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Sample records for nino southern oscillation

  1. A theory for El Nino and the Southern Oscillation

    NASA Technical Reports Server (NTRS)

    Cane, M. A.; Zebiak, S. E.

    1985-01-01

    A coupled atmosphere-ocean model is presented for El Nino and the Southern Oscillation that reproduces its major features, including its recurrence at irregular intervals. The interannual El Nino-Southern Oscillation cycle is maintained by deterministic interactions in the tropical Pacific region. Ocean dynamics alter sea-surface temperature, changing the atmospheric heating; the resulting changes in surface wind alter the ocean dynamics. Annually varying mean conditions largely determine the spatial pattern and temporal evolution of El Nino events.

  2. Theory for El Nino and the Southern Oscillation

    SciTech Connect

    Cane, M.A.; Zebiak, S.E.

    1985-05-31

    A coupled atmosphere-ocean model is presented for El Nino and the Southern Oscillation that reproduces its major features, including its recurrence at irregular intervals. The interannual El Nino-Southern Oscillation cycle is maintained by deterministic interactions in the tropical Pacific region. Ocean dynamics alter sea-surface temperature, changing the atmospheric heating; the resulting changes in surface wind alter the ocean dynamics. Annually varying mean conditions largely determine the spatial pattern and temporal evolution of El Nino events. 20 references, 3 figures.

  3. El Nino: Historical and paleoclimatic aspects of the Southern Oscillation

    SciTech Connect

    Diaz, H.F.; Markgraf, V.

    1992-01-01

    This book about El Nino/Southern Oscillation is divided into the following major sections: ENSO in the modern record; the use of historical records in ENSO reconstruction; Paleoclimate reconstructions of ENSO from tree-ring records, ice cores, corals; Low resolution paleoclimatic reconstruction of ENSO from marine and terrestrial proxy indicators. The overall theme of the book is the that improved reliability of individual ENSO indices might be achieved by pooling together as many of the proxy series as feasible.

  4. The Child's Tantrum: El Nino. The Origin of the El Nino-Southern Oscillation

    NASA Technical Reports Server (NTRS)

    Picault, Joel; Hackert, Eric; Busalacchi, Antonio; Murtugudde, Ragu; Lagerloef, Gary

    2000-01-01

    In 1997, a child's tantrums caught the world's attention. These tantrums took the form not of crying and foot stamping, but of droughts and floods. Obviously, this was no ordinary child. It was, in fact, The Child, or El Nino, as it was, named in the late 1800s by South American observers, who noted that its timing coincided with the Christmas holiday. El Nino is a reversal in sea surface temperature (SST) distributions that occurs once every few years in the tropical Pacific. When it coincides with a cyclical shift in air pressure, known as the Southern Oscillation, normal weather patterns are drastically altered. The combined phenomenon is known as El Nino-Southern Oscillation (ENSO). Although ENSO is a regular phenomenon, it was unusually strong in 1997. It produced heavy rainfall and floods in California and bestowed spring-like temperatures on the Midwest during the winter. These drastic changes in normal weather patterns captured the public imagination, from news reports to jokes on late-night talk shows. Naturally, people wanted to. know as much, about El Nino as possible. Fortunately, scientists had at their disposal new satellites and ocean sensors that provided an unprecedented level of information. Consequently, not only was the 1997 ENSO the strongest in recent memory, but it was also the most thoroughly studied. Prominent groups such as the NASA Seasonalto-Interannual Prediction Project (NSIPP) combined numerous aspects of climate modeling into a single, predictive endeavor.

  5. The El Nino/Southern Oscillation and Future Soybean Prices

    NASA Technical Reports Server (NTRS)

    Keppenne, C.

    1993-01-01

    Recently, it was shown that the application of a method combining singular spectrum analysis (SSA) and the maximum entropy method to univariate indicators of the coupled ocean-atmosphere El Nino/Southern Oscillation (ENSO) phenomenon can be helpful in determining whether an El Nino (EN) or La Nina (LN) event will occur. SSA - a variant of principal component analysis applied in the time domain - filters out variability unrelated to ENSO and separates the quasi-biennial (QB), two-to-three year variability, from a lower-frequency (LF) four-to-six year EN-LN cycle; the total variance associated with ENSO combines the QB and LF modes. ENSO has been known to affect weather conditions over much of the globe. For example, EN events have been connected with unusually rainy weather over the Central and Western US, while the opposite phases of the oscillation (LN) have been plausibly associated with extreme dry conditions over much of the same geographical area...

  6. The El Nino/Southern Oscillation and Future Soybean Prices

    NASA Technical Reports Server (NTRS)

    Keppenne, C.

    1993-01-01

    Recently, it was shown that the application of a method combining singular spectrum analysis (SSA) and the maximum entropy method to univariate indicators of the coupled ocean-atmosphere El Nino/Southern Oscillation (ENSO) phenomenon can be helpful in determining whether an El Nino (EN) or La Nina (LN) event will occur. SSA - a variant of principal component analysis applied in the time domain - filters out variability unrelated to ENSO and separates the quasi-biennial (QB), two-to-three year variability, from a lower-frequency (LF) four-to-six year EN-LN cycle; the total variance associated with ENSO combines the QB and LF modes. ENSO has been known to affect weather conditions over much of the globe. For example, EN events have been connected with unusually rainy weather over the Central and Western US, while the opposite phases of the oscillation (LN) have been plausibly associated with extreme dry conditions over much of the same geographical area...

  7. 40-50 day oscillation and the El-Nino/Southern Oscillation - a new perspective

    SciTech Connect

    Lau, K.M.; Chan, P.H.

    1986-05-01

    The tropical ocean-atmosphere exhibits two prominent modes of low-frequency oscillations, i.e, the 40-50 day oscillation and the El Nino/Southern Oscillation (ENSO). The two phenomena are viewed in the same perspective from 10 years of satellite-derived out-going-longwave-radiation data. Results reveal some interesting features that may lead to new insights into the understanding of the two phenomena.

  8. A delayed action oscillator for ENSO. [El Nino/Southern Oscillation

    NASA Technical Reports Server (NTRS)

    Suarez, Max J.; Schopf, Paul S.

    1988-01-01

    A simple nonlinear model is proposed for the El Nino/Southern Oscillation (ENSO) phenomenon. Its key feature is the inclusion of oceanic wave transit effects through a negative, delayed feedback. A linear stability analysis and numerical results are presented, showing that the period of the oscillation is typically several times the delay. It is suggested that such an effect can account for the long time scale of ENSO.

  9. El Nino Southern Oscillation and Tuna in the Western Pacific

    NASA Technical Reports Server (NTRS)

    Lehodey, P.; Bertignac, M.; Hampton, J.; Lewis, A.; Picaut, J.

    1997-01-01

    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 warm 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 warm pool, which is fundamental to the El Nino Southern Oscillation (ENSO) 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 warm pool that occur during ENSO events. 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.

  10. El Nino Southern Oscillation and Tuna in the Western Pacific

    NASA Technical Reports Server (NTRS)

    Lehodey, P.; Bertignac, M.; Hampton, J.; Lewis, A.; Picaut, J.

    1997-01-01

    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 warm 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 warm pool, which is fundamental to the El Nino Southern Oscillation (ENSO) 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 warm pool that occur during ENSO events. 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.

  11. Central Pacific Seabirds and the El Nino Southern Oscillation: 1982 to 1983 Perspectives

    NASA Astrophysics Data System (ADS)

    Schreiber, Ralph W.; Schreiber, Elizabeth Anne

    1984-08-01

    The breeding chronology and reproductive attempts of the seabird community on Christmas Island in the central Pacific Ocean (2 degrees N, 157 degrees W) were interrupted by the 1982-1983 El Nino Southern Oscillation. The resultant reproductive failure and disappearance of the entire seabird community of this equatorial atoll represents the most dramatic interruption on record of a seabird community located distant from coastal upwelling. Our data indicate the effect that the abiotic and biotic aspects of a global atmospheric-oceanic anomaly have on marine birds. The 1982-1983 El Nino Southern Oscillation provides an example of selective pressures and a natural experiment in the study of vertebrate population dynamics.

  12. Optimizing irrigation strategies as influenced by El Nino southern oscillation

    USDA-ARS?s Scientific Manuscript database

    Equatorial Pacific sea surface temperature anomalies (SSTA) can cause a systematic El Niño-Southern Oscillation (ENSO) coupling with the atmosphere to produce predictable weather patterns in much of North America. Adapting irrigation strategies for drought tolerant crops like cotton [Gossypium hirsu...

  13. El Nino: Historical and paleoclimatic aspects of the southern oscillation

    SciTech Connect

    Diaz, H.F.; Markgraf, V.

    1992-01-01

    This book, including 22 papers by well-known authorities, presents a balanced picture of the possible types of information that can be bound about the past occurrence of El Nino. Topics presented include the following: oxygen-isotope analyses of ice cores in the Andes; tree-ring growth; trace mineral concentrations in annual layers of coral reefs; Nile River flood records back 13 centuries. The book is accessible to outsiders whose interests require a knowledge of El Nino and its historical manifestations.

  14. 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.

  15. Influence of El Nino Southern Oscillation on the Mesospheric Temperature

    NASA Technical Reports Server (NTRS)

    Li, Tao; Calvo, Natalia; Yue, Jia; Dou, Xiankang; Russell, J. M, III; Mlynczak, M. G.; She, Chiao-Yao; Xue, Xianghui

    2013-01-01

    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 (ENSO) on middle atmosphere temperature during the Northern Hemisphere (NH) wintertime. For the first time, a significant winter temperature response to ENSO in the middle mesosphere has been observed, with an anomalous warming of approximately 1.0 K/MEI (Multivariate ENSO Index) in the tropics and an anomalous cooling of approximately 2.0 K/MEI in the NH middle latitudes. The observed temperature responses to ENSO in the mesosphere are opposite to those in the stratosphere, in agreement with previous modeling studies. Temperature responses to ENSO 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 ENSO reveals a significant downwelling in the tropical mesosphere and upwelling in the NH middle and high latitudes during warm ENSO events, which is mostly driven by anomalous eastward gravity wave forcing in the NH mesosphere.

  16. Influence of El Nino Southern Oscillation on the Mesospheric Temperature

    NASA Technical Reports Server (NTRS)

    Li, Tao; Calvo, Natalia; Yue, Jia; Dou, Xiankang; Russell, J. M, III; Mlynczak, M. G.; She, Chiao-Yao; Xue, Xianghui

    2013-01-01

    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 (ENSO) on middle atmosphere temperature during the Northern Hemisphere (NH) wintertime. For the first time, a significant winter temperature response to ENSO in the middle mesosphere has been observed, with an anomalous warming of approximately 1.0 K/MEI (Multivariate ENSO Index) in the tropics and an anomalous cooling of approximately 2.0 K/MEI in the NH middle latitudes. The observed temperature responses to ENSO in the mesosphere are opposite to those in the stratosphere, in agreement with previous modeling studies. Temperature responses to ENSO 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 ENSO reveals a significant downwelling in the tropical mesosphere and upwelling in the NH middle and high latitudes during warm ENSO events, which is mostly driven by anomalous eastward gravity wave forcing in the NH mesosphere.

  17. El Nino Southern Oscillation (ENSO) impact on tuna fisheries in Indian Ocean.

    PubMed

    Kumar, Palanisamy Satheesh; Pillai, Gopalakrishna N; Manjusha, Ushadevi

    2014-01-01

    El Nino Southern Oscillation (ENSO) is an important driver of interannual variations in climate and ecosystem productivity in tropical regions. However, detailed information about this important phenomenon of the Indian Ocean is scarce. Consequently, the objective of this study is to improve understanding of the impact of warm event El Nino and cool event La Nina on annual tuna landings from the Indian Ocean from 1980 to 2010. In this study, maximum tuna landings were recorded during a weak El Nino year (1456054 t in 2006) and during a weak La Nina year (1243562 t in 2000), although the lowest tuna catch was followed during the strong El Nino year (1204119 t in 2009) and during a strong La Nina year (706546 t in 1988). Validation of predicted tuna landings and SST were showing a significant positive correlation (p < 0.01) was observed all the major tuna species except Southern Bluefin Tuna. Whereas the other relationships such as sea level pressure, Wind actions; Zonal Wind (U), Meridonial Wind (V), and Scalar Wind (W) are less well-defined. In contrast with principal component analysis we find that Principal Components 1 explains 75.5% of the total variance and suggest that sea surface temperature plays a major role in determining tuna availability in the region especially during warm event El Nino years; landings in Indian Ocean tend to be optimum SST 25 to 26°C in ENSO event. Our results confirm the ENSO impact on climate, tuna abundance and production in the Indian Ocean. However, among the oceanic variables SST explained the highest deviance in generalized additive models and therefore considered the best habitat predictor in the Indian Ocean followed by sea level pressure and Winds (U, V, W).

  18. Tropical ocean-atmosphere interaction, the Pacific cold tongue, and the El Nino-Southern Oscillation

    SciTech Connect

    Jin, F.F.

    1996-10-04

    The tropical Pacific basin allows strong feedbacks among the trade winds, equatorial zonal sea surface temperature contrast, and upper ocean heat content. Coupled atmosphere-ocean dynamics produce both the strong Pacific cold tongue climate state and the El Nino-Southern Oscillation phenomenon. A simple paradigm of the tropical climate system is presented, capturing the basic physics of these two important aspects of the tropic Pacific and basic features of the climate states of the Atlantic and Indian ocean basins. 21 refs., 3 figs.

  19. El Nino-southern oscillation simulated in an MRI atmosphere-ocean coupled general circulation model

    SciTech Connect

    Nagai, T.; Tokioka, T.; Endoh, M.; Kitamura, Y. )

    1992-11-01

    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 (ENSO) with realistic seasonal variations in the atmospheric and oceanic fields. The model ENSO cycle has a time scale of approximately 5 years and the model El Nino (warm) events are locked roughly in phase to the seasonal cycle. The cold events, however, are less evident in comparison with the El Nino events. The time scale of the model ENSO 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 ENSO 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.

  20. El Nino Southern Oscillation (ENSO) enhances CO2 exchange rates in freshwater marsh ecosystems in the Florida Everglades

    Treesearch

    Sparkle L. Malone; Christina L. Staudhammer; Steven F. Oberbauer; Paulo Olivas; Michael G. Ryan; Jessica L. Schedlbauer; Henry W. Loescher; Gregory Starr

    2014-01-01

    This research examines the relationships between El Nino Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009–2013) from two freshwater marsh sites located in Everglades National Park that differ...

  1. The hydroclimatology of the United States during El Nino/Southern Oscillation

    SciTech Connect

    Dracup, J.A.; Piechota, T.C.; Khachikian, C.S.

    1995-12-31

    Palmer Drought Severity Index (PDSI) monthly data are analyzed, building on a previous study that investigated the influence of the El Nino/Southern Oscillation (ENSO) on US streamflow. Harmonic analysis is performed using data from 1,035 selected climatological stations, allowing observation of the biennial tendency in climate data. With the middle twelve months defined as the El Nino year (0), an idealized first harmonic fit to a 24-month ENSO composite is computed for each station. By plotting the first harmonic vectors of each station, regions of similar, or coherent, response are identified. The regions identified using PDSI data represent wet conditions in the Gulf of Mexico (Gm1 and GM2) and central (C) US, and dry conditions in the Pacific northwest (PNW) and northeast (NE) US. The PNW region exhibits the strongest interrelationship between ENSO and extreme drought events. Comparing PDSI data results with other hydroclimatic data (temperature, precipitation, and streamflow) reveals consistent responses. The most filtered response is seen in the PDSI and streamflow data, and these data are probably the best measure of the overall hydroclimatic response within a region. Results of this study suggest that conditions in the tropical Pacific (e.g., sea surface temperatures) may be excellent precursors of future climate. These conditions may also enhance long range prediction of droughts and floods for certain regions of the US.

  2. Impacts of El Nino Southern Oscillation on the Global Yields of Major Crops

    NASA Technical Reports Server (NTRS)

    Iizumi, Toshichika; Luo, Jing-Jia; Challinor, Andrew J.; Sakurai, Gen; Yokozawa, Masayuki; Sakuma, Hirofumi; Brown, Molly Elizabeth; Yamagata, Toshio

    2014-01-01

    The monitoring and prediction of climate-induced variations in crop yields, production and export prices in major food-producing regions have become important to enable national governments in import-dependent countries to ensure supplies of affordable food for consumers. Although the El Nino/Southern Oscillation (ENSO) often affects seasonal temperature and precipitation, and thus crop yields in many regions, the overall impacts of ENSO on global yields are uncertain. Here we present a global map of the impacts of ENSO on the yields of major crops and quantify its impacts on their global-mean yield anomalies. Results show that El Nino likely improves the global-mean soybean yield by 2.15.4 but appears to change the yields of maize, rice and wheat by -4.3 to +0.8. The global-mean yields of all four crops during La Nina years tend to be below normal (-4.5 to 0.0).Our findings highlight the importance of ENSO to global crop production.

  3. Excitation of the Earth's Chandler wobble by southern oscillation/El Nino, 1900-1979

    NASA Technical Reports Server (NTRS)

    Chao, B. F.

    1985-01-01

    The southern oscillation/El Nino (ENSO) is the single most prominent interannual signal in global atmospheric/oceanic fluctuations. The following question is addressed: how important is the angular momentum carried by ENSO in exciting the Earth's Chandler wobble? The question is attacked through a statistical analysis of the coherence spectra (correlation as a function of frequency) between two data sets spanning 1900 to 1979-the southern oscillation index (SOI) time series and the excitation function psi (with x-component psi sub x and y-component psi sub y) of the Chandler wobble derived from the homogeneous ILS (International Latitude Service) polar motion data. The coherence power and phase in the Chandler frequency band (approx. 0.79 to 0.89 cpy) are studied. It is found that, during 1900 to 1979 the coherence between SOI and psi sub x is significant well over the 95% confidence threshold whereas that between SOI and psi sub y is practically nil. Quantitatively, the coherence study shows that ENSO provides some 20% of the observed Chandler wobble excitation power. Since earlier investigations have shown that the total atmospheric/oceanic variation can account for the Chandler wobble excitation at about 20% level, the implication is that ENSO maybe an important (interannual) part of the atmospheric/oceanic variation that is responsible for the Chandler wobble excitation during 1900 to 1979.

  4. Use of Data to Improve El Nino Southern Oscillation Simulations and Forecasts

    NASA Technical Reports Server (NTRS)

    Perigaud, Claire

    1999-01-01

    Various data over the period 1980-1998 have been used to improve El Nino Southern Oscillation (ENSO) simulations and forecasts performed by coupled ocean/atmosphere models. For such a study, oceanic and atmospheric satellite data are necessary. Models assume a baroclinic ocean with a mixed layer coupled to a baroclinic atmosphere to simulate the anomalous fields. The various data have been used to revisit the parameterizations of the subsurface temperature in the mixed layer, atmospheric convection, and friction in the baroclinic ocean. This new model, named Tsub.Conv, simulates 4-year oscillations like the model with the original parameterization, but with anomalous thermocline and wind anomalies that agree a lot better with reality. The atmospheric model still presents some deficiencies in the eastern Pacific and when it is replaced by a statistical atmosphere, the coupled model (Tsub.Astat) performs even better. It is found that the off-equatorial ocean and wind curl anomalies play a crucial role for all these models and that Tsub.Astat simulates an ocean heat content recharge coming from the north prior to a warm event like the ones observed during the 1985-1992 period. The ENSO forecasts over 1980-1998 are considerably improved with Tsub.Astat. One needs to add the simulation of westerly wind bursts to be able to forecast the 1997 event one year in advance. Additional information is contained in the original.

  5. Use of Data to Improve El Nino Southern Oscillation Simulations and Forecasts

    NASA Technical Reports Server (NTRS)

    Perigaud, Claire

    1999-01-01

    Various data over the period 1980-1998 have been used to improve El Nino Southern Oscillation (ENSO) simulations and forecasts performed by coupled ocean/atmosphere models. For such a study, oceanic and atmospheric satellite data are necessary. Models assume a baroclinic ocean with a mixed layer coupled to a baroclinic atmosphere to simulate the anomalous fields. The various data have been used to revisit the parameterizations of the subsurface temperature in the mixed layer, atmospheric convection, and friction in the baroclinic ocean. This new model, named Tsub.Conv, simulates 4-year oscillations like the model with the original parameterization, but with anomalous thermocline and wind anomalies that agree a lot better with reality. The atmospheric model still presents some deficiencies in the eastern Pacific and when it is replaced by a statistical atmosphere, the coupled model (Tsub.Astat) performs even better. It is found that the off-equatorial ocean and wind curl anomalies play a crucial role for all these models and that Tsub.Astat simulates an ocean heat content recharge coming from the north prior to a warm event like the ones observed during the 1985-1992 period. The ENSO forecasts over 1980-1998 are considerably improved with Tsub.Astat. One needs to add the simulation of westerly wind bursts to be able to forecast the 1997 event one year in advance. Additional information is contained in the original.

  6. El Nino-southern oscillation: A coupled response to the greenhouse effect?

    SciTech Connect

    Sun, De-Zheng

    1997-11-01

    The purpose of this article to elucidate the link between the El Nino-Southern Oscillation (ENSO) and radiative forcing (of which the greenhouse effect is a major part). A unified theory for the tropical Pacific climate is developed by considering the response of the coupled ocean-atmosphere to a changing radiative forcing. The hypothesis is that both the zonal surface sea temperature (SST) gradients and ENSO are a coupled response to the strong radiative heating or the tropical warmth. Owing to ocean-atmosphere interaction, the stronger the radiative heating, the larger the zonal SST gradients. When the SST gradients exceed a critical value, however, the ocean-atmosphere interaction in the cold-tongue region is too strong for the coupled system to hold steady. Consequently, the coupled system enters an oscillatory state. These coupled dynamics are examined in a simple mathematical model whose behavior is consistent with the hypothesis. With a linear temperature profile throughout the depth of subsurface ocean, the model predicts that both the magnitude and period of the oscillation increase with increases in radiative forcing or the greenhouse effect. The increase in the magnitude of the oscillation largely comes from an enhancement of the magnitude of the cold anomalies, while the increase in the period mostly comes from a prolonged duration of the warm events. With a profile in which the lapse rate decreases with depth, the sensitivity is more moderate. The simplicity of the model prevents a quantitative simulation of the sensitivity of ENSO to increases in the greenhouse effect, but qualitatively the model results support the empirical interpretation of the prolonged duration of the 1990-1995 ENSO event. 5 refs., 7 figs.

  7. Simulated Impacts of El Nino/Southern Oscillation on United States Water Resources

    SciTech Connect

    Thomson, Allison M. ); Brown, Robert A. ); Rosenberg, Norman J. ); Izaurralde, R Cesar C. ); Legler, David; Srinivasan, Ragahvan

    2003-02-01

    The El Nino/Southern Oscillation alters global weather patterns with consequences for fresh water quality and supply. ENSO events impact regions and natural resource sectors around the globe. For example, in 1997-98, a strong El Ni?o brought warm ocean temperatures, flooding and record snowfall to the west coast of the US. Research on ENSO events 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 ENSO states on water resources in the conterminous United States. We distinguish between Neutral, El Ni?o, La Ni?a and strong El Ni?o years over the period of 1960-1989. Using climate statistics that characterize these ENSO states to drive the HUMUS water resources model, we examine the effects of 'pure' ENSO events, 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.

  8. Influences of the El Nino Southern Oscillation and the Pacific Decadal Oscillation on the Timing of the North American Spring

    NASA Technical Reports Server (NTRS)

    McCabe, Gregory J.; Ault, Toby R.; Cook, Benjamin I.; Betancourt, Julio L.; Schwartz, Mark D.

    2012-01-01

    Detrended, modelled first leaf dates for 856 sites across North America for the period 1900-2008 are used to examine how the El Nino Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) separately and together might influence the timing of spring. Although spring (mean March through April) ENSO and PDO signals are apparent in first leaf dates, the signals are not statistically significant (at a 95% confidence level (p <0.05)) for most sites. The most significant ENSO/PDO signal in first leaf dates occurs for El Nino and positive PDO conditions. An analysis of the spatial distributions of first leaf dates for separate and combined ENSO/PDO conditions features a northwest-southeast dipole that is significantly (at p <0.05) different than the distributions for neutral conditions. The nature of the teleconnection between Pacific SST's and first leaf dates is evident in comparable composites for detrended sea level pressure (SLP) in the spring months. During positive ENSO/PDO, there is an anomalous flow of warm air from the southwestern US into the northwestern US and an anomalous northeasterly flow of cold air from polar regions into the eastern and southeastern US. These flow patterns are reversed during negative ENSO/PDO. Although the magnitudes of first leaf date departures are not necessarily significantly related to ENSO and PDO, the spatial patterns of departures are significantly related to ENSO and PDO. These significant relations and the long-lived persistence of SSTs provide a potential tool for forecasting the tendencies for first leaf dates to be early or late.

  9. Oceanic Internal Variability, Tropical Instability Waves and the El Nino-Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Holmes, Ryan; McGregor, Shayne; Santoso, Agus; England, Matthew

    2017-04-01

    Tropical instability waves (TIWs) are a major source of internally-generated oceanic variability in the central and eastern equatorial Pacific Ocean. These non-linear processes play an important role in the heat and momentum budgets and influence the sea surface temperature (SST) in a region critical for low-frequency coupled modes of variability such as the El Nino-Southern Oscillation (ENSO). However, their direct contribution to this type of interannual variability has received little attention. Previous studies using ocean- or atmosphere-only models suggest that TIW rectification may drive low-frequency SST and wind stress variability in the eastern Pacific that is comparable in magnitude to that driven by the Madden-Julian Oscillation (MJO) in the western Pacific. Other work suggests that TIWs can interact with equatorial Kelvin waves, limiting the magnitude of the associated thermocline depth and SST anomalies. In this study, we investigate the influence of TIWs on coupled variability using a 1/4-degree ocean model of the equatorial Pacific coupled to a simple atmosphere. The use of a simple atmosphere, in which a large portion of complex intrinsic atmospheric variability is absent, is intended to facilitate an examination of the first-order TIW effect on coupled variability. This setup allows the dominant mode of air-sea coupling, represented as a statistical relationship between SST and wind stress anomalies, while also permitting the effects of TIW-rectification on the variability of thermodynamic fields near the air-sea interface. Using this model setup, we perform two ensembles of idealised coupled model forecast experiments which are initiated with either downwelling or upwelling Kelvin waves in the western Pacific. By examining the results of these ensemble experiments, which only differ due to internal oceanic variability, we quantify the impact of TIWs on the characteristics of subsequent coupled events. The results have implications for our

  10. Explosive volcanic eruptions, the El Nino-southern oscillation, and U.S. climate variability

    SciTech Connect

    Portman, D.A.

    1996-01-01

    A study was conducted to identify and separate possible signals of volcanic eruptions and of the El Nino Southern Oscillation (ENSO) in U.S. surface climate records. Anomalies of monthly mean surface air temperature and total precipitation taken from the U.S. Historical Climatology Network were composited (averaged) over years of major explosive volcanic eruptions, ENSO warm events, and ENSO cold events since the year 1900. It was assumed that volcanic eruptions and ENSO events occur independently of each other. All composite anomalies were assessed for significance with regard to several statistical and physical criteria. The composite ENSO-related anomalies were then subtracted from anomalies of temperature and precipitation associated with the volcanic eruptions. Removal of large magnitude and highly significant anomalies associated with the ENSO warm and cold events is found to facilitate detection of volcanic signals in monthly records of U.S. temperature and precipitation. Volcanic signals are strongly suggested east of the Continental Divide, for example, where positive monthly temperature anomalies exceeding 1{degrees}C occur during the first fall and winter after eruptions. Negative temperature anomalies occur west of the Continental Divide during the first winter and spring after eruptions and in the southern United States during the summer of the first post-eruption calendar year. Positive monthly precipitation anomalies exceeding 15 mm in magnitude are found in the southeastern United States during the first winter and spring after eruptions. Precipitation anomalies that are smaller in magnitude and yet significant, such as positive anomalies in the northwestern United States and negative anomalies in the central and eastern United States, are found during the summer of the first post-eruption calendar year. 62 refs., 9 figs., 4 tabs.

  11. The Past, Present and Future of the El Nino/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Stevenson, Samantha

    Predicting how the strength and character of the El Nino/Southern Oscillation (ENSO) will change as the climate warms is crucial for a number of societal impacts, yet there are fundamental limitations to our understanding of ENSO dynamics. The major obstacles are related to sampling length, physical adjustments to climate changes, errors in model physics and uncertainties in forcing projections. This dissertation uses these issues to assess what we currently can and cannot say about future ENSO variability. The temporal extent of modern observations is too short to properly measure natural ENSO variations: averaging together at least 200 years is required to obtain robust ENSO statistics in a stable climate. Using paleoclimate 'proxies' to extend the observational record is another option, but is complicated by the uncertainties involved in translating between model and proxy signals. Coral oxygen isotopes, the most commonly used ENSO proxy, are shown to be governed by nonlinear dynamics: a more accurate 'forward model' for coral delta18O is needed. Even using such a model, at least 4-5 contemporaneous records will be required for accurate ENSO amplitude estimation. Simulations using several IPCC-class general circulation models (GCMs) are used to demonstrate that the adjustment to climate change itself takes place over decadal timescales, meaning that ENSO response is not statistically significant during the 21st century. This implies that current model intercomparison experiments are insufficient to measure the true range of ENSO climate sensitivity. However, significant changes to atmospheric teleconnections may take place within the 21st century: the NCAR Community Climate System Model version 4 (CCSM4), for example, predicts harsher winters in the Southwestern US during La Nina and weaker Australian teleconnections during both El Nino and La Nina. Stabilized CCSM3.5 simulations are then performed, which show that once the climate has equilibrated, the ENSO

  12. El-Nino Southern Oscillation simulated and predicted in SNU coupled GCMs

    NASA Astrophysics Data System (ADS)

    Ham, Yoo-Geun; Kang, In-Sik; Kim, Daehyun; Kug, Jong-Seong

    2012-06-01

    The characteristics of the El-Nino Southern Oscillation (ENSO) simulated in free integrations using two versions of the Seoul National University (SNU) ocean-atmosphere coupled global climate model (CGCM) are examined. A revised version of the SNU CGCM is developed by incorporating a reduced air-sea coupling interval (from 1 day to 2 h), a parameterization for cumulus momentum transport, a minimum entrainment rate threshold for convective plumes, and a shortened auto-conversion time scale of cloud water to raindrops. With the revised physical processes, lower tropospheric zonal wind anomalies associated with the ENSO-related sea surface temperature anomalies (SSTA) are represented with more realism than those in the original version. From too weak, the standard deviation of SST over the eastern Pacific becomes too strong in the revised version due to the enhanced air-sea coupling strength and intraseasonal variability associated with ENSO. From the oceanic side, the stronger stratification and the shallower-than-observed thermocline over the eastern Pacific also contribute to the excessive ENSO. The impacts of the revised physical processes on the seasonal predictability are investigated in two sets of the hindcast experiment performed using the two versions of CGCMs. The prediction skill measured by anomaly correlation coefficients of monthly-mean SSTA shows that the new version has a higher skill over the tropical Pacific regions compared to the old version. The better atmospheric responses to the ENSO-related SSTA in the revised version lead to the basin-wide SSTA maintained and developed in a manner that is closer to observations. The symptom of an excessively strong ENSO of the new version in the free integration is not prominent in the hindcast experiment because the thermocline depth over the eastern Pacific is maintained as initialized over the arc of time of the hindcast (7 months).

  13. How are streamflow responses to the El Nino Southern Oscillation affected by watershed characteristics?

    NASA Astrophysics Data System (ADS)

    Rice, Joshua S.; Emanuel, Ryan E.

    2017-05-01

    Understanding the factors that influence how global climate phenomena, such as the El-Nino Southern Oscillation (ENSO), affect streamflow behavior is an important area of research in the hydrologic sciences. While large-scale patterns in ENSO-streamflow relationships have been thoroughly studied, and are relatively well-understood, information is scarce concerning factors that affect variation in ENSO responses from one watershed to another. To this end, we examined relationships between variability in ENSO activity and streamflow for 2731 watersheds across the conterminous U.S. from 1970 to 2014 using a novel approach to account for the intermediary role of precipitation. We applied an ensemble of regression techniques to describe relationships between variability in ENSO activity and streamflow as a function of watershed characteristics including: hydroclimate, topography, geomorphology, geographic location, land cover, soil characteristics, bedrock geology, and anthropogenic influences. We found that variability in watershed scale ENSO-streamflow relationships was strongly related to factors including: precipitation timing and phase, forest cover, and interactions between watershed topography and geomorphology. These, and other influential factors, share in common the ability to affect the partitioning and movement of water within watersheds. Our results demonstrate that the conceptualization of watersheds as signal filters for hydroclimate inputs, commonly applied to short-term rainfall-runoff responses, also applies to long-term hydrologic responses to sources of recurrent climate variability. These results also show that watershed processes, which are typically studied at relatively fine spatial scales, are also critical for understanding continental scale hydrologic responses to global climate.

  14. North American precipitation and temperature patterns associated with the El Nino/Southern Oscillation (ENSO)

    SciTech Connect

    Ropelewski, C.F.; Halpert, M.S.

    1986-01-01

    This paper describes an investigation of the typical North American precipitation and temperature patterns associated with the El Nino/Southern Oscillation (ENSO). Monthly composites, covering idealized two-year ENSO episodes, are computed at all stations with data spanning seven or more ENSO events. The first harmonic is extracted from the 24 monthly composite values and plotted in the form of a two-year harmonic dial vector. When plotted on a map of North America, these vectors reveal both the regions of coherent response and the phase of the response with respect to the evolution of the ENSO episode. Time series of temperature and precipitation for the regions identified in the harmonic vector maps are examined to determine the magnitudes of the responses and the percentage of the time that the identified response actually occurred in association with the ENSO events. The analysis shows that above normal precipitation was associated with ENSO in 18 out of 22 cases in the season starting with October of the ENSO year to March of the following year for an area of North America that includes parts of the southeastern US and northern Mexico. Above normal precipitation was also observed in the Great Basin area of the western US in 9 out of 11 cases for the April through October season during ENSO years. No high latitude precipitation signals were indicated by this analysis. Areas of Alaska and western Canada experienced positive temperature anomalies in 17 out of 21 ENSO episodes (81%) during the season defined by December of the ENSO year through the following March. Parts of the southeastern US near the Gulf of Mexico were found to have negative temperature anomalies associated with 20 out of 25 ENSO episodes for the season October of the ENSO year through the following March.

  15. Shortwave feedbacks and El Nino-Southern Oscillation: Forced ocean coupled ocean-atmosphere experiments

    NASA Technical Reports Server (NTRS)

    Waliser, Duane E.; Blanke, Bruno; Neelin, J. David; Gautier, C.

    1994-01-01

    Changes in tropical sea surface temperature (SST) can produce changes in cloudiness that modify incoming solar shortwave (SW) radiation, which in turn affects SST. The effects of this negative feedback on Pacific interannual variability are examined in forced ocean model and hybrid coupled ocean-atmosphere model simulations. Two empirical schemes are used to model the large-scale, low-frequency response of surface SW to SST anomalies. The first scheme attempts to account for the nonlocal nature of the atmospheric response to SST based patterns of covariability analyzed through singular value decomposition. In the observations the primary coupled mode of variability is composed of a SW anomaly in the central Pacific that covaries with anomalous SST in the eastern Pacific. This is applied in the model as a nonlocal feedback. The second scheme examines the effects of a purely local feedback with a spatially varying coefficient of magnitude chosen similar to the first scheme. In almost all cases the second scheme behaved similarly to the first, presumably because the correlation scale of SST is large enough for El Nino-Southern Oscillation (ENSO) dynamics that there is little sensitivity to the local approximation in the SW feedback. In simulations forced by time series of observed wind stress the SW feedback induced very minor SST damping. Results for a simpified heat budget analysis showed that while the SW feedback increased the local heat flux damping on SST, it also induced a mean shallowing of the mixed layer. The resulting changes in both the local mean vertical temperature gradient and the zonal velocity response to the wind stress acted to oppose the local heat flux damping effects. When the observed SW anomalies were applied to forced simulations, the simulated SST anomalies were modified as expected, and agreement with observed SST improved. In coupled simulations the SW feedbacks had greater impact than in the case of specified stress. The main effects were

  16. A GCM study of El Nino-Southern Oscillation and its relation with the seasonal cycle

    NASA Astrophysics Data System (ADS)

    Xiao, Heng

    The main objectives in this dissertation are to examine the impact of the seasonal cycle on El Nino-Southern Oscillation (ENSO), and to provide a quantitative validation of the mechanisms for the impact proposed by previous studies. Hypothesis-validation studies are performed in the control environment provided by ENSO events simulated with a coupled general circulation model (CGCM). Using this approach the simulated seasonal cycle and interannual variability can be separated and artificially modified in view of the aspect selected for examination. The CGCM used in this study is the tropical Pacific version of the UCLA CGCM. An analysis of the energy balance in the tropical Pacific Ocean in simulations by the CGCM and by its OGCM component with forcing based on observational data address the irregularities of ENSO. The results suggest that ENSO irregular features manifested in the evolution of energy components on interannual time scales are due to the impacts of seasonal cycle-ENSO interactions. The impact on ENSO of the seasonal cycle in the upper ocean current system and thermocline structure is tested with uncoupled OGCM by shifting the phase relation between the seasonal and interannual components of the surface forcing. It is found that such a shift can significantly affect the evolution of heat content anomalies in the equatorial eastern basin. The impact is primarily due to changes in the anomalous zonal advection of temperature. The following hypotheses about the impact on ENSO of the atmospheric seasonal cycle are validated in a coupled setup with the CGCM: (1) the seasonal warming of the cold tongue during January-April favors the initial growth of warm events; (2) the northward migration of the convergence zone in the western part of the basin during April-May plays a significant role in the initial growth of warm events; and (3) the southward migration of the convergence zone in the western part of the basin during December-January favors the demise of

  17. El Nino-Southern Oscillation Correlated Aerosol Angstrom Exponent Anomaly Over the Tropical Pacific Discovered in Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

    2011-01-01

    El Nino.Southern Oscillation (ENSO) is the dominant mode of interannual variability in the tropical atmosphere. ENSO could potentially impact local and global aerosol properties through atmospheric circulation anomalies and teleconnections. By analyzing aerosol properties, including aerosol optical depth (AOD) and Angstrom exponent (AE; often used as a qualitative indicator of aerosol particle size) from the Moderate Resolution Imaging Spectrometer, the Multiangle Imaging Spectroradiometer and the Sea ]viewing Wide Field ]of ]view Sensor for the period 2000.2011, we find a strong correlation between the AE data and the multivariate ENSO index (MEI) over the tropical Pacific. Over the western tropical Pacific (WTP), AE increases during El Nino events and decreases during La Nina events, while the opposite is true over the eastern tropical Pacific (ETP). The difference between AE anomalies in the WTP and ETP has a higher correlation coefficient (>0.7) with the MEI than the individual time series and could be considered another type of ENSO index. As no significant ENSO correlation is found in AOD over the same region, the change in AE (and hence aerosol size) is likely to be associated with aerosol composition changes due to anomalous meteorological conditions induced by the ENSO. Several physical parameters or mechanisms that might be responsible for the correlation are discussed. Preliminary analysis indicates surface wind anomaly might be the major contributor, as it reduces sea ]salt production and aerosol transport during El Nino events. Precipitation and cloud fraction are also found to be correlated with tropical Pacific AE. Possible mechanisms, including wet removal and cloud shielding effects, are considered. Variations in relative humidity, tropospheric ozone concentration, and ocean color during El Nino have been ruled out. Further investigation is needed to fully understand this AE ]ENSO covariability and the underlying physical processes responsible for

  18. El Nino-Southern Oscillation Correlated Aerosol Angstrom Exponent Anomaly Over the Tropical Pacific Discovered in Satellite Measurements

    NASA Technical Reports Server (NTRS)

    Li, Jing; Carlson, Barbara E.; Lacis, Andrew A.

    2011-01-01

    El Nino.Southern Oscillation (ENSO) is the dominant mode of interannual variability in the tropical atmosphere. ENSO could potentially impact local and global aerosol properties through atmospheric circulation anomalies and teleconnections. By analyzing aerosol properties, including aerosol optical depth (AOD) and Angstrom exponent (AE; often used as a qualitative indicator of aerosol particle size) from the Moderate Resolution Imaging Spectrometer, the Multiangle Imaging Spectroradiometer and the Sea ]viewing Wide Field ]of ]view Sensor for the period 2000.2011, we find a strong correlation between the AE data and the multivariate ENSO index (MEI) over the tropical Pacific. Over the western tropical Pacific (WTP), AE increases during El Nino events and decreases during La Nina events, while the opposite is true over the eastern tropical Pacific (ETP). The difference between AE anomalies in the WTP and ETP has a higher correlation coefficient (>0.7) with the MEI than the individual time series and could be considered another type of ENSO index. As no significant ENSO correlation is found in AOD over the same region, the change in AE (and hence aerosol size) is likely to be associated with aerosol composition changes due to anomalous meteorological conditions induced by the ENSO. Several physical parameters or mechanisms that might be responsible for the correlation are discussed. Preliminary analysis indicates surface wind anomaly might be the major contributor, as it reduces sea ]salt production and aerosol transport during El Nino events. Precipitation and cloud fraction are also found to be correlated with tropical Pacific AE. Possible mechanisms, including wet removal and cloud shielding effects, are considered. Variations in relative humidity, tropospheric ozone concentration, and ocean color during El Nino have been ruled out. Further investigation is needed to fully understand this AE ]ENSO covariability and the underlying physical processes responsible for

  19. Strategic adaptation of nitrogen management for el nino southern oscillation-induced winter wheat system

    USDA-ARS?s Scientific Manuscript database

    The rainfall anomaly (RA) associated with El Niño-Southern Oscillation (ENSO) has various unwanted impacts on agricultural system globally. The loss of inorganic nitrogen (N) depending on extreme wet or dry conditions is a major concern. The main objective of this study was to adapt site-specific N ...

  20. Relating El Nino-Southern oscillation climate conditions to irrigation strategies for increased cotton yield

    USDA-ARS?s Scientific Manuscript database

    The global-scale El Nino–Southern Oscillation (ENSO) of sea surface temperature that causes monsoonal rain in India also affects precipitation in North America.The ENSO phases and related rain expectations have been used to limit climate uncertainties when producing wheat for grazing and grain. Insi...

  1. Evolution of Oceanic Precipitation Anomalies During El Nino Southern Oscillation (ENSO) Events of the Last Two Decades

    NASA Technical Reports Server (NTRS)

    Yuan, Jinchun; Miller, Richard

    2001-01-01

    The Global Precipitation Climatology Program (GPCP) recently released monthly global precipitation data that allowed an analysis of oceanic precipitation anomalies before, during, and after El Nino Southern Oscillation (ENSO) events of the last two decades. During each ENSO event, a major positive precipitation anomaly was observed in the Central and Eastern Equatorial Pacific, while a major negative precipitation anomaly was observed in the Western Equatorial Pacific and Eastern Equatorial Indian Ocean. These precipitation anomalies co-varied strongly with sea surface temperature of the eastern equatorial Pacific, and may therefore be a good indicator of ENSO events. The precipitation anomaly pattern of 1997-98 differs significantly from previous ENSO events and calls certain aspects of current theories on ENSO into question.

  2. Structure and predictability of the El Nino/Southern Oscillation phenomenon in a coupled ocean-atmosphere general circulation model

    SciTech Connect

    Latif, M.; Sterl, A.; Maier-Reimer, E.; Junge, M.M. )

    1993-04-01

    The space-time structure and predictability of the El Nino/Southern Oscillation (ENSO) phenomenon was investigated. Two comprehensive datasets were analyzed by means of an advanced statistical method, one based on observational data and other on data derived from an extended-range integration performed with a coupled ocean atmosphere general circulation model. It is shown that a considerable portion of the ENSO related low-frequency climate variability in both datasets is associated with a cycle implies the possibility of climate predictions in the tropics up to lead times of about one year. This is shown by conducting an ensemble of predictions with our coupled general circulation model. For the first time a coupled model of this type was successfully applied to ENSO predictions. 34 refs., 6 figs.

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

    SciTech Connect

    Collins, M.

    2000-04-01

    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 approach 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.

  4. Stable isotope geochemistry of corals from Costa Rica as proxy indicator of the El Nino/Southern Oscillation (ENSO)

    SciTech Connect

    Carriquiry, J.D.; Risk, M.J.; Schwarcz, H.P. )

    1994-01-01

    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 warming event. 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 lobata 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 (ENSO) event. Therefore, the El Nino event is not only recorded as negative [delta][sup 18]O anomalies in the skeleton, suggesting the warming 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.

  5. Dengue fever and El Nino/Southern Oscillation in Queensland, Australia: a time series predictive model.

    PubMed

    Hu, Wenbiao; Clements, Archie; Williams, Gail; Tong, Shilu

    2010-05-01

    It remains unclear over whether it is possible to develop an epidemic forecasting model for transmission of dengue fever in Queensland, Australia. To examine the potential impact of El Niño/Southern Oscillation on the transmission of dengue fever in Queensland, Australia and explore the possibility of developing a forecast model of dengue fever. Data on the Southern Oscillation Index (SOI), an indicator of El Niño/Southern Oscillation activity, were obtained from the Australian Bureau of Meteorology. Numbers of dengue fever cases notified and the numbers of postcode areas with dengue fever cases between January 1993 and December 2005 were obtained from the Queensland Health and relevant population data were obtained from the Australia Bureau of Statistics. A multivariate Seasonal Auto-regressive Integrated Moving Average model was developed and validated by dividing the data file into two datasets: the data from January 1993 to December 2003 were used to construct a model and those from January 2004 to December 2005 were used to validate it. A decrease in the average SOI (ie, warmer conditions) during the preceding 3-12 months was significantly associated with an increase in the monthly numbers of postcode areas with dengue fever cases (beta=-0.038; p = 0.019). Predicted values from the Seasonal Auto-regressive Integrated Moving Average model were consistent with the observed values in the validation dataset (root-mean-square percentage error: 1.93%). Climate variability is directly and/or indirectly associated with dengue transmission and the development of an SOI-based epidemic forecasting system is possible for dengue fever in Queensland, Australia.

  6. Intraseasonal and interannual variations of tropical convection - A possible link between the 40-50 day oscillation and ENSO?. [El Nino/Southern Oscillation

    NASA Technical Reports Server (NTRS)

    Lau, Ka-Ming; Chan, Paul H.

    1988-01-01

    Twelve-years of NOAA data on outgoing longwave radiation (OLR) are used to trace intraseasonal variations of tropical convection by examining the spatial patterns of OLR variance in the 1-5 day, 20-70 day, and longer-than-180 day bands separately for the northern summer and winter. Based on these patterns, the relative importance of these bands are evaluated and the natural variability of the climate signal and the geographical distribution of potential predictability is assessed. The results of empirical orthogonal functional analyses show that multiple time scales exist in the most dominant patterns of tropical convection variation. These time scales can be identified with those of the 40-50-day oscillation, the El Nino/Southern Oscillation, and the annual cycle. Interpretation of the results in terms of possible interaction between these various time scales is presented.

  7. Correlation of interannual length-of-day variation with El Nino/Southern Oscillation, 1972-1986

    NASA Technical Reports Server (NTRS)

    Chao, B. Fong

    1988-01-01

    Correlation between interannual length-of-day (LOD) changes and an index representation of El Nino/Southern Oscillation (ENSO) for the period of 1972-1986 was examined in two ways: as the cross-correlation function in the time domain and as the complex coherence spectrum in the frequency domain. The ENSO representation was derived from barometric measurements from the Tahiti and Darwin, Australia, meteorological stations, as the difference of the sea-level pressure between the two locations. The cross correlation between this ENSO representation and LOD variation on the interannual time scale was found to have a maximum value of 0.68 and the LOD phase lag of 2 months, indicating that most of the interannual LOD variation is caused by ENSO, and that the transfer of ENSO's axial angular momentum to the solid earth lags behind the Tahiti-Darwin pressure variation by about 2 months. The corresponding coherence spectrum showed minimum correlation around biennial periods, indicating an influence of the stratospheric quasi-biennial oscillation on LOD variations.

  8. El Nino-Southern Oscillation and vector-borne diseases in Anhui, China.

    PubMed

    Bi, Peng; Parton, Kevin A; Tong, Shilu

    2005-01-01

    This paper examines the relationship between monthly Southern Oscillation Index (SOI) and monthly incidences of hemorrhagic fever with renal syndrome (HFRS) and malaria in Anhui Province, China, over the periods 1971-1992 and 1966-1987, respectively. On the basis of monthly data over a 22-year period, results indicated that there were positive and negative relationships, respectively, between the SOI and monthly incidences of malaria and HFRS. The results suggest that the SOI could be used as an index in the study of the association of climate variability with the transmission of such diseases, particularly over larger areas, such as at a provincial or even state level, where averaging rainfall or temperature data across regions is inappropriate.

  9. The El Nino-Southern Oscillation (ENSO)-pandemic influenza connection: coincident or causal?

    PubMed

    Shaman, Jeffrey; Lipsitch, Marc

    2013-02-26

    We find that the four most recent human influenza pandemics (1918, 1957, 1968, and 2009), all of which were first identified in boreal spring or summer, were preceded by La Niña conditions in the equatorial Pacific. Changes in the phase of the El Niño-Southern Oscillation 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.

  10. Zonal and Meridional Mass Redistribution in the Tropical Pacific During El Nino Southern Oscillation Events

    NASA Technical Reports Server (NTRS)

    Delcroix, Thierry; Gourdeau, Lionel; Rual, Pierre; Murtugudde, Raghuram

    1997-01-01

    This note aims at documenting the ENSO-related sea level changes for the whole tropical Pacific, and for the 1979-1996 period which covers numerous El Nino and La Nina events. For this purpose, we rely on (a) 0/450 dbar surface dynamic height anomaly (an alias for sea level) derived from XBT and TOGA-TAO measurements during 1979-1996, (b) TOPEX/Poseidon derived sea level anomaly during 1993-1996, and (c) Murtugudde et al. [1996] model sea level output during 1979-1995.

  11. Coupled atmosphere-ocean model simulations of El Nino/Southern Oscillation with and without an active Indian Ocean

    SciTech Connect

    Nagai, T.; Kitamura, Y.; Endoh, M.; Tokioka, T.

    1995-01-01

    An atmospheric general circulation model (GCM) was coupled with an ocean GCM covering the Pacific. This coupled model (PAC) was integrated over a 30-year period. The PAC model stimulates well the mean seasonally varying atmospheric and ocean fields and reproduces interannual variations corresponding to ENSO (El Nino/Southern Oscillation). The same atmospheric GCM was coupled with an ocean GCM covering the Indian Ocean and the tropical Pacific. This coupled model (IPC) was integrated over a 35-year period. The model climate in IPC is fairly reasonable, and its Pacific part is very similar to the Pacific climate of the PAC model. ENSO is the major interannual variability in the IPC model. The dynamics of ENSO in IPC are essentially the same as that in PAC. In the Pacific, the subsurface ocean heat content anomalies are formed by wind anomalies and show westward propagation centered off the equator. After they reach the western Pacific, they show eastward propagation along the equator. They produce changes in the thermocline structure in the eastern equatorial Pacific resulting in anomalies in SSTs. The SST anomalies provide wind anomalies, the sign of which is opposite to that of the wind anomalies in the first stage, so that this chain will continue. ENSO in the PAC and IPC models can be regarded as the {open_quotes}delayed oscillator{close_quotes} operating in the Pacific. Although the major interannual variability in the Indian Ocean is linked to ENSO in the Pacific, the Indian Ocean does not play any active role in the ENSO cycle in the IPC model. Interannual variability of monsoon activity in the IPC model is more reasonable than that in the PAC model. However, any definite mechanism for the relationship between monsoon activity and ENSO does not emerge in the present study. 31 refs., 14 figs.

  12. Utilizing TRMM to Analyze Sea Breeze Thunderstorm Patterns During El Nino Southern Oscillations and Their Effects upon Available Fresh Water for South Florida Agricultural Planning and Management

    NASA Technical Reports Server (NTRS)

    Cooley, Clayton; Billiot, Amanda; Lee, Lucas; McKee, Jake

    2010-01-01

    Water is in high demand for farmers regardless of where you go. Unfortunately, farmers in southern Florida have fewer options for water supplies than public users and are often limited to using available supplies from surface and ground water sources which depend in part upon variable weather patterns. There is an interest by the agricultural community about the effect weather has on usable surface water, however, research into viable weather patterns during La Nina and El Nino has yet to be researched. Using rainfall accumulation data from NASA Tropical Rainfall Measurement Mission (TRMM) satellite, this project s purpose was to assess the influence of El Nino and La Nina Oscillations on sea breeze thunderstorm patterns, as well as general rainfall patterns during the summer season in South Florida. Through this research we were able to illustrate the spatial and temporal variations in rainfall accumulation for each oscillation in relation to major agricultural areas. The study period for this project is from 1998, when TRMM was first launched, to 2009. Since sea breezes in Florida typically occur in the months of May through October, these months were chosen to be the months of the study. During this time, there were five periods of El Nino and two periods of La Nina, with a neutral period separating each oscillation. In order to eliminate rainfall from systems other than sea breeze thunderstorms, only days that were conducive to the development of a sea breeze front were selected.

  13. Modeling cotton lint yield response to irrigation management as influenced by El Nino-Southern Oscillation

    USDA-ARS?s Scientific Manuscript database

    The declining Ogallala Aquifer in the U.S. Southern High Plains motivates producers to optimize water use and yield of crops that can tolerate short-term water stress like cotton [Gossypium hirsutum (L.)]. Measurable and systematic sea surface temperature anomalies (SSTA) drive the El Niño-Southern ...

  14. Northern Hemisphere summer monsoon intensified by mega-El Nino/southern oscillation and Atlantic multidecadal oscillation.

    PubMed

    Wang, Bin; Liu, Jian; Kim, Hyung-Jin; Webster, Peter J; Yim, So-Young; Xiang, Baoqiang

    2013-04-02

    Prediction of monsoon changes in the coming decades is important for infrastructure planning and sustainable economic development. The decadal prediction involves both natural decadal variability and anthropogenic forcing. Hitherto, the causes of the decadal variability of Northern Hemisphere summer monsoon (NHSM) are largely unknown because the monsoons over Asia, West Africa, and North America have been studied primarily on a regional basis, which is unable to identify coherent decadal changes and the overriding controls on planetary scales. Here, we show that, during the recent global warming of about 0.4 °C since the late 1970s, a coherent decadal change of precipitation and circulation emerges in the entirety of the NHSM system. Surprisingly, the NHSM as well as the Hadley and Walker circulations have all shown substantial intensification, with a striking increase of NHSM rainfall by 9.5% per degree of global warming. This is unexpected from recent theoretical prediction and model projections of the 21st century. The intensification is primarily attributed to a mega-El Niño/Southern Oscillation (a leading mode of interannual-to-interdecadal variation of global sea surface temperature) and the Atlantic Multidecadal Oscillation, and further influenced by hemispherical asymmetric global warming. These factors driving the present changes of the NHSM system are instrumental for understanding and predicting future decadal changes and determining the proportions of climate change that are attributable to anthropogenic effects and long-term internal variability in the complex climate system.

  15. Combined Effect of El Nino Southern Oscillation and Atlantic Multidecadal Oscillation on Lake Chad Level Variability Region

    NASA Technical Reports Server (NTRS)

    Okonkwo, Churchill; Demoz, Belay; Sakai, Ricardo; Ichoku, Charles; Anarado, Chigozie; Adegoke, Jimmy; Amadou, Angelina; Abdullahi, Sanusu Imran

    2015-01-01

    In this study, the combined effect of the Atlantic Multidecadal Oscillation (AMO) and El Niño Southern Oscillation (ENSO) on the Lake Chad (LC) level variability is explored. Our results show that the lake level at the Bol monitoring station has a statistically significant correlation with precipitation (R2 = 0.6, at the 99.5% confidence level). The period between the late 1960s and early 1970s marked a turning point in the response of the regional rainfall to climatic drivers, thereby severely affecting the LC level. Our results also suggest that the negative impact of the cold phase of AMO on Sahel precipitation masks and supersedes the positive effect of La Niña in the early the 1970s. The drop in the size of LC level from 282.5 m in the early 1960s to about 278.1 m in 1983/1984 was the largest to occur within the period of study (1900-2010) and coincides with the combined cold phase of AMO and strong El Niño phase of ENSO. Further analyses show that the current warm phase of AMO and increasing La Niña episodes appear to be playing a major role in the increased precipitation in the Sahel region. The LC level is responding to this increase in precipitation by a gradual recovery, though it is still below the levels of the 1960s. This understanding of the AMO-ENSO-rainfall-LC level association will help in forecasting the impacts of similar combined episodes in the future. These findings also have implications for long-term water resources management in the LC region.

  16. Combined Effect of El Nino Southern Oscillation and Atlantic Multidecadal Oscillation on Lake Chad Level Variability Region

    NASA Technical Reports Server (NTRS)

    Okonkwo, Churchill; Demoz, Belay; Sakai, Ricardo; Ichoku, Charles; Anarado, Chigozie; Adegoke, Jimmy; Amadou, Angelina; Abdullahi, Sanusu Imran

    2015-01-01

    In this study, the combined effect of the Atlantic Multidecadal Oscillation (AMO) and El Niño Southern Oscillation (ENSO) on the Lake Chad (LC) level variability is explored. Our results show that the lake level at the Bol monitoring station has a statistically significant correlation with precipitation (R2 = 0.6, at the 99.5% confidence level). The period between the late 1960s and early 1970s marked a turning point in the response of the regional rainfall to climatic drivers, thereby severely affecting the LC level. Our results also suggest that the negative impact of the cold phase of AMO on Sahel precipitation masks and supersedes the positive effect of La Niña in the early the 1970s. The drop in the size of LC level from 282.5 m in the early 1960s to about 278.1 m in 1983/1984 was the largest to occur within the period of study (1900-2010) and coincides with the combined cold phase of AMO and strong El Niño phase of ENSO. Further analyses show that the current warm phase of AMO and increasing La Niña episodes appear to be playing a major role in the increased precipitation in the Sahel region. The LC level is responding to this increase in precipitation by a gradual recovery, though it is still below the levels of the 1960s. This understanding of the AMO-ENSO-rainfall-LC level association will help in forecasting the impacts of similar combined episodes in the future. These findings also have implications for long-term water resources management in the LC region.

  17. El Nino southern oscillation effects on dryland crop production in the Texas High Plains

    USDA-ARS?s Scientific Manuscript database

    Risk adverse dryland crop management in the US Southern High Plains may stabilize year to year productivity, however in some years the full yield potential is unrealized thereby reducing the overall cropping system productivity. Equatorial Pacific sea surface temperature anomalies (SSTA) systematica...

  18. Isotope evidence of paleo - El Nino - Southern Oscillation cycles in loess-paleosol record in the central United States

    USGS Publications Warehouse

    Wang, Hongfang; Follmer, L.R.; Chao-li, Liu

    2000-01-01

    The ??13C of soil carbonate in rhizoconcretions collected from a loess-paleosol sequence in the central United States indicates that growing-season C3/C4 plant ratio oscillated by 35% on a 900 ?? 200 yr time scale during the late Wisconsinan glaciation. The pattern appears in phase with advance and retreat of the southern margin of the Laurentide ice sheet, suggesting influence by paleo-El Nin??o-Southern Oscillation cycles. The ??13C of soil organic matter indicates that the annual average C3/C4 plant ratio oscillated only by 18%, with a periodicity of 450 ?? 100 yr, and closely matched the cyclic pattern of loess-paleosol layers. It suggests a periodic enhancement of the penetration of the Gulf of Mexico air over the region during this time.

  19. Interannual variations in wheat rust development in China and the United States in relation to the El Nino/Southern oscillation

    SciTech Connect

    Scherm, H.; Yang, X.B.

    1995-09-01

    The El Nino/Southern Oscillation (ENSO) is one of the most important and best-characterized mechanisms of global climatic variation. Because regional temperature and precipitation patterns are influenced by the ENSO and plant diseases are responsive to these factors, historical disease records may contain an ENSO-related signal. We used cross-spectral analysis to establish coherence and phase relationships between the Southern Oscillation Index (SOI), which is a measure of the ENSO, and long-term (>40 years) data on wheat stripe rust in five regions of northern China and wheat stem rust in four climatic divisions of the midwestern United States. Monthly SOI values were averaged from March to June and October to March for analysis of the rust data from China and the United States, respectively, based when weather patterns in these regions are influenced by the ENSO. The coherence relationships showed consistent and significant (0.01 {le} P {le} 0.10) cooscillations between the rust and SOI series at temporal scales characteristic of the ENSO. The five stripe rust series were coherent with the SOI series at periodicities of 2.0 to 3.0 and 8.0 to 10.0 years, and three of the four stem rust series were coherent with the SOI series at a periodicity of 6.8 to 8.2 years. The phase relationships showed that, in most cases, the rust and SOI series cooscillated out of phase, suggesting that the associations between them are indirect. In a separate analysis of a shorter (18 years) stripe rust series form the Pacific Northwest of the United States, disease severity was significantly lower during El Nino years (warm phases of the ENSO) than during non-El Nino years (P {le} 0.0222) or during La Nina years (cold phases of the ENSO) (P {le}0.0253). Although no cause-and-effect relationships could be deduced, this analysis identified methods and directions for future research into relationships between climate and disease at extended temporal scales. 34 refs., 5 figs., 1 tab.

  20. Simulation of El Nino-Southern Oscillation - like variability in a global AOGCM and its response to CO{sub 2} increase

    SciTech Connect

    Tett, S.

    1995-06-01

    A 75-year integration of a coupled atmosphere-ocean model is examined for tropical interannual variability. The atmospheric model has interactive cloud and a seasonal cycle. The fluxes of heat and salinity into the ocean component of the model are flux corrected. The model has tropical variability that is qualitatively similar to that of the observed El Nino/Southern Oscillation (ENSO). The maximum amplitude of the model Nino3 signal is approximately half that observed and the modeled ENSO timescale is greater than that observed. In the first 50 years of the integration the model has eight warm events. Each event is one of two types: one characterized by a standing SST anomaly in the central and eastern Pacific and the other by a westward propagating sea surface temperature anomaly. The majority of the model warm events are of the first type. The first type of event is triggered by the eastward propagation of Kelvin waves across the Pacific, and the second by westward propagation of warm temperature anomalies through the atmospheric response to a warm anomaly causing the suppression of equatorial upwelling. There is a coupling to the seasonal cycle for the first type of event. A positive feedback through changes in marine stratocumulus in the east Pacific is an important factor in some simulated warm events. Another integration was carried out in which atmospheric CO{sub 2} was increased at a rate of 1% (compounded) per annum. There is no significant change in the one to ten year interannual variance of SST in the east Pacific, and this suggests that the size of the SST anomalies during warm or cold events in the {open_quotes}greenhouse{close_quotes} world may not be significantly different from those of today. 63 refs., 23 figs.

  1. El nino-southern oscillation events recorded in the stratigraphy of the tropical quelccaya ice cap, peru.

    PubMed

    Thompson, L G; Mosley-Thompson, E; Arnao, B M

    1984-10-05

    Snow accumulation measured during 1982-1983 on the Quelccaya ice cap, Peru, was 70 percent of the average from 1975 through 1983. Inspection of 19 years (1964 through 1983) of accumulation measured near the summit of Quelccaya reveals a substantial decrease ( approximately 30 percent) in association with the last five El Niño-Southern Oscillation (ENSO) occurrences in the equatorial Pacific. The ENSO phenomenon is now recognized as a global event arising from large-scale interactions between the ocean and the atmosphere. Understanding this extreme event, with the goal of prediction, requires a record of past occurrences. The Quelccaya ice cap, which contains 1500 years of annually accumulated ice layers, may provide a long and detailed record of the most extreme ENSO events.

  2. Prediction and assessment of impacts on Asian river deltas by extreme climate events and their association with El Nino and Southern Oscillation (ENSO)

    SciTech Connect

    Chang, W.Y.B. |

    1995-12-31

    Impacts of hydrological consequences of extreme climate events such as major floods and droughts on human systems have long been among the foremost concerns of the Pacific Rim countries. Proxy climate data for the last 500 years collected form the archives of counties in the Yangtze River Delta, China, were analyzed to understand the occurrence of extreme climate events, the pattern of such occurrences and their relationships to global climate changes. There have been 16 regional (delta wide) extreme climate events during the last 500 years (since 1,500 A.D.); all occurred in conjunction with reported El Nino-Southern Oscillation (ENSO) activities. Large interannual variability in precipitation is found to occur during or immediately following the ENSO events in the Delta. Management of systems increasingly dominated by humans, such as Asian delta regions, should include consideration of major climate variability, cycle periods and the extent of climate changes, as well as the trends associated with human growth and institutional changes.

  3. 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.

  4. Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Nino-Southern Oscillation variability.

    PubMed

    Brienen, Roel J W; Helle, Gerd; Pons, Thijs L; Guyot, Jean-Loup; Gloor, Manuel

    2012-10-16

    We present a unique proxy for the reconstruction of variation in precipitation over the Amazon: oxygen isotope ratios in annual rings in tropical cedar (Cedrela odorata). A century-long record from northern Bolivia shows that tree rings preserve the signal of oxygen isotopes in precipitation during the wet season, with weaker influences of temperature and vapor pressure. Tree ring δ(18)O correlates strongly with δ(18)O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ(18)O showing that the signal is coherent over large areas. The signal correlates most strongly with basin-wide precipitation and Amazon river discharge. We attribute the strength of this (negative) correlation mainly to the cumulative rainout processes of oxygen isotopes (Rayleigh distillation) in air parcels during westward transport across the basin. We further find a clear signature of the El Niño-Southern Oscillation (ENSO) in the record, with strong ENSO influences over recent decades, but weaker influence from 1925 to 1975 indicating decadal scale variation in the controls on the hydrological cycle. The record exhibits a significant increase in δ(18)O over the 20th century consistent with increases in Andean δ(18)O ice core and lake records, which we tentatively attribute to increased water vapor transport into the basin. Taking these data together, our record reveals a fresh path to diagnose and improve our understanding of variation and trends of the hydrological cycle of the world's largest river catchment.

  5. Meteorological factors and El Nino Southern Oscillation are associated with paediatric varicella infections in Hong Kong, 2004-2010.

    PubMed

    Chan, J Y C; Lin, H L; Tian, L W

    2014-07-01

    Varicella accounts for substantial morbidities and remains a public health issue worldwide, especially in children. Little is known about the effect of meteorological variables on varicella infection risk for children. This study described the epidemiology of paediatric varicella notifications in Hong Kong from 2004 to 2010, and explored the association between paediatric varicella notifications in children aged <18 years and various meteorological factors using a time-stratified case-crossover model, with adjustment of potential confounding factors. The analysis found that daily mean temperature, atmospheric pressure and Southern Oscillation Index (SOI) were positively associated with paediatric varicella notifications. We found that an interquartile range (IQR) increase in temperature (8·38°C) at lag 1 day, a 9·50 hPa increase in atmospheric pressure for the current day, and a 21·91 unit increase in SOI for the current day may lead to an increase in daily cases of 5·19% [95% confidence interval (CI) 1·90-8·58], 5·77% (95% CI 3·01-8·61), and 4·32% (95% CI 2·98-5·68), respectively. An IQR increase in daily relative humidity (by 11·96%) was associated with a decrease in daily paediatric varicella (-2·79%, 95% CI -3·84 to -1·73). These findings suggest that meteorological factors might be important predictors of paediatric varicella infection in Hong Kong.

  6. Tales of volcanoes and El-Nino southern oscillations with the oxygen isotope anomaly of sulfate aerosol.

    PubMed

    Shaheen, Robina; Abauanza, Mariana; Jackson, Teresa L; McCabe, Justin; Savarino, Joel; Thiemens, Mark H

    2013-10-29

    The ability of sulfate aerosols to reflect solar radiation and simultaneously act as cloud condensation nuclei renders them central players in the global climate system. The oxidation of S(IV) compounds and their transport as stable S(VI) in the Earth's system are intricately linked to planetary scale processes, and precise characterization of the overall process requires a detailed understanding of the linkage between climate dynamics and the chemistry leading to the product sulfate. This paper reports a high-resolution, 22-y (1980-2002) record of the oxygen-triple isotopic composition of sulfate (SO4) aerosols retrieved from a snow pit at the South Pole. Observed variation in the O-isotopic anomaly of SO4 aerosol is linked to the ozone variation in the tropical upper troposphere/lower stratosphere via the Ozone El-Niño Southern Oscillations (ENSO) Index (OEI). Higher (17)O values (3.3‰, 4.5‰, and 4.2‰) were observed during the three largest ENSO events of the past 2 decades. Volcanic events inject significant quantities of SO4 aerosol into the stratosphere, which are known to affect ENSO strength by modulating stratospheric ozone levels (OEI = 6 and (17)O = 3.3‰, OEI = 11 and (17)O = 4.5‰) and normal oxidative pathways. Our high-resolution data indicated that (17)O of sulfate aerosols can record extreme phases of naturally occurring climate cycles, such as ENSOs, which couple variations in the ozone levels in the atmosphere and the hydrosphere via temperature driven changes in relative humidity levels. A longer term, higher resolution oxygen-triple isotope analysis of sulfate aerosols from ice cores, encompassing more ENSO periods, is required to reconstruct paleo-ENSO events and paleotropical ozone variations.

  7. Delineating the effect of El-Nino Southern Oscillations using oxygen and sulfur isotope anomalies of sulfate aerosols

    NASA Astrophysics Data System (ADS)

    Shaheen, R.; Abaunza Quintero, M. M.; Jackson, T.; McCabe, J.; Savarino, J. P.; Thiemens, M. H.

    2013-12-01

    sulfate aerosol to the stratosphere. The new results demonstrate that combined O-triple isotopes and S-quadruple isotopes may help to recognize paleo ENSO events and their impact on the oxidation history of sulfate aerosols. 1. R. Shaheen, M. A., T. Jackson, J. McCabe, J. Savarino, M. H. Thiemens. (2013) A Window to the Paleoclimate- Tales of Volcanoes and El-Ninño Southern Oscillations with the Oxygen Isotope Anomaly of Sulfate Aerosols, Proceedings of the National Academy of Sciences of the United States of America. 2. Farquhar, J., Savarino, J., Airieau, S., and Thiemens, M. H. (2001) Observation of wavelength-sensitive mass-independent sulfur isotope effects during SO2 photolysis: Implications for the early atmosphere, Journal of Geophysical Research-Planets 106, 32829-32839.

  8. Effect of the El Nino/southern oscillation on Gulf of Mexico, winter, frontal-wave cyclones: 1960-1989. (Volumes I and II)

    SciTech Connect

    Manty, R.E.

    1993-01-01

    Seasonal counts of frontal-wave cyclones forming over the Gulf of Mexico and its coastal plain show more storms in the five El Nino winters and fewer storms in the eight La Nina winters, from 1960 to 1989, significant at the .01 level by a rank sum test. This is corroborated by two results. First, during the same period, the frequency of frontal-overrunning weather conditions in the region, indicative of storms, was higher in El Nino winters and lower in La Nina winters. Second, 100 years of precipitation and temperature records show wetter, cooler El Nino winters and drier, warmer La Nina winters at gulf-region land stations and climatic divisions. A threefold explanation, based on National Meteorological Center, upper-air data, is offered for the greater frequency of gulf-region cyclogenesis during El Nino winters between 1960 and 1989. (1) The winter, mean, 250-mb jet over the southern US is intensified by 5 to 10 ms[sup [minus]1] and displaced southward between 110[degrees] and 75[degrees]W by an average of 200 to 285 km during the five El Nino winters. This implies stronger and more frequent episodes of jet-associated, upper-level troughing and divergence over the region, reinforcing surface, frontal-wave cyclones. (2) In the five El Nino winters between 1963 and 1989, seasonal average heights and temperatures of the 850-, 700-, 500-, and 200-mb surfaces are lower over the region than they are in non-El Nino winters. This implies more-common presence of cold, low-pressure troughs at upper levels, reinforcing surface cyclones. (3) A 10[degrees] eastward shift, at sea level, of the western edge of the Bermuda high during the eight El Nino winters, changes normally due-easterly trades in the northwestern Caribbean Sea to slightly south of east, allowing greater advection of moisture and heat into the gulf from the tropics, preconditioning the area for development of surface cyclones. Only winter season shows all three conditions and an increase in cyclogenesis.

  9. Southern Peru desert shattered by the great 2001 earthquake: Implications for paleoseismic and paleo-El Nino-Southern Oscillation records

    USGS Publications Warehouse

    Keefer, David K.; Moseley, Michael E.

    2004-01-01

    In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2-8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term "shattered landscape" to describe the severity of these effects. Long-term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthquake rainstorms. This inference was confirmed during the first minor postearthquake rainstorm there, which occurred in June and July of 2002. Greater amounts of rainfall in this desert region have historically been associated with El Nin??o events. Previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of El Nin??o-generated precipitation falling on seismically disturbed landscapes. The effects of the 2001 earthquake and 2002 rainstorm support that conclusion.

  10. Drought stress signals in modern and subfossil Quercus laurifolia (Fagaceae) leaves reflect winter precipitation in southern Florida tied to El Nino-Southern Oscillation activity.

    PubMed

    Wagner-Cremer, Friederike; Donders, Timme H; Visscher, Henk

    2010-05-01

    In the present study, structural xeromorphic features in modern and subfossil Quercus laurifolia leaves from southern Florida were quantified to reconstruct past precipitation changes in sensitive terrestrial settings. Absolute cell numbers/mm(2), quantified as epidermal cell density (ED) have been analyzed on leaves from herbarium collections as well as the leaves accumulated during the past 125 years in peat deposits. The results reveal a common principal correlation between the measured ED and winter precipitation (November through March, NDJFM: Herbarium r = -0.74; peat profiles FAK98 r = -0.72, FAK02 r = -0.53) providing a measure of seasonal drought stress. In Florida, the amount of winter precipitation depends on El Niño-Southern Oscillation (ENSO) activity, where El Niño years produce wet and cold winters, while La Niña winters are dry and warm. The negative correlation between cell numbers and winter precipitation has the potential to record precipitation variability from subfossil leaves on near-annual to decadal time scales. In subtropical, terrestrial environments, where traditional paleo-proxies are limited, systematic analysis of leaf morphological characteristics can provide important information on precipitation changes through time.

  11. Theileria parva seroprevalence in traditionally kept cattle in southern Zambia and El Nino.

    PubMed

    Fandamu, P; Duchateau, L; Speybroeck, N; Marcotty, T; Mbao, V; Mtambo, J; Mulumba, M; Berkvens, D

    2005-04-01

    Sero-epidemiological surveys involving 27,526 cattle over a period of 8 years show that Theileria parva, the parasite causing East Coast fever (ECF) is found throughout southern Zambia. Higher values of T. parva sero-prevalence were observed in the plateau districts of Monze, Choma and Mazabuka than in the valley districts of Siavonga and Sinazongwe. Our results reveal a strong association between high T. parva sero-prevalence and the presence of the periodic climatic phenomenon known as the El Nino Southern Oscillation. More T. parva sero-positive samples were recorded during El Nino years (1997/98) (P<0.001) than other years in the study period. From this association, we conclude that Multiple El Nino Southern Oscillation Indices can be used to predict years with high or low ECF infection prevalence thereby contributing to the improved control of ECF in the area.

  12. Florida Agriculture - Utilizing TRMM to Analyze Sea Breeze Thunderstorm Patterns During El Nino Southern Oscillations and Their Effects Upon Available Fresh Water for South Florida Agricultural Planning and Management

    NASA Technical Reports Server (NTRS)

    Billiot, Amanda; Lee, Lucas; McKee, Jake; Cooley, Zachary Clayton; Mitchell, Brandie

    2010-01-01

    This project utilizes Tropical Rainfall Measuring Mission (TRMM) and Landsat satellite data to assess the impact of sea breeze precipitation upon areas of agricultural land use in southern Florida. Water is a critical resource to agriculture, and the availability of water for agricultural use in Florida continues to remain a key issue. Recent projections of statewide water use by 2020 estimate that 9.3 billion gallons of water per day will be demanded, and agriculture represents 47% of this demand (Bronson 2003). Farmers have fewer options for water supplies than public users and are often limited to using available supplies from surface and ground water sources which depend in part upon variable weather patterns. Sea breeze thunderstorms are responsible for much of the rainfall delivered to Florida during the wet season (May-October) and have been recognized as an important overall contributor of rainfall in southern Florida (Almeida 2003). TRMM satellite data was used to analyze how sea breeze-induced thunderstorms during El Nino and La Nina affected interannual patterns of precipitation in southern Florida from 1998-2009. TRMM's Precipitation Radar and Microwave Imager provide data to quantify water vapor in the atmosphere, precipitation rates and intensity, and the distribution of precipitation. Rainfall accumulation data derived from TRMM and other microwave sensors were used to analyze the temporal and spatial variations of rainfall during each phase of the El Nino Southern Oscillation (ENSO). Through the use of TRMM and Landsat, slight variations were observed, but it was determined that neither sea breeze nor total rainfall patterns in South Florida were strongly affected by ENSO during the study period. However, more research is needed to characterize the influence of ENSO on summer weather patterns in South Florida. This research will provide the basis for continued observations and study with the Global Precipitation Measurement Mission.

  13. A Comparison of Crop Yields Using El Nino and Non-El Nino Climatological Data in a Crop Model

    DTIC Science & Technology

    1990-01-01

    1974. Characteristics of El Nino in 1972. J. Mar. Res. 32:378-404. Yasunari , T. 1987. Global structure of the El Nino/Southern Oscillation. Part I. El...Nino composites. J. Met. Soc. Japan 65:67-80. Yasunari , T. 1987. Global structure of the El Nino/Southern Oscillation. Part II. Time Evolution. J. Met

  14. Southern Peru desert shattered by the great 2001 earthquake: implications for paleoseismic and paleo-El Nino-Southern Oscillation records.

    PubMed

    Keefer, David K; Moseley, Michael E

    2004-07-27

    In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2-8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term "shattered landscape" to describe the severity of these effects. Long-term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthquake rainstorms. This inference was confirmed during the first minor postearthquake rainstorm there, which occurred in June and July of 2002. Greater amounts of rainfall in this desert region have historically been associated with El Niño events. Previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of El Niño-generated precipitation falling on seismically disturbed landscapes. The effects of the 2001 earthquake and 2002 rainstorm support that conclusion.

  15. Outbreak of hantavirus infection in the Four Corners region of the United States in the wake of the 1997-1998 El Nino-southern oscillation.

    PubMed

    Hjelle, B; Glass, G E

    2000-05-01

    Hantavirus cardiopulmonary syndrome (HCPS), a rodent-borne zoonosis, has been endemic in the Americas for at least several decades. It is hypothesized that the 1991-1992 El Niño-southern oscillation (ENSO) caused increased precipitation that allowed an increase in rodent population densities, thereby increasing the possibility of transmission to humans. The result was a 1993-1994 outbreak of the disease in the Four Corners states of the southwestern United States. A second strong ENSO occurred in 1997-1998, after a period of considerable public education about the risks of hantavirus infection that began during the 1993-1994 outbreak. The caseload of HCPS increased 5-fold above baseline in the Four Corners states in 1998-1999. Regions that had received increased rainfall in 1998 were especially affected. A large majority of the 1998-1999 case patients reported indoor exposure to deer mice. Hantavirus outbreaks can occur in response to abiotic events, even in the face of extensive public education and awareness.

  16. Canadian precipitation patterns associated with the southern oscillation

    SciTech Connect

    Shabbar, A.; Bonsal, B.; Khandekar, M.

    1997-12-01

    Precipitation responses over Canada associated with the two extreme phases of the Southern Oscillation (SO), namely El Nino and La Nina are identified. Using the best available precipitation data from 1911 to 1994, both the spatial and temporal behavior of the responses are analyzed from the El Nino/La Nino onset to several seasons afterward. Composite and correlation analyses indicate that precipitation over a large region of southern Canada extending from British Columbia, through the prairies, and into the Great Lakes region is significantly influenced by the SO phenomenon. The results show a distinct pattern of negative (positive) precipitation anomalies in this region during the first winter following the onset of El Nino (La Nina) events. During this same period, significant positive precipitation anomalies occur over the northern prairies and southeastern Northwest Territories in association with El Nino events. Statistical significance of the responses is tested by the Student`s t-test and the Wilcoxon rank-sum test, while field significance is established through the Monte Carlo procedure. All of the significant precipitation anomalies can be explained by the associated upper-atmospheric flow patterns, which during the first winter following the onset of El Nino events resemble the positive (negative) phase of the Pacific-North American (PNA) pattern. Significant correlations between Southern Oscillation index (SOI) values and the observed precipitation anomalies over southern Canada suggest the possibility of developing a long-range forecasting technique for Canadian precipitation based on the occurrence and evolution of the various phases of the SO. 31 refs., 10 figs., 3 tabs.

  17. Global Weather's Problem Child--El Nino.

    ERIC Educational Resources Information Center

    Rasmusson, Eugene M.

    1984-01-01

    Discusses the nature and effects of the El Nino/Southern Oscillation phenomenon. Indicates that new understanding of the phenomenon from current data will provide a global view of climate that has never before been within reach. (JN)

  18. Global Weather's Problem Child--El Nino.

    ERIC Educational Resources Information Center

    Rasmusson, Eugene M.

    1984-01-01

    Discusses the nature and effects of the El Nino/Southern Oscillation phenomenon. Indicates that new understanding of the phenomenon from current data will provide a global view of climate that has never before been within reach. (JN)

  19. Atmospheric moisture transport and its impact on the water cycle over Alaska and Hawaii: The roles of the Pacific Decadal Oscillation and El Nino

    NASA Astrophysics Data System (ADS)

    Borries, Cecilia J.

    Precipitation over the North Pacific can fluctuate under climate patterns such as the Pacific Decadal Oscillation (PDO) and El Nino-Southern Oscillation (ENSO). In order to better understand the role which these climatic patterns play in the North Pacific water budgets and pathways, we employed the Community Atmosphere Model 5.0 (CAM) and conducted sensitivity experiments to examine how atmospheric moisture convergence and moisture transport respond to sea surface temperature (SST) anomalies associated with the PDO and ENSO phase transitions. We have found that changes in transient moisture transport, as the PDO phase shifts from cool to warm, are due to increases in specific humidity and decreases in wind speeds over Alaska and the North Pacific. Additionally, increases in moisture convergence, specific humidity, and wind speeds and decreases in transient moisture transport are seen over the North Pacific during El Nino events compared to La Nina events.

  20. A review of the Southern Oscillation - Oceanic-atmospheric circulation changes and related rainfall anomalies

    NASA Technical Reports Server (NTRS)

    Kousky, V. E.; Kagano, M. T.; Cavalcanti, I. F. A.

    1984-01-01

    The region of South America is emphasized in the present consideration of the Southern Oscillation (SO) oceanic and atmospheric circulation changes. The persistence of climate anomalies associated with El Nino-SO events is due to strong atmosphere-ocean coupling. Once initiated, the SO follows a certain sequence of events with clearly defined effects on tropical and subtropical rainfall. Excessive rainfall related to the SO in the central and eastern Pacific, Peru, Ecuador, and southern Brazil, are complemented by drought in Australia, Indonesia, India, West Africa, and northeast Brazil. El Nino-SO events are also associated with dramatic changes in the tropospheric flow pattern over a broad area of both hemispheres.

  1. A review of the Southern Oscillation - Oceanic-atmospheric circulation changes and related rainfall anomalies

    NASA Technical Reports Server (NTRS)

    Kousky, V. E.; Kagano, M. T.; Cavalcanti, I. F. A.

    1984-01-01

    The region of South America is emphasized in the present consideration of the Southern Oscillation (SO) oceanic and atmospheric circulation changes. The persistence of climate anomalies associated with El Nino-SO events is due to strong atmosphere-ocean coupling. Once initiated, the SO follows a certain sequence of events with clearly defined effects on tropical and subtropical rainfall. Excessive rainfall related to the SO in the central and eastern Pacific, Peru, Ecuador, and southern Brazil, are complemented by drought in Australia, Indonesia, India, West Africa, and northeast Brazil. El Nino-SO events are also associated with dramatic changes in the tropospheric flow pattern over a broad area of both hemispheres.

  2. El Nino During the 1990s: Harbinger of Climatic Change or Normal Fluctuation

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2000-01-01

    Today, El Nino refers to the extreme warming episodes of the globally effective, coupled ocean-atmospheric interaction commonly known as ENSO (i.e., "El Nino-Southern Oscillation"). Concerning its observed decadal frequency and severity, El Nino during the 1990's has often been regarded as being anomalous. Results of analysis reported herein; however, appear to mitigate this belief.

  3. El Nino During the 1990's: Harbinger of Climatic Change or Normal Fluctuation?

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2000-01-01

    Today, El Nino refers to the extreme warming episodes of the globally effective, coupled ocean-atmospheric interaction commonly known as ENSO (i.e., "El Nino-Southern Oscillation"). Concerning its observed decadal frequency and severity, El Nino during the 1990's has often been regarded as being anomalous. Results of analysis reported herein; however, appear to mitigate this belief.

  4. Triggering of strong El Nino events with meridional redistribution of convective sources by distinct down penetration of equatorial-quasi-biennial oscillation

    NASA Astrophysics Data System (ADS)

    Narayana Rao, D.; Ramkumar, T. K.

    Gray et al 1992 GRL JMSJ hypothesized a mechanism by which the equatorial stratospheric Quasi-Biennial Oscillation QBO of zonal winds actively modulates the timing of El Nino-Southern Oscillation ENSO events The variable wind shear in vertical direction associated with opposing phases of QBO modifies the meridional distribution of convective sources which ultimately leads to the development of warm El Nino events through the modification of regional east-west Walker and north-south Hadley circulations Based on the analyses of the NCEP-NCAR reanalyses data in almost all the longitude zones of tropical region from 1948 to the present January 2006 we report in the present work that when the stratospheric QBO penetrates down to below 50hPa level and influences the upper troposphere modification of the meridional Hadley cell particularly over India and Indonesia or west Pacific region and the triggering of the strong El Nino events occur Further it is observed that the severity of the modification of the Hadley cell is associated with intensity of the El Nino events and the said both are closely associated with the intensity of the down penetrated QBO in zonal winds The influence of the down penetrated QBO and the modification of the Hadley cells during strong El Nino events of global economic importance like the ones happened in the years 1972 73 1982 83 and 1997 98 are also manifested in the radiosonde data obtained over India as well as the other tropical regions and in the Indian MST radar data

  5. El Nino. [influence on climatic conditions

    NASA Technical Reports Server (NTRS)

    Cane, M. A.

    1986-01-01

    An attempt is made to provide the background for a coupled model of ENSO (El Nino-Southern Oscillation) with emphasis placed on the oceanography (i.e. on El Nino). Observations of the normal annual cycle in the Pacific and of the evolution of a typical El Nino event are reviewed, and a theory for the oceanography of El Nino is proposed. The influence of SST anomalies on the tropical atmosphere is assessed, and results from a numerical model for the coupled system able to generate El Nino events are presented. Implications for the real ENSO cycle are discussed. In both the model and nature, ENSO has the character of a relaxation oscillation of the coupled system, and its cycle is aperiodic. Results on the predictability of dynamical systems show the impossibility of predicting ahead several events.

  6. Recent variability in the Southern Oscillation: Isotopic results from a Tarawa Atoll coral

    SciTech Connect

    Cole, J.E.; Fairbanks, R.G. ); Shen, G.T. )

    1993-06-18

    In the western tropical Pacific, the interannual migration of the Indonesian Low convective system causes changes in rainfall that dominate the regional signature of the El Nino-Southern Oscillation (ENSO) system. A 96-year oxygen isotope record from a Tarawa Atoll coral (1[degrees]N, 172[degrees]E) reflects regional convective activity through rainfall-induced salinity changes. This monthly resolution record spans twice the length of the local climatological record and provides a history of ENSO variability comparable in quality with those derived from instrumental climate data. Comparison of this coral record with a historical chronology of El Nino events indicates that climate anomalies in coastal South America are occasionally decoupled from Pacific-wide ENSO extremes. Spectral analysis suggests that the distribution of variance in this record has shifted among annual to interannual periods during the present century, concurrent with observed changes in the strength of the Southern Oscillation. 28 refs., 2 figs., 1 tab.

  7. Geomorphic Effects, Chronologies, and Archaeological Significance of El Nino Floods in Southern Peru

    NASA Astrophysics Data System (ADS)

    Magilligan, F. J.; Manners, R.; Goldstein, P.

    2003-12-01

    The catastrophic effects of large floods have been well documented, on both contemporary and paleo-timecales, especially for the conterminous U.S. Less is known, however, about extreme events in hyper-arid sub-tropical climates where synoptic scale meteorological causes, such as El Nino-Southern Oscillation events, are the driving atmospheric mechanism. This research documents the geomorphic effects of extreme floods in the Moquegua River valley of southern Peru, in the core of the Atacama Desert. Using a combination of geomorphic mapping, hydrolologic modeling, aerial photography, ASTER satellite imagery, and GIS, we document the geomorphic signature of large contemporary floods within the mid-valley section (1500 masl) of the Rio Moquegua. Stratigraphic evidence and paleostage indicators of paleofloods, such as slackwater deposits and preserved high level flood gravels, are used to evidence late Holocene paleoflood magnitude-frequency relationships. On contemporary timescales, channel belt expansion by lateral erosion during large floods, such as the recent '97 and '98 floods, correspond to as much as 30-40 hectares of floodplain loss along the 20 km study reach. Sixty years of repeat aerial photography indicates that channel belt expansion and floodplain erosion commonly occurs along the Rio Moquegua. The frequent resetting of floodplain alluvium conditioned by these large floods is supported by radiocarbon dating of floodplain exposures. These dates indicate that most of the contemporary floodplain alluvium is younger that 560 14C yrs BP. The highest terrace remnants date to 3250 14C yrs BP and record a series of overbank flood gravels. Evidence for the regionally extensive Miraflores ENSO flood, ca. 1300 AD, exists in tributary and along mainstem sections. This flood has been documented along the coasts of Northern Chile to northern Peru, and has been evoked to explain significant social collapse. Our field evidence indicates that it catastrophically affected

  8. Reviewing Predictions of the 2015-16 El Nino

    NASA Astrophysics Data System (ADS)

    L'heureux, M. L.

    2016-12-01

    Here, we will evaluate the evolution of El Nino-Southern Oscillation (ENSO) outlooks made by models and forecasters at the NOAA Climate Prediction Center (CPC) during the 2015-16 El Nino event. By many measures, the El Nino became one of the top 3 strongest events in the historical record dating back to 1950. However, most operational forecast models of the Nino-3.4 SST index values appeared to underpredict the ultimate strength of the event, particularly at the longest lead times. Finally, we will discuss where there is room for future development of ENSO predictions and outlooks.

  9. The Modal Evolution of the Southern Oscillation.

    NASA Astrophysics Data System (ADS)

    Brassington, Gary B.

    1997-05-01

    The implementation of a progressive Fourier transform, applied to time series representative of the El Niño-Southern Oscillation (ENSO), provides a visual review of the frequency modes that have dominated throughout the available time series record. The modal evolution maps, constructed from the progressive Fourier transform, demonstrate that the ENSO is largely composed of a discrete number of low-frequency modes and that these dominant modes demonstrate a localized influence, in a temporal sense, persisting for periods of years before showing deviations in characteristic frequency. In support of other research, significant energy is maintained in the quasi-biennial and quasi-quadrennial period modes throughout the length of available Southern Oscillation index (SOI) record. Evident through the most recent record of both the SOI and Nino region sea surface temperature (SST) time series is the emergence of energy in the quasi-decadal period modes. The presence of a quasi-decadal mode has also been noted in the North Pacific over the same period and has been related to the warming SSTs near Alaska. During the period in which the quasi-decadal mode has been present, the most severe and the longest-lasting El Niños on instrument record in 1982-83 and 1991-93, respectively, have occurred. This suggests that the superposition of the quasi-decadal mode with the well-recognized quasi-biennial and quasi-quadrennial modes can lead to more severe and longer-lasting climate anomalies. Despite the absence of significant energy in the lower-frequency modes in the earlier instrument-recorded SOI, which corresponds to moderate ENSO activity, the existence of such a mode is suggested by an analysis of a paleoclimatic reconstruction of seasonal SOI presented in this paper and other similar analyses found in scientific literature. The last period of very strong ENSO activity occurred during the period 1870-1930. This same period corresponded to the presence of significant energy

  10. Determining the early history of El Nino

    SciTech Connect

    DeVries, T.J.; Ortlieb, L.; Diaz, A.

    1997-05-09

    This technical comment presents two analyses of Daniel H. Sandweiss article which reiterates arguments advanced a decade ago that climatic and oceanic changes 5000 years before present (B.P.) resulted in the onset of El Nino/Southern Oscillation (ENSO) events along the coast of Peru. Included is a rebuttal by the original author. 32 refs.

  11. On the relation among the solar activity, the quasi-biennial oscillation in the equatorial stratosphere and El Nino.

    NASA Astrophysics Data System (ADS)

    Gul, Zhennian

    The possibility of a relation among Quasi-Biennial Oscillation (QBO) of zonal winds in the equatorial stratosphere, sunspot Wolf number and SST's in the eastern Pacific during the same interval are analyzed. The band filter and the wavelet method which are capable of finding local periods and amplitudes are used in the data processing. It is shown that the coherence estimates between the series of QBO in Wolf and in lower tropical stratosphere are of order of -0.6. A possible dynamical explanation for skip a beat of QBO linked El Nino suggested by Angel and Gray is presented. Solar activity is a hypothetical mechanism of this skip.

  12. Spatial Patterns of Variability in Antarctic Surface Temperature: Connections to the Southern Hemisphere Annular Mode and the Southern Oscillation

    NASA Technical Reports Server (NTRS)

    Kwok, Ron; Comiso, Josefino C.; Koblinsky, Chester J. (Technical Monitor)

    2002-01-01

    The 17-year (1982-1998) trend in surface temperature shows a general cooling over the Antarctic continent, warming of the sea ice zone, with moderate changes over the oceans. Warming of the peripheral seas is associated with negative trends in the regional sea ice extent. Effects of the Southern Hemisphere Annular Mode (SAM) and the extrapolar Southern Oscillation (SO) on surface temperature are quantified through regression analysis. Positive polarities of the SAM are associated with cold anomalies over most of Antarctica, with the most notable exception of the Antarctic Peninsula. Positive temperature anomalies and ice edge retreat in the Pacific sector are associated with El Nino episodes. Over the past two decades, the drift towards high polarity in the SAM and negative polarity in the SO indices couple to produce a spatial pattern with warmer temperatures in the Antarctic Peninsula and peripheral seas, and cooler temperatures over much of East Antarctica.

  13. Can El Nino Amplify the Solar Forcing of Climate?

    NASA Technical Reports Server (NTRS)

    Ruzmaikin, A.

    1999-01-01

    ENSO (El Nino and the Southern Oscillation) is considered as a stochastic driver that excites the atmospheric anomaly states, such as Pacific North American pattern. This can make the 11 year solar activity forcing feasible to climate through stochastic resonance -- a phenomenon that amplifies a weak input to a nonlinear bistable system by the assistance of noise.

  14. On the predictability of the interannual behaviour of the Madden-Julian oscillation and its relationship with El Nino

    SciTech Connect

    Sperber, K.R., LLNL

    1998-03-01

    The Madden-Julian Oscillation (MJO) is the dominant mode of tropical variability at intraseasonal timescales. It displays substantial interannual variability in intensity which may have important implications for the predictability of the coupled system. The reasons for this interannual variability are not understood. The aim of this paper is to investigate whether the interannual behavior of the MJO is related to tropical sea surface temperature (SST) anomalies, particularly El Nino, and hence whether it is predictable. The interannual behavior of the MJO has been diagnosed initially in the 40-year NCEP/ NCAR Reanalysis. The results suggest that prior to the mid-1970s the activity of the MJO was consistently lower than during the latter part of the record. This may be related to either inadequacies in the data coverage, particularly over the tropical Indian Ocean prior to the introduction of satellite observations, or to the real effects of a decadal timescale warming in the tropical SSTs. The teleconnection patterns between interannual variations in MJO activity and SST show only a weak, barely significant, influence of El Nino in which the MJO is more active during the cold phase. As well as the NCEP/NCAR Reanalysis, a 4-member ensemble of 45 year integrations with the Hadley Centre climate model (HadAM2a), forced by observed SSTs for 1949-93, has been used to investigate the relationship between MJO activity and SST. HadAM2a is known to give a reasonable simulation of the MJO and the extended record provided by this ensemble of integrations allows a more robust investigation of the predictability of MJO activity than was possible with the 40-year NCEP/NCAR Reanalysis. The results have shown that, for the uncoupled system, with the atmosphere being driven by imposed SSTS, there is no reproducibility for the activity of the MJO from year to year. The interannual behavior of the MJO is not controlled by the phase of El Nino and would appear to be chaotic in

  15. Evidence of recent warming and El Nino-related variations in ice breakup of Wisconsin lakes

    USGS Publications Warehouse

    Anderson, W.L.; Robertson, D.M.; Magnuson, J.J.

    1996-01-01

    Ice breakup dates from 1968 to 1988 were examined for 20 Wisconsin lakes to determine whether consistent interannual and long-term changes exist. Each ice record had a trend toward earlier breakup dates, as demonstrated by a negative slope with time, indicating a recent warming trend. The average change in breakup dates was 0.82 d earlier per year for the lakes in southern Wisconsin, which was more extreme than that for the northern Wisconsin lakes (0.45 d yr-1). Interannual variation in breakup dates was related to the warm phase of El Nino/Southern Oscillation (ENSO) episodes. El Nino events occurred five times during this period (1965, 1972, 1976, 1982, and 1986). Average breakup dates were significantly earlier than average (5-14 d) during the mature phase of El Nino. This variability was affected by the location of the lake: El Nino-related variation was more evident for the southern lakes than the northern lakes. This difference was caused by the average date of breakup for the southern lakes being in late March directly following the period when air temperatures were strongly related to El Nino events, whereas the average dates of breakup of the northern lakes was in mid- to late April following a period when air temperatures were not significantly related to El Nino events. Overall, the interannual and long-term patterns across Wisconsin were relatively consistent, indicating that recent warming and El Nino- related variation are regional climatic responses.

  16. 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.

  17. 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.

  18. Evolution of the Southern Oscillation as observed by the Nimbus-7 ERB experiment

    NASA Technical Reports Server (NTRS)

    Ardanuy, Philip E.; Kyle, H. Lee; Chang, Hyo-Duck

    1987-01-01

    The Nimbus-7 satellite has been in a 955-km, sun-synchronous orbit since October 1978. The Earth Radiation Budget (ERB) experiment has taken approximately 8 years of high-quality data during this time, of which seven complete years have been archived at the National Space Science Data Center. A final reprocessing of the wide-field-of-view channel dataset is underway. Error analyses indicate a long-term stability of 1 percent better over the length of the data record. As part of the validation of the ERB measurements, the archived 7-year Nimbus-7 ERB dataset is examined for the presence and accuracy of interannual variations including the Southern Oscillation signal. Zonal averages of broadband outgoing longwave radiation indicate a terrestrial response of more than 2 years to the oceanic and atmospheric manifestations of the 1982-83 El Nino/Southern Oscillation (ENSO) event, especially in the tropics. This signal is present in monthly and seasonal averages and is shown here to derive primarily from atmospheric responses to adjustments in the Pacific Ocean. The calibration stability of this dataset thus provides a powerful new tool to examine the physics of the ENSO phenomena.

  19. Evolution of the Southern Oscillation as observed by the Nimbus-7 ERB experiment

    NASA Technical Reports Server (NTRS)

    Ardanuy, Philip E.; Kyle, H. Lee; Chang, Hyo-Duck

    1987-01-01

    The Nimbus-7 satellite has been in a 955-km, sun-synchronous orbit since October 1978. The Earth Radiation Budget (ERB) experiment has taken approximately 8 years of high-quality data during this time, of which seven complete years have been archived at the National Space Science Data Center. A final reprocessing of the wide-field-of-view channel dataset is underway. Error analyses indicate a long-term stability of 1 percent better over the length of the data record. As part of the validation of the ERB measurements, the archived 7-year Nimbus-7 ERB dataset is examined for the presence and accuracy of interannual variations including the Southern Oscillation signal. Zonal averages of broadband outgoing longwave radiation indicate a terrestrial response of more than 2 years to the oceanic and atmospheric manifestations of the 1982-83 El Nino/Southern Oscillation (ENSO) event, especially in the tropics. This signal is present in monthly and seasonal averages and is shown here to derive primarily from atmospheric responses to adjustments in the Pacific Ocean. The calibration stability of this dataset thus provides a powerful new tool to examine the physics of the ENSO phenomena.

  20. A note on the modulation of Southern Oscillation-Southern Afican rainfall associations with the Quasi-Biennial Oscillation

    SciTech Connect

    Mason, S.J.; Lindesay, J.A. )

    1993-05-20

    The authors look at correlations between the southern oscillation and rainfall in South Africa. Since the 1950's there has been a reasonably stable correlation, but there have been times when the correlation seems to have broken down. They look at the question of whether the phase of the quasi-biennial oscillation can be involved in this correlation. There is a limited correlation found, but its evidence depends upon the westerly or easterly phase of the quasi-biennial oscillation, and only correlates certain seasonal conditions of the southern oscillation, South African rainfall data.

  1. Impact of El Niño-southern oscillation on Indian foodgrain production

    NASA Astrophysics Data System (ADS)

    Selvaraju, R.

    2003-02-01

    The impact of El Niño-southern oscillation (ENSO) on Indian foodgrain production was analysed for the period 1950-99. The inverse relationship between sea-surface temperature (SST) anomalies from June to August (JJA) over the NINO3 sector of the tropical Pacific Ocean and Indian foodgrain production anomalies (r = -0.50) was significant at the 1% level. During the warm ENSO phase, the total foodgrain production frequently decreased (12 out of 13 years) by 1 to 15%. In 10 out of 13 cold ENSO-phase years, the total foodgrain production increased from normal. The relationship between the SST-based NINO3 ENSO index and the Kharif season (June-September) foodgrain production anomalies (r = -0.52) was greater than for the Rabi season (October-February) foodgrain production (r = -0.27). The ENSO impact on rice production was greatest among the individual crops. The average drop in rice (Kharif season crop) production during a warm ENSO-phase year was 3.4 million tonnes (7%). In a cold ENSO-phase year the average production increase was 1.3 million tones (3%). Wheat (Rabi season crop) production was also influenced by ENSO, as it depends on the carryover soil water storage from the Kharif season. Sorghum and chickpea production are not significantly influenced by ENSO extremes. Inter-annual fluctuation of the gross value of Indian foodgrain production was very large, reducing up to US2183 million in a warm ENSO year and increasing up to US1251 million in a cold ENSO year. On average, a warm ENSO year costs US773 million and a cold ENSO year had a financial gain of US437 million from normal. The cumulative probability distributions of foodgrain production anomalies during cold and warm ENSO phases are shifted positively or negatively, relative to the neutral distribution. The warm ENSO forcing significantly (1% level) reduced the probability of above-average production. The cold ENSO forcing moderately increased the above-average foodgrain production over the neutral ENSO

  2. Does Terrestrial Drought Explain Global CO2 Flux Anomalies Induced by El Nino?

    NASA Technical Reports Server (NTRS)

    Schwalm. C. R.; Williams, C. A.; Schaefer, K.; Baker, I.; Collatz, G. J.; Roedenbeck, C.

    2011-01-01

    The El Nino Southern Oscillation is the dominant year-to-year mode of global climate variability. El Nino effects on terrestrial carbon cycling are mediated by associated climate anomalies, primarily drought, influencing fire emissions and biotic net ecosystem exchange (NEE). Here we evaluate whether El Nino produces a consistent response from the global carbon cycle. We apply a novel bottom-up approach to estimating global NEE anomalies based on FLUXNET data using land cover maps and weather reanalysis. We analyze 13 years (1997-2009) of globally gridded observational NEE anomalies derived from eddy covariance flux data, remotely-sensed fire emissions at the monthly time step, and NEE estimated from an atmospheric transport inversion. We evaluate the overall consistency of biospheric response to El Nino and, more generally, the link between global CO2 flux anomalies and El Nino-induced drought. Our findings, which are robust relative to uncertainty in both methods and time-lags in response, indicate that each event has a different spatial signature with only limited spatial coherence in Amazonia, Australia and southern Africa. For most regions, the sign of response changed across El Nino events. Biotic NEE anomalies, across 5 El Nino events, ranged from -1.34 to +0.98 Pg Cyr(exp -1, whereas fire emissions anomalies were generally smaller in magnitude (ranging from -0.49 to +0.53 Pg C yr(exp -1). Overall drought does not appear to impose consistent terrestrial CO2 flux anomalies during El Ninos, finding large variation in globally integrated responses from 11.15 to +0.49 Pg Cyr(exp -1). Despite the significant correlation between the CO2 flux and El Nino indices, we find that El Nino events have, when globally integrated, both enhanced and weakened terrestrial sink strength, with no consistent response across events

  3. 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.

  4. 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.

  5. El Nino.

    ERIC Educational Resources Information Center

    Blueford, Joyce

    1988-01-01

    Information is presented regarding "El Nino," a warm ocean current which has a profound worldwide effect on ocean life and weather patterns. Suggestions are provided for teaching students about the current and other related topics. (CB)

  6. El Nino.

    ERIC Educational Resources Information Center

    Blueford, Joyce

    1988-01-01

    Information is presented regarding "El Nino," a warm ocean current which has a profound worldwide effect on ocean life and weather patterns. Suggestions are provided for teaching students about the current and other related topics. (CB)

  7. Impact of El Nino and logging on canopy tree recruitment in borneo

    PubMed

    Curran; Caniago; Paoli; Astianti; Kusneti; Leighton; Nirarita; Haeruman

    1999-12-10

    Dipterocarpaceae, the dominant family of Bornean canopy trees, display the unusual reproductive strategy of strict interspecific mast-fruiting. During 1986-99, more than 50 dipterocarp species dispersed seed only within a 1- to 2-month period every 3 to 4 years during El Nino-Southern Oscillation events. Synchronous seed production occurred across extensive areas and was essential for satiating seed predators. Logging of dipterocarps reduced the extent and intensity of these reproductive episodes and exacerbated local El Nino conditions. Viable seed and seedling establishment have declined as a result of climate, logging, and predators. Since 1991, dipterocarps have experienced recruitment failure within a national park, now surrounded by logged forest.

  8. Future Changes in Rainfall Extremes Associated with El Nino Projected by a Global 20-km Mesh Atmospheric Model

    NASA Astrophysics Data System (ADS)

    Kitoh, A.; Endo, H.

    2015-12-01

    El Nino/Southern Oscillation (ENSO) will still be the most dominant year-to-year variations of the future tropical climate system. A global high-resolution atmospheric general circulation model with grid size about 20 km is used to project future changes in rainfall extremes associated with El Nino at the end of the 21st century. Four different spatial patterns in sea surface temperature (SST) changes are used as future boundary conditions based on the CMIP5 RCP8.5 scenario. Rainfall extremes such as the maximum 5-day precipitation total (Rx5d) over the western Pacific are positively correlated to the Nino3.4 SST anomalies. It is found that Rx5d regressed to the Nino3.4 SST will increase two times in the future compared to the present value. This implies drastic increase of risk of heavy-rainfall induced disasters under by global warming over the western Pacific countries.

  9. Decadal Variability of the Tropical Stratosphere: Secondary Influence of the El Nino-Southern Oscillation

    DTIC Science & Technology

    2010-02-04

    solar cycle variation of ozone in the strato - sphere inferred from Nimbus 7 and NOAA 11 satellites, J. Geophys. Res., 99, 20,665- 20,671. Chipperfield...tropical lower stratosphere: The role of extratropical wave forcing, J. Atmos. Sci., 60, 2389-2403. Hoppel, K. W., N. L. Baker, L. Coy, S. D. Eckermann...solar cycle: Winter strato - pause and lower stratosphere, J. Geophys. Res., 101, 4749, doi:10.1029/2002JD002224. Labitzke, K. (2004), On the signal of

  10. Long-term central coastal California precipitation variability and relationships to El-Nino-Southern Oscillation

    SciTech Connect

    Haston, L. ); Michaelsen, J. )

    1994-09-01

    Long precipitation reconstructions (600 years) developed for Santa Barbara, California, using new big-cone spruce tree-ring chronologies capture over 55% of the annual precipitation variance. The modern period of the reconstruction is characterized by low variability and one of the lowest rates of extreme events within the last 600 years. Precipitation has reached lower levels in the past than recorded during the modern period. The 1987-91 drought ranks as only the tenth worst in the last 600 years. Furthermore, although the modem period contains some of the most extreme periods of wetness in the last 600 years, wet years have been relatively infrequent and the mean level of precipitation close to average since the time that most population growth and dam building has occurred in this area. The most unusual feature of the reconstruction is increased variability and frequency of wet events during the late 1500s and early 1600s, which may be related to Little Ice Age climatic changes. An analysis of the relationship between ENSO events and reconstructed precipitation shows no clear, consistent response to ENSO in this area. The probability of a wet year during an ENSO is no greater than during a non-ENSO year. However, when wet years do occur during an ENSO they are often extremely wet. 56 refs., 9 figs., 4 tabs.

  11. An Important Ocean Feature Overlooked in Current El Nino-Southern Oscillation Theories

    DTIC Science & Technology

    1992-01-01

    t " an ’’’’’’’Me of r; - n . ",hreh 111 ’u’" a,,!p’W:"" (I", OMI, dC<:I"""" g ...almo· sphcric C(> n ,·e ..gcn~~ .11\\d ~o""",,li,," (Tn,weclion /1-) a,c gencrally ." soci .1Ied wilh Ihe 11""’" waler (Gill. 19~0). III Ihc~a’l (0’ Wt., t ...34 il u,uMly i’ i" Ih" 1t0IHes. With rollsi<l..."i"" uf lhi’ fe,.eu",. b(Hh 1>0ŕ"’" a,,ə n " g

  12. Interannual variability of the Indian monsoon and the Southern Oscillation

    SciTech Connect

    Wu, M.; Hastenrath, S.

    1986-01-01

    Years with abundant Southwest monsoon rainfall in India are characterized by anomalously low pressure over South Asia and the adjacent waters, enhanced cross-equatorial flow in the western, and increased cloudiness over the northern portion of the Indian Ocean, continuing from the pre-monsoon through the post-monsoon season; positive temperature anomalies over land and in the Arabian Sea in the pre-monsoon season, changing to negative departures after the monsoon onset. The following causality chain is suggested: the anomalously warm surfaces of south Asia and the adjacent ocean in the pre-monsoon season induce a thermal low, thus enhancing the northward directed pressure gradient, and favoring a vigorous cross-equatorial flow over the Indian Ocean. After the monsoon onset the land surfaces are cooled by evaporation, and the Arabian Sea surface waters by various wind stress effects. However, latent heat release over South Asia can now maintain the meridional topography gradients essential to the monsoon circulation. The positive phase of the Southern Oscillation (high pressure over the Eastern South Pacific) is associated with circulation departures in the Indian Ocean sector similar to those characteristic of years with abundant India monsoon rainfall. Abundant rainfall over India during the northern summer monsoon leads the positive mode of the southern Oscillation, and this in turn leads Java rainfall, whose peak is timed about half a year after that of India. A rising Southern Oscillation tendency presages abundant India Southwest Monsoon rainfall but a late monsoon onset. 46 references, 9 figures, 4 tables.

  13. Modulation of the Global Wind Resource by the El-Nino

    NASA Astrophysics Data System (ADS)

    Gunturu, U. B.; Yip, C. M. A.; Stenchikov, G. L.

    2014-12-01

    El-Nino is the most important climate scale oscillation in the tropical atmosphere and earlier studies have shown that it impacts weather in different parts of the world. Since the long-term stability of wind resource is a primary requirement for the reliability of wind power generation, any modulation of the wind resource by the El-Nino constitutes valuable information for efficient harvesting of wind. In this study, we construct the global wind resource as described in Gunturu & Schlosser (2012) and use the method of composites to understand the impact of the El-Nino on the global wind resource. The results show that the impact of the El-Nino is to decrease the wind resource in the central United States, southern Australia and north central Africa. Further, interestingly, the wind resource increases in the Nordic sea and the continental areas around it. The Deccan plateau region of India also has reduced WPD due to the El-Nino as shown by the composites. On the other hand, the central US and southern Australia have increased WPD due to La-Nina and the resource decreases in India. The statistically significant results will be further discussed for their implications to the long term stability of the wind resource in the different regions of the world. We also substantiate the results with other suitable metrics.

  14. El Nino and outgoing longwave radiation: An atlas of Nimbus-7 Earth radiation budget observations

    NASA Technical Reports Server (NTRS)

    Kyle, H. L.; Ardanuy, P. E.; Hucek, R. R.

    1986-01-01

    Five years of broadband Earth Radiation Budget (ERB) measurements taken by the Nimbus-7 ERB experiment have been archived. This five year period included the 1982 to 1983 El Nino/Southern Oscillation event, which reached its peak in January 1983 (near the beginning of the fifth data year). An outgoing longwave radiation subset of the data, for the period June 1980 to October 1983, was processed to enhance spatial resolution. This atlas contains the analyses of the resultant fields. In addition, a set of anomaly maps, based on a definition of pre-El Nino climatology, is included. Together, these two sets of maps provide the first broadband glimpse of the terrestrial outgoing longwave radiation response to the El Nino event.

  15. Non-ENSO control on southern Africa precipitation variability.

    PubMed

    Lizcano, Gil; Todd, Martin

    2005-01-15

    The objective of this study is to quantify the nature of the mechanisms of southern Africa rainfall variability, unrelated to the El Nino Southern Oscillation, by means of a simple empirical composite analysis, as a baseline for a more detailed study.

  16. United States Streamflow Patterns Associated with the Extreme Phases of the Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Kahya, Ercan

    The potential for long-term streamflow forecasts based on atmospheric circulation indices in the United States has been assessed. The extreme phases of the Southern Oscillation (SO) have been linked to fairly persistent classes of atmospheric anomalies (e.g., precipitation) over the low and middle latitudes at regional and global sale. This study examines the relationships between the extreme phases of the SO and unimpaired stream discharges over the contiguous U.S. Of particular interest in this investigation is the identification of areas of land that appear to have consistent and strong El Nino/Southern Oscillation (ENSO)-related streamflow signals. The first harmonic extracted from a 24-month ENSO composite at each station is assumed to be the ENSO-related signal appearing stream flow anomalies. The vectorial display of these harmonics over a map of the U.S. provides the areal extents of ENSO influence on streamflows. Similar analysis is performed for the La Nina phase of the SO. Strong and consistent streamflow responses to hypothesized ENSO forcing are found during a detected season in the four core areas: Gulf of Mexico, North East, North Central and Pacific Northwest. The Southwest is found to be another key region for the Type 1 ENSO events. For the La Nina phase, each of these regions exhibit an equally reliable signal and almost same timing with that of ENSO signal. The appearance of both ENSO and La Nina signals is analyzed in conjunction with the annual cycle. Almost reversal in sign of streamflow anomalies during ENSO events compared to these during La Nina events. The significance of relationships between the extremes of the SO and streamflows within each core area are determined by the hypergeometric distribution. A proper season that the SO index can be averaged to obtain a higher correlation value is found for each core area. Moreover, some clues are presented so that ENSO events influence significantly the persistence in streamflow. Finally

  17. Spatiotemporal Variability of El Niño Southern Oscillation from Geodetic Satellites

    NASA Astrophysics Data System (ADS)

    Wu, Y.-H.; García-García, D.; Chao, B. F.

    2009-04-01

    The global mean sea level rose at about 2.46 mm/year during 1930 and 2007. Many global change phenomena have been well observed and monitored, such as temperature rise in the polar region and large-scale ice melting, precipitation and ocean salinity changes, wind field and severe weather intensification, etc. The two main causes of the sea level variation (SLV) are thermal expansion and mass changes within oceans resulting from climate shift, but their relative share in the total SLV is still uncertain. We hereby study the SLV around tropical oceans in relation to El Niño Southern Oscillation (ENSO) and their variability in space-time. We employ the method of C/EOF (Complex/Empirical Orthogonal Function) to analyze various physical parameters in the region and their space-time variability. We find: (1) Using the satellite ocean altimeter data to study SLV in relation to ENSO variations revealed that from 1993 to 2007 the first mode's time series of Complex EOF suggests high correspondence to the SOI and Nino3.4 index; (2) We additionally extracted the spatial propagation with time evolution of ENSO SLV; (3) Time variable gravity (TVG) over the ENSO region obtained from GRACE satellite data suggests weaker mass migration signals than SLV, although larger uncertainty is expected from GRACE over low latitudes; (4) Using the GCM output (such as ECCO, and MERCATOR), e.g. salinity and temperature profiles with reference to the ocean altimeter and GRACE data revealed the characters of steric or mass-induced SLV during the ENSO events. Preliminary results show that both SLV and SST anomaly had a steady increase after the strongest 1997-98 ENSO event, but not present in the steric SLV conducted according to the GCMs, presumably due to the general underestimation in the latter.

  18. Effect of geomagnetic and volcanic activity on the El Nino and La Nina phenomena

    NASA Astrophysics Data System (ADS)

    Vovk, V. Ya.; Egorova, L. V.

    2009-04-01

    The monthly values of the southern atmospheric oscillation indices (SOI), the corresponding values of the Nino-3.4 index, the data on the onsets of intense volcanic eruptions from 1870 to 2002, the daily values of the Ap and AE indices and the IMF B z component, and the data on cloudiness and wind characteristics at 14 Antarctic stations have been considered. The beginning of the warm El Nino current is observed after an increase in the amplitude of the Ap magnetic indices, which continues for more than five months. The beginning of the cold period of the La Nina southern atmospheric oscillation is as a rule related to a decrease in Ap. A change in atmospheric transparency caused by volcanic eruptions is often followed by the beginning of the cold period of the southern atmospheric oscillation (ENSO). A change in the wind system in the Antarctic Regions, related to a change in the temperature balance caused by variations in the solar wind parameters in the winter season, promotes a short-term disturbance of the circumpolar vortex and the beginning of the El Nino warm period.

  19. Global Precipitation during the 1997-98 El Nino and Initiation of the 1998-99 La Nina

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    The 1997-99 ENSO (El nino Southern Oscillation) cycle was very powerful, but also well observed. The best satellite rainfall estimates combined with gauge observations allow for a global analysis of precipitation anomalies accompanying the 1997-98 El Nino and initiation of the 1998-99 La Nina. For the period April 1997 to March 1998 the central to eastern Pacific, southeastern and western U.S., Argentina, eastern Africa, South China, eastern Russia, and North Atlantic were all more than two standard deviations wetter than normal. During the same year the Maritime Continent, eastern Indian Ocean, subtropical North Pacific, northeastern South America, and much of the mid- latitude southern oceans were more than two standard deviations drier than normal. An analysis of the evolution of the El Nino and accompanying precipitation anomalies revealed that a dry Maritime Continent led the formation of the El Nino SST (Sea Surface Temperature), while in the central Pacific, precipitation anomalies lagged the El Nino SST by a season. A rapid transition from El Nino to La Nina occurred in May 1998, but as early as October-November 1997 precipitation indices captured precursor changes in Pacific rainfall anomalies. Differences were found between observed and modeled [NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis] precipitation anomalies for 1997 and 98. 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. One degree daily estimates of rainfall show clearly the MaddenJulian Oscillation and related westerly wind burst events over the Maritime Continent, which are key

  20. The influence of different El Nino types on the northern hemisphere stratosphere simulated by the MPI-ESM

    NASA Astrophysics Data System (ADS)

    Bittner, Matthias; Timmreck, Claudia; Schmidt, Hauke

    2013-04-01

    It is known that the El Nino Southern Oscillation (ENSO), although it is mainly a tropospheric phenomenon, has an impact on the polar winter stratosphere [e.g. van Loon and Labitzke, 1987: Camp and Tung, 2007]. This has also been shown in simulations with general circulation models (GCM) [Sassi,et al. 2004, Manzini et al. 2006]. For a couple of years there are discussions about two different "flavors" of the the El Nino, the central Pacific (or Modoki) El Nino and the east Pacific El Nino [e.g. Wang and Weisberg, 2000; Yu and Kao, 2007; Ashok et al. 2007]. An observational study [Graf and Zanchettin, 2012] indicate that the polar vortex is more disturbed during EP El Ninos. Here we to investigate the influence of the equatorial sea surface temperatures on the stratosphere-troposphere coupling in the northern hemisphere winter season in a fully coupled atmosphere-ocean-land GCM. We use two versions of the Max-Planck-Institute for Meteorology model MPI-ESM, namely MPI-ESM-LR with lower T63 L47 atmosphere and GR15 ocean resolution and the MPI-ESM-MR with the same horizontal resolution in the atmosphere but a higher resolution in the vertical (L95) and in the ocean (TP04). To exclude effects of natural and anthropogenic forcing, we analyze a 1000 year coupled control simulation with pre-industrial greenhouse gas concentration and constant solar forcing (piControl). For comparison with reananlyis data we also analyze uncoupled atmosphere-only simulations with observed sea surface temperatures from 1979 until 2008 (AMIP). We compare three ways of defining El Nino: the central Pacific (CP), the east Pacific (EP) and the canonical Nino3.4 El Nino. We show to what extent the MPI-ESM is able to simulate these different types of El Nino and how they affect the polar stratosphere. The MPI-ESM model is in both versions capable of producing CP and EP El Ninos. However, the CP El Nino is dominant one in terms of magnitude and the EP El Nino has a relative small impact on global

  1. El Nino, volcanism, and global climate

    SciTech Connect

    Handler, P.; Andsager, K. )

    1994-03-01

    The June 1991 eruption of Mt. Pinatubo in the Philippines produced one of the greatest volcanic aerosols in the last hundred years. The estimated net decrease of radiation may have peaked at 10% in the tropics. What was the impact of the Pinatubo aerosol on regional and global climate Besides the expected net cooling of the average global surface temperature, correlation studies indicate that other types of climate anomalies may also be expected. These include the appearance of an El Nino event, decreased Indian monsoon rainfall, fewer tropical storms in the north Atlantic Ocean in 1991-1993, and normal to above normal winter rainfall in California in 1991/92, all of which were observed. A proposed physical mechanism for the almost-simultaneous occurrence of this constellation of climate anomalies is presented. The results of correlation studies between low-latitude volcanic aerosols and the El Nino/Southern Oscillation are presented in some detail as one example. The correlation between Indian monsoon rainfall and tropical storms in the north Atlantic Ocean is also shown and is updated for the most recent 5 years.

  2. Disruptions of El Niño–Southern Oscillation teleconnections by the Madden–Julian Oscillation

    USGS Publications Warehouse

    Hoell, Andrew; Barlow, Mathew; Wheeler, Mathew; Funk, Christopher C.

    2014-01-01

    The El Niño–Southern Oscillation (ENSO) is the leading mode of interannual variability, with global impacts on weather and climate that have seasonal predictability. Research on the link between interannual ENSO variability and the leading mode of intraseasonal variability, the Madden–Julian oscillation (MJO), has focused mainly on the role of MJO initiating or terminating ENSO. We use observational analysis and modeling to show that the MJO has an important simultaneous link to ENSO: strong MJO activity significantly weakens the atmospheric branch of ENSO. For weak MJO conditions relative to strong MJO conditions, the average magnitude of ENSO-associated tropical precipitation anomalies increases by 63%, and the strength of hemispheric teleconnections increases by 58%. Since the MJO has predictability beyond three weeks, the relationships shown here suggest that there may be subseasonal predictability of the ENSO teleconnections to continental circulation and precipitation.

  3. El Nino during the 1990s: Harbinger of Climatic Change or Normal Fluctuation?

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    1999-01-01

    Today, El Nino refers to the extreme warming episodes of the globally effective, coupled ocean-atmospheric interaction commonly known as ENSO (i.e., "El Nino-Southern Oscillation"). Concerning its observed decadal frequency and severity, El Nino during the 1990s has often been regarded as being anomalous. Results of analysis reported herein, however, appear to mitigate this belief. For example, regarding the frequency and severity of El Nino, the decade of the 1990s is found to compare quite favorably with that of preceding decades. Hence, the 1990s probably should not be regarded as being anomalous. On the other hand, the number of El Nino-related months per decade has sharply increased during the 1990s, as compared to the preceding four decades, hinting of a marginally significant upward trend. Perhaps, this is an indication that the Earth is now experiencing an ongoing global climatic change. Continued vigilance during the new millennium, therefore, is of paramount importance for determining whether or not this "hint" of a global change is real or if it merely reflects a normal fluctuation of climate.

  4. The Semiannual Oscillation of Southern Ocean Sea Level

    NASA Astrophysics Data System (ADS)

    Hibbert, A.

    2012-04-01

    The atmospheric Semiannual Oscillation (SAO) is a half-yearly wave in mean sea level air pressure, which exhibits equinoctial maxima between 45°S and 50°S and solstitial maxima between 55°S and 65°s, with a phase reversal occurring at around 60°S. Its existence has been attributed to a phase difference in the annual temperature cycle between mid- and high-latitudes which sets up meridional temperature and pressure gradients that are largest during September and March, enhancing atmospheric baroclinicity and inducing equinoctial maxima in the Southern Hemisphere Westerlies. In this study, we use harmonic analysis of atmospheric and oceanic Southern Ocean datasets to show that this atmospheric SAO induces oceanic counterparts in sea level and circumpolar transport. This aspect of atmosphere-ocean interaction is particularly important, given the capacity of the Antarctic Circumpolar Current (ACC) to influence regional climate through the exchange of heat, fresh water and nutrients to each of the major ocean basins. We examine the relative contributions of local and regional semiannual atmospheric fluctuations in explaining the observed sea level response at 20 Southern Ocean and South Atlantic tide gauge stations and find that the oceanic SAO is associated with a modulation of zonal surface wind strength at key latitudes between ~55°S and 65°S. We also explore whether a seasonal inequality in SAO amplitude might facilitate the deduction of the timescales upon which Southern Ocean 'eddy saturation' theory might operate. However, though we find evidence of biannual fluctuations in eddy kinetic energy, regional variations in the phases and amplitudes of these emergent harmonics prevent us from elucidating the possible timescales upon which an eddy response to the atmospheric SAO might arise.

  5. El Niño−Southern Oscillation frequency cascade

    PubMed Central

    Stuecker, Malte F.; Jin, Fei-Fei; Timmermann, Axel

    2015-01-01

    The El Niño−Southern Oscillation (ENSO) phenomenon, the most pronounced feature of internally generated climate variability, occurs on interannual timescales and impacts the global climate system through an interaction with the annual cycle. The tight coupling between ENSO and the annual cycle is particularly pronounced over the tropical Western Pacific. Here we show that this nonlinear interaction results in a frequency cascade in the atmospheric circulation, which is characterized by deterministic high-frequency variability on near-annual and subannual timescales. Through climate model experiments and observational analysis, it is documented that a substantial fraction of the anomalous Northwest Pacific anticyclone variability, which is the main atmospheric link between ENSO and the East Asian Monsoon system, can be explained by these interactions and is thus deterministic and potentially predictable. PMID:26483455

  6. El Niño$-$Southern Oscillation frequency cascade

    DOE PAGES

    Stuecker, Malte F.; Jin, Fei -Fei; Timmermann, Axel

    2015-10-19

    The El Niño$-$Southern Oscillation (ENSO) phenomenon, the most pronounced feature of internally generated climate variability, occurs on interannual timescales and impacts the global climate system through an interaction with the annual cycle. The tight coupling between ENSO and the annual cycle is particularly pronounced over the tropical Western Pacific. In this paper, we show that this nonlinear interaction results in a frequency cascade in the atmospheric circulation, which is characterized by deterministic high-frequency variability on near-annual and subannual timescales. Finally, through climate model experiments and observational analysis, it is documented that a substantial fraction of the anomalous Northwest Pacific anticyclonemore » variability, which is the main atmospheric link between ENSO and the East Asian Monsoon system, can be explained by these interactions and is thus deterministic and potentially predictable.« less

  7. Planetary period oscillations in Saturn's magnetosphere: Evolution of magnetic oscillation properties from southern summer to post-equinox

    NASA Astrophysics Data System (ADS)

    Andrews, D. J.; Cowley, S. W. H.; Dougherty, M. K.; Lamy, L.; Provan, G.; Southwood, D. J.

    2012-04-01

    We investigate the evolution of the properties of planetary period magnetic field oscillations observed by the Cassini spacecraft in Saturn's magnetosphere over the interval from late 2004 to early 2011, spanning equinox in mid-2009. Oscillations within the inner quasi-dipolar region ( L < 12 ) consist of two components of close but distinct periods, corresponding essentially to the periods of the northern and southern Saturn kilometric radiation (SKR) modulations. These give rise to modulations of the combined amplitude and phase at the beat period of the two oscillations, from which the individual oscillation amplitudes and phases (and hence periods) can be determined. Phases are also determined from northern and southern polar oscillation data when available. Results indicate that the southern-period amplitude declines modestly over this interval, while the northern-period amplitude approximately doubles to become comparable with the southern-period oscillations during the equinox interval, producing clear effects in pass-to-pass oscillation properties. It is also shown that the periods of the two oscillations strongly converge over the equinox interval, such that the beat period increases significantly from ~20 to more than 100 days, but that they do not coalesce or cross during the interval investigated, contrary to recent reports of the behavior of the SKR periods. Examination of polar oscillation data for similar beat phase effects yields a null result within a ~10% upper limit on the relative amplitude of northern-period oscillations in the south and vice versa. This result strongly suggests a polar origin for the oscillation periods.

  8. Planetary period oscillations in Saturn's magnetosphere: Evolution of magnetic oscillation properties from southern summer to post-equinox

    NASA Astrophysics Data System (ADS)

    Andrews, D. J.; Cowley, S. W. H.; Dougherty, M. K.; Lamy, L.; Provan, G.; Southwood, D. J.

    2012-04-01

    We investigate the evolution of the properties of planetary period magnetic field oscillations observed by the Cassini spacecraft in Saturn's magnetosphere over the interval from late 2004 to early 2011, spanning equinox in mid-2009. Oscillations within the inner quasi-dipolar region (L ≤ 12) consist of two components of close but distinct periods, corresponding essentially to the periods of the northern and southern Saturn kilometric radiation (SKR) modulations. These give rise to modulations of the combined amplitude and phase at the beat period of the two oscillations, from which the individual oscillation amplitudes and phases (and hence periods) can be determined. Phases are also determined from northern and southern polar oscillation data when available. Results indicate that the southern-period amplitude declines modestly over this interval, while the northern-period amplitude approximately doubles to become comparable with the southern-period oscillations during the equinox interval, producing clear effects in pass-to-pass oscillation properties. It is also shown that the periods of the two oscillations strongly converge over the equinox interval, such that the beat period increases significantly from ˜20 to more than 100 days, but that they do not coalesce or cross during the interval investigated, contrary to recent reports of the behavior of the SKR periods. Examination of polar oscillation data for similar beat phase effects yields a null result within a ˜10% upper limit on the relative amplitude of northern-period oscillations in the south and vice versa. This result strongly suggests a polar origin for the two oscillation periods.

  9. Proxy Records of the Indonesian Low and the El Ni{tilde n}o-Southern Oscillation (ENSO) from Stable Isotope Measurements of Indonesian Reef Corals

    SciTech Connect

    Moore, M.D.

    1995-12-31

    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 (ENSO). 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 ENSO events are a possible manifestation of global warming. 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 a 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.

  10. El Niño Southern Oscillation (ENSO) and annual malaria incidence in Southern Africa.

    PubMed

    Mabaso, Musawenkosi L H; Kleinschmidt, Immo; Sharp, Brian; Smith, Thomas

    2007-04-01

    We evaluated the association between annual malaria incidence and El Niño Southern Oscillation (ENSO) as measured by the Southern Oscillation Index (SOI) in five countries in Southern Africa from 1988 to 1999. Below normal incidence of malaria synchronised with a negative SOI (El Niño) and above normal incidence with a positive SOI (La Niña), which lead to dry and wet weather conditions, respectively. In most countries there was a positive relationship between SOI and annual malaria incidence, especially where Anopheles arabiensis is a major vector. This mosquito breeds in temporary rain pools and is highly sensitive to fluctuations in weather conditions. South Africa and Swaziland have the most reliable data and showed the strongest associations, but the picture there may also be compounded by the moderating effect of other oscillatory systems in the Indian Ocean. The impact of ENSO also varies over time within countries, depending on existing malaria control efforts and response capacity. There remains a need for quantitative studies that at the same time consider both ENSO-driven climate anomalies and non-ENSO factors influencing epidemic risk potential to assess their relative importance in order to provide an empirical basis for malaria epidemic forecasting models.

  11. The Evolution of El Nino-Precipitation Relationships from Satellites and Gauges

    NASA Technical Reports Server (NTRS)

    Curtis, Scott; Adler, Robert F.; Starr, David OC (Technical Monitor)

    2002-01-01

    This study uses a twenty-three year (1979-2001) satellite-gauge merged community data set to further describe the relationship between El Nino Southern Oscillation (ENSO) and precipitation. The globally complete precipitation fields reveal coherent bands of anomalies that extend from the tropics to the polar regions. Also, ENSO-precipitation relationships were analyzed during the six strongest El Ninos from 1979 to 2001. Seasons of evolution, Pre-onset, Onset, Peak, Decay, and Post-decay, were identified based on the strength of the El Nino. Then two simple and independent models, first order harmonic and linear, were fit to the monthly time series of normalized precipitation anomalies for each grid block. The sinusoidal model represents a three-phase evolution of precipitation, either dry-wet-dry or wet-dry-wet. This model is also highly correlated with the evolution of sea surface temperatures in the equatorial Pacific. The linear model represents a two-phase evolution of precipitation, either dry-wet or wet-dry. These models combine to account for over 50% of the precipitation variability for over half the globe during El Nino. Most regions, especially away from the Equator, favor the linear model. Areas that show the largest trend from dry to wet are southeastern Australia, eastern Indian Ocean, southern Japan, and off the coast of Peru. The northern tropical Pacific and Southeast Asia show the opposite trend.

  12. Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation.

    NASA Astrophysics Data System (ADS)

    Kwok, R.; Comiso, J. C.

    2002-03-01

    The anomalies in the climate and sea ice cover of the Southern Ocean and their relationships with the Southern Oscillation (SO) are investigated using a 17-yr dataset from 1982 to 1998. The polar climate anomalies are correlated with the Southern Oscillation index (SOI) and the composites of these anomalies are examined under the positive (SOI > 0), neutral (0 > SOI > 1), and negative (SOI < 1) phases of SOI. The climate dataset consists of sea level pressure, wind, surface air temperature, and sea surface temperature fields, while the sea ice dataset describes its extent, concentration, motion, and surface temperature. The analysis depicts, for the first time, the spatial variability in the relationship of the above variables with the SOI. The strongest correlation between the SOI and the polar climate anomalies are found in the Bellingshausen, Amundsen, and Ross Seas. The composite fields reveal anomalies that are organized in distinct large-scale spatial patterns with opposing polarities at the two extremes of SOI, and suggest oscillations that are closely linked to the SO. Within these sectors, positive (negative) phases of the SOI are generally associated with lower (higher) sea level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are evident. Recent anomalies in the sea ice cover that are clearly associated with the SOI include the following: the record decrease in the sea ice extent in the Bellingshausen Sea from mid-1988 to early 1991; the relationship between Ross Sea SST and the ENSO signal, and reduced sea ice concentration in the Ross Sea; and the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea and lengthening of the ice season in the western Ross Sea, Bellinghausen Sea, and central Weddell Sea gyre during the period 1988-94. Four ENSO episodes over the

  13. Spatio-temporal Variability of El Niño Southern Oscillation from Geodetic Satellites and Model Data

    NASA Astrophysics Data System (ADS)

    Wu, H. Y.; Li, Y.; Chao, B. F.

    2010-12-01

    The global sea level varies primarily by two causes: thermal expansion and mass transports. They reflect the responses of the oceans to global climatic changes, but their relative share in the total sea-level variation (SLV) as a function of space-time is a very complex phenomenon to be continuously monitored. We examine several geophysical data sets (for SLV, ocean temperature, surface currents, mixed-layer depth), using the method of C/EOF (Complex/Empirical Orthogonal Function) to study the space-time variability and propagation of the El Niño Southern Oscillation (ENSO) in the tropical oceans. The SLV from satellite altimetry reveals that from 1993 to 2009 the first C/EOF mode’s time series has high correspondence to the SOI and Nino3.4 index, whereas the time variable gravity obtained from the GRACE satellite data indicates weaker mass migration signals than SLV over the ENSO region, although larger uncertainty is expected from GRACE data over low latitudes. Thus we can characterize the steric vs. mass-induced SLV for ENSO. We also examine the in-situ and OGCM output (such as Ishii & Kimoto (2009) and ECCO-2), e.g. salinity and temperature profiles, and identify the depth anomaly of the ocean mixed-layer of the ENSO region and its variability over the past few decades, showing strong ENSO signals but a general underestimation in the OGCMs.

  14. El Nino Continues to Grow

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The latest image from NASA's Jason oceanography satellite, taken during a 10-day collection cycle ending December 2, 2002, shows the Pacific dominated by two significant areas of higher-than-normal sealevel (warmer ocean temperatures). In the central equatorial Pacific, the large area of higher than normal sea surface heights(warmer than normal sea surface temperatures) associated with growing El Nino conditions has recently migrated eastward toward the coast of South America. Meanwhile, the influence of the 20- to 30-year larger than El Nino/La Nina pattern called the Pacific Decadal Oscillation continues to create warm, higher-than-normal sea-surface heights in the north Pacific that are connected in a warm horseshoe pattern with the western and southern Pacific. Sea-surface heights are a measure of how much heat is stored in the ocean below. This heat influences both present weather and future planetary climate events.

    The image shows red areas in the north Pacific and at the equator that are about 10 centimeters (4 inches) above normal; white areas indicate sea surface heights between 14 and 32 centimeters (6 to 13 inches) above normal. These regions contrast with the western tropical Pacific, where lower-than-normal sea levels (blue areas) have developed that are between 5 and 13 centimeters (2 and 5 inches) below normal, while purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. Along the equator, the red sea surface heights equate to sea surface temperature departures greater than one degree Celsius (two degrees Fahrenheit) and the white sea surface heights are sea surface temperatures 1.5 to 2.5 degrees Celsius(three to five degrees Fahrenheit) above normal.

    The U.S. portion of the Jason mission is managed by JPL for NASA's Earth Science Enterprise, Washington, D.C. Research on Earth's oceans using Jason and other space-based capabilities is conducted by NASA's Earth Science Enterprise to better understand and protect our

  15. El Nino Continues to Grow

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The latest image from NASA's Jason oceanography satellite, taken during a 10-day collection cycle ending December 2, 2002, shows the Pacific dominated by two significant areas of higher-than-normal sealevel (warmer ocean temperatures). In the central equatorial Pacific, the large area of higher than normal sea surface heights(warmer than normal sea surface temperatures) associated with growing El Nino conditions has recently migrated eastward toward the coast of South America. Meanwhile, the influence of the 20- to 30-year larger than El Nino/La Nina pattern called the Pacific Decadal Oscillation continues to create warm, higher-than-normal sea-surface heights in the north Pacific that are connected in a warm horseshoe pattern with the western and southern Pacific. Sea-surface heights are a measure of how much heat is stored in the ocean below. This heat influences both present weather and future planetary climate events.

    The image shows red areas in the north Pacific and at the equator that are about 10 centimeters (4 inches) above normal; white areas indicate sea surface heights between 14 and 32 centimeters (6 to 13 inches) above normal. These regions contrast with the western tropical Pacific, where lower-than-normal sea levels (blue areas) have developed that are between 5 and 13 centimeters (2 and 5 inches) below normal, while purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. Along the equator, the red sea surface heights equate to sea surface temperature departures greater than one degree Celsius (two degrees Fahrenheit) and the white sea surface heights are sea surface temperatures 1.5 to 2.5 degrees Celsius(three to five degrees Fahrenheit) above normal.

    The U.S. portion of the Jason mission is managed by JPL for NASA's Earth Science Enterprise, Washington, D.C. Research on Earth's oceans using Jason and other space-based capabilities is conducted by NASA's Earth Science Enterprise to better understand and protect our

  16. Historical effects of El Nino and La Nina events on the seasonal evolution of the montane snowpack in the Columbia and Colorado River Basins

    USGS Publications Warehouse

    Clark, M.P.; Serreze, M.C.; McCabe, G.J.

    2001-01-01

    Snow-water equivalent (SWE) data measured at several hundred montane sites in the western United States are used to examine the historic effects of El Nino and La Nina events on seasonal snowpack evolution in the major subbasins in the Columbia and Colorado River systems. Results are used to predict annual runoff. In the Columbia River Basin, there is a general tendency for decreased SWE during El Nino years and increased SWE in La Nina years. However, the SWE anomalies for El Nino years are much less pronounced. This occurs in part because midlatitude circulation anomalies in El Nino years are located 35?? east of those in La Nina years. This eastward shift is most evident in midwinter, at which time, SWE anomalies associated with El Nino are actually positive in coastal regions of the Columbia River Basin. In the Colorado River Basin, mean anomalies in SWE and annual runoff during El Nino years depict a transition between drier-than-average conditions in the north, and wetter-than-average conditions in the southwest. Associations during La Nina years are generally opposite those in El Nino years. SWE anomalies tend to be more pronounced in spring in the Lower Colorado River Basin. Our predictions of runoff reveal modest skill for scenarios using only historic El Nino and La Nina information. Predictions based on the water stored in the seasonal snowpack are, in almost all cases, much higher than those based on El Nino-Southern Oscillation (ENSO) information alone. However, combining observed midwinter snow conditions with information on seasonal snowpack evolution associated with ENSO improves predictions for basins in which ENSO signals exhibit strong seasonality.

  17. El Niño–Southern Oscillation diversity and Southern Africa teleconnections during Austral Summer

    USGS Publications Warehouse

    Hoell, Andrew; Funk, Christopher C.; Magadzire, Tamuka; Zinke, Jens; Husak, Gregory J.

    2014-01-01

    A wide range of sea surface temperature (SST) expressions have been observed during the El Niño–Southern Oscillation events of 1950–2010, which have occurred simultaneously with different global atmospheric circulations. This study examines the atmospheric circulation and precipitation during December–March 1950–2010 over the African Continent south of 15∘S, a region hereafter known as Southern Africa, associated with eight tropical Pacific SST expressions characteristic of El Niño and La Niña events. The self-organizing map method along with a statistical distinguishability test was used to isolate the SST expressions of El Niño and La Niña. The seasonal precipitation forcing over Southern Africa associated with the eight SST expressions was investigated in terms of the horizontal winds, moisture budget and vertical motion. El Niño events, with warm SST across the east and central Pacific Ocean and warmer than average SST over the Indian Ocean, are associated with precipitation reductions over Southern Africa. The regional precipitation reductions are forced primarily by large-scale mid-tropospheric subsidence associated with anticyclonic circulation in the upper troposphere. El Niño events with cooler than average SST over the Indian Ocean are associated with precipitation increases over Southern Africa associated with lower tropospheric cyclonic circulation and mid-tropospheric ascent. La Niña events, with cool SST anomalies over the central Pacific and warm SST over the west Pacific and Indian Ocean, are associated with precipitation increases over Southern Africa. The regional precipitation increases are forced primarily by lower tropospheric cyclonic circulation, resulting in mid-tropospheric ascent and an increased flux of moisture into the region.

  18. Emergency and institutional crisis in Peru during El Nino 1982-1983.

    PubMed

    Cavledes, C N

    1985-03-01

    From December 1982 through July 1983, Peru was plagued by disastrous consequences of El Nino/Southern Oscillation phenomenon. While the northern part of the country was devastated by torrential rains and floods, central Andean Peru endured landslides and flash floods, the southern Altiplano suffered a severe drought. Hazard preparedness was nonexistent, and official disaster relief uncoordinated and slow in coming. Administrative inefficiency magnified the stress upon the populations under disaster conditions. Provisions of disaster training from specialized international organizations is recommended as a preventive measure and as a policy to improve catastrophe-coping abilities in developing nations.

  19. Evolution of the 1997-98 El Nino and La Nina: the Role of Altimetry in ENSO Studies and Prediction

    NASA Technical Reports Server (NTRS)

    Busalacchi, Antonio J.

    1998-01-01

    El Nino and the Southern Oscillation (ENSO) are known to be a quasi-periodic coupled ocean-atmosphere phenomenon occurring roughly every 3-7 years. Its largest oceanic manifestations are found in the equatorial Pacific, but it is of global climatic significance. During the flight of the TOPEX]Poseidon altimeter, the equatorial Pacific was in the midst of an unusual period of prolonged ENSO warming in the mid-1990's. In 1997, the tropical Pacific witnessed the development of a major El Nino event, rivaling in strength the 1982-83 El Nino. The intensity of this El Nino, and its rapid intensification early in the calendar year, caught the scientific community by surprise. None of the forecast models, statistical or dynamical, captured these features of the 1997 El Nino, although those models that assimilated in situ ocean observations did better than most in predicting that the event would occur in 1997. The onset of the El Nino coincided with the occurrence of several westerly wind events in the western Pacific rather than to delayed oscillator physics. However, western Pacific sea levels were anomalously elevated a year and a half prior to the onset, which may have helped precondition the system to a particularly strong ENSO episode. The coming of La Nina was foreshadowed by large-scale drops in sea level in the western tropical Pacific and cyclonic wind stress curl anomalies far beyond the +\\- 8 degrees latitude bounds of the TAO mooring array. In past El Nino events, the evolution of the coupled system could only be studied from the perspective of in situ observations. The 1997-1998 El Nino event will be the first time a major El Nino event will have been observed from start to finish via remotely-sensed measurements of sea surface topography, sea surface temperature, sea surface winds, ocean color, and precipitation. These observations have considerable potential for advancing coupled climate forecasts on time scales from seasons to decades. This presentation

  20. Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation

    NASA Technical Reports Server (NTRS)

    Kwok, R.; Comiso, J. C.

    2001-01-01

    The anomalies in the climate and sea ice cover of the Southern Ocean and their relationships with the Southern Oscillation (SO) are investigated using a 17-year of data set from 1982 through 1998. We correlate the polar climate anomalies with the Southern Oscillation index (SOI) and examine the composites of these anomalies under the positive (SOI > 0), neutral (0 > SOI > -1), and negative (SOI < -1) phases of SOL The climate data set consists of sea-level pressure, wind, surface air temperature, and sea surface temperature fields, while the sea ice data set describes its extent, concentration, motion, and surface temperature. The analysis depicts, for the first time, the spatial variability in the relationship of the above variables and the SOL The strongest correlation between the SOI and the polar climate anomalies are found in the Bellingshausen, Amundsen and Ross sea sectors. The composite fields reveal anomalies that are organized in distinct large-scale spatial patterns with opposing polarities at the two extremes of SOI, and suggest oscillating climate anomalies that are closely linked to the SO. Within these sectors, positive (negative) phases of the SOI are generally associated with lower (higher) sea-level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are clearly evident. Recent anomalies in the sea ice cover that are apparently associated with the SOI include: the record decrease in the sea ice extent in the Bellingshausen Sea from mid- 1988 through early 199 1; the relationship between Ross Sea SST and ENSO signal, and reduced sea ice concentration in the Ross Sea; and, the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea, and the lengthening of the ice season in the western Ross Sea, Bellingshausen Sea and central Weddell Sea gyre over the period 1988

  1. The Relationship Between El Nino/La Nina Oscillations and Recent Anomaly Time Series of OLR Determined by CERES and AIRS

    NASA Technical Reports Server (NTRS)

    Susskind, Joel; Molnar, Gyula; Iredell, Lena; Loeb, Norman G.

    2011-01-01

    This paper compares recent spatial anomaly time series of OLR (Outgoing Longwave Radiation) and OLRCLR (Clear Sky OLR) as determined using CERES and AIRS observations over the time period September 2002 through June 2010. We find excellent agreement in OLR anomaly time series of both data sets in almost every detail, down to the 1 x 1 spatial grid point level. This extremely close agreement of OLR anomaly time series derived from observations by two different instruments implies that both sets of results must be highly stable. This agreement also validates to some extent the anomaly time series of the AIRS derived products used in the computation of the AIRS OLR product. The paper then examines anomaly time series of AIRS derived products over the extended time period September 2002 through April 2011. We show that OLR anomalies during this period are closely in phase with those of an El Nino index, and that the recent global and tropical mean decreases in OLR and OLRCLR are a result of a transition from an El Nino condition at the beginning of the data record to La Nina conditions toward the end of the data period. We show that the relationship between global mean, and especially tropical mean, OLR anomalies to the El Nino index can be explained by temporal changes of the distribution of mid-tropospheric water vapor and cloud cover in two spatial regions that are in direct response to El Nino/La Nina activity which occurs outside these spatial regions.

  2. Rethinking the Ocean's Role in the Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Clement, A. C.; di Nezio, P. N.; Deser, C.

    2010-12-01

    The usual explanation for variability in the Southern Oscillation (SO), a shift of atmospheric mass between the Indo-Pacific warm pool region and the eastern Pacific reflected in opposite sign changes in sea level pressure, involves dynamical coupling between the atmosphere and ocean via the ‘Bjerknes feedback’ mechanism. Here we revisit this explanation using a collection of simulations with atmospheric general circulation models that have varying degrees of coupling to the ocean. The main finding is that the SO emerges as a dominant mode of tropical Pacific variability without dynamical coupling to the ocean. Atmospheric models coupled to a mixed layer ocean (i.e. with no coupled ocean dynamics) simulate what is refered to here as an ‘Atmospheric Walker Mode’ (AWM). This mode of variability has patterns in sea level pressure, sea surface temperature, and precipitation which strongly resemble observed patterns associated with the SO. The spectrum of the AWM is red out to about a decadal timescale, consistent with a stochastically forced, weakly damped process, and our analysis suggests that variability in the AWM is related to variability in the NE and SE trade winds and associated surface wind divergence in the warm pool. The main influence of ocean dynamics on the SO in fully coupled climate models is the addition power primarily at interannual timescales, as expected from the positive Bjerknes feedback. On decadal and longer timescales, ocean dynamics enhance the damping of (or act as a negative feedback on) SO variability. However, interactive ocean dynamics do not appear to be required to set the first-order spatial structure of the SO or associated patterns in SST, precipitation, or atmospheric circulation. Implications for Pacific climate variability on interannual, decadal, and century timescales are discussed.

  3. Relationships between the El Niño-Southern Oscillation, precipitation, and nitrogen wet deposition rates in the contiguous United States

    NASA Astrophysics Data System (ADS)

    Nergui, Tsengel; Evans, R. David; Adam, Jennifer C.; Chung, Serena H.

    2016-11-01

    Human activities have significantly increased reactive nitrogen (N) in the environment, leading to adverse effects on various ecosystems. We used 1979-2012 seasonal inorganic N wet deposition data from the National Atmospheric Deposition Program to evaluate the relationship between the El Niño-Southern Oscillation (ENSO) and N wet deposition in the contiguous U.S. The correlations between precipitation and inorganic N wet deposition were the strongest and most spatially extensive during winter; up to 62% and 53% of the 2 to 6 year variations of precipitation and N wet deposition rates, respectively, in the Rocky Mountains, along the coast of the Gulf of Mexico and near the Great Lakes, can be explained by variation in the NINO3.4 climate index, which was used as a measure of ENSO activity. During El Niño winters, precipitation and N wet deposition rates were higher than normal in the southern U.S., while La Niña events brought higher precipitation and N wet deposition to the Rocky Mountains and Great Lakes regions. Wintertime N wet deposition correlations held through springtime in the Great Lakes and the northeast; however, correlations between NINO3.4 and precipitation were not significant at most sites, suggesting factors besides precipitation amount contributed to the 2 to 6 year variation of N wet deposition in these regions. As the frequency, strength, and types of ENSO change in the future, interannual variability of N wet deposition will be affected, indirectly affecting spatial distribution of dry N deposition and potentially changing the overall spatial patterns of N deposition.

  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. Use of Microgravity to Assess the Effects of El Nino on Ground-Water Storage in Southern Arizona

    USGS Publications Warehouse

    Parker, John T.C.; Pool, Donald R.

    1998-01-01

    The availability of ground water is of extreme importance in areas, such as southern Arizona, where it is the main supply for agricultural, industrial, or domestic purposes. Where ground-water use exceeds recharge, monitoring is critical for managing water supplies. Typically, monitoring has been done by measuring water levels in wells; however, this technique only partially describes ground-water conditions in a basin. A new application of geophysical technology is enabling U.S. Geological Survey (USGS) scientists to measure changes in the amount of water in an aquifer using a network of microgravity stations. This technique enables a direct measurement of ground-water depletion and recharge. In Tucson, Arizona, residents have relied solely upon ground water for most of their needs since the 19th century. Water levels in some wells in the Tucson area have declined more than 200 ft in the past 50 years. Similar drops in water levels have occurred elsewhere in Arizona. In response to the overdrafting of ground water, the State of Arizona passed legislation designed to attain 'safe yield,' which is defined as a balance between ground-water withdrawals and annual recharge of aquifers. To monitor progress in complying with the legislation, ground-water withdrawals are measured and estimated, and annual recharge is estimated. The Tucson Basin and Avra Valley are two ground-water basins that form the Tucson Active Management Area (TAMA), which by State statute must attain 'safe yield' by the year 2025.

  6. Interactions between the seasonal cycle and the southern oscillation-frequency entrainment and chaos in a coupled ocean-atmosphere model

    SciTech Connect

    Chang, P.; Ji, L.; Wang, B.; Li, T.

    1994-12-15

    Nonlinear interactions between the seasonal cycle and interannual variations in the coupled ocean-atmosphere system have recently been proposed as the cause of irregularity of El Nino - Southern Oscillation (ENSO). The authors investigated such a hypothesis using a coupled ocean-atmosphere model which allows coupling between total sea surface temperature (SST) and total surface winds. Numerical simulations indicate that the model is capable of capturing the essential SST variability on seasonal-to-interannual time scale. Furthermore, it is shown that, as the seasonal forcing amplitude is gradually increased from zero, the coupled model undergoes several transitions between periodic (frequency-locking) and chaotic states before it finally {open_quotes}gives up{close_quotes} its intrinsic ENSO mode of oscillation entirely and acquires the frequency of the seasonal forcing. Chaotic response is found as the forcing amplitude approaches the observed value and the route to ENSO chaos is identified to be the period-doubling cascade. The study suggests that the response of a coupled system, coupled General Circulation Models of the ocean and atmosphere for example, can be very sensitive not only to changes in the internal model parameters but also to changes in the external forcing conditions. 15 refs., 3 figs.

  7. The Roles of El Nino and Solar Forcing on Cloud Cover

    NASA Astrophysics Data System (ADS)

    Rohde, R. A.; Levine, J.; Muller, R. A.

    2003-12-01

    Although cloud cover has a very strong effect on climate, its behavior is so poorly understood that its role is frequently neglected. A potential breakthrough occurred with initial reports that cloud cover could be driven by variations in cosmic rays (H. Svensmark & E. Friis-Christensen, J. Atmos. Solar-Terr. Phys. v. 59, n. 11, pp 1225-32, 1997, and N.D. Marsh & H. Svensmark, Space Sci. Rev., pp 1-16, 2000). In this paper we report a detailed analysis of recently extended data now available from the International Satellite Cloud Climatology Project. In a surprise, we find that the major driving force for cloud cover is ENSO (El Nino / Southern Oscillation). In addition, we do find a weak but significant response to solar forcing; however, in contradiction to the previous reports, we find no stronger relationship to cosmic rays than to other solar parameters. For the majority of the 23 cloud types available to us, interannual variability is dominated by changes that follow the NINO3 index of Pacific sea surface temperatures. In particular, increases in high-altitude and vertically extensive cloud cover are observed to follow the motions of warm water throughout the El Nino cycle. Even far from the Pacific, many cloud cover changes are observed to correlate with El Nino, and these data provide a new and previously unexplored tool for understanding the global nature and influence of the El Nino / Southern Oscillation. In contrast, solar forcing of cloud cover is observed in, at most, a few cloud types. Only in the cloud type emphasized by Svensmark, low-altitude clouds detected in the infrared, does the dominant mode of interannual variability make a good match with solar forcing. The extended cloud record provides continued support for solar forcing of this cloud type; however, unlike Svensmark, we find no empirical reason to prefer cosmic ray flux as the forcing mechanism over any other type of solar cycle variation (e.g. irradiance or UV flux changes). Our

  8. Greenhouse warming, decadal variability, or El Nino? An attempt to understand the anomalous 1990s

    SciTech Connect

    Latif, M.; Eckert, C.; Kleeman, R.

    1997-09-01

    The dominant variability modes in the Tropics are investigated and contrasted with the anomalous situation observed during the last few years. The prime quantity analyzed is anomalous sea surface temperature (SST) in the region 30{degrees}S-60{degrees}N. Additionally, observed tropical surface wind stress fields were investigated. Further tropical atmospheric information was derived from a multidecadal run with an atmospheric general circulation model that was forced by the same SSTs. The tropical SST variability can be characterized by three modes: an interannual mode [the El Nino-Southern Oscillation (ENSO)], a decadal mode, and a trend or unresolved ultra-low-frequency variability. 48 refs., 20 figs.

  9. Geoarchaeological evidence from Peru for a 5000 years B.P. onset of El Nino

    SciTech Connect

    Sandweiss, D.H.; Richardson, J.B. III; Rollins, H.B.

    1996-09-13

    For the tropical west coast of South America, where El Nino/Southern Oscillation (ENSO) is most pronounced, archaeological and associated paleontological deposits in northern Peru revealed a major climate change at about 5000 years before the present (yr B.P.). The data implied the presence of stable, warm tropical water as far south as 10{degrees}S during the early mid-Holocene (about 8000 to 5000 yr B.P.). These data suggest that ENSO did not occur for some millennia preceding 5000 yr B.P., when global and regional climate was warmer than today. 36 refs., 1 fig., 3 tabs.

  10. Sulfate aerosol distributions and cloud variations during El Nino anomalies

    SciTech Connect

    Parungo, F. ); Hicks, B. )

    1993-02-20

    The effects of aerosols on cloud characteristics, albedo, rainfall amount, and overall climate changes were investigated by assessing the qualitative associations and quantitative correlations between the relevant variables during El Nino-Southern Oscillation (ENSO) perturbations. Both historical records and data from recent field measurements for the Pacific Ocean region were used for the investigation. The results show that ENSO perturbations could change sulfate aerosol production and distribution over the surveyed regions. Strong correlations were observed between condensation nucleus concentrations and sulfate aerosol concentrations, and between cloud amount and albedo. Weak but significant correlations were also observed between condensation nucleus concentrations and cloud amounts, and between sulfate aerosol concentrations and rainfall amounts. Although sulfate aerosols appeared to have a strong impact on cloud microphysics, the present data confirm that cloud dynamics play the pivotal role in control of cloud types and cloud amount in the studied regions. 31 refs., 5 figs., 3 tabs.

  11. Predicting total organic carbon load with El Nino southern oscillation phase using hybrid and fuzzy logic approaches

    USDA-ARS?s Scientific Manuscript database

    During drinking water treatment chlorine reacts with total organic carbon (TOC) to form disinfection byproducts (DBP), some of which can be carcinogenic. Additional treatment required to remove TOC before chlorination significantly increases treatment cost. There are two main sources of TOC in a wat...

  12. A Brief Overview of the Southern United States Fire Situation January - July 1998

    Treesearch

    Dale D. Wade

    1998-01-01

    Unusually wet conditions associated with El Nino-Southern Oscillation (ENSO) this past winter had a significant negative impact on prescribed burning operations. In spite of the high rainfall, natural resource managers in Florida still succeeded in treating more than 500,000 acres during the first three months of 1998. (In a typical year about 2,000,000 acres are...

  13. El-Niño/Southern Oscillation (ENSO) influences on monthly NO 3 load and concentration, stream flow and precipitation in the Little River Watershed, Tifton, Georgia (GA)

    NASA Astrophysics Data System (ADS)

    Keener, V. W.; Feyereisen, G. W.; Lall, U.; Jones, J. W.; Bosch, D. D.; Lowrance, R.

    2010-02-01

    SummaryAs climate variability increases, it is becoming increasingly critical to find predictable patterns that can still be identified despite overall uncertainty. The El-Niño/Southern Oscillation is the best known pattern. Its global effects on weather, hydrology, ecology and human health have been well documented. Climate variability manifested through ENSO has strong effects in the southeast United States, seen in precipitation and stream flow data. However, climate variability may also affect water quality in nutrient concentrations and loads, and have impacts on ecosystems, health, and food availability in the southeast. In this research, we establish a teleconnection between ENSO and the Little River Watershed (LRW), GA., as seen in a shared 3-7 year mode of variability for precipitation, stream flow, and nutrient load time series. Univariate wavelet analysis of the NINO 3.4 index of sea surface temperature (SST) and of precipitation, stream flow, NO 3 concentration and load time series from the watershed was used to identify common signals. Shared 3-7 year modes of variability were seen in all variables, most strongly in precipitation, stream flow and nutrient load in strong El Niño years. The significance of shared 3-7 year periodicity over red noise with 95% confidence in SST and precipitation, stream flow, and NO 3 load time series was confirmed through cross-wavelet and wavelet-coherence transforms, in which common high power and co-variance were computed for each set of data. The strongest 3-7 year shared power was seen in SST and stream flow data, while the strongest co-variance was seen in SST and NO 3 load data. The strongest cross-correlation was seen as a positive value between the NINO 3.4 and NO 3 load with a three-month lag. The teleconnection seen in the LRW between the NINO 3.4 index and precipitation, stream flow, and NO 3 load can be utilized in a model to predict monthly nutrient loads based on short-term climate variability

  14. El Niño-Southern Oscillation and Pacific Decadal Oscillation impacts on precipitation in the southern and central United States: Evaluation of spatial distribution and predictions

    NASA Astrophysics Data System (ADS)

    Kurtzman, Daniel; Scanlon, Bridget R.

    2007-10-01

    Understanding and predicting regional impacts of El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) on winter (October-March) precipitation can provide valuable inputs to agricultural and water resources managers. Effects of ENSO and PDO on winter precipitation were assessed in 165 climate divisions throughout the southern United States. A continuous region of significantly (P < 0.05) increased (decreased) winter precipitation in response to El Niño (La Niña) conditions in the preceding summer (June-September Southern Oscillation Index (SOI)) extends across the entire southern United States and as far north as South Dakota. Within this region stronger correlations (r ≤ -0.45) are found along the Gulf of Mexico, southern Arizona, and central Nebraska. Winter precipitation differs significantly (P < 0.1) between warm and cold phase PDO periods only in the south central region, with greatest significance centered in Oklahoma. Enhanced negative La Niña anomalies during PDO cold phases are dominant in the central region (Texas to South Dakota) whereas enhanced positive El Niño anomalies during PDO warm phases are dominant in the southwest (Arizona, Nevada, and California) and southeast (Louisiana to Florida). Validation tests of winter precipitation predictions based on summer SOI and/or PDO-phase show a decrease of 9% to 16% in the relative Mean Absolute Error (MAE) from the MAE obtained by using the mean as a predictor in areas with strong correlation (r < -0.45) between SOI and precipitation. Logistic regression probability models of having above or below average winter precipitation had up to 77% successful predictions. The advantage of having probabilities of exceeding certain precipitation thresholds at the beginning of a hydrologic year makes logistic regression models attractive for decision makers.

  15. Middle and high latitude Southern Hemispheric oscillations on the 35-60 day time scale

    NASA Technical Reports Server (NTRS)

    Graves, Charles E.; Stanford, John L.

    1989-01-01

    The low-frequency geopotential height fluctuations in the Southern Hemisphere were examined on the basis of one-point correlation maps. Results indicate that the 35-60 day fluctuations in the Southern-Hemisphere geopotential heights exhibit wavetrainlike characteristics. Correlations between a midlatitude reference point and tropical microwave temperature data were found to be weak, suggesting that the midlatitude wavetrain is not strongly coupled to the Madden and Julian (1971) 40-50 day oscillation.

  16. Intraseasonal oscillation of convective activity in the tropical Southern Hemisphere - May 1984-April 1986

    NASA Technical Reports Server (NTRS)

    Vincent, Dayton G.; Sperling, Thomas; Fink, Andreas; Zube, Stefan; Speth, Peter

    1991-01-01

    This paper studies the intraseasonal oscillation of convection and related variables in the Southern Hemisphere tropics utilizing European Centre for Medium-range Weather Forecasts analyses of 1984 to 1986. One aspect of the research was that the original, unfiltered, time series of various variables was first analyzed to determine if a statistically significant signal occurred on the intraseasonal time scale. The analysis showed that two variables, outgoing longwave radiation and velocity potential at 200 hPa, provided the best evidence of an intraseasonal oscillation. The oscillation propagated eastward, and the convective activity for both years was more intense over the Indian Ocean-Indonesia-western Pacific region than elsewhere.

  17. The Southern Oscillation, Hypoxia, and the Eastern Pacific Tuna Fishery

    NASA Astrophysics Data System (ADS)

    Webster, D.; Kiefer, D.; Lam, C. H.; Harrison, D. P.; Armstrong, E. M.; Hinton, M.; Luo, L.

    2012-12-01

    The Eastern Pacific tuna fishery, which is one of the world's major fisheries, covers thousands of square kilometers. The vessels of this fishery are registered in more than 30 nations and largely target bigeye (Thunnus obesus), skipjack (Katsuwonus pelamis), and yellowfin (T. albacores) tuna. In both the Pelagic Habitat Analysis Module project, which is sponsored by NASA, and the Fishscape project, which is sponsored by NSF, we have attempted to define the habitat of the three species by matching a 50 year time series on fish catch and effort with oceanographic information obtained from satellite imagery and from a global circulation model. The fishery time series, which was provided by the Inter-American Tropical Tuna Commission, provided spatial maps of catch and effort at monthly time steps; the satellite imagery of the region consisted of sea surface temperature, chlorophyll, and height from GHRSST, SEAWiFS, and AVISO products, and the modeled flow field at selected depths was output from ECCO-92 simulations from 1992 to present. All information was integrated and analyzed within the EASy marine geographic information system. This GIS will also provides a home for the Fishscape spatial simulation model of the coupled dynamics of the ocean, fish, fleets, and markets. This model will then be applied to an assessment of the potential ecological and economic impacts of climate change, technological advances in fleet operations, and increases in fuel costs. We have determined by application of EOF analysis that the ECCO-2 simulation of sea surface height fits well with that of AVISO imagery; thus, if driven properly by predictions of future air-sea exchange, the model should provide good estimates of circulation patterns. We have also found that strong El Nino events lead to strong recruitment of all three species and strong La Nina events lead to weak recruitment. Finally, we have found that the general spatial distribution of the Eastern Pacific fishing grounds

  18. Forecast EL NIÑO–Southern oscillation phases and best irrigation strategies to increase cotton yield

    USDA-ARS?s Scientific Manuscript database

    Equatorial Pacific sea surface temperatures cause a systematic El Niño-Southern Oscillation (ENSO) coupling with the atmosphere to produce predictable weather patterns in much of North America. Forecast ENSO phases and associated rainfall frequency and amount were related to modeled dual purpose whe...

  19. On the statistics of El Nino occurrences and the relationship of El Nino to volcanic and solar/geomagnetic activity

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    1989-01-01

    El Nino is conventionally defined as an anomalous and persistent warming of the waters off the coasts of Ecuador and Peru in the eastern equatorial Pacific, having onset usually in Southern Hemispheric summer/fall. Some of the statistical aspects of El Nino occurrences are examined, especially as they relate to the normal distribution and to possible associations with volcanic, solar, and geomagnetic activity. With regard to the very strong El Nino of 1982 to 1983, it is noted that, although it may very well be related to the 1982 eruptions of El Chichon, the event occurred essentially on time (with respect to the past behavior of elapsed times between successive El Nino events; a moderate-to-stronger El Nino was expected during the interval 1978 to 1982, assuming that El Nino occurrences are normally distributed, having a mean elapsed time between successive onsets of 4 years and a standard deviation of 2 years and a last known occurrence in 1976). Also, although not widely recognized, the whole of 1982 was a record year for geomagnetic activity (based on the aa geomagnetic index, with the aa index registering an all time high in February 1982), perhaps, important for determining a possible trigger for this and other El Nino events. A major feature is an extensive bibliography (325 entries) on El Nino and volcanic-solar-geomagnetic effects on climate. Also, included is a tabular listing of the 94 major volcanic eruptions of 1835 to 1986.

  20. Antarctic warming driven by internal Southern Ocean deep convection oscillations

    NASA Astrophysics Data System (ADS)

    Martin, Torge; Pedro, Joel B.; Steig, Eric J.; Jochum, Markus; Park, Wonsun; Rasmussen, Sune O.

    2016-04-01

    Simulations with the free-running, complex coupled Kiel Climate Model (KCM) show that heat release associated with recurring Southern Ocean deep convection can drive centennial-scale Antarctic temperature variations of 0.5-2.0 °C. We propose a mechanism connecting the intrinsic ocean variability with Antarctic warming that involves the following three steps: Preconditioning: heat supplied by the lower branch of the Atlantic Meridional Overturning Circulation (AMOC) accumulates at depth in the Southern Ocean, trapped by the Weddell Gyre circulation; Convection onset: wind and/or sea-ice changes tip the preconditioned, thermally unstable system into the convective state; Antarctic warming: fast sea-ice-albedo feedbacks (on annual to decadal timescales) and slower Southern Ocean frontal and sea-surface temperature adjustments to the convective heat release (on multi-decadal to centennial timescales), drive an increase in atmospheric heat and moisture transport towards Antarctica resulting in warming over the continent. Further, we discuss the potential role of this mechanism to explain climate variability observed in Antarctic ice-core records.

  1. Estimating the coupling between variations in the atlantic multidecadal oscillation and the El Niño/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Mokhov, I. I.; Smirnov, D. A.

    2015-09-01

    On the basis of monthly mean data obtained over a period of 1870-2013, relations between the Atlantic Multidecadal Oscillation (AMO) and the El Niño/Southern Oscillation (ENSO) have been studied using the Granger causality analysis and estimates of long-Term effects. A bidirectional relationship has been revealed in the dynamics of these processes; moreover, over the entire period as a whole, the ENSO influence on the AMO was significantly stronger than the AMO influence on the ENSO. However, a more detailed analysis has revealed the variable character of this relationship: the ENSO influence on the AMO was stronger at the beginning of the period under study, while, in recent years, the reverse influence and its increase have become more significant against the background of a decrease in the ENSO influence on the AMO.

  2. Prediction, Assessment of the Rift Valley fever Activity in East and Southern Africa 2006 - 2008 and Possible Vector Control Strategies

    USDA-ARS?s Scientific Manuscript database

    Historical outbreaks of Rift Valley fever (RVF) since the early 1950s have been associated with cyclical patterns of the El Nino/Southern Oscillation (ENSO) phenomenon which results in elevated and widespread rainfall over the RVF endemic areas of Africa. Using satellite measurements of global and ...

  3. Prediction, Assessment of the Rift Valley fever Activity in East and Southern Africa 2006 - 2008 and Possible Vector Control Strategies

    USDA-ARS?s Scientific Manuscript database

    Historical outbreaks of Rift Valley fever (RVF) since the early 1950s have been associated with cyclical patterns of the El Nino/Southern Oscillation (ENSO) phenomenon which results in elevated and widespread rainfall over the RVF endemic areas of Africa. Using satellite measurements of global and ...

  4. The southern oscillation and prediction of Der season rainfall in Somalia

    SciTech Connect

    Hutchinson, P. )

    1992-05-01

    Somalia survives in semiarid to and conditions, with annual rainfall totals rarely exceeding 700 mm, which are divided between two seasons. Many areas are arid, with negligible precipitation. Seasonal totals are highly variable. Thus, any seasonal rainfall forecast would be of significant importance to both the agricultural and animal husbandry communities. An investigation was carried out to determine whether there is a relationship between the Southern Oscillation and seasonal rainfall. No relationship exists between the Southern Oscillation and rainfall during the midyear [open quotes]Gu[close quotes] season, but it is shown that the year-end [open quotes]Der[close quotes] season precipitation is affected by the Southern Oscillation in southern and central areas of Somalia. Three techniques were used: correlation, regression, and simple contingency tables. Correlations between the SOI (Southern Oscillation index) and seasonal rainfall vary from zero up to about -0.8, with higher correlations in the south, both for individual stations and for area-averaged rainfall. Regression provides some predictive capacity, but the [open quotes]explanation[close quotes] of the variation in rainfall is not particularly high. The contingency tables revealed that there were very few occasions of both high SOI and high seasonal rainfall, although there was a wide scatter of seasonal rainfall associated with a low SOI. It is concluded that the SOI would be useful for planners, governments, and agencies as one tool in food/famine early warning but that the relationships are not strong enough for the average farmer to place much reliance on forecasts produced solely using the SOI.

  5. The role of the Southern Hemisphere semiannual oscillation in the development of a precursor to central and eastern Pacific Southern Oscillation warm events

    NASA Astrophysics Data System (ADS)

    Meehl, Gerald A.; van Loon, Harry; Arblaster, Julie M.

    2017-07-01

    The semiannual oscillation (SAO) is a twice-yearly northward movement (in May-June-July (MJJ) and November-December-January (NDJ)) of the circumpolar trough of sea level pressure (SLP) in the Southern Hemisphere with effects throughout the troposphere. During MJJ the second harmonic of SLP, describing the SAO, has low values of SLP north of 50°S in the subtropical South Pacific, while the first harmonic, which is dominant over the Australian sector, increases to its peak. This once-a-year peak in negative SLP gradients (decreasing to the east) between Australia and the ocean to its east extends to the equatorial Pacific. Southern Oscillation warm events since 1950, with an intensification of this seasonal cycle, have larger-amplitude SST anomalies in the eastern equatorial Pacific in MJJ and during the following mature phase in NDJ. Weak amplification of the seasonal cycle in MJJ tends to be followed by larger-amplitude SST anomalies in the central equatorial Pacific during NDJ.

  6. Effects of 1997-1998 El Nino on Tropospheric Ozone and Water Vapor

    NASA Technical Reports Server (NTRS)

    Chandra, S.; Ziemke, J. R.; Min, W.; Read, W. G.

    1998-01-01

    This paper analyzes the impact of the 1997-1998 El Nino on tropospheric column ozone and tropospheric water vapor derived respectively from the Total Ozone Mapping Spectrometer (TOMS) on Earth Probe and the Microwave Limb Scanning instrument on the Upper Atmosphere Research Satellite. The 1997-1998 El Nino, characterized by an anomalous increase in sea-surface temperature (SST) across the eastern and central tropical Pacific Ocean, is one of the strongest El Nino Southern Oscillation (ENSO) events of the century, comparable in magnitude to the 1982-1983 episode. The major impact of the SST change has been the shift in the convection pattern from the western to the eastern Pacific affecting the response of rain-producing cumulonimbus. As a result, there has been a significant increase in rainfall over the eastern Pacific and a decrease over the western Pacific and Indonesia. The dryness in the Indonesian region has contributed to large-scale burning by uncontrolled wildfires in the tropical rainforests of Sumatra and Borneo. Our study shows that tropospheric column ozone decreased by 4-8 Dobson units (DU) in the eastern Pacific and increased by about 10-20 DU in the western Pacific largely as a result of the eastward shift of the tropical convective activity as inferred from National Oceanic and Atmospheric Administration (NOAA) outgoing longwave radiation (OLR) data. The effect of this shift is also evident in the upper tropospheric water vapor mixing ratio which varies inversely as ozone (O3). These conclusions are qualitatively consistent with the changes in atmospheric circulation derived from zonal and vertical wind data obtained from the Goddard Earth Observing System data assimilation analyses. The changes in tropospheric column O3 during the course of the 1997-1998 El Nino appear to be caused by a combination of large-scale circulation processes associated with the shift in the tropical convection pattern and surface/boundary layer processes associated with

  7. Effects of 1997-1998 El Nino on Tropospheric Ozone and Water Vapor

    NASA Technical Reports Server (NTRS)

    Chandra, S.; Ziemke, J. R.; Min, W.; Read, W. G.

    1998-01-01

    This paper analyzes the impact of the 1997-1998 El Nino on tropospheric column ozone and tropospheric water vapor derived respectively from the Total Ozone Mapping Spectrometer (TOMS) on Earth Probe and the Microwave Limb Scanning instrument on the Upper Atmosphere Research Satellite. The 1997-1998 El Nino, characterized by an anomalous increase in sea-surface temperature (SST) across the eastern and central tropical Pacific Ocean, is one of the strongest El Nino Southern Oscillation (ENSO) events of the century, comparable in magnitude to the 1982-1983 episode. The major impact of the SST change has been the shift in the convection pattern from the western to the eastern Pacific affecting the response of rain-producing cumulonimbus. As a result, there has been a significant increase in rainfall over the eastern Pacific and a decrease over the western Pacific and Indonesia. The dryness in the Indonesian region has contributed to large-scale burning by uncontrolled wildfires in the tropical rainforests of Sumatra and Borneo. Our study shows that tropospheric column ozone decreased by 4-8 Dobson units (DU) in the eastern Pacific and increased by about 10-20 DU in the western Pacific largely as a result of the eastward shift of the tropical convective activity as inferred from National Oceanic and Atmospheric Administration (NOAA) outgoing longwave radiation (OLR) data. The effect of this shift is also evident in the upper tropospheric water vapor mixing ratio which varies inversely as ozone (O3). These conclusions are qualitatively consistent with the changes in atmospheric circulation derived from zonal and vertical wind data obtained from the Goddard Earth Observing System data assimilation analyses. The changes in tropospheric column O3 during the course of the 1997-1998 El Nino appear to be caused by a combination of large-scale circulation processes associated with the shift in the tropical convection pattern and surface/boundary layer processes associated with

  8. A connection from Arctic stratospheric ozone to El Niño-Southern oscillation

    NASA Astrophysics Data System (ADS)

    Xie, Fei; Li, Jianping; Tian, Wenshou; Fu, Qiang; Jin, Fei-Fei; Hu, Yongyun; Zhang, Jiankai; Wang, Wuke; Sun, Cheng; Feng, Juan; Yang, Yun; Ding, Ruiqiang

    2016-12-01

    Antarctic stratospheric ozone depletion is thought to influence the Southern Hemisphere tropospheric climate. Recently, Arctic stratospheric ozone (ASO) variations have been found to affect the middle-high latitude tropospheric climate in the Northern Hemisphere. This paper demonstrates that the impact of ASO can extend to the tropics, with the ASO variations leading El Niño-Southern Oscillation (ENSO) events by about 20 months. Using observations, analysis, and simulations, the connection between ASO and ENSO is established by combining the high-latitude stratosphere to troposphere pathway with the extratropical to tropical climate teleconnection. This shows that the ASO radiative anomalies influence the North Pacific Oscillation (NPO), and the anomalous NPO and induced Victoria Mode anomalies link to the North Pacific circulation that then influences ENSO. Our results imply that incorporating realistic and time-varying ASO into climate system models may help to improve ENSO predictions.

  9. Late Pleistocene oscillations of the Drau Glacier (southern Austria)

    NASA Astrophysics Data System (ADS)

    Karnitschar, Christina; Reitner, Jürgen; Draganits, Erich

    2016-04-01

    The Drau Glacier was the largest Pleistocene glacier in the southeastern part of the Alps and significantly shaped the landscape in this region. The study area is located at the termination of the Drau Glacier in the southern part of Austria (Carinthia). The investigation aims to decipher glacial dynamics during the Late Pleistocene glacial advance, stabilisation and final recession of this glacier based on geological/geomorphological mapping, interpretation of airborne laser scan (ALS) topographic data and lithostratigraphic investigations of glacial and periglacial sediments. Special emphasis is laid on the reconstruction of the maximum extent of the glaciation (LGM). Based on previous mapping by Bobek (1959) and Ucik (1996-1998) more details have been gained for the paleogeographic reconstruction based on glacial and non-glacial erosion and accumulation features. These include traces of pre-Upper Pleistocene glaciation, drumlins, terminal moraines and kettle holes. Paleogeographic reconstruction was done with correlation of different outcrops based on lithostratigraphy and ALS topography. Sequences of gravel related to glacial advance covered by till, followed by periglacial sediments allowed detailed reconstruction of the glacial sequence in this area and the complex succession of various extents of the Drau Glacier. References Bobek, Hans. 1959: Der Eisrückgang im östlichen Klagenfurter Becken. In: Mitteilungen der österreichischen geographischen Gesellschaft, Wien. Ucik, Friedrich Hans. 1996: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 340, Wien. Ucik, Friedrich Hans. 1997: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 325-326, Wien. Ucik, Friedrich Hans. 1998: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 142, S. 333-334, Wien.

  10. El Niño Southern Oscillation (ENSO) and dysentery in Shandong province, China.

    PubMed

    Zhang, Ying; Bi, Peng; Wang, Guoyong; Hiller, Janet E

    2007-01-01

    To investigate the impact of the El Niño Southern Oscillation (ENSO) on dysentery transmission, the relationship between monthly dysentery cases in Shandong Province of China and the monthly Southern Oscillation Index (SOI), a broad index of ENSO, was examined over the period 1991-2003. Spearman correlations and generalized linear models were calculated to detect the association between the SOI and dysentery cases. Data from 1991 to 2001 were used to estimate the parameters, while data from 2002 to 2003 were used to test the forecasting ability of the model. After controlling for seasonality, autocorrelation, and a time-lagged effect, the results indicate that there was a significant negative association between the number of dysentery cases and the SOI, with a lagged effect of 2 months. A one-standard-deviation decrease in the SOI might cause up to 207 more dysentery cases per month in Shandong Province. This is the first report of the impact of the Southern Oscillation on dysentery risk in China, indicating that the SOI may be a useful early indicator of potential dysentery risk in Shandong Province.

  11. Magnetospheric period magnetic field oscillations at Saturn: Equatorial phase “jitter” produced by superposition of southern and northern period oscillations

    NASA Astrophysics Data System (ADS)

    Provan, G.; Andrews, D. J.; Cecconi, B.; Cowley, S. W. H.; Dougherty, M. K.; Lamy, L.; Zarka, P. M.

    2011-04-01

    We investigate magnetic field oscillations near the planetary rotation period in Saturn's magnetosphere observed during the initial near-equatorial phase of the Cassini mission. Phase determinations on 28 periapsis passes during this ˜2 year interval display pronounced nonrandom “jitter” relative to the ˜10.8 h modulations in the dominant southern Saturn kilometric radiation (SKR) emissions. Phase deviations in the radial and azimuthal components are strongly positively correlated, while being anticorrelated with the phase deviations in the colatitudinal component. This suggests the presence in the equatorial magnetosphere of superposed weaker field oscillations at the ˜10.6 h period of the northern SKR modulations, the phase deviations being shown to be periodic near the corresponding ˜23 day “beat” period. Modeling the effect of the northern period oscillations shows that their amplitude is ˜30%-40% of the southern period oscillations, producing phase deviations of ˜±25°. The relative phasing of the northern period radial and azimuthal fields is such as to form a rotating quasi-uniform field, as for the southern period oscillations, while the phasing of the colatitudinal component indicates perturbation field lines arched with apices pointing to the south, opposite to the southern period field lines that are arched with apices pointing to the north. The northern period field points sunward at northern SKR maxima, consistent with previous observations of the northern polar oscillations and opposite to the southern period field that points tailward at southern SKR maxima. The results support the view that the field oscillations are due to two auroral current systems that rotate with differing periods in the two hemispheres.

  12. On the Cause of Eastern Equatorial Pacific Ocean T-S Variations Associated with El Nino

    NASA Technical Reports Server (NTRS)

    Wang, Ou; Fukumori, Ichiro; Lee, Tong; Cheng, Benny

    2004-01-01

    The nature of observed variations in temperature-salinity (T-S) relationship between El Nino and non-El Nino years in the pycnocline of the eastern equatorial Pacific Ocean (NINO3 region, 5(deg)S-5(deg)N, 150(deg)W-90(deg)W) is investigated using an ocean general circulation model. The origin of the subject water mass is identified using the adjoint of a simulated passive tracer. The higher salinity during El Nino is attributed to larger convergence of saltier water from the Southern Hemisphere and smaller convergence of fresher water from the Northern Hemisphere.

  13. On the Cause of Eastern Equatorial Pacific Ocean T-S Variations Associated with El Nino

    NASA Technical Reports Server (NTRS)

    Wang, Ou; Fukumori, Ichiro; Lee, Tong; Cheng, Benny

    2004-01-01

    The nature of observed variations in temperature-salinity (T-S) relationship between El Nino and non-El Nino years in the pycnocline of the eastern equatorial Pacific Ocean (NINO3 region, 5(deg)S-5(deg)N, 150(deg)W-90(deg)W) is investigated using an ocean general circulation model. The origin of the subject water mass is identified using the adjoint of a simulated passive tracer. The higher salinity during El Nino is attributed to larger convergence of saltier water from the Southern Hemisphere and smaller convergence of fresher water from the Northern Hemisphere.

  14. Coherent Modes of Global SST and Summer Rainfall over China: An Assessment of the Regional Impacts of the 1997-98 El Nino/ La Nina

    NASA Technical Reports Server (NTRS)

    Lau, K.-M.; Weng, Hengyi

    1999-01-01

    In this paper, we have identified three principal modes of summertime rainfall variability over China and global sea surface temperature (SST) for the period 1955-1998. Using these modes, we have assessed the impact of the El Nino/La Nina on major drought and flood occurrence over China during 1997-1998. The first mode can be identified with the growth phase of El Nino superimposed on a linear warming trend since the mid-1950s. This mode strongly influences rainfall over northern China. The second mode comprises of a quasi-biennial tendency manifested in alternate wet and dry years over the Yangtze River Valley (YRV) of central China. The third mode is dominated by a quasi-decadal oscillation in eastern China between the Yangtze River and the Yellow River. Using a mode-by-mode reconstruction, we evaluate the impacts of the various principal modes on the 1997 and 1998 observed rainfall anomaly. We find that the severe drought in northern China, and to a lesser degree the flood in southern China, in 1997 is likely a result of the influence of anomalous SST forcing during the growth phase of the El Nino. In addition, rainfall in southern China may be influenced by the decadal or long-term SST variability. The severe flood over the Yangtze River Valley in 1998 is associated with the biennial tendency of basin scale SST during the transition from El Nino to La Nina in 1997-98. Additionally, the observed prolonged drought over northern China and increasing flooding over the YRV since the 1950s may be associated with a long-term warming trend in the tropical Indian and western Pacific ocean. During 1997, the El Nino SST exacerbated the drought situation over northern China. In 1998, the drought appeared to get temporary relief from the La Nina anomalous SST forcing.

  15. Assessing the persistence of millennial-scale oscillations during the penultimate glacial phase in southern Europe

    NASA Astrophysics Data System (ADS)

    Wilson, Graham; Frogley, Mick; Jones, Tim; Leng, Melanie

    2016-04-01

    There is growing evidence that millennial-scale climate oscillations are a pervasive feature of glacial intervals. During the last glaciation (Marine Isotope Stage (MIS) 2-4), incursions of cold water into the North Atlantic appeared to coincide with abrupt reductions in southern European tree populations (Tzedakis et al., 2004: Geology 32, 109-112), suggesting down-stream impacts on continental temperature and hydroclimate. Ice-rafting into the North Atlantic during the penultimate glacial (MIS 6) is thought to be less extensive than at times during MIS 2-4, perhaps resulting in more subdued climate oscillations. Published pollen data from Lake Ioannina core I-284 (Epirus, NW Greece) suggest pronounced oscillations in tree population extent during early MIS 6 (185-155 ka), followed by much-reduced tree populations and subdued oscillations throughout late MIS 6 (155-135 ka) (Roucoux et al., 2011: Journal of Quaternary Science 26, 616-626). Previous studies of the diatom and isotope records from the MIS 7/6, 6/5e and 2/1 transitions, and from MIS 5e and 1 in Lake Ioannina core I-284 demonstrate the sensitivity of these proxies to changes in regional climate. Here we apply a combined diatom and stable isotope (carbon and oxygen) approach to evaluate the influence of millennial-scale oscillations on southern Europe hydroclimate during MIS 6. The new isotope data from Lake Ioannina core I-284 demonstrates higher precipitation / evaporation (P/E) ratios between c. 178 and 164 ka, associated with peak insolation during MIS 6e, and episodes of planktonic diatom expansion likely reflecting the interstadials of the 6e complex. Close correspondence between diatom planktonic frequencies, arboreal pollen and regional sea-surface temperatures together provide strong evidence for millennial-scale oscillations in regional precipitation at times during the early‒mid MIS 6. The isotope data suggest overall cooler and drier conditions during the mid-late MIS 6, consistent with

  16. Can El Niño-Southern Oscillation (ENSO) events modulate intraseasonal oscillations of Indian summer monsoon?

    NASA Astrophysics Data System (ADS)

    Joseph, S.; Sahai, A. K.; Chattopadhyay, R.; Goswami, B. N.

    2011-10-01

    Prediction of interannual variability (IAV) of Indian summer monsoon (ISM) rainfall is limited by "internal" dynamics, and the monsoon intraseasonal oscillations (MISOs) seems to be at the heart of producing internal IAV of the ISM. If one could find an identifiable way through which these MISOs are modulated by slowly varying "external" forcing, such as El Niño-Southern Oscillation (ENSO), the uncertainty in the prediction of IAV could be reduced, leading to improvement of seasonal prediction. Such efforts, so far, have been inconclusive. In this study, the modulation of MISOs by ENSO is assessed by using a nonlinear pattern recognition technique known as the Self-Organizing Map (SOM). The SOM technique is efficient in handling the nonlinearity/event-to-event variability of the MISOs and capable of identifying various shades of MISO from large-scale dynamical/thermodynamical indices, without providing information on rainfall. It is shown that particular MISO phases are preferred during ENSO years, that is, the canonical break phase is preferred more in the El Niño years and the typical active phase is preferred during La Niña years. Interestingly, if the SOM clustering is done by removing the ENSO effect on seasonal mean, the preference for the break node remains relatively unchanged; whereas, the preference reduces/vanishes for the active node. The results indicate that the El Niño-break relationship is almost independent of the ENSO-monsoon relationship on seasonal scale whereas the La Niña-active association seems to be interwoven with the seasonal relationship.

  17. ENSO and disaster: droughts, floods and El Niño/Southern Oscillation warm events.

    PubMed

    Dilley, M; Heyman, B N

    1995-09-01

    The connection between El Niño/Southern Oscillation (ENSO) events and precipitation and temperature variability worldwide is increasingly well understood. ENSO has been linked to droughts and flooding in some regions. This paper uses the disaster history database of the U.S. Agency for International Development's Office of U.S. Foreign Disaster Assistance to examine the link between ENSO events and droughts or floods of sufficient magnitude to trigger international disasters. Worldwide, disasters triggered by droughts are twice as frequent during year two of ENSO warm events than during other years. No such relationship is apparent in the case of flood disasters. Drought disasters occur during year two of ENSO warm events significantly more frequently than in other years in Southern Africa and Southeast Asia. No regional pattern emerges from a comparable analysis of flood disasters. Those places likely to be affected by ENSO-triggered droughts can take proactive measures to mitigate the impacts.

  18. Coastal vulnerability across the Pacific dominated by El Niño-Southern Oscillation

    USGS Publications Warehouse

    Barnard, Patrick L.; Short, Andrew D.; Harley, Mitchell D.; Splinter, Kristen D.; Vitousek, Sean; Turner, Ian L.; Allan, Jonathan; Banno, Masayuki; Bryan, Karin R.; Doria, André; Hansen, Jeff E.; Kato, Shigeru; Kuriyama, Yoshiaki; Randall-Goodwin, Evan; Ruggiero, Peter; Walker, Ian J.; Heathfield, Derek K.

    2015-01-01

    To predict future coastal hazards, it is important to quantify any links between climate drivers and spatial patterns of coastal change. However, most studies of future coastal vulnerability do not account for the dynamic components of coastal water levels during storms, notably wave-driven processes, storm surges and seasonal water level anomalies, although these components can add metres to water levels during extreme events. Here we synthesize multi-decadal, co-located data assimilated between 1979 and 2012 that describe wave climate, local water levels and coastal change for 48 beaches throughout the Pacific Ocean basin. We find that observed coastal erosion across the Pacific varies most closely with El Niño/Southern Oscillation, with a smaller influence from the Southern Annular Mode and the Pacific North American pattern. In the northern and southern Pacific Ocean, regional wave and water level anomalies are significantly correlated to a suite of climate indices, particularly during boreal winter; conditions in the northeast Pacific Ocean are often opposite to those in the western and southern Pacific. We conclude that, if projections for an increasing frequency of extreme El Niño and La Niña events over the twenty-first century are confirmed, then populated regions on opposite sides of the Pacific Ocean basin could be alternately exposed to extreme coastal erosion and flooding, independent of sea-level rise.

  19. Precipitation Variability over the Caribbean and Tropical Americas Associated with the Southern Oscillation.

    NASA Astrophysics Data System (ADS)

    Rogers, Jeffery C.

    1988-02-01

    Seasonal and annual (July through June) precipitation data for up to 197 stations are used to analyze variability in the High/Dry (H/D) and Low/Wet (L/W or warm event) modes of the Southern Oscillation (SO) over the tropical Americas and the Caribbean Islands to 30°S latitude. Precipitation is significantly higher during H/D events than during L/W in northern summer, autumn and winter at most stations in the southern Caribbean and northern South America including the northern Andes and Amazon River basin. Precipitation is, in general, significantly higher in L/W than in H/D modes at higher subtropical latitudes of both hemispheres, especially in northern autumn and winter over the southern United States, Cuba and Mexico, and in spring and autumn over southern Brazil, Paraguay and Argentina. A similar pattern of spatial precipitation variability occurs in the July-June data and significant H/D minus L/W precipitation differences are found at one-third of the stations. Although drought occurs in Northeast Brazil in some L/W years such as 1982-83, rainfall in other L/W events is above normal, and overall the role of the SO in precipitation variability is not as apparent in Northeast Brazil as it is in northern South America and the Caribbean.

  20. Coastal vulnerability across the Pacific dominated by El Niño/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Barnard, Patrick L.; Short, Andrew D.; Harley, Mitchell D.; Splinter, Kristen D.; Vitousek, Sean; Turner, Ian L.; Allan, Jonathan; Banno, Masayuki; Bryan, Karin R.; Doria, André; Hansen, Jeff E.; Kato, Shigeru; Kuriyama, Yoshiaki; Randall-Goodwin, Evan; Ruggiero, Peter; Walker, Ian J.; Heathfield, Derek K.

    2015-10-01

    To predict future coastal hazards, it is important to quantify any links between climate drivers and spatial patterns of coastal change. However, most studies of future coastal vulnerability do not account for the dynamic components of coastal water levels during storms, notably wave-driven processes, storm surges and seasonal water level anomalies, although these components can add metres to water levels during extreme events. Here we synthesize multi-decadal, co-located data assimilated between 1979 and 2012 that describe wave climate, local water levels and coastal change for 48 beaches throughout the Pacific Ocean basin. We find that observed coastal erosion across the Pacific varies most closely with El Niño/Southern Oscillation, with a smaller influence from the Southern Annular Mode and the Pacific North American pattern. In the northern and southern Pacific Ocean, regional wave and water level anomalies are significantly correlated to a suite of climate indices, particularly during boreal winter; conditions in the northeast Pacific Ocean are often opposite to those in the western and southern Pacific. We conclude that, if projections for an increasing frequency of extreme El Niño and La Niña events over the twenty-first century are confirmed, then populated regions on opposite sides of the Pacific Ocean basin could be alternately exposed to extreme coastal erosion and flooding, independent of sea-level rise.

  1. The effect of El Niño - Southern Oscillation events on CO2 and H2O fluxes in a mountainous tropical rainforest in equatorial Indonesia

    NASA Astrophysics Data System (ADS)

    Olchev, Alexander; Ibrom, Andreas; Panferov, Oleg; Gushchina, Darija; Kreilein, Heinrich; Popov, Victor; Propastin, Pavel; June, Tania; Rauf, Abdul; Gravenhorst, Gode; Knohl, Alexander

    2016-04-01

    The possible impact of El Niño-Southern Oscillation (ENSO) events on the main components of CO2 and H2O fluxes between the tropical rainforest and the atmosphere was investigated. The fluxes were continuously measured in an old-growth mountainous tropical rainforest in Central Sulawesi in Indonesia (1°39.47'S and 120°10.409'E) using the eddy covariance method for the period from January 2004 to June 2008 (Ibrom et al. 2007). During the period of measurements two episodes of El Niño and one episode of La Niña were observed. All these ENSO episodes had moderate intensity and were of the central Pacific type. To quantify the ENSO impacts on meteorological parameters and fluxes and to distinguish them from effects caused by the seasonal migration of the Intertropical Convergence Zone (ITCZ) we analyzed the correlation between the deviations of monthly meteorological parameter and flux values from their monthly averages over the entire measuring period and the Nino4 and Nino3.4 indexes. The typical timescale of the full ENSO cycle is estimated to be about 48-52 months (Setoh et al., 1999), whereas the timescale of the main meteorological parameters (global solar radiation (G), precipitation amount (P), air temperature (T)) is characterized by much higher month-to-month variability even after annual trend filtering. In order to filter the high-frequency oscillation in the time series of atmospheric characteristics and monthly Net Ecosystem Exchange of CO2 (NEE), Gross Primary Production (GPP), Ecosystem Respiration (RE) and evapotranspiration (ET) anomalies, the simple centered moving average smoothing procedure was applied. The moving averages of variables were calculated over 7 months (centered value ± 3 months). Statistical analysis included both simple correlation and cross-correlation analysis. Analysis of the temporal variability of CO2 and H2O fluxes showed a high sensitivity of monthly GPP and ET of the mountainous tropical rainforest to ENSO intensity

  2. El Niño-Southern Oscillation, local weather and occurrences of dengue virus serotypes

    NASA Astrophysics Data System (ADS)

    Huang, Xiaodong; Clements, Archie C. A.; Williams, Gail; Devine, Gregor; Tong, Shilu; Hu, Wenbiao

    2015-11-01

    Severe dengue fever is usually associated with secondary infection by a dengue virus (DENV) serotype (1 to 4) that is different to the serotype of the primary infection. Dengue outbreaks only occur following importations of DENV in Cairns, Australia. However, the majority of imported cases do not result in autochthonous transmission in Cairns. Although DENV transmission is strongly associated with the El Niño-Southern Oscillation (ENSO) climate cycle and local weather conditions, the frequency and potential risk factors of infections with the different DENV serotypes, including whether or not they differ, is unknown. This study used a classification tree model to identify the hierarchical interactions between Southern Oscillation Index (SOI), local weather factors, the presence of imported serotypes and the occurrence of the four autochthonous DENV serotypes from January 2000-December 2009 in Cairns. We found that the 12-week moving average of SOI and the 2-week moving average of maximum temperature were the most important factors influencing the variation in the weekly occurrence of the four DENV serotypes, the likelihoods of the occurrence of the four DENV serotypes may be unequal under the same environmental conditions, and occurrence may be influenced by changes in global and local environmental conditions in Cairns.

  3. El Niño-Southern Oscillation, local weather and occurrences of dengue virus serotypes.

    PubMed

    Huang, Xiaodong; Clements, Archie C A; Williams, Gail; Devine, Gregor; Tong, Shilu; Hu, Wenbiao

    2015-11-19

    Severe dengue fever is usually associated with secondary infection by a dengue virus (DENV) serotype (1 to 4) that is different to the serotype of the primary infection. Dengue outbreaks only occur following importations of DENV in Cairns, Australia. However, the majority of imported cases do not result in autochthonous transmission in Cairns. Although DENV transmission is strongly associated with the El Niño-Southern Oscillation (ENSO) climate cycle and local weather conditions, the frequency and potential risk factors of infections with the different DENV serotypes, including whether or not they differ, is unknown. This study used a classification tree model to identify the hierarchical interactions between Southern Oscillation Index (SOI), local weather factors, the presence of imported serotypes and the occurrence of the four autochthonous DENV serotypes from January 2000-December 2009 in Cairns. We found that the 12-week moving average of SOI and the 2-week moving average of maximum temperature were the most important factors influencing the variation in the weekly occurrence of the four DENV serotypes, the likelihoods of the occurrence of the four DENV serotypes may be unequal under the same environmental conditions, and occurrence may be influenced by changes in global and local environmental conditions in Cairns.

  4. U.S. streamflow patterns in relation to the El Niño/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Kahya, Ercan; Dracup, John A.

    1993-08-01

    The relationship between the El Niño/Southern Oscillation (ENSO) and unimpaired streamflow over the contiguous United States is studied. The extreme phases of the Southern Oscillation have been linked to fairly persistent classes of atmospheric anomalies over the low and middle latitudes at regional and global scales. Of particular interest in this investigation is the identification of regions of land that appear to have strong and consistent ENSO-related streamflow signals. The first harmonic extracted from a 24-month ENSO composite at each station is assumed to be the ENSO-related signal appearing in streamflow anomalies. These regions were identified by the similarity in phase of the harmonic vectors. The vectorial display of these harmonics over a map of the United States provides the areal extents of ENSO influence on streamflow. Coherent and significant streamflow responses to hypothesized ENSO forcing are found in four regions of the United States: the Gulf of Mexico, the Northeast, the North Central, and the Pacific Northwest. Once an ENSO event sets in, a long-range forecasting utility may be available for these regions. The results of this analysis, which are consistent with previous studies on precipitation and temperature, demonstrate the mid-latitude hydrologic response to the tropical ENSO phenomena.

  5. Human disturbance amplifies Amazonian El Niño-Southern Oscillation signal.

    PubMed

    Bush, Mark B; Correa-Metrio, Alexander; van Woesik, Robert; Shadik, Courtney R; McMichael, Crystal N H

    2017-08-01

    The long-term interaction between human activity and climate is subject to increasing scrutiny. Humans homogenize landscapes through deforestation, agriculture, and burning and thereby might reduce the capacity of landscapes to provide archives of climate change. Alternatively, land-use change might overwhelm natural buffering and amplify latent climate signals, rendering them detectable. Here we examine a sub-annually resolved sedimentary record from Lake Sauce in the western Amazonian lowlands that spans 6900 years. Finely-laminated sediments were deposited from ca. 5000 years ago until the present, and human activity in the watershed was revealed through the presence of charcoal and maize agriculture. The laminations, analyzed for color content and bandwidth, showed distinctive changes that were coupled to more frequent occurrence of fossil maize pollen. As agricultural activity intensified ca. 2200 cal. BP, the 2- to 8-year periodicity characteristic of El Niño-Southern Oscillation became evident in the record. These agricultural activities appeared to have amplified an existing, but subtle climatic signal that was previously absorbed by natural vegetation. When agricultural activity slowed, or land use around Lake Sauce changed at ca. 800 cal. BP, the signal of El Niño-Southern Oscillation (ENSO) activity became erratic. © 2017 John Wiley & Sons Ltd.

  6. Bifurcation analysis of delay-induced resonances of the El-Niño Southern Oscillation

    PubMed Central

    Krauskopf, Bernd; Sieber, Jan

    2014-01-01

    Models of global climate phenomena of low to intermediate complexity are very useful for providing an understanding at a conceptual level. An important aspect of such models is the presence of a number of feedback loops that feature considerable delay times, usually due to the time it takes to transport energy (for example, in the form of hot/cold air or water) around the globe. In this paper, we demonstrate how one can perform a bifurcation analysis of the behaviour of a periodically forced system with delay in dependence on key parameters. As an example, we consider the El-Niño Southern Oscillation (ENSO), which is a sea-surface temperature (SST) oscillation on a multi-year scale in the basin of the Pacific Ocean. One can think of ENSO as being generated by an interplay between two feedback effects, one positive and one negative, which act only after some delay that is determined by the speed of transport of SST anomalies across the Pacific. We perform here a case study of a simple delayed-feedback oscillator model for ENSO, which is parametrically forced by annual variation. More specifically, we use numerical bifurcation analysis tools to explore directly regions of delay-induced resonances and other stability boundaries in this delay-differential equation model for ENSO. PMID:25197254

  7. Bifurcation analysis of delay-induced resonances of the El-Niño Southern Oscillation.

    PubMed

    Krauskopf, Bernd; Sieber, Jan

    2014-09-08

    Models of global climate phenomena of low to intermediate complexity are very useful for providing an understanding at a conceptual level. An important aspect of such models is the presence of a number of feedback loops that feature considerable delay times, usually due to the time it takes to transport energy (for example, in the form of hot/cold air or water) around the globe. In this paper, we demonstrate how one can perform a bifurcation analysis of the behaviour of a periodically forced system with delay in dependence on key parameters. As an example, we consider the El-Niño Southern Oscillation (ENSO), which is a sea-surface temperature (SST) oscillation on a multi-year scale in the basin of the Pacific Ocean. One can think of ENSO as being generated by an interplay between two feedback effects, one positive and one negative, which act only after some delay that is determined by the speed of transport of SST anomalies across the Pacific. We perform here a case study of a simple delayed-feedback oscillator model for ENSO, which is parametrically forced by annual variation. More specifically, we use numerical bifurcation analysis tools to explore directly regions of delay-induced resonances and other stability boundaries in this delay-differential equation model for ENSO.

  8. Application of Spaceborne Scatterometer to Study Typhoon, Tropical Hydrologic Balance and El Nino

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy

    1995-01-01

    The high spatial resolution and global coverage of a spaceborne microwave scatterometer make it a power instrument to study phenomena ranging from typhoon to El Nino Southern Oscillation which have regional and short term economic and ecological impacts as well as effects on long term and global climate changes. In this report, the application of scatterometer data, by itself, to study the intensity and the evolution of typhoon is demonstrated. The potential of combining wind vector and precipitable water derived from two spaceborne sensors to study the hydrologic balance in the tropics is discussed. The role of westerly wind bursts as a precursor of anomalous warming in the equatorial Pacific is investigated with coincident data from microwave scatterometer, altimeter and radiometer.

  9. Application of Spaceborne Scatterometer to Study Typhoon, Tropical Hydrologic Balance and El Nino

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy

    1995-01-01

    The high spatial resolution and global coverage of a spaceborne microwave scatterometer make it a power instrument to study phenomena ranging from typhoon to El Nino Southern Oscillation which have regional and short term economic and ecological impacts as well as effects on long term and global climate changes. In this report, the application of scatterometer data, by itself, to study the intensity and the evolution of typhoon is demonstrated. The potential of combining wind vector and precipitable water derived from two spaceborne sensors to study the hydrologic balance in the tropics is discussed. The role of westerly wind bursts as a precursor of anomalous warming in the equatorial Pacific is investigated with coincident data from microwave scatterometer, altimeter and radiometer.

  10. Application of spaceborne scatterometer to study typhoon, tropical hydrologic balance, and EL Nino

    NASA Astrophysics Data System (ADS)

    Liu, W. T.

    1995-12-01

    The high spatial resolution and global coverage of a spaceborne microwave scatterometer make it a powerful instrument to study phenomena ranging from typhoons to El Nino Southern Oscillations which have regional and short term economic and ecological impacts as well as effects on long term and global climate changes. In this report, the application of scatterometer data, by itself, to study the intensity and the evolution of a typhoon is demonstrated. The potential of combining wind vector and precipitable water derived from two spaceborne sensors to study the hydrologic balance in the tropics is discussed. The role of westerly wind bursts as a precursor of anomalous warming in the equatorial Pacific is investigated with coincident data from microwave scatterometer, altimeter, and radiometer.

  11. Impact of an El Nino forcing on intense tropical cyclones in ensemble simulations of a high-resolution nonhydrostatic model

    NASA Astrophysics Data System (ADS)

    Yamada, Y.; Kodama, C.; Masaki, S.; Nakano, M.; Nasuno, T.; Sugi, M.

    2016-12-01

    Previous studies indicated that the El Nino-Southern Oscillation affects TC activities over the western North Pacific, and intense TCs increases during El Nino events. A global warming had been on a hiatus since 2000's. The hiatus finished in 2013 and the global warming has been accelerated since 2014. In 2015, the number of category 4 or 5 tropical cyclones (TCs) in the northern hemisphere was beyond the previous record; and an extreme El Nino event was observed. In 1997, the most extreme El Nino event has been observed. An intense TC was defined as a TC whose minimum central sea-level pressure reaches 945 hPa or less. The numbers of the intense TC between June and October are 9 in 1997 and 10 in 2015, which is archived in a best-track dataset of Japan Meteorology Agency. The average of genesis number between 1979 and 2015 was about 5.60. In both years, more intense TCs occurred than the average as the previous studies showed. In the present study, we conducted two cases of ensemble simulations which were driven by sea surface temperature observed in 1997 and 2015. Those simulation spans are 5 months, from June to October. The number of ensemble is 50 for the each case. Ensemble members were generated by altering their start date by 6 hour between 00UTC June 1 and 18UTC May 19. A nonhydrostatic icosahedral atmospheric model was used in those simulations; the horizontal grid spacing was 14-km; and a cumulus convective scheme was not used. A result of the simulation shows that the number of intense TCs varies among ensemble members for the each case; one of 50 members generated intense TC of 10 (12) in 2015's (1997's) simulation, and another member generated intense TC of 1 (3). This indicates a possibility that the number of intense TCs increases not only because of El Nino but also because of internal variation in response of atmosphere to El Nino.

  12. Effects of the El Niño--Southern Oscillation (ENSO) cycle on mosquito populations in southern California.

    PubMed

    Heft, David E; Walton, William E

    2008-06-01

    The abundance and species composition of adult mosquitoes collected by carbon dioxide-baited suction traps and gravid traps in western Los Angeles County, CA, were compared before and during a strong El Niño--Southern Oscillation (ENSO) cycle from December 1996 until November 1999. Following El Niño conditions in the winter 1997-1998, adult host-seeking mosquito abundance during spring was twice that observed during spring 1997 and species composition favored cool-weather mosquitoes such as Culiseta incidens and Culex tarsalis. The comparatively cool temperatures from early April until early June and increased rainfall of the 1998 El Niño negatively affected warm-weather mosquitoes such as Culex quinquefasciatus that inhabit eutrophic habitats such as urban storm drains. Gravid mosquito abundance during the early summer following El Niño conditions also increased 2- to 3-fold relative to 1997, but gravid mosquito species composition was not significantly affected by ENSO cycles, reflecting an inherent bias of gravid traps to collect predominantly Cx. quinquefasciatus. Relative to spring 1997, host-seeking and gravid mosquito abundances were reduced 3- to 7-fold from March until June 1999 under the comparatively dry La Niña conditions. The increased abundance and prolonged host-seeking activity of Cx. tarsalis during the spring and early summer following a strong El Niño may have a significant impact on public health in urban southern California because this mosquito is an important arbovirus vector and constructed wetlands in urban areas may increase suitable, comparatively permanent developmental sites for important mosquito vectors such as Cx. tarsalis that are usually rare in urban environments.

  13. TOPEX/El Nino Watch - El Nino Moisture in the Atmosphere, February 22, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This image shows differences in atmospheric water vapor relative to a normal (average) year in the Earth's upper troposphere about 10 kilometers (6 miles) above the surface. These measurements were made by the Microwave Limb Sounder (MLS) instrument aboard NASA's Upper Atmosphere Research Satellite (UARS). This image, obtained on February 22, 1998, shows that high levels of atmospheric water vapor (red) continue to persist above the warm water pool, commonly referred to as El Nino, in the eastern equatorial Pacific Ocean. This image also shows high levels of atmospheric moisture above Southern California. The extent of this high moisture area along the equator has slightly decreased since late January, which corresponds to the shrinking volume of the warm water pool on the ocean's surface. During El Nino, the warmer ocean water off the coast of Peru evaporates at a higher rate, and the resulting warm moist air rises, forming tall cloud towers. In the tropics, the warm water and the resulting tall cloud towers typically produce large amounts of rain. These data show a new formation of high levels of moisture off the coast of Japan in an area that is the typical breeding ground for winter storms. Storms produced off the coast of Japan normally migrate eastward toward the western United States. During this El Nino condition, the southern tropical jet stream has shifted northward, bringing additional moisture from the tropics. When these two sources of moisture converge near California, they produce storms with higher-than-normal rainfall.

  14. Variations in the tropical greenhouse effect during El Nino

    SciTech Connect

    Soden, B.J.

    1997-05-01

    Observations of the clear-sky outgoing longwave radiation and sea surface temperature are combined to examine the evolution of the tropical greenhouse effect from colder La Nina conditions in early 1985 to warmer El Nino conditions in late 1987. Although comparison of individual months can suggest a decrease in greenhouse trapping from cold to warm conditions, when the entire 4-yr record is considered a distinct increase in tropical-mean greenhouse trapping of {approximately}2 W m{sup -2} is observed in conjunction with a {approximately}0.4 K increase in tropical-mean sea surface temperature. This observed increase compares favorably with GCM simulations of the change in the clear-sky greenhouse effect during El Nifio-Southern Oscillation (ENSO). Superimposed on top of the SST-driven change in greenhouse trapping are dynamically induced changes in tropical moisture apparently associated with a redistribution of SST during ENSO. The GCM simulations also successfully reproduce this feature, providing reassurance in the ability of GCMs to predict both dynamically and thermodynamically driven changes in greenhouse trapping. 25 refs., 3 figs., 1 tab.

  15. TOPEX/El Nino Watch - El Nino Moisture in the Atmosphere, January and February, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This series of six images shows the evolution of atmospheric water vapor over the Pacific Ocean during the 1998 El Nino condition. Higher than normal ocean water temperatures increase the rate of evaporation, and the resulting warm moist air rises into the atmosphere, altering global weather patterns. Data obtained by the Microwave Limb Sounder (MLS) on NASA's Upper Atmosphere Research Satellite (UARS) during January and February 1998 show a decrease in the extent of high levels of water vapor (red) over the eastern equatorial Pacific and an increase in water vapor (yellow to red) over the northwestern Pacific off the coast of Japan. This area is a breeding ground for winter storms that move eastward toward North America. During this El Nino condition, the southern tropical jet stream has shifted northward, bringing additional moisture from the tropics. When these two sources of moisture converge near California, they produce storms with higher-than-normal rainfall.

  16. Reduced El Niño-Southern Oscillation during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Ford, Heather L.; Ravelo, A. Christina; Polissar, Pratigya J.

    2015-01-01

    El Niño-Southern Oscillation (ENSO) is a major source of global interannual variability, but its response to climate change is uncertain. Paleoclimate records from the Last Glacial Maximum (LGM) provide insight into ENSO behavior when global boundary conditions (ice sheet extent, atmospheric partial pressure of CO2) were different from those today. In this work, we reconstruct LGM temperature variability at equatorial Pacific sites using measurements of individual planktonic foraminifera shells. A deep equatorial thermocline altered the dynamics in the eastern equatorial cold tongue, resulting in reduced ENSO variability during the LGM compared to the Late Holocene. These results suggest that ENSO was not tied directly to the east-west temperature gradient, as previously suggested. Rather, the thermocline of the eastern equatorial Pacific played a decisive role in the ENSO response to LGM climate.

  17. Precipitation change in Southern Italy linked to global scale oscillation indexes

    NASA Astrophysics Data System (ADS)

    Caloiero, T.; Coscarelli, R.; Ferrari, E.; Mancini, M.

    2009-09-01

    Hydrological impacts from climate change are of principal interest to water resources policy-makers and practising engineers. Climate change has attracted extensive attention from every sector of the society because of the potentially large scale negative environmental and economic consequences. Particularly the analysis of the temporal evolution of precipitation is fundamental to evaluate water resources availability, especially in areas with a marked orography like in Southern Italy. To this aim several statistical tests can be used for exploratory analyses and detection of monotonic trends in time series data. Moreover rainfall amounts occurred in seasonal periods, directly responsible for availability of water resources on a specified area, are strongly dependent on climate system. In order to highlight some features of such dependence, planetary-scale indexes based on the difference in the sea level pressure between two geographic areas tagging centres of climatic action have been taken into account. Such procedure, called teleconnection, shows that climatic conditions in different geographical areas, even relatively far from each other, can be interdependent. For instance, the conditions of the Atlantic, Pacific and Indian Oceans, which constitute heat and steam sources for the masses of air which cross them, in the intertropical zone are related to the precipitation regime, while at the latitudes of the temperate zones they modulate the circulation of the western winds, the high and low pressure zones distribution and the track of the low pressure areas responsible for the atmospheric phenomena. Within this purview, some authors have drawn correlations between precipitation and indexes describing some planetary-scale oscillations, like the well-known El Niño-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). As example, several analyses of the relationships between large-scale pressure fields, such as the NAO, and European climate have

  18. Highly variable El Niño-Southern Oscillation throughout the Holocene.

    PubMed

    Cobb, Kim M; Westphal, Niko; Sayani, Hussein R; Watson, Jordan T; Di Lorenzo, Emanuele; Cheng, H; Edwards, R L; Charles, Christopher D

    2013-01-04

    The El Niño-Southern Oscillation (ENSO) drives large changes in global climate patterns from year to year, yet its sensitivity to continued anthropogenic greenhouse forcing is uncertain. We analyzed fossil coral reconstructions of ENSO spanning the past 7000 years from the Northern Line Islands, located in the center of action for ENSO. The corals document highly variable ENSO activity, with no evidence for a systematic trend in ENSO variance, which is contrary to some models that exhibit a response to insolation forcing over this same period. Twentieth-century ENSO variance is significantly higher than average fossil coral ENSO variance but is not unprecedented. Our results suggest that forced changes in ENSO, whether natural or anthropogenic, may be difficult to detect against a background of large internal variability.

  19. Reduced El Niño-Southern Oscillation during the Last Glacial Maximum.

    PubMed

    Ford, Heather L; Ravelo, A Christina; Polissar, Pratigya J

    2015-01-16

    El Niño-Southern Oscillation (ENSO) is a major source of global interannual variability, but its response to climate change is uncertain. Paleoclimate records from the Last Glacial Maximum (LGM) provide insight into ENSO behavior when global boundary conditions (ice sheet extent, atmospheric partial pressure of CO2) were different from those today. In this work, we reconstruct LGM temperature variability at equatorial Pacific sites using measurements of individual planktonic foraminifera shells. A deep equatorial thermocline altered the dynamics in the eastern equatorial cold tongue, resulting in reduced ENSO variability during the LGM compared to the Late Holocene. These results suggest that ENSO was not tied directly to the east-west temperature gradient, as previously suggested. Rather, the thermocline of the eastern equatorial Pacific played a decisive role in the ENSO response to LGM climate.

  20. Pre-1866 Extensions of the Southern Oscillation Index Using Early Indonesian and Tahitian Meteorological Readings.

    NASA Astrophysics Data System (ADS)

    Können, G. P.; Jones, P. D.; Kaltofen, M. H.; Allan, R. J.

    1998-09-01

    Pressure data from Indonesia and Tahiti for years before 1866 are used to extend the Southern Oscillation index (SOI) back to 1841, with a gap between 1861 and 1865. Further extension is possible using an index of Jakarta rainday counts back to 1829. Rainday counts correlate (r = 0.60) with average Jakarta pressure for the June-November dry season over the 1876-1944 period. Although low, this correlation is still better than the correlation of tree rings with pressure or SOI. After 1950 the rainday count-pressure relationship alters, and by the 1990s 18% more raindays (an increase of seven per dry season) occur than the pressure would indicate. The dramatic increase in the size and population of Jakarta since 1950 is considered the most likely reason.

  1. Variability in the El Niño-Southern Oscillation through a glacial-interglacial cycle.

    PubMed

    Tudhope, A W; Chilcott, C P; McCulloch, M T; Cook, E R; Chappell, J; Ellam, R M; Lea, D W; Lough, J M; Shimmield, G B

    2001-02-23

    The El Niño-Southern Oscillation (ENSO) is the most potent source of interannual climate variability. Uncertainty surrounding the impact of greenhouse warming on ENSO strength and frequency has stimulated efforts to develop a better understanding of the sensitivity of ENSO to climate change. Here we use annually banded corals from Papua New Guinea to show that ENSO has existed for the past 130,000 years, operating even during "glacial" times of substantially reduced regional and global temperature and changed solar forcing. However, we also find that during the 20th century ENSO has been strong compared with ENSO of previous cool (glacial) and warm (interglacial) times. The observed pattern of change in amplitude may be due to the combined effects of ENSO dampening during cool glacial conditions and ENSO forcing by precessional orbital variations.

  2. Climate Variability Drives Plankton Community Composition Changes: the 2010-2011 El Nino to La Nina Transition Around Australia

    NASA Technical Reports Server (NTRS)

    Thompson, Peter A.; Bonham, Pru; Thomson, Paul; Rochester, Wayne; Doblin, Martina A.; Waite, Anya M.; Richardson, Anthony; Rousseaux, Cecile S.

    2015-01-01

    The strong La Nina of 2010-2011 provided an opportunity to investigate the ecological impacts of El Nino-Southern Oscillation on coastal plankton communities using the nine national reference stations around Australia. Based on remote sensing and across the entire Australian region 2011 (La Nina) was only modestly different from 2010 (El Nino) with the average temperature declining 0.2 percent surface chlorophyll a up 3 percent and modelled primary production down 14 percent. Other changes included a poleward shift in Prochlorococcus and Synechococcus. Along the east coast, there was a reduction in salinity, increase in nutrients, Chlorophytes and Prasinophytes (taxa with chlorophyll b, neoxanthin and prasinoxanthin). The southwest region had a rise in the proportion of 19-hexoyloxyfucoxanthin; possibly coccolithophorids in eddies of the Leeuwin Current and along the sub-tropical front. Pennate diatoms increased, Ceratium spp. decreased and Scrippsiella spp. increased in 2011. Zooplankton biomass declined significantly in 2011. There was a reduction in the abundance of Calocalanus pavo and Temora turbinata and increases in Clausocalanus farrani, Oncaea scottodicarloi and Macrosetella gracilis in 2011. The changes in the plankton community during the strong La Nina of 2011 suggest that this climatic oscillation exacerbates the tropicalization of Australia.

  3. Climate Variability Drives Plankton Community Composition Changes: the 2010-2011 El Nino to La Nina Transition Around Australia

    NASA Technical Reports Server (NTRS)

    Thompson, Peter A.; Bonham, Pru; Thomson, Paul; Rochester, Wayne; Doblin, Martina A.; Waite, Anya M.; Richardson, Anthony; Rousseaux, Cecile S.

    2015-01-01

    The strong La Nina of 2010-2011 provided an opportunity to investigate the ecological impacts of El Nino-Southern Oscillation on coastal plankton communities using the nine national reference stations around Australia. Based on remote sensing and across the entire Australian region 2011 (La Nina) was only modestly different from 2010 (El Nino) with the average temperature declining 0.2 percent surface chlorophyll a up 3 percent and modelled primary production down 14 percent. Other changes included a poleward shift in Prochlorococcus and Synechococcus. Along the east coast, there was a reduction in salinity, increase in nutrients, Chlorophytes and Prasinophytes (taxa with chlorophyll b, neoxanthin and prasinoxanthin). The southwest region had a rise in the proportion of 19-hexoyloxyfucoxanthin; possibly coccolithophorids in eddies of the Leeuwin Current and along the sub-tropical front. Pennate diatoms increased, Ceratium spp. decreased and Scrippsiella spp. increased in 2011. Zooplankton biomass declined significantly in 2011. There was a reduction in the abundance of Calocalanus pavo and Temora turbinata and increases in Clausocalanus farrani, Oncaea scottodicarloi and Macrosetella gracilis in 2011. The changes in the plankton community during the strong La Nina of 2011 suggest that this climatic oscillation exacerbates the tropicalization of Australia.

  4. Teleconnections of the Southern Oscillation in the tropical Atlantic sector in the OSU coupled upper ocean-atomosphere GCM

    SciTech Connect

    Hameed, S.; Meinster, A. ); Sperber, K.R. )

    1993-03-01

    The Oregon State University coupled upper ocean-atmosphere GCM has been shown to qualitatively simulate the Southern Oscillation. A composite analysis of the warm and cold events simulated in this 23-year integration has been performed. During the low phase of the Southern Oscillation, when warm anomalies occur in the eastern Pacific, the model simulates for the Atlantic region during March-May (1) a deficit of precipitation over the tropical South American continent, (2) Caribbean and Gulf of Mexico sea level pressure and sea surface temperature are in phase with the eastern Pacific anomalies, while those east of the Nordeste region are out of phase, and (3) northeast trade winds are anomalously weak and southwest trade winds are anomalously strong (as inferred from surface current anomalies). The anomalies in the oceanic processes are induced by perturbations in the atmospheric circulation over the Atlantic and are coupled to changes in the Walker circulation. During the high phase of the simulated Southern Oscillation, conditions in the atmosphere and ocean are essentially the reverse of the low phase. The model produces a response in the South American region during the opposing phases of the Southern Oscillation that is in general agreement with observations. The interannual variation of Nordeste rainfall is shown to be dominated by a few band-limited frequencies. These frequencies are found in the SST series of those regions of the Atlantic and Pacific oceans where strong correlations with Nordeste precipitation exist.

  5. Correlations between El Niño Southern Oscillation and changes in Nearctic-Neotropic migrant condition in Central America

    Treesearch

    J.D. Wolfe; C.J. Ralph

    2009-01-01

    Climatic changes induced by the El Niño–Southern Oscillation (ENSO) commonly influence biological systems; however, climatic variability and multitrophic interactions within tropical latitudes remain poorly understood. We examined relationships between migrant condition and ENSO during spring migration in Costa Rica. Our study is based on correlating an ENSO index with...

  6. Modulation of Southern Oscillation-Northern Hemisphere Mid-Winter Climate Relationships by the QBO.

    NASA Astrophysics Data System (ADS)

    Barnston, Anthony G.; Livezey, Robert E.; Halpert, Michael S.

    1991-02-01

    A possible relationship between the phase of the Quasi-Biennial Oscillation (QBO) and the effect of the Southern Oscillation (SO) on the January-February climate in the Northern Hemisphere is examined. Findings suggest a preference for the tropical/Northern Hemisphere (TNH) circulation pattern in response to anomalies in the SO in east QBO phase years, and for the Pacific/North American (PNA) pattern in west QBO phase years. This extends previous findings relating the strength of the TNH pattern to tropical Pacific sea surface temperature during ENSO episodes.This differentiation has fairly clear-cut implications for the January-February United States surface temperature anomaly pattern when a low (high) SO episode is in progress. The TNH emphasizes warmth (cold) in the Great Lakes/western Midwest; whereas the PNA induces a generally higher amplitude pattern, emphasizing cold (warmth) in the Southeast and warmth (cold) in the western third of the country. The SO-climate relationships appear approximately linear for each of the two QBO phases. A hypothetical physical mechanism through which this process might operate is briefly mentioned.

  7. An Examination of the Hadley Sea-Surface Temperature Time Series for the Nino 3.4 Region

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2010-01-01

    The Hadley sea-surface temperature (HadSST) dataset is investigated for the interval 1871-2008. The purpose of this investigation is to determine the degree of success in identifying and characterizing El Nino (EN) southern (ENSO) extreme events, both EN and La Nina (LN) events. Comparisons are made against both the Southern Oscillation Index for the same time interval and with published values of the Oceanic Nino Index for the interval since 1950. Some 60 ENSO extreme events are identified in the HadSST dataset, consisting of 33 EN and 27 LN events. Also, preferential associations are found to exist between the duration of ENSO extreme events and their maximum anomalous excursion temperatures and between the recurrence rate for an EN event and the duration of the last known EN event. Because the present ongoing EN is a strong event, it should persist 11 months or longer, inferring that the next EN event should not be expected until June 2012 or later. Furthermore, the decadal sum of EN-related months is found to have increased somewhat steadily since the decade of 1920-1929, suggesting that the present decade (2010-2019) possibly will see about 3-4 EN events, totaling about 37 +/- 3 EN-related months (i.e., months that meet the definition for the occurrence of an EN event).

  8. El Niño-Southern Oscillation and dengue early warning in Ecuador

    NASA Astrophysics Data System (ADS)

    Stewart, A. M.; Lowe, R.

    2012-04-01

    Dengue fever, a mosquito-borne viral disease, is one of the most important emerging tropical diseases. Dengue is hyper-endemic in coastal Ecuador, where all four serotypes co-circulate. The El Niño-Southern Oscillation (ENSO) influences climate in Ecuador, with positive phase ENSO (El Niño) associated with wetter and warmer conditions over the southern coastal region. In turn, greater rainfall increases the availability of mosquito breeding sites for the dengue mosquito (Aedes aegypti), while warmer temperatures increase rates of larval development, mosquito biting, and viral replication in the mosquito. We report a statistical model for assessing the importance of climate as a driver for inter-annual variability in dengue fever in southern coastal Ecuador. Climate variables from a local meteorology station (precipitation, number of rainy days, minimum/maximum/mean air temperature), combined with gridded climate products, and anomalies of Pacific sea surface temperatures (Oceanic Niño Index, ONI) were used to predict monthly dengue standardized morbidity ratios (SMR) (1995-2010). Non-climatic confounding factors such as serotype introduction and vector control effort were also considered. Preliminary results indicated a statistically significant positive association between dengue risk and the number of rainy days during the previous month. Both the number of rainy days and dengue SMR were positively associated with the Pacific SST anomalies with a lead time of several months. Due to time lags involved in the climate-disease transmission system, monitoring El Niño / La Niña evolution in the Pacific Ocean could provide some predictive lead time for forecasting dengue epidemics. This is the first study of dengue fever and climate in this region. This research provides the foundation to develop a climate-driven early warning system for dengue fever in Ecuador.

  9. Climate Regimes, El Niño-Southern Oscillation, and Meningococcal Meningitis Epidemics.

    PubMed

    Oluwole, Olusegun Steven Ayodele

    2015-01-01

    Meningococcal meningitis is a major public health problem that kills thousands annually in Africa, Europe, North, and South America. Occurrence is, however, highest during the dry seasons in Sahel Africa. Interannual changes in precipitation correlate with interannual changes in El Niño-Southern Oscillation (ENSO), while interdecadal changes in precipitation correlate with Pacific Decadal Oscillation (PDO). The objective of the study was to determine if there is spectral coherence of seasonal, interannual, and interdecadal changes in occurrence of meningococcal meningitis in Sahel, Central, and East Africa with interannual and interdecadal changes of PDO and ENSO. Time series were fitted to occurrence of meningococcal meningitis in Sahel, Central, and East Africa, to indices of precipitation anomalies in the Sahel, and to indices of ENSO and PDO anomalies. Morlet wavelet was used to transform the time series to frequency-time domain. Wavelet spectra and coherence analyses were performed. Occurrence of meningococcal meningitis showed seasonal, interannual, and interdecadal changes. The magnitude of occurrence was higher during warm climate regime, and strong El Niños. Spectra coherence of interannual and interdecadal changes of ENSO and PDO with occurrence of meningococcal meningitis in Sahel, Central, and East Africa were significant at p < 0.0001. Precipitation in Sahel was low during warm climate regimes. Spectra coherence of changes in precipitation in Sahel with ENSO was significant at p < 0.0001. ENSO and PDO are determinants of the seasonal, interannual, and interdecadal changes in occurrence of meningococcal meningitis. Public health management of epidemics of meningococcal meningitis should include forecast models of changes in ENSO to predict periods of low precipitation, which initiate occurrence.

  10. Climate Regimes, El Niño-Southern Oscillation, and Meningococcal Meningitis Epidemics

    PubMed Central

    Oluwole, Olusegun Steven Ayodele

    2015-01-01

    Meningococcal meningitis is a major public health problem that kills thousands annually in Africa, Europe, North, and South America. Occurrence is, however, highest during the dry seasons in Sahel Africa. Interannual changes in precipitation correlate with interannual changes in El Niño-Southern Oscillation (ENSO), while interdecadal changes in precipitation correlate with Pacific Decadal Oscillation (PDO). The objective of the study was to determine if there is spectral coherence of seasonal, interannual, and interdecadal changes in occurrence of meningococcal meningitis in Sahel, Central, and East Africa with interannual and interdecadal changes of PDO and ENSO. Time series were fitted to occurrence of meningococcal meningitis in Sahel, Central, and East Africa, to indices of precipitation anomalies in the Sahel, and to indices of ENSO and PDO anomalies. Morlet wavelet was used to transform the time series to frequency-time domain. Wavelet spectra and coherence analyses were performed. Occurrence of meningococcal meningitis showed seasonal, interannual, and interdecadal changes. The magnitude of occurrence was higher during warm climate regime, and strong El Niños. Spectra coherence of interannual and interdecadal changes of ENSO and PDO with occurrence of meningococcal meningitis in Sahel, Central, and East Africa were significant at p < 0.0001. Precipitation in Sahel was low during warm climate regimes. Spectra coherence of changes in precipitation in Sahel with ENSO was significant at p < 0.0001. ENSO and PDO are determinants of the seasonal, interannual, and interdecadal changes in occurrence of meningococcal meningitis. Public health management of epidemics of meningococcal meningitis should include forecast models of changes in ENSO to predict periods of low precipitation, which initiate occurrence. PMID:26284234

  11. Influence of El Niño Southern Oscillation on global scale flood and drought risk

    NASA Astrophysics Data System (ADS)

    Ward, Philip; Jongman, Brenden; Veldkamp, Ted; Kummu, Matti; Dettinger, Michael; Sperna Weiland, Frederiek; Winsemius, Hessel

    2015-04-01

    In this contribution we demonstrate the influence of climate variability on flood and drought risk. El Niño Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability, and has a strong influence on climate over large parts of the world. In turn, it strongly influences many extreme hazards and their resulting socioeconomic impacts, including economic damage and loss of life. Whilst ENSO is known to influence hydrology in many regions of the world, little is known about its influence on the socioeconomic impacts of either floods or droughts. To address this, we developed new modelling frameworks to assess ENSO's influence on both flood risk and drought risk at the global scale. Flood risk is expressed in terms of annual expected damages and annual affected population. Drought risk is expressed in terms of water shortage and water stress. We show that ENSO exerts strong and widespread influences on flood hazard and risk, as well as drought risk. Reliable anomalies of flood risk exist during El Niño or La Niña years, or both, in basins spanning almost half (44%) of Earth's land surface. Significant correlations between ENSO and water scarcity conditions were found for 43% of the global land area, meaning that more than half of the global population is effectively affected by water shortage and stress events under 2010 conditions. Our results show that climate variability, especially from ENSO, should be incorporated into disaster risk analyses and policies. Since ENSO has some predictive skill with lead times of several seasons, the findings suggest the possibility to develop probabilistic risk projections, which could be used for improved disaster planning. The findings are also relevant in the context of climate change. If the frequency and/or magnitude of ENSO events were to change in the future, this could imply changes in flood and drought risk variations across almost half of the world's terrestrial regions. The flood part of

  12. Field-aligned currents in Saturn's southern nightside magnetosphere: Subcorotation and planetary period oscillation components

    NASA Astrophysics Data System (ADS)

    Hunt, G. J.; Cowley, S. W. H.; Provan, G.; Bunce, E. J.; Alexeev, I. I.; Belenkaya, E. S.; Kalegaev, V. V.; Dougherty, M. K.; Coates, A. J.

    2014-12-01

    We investigate magnetic data showing the presence of field-aligned magnetosphere-ionosphere coupling currents on 31 Cassini passes across Saturn's southern postmidnight auroral region. The currents are strongly modulated in magnitude, form, and position by the phase of the southern planetary period oscillations (PPOs). PPO-independent currents are separated from PPO-related currents using the antisymmetry of the latter with respect to PPO phase. PPO-independent downward currents ~1.1 MA per radian of azimuth flow over the polar open field region indicative of significant plasma subcorotation are enhanced in an outer plasma sheet layer of elevated ionospheric conductivity carrying ~0.8 MA rad-1 and close principally in an upward directed current sheet at ~17°-19° ionospheric colatitude carrying ~2.3 MA rad-1 that maps to the outer hot plasma region in Saturn's magnetosphere (equatorial range ~11-16 Saturn radii (RS)) colocated with the UV oval. Subsidiary downward and upward currents ~0.5 MA rad-1 lie at ~19°-20.5° colatitude mapping to the inner hot plasma region, but no comparable currents are detected at larger colatitudes mapping to the cool plasma regime inside ~8 RS. PPO-related currents at ~17.5°-20° colatitude overlap the main upward and subsidiary downward currents and carry comparable rotating upward and downward currents peaking at ~1.7 MA rad-1. The overall current layer colatitude is also modulated with 1° amplitude in the PPO cycle, maximum equatorward adjacent to the peak upward PPO current and maximum poleward adjacent to peak downward PPO current. This phasing requires the current system to be driven from the planetary atmosphere rather than directly from the magnetosphere.

  13. Extreme cyclone wave climate in the Southwest Pacific Ocean: Influence of the El Niño Southern Oscillation and projected climate change

    NASA Astrophysics Data System (ADS)

    Stephens, Scott A.; Ramsay, D. L.

    2014-12-01

    This paper describes the first use of a stochastic cyclone model (SCM) to quantify the extreme significant wave height from tropical cyclones across the Southwest Pacific Ocean. The median extreme significant wave heights across the entire SW Pacific Ocean were 7.5, 10 and 11 m for annual exceedance probabilities (AEPs) of 0.1, 0.02 and 0.01 respectively. Maximum significant wave heights in the region were approximately 1.5 times these values for the same AEP. Tables of extreme significant wave heights are provided for selected inhabited locations. The SCM was used to quantify the effects of the El Niño-Southern Oscillation (ENSO) on extreme significant wave heights, and also the effects of projected climate change on cyclone intensity and frequency of occurrence. West of the International Dateline in the region of the Vanuatu archipelago, the extreme cyclone wave climate was relatively consistent during all phases of the ENSO cycle, but highest during El Niño. Cyclone formation and propagation eastward of the Dateline are more likely to occur during El Niño conditions, however these cyclones tended to be more intense, particularly during extreme El Niño events, leading to a higher long-term extreme wave climate in the eastern SW Pacific, despite the relatively low cyclone observation rate there. Simulations of climate change cyclone intensity increases of 10-20% of the most intense cyclones (categories 4 and 5) along with 10-20% reduction in number of cyclones indicated little change in extreme significant wave heights for low-occurrence AEPs of 1/20 or less. These changes were much less than induced by present-day ENSO variability, suggesting that future changes in extreme wave climate will be sensitive to climate change influences on the frequency and intensity of ENSO events. These results are significant in the light of indications that the frequency of extreme El Nino events might double in response to greenhouse warming.

  14. El Niño-Southern Oscillation, Pliocene climate and equifinality.

    PubMed

    Bonham, Sarah G; Haywood, Alan M; Lunt, Daniel J; Collins, Mathew; Salzmann, Ulrich

    2009-01-13

    It has been suggested that, during the Pliocene (ca 5-1.8Ma), an El Niño state existed as a permanent rather than an intermittent feature; that is, the tropical Pacific Ocean was characterized by a much weaker east-west gradient than today. One line of inquiry used to investigate this idea relates modern El Niño teleconnections to Pliocene proxy data by comparing regional differences in precipitation and surface temperature with climate patterns associated with present-day El Niño events, assuming that agreement between Pliocene data and observations of modern El Niño events supports this interpretation. Here, we examine this assumption by comparing outputs from a suite of Mid-Pliocene climate simulations carried out with the UK Met Office climate model. Regional patterns of climate change associated with changes in model boundary conditions are compared with observed El Niño-Southern Oscillation teleconnection patterns. Our results indicate that many of the proposed 'permanent El Niño' surface temperature and precipitation patterns are observable in Mid-Pliocene climate simulations even when they display variability in tropical Pacific sea surface temperatures (SSTs) or when forced with a modern east-west SST gradient. Our experiments highlight the possibility that the same outcome may be achieved through different initial conditions (equifinality); an important consideration for reconstructed patterns of regional Mid-Pliocene climate.

  15. Evidence for the effect of sunspot activity on the El Niño/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Zhai, Qian

    2017-04-01

    The El Niño No. 3 area index (5°S∼ 5°N, 150°W∼ 90°W) and yearly sunspot number (SSN) from 1408 to 1978 are used to investigate the influence of solar activity on the El Niño/Southern Oscillation (ENSO), through periodicity analysis, cross wavelet transform (XWT), cross correlation and ensemble empirical mode decomposition (EEMD) analyses. The solar activity period, the Hale period, and the Gleissberg period are determined in the El Niño index time series, but of weak statistical significance. Cross correlation analysis of the index with SSN, and that of its low-frequency components decomposed by EEMD clearly indicate that solar activity may take effect on the ENSO, and such an impact should undergo an accumulation procedure (phase delay). XWT also indicates the existence of the impact. It is found that the index is negatively correlated with SSN when SSN is large during a certain long-term interval, and positively when SSN is small. Strong El Niño is inferred to be taken place in decade(s) to come.

  16. Influence of El Niño Southern Oscillation on global hydropower production

    NASA Astrophysics Data System (ADS)

    Ng, Jia Yi; Turner, Sean W. D.; Galelli, Stefano

    2017-03-01

    El Niño Southern Oscillation (ENSO) strongly influences the global climate system, affecting hydrology in many of the world’s river basins. This raises the prospect of ENSO-driven variability in global and regional hydroelectric power generation. Here we study these effects by generating time series of power production for 1593 hydropower dams, which collectively represent more than half of the world’s existing installed hydropower capacity. The time series are generated by forcing a detailed dam model with monthly-resolution, 20th century inflows—the model includes plant specifications, storage dynamics and realistic operating schemes, and runs irrespectively of the dam construction year. More than one third of simulated dams exhibit statistically significant annual energy production anomalies in at least one of the two ENSO phases of El Niño and La Niña. For most dams, the variability of relative anomalies in power production tends to be less than that of the forcing inflows—a consequence of dam design specifications, namely maximum turbine release rate and reservoir storage, which allows inflows to accumulate for power generation in subsequent dry years. Production is affected most prominently in Northwest United States, South America, Central America, the Iberian Peninsula, Southeast Asia and Southeast Australia. When aggregated globally, positive and negative energy production anomalies effectively cancel each other out, resulting in a weak and statistically insignificant net global anomaly for both ENSO phases.

  17. Impacts of El Niño Southern Oscillation on the global yields of major crops.

    PubMed

    Iizumi, Toshichika; Luo, Jing-Jia; Challinor, Andrew J; Sakurai, Gen; Yokozawa, Masayuki; Sakuma, Hirofumi; Brown, Molly E; Yamagata, Toshio

    2014-05-15

    The monitoring and prediction of climate-induced variations in crop yields, production and export prices in major food-producing regions have become important to enable national governments in import-dependent countries to ensure supplies of affordable food for consumers. Although the El Niño/Southern Oscillation (ENSO) often affects seasonal temperature and precipitation, and thus crop yields in many regions, the overall impacts of ENSO on global yields are uncertain. Here we present a global map of the impacts of ENSO on the yields of major crops and quantify its impacts on their global-mean yield anomalies. Results show that El Niño likely improves the global-mean soybean yield by 2.1-5.4% but appears to change the yields of maize, rice and wheat by -4.3 to +0.8%. The global-mean yields of all four crops during La Niña years tend to be below normal (-4.5 to 0.0%). Our findings highlight the importance of ENSO to global crop production.

  18. El Niño Southern Oscillation and leptospirosis outbreaks in New Caledonia.

    PubMed

    Weinberger, Daniel; Baroux, Noémie; Grangeon, Jean-Paul; Ko, Albert I; Goarant, Cyrille

    2014-04-01

    Leptospirosis is an important cause of seasonal outbreaks in New Caledonia and the tropics. Using time series derived from high-quality laboratory-based surveillance from 2000-2012, we evaluated whether climatic factors, including El Niño Southern Oscillation (ENSO) and meteorological conditions allow for the prediction of leptospirosis outbreaks in New Caledonia. We found that La Niña periods are associated with high rainfall, and both of these factors were in turn, temporally associated with outbreaks of leptospirosis. The sea surface temperature in El Niño Box 4 allowed forecasting of leptospirosis outbreaks four months into the future, a time lag allowing public health authorities to increase preparedness. To our knowledge, our observations in New Caledonia are the first demonstration that ENSO has a strong association with leptospirosis. This association should be tested in other regions in the South Pacific, Asia or Latin America where ENSO may drive climate variability and the risk for leptospirosis outbreaks.

  19. Influence of the solar cycle on the Polar-night Jet Oscillation in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Kuroda, Yuhji; Deushi, Makoto

    2016-10-01

    The Polar-night Jet Oscillation (PJO) is the dominant mode of stratospheric variability in the Southern Hemisphere and persists from midwinter to spring. The influence of the 11 year solar cycle on modulation of the PJO from late winter to spring is examined using observations and three 42 year simulations from a chemistry-climate model. The only variation applied to model boundary conditions was the strength of ultraviolet (UV) radiation. This is set at 2 times larger than observations to enhance the strength of the solar signal. Simulations show a downward propagation of the stratospheric signal into the troposphere from late winter to spring, which tends to be enhanced as UV strength increases. This result is similar to observations but with a 1-2 month lag. The behavior of the PJO with respect to wave-mean flow interactions is examined using a newly developed momentum budget analysis as well as wave energy analysis. We suggest that UV modulation of the interactions between planetary waves and zonal-mean flow in the stratosphere, rather than direct diabatic processes as suggested in a previous study, is the source of solar cycle modulation of the PJO.

  20. The El Niño southern oscillation and malaria epidemics in South America.

    PubMed

    Gagnon, Alexandre S; Smoyer-Tomic, Karen E; Bush, Andrew B G

    2002-05-01

    A better understanding of the relationship between the El Niño Southern Oscillation (ENSO), the climatic anomalies it engenders, and malaria epidemics could help mitigate the world-wide increase in incidence of this mosquito-transmitted disease. The purpose of this paper is to assess the possibility of using ENSO forecasts for improving malaria control. This paper analyses the relationship between ENSO events and malaria epidemics in a number of South American countries (Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela). A statistically significant relationship was found between El Niño and malaria epidemics in Colombia, Guyana, Peru, and Venezuela. We demonstrate that flooding engenders malaria epidemics in the dry coastal region of northern Peru, while droughts favor the development of epidemics in Colombia and Guyana, and epidemics lag a drought by 1 year in Venezuela. In Brazil, French Guiana, and Ecuador, where we did not detect an ENSO/malaria signal, non-climatic factors such as insecticide sprayings, variation in availability of anti-malaria drugs, and population migration are likely to play a stronger role in malaria epidemics than ENSO-generated climatic anomalies. In some South American countries, El Niño forecasts show strong potential for informing public health efforts to control malaria.

  1. Aquifer responses to El Niño-Southern Oscillation, Southwest British Columbia.

    PubMed

    Fleming, Sean W; Quilty, Edward J

    2006-01-01

    We used climatological composite analysis to investigate El Niño-Southern Oscillation (ENSO) signals in long-term shallow ground water level observations from four wells in the lower Fraser Valley of British Columbia. Significance of differences between warm-phase, cold-phase, and neutral climate states was assessed with a Monte Carlo bootstrap technique. We also considered time series of local precipitation and streamflow for comparison. Composite annual hyetographs suggest that ENSO precipitation impacts are largely limited to winter and spring, with higher and lower rainfall occurring, respectively, under cold-phase and warm-phase episodes. This is consistent with prior work in the region and is found to be directly reflected in both streamflow and ground water level data. The mean magnitude of ENSO terrestrial hydrologic anomalies can be up to approximately 50% of the average seasonal cycle amplitude. ENSO does not appear to systematically affect annual hydrometeorological cycle timing in this study area. However, relative to the surface hydrologic systems considered, aquifers are observed to retain a stronger memory of seasonal ENSO-related precipitation anomalies, with changes potentially extending through the following summer, presumably reflecting storage effects. Most responses appear to be somewhat nonlinear.

  2. El Niño Southern Oscillation and Leptospirosis Outbreaks in New Caledonia

    PubMed Central

    Weinberger, Daniel; Baroux, Noémie; Grangeon, Jean-Paul; Ko, Albert I.; Goarant, Cyrille

    2014-01-01

    Leptospirosis is an important cause of seasonal outbreaks in New Caledonia and the tropics. Using time series derived from high-quality laboratory-based surveillance from 2000–2012, we evaluated whether climatic factors, including El Niño Southern Oscillation (ENSO) and meteorological conditions allow for the prediction of leptospirosis outbreaks in New Caledonia. We found that La Niña periods are associated with high rainfall, and both of these factors were in turn, temporally associated with outbreaks of leptospirosis. The sea surface temperature in El Niño Box 4 allowed forecasting of leptospirosis outbreaks four months into the future, a time lag allowing public health authorities to increase preparedness. To our knowledge, our observations in New Caledonia are the first demonstration that ENSO has a strong association with leptospirosis. This association should be tested in other regions in the South Pacific, Asia or Latin America where ENSO may drive climate variability and the risk for leptospirosis outbreaks. PMID:24743322

  3. An analysis of high cloud variability: imprints from the El Niño-Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Li, King-Fai; Su, Hui; Mak, Sze-Ning; Chang, Tiffany M.; Jiang, Jonathan H.; Norris, Joel R.; Yung, Yuk L.

    2017-01-01

    Using data from the International Satellite Cloud Climatology Project (ISCCP), we examine how near-global (60°N-60°S) high cloud fraction varies over time in the past three decades. Our focus is on identifying dominant modes of variability and associated spatial patterns, and how they are related to sea surface temperature. By performing the principal component analysis, we find that the first two principal modes of high cloud distribution show strong imprints of the two types of El Niño-Southern Oscillation (ENSO)—the canonical ENSO and the ENSO Modoki. Comparisons between ISCCP data and 14 models from the Atmospheric Model Intercomparison Project Phase 5 (AMIP5) show that models simulate the spatial pattern and the temporal variations of high cloud fraction associated with the canonical ENSO very well but the magnitudes of the canonical ENSO vary among the models. Furthermore, the multi-model mean of the second principal mode in the AMIP5 simulations appears to capture the temporal behavior of the second mode but individual AMIP5 models show large discrepancies in capturing observed temporal variations. A new metric, defined by the relative variances of the first two principal components, suggests that most of the AMIP5 models overestimate the second principal mode of high clouds.

  4. The El Niño Southern Oscillation and malaria epidemics in South America

    NASA Astrophysics Data System (ADS)

    Gagnon, Alexandre S.; Smoyer-Tomic, Karen E.; Bush, Andrew B.

    2002-05-01

    A better understanding of the relationship between the El Niño Southern Oscillation (ENSO), the climatic anomalies it engenders, and malaria epidemics could help mitigate the world-wide increase in incidence of this mosquito-transmitted disease. The purpose of this paper is to assess the possibility of using ENSO forecasts for improving malaria control. This paper analyses the relationship between ENSO events and malaria epidemics in a number of South American countries (Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela). A statistically significant relationship was found between El Niño and malaria epidemics in Colombia, Guyana, Peru, and Venezuela. We demonstrate that flooding engenders malaria epidemics in the dry coastal region of northern Peru, while droughts favor the development of epidemics in Colombia and Guyana, and epidemics lag a drought by 1 year in Venezuela. In Brazil, French Guiana, and Ecuador, where we did not detect an ENSO/malaria signal, non-climatic factors such as insecticide sprayings, variation in availability of anti-malaria drugs, and population migration are likely to play a stronger role in malaria epidemics than ENSO-generated climatic anomalies. In some South American countries, El Niño forecasts show strong potential for informing public health efforts to control malaria.

  5. El Niño-Southern oscillation variability from the late cretaceous marca shale of California

    USGS Publications Warehouse

    Davies, Andrew; Kemp, Alan E.S.; Weedon, Graham P.; Barron, John A.

    2012-01-01

    Changes in the possible behavior of El Niño–Southern Oscillation (ENSO) with global warming have provoked interest in records of ENSO from past “greenhouse” climate states. The latest Cretaceous laminated Marca Shale of California permits a seasonal-scale reconstruction of water column flux events and hence interannual paleoclimate variability. The annual flux cycle resembles that of the modern Gulf of California with diatoms characteristic of spring upwelling blooms followed by silt and clay, and is consistent with the existence of a paleo–North American Monsoon that brought input of terrigenous sediment during summer storms and precipitation runoff. Variation is also indicated in the extent of water column oxygenation by differences in lamina preservation. Time series analysis of interannual variability in terrigenous sediment and diatom flux and in the degree of bioturbation indicates strong periodicities in the quasi-biennial (2.1–2.8 yr) and low-frequency (4.1–6.3 yr) bands both characteristic of ENSO forcing, as well as decadal frequencies. This evidence for robust Late Cretaceous ENSO variability does not support the theory of a “permanent El Niño,” in the sense of a continual El Niño–like state, in periods of warmer climate.

  6. The 1997-98 El Nino Event and Related Wintertime Lightning Variations in the Southeastern United States

    NASA Technical Reports Server (NTRS)

    Goodman, S. J.; Buechler, D. E.; Knupp, K.; Driscoll, K.; McCaul, E. W.

    1999-01-01

    The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for world-wide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast US Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the latest warm-episode year. The 1997-98 warm episode, notable for being the strongest event since 1982-83, presents our first opportunity to examine the response to a major ENSO event and determine the variation of wintertime thunderstorm activity in this part of the world. Due to the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the expanded coverage of the National Lightning Detection Network (NLDN), we are able to examine such year-to-year changes in lightning activity with far greater detail than ever before.

  7. The 1997-98 El-Nino Event and Related Lightning Variations in the Southeastern United States

    NASA Technical Reports Server (NTRS)

    Buechler, D. E.; Goodman, S. J.; McCaul, E. W.; Knupp, K.

    1999-01-01

    The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for world-wide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast US Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the current warm-episode year. The 1997-98 warm episode, notable for being the strongest event since 1982-83, presents our first opportunity to examine the response to a major ENSO event and determine the variation of wintertime thunderstorm activity in this part of the world. Due to the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the expanded coverage of the National Lightning Detection Network (NLDN), we are able to examine such year-to-year changes in lightning activity with far greater detail than ever before.

  8. A RETROSPECTIVE ANALYSIS OF THE EFFECT OF EL NINO-SOUTHERN OSCILLATION EVENTS ON COASTAL WATER QUALITY IN SOUTHWEST FLORIDA. (R825197)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  9. A RETROSPECTIVE ANALYSIS OF THE EFFECT OF EL NINO-SOUTHERN OSCILLATION EVENTS ON COASTAL WATER QUALITY IN SOUTHWEST FLORIDA. (R825197)

    EPA Science Inventory

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  10. Planetary period oscillations in Saturn's magnetosphere: Coalescence and reversal of northern and southern periods in late northern spring

    NASA Astrophysics Data System (ADS)

    Provan, G.; Cowley, S. W. H.; Lamy, L.; Bunce, E. J.; Hunt, G. J.; Zarka, P.; Dougherty, M. K.

    2016-10-01

    We investigate planetary period oscillations (PPOs) in Saturn's magnetosphere using Cassini magnetic field and Saturn kilometric radiation (SKR) data over the interval from late 2012 to the end of 2015, beginning 3 years after vernal equinox and ending 1.5 years before northern solstice. Previous studies have shown that the northern and southern PPO periods converged across equinox from southern summer values 10.8 h for the southern system and 10.6 h for the northern system and near coalesced 1 year after equinox, before separating again with the southern period 10.69 h remaining longer than the northern 10.64 h. We show that these conditions ended in mid-2013 when the two periods coalesced at 10.66 h and remained so until mid-2014, increasing together to longer periods 10.70 h. During coalescence the two systems were locked near magnetic antiphase with SKR modulations in phase, a condition in which the effects of the generating rotating twin vortex flows in the two ionospheres reinforce each other via hemisphere-to-hemisphere coupling. The magnetic-SKR relative phasing indicates the dominance of postdawn SKR sources in both hemispheres, as was generally the case during the study interval. In mid-2014 the two periods separated again, the northern increasing to 10.78 h by the end of 2015, similar to the southern period during southern summer, while the southern period remained fixed near 10.70 h, well above the northern period during southern summer. Despite this difference, this behavior resulted in the first enduring reversal of the two periods, northern longer than southern, during the Cassini era.

  11. On the dynamics of intraseasonal oscillations and ENSO

    NASA Technical Reports Server (NTRS)

    Lau, K.-M.; Shen, Suhung

    1988-01-01

    This paper investigates some basic properties of low-frequency phenomena in the tropical atmosphere and the coupled ocean-atmosphere system, with an aim of seeking a unified dynamical framework for studies of the mechanisms of intraseasonal oscillations and the El Nino Southern Oscillation (ENSO). The role of specific processes leading to intraseasonal oscillations and to ENSO, both separately and collectively, are considered, using a simple shallow-water system. The results demonstrated the effect of including a time-dependent moist atmosphere in studies of the coupled atmosphere-ocean system. It is suggested that the interaction of several atmospheric processes and oceanic processes through evaporation-SST feedback and wind stress at the atmosphere-ocean interface may be important for the onset and evolution of an ENSO event.

  12. Strong influence of El Niño Southern Oscillation on flood risk around the world

    PubMed Central

    Ward, Philip J.; Jongman, Brenden; Kummu, Matti; Dettinger, Michael D.; Sperna Weiland, Frederiek C.; Winsemius, Hessel C.

    2014-01-01

    El Niño Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability and has a strong influence on climate over large parts of the world. In turn, it strongly influences many natural hazards (such as hurricanes and droughts) and their resulting socioeconomic impacts, including economic damage and loss of life. However, although ENSO is known to influence hydrology in many regions of the world, little is known about its influence on the socioeconomic impacts of floods (i.e., flood risk). To address this, we developed a modeling framework to assess ENSO’s influence on flood risk at the global scale, expressed in terms of affected population and gross domestic product and economic damages. We show that ENSO exerts strong and widespread influences on both flood hazard and risk. Reliable anomalies of flood risk exist during El Niño or La Niña years, or both, in basins spanning almost half (44%) of Earth’s land surface. Our results show that climate variability, especially from ENSO, should be incorporated into disaster-risk analyses and policies. Because ENSO has some predictive skill with lead times of several seasons, the findings suggest the possibility to develop probabilistic flood-risk projections, which could be used for improved disaster planning. The findings are also relevant in the context of climate change. If the frequency and/or magnitude of ENSO events were to change in the future, this finding could imply changes in flood-risk variations across almost half of the world’s terrestrial regions. PMID:25331867

  13. Strong influence of El Niño Southern Oscillation on flood risk around the world

    NASA Astrophysics Data System (ADS)

    Ward, Philip J.; Jongman, Brenden; Kummu, Matti; Dettinger, Michael D.; Sperna Weiland, Frederiek C.; Winsemius, Hessel C.

    2014-11-01

    El Niño Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability and has a strong influence on climate over large parts of the world. In turn, it strongly influences many natural hazards (such as hurricanes and droughts) and their resulting socioeconomic impacts, including economic damage and loss of life. However, although ENSO is known to influence hydrology in many regions of the world, little is known about its influence on the socioeconomic impacts of floods (i.e., flood risk). To address this, we developed a modeling framework to assess ENSO's influence on flood risk at the global scale, expressed in terms of affected population and gross domestic product and economic damages. We show that ENSO exerts strong and widespread influences on both flood hazard and risk. Reliable anomalies of flood risk exist during El Niño or La Niña years, or both, in basins spanning almost half (44%) of Earth's land surface. Our results show that climate variability, especially from ENSO, should be incorporated into disaster-risk analyses and policies. Because ENSO has some predictive skill with lead times of several seasons, the findings suggest the possibility to develop probabilistic flood-risk projections, which could be used for improved disaster planning. The findings are also relevant in the context of climate change. If the frequency and/or magnitude of ENSO events were to change in the future, this finding could imply changes in flood-risk variations across almost half of the world's terrestrial regions.

  14. Annual flood sensitivities to El Niño-Southern Oscillation at the global scale

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Floods are amongst the most dangerous natural hazards in terms of economic damage. Whilst a growing number of studies have examined how river floods are influenced by climate change, the role of natural modes of interannual climate variability remains poorly understood. We present the first global assessment of the influence of El Niño-Southern Oscillation (ENSO) on annual river floods, defined here as the peak daily discharge in a given year. The analysis was carried out by simulating daily gridded discharges using the WaterGAP model (Water - a Global Assessment and Prognosis), and examining statistical relationships between these discharges and ENSO indices. We found that, over the period 1958-2000, ENSO exerted a significant influence on annual floods in river basins covering over a third of the world's land surface, and that its influence on annual floods has been much greater than its influence on average flows. We show that there are more areas in which annual floods intensify with La Niña and decline with El Niño than vice versa. However, we also found that in many regions the strength of the relationships between ENSO and annual floods have been non-stationary, with either strengthening or weakening trends during the study period. We discuss the implications of these findings for science and management. Given the strong relationships between ENSO and annual floods, we suggest that more research is needed to assess relationships between ENSO and flood impacts (e.g. loss of lives or economic damage). Moreover, we suggest that in those regions where useful relationships exist, this information could be combined with ongoing advances in ENSO prediction research, in order to provide year-to-year probabilistic flood risk forecasts.

  15. El Niño-Southern Oscillation Impacts on Winter Vegetable Production in Florida*.

    NASA Astrophysics Data System (ADS)

    Hansen, James W.; Jones, James W.; Kiker, Clyde F.; Hodges, Alan W.

    1999-01-01

    Florida's mild winters allow the state to play a vital role in supplying fresh vegetables for U.S. consumers. Producers also benefit from premium prices when low temperatures prevent production in most of the country. This study characterizes the influence of the El Niño-Southern Oscillation (ENSO) on the Florida vegetable industry using statistical analysis of the response of historical crop (yield, prices, production, and value) and weather variables (freeze hazard, temperatures, rainfall, and solar radiation) to ENSO phase and its interaction with location and time of year. Annual mean yields showed little evidence of response to ENSO phase and its interaction with location. ENSO phase and season interacted to influence quarterly yields, prices, production, and value. Yields (tomato, bell pepper, sweet corn, and snap bean) were lower and prices (bell pepper and snap bean) were higher in El Niño than in neutral or La Niña winters. Production and value of tomatoes were higher in La Niña winters. The yield response can be explained by increased rainfall, reduced daily maximum temperatures, and reduced solar radiation in El Niño winters. Yield and production of winter vegetables appeared to be less responsive to ENSO phase after 1980; for tomato and bell pepper, this may be due to improvements in production technology that mitigate problems associated with excess rainfall. Winter yield and price responses to El Niño events have important implications for both producers and consumers of winter vegetables, and suggest opportunities for further research.

  16. Southern Oscillation Signal in South American Palaeoclimatic Data of the Last 7000 Years

    NASA Astrophysics Data System (ADS)

    Martin, Louis; Fournier, Marc; Mourguiart, Philippe; Sifeddine, Abdelfatah; Turcq, Bruno; Flexor, Jean-Marie; Absy, Maria Lucia

    1993-05-01

    During strong El Niño events, rainfall anomalies and changes in wind patterns are observed in different regions of South America. Along the central Brazilian coast, during the 1983 El Niño year, the frontal systems were blocked to the south, provoking a reversal of the longshore sand transport. Long-duration reversals of longshore transport were also recorded in Holocene beach-ridge terraces from the Rio Doce coastal plain. This led to the formulation of a model relating these reversals of longshore transport to El Niño-like conditions. El Niño-like conditions are past average climate situations that generate the same perturbations as the strong El Niño events observed during the last decade. They are likely to correspond to the long-duration low phase of the Southern Oscillation. To confirm this hypothesis we compared the Holocene beach-ridge record with other palaeoenvironmental records from regions where strong El Niño events would have a substancial signal as well: (1) water-level fluctuations of Lake Titicaca, (2) a pollen and sediment record in an eastern Amazonian lake, (3) changes of the Rio Xingu discharge in eastern Amazonia, and (4) variations of sand supply at the Rio Piura and Rio Chira outlets in the Sechura Desert. The occurrences of El Niño-like conditions were numerous before 3900-3600 yr B.P., absent between 39003600 and 2800-2500 yr B.P., and infrequent after 2800-2500 yr B.P.

  17. Multiproxy reconstructions of the El Niño-Southern Oscillation: progress and challenges (Invited)

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Comboul, M.; Guillot, D.; Cobb, K.; Evans, M. N.; Correge, T.; Carré, M.; Driscoll, R. E.; Elliot, M.; Mcgregor, H. V.; Tudhope, A. W.; Cole, J. E.; Rajaratnam, B.

    2013-12-01

    A major source of uncertainty in climate model projections of the twenty-first century is the evolution of the tropical Pacific ocean/atmosphere system, home to the El Niño-Southern Oscillation (ENSO), the dominant mode of global climate variability on interannual to decadal timescales. Indeed, there is no consensus among models as to how its mean state, amplitude, frequency, spatial structure, and atmospheric teleconnections will evolve with continued anthropogenic forcing. Since the instrumental record is too short to usefully characterize low-frequency climate variability, one must turn to the paleoclimate record for a longer view. Because each paleo archive is limited by its own sets of errors and biases, it is generally believed that a multiproxy approach holds the best promise in estimating past climate variations. However, multiproxy-based estimates of past tropical Pacific climate, in particular ENSO, are hindered by three main challenges: - weighing information from different proxy types - treating uncertainties due to chronological errors - treating uncertainties due to the statistical calibration process These sources of uncertainty complicate the interpretation of multiproxy reconstructions, prompting inquiries as to whether reconstructed variations reflect a true change in the phenomenon of interest (here, ENSO), or merely a change in the relative contribution of different observations, sensors, archives, observing sites, or statistical artifacts due to the extremely illl-posed nature of the multivariate estimation problem. In this presentation, I will synthesize lessons gleaned from recent multiproxy studies I have led - univariate and multivariate, coral-only and multiproxy, and explicitly quantifying age errors. The comparison will illustrate how the challenges identified above play out in different settings over the last millennium and Holocene, and how the resulting uncertainties may be quantified and communicated to end-users of such

  18. Strong influence of El Niño Southern Oscillation on flood risk around the world.

    PubMed

    Ward, Philip J; Jongman, Brenden; Kummu, Matti; Dettinger, Michael D; Sperna Weiland, Frederiek C; Winsemius, Hessel C

    2014-11-04

    El Niño Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability and has a strong influence on climate over large parts of the world. In turn, it strongly influences many natural hazards (such as hurricanes and droughts) and their resulting socioeconomic impacts, including economic damage and loss of life. However, although ENSO is known to influence hydrology in many regions of the world, little is known about its influence on the socioeconomic impacts of floods (i.e., flood risk). To address this, we developed a modeling framework to assess ENSO's influence on flood risk at the global scale, expressed in terms of affected population and gross domestic product and economic damages. We show that ENSO exerts strong and widespread influences on both flood hazard and risk. Reliable anomalies of flood risk exist during El Niño or La Niña years, or both, in basins spanning almost half (44%) of Earth's land surface. Our results show that climate variability, especially from ENSO, should be incorporated into disaster-risk analyses and policies. Because ENSO has some predictive skill with lead times of several seasons, the findings suggest the possibility to develop probabilistic flood-risk projections, which could be used for improved disaster planning. The findings are also relevant in the context of climate change. If the frequency and/or magnitude of ENSO events were to change in the future, this finding could imply changes in flood-risk variations across almost half of the world's terrestrial regions.

  19. Precipitation Producing Synoptic-Scale Flow and El Niño-Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2014-12-01

    The differences in winter synoptic-scale flow during precipitation events between phases of El Niño-Southern Oscillation are established for the coastal southwest United States. Principal component analysis in T-mode with Varimax rotation was performed on fields of 500-hPa, 700-hPa, and 850-hPa geopotential height and specific humidity (from the North American Regional Reanalysis) during days with precipitation. These precipitation days were grouped through a k-means cluster analysis of the loadings on the extracted components from all atmospheric variables. Eight clusters were ultimately analyzed based on separation and cohesion statistics. Analyses of cluster membership and cluster composite maps reveal synoptic-scale patterns that are most common during particular phases of ENSO. Distinctly El Niño patterns are charactized by a broad offshore upper level trough with relatively moist low-level onshore flow. Distinctly La Niña patterns display a deep southwest-northeast oriented trough over the western United States with drier low-level onshore flow. Analysis of 250-hPa potential vorticity suggests that the La Niña (El Niño) patterns are linked to anticyclonic (cyclonic) baroclinic wave breaking events. This agrees with a recent line of investigations which find anticyclonic (cyclonic) wave breaking in the Pacific North American region to be more common during La Niña (El Niño) events. Knowledge of interannual variability in winter precipitation event characteristics can improve seasonal runoff forecasts and advance understanding of interdecadal variability and the effects of climate change in the western United States.

  20. Stratospheric geoengineering impacts on El Niño/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Gabriel, C. J.; Robock, A.

    2015-10-01

    To examine the impact of proposed stratospheric geoengineering schemes on the amplitude and frequency of El Niño/Southern Oscillation (ENSO) variations we examine climate model simulations from the Geoengineering Model Intercomparison Project (GeoMIP) G1-G4 experiments. Here we compare tropical Pacific behavior under anthropogenic global warming (AGW) using several scenarios: an instantaneous quadrupling of the atmosphere's CO2 concentration, a 1 % annual increase in CO2 concentration, and the representative concentration pathway resulting in 4.5 W m-2 radiative forcing at the end of the 21st century, the Representative Concentration Pathway 4.5 scenario, with that under G1-G4 and under historical model simulations. Climate models under AGW project relatively uniform warming across the tropical Pacific over the next several decades. We find no statistically significant change in ENSO frequency or amplitude under stratospheric geoengineering as compared with those that would occur under ongoing AGW, although the relative brevity of the G1-G4 simulations may have limited detectability of such changes. We also find that the amplitude and frequency of ENSO events do not vary significantly under either AGW scenarios or G1-G4 from the variability found within historical simulations or observations going back to the mid-19th century. Finally, while warming of the Niño3.4 region in the tropical Pacific is fully offset in G1 and G2 during the 40-year simulations, the region continues to warm significantly in G3 and G4, which both start from a present-day climate.

  1. Influence of El Niño Southern Oscillation on global hydropower production

    NASA Astrophysics Data System (ADS)

    Ng, Jia Yi; Turner, Sean; Galelli, Stefano

    2016-04-01

    Hydropower contributes significantly to meeting the world's energy demand, accounting for at least 16% of total electrical output. Its role as a mature and cost competitive renewable energy source is expected to become increasingly important as the world transits to a low-carbon economy. A key component of hydropower production is runoff, which is highly dependent on precipitation and other climate variables. As such, it becomes critical to understand how the drivers of climate variability impact hydropower production. One globally-important driver is the El Niño Southern Oscillation (ENSO). While it is known that ENSO influences hydrological processes, the potential value of its associated teleconnection in design related tasks has yet to be explored at the global scale. Our work seeks to characterize the impact of ENSO on global hydropower production so as to quantify the potential for increased production brought about by incorporating climate information within reservoir operating models. We study over 1,500 hydropower reservoirs - representing more than half the world's hydropower capacity. A historical monthly reservoir inflow time series is assigned to each reservoir from a 0.5 degree gridded global runoff dataset. Reservoir operating rules are designed using stochastic dynamic programming, and storage dynamics are simulated to assess performance under the climate conditions of the 20th century. Results show that hydropower reservoirs in the United States, Brazil, Argentina, Australia, and Eastern China are strongly influenced by ENSO episodes. Statistically significant lag correlations between ENSO indicators and hydropower production demonstrate predictive skill with lead times up to several months. Our work highlights the potential for using these indicators to increase the contribution of existing hydropower plants to global energy supplies.

  2. Annual flood sensitivities to El Niño-Southern Oscillation at the global scale

    USGS Publications Warehouse

    Ward, Philip J.; Eisner, S.; Flörke, M.; Dettinger, Michael D.; Kummu, M.

    2013-01-01

    Floods are amongst the most dangerous natural hazards in terms of economic damage. Whilst a growing number of studies have examined how river floods are influenced by climate change, the role of natural modes of interannual climate variability remains poorly understood. We present the first global assessment of the influence of El Niño–Southern Oscillation (ENSO) on annual river floods, defined here as the peak daily discharge in a given year. The analysis was carried out by simulating daily gridded discharges using the WaterGAP model (Water – a Global Assessment and Prognosis), and examining statistical relationships between these discharges and ENSO indices. We found that, over the period 1958–2000, ENSO exerted a significant influence on annual floods in river basins covering over a third of the world's land surface, and that its influence on annual floods has been much greater than its influence on average flows. We show that there are more areas in which annual floods intensify with La Niña and decline with El Niño than vice versa. However, we also found that in many regions the strength of the relationships between ENSO and annual floods have been non-stationary, with either strengthening or weakening trends during the study period. We discuss the implications of these findings for science and management. Given the strong relationships between ENSO and annual floods, we suggest that more research is needed to assess relationships between ENSO and flood impacts (e.g. loss of lives or economic damage). Moreover, we suggest that in those regions where useful relationships exist, this information could be combined with ongoing advances in ENSO prediction research, in order to provide year-to-year probabilistic flood risk forecasts.

  3. Simple stochastic dynamical models capturing the statistical diversity of El Niño Southern Oscillation.

    PubMed

    Chen, Nan; Majda, Andrew J

    2017-02-14

    The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean-atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model.

  4. Response of the terrestrial carbon cycle to the El Niño-Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Qian, Haifeng; Joseph, Renu; Zeng, Ning

    2008-09-01

    Land plays a dominant role in the interannual variability of the global carbon cycle. The canonical warming and drying of the terrestrial tropics observed during El Niño events calls for the study of the role of precipitation and temperature on carbon cycle variability. Here we use a dynamic vegetation and terrestrial carbon model vegetation-global-atmosphere-soil (VEGAS) to investigate the response of terrestrial carbon cycle to El Niño-Southern Oscillation (ENSO) for the period 1980-2004. The simulated global total land-atmosphere flux (Fta) by VEGAS agrees well with the atmospheric CO2 inversion modelling results on ENSO timescales and is dominated by the tropics. Analysis of composites of terrestrial responses and climate factors during ENSO events and lead-lag correlations have identified that in the tropics, anomalous precipitation lags ENSO by 1 month and temperature by 5-6 months, while simulated soil moisture lags by 5 months. Warmer and drier conditions there cause suppression of Net Primary Production (NPP) and enhancement of Heteotrophic Respiration (Rh) simultaneously, resulting in the lagging of tropical Fta by 6 months. Sensitivity simulations reveal that 2/3 of Fta change comes from NPP and 1/3 from Rh. In VEGAS, fire burning accounts for about 25% of total Fta anomalies. Precipitation during ENSO events contributes 56% of variation of Fta; temperature accounts for 44%, which includes 25% from the enhancement of Rh and 7% from the increase of the vegetation respiration. We identify the remaining 12% variation of Fta to be from an indirect effect of temperature through its effect on soil wetness, which in turn affects NPP. Such insight into the direct and indirect effects of climatic factors highlights the critical role of soil moisture in ecosystem and carbon cycle-a poorly constrained factor.

  5. El Niño-Southern Oscillation Link to South Florida Hydrology and Water Management Applications

    NASA Astrophysics Data System (ADS)

    Abtew, Wossenu; Trimble, Paul

    2010-12-01

    This study evaluates the relationships between El Niño-Southern Oscillation (ENSO) indices and South Florida hydrology and proposes applications to water management decision making. ENSO relations to the Upper Kissimmee Basin rainfall, watershed for Lake Okeechobee, and cumulative sea surface temperature (SST) anomalies at Niño 3.4 were evaluated. Additionally, relationship between ENSO and Lake Okeechobee inflows, Arbuckle Creek and Josephine Creek flows were analyzed. Hydrology of the northern watersheds of the South Florida water management system is linked to ENSO events. Dry season (November-May) rainfall and flows are higher than average during El Niño years and lower during La Niña years, at the 90% confidence level or higher. The relationship is strongest when the ENSO event is strong as shown with analysis of correlation. ENSO prediction has more certainty than hydrologic prediction for a region. Identifying ENSO and hydrologic relationships can aid water management decision making by providing a lead-time of months to mitigate drought or flood impacts. The ENSO tracking method, which was published in a previous study, is presented to track ENSO strength and event type to provide supplemental outlook on dry season rainfall for Lake Okeechobee operations. Lake Okeechobee, which is the main storage in the South Florida water management system, is regulated by a schedule with a limited band of stage fluctuation because of susceptibility of the Herbert Hoover Dike to wave erosion and seepage at high stages. An early decision making approach to storage management with respect to ENSO related hydrology, is presented based on tracking the strength of ENSO events.

  6. Simple stochastic dynamical models capturing the statistical diversity of El Niño Southern Oscillation

    PubMed Central

    Chen, Nan; Majda, Andrew J.

    2017-01-01

    The El Niño Southern Oscillation (ENSO) has significant impact on global climate and seasonal prediction. A simple modeling framework is developed here that automatically captures the statistical diversity of ENSO. First, a stochastic parameterization of the wind bursts including both westerly and easterly winds is coupled to a simple ocean–atmosphere model that is otherwise deterministic, linear, and stable. Second, a simple nonlinear zonal advection with no ad hoc parameterization of the background sea-surface temperature (SST) gradient and a mean easterly trade wind anomaly representing the multidecadal acceleration of the trade wind are both incorporated into the coupled model that enables anomalous warm SST in the central Pacific. Then a three-state stochastic Markov jump process is used to drive the wind burst activity that depends on the strength of the western Pacific warm pool in a simple and effective fashion. It allows the coupled model to simulate the quasi-regular moderate traditional El Niño, the super El Niño, and the central Pacific (CP) El Niño as well as the La Niña with realistic features. In addition to the anomalous SST, the Walker circulation anomalies at different ENSO phases all resemble those in nature. In particular, the coupled model succeeds in reproducing the observed episode during the 1990s, where a series of 5-y CP El Niños is followed by a super El Niño and then a La Niña. Importantly, both the variance and the non-Gaussian statistical features in different Niño regions spanning from the western to the eastern Pacific are captured by the coupled model. PMID:28137886

  7. Strong influence of El Niño Southern Oscillation on flood risk around the world

    USGS Publications Warehouse

    Ward, Philip J.; Jongman, B; Kummu, M.; Dettinger, Mike; Sperna Weiland, F.C; Winsemius, H.C

    2014-01-01

    El Niño Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability and has a strong influence on climate over large parts of the world. In turn, it strongly influences many natural hazards (such as hurricanes and droughts) and their resulting socioeconomic impacts, including economic damage and loss of life. However, although ENSO is known to influence hydrology in many regions of the world, little is known about its influence on the socioeconomic impacts of floods (i.e., flood risk). To address this, we developed a modeling framework to assess ENSO’s influence on flood risk at the global scale, expressed in terms of affected population and gross domestic product and economic damages. We show that ENSO exerts strong and widespread influences on both flood hazard and risk. Reliable anomalies of flood risk exist during El Niño or La Niña years, or both, in basins spanning almost half (44%) of Earth’s land surface. Our results show that climate variability, especially from ENSO, should be incorporated into disaster-risk analyses and policies. Because ENSO has some predictive skill with lead times of several seasons, the findings suggest the possibility to develop probabilistic flood-risk projections, which could be used for improved disaster planning. The findings are also relevant in the context of climate change. If the frequency and/or magnitude of ENSO events were to change in the future, this finding could imply changes in flood-risk variations across almost half of the world’s terrestrial regions.

  8. El Niño Southern Oscillation during the Medieval Climate Anomaly

    NASA Astrophysics Data System (ADS)

    Rustic, G. T.; Koutavas, A.; Linsley, B. K.

    2013-12-01

    The dynamic response of the El Niño Southern Oscillation (ENSO) to varying solar and volcanic forcing is thought to be an important influence on climate during the Medieval Climate Anomaly (MCA), but proxy evidence of ENSO variability during the MCA is sparse. Insight into past oceanographic variability can be provided through the analysis of δ18O from individual foraminifera found in deep-sea sediments. This approach is applied here to a high-resolution (>10cm/ky) multi-core from the Eastern Tropical Pacific (MC42) near the Galapagos Islands (01° 15.58'S, 89° 41.13'W, 615m depth). At this location, sea surface variability is strongly influenced by ENSO and the seasonal cycle. δ18O from individual mixed-layer dwelling Globigerinoides ruber was analyzed at multiple time intervals throughout the instrumental era and the MCA (900-1350CE). δ18O from instrumental-era samples captured the variability and full range of oceanographic conditions predicted by δ18O calculated from sea surface temperature and salinity reanalysis data, including peak El Niño and La Niña conditions. δ18O from individual foraminifera from MCA samples display variability reductions from 27% to 33% compared to late twentieth century values, as well as reduced range and fewer δ18O outliers, suggesting weaker ENSO activity. This reduction in variability is accompanied by an increase in mean δ18O and is consistent with existing paleoclimate reconstructions and the modeled response of the tropical Pacific to increased solar forcing during the MCA. Additional data other pre-instrumental time intervals will be presented to characterize ENSO dynamics during the past millennium.

  9. Investigations of the middle atmospheric thermal structure and oscillations over sub-tropical regions in the Northern and Southern Hemispheres

    NASA Astrophysics Data System (ADS)

    Sharma, Som; Kumar, Prashant; Jethva, Chintan; Vaishnav, Rajesh; Bencherif, Hassan

    2016-08-01

    The temperature retrieved from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) onboard Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite during January 2002 to September 2015 are used in this study to delineate the differences of middle atmospheric thermal structure in the Northern Hemisphere (NH) and Southern Hemisphere (SH). Two stations namely Mt. Abu (24.59°N, 72.70°E) in NH and Reunion Island (21.11°S, 55.53°E) in SH are chosen over sub-tropical regions. Temperature climatology from SABER observations suggests that stratopause is warmer, and upper mesosphere is cooler in NH as compared to SH. Three atmospheric models are used to understand the monthly thermal structure differences for different altitudes. Moreover, semi-annual, annual and quasi-biennial oscillations are studied using Lomb Scargle Periodogram and Wavelet transform techniques. Over NH, summer and winter season are warmer (~4 K) and cooler (~3 K) respectively in stratosphere as compared to SH. It is important to note here that Mt. Abu temperature is warmer (~9 K) than Reunion Island in winter but in summer season Mt. Abu temperature is cooler in upper mesosphere and above mesosphere NH shows warming. Results show that annual oscillations are dominated in both hemisphere as compared to semi-annual and quasi-biennial oscillations. In upper mesosphere, strength of annual oscillations is substantial in NH, while semi-annual oscillations are stronger in SH. Wavelet analyses found that annual oscillations are significant in NH near mesopause, while semi-annual oscillations are strengthening in SH.

  10. Decadal variability of drought conditions over the southern part of Europe based on Principal Oscillation Pattern Analysis

    NASA Astrophysics Data System (ADS)

    Ionita-Scholz, Monica; Tallaksen, Lena M.; Scholz, Patrick

    2017-04-01

    This study introduces a novel method of estimating the decay time, mean period and forcing statistics of drought conditions over large spatial domains, demonstrated here for southern part of Europe (10°E - 40°E, 35°N - 50°N). It uses a two-dimensional stochastically forced damped linear oscillator model with the model parameters estimated from a Principal Oscillation Pattern (POP) analysis and associated observed power spectra. POP is a diagnostic technique that aims to derive the space-time characteristics of a data set objectively. This analysis is performed on an extended observational time series of 114 years (1902 - 2015) of the Standardized Precipitation Evapotranspiration Index for an accumulation period of 12 months (SPEI12), based on the Climate Research Unit (CRU TS v. 3.24) data set. The POP analysis reveals four exceptionally stable modes of variability, which together explain more than 62% of the total explained variance. The most stable POP mode, which explains 16.3% of the total explained variance, is characterized by a period of oscillation of 14 years and a decay time of 31 years. The real part of POP1 is characterized by a monopole-like structure with the highest loadings over Portugal, western part of Spain and Turkey. The second stable mode, which explains 15.9% of the total explained variance, is characterized by a period of oscillation of 20 years and a decay time of 26.4 years. The spatial structure of the real part of POP2 has a dipole-like structure with the highest positive loadings over France, southern Germany and Romania and negative loadings over southern part of Spain. The third POP mode, in terms of stability, explains 14.0% of the total variance and is characterized by a period of oscillation of 33 years and a decay time of 43.5 years. The real part of POP3 is characterized by negative loadings over the eastern part of Europe and positive loadings over Turkey. The fourth stable POP mode, explaining 15.5% of the total variance

  11. Extended-range forecast of spring rainfall in southern China based on the Madden-Julian Oscillation

    NASA Astrophysics Data System (ADS)

    Li, Wenkai; Hsu, Pang-chi; He, Jinhai; Zhu, Zhiwei; Zhang, Wenjun

    2016-06-01

    Spring (March-May) rainfall after a dry period in winter has a substantial impact on agriculture and water management in populous southern China. The occurrence of low-frequency spring rainfall anomalies has been linked with the tropical Madden-Julian Oscillation (MJO) through its modulation of large-scale circulation and moisture supply over southern China. Using the spatial and temporal information of the MJO as a predictor, an empirical model for extended-range forecasting of spring rainfall in southern China was constructed. We first obtained the coupled patterns between the preceding MJO evolutions (real-time multivariate MJO index) and the succeeding rainfall variability in southern China based on singular value decomposition analysis. Then, a prediction was carried out by projecting the predictor onto the spatiotemporal coupled patterns. Useful skill, in terms of the temporal correlation coefficient (TCC) between the predicted and observed rainfall over southern China, persisted up to a forecast lead-time of six pentads. The forecast amplitude bias in terms of root-mean-square error was around 1.0 standard deviation. Also, the forecast skill was highly dependent on the strength of the MJO signal. During active MJO periods, the TCC skill was around twofold larger than that during weak MJO periods. The current statistical model shows encouraging ability, but additional work is required to improve its forecasting skill.

  12. Data Assimilation Into a Coupled Ocean Atmosphere Model: Application to the 1997-1998 El Nino

    NASA Technical Reports Server (NTRS)

    Lee, Tong

    1999-01-01

    As part of JPL's ocean data assimilation effort to study ocean circulation and seasonal-interannual climate variability, sea level anomaly observed by TOPEX altimeter, together with sea surface temperature and wind stress data, are assimilated into a simple coupled ocean atmosphere model of the tropical Pacific. Model-data consistency is examined. Impact of the assimilation (as initialization) on El Nino Southern Oscillation (ENSO) forecasts is evaluated. The coupled model consists of a shallow water component with two baroclinic modes, an Ekman shear layer, a simplified mixed-layer temperature equation, and a statistical atmosphere based on dominant correlations between historical surface temperature and wind stress anomaly data. The adjoins method is used to fit the coupled model to the data over various six-month periods from late 1996 to early 1998 by optimally adjusting the initial state, model parameters, and basis functions of the statistical atmosphere. On average, the coupled model can be fitted to the data to approximately within the data and representation errors (5 cm, 0.5 C, and 10 sq m/sq m for sea level, surface temperature, and pseudo wind stress anomalies, respectively). The estimated fields resemble observed spatio-temporal structure reasonably well. Hindcasts/forecasts of the 1997/1998 El Nino initialized from forced estimated ocean states and parameters are much more realistic than those simply initialized from ocean states (see figure below). In particular, the ability of the model to produce significant warming beyond the initial state is dramatically improved. Parameter estimation, which compensates for some model errors, is found to be important to obtaining better fits of the model to data and to improving forecasts.

  13. Data Assimilation Into a Coupled Ocean Atmosphere Model: Application to the 1997-1998 El Nino

    NASA Technical Reports Server (NTRS)

    Lee, Tong

    1999-01-01

    As part of JPL's ocean data assimilation effort to study ocean circulation and seasonal-interannual climate variability, sea level anomaly observed by TOPEX altimeter, together with sea surface temperature and wind stress data, are assimilated into a simple coupled ocean atmosphere model of the tropical Pacific. Model-data consistency is examined. Impact of the assimilation (as initialization) on El Nino Southern Oscillation (ENSO) forecasts is evaluated. The coupled model consists of a shallow water component with two baroclinic modes, an Ekman shear layer, a simplified mixed-layer temperature equation, and a statistical atmosphere based on dominant correlations between historical surface temperature and wind stress anomaly data. The adjoins method is used to fit the coupled model to the data over various six-month periods from late 1996 to early 1998 by optimally adjusting the initial state, model parameters, and basis functions of the statistical atmosphere. On average, the coupled model can be fitted to the data to approximately within the data and representation errors (5 cm, 0.5 C, and 10 sq m/sq m for sea level, surface temperature, and pseudo wind stress anomalies, respectively). The estimated fields resemble observed spatio-temporal structure reasonably well. Hindcasts/forecasts of the 1997/1998 El Nino initialized from forced estimated ocean states and parameters are much more realistic than those simply initialized from ocean states (see figure below). In particular, the ability of the model to produce significant warming beyond the initial state is dramatically improved. Parameter estimation, which compensates for some model errors, is found to be important to obtaining better fits of the model to data and to improving forecasts.

  14. El Niño Southern Oscillation Influences River Bank Erosion on the Lower Mekong River

    NASA Astrophysics Data System (ADS)

    Darby, S. E.; Trieu, H. Q.; Carling, P. A.

    2009-12-01

    . However, both simulated time series exhibit quasi-periodic oscillations about these means. The Mekong’s flow regime is controlled by variations in meltwater regime, the intensity of the SE Asian monsoon, and the frequency and intensity of tropical cyclones that penetrate inland from the South China Sea. Since melt contributes only to (non-erosive) base flows, variability in glacier and snow melt contributions from Himalayan source areas are unlikely to significantly impact inter-annual variations in river bank erosion. However, inter-annual variability in the SE Asian monsoon and tropical cyclone dynamics may both be related, albeit in a complex manner, to the El Niño Southern Oscillation (ENSO). Cross-wavelet transform and wavelet coherence analyses indicate statistically significant (at 95% limit) coherence between ENSO and simulated river bank erosion, but at both sites only since about 1980. During this recent period the ENSO and fluvial erosion time series are in anti-phase; that is ENSO cold phases are associated with enhanced rates of river bank erosion. This is as expected, since ENSO cold phases are associated with earlier onset and enhanced intensity of the monsoon, while the number of intense tropical storm systems making landfall over Vietnam and moving across the Lower Mekong Basin is also higher.

  15. Mechanisms of the Indian Ocean Dipole influence on El Niño/Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Izumo, Takeshi; Vialard, Jérome; Lengaigne, Matthieu; Jourdain, Nicolas; Dayan, Hugo; Suresh, Iyyappan

    2017-04-01

    Despite the tremendous socio-economic and environmental impacts of the El Niño-Southern Oscillation (ENSO), its forecasts at lead times longer than a few months remain challenging, as recently evidenced by the unexpected 2014-2015 El Niño sequence. Recent studies have suggested that negative (postive) Indian Ocean Dipole events may favour the development of El Niño (La Niña) events peaking one year later, hence possibly improving ENSO predictability and explaining ENSO biennal variability. These studies essentially show that this IOD influence on ENSO evolution is indeed robust in observations and most CMIP climate models. Accounting for the IOD influence in linear ENSO forecasts based on the tropical Pacific recharge-discharge process increases the explained variance by 10-30% at 14 months lead. This IOD influence on the ENSO forecast skill appears stronger than that of the Indian Ocean Basin-wide warming/cooling or ENSO itself. However, its underlying mechanisms are still debated. Here we use dedicated experiments from atmospheric and oceanic numerical models, and a conceptual approach based on the Pacific ocean linear response to a wind pulse, to investigate the mechanisms by which the IOD influences ENSO evolution. Our results suggest that: (1) the atmospheric bridge (through atmospheric teleconnections) dominates the oceanic bridge (through the Indonesian throughflow); (2) the temporal change of west Pacific zonal wind stress over a six month period (e.g. related to IOD demise) matters as much as the wind seasonal anomaly for the dynamical response of the equatorial Pacific; (3) the IOD eastern pole, and its demise, is the main driver of this wind change. The abrupt demise of the IOD eastern pole favours a fast temporal change of the zonal wind in the western Pacific between fall and winter-spring, thereby favouring ENSO phase transition. Revisiting statistical approaches by using relative sea surface temperature (i.e. with tropical mean removed) confirms

  16. Geologic events coupled with Pleistocene climatic oscillations drove genetic variation of Omei treefrog (Rhacophorus omeimontis) in southern China.

    PubMed

    Li, Jun; Zhao, Mian; Wei, Shichao; Luo, Zhenhua; Wu, Hua

    2015-12-21

    Pleistocene climatic oscillations and historical geological events may both influence current patterns of genetic variation, and the species in southern China that faced unique climatic and topographical events have complex evolutionary histories. However, the relative contributions of climatic oscillations and geographical events to the genetic variation of these species remain undetermined. To investigate patterns of genetic variation and to test the hypotheses about the factors that shaped the distribution of this genetic variation in species of southern China, mitochondrial genes (cytochrome b and NADH dehydrogenase subunit 2) and nine microsatellite loci of the Omei tree frog (Rhacophorus omeimontis) were amplified in this study. The genetic diversity in the populations of R. omeimontis was high. The phylogenetic trees reconstructed from the mitochondrial DNA (mtDNA) haplotypes and the Bayesian genetic clustering analysis based on microsatellite data both revealed that all populations were divided into three lineages (SC, HG and YN). The two most recent splitting events among the lineages coincided with recent geological events (including the intense uplift of the Qinghai-Tibet Plateau, QTP and the subsequent movements of the Yun-Gui Plateau, YGP) and the Pleistocene glaciations. Significant expansion signals were not detected in mismatch analyses or neutrality tests. And the effective population size of each lineage was stable during the Pleistocene. Based on the results of this study, complex geological events (the recent dramatic uplift of the QTP and the subsequent movements of the YGP) and the Pleistocene glaciations were apparent drivers of the rapid divergence of the R. omeimontis lineages. Each diverged lineages survived in situ with limited gene exchanges, and the stable demographics of lineages indicate that the Pleistocene climatic oscillations were inconsequential for this species. The analysis of genetic variation in populations of R. omeimontis

  17. Austral summer Southern Africa precipitation extremes forced by the El Niño-Southern oscillation and the subtropical Indian Ocean dipole

    NASA Astrophysics Data System (ADS)

    Hoell, Andrew; Cheng, Linyin

    2017-07-01

    Southern Africa, defined here as the African continent south of 15°S latitude, is prone to seasonal precipitation extremes during December-March that have profound effects on large populations of people. The intensity of summertime precipitation extremes can be remarkable, with wet seasons experiencing up to a doubling of the seasonal average precipitation. Recognizing the importance of understanding the causes of Southern Africa precipitation extremes for the purpose of improved early warning, an 80-member ensemble of atmospheric model simulations forced by observed time-varying boundary conditions during 1979-2016 is used to examine the mechanisms by which December-March precipitation extremes are delivered to Southern Africa and whether the El Niño-Southern Oscillation (ENSO) and the Subtropical Indian Ocean Dipole (SIOD) modify the probabilities of extreme seasonal precipitation occurrences. The model simulations reveal that the synchronous ENSO and SIOD phasing conditions the probability of December-March extreme precipitation occurrences. The probability of extreme wet seasons is greatly increased by La Niña, especially so when combined with a positive SIOD, and greatly decreased by El Niño regardless of SIOD phasing. By contrast, the probability of extreme dry seasons is increased by El Niño and is decreased by La Niña. The mechanisms by which extreme precipitation are delivered are the same regardless of ENSO and SIOD phase. Extreme wet seasons are a result of an anomalous lower tropospheric cyclone over Southern Africa that increases convergence and moisture fluxes into the region while extreme dry seasons are a result of an anomalous lower tropospheric anticyclone that decreases convergence and moisture fluxes into the region.

  18. Land surface anomaly simulations and predictions with a climate model: an El Niño Southern Oscillation case study.

    PubMed

    Putt, Debbie; Haines, Keith; Gurney, Robert; Liu, Chunlei

    2009-03-13

    The ability of climate models to reproduce and predict land surface anomalies is an important but little-studied topic. In this study, an atmosphere and ocean assimilation scheme is used to determine whether HadCM3 can reproduce and predict snow water equivalent and soil moisture during the 1997-1998 El Niño Southern Oscillation event. Soil moisture is reproduced more successfully, though both snow and soil moisture show some predictability at 1- and 4-month lead times. This result suggests that land surface anomalies may be reasonably well initialized for climate model predictions and hydrological applications using atmospheric assimilation methods over a period of time.

  19. Effects of the 1982-83 El Niño – Southern Oscillation on Pacific Ocean bird populations

    USGS Publications Warehouse

    Ainley, David G.; Carter, H.R.; Anderson, Daniel W.; Briggs, Kenneth T.; Coulter, Malcom C.; Cruz, F.; Cruz, J.B.; Valle, C.A.; Fefer, S.I.; Hatch, Scott A.; Schreiber, Elizabeth Anne; Schreiber, Ralph W.; Smith, N.G.; Ouellet, Henri

    1988-01-01

    Seabird reproductive success, population size, and movements in the Pacific region responded dramatically to the 1982-83 El Niño – Southern Oscillation (ENSO). At sites within the North and South Pacific Gyres, the onset of seabird responses tracked oceanographic changes related to ENSO; to the north of the gyres, responses were delayed 1 yr. Reproductive failures and high adult mortality were detected at all sites investigated. Post-ENSO, the return to “normal” nesting patterns depended on species and locality. The 1982-83 ENSO revealed a dimension to the variability in seabird reproductive biology only now appreciated by ornithologists.

  20. Interannual Atmospheric Oscillations and Their Gravitational Effects

    NASA Technical Reports Server (NTRS)

    Chao, Benjamin F.; Au, A. Y.

    2000-01-01

    Past studies have examined the effects of the interannual atmospheric oscillations (IAO), or often called teleconnection patterns, on the Earth's rotation, such as El Nino/Southern Oscillation (ENSO), the quasi-biennial oscillation, and to a lesser extent the North Atlantic Oscillation (NAO). The present study focuses on IAO's effects on the gravitational field and geocenter; the purpose is to be able to identify and isolate the contributions of each prominent IAO in relation to the total contribution of the atmosphere, in terms of their magnitudes, their geographical patterns, and their interannual time history. We use the 40-year NCEP reanalysis of the monthly, global atmospheric surface pressure field as our basic data set. The method we apply to isolate the IAOs is the empirical orthogonal function (EOF) decomposition which is widely used in meteorological investigations. We do the EOF analysis first on IAOs' seasonal signals (by "collapsing" the 40-year series into 12 mean-months for each grid point) and obtain estimates for their respective contributions. Then we remove these seasonal signals from the data to focus on the (broad-band) interannual EOFs. We examine ENSO, NAO, North Pacific Oscillation, and other less prominent IAOs that can be identified from our data set, and compute their respective contributions to the variation of global gravitational field and geocenter motion. Finally, we compare the results with the available observational data, and discuss the implications w.r.t. the upcoming space missions such as GRACE.

  1. Review article. Studying climate effects on ecology through the use of climate indices: the North Atlantic Oscillation, El Niño Southern Oscillation and beyond.

    PubMed Central

    Stenseth, Nils Chr; Ottersen, Geir; Hurrell, James W; Mysterud, Atle; Lima, Mauricio; Chan, Kung-Sik; Yoccoz, Nigel G; Adlandsvik, Bjørn

    2003-01-01

    Whereas the El Niño Southern Oscillation (ENSO) affects weather and climate variability worldwide, the North Atlantic Oscillation (NAO) represents the dominant climate pattern in the North Atlantic region. Both climate systems have been demonstrated to considerably influence ecological processes. Several other large-scale climate patterns also exist. Although less well known outside the field of climatology, these patterns are also likely to be of ecological interest. We provide an overview of these climate patterns within the context of the ecological effects of climate variability. The application of climate indices by definition reduces complex space and time variability into simple measures, 'packages of weather'. The disadvantages of using global climate indices are all related to the fact that another level of problems are added to the ecology-climate interface, namely the link between global climate indices and local climate. We identify issues related to: (i) spatial variation; (ii) seasonality; (iii) non-stationarity; (iv) nonlinearity; and (v) lack of correlation in the relationship between global and local climate. The main advantages of using global climate indices are: (i) biological effects may be related more strongly to global indices than to any single local climate variable; (ii) it helps to avoid problems of model selection; (iii) it opens the possibility for ecologists to make predictions; and (iv) they are typically readily available on Internet. PMID:14561270

  2. Combined effects of the Pacific Decadal Oscillation and El Niño-Southern Oscillation on Global Land Dry–Wet Changes

    PubMed Central

    Wang, Shanshan; Huang, Jianping; He, Yongli; Guan, Yuping

    2014-01-01

    The effects of natural variability, especially El Niño-Southern Oscillation (ENSO) effects, have been the focus of several recent studies on the change of drought patterns with climate change. The interannual relationship between ENSO and the global climate is not stationary and can be modulated by the Pacific Decadal Oscillation (PDO). However, the global land distribution of the dry–wet changes associated with the combination of ENSO and the PDO remains unclear. In the present study, this is investigated using a revised Palmer Drought Severity Index dataset (sc_PDSI_pm). We find that the effect of ENSO on dry–wet changes varies with the PDO phase. When in phase with the PDO, ENSO-induced dry–wet changes are magnified with respect to the canonical pattern. When out of phase, these dry–wet variations weaken or even disappear. This remarkable contrast in ENSO's influence between the two phases of the PDO highlights exciting new avenues for obtaining improved global climate predictions. In recent decades, the PDO has turned negative with more La Niña events, implying more rain and flooding over land. La Niña-induced wet areas become wetter and the dry areas become drier and smaller due to the effects of the cold PDO phase. PMID:25323549

  3. Combined effects of the Pacific Decadal Oscillation and El Niño-Southern Oscillation on global land dry-wet changes.

    PubMed

    Wang, Shanshan; Huang, Jianping; He, Yongli; Guan, Yuping

    2014-10-17

    The effects of natural variability, especially El Niño-Southern Oscillation (ENSO) effects, have been the focus of several recent studies on the change of drought patterns with climate change. The interannual relationship between ENSO and the global climate is not stationary and can be modulated by the Pacific Decadal Oscillation (PDO). However, the global land distribution of the dry-wet changes associated with the combination of ENSO and the PDO remains unclear. In the present study, this is investigated using a revised Palmer Drought Severity Index dataset (sc_PDSI_pm). We find that the effect of ENSO on dry-wet changes varies with the PDO phase. When in phase with the PDO, ENSO-induced dry-wet changes are magnified with respect to the canonical pattern. When out of phase, these dry-wet variations weaken or even disappear. This remarkable contrast in ENSO's influence between the two phases of the PDO highlights exciting new avenues for obtaining improved global climate predictions. In recent decades, the PDO has turned negative with more La Niña events, implying more rain and flooding over land. La Niña-induced wet areas become wetter and the dry areas become drier and smaller due to the effects of the cold PDO phase.

  4. Review article. Studying climate effects on ecology through the use of climate indices: the North Atlantic Oscillation, El Niño Southern Oscillation and beyond.

    PubMed

    Stenseth, Nils Chr; Ottersen, Geir; Hurrell, James W; Mysterud, Atle; Lima, Mauricio; Chan, Kung-Sik; Yoccoz, Nigel G; Adlandsvik, Bjørn

    2003-10-22

    Whereas the El Niño Southern Oscillation (ENSO) affects weather and climate variability worldwide, the North Atlantic Oscillation (NAO) represents the dominant climate pattern in the North Atlantic region. Both climate systems have been demonstrated to considerably influence ecological processes. Several other large-scale climate patterns also exist. Although less well known outside the field of climatology, these patterns are also likely to be of ecological interest. We provide an overview of these climate patterns within the context of the ecological effects of climate variability. The application of climate indices by definition reduces complex space and time variability into simple measures, 'packages of weather'. The disadvantages of using global climate indices are all related to the fact that another level of problems are added to the ecology-climate interface, namely the link between global climate indices and local climate. We identify issues related to: (i) spatial variation; (ii) seasonality; (iii) non-stationarity; (iv) nonlinearity; and (v) lack of correlation in the relationship between global and local climate. The main advantages of using global climate indices are: (i) biological effects may be related more strongly to global indices than to any single local climate variable; (ii) it helps to avoid problems of model selection; (iii) it opens the possibility for ecologists to make predictions; and (iv) they are typically readily available on Internet.

  5. El Nino's Family Tree (Invited)

    NASA Astrophysics Data System (ADS)

    Philander, S. G.

    2013-12-01

    Fluctuations in tropical Pacific rainfall and sea surface temperature (SST) patterns involve different processes on different timescales, but nonetheless have certain features (traits) in common so that all can be viewed as members of the same family. Best-known are the children El Niño and La Niña who, in their performance of the Southern Oscillation, move warm surface waters adiabatically back and forth across the Pacific. They and their nephews and nieces in the Atlantic and Indian Ocean all depend on favorable background conditions, especially a suitable depth for the thermocline whose tilt they oscillate to produce SST changes. The parents El Padre and La Madre are in control of that depth and invoke diabatic processes to change it gradually over the course of decades, at times making it so deep that El Niño becomes permanent. This is the spontaneous, natural branch of the family. Another branch responds to external forcing (externally imposed variations in sunlight) and has as members the cycles of the seasons, of obliquity, and of the precession of the equinoxes. These cousins, aunts and uncles of El Niño are protagonists in the drama of the recurrent Ice Ages.

  6. The impact of tropical intraseasonal oscillation on the summer rainfall increase over southern China around 1992/1993

    NASA Astrophysics Data System (ADS)

    Wang, Jiabao; Wen, Zhiping; Wu, Renguang; Lin, Ailan

    2017-09-01

    A pronounced summer rainfall increase over southern China occurred around 1992/1993. In the present study, the impact of the boreal summer intraseasonal oscillation (BSISO) on this decadal increase is investigated through diagnostic analysis. It is found that the BSISO-induced rainfall increase accounts for approximately 17.4% of the observed decadal rainfall increase, with a primary part coming from changes in the rainfall pattern associated with phases 3-5 of the BSISO. A further analysis reveals that changes in rainfall pattern over southern China are mainly ascribed to changes in spatial structure of anomalous convection associated with interdecadal change in BSISO tracks. Apart from significant influence of changes in BSISO tracks, changes in the frequency of individual active BSISO phases also have considerable influence on the interdecadal change in summer rainfall over southern China. Based on our analysis, the increase in absolute and relative frequency of occurrence of phases 1 and 8, coupled with their corresponding rainfall pattern, makes a positive contribution to the increase in southern China summer rainfall. The interdecadal change in the BSISO tracks and the frequency of active BSISO phases is likely related to coherent changes in atmospheric circulation and sea surface temperature over the Indian Ocean and the western Pacific.

  7. The impact of tropical intraseasonal oscillation on the summer rainfall increase over southern China around 1992/1993

    NASA Astrophysics Data System (ADS)

    Wang, Jiabao; Wen, Zhiping; Wu, Renguang; Lin, Ailan

    2016-10-01

    A pronounced summer rainfall increase over southern China occurred around 1992/1993. In the present study, the impact of the boreal summer intraseasonal oscillation (BSISO) on this decadal increase is investigated through diagnostic analysis. It is found that the BSISO-induced rainfall increase accounts for approximately 17.4% of the observed decadal rainfall increase, with a primary part coming from changes in the rainfall pattern associated with phases 3-5 of the BSISO. A further analysis reveals that changes in rainfall pattern over southern China are mainly ascribed to changes in spatial structure of anomalous convection associated with interdecadal change in BSISO tracks. Apart from significant influence of changes in BSISO tracks, changes in the frequency of individual active BSISO phases also have considerable influence on the interdecadal change in summer rainfall over southern China. Based on our analysis, the increase in absolute and relative frequency of occurrence of phases 1 and 8, coupled with their corresponding rainfall pattern, makes a positive contribution to the increase in southern China summer rainfall. The interdecadal change in the BSISO tracks and the frequency of active BSISO phases is likely related to coherent changes in atmospheric circulation and sea surface temperature over the Indian Ocean and the western Pacific.

  8. El Nino winners and losers declared

    SciTech Connect

    Kerr, R.A.

    1991-03-08

    Last spring human forecasters thought they saw signs of an imminent warming of the tropical Pacific, a classic El Nino, that could wreak havoc with weather around the globe. Researchers running computer models, on the other hand, saw a slight warming but not enough for an El Nino. The modelers were right. The season for El Ninos has ended and nothing happened. Since the models came online about 5 years ago, there have been two contests to predict El Ninos, which occur every 3 to 7 years, and the models have won both. The models are still experimental, but the general feeling is that they're indicating the right trends. The prospect of having reliable El Nino prediction models is good news beyond the small coterie of tropical Pacific specialists. Worldwide weather patterns are closely tied to El Nino cycles.

  9. A connection from stratospheric ozone to El Niño-Southern Oscillation.

    PubMed

    Manatsa, Desmond; Mukwada, Geoffrey

    2017-07-17

    We use reanalysis and observational data to link the lower stratospheric ozone regulation of the ultraviolet radiation (UV-B) component of solar energy to ENSO modulation. Results indicate that during ENSO extremes, the Walker Circulation (WC) and Brewer Dobson Circulation are related to lower stratospheric ozone alterations east of the date line over the Pacific. These in turn are linked to upper tropospheric anomalous dipole temperature patterns on either side of the equator. The ensuing changes in geopotential height values do not only drive equatorial zonal wind anomalies in the upper troposphere that are reversed at the equatorial surface, but also impact on the intensity of the South Pacific High circulation. When the WC is enhanced, a La Nina type of circulation is indentified but if the circulation cell is inverted, the anomalous circulation results in an El Nino. Though the anomalous lower stratospheric ozone peaks during austral summer it is significant throughout the ENSO lifecycle. Hence, ENSO structure and variability are mainly linked to the lower stratospheric ozone instigated internal dynamics of the Pacific atmosphere. The ENSO forcing most likely originates from the ozone related regulation of the incoming solar UV-B radiation rather than the Pacific Ocean surface.

  10. El Nino-like events during Miocene

    SciTech Connect

    Casey, R.E.; Nelson, C.O.; Weinheimer, A.L.; Oeth, P.A.; Swanson, R.J.

    1988-03-01

    El Nino-like events have been recorded from the Miocene laminated siliceous facies of the Monterey Formation. These El Nino-like Miocene events are compared to El Nino events recorded from Holocene varved sediments deposited within the anoxic Santa Barbara basin. Strong El Nino events can be recognized from Holocene Santa Barbara basin sediments by increases in radiolarian flux to the sea floor during those events. For the last 100-plus years, frequency of strong El Ninos has been on the order of one extremely strong event about every 100 years, and one easily recognizable event about every 18 years. Frequencies in the laminated (varved) Miocene range from about every 4-5 years to over 20 years. The higher frequencies occur within generally warm intervals and the lower frequencies within generally cold intervals. Perhaps the frequencies of these events may, in fact, be an important indicator in determining whether the intervals were cold or warm. Reconstructions of the paleo-California Current system during El Nino-like periods have been made for the west coast from the Gulf of California to northern California. Strong El Nino-like events occurred 5.5 and 8 Ma, and a strong anti-El Nino-like event occurred at about 6.5 Ma. Evidence from the 5.5 and 8 Ma events combined with other evidence suggests that modern El Ninos, similar to today's, were initiated at 5.5 Ma or earlier.

  11. The influence of the North Atlantic Oscillation and El Niño-Southern Oscillation on mean and extreme values of column ozone over the United States

    NASA Astrophysics Data System (ADS)

    Petropavlovskikh, I.; Evans, R.; McConville, G.; Manney, G. L.; Rieder, H. E.

    2014-08-01

    Continuous measurements of total ozone (by Dobson spectrophotometers) across the contiguous United States (US) began in the early 1960s. Here, we analyze temporal and spatial variability and trends in total ozone from the five US sites with long-term records. While similar long-term ozone changes are detected at all five sites, we find differences in the patterns of ozone variability on shorter time scales. In addition to standard evaluation techniques, STL-decomposition methods (Seasonal Trend decomposition of time series based on LOcally wEighted Scatterplot Smoothing, LOESS) are used to address temporal variability and trends in the Dobson data. The LOESS-smoothed trend components show a decline of total ozone between the 1970s and 2000s and a "stabilization" at lower levels in recent years, which is also confirmed by linear trend analysis. Methods from statistical extreme value theory (EVT) are used to characterize days with high and low total ozone (termed EHOs and ELOs, respectively) at each station and to analyze temporal changes in the frequency of ozone extremes and their relationship to dynamical features such as the North Atlantic Oscillation and El Niño Southern Oscillation. A comparison of the "fingerprints" detected in the frequency distribution of the extremes with those for standard metrics (i.e., the mean) shows that more "fingerprints" are found for the extremes, particularly for the positive phase of the NAO, at all five US monitoring sites. Results from the STL-decomposition support the findings of the EVT analysis. Finally, we analyze the relative influence of low and high ozone events on seasonal mean column ozone at each station. The results show that the influence of ELOs and EHOs on seasonal mean column ozone can be as much as ±5%, or about twice as large as the overall long-term decadal ozone trends.

  12. Influences of the El Niño Southern Oscillation and the Pacific Decadal Oscillation on the timing of the North American spring

    USGS Publications Warehouse

    McCabe, Gregory J.; Ault, Toby R.; Cook, Benjamin I.; Betancourt, Julio L.; Schwartz, Mark D.

    2012-01-01

    Detrended, modelled first leaf dates for 856 sites across North America for the period 1900–2008 are used to examine how the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) separately and together might influence the timing of spring. Although spring (mean March through April) ENSO and PDO signals are apparent in first leaf dates, the signals are not statistically significant (at a 95% confidence level (p < 0.05)) for most sites. The most significant ENSO/PDO signal in first leaf dates occurs for El Niño and positive PDO conditions. An analysis of the spatial distributions of first leaf dates for separate and combined ENSO/PDO conditions features a northwest–southeast dipole that is significantly (at p < 0.05) different than the distributions for neutral conditions. The nature of the teleconnection between Pacific SST's and first leaf dates is evident in comparable composites for detrended sea level pressure (SLP) in the spring months. During positive ENSO/PDO, there is an anomalous flow of warm air from the southwestern US into the northwestern US and an anomalous northeasterly flow of cold air from polar regions into the eastern and southeastern US. These flow patterns are reversed during negative ENSO/PDO. Although the magnitudes of first leaf date departures are not necessarily significantly related to ENSO and PDO, the spatial patterns of departures are significantly related to ENSO and PDO. These significant relations and the long-lived persistence of SSTs provide a potential tool for forecasting the tendencies for first leaf dates to be early or late.

  13. Relationships between El Niño-Southern Oscillation and nitrogen concentrations in a Western Mediterranean river

    NASA Astrophysics Data System (ADS)

    Sigro, J.; Vegas-Vilarrúbia, T.; Giralt, S.; Brunet, M.

    2010-05-01

    El Niño-Southern Oscillation (ENSO) is the dominating mode of interannual climate variability at global scale (Brönnimann, 2007). ENSO extreme negative and positive phases can significantly influence on climatic conditions in Europe, affecting precipitation mainly in spring and autumn (Mariotti et al., 2002; Moron and Ward 1998), but also during winter (Brönnimann et al., 2007; Pozo-Vázquez et al., 2005). Over the Iberian Peninsula (IP), ENSO teleconnections can modulate the frequency and intensity of precipitation (Brunet and López, 1991; Rodó et al., 1997; Rodríguez-Puebla et al., 1998), with a time-lag between the ENSO and its effect on precipitation ranging from 3 to 21 months (Rodó et al., 1997). Large areas of the IP are also affected by severe droughts during the final months of La Niña years and the initial months of the following year, while other areas are affected by dry conditions during the first months of El Niño years, as well as during the summers and autumns of the following year (Muñoz-Diaz and Rodrigo, 2005; Vicente-Serrano, 2005). Here we explore the possibility that nitrate concentration in the Llobregat River (North-eastern Spain) is influenced by ENSO events, which are modulating precipitation variability over the Western Mediterranean basin. The Southern Oscillation Index during La Niña years, the self-calibrating Palmer Hydrological Drought Index (van der Schrier et al., 2006; Wells et al., 2004), and nitrate concentrations were significantly correlated on a seasonal basis in the Llobregat River, with both drought and nitrate concentrations increasing during positive ENSO phases. Our hypothesis is that initially unusual within-stream nitrate increases would take place, owing to higher-than-normal evaporation from the river. During drought periods, the hydrological deficit favours nitrate accumulation in the catchment's soils and, thus, a decline in allochthonous inputs to the river water would be expectable. Besides, on the late

  14. Amplitude-dependent relationship between the Southern Annular Mode and the El Niño Southern Oscillation in austral summer

    NASA Astrophysics Data System (ADS)

    Kim, Baek-Min; Choi, Hyesun; Kim, Seong-Joong; Choi, Wookap

    2017-02-01

    Co-variability between the Southern Annular Mode (SAM) and the El Niño Southern Oscillation (ENSO) during the austral summer is examined, and it is found that there exists an apparent co-variability of a negative (positive) SAM during the mature period of El Niño (La Niña). However, this co-variability is largely controlled by the small number of strong ENSO cases. When strong ENSO cases are excluded, the correlation becomes non-significant. This behavior in the relationship between SAM and ENSO is supported by a series of general circulation model experiments with prescribed sea surface temperature boundary conditions that represent the incremental strengthening of El Niño (La Niña) conditions. The modeled Antarctic sub-polar jet exhibits similar behavior to that identified through observational analysis. Marked changes in both the magnitude and position of the sub-polar jet are largely controlled by particularly strong transient eddy forcing. Planetary wave forcing plays only a minor role in the co-variability, but it can explain in part the asymmetric response of the sub-polar jet between El Niño and La Niña.

  15. Geosat-derived sea level and surface current anomalies in the equatorial Pacific during the 1986-1989 El Nino and La Nina

    NASA Technical Reports Server (NTRS)

    Delcroix, Thierry; Boulanger, Jean-Philippe; Masia, F.; Menkes, C.

    1994-01-01

    Equatorial wave dynamics are essential in most oceanic models for reproducing aspects of the El Nino-Southern Oscillation (ENSO) phenomenon. Observational evidence of first baroclinic equatorial Kelvin and first symmetric meridional Rossby waves is found in Geosat-derived sea level anomalies (SLA) and surface zonal current anomalies (ZCA) in the equatorial Pacific ocean during the 1986-1987 El Nino and the ensuing 1988-1989 La Nina. This was made possible after extensive quality control and specific processing of the recently improved Geosat geophysical data records pertaining to the 17-day Exact Repeat Mission. In particular, the processing was made so that the Geosat-derived ZCA best fit near-surface zonal currents from three equatorial moorings at 165 deg E, 140 deg W, and 110 deg W. The Geosat-derived SLA and ZCA are decomposed into first baroclinic equatorial Kelvin and gravest Rossby modes. The emphasis is then put on the chronology of the ZCA at the equator where the currents are the most energetic and where Kelvin and first symmetric Rossby waves explain most of the variance in ZCA, in similar proportion. The 1986-1987 El Nino is mostly characterized by a strong downwelling Kelvin wave in December 1986, a series of downwelling Kelvin waves in March-October 1987, and a strong upwelling Rossby wave in March-September 1987. These waves are consistent with wind forcing, and all give rise to notable eastward ZCA for almost an entire year. During El Nino-La Nina transition period there is the occurrence of two downwelling Rossby waves originating from the eastern Pacific at times of favorable wind forcing. These Rossby waves switch the basin-wide ZCA from eastward to westward, terminating the warm event. Then, the 1988-1989 La Nina shows the generation of a series of upwelling Kelvin waves which are clearly identified in March/April and September/October 1988. These upwelling Kelvin waves are apparently related to the enhencement of the trade wind in the western

  16. Geosat-derived sea level and surface current anomalies in the equatorial Pacific during the 1986-1989 El Nino and La Nina

    NASA Technical Reports Server (NTRS)

    Delcroix, Thierry; Boulanger, Jean-Philippe; Masia, F.; Menkes, C.

    1994-01-01

    Equatorial wave dynamics are essential in most oceanic models for reproducing aspects of the El Nino-Southern Oscillation (ENSO) phenomenon. Observational evidence of first baroclinic equatorial Kelvin and first symmetric meridional Rossby waves is found in Geosat-derived sea level anomalies (SLA) and surface zonal current anomalies (ZCA) in the equatorial Pacific ocean during the 1986-1987 El Nino and the ensuing 1988-1989 La Nina. This was made possible after extensive quality control and specific processing of the recently improved Geosat geophysical data records pertaining to the 17-day Exact Repeat Mission. In particular, the processing was made so that the Geosat-derived ZCA best fit near-surface zonal currents from three equatorial moorings at 165 deg E, 140 deg W, and 110 deg W. The Geosat-derived SLA and ZCA are decomposed into first baroclinic equatorial Kelvin and gravest Rossby modes. The emphasis is then put on the chronology of the ZCA at the equator where the currents are the most energetic and where Kelvin and first symmetric Rossby waves explain most of the variance in ZCA, in similar proportion. The 1986-1987 El Nino is mostly characterized by a strong downwelling Kelvin wave in December 1986, a series of downwelling Kelvin waves in March-October 1987, and a strong upwelling Rossby wave in March-September 1987. These waves are consistent with wind forcing, and all give rise to notable eastward ZCA for almost an entire year. During El Nino-La Nina transition period there is the occurrence of two downwelling Rossby waves originating from the eastern Pacific at times of favorable wind forcing. These Rossby waves switch the basin-wide ZCA from eastward to westward, terminating the warm event. Then, the 1988-1989 La Nina shows the generation of a series of upwelling Kelvin waves which are clearly identified in March/April and September/October 1988. These upwelling Kelvin waves are apparently related to the enhencement of the trade wind in the western

  17. Effects of climate warming, North Atlantic Oscillation, and El Niño-Southern Oscillation on thermal conditions and plankton dynamics in northern hemispheric lakes.

    PubMed

    Gerten, Dieter; Adrian, Rita

    2002-03-08

    Impacts of climate warming on freshwater ecosystems have been documented recently for a variety of sites around the globe. Here we provide a review of studies that report long-term (multidecadal) effects of warming trends on thermal properties and plankton dynamics in northern hemispheric lakes. We show that higher lake temperatures, shorter periods with ice cover, and shorter stagnation periods were common trends for lakes across the hemisphere in response to the warmer conditions. Only for shallow dimictic lakes was it observed that deep-water temperatures decreased. Moreover, it became evident that phytoplankton dynamics and primary productivity altered in conjunction with changes in lake physics. Algal spring blooms developed early and were more pronounced in several European lakes after mild winters with short ice cover periods, and primary productivity increased in North American lakes. Effects of elevated temperatures on zooplankton communities were seen in an early development of various species and groups, as is documented for cladocerans, copepods, and rotifers in European lakes. Furthermore, thermophile species reached higher abundance in warmer years. Obviously, the nature of responses is species specific, and depends on the detailed seasonal patterning of warming. Complex responses such as effects propagating across trophic levels are likely, indicating that observed climate-ecosystem relationships are not generally applicable. Nonetheless, the picture emerges that climate-driven changes in freshwater ecosystems may be synchronised to a certain extent among lakes even over great distances if climatic influences are not masked by anthropogenic impacts or differences in lake morphology. Macro-scale climatic fluctuations--such as the North Atlantic Oscillation or the El Niño-Southern Oscillation--were identified as the most important candidates responsible for such coherence, with the former predominating in Europe and the latter in North America. We

  18. Hydrologic variability and the onset of modern El Niño-Southern Oscillation: a 19 250-year record from Lake Elsinore, southern California

    NASA Astrophysics Data System (ADS)

    Kirby, Matthew E.; Lund, Steve P.; Poulsen, Christopher J.

    2005-03-01

    There are very few terrestrial palaeoclimate archives spanning the Last Glacial Maximum through the Holocene from coastal southern California. Yet, knowledge of past climate dynamics is critical for assessing present and future constraints on the region's dwindling freshwater resources. We present initial results from two drill cores extracted from the present-day edge of Lake Elsinore, southern California's largest natural lake. Using a multiproxy approach including lithologic description, mass magnetic susceptibility, LOI 550°C (total organic matter), and LOI 950°C (total carbonate), we infer first-order, long-term climate change over the past 19 250 calendar years. Furthermore, we suggest possible first-order forcing mechanisms that drive this change, which include presence/absence of continental ice sheets, insolation, and complex ocean-atmosphere interactions. Our results indicate four distinct millennial-scale climate modes over the past 19 250 calendar years. These modes include a wet Last Glacial Maximum (19 250-17 120 cal. yr BP), a relatively dry late-Glacial/Holocene transition (17 120-9450 cal. yr BP), a wet early Holocene (9450-7670 cal. yr BP), and a highly variable mid-to-late Holocene climate (i.e., alternating wet/dry cycles; 7670 cal. yr BP-present). We attribute the mid-to-late Holocene climate interval to the onset of El Niño-Southern Oscillation ca. 7000 cal. yr BP and a more vigorous hydrologic system. These results are supported by a variety of regional terrestrial and marine palaeoclimate archives.

  19. Dynamics of Quasi-biennial Oscillations in Tropical Ocean-Atmosphere Coupled System

    NASA Technical Reports Server (NTRS)

    Kim, K.-M.; Lau, K.-M.

    1999-01-01

    In this study, quasi-biennial oscillation (QBO) in atmosphere-ocean coupled system is investigated using intermediate coupled model. Observation studies show that the easterly zonal winds anomalies prevail over the equatorial western Pacific during the warm phase of El Nino/Southern Oscillation (ENSO). At the time scale of QBO, SST variations and east Asia Summer monsoon rainfall are closely linked to the eastward propagating zonal winds anomalies originated from Indian ocean. To investigate the effect of zonal wind anomalies over western Pacific on the evolution of ENSO, simple anomalous winds are added to the western part of model domain as external forcing. Wind forcing is parameterized as a function of SST anomalies in the eastern Pacific with time lag. Time lag is adopted to mimic the relation between east Asian monsoon and ENSO. The results shows that the winds anomalies make coupled system oscillate through generating forced Kelvin waves even without the western boundary reflection of Rossby waves. Kelvin waves generated by external forcing are also crucial for the model to oscillate as well as Rossby wave reflections at the western boundary. When the monsoon forced Kelvin wave is strong during the northern winter, the coupled system damped out very quickly. In certain range of external winds amplitude and time lag, the model El Nino shows QBO features. It is suggested that the external wind forcing which is related to summer monsoon flow over western Pacific intensify the negative feedback process of off-equatorial Rossby waves and modify the ENSO periodicity.

  20. The 1982-1983 El Nino Atlas: Nimbus-7 microwave radiometer data

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy

    1987-01-01

    Monthly maps of sea surface temperature, atmospheric water vapor, and surface level wind speed as measured by the Scanning Multichannel Microwave Radiometer (SMMR) on the Nimbus-7 satellite for the tropical Pacific from June 1982 to October 1983, during one of the most intense El Nino Southern Oscillations (ENSO) episodes, are presented. The non-ENSO annual cycle was compiled by averaging the 1980 and 1981 data for each calendar month and was removed from monthly fields of 1982 and 1983 to reveal the anomalous distributions. The anomaly fields and part of the non-ENSO annual cycle are also presented. This study and earlier evaluations demonstrate that the Nimbus/SMMR can be used to monitor large scale and low frequency variabilities in the tropical ocean. The SMMR data support and extend conventional measurements. The variabilities of the three parameters are found to represent various aspects of ENSO related through ocean atmosphere interaction. Their simultaneous and quantitative descriptions pave the way for the derivation of ocean atmosphere latent heat exchange and further the understanding of the coupled atmospheric and oceanic thermodynamics.

  1. Atmosphere-ocean interactions at strong couplings in a simple model of El Nino

    NASA Astrophysics Data System (ADS)

    Navarra, Antonio; Tribbia, Joe; Conti, Giovanni

    2014-05-01

    The understanding of the dynamics of the El Nino/La Nina phenomenon in the tropical Pacific has been the subject of an impressive number of works in the last 20 years. The delayed oscillator theory provides an interpretative framework that has allowed enormous advances in our understanding. Much evidence that stochastic forcing does play a role in the dynamics of ENSO has been discussed and it is possible to shape a theory of El Nino as a stochastically forced linear system. However it is still uncertain if El Nino is a self-sustained nonlinear oscillatory system, a chaotic system or a stochastically forced linear system. We propose in this paper that it is possible to have realistic El Nino probability distributions assuming that the system is a nonlinear stochastically forced system. In this paper a simple system is proposed that retains the main characteristics of the El Nino - La Nina variations, like the skewness and the autocorrelation, and we also show how solutions for the probability distribution can be obtained using a Fokker-Planck equation.

  2. Reconstruction of El Niño Southern Oscillation using data from ships' logbooks, 1750-1855

    NASA Astrophysics Data System (ADS)

    Barrett, Hannah; Jones, Julie; Bigg, Grant

    2016-04-01

    The logbooks from ships which historically travelled the World's oceans contain a vast amount of meteorological information useful for studies of historical climate. They provide daily, marine-based weather observations from the pre-instrumental era. The Climatological Database for the World's Oceans (CLIWOC) and digitised English East India Company (EEIC) logbooks have been used to investigate the climate during the period 1750-1855. A statistical-based reconstruction of El Niño Southern Oscillation (ENSO) has been carried out using these databases, focusing on observations from the Indo-Pacific region. The coherency between previous ENSO reconstructions and this new, logbook ENSO reconstruction has been assessed. By uncovering the potential uses of ships' logbook data, and establishing methodologies to reconstruct climate indices, it is hoped that further efforts will be made to digitise ship logbook. Further digitisation would make this unique data source even more valuable to historical climatology.

  3. Mid- to late-Holocene El Niño-Southern Oscillation dynamics reflected in the subtropical terrestrial realm

    PubMed Central

    Donders, Timme H.; Wagner, Friederike; Dilcher, David L.; Visscher, Henk

    2005-01-01

    High resolution pollen analysis of mid- to late-Holocene peat deposits from southwest Florida reveals a stepwise increase in wetland vegetation that points to an increased precipitation-driven fresh water flow during the past 5,000 years. The tight coupling between winter precipitation patterns in Florida and the strength of the El Niño-Southern Oscillation (ENSO) strongly suggests that the paleo-hydrology record reflects changes in ENSO intensity. A terrestrial subtropical record outside the Indo Pacific Warm Pool both documents ecosystem response to the known onset of modern-day ENSO periodicities, between ≈7,000 and 5,000 years B.P., and subsequent ENSO intensification after 3,500 years B.P. The observed increases in “wetness” are sustained by a gradual rise in relative sea level that prevents a return to drier vegetation through natural succession. PMID:16043705

  4. Does El Niño-Southern Oscillation affect the precipitation in Korea on seasonal time scales?

    NASA Astrophysics Data System (ADS)

    Ho, Chang-Hoi; Choi, Woosuk; Kim, Jinwon; Kim, Maeng-Ki; Yoo, Hee-Dong

    2016-08-01

    A number of studies in the past two decades have attempted to find the relationship between the precipitation in Korea and the El Niño-Southern Oscillation (ENSO) on various time scales. Comprehensive analyses of station precipitation data in Korea for the 61-year period, 1954-2014, in this study show that the effects of ENSO on the seasonal precipitation in Korea are practically negligible. The correlation between summer precipitation and ENSO is insignificant regardless of the intensity, type (e.g., eastern-Pacific or central-Pacific), and stage (e.g., developing, mature, or decaying) of ENSO. Somewhat meaningful correlation between ENSO and precipitation in Korea occurs only in the ENSO-developing fall. Because summer rainfall accounts for over half of the annual total and fall is a dry season in Korea, the overall effects of ENSO on precipitation in Korea are practically nonexistent.

  5. Palaeoclimate reconstructions reveal a strong link between El Niño-Southern Oscillation and Tropical Pacific mean state.

    PubMed

    Sadekov, Aleksey Yu; Ganeshram, Raja; Pichevin, Laetitia; Berdin, Rose; McClymont, Erin; Elderfield, Henry; Tudhope, Alexander W

    2013-01-01

    The El Niño-Southern Oscillation (ENSO) is one of the most important components of the global climate system, but its potential response to an anthropogenic increase in atmospheric CO2 remains largely unknown. One of the major limitations in ENSO prediction is our poor understanding of the relationship between ENSO variability and long-term changes in Tropical Pacific oceanography. Here we investigate this relationship using palaeorecords derived from the geochemistry of planktonic foraminifera. Our results indicate a strong negative correlation between ENSO variability and zonal gradient of sea-surface temperatures across the Tropical Pacific during the last 22 ky. This strong correlation implies a mechanistic link that tightly couples zonal sea-surface temperature gradient and ENSO variability during large climate changes and provides a unique insight into potential ENSO evolution in the future by suggesting enhanced ENSO variability under a global warming scenario.

  6. El Niño and the related phenomenon Southern Oscillation (ENSO): the largest signal in interannual climate variation.

    PubMed

    Wang, H J; Zhang, R H; Cole, J; Chavez, F

    1999-09-28

    El Niño and the related phenomenon Southern Oscillation (ENSO) is the strongest signal in the interannual variation of ocean-atmosphere system. It is mainly a tropical event but its impact is global. ENSO has been drawing great scientific attention in many international research programs. There has been an observational system for the tropical ocean, and scientists have known the climatologies of the upper ocean, developed some theories about the ENSO cycle, and established coupled ocean-atmosphere models to give encouraging predictions of ENSO for a 1-year lead. However, questions remain about the physical mechanisms for the ENSO cycle and its irregularity, ENSO-monsoon interactions, long-term variation of ENSO, and increasing the predictive skill of ENSO and its related climate variations.

  7. Forecasting Andean rainfall and crop yield from the influence of El Nino on Pleiades visibility

    PubMed

    Orlove; Chiang; Cane

    2000-01-06

    Farmers in drought-prone regions of Andean South America have historically made observations of changes in the apparent brightness of stars in the Pleiades around the time of the southern winter solstice in order to forecast interannual variations in summer rainfall and in autumn harvests. They moderate the effect of reduced rainfall by adjusting the planting dates of potatoes, their most important crop. Here we use data on cloud cover and water vapour from satellite imagery, agronomic data from the Andean altiplano and an index of El Nino variability to analyse this forecasting method. We find that poor visibility of the Pleiades in June-caused by an increase in subvisual high cirrus clouds-is indicative of an El Nino year, which is usually linked to reduced rainfall during the growing season several months later. Our results suggest that this centuries-old method of seasonal rainfall forecasting may be based on a simple indicator of El Nino variability.

  8. Using transfer functions to quantify El Niño Southern Oscillation dynamics in data and models.

    PubMed

    MacMartin, Douglas G; Tziperman, Eli

    2014-09-08

    Transfer function tools commonly used in engineering control analysis can be used to better understand the dynamics of El Niño Southern Oscillation (ENSO), compare data with models and identify systematic model errors. The transfer function describes the frequency-dependent input-output relationship between any pair of causally related variables, and can be estimated from time series. This can be used first to assess whether the underlying relationship is or is not frequency dependent, and if so, to diagnose the underlying differential equations that relate the variables, and hence describe the dynamics of individual subsystem processes relevant to ENSO. Estimating process parameters allows the identification of compensating model errors that may lead to a seemingly realistic simulation in spite of incorrect model physics. This tool is applied here to the TAO array ocean data, the GFDL-CM2.1 and CCSM4 general circulation models, and to the Cane-Zebiak ENSO model. The delayed oscillator description is used to motivate a few relevant processes involved in the dynamics, although any other ENSO mechanism could be used instead. We identify several differences in the processes between the models and data that may be useful for model improvement. The transfer function methodology is also useful in understanding the dynamics and evaluating models of other climate processes.

  9. Exploring linkages between coastal progradation rates and the El Niño Southern Oscillation, Southwest Washington, USA

    NASA Astrophysics Data System (ADS)

    Moore, L. J.; Kaminsky, G. M.; Jol, H. M.

    2003-05-01

    Climate oscillations such as the El Niño-Southern Oscillation (ENSO) affect storm tracks, wave climate, precipitation and sea level in the U.S. Pacific Northwest. The impacts of these changes on coastal behavior have not been investigated in detail beyond the study of recent El Niño events, largely because existing historical records of coastal behavior are not of sufficient resolution to study annual responses to climatic forcing. We compare a newly developed annual record of coastal progradation for a location on the Washington coast, generated using high-resolution subsurface ground penetrating radar (GPR), with ENSO indices. This analysis reveals higher rates of seaward coastal growth following the warm, El Niño, ENSO phase and lower rates of coastal growth following the cold, La Niña, ENSO phase. The observed relationship between ENSO and progradation, although weak, is hypothesized to result from differences in sediment transport patterns and beach recovery rates following El Niño and La Niña events.

  10. Centennial-scale vegetation and North Atlantic Oscillation changes during the Late Holocene in the southern Iberia

    NASA Astrophysics Data System (ADS)

    Ramos-Román, M. J.; Jiménez-Moreno, G.; Anderson, R. S.; García-Alix, A.; Toney, J. L.; Jiménez-Espejo, F. J.; Carrión, J. S.

    2016-07-01

    High-reso CE to lution pollen analysis, charcoal, non-pollen palynomorphs and magnetic susceptibility have been analyzed in the sediment record of a peat bog in Sierra Nevada in southern Iberia. The study of these proxies provided the reconstruction of vegetation, climate, fire and human activity of the last ∼4500 cal yr BP. A progressive trend towards aridification during the late Holocene is observed in this record. This trend is interrupted by millennial- and centennial-scale variability of relatively more humid and arid periods. Arid conditions are recorded between ∼4000 and 3100 cal yr BP, being characterized by a decline in arboreal pollen and with a spike in magnetic susceptibility. This is followed by a relatively humid period from ∼3100 to 1600 cal yr BP, coinciding partially with the Iberian-Roman Humid Period, and is indicated by the increase of Pinus and the decrease in xerophytic taxa. The last 1500 cal yr BP are characterized by several centennial-scale climatic oscillations. Generally arid conditions from ∼450 to 1300 CE, depicted by a decrease in Pinus and an increase in Artemisia, comprise the Dark Ages and the Medieval Climate Anomaly. Since ∼ 1300 to 1850 CE pronounced oscillations occur between relatively humid and arid conditions. Four periods depicted by relatively higher Pinus coinciding with the beginning and end of the Little Ice Age are interrupted by three arid events characterized by an increase in Artemisia. These alternating arid and humid shifts could be explained by centennial-scale changes in the North Atlantic Oscillation and solar activity.

  11. Field-Aligned Currents in Saturn's Southern Nightside Magnetosphere: Sub-Corotation and Planetary Period Oscillation Currents

    NASA Astrophysics Data System (ADS)

    Hunt, G. J.; Cowley, S. W. H.; Provan, G.; Bunce, E. J.; Alexeev, I. I.; Belenkaya, E. S.; Kalegaev, V. V.; Dougherty, M. K.; Coates, A. J.

    2014-12-01

    We have investigated azimuthal magnetic field data showing the presence of field-aligned current sheets on 31 similar Cassini passes during the 2008 interval of near polar orbits across Saturn's southern post-midnight auroral region at radial distances ~3-5 RS. The currents are found to be strongly modulated in magnitude, form, and position by the phase of the southern planetary period oscillations (PPOs). We separate currents independent of PPO phase from PPO-related currents, by exploiting the expected anti-symmetry of the latter with respect to PPO phase. The PPO-independent current system is thought to be associated mainly with sub-corotation of magnetospheric plasma, and consists of a weak distributed downward current over the whole polar region, enhanced downward currents in a layer mapping to the outer magnetosphere where the ionospheric conductivity is elevated, and a main upward-directed current layer ~2° wide centered at ~18° co-latitude with respect to the southern pole carrying ~2.5 MA per radian of azimuth. The latter current maps to the main region of the hot plasma in Saturn's magnetosphere and is co-located with Saturn's main UV oval in this hemisphere and local time sector. No major currents are detected mapping to the inner equatorial magnetosphere ~4-8 RS dominated by cool Enceladus plasma. The PPO-related currents map to the inner part of the hot plasma region at ~18°-20° co-latitude, and carry rotating upward and downward currents peaking at ~1.7 MA rad-1. The co-latitude of the current layers is also modulated by 1° amplitude in the PPO cycle, with maximum equatorward and poleward excursions adjacent to maximum upward and downward PPO currents, respectively. It is shown that this phasing requires the current system to be driven upward from the planetary atmosphere rather than downward from the magnetosphere.

  12. Effects of the El Niño-southern oscillation on dengue epidemics in Thailand, 1996-2005.

    PubMed

    Tipayamongkholgul, Mathuros; Fang, Chi-Tai; Klinchan, Suratsawadee; Liu, Chung-Ming; King, Chwan-Chuen

    2009-11-20

    Despite intensive vector control efforts, dengue epidemics continue to occur throughout Southeast Asia in multi-annual cycles. Weather is considered an important factor in these cycles, but the extent to which the El Niño-Southern Oscillation (ENSO) is a driving force behind dengue epidemics remains unclear. We examined the temporal relationship between El Niño and the occurrence of dengue epidemics, and constructed Poisson autoregressive models for incidences of dengue cases. Global ENSO records, dengue surveillance data, and local meteorological data in two geographically diverse regions in Thailand (the tropical southern coastal region and the northern inland mountainous region) were analyzed. The strength of El Niño was consistently a predictor for the occurrence of dengue epidemics throughout time lags from 1 to 11 months in the two selected regions of Thailand. Up to 22% (in 8 northern inland mountainous provinces) and 15% (in 5 southern tropical coastal provinces) of the variation in the monthly incidence of dengue cases were attributable to global ENSO cycles. Province-level predictive models were fitted using 1996-2004 data and validated with out-of-fit data from 2005. The multivariate ENSO index was an independent predictor in 10 of the 13 studied provinces. El Niño is one of the important driving forces for dengue epidemics across the geographically diverse regions of Thailand; however, spatial heterogeneity in the effect exists. The effects of El Niño should be taken into account in future epidemic forecasting for public health preparedness.

  13. The influence of El Niño-Southern Oscillation on boreal winter rainfall over Peninsular Malaysia

    NASA Astrophysics Data System (ADS)

    Richard, Sandra; Walsh, Kevin J. E.

    2017-09-01

    Multi-scale interactions between El Niño-Southern Oscillation and the Boreal Winter Monsoon contribute to rainfall variations over Malaysia. Understanding the physical mechanisms that control these spatial variations in local rainfall is crucial for improving weather and climate prediction and related risk management. Analysis using station observations and European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim) reanalysis reveals a significant decrease in rainfall during El Niño (EL) and corresponding increase during La Niña particularly north of 2°N over Peninsular Malaysia (PM). It is noted that the southern tip of PM shows a small increase in rainfall during El Niño although not significant. Analysis of the diurnal cycle of rainfall and winds indicates that there are no significant changes in morning and evening rainfall over PM that could explain the north-south disparity. Thus, we suggest that the key factor which might explain the north-south rainfall disparity is the moisture flux convergence (MFC). During the December to January (DJF) period of EL years, except for the southern tip of PM, significant negative MFC causes drying as well as suppression of uplift over most areas. In addition, lower specific humidity combined with moisture flux divergence results in less moisture over PM. Thus, over the areas north of 2°N, less rainfall (less heavy rain days) with smaller diurnal rainfall amplitude explains the negative rainfall anomaly observed during DJF of EL. The same MFC argument might explain the dipolar pattern over other areas such as Borneo if further analysis is performed.

  14. Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Currie, J. C.; Lengaigne, M.; Vialard, J.; Kaplan, D. M.; Aumont, O.; Naqvi, S. W. A.; Maury, O.

    2013-10-01

    The Indian Ocean Dipole (IOD) and the El Niño/Southern Oscillation (ENSO) are independent climate modes, which frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled biophysical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997/1998 ENSO and IOD event. Results suggest that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. A negative influence of IOD on chlorophyll concentrations is shown in a region around the southern tip of India in fall. IOD also depresses depth-integrated chlorophyll in the 5-10° S thermocline ridge region, yet the signal is negligible in surface chlorophyll. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Yet unlike most other regions examined, the combined explanatory power of IOD and ENSO in predicting depth-integrated chlorophyll anomalies is relatively low in this region, suggestive that other drivers are important there. We show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. Our results suggest that ENSO and IOD cause significant and predictable regional re-organisation of chlorophyll via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries, ecosystems and carbon

  15. Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Currie, J. C.; Lengaigne, M.; Vialard, J.; Kaplan, D. M.; Aumont, O.; Naqvi, S. W. A.; Maury, O.

    2013-03-01

    The Indian Ocean Dipole (IOD) and the El Niño-Southern Oscillation (ENSO) frequently co-occur, driving significant interannual changes within the Indian Ocean. We use a four-decade hindcast from a coupled bio-physical ocean general circulation model, to disentangle patterns of chlorophyll anomalies driven by these two climate modes. Comparisons with remotely-sensed records show that the simulation competently reproduces the chlorophyll seasonal cycle, as well as open-ocean anomalies during the 1997-1998 ENSO and IOD event. Results show that anomalous surface and euphotic-layer chlorophyll blooms in the eastern equatorial Indian Ocean in fall, and southern Bay of Bengal in winter, are primarily related to IOD forcing. IOD depresses integrated chlorophyll in the 5° S-10° S thermocline ridge region, even though the signal is negligible in surface chlorophyll. A previously-unreported negative influence of IOD on chlorophyll concentrations is also shown in a region around the southern tip of India. The only investigated region where ENSO has a greater influence on chlorophyll than does IOD, is in the Somalia upwelling region, where it causes a decrease in fall and winter chlorophyll by reducing local upwelling winds. Lastly, we show that the chlorophyll impact of climate indices is frequently asymmetric, with a general tendency for larger positive than negative chlorophyll anomalies. ENSO and IOD cause significant and predictable regional re-organisation of phytoplankton productivity via their influence on near-surface oceanography. Resolving the details of these effects should improve our understanding, and eventually gain predictability, of interannual changes in Indian Ocean productivity, fisheries, ecosystems and carbon budgets.

  16. Differential modulation of eastern oyster ( Crassostrea virginica) disease parasites by the El-Niño-Southern Oscillation and the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Soniat, Thomas M.; Hofmann, Eileen E.; Klinck, John M.; Powell, Eric N.

    2009-02-01

    The eastern oyster ( Crassostrea virginica) is affected by two protozoan parasites, Perkinsus marinus which causes Dermo disease and Haplosporidium nelsoni which causes MSX (Multinucleated Sphere Unknown) disease. Both diseases are largely controlled by water temperature and salinity and thus are potentially sensitive to climate variations resulting from the El Niño-Southern Oscillation (ENSO), which influences climate along the Gulf of Mexico coast, and the North Atlantic Oscillation (NAO), which influences climate along the Atlantic coast of the United States. In this study, a 10-year time series of temperature and salinity and P. marinus infection intensity for a site in Louisiana on the Gulf of Mexico coast and a 52-year time series of air temperature and freshwater inflow and oyster mortality from Delaware Bay on the Atlantic coast of the United States were analyzed to determine patterns in disease and disease-induced mortality in C. virginica populations that resulted from ENSO and NAO climate variations. Wavelet analysis was used to decompose the environmental, disease infection intensity and oyster mortality time series into a time-frequency space to determine the dominant modes of variability and the time variability of the modes. For the Louisiana site, salinity and Dermo disease infection intensity are correlated at a periodicity of 4 years, which corresponds to ENSO. The influence of ENSO on Dermo disease along the Gulf of Mexico is through its effect on salinity, with high salinity, which occurs during the La Niña phase of ENSO at this location, favoring parasite proliferation. For the Delaware Bay site, the primary correlation was between temperature and oyster mortality, with a periodicity of 8 years, which corresponds to the NAO. Warmer temperatures, which occur during the positive phase of the NAO, favor the parasites causing increased oyster mortality. Thus, disease prevalence and intensity in C. virginica populations along the Gulf of Mexico

  17. The influence of El-Niño Southern Oscillation and Pacific Decadal Oscillation on secular rainfall variations in Hawai'i

    NASA Astrophysics Data System (ADS)

    Frazier, A. G.; Elison Timm, O.; Giambelluca, T. W.

    2014-12-01

    Large-scale teleconnections, particularly the El-Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), have a strong influence on rainfall patterns in Hawai'i. Over the last century, we have observed statistically significant declines in rainfall across the state, and it is unknown whether these declines are due to changes in these natural large-scale variations in climate, or whether these downward trends can be explained by anthropogenic effects. To better aid managers and decision-makers, it is important to understand what is driving current trends. Here we use an empirical approach to study long-term trends in a geographically complex region and diverse climate. Using a time series of month-year rainfall maps for Hawai'i starting in January 1920 at 250 m resolution, an empirical orthogonal function (EOF) analysis was performed to study the spatiotemporal variations and trend patterns. We further correlate the leading spatial and temporal components with ENSO and PDO indices, linear trends, and secular trends. More of the variability is contained in the first component in the winter (December-January-February) than in the summer (June-July-August), especially in the northern islands (Kaua'i and O'ahu) suggesting that natural climate variability has a stronger effect on the spatiotemporal rainfall patterns during the winter season than the summer season. Currently, independent efforts to downscale future climate projections for Hawai'i have produced different future outlooks for rainfall. In the absence of adequately designed control experiments with regional climate models, we propose evaluating differences between observed and projected trend patterns as an alternative criterion for measuring the significance and plausibility of future climate change projections. Our results show the difficulties of separating anthropogenic and natural rainfall trends, e.g., identifying spatial (and seasonal) patterns of the trends that are different from

  18. Possible impacts of mega-El Niño/Southern Oscillation and Atlantic multidecadal oscillation on Eurasian heat wave frequency variability

    NASA Astrophysics Data System (ADS)

    Zhou, Yefan; Wu, Zhiwei

    2016-04-01

    Identifying predictability sources of heat wave variations is a scientific challenge and of practical importance. This study investigates the summertime heat wave frequency (HWF) over Eurasia for 19502014. The Eurasian HWF is dominated by two distinct modes: the interdecadal (ID) mode featured by an increasing pattern overall, centered around eastern Europe-central Asia and Mongolia-southwestern China; the interannual (IA) mode resembling a tri-pole anomaly pattern with three centers over western-northern Europe, northeastern Asia and East Asia. The ID mode is found to be influenced by mega-El Niño/Southern Oscillation (mega-ENSO) and the Atlantic multidecadal oscillation (AMO), and the latter has far more effect, whereas the IA mode is connected with mega-ENSO. Further analysis suggests that mega-ENSO variations can incite a Gill-type response spreading to Eurasia, while the AMO changes cause eastward-propagating Rossby wave trains toward Eurasia. These two teleconnection patterns together contribute to the large-scale circulation anomalies of the ID mode, and those related to the IA mode arise from the teleconnection pattern excited by mega-ENSO. A strong mega-ENSO triggers subsidence with high pressure anomalies, warms the surface and increases the HWF significantly over northeastern Asia particularly. Likewise, the warm AMO-induced circulation anomalies engender surface radiative heating and HWF growth in most of Eurasian continent except some localized Siberian and Asian regions. The situation is opposite for a weak mega-ENSO and AMO. Those models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) which realistically capture the features of the ID mode can reproduce the AMO-like sea surface temperature anomalies (SSTAs), while signals resembling mega-ENSO are found in those with favorable capability of simulating the IA mode. On the contrary, these relevant SSTAs linked to the respective modes vanish in the models with little skills. Thus

  19. Influence of El Niño-Southern Oscillation (ENSO) on the behavior of floods in the Itajaí River basin in Southern Brazil

    NASA Astrophysics Data System (ADS)

    Tiago Silva, Artur; Portela, Maria Manuela; Naghettini, Mauro; Fernandes, Wilson

    2016-04-01

    The Itajaí River basin is located in the Southeastern South America (SESA) region, where the influence of El Niño-Southern Oscillation (ENSO) on hydrometeorological extremes has been reported. The lower reaches of the river are prone to calamitous floods as the basin is frequently subjected to extreme rainfall events. The history of devastating floods motivated the construction of detention dams in the upper reaches of the river during the 1970s-1990s. This work presents a study on the nonstationarity of floods in the Itajaí River, using a peaks-over-threshold (POT) approach applied to flood data from 3 gauging stations located in the Basin. Exploratory data analysis methods and nonstationary Poisson-Generalized Pareto models are used to study the joint influence of ENSO and upstream flood control dams on the flood regime of the river. Bayesian model estimation techniques are used with prior belief about the Generalized Pareto shape parameter elicited from regional information. The analysis revealed that occurrence rate and over-threshold peak magnitudes exhibit statistically significant and complex relationships with ENSO. Results also show evidence that, while upstream flood detention dams play a perceptible, though small, role in reducing flood hazard, the influence of the climate covariate on the flood regime is dominant. Furthermore, increased ENSO activity in recent decades, possibly related to a reported climate regime shift in the mid-1970s, has increased flood hazard and led to the occurrence of very large annual floods.

  20. El Nino and the Teacher at Sea.

    ERIC Educational Resources Information Center

    Johnson, Kerry Anne

    1998-01-01

    Details the experiences of a teacher who spent a month on a National Oceanic and Atmospheric Administration (NOAA) ship. Reports observations of developing El Nino conditions and presents related classroom activities. (DDR)

  1. El Nino and the Teacher at Sea.

    ERIC Educational Resources Information Center

    Johnson, Kerry Anne

    1998-01-01

    Details the experiences of a teacher who spent a month on a National Oceanic and Atmospheric Administration (NOAA) ship. Reports observations of developing El Nino conditions and presents related classroom activities. (DDR)

  2. Impact of El Niño Southern Oscillation on infectious disease hospitalization risk in the United States.

    PubMed

    Fisman, David N; Tuite, Ashleigh R; Brown, Kevin A

    2016-12-20

    Although the global climate is changing at an unprecedented rate, links between weather and infectious disease have received little attention in high income countries. The "El Niño Southern Oscillation" (ENSO) occurs irregularly and is associated with changing temperature and precipitation patterns. We studied the impact of ENSO on infectious diseases in four census regions in the United States. We evaluated infectious diseases requiring hospitalization using the US National Hospital Discharge Survey (1970-2010) and five disease groupings that may undergo epidemiological shifts with changing climate: (i) vector-borne diseases, (ii) pneumonia and influenza, (iii) enteric disease, (iv) zoonotic bacterial disease, and (v) fungal disease. ENSO exposure was based on the Multivariate ENSO Index. Distributed lag models, with adjustment for seasonal oscillation and long-term trends, were used to evaluate the impact of ENSO on disease incidence over lags of up to 12 mo. ENSO was associated more with vector-borne disease [relative risk (RR) 2.96, 95% confidence interval (CI) 1.03-8.48] and less with enteric disease (0.73, 95% CI 0.62-0.87) in the Western region; the increase in vector-borne disease was attributable to increased risk of rickettsioses and tick-borne infectious diseases. By contrast, ENSO was associated with more enteric disease in non-Western regions (RR 1.12, 95% CI 1.02-1.15). The periodic nature of ENSO may make it a useful natural experiment for evaluation of the impact of climatic shifts on infectious disease risk. The impact of ENSO suggests that warmer temperatures and extreme variation in precipitation events influence risks of vector-borne and enteric disease in the United States.

  3. Climate variability and El Niño Southern Oscillation: implications for natural coastal resources and management

    NASA Astrophysics Data System (ADS)

    Thatje, Sven; Heilmayer, Olaf; Laudien, Jürgen

    2008-03-01

    The El Niño Southern Oscillation (ENSO) significantly influences marine ecosystems and the sustained exploitation of marine resources in the coastal zone of the Humboldt Current upwelling system. Both its warm (El Niño: EN) and cold (La Niña: LN) phase have drastic implications for the ecology, socio-economy and infrastructure along most of Pacific South America. Local artisanal fisheries, which especially suffer from the effects of EN, represent a major part for the domestic economy of Chile and Peru and in consequence a huge amount of published and unpublished studies exists aiming at identifying effects of EN and LN. However, most processes and underlying mechanisms fostering the ecology of organisms along Pacific South America have not been analyzed yet and for the marine realm most knowledge is traditionally based on rather descriptive approaches. We herein advocate that small-scale comparative and interdisciplinary process studies work as one possible solution to understand better the variability observed in EN/LN effects at local scale. We propose that differences in small-scale impacts of ENSO along the coast rather than the macro-ecological and oceanographic view are essential for the sustainable management of costal ecosystems and the livelihood of the people depending on it. Based on this, we summarize the conceptual approach from the EU-funded International Science and Technology Cooperation (INCO) project “Climate variability and El Niño Southern Oscillation: Implications for Natural Coastal Resources and Management (CENSOR)” that aims at enhancing the detection, compilation, and understanding of EN and LN effects on the coastal zone and its natural resources. We promote a multidisciplinary avenue within present international funding schemes, with the intention to bridge the traditional gap between basic and applied coastal research. The long-term aim is an increased mitigation of harm caused by EN as well as a better use of beneficial effects

  4. Tropical Cyclones in the Southwest Pacific: Spatial Patterns and Relationships to Southern Oscillation and Sea Surface Temperature.

    NASA Astrophysics Data System (ADS)

    Basher, R. E.; Zheng, X.

    1995-05-01

    An analysis of a 20-yr dataset of tropical cyclones in the southwest Pacific has been made to determine the spatial patterns of cyclone occurrence and how these depend on the Southern Oscillation (SO) and sea surface temperature. A local measure of cyclone incidence is defined as the number of cyclones that enter into a 2° lat-long square during some period (eg., within one season) and this quantity is mapped for four Southern Oscillation index (SOI) categories. The maps show that the geographical distribution of cyclone incidence shifts eastward and northward during negative SOI phases and vice versa. The mean annual incidence for the whole region is 28% higher than average for our strongly negative SO category and 16% below average for our near-zero category.To explore the roles of the SO and local SST, correlation analysis was applied to mean values of cyclone incidence for four subregions of 20° longitude width between 10° and 22°S. Markedly different SOI/SST responses were found on either side of 170°E. In the Coral Sea subregion (150°-170°E), seasons with a relatively high tropical cyclone incidence were preceded by significant positive anomalies in SST and weak positive anomalies of the SOI. The behaviors of the three eastern subregions (lying between 170°E and 130°W) were similar to each other, but were very different to that of the Coral Sea subregion. Their seasons of higher cyclone incidence were preceded by significant negative anomalies of SOI and Tahiti pressure, which continued into the cyclone season, but with only weak or nil SST relationships. Analysis of variance was used to determine the relative contributions of the main variables for each subregion. Altogether, SOI/SST variables before the cyclone season can explain from 20% to 50% of the variance for the individual subregions. Concurrent variables can explain 70% of the variance for the three eastern subregions taken as a single unit.On the basis of these statistical results, the

  5. Early-season warning of soybean rust regional epidemics using El Niño Southern/Oscillation information.

    PubMed

    Del Ponte, Emerson M; Maia, Aline de H N; dos Santos, Thiago V; Martins, Eduardo J; Baethgen, Walter E

    2011-07-01

    Soybean rust (SBR) is a disease of significant impact to Brazilian soybean production. Twenty-four locations in a major growing region in southern Brazil, where long-term (30 years) weather information was available, were selected to estimate the risk of SBR epidemics and identify potential predictors derived from El Niño 3.4 region. A rainfall-based model was used to predict SBR severity in an "epidemic development window" (the months of February and March for the studied region) in the time series. Twenty-eight daily simulations for each year-location (n = 720) were performed considering each day after 31 January as a hypothetical detection date (HDD) to estimate a severity index (SBRindex). The mean SBRindex in a single year was defined as the 'growing season severity index' (GSSI) for that year. A probabilistic risk assessment related GSSI and sea surface temperatures (SST) at the El Niño 3.4. region (here categorized as warm, cold or neutral phase) in October-November-December (OND) of the same growing season. Overall, the median GSSI across location-years was 34.5%. The risk of GSSI exceeding 60% was generally low and ranged from 0 to 20 percentage points, with the higher values found in the northern regions of the state when compared to the central-western. During a warm OND-SST phase, the probability of GSSI exceeding its overall mean (locations pooled) increased significantly by around 25 percentage points compared to neutral and cold SST phases, especially over the central western region. This study demonstrates the potential to use El Niño/Southern Oscillation information to anticipate the risk of SBR epidemics up to 1 month in advance at a regional scale.

  6. El Niño Southern Oscillation influences the abundance and movements of a marine top predator in coastal waters.

    PubMed

    Sprogis, Kate R; Christiansen, Fredrik; Wandres, Moritz; Bejder, Lars

    2017-10-08

    Large-scale climate modes such as El Niño Southern Oscillation (ENSO) influence population dynamics in many species, including marine top predators. However, few quantitative studies have investigated the influence of large-scale variability on resident marine top predator populations. We examined the effect of climate variability on the abundance and temporary emigration of a resident bottlenose dolphin (Tursiops aduncus) population off Bunbury, Western Australia (WA). This population has been studied intensively over six consecutive years (2007-2013), yielding a robust dataset that captures seasonal variations in both abundance and movement patterns. In WA, ENSO affects the strength of the Leeuwin Current (LC), the dominant oceanographic feature in the region. The strength and variability of the LC affects marine ecosystems and distribution of top predator prey. We investigated the relationship between dolphin abundance and ENSO, Southern Annular Mode, austral season, rainfall, sea surface salinity and sea surface temperature (SST). Linear models indicated that dolphin abundance was significantly affected by ENSO, and that the magnitude of the effect was dependent upon season. Dolphin abundance was lowest during winter 2009, when dolphins had high temporary emigration rates out of the study area. This coincided with the single El Niño event that occurred throughout the study period. Coupled with this event, there was a negative anomaly in SST and an above average rainfall. These conditions may have affected the distribution of dolphin prey, resulting in the temporary emigration of dolphins out of the study area in search of adequate prey. This study demonstrated the local effects of large-scale climatic variations on the short-term response of a resident, coastal delphinid species. With a projected global increase in frequency and intensity of extreme climatic events, resident marine top predators may not only have to contend with increasing coastal

  7. El Niño-southern oscillation effect on a fire regime in northeastern Mexico has changed over time.

    PubMed

    Yocom, Larissa L; Fulé, Peter Z; Brown, Peter M; Cerano, Julian; Villanueva-Díaz, José; Falk, Donald A; Cornejo-Oviedo, Eladio

    2010-06-01

    The El Niño Southern Oscillation (ENSO) is a climate-forcing mechanism that has been shown to affect precipitation and the occurrence of wildfires in many parts of the world. In the southern United States and northern Mexico, warm events (El Niño) are associated with moist winter conditions and fewer fires, while cool events (La Niñia) tend to favor dry winters and more fires. We tested this relationship in a region of northeastern Mexico by characterizing the historical fire regime and climatic influences: Fire regimes were reconstructed from fire-scar samples collected from 100 trees in three high-elevation sites on Peña Nevada in southern Nuevo Le6n. The sites were approximately 25 ha each, and the site centers were approximately 1 km apart. The earliest recorded fire occurred in 1521 and the time period we used for analysis was 1645-1929. The sites were characterized by frequent surface fires before the 1920s. In the three sites, mean fire intervals ranged from 8.6 to 9.6 years (all fires) and 11.9 to 18.6 years (fires that scarred > or = 25% of recording trees). The per-tree mean fire return interval was 17 years, and all three sites burned in the same year seven times between 1774 and 1929. After 1929, fires were nearly eliminated in all sites, likely due to human causes. We found a temporal change in the association between ENSO events and fires; before the 1830s La Niña events were significantly associated with fire years, while after the 1830s this association was not significant. In 1998, when the most severe El Niño event of the past century occurred, the three sites experienced severe, stand-replacing fires that killed many trees that had survived multiple surface fires in the past. Prior to the 1830s, fires tended to occur during dry La Niña years, but since then both La Niña and El Niño have been associated with dry years in this region, especially during the last three decades. This result suggests that ENSO effects have changed over time in

  8. People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands.

    PubMed

    Bliege Bird, Rebecca; Bird, Douglas W; Codding, Brian F

    2016-06-05

    While evidence mounts that indigenous burning has a significant role in shaping pyrodiversity, the processes explaining its variation across local and external biophysical systems remain limited. This is especially the case with studies of climate-fire interactions, which only recognize an effect of humans on the fire regime when they act independently of climate. In this paper, we test the hypothesis that an anthropogenic fire regime (fire incidence, size and extent) does not covary with climate. In the lightning regime, positive El Niño southern oscillation (ENSO) values increase lightning fire incidence, whereas La Niña (and associated increases in prior rainfall) increase fire size. ENSO has the opposite effect in the Martu regime, decreasing ignitions in El Niño conditions without affecting fire size. Anthropogenic ignition rates covary positively with high antecedent rainfall, whereas fire size varies only with high temperatures and unpredictable winds, which may reduce control over fire spread. However, total area burned is similarly predicted by antecedent rainfall in both regimes, but is driven by increases in fire size in the lightning regime, and fire number in the anthropogenic regime. We conclude that anthropogenic regimes covary with climatic variation, but detecting the human-climate-fire interaction requires multiple measures of both fire regime and climate.This article is part of the themed issue 'The interaction of fire and mankind'.

  9. Impacts of El Niño Southern Oscillation and Indian Ocean Dipole on dengue incidence in Bangladesh.

    PubMed

    Banu, Shahera; Guo, Yuming; Hu, Wenbiao; Dale, Pat; Mackenzie, John S; Mengersen, Kerrie; Tong, Shilu

    2015-11-05

    Dengue dynamics are driven by complex interactions between hosts, vectors and viruses that are influenced by environmental and climatic factors. Several studies examined the role of El Niño Southern Oscillation (ENSO) in dengue incidence. However, the role of Indian Ocean Dipole (IOD), a coupled ocean atmosphere phenomenon in the Indian Ocean, which controls the summer monsoon rainfall in the Indian region, remains unexplored. Here, we examined the effects of ENSO and IOD on dengue incidence in Bangladesh. According to the wavelet coherence analysis, there was a very weak association between ENSO, IOD and dengue incidence, but a highly significant coherence between dengue incidence and local climate variables (temperature and rainfall). However, a distributed lag nonlinear model (DLNM) revealed that the association between dengue incidence and ENSO or IOD were comparatively stronger after adjustment for local climate variables, seasonality and trend. The estimated effects were nonlinear for both ENSO and IOD with higher relative risks at higher ENSO and IOD. The weak association between ENSO, IOD and dengue incidence might be driven by the stronger effects of local climate variables such as temperature and rainfall. Further research is required to disentangle these effects.

  10. Influence of the El Niño/Southern Oscillation on tornado and hail frequency in the United States

    NASA Astrophysics Data System (ADS)

    Allen, John T.; Tippett, Michael K.; Sobel, Adam H.

    2015-04-01

    The El Niño/Southern Oscillation (ENSO) is characterized by changes in sea surface temperature (SST) and atmospheric convection in the tropical Pacific, and modulates global weather and climate. The phase of ENSO influences United States (US) temperature and precipitation and has long been hypothesized to influence severe thunderstorm occurrence over the US. However, limitations of the severe thunderstorm observational record, combined with large year-to-year variability, have made it difficult to demonstrate an ENSO influence during the peak spring season. Here we use environmental indices that are correlated with tornado and hail activity, and show that ENSO modulates tornado and hail occurrence during the winter and spring by altering the large-scale environment. We show that fewer tornadoes and hail events occur over the central US during El Niño and conversely more occur during La Niña conditions. Moreover, winter ENSO conditions often persist into early spring, and consequently the winter ENSO state can be used to predict changes in tornado and hail frequency during the following spring. Combined with our current ability to predict ENSO several months in advance, our findings provide a basis for long-range seasonal prediction of severe thunderstorm activity.

  11. Impacts of El Niño Southern Oscillation and Indian Ocean Dipole on dengue incidence in Bangladesh

    NASA Astrophysics Data System (ADS)

    Banu, Shahera; Guo, Yuming; Hu, Wenbiao; Dale, Pat; MacKenzie, John S.; Mengersen, Kerrie; Tong, Shilu

    2015-11-01

    Dengue dynamics are driven by complex interactions between hosts, vectors and viruses that are influenced by environmental and climatic factors. Several studies examined the role of El Niño Southern Oscillation (ENSO) in dengue incidence. However, the role of Indian Ocean Dipole (IOD), a coupled ocean atmosphere phenomenon in the Indian Ocean, which controls the summer monsoon rainfall in the Indian region, remains unexplored. Here, we examined the effects of ENSO and IOD on dengue incidence in Bangladesh. According to the wavelet coherence analysis, there was a very weak association between ENSO, IOD and dengue incidence, but a highly significant coherence between dengue incidence and local climate variables (temperature and rainfall). However, a distributed lag nonlinear model (DLNM) revealed that the association between dengue incidence and ENSO or IOD were comparatively stronger after adjustment for local climate variables, seasonality and trend. The estimated effects were nonlinear for both ENSO and IOD with higher relative risks at higher ENSO and IOD. The weak association between ENSO, IOD and dengue incidence might be driven by the stronger effects of local climate variables such as temperature and rainfall. Further research is required to disentangle these effects.

  12. Parallel responses of species and genetic diversity to El Niño Southern Oscillation-induced environmental destruction.

    PubMed

    Cleary, Daniel F R; Fauvelot, Cécile; Genner, Martin J; Menken, Steph B J; Mooers, Arne Ø

    2006-03-01

    Species diversity within communities and genetic diversity within species are two fundamental levels of biodiversity. Positive relationships between species richness and within-species genetic diversity have recently been documented across natural and semi-natural habitat islands, leading Vellend to suggest a novel macro-ecological pattern termed the species-genetic diversity correlation. We tested whether this prediction holds for areas affected by recent habitat disturbance using butterfly communities in east Kalimantan, Indonesia. Here, we show that both strong spatial and temporal correlations exist between species and allelic richness across rainforest habitats affected by El Niño Southern Oscillation-induced disturbance. Coupled with evidence that changes in species richness are a direct result of local extirpation and lower recruitment, these data suggest that forces governing variation at the two levels operate over parallel and short timescales, with implications for biodiversity recovery following disturbance. Remnant communities may be doubly affected, with reductions in species richness being associated with reductions in genetic diversity within remnant species.

  13. El Niño-Southern Oscillation sensitivity to cumulus entrainment in a coupled general circulation model

    NASA Astrophysics Data System (ADS)

    Kim, Daehyun; Jang, Yeon-Soo; Kim, Dong-Hoon; Kim, Young-Ho; Watanabe, Masahiro; Jin, Fei-Fei; Kug, Jong-Seong

    2011-11-01

    A series of 200 year long integrations is performed using the Geophysical Fluid Dynamics Laboratory CM2.1 by varying the Tokioka parameter, a minimum entrainment rate threshold in the cumulus parameterization. Changing the threshold alters both the tropical Pacific mean state and the El Niño-Southern Oscillation (ENSO) variability. Increasing the Tokioka parameter causes a basin-wide cooling in the tropical Pacific with the reduction of high clouds. The degree of cooling in the western part of the basin is bigger than that in the east. As a result, the east-west asymmetry in the tropical Pacific sea surface temperature (SST) decreases with increasing the Tokioka parameter. Accompanied with the reduced east-west SST asymmetry are the increase of mean precipitation over the eastern Pacific and the eastward shift of the atmospheric responses to the ENSO-related SST forcing. The eastward shifted wind stress anomaly associated with ENSO leads to the stronger ENSO variability. In this way the magnitude of ENSO simulated in this model increases with the Tokioka parameter. Implication of our results on the relationship between the tropical Pacific mean state and ENSO is discussed.

  14. 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.

  15. Impacts of El Niño-Southern Oscillation on the wheat market: A global dynamic analysis.

    PubMed

    Gutierrez, Luciano

    2017-01-01

    Although the widespread influence of the El Niño-Southern Oscillation (ENSO) occurrences on crop yields of the main agricultural commodities is well known, the global socio-economic consequences of ENSO still remain uncertain. Given the global importance of wheat for global consumption by providing 20% of global calories and nourishment, the monitoring and prediction of ENSO-induced variations in the worldwide wheat market are essential for allowing national governments to manage the associated risks and to ensure the supplies of wheat for consumers, including the underprivileged. To this end, we propose a global dynamic model for the analysis of ENSO impacts on wheat yield anomalies, export prices, exports and stock-to-use ratios. Our framework focuses on seven countries/regions: the six main wheat-exporting countries-the United States, Argentina, Australia, Canada, the EU, and the group of the main Black Sea export countries, i.e. Russia, Ukraine, and Kazakhstan-plus the rest of the world. The study shows that La Niña exerts, on average, a stronger and negative impact on wheat yield anomalies, exports and stock-to-use ratios than El Niño. In contrast, wheat export prices are positively related to La Niña occurrences evidencing, once again, its steady impact in both the short and long run. Our findings emphasize the importance of the two ENSO extreme phases for the worldwide wheat market.

  16. Impacts of El Niño Southern Oscillation and Indian Ocean Dipole on dengue incidence in Bangladesh

    PubMed Central

    Banu, Shahera; Guo, Yuming; Hu, Wenbiao; Dale, Pat; Mackenzie, John S.; Mengersen, Kerrie; Tong, Shilu

    2015-01-01

    Dengue dynamics are driven by complex interactions between hosts, vectors and viruses that are influenced by environmental and climatic factors. Several studies examined the role of El Niño Southern Oscillation (ENSO) in dengue incidence. However, the role of Indian Ocean Dipole (IOD), a coupled ocean atmosphere phenomenon in the Indian Ocean, which controls the summer monsoon rainfall in the Indian region, remains unexplored. Here, we examined the effects of ENSO and IOD on dengue incidence in Bangladesh. According to the wavelet coherence analysis, there was a very weak association between ENSO, IOD and dengue incidence, but a highly significant coherence between dengue incidence and local climate variables (temperature and rainfall). However, a distributed lag nonlinear model (DLNM) revealed that the association between dengue incidence and ENSO or IOD were comparatively stronger after adjustment for local climate variables, seasonality and trend. The estimated effects were nonlinear for both ENSO and IOD with higher relative risks at higher ENSO and IOD. The weak association between ENSO, IOD and dengue incidence might be driven by the stronger effects of local climate variables such as temperature and rainfall. Further research is required to disentangle these effects. PMID:26537857

  17. Impacts of El Niño-Southern Oscillation on the wheat market: A global dynamic analysis

    PubMed Central

    2017-01-01

    Although the widespread influence of the El Niño-Southern Oscillation (ENSO) occurrences on crop yields of the main agricultural commodities is well known, the global socio-economic consequences of ENSO still remain uncertain. Given the global importance of wheat for global consumption by providing 20% of global calories and nourishment, the monitoring and prediction of ENSO-induced variations in the worldwide wheat market are essential for allowing national governments to manage the associated risks and to ensure the supplies of wheat for consumers, including the underprivileged. To this end, we propose a global dynamic model for the analysis of ENSO impacts on wheat yield anomalies, export prices, exports and stock-to-use ratios. Our framework focuses on seven countries/regions: the six main wheat-exporting countries—the United States, Argentina, Australia, Canada, the EU, and the group of the main Black Sea export countries, i.e. Russia, Ukraine, and Kazakhstan—plus the rest of the world. The study shows that La Niña exerts, on average, a stronger and negative impact on wheat yield anomalies, exports and stock-to-use ratios than El Niño. In contrast, wheat export prices are positively related to La Niña occurrences evidencing, once again, its steady impact in both the short and long run. Our findings emphasize the importance of the two ENSO extreme phases for the worldwide wheat market. PMID:28594886

  18. People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands

    PubMed Central

    Bird, Douglas W.; Codding, Brian F.

    2016-01-01

    While evidence mounts that indigenous burning has a significant role in shaping pyrodiversity, the processes explaining its variation across local and external biophysical systems remain limited. This is especially the case with studies of climate–fire interactions, which only recognize an effect of humans on the fire regime when they act independently of climate. In this paper, we test the hypothesis that an anthropogenic fire regime (fire incidence, size and extent) does not covary with climate. In the lightning regime, positive El Niño southern oscillation (ENSO) values increase lightning fire incidence, whereas La Niña (and associated increases in prior rainfall) increase fire size. ENSO has the opposite effect in the Martu regime, decreasing ignitions in El Niño conditions without affecting fire size. Anthropogenic ignition rates covary positively with high antecedent rainfall, whereas fire size varies only with high temperatures and unpredictable winds, which may reduce control over fire spread. However, total area burned is similarly predicted by antecedent rainfall in both regimes, but is driven by increases in fire size in the lightning regime, and fire number in the anthropogenic regime. We conclude that anthropogenic regimes covary with climatic variation, but detecting the human–climate–fire interaction requires multiple measures of both fire regime and climate. This article is part of the themed issue ‘The interaction of fire and mankind’. PMID:27216513

  19. Flood frequencies and durations and their response to El Niño Southern Oscillation: Global analysis

    NASA Astrophysics Data System (ADS)

    Ward, P. J.; Kummu, M.; Lall, U.

    2016-08-01

    Floods are one of the most serious forms of natural hazards in terms of the damages they cause. In 2012 alone, flood damages exceeded 19 billion. A large proportion of the damages from several recent major flood disasters, such as those in South India and South Carolina (2015), England and Wales (2014), the Mississippi (2012), Thailand (2011), Queensland (Australia) (2010-2011), and Pakistan (2010), were related to the long duration of those flood events. However, most flood risk studies to date do not account for flood duration. In this paper, we provide the first global modelling exercise to assess the link between interannual climate variability and flood duration and frequency. Specifically, we examine relationships between simulated flood events and El Niño Southern Oscillation (ENSO). Our results show that the duration of flooding appears to be more sensitive to ENSO than is the case for flood frequency. At the globally aggregated scale, we found floods to be significantly longer during both El Niño and La Niña years, compared to neutral years. At the scale of individual river basins, we found strong correlations between ENSO and both flood frequency and duration for a large number of basins, with generally stronger correlations for flood duration than for flood frequency. Future research on flood impacts should attempt to incorporate more information on flood durations.

  20. The El Niño Southern Oscillation (ENSO) induced modulations in precipitation and nitrogen wet deposition rates in the continental United States

    NASA Astrophysics Data System (ADS)

    Nergui, T.; Chung, S. H.; Adam, J. C.; Evans, R. D.

    2015-12-01

    The ENSO affects atmospheric nitrogen (N) deposition rates through its modulation on N wet deposition. Precipitation and wet deposition measurements at 151 sites of the National Atmospheric Deposition Program/National Trends Network and the NINO3.4 SST climate index from the NOAA's Climate Prediction Center are analyzed to determine the impacts of the ENSO on N wet deposition and precipitation rates in the continental U.S. Precipitation and N wet deposition time series are dominated by high frequency components; however, they contain a wide range of inter-annual frequency components depending on the location. At the 2-to 6-year timescale, variability of precipitation and N wet deposition rates in the Pacific Northwest, the Rocky Mountains, the Gulf States, the Northeast, and the Great Lakes regions are correlated with that of the NINO3.4 index (r2= 0.09-0.59 for precipitation and r2= 0.09-0.52 for N wet deposition, p<0.05). The spatial patterns and strength of the correlations vary by region and season. The correlations are the strongest and most spatially extensive during winter; 46-62% and 46-53% of the 2- to 6-year variability of precipitation and N wet deposition rates in the Rocky Mountains, the Gulf of Mexico, and near the Great Lakes can be explained by ENSO activity. The wintertime relationships tend to hold through springtime in the Great Lakes, the Ohio River Valley, and the Northeast. During the El Niño winters and springs, N wet deposition rates are higher than normal (greater than the 70thpercentile) in the southern Great Plains and the Gulf Coast. Winter and spring La Niña episodes bring precipitation and N wet deposition rates above normal over the Cascades, the Ohio River Valley, the Northeast and the Great Lakes regions. The ensemble mean of eleven coupled General Circulation Models (Yeh et al., 2009) shows that the weak ENSO cycles, having small to moderate amplitudes and reoccurring in shorter time intervals, are projected to dominate in the 21

  1. Inter-decadal change in El Niño-Southern Oscillation examined with Bjerknes stability index analysis

    NASA Astrophysics Data System (ADS)

    An, Soon-Il; Bong, Hayoung

    2016-08-01

    Characteristics of El Niño-Southern Oscillation (ENSO) have changed since the late 1970s as it synchronized with the Pacific Decadal Oscillation (PDO). In order to investigate the primary feedback process responsible for the interdecadal change in ENSO characteristics according to the PDO, using the ocean assimilation data (SODA) and the reanalysis data (NCEP/NCAR), we performed Bjerknes linear stability index (BJ index) analysis of two decadal periods: one before the late 1970s (the nPDO period) and the other after the late 1970s (the pPDO period). The BJ index for the pPDO period (-0.07 year-1 for the growth rate of the eastern Pacific SST anomaly) is significantly larger than that for the nPDO period (-0.25 year-1). The larger BJ index value is primarily due to the enhanced zonal advection feedback (ZA; +0.44 year-1), thermocline feedback (TH; +0.33 year-1), and the reduced damping by the mean meridional current (MD; +0.16 year-1). The increases in ZA and TH are mainly attributed to the shoaling of the mean thermocline depth, which increased the sensitivity of the ocean dynamic fields to the wind forcing; and the reduced MD is related to the reduced mean meridional current associated with the weakened trade wind. The enhanced positive feedback is partly compensated by the enhanced thermodynamic damping including the shortwave, sensible heat flux and latent heat flux (collectively, -0.88 year-1). Interestingly, the change in air-sea coupling strength from the nPDO to the pPDO period was small. Without the two extreme El Niño events (1982-1983 and 1997-1998) in the pPDO period (pPDO_noBIG), the difference in BJ index between nPDO and pPDO_noBIG periods became smaller (~0.07 year-1), indicating that the two extreme El Niño events largely contribute to the larger ENSO variability of the pPDO period, possibly due to nonlinear feedback processes. Nevertheless, qualitative similarity in each of the feedback and damping components of BJ index exists between the p

  2. Coupled decadal variability of the North Atlantic Oscillation, regional rainfall and karst spring discharges in the Campania region (southern Italy)

    NASA Astrophysics Data System (ADS)

    De Vita, P.; Allocca, V.; Manna, F.; Fabbrocino, S.

    2012-05-01

    Thus far, studies on climate change have focused mainly on the variability of the atmospheric and surface components of the hydrologic cycle, investigating the impact of this variability on the environment, especially with respect to the risks of desertification, droughts and floods. Conversely, the impacts of climate change on the recharge of aquifers and on the variability of groundwater flow have been less investigated, especially in Mediterranean karst areas whose water supply systems depend heavily upon groundwater exploitation. In this paper, long-term climatic variability and its influence on groundwater recharge were analysed by examining decadal patterns of precipitation, air temperature and spring discharges in the Campania region (southern Italy), coupled with the North Atlantic Oscillation (NAO). The time series of precipitation and air temperature were gathered over 90 yr, from 1921 to 2010, using 18 rain gauges and 9 air temperature stations with the most continuous functioning. The time series of the winter NAO index and of the discharges of 3 karst springs, selected from those feeding the major aqueducts systems, were collected for the same period. Regional normalised indexes of the precipitation, air temperature and karst spring discharges were calculated, and different methods were applied to analyse the related time series, including long-term trend analysis using smoothing numerical techniques, cross-correlation and Fourier analysis. The investigation of the normalised indexes highlighted the existence of long-term complex periodicities, from 2 to more than 30 yr, with differences in average values of up to approximately ±30% for precipitation and karst spring discharges, which were both strongly correlated with the winter NAO index. Although the effects of the North Atlantic Oscillation (NAO) had already been demonstrated in the long-term precipitation and streamflow patterns of different European countries and Mediterranean areas, the results

  3. Magmatic heat and the El Nino cycle

    USGS Publications Warehouse

    Shaw, H.R.; Moore, J.G.

    1988-01-01

    Large submarine lava flows with apparent volumes exceeding 10 km3 have recently been imaged on the deep ocean floor in various parts of the Pacific by means of GLORIA and SeaMarc side-looking sonar surveys. Such flows may produce thermal anomalies large enough to perturb the cyclic processes of the ocean and could be a factor in the genesis of El Nino phenomena. We find that known volume rates of mid-ocean magma production could generate repetitive thermal anomalies as large as 10% of the average El Nino sea surface anomaly at intervals of about 5 years (the mean interval of El Nino events between 1935 and 1984). Likewise, estimated rates of eruption, cooling of lava on the seafloor, and transfer of heat to the near-surface environment could reasonably produce a thermal anomaly comparable to that associated with El Nino. Larger magmatic events, associated with fluctuations in the total magmatic power and seismicity along the East Pacific Rise, are possible at longer intervals and may explain the extreme size of some El Nino events, such as that of 1982-1983. -Authors

  4. Interannual and interdecadal oscillation patterns in sea level

    SciTech Connect

    Unal, Y.S.; Ghil, M.

    1995-07-01

    Relative sea-level height (RSLH) data at 213 tide-gauge stations have been analyzed on a monthly an an annual basis to study interannual and interdecadal oscillations. The main tools of the study are similar spectrum analysis (SSA) and multichannel SSA (M-SSA). Very-low-frequency variability of RSLH was filtered by SSA to estimate the linear trend at each station. Global sea-level rise, after post-glacial rebound corrections, has been found to equal 1.62{+-}0.38 mm/y, by averaging over 175 stations. The study identified two dominant time scales of El Nino-Southern Oscillation (ENSO) variability, quasi-biennial and low-frequency, in the RSLH data at almost all stations. However, the amplitudes of both ENSO signals are higher in the equatorial Pacific and along the west coast of North America. Throughout the Pacific, the study found three dominant spatio-temporal oscillatory patterns, associated with time scales of ENSO variability; their periods are 2.2.5-3 and 4-6 y. Strong and weak El Nino years are evident in the sea-level time series reconstructed from the quasi-biennial and low-frequency modes. Interannual variability with periods of 3 and 4-8 y is detected in the Atlantic RSLH data. In the eastern Atlantic region, we have found slow propagation of both modes northward and southward, away from 40-45{degrees}N. Interdecadal oscillations were studied using 81 stations with sufficiently long and continuous records. Most of these have variability at 9-13 and some at 18 y. Two significant eigenmode pairs, corresponding to periods of 11.6 and 12.8 y, are found in the eastern and western Atlantic ocean at latitudes 40{degrees}N-70{degrees}N and 10{degrees}N-50{degrees}N, respectively. 60 refs., 23 figs., 3 tabs.

  5. El Niño-Southern Oscillation (ENSO) effects on Hessian fly (Diptera: Cecidomyiidae) infestation in the southeastern United States.

    PubMed

    Woli, P; Ortiz, B V; Buntin, D; Flanders, K

    2014-12-01

    Climate variability is expected to have an influence on the population of Hessian fly, Mayetiola destructor Say (Diptera: Cecidomyiidae), a serious insect pest of winter wheat in the southeastern United States. This study had two objectives: 1) to examine the effects of El Niño-Southern Oscillation (ENSO) on Hessian fly infestation and 2) to develop a weather-based Hessian fly infestation model for wheat yield loss prediction. At least 20 years of Hessian fly infestation and wheat yield records from two locations in South Georgia were used for this study. The yearly values of infestation were separated by ENSO phase and tested to assess the infestation differences across ENSO phases. Each year, yield losses from infestation were calculated by subtracting the yields of resistant varieties from those of susceptible ones. The yield losses were then separated by ENSO phase and tested. Multiple regression analyses were conducted to identify the contribution of monthly weather variables and changes in wheat acreage to Hessian fly infestation. Results showed that Hessian fly infestation and yield losses were greatest during the La Niña and least during the El Niño phase. The weather conditions that significantly increased the risk for infestation were those of the August-February period. The risk of infestation was higher during August-September under wetter, cooler conditions and during October-February under drier, warmer conditions. These findings could help wheat growers reduce the risk of infestation in the years that are expected to have more infestation through the adoption of necessary mitigation measures before the crop season.

  6. El Niño Southern Oscillation and vegetation dynamics as predictors of dengue fever cases in Costa Rica

    NASA Astrophysics Data System (ADS)

    Fuller, D. O.; Troyo, A.; Beier, J. C.

    2009-01-01

    Dengue fever (DF) and dengue hemorrhagic fever (DHF) are growing health concerns throughout Latin America and the Caribbean. This study focuses on Costa Rica, which experienced over 100 000 cases of DF/DHF from 2003 to 2007. We utilized data on sea-surface temperature anomalies related to the El Niño Southern Oscillation (ENSO) and two vegetation indices derived from the Moderate Resolution Imaging Spectrometer (MODIS) from the Terra satellite to model the influence of climate and vegetation dynamics on DF/DHF cases in Costa Rica. Cross-correlations were calculated to evaluate both positive and negative lag effects on the relationships between independent variables and DF/DHF cases. The model, which utilizes a sinusoid and non-linear least squares to fit case data, was able to explain 83% of the variance in weekly DF/DHF cases when independent variables were shifted backwards in time. When the independent variables were shifted forward in time, consistently with a forecasting approach, the model explained 64% of the variance. Importantly, when five ENSO and two vegetation indices were included, the model reproduced a major DF/DHF epidemic of 2005. The unexplained variance in the model may be due to herd immunity and vector control measures, although information regarding these aspects of the disease system are generally lacking. Our analysis suggests that the model may be used to predict DF/DHF outbreaks as early as 40 weeks in advance and may also provide valuable information on the magnitude of future epidemics. In its current form it may be used to inform national vector control programs and policies regarding control measures; it is the first climate-based dengue model developed for this country and is potentially scalable to the broader region of Latin America and the Caribbean where dramatic increases in DF/DHF incidence and spread have been observed.

  7. Impact of El Niño Southern Oscillation on infectious disease hospitalization risk in the United States

    PubMed Central

    Fisman, David N.; Tuite, Ashleigh R.; Brown, Kevin A.

    2016-01-01

    Although the global climate is changing at an unprecedented rate, links between weather and infectious disease have received little attention in high income countries. The “El Niño Southern Oscillation” (ENSO) occurs irregularly and is associated with changing temperature and precipitation patterns. We studied the impact of ENSO on infectious diseases in four census regions in the United States. We evaluated infectious diseases requiring hospitalization using the US National Hospital Discharge Survey (1970–2010) and five disease groupings that may undergo epidemiological shifts with changing climate: (i) vector-borne diseases, (ii) pneumonia and influenza, (iii) enteric disease, (iv) zoonotic bacterial disease, and (v) fungal disease. ENSO exposure was based on the Multivariate ENSO Index. Distributed lag models, with adjustment for seasonal oscillation and long-term trends, were used to evaluate the impact of ENSO on disease incidence over lags of up to 12 mo. ENSO was associated more with vector-borne disease [relative risk (RR) 2.96, 95% confidence interval (CI) 1.03–8.48] and less with enteric disease (0.73, 95% CI 0.62–0.87) in the Western region; the increase in vector-borne disease was attributable to increased risk of rickettsioses and tick-borne infectious diseases. By contrast, ENSO was associated with more enteric disease in non-Western regions (RR 1.12, 95% CI 1.02–1.15). The periodic nature of ENSO may make it a useful natural experiment for evaluation of the impact of climatic shifts on infectious disease risk. The impact of ENSO suggests that warmer temperatures and extreme variation in precipitation events influence risks of vector-borne and enteric disease in the United States. PMID:27791069

  8. Tales of volcanoes and El-Niño southern oscillations with the oxygen isotope anomaly of sulfate aerosol

    PubMed Central

    Shaheen, Robina; Abauanza, Mariana; Jackson, Teresa L.; McCabe, Justin; Savarino, Joel; Thiemens, Mark H.

    2013-01-01

    The ability of sulfate aerosols to reflect solar radiation and simultaneously act as cloud condensation nuclei renders them central players in the global climate system. The oxidation of S(IV) compounds and their transport as stable S(VI) in the Earth’s system are intricately linked to planetary scale processes, and precise characterization of the overall process requires a detailed understanding of the linkage between climate dynamics and the chemistry leading to the product sulfate. This paper reports a high-resolution, 22-y (1980–2002) record of the oxygen-triple isotopic composition of sulfate (SO4) aerosols retrieved from a snow pit at the South Pole. Observed variation in the O-isotopic anomaly of SO4 aerosol is linked to the ozone variation in the tropical upper troposphere/lower stratosphere via the Ozone El-Niño Southern Oscillations (ENSO) Index (OEI). Higher ∆17O values (3.3‰, 4.5‰, and 4.2‰) were observed during the three largest ENSO events of the past 2 decades. Volcanic events inject significant quantities of SO4 aerosol into the stratosphere, which are known to affect ENSO strength by modulating stratospheric ozone levels (OEI = 6 and ∆17O = 3.3‰, OEI = 11 and ∆17O = 4.5‰) and normal oxidative pathways. Our high-resolution data indicated that ∆17O of sulfate aerosols can record extreme phases of naturally occurring climate cycles, such as ENSOs, which couple variations in the ozone levels in the atmosphere and the hydrosphere via temperature driven changes in relative humidity levels. A longer term, higher resolution oxygen-triple isotope analysis of sulfate aerosols from ice cores, encompassing more ENSO periods, is required to reconstruct paleo-ENSO events and paleotropical ozone variations. PMID:23447567

  9. El Niño Southern Oscillation and vegetation dynamics as predictors of dengue fever cases in Costa Rica.

    PubMed

    Fuller, D O; Troyo, A; Beier, J C

    2009-03-04

    Dengue fever (DF) and dengue hemorrhagic fever (DHF) are growing health concerns throughout Latin America and the Caribbean. This study focuses on Costa Rica, which experienced over 100 000 cases of DF/DHF from 2003 to 2007. We utilized data on sea-surface temperature anomalies related to the El Niño Southern Oscillation (ENSO) and two vegetation indices derived from the Moderate Resolution Imaging Spectrometer (MODIS) from the Terra satellite to model the influence of climate and vegetation dynamics on DF/DHF cases in Costa Rica. Cross-correlations were calculated to evaluate both positive and negative lag effects on the relationships between independent variables and DF/DHF cases. The model, which utilizes a sinusoid and non-linear least squares to fit case data, was able to explain 83% of the variance in weekly DF/DHF cases when independent variables were shifted backwards in time. When the independent variables were shifted forward in time, consistently with a forecasting approach, the model explained 64% of the variance. Importantly, when five ENSO and two vegetation indices were included, the model reproduced a major DF/DHF epidemic of 2005. The unexplained variance in the model may be due to herd immunity and vector control measures, although information regarding these aspects of the disease system are generally lacking. Our analysis suggests that the model may be used to predict DF/DHF outbreaks as early as 40 weeks in advance and may also provide valuable information on the magnitude of future epidemics. In its current form it may be used to inform national vector control programs and policies regarding control measures; it is the first climate-based dengue model developed for this country and is potentially scalable to the broader region of Latin America and the Caribbean where dramatic increases in DF/DHF incidence and spread have been observed.

  10. El Niño-Southern Oscillation is linked to decreased energetic condition in long-distance migrants.

    PubMed

    Paxton, Kristina L; Cohen, Emily B; Paxton, Eben H; Németh, Zoltán; Moore, Frank R

    2014-01-01

    Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in

  11. Betting with single forams: Uncertainty constraints on El Niño Southern Oscillation reconstructions using individual foraminiferal analyses

    NASA Astrophysics Data System (ADS)

    Quinn, T. M.; Thirumalai, K.; Partin, J. W.; Jackson, C. S.

    2012-12-01

    Recent scientific investigations of sub-millennial paleoceanographic variability have attempted to use the population statistics of individual planktic foraminiferal δ18O to resolve high-frequency climate signals such as the El Niño Southern Oscillation (ENSO). However, this approach is complicated by the relatively short lifespan of individual foraminifera (~2-4 weeks) compared to the time represented by a typical marine sediment sample (decades to millennia). The resolving ability of individual foraminiferal analyses (IFA) is investigated through simulations on idealized virtual sediment samples constructed from the instrumental record. We focus on ENSO-related sea surface temperatures (SST) anomalies in the Niño3.4 region of the tropical Pacific Ocean. We constrain uncertainties on the range and standard deviation associated with the IFA technique using a bootstrap Monte Carlo approach. Sensitivity to changes in ENSO amplitude and frequency and the influence of the seasonal cycle on IFA are tested by constructing synthetic time series containing different characteristics of variability. We find that the standard deviation and range may be used to detect ENSO amplitude changes at particular thresholds (though the uncertainty in range is much larger than in standard deviation); however, it is improbable that IFA can resolve changes in ENSO frequency. We also determine that ENSO amplitude is the main driver of the IFA signal at Niño3.4 where the SST response to ENSO is large, and the seasonal cycle is relatively small. Our results suggest that rigorous uncertainty analysis should become a standard for IFA studies as it is crucial for accurate interpretation.

  12. Statistical constraints on El Niño Southern Oscillation reconstructions using individual foraminifera: A sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Thirumalai, Kaustubh; Partin, Judson W.; Jackson, Charles S.; Quinn, Terrence M.

    2013-09-01

    Recent investigations of submillennial paleoceanographic variability have attempted to resolve high-frequency climate signals such as the El Niño Southern Oscillation (ENSO) using the population statistics of individual planktic foraminiferal δ18O analyses. This approach is complicated by the relatively short lifespan of individual foraminifers (~2-4 weeks) compared to the time represented by a typical marine sediment sample (~decades to millennia). Here, we investigate the uncertainty associated with individual foraminiferal analyses (IFA) through simulations on forward modeled δ18Ocarbonate. First, focusing on the Niño3.4 region of the tropical Pacific Ocean, a bootstrap Monte Carlo algorithm is developed to constrain the uncertainty on IFA-statistics. Subsequently, to test the sensitivity of IFA to changes in seasonal cycle amplitude, ENSO amplitude, and ENSO frequency, synthetic time series of δ18Ocarbonate with differing variability are constructed and tested with our algorithm. The probabilities of the IFA technique in detecting changes in ENSO amplitude and seasonal cycle amplitude (or a combination of both) for the surface ocean and thermocline at different locations in the tropical Pacific are quantified. We find that the uncertainty in the standard deviation is smaller than the range, that the IFA-signal is insensitive to ENSO frequency, and at certain locations the seasonal cycle may dominate ENSO. IFA sensitivity towards ENSO is highest at the central equatorial Pacific surface ocean and the eastern equatorial Pacific (EEP) thermocline whereas sensitivity towards the seasonal cycle is highest at the EEP surface ocean. Our results suggest that rigorous uncertainty quantification should become standard practice for accurately interpreting IFA-data.

  13. El Niño-Southern Oscillation-based index insurance for floods: Statistical risk analyses and application to Peru

    NASA Astrophysics Data System (ADS)

    Khalil, Abedalrazq F.; Kwon, Hyun-Han; Lall, Upmanu; Miranda, Mario J.; Skees, Jerry

    2007-10-01

    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 because of 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 El Niño-Southern Oscillation (ENSO) related climate indices are explored for use as a proxy to extreme rainfall in one of the districts of Peru, Piura. The ENSO index insurance product may be purchased by banks or microfinance institutions 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 events. This disrupts trade for many microenterprises. The reliability and quality of the local rainfall data are variable. Averaging the financial risk across the region is desirable. Some issues with the implementation of the proxy ENSO index are identified and discussed. Specifically, we explore (1) the reliability of the index at different levels of probability of exceedance of maximum seasonal rainfall, (2) the effect of sampling uncertainties and the strength of the proxy's association to local outcome, (3) the potential for clustering of payoffs, (4) the potential that the index could be predicted with some lead time prior to the flood season, and (5) evidence

  14. Exploring impacts of El Niño Southern Oscillation on Meteorological Forcing within the Glaciated Llanganuco Valley, Peru

    NASA Astrophysics Data System (ADS)

    Covert, J. M.; Hellstrom, R. A.

    2015-12-01

    El Niño Southern Oscillation (ENSO) is known to be the primary modulator of inter-annual weather patterns in the Andes, but its impact in the Cordillera Blanca (White Range) is not fully understood. In 2004 an autonomous sensor network (ASN) was installed in the Llanganuco Valley in the Cordillera Blanca, Peru consisting of two automatic weather stations (AWS) located at the base and upper ridge of the valley connected by four air temperature/humidity micro-loggers at equal elevation intervals. The ASN permits high resolution evaluations of the micro-scale meteorology within the valley. Twenty-four hour composites and monthly averages of wind, solar insolation, air temperature profiles, and precipitation obtained from the ASN were analyzed for the historical wet and dry seasons between the years of 2005 and 2015. The evidence suggests that teleconnections exist between eastern equatorial Pacific Ocean sea surface temperatures and meteorological forcing within the Valley. Comparisons between the two AWS units reveal similar ENSO impacts during the wet season that are not replicated in the dry season. We found that warm and cold ENSO create anomalies that appear unique to this region of the outer Tropics. Warm ENSO phases promote wetter than normal dry seasons and dryer than normal wet seasons and visa versa for cold phases of ENSO. Air temperature is strongly positively correlated to warm ENSO phases during the wet season and depends on elevation during the dry season. Insolation is negatively correlated to warm ENSO phases at higher elevations with weak positive correlation at lower elevations. We attribute observed seasonality, in part, to interactions between channeling of synoptic flow and thermally driven winds. Although the sporadic availability of data prevents definitive conclusions at this time, recent improvements in the ASN infrastructure will facilitate deeper understanding of ENSO impacts on meteorological forcing within pro-glacial valleys of the

  15. Analysis of El Niño-Southern Oscillation Phenomena's Effect on the Gross Domestic Product of Western Pacific Nations

    NASA Astrophysics Data System (ADS)

    O'Connell, M.; Lewis, A.; Mezzafonte, D.

    2014-12-01

    El Niño Southern Oscillation (ENSO) is a climatological phenomenon that occurs in the tropical Pacific Ocean which has a direct influence on the climate of western Pacific nations. This study evaluated the meteorological effects of ENSO on the economies of Indonesia and the Philippines. It was hypothesized that decreased precipitation in the western Tropical Pacific region during El Niño events causes decreases in agricultural production in the region resulting in a negative effect on a nation's Gross Domestic Product (GDP). Furthermore, during La Niña events, when precipitation increases, an increase in the nation's agricultural GDP and overall GDP is expected. Annual GDP data were obtained from the World Bank and the Bank of Indonesia for 1960-2012. Sea surface temperatures (SST) data, in the Niño 3.4 region, were obtained from the National Oceanic and Atmospheric Administration (NOAA) National Climate Data Center. Data of the agricultural and total GDP of Indonesia and the Philippines had inconclusive correlations with ENSO signal data. By examining data between smaller time segments of the overall 1960-2012 timeframe, more conclusive results could not be discerned. Indonesia's quarterly non-oil GDP for 2000-2009 was independently correlated with ENSO providing better insight on the variables' relationship during discrete ENSO phenomena. The results provided strong correlation coefficients of 0.831 and 0.624 in support of the antithesis as well as -0.421 in support of the hypothesis. An economic anomaly known as the East Asian Financial Crisis may have been the cause of the unexpected correlations however more data is needed to be certain. Overall, the results demonstrated weak to moderate correlations between studied variables. However, more data is needed to reach substantial conclusions.

  16. Simultaneous modulations of precipitation and temperature extremes in Southern parts of China by the boreal summer intraseasonal oscillation

    NASA Astrophysics Data System (ADS)

    Chen, Yang; Zhai, Panmao

    2017-01-01

    The boreal summer intraseasonal oscillation (BSISO), including a 30-60 day component (BSISO1) and a quasi-biweekly component (BSISO2), is the most prominent form of subtropical intraseasonal variability. Influences of BSISOs on summertime precipitation and temperature extremes in China are examined. Results indicate that BSISOs can simultaneously facilitate precipitation extremes in central-eastern China and extreme high temperatures in South China-Southeast China. During phase 2-4 of active BSISO1, accompanying precipitation extremes in central-eastern China, there is a fourfold-fivefold increase in probability of extreme high temperatures in Southeast China. About 50% of such simultaneous extremes fall into phase 2-3. BSISO2's influences are pronounced from phase 6 to the next phase 2, with about 58% simultaneous extremes clustered within phase 7 to the next phase 1. It is the BSISO-induced vertical cell, with ascending motion in the Yangtze-Huai River Valley and descending motion in the south, that contributes to simultaneous extremes. Enhanced low-level southwesterlies convey moist and warm air towards southern parts of China. Strengthened ascending branch loaded by anomalously abundant moisture produces precipitation extremes in the north. Concurrently, combined effects of warm advection and descent-triggered adiabatic heating anchors extreme high temperatures well located in South China. The northeastward propagation of the BSISO1 confines influenced regions to eastern-southeastern parts of China, with gradually narrowing spatial extents. The BSISO2-induced simultaneous extremes sweep much broader areas, from southeast coasts to the central inlands. Above analyses on BSISOs-simultaneous extremes relationship lay a crucial scientific basis for predicting these high-impact events on sub-seasonal to seasonal scales.

  17. Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation.

    PubMed

    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

    2017-11-01

    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 warming and vice versa. The impact of the El Niño-Southern Oscillation (ENSO) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño events 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 ENSO 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 ENSO events, 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 ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO 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 ENSO periods. The occurrence of several El Niño events 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 warming. © 2017 John Wiley & Sons Ltd.

  18. Association of early annual peak influenza activity with El Niño southern oscillation in Japan.

    PubMed

    Zaraket, Hassan; Saito, Reiko; Tanabe, Naohito; Taniguchi, Kiyosu; Suzuki, Hiroshi

    2008-07-01

    Seasonality characterizing influenza epidemics suggests susceptibility to climate variation. El Niño southern oscillation (ENSO), which involves two extreme events, El Niño and La Niña, is well-known for its large effects on inter-annual climate variability. The influence of ENSO on several diseases has been described. In this study, we attempt to analyze the possible influence of ENSO on the timing of the annual influenza activity peak using influenza-like illness report data in Japan during 1983-2007. Influenza surveillance data for 25 influenza epidemics, available under the National Epidemiological Surveillance of the Infectious Diseases, was used in this study. ENSO data were obtained from the Japan Meteorological Agency. Influenza-like illness peak week varied largely during the study period, ranging between 4th and 11th weeks (middle of winter to early spring). The average of peak week during ENSO cycles (n = 11, average = 4.5 +/- 0.9) was significantly earlier than in non-ENSO years (n = 14, average = 7.6 +/- 2.9; P = 0.01), but there was no significant difference in the peak timing between hot (El Niño) and cold (La Niña) phases. Earlier peaks of influenza activity were observed in 16, out of 25, epidemics. These coincided with 10 (90.9%) out of 11 ENSO and 6 (85.7%) out of seven large-scale epidemics. Influenza activity peak occurred earlier in years associated with ENSO and/or large scale epidemics.

  19. Asynchronous food-web pathways could buffer the response of Serengeti predators to El Niño Southern Oscillation.

    PubMed

    Sinclair, A R E; Metzger, Kristine L; Fryxell, John M; Packer, Craig; Byrom, Andrea E; Craft, Meggan E; Hampson, Katie; Lembo, Tiziana; Durant, Sarah M; Forrester, Guy J; Bukombe, John; Mchetto, John; Dempewolf, Jan; Hilborn, Ray; Cleaveland, Sarah; Nkwabi, Ally; Mosser, Anna; Mduma, Simon A R

    2013-05-01

    Understanding how entire ecosystems maintain stability in the face of climatic and human disturbance is one of the most fundamental challenges in ecology. Theory suggests that a crucial factor determining the degree of ecosystem stability is simply the degree of synchrony with which different species in ecological food webs respond to environmental stochasticity. Ecosystems in which all food-web pathways are affected similarly by external disturbance should amplify variability in top carnivore abundance over time due to population interactions, whereas ecosystems in which a large fraction of pathways are nonresponsive or even inversely responsive to external disturbance will have more constant levels of abundance at upper trophic levels. To test the mechanism underlying this hypothesis, we used over half a century of demographic data for multiple species in the Serengeti (Tanzania) ecosystem to measure the degree of synchrony to variation imposed by an external environmental driver, the El Niño Southern Oscillation (ENSO). ENSO effects were mediated largely via changes in dry-season vs. wet-season rainfall and consequent changes in vegetation availability, propagating via bottom-up effects to higher levels of the Serengeti food web to influence herbivores, predators and parasites. Some species in the Serengeti food web responded to the influence of ENSO in opposite ways, whereas other species were insensitive to variation in ENSO. Although far from conclusive, our results suggest that a diffuse mixture of herbivore responses could help buffer top carnivores, such as Serengeti lions, from variability in climate. Future global climate changes that favor some pathways over others, however, could alter the effectiveness of such processes in the future.

  20. El Niño-Southern Oscillation is linked to decreased energetic condition in long-distance migrants

    USGS Publications Warehouse

    Paxton, Kristina L.; Cohen, Emily B.; Paxton, Eben; Németh, Zoltan; Moore, Frank R.

    2014-01-01

    Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in

  1. El Niño-Southern Oscillation Is Linked to Decreased Energetic Condition in Long-Distance Migrants

    PubMed Central

    Paxton, Kristina L.; Cohen, Emily B.; Paxton, Eben H.; Németh, Zoltán; Moore, Frank R.

    2014-01-01

    Predicting how migratory animals respond to changing climatic conditions requires knowledge of how climatic events affect each phase of the annual cycle and how those effects carry-over to subsequent phases. We utilized a 17-year migration dataset to examine how El Niño-Southern Oscillation climatic events in geographically different regions of the Western hemisphere carry-over to impact the stopover biology of several intercontinental migratory bird species. We found that migratory birds that over-wintered in South America experienced significantly drier environments during El Niño years, as reflected by reduced Normalized Difference Vegetation Index (NDVI) values, and arrived at stopover sites in reduced energetic condition during spring migration. During El Niño years migrants were also more likely to stopover immediately along the northern Gulf coast of the southeastern U.S. after crossing the Gulf of Mexico in small suboptimal forest patches where food resources are lower and migrant density often greater than larger more contiguous forests further inland. In contrast, NDVI values did not differ between El Niño and La Niña years in Caribbean-Central America, and we found no difference in energetic condition or use of coastal habitats for migrants en route from Caribbean-Central America wintering areas. Birds over-wintering in both regions had consistent median arrival dates along the northern Gulf coast, suggesting that there is a strong drive for birds to maintain their time program regardless of their overall condition. We provide strong evidence that not only is the stopover biology of migratory landbirds influenced by events during the previous phase of their life-cycle, but where migratory birds over-winter determines how vulnerable they are to global climatic cycles. Increased frequency and intensity of ENSO events over the coming decades, as predicted by climatic models, may disproportionately influence long-distance migrants over-wintering in

  2. The 1997-98 El Nino Event and Related Wintertime Lightning Variations in the Southeastern United States

    NASA Technical Reports Server (NTRS)

    Goodman, S. J.; Buechler, D. E.; Knupp, K.; Driscoll, K.; McCaul, E. W.

    1999-01-01

    The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for world-wide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast US Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the latest warm-episode year. The 1997-98 warm episode is notable for being the strongest event since 1982-83. With the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the expanded coverage of the National Lightning Detection Network (NLDN), such year-to-year changes in lightning activity can be examined with far greater detail than ever before. For the recent ENSO event the greatest year-to-year changes in lightning frequency occur within a broad swath across the northern Gulf of Mexico basin where there is nearly a 200% increase in lightning days year-to-year (35 days in 1997-98 vs. 13 days in 1996-97) and a 200% increase in lightning hours (150 hours vs. 50). These changes occur in association with a 100% increase in the number of synoptic scale cyclones and an anomalously strong jet stream encompassing much of the Gulf basin.

  3. Early Warning of El Nino Impacts on Food Security

    NASA Astrophysics Data System (ADS)

    Rowland, J.; Verdin, J. P.; Hillbruner, C.; Budde, M. E.

    2016-12-01

    Before and during the El Niño of 2015-2016, regular and frequent application of climate monitoring and seasonal forecasts enabled early warning of food insecurity in Africa, Central America, and the Caribbean. As it happened, drought associated with the quasi-El Niño of 2014 had already adversely impacted harvests in Central America, Haiti, and Southern Africa, so the effects of the El Niño of 2015-2016 were especially hard-hitting and particularly devastating to crop conditions and food security. In the case of Ethiopia, 2014 conditions were normal but there were record rainfall deficits in 2015, with consequent crop failure, inadequate forage, and sharply curtailed water availability. Combining such agro-climatological information with knowledge of household economies, livelihood systems, markets & trade, and health & nutrition, FEWS NET constructed scenarios of food insecurity eight months into the future, with monthly updates. These scenarios informed assistance programming by USAID and partners. Overall, FEWS NET estimates that at least 18 million people will be severely food insecure during 2015/16 as a direct result of the impact of El Nino on rainfall. However, in Ethiopia, the contrast with the 1982-1983 El Niño is dramatic; though the two events were climatically similar, the human impacts of the 2015-2016 El Niño are much less, thanks not only to well-functioning early warning systems and large scale emergency response, but also improved social safety nets and lack of ongoing armed conflict. In southern Africa, El Nino resulted in extensive failed crops, with some areas of South Africa and Zimbabwe having insufficient rain to plant crops. Remote sensing products provided relevant information to depict the severity of rainfall and vegetation deficits. Likewise, in Central America and the Caribbean (Hispaniola), rainfall deficits were portrayed in the perspective of 30+ years of data.

  4. Initialized decadal prediction for transition to positive phase of the Interdecadal Pacific Oscillation

    DOE PAGES

    Meehl, Gerald A.; Hu, Aixue; Teng, Haiyan

    2016-06-02

    The negative phase of the Interdecadal Pacific Oscillation (IPO), a dominant mode of multi-decadal variability of sea surface temperatures (SSTs) in the Pacific, contributed to the reduced rate of global surface temperature warming in the early 2000s. Here, a proposed mechanism for IPO multidecadal variability indicates that the presence of decadal timescale upper ocean heat content in the off-equatorial western tropical Pacific can provide conditions for an interannual El Nino/Southern Oscillation event to trigger a transition of tropical Pacific SSTs to the opposite IPO phase. Here we show that a decadal prediction initialized in 2013 simulates predicted Nino3.4 SSTs thatmore » have qualitatively tracked the observations through 2015. The year three to seven average prediction (2015-2019) from the 2013 initial state shows a transition to the positive phase of the IPO from the previous negative phase and a resumption of larger rates of global warming over the 2013-2022 period consistent with a positive IPO phase.« less

  5. Initialized decadal prediction for transition to positive phase of the Interdecadal Pacific Oscillation

    SciTech Connect

    Meehl, Gerald A.; Hu, Aixue; Teng, Haiyan

    2016-06-02

    The negative phase of the Interdecadal Pacific Oscillation (IPO), a dominant mode of multi-decadal variability of sea surface temperatures (SSTs) in the Pacific, contributed to the reduced rate of global surface temperature warming in the early 2000s. Here, a proposed mechanism for IPO multidecadal variability indicates that the presence of decadal timescale upper ocean heat content in the off-equatorial western tropical Pacific can provide conditions for an interannual El Nino/Southern Oscillation event to trigger a transition of tropical Pacific SSTs to the opposite IPO phase. Here we show that a decadal prediction initialized in 2013 simulates predicted Nino3.4 SSTs that have qualitatively tracked the observations through 2015. The year three to seven average prediction (2015-2019) from the 2013 initial state shows a transition to the positive phase of the IPO from the previous negative phase and a resumption of larger rates of global warming over the 2013-2022 period consistent with a positive IPO phase.

  6. A study of quasi-millennial extratropical winter cyclone activity over the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Xia, Lan; von Storch, Hans; Feser, Frauke; Wu, Jian

    2016-10-01

    The winter extratropical cyclone activity in the Southern Hemisphere during the last one thousand years within a global climate simulation was analyzed by tracking cyclones, and then clustering them into ten clusters consecutively for each hundred years. There is very strong year-to-year variability for Southern Hemispheric winter extratropical cyclone numbers and larger variations on centennial time scale, more so than for its Northern Hemispherical counterparts. However, no obvious trend can be found. The mean tracks of clusters over the Southern Indian Ocean and near New Zealand shift poleward from the eleventh to the twentieth century while the clusters in the central Southern Pacific shift equatorward. Storm track clusters with largest deepening rates are found over the Southwestern Indian Ocean. In the twentieth century, rapidly deepening cyclones appear more often while long lifespan cyclones appear less frequently. The winter storm activity in the Southern Hemisphere is closely related to the Antarctic Oscillation. The cyclone frequency over the Indian Ocean and South Pacific Ocean can be associated with the Indian Ocean Dipole and El Nino-Southern Oscillation respectively.

  7. Coral luminescence identifies the Pacific Decadal Oscillation as a primary driver of river runoff variability impacting the southern Great Barrier Reef.

    PubMed

    Rodriguez-Ramirez, Alberto; Grove, Craig A; Zinke, Jens; Pandolfi, John M; Zhao, Jian-xin

    2014-01-01

    The Pacific Decadal Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere variability on decadal time scales. While precipitation and river flow variability in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence variability (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and decadal variability of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the variability in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate variability.

  8. Coral Luminescence Identifies the Pacific Decadal Oscillation as a Primary Driver of River Runoff Variability Impacting the Southern Great Barrier Reef

    PubMed Central

    Rodriguez-Ramirez, Alberto; Grove, Craig A.; Zinke, Jens; Pandolfi, John M.; Zhao, Jian-xin

    2014-01-01

    The Pacific Decadal Oscillation (PDO) is a large-scale climatic phenomenon modulating ocean-atmosphere variability on decadal time scales. While precipitation and river flow variability in the Great Barrier Reef (GBR) catchments are sensitive to PDO phases, the extent to which the PDO influences coral reefs is poorly understood. Here, six Porites coral cores were used to produce a composite record of coral luminescence variability (runoff proxy) and identify drivers of terrestrial influence on the Keppel reefs, southern GBR. We found that coral skeletal luminescence effectively captured seasonal, inter-annual and decadal variability of river discharge and rainfall from the Fitzroy River catchment. Most importantly, although the influence of El Niño-Southern Oscillation (ENSO) events was evident in the luminescence records, the variability in the coral luminescence composite record was significantly explained by the PDO. Negative luminescence anomalies (reduced runoff) were associated with El Niño years during positive PDO phases while positive luminescence anomalies (increased runoff) coincided with strong/moderate La Niña years during negative PDO phases. This study provides clear evidence that not only ENSO but also the PDO have significantly affected runoff regimes at the Keppel reefs for at least a century, and suggests that upcoming hydrological disturbances and ecological responses in the southern GBR region will be mediated by the future evolution of these sources of climate variability. PMID:24416214

  9. Angular momentum exchange among the solid Earth, atmosphere, and oceans: A case study of the 1982-1983 El Nino event

    NASA Technical Reports Server (NTRS)

    Dickey, J. O.; Marcus, S. L.; Hide, R.; Eubanks, T. M.; Boggs, D. H.

    1994-01-01

    The 1982-1983 El Nino/Southern Oscillation (ENSO) event was accompanied by the largest interannual variation in the Earth's rotation rate on record. In this study we demonstrate that atmospheric forcing was the dominant cause for this rotational anomaly, with atmospheric angular momentum (AAM) integrated from 1000 to 1 mbar (troposphere plus stratosphere) accounting for up to 92% of the interannual variance in the length of day (LOD). Winds between 100 and 1 mbar contributed nearly 20% of the variance explained, indicating that the stratosphere can play a significant role in the Earth's angular momentum budget on interannual time scales. Examination of LOD, AAM, and Southern Oscillation Index (SOI) data for a 15-year span surrounding the 1982-1983 event suggests that the strong rotational response resulted from constructive interference between the low-frequency (approximately 4-6 year) and quasi-biennial (approximately 2-3 year) components of the ENSO phenomenon, as well as the stratospheric Quasi-Biennial Oscillation (QBO). Sources of the remaining LOD discrepancy (approximately 55 and 64 microseconds rms residual for the European Centre for Medium-Range Forecasting (EC) and U.S. National Meteorological Center (NMC) analyses) are explored; noise and systematic errors in the AAM data are estimated to contribute 18 and 33 microseconds, respectively, leaving a residual (rms) of 40 (52) microseconds unaccounted for by the EC (NMC) analysis. Oceanic angular momentum contributions (both moment of inertia changes associated with baroclinic waves and motion terms) are shown to be candidates in closing the interannual axial angular momentum budget.

  10. Angular momentum exchange among the solid Earth, atmosphere, and oceans: A case study of the 1982-1983 El Nino event

    NASA Technical Reports Server (NTRS)

    Dickey, J. O.; Marcus, S. L.; Hide, R.; Eubanks, T. M.; Boggs, D. H.

    1994-01-01

    The 1982-1983 El Nino/Southern Oscillation (ENSO) event was accompanied by the largest interannual variation in the Earth's rotation rate on record. In this study we demonstrate that atmospheric forcing was the dominant cause for this rotational anomaly, with atmospheric angular momentum (AAM) integrated from 1000 to 1 mbar (troposphere plus stratosphere) accounting for up to 92% of the interannual variance in the length of day (LOD). Winds between 100 and 1 mbar contributed nearly 20% of the variance explained, indicating that the stratosphere can play a significant role in the Earth's angular momentum budget on interannual time scales. Examination of LOD, AAM, and Southern Oscillation Index (SOI) data for a 15-year span surrounding the 1982-1983 event suggests that the strong rotational response resulted from constructive interference between the low-frequency (approximately 4-6 year) and quasi-biennial (approximately 2-3 year) components of the ENSO phenomenon, as well as the stratospheric Quasi-Biennial Oscillation (QBO). Sources of the remaining LOD discrepancy (approximately 55 and 64 microseconds rms residual for the European Centre for Medium-Range Forecasting (EC) and U.S. National Meteorological Center (NMC) analyses) are explored; noise and systematic errors in the AAM data are estimated to contribute 18 and 33 microseconds, respectively, leaving a residual (rms) of 40 (52) microseconds unaccounted for by the EC (NMC) analysis. Oceanic angular momentum contributions (both moment of inertia changes associated with baroclinic waves and motion terms) are shown to be candidates in closing the interannual axial angular momentum budget.

  11. El Niño Southern Oscillation as an early warning tool for malaria outbreaks in India.

    PubMed

    Dhiman, Ramesh C; Sarkar, Soma

    2017-03-20

    Risks of malaria epidemics in relation to El Niño and Southern Oscillation (ENSO) events have been mapped and studied at global level. In India, where malaria is a major public health problem, no such effort has been undertaken that inter-relates El Niño, Indian Summer Monsoon Rainfall (ISMR) and malaria. The present study has been undertaken to find out the relationship between ENSO events, ISMR and intra-annual variability in malaria cases in India, which in turn could help mitigate the malaria outbreaks. Correlation coefficients among 'rainfall index' (ISMR), '+ winter ONI' (NDJF) and 'malaria case index' were calculated using annual state-level data for the last 22 years. The 'malaria case index' representing 'relative change from mean' was correlated to the 4 month (November-February) average positive Oceanic Niño Index (ONI). The resultant correlations between '+ winter ONI' and 'malaria case index' were further analysed on geographical information system platform to generate spatial correlation map. The correlation between '+ winter ONI' and 'rainfall index' shows that there is great disparity in effect of ENSO over ISMR distribution across the country. Correlation between 'rainfall index' and 'malaria case index' shows that malaria transmission in all geographical regions of India are not equally affected by the ISMR deficit or excess. Correlation between '+ winter ONI' and 'malaria case index' was found ranging from -0.5 to + 0.7 (p < 0.05). A positive correlation indicates that increase in El Niño intensity (+ winter ONI) will lead to rise in total malaria cases in the concurrent year in the states of Orissa, Chhattisgarh, Jharkhand, Bihar, Goa, eastern parts of Madhya Pradesh, part of Andhra Pradesh, Uttarakhand and Meghalaya. Whereas, negative correlations were found in the states of Rajasthan, Haryana, Gujarat, part of Tamil Nadu, Manipur, Mizoram and Sikkim indicating the likelihood of outbreaks in La Nina condition. The generated map

  12. An Atmospheric Nitrogen Budget in the Pacific Northwest during the 1997-99 El Niño Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Nergui, T.; Lamb, B. K.; Chung, S. H.

    2016-12-01

    Excess reactive nitrogen (N) from anthropogenic activities is known to cause detrimental effects on the environment. Natural climate variability such as the El Niño Southern Oscillation (ENSO) can affect regional N budgets due to spatial patterns of atmospheric transport and other meteorological conditions associated with ENSO forcing. This study aims to quantify atmospheric N fluxes over the Pacific Northwest to improve our understanding of how ENSO influences regional N budget. The WRF-MEGAN-SMOKE-CMAQ modeling framework is used to simulate atmospheric physical and chemical processes from summer of 1997 to summer of 1999, which includes one of the strongest ENSO events on record. Total N emissions over Washington, Idaho, and Oregon were about 357 Gg N in 1998, of which 96% was from transportation, electricity generation, and industrial activities. The emissions were about 110 Gg N in summer (Jun-Aug) and 63 Gg N in winter (Dec-Feb). This seasonality is mainly driven by emissions from agriculture, wildfire, and biogenic sources (32±16 Gg N), with a maximum in summer (49 Gg N) and a minimum in winter (9 Gg N). Regional total N deposition was about 259 Gg N in 1998, which was 72 % of the regional emissions. Total N deposition rates were lower (36 Gg N) in winter of 1997/1998 and higher in the following spring (82 Gg N) and summer (81 Gg N). Dry deposition is dominant over wet deposition in the region. Depending on the season, dry and wet deposition accounted for 49-70% and 30-51% of the total deposition rates, respectively. During the 1997-98 El Niño and 1998-99 La Niña winters, wet and dry deposition contributed about equally to the total deposition. A mass balance calculation with an assumption of no N accumulation in the troposphere indicates that about 26±9 Gg N was transported out of the region on a seasonal basis. Initial results for 1999 show that 32 Gg N was transported out of the region in 1997-98 El Niño winter, while the net N transport was about 27

  13. Orbital-scale El Niño/Southern Oscillation-Like Variability During the Last Glacial-Interglacial Cycle

    NASA Astrophysics Data System (ADS)

    Yamamoto, M.; Oba, T.; Shimamune, J.; Ueshima, T.

    2003-12-01

    How have the changes in the Earth's orbit have driven glacial-interglacial climate changes? Recently, a new hypothesis has been proposed that the tropical Pacific ocean-atmosphere interactions have a strong influence on global climate changes on an orbital timescale (Cane, 1998; Clement et al., 1999; Lea et al., 2000). Nevertheless, the orbital-scale changes in the tropical interactions are less clear, and their impacts on a global climate have not yet been proven. Our study was aimed at understanding whether or not and how the long-term tropical El Niño-Southern Oscillation (ENSO)-like variability has a global impact on orbital-scale climate changes. We generated continuous records of the alkenone sea surface temperature (SST) at the western and eastern margins of the mid-latitude North Pacific (MD012421 and ODP1014) during the last 145,000 years. We found that the difference between the SSTs of the NE and NW Pacific margins (Δ SST) reflected an orbital-controlled ENSO-like variability, and the Δ SST can be used as an indication of the long-term ENSO. The variation of Δ SST was large and pronounced at the 23-kyr cycle during 0-60 ka (MIS-1 to MIS-3) and 120-145 ka (MIS-5e to MIS-6), which agreed well with the long-term ENSO behavior predicted by the Zebiak-Cane ENSO model (Clement et al., 1999), as regards both the timing and frequency. In contrast, the variation was relatively small and pronounced at the 41-kyr cycle during 60-120 ka (MIS-4 to MIS-5d), which disagreed with the model prediction. Our observation also demonstrated that a strongly El Niño-like SST pattern prevailed in the mid-latitude North Pacific during the last two deglaciations. The synchronous warming of the Antarctica (Petit et al., 1999) and the tropical Pacific (Lea, 2000; Koutavas et al., 2002; Visser et al., 2003) prevailed within these strongly El Niño-like intervals during deglaciations. These findings are concordant with Cane (1998)'s hypothesis that a long-term El Niño must have

  14. Extreme Winter Precipitation Events in the Western United States: The impact of ENSO and the Madden-Julian Oscillation

    NASA Astrophysics Data System (ADS)

    Schubert, S.; Chang, Y.; Suarez, M.; Pegion, P.

    2005-05-01

    The west coast of the United States occasionally experiences intense winter storms that account for a major fraction of the total seasonal rain(snow)fall. In some cases, it is not a single storm, but a series of storms, that batter the west coast in a matter of few weeks. These storms, unfortunately, are often associated with flooding, mudslides and other disasters that can lead to extensive property damage and even loss of life. In this talk, I will review our current understanding of the nature of these storms and the extent to which their occurrence is impacted by El Nino/Southern Oscillation and the Madden Julian Oscillation. The results are based on 50 years of precipitation observations, NCEP/NCAR reanalyses, and idealized experiments with a global atmospheric general circulation model.

  15. Section on Observed Impacts on El Nino

    NASA Technical Reports Server (NTRS)

    Rosenzweig, Cynthia

    2000-01-01

    Agricultural applications of El Nino forecasts are already underway in some countries and need to be evaluated or re-evaluated. For example, in Peru, El Nino forecasts have been incorporated into national planning for the agricultural sector, and areas planted with rice and cotton (cotton being the more drought-tolerant crop) are adjusted accordingly. How well are this and other such programs working? Such evaluations will contribute to the governmental and intergovernmental institutions, including the Inter-American Institute for Global Change Research and the US National Ocean and Atmospheric Agency that are fostering programs to aid the effective use of forecasts. As El Nino climate forecasting grows out of the research mode into operational mode, the research focus shifts to include the design of appropriate modes of utilization. Awareness of and sensitivity to the costs of prediction errors also grow. For example, one major forecasting model failed to predict the very large El Nino event of 1997, when Pacific sea-surface temperatures were the highest on record. Although simple correlations between El Nino events and crop yields may be suggestive, more sophisticated work is needed to understand the subtleties of the interplay among the global climate system, regional climate patterns, and local agricultural systems. Honesty about the limitations of an forecast is essential, especially when human livelihoods are at stake. An end-to-end analysis links tools and expertise from the full sequence of ENSO cause-and-effect processes. Representatives from many disciplines are needed to achieve insights, e.g, oceanographers and atmospheric scientists who predict El Nino events, climatologists who drive global climate models with sea-surface temperature predictions, agronomists who translate regional climate connections in to crop yield forecasts, and economists who analyze market adjustments to the vagaries of climate and determine the value of climate forecasts

  16. Section on Observed Impacts on El Nino

    NASA Technical Reports Server (NTRS)

    Rosenzweig, Cynthia

    2000-01-01

    Agricultural applications of El Nino forecasts are already underway in some countries and need to be evaluated or re-evaluated. For example, in Peru, El Nino forecasts have been incorporated into national planning for the agricultural sector, and areas planted with rice and cotton (cotton being the more drought-tolerant crop) are adjusted accordingly. How well are this and other such programs working? Such evaluations will contribute to the governmental and intergovernmental institutions, including the Inter-American Institute for Global Change Research and the US National Ocean and Atmospheric Agency that are fostering programs to aid the effective use of forecasts. As El Nino climate forecasting grows out of the research mode into operational mode, the research focus shifts to include the design of appropriate modes of utilization. Awareness of and sensitivity to the costs of prediction errors also grow. For example, one major forecasting model failed to predict the very large El Nino event of 1997, when Pacific sea-surface temperatures were the highest on record. Although simple correlations between El Nino events and crop yields may be suggestive, more sophisticated work is needed to understand the subtleties of the interplay among the global climate system, regional climate patterns, and local agricultural systems. Honesty about the limitations of an forecast is essential, especially when human livelihoods are at stake. An end-to-end analysis links tools and expertise from the full sequence of ENSO cause-and-effect processes. Representatives from many disciplines are needed to achieve insights, e.g, oceanographers and atmospheric scientists who predict El Nino events, climatologists who drive global climate models with sea-surface temperature predictions, agronomists who translate regional climate connections in to crop yield forecasts, and economists who analyze market adjustments to the vagaries of climate and determine the value of climate forecasts

  17. Short-term effect of El Niño-Southern Oscillation on pediatric hand, foot and mouth disease in Shenzhen, China.

    PubMed

    Lin, Hualiang; Zou, Hong; Wang, Qinzhou; Liu, Chunxiao; Lang, Lingling; Hou, Xuexin; Li, Zhenjun

    2013-01-01

    Hand, foot and mouth disease (HFMD) was an emerging viral infectious disease in recent years in Shenzhen. The underlying risk factors have not yet been systematically examined. This study analyzed the short-term effect of El Niño-Southern Oscillation on pediatric HFMD in Shenzhen, China. Daily count of HFMD among children aged below 15 years old, Southern Oscillation Index (SOI), and weather variables were collected to construct the time series. A distributed lag non-linear model was applied to investigate the effect of daily SOI on pediatric HFMD occurrence during 2008-2010. We observed an acute effect of SOI variation on HFMD occurrence. The extremely high SOI (SOI = 45, with 0 as reference) was associated with increased HFMD, with the relative risk (RR) being 1.66 (95% Confidence Interval [CI]: 1.34-2.04). Further analyses of the association between HFMD and daily mean temperature and relative humidity supported the correlation between pediatric HFMD and SOI. Meteorological factors might be important predictors of pediatric HFMD occurrence in Shenzhen.

  18. Statistical analysis of the El Niño-Southern Oscillation and sea-floor seismicity in the eastern tropical Pacific.

    PubMed

    Guillas, Serge; Day, Simon J; McGuire, B

    2010-05-28

    We present statistical evidence for a temporal link between variations in the El Niño-Southern Oscillation (ENSO) and the occurrence of earthquakes on the East Pacific Rise (EPR). We adopt a zero-inflated Poisson regression model to represent the relationship between the number of earthquakes in the Easter microplate on the EPR and ENSO (expressed using the southern oscillation index (SOI) for east Pacific sea-level pressure anomalies) from February 1973 to February 2009. We also examine the relationship between the numbers of earthquakes and sea levels, as retrieved by Topex/Poseidon from October 1992 to July 2002. We observe a significant (95% confidence level) positive influence of SOI on seismicity: positive SOI values trigger more earthquakes over the following 2 to 6 months than negative SOI values. There is a significant negative influence of absolute sea levels on seismicity (at 6 months lag). We propose that increased seismicity is associated with ENSO-driven sea-surface gradients (rising from east to west) in the equatorial Pacific, leading to a reduction in ocean-bottom pressure over the EPR by a few kilopascal. This relationship is opposite to reservoir-triggered seismicity and suggests that EPR fault activity may be triggered by plate flexure associated with the reduced pressure.

  19. El Niño-Southern Oscillation determines the salinity of the freshwater lens under a coral atoll in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    van der Velde, M.; Javaux, M.; Vanclooster, M.; Clothier, B. E.

    2006-11-01

    The freshwater resources of coral atolls occur mainly as lenses floating on salt water underneath the islands. The size and shape of these lenses are determined by hydrogeologic characteristics, the rainfall recharge rate and its temporal variation, plus extractions (Underwood et al., 1992; Jones and Banner, 2003; Jocson et al., 2002). In the South Pacific, rainfall exhibits seasonal as well as interannual variability related to the El Niño-Southern Oscillation (ENSO) (Ropelewski and Halpert, 1987). We used electric conductivity measurements from pumped wells on Tongatapu to show a moderate ENSO control on the temporal fluctuation of the pumped freshwater salinity. The salinity dynamics depended on low or increased rainfall recharge during respectively dry El Niño periods or wet La Niña events. ENSO events cause a large variation around the mean salinity and determine the relative salinity over the time-scale of several years, while a smaller variation is introduced by seasonal rainfall. The Southern Oscillation Index (SOI) (Troup, 1965; Stone et al., 1996) was used to predict freshwater salinity with a lag time of 10 months.

  20. Reconstructing El Niño Southern Oscillation using data from ships' logbooks, 1815-1854. Part I: methodology and evaluation

    NASA Astrophysics Data System (ADS)

    Barrett, Hannah G.; Jones, Julie M.; Bigg, Grant R.

    2017-04-01

    The meteorological information found within ships' logbooks is a unique and fascinating source of data for historical climatology. This study uses wind observations from logbooks covering the period 1815 to 1854 to reconstruct an index of El Niño Southern Oscillation (ENSO) for boreal winter (DJF). Statistically-based reconstructions of the Southern Oscillation Index (SOI) are obtained using two methods: principal component regression (PCR) and composite-plus-scale (CPS). Calibration and validation are carried out over the modern period 1979-2014, assessing the relationship between re-gridded seasonal ERA-Interim reanalysis wind data and the instrumental SOI. The reconstruction skill of both the PCR and CPS methods is found to be high with reduction of error skill scores of 0.80 and 0.75, respectively. The relationships derived during the fitting period are then applied to the logbook wind data to reconstruct the historical SOI. We develop a new method to assess the sensitivity of the reconstructions to using a limited number of observations per season and find that the CPS method performs better than PCR with a limited number of observations. A difference in the distribution of wind force terms used by British and Dutch ships is found, and its impact on the reconstruction assessed. The logbook reconstructions agree well with a previous SOI reconstructed from Jakarta rain day counts, 1830-1850, adding robustness to our reconstructions. Comparisons to additional documentary and proxy data sources are provided in a companion paper.

  1. Evaluating and classifying the phase cycles of the Madden-Julian Oscillation

    NASA Astrophysics Data System (ADS)

    Walsh, Thomas Robert

    Madden-Julian Oscillation (MJO) is the largest element of intraseasonal variability in the tropical atmosphere recognized by an eastward propagating pattern of cloud cover primarily in the equatorial Indian and western Pacific Oceans. This 30- to 60-day cycle oscillates eastward in a longitudinal fashion and is a teleconnection to global weather patterns. As MJO progresses across the Indian and Pacific basins, it is associated with the development of distinct weather patterns and regimes across the mid-latitudes. This research further clarifies how MJO can be classified in terms of phase in an attempt to enhance the use of MJO as a weather and climate predictor. In this research, 16 MJO phase cycle event types were identified and classified in terms of movement (steady progressing, variable, oscillating, and unclassified) and event length (0 to 29 days, 30 to 44 days, 45 to 59 days, and 60+ days). Phase cycle (PC) was defined as the time in days it takes for a MJO to evolve from the first day in phase 2 (western Indian Ocean) progressively back to the final day in phase 1 (Africa). In observing and analyzing 248 MJO events, from February 4, 1979 through April 30, 2010, climatological background information was defined while the PC events were characterized in terms of duration and magnitude. It was discovered that the number of annual events has decreased from an average of 8.5 events per year in 1980 to 7.5 events per year in 2009, and the length of these events has increased from an average of 42.5 days per event in 1979 to 49.5 days per event in 2010. Additionally, steady progressing PC events went through their cycles much quicker and had a higher amplitude value (including number of days where amplitude is greater than 1) than the remaining three PC types. MJO data were additionally related to sea surface temperature (SST) data fluctuations, primarily involving the well-studied El Nino Southern Oscillation (ENSO). Results indicated that MJO events are most

  2. Stable isotopic signature of El Niño-Southern Oscillation events in eastern tropical Pacific reef corals

    NASA Astrophysics Data System (ADS)

    Wellington, G. M.; Dunbar, R. B.

    1995-02-01

    In this study we measured stable oxygen and carbon isotope ratios in the skeletons of massive reef-building corals ( Porites lobata and Pavona gigantea) at four widespread locations in the tropical eastern Pacific, each with a unique marine climate. Annual variation in sea surface temperature (SST) varied from 5 7°C at upwelling sites (Gulf of Panamá and Galápagos Islands) to 2 3°C where upwelling was absent [Caño Isand (Costa Rica) and Gulf of Chiriquí (Panamá)]. Annual range in salinity was high in the gulfs of Panamá and Chiriquí (up to 15‰) and low at Cãno Island and Galápagos (2 3‰). We characterize the isotopic signatures of recent (15 40 y long records) El Niño/Southern Oscillation (ENSO) events, particularly the very severe 1982 1983 event. Subannual sampling at 1 2 month resolution reveals that the δ18O signal at Caño Island records strong to very strong ENSOs. In the Gulf of Chiriquí, this signal is governed mainly (80%) by salinity and thus is a weak recorder of ENSO events: only the 1951 1952, 1957 1958 and 1972 1973 events appear as significant δ18O anomalies over the period 1940 1984. In the Gulf of Panamá, high variation in both SST and salinity contribute to the δ18O signal. ENSO events at this site are poorly recorded, probably due to ameliorating effects of cool upwelled water during the early stage of the ENSO event. The δ18O record in Galápagos, however, shows a strong correlation with SST and accurately records all but the most severe 1982 1983 ENSO event. Thus, ENSOs are most clearly recorded at sites where salinity variation is minimal. At Caño only strong ENSOs are recorded while mild to strong events appear in the Galápagos record. Nowhere did the δ18O signal accurately record the full range of temperatures that occurred during the 1982 1983 ENSO; however, a stress band on the coral skeleton was evident at all sites. By comparing the δ18O records and skeletal features across sites it may be possible to identify

  3. Teleconnected influence of the boreal winter Antarctic Oscillation on the Somali Jet: Bridging role of sea surface temperature in southern high and middle latitudes

    NASA Astrophysics Data System (ADS)

    Shi, Wenjing; Xiao, Ziniu; Xue, Jianjun

    2016-01-01

    The teleconnection impact of the boreal winter Antarctic Oscillation (AAO) on the Somali Jet (SMJ) intensity in the following spring and summer is examined in this paper. The variability of the boreal winter AAO is positively related to the SMJ intensity in both spring and summer. The analyses show that the SST in southern high and middle latitudes seems to serve as a bridge linking these two systems. When the AAO is in strong positive phase, SST over the Southern Ocean cools in the high latitudes and warms in the middle latitudes, which persists into summer; however, the variability of SST in southern high and middle latitudes is also closely correlated to SMJ intensity. A possible mechanism that links SST variability with the AAO-SMJ relationship is also discussed. The AAO in boreal winter produces an SST anomaly pattern in southern high and middle latitudes through the air-sea coupling. This AAOrelated SST anomaly pattern modulates the local Ferrel cell anomaly in summer, followed by the regional Hadley cell anomaly in tropics. The anomalous vertical motion in tropics then changes the land-sea thermal contrast between the tropical Indian Ocean and the Asian continent through the variability of low cloud cover and downward surface longwave radiation flux. Finally, the land-sea thermal contrast anomaly between the tropical Indian Ocean and the Asian continent changes the SMJ intensity. The results from Community Atmosphere Model experiments forced by the SST anomaly in southern high and middle latitudes also confirm this diagnostic physical process to some extent.

  4. El Nino as an element of a global-scale wave in the atmosphere-ocean system

    NASA Astrophysics Data System (ADS)

    Serykh, Ilya; Sonechkin, Dmitry

    2016-04-01

    The analyses of the real meteorological and oceanographical data, and long runs of the coupled atmosphere-ocean hydro- thermodynamical models identify a spatial-temporal structure of the main mode of the interannual to decadal climatic variations. This mode looks like a global-scale wave that extends from West to East around the Earth, and varies rhythmically. In fact, the establishment of this wave is a generalization and development of the well-known structures of the so-called "teleconnections" in the ocean-atmosphere system. The known regional structures like ENSO, IOD, PDO, IPO, PNA, NAO, AO, ACW and other can be considered as parts of this global-scale wave. Moving eastward around the Earth, this wave triggers El Nino - Southern oscillation events. An index of this wave is proposed as a sum of normalized anomalies of the sea level pressure and the near-surface temperature in 20 locations around the globe. It is proven that the power spectrum of this index is not continuous but discrete in its character. Thus, one can suppose that the dynamics of the global-scale wave is nonchaotic, and so predictable with no limit in principle. The index power spectrum reveals statistically significant peaks at the same periods that are inherent to the power spectra of the traditional ENSO indices. The main peaks are at the sub-harmonics of the well-known Chandler wobble (of the ~1.2 year period) in the Earth's pole motion: 3.6; 4.8; 2.4 years. Some other statistically significant peaks also are seen at the super-harmonics of the Luni-Solar nutation (of the ~18.6 year period), and combinational harmonics of the Schwabe's and Hale's solar activity cycles. Based on the eastward propagation of the global-scale wave, a predictor of ENSO events was suggested. It has high correlation (about 0.7) with Nino indices but leads them on about 12 months. The use of this predictor opens a possibility to overcome the Spring Predictability Barrier in ENSO forecasting.

  5. An application of vessel-based LiDAR to quantify coastal retreat in Southern Monterey Bay, CA during the 2008-2009 year and the 2009-2010 El Nino

    NASA Astrophysics Data System (ADS)

    Quan, S.; Kvitek, R. G.; Smith, D. P.

    2010-12-01

    Coastal erosion has become a prominent issue in Monterey Bay, California. Areas at high risk include native coastal dunes, private and public beachfront properties, municipal sewage lines, and areas of the highway 1 corridor. Traditional airborne LiDAR has been an effective but costly method for measuring coastal topography by providing high resolution and broad coverage. In 1997 and 1998, NASA, USGS, and NOAA collaborated to conduct pre-and post-El Niño airborne LiDAR surveys of the California coastline. The anticipation of this ENSO event coupled with LiDAR technology resulted in high resolution snapshots of the coastline pre-post El Niño, with analyses yielding erosion rates on the order of nearly seven times the historical annual dune erosion average (Thornton et al 2006). Since then, there have been no further, publicly available LiDAR surveys of the Monterey Bay shoreline. The goal of this project is to apply a vessel-based LiDAR system to measure coastal geomorphology, determine the efficacy of vessel-based topographic LiDAR for mapping coastal geomorphology, and quantify the spatial distribution of coastal retreat for Southern Monterey Bay, California during the 2009-10 El Niño and the 2008-2009 normal (non- El Niño) year. The area of study was the Monterey Bay coastline from Monterey harbor, CA north to Marina State Beach at Reservation Road. Sea cliff morphology data were measured on Dec 9th and 10th, 2008, Nov 4th 2009, and on July 15, 16, and 17th 2010 through the use of a terrestrial LiDAR system mounted atop the CSUMB Seafloor Mapping Lab’s R/V VenTresca. These vessel based LiDAR data were compared using mapping and spatial analysis tools in ArcGIS to quantify the spatial distribution of coastal retreat and calculate erosion rates for the Monterey Bay shoreline during the 2009-2010 El Niño and the 2008-2009 normal year. In keeping with previous published work based on other methods, preliminary results show numerous erosional hotspots which

  6. Circulation patterns associated with droughts over southern Africa

    NASA Astrophysics Data System (ADS)

    Garanganga, B.

    2002-12-01

    The paper highlights the circulation patterns associated with droughts that have demonstrated the vulnerability of the socioeconomic development of around 200 million people from 14 the Southern African Development Community (SADC) countries to the vagaries of the climate system. The recent, apparently perennial droughts juxtaposed with floods across southern Africa have to be seen against the background of advances made by the scientific community in the understanding of the global ocean-atmosphere system. The paper seeks to contribute to such advances science is making in order to make humankind benefit from the knowledge science has provided. The data used in the analyses include actual rainfall from the SADC countries and those from the United States NOAA (NCEP/NCAR Reanalysis) data banks. The paper briefly looks at the regional climatology of the SADC countries, which shows that rains fall within the period October during one year to March of the following year. Most of the damaging droughts have tended to occur during January to March. Thus, the more detailed analysis of the circulation characteristics has a focus of composite of these months. A few recent drought years are selected for analyzing of the dynamical structures of the regional circulation patterns and the tropical ocean and global atmosphere. These tended to coincide with El Ninos. However, the selected years include the recent drought during the 2001/2002 rainfall season, which occurred in a neutral El Nino-Southern Oscillation (ENSO) phase. There emerged significant similarity between rainfall anomaly variability and the ENSO signals. The many parameters of the atmosphere showed consistent characteristics in different drought years. The regional circulation patterns associated with droughts show similarities in both active and neutral ENSO years. The study also shows how possible generators of the climate anomalies can be grouped together. Thus the diagnosis of the various fields contributes to

  7. Decadal Variation of the Number of El Nino Onsets and El Nino-Related Months and Estimating the Likelihood of El Nino Onset in a Warming World

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2009-01-01

    Examination of the decadal variation of the number of El Nino onsets and El Nino-related months for the interval 1950-2008 clearly shows that the variation is better explained as one expressing normal fluctuation and not one related to global warming. Comparison of the recurrence periods for El Nino onsets against event durations for moderate/strong El Nino events results in a statistically important relationship that allows for the possible prediction of the onset for the next anticipated El Nino event. Because the last known El Nino was a moderate event of short duration (6 months), having onset in August 2006, unless it is a statistical outlier, one expects the next onset of El Nino probably in the latter half of 2009, with peak following in November 2009-January 2010. If true, then initial early extended forecasts of frequencies of tropical cyclones for the 2009 North Atlantic basin hurricane season probably should be revised slightly downward from near average-to-above average numbers to near average-to-below average numbers of tropical cyclones in 2009, especially as compared to averages since 1995, the beginning of the current high-activity interval for tropical cyclone activity.

  8. The Variability of the Atlantic Meridional Overturning Circulation, the North Atlantic Oscillation, and the El Niño-Southern Oscillation in the Bergen Climate Model.

    NASA Astrophysics Data System (ADS)

    Mignot, Juliette; Frankignoul, Claude

    2005-07-01

    The link between the interannual to interdecadal variability of the Atlantic meridional overturning circulation (AMOC) and the atmospheric forcing is investigated using 200 yr of a control simulation of the Bergen Climate Model, where the mean circulation cell is rather realistic, as is also the location of deep convection in the northern North Atlantic. The AMOC variability has a slightly red frequency spectrum and is primarily forced by the atmosphere. The maximum value of the AMOC is mostly sensitive to the deep convection in the Irminger Sea, which it lags by about 5 yr. The latter is mostly forced by a succession of atmospheric patterns that induce anomalous northerly winds over the area. The impact of the North Atlantic Oscillation on deep convection in the Labrador and Greenland Seas is represented realistically, but its influence on the AMOC is limited to the interannual time scale and is primarily associated with wind forcing. The tropical Pacific shows a strong variability in the model, with too strong an influence on the North Atlantic. However, its influence on the tropical Atlantic is realistic. Based on lagged correlations and the release of fictitious Lagrangian drifters, the tropical Pacific seems to influence the AMOC with a time lag of about 40 yr. The mechanism is as follows: El Niño events induce positive sea surface salinity anomalies in the tropical Atlantic that are advected northward, circulate in the subtropical gyre, and then subduct. In the ocean interior, part of the salinity anomaly is advected along the North Atlantic current, eventually reaching the Irminger and Labrador Seas after about 35 yr where they destabilize the water column and favor deep convection.

  9. El Nino influence on Holocene reef accretion in Hawai'i

    USGS Publications Warehouse

    Rooney, J.; Fletcher, C.; Grossman, E.; Engels, M.; Field, M.

    2004-01-01

    intertidal zone. We infer that forcing other than relative sea-level rise has altered the natural ability to support reef accretion on Hawaiian insular shelves. The limiting factor in these areas today is wave energy. Numbers of both large North Pacific swell events and hurricanes in Hawai'i are greater during El Nino years. We infer that if these major reef-limiting forces were suppressed, net accretion would occur in some areas in Hawai'i that are now wave-limited. Studies have shown that El Nino/Southern Oscillation (ENSO) was significantly weakened during early-mid Holocene time, only attaining an intensity similar to the current one ca. 5000 yr ago. We speculate that this shift in ENSO may assist in explaining patterns of Holocene Hawaiian reef accretion that are different from those of the present and apparently not related to relative sen-level rise.

  10. Amplification of the Atlantic Multidecadal Oscillation at the end of the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Moore, K.; Halfar, J.; Hajeed, H.; Adey, W.; Kronz, A.

    2016-12-01

    The North Atlantic sea surface temperature experiences variability on multidecadal timescales known as the Atlantic Multidecadal Oscillation (AMO). It has a profound imprint on the global climate that includes modulating the Northern Hemisphere's response to the El-Nino Southern Oscillation as well as impacting African drought, hurricane frequency and marine ecosystems. The AMO has a period of 60-80 years and as such the instrumental record, i.e. the middle of the 19th century onwards, contains only two full cycles of the AMO making it difficult to fully characterize this oscillation. There is a clear need to identify paleoclimate records extending into the pre-instrumental period that contains information on the AMO. This is especially true for extratropical marine proxies where such expressions are currently unavailable. Here we present an annually resolved coralline algal time series from the Labrador Sea that exhibits multidecadal variability extending back six centuries. The time series also contains a statistically significant trend towards higher values, i.e. warmer conditions, beginning in the 19th century that coincided with a increase in the time series' multidecadal power, a result also seen in another AMO reconstruction. We argue that these changes are associated with a hitherto unrecognized amplification of the AMO that was associated with a regional climate reorganization at the end of the Little Ice Age involving the Arctic Oscillation.

  11. El Niño-Southern Oscillation-time scale covariation of sea surface salinity and freshwater flux in the western tropical and northern subtropical Pacific

    NASA Astrophysics Data System (ADS)

    Nagano, Akira; Hasegawa, Takuya; Ueki, Iwao; Ando, Kentaro

    2017-07-01

    We examined the covariation of sea surface salinity (SSS) and freshwater flux in the western tropical and northern subtropical Pacific on the El Niño-Southern Oscillation time scale, using a canonical correlation analysis of monthly data between 2001 and 2013. The dominant covariation, i.e., the first canonical mode, has large positive and negative amplitudes in regions east of the Philippines and New Guinea, respectively, and reaches peaks in autumn to winter of El Niño years. The positive SSS anomaly east of the Philippines is advected to the Kuroshio Extension region. We found that the second canonical mode is another coupled variation with localized amplitudes of SSS under the atmospheric convergence zones in winter to spring of La Niña years. However, the negative SSS anomaly is annihilated possibly by the evaporation in the subtropical region.

  12. The impact of the 1982-1983 El Niño-Southern Oscillation on seabirds in the Galapagos Islands, Ecuador

    NASA Astrophysics Data System (ADS)

    Valle, Carlos A.; Cruz, Felipe; Cruz, Justine B.; Merlen, Godfrey; Coulter, Malcolm C.

    1987-12-01

    October 1982 through July 1983, the Galapagos Islands experienced the strongest El Niño-Southern Oscillation (ENSO) event yet recorded, with heavy rains and a warm, unproductive ocean. During this period most seabirds did not breed, and many left the archipelago altogether. Dark-rumped petrels which did breed during the event demonstrated low growth rate of chicks. Censuses and observations demonstrated substantial population decreases of other seabirds during the ENSO. Magnificent frigate birds suffered decreased nesting success, while blue-footed boobies abandoned all nesting attempts. Total censuses of Galapagos penguins and flightless cormorants taken before and after the ENSO demonstrated declines of 77% and 49%, respectively. We discuss the seabird population declines during ENSO and their subsequent recovery.

  13. What Is El Nino and How Does It Affect Us?

    ERIC Educational Resources Information Center

    Biachi, Janine; Nutter, Ann; Price, Jon

    This teaching unit provides materials and information about the effects of El Nino on people, the economy, and nature around the world. It is important for students to know the impact El Nino has had on the world. The unit presents information that builds student's interest in other environmental phenomena as well. This unit offers information on…

  14. Pastoral del Nino: Bringing the Abundant Life to Paraguayan Children

    ERIC Educational Resources Information Center

    Austin, Ann Berghout; Aquino, Cyle; Burro, Elizabeth

    2007-01-01

    Pastoral del Nino is transforming children's lives in rural Paraguay. Part of Pastoral Social (Catholic Social Services), Pastoral del Nino's primary focus is to bring "vida en abundancia" (the abundant life) to families by ensuring that mothers survive childbirth and children reach their first birthdays. In addition, the organization…

  15. Pastoral del Nino: Bringing the Abundant Life to Paraguayan Children

    ERIC Educational Resources Information Center

    Austin, Ann Berghout; Aquino, Cyle; Burro, Elizabeth

    2007-01-01

    Pastoral del Nino is transforming children's lives in rural Paraguay. Part of Pastoral Social (Catholic Social Services), Pastoral del Nino's primary focus is to bring "vida en abundancia" (the abundant life) to families by ensuring that mothers survive childbirth and children reach their first birthdays. In addition, the organization…

  16. What Is El Nino and How Does It Affect Us?

    ERIC Educational Resources Information Center

    Biachi, Janine; Nutter, Ann; Price, Jon

    This teaching unit provides materials and information about the effects of El Nino on people, the economy, and nature around the world. It is important for students to know the impact El Nino has had on the world. The unit presents information that builds student's interest in other environmental phenomena as well. This unit offers information on…

  17. Performance of Simulated El Niño-Southern Oscillation Climate Reconstructions over the Last Millennium: Comparison of Methods

    NASA Astrophysics Data System (ADS)

    Wahl, Eugene R.; Amrhein, Dan E.; Smerdon, Jason E.; Ammann, Caspar M.

    2010-05-01

    A key question in late-Holocene climate dynamics is the role of dominant modes in influencing climates in teleconnected regions of the world. For example, it has recently been proposed that ENSO had a key role in influencing the extended period of largely positive-phase NAO during ~1100-1400 CE (Trouet et al., 2009, Science, 324, 78). Fundamental to understanding the global and regional climatological roles of dominant modes are primary data on the variations of the modes themselves, in particular paleoclimate data that greatly extend instrumental-period information. Establishing records of ENSO indices that span the past millennium has proven difficult, and well-verified reconstructions produced to date have non-trivial differences (cf., e.g., Braganza et al., 2009, Journal of Geophysical Research, 114, D05106). This presentation examines important general questions regarding reconstructions of modal indices, including ENSO: is it best (1) to focus on proxy evidence from the most strongly influenced (or most strongly teleconnected) areas, (2) to combine proxy data from a large regional network encompassing the primary area of modal activity and teleconnections (e.g., around the Pacific Rim in the case of ENSO), or (3) to use climate field reconstruction (CFR) methods that assimilate up-to-global-scale proxy information? A systematic suite of reconstruction simulation experiments (RSEs), derived from NCAR CSM 1.4 millennium transient model output, is explored to test the various strengths and weaknesses of these three approaches for reconstructing the NINO3 index. By doing this, NINO3 reconstruction fidelity can be gauged over the entire simulated millennium via comparison to the known model target; such comparisons are restricted to brief "validation" periods in real-world reconstructions due to the length of the instrumental record. For strategies (1) and (2), pseudoproxies are formed by adding white noise to the model output (seasonally-appropriate precipitation

  18. Non-stationary influence of El Niño-Southern Oscillation and winter temperature on oak latewood growth in NW Iberian Peninsula.

    PubMed

    Rozas, Vicente; García-González, Ignacio

    2012-09-01

    The properties of El Niño-Southern Oscillation (ENSO), such as period, amplitude, and teleconnection strength to extratropical regions, have changed since the mid-1970s. ENSO affects the regional climatic regime in SW Europe, thus tree performance in the Iberian Peninsula could be affected by recent ENSO dynamics. We established four Quercus robur chronologies of earlywood and latewood widths in the NW Iberian Peninsula. The relationship between tree growth and the Southern Oscillation Index (SOI), the atmospheric expression of ENSO, showed that only latewood growth was correlated negatively with the SOI of the previous summer-autumn-winter. This relationship was non-stationary, with significant correlations only during the period 1952-1980; and also non-linear, with enhanced latewood growth only in La Niña years, i.e. years with a negative SOI index for the previous autumn. Non-linear relationship between latewood and SOI indicates an asymmetric influence of ENSO on tree performance, biassed towards negative SOI phases. During La Niña years, climate in the study area was warmer and wetter than during positive years, but only for 1952-1980. Winter temperatures became the most limiting factor for latewood growth since 1980, when mean regional temperatures increased by 1°C in comparison to previous periods. As a result, higher winter respiration rates, and the extension of the growing season, would probably cause an additional consumption of stored carbohydrates. The influence of ENSO and winter temperatures proved to be of great importance for tree growth, even at lower altitudes and under mild Atlantic climate in the NW Iberian Peninsula.

  19. Long-Term Data Reveal a Population Decline of the Tropical Lizard Anolis apletophallus, and a Negative Affect of El Nino Years on Population Growth Rate

    PubMed Central

    Stapley, Jessica; Garcia, Milton; Andrews, Robin M.

    2015-01-01

    Climate change threatens biodiversity worldwide, however predicting how particular species will respond is difficult because climate varies spatially, complex factors regulate population abundance, and species vary in their susceptibility to climate change. Studies need to incorporate these factors with long-term data in order to link climate change to population abundance. We used 40 years of lizard abundance data and local climate data from Barro Colorado Island to ask how climate, total lizard abundance and cohort-specific abundance have changed over time, and how total and cohort-specific abundance relate to climate variables including those predicted to make the species vulnerable to climate change (i.e. temperatures exceeding preferred body temperature). We documented a decrease in lizard abundance over the last 40 years, and changes in the local climate. Population growth rate was related to the previous years’ southern oscillation index; increasing following cooler-wetter, la niña years, decreasing following warmer-drier, el nino years. Within-year recruitment was negatively related to rainfall and minimum temperature. This study simultaneously identified climatic factors driving long-term population fluctuations and climate variables influencing short-term annual recruitment, both of which may be contributing to the population decline and influence the population’s future persistence. PMID:25671423

  20. Potential Predictability and Prediction Skill for Southern Peru Summertime Rainfall

    NASA Astrophysics Data System (ADS)

    WU, S.; Notaro, M.; Vavrus, S. J.; Mortensen, E.; Block, P. J.; Montgomery, R. J.; De Pierola, J. N.; Sanchez, C.

    2016-12-01

    The central Andes receive over 50% of annual climatological rainfall during the short period of January-March. This summertime rainfall exhibits strong interannual and decadal variability, including severe drought events that incur devastating societal impacts and cause agricultural communities and mining facilities to compete for limited water resources. An improved seasonal prediction skill of summertime rainfall would aid in water resource planning and allocation across the water-limited southern Peru. While various underlying mechanisms have been proposed by past studies for the drivers of interannual variability in summertime rainfall across southern Peru, such as the El Niño-Southern Oscillation (ENSO), Madden Julian Oscillation (MJO), and extratropical forcings, operational forecasts continue to be largely based on rudimentary ENSO-based indices, such as NINO3.4, justifying further exploration of predictive skill. In order to bridge this gap between the understanding of driving mechanisms and the operational forecast, we performed systematic studies on the predictability and prediction skill of southern Peru summertime rainfall by constructing statistical forecast models using best available weather station and reanalysis datasets. At first, by assuming the first two empirical orthogonal functions (EOFs) of summertime rainfall are predictable, the potential predictability skill was evaluated for southern Peru. Then, we constructed a simple regression model, based on the time series of tropical Pacific sea-surface temperatures (SSTs), and a more advanced Linear Inverse Model (LIM), based on the EOFs of tropical ocean SSTs and large-scale atmosphere variables from reanalysis. Our results show that the LIM model consistently outperforms the more rudimentary regression models on the forecast skill of domain averaged precipitation index and individual station indices. The improvement of forecast correlation skill ranges from 10% to over 200% for different

  1. The 1997-98 El Nino Event and Related Wintertime Lightning Variations in the Southeastern United States

    NASA Technical Reports Server (NTRS)

    Goodman, S. J.; Buechler, D. E.; Knupp, K.; Driscoll, K.; McCaul, E. W., Jr.

    2000-01-01

    The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for worldwide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast U.S. Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the warm episode year. The 1997-98 warm episode is notable for being the strongest event since 198283. With the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the detailed coverage of the U.S. National Lightning Detection Network (NLDN), such interannual changes in lightning activity can be examined with far greater detail than ever before. For the 1997-98 ENSO event the most significant year-to-year changes in lightning frequency worldwide occurred along the Gulf Coast and within the Gulf of Mexico basin during the Northern Hemisphere winter. Within a broad swath across the northern Gulf of Mexico basin there is a 100-150% increase in lightning days year-to-year (a peak of 33 days in the winter of 1997-98 vs. only 15 days or fewer in both the 1996-97 and 1998-99 winter). In addition, there is a nearly 200% increase in lightning hours (a peak of 138 hours in 1996-97 vs. 50 hours in both 1996-97 and 1998-99). The increase in lightning activity during ENSO occurs in association with a 100% increase in the number of synoptic scale cyclones that developed within or moved through the Gulf basin. The primary variables controlling these enhancements in thunderstorm activity are the position and strength of the jet stream.

  2. The 1997-98 El Nino Event and Related Wintertime Lightning Variations in the Southeastern United States

    NASA Technical Reports Server (NTRS)

    Goodman, S. J.; Buechler, D. E.; Knupp, K.; Driscoll, K.; McCaul, E. W., Jr.

    2000-01-01

    The El Nino Southern Oscillation (ENSO) is a climate anomaly responsible for worldwide weather impacts ranging from droughts to floods. In the United States, warm episode years are known to produce above normal rainfall along the Southeast U.S. Gulf Coast and into the Gulf of Mexico, with the greatest response observed in the October-March period of the warm episode year. The 1997-98 warm episode is notable for being the strongest event since 198283. With the recent launch of a lightning sensor on NASA's Tropical Rainfall Measuring Mission (TRMM) in November 1997 and the detailed coverage of the U.S. National Lightning Detection Network (NLDN), such interannual changes in lightning activity can be examined with far greater detail than ever before. For the 1997-98 ENSO event the most significant year-to-year changes in lightning frequency worldwide occurred along the Gulf Coast and within the Gulf of Mexico basin during the Northern Hemisphere winter. Within a broad swath across the northern Gulf of Mexico basin there is a 100-150% increase in lightning days year-to-year (a peak of 33 days in the winter of 1997-98 vs. only 15 days or fewer in both the 1996-97 and 1998-99 winter). In addition, there is a nearly 200% increase in lightning hours (a peak of 138 hours in 1996-97 vs. 50 hours in both 1996-97 and 1998-99). The increase in lightning activity during ENSO occurs in association with a 100% increase in the number of synoptic scale cyclones that developed within or moved through the Gulf basin. The primary variables controlling these enhancements in thunderstorm activity are the position and strength of the jet stream.

  3. On the interannual oscillations in the northern temperate total ozone

    SciTech Connect

    Krzyscin, J.W.

    1994-07-01

    The interannual variations in total ozone are studied using revised Dobson total ozone records (1961-1990) from 17 stations located within the latitude band 30 deg N - 60 deg N. To obtain the quasi-biennial oscillation (QBO), El Nino-Southern Oscillation (ENSO), and 11-year solar cycle manifestation in the `northern temperate` total ozone data, various multiple regression models are constructed by the least squares fitting to the observed ozone. The statistical relationships between the selected indices of the atmospheric variabilities and total ozone are described in the linear and nonlinear regression models. Nonlinear relationships to the predictor variables are found. That is, the total ozone variations are statistically modeled by nonlinear terms accounting for the coupling between QBO and ENSO, QBO and solar activity, and ENSO and solar activity. It is suggested that large reduction of total ozone values over the `northern temperate` region occurs in cold season when a strong ENSO warm event meets the west phase of the QBO during the period of high solar activity.

  4. An ˜1500 year history of El Niño Southern Oscillation rainfall anomalies and land use for the Isthmus of Panama from speleothem calcite

    NASA Astrophysics Data System (ADS)

    Lachniet, M. S.; Burns, S. J.; Piperno, D. R.; Asmerom, Y.; Polyak, V. P.

    2003-12-01

    The history of the El Niño Southern Oscillation (ENSO) over the past two millennia remains poorly constrained. To document further the tropical paleoclimatic response to ENSO, we present a precisely-dated (180 B.C. to 1310 A.D.), high-resolution ( ˜3 yr / sample), cave calcite isotopic time series from the Isthmus of Panama, a region that experiences ENSO-forced rainfall anomalies. We show evidence for rapid and dramatic rainfall variation in southern Central America, as inferred from stalagmite δ 18O isotope stratigraphy. Isthmian convective rainfall from 550 A.D. to 1300 A.D. was both less intense and more variable than the period 180 B.C. to 550 A.D. Speleothem growth spanned the interval of the Classic Maya Collapse (750 - 950 A.D.), and provides additional evidence for dry anomalies at this time. Carbon isotopes document changing vegetation from native rainforest to grasslands and/or maize, a period of soil erosion associated with pre-Colombian agriculture, and final forest recovery. We suggest that ENSO-forced sea surface temperature anomalies in the eastern equatorial Pacific Ocean resulted in isthmian rainfall anomalies over much of the past two millennia. Our data suggest that El Niño events are associated with decreased isthmian rainfall, and that increased ENSO activity results in generally drier and more variable conditions.

  5. Watching for the Next El Nino

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This Topex/Poseidon image of sea-surface heights was taken during a 10-day collection cycle ending August 7, 2002. Sea-surface heights are a measure of how much heat is stored in the ocean below to influence future planetary climate events. Since May 2001, there have been a series of warm Kelvin waves--eastward-moving ocean waves that cross the equatorial Pacific in about two months. A sizable one arrived at the South American coast last February, raising the ocean temperature by 2 degrees Celsius (3.6 degrees Fahrenheit) and triggering the National Oceanic and Atmospheric Administration's forecast for a mild El Nino in 2002. There was another wave in June, followed by the current large pool of warm water in the tropical Pacific that is now moving toward the coast of South America at a speed of 215 kilometers (134 miles) a day and will arrive there in three to four weeks, raising ocean temperatures. Scientists will continue to monitor the Pacific closely for further signs of El Nino formation and intensity.

  6. El Nino Threatens, but Fizzles (for Now)

    NASA Technical Reports Server (NTRS)

    2002-01-01

    For the first two weeks in June, the surface winds and sea surface temperatures across the Pacific Ocean began to display an all-too-familiar pattern. Normally, the trade winds in the equatorial Pacific blow from east to west and push warm surface waters from the eastern Pacific westward. As is indicated by the arrows displaying wind speed and direction in the above Quick Scatterometer (QuikScat) satellite data, the trade winds stopped and in some cases reversed course across the equatorial Pacific in early June. Consequently, the waters in the eastern Pacific grew warmer than usual. If this trend continued or intensified, another El Nino would have settled in by fall 2002 and rainfall and atmospheric circulation patterns would have begun to change across North and South America. However, in the later half of June conditions returned to normal. Scientists hope that satellite data from QuikScat will help them to study and even forecast future El Nino events. Launched aboard the SeaWinds satellite in 1999, the QuickScat instrument essentially sends out high frequency radio waves to detect the frothiness of ocean water. Since choppy ocean water is created almost solely by the surface winds blowing across the ocean, scientists can obtain an accurate measure of wind speed and direction from these data. Image courtesy NASA JPL Air-Sea Interaction and Climate Team

  7. GlobalHawk_SHOUT_ElNino

    NASA Image and Video Library

    2016-05-01

    NASA’s autonomously flown Global Hawk aircraft flew a series of flights over the Pacific Ocean during February 2016, as part of the NOAA-led mission called Sensing Hazards Operational Unmanned Technology, or SHOUT. This year’s El Nino season offered a unique opportunity for the aircraft to contribute data directly to NOAA’s El Nino Rapid Response field campaign. The campaign is seeking to determine key mechanisms affecting El Niño's impacts on the U.S. and their implications for improving NOAA's observational systems, models and predictions. The Global Hawk aircraft offers both NASA and NOAA scientists an exclusive vantage point to observe atmospheric conditions with the plane's ability to fly at 65,000 feet for a time period up to 30 hours. These long-endurance and high-altitude observations give NOAA scientists the opportunity to see a larger picture of how atmospheric changes in the tropics are directly impacting weather activity in the Western U.S.

  8. El Nino Threatens, but Fizzles (for Now)

    NASA Technical Reports Server (NTRS)

    2002-01-01

    For the first two weeks in June, the surface winds and sea surface temperatures across the Pacific Ocean began to display an all-too-familiar pattern. Normally, the trade winds in the equatorial Pacific blow from east to west and push warm surface waters from the eastern Pacific westward. As is indicated by the arrows displaying wind speed and direction in the above Quick Scatterometer (QuikScat) satellite data, the trade winds stopped and in some cases reversed course across the equatorial Pacific in early June. Consequently, the waters in the eastern Pacific grew warmer than usual. If this trend continued or intensified, another El Nino would have settled in by fall 2002 and rainfall and atmospheric circulation patterns would have begun to change across North and South America. However, in the later half of June conditions returned to normal. Scientists hope that satellite data from QuikScat will help them to study and even forecast future El Nino events. Launched aboard the SeaWinds satellite in 1999, the QuickScat instrument essentially sends out high frequency radio waves to detect the frothiness of ocean water. Since choppy ocean water is created almost solely by the surface winds blowing across the ocean, scientists can obtain an accurate measure of wind speed and direction from these data. Image courtesy NASA JPL Air-Sea Interaction and Climate Team

  9. Watching for the Next El Nino

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This Topex/Poseidon image of sea-surface heights was taken during a 10-day collection cycle ending August 7, 2002. Sea-surface heights are a measure of how much heat is stored in the ocean below to influence future planetary climate events. Since May 2001, there have been a series of warm Kelvin waves--eastward-moving ocean waves that cross the equatorial Pacific in about two months. A sizable one arrived at the South American coast last February, raising the ocean temperature by 2 degrees Celsius (3.6 degrees Fahrenheit) and triggering the National Oceanic and Atmospheric Administration's forecast for a mild El Nino in 2002. There was another wave in June, followed by the current large pool of warm water in the tropical Pacific that is now moving toward the coast of South America at a speed of 215 kilometers (134 miles) a day and will arrive there in three to four weeks, raising ocean temperatures. Scientists will continue to monitor the Pacific closely for further signs of El Nino formation and intensity.

  10. TOPEX/El Nino Watch - El Nino Rhythm, Dec, 10, 1997

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image of the Pacific Ocean was produced using sea surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea surface height relative to normal ocean conditions on Dec.10, 1997 and sea surface height is an indicator of the heat content of the ocean. The volume and area of the warm water pool related to El Nino has increased again after reaching a temporary low around Dec. 1. TOPEX/Poseidon has been tracking the fluctuations of the El Nino warm pool since it began early this year. Oceanographers believe the recent increases and decreases in the size of the warm water pool at the equator are part of the natural rhythm of El Nino and that the warm pool is occasionally pumped up by wind bursts blowing from the western and central Pacific Ocean. Each wind burst has triggered a temporary increase in area and volume of the warm pool. These data collected throughout 1997 have provided scientists with their first detailed view of how El Nino's warm pool behaves because the TOPEX/Poseidon satellite measures the changing sea surface height with unprecedented precision. In this image, the white and red areas indicate unusual patterns of heat storage; in the white areas, the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions, while purple (the western Pacific) means at least 18 centimeters (7 inches) below normal sea level.

    The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds weaken and even reverse direction. This change in the winds allows a large mass of warm water (the red and white area) that is normally located near Australia to move eastward along the equator until it reaches the coast of South America. The displacement of so much warm water affects evaporation, where rain clouds form and, consequently, alters the typical atmospheric jet stream

  11. TOPEX/El Nino Watch - El Nino Rhythm, Dec, 10, 1997

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image of the Pacific Ocean was produced using sea surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea surface height relative to normal ocean conditions on Dec.10, 1997 and sea surface height is an indicator of the heat content of the ocean. The volume and area of the warm water pool related to El Nino has increased again after reaching a temporary low around Dec. 1. TOPEX/Poseidon has been tracking the fluctuations of the El Nino warm pool since it began early this year. Oceanographers believe the recent increases and decreases in the size of the warm water pool at the equator are part of the natural rhythm of El Nino and that the warm pool is occasionally pumped up by wind bursts blowing from the western and central Pacific Ocean. Each wind burst has triggered a temporary increase in area and volume of the warm pool. These data collected throughout 1997 have provided scientists with their first detailed view of how El Nino's warm pool behaves because the TOPEX/Poseidon satellite measures the changing sea surface height with unprecedented precision. In this image, the white and red areas indicate unusual patterns of heat storage; in the white areas, the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions, while purple (the western Pacific) means at least 18 centimeters (7 inches) below normal sea level.

    The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds weaken and even reverse direction. This change in the winds allows a large mass of warm water (the red and white area) that is normally located near Australia to move eastward along the equator until it reaches the coast of South America. The displacement of so much warm water affects evaporation, where rain clouds form and, consequently, alters the typical atmospheric jet stream

  12. Southern Peru desert shattered by the great 2001 earthquake: Implications for paleoseismic and paleo-El Niño–Southern Oscillation records

    PubMed Central

    Keefer, David K.; Moseley, Michael E.

    2004-01-01

    In the desert region around the coastal city of Ilo, the great southern Peru earthquake of June 23, 2001 (8.2–8.4 moment magnitude), produced intense and widespread ground-failure effects. These effects included abundant landslides, pervasive ground cracking, microfracturing of surficial hillslope materials, collapse of drainage banks over long stretches, widening of hillside rills, and lengthening of first-order tributary channels. We have coined the term “shattered landscape” to describe the severity of these effects. Long-term consequences of this landscape shattering are inferred to include increased runoff and sediment transport during postearthquake rainstorms. This inference was confirmed during the first minor postearthquake rainstorm there, which occurred in June and July of 2002. Greater amounts of rainfall in this desert region have historically been associated with El Niño events. Previous studies of an unusual paleoflood deposit in this region have concluded that it is the product of El Niño-generated precipitation falling on seismically disturbed landscapes. The effects of the 2001 earthquake and 2002 rainstorm support that conclusion. PMID:15263069

  13. Remote Sensing the Patterns of Vector-borne Disease in El Nino and non-El Nino Years

    NASA Technical Reports Server (NTRS)

    Wood, B. L.; Chang, J.; Lobitz, B.; Beck, L.; DAntoni, Hector (Technical Monitor)

    1997-01-01

    The relationship between El Nino and non-El Nino and the patterns of vector-borne disease can be viewed at a variety of spatial and temporal scales. At one extreme are long term predictions of changing precipitation and temperature patterns at continental and global scales. At the opposite extreme are the local or site specific ecological changes associated with the long term events. In order to understand and address the human health consequences of El Nino events, especially the patterns of vector-borne diseases, it is necessary to combine both scales of observation. At a local or regional scale the patterns of vector-borne diseases are determined by temperature, precipitation, and habitat availability. These factors, as well as disease incidence can be altered by El Nino events. Remote sensing data such as that acquired by the NOAA AVHRR and Landsat TM sensors can be used to characterize and monitor changing ecological conditions and therefore predict vector-borne disease patterns. The authors present the results of preliminary work on the analysis of historical AVHRR and TM data acquired during El Nino and nonfatal Nino years to characterize ecological conditions in Peru on a monthly basis. This information will then be combined with disease data to determine the relationship between changes in ecological conditions and disease incidence. Our goal is to produce a sequence of remotely sensed images which can be used to show the ecological and disease patterns associated with long term El Nino events and predictions.

  14. Remote Sensing the Patterns of Vector-borne Disease in El Nino and non-El Nino Years

    NASA Technical Reports Server (NTRS)

    Wood, B. L.; Chang, J.; Lobitz, B.; Beck, L.; DAntoni, Hector (Technical Monitor)

    1997-01-01

    The relationship between El Nino and non-El Nino and the patterns of vector-borne disease can be viewed at a variety of spatial and temporal scales. At one extreme are long term predictions of changing precipitation and temperature patterns at continental and global scales. At the opposite extreme are the local or site specific ecological changes associated with the long term events. In order to understand and address the human health consequences of El Nino events, especially the patterns of vector-borne diseases, it is necessary to combine both scales of observation. At a local or regional scale the patterns of vector-borne diseases are determined by temperature, precipitation, and habitat availability. These factors, as well as disease incidence can be altered by El Nino events. Remote sensing data such as that acquired by the NOAA AVHRR and Landsat TM sensors can be used to characterize and monitor changing ecological conditions and therefore predict vector-borne disease patterns. The authors present the results of preliminary work on the analysis of historical AVHRR and TM data acquired during El Nino and nonfatal Nino years to characterize ecological conditions in Peru on a monthly basis. This information will then be combined with disease data to determine the relationship between changes in ecological conditions and disease incidence. Our goal is to produce a sequence of remotely sensed images which can be used to show the ecological and disease patterns associated with long term El Nino events and predictions.

  15. Influence of El Nino and ITCZ on Brazilian River Streamflows

    NASA Astrophysics Data System (ADS)

    Lopes, A.; Dracup, J. A.

    2010-12-01

    This study analyzes effects of climatic phenomena El Nino and ITCZ latitudinal movements on streamflow patterns in major Brazilian river basins: Amazon (north), Araguaia-Tocantins (central-north), Parana (central-south) and Sao Francisco (central-northeast). Multiple correlation between annual streamflows and the NINO 3.4 and North Tropical Atlantic SST indexes (NTA) were analyzed for each river basin using different annual periods in order to account for the delay in streamflow response. The data consists of unimpaired river discharge time series at key points (from the Brazilian National Water Agency (ANA)); normalized yearly averaged NINO3.4 index characterizing El Nino (from NOAA); and NTA index (from NOAA), as a surrogate of the latitudinal movement of the ITCZ, since it is correlated to the Atlantic SST gradient. As a result, each river basin showed a different response. At the Amazon river basin, almost all dry years occurred when NINO3.4 was above average (El Nino years). Moreover, in almost every year when NINO3.4 was below average (La Nina) the streamflows were above average. Thus, it seems that La Nina have strong effects in floods in Amazon river. Moreover, El Nino events seem to be a necessary, but not sufficient condition for low streamflows at Amazon river. A weaker relationship was found for Xingu river basin, since it is probably affected by cold fronts from the south. As the location of river basins changes towards the south, the effect of El Nino events gets weaker as for Araguaia-Tocantins and Sao Francisco river basins. At the Parana river basin, the relationship is reversed. Almost all extreme wet years occurred during El Nino years. The correlation between streamflows and the NTA indexes were very weak for all river basins except for the Amazon. When the NTA anomaly is negative, wet years occurs, since the ITCZ moves southwards and stays longer at that position, increasing rainfall over the Amazon and Northeast of Brazil. In contrast, almost

  16. January-february Tropospheric Climate for the Northern Hemisphere and the 11-year Solar Cycle, the QBO and the Southern Oscillation

    NASA Technical Reports Server (NTRS)

    Barnston, Anthony G.; Livezey, Robert E.

    1990-01-01

    Examined here is a recently discovered association between the 11-year solar cycle and the atmosphere that is most easily detectable when the two phases of the Quasi-biennial Oscillation (QBO) are considered individually rather than pooled. The influence of the Southern Oscillation (SO) for either of the two QBO phases is then combined with that of the solar cycle in the form of two-predictor multiple regression. The strong and well-defined relationship between the 11-year 10.7 cm solar flux cycle and the lower troposphere Northern Hemisphere January-February climate for QBO phase-stratified samples (van Loon and Labitzke 1988, Barnston and Livezey 1989) failed for the west QBO phase in 1989. Here, the opposing 1989 event is explained, at least in part, on the basis of the phase of the SO (the cold tropical Pacific SST event of 1988 to 1989). It is demonstrated that both the SO and the solar flux have moderate and quasi-independent correlations with the climate over certain regions, and where there is strong overlap they can work either in harmony or in opposition. In 1989 in North America the influences of the SO and the flux conflicted to an unprecedented extent, and the SO was the controlling influence in most regions of the continent (western Canada being one exception). The 1989 event draws attention to the smallness of the QBO phase-stratified samples and the still more serious holes in the two-dimensional sample space of flux and SO when both factors are viewed as predictors within one QBO phase.

  17. Pacific Decadal Variability in the Southern Indian Ocean: A 1 ky Interdecadal Pacific Oscillation and Australian Megadrought Reconstruction from Law Dome, East Antarctica.

    NASA Astrophysics Data System (ADS)

    Vance, T.; Roberts, J. L.; Plummer, C. T.; Kiem, A.; van Ommen, T. D.

    2014-12-01

    The Interdecadal Pacific Oscillation (IPO) is a multidecadal mode of Pacific basin SST anomalies, and is the basin-wide, bi-hemispheric expression of the Pacific Decadal Oscillation (PDO). The two indices are highly correlated, but the extent to which they are merely low frequency ENSO is debated. Nonetheless, the IPO/PDO significantly influences interannual rainfall variability and drought risk across and beyond the Pacific region on multi-decadal timescales, thus an understanding of long-term IPO/PDO variability will help with assessing past and future drought risk. A new and highly accurate 1 ky IPO reconstruction has been produced from the Law Dome ice core (East Antarctica). Law Dome is a high accumulation site on the coast of Antarctica in the Indian Ocean sector of the Southern Ocean, and the Law Dome record is directly related to atmospheric anomalies across a broad mid-latitude swathe of this region. The reconstruction utilizes both the accumulation (snowfall) and sea salt (wind proxy) records to produce a reconstruction that is highly calibrated to the instrumental IPO record from 1870-2009 and shows excellent skill (reduction of error value of 0.86). We then super-imposed the 1 ky IPO on a Law Dome proxy for rainfall in eastern subtropical Australia (previously shown to represent rainfall with high significance during IPO positive phases (r =0.406-0.677, p <0.0001-0.01) to identify eight Australian 'mega-droughts' (dry periods >5 y duration) over the last millennium. Six mega-droughts occur between AD 1000-1320 including one 39 y drought (AD 1174-1212). Water resources and infrastructure planning in Australia has been based on very limited statistical certainty around drought risk due to the short instrumental record and lack of rainfall proxies. A recent drought (the 'Big Dry' ~1995-2009) brought both agricultural and urban water supplies to critically low levels, while the Murray-Darling Basin river system, which provides 65% of the water used for

  18. Seasonal to decadal modulation of the impact of El Niño-Southern Oscillation on New Caledonia (SW Pacific) rainfall (1950-2010)

    NASA Astrophysics Data System (ADS)

    Barbero, Renaud; Moron, Vincent

    2011-12-01

    New Caledonia (NC; ˜166°E, 22°S) rainfall anomalies are more sensitive to central Pacific (CP) El Niño and La Niña events than to those exhibiting highest sea surface temperature (SST) anomalies in the eastern Pacific (EP). The linear relationship between NC rainfall anomalies and CP SST indices peaks from September to March (S-M). The seasonal S-M atmospheric anomalies observed in the South West (SW) Pacific during the warm CP events are highly dissimilar to the EP ones, while there are more similarities during the cold events with a higher amplitude during the CP ones. The warm CP events strengthen the southern Hadley cell around NC longitudes, with positive rainfall anomalies in the equatorial Pacific leading to an anomalous release of latent heat in the upper troposphere and an increased subsidence in the SW Pacific. Atmospheric anomalies are strongest in September-November because of a combination of a rather strong zonal SST gradient with the warmest SST in the equatorial Pacific just west of the dateline. The cold CP and EP events are associated with a southwestward shift of the South Pacific Convergence Zone with strongest atmospheric anomalies during the CP events. Squared wavelet coherence between NC rainfall and Niño 4 SST index shows that their negative correlations are mostly carried by two distinct timescales: the classical El Niño-Southern Oscillation (i.e., 3-6 years) variability and a quasi-decadal one (i.e., 10-12 years). The high-frequency (>1/8 cycle per year) correlations peak around Christmas and are quasi-stationary since 1950, whereas the low-frequency ones (<1/8 cycle per year) peak from the austral autumn to the austral spring and have strengthened from ˜1975 to 1980 onward with a subtle warming trend in the equatorial Pacific near the dateline.

  19. Changes in El Niño - Southern Oscillation (ENSO) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings

    NASA Astrophysics Data System (ADS)

    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

    2016-12-01

    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 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 (ENSO). 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 ENSO-like periodicities occurring after the downturn event. Comparison to low- and mid-latitude Pacific records suggests a coherency with ENSO and Southern Hemisphere atmospheric circulation change during this period. The driver(s) 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.

  20. The Origins of Mexico's Universidad de los Ninos.

    ERIC Educational Resources Information Center

    Levy, Raquel

    1989-01-01

    The article describes an after school program, the Universidad de los Ninos, in Mexico City, for children with special abilities. The program stresses development of individual potential, a flexible curriculum, parent involvement, and development of social responsibility. (DB)

  1. Did El Nino Weather Give Zika a Boost?

    MedlinePlus

    ... fullstory_162611.html Did El Nino Weather Give Zika a Boost? Climate phenomenon could have helped infection- ... might have aided the explosive spread of the Zika virus throughout South America, a new study reports. ...

  2. El Nino - La Nina Implications on Flood Hazard Mitigation

    SciTech Connect

    R. French; J. Miller

    2006-03-31

    The effects of El Nino and La Nina periods on the maximum daily winter period depths of precipitation are examined using records from five precipitation gages on the Nevada Test Site. The potential implications of these effects are discussed.

  3. The Origins of Mexico's Universidad de los Ninos.

    ERIC Educational Resources Information Center

    Levy, Raquel

    1989-01-01

    The article describes an after school program, the Universidad de los Ninos, in Mexico City, for children with special abilities. The program stresses development of individual potential, a flexible curriculum, parent involvement, and development of social responsibility. (DB)

  4. TOPEX/El Nino Watch - El Nino is Still Lingering in the Pacific May 3, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This image of the Pacific Ocean was produced using sea-surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea-surface height relative to normal ocean conditions on May 3, 1998, and sea-surface height is an indicator of the heat content of the ocean. The image shows that sea-surface height along the central and eastern equatorial Pacific has maintained a near normal state since March 1998. However, the western equatorial Pacific, shown here in purple, has not returned to a normal state and is still about 30 centimeters (12 inches) below normal sea level. Remnants of the El Nino warm water pool, shown in red and white, are situated to the north of the equator. Oceanographers indicate these measurements show that the Pacific has not yet fully recovered from this large El Nino event. These sea-surface height measurements have provided scientists with a detailed view of how the 1997-98 El Nino's warm water pool behaves because the TOPEX/Poseidon satellite measures the changing sea-surface height with unprecedented precision. In this image, the white and red areas indicate unusual patterns of heat storage; in the white areas, the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions. The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds weaken and even reverse direction. This change in the winds allows a large mass of warm water (the red and white area) that is normally located near Australia to move eastward along the equator until it reaches the coast of South America. The displacement of so much warm water affects evaporation, where rain clouds form and, consequently, alters the typical atmospheric jet stream patterns around the world. Using satellite imagery, buoy and ship data, and a forecasting model of the ocean-atmosphere system, the National

  5. TOPEX/El Nino Watch - El Nino is Still Lingering in the Pacific May 3, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This image of the Pacific Ocean was produced using sea-surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea-surface height relative to normal ocean conditions on May 3, 1998, and sea-surface height is an indicator of the heat content of the ocean. The image shows that sea-surface height along the central and eastern equatorial Pacific has maintained a near normal state since March 1998. However, the western equatorial Pacific, shown here in purple, has not returned to a normal state and is still about 30 centimeters (12 inches) below normal sea level. Remnants of the El Nino warm water pool, shown in red and white, are situated to the north of the equator. Oceanographers indicate these measurements show that the Pacific has not yet fully recovered from this large El Nino event. These sea-surface height measurements have provided scientists with a detailed view of how the 1997-98 El Nino's warm water pool behaves because the TOPEX/Poseidon satellite measures the changing sea-surface height with unprecedented precision. In this image, the white and red areas indicate unusual patterns of heat storage; in the white areas, the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions. The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds weaken and even reverse direction. This change in the winds allows a large mass of warm water (the red and white area) that is normally located near Australia to move eastward along the equator until it reaches the coast of South America. The displacement of so much warm water affects evaporation, where rain clouds form and, consequently, alters the typical atmospheric jet stream patterns around the world. Using satellite imagery, buoy and ship data, and a forecasting model of the ocean-atmosphere system, the National

  6. Using oceanic-atmospheric oscillations for long lead time streamflow forecasting

    NASA Astrophysics Data System (ADS)

    Kalra, Ajay; Ahmad, Sajjad

    2009-03-01

    We present a data-driven model, Support Vector Machine (SVM), for long lead time streamflow forecasting using oceanic-atmospheric oscillations. The SVM is based on statistical learning theory that uses a hypothesis space of linear functions based on Kernel approach and has been used to predict a quantity forward in time on the basis of training from past data. The strength of SVM lies in minimizing the empirical classification error and maximizing the geometric margin by solving inverse problem. The SVM model is applied to three gages, i.e., Cisco, Green River, and Lees Ferry in the Upper Colorado River Basin in the western United States. Annual oceanic-atmospheric indices, comprising Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), and El Nino-Southern Oscillations (ENSO) for a period of 1906-2001 are used to generate annual streamflow volumes with 3 years lead time. The SVM model is trained with 86 years of data (1906-1991) and tested with 10 years of data (1992-2001). On the basis of correlation coefficient, root means square error, and Nash Sutcliffe Efficiency Coefficient the model shows satisfactory results, and the predictions are in good agreement with measured streamflow volumes. Sensitivity analysis, performed to evaluate the effect of individual and coupled oscillations, reveals a strong signal for ENSO and NAO indices as compared to PDO and AMO indices for the long lead time streamflow forecast. Streamflow predictions from the SVM model are found to be better when compared with the predictions obtained from feedforward back propagation artificial neural network model and linear regression.

  7. Recent Decadal Variations of El Nino Predictability

    NASA Astrophysics Data System (ADS)

    Wang, Guomin; Hendon, Harry; Zhao, Mei

    2017-04-01

    Predictive skill for El Niño in the equatorial eastern Pacific across a range of forecast models declined in the early 21st century relative to what was achieved in the late 20th century. This decline coincided with a reduction of El Niño variability in the eastern Pacific and a shift in Pacific climate to an enhanced east-west surface temperature gradient and stronger trade winds in the central Pacific, which has previously been associated with the recent hiatus in global surface warming. It is an outstanding question as to whether this shift in climate at the end of the 20th century acted to weaken El Niño variability, hence predictability, or whether El Niño variability weakened by chance thus reducing predictability but in so doing resulted in the shift in climate. Using seasonal forecast sensitivity experiments with the Australian Bureau of Meteorology coupled model POAMA2.4, the shift to intensified east-west surface temperature gradient and stronger central Pacific trade winds is shown to weaken the ocean-atmosphere feedback that amplify eastern Pacific El Niño, thus resulting in weaker variability that is less predictable. This weakened coupling helps explain the fitful behaviour and challenges for forecasting the non-developing El Niño in early 2014. In contrast, the Pacific mean state appears to have swung to a more favourable condition for promoting El Nino toward the end of 2014, thus supporting stronger development of El Nino in 2015.

  8. Recent Decadal Variations of El Nino Predictability

    NASA Astrophysics Data System (ADS)

    Hendon, H.; Wang, G.; Zhao, M.

    2016-12-01

    Predictive skill for El Niño in the equatorial eastern Pacific across a range of forecast models declined in the early 21st century relative to what was achieved in the late 20th century. This decline coincided with a reduction of El Niño variability in the eastern Pacific and a shift in Pacific climate to an enhanced east-west surface temperature gradient and stronger trade winds in the central Pacific, which has previously been associated with the recent hiatus in global surface warming. It is an outstanding question as to whether this shift in climate at the end of the 20th century acted to weaken El Niño variability, hence predictability, or whether El Niño variability weakened by chance thus reducing predictability but in so doing resulted in the shift in climate. Using seasonal forecast sensitivity experiments with the Australian Bureau of Meteorology coupled model POAMA2.4, the shift to intensified east-west surface temperature gradient and stronger central Pacific trade winds is shown to weaken the ocean-atmosphere feedback that amplify eastern Pacific El Niño, thus resulting in weaker variability that is less predictable. This weakened coupling helps explain the fitful behaviour and challenges for forecasting the non-developing El Niño in early 2014. In contrast, the Pacific mean state appears to have swung to a more favourable condition for promoting El Nino toward the end of 2014, thus supporting stronger development of El Nino in 2015.

  9. Volcanos and El Nino: Signal separation in northern hemisphere winter

    SciTech Connect

    Kirchner, I.; Graf, H.F.

    1995-08-01

    The frequent coincidence of volcanic forcing with El Nino events disables the clear assignment of climate anomalies to either volcanic or El Nino forcing. In order to select the signals, a set of four different perpetual January GCM experiments was performed (control, volcano case, El Nino case and combined volcano/El Nino case) and studied with advanced statistical methods for the Northern Hemisphere winter. The results were compared with observations. The signals for the different forcings are discussed for three variables (temperature, zonal wind and geopotential height) and five levels (surface, 850 hPa. 500 hPa, 200 hPa and 50 hPa). The global El Nino signal can be selected more clearly in the troposphere than in the stratosphere. In contrast, the global volcano signal is strongest in the stratospheric temperature field. The amplitude of the perturbation for the volcano case is largest in the Atlantic region. The observed effect of local cooling due to the volcanic reduction of short-wave radiation over large land areas (like Asia) in sub-tropical regions, the observed advective warming over Eurasia and the advective cooling over Greenland are well simulated in the model. The radiative cooling near the surface is important for the volcano signal in the subtropics, but it is weak in high latitudes during winter. A statistically significant tropospheric signal of El Nino forcing occurs in the subtropics and in the mid-latitudes of the North Pacific. The local anomalies in the El Nino forcing region in the tropics, and the warming over North America in middle and high latitudes are simulated as observed. The combined signal is different from a simple linear combination of the separate signals. It leads to a climate perturbation stronger than for forcing with El Nino or stratospheric aerosol alone and to a somewhat modified pattern. 73 refs., 16 figs., 2 tabs.

  10. On the impact of spiciness on El Nino

    NASA Astrophysics Data System (ADS)

    Schneider, N.; Di Lorenzo, E.; Nonaka, M.; Taguchi, B.

    2015-12-01

    We investigate the modulation of ENSO location and amplitude by spiciness anomalies in the tropical thermocline. First, Argo observations constrain the size of observed spiciness anomalies. Realistic perturbations are then used to investigate the impact on an intermediate El Nino model. This shows that spiciness anomalies can increase the thermocline feedback and thus enhance the Bjerknes feedback and ENSO amplitudes. Experiments with coupled general circulation model are analyzed to investigate the impact on the character of El Nino.

  11. TOPEX/El Nino Watch - El Nino Warm Water Pool Decreasing, Jan, 08, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This image of the Pacific Ocean was produced using sea surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea surface height relative to normal ocean conditions on Jan. 8, 1998, and sea surface height is an indicator of the heat content of the ocean. The volume of the warm water pool related to the El Nino has decreased by about 40 percent since its maximum in early November, but the area of the warm water pool is still about one and a half times the size of the continental United States. The volume measurements are computed as the sum of all the sea surface height changes as compared to normal ocean conditions. In addition, the maximum water temperature in the eastern tropical Pacific, as measured by the National Oceanic and Atmospheric Administration (NOAA), is still higher than normal. Until these high temperatures diminish, the El Nino warm water pool still has great potential to disrupt global weather because the high water temperatures directly influence the atmosphere. Oceanographers believe the recent decrease in the size of the warm water pool is a normal part of El Nino's natural rhythm. TOPEX/Poseidon has been tracking these fluctuations of the El Nino warm pool since it began in early 1997. These sea surface height measurements have provided scientists with their first detailed view of how El Nino's warm pool behaves because the TOPEX/Poseidon satellite measures the changing sea surface height with unprecedented precision. In this image, the white and red areas indicate unusual patterns of heat storage; in the white areas, the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions, while purple (the western Pacific) means at least 18 centimeters (7 inches) below normal sea level.

    The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds

  12. TOPEX/El Nino Watch - El Nino Warm Water Pool Decreasing, Jan, 08, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This image of the Pacific Ocean was produced using sea surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea surface height relative to normal ocean conditions on Jan. 8, 1998, and sea surface height is an indicator of the heat content of the ocean. The volume of the warm water pool related to the El Nino has decreased by about 40 percent since its maximum in early November, but the area of the warm water pool is still about one and a half times the size of the continental United States. The volume measurements are computed as the sum of all the sea surface height changes as compared to normal ocean conditions. In addition, the maximum water temperature in the eastern tropical Pacific, as measured by the National Oceanic and Atmospheric Administration (NOAA), is still higher than normal. Until these high temperatures diminish, the El Nino warm water pool still has great potential to disrupt global weather because the high water temperatures directly influence the atmosphere. Oceanographers believe the recent decrease in the size of the warm water pool is a normal part of El Nino's natural rhythm. TOPEX/Poseidon has been tracking these fluctuations of the El Nino warm pool since it began in early 1997. These sea surface height measurements have provided scientists with their first detailed view of how El Nino's warm pool behaves because the TOPEX/Poseidon satellite measures the changing sea surface height with unprecedented precision. In this image, the white and red areas indicate unusual patterns of heat storage; in the white areas, the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions, while purple (the western Pacific) means at least 18 centimeters (7 inches) below normal sea level.

    The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds

  13. Bacterial community composition and physiological shifts associated with the El Niño Southern Oscillation (ENSO) in the Patos Lagoon estuary.

    PubMed

    They, Ng Haig; Ferreira, Lise Maria Holanda; Marins, Luís Fernando; Abreu, Paulo Cesar

    2015-04-01

    The Patos Lagoon estuary is a microtidal system that is strongly regulated by atmospheric forces, including remote large-scale phenomena such as the El Niño Southern Oscillation (ENSO), which affects precipitation patterns in the region. In this study, we investigated whether the bacterial community composition (BCC), community-level physiological profiles (CLPP), and a set of environmental variables were affected by the transition from a moderate El Niño to a strong La Niña event (June 2010 to May 2011). We identified two distinct periods: a period following El Niño that was characterized by low salinity and high concentrations of NO3(-) and PO4(-3) and low molecular weight (LMW) substances and a period following La Niña during which salinity, temperature, and transparency increased and the concentrations of nutrients and LMW substances decreased. The BCC and CLPP were significantly altered in response to this transition. This is the first study addressing the effect of ENSO on bacteria at the community level in an estuarine system. Our results suggest that there is a link between ENSO and bacteria, indicating the role of climate variability in bacterial activities and, hence, the cycling of organic matter by these microorganisms.

  14. Changes in the apparent survival of a tropical bird in response to the El Niño Southern Oscillation in mature and young forest in Costa Rica.

    PubMed

    Wolfe, Jared D; Ralph, C John; Elizondo, Pablo

    2015-07-01

    The effects of habitat alteration and climatic instability have resulted in the loss of bird populations throughout the globe. Tropical birds in particular may be sensitive to climate and habitat change because of their niche specialization, often sedentary nature, and unique life-cycle phenologies. Despite the potential influence of habitat and climatic interactions on tropical birds, we lack comparisons of avian demographics from variably aged forests subject to different climatic phenomena. Here, we measured relationships between forest type and climatic perturbations on White-collared Manakin (Manacus candei), a frugivorous tropical bird, by using 12 years of capture data in young and mature forests in northeastern Costa Rica. We used Cormack-Jolly-Seber models and an analysis of deviance to contrast the influence of the El Niño Southern Oscillation (ENSO) on manakin survival. We found that ENSO had little effect on manakin survival in mature forests. Conversely, in young forests, ENSO explained 79% of the variation where dry El Niño events negatively influenced manikin survival. We believe mature forest mitigated negative effects of dry El Niño periods and can serve as refugia for some species by buffering birds from climatic instability. Our results represent the first published documentation that ENSO influences the survival of a resident Neotropic landbird.

  15. Influence of El Niño-Southern Oscillation on the population structure of a sea lion breeding colony in the Gulf of California

    NASA Astrophysics Data System (ADS)

    Shirasago-Germán, Bernardo; Pérez-Lezama, Edgar L.; Chávez, Ernesto A.; García-Morales, Ricardo

    2015-03-01

    The El Niño-Southern Oscillation (ENSO) phenomenon has a significant influence on Pacific marine ecosystems from primary trophic levels to top predators that cause fluctuations in their populations. Based on this fact we analyzed the sea lion Zalophus californianus population structure variability using censuses performed from 1979 to 2004 in Los Islotes breeding colony located at La Paz Bay as well as concomitant the ENSO phenomenon variability. To discriminate variations in the population structure not ascribable to the population attributes, a virtual population was created and compared to the census population. The residuals obtained from this comparison were correlated with the MEI (Multivariate ENSO Index) and BEST (Bivariate ENSO Time Series) indices, descriptors of the ENSO variability. The results showed that the population structure is an adequate descriptor of the conditions of the population instead of the abundance, and the total population is affected by the ENSO. The adult, subadult and pup male groups were the most sensitive groups to this phenomenon due to their intrinsic development and behavior. Likewise the BEST index is a better descriptor than the MEI index of the ENSO influence in the region where the breeding colony Los Islotes resides. Therefore we demonstrate in this work that changes caused by the ENSO not directly affect the sea lion due to its homeothermic capacity but affects the habitat where this organism performs its biological functions, producing behavioral changes in the population.

  16. Local temperature and El Niño Southern Oscillation influence migration phenology of East Asian migratory waterbirds wintering in Poyang, China.

    PubMed

    Xu, Fei; Liu, Guanhua; Si, Yali

    2016-12-19

    Temperature is a critical factor influencing avian phenology, due to its direct impact on food and water availability. Most previous studies have focused on the timing of spring migration and arrival of birds at breeding grounds along the European and American flyways; little is known about migration ecology at the wintering sites along the Asian flyways. This study investigates how local temperature variation and EI Niño Southern Oscillation (ENSO) influences the arrival and departure timing of nine waterbird species breeding in Mongolia or Siberia and overwintering in Poyang, China from 2002 to 2013, using linear regression models. Birds mainly arrive at Poyang in October and depart for their breeding sites in March. Six out of nine species show a strong negative relationship between departure time and overwintering temperature in Poyang. Departure dates also show a negative association with overwintering ENSO and March ENSO for two species. Both local and large-scale climate indices show no influence on the arrival timing of waterbirds. We suggest that birds react to the annual variation of overwintering temperature: an earlier departure of waterbirds is facilitated by a warmer overwintering period and vice versa. The long-term accumulated temperature effect is more pronounced than ENSO and the short-term local temperature effect. Our findings could help quantify the potential impact of global warming on waterbirds. This article is protected by copyright. All rights reserved.

  17. 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.

  18. Extreme rainfall activity in the Australian tropics reflects changes in the El Niño/Southern Oscillation over the last two millennia.

    PubMed

    Denniston, Rhawn F; Villarini, Gabriele; Gonzales, Angelique N; Wyrwoll, Karl-Heinz; Polyak, Victor J; Ummenhofer, Caroline C; Lachniet, Matthew S; Wanamaker, Alan D; Humphreys, William F; Woods, David; Cugley, John

    2015-04-14

    Assessing temporal variability in extreme rainfall events before the historical era is complicated by the sparsity of long-term "direct" storm proxies. Here we present a 2,200-y-long, accurate, and precisely dated record of cave flooding events from the northwest Australian tropics that we interpret, based on an integrated analysis of meteorological data and sediment layers within stalagmites, as representing a proxy for extreme rainfall events derived primarily from tropical cyclones (TCs) and secondarily from the regional summer monsoon. This time series reveals substantial multicentennial variability in extreme rainfall, with elevated occurrence rates characterizing the twentieth century, 850-1450 CE (Common Era), and 50-400 CE; reduced activity marks 1450-1650 CE and 500-850 CE. These trends are similar to reconstructed numbers of TCs in the North Atlantic and Caribbean basins, and they form temporal and spatial patterns best explained by secular changes in the dominant mode of the El Niño/Southern Oscillation (ENSO), the primary driver of modern TC variability. We thus attribute long-term shifts in cyclogenesis in both the central Australian and North Atlantic sectors over the past two millennia to entrenched El Niño or La Niña states of the tropical Pacific. The influence of ENSO on monsoon precipitation in this region of northwest Australia is muted, but ENSO-driven changes to the monsoon may have complemented changes to TC activity.

  19. Extreme rainfall activity in the Australian tropics reflects changes in the El Niño/Southern Oscillation over the last two millennia

    PubMed Central

    Denniston, Rhawn F.; Villarini, Gabriele; Gonzales, Angelique N.; Wyrwoll, Karl-Heinz; Polyak, Victor J.; Ummenhofer, Caroline C.; Lachniet, Matthew S.; Wanamaker, Alan D.; Humphreys, William F.; Woods, David; Cugley, John

    2015-01-01

    Assessing temporal variability in extreme rainfall events before the historical era is complicated by the sparsity of long-term “direct” storm proxies. Here we present a 2,200-y-long, accurate, and precisely dated record of cave flooding events from the northwest Australian tropics that we interpret, based on an integrated analysis of meteorological data and sediment layers within stalagmites, as representing a proxy for extreme rainfall events derived primarily from tropical cyclones (TCs) and secondarily from the regional summer monsoon. This time series reveals substantial multicentennial variability in extreme rainfall, with elevated occurrence rates characterizing the twentieth century, 850–1450 CE (Common Era), and 50–400 CE; reduced activity marks 1450–1650 CE and 500–850 CE. These trends are similar to reconstructed numbers of TCs in the North Atlantic and Caribbean basins, and they form temporal and spatial patterns best explained by secular changes in the dominant mode of the El Niño/Southern Oscillation (ENSO), the primary driver of modern TC variability. We thus attribute long-term shifts in cyclogenesis in both the central Australian and North Atlantic sectors over the past two millennia to entrenched El Niño or La Niña states of the tropical Pacific. The influence of ENSO on monsoon precipitation in this region of northwest Australia is muted, but ENSO-driven changes to the monsoon may have complemented changes to TC activity. PMID:25825740

  20. Breaking out of the comfort zone: El Niño-Southern Oscillation as a driver of trophic flows in a benthic consumer of the Humboldt Current ecosystem.

    PubMed

    Riascos, José M; Solís, Marco A; Pacheco, Aldo S; Ballesteros, Manuel

    2017-06-28

    The trophic flow of a species is considered a characteristic trait reflecting its trophic position and function in the ecosystem and its interaction with the environment. However, climate patterns are changing and we ignore how patterns of trophic flow are being affected. In the Humboldt Current ecosystem, arguably one of the most productive marine systems, El Niño-Southern Oscillation is the main source of interannual and longer-term variability. To assess the effect of this variability on trophic flow we built a 16-year series of mass-specific somatic production rate (P/B) of the Peruvian scallop (Argopecten purpuratus), a species belonging to a former tropical fauna that thrived in this cold ecosystem. A strong increase of the P/B ratio of this species was observed during nutrient-poor, warmer water conditions typical of El Niño, owing to the massive recruitment of fast-growing juvenile scallops. Trophic ecology theory predicts that when primary production is nutrient limited, the trophic flow of organisms occupying low trophic levels should be constrained (bottom-up control). For former tropical fauna thriving in cold, productive upwelling coastal zones, a short time of low food conditions but warm waters during El Niño could be sufficient to waken their ancestral biological features and display massive proliferations. © 2017 The Author(s).

  1. Complex network analysis helps to identify impacts of the El Niño Southern Oscillation on moisture divergence in South America

    NASA Astrophysics Data System (ADS)

    Boers, Niklas; Donner, Reik V.; Bookhagen, Bodo; Kurths, Jürgen

    2015-08-01

    We investigate the temporal evolution of moisture divergence and its spatial clustering properties over South America. Our analysis focuses on dependencies on the phase of the El Niño Southern Oscillation (ENSO). Moisture divergence is computed from daily reanalysis data of vertically integrated moisture flux provided by Modern-Era Retrospective Analysis for Research and Applications for the time period from 1979 to 2010. We use a sliding-window approach to construct a sequence of complex networks, each obtained from synchronization of events of strong positive (negative) moisture divergence, which we interpret as strong evapotranspiration (precipitation) events. We make the following three key observations: (1) Moisture divergence values over the Amazon rainforest are typically higher during positive ENSO periods (El Niño events). (2) The spatial coherence of strong positive (upwelling) events assumes a characteristic pattern of reduced coherence in this area during El Niño conditions. This influence of ENSO on moisture divergence and its spatial coherence is dominated by the El Niño events of 1982, 1987, and 1997. (3) The clustering characteristics of the obtained climate networks qualitatively agree with the spatial distribution of connected regions with simultaneous events (i.e., events that occur at the same time), but provide a more detailed view on the spatial organization of strong atmospheric upwelling events. Interestingly, no comparable results are found for negative extremes of moisture divergence (strong precipitation events).

  2. Analysis of the El Niño/La Niña-Southern Oscillation variability and malaria in the Estado Sucre, Venezuela.

    PubMed

    Delgado-Petrocelli, Laura; Córdova, Karenia; Camardiel, Alberto; Aguilar, Víctor H; Hernández, Denise; Ramos, Santiago

    2012-09-01

    The last decade has seen an unprecedented, worldwide acceleration of environmental and climate changes. These processes impact the dynamics of natural systems, which include components associated with human communities such as vector-borne diseases. The dynamics of environmental and climate variables, altered by global change as reported by the Intergovernmental Panel on Climate Change, affect the distribution of many tropical diseases. Complex systems, e.g. the El Niño/La Niña-Southern Oscillation (ENSO), in which environmental variables operate synergistically, can provoke the reemergence and emergence of vector-borne diseases at new sites. This research investigated the influence of ENSO events on malaria incidence by determining the relationship between climate variations, expressed as warm, cold and neutral phases, and their relation to the number of malaria cases in some north-eastern municipalities of Venezuela (Estado Sucre) during the period 1990-2000. Significant differences in malaria incidence were found, particularly in the La Niña ENSO phases (cold) of moderate intensity. These findings should be taken into account for surveillance and control in the future as they shed light on important indicators that can lead to reduced vulnerability to malaria.

  3. Recharge beneath low-impact design rain gardens and the influence of El Niño Southern Oscillation on urban, coastal groundwater resources

    NASA Astrophysics Data System (ADS)

    Newcomer, M. E.; Gurdak, J. J.

    2011-12-01

    Groundwater resources in urban, coastal environments are highly vulnerable to increased human pressures and climate variability. Impervious surfaces, such as buildings, roads, and parking lots prevent infiltration, reduce recharge to underlying aquifers, and increase contaminants in surface runoff that often overflow sewage systems. To mitigate these effects, cities worldwide are adopting low impact design (LID) approaches that direct runoff into natural vegetated systems, such as rain gardens that reduce, filter, and slow stormwater runoff, and are hypothesized to increase infiltration and recharge rates to aquifers. The effects of LID on recharge rates and quality is unknown, particularly during intense precipitation events for cities along the Pacific coast in response to interannual variability of the El Niño Southern Oscillation (ENSO). Using vadose zone monitoring sensors and instruments, I collected and monitored soil, hydraulic, and geochemical data to quantify the rates and quality of infiltration and recharge to the California Coastal aquifer system beneath a LID rain garden and traditional turf-lawn setting in San Francisco, CA. The data were used to calibrate a HYDRUS-3D model to simulate recharge rates under historical and future variability of ENSO. Understanding these processes has important implications for managing groundwater resources in urban, coastal environments.

  4. El Niño-Southern Oscillation influence on the dust storm activity in Australia: Can the past provide a key to the future?

    NASA Astrophysics Data System (ADS)

    Pudmenzky, C.; Stone, R.; Allan, R.; Butler, H.

    2011-12-01

    Wind erosion is an internationally recognised land degradation problem and affects approximately 28% of the global land area. The Australian continent is the largest dust source in the Southern Hemisphere with an emission rate of around 100 Tg yr-1 or approximate 5% of the global total. The climate (especially eastern Australian climate) is greatly influenced by the El Niño-Southern Oscillation (ENSO) which is the strongest natural fluctuation of climate on interannual time-scales and also affects climate conditions globally. ENSO is the core driver of extreme weather events such as drought, flooding, bushfires, dust storms and tropical cyclones and up to 50% of annual rainfall variability in northern and eastern Australia is linked to ENSO. These drier conditions will reduce vegetation cover and result in an increased dust storm activity in the future in central eastern Australia during dry El Niño phases of the Southern Oscillation. The Lake Eyre Basin, Channel Country and the Mallee region are the main dust source areas and severe dust storms have the potential to transport millions of tonnes of fertile topsoil from inland Australia to places as far as New Zealand, New Caledonia and Antarctic. The research project will investigate the influence of the ENSO on dust storm activity in Australia. This will be achieved through major reanalysis of past climate conditions for the past 150 years or more using the global 'Atmospheric Circulation Reconstruction over the Earth' (ACRE) project outputs which will reconstruct both upper-air dynamics, surface conditions and then all major dust storm events of the past. Australia has one of the most variable rainfall climates in the world and observational and modelling results suggest that more frequent or stronger ENSO events are possible in the future. Drought in Australia is probably the most economically costly climate event and has environmental and social impacts by reducing agricultural output and having social

  5. Variability in fusarium head blight epidemics in relation to global climate fluctuations as represented by the El Niño-Southern Oscillation and other atmospheric patterns.

    PubMed

    Kriss, A B; Paul, P A; Madden, L V

    2012-01-01

    Cross-spectral analysis was used to characterize the relationship between climate variability, represented by atmospheric patterns, and annual fluctuations of Fusarium head blight (FHB) disease intensity in wheat. Time series investigated were the Oceanic Niño Index (ONI), which is a measure of the El Niño-Southern Oscillation (ENSO), the Pacific-North American (PNA) pattern and the North Atlantic Oscillation (NAO), which are known to have strong influences on the Northern Hemisphere climate, and FHB disease intensity observations in Ohio from 1965 to 2010 and in Indiana from 1973 to 2008. For each climate variable, mean climate index values for the boreal winter (December to February) and spring (March to May) were utilized. The spectral density of each time series and the (squared) coherency of each pair of FHB-climate-index series were estimated. Significance for coherency was determined by a nonparametric permutation procedure. Results showed that winter and spring ONI were significantly coherent with FHB in Ohio, with a period of about 5.1 years (as well as for some adjacent periods). The estimated phase-shift distribution indicated that there was a generally negative relation between the two series, with high values of FHB (an indication of a major epidemic) estimated to occur about 1 year following low values of ONI (indication of a La Niña); equivalently, low values of FHB were estimated to occur about 1 year after high values of ONI (El Niño). There was also limited evidence that winter ONI had significant coherency with FHB in Indiana. At periods between 2 and 7 years, the PNA and NAO indices were coherent with FHB in both Ohio and Indiana, although results for phase shift and period depended on the specific location, climate index, and time span used in calculating the climate index. Differences in results for Ohio and Indiana were expected because the FHB disease series for the two states were not similar. Results suggest that global climate indices

  6. TOPEX/El Nino Watch - Moisture in the Atmosphere, Jan & Feb, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    his series of six images shows the evolution of atmospheric water vapor over the Pacific Ocean during the 1998 El Nino condition. Higher than normal ocean water temperatures increase the rate of evaporation, and the resulting warm moist air rises into the atmosphere, altering global weather patterns. Data obtained by the Microwave Limb Sounder (MLS) on NASA's Upper Atmosphere Research Satellite (UARS) during January and February 1998 show a decrease in the extent of high levels of water vapor (red) over the eastern equatorial Pacific and an increase in water vapor (yellow to red) over the northwestern Pacific off the coast of Japan. This area is a breeding ground for winter storms that move eastward toward North America. During this El Nino condition, the southern tropical jet stream has shifted northward, bringing additional moisture from the tropics. When these two sources of moisture converge near California, they produce storms with higher-than-normal rainfall.

    For more information, please visit the TOPEX/Poseidon project web page at http://topex-www.jpl.nasa.gov

  7. Insights into Tropical Tropospheric Ozone from the 1998-2000 SHADOZ (Southern Hemisphere Additional Ozonesondes) Data Record

    NASA Technical Reports Server (NTRS)

    Thompson, Anne M.; Witte, Jacquelyn C.; Oltmans, Samuel J.; Schmidlin, Francis J.; Volker, W.; Kirchhoff, J. H.; Posny, Franaoise; Gert, J.; Coetzee, R.; Hoegger, Bruno; hide

    2002-01-01

    We describe the first overview of total, stratospheric and tropospheric ozone in the southern hemisphere tropics based on a three year, ten site record of ozone soundings from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network. Observations covering 1998-2000 were made over Ascension Island; Nairobi, Kenya; Irene, South Africa; Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; Natal, Brazil. The ozone data, with simultaneous temperature profiles to approximately 7 hPa and relative humidity to approximately 200 hPa, are at an archive: http://code9l6. gsfc.nasa.gov/Data_services/shadoz. Prominent features are highly variable tropospheric ozone, a zonal wave-one pattern in total (and tropospheric) column ozone, and signatures of the Quasi-Biennial Oscillation (QBO) in stratospheric ozone. Total, stratospheric and tropospheric column ozone amounts usually peak between August and November and are lowest in the first half of the year. Tropospheric ozone variability over the Indian and Pacific Ocean displays influences of the waning 1997-1998 Indian Ocean Dipole and ENSO (El Nino / Southern Oscillation), seasonal convection and pollution transport from Africa. Tropospheric ozone over the Atlantic Basin reflects regional subsidence and recirculation as well as pollution ozone from biomass burning.

  8. Insights into Tropical Tropospheric Ozone from the 1998-2000 SHADOZ (Southern Hemisphere Additional Ozonesondes) Data Record

    NASA Technical Reports Server (NTRS)

    Thompson, Anne M.; Witte, Jacquelyn C.; Oltmans, Samuel J.; Schmidlin, Francis J.; Volker, W.; Kirchhoff, J. H.; Posny, Franaoise; Gert, J.; Coetzee, R.; Hoegger, Bruno; Bhartia, P. K. (Technical Monitor)

    2002-01-01

    We describe the first overview of total, stratospheric and tropospheric ozone in the southern hemisphere tropics based on a three year, ten site record of ozone soundings from the Southern Hemisphere Additional Ozonesondes (SHADOZ) network. Observations covering 1998-2000 were made over Ascension Island; Nairobi, Kenya; Irene, South Africa; Reunion Island; Watukosek, Java; Fiji; Tahiti; American Samoa; San Cristobal, Galapagos; Natal, Brazil. The ozone data, with simultaneous temperature profiles to approximately 7 hPa and relative humidity to approximately 200 hPa, are at an archive: http://code9l6. gsfc.nasa.gov/Data_services/shadoz. Prominent features are highly variable tropospheric ozone, a zonal wave-one pattern in total (and tropospheric) column ozone, and signatures of the Quasi-Biennial Oscillation (QBO) in stratospheric ozone. Total, stratospheric and tropospheric column ozone amounts usually peak between August and November and are lowest in the first half of the year. Tropospheric ozone variability over the Indian and Pacific Ocean displays influences of the waning 1997-1998 Indian Ocean Dipole and ENSO (El Nino / Southern Oscillation), seasonal convection and pollution transport from Africa. Tropospheric ozone over the Atlantic Basin reflects regional subsidence and recirculation as well as pollution ozone from biomass burning.

  9. Precipitation Anomalies in the Tropical Indian Ocean and Possible Links to the Initiation of El Nino

    NASA Technical Reports Server (NTRS)

    Curtis, Scott; Adler, Robert F.; Huffman, George J.; Starr, David OC. (Technical Monitor)

    2001-01-01

    A pattern of variability in precipitation and 1000mb zonal winds for the tropical Indian Ocean during, 1979 to 1999 (AtmIO mode) is described using EOFs. The AtmIO mode consists of a cross-equatorial gradient of precipitation anomalies and equatorial wind anomalies of alternating signs on the Equator. The positive phase is defined as enhanced precipitation to the In "n south of the equator, suppressed precipitation to the north, and anomalous westerlies centered on the island of Sumatra. In September-October 1981, February-March 1990, and October-December 1996 the AtmIO mod-, was positive and there was a significant 30-60 day variability in the gradient of precipitation anomalies. These cases coincided with moderate to heavy ,activity in the Madden-Jullan Oscillation (MJO). Links between the AtmIO, MJO, and El Nino are discussed.

  10. Tolerance of sponge assemblages to temperature anomalies: resilience and proliferation of sponges following the 1997-8 El-Niño southern oscillation.

    PubMed

    Kelmo, Francisco; Bell, James J; Attrill, Martin J

    2013-01-01

    Coral reefs across the world are under threat from a range of stressors, and while there has been considerable focus on the impacts of these stressors on corals, far less is known about their effect on other reef organisms. The 1997-8 El-Niño Southern Oscillation (ENSO) had notable and severe impacts on coral reefs worldwide, but not all reef organisms were negatively impacted by this large-scale event. Here we describe how the sponge fauna at Bahia, Brazil was influenced by the 1997-8 ENSO event. Sponge assemblages from three contrasting reef habitats (reef tops, walls and shallow banks) at four sites were assessed annually from 1995 to 2011. The within-habitat sponge diversity did not vary significantly across the study period; however, there was a significant increase in density in all habitats. Multivariate analyses revealed no significant difference in sponge assemblage composition (ANOSIM) between pre- and post-ENSO years for any of the habitats, suggesting that neither the 1997-8 nor any subsequent smaller ENSO events have had any measurable impact on the reef sponge assemblage. Importantly, this is in marked contrast to the results previously reported for a suite of other taxa (including corals, echinoderms, bryozoans, and ascidians), which all suffered mass mortalities as a result of the ENSO event. Our results suggest that of all reef taxa, sponges have the potential to be resilient to large-scale thermal stress events and we hypothesize that sponges might be less affected by projected increases in sea surface temperature compared to other major groups of reef organisms.

  11. A Spatial Hierarchical Analysis of the Temporal Influences of the El Niño-Southern Oscillation and Weather on Dengue in Kalutara District, Sri Lanka

    PubMed Central

    Liyanage, Prasad; Tissera, Hasitha; Sewe, Maquins; Quam, Mikkel; Amarasinghe, Ananda; Palihawadana, Paba; Wilder-Smith, Annelies; Louis, Valérie R.; Tozan, Yesim; Rocklöv, Joacim

    2016-01-01

    Dengue is the major public health burden in Sri Lanka. Kalutara is one of the highly affected districts. Understanding the drivers of dengue is vital in controlling and preventing the disease spread. This study focuses on quantifying the influence of weather variability on dengue incidence over 10 Medical Officer of Health (MOH) divisions of Kalutara district. Weekly weather variables and data on dengue notifications, measured at 10 MOH divisions in Kalutara from 2009 to 2013, were retrieved and analysed. Distributed lag non-linear model and hierarchical-analysis was used to estimate division specific and overall relationships between weather and dengue. We incorporated lag times up to 12 weeks and evaluated models based on the Akaike Information Criterion. Consistent exposure-response patterns between different geographical locations were observed for rainfall, showing increasing relative risk of dengue with increasing rainfall from 50 mm per week. The strongest association with dengue risk centred around 6 to 10 weeks following rainfalls of more than 300 mm per week. With increasing temperature, the overall relative risk of dengue increased steadily starting from a lag of 4 weeks. We found similarly a strong link between the Oceanic Niño Index to weather patterns in the district in Sri Lanka and to dengue at a longer latency time confirming these relationships. Part of the influences of rainfall and temperature can be seen as mediator in the causal pathway of the Ocean Niño Index, which may allow a longer lead time for early warning signals. Our findings describe a strong association between weather, El Niño-Southern Oscillation and dengue in Sri Lanka. PMID:27827943

  12. The relationship between the Southern Oscillation Index, rainfall and the occurrence of canine tick paralysis, feline tick paralysis and canine parvovirus in Australia.

    PubMed

    Rika-Heke, Tamara; Kelman, Mark; Ward, Michael P

    2015-07-01

    The aim of this study was to describe the association between climate, weather and the occurrence of canine tick paralysis, feline tick paralysis and canine parvovirus in Australia. The Southern Oscillation Index (SOI) and monthly average rainfall (mm) data were used as indices for climate and weather, respectively. Case data were extracted from a voluntary national companion animal disease surveillance resource. Climate and weather data were obtained from the Australian Government Bureau of Meteorology. During the 4-year study period (January 2010-December 2013), a total of 4742 canine parvovirus cases and 8417 tick paralysis cases were reported. No significant (P ≥ 0.05) correlations were found between the SOI and parvovirus, canine tick paralysis or feline tick paralysis. A significant (P < 0.05) positive cross-correlation was found between parvovirus occurrence and rainfall in the same month (0.28), and significant negative cross-correlations (-0.26 to -0.36) between parvovirus occurrence and rainfall 4-6 months previously. Significant (P < 0.05) negative cross-correlations (-0.34 to -0.39) were found between canine tick paralysis occurrence and rainfall 1-3 months previously, and significant positive cross-correlations (0.29-0.47) between canine tick paralysis occurrence and rainfall 7-10 months previously. Significant positive cross-correlations (0.37-0.68) were found between cases of feline tick paralysis and rainfall 6-10 months previously. These findings may offer a useful tool for the management and prevention of tick paralysis and canine parvovirus, by providing an evidence base supporting the recommendations of veterinarians to clients thus reducing the impact of these diseases. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Tolerance of Sponge Assemblages to Temperature Anomalies: Resilience and Proliferation of Sponges following the 1997–8 El-Niño Southern Oscillation

    PubMed Central

    Kelmo, Francisco; Bell, James J.; Attrill, Martin J.

    2013-01-01

    Coral reefs across the world are under threat from a range of stressors, and while there has been considerable focus on the impacts of these stressors on corals, far less is known about their effect on other reef organisms. The 1997–8 El-Niño Southern Oscillation (ENSO) had notable and severe impacts on coral reefs worldwide, but not all reef organisms were negatively impacted by this large-scale event. Here we describe how the sponge fauna at Bahia, Brazil was influenced by the 1997–8 ENSO event. Sponge assemblages from three contrasting reef habitats (reef tops, walls and shallow banks) at four sites were assessed annually from 1995 to 2011. The within-habitat sponge diversity did not vary significantly across the study period; however, there was a significant increase in density in all habitats. Multivariate analyses revealed no significant difference in sponge assemblage composition (ANOSIM) between pre- and post-ENSO years for any of the habitats, suggesting that neither the 1997–8 nor any subsequent smaller ENSO events have had any measurable impact on the reef sponge assemblage. Importantly, this is in marked contrast to the results previously reported for a suite of other taxa (including corals, echinoderms, bryozoans, and ascidians), which all suffered mass mortalities as a result of the ENSO event. Our results suggest that of all reef taxa, sponges have the potential to be resilient to large-scale thermal stress events and we hypothesize that sponges might be less affected by projected increases in sea surface temperature compared to other major groups of reef organisms. PMID:24116109

  14. The influence of El Niño-Southern Oscillation (ENSO) cycles on wave-driven sea-floor sediment mobility along the central California continental margin

    USGS Publications Warehouse

    Storlazzi, Curt D.; Reid, Jane A.

    2010-01-01

    Ocean surface waves are the dominant temporally and spatially variable process influencing sea floor sediment resuspension along most continental shelves. Wave-induced sediment mobility on the continental shelf and upper continental slope off central California for different phases of El Niño-Southern Oscillation (ENSO) events was modeled using monthly statistics derived from more than 14 years of concurrent hourly oceanographic and meteorologic data as boundary input for the Delft SWAN wave model, gridded sea floor grain-size data from the usSEABED database, and regional bathymetry. Differences as small as 0.5 m in wave height, 1 s in wave period, and 10° in wave direction, in conjunction with the spatially heterogeneous unconsolidated sea-floor sedimentary cover, result in significant changes in the predicted mobility of continental shelf surficial sediment in the study area. El Niño events result in more frequent mobilization on the inner shelf in the summer and winter than during La Niña events and on the outer shelf and upper slope in the winter months, while La Niña events result in more frequent mobilization on the mid-shelf during spring and summer months than during El Niño events. The timing and patterns of seabed mobility are addressed in context of geologic and biologic processes. By understanding the spatial and temporal variability in the disturbance of the sea floor, scientists can better interpret sedimentary patterns and ecosystem structure, while providing managers and planners an understanding of natural impacts when considering the permitting of offshore activities that disturb the sea floor such as trawling, dredging, and the emplacement of sea-floor engineering structures.

  15. Season-dependent dynamics of nonlinear optimal error growth and El Niño-Southern Oscillation predictability in a theoretical model

    NASA Astrophysics Data System (ADS)

    Mu, Mu; Duan, Wansuo; Wang, Bin

    2007-05-01

    Most state-of-the-art climate models have difficulty in the prediction of El Niño-Southern Oscillation (ENSO) starting from preboreal spring seasons. The causes of this spring predictability barrier (SPB) remain elusive. With a theoretical ENSO system model, we investigate this controversial issue by tracing the evolution of conditional nonlinear optimal perturbation (CNOP) and by analyzing the behavior of initial error growth. The CNOPs are the errors in the initial states of ENSO events, which have the biggest impact on the uncertainties at the prediction time under proper physical constraints. We show that the evolution of CNOP-type errors associated with El Niño episodes depends remarkably on season with the fastest growth occurring during boreal spring in the onset phase. There also exist other kinds of initial errors, which have either somewhat smaller growth rates or neutral ones during spring. However, for La Niña events, even if initial errors are of CNOP-type, the errors grow without significant seasonal dependence. These findings suggest that the SPB in this model results from combined effects of three factors: the annual cycle of the mean state, the structure of El Niño, and the pattern of the initial errors. On the basis of the error tendency equations derived from the model, we addressed how the combination of the three factors causes the SPB and proposed a mechanism responsible for the error growth in the model ENSO events. Our results help in clarifying the role of the initial error pattern in SPB, which may provide a clue for explaining why SPB can be eliminated by improving initial conditions. The results also illustrate a theoretical basis for improving data assimilation in ENSO prediction.

  16. Interannual variability of summertime aerosol optical depth over East Asia during 2000-2011: a potential influence from El Niño Southern Oscillation

    NASA Astrophysics Data System (ADS)

    Liu, Yikun; Liu, Junfeng; Tao, Shu

    2013-12-01

    Aerosols degrade air quality, perturb atmospheric radiation, and impact regional and global climate. Due to the rapid increase in anthropogenic emissions, aerosol loading over East Asia (EA) is markedly higher than other industrialized regions, which motivates a need to characterize the evolution of aerosols and understand the associated drivers. Based on the MISR satellite data during 2000-2011, a wave-like interannual variation of summertime aerosol optical depth (SAOD) is observed over the highly populated North China Plain (NCP) in East Asia. Specifically, the peak-to-trough ratio of SAOD ranges from 1.4 to 1.6, with a period of 3-4 years. This variation pattern differs apparently from what has been seen in EA emissions, indicating a periodic change in regional climate pattern during the past decade. Investigations of meteorological fields over the region reveal that the high SAOD is generally associated with the enhanced Philippine Sea Anticyclone Anomaly (PSAA) which weakens southeasterlies over northeastern EA and depresses air ventilation. Alternatively, higher temperature and lower relative humidity are found to be coincident with reduced SAOD. The behavior of PSAA has been found previously to be modulated by the El Niño Southern Oscillations (ENSO), therefore ENSO could disturb the EA SAOD as well. Rather than changing coherently with the ENSO activity, the SAOD peaks over NCP are found to be accompanied by the rapid transition of El Niño warm to cold phases developed four months ahead. An index measuring the development of ENSO during January-April is able to capture the interannual variability of SAOD over NCP during 2000-2011. This finding indicates a need to integrate the large-scale periodic climate variability in the design of regional air quality policy.

  17. A Spatial Hierarchical Analysis of the Temporal Influences of the El Niño-Southern Oscillation and Weather on Dengue in Kalutara District, Sri Lanka.

    PubMed

    Liyanage, Prasad; Tissera, Hasitha; Sewe, Maquins; Quam, Mikkel; Amarasinghe, Ananda; Palihawadana, Paba; Wilder-Smith, Annelies; Louis, Valérie R; Tozan, Yesim; Rocklöv, Joacim

    2016-11-04

    Dengue is the major public health burden in Sri Lanka. Kalutara is one of the highly affected districts. Understanding the drivers of dengue is vital in controlling and preventing the disease spread. This study focuses on quantifying the influence of weather variability on dengue incidence over 10 Medical Officer of Health (MOH) divisions of Kalutara district. Weekly weather variables and data on dengue notifications, measured at 10 MOH divisions in Kalutara from 2009 to 2013, were retrieved and analysed. Distributed lag non-linear model and hierarchical-analysis was used to estimate division specific and overall relationships between weather and dengue. We incorporated lag times up to 12 weeks and evaluated models based on the Akaike Information Criterion. Consistent exposure-response patterns between different geographical locations were observed for rainfall, showing increasing relative risk of dengue with increasing rainfall from 50 mm per week. The strongest association with dengue risk centred around 6 to 10 weeks following rainfalls of more than 300 mm per week. With increasing temperature, the overall relative risk of dengue increased steadily starting from a lag of 4 weeks. We found similarly a strong link between the Oceanic Niño Index to weather patterns in the district in Sri Lanka and to dengue at a longer latency time confirming these relationships. Part of the influences of rainfall and temperature can be seen as mediator in the causal pathway of the Ocean Niño Index, which may allow a longer lead time for early warning signals. Our findings describe a strong association between weather, El Niño-Southern Oscillation and dengue in Sri Lanka.

  18. Multiyear Climate Variability and Dengue—El Niño Southern Oscillation, Weather, and Dengue Incidence in Puerto Rico, Mexico, and Thailand: A Longitudinal Data Analysis

    PubMed Central

    Johansson, Michael A.; Cummings, Derek A. T.; Glass, Gregory E.

    2009-01-01

    Background The mosquito-borne dengue viruses are a major public health problem throughout the tropical and subtropical regions of the world. Changes in temperature and precipitation have well-defined roles in the transmission cycle and may thus play a role in changing incidence levels. The El Niño Southern Oscillation (ENSO) is a multiyear climate driver of local temperature and precipitation worldwide. Previous studies have reported varying degrees of association between ENSO and dengue incidence. Methods and Findings We analyzed the relationship between ENSO, local weather, and dengue incidence in Puerto Rico, Mexico, and Thailand using wavelet analysis to identify time- and frequency-specific association. In Puerto Rico, ENSO was transiently associated with temperature and dengue incidence on multiyear scales. However, only local precipitation and not temperature was associated with dengue on multiyear scales. In Thailand, ENSO was associated with both temperature and precipitation. Although precipitation was associated with dengue incidence, the association was nonstationary and likely spurious. In Mexico, no association between any of the variables was observed on the multiyear scale. Conclusions The evidence for a relationship between ENSO, climate, and dengue incidence presented here is weak. While multiyear climate variability may play a role in endemic interannual dengue dynamics, we did not find evidence of a strong, consistent relationship in any of the study areas. The role of ENSO may be obscured by local climate heterogeneity, insufficient data, randomly coincident outbreaks, and other, potentially stronger, intrinsic factors regulating transmission dynamics. Please see later in the article for the Editors' Summary PMID:19918363

  19. A long-term trend in precipitation of different spatial regions of Bangladesh and its teleconnections with El Niño/Southern Oscillation and Indian Ocean Dipole

    NASA Astrophysics Data System (ADS)

    Ahmed, Md. Kawser; Alam, Mohammad Samsul; Yousuf, Abu Hena Muhammad; Islam, Md. Monirul

    2017-07-01

    A long-term (1948 to 2012) trend of precipitation (annual, pre-monsoon, monsoon, and post-monsoon seasons) in Bangladesh was analyzed in different regions using both parametric and nonparametric approaches. Moreover, the possible teleconnections of precipitation (annual and monsoon) variability with El Niño/Southern Oscillation (ENSO) episode and Indian Ocean Dipole (IOD) were investigated using both average and individual (both positive and negative) values of ENSO index and IOD. Our findings suggested that for annual precipitation, a significant increasing monotonic trend was found in whole Bangladesh (4.87 mm/year), its western region (5.82 mm/year) including Rangpur (9.41 mm/year) and Khulna (4.95 mm/year), and Sylhet (10.12 mm/year) and Barisal (6.94 mm/year) from eastern region. In pre-monsoon, only Rangpur (2.88 mm/year) showed significant increasing trend, while in monsoon, whole Bangladesh (3.04 mm/year), Sylhet (7.17 mm/year), and Barisal (6.94 mm/year) showed similar trend. In post-monsoon, there was no significant trend. Our results also revealed that the precipitation (annual or monsoon) of whole Bangladesh and almost all of the spatial regions did not show any significant correlation with ENSO events, whereas the average IOD values showed significant correlation only in monsoon precipitation of western region. The individual positive IODs showed significant correlation in whole Bangladesh, western region, and its two divisions (Rajshahi and Khulna). So, in the context of Bangladesh climate, IOD has the more teleconnection to precipitation than that of ENSO. Our findings indicate that the co-occurrence of ENSO and IOD events may suppress their influence on each other.

  20. A long-term trend in precipitation of different spatial regions of Bangladesh and its teleconnections with El Niño/Southern Oscillation and Indian Ocean Dipole

    NASA Astrophysics Data System (ADS)

    Ahmed, Md. Kawser; Alam, Mohammad Samsul; Yousuf, Abu Hena Muhammad; Islam, Md. Monirul

    2016-04-01

    A long-term (1948 to 2012) trend of precipitation (annual, pre-monsoon, monsoon, and post-monsoon seasons) in Bangladesh was analyzed in different regions using both parametric and nonparametric approaches. Moreover, the possible teleconnections of precipitation (annual and monsoon) variability with El Niño/Southern Oscillation (ENSO) episode and Indian Ocean Dipole (IOD) were investigated using both average and individual (both positive and negative) values of ENSO index and IOD. Our findings suggested that for annual precipitation, a significant increasing monotonic trend was found in whole Bangladesh (4.87 mm/year), its western region (5.82 mm/year) including Rangpur (9.41 mm/year) and Khulna (4.95 mm/year), and Sylhet (10.12 mm/year) and Barisal (6.94 mm/year) from eastern region. In pre-monsoon, only Rangpur (2.88 mm/year) showed significant increasing trend, while in monsoon, whole Bangladesh (3.04 mm/year), Sylhet (7.17 mm/year), and Barisal (6.94 mm/year) showed similar trend. In post-monsoon, there was no significant trend. Our results also revealed that the precipitation (annual or monsoon) of whole Bangladesh and almost all of the spatial regions did not show any significant correlation with ENSO events, whereas the average IOD values showed significant correlation only in monsoon precipitation of western region. The individual positive IODs showed significant correlation in whole Bangladesh, western region, and its two divisions (Rajshahi and Khulna). So, in the context of Bangladesh climate, IOD has the more teleconnection to precipitation than that of ENSO. Our findings indicate that the co-occurrence of ENSO and IOD events may suppress their influence on each other.

  1. Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Niño-Southern Oscillation variability

    PubMed Central

    Brienen, Roel J. W.; Helle, Gerd; Pons, Thijs L.; Guyot, Jean-Loup; Gloor, Manuel

    2012-01-01

    We present a unique proxy for the reconstruction of variation in precipitation over the Amazon: oxygen isotope ratios in annual rings in tropical cedar (Cedrela odorata). A century-long record from northern Bolivia shows that tree rings preserve the signal of oxygen isotopes in precipitation during the wet season, with weaker influences of temperature and vapor pressure. Tree ring δ18O correlates strongly with δ18O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ18O showing that the signal is coherent over large areas. The signal correlates most strongly with basin-wide precipitation and Amazon river discharge. We attribute the strength of this (negative) correlation mainly to the cumulative rainout processes of oxygen isotopes (Rayleigh distillation) in air parcels during westward transport across the basin. We further find a clear signature of the El Niño-Southern Oscillation (ENSO) in the record, with strong ENSO influences over recent decades, but weaker influence from 1925 to 1975 indicating decadal scale variation in the controls on the hydrological cycle. The record exhibits a significant increase in δ18O over the 20th century consistent with increases in Andean δ18O ice core and lake records, which we tentatively attribute to increased water vapor transport into the basin. Taking these data together, our record reveals a fresh path to diagnose and improve our understanding of variation and trends of the hydrological cycle of the world’s largest river catchment. PMID:23027960

  2. Farming and fishing in the wake of El Nino

    SciTech Connect

    Tibbetts, J.

    1996-09-01

    How does the periodic warming of the waters of the central Pacific relate to global climate change and food production? In Queensland, Australia, savvy farmers keep a sharp eye on signs of El Nino, which usually brings drought that withers the state`s winter wheat crop. Returning every four years on average and usually lasting approximately a year, El Nino is an unusual warming in the central Pacific that builds storms and disrupts wind patterns, turning weather upside down in far-removed regions. But El Nino took scientists by surprise when it persisted from 1991 to 1995. This was the first time that El Nino had lasted for more than three years since monitoring began in the 1870s. And true to form, El Nino of 1991-1995 brought extreme drought to Queensland, in north-eastern Australia, drying out farmland and costing the state economy approximately $1 billion (Australian) a year. The drought, for example, dropped rainfall levels to all-time lows in Toowoomba, one of the state`s prime cereal-growing regions.

  3. Comparison of the 2016 and 1998 El Nino events with UV Lambertian-Equivalent Reflectivity data from the TOMS, SBUV and OMI instruments.

    NASA Astrophysics Data System (ADS)

    Weaver, C. J.

    2016-12-01

    Based on climatology and warm sea surface temperatures, the recent 2016 El Nino was expected to bring near record rainfall to California. Instead, 2016 winter precipitation amounts were near normal for mid and southern CA but Washington State experienced significant rainfall. In contrast, during the 1998 El Nino, California received record-breaking precipitation. To better understand the diflerences between these two El Nino events, we compare UV Lambertian-Equivalent (LER) reflectivity data (mostly cloud reflectivity) from Earth Probe (EP) TOMS (1998 El Nino), OMI (2016 El Nino) and the NOAA-14 and NOAA-19 SBUV/2 polar orbiting instruments. These satellite measurements show that the recent 2016 event has a shifted cloud pattern compared to the 1998 event. The northward shift of cloud amount in the extra-tropics led to less precipitation over the Southwest US, and was perhaps responsible for enhanced precipitation over the eastern US. Both TOMS and OMI instruments provide near global daily coverage, so we can clearly identify the brighter than normal LER values (increased cloud amount) associated with the 2016 Washington State precipitation events. Similarly, relatively lower LER values (decreased cloud amounts) were seen near Southern California during early 2016. In contrast, during 1998, streams of high LER features were seen in the extratropical Pacific and are associated with "pine-apple express" events that drove record breaking precipitation over the Bay area, especially in January 1998. An advantage of using this suite of instruments is that they have all been inter-calibrated over the bright East Antarctic Plateau. This allows comparison of past El Nino events observed by diflerent instruments. Shortwave Cloud albedo radiative forcing is easily derived from LER values. Since the UV LER record extends back to 1980 (Nimbus-7 TOMS & SBUV), we can discuss SW radiative forcing changes observed during the 2016 event with respect to past events (1983, 1986, 1998

  4. TOPEX/El Nino Watch - El Nino in Retreat, Pacific in Transition, June 14, 1998

    NASA Technical Reports Server (NTRS)

    1998-01-01

    This image of the Pacific Ocean was produced using sea-surface height measurements taken by the U.S.-French TOPEX/Poseidon satellite. The image shows sea-surface height relative to normal ocean conditions on June 14, 1998, and sea-surface height is an indicator of the heat content of the ocean. This image shows that the tropical Pacific has been switching from warm to cold during the last few months. The purple area in the center of the image is a pulse of cold water moving across the equator which the satellite measures as a region of lower than normal sea level. Scientists indicate that it appears that the central equatorial Pacific ocean will stay colder than normal for some time to come because sea level is about 18 centimeters (7 inches) below normal, creating a deficit in the heat supply to the surface waters. It is not certain yet, if this current cooling trend (shown in purple) will eventually evolve into a long-lasting La Nina situation. Remnants of the El Nino warm water pool, shown here in red and white, are still lingering north of the equator in the center of this image. The effects of El Nino can remain in the climate system for a long time and could still impact weather conditions around the world. The satellite's sea-surface height measurements have provided scientists with a detailed view of the 1997-98 El Nino because the TOPEX/Poseidon satellite measures the changing sea-surface height with unprecedented precision. In this image, the white areas show the sea surface is between 14 and 32 centimeters (6 to 13 inches) above normal; in the red areas, it's about 10 centimeters (4 inches) above normal. The green areas indicate normal conditions. The purple areas are 14 to 18 centimeters (6 to 7 inches) below normal and the blue areas are 5 to 13 centimeters (2 to 5 inches) below normal. The El Nino phenomenon is thought to be triggered when the steady westward blowing trade winds weaken and even reverse direction. This change in the winds allows a

  5. Increase in the potential predictability of the Arctic Oscillation via intensified teleconnection with ENSO after the mid-1990s

    NASA Astrophysics Data System (ADS)

    Kang, Daehyun; Lee, Myong-In

    2017-09-01

    This study examines why the seasonal prediction skill of the Arctic Oscillation (AO) has increased significantly since the mid-1990s in state-of-the-art seasonal forecasting systems in operation. This skill increase is primarily attributed to variability over the North Atlantic with an enhanced connection between the AO and the El Niño and Southern Oscillation (ENSO). The relationship between ENSO and AO depends primarily on low-frequency variability in the North Pacific driven by the North Pacific Gyre Oscillation, as represented by the Hawaiian sea level pressure (SLPHI) index. When the sign of the SLPHI index and that of the NINO3.4 index are out-of-phase (in-phase) with the variability center of ENSO shifted to the central Pacific (eastern Pacific), more intense (weaker) ENSO-AO teleconnection results. Linear barotropic model experiments with prescribed ENSO forcing and differing phase and intensity of SLPHI support the observed relationship in La Niña years, highlighting the important and independent role of the SLPHI variability as a modulator of the ENSO teleconnection to higher latitudes.

  6. Increase in the potential predictability of the Arctic Oscillation via intensified teleconnection with ENSO after the mid-1990s

    NASA Astrophysics Data System (ADS)

    Kang, Daehyun; Lee, Myong-In

    2016-11-01

    This study examines why the seasonal prediction skill of the Arctic Oscillation (AO) has increased significantly since the mid-1990s in state-of-the-art seasonal forecasting systems in operation. This skill increase is primarily attributed to variability over the North Atlantic with an enhanced connection between the AO and the El Niño and Southern Oscillation (ENSO). The relationship between ENSO and AO depends primarily on low-frequency variability in the North Pacific driven by the North Pacific Gyre Oscillation, as represented by the Hawaiian sea level pressure (SLPHI) index. When the sign of the SLPHI index and that of the NINO3.4 index are out-of-phase (in-phase) with the variability center of ENSO shifted to the central Pacific (eastern Pacific), more intense (weaker) ENSO-AO teleconnection results. Linear barotropic model experiments with prescribed ENSO forcing and differing phase and intensity of SLPHI support the observed relationship in La Niña years, highlighting the important and independent role of the SLPHI variability as a modulator of the ENSO teleconnection to higher latitudes.

  7. Nimbus 7 earth radiation budget wide field of view climate data set improvement. II - Deconvolution of earth radiation budget products and consideration of 1982-1983 El Nino event

    NASA Technical Reports Server (NTRS)

    Ardanuy, Phillip E.; Hucek, Richard R.; Groveman, Brian S.; Kyle, H. Lee

    1987-01-01

    A deconvolution technique is employed that permits recovery of daily averaged earth radiation budget (ERB) parameters at the top of the atmosphere from a set of the Nimbus 7 ERB wide field of view (WFOV) measurements. Improvements in both the spatial resolution of the resultant fields and in the fidelity of the time averages is obtained. The algorithm is evaluated on a set of months during the period 1980-1983. The albedo, outgoing long-wave radiation, and net radiation parameters are analyzed. The amplitude and phase of the quasi-stationary patterns that appear in the spatially deconvolved fields describe the radiation budget components for 'normal' as well as the El Nino/Southern Oscillation (ENSO) episode years. They delineate the seasonal development of large-scale features inherent in the earth's radiation budget as well as the natural variability of interannual differences. These features are underscored by the powerful emergence of the 1982-1983 ENSO event in the fields displayed. The conclusion is that with this type of resolution enhancement, WFOV radiometers provide a useful tool for the observation of the contemporary climate and its variability.

  8. An improved procedure for El Nino forecasting: Implications for predictability

    SciTech Connect

    Chen, D.; Zebiak, S.E.; Cane, M.A.

    1995-09-22

    A coupled ocean-atmosphere data assimilation procedure yields improved forecasts of El Nino for the 1980s compared with previous forecasting procedures. As in earlier forecasts with the same model, no oceanic data were used, and only wind information was assimilated. The improvement is attributed to the explicit consideration of air-sea interaction in the initialization. These results suggest that El Nino is more predictable than previously estimated, but that predictability may vary on decadal or longer time scales. This procedure also eliminates the well-known spring barrier to El Nino prediction, which implies that it may not be intrinsic to the real climate system. 24 refs., 5 figs., 1 tab.

  9. 78 FR 49468 - Arturo Guillermo Nino, Inmate Number #04908-379, FCI Beaumont Low, Federal Correctional Institute...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-14

    ... Bureau of Industry and Security Arturo Guillermo Nino, Inmate Number 04908-379, FCI Beaumont Low, Federal..., in the U.S. District Court, Western District of Texas, Arturo Guillermo Nino (``Nino''), was...)) (``AECA''). Specifically, Nino was convicted of intentionally and knowingly conspiring with persons...

  10. Ocean wave dynamics and El Nino

    SciTech Connect

    Schneider, E.K.; Huang, B.; Shukla, J.

    1995-10-01

    The response of an ocean general circulation model to specified wind stress is used to understand the role of ocean wave propagation in the evolution of El Nino events in sea surface temperatures (SST) in the equatorial Pacific Ocean. In a control experiment the ocean model reproduces observed equatorial Pacific interannual variability in response to forcing by the observed wind stress. The ocean model is then forced with the same wind stress but with the time evolution of the wind stress forcing reversed. An analysis of the anomalies from the annual cycle in these two experiments delineates the parts of the response that are in equilibrium with and out of equilibrium with the wind stress forcing. The experiment demonstrates that the heat content is not in equilibrium with the wind stress forcing either on or near the equator. Very close to the equator the slope of the thermocline is in equilibrium with the wind stress, but the mean heat content is far from equilibrium. Slightly off of the equator in the western Pacific westward propagating heat content anomalies appear to originate in regions of strong wind stress forcing and then propagate to the western boundary. These westward propagating anomalies also depart significantly from equilibrium with the wind stress forcing. Additional experiments allow these westward propagating anomalies to be identified as freely propagating Rossby waves. The Rossby waves are shown to determine the equatorial heat content response to the wind stress forcing when they arrive at the western boundary and to be responsible for the nonequilibrium behavior of the equatorial mean heat content. A simplified coupled model is derived by fitting the results and estimating parameter values from the numerical experiments. 45 refs., 16 figs.

  11. Understanding and modelling extreme El Nino events

    NASA Astrophysics Data System (ADS)

    Oreskes, N.; Guertin, L. A.; Kumano, Y.; Kelemen, P. B.; Guilyardi, E.

    2016-12-01

    The recent 2015/16 El Niño event was the third well observed extreme event since the development of Tropical Pacific observation system in the 1980s. Even though the sample remains small, we are now in a better position to understand, model and ultimately forecast these large impact events with a 2 to 3 season lead time. We know that when the heat recharge of the equatorial Pacific is high and when Westerly Wind Events (WWE) occur at the end of the boreal winter, the odds of having El Niño 6 to 9 months later increase significantly (and La Niña can be safely ruled out). These forecasts are essentially probabilistic as seen for instance in 2014 which had these precursors, but chose to follow the low probably outcome of a quite weak event. The current challenge is therefore to understand and identify if there are additional precursors that will increase the probability of having an extreme El Nino event. A few recent studies show that the subsequent occurrence of WWE during summer and fall significantly multiplies the odds of an extreme event, as seen in 2015 in contrast to 2014. Other intraseasonal events may play a role during the development phase of the event, such as easterly pulses of trade winds counteracting the amplifying Bjerknes feedback. This talk will review these recent findings and also address how models are able to reproduce the physical mechanisms at the source of extreme El Niño occurrence and predictability.

  12. The Interdecadal Pacific Oscillation and mid-stratospheric tropical ozone trends

    NASA Astrophysics Data System (ADS)

    Iglesias-Suarez, Fernando; Young, Paul J.; Wild, Oliver; Kinnison, Douglas E.

    2016-04-01

    In recent years, the global ozone layer has started to show the first signs of recovery, but puzzlingly tropical mid-stratospheric ozone has decreased since the beginning of the 90s. This is a key region of the stratosphere where most ozone is produced. Previous studies have shown that interannual variability in the troposphere (e.g. El Nino-Southern Oscillation) can affect the lower stratosphere, both dynamics and composition. Here for the first time, we show how multidecadal internal climate variability - in the Pacific Ocean's sea surface temperatures (i.e. the Interdecadal Pacific Oscillation, IPO) - have an impact in mid-stratospheric tropical ozone, and account for the observed trends. We suggest a mechanism that involves dynamical (i.e. Brewer Dobson circulation) and chemical (i.e. ozone loss chemistry via NOy chemistry) processes to explain this IPO-ozone link. Understanding internally generated multidecadal variability in this region of the stratosphere is crucial to distinguish between forced and unforced signals and better describe ozone recovery.

  13. Radiolarian indicators of El Nino and anti-El Nino events in Holocene sediments of Santa Barbara basin

    SciTech Connect

    Weinheimer, A.L.

    1986-04-01

    Radiolarian distributions and physical oceanographic data from the Santa Barbara basin indicate the following. Strong anti-El Nino periods can be characterized by (1) intermediate radiolarian density, (2) high percentage of transition-central radiolarian fauna, and (3) low percentage and number of warm-water radiolarian fauna. This distribution pattern is attributed to strong wind-driven upwelling and reduced northward transport by the California Countercurrent during anti-El Nino periods. Strong El Nino periods are typically (1) high in radiolarian density, and (2) low in percentage but high in number of warm-water fauna. This distribution is attributed to reduced wind-driven upwelling, enhanced northward countercurrent transport, and geostrophic doming of the cold-water masses in the shear zone between the California Current and California Countercurrent.

  14. El Niño Southern Oscillation (ENSO) enhances CO2 exchange rates in freshwater Marsh ecosystems in the Florida everglades.

    PubMed

    Malone, Sparkle L; Staudhammer, Christina L; Oberbauer, Steven F; Olivas, Paulo; Ryan, Michael G; Schedlbauer, Jessica L; Loescher, Henry W; Starr, Gregory

    2014-01-01

    This research examines the relationships between El Niño Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009-2013) from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS) and the long-hydroperiod site (Shark River Slough; SRS) fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Niño and La Niña phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Niña phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (-11 to -110 g CO2 m-2 yr-1) compared to El Niño and neutral years (-5 to -43.5 g CO2 m-2 yr-1). SRS was a small source for CO2 annually (1.81 to 80 g CO2 m-2 yr-1) except in one exceptionally wet year that was associated with an El Niño phase (-16 g CO2 m-2 yr-1). Considering that future climate predictions suggest a higher frequency and intensity in El Niño and La Niña phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades.

  15. Assessing the El Niño/Southern Oscillation proxy potential of the sediment record from Genovesa Crater Lake, Galápagos

    NASA Astrophysics Data System (ADS)

    Conroy, J.; Overpeck, J. T.; Cole, J. E.; Collins, A.; Bush, M. B.; Steinitz-Kannan, M.

    2009-12-01

    Paleoclimate records from the tropical Pacific Ocean suggest significant changes in sea surface temperature (SST) and El Niño/Southern Oscillation (ENSO) 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 ENSO 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 events. 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 ENSO phenomenon. Records from other lakes in the Galápagos have already suggested significant changes in ENSO 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 ENSO 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 ENSO reconstructions. Scanning μ-XRF time series of elemental abundances in the Genovesa sediment cores indicate that peaks in Ca abundance reflect the warm/wet season and El Niño events. We hypothesize that during warm/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 events, guano input dilutes the precipitated carbonate. High-resolution pollen and diatom analyses will provide additional constraints on

  16. El Niño Southern Oscillation (ENSO) Enhances CO2 Exchange Rates in Freshwater Marsh Ecosystems in the Florida Everglades

    PubMed Central

    Malone, Sparkle L.; Staudhammer, Christina L.; Oberbauer, Steven F.; Olivas, Paulo; Ryan, Michael G.; Schedlbauer, Jessica L.; Loescher, Henry W.; Starr, Gregory

    2014-01-01

    This research examines the relationships between El Niño Southern Oscillation (ENSO), water level, precipitation patterns and carbon dioxide (CO2) exchange rates in the freshwater wetland ecosystems of the Florida Everglades. Data was obtained over a 5-year study period (2009–2013) from two freshwater marsh sites located in Everglades National Park that differ in hydrology. At the short-hydroperiod site (Taylor Slough; TS) and the long-hydroperiod site (Shark River Slough; SRS) fluctuations in precipitation patterns occurred with changes in ENSO phase, suggesting that extreme ENSO phases alter Everglades hydrology which is known to have a substantial influence on ecosystem carbon dynamics. Variations in both ENSO phase and annual net CO2 exchange rates co-occurred with changes in wet and dry season length and intensity. Combined with site-specific seasonality in CO2 exchanges rates, El Niño and La Niña phases magnified season intensity and CO2 exchange rates at both sites. At TS, net CO2 uptake rates were higher in the dry season, whereas SRS had greater rates of carbon sequestration during the wet season. As La Niña phases were concurrent with drought years and extended dry seasons, TS became a greater sink for CO2 on an annual basis (−11 to −110 g CO2 m−2 yr−1) compared to El Niño and neutral years (−5 to −43.5 g CO2 m−2 yr−1). SRS was a small source for CO2 annually (1.81 to 80 g CO2 m−2 yr−1) except in one exceptionally wet year that was associated with an El Niño phase (−16 g CO2 m−2 yr−1). Considering that future climate predictions suggest a higher frequency and intensity in El Niño and La Niña phases, these results indicate that changes in extreme ENSO phases will significantly alter CO2 dynamics in the Florida Everglades. PMID:25521299

  17. El Niño revisited: the influence of El Niño Southern Oscillation on the world's largest tuna fisheries.

    NASA Astrophysics Data System (ADS)

    Receveur, A.; Simon, N.; Menkes, C.; Tremblay-Boyer, L.; Senina, I.; Lehodey, P.

    2016-12-01

    El Niño Southern Oscillation (ENSO) drives global climate on inter-annual scales and impacts the ecosystem structure in the warm-pool and cold-tongue of the Pacific Ocean. During the El Niño phase of ENSO, the warm-pool can stretch from the western equatorial Pacific to the eastern Pacific allowing species associated with the warm-pool to correspondingly spread eastwards. Conversely, during the la Niña phase the warm-pool is pushed to the far western equatorial Pacific by the cold-tongue allowing species associated with this ecosystem to spread westwards. Consequently, ENSO dynamics are likely to be critical for understanding the ecological processes supporting fisheries in the equatorial Pacific Ocean. Surface inhabiting tuna, such as skipjack, are thought to track the convergence of the warm-pool and cold-tongue with fishing vessels tracking this tuna behavior. Given the reliance of Pacific Island economies on tuna fisheries, knowing when tunas are more likely to be present in high density in their territorial waters is beneficial for harvest control policies such as effort trading between nations. We use the SEAPODYM model to investigate the response of bigeye and skipjack tuna species to the phases of ENSO. SEAPODYM is an age structured model that integrates fisheries dependent and independent data with environmental data. We analyze the outputs of SEAPODYM using wavelets to assess the impact of environmental and biotic variables on the abundance and distribution of adult and juvenile age classes and to study time series cycle and temporal lags to ENSO. The main result for skipjack is the eastward or westward movement of the biomass pattern which is significantly lagged with the warm pool ENSO displacement. That lag ranges from 8 months for juvenile up to 18 months for adults. Such delayed response, can be traced in the model. Higher temperature in the central Pacific during El Niño leads to better recruitment which leads to lagged increase of juvenile

  18. Modulation of Atlantic Aerosols by the Madden-Julian Oscillation