. RPSS values for monthly <span class="hlt">ENSO</span> forecasts show little dependence on the number of categories. However, the LSS of multimodel ensemble forecasts with five and seven categories show statistically significant advantages over the three-category forecasts for the targets and leads that are least affected by the spring predictability barrier. These findings indicate that current prediction systems are capable of providing more detailed probabilistic forecasts of <span class="hlt">ENSO</span> phase and amplitude than are typically provided.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ClDy...48..405V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ClDy...48..405V"><span>The complex influence of <span class="hlt">ENSO</span> on droughts in Ecuador</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vicente-Serrano, S. M.; Aguilar, E.; Martínez, R.; Martín-Hernández, N.; Azorin-Molina, C.; Sanchez-Lorenzo, A.; El Kenawy, A.; Tomás-Burguera, M.; Moran-Tejeda, E.; López-Moreno, J. I.; Revuelto, J.; Beguería, S.; Nieto, J. J.; Drumond, A.; Gimeno, L.; Nieto, R.</p> <p>2017-01-01</p> <p>In this study, we analyzed the influence of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) on the spatio-temporal variability of droughts in Ecuador for a 48-year period (1965-2012). Droughts were quantified from 22 high-quality and homogenized time series of precipitation and air temperature by means of the Standardized Precipitation Evapotranspiration Index. In addition, the propagation of two different <span class="hlt">ENSO</span> indices (El Niño 3.4 and El Niño 1 + 2 indices) and other atmospheric circulation processes (e.g., vertical velocity) on different time-scales of drought severity were investigated. The results showed a very complex influence of <span class="hlt">ENSO</span> on drought behavior across Ecuador, with two regional patterns in the evolution of droughts: (1) the Andean chain with no changes in drought severity, and (2) the Western plains with less severe and frequent droughts. We also detected that drought variability in the Andes mountains is explained by the El Niño 3.4 index [sea surface temperature (SST) anomalies in the central Pacific], whereas the Western plains are much more driven by El Niño 1 + 2 index (SST anomalies in the eastern Pacific). Moreover, it was also observed that El Niño and La Niña phases enhance droughts in the Andes and Western plains regions, respectively. The results of this work could be crucial for predicting and monitoring drought variability and intensity in Ecuador.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CliPa..10.1857W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CliPa..10.1857W"><span>Late Holocene environmental reconstructions and their implications on flood <span class="hlt">events</span>, typhoon, and agricultural activities in NE Taiwan</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, L.-C.; Behling, H.; Lee, T.-Q.; Li, H.-C.; Huh, C.-A.; Shiau, L.-J.; Chang, Y.-P.</p> <p>2014-10-01</p> <p>We reconstructed paleoenvironmental changes from a sediment archive of a lake in the floodplain of the Ilan Plain of NE Taiwan on multi-decadal resolution for the last ca. 1900 years. On the basis of pollen and diatom records, we evaluated past floods, typhoons, and agricultural activities in this area which are sensitive to the hydrological conditions in the western Pacific. Considering the high sedimentation rates with low microfossil preservations in our sedimentary record, multiple flood <span class="hlt">events</span> were. identified during the period AD 100-1400. During the Little Ice Age phase 1 (LIA 1 - AD 1400-1620), the abundant occurrences of wetland plant (Cyperaceae) and diatom frustules imply less flood <span class="hlt">events</span> under stable climate conditions in this period. Between AD 500 and 700 and the Little Ice Age phase 2 (LIA 2 - AD 1630-1850), the frequent typhoons were inferred by coarse sediments and planktonic diatoms, which represented more dynamical climate conditions than in the LIA 1. By comparing our results with the reconstructed changes in tropical hydrological conditions, we suggested that the local hydrology in NE Taiwan is strongly influenced by typhoon-triggered heavy rainfalls, which could be influenced by the variation of global temperature, the expansion of the Pacific <span class="hlt">warm</span> pool, and the intensification of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMPA21B1869C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMPA21B1869C"><span>Communicating Climate Uncertainties: Challenges and Opportunities Related to Spatial Scales, Extreme <span class="hlt">Events</span>, and the <span class="hlt">Warming</span> 'Hiatus'</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Casola, J. H.; Huber, D.</p> <p>2013-12-01</p> <p>Many media, academic, government, and advocacy organizations have achieved sophistication in developing effective messages based on scientific information, and can quickly translate salient aspects of emerging climate research and evolving observations. However, there are several ways in which valid messages can be misconstrued by decision makers, leading them to inaccurate conclusions about the risks associated with climate impacts. Three cases will be discussed: 1) Issues of spatial scale in interpreting climate observations: Local climate observations may contradict summary statements about the effects of climate change on larger regional or global spatial scales. Effectively addressing these differences often requires communicators to understand local and regional climate drivers, and the distinction between a 'signal' associated with climate change and local climate 'noise.' Hydrological statistics in Missouri and California are shown to illustrate this case. 2) Issues of complexity related to extreme <span class="hlt">events</span>: Climate change is typically invoked following a wide range of damaging meteorological <span class="hlt">events</span> (e.g., heat waves, landfalling hurricanes, tornadoes), regardless of the strength of the relationship between anthropogenic climate change and the frequency or severity of that type of <span class="hlt">event</span>. Examples are drawn from media coverage of several recent <span class="hlt">events</span>, contrasting useful and potentially confusing word choices and frames. 3) Issues revolving around climate sensitivity: The so-called 'pause' or 'hiatus' in global <span class="hlt">warming</span> has reverberated strongly through political and business discussions of climate change. Addressing the recent slowdown in <span class="hlt">warming</span> yields an important opportunity to raise climate literacy in these communities. Attempts to use recent observations as a wedge between climate 'believers' and 'deniers' is likely to be counterproductive. Examples are drawn from Congressional testimony and media stories. All three cases illustrate ways that decision</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22314889-enso-regimes-late-climate-shift-role-synoptic-weather-south-pacific-ocean-spiciness','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22314889-enso-regimes-late-climate-shift-role-synoptic-weather-south-pacific-ocean-spiciness"><span><span class="hlt">ENSO</span> regimes and the late 1970's climate shift: The role of synoptic weather and South Pacific ocean spiciness</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>O'Kane, Terence J.; Matear, Richard J.; Chamberlain, Matthew A.</p> <p></p> <p>South Pacific subtropical density compensated temperature and salinity (spiciness) anomalies are known to be associated with decadal equatorial variability, however, the mechanisms by which such disturbances are generated, advect and the degree to which they modulate the equatorial thermocline remains controversial. During the late 1970's a climate regime transition preceded a period of strong and sustained El Nino <span class="hlt">events</span>. Using an ocean general circulation model forced by the constituent mechanical and thermodynamic components of the reanalysed atmosphere we show that the late 1970's transition coincided with the arrival of a large-scale, subsurface cold and fresh water anomaly in the centralmore » tropical Pacific. An ocean reanalysis for the period 1990–2007 that assimilates subsurface Argo, XBT and CTD data, reveals that disturbances occur due to the subduction of negative surface salinity anomalies from near 30° S, 100° W which are advected along the σ=25–26 kgm{sup −3} isopycnal surfaces. These anomalies take, on average, seven years to reach the central equatorial Pacific where they may substantially perturb the thermocline before the remnants ultimately ventilate in the region of the western Pacific <span class="hlt">warm</span> pool. Positive (warm–salty) disturbances, known to occur due to late winter diapycnal mixing and isopycnal outcropping, arise due to both subduction of subtropical mode waters and subsurface injection. On reaching the equatorial band (10° S–0° S) these disturbances tend to deepen the thermocline reducing the model's <span class="hlt">ENSO</span>. In contrast the emergence of negative (cold–fresh) disturbances at the equator are associated with a shoaling of the thermocline and El Nino <span class="hlt">events</span>. Process studies are used to show that the generation and advection of anomalous density compensated thermocline disturbances critically depend on stochastic forcing of the intrinsic ocean by weather. We further show that in the absence of the inter-annual component of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28317857','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28317857"><span>Enhanced biennial variability in the Pacific due to Atlantic capacitor effect.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Lei; Yu, Jin-Yi; Paek, Houk</p> <p>2017-03-20</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in <span class="hlt">ENSO</span> and the PSHs during recent decades. The 'charging' (that is, <span class="hlt">ENSO</span> imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and 'discharging' (that is, the NTA SST triggering the following <span class="hlt">ENSO</span> via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global <span class="hlt">warming</span> trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5364382','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5364382"><span>Enhanced biennial variability in the Pacific due to Atlantic capacitor effect</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Wang, Lei; Yu, Jin-Yi; Paek, Houk</p> <p>2017-01-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in <span class="hlt">ENSO</span> and the PSHs during recent decades. The ‘charging' (that is, <span class="hlt">ENSO</span> imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and ‘discharging' (that is, the NTA SST triggering the following <span class="hlt">ENSO</span> via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global <span class="hlt">warming</span> trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard <span class="hlt">events</span>. PMID:28317857</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatCo...814887W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatCo...814887W"><span>Enhanced biennial variability in the Pacific due to Atlantic capacitor effect</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Lei; Yu, Jin-Yi; Paek, Houk</p> <p>2017-03-01</p> <p>The El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in <span class="hlt">ENSO</span> and the PSHs during recent decades. The `charging' (that is, <span class="hlt">ENSO</span> imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and `discharging' (that is, the NTA SST triggering the following <span class="hlt">ENSO</span> via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global <span class="hlt">warming</span> trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard <span class="hlt">events</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.A41L..05G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.A41L..05G"><span>The contrasting role of Westerly Wind <span class="hlt">Events</span> in the evolution of El Niño during 2014 and 2015</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guilyardi, E.; Puy, M.; Vialard, J.; Lengaigne, M.; Voldoire, A.; Balmaseda, M.; Menkes, C.; Madec, G.; McPhaden, M. J.</p> <p>2016-12-01</p> <p>Short-lived wind <span class="hlt">events</span> in the equatorial Pacific strongly influence the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>). Contrasting the tropical Pacific evolution in 2014 against that of 2015 (or 1997) provides a compelling illustration of the key role of westerly wind <span class="hlt">events</span> (WWEs) on <span class="hlt">ENSO</span>. In late march, the years of 1997, 2014 and 2015 displayed relatively similar oceanic conditions in the tropical Pacific. Those three years were characterized by higher than normal (>1 std) equatorial Pacific heat content, and an abnormal extension of the <span class="hlt">warm</span> pool towards the central Pacific following the occurrence of one or several strong WWEs during winter. Yet, 1997 and 2015 developed into some of the strongest observed El Niño <span class="hlt">events</span> on record while only a weak <span class="hlt">warming</span> occurred in 2014. One major difference between 2014 and 1997/2015 was however a series of strong WWEs during the summer of the two later years while almost none occurred in 2014. In this study, we investigate the role of summer WWEs in the El Niño development using the CNRM-CM5 coupled model. We find analogs to the state of the Pacific in 1997, 2014 and 2015 in a 200-years control simulation of the model, and perform series of ensemble experiments starting from those initial states with added infinitesimal perturbations. While the recharged equatorial Pacific Ocean heat content excluded the occurrence of a La Niña in any of those years, the intrinsic atmospheric stochasticity leads to a Pacific state that ranges from almost neutral to an extreme El Niño at the end of the year. The amplitude of the El Niño at the end of the year is strongly associated with the number of WWEs that occur during summer. An ensemble sensitivity experiment in which WWEs are artificially removed displays a clear reduction in the number of extreme El Niños and a more peaked density probability toward "typical" El Niño <span class="hlt">events</span>, confirming the important role of WWEs for the occurrence of extreme El Niños. The observed 2014 evolution is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1395870-enso-related-precipitation-its-statistical-relationship-walker-circulation-trend-cmip5-amip-models','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1395870-enso-related-precipitation-its-statistical-relationship-walker-circulation-trend-cmip5-amip-models"><span><span class="hlt">ENSO</span>-Related Precipitation and Its Statistical Relationship with the Walker Circulation Trend in CMIP5 AMIP Models</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Yim, Bo; Yeh, Sang -Wook; Sohn, Byung -Ju</p> <p>2016-01-29</p> <p>Observational evidence shows that the Walker circulation (WC) in the tropical Pacific has strengthened in recent decades. In this study, we examine the WC trend for 1979–2005 and its relationship with the precipitation associated with the El Niño Southern Oscillation (<span class="hlt">ENSO</span>) using the sea surface temperature (SST)-constrained Atmospheric Model Intercomparison Project (AMIP) simulations of the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. All of the 29 models show a strengthening of the WC trend in response to an increase in the SST zonal gradient along the equator. Despite the same SST-constrained AMIP simulations, however, a large diversity ismore » found among the CMIP5 climate models in the magnitude of the WC trend. The relationship between the WC trend and precipitation anomalies (PRCPAs) associated with <span class="hlt">ENSO</span> (<span class="hlt">ENSO</span>-related PRCPAs) shows that the longitudinal position of the <span class="hlt">ENSO</span>-related PRCPAs in the western tropical Pacific is closely related to the magnitude of the WC trend. Specifically, it is found that the strengthening of the WC trend is large (small) in the CMIP5 AMIP simulations in which the <span class="hlt">ENSO</span>-related PRCPAs are located relatively westward (eastward) in the western tropical Pacific. Furthermore, the zonal shift of the <span class="hlt">ENSO</span>-related precipitation in the western tropical Pacific, which is associated with the climatological mean precipitation in the tropical Pacific, could play an important role in modifying the WC trend in the CMIP5 climate models.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMNG31A0159G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMNG31A0159G"><span>Using a 4D-Variational Method to Optimize Model Parameters in an Intermediate Coupled Model of <span class="hlt">ENSO</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, C.; Zhang, R. H.</p> <p>2017-12-01</p> <p>Large biases exist in real-time <span class="hlt">ENSO</span> prediction, which is attributed to uncertainties in initial conditions and model parameters. Previously, a four dimentional variational (4D-Var) data assimilation system was developed for an intermediate coupled model (ICM) and used to improve <span class="hlt">ENSO</span> modeling through optimized initial conditions. In this paper, this system is further applied to optimize model parameters. In the ICM used, one important process for <span class="hlt">ENSO</span> is related to the anomalous temperature of subsurface water entrained into the mixed layer (Te), which is empirically and explicitly related to sea level (SL) variation, written as Te=αTe×FTe (SL). The introduced parameter, αTe, represents the strength of the thermocline effect on sea surface temperature (SST; referred as the thermocline effect). A numerical procedure is developed to optimize this model parameter through the 4D-Var assimilation of SST data in a twin experiment context with an idealized setting. Experiments having initial condition optimized only and having initial condition plus this additional model parameter optimized both are compared. It is shown that <span class="hlt">ENSO</span> evolution can be more effectively recovered by including the additional optimization of this parameter in <span class="hlt">ENSO</span> modeling. The demonstrated feasibility of optimizing model parameter and initial condition together through the 4D-Var method provides a modeling platform for <span class="hlt">ENSO</span> studies. Further applications of the 4D-Var data assimilation system implemented in the ICM are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27432777','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27432777"><span>Climate Change and <span class="hlt">ENSO</span> Effects on Southeastern US Climate Patterns and Maize Yield.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mourtzinis, Spyridon; Ortiz, Brenda V; Damianidis, Damianos</p> <p>2016-07-19</p> <p>Climate change has a strong influence on weather patterns and significantly affects crop yields globally. El Niño Southern Oscillation (<span class="hlt">ENSO</span>) has a strong influence on the U.S. climate and is related to agricultural production variability. <span class="hlt">ENSO</span> effects are location-specific and in southeastern U.S. strongly connect with climate variability. When combined with climate change, the effects on growing season climate patterns and crop yields might be greater than expected. In our study, historical monthly precipitation and temperature data were coupled with non-irrigated maize yield data (33-43 years depending on the location) to show a potential yield suppression of ~15% for one °C increase in southeastern U.S. growing season maximum temperature. Yield suppression ranged between -25 and -2% among locations suppressing the southeastern U.S. average yield trend since 1981 by 17 kg ha(-1)year(-1) (~25%), mainly due to year-to-year June temperature anomalies. Yields varied among <span class="hlt">ENSO</span> phases from 1971-2013, with greater yields observed during El Niño phase. During La Niña years, maximum June temperatures were higher than Neutral and El Niño, whereas June precipitation was lower than El Niño years. Our data highlight the importance of developing location-specific adaptation strategies quantifying both, climate change and <span class="hlt">ENSO</span> effects on month-specific growing season climate conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AdAtS..35..495L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AdAtS..35..495L"><span><span class="hlt">ENSO</span> Frequency Asymmetry and the Pacific Decadal Oscillation in Observations and 19 CMIP5 Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lin, Renping; Zheng, Fei; Dong, Xiao</p> <p>2018-05-01</p> <p>Using observational data and the pre-industrial simulations of 19 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), the El Niño (EN) and La Niña (LN) <span class="hlt">events</span> in positive and negative Pacific Decadal Oscillation (PDO) phases are examined. In the observational data, with EN (LN) <span class="hlt">events</span> the positive (negative) SST anomaly in the equatorial eastern Pacific is much stronger in positive (negative) PDO phases than in negative (positive) phases. Meanwhile, the models cannot reasonably reproduce this difference. Besides, the modulation of <span class="hlt">ENSO</span> frequency asymmetry by the PDO is explored. Results show that, in the observational data, EN is 300% more (58% less) frequent than LN in positive (negative) PDO phases, which is significant at the 99% confidence level using the Monte Carlo test. Most of the CMIP5 models exhibit results that are consistent with the observational data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatCC...4..143Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatCC...4..143Z"><span>How <span class="hlt">warm</span> days increase belief in global <span class="hlt">warming</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zaval, Lisa; Keenan, Elizabeth A.; Johnson, Eric J.; Weber, Elke U.</p> <p>2014-02-01</p> <p>Climate change judgements can depend on whether today seems warmer or colder than usual, termed the local <span class="hlt">warming</span> effect. Although previous research has demonstrated that this effect occurs, studies have yet to explain why or how temperature abnormalities influence global <span class="hlt">warming</span> attitudes. A better understanding of the underlying psychology of this effect can help explain the public's reaction to climate change and inform approaches used to communicate the phenomenon. Across five studies, we find evidence of attribute substitution, whereby individuals use less relevant but available information (for example, today's temperature) in place of more diagnostic but less accessible information (for example, global climate change patterns) when making judgements. Moreover, we rule out alternative hypotheses involving climate change labelling and lay mental models. Ultimately, we show that present temperature abnormalities are given undue weight and lead to an overestimation of the frequency of similar past <span class="hlt">events</span>, thereby increasing belief in and concern for global <span class="hlt">warming</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H41A1408D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H41A1408D"><span>Forecasting of Seasonal Rainfall using <span class="hlt">ENSO</span> and IOD teleconnection with Classification Models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>De Silva, T.; Hornberger, G. M.</p> <p>2017-12-01</p> <p>Seasonal to annual forecasts of precipitation patterns are very important for water infrastructure management. In particular, such forecasts can be used to inform decisions about the operation of multipurpose reservoir systems in the face of changing climate conditions. Success in making useful forecasts often is achieved by considering climate teleconnections such as the El-Nino-Southern Oscillation (<span class="hlt">ENSO</span>), Indian Ocean Dipole (IOD) as related to sea surface temperature variations. We present an analysis to explore the utility of using rainfall relationships in Sri Lanka with <span class="hlt">ENSO</span> and IOD to predict rainfall to the Mahaweli, river basin. Forecasting of rainfall as classes - above normal, normal, and below normal - can be useful for water resource management decision making. Quadratic discrimination analysis (QDA) and random forest models are used to identify the patterns of rainfall classes with respect to <span class="hlt">ENSO</span> and IOD indices. These models can be used to forecast the likelihood of areal rainfall anomalies using predicted climate indices. Results can be used for decisions regarding allocation of water for agriculture and electricity generation within the Mahaweli project of Sri Lanka.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6666979-el-nino-southern-oscillation-simulated-mri-atmosphere-ocean-coupled-general-circulation-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6666979-el-nino-southern-oscillation-simulated-mri-atmosphere-ocean-coupled-general-circulation-model"><span>El Nino-southern oscillation simulated in an MRI atmosphere-ocean coupled general circulation model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Nagai, T.; Tokioka, T.; Endoh, M.</p> <p></p> <p>A coupled atmosphere-ocean general circulation model (GCM) was time integrated for 30 years to study interannual variability in the tropics. The atmospheric component is a global GCM with 5 levels in the vertical and 4[degrees]latitude X 5[degrees] longitude grids in the horizontal including standard physical processes (e.g., interactive clouds). The oceanic component is a GCM for the Pacific with 19 levels in the vertical and 1[degrees]x 2.5[degrees] grids in the horizontal including seasonal varying solar radiation as forcing. The model succeeded in reproducing interannual variations that resemble the El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) with realistic seasonal variations in the atmospheric andmore » oceanic fields. The model <span class="hlt">ENSO</span> cycle has a time scale of approximately 5 years and the model El Nino (<span class="hlt">warm</span>) <span class="hlt">events</span> are locked roughly in phase to the seasonal cycle. The cold <span class="hlt">events</span>, however, are less evident in comparison with the El Nino <span class="hlt">events</span>. The time scale of the model <span class="hlt">ENSO</span> cycle is determined by propagation time of signals from the central-eastern Pacific to the western Pacific and back to the eastern Pacific. Seasonal timing is also important in the <span class="hlt">ENSO</span> time scale: wind anomalies in the central-eastern Pacific occur in summer and the atmosphere ocean coupling in the western Pacific operates efficiently in the first half of the year.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AGUFMOS24C..08S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AGUFMOS24C..08S"><span>Long-Term <span class="hlt">ENSO</span> Variation Over the Last 20,000 Years From the Peru Continental Margin</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Skilbeck, G.; Fink, D.; Gagan, M.; Rein, B.</p> <p>2006-12-01</p> <p>Three ODP Leg 201 cores from the Peru continental margin comprise highly laminated diatomaceous ooze spanning Last Glacial Maximum to present. Geochemical proxy data, layer counting and spectral analysis of red color variation suggest the layers represent interannual accumulation under the influence tropical <span class="hlt">ENSO</span> conditions, with darker layers representing El Niño <span class="hlt">events</span>. AMS 14-C dating (Skilbeck &Fink, 2006) of bulk sediment from Sites 201-1228 and -1229 (~11°S) and comparison with Rein et al. (2005) Core SO147-106KL (~12°S) show that where the shelf is narrow south of ~10.5°S, regionally consistent rates of sediment accumulation have occurred over the late Deglaciation and Holocene, with high rates characterising the late (0-2.0 kyrBP, ~100 cm/ka) and the early (8.5-10 kyrBP, ~80 cm/ka) Holocene. Over these intervals laminae are of interannual resolution. Further north where the shelf is broader, Holocene-Late Deglaciation sediments are thin or absent, but the Early Deglaciation is well represented. In a core from ODP Site 201-1227 (~9°S, 427m water depth), the period 15.5-17.5 kyrBP is characterised by sediment accumulation rates in excess of 300 cm/ka, and interannual laminations are again present. Spectral analysis of the instrumental record of <span class="hlt">ENSO</span>, the SOI, shows a relative stable mode of variation with an average frequency of about 5.5 yr for the past 130 years. Analysis of our ODP cores shows that the <span class="hlt">ENSO</span> mode appears to be relatively stable for periods of 300-500 years throughout the Holocene with frequencies varying mostly between 5 and 8 years and relatively sudden mode switches, suggesting inter alia that the instrumental record is not long enough to test predictive models of <span class="hlt">ENSO</span> variation. Throughout the Holocene, this pattern of variation transcends the sedimentation-rate zones identified above, with the inference that changes in the rate of sedimentation have not influenced the temporal pattern. The later part of the deglaciation period (10</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20170007411&hterms=gravity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgravity','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20170007411&hterms=gravity&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dgravity"><span>The QBO, Gravity Waves Forced by Tropical Convection, and <span class="hlt">ENSO</span>.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Geller, Marvin A.; Zhou, Tiehan; Yuan, Wei</p> <p>2016-01-01</p> <p>By means of theory, a simplified cartoon illustrating wave forcing of the stratospheric quasi-biennial oscillation (QBO), and general circulation modeling of the QBO, it is argued that the period of the QBO is mainly controlled by the magnitude of the gravity wave (GW) vertical fluxes of horizontal momentum (GWMF) forcing the QBO, while the QBO amplitude is mainly determined by the phase speeds of the GWs that make up this momentum flux. It is furthermore argued that it is the zonally averaged GWMF that principally determines the QBO period irrespective of the longitudinal distribution of this GW momentum flux. These concepts are used to develop a hypothesis for the cause of a previously reported El Nino- Southern Oscillation (<span class="hlt">ENSO</span>) modulation of QBO periods and amplitudes. Some observational evidence is reported for the <span class="hlt">ENSO</span> modulation of QBO amplitudes to have been different before the 1980s than after about 1990. A hypothesis is also given to explain this in terms of the different <span class="hlt">ENSO</span> modulation of tropical deep convection that took place before the 1980s from that which occurred after about 1990. The observational evidence, while consistent with our hypotheses, does not prove that our hypotheses are correct given the small number of El Ninos and La Ninas that occurred in the early and later periods. Further research is needed to support or refute our hypotheses</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PalOc..32..903T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PalOc..32..903T"><span>Tropical Pacific climate variability over the last 6000 years as recorded in Bainbridge Crater Lake, Galápagos</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thompson, Diane M.; Conroy, Jessica L.; Collins, Aaron; Hlohowskyj, Stephan R.; Overpeck, Jonathan T.; Riedinger-Whitmore, Melanie; Cole, Julia E.; Bush, Mark B.; Whitney, H.; Corley, Timothy L.; Kannan, Miriam Steinitz</p> <p>2017-08-01</p> <p>Finely laminated sediments within Bainbridge Crater Lake, Galápagos, provide a record of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) <span class="hlt">events</span> over the Holocene. Despite the importance of this sediment record, hypotheses for how climate variability is preserved in the lake sediments have not been tested. Here we present results of long-term monitoring of the local climate and limnology and a revised interpretation of the sediment record. Brown-green, organic-rich, siliciclastic laminae reflect <span class="hlt">warm</span>, wet conditions typical of El Niño <span class="hlt">events</span>, whereas carbonate and gypsum precipitate during cool, dry La Niña <span class="hlt">events</span> and persistent dry periods, respectively. Applying this new interpretation, we find that <span class="hlt">ENSO</span> <span class="hlt">events</span> of both phases were generally less frequent during the mid-Holocene ( 6100-4000 calendar years B.P.) relative to the last 1500 calendar years. Abundant carbonate laminations between 3500 and 3000 calendar years B.P. imply that conditions in the Galápagos region were cool and dry during this period when the tropical Pacific E-W sea surface temperature (SST) gradient likely strengthened. The frequency of El Niño and La Niña <span class="hlt">events</span> then intensified dramatically around 1750-2000 calendar years B.P., consistent with a weaker SST gradient and an increased frequency of <span class="hlt">ENSO</span> <span class="hlt">events</span> in other regional records. This strong interannual variability persisted until 700 calendar years B.P., when <span class="hlt">ENSO</span>-related variability at the lake decreased as the SST gradient strengthened. Persistent, dry conditions then dominated between 300 and 50 calendar years B.P. (A.D. 1650-1900, ± 100 years), whereas wetter conditions and frequent El Niño <span class="hlt">events</span> dominated in the most recent century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4111296','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4111296"><span>δ 18O in the Tropical Conifer Agathis robusta Records <span class="hlt">ENSO</span>-Related Precipitation Variations</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Boysen, Bjorn M. M.; Evans, Michael N.; Baker, Patrick J.</p> <p>2014-01-01</p> <p>Long-lived trees from tropical Australasia are a potential source of information about internal variability of the El Niño-Southern Oscillation (<span class="hlt">ENSO</span>), because they occur in a region where precipitation variability is closely associated with <span class="hlt">ENSO</span> activity. We measured tree-ring width and oxygen isotopic composition (O) of -cellulose from Agathis robusta (Queensland Kauri) samples collected in the Atherton Tablelands, Queensland, Australia. Standard ring-width chronologies yielded low internal consistency due to the frequent presence of false ring-like anatomical features. However, in a detailed examination of the most recent 15 years of growth (1995–2010), we found significant correlation between O and local precipitation, the latter associated with <span class="hlt">ENSO</span> activity. The results are consistent with process-based forward modeling of the oxygen isotopic composition of -cellulose. The O record also enabled us to confirm the presence of a false growth ring in one of the three samples in the composite record, and to determine that it occurred as a consequence of anomalously low rainfall in the middle of the 2004/5 rainy season. The combination of incremental growth and isotopic measures may be a powerful approach to development of long-term (150+ year) <span class="hlt">ENSO</span> reconstructions from the terrestrial tropics of Australasia. PMID:25062034</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SZF.....1d..47P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SZF.....1d..47P"><span>Ionospheric reaction on sudden stratospheric <span class="hlt">warming</span> <span class="hlt">events</span> in Russiás Asia region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Polyakova, Anna; Perevalova, Natalya; Chernigovskaya, Marina</p> <p>2015-12-01</p> <p>The response of the ionosphere to sudden stratospheric <span class="hlt">warmings</span> (SSWs) in the Asian region of Russia is studied. Two SSW <span class="hlt">events</span> observed in 2008-2009 and 2012-2013 winter periods of extreme solar minimum and moderate solar maximum are considered. To detect the ionospheric effects caused by SSWs, we carried out a joint analysis of global ionospheric maps (GIM) of the total electron content (TEC), MLS (Microwave Limb Sounder, EOS Aura) measurements of temperature vertical profiles, as well as NCEP/NCAR and UKMO Reanalysis data. For the first time, it was found that during strong SSWs, in the mid-latitude ionosphere the amplitude of diurnal TEC variation decreases nearly half compared to quiet days. At the same time, the intensity of TEC deviations from the background level increases. It was also found that at SSW peak the midday TEC maximum decreases, and night/morning TEC values increase compared to quiet days. It was shown that during SSWs, TEC dynamics was identical for different geophysical conditions.The response of the ionosphere to sudden stratospheric <span class="hlt">warmings</span> (SSWs) in the Asian region of Russia is studied. Two SSW <span class="hlt">events</span> observed in 2008-2009 and 2012-2013 winter periods of extreme solar minimum and moderate solar maximum are considered. To detect the ionospheric effects caused by SSWs, we carried out a joint analysis of global ionospheric maps (GIM) of the total electron content (TEC), MLS (Microwave Limb Sounder, EOS Aura) measurements of temperature vertical profiles, as well as NCEP/NCAR and UKMO Reanalysis data. For the first time, it was found that during strong SSWs, in the mid-latitude ionosphere the amplitude of diurnal TEC variation decreases nearly half compared to quiet days. At the same time, the intensity of TEC deviations from the background level increases. It was also found that at SSW peak the midday TEC maximum decreases, and night/morning TEC values increase compared to quiet days. It was shown that during SSWs, TEC dynamics was</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040123716&hterms=aedes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Daedes','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040123716&hterms=aedes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Daedes"><span>Climate-disease connections: Rift Valley Fever in Kenya</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Anyamba, A.; Linthicum, K. J.; Tucker, C. J.</p> <p>2001-01-01</p> <p>All known Rift Valley fever(RVF) outbreaks in Kenya from 1950 to 1998 followed periods of abnormally high rainfall. On an interannual scale, periods of above normal rainfall in East Africa are associated with the <span class="hlt">warm</span> phase of the El Nino/Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon. Anomalous rainfall floods mosquito-breeding habitats called dambos, which contain transovarially infected mosquito eggs. The eggs hatch Aedes mosquitoes that transmit the RVF virus preferentially to livestock and to humans as well. Analysis of historical data on RVF outbreaks and indicators of <span class="hlt">ENSO</span> (including Pacific and Indian Ocean sea surface temperatures and the Southern Oscillation Index) indicates that more than three quarters of the RVF outbreaks have occurred during <span class="hlt">warm</span> <span class="hlt">ENSO</span> <span class="hlt">event</span> periods. Mapping of ecological conditions using satellite normalized difference vegetation index (NDVI) data show that areas where outbreaks have occurred during the satellite recording period (1981-1998) show anomalous positive departures in vegetation greenness, an indicator of above-normal precipitation. This is particularly observed in arid areas of East Africa, which are predominantly impacted by this disease. These results indicate a close association between interannual climate variability and RVF outbreaks in Kenya.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11426274','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11426274"><span>Climate-disease connections: Rift Valley Fever in Kenya.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Anyamba, A; Linthicum, K J; Tucker, C J</p> <p>2001-01-01</p> <p>All known Rift Valley fever(RVF) outbreaks in Kenya from 1950 to 1998 followed periods of abnormally high rainfall. On an interannual scale, periods of above normal rainfall in East Africa are associated with the <span class="hlt">warm</span> phase of the El Niño/Southern Oscillation (<span class="hlt">ENSO</span>) phenomenon. Anomalous rainfall floods mosquito-breeding habitats called dambos, which contain transovarially infected mosquito eggs. The eggs hatch Aedes mosquitoes that transmit the RVF virus preferentially to livestock and to humans as well. Analysis of historical data on RVF outbreaks and indicators of <span class="hlt">ENSO</span> (including Pacific and Indian Ocean sea surface temperatures and the Southern Oscillation Index) indicates that more than three quarters of the RVF outbreaks have occurred during <span class="hlt">warm</span> <span class="hlt">ENSO</span> <span class="hlt">event</span> periods. Mapping of ecological conditions using satellite normalized difference vegetation index (NDVI) data show that areas where outbreaks have occurred during the satellite recording period (1981-1998) show anomalous positive departures in vegetation greenness, an indicator of above-normal precipitation. This is particularly observed in arid areas of East Africa, which are predominantly impacted by this disease. These results indicate a close association between interannual climate variability and RVF outbreaks in Kenya.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000037976&hterms=fishing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfishing','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000037976&hterms=fishing&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dfishing"><span>El Nino Southern Oscillation and Tuna in the Western Pacific</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lehodey, P.; Bertignac, M.; Hampton, J.; Lewis, A.; Picaut, J.</p> <p>1997-01-01</p> <p>Nearly 70% of the world's annual tuna harvest, currently 3.2 million tonnes, comes from the Pacific Ocean. Skipjack tuna (Katsuwonus pelamis) dominate the catch. Although skipjack are distributed in the surface mixed layer throughout the equatorial and subtropical Pacific, catches are highest in the western equatorial Pacific <span class="hlt">warm</span> pool, a region characterized by low primary productivity rates that has the warmest surface waters of the world's oceans. Assessments of tuna stocks indicate that recent western Pacific skipjack catches approaching one million tonnes annually are sustainable. The <span class="hlt">warm</span> pool, which is fundamental to the El Nino Southern Oscillation (<span class="hlt">ENSO</span>) and the Earth's climate in general, must therefore also provide a habitat capable of supporting this highly productive tuna population. Here we show that apparent spatial shifts in the skipjack population are linked to large zonal displacements of the <span class="hlt">warm</span> pool that occur during <span class="hlt">ENSO</span> <span class="hlt">events</span>. This relationship can be used to predict (several months in advance) the region of highest skipjack abundance, within a fishing ground extending over 6,000 km along the Equator.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMNH51B1610G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMNH51B1610G"><span>Non-stationarity of extreme weather <span class="hlt">events</span> in a changing climate - an application to long-term droughts in the US Southwest</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grossmann, I.</p> <p>2013-12-01</p> <p>Return periods of many extreme weather <span class="hlt">events</span> are not stationary over time, given increasing risks due to global <span class="hlt">warming</span> and multidecadal variability resulting from large scale climate patterns. This is problematic as extreme weather <span class="hlt">events</span> and long-term climate risks such as droughts are typically conceptualized via measures such as return periods that implicitly assume non-stationarity. I briefly review these problems and present an application to the non-stationarity of droughts in the US Southwest. The US Southwest relies on annual precipitation maxima during winter and the North American Monsoon (NAM), both of which vary with large-scale climate patterns, in particular <span class="hlt">ENSO</span>, the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). The latter two exhibit variability on longer (multi-decadal) time scales in addition to short-term variations. The region is also part of the subtropical belt projected to become more arid in a <span class="hlt">warming</span> climate. The possible multidecadal impacts of the PDO on precipitation in the study region are analyzed with a focus on Arizona and New Mexico, using GPCC and CRU data since 1900. The projected impacts of the PDO on annual precipitation during the next three decades with GPCC data are similar in scale to the impacts of global <span class="hlt">warming</span> on precipitation according to the A1B scenario and the CMIP2 multi-model means, while the combined impact of the PDO and AMO is about 19% larger. The effects according to the CRU dataset are about half as large as the projected global <span class="hlt">warming</span> impacts. Given the magnitude of the projected impacts from both multidecadal variability and global <span class="hlt">warming</span>, water management needs to explicitly incorporate both of these trends into long-term planning. Multi-decadal variability could be incorporated into the concept of return periods by presenting return periods as time-varying or as conditional on the respective 'phase' of relevant multidecadal patterns and on global <span class="hlt">warming</span>. Problems</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GBioC..31..901E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GBioC..31..901E"><span>Impacts of <span class="hlt">ENSO</span> on air-sea oxygen exchange: Observations and mechanisms</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Eddebbar, Yassir A.; Long, Matthew C.; Resplandy, Laure; Rödenbeck, Christian; Rodgers, Keith B.; Manizza, Manfredi; Keeling, Ralph F.</p> <p>2017-05-01</p> <p>Models and observations of atmospheric potential oxygen (APO ≃ O2 + 1.1 * CO2) are used to investigate the influence of El Niño-Southern Oscillation (<span class="hlt">ENSO</span>) on air-sea O2 exchange. An atmospheric transport inversion of APO data from the Scripps flask network shows significant interannual variability in tropical APO fluxes that is positively correlated with the Niño3.4 index, indicating anomalous ocean outgassing of APO during El Niño. Hindcast simulations of the Community Earth System Model (CESM) and the Institut Pierre-Simon Laplace model show similar APO sensitivity to <span class="hlt">ENSO</span>, differing from the Geophysical Fluid Dynamics Laboratory model, which shows an opposite APO response. In all models, O2 accounts for most APO flux variations. Detailed analysis in CESM shows that the O2 response is driven primarily by <span class="hlt">ENSO</span> modulation of the source and rate of equatorial upwelling, which moderates the intensity of O2 uptake due to vertical transport of low-O2 waters. These upwelling changes dominate over counteracting effects of biological productivity and thermally driven O2 exchange. During El Niño, shallower and weaker upwelling leads to anomalous O2 outgassing, whereas deeper and intensified upwelling during La Niña drives enhanced O2 uptake. This response is strongly localized along the central and eastern equatorial Pacific, leading to an equatorial zonal dipole in atmospheric anomalies of APO. This dipole is further intensified by <span class="hlt">ENSO</span>-related changes in winds, reconciling apparently conflicting APO observations in the tropical Pacific. These findings suggest a substantial and complex response of the oceanic O2 cycle to climate variability that is significantly (>50%) underestimated in magnitude by ocean models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4645176','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4645176"><span>Impacts of the <span class="hlt">ENSO</span> Modoki and other Tropical Indo-Pacific Climate-Drivers on African Rainfall</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Preethi, B.; Sabin, T. P.; Adedoyin, J. A.; Ashok, K.</p> <p>2015-01-01</p> <p>The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (<span class="hlt">ENSO</span>), <span class="hlt">ENSO</span> Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (enhancement) of rainfall in southern (northern) hemispheric regions during March-May season. However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September. Interestingly, during boreal spring and summer, in many regions, the Indian Ocean drivers have influences opposite to those from tropical Pacific drivers. On the other hand, during the October-December season, the canonical El Niño and/or positive IOD are associated with an anomalous enhancement of rainfall in the Eastern Africa, while the El Niño Modoki <span class="hlt">events</span> are associated with an opposite impact. In addition to the Walker circulation changes, the Indo-Pacific drivers influence the African rainfall through modulating jet streams. During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet. This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa. PMID:26567458</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26567458','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26567458"><span>Impacts of the <span class="hlt">ENSO</span> Modoki and other Tropical Indo-Pacific Climate-Drivers on African Rainfall.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Preethi, B; Sabin, T P; Adedoyin, J A; Ashok, K</p> <p>2015-11-16</p> <p>The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (<span class="hlt">ENSO</span>), <span class="hlt">ENSO</span> Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (enhancement) of rainfall in southern (northern) hemispheric regions during March-May season. However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September. Interestingly, during boreal spring and summer, in many regions, the Indian Ocean drivers have influences opposite to those from tropical Pacific drivers. On the other hand, during the October-December season, the canonical El Niño and/or positive IOD are associated with an anomalous enhancement of rainfall in the Eastern Africa, while the El Niño Modoki <span class="hlt">events</span> are associated with an opposite impact. In addition to the Walker circulation changes, the Indo-Pacific drivers influence the African rainfall through modulating jet streams. During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet. This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy..tmp...35H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy..tmp...35H"><span>Uncertainty in Indian Ocean Dipole response to global <span class="hlt">warming</span>: the role of internal variability</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hui, Chang; Zheng, Xiao-Tong</p> <p>2018-01-01</p> <p>The Indian Ocean Dipole (IOD) is one of the leading modes of interannual sea surface temperature (SST) variability in the tropical Indian Ocean (TIO). The response of IOD to global <span class="hlt">warming</span> is quite uncertain in climate model projections. In this study, the uncertainty in IOD change under global <span class="hlt">warming</span>, especially that resulting from internal variability, is investigated based on the community earth system model large ensemble (CESM-LE). For the IOD amplitude change, the inter-member uncertainty in CESM-LE is about 50% of the intermodel uncertainty in the phase 5 of the coupled model intercomparison project (CMIP5) multimodel ensemble, indicating the important role of internal variability in IOD future projection. In CESM-LE, both the ensemble mean and spread in mean SST <span class="hlt">warming</span> show a zonal positive IOD-like (pIOD-like) pattern in the TIO. This pIOD-like mean <span class="hlt">warming</span> regulates ocean-atmospheric feedbacks of the interannual IOD mode, and weakens the skewness of the interannual variability. However, as the changes in oceanic and atmospheric feedbacks counteract each other, the inter-member variability in IOD amplitude change is not correlated with that of the mean state change. Instead, the ensemble spread in IOD amplitude change is correlated with that in <span class="hlt">ENSO</span> amplitude change in CESM-LE, reflecting the close inter-basin relationship between the tropical Pacific and Indian Ocean in this model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70021246','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70021246"><span>Decadal variations in the strength of <span class="hlt">ENSO</span> teleconnections with precipitation in the western United States</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>McCabe, G.J.; Dettinger, M.D.</p> <p>1999-01-01</p> <p>Changing patterns of correlations between the historical average June-November Southern Oscillation Index (SOI) and October-March precipitation totals for 84 climate divisions in the western US indicate a large amount of variability in SOI/precipitation relations on decadal time scales. Correlations of western US precipitation with SOI and other indices of tropical El Nino-Southern Oscillation (<span class="hlt">ENSO</span>) processes were much weaker from 1920 to 1950 than during recent decades. This variability in teleconnections is associated with the character of tropical air-sea interactions as indexed by the number of out-of-phase SOI/tropical sea surface temperature (SST) episodes, and with decadal variability in the North Pacific Ocean as indexed by the Pacific Decadal Oscillation (PDO). <span class="hlt">ENSO</span> teleconnections with precipitation in the western US are strong when SOI and NINO3 are out-of-phase and PDO is negative. <span class="hlt">ENSO</span> teleconnections are weak when SOI and NINO3 are weakly correlated and PDO is positive. Decadal modes of tropical and North Pacific Ocean climate variability are important indicators of periods when <span class="hlt">ENSO</span> indices, like SOI, can be used as reliable predictors of winter precipitation in the US.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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