Distinct persistence barriers in two types of ENSO: PERSISTENCE BARRIERS OF TWO ENSO TYPES
DOE Office of Scientific and Technical Information (OSTI.GOV)
Ren, Hong-Li; Jin, Fei-Fei; Tian, Ben
El Niño–Southern Oscillation (ENSO) is usually subject to a persistence barrier (PB) in boreal spring. This study quantifies the PB and then reveals its distinct features in the two types of ENSO, the eastern Pacific (EP) and central Pacific (CP) types. We suggest that the PB of ENSO can be measured by the maximum rate of autocorrelation decline of Niño sea surface temperature anomaly (SSTA) indices. Results show that the PB of ENSO generally occurs in boreal late spring to early summer in terms of Niño3.4 index, and the EP ENSO has the PB in late spring, while the CPmore » type has the PB in summer. By defining an index to quantify PB intensity of ENSO, we find that the CP ENSO type features a much weaker PB, compared to the EP type, and the PB intensity of equatorial SSTAs is larger over the EP than the western Pacific and the far EP.« less
Distinct persistence barriers in two types of ENSO: PERSISTENCE BARRIERS OF TWO ENSO TYPES
Ren, Hong-Li; Jin, Fei-Fei; Tian, Ben; ...
2016-10-30
El Niño–Southern Oscillation (ENSO) is usually subject to a persistence barrier (PB) in boreal spring. This study quantifies the PB and then reveals its distinct features in the two types of ENSO, the eastern Pacific (EP) and central Pacific (CP) types. We suggest that the PB of ENSO can be measured by the maximum rate of autocorrelation decline of Niño sea surface temperature anomaly (SSTA) indices. Results show that the PB of ENSO generally occurs in boreal late spring to early summer in terms of Niño3.4 index, and the EP ENSO has the PB in late spring, while the CPmore » type has the PB in summer. By defining an index to quantify PB intensity of ENSO, we find that the CP ENSO type features a much weaker PB, compared to the EP type, and the PB intensity of equatorial SSTAs is larger over the EP than the western Pacific and the far EP.« less
Different impacts of mega-ENSO and conventional ENSO on the Indian summer rainfall: developing phase
NASA Astrophysics Data System (ADS)
Zhang, Lei; Wu, Zhiwei; Zhou, Yefan
2016-04-01
Mega-El Niño-Southern Oscillation (ENSO), a boarder version of conventional ENSO, is found to be a main driving force of Northern Hemisphere summer monsoon rainfall including the Indian summer rainfall (ISR). The simultaneous impacts of "pure" mega-ENSO and "pure" conventional ENSO events on the ISR in its developing summer remains unclear. This study examines the different linkages between mega-ENSO-ISR and conventional ENSO-ISR. During the developing summer of mega-El Niño, negative rainfall anomalies are seen over the northeastern Indian subcontinent, while the anomalous rainfall pattern is almost the opposite for mega-La Niña; as for the conventional ENSO, the approximate "linear opposite" phenomenon vanishes. Furthermore, the global zonal wave trains anomalous are found at mid-latitude zones, with a local triple circulation pattern over the central-east Eurasia during mega-ENSO events, which might be an explanation of corresponding rainfall response over the Indian Peninsula. Among 106-year historical run (1900-2005) of 9 state-of-the-art models from the Coupled Model Inter-comparison Project Phase 5 (CMIP5), HadGEM2-ES performs a promising skill in simulating the anomalous circulation pattern over mid-latitude and central-east Eurasia while CanESM2 cannot. Probably, it is the models' ability of capturing the mega-ENSO-ISR linkage and the characteristic of mega-ENSO that make the difference.
De Marco, Paolo; Origgi, Daniela
2018-03-01
To assess the noise characteristics of the new adaptive statistical iterative reconstruction (ASiR-V) in comparison to ASiR. A water phantom was acquired with common clinical scanning parameters, at five different levels of CTDI vol . Images were reconstructed with different kernels (STD, SOFT, and BONE), different IR levels (40%, 60%, and 100%) and different slice thickness (ST) (0.625 and 2.5 mm), both for ASiR-V and ASiR. Noise properties were investigated and noise power spectrum (NPS) was evaluated. ASiR-V significantly reduced noise relative to FBP: noise reduction was in the range 23%-60% for a 0.625 mm ST and 12%-64% for the 2.5 mm ST. Above 2 mGy, noise reduction for ASiR-V had no dependence on dose. Noise reduction for ASIR-V has dependence on ST, being greater for STD and SOFT kernels at 2.5 mm. For the STD kernel ASiR-V has greater noise reduction for both ST, if compared to ASiR. For the SOFT kernel, results varies according to dose and ST, while for BONE kernel ASIR-V shows less noise reduction. NPS for CT Revolution has dose dependent behavior at lower doses. NPS for ASIR-V and ASiR is similar, showing a shift toward lower frequencies as the IR level increases for STD and SOFT kernels. The NPS is different between ASiR-V and ASIR with BONE kernel. NPS for ASiR-V appears to be ST dependent, having a shift toward lower frequencies for 2.5 mm ST. ASiR-V showed greater noise reduction than ASiR for STD and SOFT kernels, while keeping the same NPS. For the BONE kernel, ASiR-V presents a completely different behavior, with less noise reduction and modified NPS. Noise properties of the ASiR-V are dependent on reconstruction slice thickness. The noise properties of ASiR-V suggest the need for further measurements and efforts to establish new CT protocols to optimize clinical imaging. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
High performance a-Si solar cells and new fabrication methods for a-Si solar cells
NASA Astrophysics Data System (ADS)
Nakano, S.; Kuwano, Y.; Ohnishi, M.
1986-12-01
The super chamber, a separated UHV reaction-chamber system has been developed. A conversion efficiency of 11.7% was obtained for an a-Si solar cell using a high-quality i-layer deposited by the super chamber, and a p-layer fabricated by a photo-CVD method. As a new material, amorphous superlattice-structure films were fabricated by the photo-CVD method for the first time. Superlattice structure p-layer a-Si solar cells were fabricated, and a conversion efficiency of 10.5% was obtained. For the fabrication of integrated type a-Si solar cell modules, a laser pattering method was investigated. A thermal analysis of the multilayer structure was done. It was confirmed that selective scribing for a-Si, TCO and metal film is possible by controlling the laser power density. Recently developed a-Si solar power generation systems and a-Si solar cell roofing tiles are also described.
Optimized Varian aSi portal dosimetry: development of datasets for collective use.
Van Esch, Ann; Huyskens, Dominique P; Hirschi, Lukas; Baltes, Christof
2013-11-04
Although much literature has been devoted to portal dosimetry with the Varian amorphous silicon (aSi) portal imager, the majority of the described methods are not routinely adopted because implementation procedures are cumbersome and not within easy reach of most radiotherapy centers. To make improved portal dosimetry solutions more generally available, we have investigated the possibility of converting optimized configurations into ready-to-use standardized datasets. Firstly, for all commonly used photon energies (6, 10, 15, 18, and 20 MV), basic beam data acquired on 20 aSi panels were used to assess the interpanel reproducibility. Secondly, a standardized portal dose image prediction (PDIP) algorithm configuration was created for every energy, using a three-step process to optimize the aSi dose response function and profile correction files for the dosimetric calibration of the imager panel. An approximate correction of the backscatter of the Exact arm was also incorporated. Thirdly, a set of validation fields was assembled to assess the accuracy of the standardized configuration. Variations in the basic beam data measured on different aSi panels very rarely exceeded 2% (2 mm) and are of the same order of magnitude as variations between different Clinacs when measuring in reference conditions in water. All studied aSi panels can hence be regarded as nearly identical. Standardized datasets were successfully created and implemented. The test package proved useful in highlighting possible problems and illustrating remaining limitations, but also in demonstrating the good overall results (95% pass rate for 3%,3 mm) that can be obtained. The dosimetric behavior of all tested aSi panels was found to be nearly identical for all tested energies. The approach of using standardized datasets was then successfully tested through the creation and evaluation of PDIP preconfigured datasets that can be used within the Varian portal dosimetry solution.
NASA Astrophysics Data System (ADS)
Cane, M. A.; Chen, D.; Kaplan, A.
2008-12-01
Mark A. Cane, Dake Chen, Alexey Kaplan The description of this session begins: "Historical SST records suggest that for the past three decades, ENSO has been anomalously strong" and goes on to ask why. In this talk we dispute this interpretation of the historical record from within the historical record. In particular, we suggest that the most "anomalously strong" period in the historical ENSO record is the late nineteenth century. This claim requires a discussion of how we measure "ENSO strength". We also speculate on possible reasons for the strength of ENSO in this earlier period. Finally, we consult the models, and in reiteration of the collective conclusion of all speakers at this session, find that the riddles the models provide are inelegant and disobliging, lacking the cryptic wisdom of the classical oracles.
ENSO influences the onset of violent conflicts
NASA Astrophysics Data System (ADS)
Meng, K. C.; Hsiang, S. M.
2009-12-01
Climatic changes are frequently cited as a possible external driver of violent conflict in human societies. Qualitative studies suggest that climatic shifts may stress populations and be conducive to violent conflict. Statistical evidence has shown that anomalous local rainfall is correlated with the onset of conflict. This study finds that in addition to idiosyncratic weather events, climatic states also play a role in triggering violent conflict. El Niño Southern Oscillation (ENSO), the semi-periodic, oceanic Kelvin wave in the tropical Pacific, induces remote temperatures in the tropical free troposphere to rise. This ``ENSO teleconnection'' is not globally uniform and is felt most strongly in the tropical regions during the boreal winter. To determine the degree in which country-level climatic conditions are affected by ENSO, an absolute correlation measure between surface temperature and two ENSO indices was calculated for every country for the period 1949-2009. Countries with high levels of correlation are labeled “ENSO affected,” while countries with low correlation are labeled “ENSO unaffected”. Thus, historical variation in ENSO serves as a ``natural experiment'': if the state of ENSO influences conflict onset, it should be apparent for ENSO affected countries but not for unaffected countries. Using the UCDP/PRIO Armed Conflict Dataset, we find evidence of a large and statistically significant influence of ENSO on the onset of violent conflict. Between 1949-2009, the average probability of a conflict beginning in any country was 0.03. For the ENSO affected countries, we find that a 1°C rise in either NINO12 or NINO34 is associated with an increased probability of conflict onset by 0.015 (or 50% of the global country average). A relationship was not detected for the ENSO unaffected group of countries. This result is robust to a range of statistical models. Nonparametric methods (see figure) also indicate a marked difference in the response of ENSO
Monsoon-Enso Relationships: A New Paradigm
NASA Technical Reports Server (NTRS)
Lau, K. M.; Einaudi, Franco (Technical Monitor)
2000-01-01
This article is partly a review and partly a new research paper on monsoon-ENSO relationship. The paper begins with a discussion of the basic relationship between the Indian monsoon and ENSO dating back to the work of Sir Gilbert Walker up to research results in more recent years. Various factors that may affect the monsoon-ENSO, relationship, including regional coupled ocean-atmosphere processes, Eurasian snow cover, land-atmosphere hydrologic feedback, intraseasonal oscillation, biennial variability and inter-decadal variations, are discussed. The extreme complex and highly nonlinear nature of the monsoon-ENSO relationship is stressed. We find that for regional impacts on the monsoon, El Nino and La Nina are far from simply mirror images of each other. These two polarities of ENSO can have strong or no impacts on monsoon anomalies depending on the strength of the intraseasonal oscillations and the phases of the inter-decadal variations. For the Asian-Australian monsoon (AAM) as a whole, the ENSO impact is effected through a east-west shift in the Walker Circulation. For rainfall anomalies over specific monsoon areas, regional processes play important roles in addition to the shift in the Walker Circulation. One of the key regional processes identified for the boreal summer monsoon is the anomalous West Pacific Anticyclone (WPA). This regional feature has similar signatures in interannual and intraseasonal time scales and appears to determine whether the monsoon-ENSO relationship is strong or weak in a given year. Another important regional feature includes a rainfall and SST dipole across the Indian Ocean, which may have strong impact on the austral summer monsoon. Results are shown indicating that monsoon surface wind forcings may induce a strong biennial signal in ENSO and that strong monsoon-ENSO coupling may translate into pronounced biennial variability in ENSO. Finally, a new paradigm is proposed for the study of monsoon variability. This paradigm provides
Chen, Li-Hong; Jin, Chao; Li, Jian-Ying; Wang, Ge-Liang; Jia, Yong-Jun; Duan, Hai-Feng; Pan, Ning; Guo, Jianxin
2018-06-06
To compare image quality of two adaptive statistical iterative reconstruction (ASiR and ASiR-V) algorithms using objective and subjective metrics for routine liver CT, with the conventional filtered back projection (FBP) reconstructions as reference standards. This institutional review board-approved study included 52 patients with clinically suspected hepatic metastases. Patients were divided equally into ASiR and ASiR-V groups with same scan parameters. Images were reconstructed with ASiR and ASiR-V from 0 (FBP) to 100% blending percentages at 10% interval in its respective group. Mean and standard deviation of CT numbers for liver parenchyma were recorded. Two experienced radiologists reviewed all images for image quality blindly and independently. Data were statistically analyzed. There was no difference in CT dose index between ASiR and ASiR-V groups. As the percentage of ASiR and ASiR-V increased from 10 to 100% , image noise reduced by 8.6 -57.9% and 8.9-81.6%, respectively, compared with FBP. There was substantial interobserver agreement in image quality assessment for ASiR and ASiR-V images. Compared with FBP reconstruction, subjective image quality scores of ASiR and ASiR-V improved significantly as percentage increased from 10 to 80% for ASiR (peaked at 50% with 32.2% noise reduction) and from 10 to 90% (peaked at 60% with 51.5% noise reduction) for ASiR-V. Both ASiR and ASiR-V improved the objective and subjective image quality for routine liver CT compared with FBP. ASiR-V provided further image quality improvement with higher acceptable percentage than ASiR, and ASiR-V60% had the highest image quality score. Advances in knowledge: (1) Both ASiR and ASiR-V significantly reduce image noise compared with conventional FBP reconstruction. (2) ASiR-V with 60 blending percentage provides the highest image quality score in routine liver CT.
What Controls ENSO-Amplitude Diversity in Climate Models?
NASA Astrophysics Data System (ADS)
Wengel, C.; Dommenget, D.; Latif, M.; Bayr, T.; Vijayeta, A.
2018-02-01
Climate models depict large diversity in the strength of the El Niño/Southern Oscillation (ENSO) (ENSO amplitude). Here we investigate ENSO-amplitude diversity in the Coupled Model Intercomparison Project Phase 5 (CMIP5) by means of the linear recharge oscillator model, which reduces ENSO dynamics to a two-dimensional problem in terms of eastern equatorial Pacific sea surface temperature anomalies (T) and equatorial Pacific upper ocean heat content anomalies (h). We find that a large contribution to ENSO-amplitude diversity originates from stochastic forcing. Further, significant interactions exist between the stochastic forcing and the growth rates of T and h with competing effects on ENSO amplitude. The joint consideration of stochastic forcing and growth rates explains more than 80% of the ENSO-amplitude variance within CMIP5. Our results can readily explain the lack of correlation between the Bjerknes Stability index, a measure of the growth rate of T, and ENSO amplitude in a multimodel ensemble.
Understanding multidecadal variability in ENSO amplitude
NASA Astrophysics Data System (ADS)
Russell, A.; Gnanadesikan, A.
2013-12-01
Sea surface temperatures (SSTs) in the tropical Pacific vary as a result of the coupling between the ocean and atmosphere driven largely by the El Niño - Southern Oscillation (ENSO). ENSO has a large impact on the local climate and hydrology of the tropical Pacific, as well as broad-reaching effects on global climate. ENSO amplitude is known to vary on long timescales, which makes it very difficult to quantify its response to climate change and constrain the physical processes that drive it. In order to assess the extent of unforced multidecadal changes in ENSO variability, a linear regression of local SST changes is applied to the GFDL CM2.1 model 4000-yr pre-industrial control run. The resulting regression coefficient strengths, which represent the sensitivity of SST changes to thermocline depth and zonal wind stress, vary by up to a factor of 2 on multi-decadal time scales. This long-term modulation in ocean-atmosphere coupling is highly correlated with ENSO variability, but do not explain the reasons for such variability. Variation in the relationship between SST changes and wind stress points to a role for changing stratification in the central equatorial Pacific in modulating ENSO amplitudes with stronger stratification reducing the response to winds. The main driving mechanism we have identified for higher ENSO variance are changes in the response of zonal winds to SST anomalies. The shifting convection and precipitation patterns associated with the changing state of the atmosphere also contribute to the variability of the regression coefficients. These mechanisms drive much of the variability in ENSO amplitude and hence ocean-atmosphere coupling in the tropical Pacific.
ENSO controls interannual fire activity in southeast Australia
NASA Astrophysics Data System (ADS)
Mariani, M.; Fletcher, M.-S.; Holz, A.; Nyman, P.
2016-10-01
El Niño-Southern Oscillation (ENSO) is the main mode controlling the variability in the ocean-atmosphere system in the South Pacific. While the ENSO influence on rainfall regimes in the South Pacific is well documented, its role in driving spatiotemporal trends in fire activity in this region has not been rigorously investigated. This is particularly the case for the highly flammable and densely populated southeast Australian sector, where ENSO is a major control over climatic variability. Here we conduct the first region-wide analysis of how ENSO controls fire activity in southeast Australia. We identify a significant relationship between ENSO and both fire frequency and area burnt. Critically, wavelet analyses reveal that despite substantial temporal variability in the ENSO system, ENSO exerts a persistent and significant influence on southeast Australian fire activity. Our analysis has direct application for developing robust predictive capacity for the increasingly important efforts at fire management.
NASA Astrophysics Data System (ADS)
Harger, J. R. E.
The major features in development of the "El Nino-Southern Oscillation" (ENSO) involve oscillation of the Pacific ocean-atmosphere in an essentially unpredictable (chaotic) fashion. The system moves between extremes of the so-called "warm events" lasting one or two years and involving movement of warm sea water from the western Pacific along the equator to impact on the west coast of the American continent and "cold-events" associated with easterly trade-wind-induced flows of colder water from the eastern Pacific towards the west. Historical data indicate that ENSO years as experienced by the Island of Java are either much warmer than non-ENSO years or only slightly, if at all, warmer than normal (non-ENSO) years. Hot-dry years within the ENSO warm event cycle are almost always followed by cooler wet years and vice versa. This pattern also extends to include the year immediately following the terminal year of an ENSO warm event set. The initial year of an ENSO warm event set may be either hot with a long dry season or relatively cool (nearer to the temperature of a non-ENSO year) and having a short dry season. In recent years, since 1950, of the 9 ENSO warm events, the initial year tends to have been hot and dry for 6 (1951, 1957, 1963, 1972, 1982, 1991) and neutral or cool and wet for 3 (1968, 1976, 1986). An area of 88,000 ha burned in 1991 (Jakarta Post 30 November 1991) largely in Kalimantan in association with the 1991-1992 ENSO event, an extensive pall of smoke developed over Kalimantan, Singapore and Malaysia during September-October of 1991. Surface vegetation-based fires continued to burn in East Kalimantan as of 29 April 1992 and extended into the 1992 dry season, in response to the ENSO conditions carrying forward from 1991. The increasing annual trend in air-temperature exhibited by the mean monthly values over the period 1866-1993, for the Jakarta and the Semarang data taken together is 1.64°C (0.0132°C per year from 25.771 to 27.409°C). The major
Influence of ENSO Modoki on Colombia Precipitation
NASA Astrophysics Data System (ADS)
Rojo Hernandez, J. D.; Mesa, O. J.; Gómez Ríos, S.; Martinez Pérez, K.
2015-12-01
In recent years, multiple observations reported contrasting effects in climate patterns around the world, due to differential warming patterns in tropical regions of Pacific Ocean during ENSO warm and cold events. Several authors have proposedthe concept that these variations are part of a new type of El Niño-Southern Oscillation (ENSO) named as "Modoki". Using the classification of periods as Canonical or Modoki ENSO proposed by Tedeschi et al. (2013) we discriminatedthe quarterly mean values of precipitation in Colombia since 1975 to 2006 in order to analyze the rainfall behavior during El Niño Modoki (ENM) and La Nina Modoki (LNM), and contrast them with Canonical El Niño and La Niña (ENC-LNC) effects. The observations show that for the precipitation in Colombia, ENSO Modoki effects are different from Canonical ENSO effects, producing in general opposite climatic conditions between ENC and ENM, as well as between LNC and LNM. In other regions, the ENSO Modoki produces anomalies with the same sign that ENC, but with lower intensity. R. G. Tedeschi, I. F. Cavalcanti, and A. M. Grimm. Influences of two types of ENSO on Southamerican precipitation. International Journal of Climatology, 33(6):1382-1400, 2013.
NASA Astrophysics Data System (ADS)
Gendre, B.; Giommi, P.
2010-12-01
The ASI Science Data Center (ASDC, www.asdc.asi.it), a facility of the Italian Space Agency (ASI) is a multi-mission science operations, data processing and data archiving center that provides support to several scientific space missions. At the moment the ASDC has significant responsibilities for a number of high-energy astronomy/astroparticle satellites (e.g. Swift, AGILE, Fermi, NuSTAR and AMS) and supports at different level other missions like, Herschel and Planck. The ASDC was established in 2000 based on the experience built with the management of the BeppoSAX Science Data Center. It is located at the ESA site of ESRIN in Frascati, near Rome (Italy).
NASA Astrophysics Data System (ADS)
Welsh, K.; Morgan, Z.; Suzuki, A.
2016-12-01
Although modeled predictions for the relative strength and frequency of ENSO under mean warming conditions suggest an increase in the number and strength of ENSO event, however there are limited seasonally resolved records of ENSO variability during previous warm periods for example the last interglacial to test these models as reliable archives such as corals are not generally well preserved over these time periods. Presented here are two multi decadal Tridacna gigas derived stable isotopic time series from a coral terrace on the island of Cebu in the Philippines that formed during MIS5e based upon geomorphology and open-system corrected U/Th dating of corals. The ENSO activity observed in these time well preserved records indicate a similar level of ENSO activity during the last interglacial period as the present day based upon comparisons with recent coral derived stable isotopic records. Though these are relatively short records they provide further windows into ENSO activity from this important time period and demonstrate this area may be provide more opportunities to gather these archives.
Modification of ENSO and ENSO-related atmospheric characteristics due to future climate change
NASA Astrophysics Data System (ADS)
Matveeva, Tatiana; Gushchina, Daria
2017-04-01
The El Niño/Southern Oscillation (ENSO) is the strongest natural climate interannual fluctuation in Tropical Pacific, it affects regional and global climate. There are two types of this phenomenon: East Pacific (EP) El Niño characterized by maximum of SST anomalies centered over the eastern tropical Pacific and Central Pacific (CP) El Niño with SST warming in the center of the Pacific Ocean [Ashok et al., 2007; Kug et al., 2009]. The ability of CMIP5 coupled ocean-atmosphere general circulation models (CGCMs) to simulate two flavors of El Niño correctly was estimated using EOF-analysis technique of SST anomalies [Takahashi et al., 2011] in the recent studies [Matveeva and Gushchina, 2016]. It was shown that only several CGCMs were able to reproduce two types of ENSO. The ENSO-related characteristics can alter due to global climate change. However, scientific community can't be sure whether ENSO activity will be enhanced or damped under global warming. In this study, we choose the 6 "best" CGCMs (BNU-ESM, CCSM4, CNRM-CM5, FIO-ESM, INM-CM4, MIROC5) which simulated spatial and temporal features of the two types of El Niño the most realistic way. To obtain a complete result we analyzed anomalies of complex ENSO-related characteristics (SST, rainfall, vertical movement, atmospheric circulation in the upper and lower troposphere) during two types of El Niño events. We compared the spatial distribution of these anomalies depending future climate scenarios (we took two scenarios with significant differences - RCP 2.6 and RCP 8.5 [Taylor et al., 2012]). It was shown the large difference in model's estimates ENSO-related anomalies' changes for future climate. The main aspect of this study is the analysis of the ENSO characteristics' modification (frequency, amplitude, the ratio between EP and CP El Niño) under different scenarios of warming. We didn't expect any significant change of frequency for two types of El Nino. It was shown that there was no well
A hierarchy of models for ENSO flavors in past climates.
NASA Astrophysics Data System (ADS)
Karamperidou, C.; Xie, R.; Di Nezio, P. N.
2017-12-01
The existence of two distinct ENSO flavors versus an ENSO continuum remains an open question. Investigating the response of ENSO diversity to past climate forcings provides a framework to approach this question. Previous work using GCMs has shown that ENSO flavors may respond differentially to mid-Holocene orbital forcing, with a significant suppression of Eastern Pacific ENSO as opposed to insensitivity of Central Pacific ENSO. Here, we employ a hierarchy of models to explore the robustness of ENSO-flavor response to orbital forcing. First, we use a modified version of the Zebiak-Cane model which simulates two ENSO modes reminiscent of ENSO flavors. We find a quasi-linear response of these two modes to orbital forcing corresponding to 6ka, 111ka, and 121ka BP in terms of growth rates, frequency and spatial pattern of SST anomalies. We then employ an Earth System Model subject only to orbital forcing to show the corresponding response in the three past climates. This investigation indicates that no extratropical influences may be required to produce such quasi-linear ENSO-flavor response to orbital forcing. Aided by paleoclimate proxies, the hierarchy of models employed here presents a paleoclimate perspective to the fundamental and elusive question of the nature and origins of ENSO diversity.
Tree growth response to ENSO in Durango, Mexico
NASA Astrophysics Data System (ADS)
Pompa-García, Marin; Miranda-Aragón, Liliana; Aguirre-Salado, Carlos Arturo
2015-01-01
The dynamics of forest ecosystems worldwide have been driven largely by climatic teleconnections. El Niño-Southern Oscillation (ENSO) is the strongest interannual variation of the Earth's climate, affecting the regional climatic regime. These teleconnections may impact plant phenology, growth rate, forest extent, and other gradual changes in forest ecosystems. The objective of this study was to investigate how Pinus cooperi populations face the influence of ENSO and regional microclimates in five ecozones in northwestern Mexico. Using standard dendrochronological techniques, tree-ring chronologies (TRI) were generated. TRI, ENSO, and climate relationships were correlated from 1950-2010. Additionally, multiple regressions were conducted in order to detect those ENSO months with direct relations in TRI ( p < 0.1). The five chronologies showed similar trends during the period they overlapped, indicating that the P. cooperi populations shared an interannual growth variation. In general, ENSO index showed correspondences with tree-ring growth in synchronous periods. We concluded that ENSO had connectivity with regional climate in northern Mexico and radial growth of P. cooperi populations has been driven largely by positive ENSO values (El Niño episodes).
Tree growth response to ENSO in Durango, Mexico.
Pompa-García, Marin; Miranda-Aragón, Liliana; Aguirre-Salado, Carlos Arturo
2015-01-01
The dynamics of forest ecosystems worldwide have been driven largely by climatic teleconnections. El Niño-Southern Oscillation (ENSO) is the strongest interannual variation of the Earth's climate, affecting the regional climatic regime. These teleconnections may impact plant phenology, growth rate, forest extent, and other gradual changes in forest ecosystems. The objective of this study was to investigate how Pinus cooperi populations face the influence of ENSO and regional microclimates in five ecozones in northwestern Mexico. Using standard dendrochronological techniques, tree-ring chronologies (TRI) were generated. TRI, ENSO, and climate relationships were correlated from 1950-2010. Additionally, multiple regressions were conducted in order to detect those ENSO months with direct relations in TRI (p < 0.1). The five chronologies showed similar trends during the period they overlapped, indicating that the P. cooperi populations shared an interannual growth variation. In general, ENSO index showed correspondences with tree-ring growth in synchronous periods. We concluded that ENSO had connectivity with regional climate in northern Mexico and radial growth of P. cooperi populations has been driven largely by positive ENSO values (El Niño episodes).
ENSO effects on stratospheric ozone: A nudged model perspective
NASA Astrophysics Data System (ADS)
Braesicke, Peter; Kirner, Oliver; Versick, Stefan; Joeckel, Patrick
2015-04-01
The El Niño/Southern Oscillation (ENSO) phenomenon is an important pacemaker for interannual variability in the Earth's atmosphere. ENSO impacts on ozone have been observed and modelled for the stratosphere and the troposphere. It is well recognized that attribution of ENSO variability is important for trend detection. ENSO impacts in low latitudes are easier to detect, because the response emerges close (temporally and spatially) to the forcing. Moving from low to high latitudes it becomes increasingly difficult to isolate ENSO driven variability, due to time-lags involved and many other modes of variability playing a role as well. Here, we use a nudged version of the EMAC chemistry-climate model to evaluate ENSO impacts on ozone over the last 35 years. In the nudged mode configuration EMAC is not entirely free running. The tropospheric meteorology is constrained using ERA-Interim data. Only the upper stratosphere and the composition (including ozone) are calculated without additional observational constraints. Using lagged correlations and supported by additional idealised modelling, we describe the ENSO impact on tropospheric and stratospheric ozone in the EMAC system. We trace the ENSO signal from the tropical lower troposphere to the polar lower and middle stratosphere. Instead of distinguishing tropospheric and stratospheric responses, we present a coherent approach detecting the ENSO signal as a function of altitude, latitude and time, and demonstrate how a concise characterisation of the ENSO impact aids improved trend detection.
Heartbeat of the Southern Oscillation explains ENSO climatic resonances
NASA Astrophysics Data System (ADS)
Bruun, John T.; Allen, J. Icarus; Smyth, Timothy J.
2017-08-01
The El Niño-Southern Oscillation (ENSO) nonlinear oscillator phenomenon has a far reaching influence on the climate and human activities. The up to 10 year quasi-period cycle of the El Niño and subsequent La Niña is known to be dominated in the tropics by nonlinear physical interaction of wind with the equatorial waveguide in the Pacific. Long-term cyclic phenomena do not feature in the current theory of the ENSO process. We update the theory by assessing low (>10 years) and high (<10 years) frequency coupling using evidence across tropical, extratropical, and Pacific basin scales. We analyze observations and model simulations with a highly accurate method called Dominant Frequency State Analysis (DFSA) to provide evidence of stable ENSO features. The observational data sets of the Southern Oscillation Index (SOI), North Pacific Index Anomaly, and ENSO Sea Surface Temperature Anomaly, as well as a theoretical model all confirm the existence of long-term and short-term climatic cycles of the ENSO process with resonance frequencies of {2.5, 3.8, 5, 12-14, 61-75, 180} years. This fundamental result shows long-term and short-term signal coupling with mode locking across the dominant ENSO dynamics. These dominant oscillation frequency dynamics, defined as ENSO frequency states, contain a stable attractor with three frequencies in resonance allowing us to coin the term Heartbeat of the Southern Oscillation due to its characteristic shape. We predict future ENSO states based on a stable hysteresis scenario of short-term and long-term ENSO oscillations over the next century.
Impacts of ENSO on global hydrology
NASA Astrophysics Data System (ADS)
Ward, P. J.; Eisner, S.; Flörke, M.; Kummu, M.
2012-04-01
The economic consequences of flooding are huge, as exemplified by recent major floods in Thailand, Pakistan, and Australia. Moreover, research shows that economic losses due to flooding have increased dramatically in recent decades. Whilst much research is being carried out to assess how this may be related to socioeconomic development (increased exposure to floods) or climate change (increased hazard), the role of interannual climate variability is poorly understood at the global scale. We provide the first global assessment of the sensitivity of extreme global river discharge to the El Niño Southern Oscillation (ENSO). Past studies have either: (a) assessed this at the local scale; or (b) assessed only global correlations between ENSO and mean river discharge. Firstly, we used a daily observed discharge dataset for 622 gauging stations (from the GRDC database), and assessed and mapped correlations and sensitivities between these time-series and several indices of ENSO. We found that, on average, for the stations studied ENSO has a greater impact on annual high-flow events than on mean annual discharge, especially in the extra-tropics. However, the geographical coverage of the dataset is poor in some regions, and is highly skewed towards certain areas (e.g. North America, Europe, and eastern Australia). This renders a truly global assessment of ENSO impacts impossible based on these observed time-series. Hence, we are also using a modelling approach to estimate correlations and sensitivities in all basins, gauged and ungauged. For this, we are using a gridded time-series of modelled daily discharge from the EU-WATCH project, and analysing relationships between these time-series (per grid-cell) and indices of ENSO. This allows for the first truly global assessment of the impact of ENSO variability on river discharge; these analyses are ongoing. Of course, this approach entails its own problems; the use of global hydrological models to derive daily discharge time
The two types of ENSO in CMIP5 models
NASA Astrophysics Data System (ADS)
Kim, Seon Tae; Yu, Jin-Yi
2012-06-01
In this study, we evaluate the intensity of the Central-Pacific (CP) and Eastern-Pacific (EP) types of El Niño-Southern Oscillation (ENSO) simulated in the pre-industrial, historical, and the Representative Concentration Pathways (RCP) 4.5 experiments of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Compared to the CMIP3 models, the pre-industrial simulations of the CMIP5 models are found to (1) better simulate the observed spatial patterns of the two types of ENSO and (2) have a significantly smaller inter-model diversity in ENSO intensities. The decrease in the CMIP5 model discrepancies is particularly obvious in the simulation of the EP ENSO intensity, although it is still more difficult for the models to reproduce the observed EP ENSO intensity than the observed CP ENSO intensity. Ensemble means of the CMIP5 models indicate that the intensity of the CP ENSO increases steadily from the pre-industrial to the historical and the RCP4.5 simulations, but the intensity of the EP ENSO increases from the pre-industrial to the historical simulations and then decreases in the RCP4.5 projections. The CP-to-EP ENSO intensity ratio, as a result, is almost the same in the pre-industrial and historical simulations but increases in the RCP4.5 simulation.
Salinity anomaly as a trigger for ENSO events
Zhu, Jieshun; Huang, Bohua; Zhang, Rong-Hua; Hu, Zeng-Zhen; Kumar, Arun; Balmaseda, Magdalena A.; Marx, Lawrence; Kinter III, James L.
2014-01-01
According to the classical theories of ENSO, subsurface anomalies in ocean thermal structure are precursors for ENSO events and their initial specification is essential for skillful ENSO forecast. Although ocean salinity in the tropical Pacific (particularly in the western Pacific warm pool) can vary in response to El Niño events, its effect on ENSO evolution and forecasts of ENSO has been less explored. Here we present evidence that, in addition to the passive response, salinity variability may also play an active role in ENSO evolution, and thus important in forecasting El Niño events. By comparing two forecast experiments in which the interannually variability of salinity in the ocean initial states is either included or excluded, the salinity variability is shown to be essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate salinity observations with large-scale spatial coverage. PMID:25352285
Salinity anomaly as a trigger for ENSO events.
Zhu, Jieshun; Huang, Bohua; Zhang, Rong-Hua; Hu, Zeng-Zhen; Kumar, Arun; Balmaseda, Magdalena A; Marx, Lawrence; Kinter, James L
2014-10-29
According to the classical theories of ENSO, subsurface anomalies in ocean thermal structure are precursors for ENSO events and their initial specification is essential for skillful ENSO forecast. Although ocean salinity in the tropical Pacific (particularly in the western Pacific warm pool) can vary in response to El Niño events, its effect on ENSO evolution and forecasts of ENSO has been less explored. Here we present evidence that, in addition to the passive response, salinity variability may also play an active role in ENSO evolution, and thus important in forecasting El Niño events. By comparing two forecast experiments in which the interannually variability of salinity in the ocean initial states is either included or excluded, the salinity variability is shown to be essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate salinity observations with large-scale spatial coverage.
Spectroscopic AC Susceptibility Imaging (sASI) of Magnetic Nanoparticles
Ficko, Bradley W.; Nadar, Priyanka M.; Diamond, Solomon G.
2014-01-01
This study demonstrates a method for alternating current (AC) susceptibility imaging (ASI) of magnetic nanoparticles (mNPs) using low cost instrumentation. The ASI method uses AC magnetic susceptibility measurement to create tomographic images using an array of drive coils, compensation coils and fluxgate magnetometers. Using a spectroscopic approach in conjunction with ASI, a series of tomographic images can be created for each frequency measurement and is termed sASI. The advantage of sASI is that mNPs can be simultaneously characterized and imaged in a biological medium. System calibration was performed by fitting the in-phase and out-of-phase susceptibility measurements of an mNP sample with a hydrodynamic diameter of 100 nm to a Brownian relaxation model (R2 = 0.96). Samples of mNPs with core diameters of 10 and 40 nm and a sample of 100 nm hydrodynamic diameter were prepared in 0.5 ml tubes. Three mNP samples were arranged in a randomized array and then scanned using sASI with six frequencies between 425 and 925 Hz. The sASI scans showed the location and quantity of the mNP samples (R2 = 0.97). Biological compatibility of the sASI method was demonstrated by scanning mNPs that were injected into a pork sausage. The mNP response in the biological medium was found to correlate with a calibration sample (R2 = 0.97, p <0.001). These results demonstrate the concept of ASI and advantages of sASI. PMID:25477704
ENSO elicits opposing responses of semi-arid vegetation between Hemispheres
NASA Astrophysics Data System (ADS)
Zhang, Anzhi; Jia, Gensuo; Epstein, Howard E.; Xia, Jiangjiang
2017-02-01
Semi-arid ecosystems are key contributors to the global carbon cycle and may even dominate the inter-annual variability (IAV) and trends of the land carbon sink, driven largely by the El Niño-Southern Oscillation (ENSO). The linkages between dynamics of semi-arid ecosystems and climate at the hemispheric scale however are not well known. Here, we use satellite data and climate observations from 2000 to 2014 to explore the impacts of ENSO on variability of semi-arid ecosystems, using the Ensemble Empirical Mode Decomposition method. We show that the responses of semi-arid vegetation to ENSO occur in opposite directions, resulting from opposing controls of ENSO on precipitation between the Northern Hemisphere (positively correlated to ENSO) and the Southern Hemisphere (negatively correlated to ENSO). Also, the Southern Hemisphere, with a robust negative coupling of temperature and precipitation anomalies, exhibits stronger and faster responses of semi-arid ecosystems to ENSO than the Northern Hemisphere. Our findings suggest that natural coherent variability in semi-arid ecosystem productivity responded to ENSO in opposite ways between two hemispheres, which may imply potential prediction of global semi-arid ecosystem variability, particularly based on variability in tropical Pacific Sea Surface Temperatures.
Effect of ENSO on Corn Aflatoxin in South Georgia
USDA-ARS?s Scientific Manuscript database
The El Niño Southern Oscillation (ENSO) is associated with climate variability around the world, and is known to adversely affect food production systems. In the Southeastern US, research has shown that ENSO influences crop production. Two multivariate ENSO Indices, MEI and Niño 3.4, are typical...
Last Millennium ENSO-Mean State Interactions in the Tropical Pacific
NASA Astrophysics Data System (ADS)
Wyman, D. A.; Conroy, J. L.; Karamperidou, C.
2017-12-01
The nature and degree of interaction between the mean state of the tropical Pacific and ENSO remains an open question. Here we use high temporal resolution, tropical Pacific sea surface temperature (SST) records from the last millennium to investigate the relationship between ENSO and the tropical Pacific zonal sea surface temperature gradient (hereafter dSST). A dSST time series was created by standardizing, interpolating, and compositing 7 SST records from the western and 3 SST records from the eastern tropical Pacific. Propagating the age uncertainty of each of these records was accomplished through a Monte Carlo Empirical Orthogonal Function analysis. We find last millennium dSST is strong from 700 to 1300 CE, begins to weaken at approximately 1300 CE, and decreases more rapidly at 1700 CE. dSST was compared to 14 different ENSO reconstructions, independent of the records used to create dSST, to assess the nature of the ENSO-mean state relationship. dSST correlations with 50-year standard deviations of ENSO reconstructions are consistently negative, suggesting that more frequent, strong El Niño events on this timescale reduces dSST. To further assess the strength and direction of the ENSO-dSST relationship, moving 100-year standard deviations of ENSO reconstructions were compared to moving 100-year averages of dSST using Cohen's Kappa statistic, which measures categorical agreement. The Li et al. (2011) and Li et al. (2013) Nino 3.4 ENSO reconstructions had the highest agreement with dSST (k=0.80 and 0.70, respectively), with greater ENSO standard deviation coincident with periods of weak dSST. Other ENSO reconstructions showed weaker agreement with dSST, which may be partly due to low sample size. The consistent directional agreement of dSST with ENSO, coupled with the inability of strong ENSO events to develop under a weak SST gradient, suggests periods of more frequent strong El Niño events reduced tropical Pacific dSST on centennial timescales over the
Seasonal ENSO forecasting: Where does a simple model stand amongst other operational ENSO models?
NASA Astrophysics Data System (ADS)
Halide, Halmar
2017-01-01
We apply a simple linear multiple regression model called IndOzy for predicting ENSO up to 7 seasonal lead times. The model still used 5 (five) predictors of the past seasonal Niño 3.4 ENSO indices derived from chaos theory and it was rolling-validated to give a one-step ahead forecast. The model skill was evaluated against data from the season of May-June-July (MJJ) 2003 to November-December-January (NDJ) 2015/2016. There were three skill measures such as: Pearson correlation, RMSE, and Euclidean distance were used for forecast verification. The skill of this simple model was than compared to those of combined Statistical and Dynamical models compiled at the IRI (International Research Institute) website. It was found that the simple model was only capable of producing a useful ENSO prediction only up to 3 seasonal leads, while the IRI statistical and Dynamical model skill were still useful up to 4 and 6 seasonal leads, respectively. Even with its short-range seasonal prediction skills, however, the simple model still has a potential to give ENSO-derived tailored products such as probabilistic measures of precipitation and air temperature. Both meteorological conditions affect the presence of wild-land fire hot-spots in Sumatera and Kalimantan. It is suggested that to improve its long-range skill, the simple INDOZY model needs to incorporate a nonlinear model such as an artificial neural network technique.
Interdecadal variations of ENSO around 1999/2000
NASA Astrophysics Data System (ADS)
Hu, Zeng-Zhen; Kumar, Arun; Huang, Bohua; Zhu, Jieshun; Ren, Hong-Li
2017-02-01
This paper discusses the interdecadal changes of the climate in the tropical Pacific with a focus on the corresponding changes in the characteristics of the El Niño-Southern Oscillation (ENSO). Compared with 1979-1999, the whole tropical Pacific climate system, including both the ocean and atmosphere, shifted to a lower variability regime after 1999/2000. Meanwhile, the frequency of ENSO became less regular and was closer to a white noise process. The lead time of the equatorial Pacific's subsurface ocean heat content in preceding ENSO decreased remarkably, in addition to a reduction in the maximum correlation between them. The weakening of the correlation and the shortening of the lead time pose more challenges for ENSO prediction, and is the likely reason behind the decrease in skill with respect to ENSO prediction after 2000. Coincident with the changes in tropical Pacific climate variability, the mean states of the atmospheric and oceanic components also experienced physically coherent changes. The warm anomaly of SST in the western Pacific and cold anomaly in the eastern Pacific resulted in an increased zonal SST gradient, linked to an enhancement in surface wind stress and strengthening of the Walker circulation, as well as an increase in the slope of the thermocline. These changes were consistent with an increase (a decrease) in precipitation and an enhancement (a suppression) of the deep convection in the western (eastern) equatorial Pacific. Possible connections between the mean state and ENSO variability and frequency changes in the tropical Pacific are also discussed.
Climate Prediction Center - The ENSO Cycle
Weather Service NWS logo - Click to go to the NWS home page Climate Prediction Center Home Site Map News Web resources and services. HOME > El Niño/La Niña > The ENSO Cycle ENSO Cycle Banner Climate for Weather and Climate Prediction Climate Prediction Center 5830 University Research Court College
Impact of ENSO longitudinal position on teleconnections to the NAO
NASA Astrophysics Data System (ADS)
Zhang, Wenjun; Wang, Ziqi; Stuecker, Malte F.; Turner, Andrew G.; Jin, Fei-Fei; Geng, Xin
2018-02-01
While significant improvements have been made in understanding how the El Niño-Southern Oscillation (ENSO) impacts both North American and Asian climate, its relationship with the North Atlantic Oscillation (NAO) remains less clear. Observations indicate that ENSO exhibits a highly complex relationship with the NAO-associated atmospheric circulation. One critical contribution to this ambiguous ENSO/NAO relationship originates from ENSO's diversity in its spatial structure. In general, both eastern (EP) and central Pacific (CP) El Niño events tend to be accompanied by a negative NAO-like atmospheric response. However, for two different types of La Niña the NAO response is almost opposite. Thus, the NAO responses for the CP ENSO are mostly linear, while nonlinear NAO responses dominate for the EP ENSO. These contrasting extra-tropical atmospheric responses are mainly attributed to nonlinear air-sea interactions in the tropical eastern Pacific. The local atmospheric response to the CP ENSO sea surface temperature (SST) anomalies is highly linear since the air-sea action center is located within the Pacific warm pool, characterized by relatively high climatological SSTs. In contrast, the EP ENSO SST anomalies are located in an area of relatively low climatological SSTs in the eastern equatorial Pacific. Here only sufficiently high positive SST anomalies during EP El Niño events are able to overcome the SST threshold for deep convection, while hardly any anomalous convection is associated with EP La Niña SSTs that are below this threshold. This ENSO/NAO relationship has important implications for NAO seasonal prediction and places a higher requirement on models in reproducing the full diversity of ENSO.
Future Changes to ENSO Temperature and Precipitation Teleconnections Under Warming
NASA Astrophysics Data System (ADS)
Perry, S.; McGregor, S.; Sen Gupta, A.; England, M. H.
2016-12-01
As the dominant mode of interannual climate variability, the El Niño-Southern Oscillation (ENSO) modulates temperature and rainfall globally, additionally contributing to weather extremes. Anthropogenic climate change has the potential to alter the strength and frequency of ENSO and may also alter ENSO-driven atmospheric teleconnections, affecting ecosystems and human activity in regions far removed from the tropical Pacific. State-of-art climate models exhibit considerable disagreement in projections of future changes in ENSO sea surface temperature variability. Despite this uncertainty, recent model studies suggest that the precipitation response to ENSO will be enhanced in the tropical Pacific under future warming, and as such the societal impacts of ENSO will increase. Here we use temperature and precipitation data from an ensemble of 41 CMIP5 models to show where ENSO teleconnections are being enhanced and dampened in a high-emission future scenario (RCP8.5) focusing on the changes that are occurring over land areas globally. Although there is some spread between the model projections, robust changes with strong ensemble agreement are found in certain locations, including amplification of teleconnections in southeast Australia, South America and the Maritime Continent. Our results suggest that in these regions future ENSO events will lead to more extreme temperature and rainfall responses.
Effects of ENSO-induced extremes on terrestrial ecosystems
NASA Astrophysics Data System (ADS)
Xu, M.; Hoffman, F. M.
2017-12-01
The El Niño Southern Oscillation (ENSO) with its warm (El Niño) and cold phase (La Niña) has well-known global impacts on the Earth system through the mechanism of teleconnections. Not only the global mean temperature and precipitation distributions will be changed but also the climate extremes will be enhanced during ENSO events. In this study, the advanced Earth System Model ACME version 0.3 was used to simulate terrestrial biogeochemistry and global climate from 1982 to 2020 with prescribed Sea Surface Temperature (SST) from data fusions of the NOAA high resolution daily Optimum Interpolation SST (OISST), CFS v2 9-month seasonal forecast and data reconstructions. We investigated how ENSO-induced climate extremes affect land carbon dynamics both regionally and globally and the implications for the functioning of different vegetated ecosystems under the influence of climate extremes. The results show that the ENSO-induced climate extremes, especially drought and heat waves, have significant impacts on the terrestrial carbon cycle. The responses to ENSO-induced climate extremes are divergent among different vegetation types.
Change of ENSO characteristics in response to global warming
NASA Astrophysics Data System (ADS)
Sun, X.; Xia, Y.; Yan, Y.; Feng, W.; Huang, F.; Yang, X. Q.
2017-12-01
By using datasets of HadISST monthly SST from 1895 to 2014 and 600-year simulations of two CESM model experiments with/without doubling of CO2 concentration, ENSO characteristics are compared pre- and post- global warming. The main results are as follows. Due to global warming, the maximum climatological SST warming occurs in the tropical western Pacific (La Niña-like background warming) and the tropical eastern Pacific (El Niño-like background warming) for observations and model, respectively, resulting in opposite zonal SST gradient anomalies in the tropical Pacific. The La Niña-like background warming induces intense surface divergence in the tropical central Pacific, which enhances the easterly trade winds in the tropical central-western Pacific and shifts the strongest ocean-atmosphere coupling westward, correspondingly. On the contrary, the El Niño-like background warming causes westerly winds in the whole tropical Pacific and moves the strongest ocean-atmosphere coupling eastward. Under the La Niña-like background warming, ENSO tends to develop and mature in the tropical central Pacific, because the background easterly wind anomaly weakens the ENSO-induced westerly wind anomaly in the tropical western Pacific, leading to the so-called "Central Pacific ENSO (CP ENSO)". However, the so-called "Eastern Pacific ENSO (EP ENSO)" is likely formed due to increased westerly wind anomaly by the El Niño-like background warming. ENSO lifetime is significantly extended under both the El Niño-like and the La Niña-like background warmings, and especially, it can be prolonged by up to 3 months in the situation of El Niño-like background warming. The prolonged El Nino lifetime mainly applies to extreme El Niño events, which is caused by earlier outbreak of the westerly wind bursts, shallower climatological thermocline depth and weaker "discharge" rate of the ENSO warm signal in response to global warming. Results from both observations and the model also show that
ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing
NASA Astrophysics Data System (ADS)
Yeh, Sang-Wook; Cai, Wenju; Min, Seung-Ki; McPhaden, Michael J.; Dommenget, Dietmar; Dewitte, Boris; Collins, Matthew; Ashok, Karumuri; An, Soon-Il; Yim, Bo-Young; Kug, Jong-Seong
2018-03-01
El Niño and Southern Oscillation (ENSO) is the most prominent year-to-year climate fluctuation on Earth, alternating between anomalously warm (El Niño) and cold (La Niña) sea surface temperature (SST) conditions in the tropical Pacific. ENSO exerts its impacts on remote regions of the globe through atmospheric teleconnections, affecting extreme weather events worldwide. However, these teleconnections are inherently nonlinear and sensitive to ENSO SST anomaly patterns and amplitudes. In addition, teleconnections are modulated by variability in the oceanic and atmopsheric mean state outside the tropics and by land and sea ice extent. The character of ENSO as well as the ocean mean state have changed since the 1990s, which might be due to either natural variability or anthropogenic forcing, or their combined influences. This has resulted in changes in ENSO atmospheric teleconnections in terms of precipitation and temperature in various parts of the globe. In addition, changes in ENSO teleconnection patterns have affected their predictability and the statistics of extreme events. However, the short observational record does not allow us to clearly distinguish which changes are robust and which are not. Climate models suggest that ENSO teleconnections will change because the mean atmospheric circulation will change due to anthropogenic forcing in the 21st century, which is independent of whether ENSO properties change or not. However, future ENSO teleconnection changes do not currently show strong intermodel agreement from region to region, highlighting the importance of identifying factors that affect uncertainty in future model projections.
Future Projections of ENSO and Drought (Invited)
NASA Astrophysics Data System (ADS)
Cane, M. A.
2009-12-01
Jule Charney, who was my advisor, worked very broadly - and profoundly - on climate dynamics. In this discussion of the present state of knowledge I will focus on two aspects of climate that I view as legacies of his work: our ability to project climate variability in the tropics and to project drought. (I have in mind his work with Shukla on predictability of monsoons, and Charney 1975, Dynamics of deserts and drought in the Sahel., Q. J. Roy. Meteor. Soc., 101, 193-202). First, I will consider the projections of ENSO (El Niño and Southern Oscillation) in a warming world. (My own interest in ENSO was piqued in discussions with Charney and others during the ENSO-influenced blocking events in the late 1970s; in good measure, the approach I took to understanding and modeling ENSO was based in my thesis work.) Current IPCC models differ markedly in their projections of the mean state of the equatorial Pacific, some favoring a more “El Niño- like”, some the opposite. Possible reasons for these disagreements will be considered in the light of our understanding of ENSO and tropical climate more generally. Observational data for the past century and a half will figure prominently. Droughts in the US Southwest have a strong ENSO signal, but IPCC models are fairly consistent in projecting enhanced drought there. The reasons for this will be discussed. Models are less consistent in their predictions of the future Sahel. I will discuss what is understood about causes of drought in the Sahel, which appear to point toward sea surface temperature as the controlling influence, in contrast to Charney’s albedo hypothesis.
Relationships between Rwandan seasonal rainfall anomalies and ENSO events
NASA Astrophysics Data System (ADS)
Muhire, I.; Ahmed, F.; Abutaleb, K.
2015-10-01
This study aims primarily at investigating the relationships between Rwandan seasonal rainfall anomalies and El Niño-South Oscillation phenomenon (ENSO) events. The study is useful for early warning of negative effects associated with extreme rainfall anomalies across the country. It covers the period 1935-1992, using long and short rains data from 28 weather stations in Rwanda and ENSO events resourced from Glantz (2001). The mean standardized anomaly indices were calculated to investigate their associations with ENSO events. One-way analysis of variance was applied on the mean standardized anomaly index values per ENSO event to explore the spatial correlation of rainfall anomalies per ENSO event. A geographical information system was used to present spatially the variations in mean standardized anomaly indices per ENSO event. The results showed approximately three climatic periods, namely, dry period (1935-1960), semi-humid period (1961-1976) and wet period (1977-1992). Though positive and negative correlations were detected between extreme short rains anomalies and El Niño events, La Niña events were mostly linked to negative rainfall anomalies while El Niño events were associated with positive rainfall anomalies. The occurrence of El Niño and La Niña in the same year does not show any clear association with rainfall anomalies. However, the phenomenon was more linked with positive long rains anomalies and negative short rains anomalies. The normal years were largely linked with negative long rains anomalies and positive short rains anomalies, which is a pointer to the influence of other factors other than ENSO events. This makes projection of seasonal rainfall anomalies in the country by merely predicting ENSO events difficult.
ENSO-driven energy budget perturbations in observations and CMIP models
Mayer, Michael; Fasullo, John T.; Trenberth, Kevin E.; ...
2016-03-19
Various observation-based datasets are employed to robustly quantify changes in ocean heat content (OHC), anomalous ocean–atmosphere energy exchanges and atmospheric energy transports during El Niño-Southern Oscillation (ENSO). These results are used as a benchmark to evaluate the energy pathways during ENSO as simulated by coupled climate model runs from the CMIP3 and CMIP5 archives. The models are able to qualitatively reproduce observed patterns of ENSO-related energy budget variability to some degree, but key aspects are seriously biased. Area-averaged tropical Pacific OHC variability associated with ENSO is greatly underestimated by all models because of strongly biased responses of net radiation atmore » top-of-the-atmosphere to ENSO. The latter are related to biases of mean convective activity in the models and project on surface energy fluxes in the eastern Pacific Intertropical Convergence Zone region. Moreover, models underestimate horizontal and vertical OHC redistribution in association with the generally too weak Bjerknes feedback, leading to a modeled ENSO affecting a too shallow layer of the Pacific. Vertical links between SST and OHC variability are too weak even in models driven with observed winds, indicating shortcomings of the ocean models. Furthermore, modeled teleconnections as measured by tropical Atlantic OHC variability are too weak and the tropical zonal mean ENSO signal is strongly underestimated or even completely missing in most of the considered models. In conclusion, results suggest that attempts to infer insight about climate sensitivity from ENSO-related variability are likely to be hampered by biases in ENSO in CMIP simulations that do not bear a clear link to future changes.« less
Intensified ENSO-Driven Precipitation Teleconnections in the Future
NASA Astrophysics Data System (ADS)
Bonfils, C.; Santer, B. D.; Phillips, T. J.; Marvel, K.; Leung, L. R.; Doutriaux, C.
2014-12-01
The El Niño-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. Most climate models project an increase in the frequency of extreme El Niño events under increased greenhouse-gas (GHG) forcing. However, it is unclear how other aspects of ENSO and ENSO-driven teleconnections will evolve in the future. Here, we identify in 20th century sea-surface temperature (SST) observations a time-invariant ENSO-like (ENSOL) pattern that is largely uncontaminated by GHG forcing. We use this pattern to investigate the future precipitation (P) response to ENSO-like SST anomalies. Models that better capture observed ENSOL characteristics produce P teleconnection patterns that are in better accord with observations and more stationary in the 21st century. We decompose the future P response to ENSOL into the sum of three terms: (1) the change in P mean state, (2) the historical P response to ENSOL, and (3) a future enhancement in the P response to ENSOL. In many regions, this last term can aggravate the P extremes associated with ENSO variability. This simple decomposition allows us to identify regions likely to experience ENSOL-induced P changes that are without precedent in the current climate. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Feedback process responsible for intermodel diversity of ENSO variability
NASA Astrophysics Data System (ADS)
An, Soon-Il; Heo, Eun Sook; Kim, Seon Tae
2017-05-01
The origin of the intermodel diversity of the El Niño-Southern Oscillation (ENSO) variability is investigated by applying a singular value decomposition (SVD) analysis between the intermodel tropical Pacific sea surface temperature anomalies (SSTA) variance and the intermodel ENSO stability index (BJ index). The first SVD mode features an ENSO-like pattern for the intermodel SSTA variance (74% of total variance) and the dominant thermocline feedback (TH) for the BJ index (51%). Intermodel TH is mainly modified by the intermodel sensitivity of the zonal thermocline gradient response to zonal winds over the equatorial Pacific (βh), and the intermodel βh is correlated higher with the intermodel off-equatorial wind stress curl anomalies than the equatorial zonal wind stress anomalies. Finally, the intermodel off-equatorial wind stress curl is associated with the meridional shape and intensity of ENSO-related wind patterns, which may cause a model-to-model difference in ENSO variability by influencing the off-equatorial oceanic Rossby wave response.
Interactions between marine biota and ENSO: a conceptual model analysis
NASA Astrophysics Data System (ADS)
Heinemann, M.; Timmermann, A.; Feudel, U.
2011-01-01
We develop a conceptual coupled atmosphere-ocean-ecosystem model for the tropical Pacific to investigate the interaction between marine biota and the El Niño-Southern Oscillation (ENSO). Ocean and atmosphere are represented by a two-box model for the equatorial Pacific cold tongue and the warm pool, including a simplified mixed layer scheme. Marine biota are represented by a three-component (nutrient, phytoplankton, and zooplankton) ecosystem model. The atmosphere-ocean model exhibits an oscillatory state which qualitatively captures the main physics of ENSO. During an ENSO cycle, the variation of nutrient upwelling, and, to a small extent, the variation of photosynthetically available radiation force an ecosystem oscillation. The simplified ecosystem in turn, due to the effect of phytoplankton on the absorption of shortwave radiation in the water column, leads to (1) a warming of the tropical Pacific, (2) a reduction of the ENSO amplitude, and (3) a prolongation of the ENSO period. We qualitatively investigate these bio-physical coupling mechanisms using continuation methods. It is demonstrated that bio-physical coupling may play a considerable role in modulating ENSO variability.
ENSO-related PM10 variability on the Korean Peninsula
NASA Astrophysics Data System (ADS)
Wie, Jieun; Moon, Byung-Kwon
2017-10-01
Particulate matter, defined as particles of less than 10 μm in diameter (PM10), was analyzed over the Korean Peninsula from 2001 to 2015 to examine the influence of the El Niño-Southern Oscillation (ENSO) on subseasonal PM10 variability. The PM10 data were obtained from 151 air quality monitoring stations provided by the Korea Environment Corporation (KECO). Lead-lag correlation analysis, which was performed to investigate the connection between NDJF (November-February) NINO3 index and seasonal mean PM10 data, did not yield any statistically significant correlations. However, using five-pentad moving-averaged PM10 data, statistically significant correlations between NDJF NINO3 index and PM10 variability were found in four subseasonal periods, with alternating positive and negative correlations. In the periods during which PM10 levels on the Korean Peninsula were positively (negatively) correlated with the ENSO index, the positive PM10 anomalies are associated with El Niño (La Niña) years, which implies that the occurrence of high-PM10 events could be modulated by the ENSO phase. In addition, this ENSO-related PM10 variation is negatively correlated with ENSO-related precipitation in the Korean Peninsula, indicating that more (less) wet deposition leads to lower (higher) PM10 level. Therefore, we conclude that the ENSO-induced precipitation anomalies over the Korean Peninsula are mainly responsible for ENSO-related PM10 variations. This study will be helpful for further identifying detailed chemistry-climate processes that control PM10 concentrations.
Anderson, R.Y.; Linsley, B.K.; Gardner, J.V.
1990-01-01
Upper Pleistocene marine sediments along the upper continental slope off northern and central California contain alternations of varved and bioturbated sediments and associated changes in biota and sediment composition. These alternations can be related to conditions that accompany El Nin??o and anti-El Nin??o (ENSO) circulation. Anti-El Nin??o conditions are characterized by increased upwelling and productivity and by low concentrations of dissolved oxygen in the oxygen minimum zone that resulted in varve preservation. El Nin??o conditions are characterized by little or no upwelling, low productivity, and higher concentrations of dissolved oxygen that resulted in zones of bioturbation. Alternations of varves and zones of bioturbation, that range from decades to millennia, occur through the upper Pleistocene section. The inferred long-term alternations in El Nin??o and anti-El Nin??o conditions appear to be a re-expression of ENSO's primary 3-7 year cycle. Decadal to millennial cycles of productivity associated with El Nin??o and anti-El Nin??o conditions may have served as a "carbon pump" and transferred atmospheric CO2 to the marine reservoir. Changes in sediment composition and organisms associated with El Nin??o or anti-El Nin??o conditions can be related to both seasonal and ENSO phenomena. Expression of these changes at lower-than-ENSO frequencies may be partly explained by adding the effects of seasonal variability to effects produced by a self-oscillating ENSO system. However, deterministic mechanisms, including solar modulation of ENSO, may also contribute to long-term alternations of El Nin??o and anti-El Nin??o conditions. ?? 1990.
Modulation of Bjerknes feedback on the decadal variations in ENSO predictability
NASA Astrophysics Data System (ADS)
Zheng, Fei; Fang, Xiang-Hui; Zhu, Jiang; Yu, Jin-Yi; Li, Xi-Chen
2016-12-01
Clear decadal variations exist in the predictability of the El Niño-Southern Oscillation (ENSO), with the most recent decade having the lowest ENSO predictability in the past six decades. The Bjerknes Feedback (BF) intensity, which dominates the development of ENSO, has been proposed to determine ENSO predictability. Here we demonstrate that decadal variations in BF intensity are largely a result of the sensitivity of the zonal winds to the zonal sea level pressure (SLP) gradient in the equatorial Pacific. Furthermore, the results show that during low-ENSO predictability decades, zonal wind anomalies over the equatorial Pacific are more linked to SLP variations in the off-equatorial Pacific, which can then transfer this information into surface temperature and precipitation fields through the BF, suggesting a weakening in the ocean-atmosphere coupling in the tropical Pacific. This result indicates that more attention should be paid to off-equatorial processes in the prediction of ENSO.
Greening of the Sahara suppressed ENSO activity during the mid-Holocene.
Pausata, Francesco S R; Zhang, Qiong; Muschitiello, Francesco; Lu, Zhengyao; Chafik, Léon; Niedermeyer, Eva M; Stager, J Curt; Cobb, Kim M; Liu, Zhengyu
2017-07-07
The evolution of the El Niño-Southern Oscillation (ENSO) during the Holocene remains uncertain. In particular, a host of new paleoclimate records suggest that ENSO internal variability or other external forcings may have dwarfed the fairly modest ENSO response to precessional insolation changes simulated in climate models. Here, using fully coupled ocean-atmosphere model simulations, we show that accounting for a vegetated and less dusty Sahara during the mid-Holocene relative to preindustrial climate can reduce ENSO variability by 25%, more than twice the decrease obtained using orbital forcing alone. We identify changes in tropical Atlantic mean state and variability caused by the momentous strengthening of the West Africa Monsoon (WAM) as critical factors in amplifying ENSO's response to insolation forcing through changes in the Walker circulation. Our results thus suggest that potential changes in the WAM due to anthropogenic warming may influence ENSO variability in the future as well.
Contribution of tropical instability waves to ENSO irregularity
NASA Astrophysics Data System (ADS)
Holmes, Ryan M.; McGregor, Shayne; Santoso, Agus; England, Matthew H.
2018-05-01
Tropical instability waves (TIWs) are a major source of internally-generated oceanic variability in the equatorial Pacific Ocean. These non-linear phenomena play an important role in the sea surface temperature (SST) budget in a region critical for low-frequency modes of variability such as the El Niño-Southern Oscillation (ENSO). However, the direct contribution of TIW-driven stochastic variability to ENSO has received little attention. Here, we investigate the influence of TIWs on ENSO using a 1/4° ocean model coupled to a simple atmosphere. The use of a simple atmosphere removes complex intrinsic atmospheric variability while allowing the dominant mode of air-sea coupling to be represented as a statistical relationship between SST and wind stress anomalies. Using this hybrid coupled model, we perform a suite of coupled ensemble forecast experiments initiated with wind bursts in the western Pacific, where individual ensemble members differ only due to internal oceanic variability. We find that TIWs can induce a spread in the forecast amplitude of the Niño 3 SST anomaly 6-months after a given sequence of WWBs of approximately ± 45% the size of the ensemble mean anomaly. Further, when various estimates of stochastic atmospheric forcing are added, oceanic internal variability is found to contribute between about 20% and 70% of the ensemble forecast spread, with the remainder attributable to the atmospheric variability. While the oceanic contribution to ENSO stochastic forcing requires further quantification beyond the idealized approach used here, our results nevertheless suggest that TIWs may impact ENSO irregularity and predictability. This has implications for ENSO representation in low-resolution coupled models.
The ENSO Effect on the Temporal and Spatial Distribution of Global Lightning Activity
NASA Technical Reports Server (NTRS)
Chronis, Themis G.; Goodman, Steven J.; Cecil, Dan; Buechler, Dennis; Pittman, Jasna; Robertson, Franklin R.; Blakeslee, Richard J.
2007-01-01
The recently reprocessed (1997-2006) OTD/LIS database is used to investigate the global lightning climatology in response to the ENSO cycle. A linear correlation map between lightning anomalies and ENSO (NINO3.4) identifies areas that generally follow patterns similar to precipitation anomalies. We also observed areas where significant lightning/ENSO correlations are found and are not accompanied of significant precipitation/ENSO correlations. An extreme case of the strong decoupling between lightning and precipitation is observed over the Indonesian peninsula (Sumatra) where positive lightning/NINO3.4 correlations are collocated with negative precipitation/NINO3.4 correlations. Evidence of linear relationships between the spatial extent of thunderstorm distribution and the respective NINO3.4 magnitude are presented for different regions on the Earth. Strong coupling is found over areas remote to the main ENSO axis of influence and both during warm and cold ENSO phases. Most of the resulted relationships agree with the tendencies of precipitation related to ENSO empirical maps or documented teleconnection patterns. Over the Australian continent, opposite behavior in terms of thunderstorm activity is noted for warm ENSO phases with NINO3.4 magnitudes with NINO3.4>+l.08 and 0
Stability of ENSO and Its Tropical Pacific Teleconnections over the Last Millennium
NASA Technical Reports Server (NTRS)
Lewis, Sophie; Legrande, A. N.
2015-01-01
Determining past changes in the amplitude, frequency and teleconnections of the El Nio Southern Oscillation (ENSO) is important for understanding its potential sensitivity to future anthropogenic climate change. Palaeo-reconstructions from proxy records provide long-term information of ENSO interactions with the background climatic state through time. However, it remains unclear how ENSO characteristics have changed through time, and precisely which signals proxies record. Proxy interpretations are underpinned by the assumption of stationarity in relationships between local and remote climates, and often utilise archives from single locations located in the Pacific Ocean to reconstruct ENSO histories. Here, we investigate the stationarity of ENSO teleconnections using the Last Millennium experiment of CMIP5 (Coupled Model Intercomparison Project phase 5) (Taylor et al., 2012). We show that modelled ENSO characteristics vary on decadal- to centennial-scales, resulting from internal variability and external forcings, such as tropical volcanic eruptions. Furthermore, the relationship between ENSO conditions and local climates across the Pacific basin varies throughout the Last Millennium. Results show the stability of teleconnections is regionally dependent and proxies may reveal complex changes in teleconnected patterns, rather than large-scale changes in base ENSO characteristics. As such, proxy insights into ENSO likely require evidence to be synthesised over large spatial areas in order to deconvolve changes occurring in the NINO3.4 region from those pertaining to proxy-relevant local climatic variables. To obtain robust histories of the ENSO and its remote impacts, we recommend interpretations of proxy records should be considered in conjunction with palaeo-reconstructions from within the Central Pacific
Fires, Floods, and Hurricanes: Is ENSO to Blame?
ERIC Educational Resources Information Center
Mjelde, James W.; Litzenberg, Kerry K.; Hoyle, Julie E.; Holochwost, Sharon R.; Funkhouser, Sarah
2007-01-01
Scientists have associated the El Nino/Southern Oscillation (ENSO) phenomenon with extreme climate events such as flooding in California, droughts in Australia, fires in Indonesia, and increased hurricane activity in the Atlantic Ocean. The popular media is constantly attributing individual storms to the ENSO phenomenon. The reality is that a…
NASA Technical Reports Server (NTRS)
Alencar, A.; Nepstad, D.; Ver-Diaz, M. Del. C.
2004-01-01
"Understory fires" that burn the floor of standing forests are one of the most important types of forest impoverishment in the Amazon, especially during the severe droughts of El Nino Southern Oscillation (ENSO) episodes. However, we are aware of no estimates of the areal extent of these fires for the Brazilian Amazon and, hence, of their contribution to Amazon carbon fluxes to the atmosphere. We calculated the area of forest understory fires for the Brazilian Amazon region during an El Nino (1998) and a non El Nino (1995) year based on forest fire scars mapped with satellite images for three locations in eastern and southern Amazon, where deforestation is concentrated. The three study sites represented a gradient of both forest types and dry season severity. The burning scar maps were used to determine how the percentage of forest that burned varied with distance from agricultural clearings. These spatial functions were then applied to similar forest/climate combinations outside of the study sites to derive an initial estimate for the Brazilian Amazon. Ninety-one percent of the forest area that burned in the study sites was within the first kilometer of a clearing for the non ENSO year and within the first four kilometers for the ENSO year. The area of forest burned by understory forest fire during the severe drought (ENSO) year (3.9 millions of hectares) was 13 times greater than the area burned during the average rainfall year (0.2 million hectares), and twice the area of annual deforestation rate. Dense forest was, proportionally, the forest area most affected by understory fires during the El Nino year, while understory fires were concentrated in transitional forests during the year of average rainfall. Our estimate of aboveground tree biomass killed by fire ranged from 0.06 Pg to 0.38 Pg during the ENSO and from 0,004 Pg to 0,024 Pg during the non ENSO.
ENSO effects on stratospheric trace gases: How do we capture reality?
NASA Astrophysics Data System (ADS)
Braesicke, Peter; Kirner, Oliver; Versick, Stefan; Joeckel, Patrick; Stiler, Gabriele
2016-04-01
The El Niño/Southern Oscillation (ENSO) phenomenon is an important pacemaker for interannual variability in the Earth's atmosphere. ENSO impacts on trace gases have been observed and modelled for the stratosphere and the troposphere. However, unambiguous attribution is often difficult due to the limited length of homogenous observational records and thus long-term (decadal) trends are sometimes difficult to detect. Generally ENSO impacts in low latitudes are easier to detect, because the response emerges close (temporally and spatially) to the forcing. Moving from low to high latitudes it becomes increasingly difficult to isolate ENSO driven variability, due to time-lags involved and many other modes of variability playing a role as well. Here, we use a nudged version of the EMAC chemistry-climate model to evaluate ENSO impacts on trace gases over the last 35 years (a so-called Ref-C1SD integration) and contrast the nudged model with its free running counterpart. We use water vapour and ozone observations from the MIPAS instrument on ENVISAT from 2002 to 2012 to test the model performance. Using lagged correlations for the longer model time-series we trace the ENSO signal from the tropical lower troposphere to the polar lower and middle stratosphere and provide a framework for simple attribution of the ENSO signal in trace gases. This concise characterisation of the ENSO impact on trace gases aids improved trend detection in temporally limited time series.
Trans-Pacific ENSO teleconnections pose a correlated risk to global agriculture
NASA Astrophysics Data System (ADS)
Anderson, W. B.; Seager, R.; Cane, M. A.; Baethgen, W.
2017-12-01
The El Niño Southern Oscillation (ENSO) is a major source of interannual climate variability, particularly in the Pacific Basin. ENSO life-cycles tend to evolve over multiple years, as do the associated trans-Pacific ENSO teleconnections. This analysis, however, represents the first attempt to characterize the structure of the risk posed by ENSO to wheat, maize and soybean production across the Pacific Basin. Our results indicate that most ENSO teleconnections relevant for crop flowering seasons are the result of a single trans-Pacific circulation anomaly that develops in boreal summer and persists through the spring. During the late summer and early fall of a developing ENSO event, the tropical Pacific forces an atmospheric anomaly in the midlatitudes that spans the Pacific Basin. This teleconnection directly links the soybean and maize growing seasons of the US, Mexico and China. It also connects the wheat growing seasons of Argentina, southern Brazil and Australia. The ENSO event peaks in boreal winter, when the atmospheric circulation anomalies intensify and affect maize and soybeans in southeast South America. As the event decays, the ENSO-induced circulation anomalies persist through the wheat flowering seasons in China and the US. While the prospect of ENSO forcing simultaneous droughts in major food producing regions seems disastrous, there may be a silver lining from the perspective of global food security: trans-Pacific ENSO teleconnections to yields are often offsetting between major producing regions in the eastern and western portions of the Pacific Basin. El Niños tend to create good maize and soybean growing conditions in the US and southeast South America, but poor growing conditions in China, Mexico and northeast Brazil. The opposite is true during La Niña. Wheat growing conditions in southeast South America generally have the opposite sign of those in Australia. Finally, we investigate how trade networks interact with this structure of ENSO
ENSO activity during the last climate cycle using IFA
NASA Astrophysics Data System (ADS)
Leduc, Guillaume; Vidal, Laurence; Thirumalai, Kaustubh
2017-04-01
The El Niño / Southern Oscillation (ENSO) is the principal mode of interannual climate variability and affects key climate parameters such as low-latitude rainfall variability. Anticipating future ENSO variability under anthropogenic forcing is vital due to its profound socioeconomic impact. Fossil corals suggest that 20th century ENSO variance is particularly high as compared to other time periods of the Holocene (Cobb et al., 2013, Science), the Last Glacial Maximum (Ford et al., 2015, Science) and the last glacial period (Tudhope et al., 2001, Science). Yet, recent climate modeling experiments suggest an increase in the frequency of both El Niño (Cai et al., 2014, Nature Climate Change) and La Niña (Cai et al., 2015, Nature Climate Change) events. We have expanded an Individual Foraminifera Analysis (IFA) dataset using the thermocline-dwelling N. dutertrei on a marine core collected in the Panama Basin (Leduc et al., 2009, Paleoceanography), that has proven to be a skillful way to reconstruct the ENSO (Thirumalai et al., 2013, Paleoceanography). Our new IFA dataset comprehensively covers the Holocene, the last deglaciation and Termination II (MIS5/6) time windows. We will also use previously published data from the Marine Isotope Stage 3 (MIS3). Our dataset confirms variable ENSO intensity during the Holocene and weaker activity during LGM than during the Holocene. As a next step, ENSO activity will be discussed with respect to the contrasting climatic background of the analysed time windows (millenial-scale variability, Terminations).
A global analysis of the asymmetric effect of ENSO on extreme precipitation
NASA Astrophysics Data System (ADS)
Sun, Xun; Renard, Benjamin; Thyer, Mark; Westra, Seth; Lang, Michel
2015-11-01
The global and regional influence of the El Niño-Southern Oscillation (ENSO) phenomenon on extreme precipitation was analyzed using a global database comprising over 7000 high quality observation sites. To better quantify possible changes in relatively rare design-relevant precipitation quantiles (e.g. the 1 in 10 year event), a Bayesian regional extreme value model was used, which employed the Southern Oscillation Index (SOI) - a measure of ENSO - as a covariate. Regions found to be influenced by ENSO include parts of North and South America, southern and eastern Asia, South Africa, Australia and Europe. The season experiencing the greatest ENSO effect varies regionally, but in most of the ENSO-affected regions the strongest effect happens in boreal winter, during which time the 10-year precipitation for |SOI| = 20 (corresponding to either a strong El Niño or La Niña episode) can be up to 50% higher or lower than for SOI = 0 (a neutral phase). Importantly, the effect of ENSO on extreme precipitation is asymmetric, with most parts of the world experiencing a significant effect only for a single ENSO phase. This finding has important implications on the current understanding of how ENSO influences extreme precipitation, and will enable a more rigorous theoretical foundation for providing quantitative extreme precipitation intensity predictions at seasonal timescales. We anticipate that incorporating asymmetric impacts of ENSO on extreme precipitation will help lead to better-informed climate-adaptive design of flood-sensitive infrastructure.
Changes in Sea Salt Emissions Enhance ENSO Variability
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Yang; Russell, Lynn M.; Lou, Sijia
Two 150-year pre-industrial simulations with and without interactive sea salt emissions from the Community Earth System Model (CESM) are performed to quantify the interactions between sea salt emissions and El Niño–Southern Oscillation (ENSO). Variations in sea salt emissions over the tropical Pacific Ocean are affected by changing wind speed associated with ENSO variability. ENSO-induced interannual variations in sea salt emissions result in decreasing (increasing) aerosol optical depth (AOD) by 0.03 over the equatorial central-eastern (western) Pacific Ocean during El Niño events compared to those during La Niña events. These changes in AOD further increase (decrease) radiative fluxes into the atmospheremore » by +0.2 W m -2 (-0.4 W m -2) over the tropical eastern (western) Pacific. Thereby, sea surface temperature increases (decreases) by 0.2–0.4 K over the tropical eastern (western) Pacific Ocean during El Niño compared to La Niña events and enhances ENSO variability by 10%. The increase in ENSO amplitude is a result of systematic heating (cooling) during the warm (cold) phase, of ENSO in the eastern Pacific. Interannual variations in sea salt emissions then produce the anomalous ascent (subsidence) over the equatorial eastern (western) Pacific between El Niño and La Niña events, which is a result of heating anomalies. Due to variations in sea salt emissions, the convective precipitation is enhanced by 0.6–1.2 mm day -1 over the tropical central-eastern Pacific Ocean and weakened by 0.9–1.5 mm day -1 over the Maritime Continent during El Niño compared to La Niña events, enhancing the precipitation variability over the tropical Pacific.« less
A Teleconnection between the West Siberian Plain and the ENSO Region
NASA Astrophysics Data System (ADS)
Liess, S.; Agrawal, S.; Chatterjee, S.; Kumar, V.
2017-12-01
This study presents a mechanism that links the El Niño/Southern Oscillation (ENSO) to extratropical waves that are deflected from the Northern Hemisphere polar regions and travel southeastward over Central Asia toward the west Pacific warm pool during northern winter. The initial wave pattern resembles the well-known East Atlantic-West Russia pattern. Here we show its influence on the ENSO region. We identify a tripole pattern between the West Siberian Plain and the two centers of action of ENSO with a graph-based approach. It indicates that the background state of ENSO with respect to global sea level pressure (SLP) has a significant negative correlation to the West Siberian Plain. The correlation with the background state, which is defined by the sum of the two centers of action of ENSO, is higher than each of the pairwise correlations with either of the ENSO centers alone. We define the centers with a clustering algorithm that detects regions with similar characteristics. The normalized monthly SLP time series for the two centers of ENSO (around Darwin, Australia and Tahiti) are area-averaged and the sum of both regions is considered as the background state of ENSO. This wave train can be detected throughout the troposphere and the lower stratosphere. Its origins can be traced back to atmospheric wave activity triggered by convection over the subtropical North Atlantic that emanates wave activity toward the West Siberian Plain. The same wave train also propagates to the central Pacific Ocean around Tahiti and can be used to predict the background state over the ENSO region. This background state also modifies the subtropical bridge between the tropical east Pacific and the subtropical North Atlantic, thus leading to a circumglobal wave train.
Active-matrix OLED using 150°C a-Si TFT backplane built on flexible plastic substrate
NASA Astrophysics Data System (ADS)
Sarma, Kalluri R.; Chanley, Charles; Dodd, Sonia R.; Roush, Jared; Schmidt, John; Srdanov, Gordana; Stevenson, Matthew; Wessel, Ralf; Innocenzo, Jeffrey; Yu, Gang; O'Regan, Marie B.; MacDonald, W. A.; Eveson, R.; Long, Ke; Gleskova, Helena; Wagner, Sigurd; Sturm, James C.
2003-09-01
Flexible displays fabricated using plastic substrates have a potential for being very thin, light weight, highly rugged with greatly minimized propensity for breakage, roll-to-roll manufacturing and lower cost. The emerging OLED display media offers the advantage of being a solid state and rugged structure for flexible displays in addition to the many potential advantages of an AM OLED over the currently dominant AM LCD. The current high level of interest in flexible displays is facilitating the development of the required enabling technologies which include development of plastic substrates, low temperature active matrix device and backplane fabrication, and display packaging. In the following we will first discuss our development efforts in the PEN based plastic substrates, active matrix backplane technology, low temperature (150°C) a-Si TFT devices and an AM OLED test chip used for evaluating various candidate designs. We will then describe the design, fabrication and successful evaluation and demonstration of a 64x64 pixel AM OLED test display using a-Si TFT backplane fabricated at 150°C on the flexible plastic substrate.
ENSO and anthropogenic impacts on phytoplankton diversity in tropical coastal waters
NASA Astrophysics Data System (ADS)
Doan-Nhu, Hai; Nguyen-Ngoc, Lam; Nguyen, Chi-Thoi
2016-01-01
16-year phytoplankton data were analysed to assess ENSO and anthropogenic impacts on biodiversity and community structure at 3 locations (Nha-Trang and Phan-Thiet Bays and near Phu-Qui Island) in South Centre Viet Nam to understand (1) the primary scales of change in phytoplankton community structure, and traditional and taxonomic diversity indices; (2) the significance of environmental changes and/or climate variability on phytoplankton diversity; and (3) the usefulness of these long-term data for analysing future impacts of anthropogenic and climate changes. Traditional and taxonomic diversity indices were compared and tested in linkage with environmental conditions and ENSO. Nutrient data indicated stronger environmental impacts in Phan-Thiet Bay, milder in Nha-Trang Bay and less noticeable near Phu-Qui Island. There were measurable impacts of both anthropogenic and ENSO on phytoplankton at different locations in various parameters, e.g. species number, diversity and community structures. The lowest diversity was recorded in the most anthropogenically impacted site, Phan-Thiet Bay. Although a stronger impact on phytoplankton was recorded in ENSO year in Phan Thiet Bay, quantitative separation between anthropogenic and ENSO impacts using phytoplankton biodiversity indices was impossible. In the waters with less anthropogenic impacts, ENSO effects on taxonomic diversity was better indicated by negative phytoplankton responses to the ONI index (Nha-Trang Bay) and recovery of phytoplankton after the ENSO events (near Phu-Qui Island). Among the diversity indices, the taxonomic diversity indices (e.g. Δ+ and Λ+) better described impacts of ENSO than the traditional ones.
The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event
NASA Astrophysics Data System (ADS)
Chen, H. C.; Hu, Z. Z.; Huang, B.; Sui, C. H.
2016-02-01
In this study, we demonstrate that a sudden reversal of anomalous equatorial zonal current at the peaking ENSO phase triggers the rapid termination of an ENSO event. Throughout an ENSO cycle, the anomalous equatorial zonal current is strongly controlled by the concavity of the anomalous thermocline meridional structure near the equator. During the ENSO developing phase, the anomalous zonal current in the central and eastern Pacific generally enhances the ENSO growth through its zonal SST advection. In the mature phase of ENSO, however, the equatorial thermocline depth anomalies are reflected in the eastern Pacific and slowly propagate westward off the equator in both hemispheres. As a result, the concavity of the thermocline anomalies near the equator is reversed, i.e., the off-equatorial thermocline depth anomalies become higher than that on the equator for El Niño events and lower for La Niño events. This meridional change of thermocline structure reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, which weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal mass transport weakens the existing zonal tilting of equatorial thermocline and suppresses the thermocline feedback. Both processes are concentrated in the eastern equatorial Pacific and can be effective on subseasonal time scales. These current reversal effects are built-in to the ENSO peak phase and independent of the zonal wind effect on thermocline slope. It functions as an oceanic control on ENSO evolution during both El Niño and La Niña events.
The seasonality and geographic dependence of ENSO impacts on U.S. surface ozone variability
NASA Astrophysics Data System (ADS)
Xu, Li; Yu, Jin-Yi; Schnell, Jordan L.; Prather, Michael J.
2017-04-01
We examine the impact of El Niño-Southern Oscillation (ENSO) on surface ozone abundance observed over the continental United States (U.S.) during 1993-2013. The monthly ozone decreases (increases) during El Niño (La Niña) years with amplitude up to 1.8 ppb per standard deviation of Niño 3.4 index. The largest ENSO influences occur over two southern U.S. regions during fall when the ENSO develops and over two western U.S. regions during the winter to spring after the ENSO decays. ENSO affects surface ozone via chemical processes during warm seasons in southern regions, where favorable meteorological conditions occur, but via dynamic transport during cold seasons in western regions, where the ENSO-induced circulation variations are large. The geographic dependence and seasonality of the ENSO impacts imply that regulations regarding air quality and its exceedance need to be adjusted for different seasons and U.S. regions to account for the ENSO-driven patterns in surface ozone.
Synthesis and characterization of (18)F-labeled active site inhibited factor VII (ASIS).
Erlandsson, Maria; Nielsen, Carsten H; Jeppesen, Troels E; Kristensen, Jesper B; Petersen, Lars C; Madsen, Jacob; Kjaer, Andreas
2015-05-15
Activated factor VII blocked in the active site with Phe-Phe-Arg-chloromethyl ketone (active site inhibited factor VII (ASIS)) is a 50-kDa protein that binds with high affinity to its receptor, tissue factor (TF). TF is a transmembrane glycoprotein that plays an important role in, for example, thrombosis, metastasis, tumor growth, and tumor angiogenesis. The aim of this study was to develop an (18)F-labeled ASIS derivative to assess TF expression in tumors. Active site inhibited factor VII was labeled using N-succinimidyl-4-[(18)F]fluorobenzoate, and the [(18)F]ASIS was purified on a PD-10 desalting column. The radiochemical yield was 25 ± 6%, the radiochemical purity was >97%, and the pseudospecific radioactivity was 35 ± 9 GBq/µmol. The binding efficacy was evaluated in pull-down experiments, which monitored the binding of unlabeled ASIS and [(18)F]ASIS to TF and to a specific anti-factor VII antibody (F1A2-mAb). No significant difference in binding efficacy between [(18)F]ASIS and ASIS could be detected. Furthermore, [(18)F]ASIS was relatively stable in vitro and in vivo in mice. In conclusion, [(18)F]ASIS has for the first time been successfully synthesized as a possible positron emission tomography tracer to image TF expression levels. In vivo positron emission tomography studies to evaluate the full potential of [(18)F]ASIS are in progress. Copyright © 2015 John Wiley & Sons, Ltd.
ENSO Dynamics and Trends, AN Alternate View
NASA Astrophysics Data System (ADS)
Rojo Hernandez, J. D.; Lall, U.; Mesa, O. J.
2017-12-01
El Niño - Southern Oscillation (ENSO) is the most important inter-annual climate fluctuation on a planetary level with great effects on the hydrological cycle, agriculture, ecosystems, health and society. This work demonstrates the use of the Non-Homogeneus hidden Markov Models (NHMM) to characterize ENSO using a set of discrete states with variable transition probabilities matrix using the data of sea surface temperature anomalies (SSTA) of the Kaplan Extended SST v2 between 120E -90W, 15N-15S from Jan-1856 to Dec-2016. ENSO spatial patterns, their temporal distribution, the transition probabilities between patterns and their temporal evolution are the main results of the NHHMM applied to ENSO. The five "hidden" states found appear to represent the different "Flavors" described in the literature: the Canonical El Niño, Central El Niño, a Neutral state, Central La Niña and the Canonical Niña. Using the whole record length of the SSTA it was possible to identify trends in the dynamic system, with a decrease in the probability of occurrence of the cold events and a significant increase of the warm events, in particular of Central El Niño events whose probability of occurrence has increased Dramatically since 1960 coupled with increases in global temperature.
Study of the global and regional climatic impacts of ENSO magnitude using SPEEDY AGCM
NASA Astrophysics Data System (ADS)
Dogar, Muhammad Mubashar; Kucharski, Fred; Azharuddin, Syed
2017-03-01
ENSO is considered as a strong atmospheric teleconnection that has pronounced global and regional circulation effects. It modifies global monsoon system, especially, Asian and African monsoons. Previous studies suggest that both the frequency and magnitude of ENSO events have increased over the last few decades resulting in a need to study climatic impacts of ENSO magnitude both at global and regional scales. Hence, to better understand the impact of ENSO amplitude over the tropical and extratropical regions focussing on the Asian and African domains, ENSO sensitivity experiments are conducted using ICTPAGCM (`SPEEDY'). It is anticipated that the tropical Pacific SST forcing will be enough to produce ENSO-induced teleconnection patterns; therefore, the model is forced using NINO3.4 regressed SST anomalies over the tropical Pacific only. SPEEDY reproduces the impact of ENSO over the Pacific, North and South America and African regions very well. However, it underestimates ENSO teleconnection patterns and associated changes over South Asia, particularly in the Indian region, which suggests that the tropical Pacific SST forcing is not sufficient to represent ENSO-induced teleconnection patterns over South Asia. Therefore, SST forcing over the tropical Indian Ocean together with air-sea coupling is also required for better representation of ENSO-induced changes in these regions. Moreover, results obtained by this pacemaker experiment show that ENSO impacts are relatively stronger over the Inter-Tropical Convergence Zone (ITCZ) compared to extratropics and high latitude regions. The positive phase of ENSO causes weakening in rainfall activity over African tropical rain belt, parts of South and Southeast Asia, whereas, the La Niña phase produces more rain over these regions during the summer season. Model results further reveal that ENSO magnitude has a stronger impact over African Sahel and South Asia, especially over the Indian region because of its significant impact
Mean state dependence of ENSO diversity resulting from an intermediate coupled model
NASA Astrophysics Data System (ADS)
Xie, Ruihuang; Jin, Fei-Fei; Mu, Mu
2016-04-01
ENSO diversity is referred to the event-to-event differences in the amplitude, longitudinal location of maximum sea surface temperature (SST) anomalies and evolutional mechanisms, as manifested in both observation data and climate model simulations. Previous studies argued that westerly wind burst (WWB) has strong influence on ENSO diversity. Here, we bring evidences, from a modified intermediate complexity Zebiak-Cane (ZC) coupled model, to illustrate that the ENSO diversity is also determined by the mean states. Stabilities of the linearized ZC model reveal that the mean state with weak (strong) wind stress and deep (shallow) thermocline prefers ENSO variation in the equitorial eastern (central) Pacific with a four-year (two-year) period. Weak wind stress and deep thermocline make the thermocline (TH) feedback the dominant contribution to the growth of ENSO SST anomalies, whereas the opposite mean state favors the zonal advective (ZA) feedback. Different leading dynamical SST-controller makes ENSO display its diversity. In a mean state that resembles the recent climate in the tropical Pacific, the four-year and two-year ENSO variations coexist with similar growth rate. Even without WWB forcing, the nonlinear integration results with adjusted parameters in this special mean state also present at least two types of El Niño, in which the maximum warming rates are contributed by either TH or ZA feedback. The consistency between linear and nonlinear model results indicates that the ENSO diversity is dependent on the mean states.
Modeling of SSME fuel preburner ASI
NASA Technical Reports Server (NTRS)
Liang, Pak-Yan
1992-01-01
The Augmented Spark Ignitor (ASI) is a LOX/H2/electrical spark system that functions as an ignition source and sustainer for stable combustion. It is used in the Space Shuttle Main Engine (SSME) preburner combustor, the SMME main combustion chamber, the J-1 and J-2 engines, as well as proposed designs of the Space Transportation Main Engine (STME) main combustor and gas generators. An undertaking to characterize the flow of the ASI is documented. The code consists of a marriage of the Implicit-Continuous Eulerian/Arbitrary Lagrangian Code (ICE-ALE) Navier-Stokes solver with the Volume-of-Fluid (VOF) Methodology for tracking of two immiscible fluids with sharp discontinuities. Spray droplets are represented by discrete numerical parcels tracked in a Lagrangian fashion. Numerous physical sub-models are also incorporated to describe the processes of atomization, droplet collision, droplet breakup, evaporation, and droplet and gas phase turbulence. An equilibrium chemistry model accounting for 8 active gaseous species is also used. Taking advantage of this symmetry plane, half of the actual ASI is modeled with a 3-D grid that geometrically resolves the LOX ports, the spark plug locations, and the hydrogen injection slots.
Greening of the Sahara suppressed ENSO activity during the mid-Holocene
Pausata, Francesco S. R.; Zhang, Qiong; Muschitiello, Francesco; Lu, Zhengyao; Chafik, Léon; Niedermeyer, Eva M.; Stager, J. Curt; Cobb, Kim M.; Liu, Zhengyu
2017-01-01
The evolution of the El Niño-Southern Oscillation (ENSO) during the Holocene remains uncertain. In particular, a host of new paleoclimate records suggest that ENSO internal variability or other external forcings may have dwarfed the fairly modest ENSO response to precessional insolation changes simulated in climate models. Here, using fully coupled ocean-atmosphere model simulations, we show that accounting for a vegetated and less dusty Sahara during the mid-Holocene relative to preindustrial climate can reduce ENSO variability by 25%, more than twice the decrease obtained using orbital forcing alone. We identify changes in tropical Atlantic mean state and variability caused by the momentous strengthening of the West Africa Monsoon (WAM) as critical factors in amplifying ENSO’s response to insolation forcing through changes in the Walker circulation. Our results thus suggest that potential changes in the WAM due to anthropogenic warming may influence ENSO variability in the future as well. PMID:28685758
Increasing ENSO-Driven Drought and Wildfire Risks in a Warming Climate
NASA Astrophysics Data System (ADS)
Fasullo, J.; Otto-Bliesner, B. L.; Stevenson, S.
2015-12-01
ENSO-related teleconnections occurring in the transient climate states of the 20th and 21st centuries are examined using the NCAR CESM1-CAM5 Large Ensemble (LE). A focus is given to quantifying the changing nature of related variability in a warming climate, the statistical robustness of which is enhanced by the numerous members of the LE (presently ~40). It is found that while the dynamical components of ENSO's teleconnections weaken considerably in a warming world, associated variability over land is in many cases sustained by changes in the background state, such as for rainfall due to the background rise in specific humidity. In some fields, particularly those associated with associated with thermal stress (e.g. drought and wildfire), ENSO-related variance increases dramatically. This, combined with the fact that ENSO variance itself increases in a warming climate in the LE, contributes to dramatic projected increases in ENSO-driven drought and wildfire risks in a warming world.
Fossil Coral Records of ENSO during the Last Glacial Period
NASA Astrophysics Data System (ADS)
Partin, J. W.; Taylor, F. W.; Shen, C. C.; Edwards, R. L.; Quinn, T. M.; DiNezro, P.
2017-12-01
Only a handful of paleoclimate records exist that can resolve interannual changes, and hence El Nino/Southern Oscillation (ENSO) variability, during the last glacial period, a time of altered mean climate. The few existing data suggest reduced ENSO variability compared to the Holocene, possibly due to a weaker zonal sea surface temperature gradient across the tropical Pacific and/or a deeper thermocline in the eastern tropical Pacific. Our goal is to add crucial data to this extremely limited subset using sub-annually resolved fossil corals that grew during this time period to reconstruct ENSO. We seek to recover fossil corals from Vanuatu, SW Pacific (16°S, 167°E) with the objective of using coral δ18O to reconstruct changes in the ENSO during and near the Last Glacial Maximum (LGM). Modern δ18O coral records from Vanuatu show a high degree of skill in capturing ENSO variability, making it a suitable site for reconstructing ENSO variability. We have custom designed and are building a drill system that can rapidly core many 0-25 m holes resulting in much more meters of penetration than achieved by previous land-based reef drilling. As the new drill system is extremely portable and can be quickly relocated by workers without landing craft or vehicles, it is time and cost efficient. Because the proposed drilling sites have uplifted extremely fast, 7 mm/year, the LGM shoreline has been raised from 120-140 m depth to within a depth range of 10 below to 20 m above present sea level. This enables all the drilling to be within the time range of interest ( 15-25 ka). A last advantage is that the LGM corals either are still submersed in seawater or emerged only within the last 2000 years at the uplift rate of 7 mm/yr. This greatly reduces the chances of disruption of the original climate signal because sea water is less diagenetically damaging than meteoric water in the mixed, phreatic, or vadose zones. LGM coral records will enable us to compare the proxy variability
Variability of lightning activity over India on ENSO time scales
NASA Astrophysics Data System (ADS)
Ahmad, Adnan; Ghosh, Mili
2017-12-01
ENSO, the reliable indicator of inter-annual climate variation of the ocean-atmosphere system in the tropical Pacific region, can affect the overall lightning activity which is another atmospheric phenomenon. In the present study, the impact of the ENSO on the total lightning activity over India has been studied for the period 2004-2014. During the El-Nino period (July 2004-April 2005 and July 2009-April 2010), total number of lightning flashes increased by 10% and 18% respectively and during La-Nina period (July 2010-April 2011 and August 2011 to March 2012), the total number of lightning flashes decreased approximately by 19% and 28% respectively as compared to the mean of corresponding period (2004-14) of the Non-ENSO. Seasonal variation of flash density is also examined for the El-Nino and La-Nina period. The result shows that in the El-Nino period of the pre-monsoon and monsoon seasons, there is an increment in the flash density approximately by 48% and 9% respectively than the Non-ENSO and the spatial variation also having high flash density along the foot of Himalayas region. In the post-monsoon season, there is a marginal change in the flash density between El-Nino and the Non-ENSO. In the winter season, there is an increment in flash density in the El-Nino period approximately by 45% than the Non-ENSO. In the La-Nina period of the pre-monsoon and monsoon seasons, there is the decrement in the flash density approximately by the 44% and 24% respectively than the Non-ENSO. In the Post-monsoon season and winter season of La-Nina, the flash density is increased by about 24% and 33% over India. These findings can be applied to do proper planning of lightning induced hazard mitigation as lightning is of one of the major natural disasters of India.
ENSO events in the northern Gulf of Alaska, and effects on selected marine fisheries
Bailey, K.M.; Macklin, S.A.; Reed, R.K.; Brodeur, R.D.; Ingraham, W.J.; Piatt, John F.; Shima, M.; Francis, R.C.; Anderson, P.J.; Royer, T.C.; Hollowed, A.; Somerton, D.A.; Wooster, W.S.
1995-01-01
The 1991-93 El Nino-Southern Oscillation (ENSO) event first appeared in the northern Gulf of Alaska in autumn 1991 with warm sea-surface temperatures. In winter 1992, there were pulses of increased sea level and anomalous circulation. El Nino conditions persisted at least through summer 1993. The effects of this ENSO event on major groundfish species and Pacific herring in the northern Gulf of Alaska were examined and compared with the effects of previous ENSO events. There is little evidence that the 1991-93 or 1982-83 ENSO events affected landings of walleye pollock, Pacific cod, Pacific halibut, or arrowtooth flounder. Some changes in distribution of groundfish species were observed in 1993, but the effect was similar to changes observed in non-ENSO warm years. In general, warm ocean conditions have a positive effect on recruitment of northern stocks, but ENSO events appear to have an inconsistent effect on year-class strength within species and among different species. For example, strong year classes of halibut and arrowtooth flounder sometimes, but not always, coincide with ENSO events; ENSO events are associated with moderate to weak year classes of cod and pollock. However, post-ENSO warm years often are associated with strong recruitment of many groundfish species. Major changes have occurred in the Gulf of Alaska ecosystem since 1977. The influence of the 1976 ENSO event in precipitating these changes and the role of the frequency or strength of subsequent El Nino events is presently unknown. Herring and other stocks of small pelagic fishes may be more affected by ENSO events. In particular, decreased catches, recruitment, and weight-at-age of herring are sometimes associated with ENSO events. Furthermore, a variety of seabirds which feed mostly on pelagic forage fishes or the pelagic juvenile stages of groundfish suffered widespread mortalities and breeding failures in the Gulf of Alaska during the ENSO years of 1983 and 1993. These effects on seabirds
Is ENSO part of an Indo-Pacific phenomenon?
NASA Astrophysics Data System (ADS)
Wieners, Claudia; de Ruijter, Wilhelmus; Dijkstra, Henk
2015-04-01
The Seychelles Dome (SD) - a thermocline ridge in the West Indian Ocean - is a dynamically active region with a strong Sea Surface Temperature (SST)-atmosphere coupling and located at the origin of the Madden-Julian Oscillation. Analysis of observational data suggests that it might influence El Niño occurrence and evolution at a lead time of 1.5 years. We find a negative correlation between SD SST in boreal summer and Nino3.4 SST about 18 months later. Such a correlation might be a mere side-effect of the fact that ENSO has influence on the SD - El Niño (La Niña) is followed by a warm (cool) SD after about 3-6 months - and of the cyclicity of ENSO with a preferred period of about 4 years. However, we find the correlation to be significantly stronger than one would expect in that case, implying that the SD contains information linearly independent from ENSO. A Multi-channel Singular Spectrum analysis (MSSA) on tropical SST, zonal wind and zonal wind variability reveals three significant oscillations. All of these show ENSO-like behaviour in the Pacific Ocean, with East Pacific SST anomalies being followed by anomalies of the same sign in the SD region after 3-5 months. Wind patterns propagate from the Indian to the Pacific Ocean. These findings suggest that the Indian and Pacific Oceans act as a unified system. The slower two oscillations, with periods around 4 years, have the strongest ENSO signal in the East Pacific (like a `Cold Tongue El Niño'). Compared to them, the fastest oscillation, with a period of 2.5 years, has a stronger signal in the Central Pacific (more resembling a `Warm Pool El Niño'). Because of the short period of the fastest mode, the time elapsed between an SD anomaly and the following ENSO anomaly (of opposite sign) is only 11 months - much less than the 18 months lag at which the correlation between SD and ENSO is minimal. This suggests that while the Cold Tongue El Niño's tend to be preceded by a cool SD event at a lead time suitable
Mean Bias in Seasonal Forecast Model and ENSO Prediction Error.
Kim, Seon Tae; Jeong, Hye-In; Jin, Fei-Fei
2017-07-20
This study uses retrospective forecasts made using an APEC Climate Center seasonal forecast model to investigate the cause of errors in predicting the amplitude of El Niño Southern Oscillation (ENSO)-driven sea surface temperature variability. When utilizing Bjerknes coupled stability (BJ) index analysis, enhanced errors in ENSO amplitude with forecast lead times are found to be well represented by those in the growth rate estimated by the BJ index. ENSO amplitude forecast errors are most strongly associated with the errors in both the thermocline slope response and surface wind response to forcing over the tropical Pacific, leading to errors in thermocline feedback. This study concludes that upper ocean temperature bias in the equatorial Pacific, which becomes more intense with increasing lead times, is a possible cause of forecast errors in the thermocline feedback and thus in ENSO amplitude.
ENSO activity during the last climate cycle using Individual Foraminifera Analysis
NASA Astrophysics Data System (ADS)
Leduc, G.; Vidal, L.; Thirumalai, K.
2017-12-01
The El Niño / Southern Oscillation (ENSO) is the principal mode of interannual climate variability and affects key climate parameters such as low-latitude rainfall variability. Recent climate modeling experiments tend to suggest an increase in the frequency of both El Niño and La Niña events in the future, but these results remain model-dependent and require to be validated by paleodata-model comparisons. Fossil corals indicate that the ENSO variance during the 20th century is particularly high as compared to other time periods of the Holocene. Beyond the Holocene, however, little is known on past ENSO changes, which makes difficult to test paleoclimate model simulations that are used to study the ENSO sensitivity to various types of forcings. We have expanded an Individual Foraminifera Analysis (IFA) dataset using the thermocline-dwelling N. dutertrei on a marine core collected in the Panama Basin (Leduc et al., 2009), that has proven to be a skillful way to reconstruct the ENSO (Thirumalai et al., 2013). Our new IFA dataset comprehensively covers the Holocene, allowing to verify how the IFA method compares with ENSO reconstructions using corals. The dataset then extends back in time to Marine Isotope Stage 6 (MIS), with a special focus the last deglaciation and Termination II (MIS5/6) time windows, as well as key time periods to tests the sensitivity of ENSO to ice volume and orbital parameters. The new dataset confirms variable ENSO activity during the Holocene and weaker activity during LGM than during the Holocene, as a recent isotope-enabled climate model simulations of the LGM suggests (Zhu et al., 2017). Such pattern is reproduced for the Termination II. Leduc, G., L. Vidal, O. Cartapanis, and E. Bard (2009), Modes of eastern equatorial Pacific thermocline variability: Implications for ENSO dynamics over the last glacial period, Paleoceanography, 24, PA3202, doi:10.1029/2008PA001701. Thirumalai, K., J. W. Partin, C. S. Jackson, and T. M. Quinn (2013
DMS role in ENSO cycle in the tropics: DMS Role in ENSO Cycle in Tropics
DOE Office of Scientific and Technical Information (OSTI.GOV)
Xu, Li; Cameron-Smith, Philip; Russell, Lynn M.
We examined the multiyear mean and variability of dimethyl sulfide (DMS) and its relationship to sulfate aerosols, as well as cloud microphysical and radiative properties. We conducted a 150 year simulation using preindustrial conditions produced by the Community Earth System Model embedded with a dynamic DMS module. The model simulated the mean spatial distribution of DMS emissions and burden, as well as sulfur budgets associated with DMS, SO2, H2SO4, and sulfate that were generally similar to available observations and inventories for a variety of regions. Changes in simulated sea-to-air DMS emissions and associated atmospheric abundance, along with associated aerosols andmore » cloud and radiative properties, were consistently dominated by El Niño–Southern Oscillation (ENSO) cycle in the tropical Pacific region. Simulated DMS, aerosols, and clouds showed a weak positive feedback on sea surface temperature. This feedback suggests a link among DMS, aerosols, clouds, and climate on interannual timescales. The variability of DMS emissions associated with ENSO was primarily caused by a higher variation in wind speed during La Niña events. The simulation results also suggest that variations in DMS emissions increase the frequency of La Niña events but do not alter ENSO variability in terms of the standard deviation of the Niño 3 sea surface temperature anomalies.« less
Validation of the Spanish Addiction Severity Index Multimedia Version (S-ASI-MV).
Butler, Stephen F; Redondo, José Pedro; Fernandez, Kathrine C; Villapiano, Albert
2009-01-01
This study aimed to develop and test the reliability and validity of a Spanish adaptation of the ASI-MV, a computer administered version of the Addiction Severity Index, called the S-ASI-MV. Participants were 185 native Spanish-speaking adult clients from substance abuse treatment facilities serving Spanish-speaking clients in Florida, New Mexico, California, and Puerto Rico. Participants were administered the S-ASI-MV as well as Spanish versions of the general health subscale of the SF-36, the work and family unit subscales of the Social Adjustment Scale Self-Report, the Michigan Alcohol Screening Test, the alcohol and drug subscales of the Personality Assessment Inventory, and the Hopkins Symptom Checklist-90. Three-to-five-day test-retest reliability was examined along with criterion validity, convergent/discriminant validity, and factorial validity. Measurement invariance between the English and Spanish versions of the ASI-MV was also examined. The S-ASI-MV demonstrated good test-retest reliability (ICCs for composite scores between .59 and .93), criterion validity (rs for composite scores between .66 and .87), and convergent/discriminant validity. Factorial validity and measurement invariance were demonstrated. These results compared favorably with those reported for the original interviewer version of the ASI and the English version of the ASI-MV.
Increased frequency of ENSO-related hydroclimate extremes in a warming climate
NASA Astrophysics Data System (ADS)
Sun, Q.; Miao, C.; AghaKouchak, A.
2017-12-01
Global warming will likely alter surface warming in tropical Pacific regions, leading to changes in the characteristics of the El Niño Southern Oscillation (ENSO) characteristics and an incresed frequency of extreme ENSO events. The ENSO-related climatic variation and associated impacts will likely be modified in a warmer climatic state. However, little is known about the effect of changes in ENSO teleconnections with regard to future dry and wet conditions over land around the globe, especially outside tropical regions. We used the model simulations of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) for different twenty-first-century emission scenarios (RCP 4.5 and RCP 8.5) to investigate the changes in the ENSO' teleconnection on dry/wet condition over global land. Our results show that 64.64% and 38.12% of 181 river basins studied are expected to experience an increase in the frequency of unusually wet/dry events forced by both ENSO phases under the RCP 4.5 and 8.5, respectively. The anomalous precipitation variability forced by ENSO events will be intensified through a "wet-get-wetter, dry-get-drier" mechanism over west North America, South America, central Asia, and west Asia. More than 850 million people are at risk of exposure to unusually dry/wet events. There is a potential increased risk of high-intensity dry/wet events, with an increase/decrease in the 50-year return level of SPI value for drying/wetting regions. These results have important implications for disaster evaluation and related policies and for appropriate engineering design.
Global Precipitation Patterns Associated with ENSO and Tropical Circulations
NASA Technical Reports Server (NTRS)
Curtis, Scott; Adler, Robert; Huffman, George; Bolvin, David; Nelkin, Eric
1999-01-01
Tropical precipitation and the accompanying latent heat release is the engine that drives the global circulation. An increase or decrease in rainfall in the tropics not only leads to the local effects of flooding or drought, but contributes to changes in the large scale circulation and global climate system. Rainfall in the tropics is highly variable, both seasonally (monsoons) and interannually (ENSO). Two experimental observational data sets, developed under the auspices of the Global Precipitation Climatology Project (GPCP), are used in this study to examine the relationships between global precipitation and ENSO and extreme monsoon events over the past 20 years. The V2x79 monthly product is a globally complete, 2.5 deg x 2.5 deg, satellite-gauge merged data set that covers the period 1979 to the present. Indices based on patterns of satellite-derived rainfall anomalies in the Pacific are used to analyze the teleconnections between ENSO and global precipitation, with emphasis on the monsoon systems. It has been well documented that dry (wet) Asian monsoons accompany warm (cold) ENSO events. However, during the summer seasons of the 1997/98 ENSO the precipitation anomalies were mostly positive over India and the Bay of Bengal, which may be related to an epoch-scale variability in the Asian monsoon circulation. The North American monsoon may be less well linked to ENSO, but a positive precipitation anomaly was observed over Mexico around the September following the 1997/98 event. For the twenty-year record, precipitation and SST patterns in the tropics are analyzed during wet and dry monsoons. For the Asian summer monsoon, positive rainfall anomalies accompany two distinct patterns of tropical precipitation and a warm Indian Ocean. Negative anomalies coincide with a wet Maritime Continent.
Direct and indirect ENSO modulation of winter temperature over the Asian–Pacific–American region
Leung, Marco Y. T.; Zhou, Wen
2016-01-01
In this study, the direct and indirect atmospheric responses over the Asian–Pacific–American region to the El Niño–Southern Oscillation (ENSO) are documented. Since ENSO is likely to induce the northward displacement of the East Asian trough (NDEAT), some of the influence of ENSO on the Asian–Pacific–American region is possibly indirect and acts by inducing NDEAT. To separate corresponding influences of ENSO and NDEAT, partial regression is utilized. It is noted that temperature variations in the East Asian–Western Pacific region are controlled mainly by NDEAT. In contrast, ENSO demonstrates a weak direct relation to the temperature variation over the East Asian–Western Pacific region. This suggests that the influence of ENSO on this region is indirect, through modulation of NDEAT. On the other hand, temperature variation over the tropical eastern Pacific is dominated by ENSO forcing. Finally, temperature variation over the eastern North American–Western Pacific region is controlled by both ENSO and NDEAT. Nevertheless, their influences on temperature and circulation over this region tend to offset each other. This implies that temperature variation is controlled by their relative strengths. PMID:27821838
Are Greenhouse Gases Changing ENSO Precursors in the Western North Pacific?
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, S-Y; Heureux, Michelle L.; Yoon, Jin-Ho
Using multiple observational and modeling datasets, we document a strengthening relationship between boreal winter sea surface temperature anomalies (SSTA) in the western North Pacific (WNP) and the development of the El Nino-Southern Oscillation (ENSO) one year later. The increased WNP-ENSO association emerged in the mid 20th century and has grown through the present, reaching correlation coefficients as high as ~0.70 in recent decades. Fully coupled climate experiments with the Community Earth System Model (CESM) replicate the WNP-ENSO association and indicate that greenhouse gases (GHG) are largely responsible for the observed increase. We speculate that shifts in the location and amplitudesmore » of positive SST trends in the subtropical-tropical western Pacific impacts the low-level circulation so that WNP variability is increasingly influencing the development of ENSO one year later. A strengthened GHG-driven relationship between the WNP and ENSO provides an example of how anthropogenic climate change can potentially improve the skill of intraseasonal-to-interannual climate prediction.« less
ENSO's non-stationary and non-Gaussian character: the role of climate shifts
NASA Astrophysics Data System (ADS)
Boucharel, J.; Dewitte, B.; Garel, B.; Du Penhoat, Y.
2009-07-01
El Niño Southern Oscillation (ENSO) is the dominant mode of climate variability in the Pacific, having socio-economic impacts on surrounding regions. ENSO exhibits significant modulation on decadal to inter-decadal time scales which is related to changes in its characteristics (onset, amplitude, frequency, propagation, and predictability). Some of these characteristics tend to be overlooked in ENSO studies, such as its asymmetry (the number and amplitude of warm and cold events are not equal) and the deviation of its statistics from those of the Gaussian distribution. These properties could be related to the ability of the current generation of coupled models to predict ENSO and its modulation. Here, ENSO's non-Gaussian nature and asymmetry are diagnosed from in situ data and a variety of models (from intermediate complexity models to full-physics coupled general circulation models (CGCMs)) using robust statistical tools initially designed for financial mathematics studies. In particular α-stable laws are used as theoretical background material to measure (and quantify) the non-Gaussian character of ENSO time series and to estimate the skill of ``naïve'' statistical models in producing deviation from Gaussian laws and asymmetry. The former are based on non-stationary processes dominated by abrupt changes in mean state and empirical variance. It is shown that the α-stable character of ENSO may result from the presence of climate shifts in the time series. Also, cool (warm) periods are associated with ENSO statistics having a stronger (weaker) tendency towards Gaussianity and lower (greater) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through nonlinear processes. The relationship between changes in mean state and nonlinearity (skewness) is further investigated both in the Zebiak and Cane (1987)'s model and the models of the Intergovernmental Panel for Climate Change (IPCC). Whereas there is a clear relationship in all
ENSO and cholera: a nonstationary link related to climate change?
Rodo, Xavier; Pascual, Mercedes; Fuchs, George; Faruque, A S G
2002-10-01
We present here quantitative evidence for an increased role of interannual climate variability on the temporal dynamics of an infectious disease. The evidence is based on time-series analyses of the relationship between El Niño/Southern Oscillation (ENSO) and cholera prevalence in Bangladesh (formerly Bengal) during two different time periods. A strong and consistent signature of ENSO is apparent in the last two decades (1980-2001), while it is weaker and eventually uncorrelated during the first parts of the last century (1893-1920 and 1920-1940, respectively). Concomitant with these changes, the Southern Oscillation Index (SOI) undergoes shifts in its frequency spectrum. These changes include an intensification of the approximately 4-yr cycle during the recent interval as a response to the well documented Pacific basin regime shift of 1976. This change in remote ENSO modulation alone can only partially serve to substantiate the differences observed in cholera. Regional or basin-wide changes possibly linked to global warming must be invoked that seem to facilitate ENSO transmission. For the recent cholera series and during specific time intervals corresponding to local maxima in ENSO, this climate phenomenon accounts for over 70% of disease variance. This strong association is discontinuous in time and can only be captured with a technique designed to isolate transient couplings.
Interhemispheric temperature difference as a predictor of boreal winter ENSO
NASA Astrophysics Data System (ADS)
Piskozub, Jacek; Gutowska, Dorota
2013-04-01
We use statistical analysis to show statistically significant relationship between the boreal winter MEI index of ENSO and HadCRUT3 temperature difference between Northern and Southern hemispheres (NH - SH) during the preceding summer. Correlation values increase (in absolute terms) if the correlated time periods are increased from month to seasonal length. For example December and January (DJ) MEI values anticorrelate stronger with the preceding MJJA period than with any of the four months taken separately. We believe this is further evidence that the correlation is caused by a real physical process as increase of the averaging period tends to reduce statistical noise. The motivation for looking for such a relationship comes from review of literature on paleoclimatic ENSO behavior. We have noticed that in many cases relatively cold NH coincided with "strong ENSO" (frequent El Niños), for example the Ice Age periods and Little Ice Age. On the other hand periods of relatively warm NH (the Holocene climate optimum or Medieval Climate Anomaly) are coincident with frequent or even "permanent" La Niñas. This relationship suggest the influence of the position of Intertropical Convergence Zone (ITCZ) on the frequency of El Niños. The simplest physical mechanism of the relationship is that the positive (negative) NH-SH temperature difference causes a north (south) shift of ITCZ with a parallel shift of trade wind zones. The North-South orographic difference between the Panama Isthmus and the South America may cause stronger (weaker) trade winds in Eastern Tropical Pacific increasing (decreasing) the thermochemical tilt which, in turn, causes a more negative (positive) ENSO values. Of course this may be only a first approximation of the real mechanism of this "teleconnection". The correlations we have found are not strong even if statistically significant. For example, the MJJA NH-SH temperature vs. DJ MEI correlation has r = -0.28 implying it explains only 8% of boreal
A Linear Stochastic Dynamical Model of ENSO. Part II: Analysis.
NASA Astrophysics Data System (ADS)
Thompson, C. J.; Battisti, D. S.
2001-02-01
In this study the behavior of a linear, intermediate model of ENSO is examined under stochastic forcing. The model was developed in a companion paper (Part I) and is derived from the Zebiak-Cane ENSO model. Four variants of the model are used whose stabilities range from slightly damped to moderately damped. Each model is run as a simulation while being perturbed by noise that is uncorrelated (white) in space and time. The statistics of the model output show the moderately damped models to be more realistic than the slightly damped models. The moderately damped models have power spectra that are quantitatively quite similar to observations, and a seasonal pattern of variance that is qualitatively similar to observations. All models produce ENSOs that are phase locked to the annual cycle, and all display the `spring barrier' characteristic in their autocorrelation patterns, though in the models this `barrier' occurs during the summer and is less intense than in the observations (inclusion of nonlinear effects is shown to partially remedy this deficiency). The more realistic models also show a decadal variability in the lagged autocorrelation pattern that is qualitatively similar to observations.Analysis of the models shows that the greatest part of the variability comes from perturbations that project onto the first singular vector, which then grow rapidly into the ENSO mode. Essentially, the model output represents many instances of the ENSO mode, with random phase and amplitude, stimulated by the noise through the optimal transient growth of the singular vectors.The limit of predictability for each model is calculated and it is shown that the more realistic (moderately damped) models have worse potential predictability (9-15 months) than the deterministic chaotic models that have been studied widely in the literature. The predictability limits are strongly correlated with the stability of the models' ENSO mode-the more highly damped models having much shorter
Shifting patterns of ENSO variability from a 492-year South Pacific coral core
NASA Astrophysics Data System (ADS)
Tangri, N.; Linsley, B. K.; Mucciarone, D.; Dunbar, R. B.
2017-12-01
Anticipating the impacts of ENSO in a changing climate requires detailed reconstructions of changes in its timing, amplitude, and spatial pattern, as well as attempts to attribute those changes to external forcing or internal variability. A continuous coral δ18O record from American Samoa, in the tropical South Pacific, sheds light on almost five centuries of these changes. We find evidence of internally-driven 50-100 year cycles with broad peaks of high variability punctuated by short transitions of low variability. We see a long, slow trend towards more frequent ENSO events, punctuated by sharp decreases in frequency; the 20th century in particular shows a strong trend towards higher-frequency ENSO. Due to the unique location of American Samoa with respect to ENSO sea surface temperature (SST) anomalies, we infer changes in the spatial pattern of ENSO. American Samoa currently lies on the ENSO 3.4 nodal line - the boomerang shape that separates waters warmed by El Niño from those that cool. Closer examination reveals that SST around American Samoa displays opposing responses to Eastern and Central Pacific ENSO events. However, this has not always been the case; in the late 19th and early 20th century, SST responded similarly to both flavors of ENSO. We interpret this to mean a geographic narrowing towards the equator of the eastern Pacific El Niño SST anomaly pattern in the first half of the 20th century.
Psychometric Characteristics of the Teen Addiction Severity Index-Two (T-ASI-2)
ERIC Educational Resources Information Center
Brodey, Benjamin B.; McMullin, Darcy; Kaminer, Yifrah; Winters, Ken C.; Mosshart, Edward; Rosen, Craig S.; Brodey, Inger S.
2008-01-01
The Teen Addiction Severity Index-Two (T-ASI-2) was developed as an extension of the T-ASI to assess the severity of substance abuse and related problems among adolescents (N = 371) 12-19 years of age. The T-ASI-2 consists of 18 domains that assess current use of alcohol, tobacco, marijuana, and other drugs, as well as mental health service…
T4 AsiA blocks DNA recognition by remodeling σ70 region 4
Lambert, Lester J; Wei, Yufeng; Schirf, Virgil; Demeler, Borries; Werner, Milton H
2004-01-01
Bacteriophage T4 AsiA is a versatile transcription factor capable of inhibiting host gene expression as an ‘anti-σ′ factor while simultaneously promoting gene-specific expression of T4 middle genes in conjunction with T4 MotA. To accomplish this task, AsiA engages conserved region 4 of Eschericia coli σ70, blocking recognition of most host promoters by sequestering the DNA-binding surface at the AsiA/σ70 interface. The three-dimensional structure of an AsiA/region 4 complex reveals that the C-terminal α helix of region 4 is unstructured, while four other helices adopt a completely different conformation relative to the canonical structure of unbound region 4. That AsiA induces, rather than merely stabilizes, this rearrangement can be realized by comparison to the homologous structures of region 4 solved in a variety of contexts, including the structure of Thermotoga maritima σA region 4 described herein. AsiA simultaneously occupies the surface of region 4 that ordinarily contacts core RNA polymerase (RNAP), suggesting that an AsiA-bound σ70 may also undergo conformational changes in the context of the RNAP holoenzyme. PMID:15257291
Asian Summer Monsoon Rainfall associated with ENSO and its Predictability
NASA Astrophysics Data System (ADS)
Shin, C. S.; Huang, B.; Zhu, J.; Marx, L.; Kinter, J. L.; Shukla, J.
2015-12-01
The leading modes of the Asian summer monsoon (ASM) rainfall variability and their seasonal predictability are investigated using the CFSv2 hindcasts initialized from multiple ocean analyses over the period of 1979-2008 and observation-based analyses. It is shown that the two leading empirical orthogonal function (EOF) modes of the observed ASM rainfall anomalies, which together account for about 34% of total variance, largely correspond to the ASM responses to the ENSO influences during the summers of the developing and decaying years of a Pacific anomalous event, respectively. These two ASM modes are then designated as the contemporary and delayed ENSO responses, respectively. It is demonstrated that the CFSv2 is capable of predicting these two dominant ASM modes up to the lead of 5 months. More importantly, the predictability of the ASM rainfall are much higher with respect to the delayed ENSO mode than the contemporary one, with the predicted principal component time series of the former maintaining high correlation skill and small ensemble spread with all lead months whereas the latter shows significant degradation in both measures with lead-time. A composite analysis for the ASM rainfall anomalies of all warm ENSO events in this period substantiates the finding that the ASM is more predictable following an ENSO event. The enhanced predictability mainly comes from the evolution of the warm SST anomalies over the Indian Ocean in the spring of the ENSO maturing phases and the persistence of the anomalous high sea surface pressure over the western Pacific in the subsequent summer, which the hindcasts are able to capture reasonably well. The results also show that the ensemble initialization with multiple ocean analyses improves the CFSv2's prediction skill of both ENSO and ASM rainfall. In fact, the skills of the ensemble mean hindcasts initialized from the four different ocean analyses are always equivalent to the best ones initialized from any individual ocean
ENSO in a warming world: interannual climate variability in the early Miocene Southern Hemisphere
NASA Astrophysics Data System (ADS)
Fox, Bethany; Wilson, Gary; Lee, Daphne
2016-04-01
The El Niño - Southern Oscillation (ENSO) is the dominant source of interannual variability in the modern-day climate system. ENSO is a quasi-periodic cycle with a recurrence interval of 2-8 years. A major question in modern climatology is how ENSO will respond to increased climatic warmth. ENSO-like (2-8 year) cycles have been detected in many palaeoclimate records for the Holocene. However, the temporal resolution of pre-Quaternary palaeoclimate archives is generally too coarse to investigate ENSO-scale variability. We present a 100-kyr record of ENSO-like variability during the second half of the Oligocene/Miocene Mi-1 event, a period of increasing global temperatures and Antarctic deglaciation (~23.032-2.93 Ma). This record is drawn from an annually laminated lacustrine diatomite from southern New Zealand, a region strongly affected by ENSO in the present day. The diatomite consists of seasonal alternations of light (diatom bloom) and dark (low diatom productivity) layers. Each light-dark couplet represents one year's sedimentation. Light-dark couplet thickness is characterised by ENSO-scale variability. We use high-resolution (sub-annual) measurements of colour spectra to detect couplet thickness variability. Wavelet analysis indicates that absolute values are modulated by orbital cycles. However, when orbital effects are taken into account, ENSO-like variability occurs throughout the entire depositional period, with no clear increase or reduction in relation to Antarctic deglaciation and increasing global warmth.
The Response of Tropical Tropospheric Ozone to ENSO
NASA Technical Reports Server (NTRS)
Oman, L. D.; Ziemke, J. R.; Douglass, A. R.; Waugh, D. W.; Lang, C.; Rodriguez, J. M.; Nielsen, J. E.
2011-01-01
We have successfully reproduced the Ozone ENSO Index (OEI) in the Goddard Earth Observing System (GEOS) chemistry-climate model (CCM) forced by observed sea surface temperatures over a 25-year period. The vertical ozone response to ENSO is consistent with changes in the Walker circulation. We derive the sensitivity of simulated ozone to ENSO variations using linear regression analysis. The western Pacific and Indian Ocean region shows similar positive ozone sensitivities from the surface to the upper troposphere, in response to positive anomalies in the Nino 3.4 Index. The eastern and central Pacific region shows negative sensitivities with the largest sensitivity in the upper troposphere. This vertical response compares well with that derived from SHADOZ ozonesondes in each region. The OEI reveals a response of tropospheric ozone to circulation change that is nearly independent of changes in emissions and thus it is potentially useful in chemistry-climate model evaluation.
Integration of ENSO Signal Power Through Hydrological Processes in the Little River Watershed
NASA Astrophysics Data System (ADS)
Keener, V. W.; Jones, J. W.; Bosch, D. D.; Cho, J.
2011-12-01
The relationship of the El-Nino/Southern Oscillation (ENSO) to hydrology is typically discussed in terms of the ability to separate significantly different hydrologic variable responses versus the anomaly that has taken place. Most of the work relating ENSO trends to proxy variables had been done on precipitation records until the mid 1990s, at which point increasing numbers of studies started to focus on ENSO relationships with streamflow as well as other environmental variables. The signals in streamflow are typically complex, representing the integration of both climatic, landscape, and anthropological responses that are able to strengthen the inherent ENSO signal in chaotic regional precipitation data. There is a need to identify climate non-stationarities related to ENSO and their links to watershed-scale outcomes. For risk-management in particular, inter-annual modes of climate variability and their seasonal expression are of interest. In this study, we analyze 36 years of historical monthly streamflow data from the Little River Watershed (LWR), a coastal plain ecosystem in Georgia, in conjunction with wavelet spectral analysis and modeling via the Soil & Water Assessment Tool (SWAT). Using both spectral and physical models allows us to identify the mechanism by which the ENSO signal power in surface and simulated groundwater flow is strengthened as compared to precipitation. The clear increase in the power of the inter-annual climate signal is demonstrated by shared patterns in water budget and exceedance curves, as well as in high ENSO related energy in the 95% significant wavelet spectra for each variable and the NINO 3.4 index. In the LRW, the power of the ENSO teleconnection is increased in both the observed and simulated stream flow through the mechanisms of groundwater flow and interflow, through confinement by a geological layer, the Hawthorn Formation. This non-intuitive relationship between ENSO signal strength and streamflow could prove to be
ENSO Related Interannual Lightning Variability from the Full TRMM LIS Lightning Climatology
NASA Technical Reports Server (NTRS)
Clark, Austin; Cecil, Daniel J.
2018-01-01
It has been shown that the El Nino/Southern Oscillation (ENSO) contributes to inter-annual variability of lightning production in the tropics and subtropics more than any other atmospheric oscillation. This study further investigated how ENSO phase affects lightning production in the tropics and subtropics. Using the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) and the Oceanic Nino Index (ONI) for ENSO phase, lightning data were averaged into corresponding mean annual warm, cold, and neutral 'years' for analysis of the different phases. An examination of the regional sensitivities and preliminary analysis of three locations was conducted using model reanalysis data to determine the leading convective mechanisms in these areas and how they might respond to the ENSO phases. These processes were then studied for inter-annual variance and subsequent correlation to ENSO during the study period to best describe the observed lightning deviations from year to year at each location.
ENSO-driven nutrient variability recorded by central equatorial Pacific corals
NASA Astrophysics Data System (ADS)
LaVigne, M.; Nurhati, I. S.; Cobb, K. M.; McGregor, H. V.; Sinclair, D. J.; Sherrell, R. M.
2012-12-01
Recent evidence for shifts in global ocean primary productivity suggests that surface ocean nutrient availability is a key link between global climate and ocean carbon cycling. Time-series records from satellite, in situ buoy sensors, and bottle sampling have documented the impact of the El Niño Southern Oscillation (ENSO) on equatorial Pacific hydrography and broad changes in biogeochemistry since the late 1990's, however, data are sparse prior to this. Here we use a new paleoceanographic nutrient proxy, coral P/Ca, to explore the impact of ENSO on nutrient availability in the central equatorial Pacific at higher-resolution than available from in situ nutrient data. Corals from Christmas (157°W 2°N) and Fanning (159°W 4°N) Islands recorded a well-documented decrease in equatorial upwelling as a ~40% decrease in P/Ca during the 1997-98 ENSO cycle, validating the application of this proxy to Pacific Porites corals. We compare the biogeochemical shifts observed through the 1997-98 event with two pre-TOGA-TAO ENSO cycles (1982-83 and 1986-87) reconstructed from a longer Christmas Island core. All three corals revealed ~30-40% P/Ca depletions during ENSO warming as a result of decreased regional wind stress, thermocline depth, and equatorial upwelling velocity. However, at the termination of each El Niño event, surface nutrients did not return to pre-ENSO levels for ~4-12 months after, SST as a result of increased biological draw down of surface nutrients. These records demonstrate the utility of high-resolution coral nutrient archives for understanding the impact of tropical Pacific climate on the nutrient and carbon cycling of this key region.
MJO influence on ENSO effects in precipitation and temperature over South America
NASA Astrophysics Data System (ADS)
Shimizu, M. H.; Bombardi, R. J.; Ambrizzi, T.
2013-12-01
Researches on the effects of the El Niño Southern Oscillation (ENSO) over precipitation and temperature, such as drought, flood, and anomalous high or cold temperatures, have great importance because of the impact of ENSO on the environment, society, and economy. Several studies have reported the influences of ENSO over South American precipitation and temperature climatological patterns, such as drier than normal conditions over northeast Brazil during the warm phase (El Niño) and wetter than normal conditions over northeast Brazil in the cold phase (La Niña). However, some recent studies focusing on the Northern Hemisphere have indicated that the basic response of ENSO is dependent on the phase of the Madden-Julian Oscillation (MJO). The MJO is characterized by the eastward propagation of the convection from Indian to Central Pacific Ocean and is related to variations in the position and intensity of the South Atlantic Convergence Zone (SACZ). The present work investigates the combined response of the phases of these two distinct phenomena, ENSO and MJO, over South America. Our goal is to explore the relative importance of the MJO to precipitation and temperature anomalies during ENSO events. MJO events were defined using the MJO index created by Jones and Carvalho (2012) based on empirical orthogonal functions analysis. ENSO phases were defined according to the Oceanic Niño Index provided by the National Oceanic and Atmospheric Administration (NOAA). A composite analysis with each combination of the phases of ENSO and MJO was performed to obtain the mean patterns of temperature and precipitation over South America for the months of November to March (austral summer). The results showed that the precipitation and temperature anomalies patterns observed during ENSO events, without the concurrent occurrence of the MJO, can be strengthened or weakened during events where ENSO and MJO occur simultaneously. Moreover, the effect on the anomalies patterns in these
DOE Office of Scientific and Technical Information (OSTI.GOV)
Bonfils, Céline; Anderson, Gemma; Santer, Benjamin D.
The 2011–16 California drought illustrates that drought-prone areas do not always experience relief once a favorable phase of El Niño–Southern Oscillation (ENSO) returns. In the twenty-first century, such an expectation is unrealistic in regions where global warming induces an increase in terrestrial aridity larger than the changes in aridity driven by ENSO variability. This premise is also flawed in areas where precipitation supply cannot offset the global warming–induced increase in evaporative demand. Here, atmosphere-only experiments are analyzed to identify land regions where aridity is currently sensitive to ENSO and where projected future changes in mean aridity exceed the range causedmore » by ENSO variability. Insights into the drivers of these changes in aridity are obtained using simulations with the incremental addition of three different factors to the current climate: ocean warming, vegetation response to elevated CO 2 levels, and intensified CO 2 radiative forcing. The effect of ocean warming overwhelms the range of ENSO-driven temperature variability worldwide, increasing potential evapotranspiration (PET) in most ENSO-sensitive regions. Additionally, about 39% of the regions currently sensitive to ENSO will likely receive less precipitation in the future, independent of the ENSO phase. Consequently aridity increases in 67%–72% of the ENSO-sensitive area. When both radiative and physiological effects are considered, the area affected by arid conditions rises to 75%–79% when using PET-derived measures of aridity, but declines to 41% when an aridity indicator for total soil moisture is employed. This reduction mainly occurs because plant stomatal resistance increases under enhanced CO 2 concentrations, resulting in improved plant water-use efficiency, and hence reduced evapotranspiration and soil desiccation. Imposing CO 2-invariant stomatal resistance may overestimate future drying in PET-derived indices.« less
Bonfils, Céline; Anderson, Gemma; Santer, Benjamin D.; ...
2017-07-27
The 2011–16 California drought illustrates that drought-prone areas do not always experience relief once a favorable phase of El Niño–Southern Oscillation (ENSO) returns. In the twenty-first century, such an expectation is unrealistic in regions where global warming induces an increase in terrestrial aridity larger than the changes in aridity driven by ENSO variability. This premise is also flawed in areas where precipitation supply cannot offset the global warming–induced increase in evaporative demand. Here, atmosphere-only experiments are analyzed to identify land regions where aridity is currently sensitive to ENSO and where projected future changes in mean aridity exceed the range causedmore » by ENSO variability. Insights into the drivers of these changes in aridity are obtained using simulations with the incremental addition of three different factors to the current climate: ocean warming, vegetation response to elevated CO 2 levels, and intensified CO 2 radiative forcing. The effect of ocean warming overwhelms the range of ENSO-driven temperature variability worldwide, increasing potential evapotranspiration (PET) in most ENSO-sensitive regions. Additionally, about 39% of the regions currently sensitive to ENSO will likely receive less precipitation in the future, independent of the ENSO phase. Consequently aridity increases in 67%–72% of the ENSO-sensitive area. When both radiative and physiological effects are considered, the area affected by arid conditions rises to 75%–79% when using PET-derived measures of aridity, but declines to 41% when an aridity indicator for total soil moisture is employed. This reduction mainly occurs because plant stomatal resistance increases under enhanced CO 2 concentrations, resulting in improved plant water-use efficiency, and hence reduced evapotranspiration and soil desiccation. Imposing CO 2-invariant stomatal resistance may overestimate future drying in PET-derived indices.« less
Decadal modulation of the relationship between intraseasonal tropical variability and ENSO
NASA Astrophysics Data System (ADS)
Gushchina, Daria; Dewitte, Boris
2018-05-01
The El Niño Southern Oscillation (ENSO) amplitude is modulated at decadal timescales, which, over the last decades, has been related to the low-frequency changes in the frequency of occurrence of the two types of El Niño events, that is the Eastern Pacific (EP) and Central Pacific (CP) El Niños. Meanwhile ENSO is tightly linked to the intraseasonal tropical variability (ITV) that is generally enhanced prior to El Niño development and can act as a trigger of the event. Here we revisit the ITV/ENSO relationship taking into account changes in ENSO properties over the last six decades. The focus is on two main components of ITV, the Madden-Julian Oscillation (MJO) and convectively coupled equatorial Rossby waves (ER). We show that the ITV/ENSO relationship exhibits a decadal modulation that is not related in a straight-forward manner to the change in occurrence of El Niño types and Pacific decadal modes. While enhanced MJO activity associated to EP El Niño development mostly took place over the period 1985-2000, the ER activity is enhanced prior to El Niño development over the whole period with a tendency to relate more to CP El Niño than to EP El Niño. In particular the relationship between ER activity and ENSO was particularly strong for the period 2000-2015, which results in a significant positive long-term trend of the predictive value of ER activity. The statistics of the MJO and ER activity is consistent with the hypothesis that they can be considered a state-dependent noise for ENSO linked to distinct lower frequency climate modes.
Indo-Pacific ENSO modes in a double-basin Zebiak-Cane model
NASA Astrophysics Data System (ADS)
Wieners, Claudia; de Ruijter, Will; Dijkstra, Henk
2016-04-01
We study Indo-Pacific interactions on ENSO timescales in a double-basin version of the Zebiak-Cane ENSO model, employing both time integrations and bifurcation analysis (continuation methods). The model contains two oceans (the Indian and Pacific Ocean) separated by a meridional wall. Interaction between the basins is possible via the atmosphere overlaying both basins. We focus on the effect of the Indian Ocean (both its mean state and its variability) on ENSO stability. In addition, inspired by analysis of observational data (Wieners et al, Coherent tropical Indo-Pacific interannual climate variability, in review), we investigate the effect of state-dependent atmospheric noise. Preliminary results include the following: 1) The background state of the Indian Ocean stabilises the Pacific ENSO (i.e. the Hopf bifurcation is shifted to higher values of the SST-atmosphere coupling), 2) the West Pacific cooling (warming) co-occurring with El Niño (La Niña) is essential to simulate the phase relations between Pacific and Indian SST anomalies, 3) a non-linear atmosphere is needed to simulate the effect of the Indian Ocean variability onto the Pacific ENSO that is suggested by observations.
NASA Astrophysics Data System (ADS)
Crétat, Julien; Terray, Pascal; Masson, Sébastien; Sooraj, K. P.; Roxy, Mathew Koll
2017-08-01
The relationship between the Indian Ocean and the Indian summer monsoon (ISM) and their respective influence over the Indo-Western North Pacific (WNP) region are examined in the absence of El Niño Southern Oscillation (ENSO) in two partially decoupled global experiments. ENSO is removed by nudging the tropical Pacific simulated sea surface temperature (SST) toward SST climatology from either observations or a fully coupled control run. The control reasonably captures the observed relationships between ENSO, ISM and the Indian Ocean Dipole (IOD). Despite weaker amplitude, IODs do exist in the absence of ENSO and are triggered by a boreal spring ocean-atmosphere coupled mode over the South-East Indian Ocean similar to that found in the presence of ENSO. These pure IODs significantly affect the tropical Indian Ocean throughout boreal summer, inducing a significant modulation of both the local Walker and Hadley cells. This meridional circulation is masked in the presence of ENSO. However, these pure IODs do not significantly influence the Indian subcontinent rainfall despite overestimated SST variability in the eastern equatorial Indian Ocean compared to observations. On the other hand, they promote a late summer cross-equatorial quadrupole rainfall pattern linking the tropical Indian Ocean with the WNP, inducing important zonal shifts of the Walker circulation despite the absence of ENSO. Surprisingly, the interannual ISM rainfall variability is barely modified and the Indian Ocean does not force the monsoon circulation when ENSO is removed. On the contrary, the monsoon circulation significantly forces the Arabian Sea and Bay of Bengal SSTs, while its connection with the western tropical Indian Ocean is clearly driven by ENSO in our numerical framework. Convection and diabatic heating associated with above-normal ISM induce a strong response over the WNP, even in the absence of ENSO, favoring moisture convergence over India.
ENSO and cholera: A nonstationary link related to climate change?
Rodó, Xavier; Pascual, Mercedes; Fuchs, George; Faruque, A. S. G.
2002-01-01
We present here quantitative evidence for an increased role of interannual climate variability on the temporal dynamics of an infectious disease. The evidence is based on time-series analyses of the relationship between El Niño/Southern Oscillation (ENSO) and cholera prevalence in Bangladesh (formerly Bengal) during two different time periods. A strong and consistent signature of ENSO is apparent in the last two decades (1980–2001), while it is weaker and eventually uncorrelated during the first parts of the last century (1893–1920 and 1920–1940, respectively). Concomitant with these changes, the Southern Oscillation Index (SOI) undergoes shifts in its frequency spectrum. These changes include an intensification of the approximately 4-yr cycle during the recent interval as a response to the well documented Pacific basin regime shift of 1976. This change in remote ENSO modulation alone can only partially serve to substantiate the differences observed in cholera. Regional or basin-wide changes possibly linked to global warming must be invoked that seem to facilitate ENSO transmission. For the recent cholera series and during specific time intervals corresponding to local maxima in ENSO, this climate phenomenon accounts for over 70% of disease variance. This strong association is discontinuous in time and can only be captured with a technique designed to isolate transient couplings. PMID:12228724
Global Terrestrial Water Storage Changes and Connections to ENSO Events
NASA Astrophysics Data System (ADS)
Ni, Shengnan; Chen, Jianli; Wilson, Clark R.; Li, Jin; Hu, Xiaogong; Fu, Rong
2018-01-01
Improved data quality of extended record of the Gravity Recovery and Climate Experiment (GRACE) satellite gravity solutions enables better understanding of terrestrial water storage (TWS) variations. Connections of TWS and climate change are critical to investigate regional and global water cycles. In this study, we provide a comprehensive analysis of global connections between interannual TWS changes and El Niño Southern Oscillation (ENSO) events, using multiple sources of data, including GRACE measurements, land surface model (LSM) predictions and precipitation observations. We use cross-correlation and coherence spectrum analysis to examine global connections between interannual TWS changes and the Niño 3.4 index, and select four river basins (Amazon, Orinoco, Colorado, and Lena) for more detailed analysis. The results indicate that interannual TWS changes are strongly correlated with ENSO over much of the globe, with maximum cross-correlation coefficients up to 0.70, well above the 95% significance level ( 0.29) derived by the Monte Carlo experiments. The strongest correlations are found in tropical and subtropical regions, especially in the Amazon, Orinoco, and La Plata basins. While both GRACE and LSM TWS estimates show reasonably good correlations with ENSO and generally consistent spatial correlation patterns, notably higher correlations are found between GRACE TWS and ENSO. The existence of significant correlations in middle-high latitudes shows the large-scale impact of ENSO on the global water cycle.
Mapping ENSO: Precipitation for the U.S. Affiliated Pacific Islands
NASA Astrophysics Data System (ADS)
Wright, E.; Price, J.; Kruk, M. C.; Luchetti, N.; Marra, J. J.
2015-12-01
The United States Affiliated Pacific Islands (USAPI) are highly susceptible to extreme precipitation events such as drought and flooding, which directly affect their freshwater availability. Precipitation distribution differs by sub-region, and is predominantly influenced by phases of the El Niño Southern Oscillation (ENSO). Forecasters currently rely on ENSO climatologies from sparse in situ station data to inform their precipitation outlooks. This project provided an updated ENSO-based climatology of long-term precipitation patterns for each USAPI Exclusive Economic Zone (EEZ) using the NOAA PERSIANN Climate Data Record (CDR). This data provided a 30-year record (1984-2015) of daily precipitation at 0.25° resolution, which was used to calculate monthly, seasonal, and yearly precipitation. Results indicated that while the PERSIANN precipitation accurately described the monthly, seasonal, and annual trends, it under-predicted the precipitation on the islands. Additionally, maps showing percent departure from normal (30 year average) were made for each three month season based on the Oceanic Niño Index (ONI) for five ENSO phases (moderate-strong El Niño and La Niña, weak El Niño and La Niña, and neutral). Local weather service offices plan on using these results and maps to better understand how the different ENSO phases influence precipitation patterns.
Biological consequences of ENSO: What have we learned recently?
NASA Astrophysics Data System (ADS)
Chavez, F.; Messié, M.
2013-12-01
A comprehensive theory regarding the biological response to El Niño was developed from observations during the 1982-83 event. The theory has withstood the test of time but additional information from remote sensing and growing in situ databases has allowed for a more comprehensive evaluation of the biological consequences of the full ENSO cycle on global scales and in relation to other climatic variability and change. Here we review the major developments over the past few decades that include a greater appreciation for the cool or La Niña phase and the relation of ENSO to other climatic variability including the Pacific Decadal Oscillation and the North Pacific Gyre Oscillation. The use of ENSO as an analog for biological consequences of a warmer world is also discussed.
Inter-model Diversity of ENSO simulation and its relation to basic states
NASA Astrophysics Data System (ADS)
Kug, J. S.; Ham, Y. G.
2016-12-01
In this study, a new methodology is developed to improve the climate simulation of state-of-the-art coupledglobal climate models (GCMs), by a postprocessing based on the intermodel diversity. Based on the closeconnection between the interannual variability and climatological states, the distinctive relation between theintermodel diversity of the interannual variability and that of the basic state is found. Based on this relation,the simulated interannual variabilities can be improved, by correcting their climatological bias. To test thismethodology, the dominant intermodel difference in precipitation responses during El Niño-SouthernOscillation (ENSO) is investigated, and its relationship with climatological state. It is found that the dominantintermodel diversity of the ENSO precipitation in phase 5 of the Coupled Model Intercomparison Project(CMIP5) is associated with the zonal shift of the positive precipitation center during El Niño. This dominantintermodel difference is significantly correlated with the basic states. The models with wetter (dryer) climatologythan the climatology of the multimodel ensemble (MME) over the central Pacific tend to shift positiveENSO precipitation anomalies to the east (west). Based on the model's systematic errors in atmosphericENSO response and bias, the models with better climatological state tend to simulate more realistic atmosphericENSO responses.Therefore, the statistical method to correct the ENSO response mostly improves the ENSO response. Afterthe statistical correction, simulating quality of theMMEENSO precipitation is distinctively improved. Theseresults provide a possibility that the present methodology can be also applied to improving climate projectionand seasonal climate prediction.
Dynamics of Monsoon-Induced Biennial Variability in ENSO
NASA Technical Reports Server (NTRS)
Kim, Kyu-Myong; Lau, K.-M.; Einaudi, Franco (Technical Monitor)
2000-01-01
The mechanism of the quasi-biennial tendency in El Nino Southern Oscillation (ENSO)-monsoon coupled system is investigated using an intermediate coupled model. The monsoon wind forcing is prescribed as a function of Sea Surface Temperature (SST) anomalies based on the relationship between zonal wind anomalies over the western Pacific to sea level change in the equatorial eastern Pacific. The key mechanism of quasi-biennial tendency in El Nino evolution is found to be in the strong coupling of ENSO to monsoon wind forcing over the western Pacific. Strong boreal summer monsoon wind forcing, which lags the maximum SST anomaly in the equatorial eastern Pacific approximately 6 months, tends to generate Kelvin waves of the opposite sign to anomalies in the eastern Pacific and initiates the turnabout in the eastern Pacific. Boreal winter monsoon forcing, which has zero lag with maximum SST in the equatorial eastern Pacific, tends to damp the ENSO oscillations.
The role of South Pacific atmospheric variability in the development of different types of ENSO
NASA Astrophysics Data System (ADS)
You, Yujia; Furtado, Jason C.
2017-07-01
Recent advances in tropical Pacific climate variability have focused on understanding the development of El Niño-Southern Oscillation (ENSO) events, specifically the types or "flavors" of ENSO (i.e., central versus eastern Pacific events). While precursors to ENSO events exist, distinguishing the particular flavor of the expected ENSO event remains unresolved. This study offers a new look at ENSO predictability using South Pacific atmospheric variability during austral winter as an indicator. The positive phase of the leading mode of South Pacific sea level pressure variability, which we term the South Pacific Oscillation (SPO), exhibits a meridional dipole with with a(n) (anti)cyclonic anomaly dominating the subtropics (extratropics/high latitudes). Once energized, the cyclonic anomalies in the subtropical node of the SPO weaken the southeasterly trade winds and promote the charging of the eastern equatorial Pacific Ocean, giving rise to eastern Pacific ENSO events. Indeed, the type of ENSO event can be determined accurately using only the magnitude and phase of the SPO during austral winter as a predictor (17 out of 23 cases). The SPO may also play a role in explaining the asymmetry of warm and cold events. Collectively, our findings present a new perspective on ENSO-South Pacific interactions that can advance overall understanding of the ENSO system and enhance its predictability across multiple timescales.
ENSO and PDO-related climate variability impacts on Midwestern United States crop yields.
Henson, Chasity; Market, Patrick; Lupo, Anthony; Guinan, Patrick
2017-05-01
An analysis of crop yields for the state of Missouri was completed to determine if an interannual or multidecadal variability existed as a result of the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). Corn and soybean yields were recorded in kilograms per hectare for each of the six climate regions of Missouri. An analysis using the Mokhov "method of cycles" demonstrated interannual, interdecadal, and multidecadal variations in crop yields. Cross-spectral analysis was used to determine which region was most impacted by ENSO and PDO influenced seasonal (April-September) temperature and precipitation. Interannual (multidecadal) variations found in the spectral analysis represent a relationship to ENSO (PDO) phase, while interdecadal variations represent a possible interaction between ENSO and PDO. Average crop yields were then calculated for each combination of ENSO and PDO phase, displaying a pronounced increase in corn and soybean yields when ENSO is warm and PDO is positive. Climate regions 1, 2, 4, and 6 displayed significant differences (p value of 0.10 or less) in yields between El Niño and La Niña years, representing 55-70 % of Missouri soybean and corn productivity, respectively. Final results give the opportunity to produce seasonal predictions of corn and soybean yields, specific to each climate region in Missouri, based on the combination of ENSO and PDO phases.
Tracking ENSO with tropical trees: Progress in stable isotope dendroclimatology
NASA Astrophysics Data System (ADS)
Evans, M. N.; Poussart, P. F.; Saleska, S. R.; Schrag, D. P.
2002-12-01
The terrestrial tropics remain an important gap in the growing proxy network used to characterize past ENSO behavior. Here we describe a strategy for development of proxy estimates of paleo-ENSO, via proxy rainfall estimates derived from stable isotope (δ18O) measurements made on tropical trees. The approach applies a new model of oxygen isotopic composition of alpha-cellulose (Roden et al., 2000), a rapid method for cellulose extraction from raw wood (Brendel et al., 2000), and continuous flow isotope ratio mass spectrometry (Brand, 1996) to develop proxy chronological, rainfall and growth rate estimates from tropical trees, even those lacking annual rings. The promise and pitfalls of the approach are illustrated in pilot datasets from the US, Costa Rica, Brazil, and Peru, which show isotopic cycles of 4-6 per mil, and interannual anomalies of up to 8 per mil. Together with the mature ENSO proxies (corals, extratropical tree-rings, varved sediments, and ice cores), replicated and well-dated stable isotope chronologies from tropical trees may eventually improve our understanding of ENSO history over the past several hundred years.
Dynamics and spatial structure of ENSO from re-analyses versus CMIP5 models
NASA Astrophysics Data System (ADS)
Serykh, Ilya; Sonechkin, Dmitry
2016-04-01
Basing on a mathematical idea about the so-called strange nonchaotic attractor (SNA) in the quasi-periodically forced dynamical systems, the currently available re-analyses data are considered. It is found that the El Niño - Southern Oscillation (ENSO) is driven not only by the seasonal heating, but also by three more external periodicities (incommensurate to the annual period) associated with the ~18.6-year lunar-solar nutation of the Earth rotation axis, ~11-year sunspot activity cycle and the ~14-month Chandler wobble in the Earth's pole motion. Because of the incommensurability of their periods all four forces affect the system in inappropriate time moments. As a result, the ENSO time series look to be very complex (strange in mathematical terms) but nonchaotic. The power spectra of ENSO indices reveal numerous peaks located at the periods that are multiples of the above periodicities as well as at their sub- and super-harmonic. In spite of the above ENSO complexity, a mutual order seems to be inherent to the ENSO time series and their spectra. This order reveals itself in the existence of a scaling of the power spectrum peaks and respective rhythms in the ENSO dynamics that look like the power spectrum and dynamics of the SNA. It means there are no limits to forecast ENSO, in principle. In practice, it opens a possibility to forecast ENSO for several years ahead. Global spatial structures of anomalies during El Niño and power spectra of ENSO indices from re-analyses are compared with the respective output quantities in the CMIP5 climate models (the Historical experiment). It is found that the models reproduce global spatial structures of the near surface temperature and sea level pressure anomalies during El Niño very similar to these fields in the re-analyses considered. But the power spectra of the ENSO indices from the CMIP5 models show no peaks at the same periods as the re-analyses power spectra. We suppose that it is possible to improve modeled
Sensitivity of ENSO teleconnections to a warming background state.
NASA Astrophysics Data System (ADS)
Drouard, Marie; Cassou, Christophe
2016-04-01
The sensitivity of ENSO teleconnections to the background state is investigated using two ensembles of coupled model experiments, one representative of the pre-industrial climate and the other one expected of the end of the 21st century based on the high emission RCP85 scenario. A 30-year period of representative ENSO events bearing resemblance to observed ones is a priori selected from a 850-year pre-industrial simulation of the CNRM-CM5 model. Following the so-called pacemaker protocol, new coupled experiments are carried with the model SST being restored in the eastern tropical Pacific towards the selected anomalies, the rest of the globe being fully coupled. In the first set of experiments, the anomalous restoring is applied on top of pre-industrial mean ocean state and in the second, on top of RCP85 mean state. Two sets of 10-member of 30-year long integrations are then generated. By construction, they share the exact same ENSO and thus make it possible to strictly isolate the dependence of the ENSO teleconnections to a warmer background state. Results confirm the eastward shift of the ENSO-induced deepening Aleutian low as documented in the literature for the winter season. They also show changes in the wintertime teleconnection over the North Atlantic. Several diagnostic tools (such as E-vectors) are used to investigate the dynamics of the teleconnection between the tropical Pacific, the North Pacific and dowstream towards the North Atlantic along the jet wave guide. A more indirect route based on the change in the Walker cell and associated signals in the tropical Atlantic leading to the excitation of forced Rossby wave is also analysed.
The increasing control of the Atlantic Ocean on ENSO after the early 1990s
NASA Astrophysics Data System (ADS)
Yu, J. Y.; Paek, H.; Wang, L.; Lyu, K.
2016-12-01
The El Niño-Southern Oscillation (ENSO) is the most powerful interannual variability in Earth's climate system. Previous studies have emphasized processes within the tropical Pacific or Indian Oceans for the generation of ENSO. Recent studies have increasingly suggested that the Atlantic Ocean may play an active role in forcing ENSO variability. In this talk, we will present evidence from observational analyses and modeling experiments to show that the Atlantic Ocean became more capable of influencing ENSO properties after the Atlantic Multidecadal Oscillation (AMO) changed to its positive phase in the early-1990s. A wave source mechanism is proposed to explain how the positive phase of the AMO can intensify the North Pacific Subtropical High (NPSH) to change the ENSO from the Eastern Pacific (EP) type to the Central Pacific (CP) type. A sequence of processes are identified to suggest that the AMO can displace the Pacific Walker circulation, induce a wave source in the tropical central Pacific, and excite a barotropic wave train toward higher-latitudes to enhance the NPSH, which then triggers subtropical Pacific atmospheric forcing and atmosphere-ocean coupling to increase the occurrence of the CP ENSO. An Atlantic capacitor mechanism is also proposed to explain how the positive phase of the AMO can intensify the quasi-biennial (QB) component of ENSO resulting in a more frequent occurrence of ENSO events. We will show that the capacitor mechanism works only after the AMO warmed up the Atlantic sea surface temperatures after the early-1990s. The increased feedback from the Atlantic to the Pacific has enabled the Atlantic capacitor mechanism to intensify the biennial variability in the Pacific during the past two decades. Our suggestion is very different from the previous prevailing views that have emphasized the Indo-Pacific Oceans as the pacemaker for the biennial variability in ENSO. The increasing control of the Atlantic has enabled the CP ENSO dynamics to
Using multi-resolution proxies to assess ENSO impacts on the mean state of the tropical Pacific.
NASA Astrophysics Data System (ADS)
Karamperidou, C.; Conroy, J. L.
2016-12-01
Observations and model simulations indicate that the relationship between ENSO and the mean state of the tropical Pacific is a two-way interaction. On one hand, a strong zonal SST gradient (dSST) in the Pacific (colder cold tongue) increases the potential intensity of upcoming ENSO events and may lead to increased ENSO variance. On the other hand, in a period of increased ENSO activity, large events can warm the cold tongue at decadal scales via residual heating, and thus lead to reduced zonal SST gradient (ENSO rectification mechanism). The short length of the observational record hinders our ability to confidently evaluate which mechanism dominates in each period, and whether it is sensitive to external climate forcing. This question is effectively a question of interaction between two timescales: interannual and decadal. Paleoclimate proxies of different resolutions can help elucidate this question, since they can be independent records of variability in these separate timescales. Here, we use coral proxies of ENSO variability from across the Pacific and multi-proxy records of dSST at longer timescales. Proxies, models, and observations indicate that in periods of increased ENSO activity, dSST is negatively correlated with ENSO variance at decadal timescales, indicating that strong ENSO events may affect the decadal mean state via warming the cold tongue. Using climate model simulations we attribute this effect to residual nonlinear dynamical heating, thus supporting the ENSO rectification mechanism. On the contrary, in periods without strong events, ENSO variance and dSST are positively correlated, which indicates that the primary mechanism at work is the effect of the mean state on ENSO. Our analysis also quantitatively identifies the regions where paleoclimate proxies are needed in order to reduce the existing uncertainties in ENSO-mean state interactions. Hence, this study is a synthesis of observations, model simulations and paleoclimate proxy evidence
Mean-state SST Response to global warming caused by the ENSO Nonlinearity
NASA Astrophysics Data System (ADS)
Kohyama, T.; Hartmann, D. L.
2017-12-01
The majority of the models that participated in the Coupled Model Intercomparison Project phase 5 (CMIP5) exhibit El Niño-like trends under global warming. GFDL-ESM2M, however, is an exception that exhibits a La Niña-like response with strengthened trade winds. Our previous studies have shown that this La Niña-like trend could be a physically consistent warming response, and we proposed the Nonlinear ENSO Warming Suppression (NEWS) mechanism to explain this La Niña-like response to global warming. The most important necessary condition of NEWS is the ENSO skewness (El Niños are stronger than La Niñas). Most CMIP5 models do not reproduce the observed ENSO skewness, while GFDL-ESM2M exhibits the realistic ENSO skewness, which suggests that, despite being in the minority, the La Niña-like trend of GFDL-ESM2M could be a plausible equatorial Pacific response to warming. In this study, we introduce another interesting outlier, MIROC5, which reproduces the observed skewness, yet exhibits an El Niño-like response. By decomposing the source of the ENSO nonlinearity into the following three components: "SST anomalies modulate winds", "winds excite oceanic waves", and "oceanic waves modulate the subsurface temperature", we show that the large inter-model spread of the third component appears to explain the most important cause of the poor reproducibility of the ENSO nonlinearity in CMIP5 models. It is concluded that the change in the response of subsurface temperature to oceanic waves is the primary explanation for the different warming response of GFDL-ESM2M and MIROC5. Our analyses suggest that the difference of the warming response are caused by difference in the climatological thermal stratification. This study may shed new light on the fundamental question of why observed ENSO has a strong skewness and on the implications of this skewed ENSO for the mean-state sea surface temperature response to global warming.
ENSO and hydrologic extremes in the western United States
Cayan, D.R.; Redmond, K.T.; Riddle, L.G.
1999-01-01
Frequency distributions of daily precipitation in winter and daily stream flow from late winter to early summer, at several hundred sites in the western United States, exhibit strong and systematic responses to the two phases of ENSO. Most of the stream flows considered are driven by snowmelt. The Southern Oscillation index (SOI) is used as the ENSO phase indicator. Both modest (median) and larger (90th percentile) events were considered. In years with negative SOI values (El Nino), days with high daily precipitation and stream flow are more frequent than average over the Southwest and less frequent over the Northwest. During years with positive SOI values (La Nina), a nearly opposite pattern is seen. A more pronounced increase is seen in the number of days exceeding climatological 90th percentile values than in the number exceeding climatological 50th percentile values, for both precipitation and stream flow. Stream flow responses to ENSO extremes are accentuated over precipitation responses. Evidence suggests that the mechanism for this amplification involves ENSO-phase differences in the persistence and duration of wet episodes, affecting the efficiency of the process by which precipitation is converted to runoff. The SOI leads the precipitation events by several months, and hydrologic lags (mostly through snowmelt) dealy the stream flow response by several more months. The combined 6-12 month predictive aspect of this relationship should be of significant benefit in responding to flood (or drought) risk and in improving overall water management in the western states.Frequency distributions of daily precipitation in winter and daily stream flow from late winter to early summer, at several hundred sites in the western United States, exhibit strong and systematic responses to the two phases of ENSO. Most of the stream flows considered are driven by snowmelt. The Southern Oscillation index (SOI) is used as the ENSO phase indicator. Both modest (median) and larger
Coupling between strong warm ENSO events and the phase of the stratospheric QBO.
NASA Astrophysics Data System (ADS)
Christiansen, Bo
2017-04-01
Although there in general are no significant long-term correlations between the QBO and the ENSO in observations we find that the QBO and the ENSO were aligned in the 3 to 4 years after the three strong warm ENSO events in 1982, 1997, and 2015. We study this possible connection between the QBO and the ENSO with a new version of the EC-Earth model which includes non-orographic gravity waves and a well modeled QBO. We analyze the modeled QBO in ensembles consisting of 10 AMIP-type experiments with climatological SSTs and 10 experiments with observed daily SSTs. The model experiments cover the period 1982-2013. For the ENSO we use the multivariate index (MEI). As expected the coherence is strong and statistically significant in the equatorial troposphere in the ensemble with observed SSTs. Here the coherence is a measure of the alignment of the ensemble members. In the ensemble with observed SSTs we find a strong and significant alignment of the ensemble members in the equatorial stratospheric winds in the 2 to 4 years after the strong ENSO event in 1997. This alignment also includes the observed QBO. No such alignment is found in the ensemble with climatological SSTs. These results indicate that strong warm ENSO events can directly influence the phase of the QBO. An open and maybe related question is what caused the anomalous QBO in 2016. This behaviour, which is unprecedented in the 50-60 years with data, has been described as a hiccup or a death-spiral. At least it is clear that in the last 18 months the QBO has been stuck in the same corner of the phase-space spanned by its two leading principal components. The possible connection to the ENSO will be investigated.
NASA Astrophysics Data System (ADS)
Chen, Sang; Hoffmann, Sharon S.; Lund, David C.; Cobb, Kim M.; Emile-Geay, Julien; Adkins, Jess F.
2016-05-01
The El Niño-Southern Oscillation (ENSO) is the primary driver of interannual climate variability in the tropics and subtropics. Despite substantial progress in understanding ocean-atmosphere feedbacks that drive ENSO today, relatively little is known about its behavior on centennial and longer timescales. Paleoclimate records from lakes, corals, molluscs and deep-sea sediments generally suggest that ENSO variability was weaker during the mid-Holocene (4-6 kyr BP) than the late Holocene (0-4 kyr BP). However, discrepancies amongst the records preclude a clear timeline of Holocene ENSO evolution and therefore the attribution of ENSO variability to specific climate forcing mechanisms. Here we present δ18 O results from a U-Th dated speleothem in Malaysian Borneo sampled at sub-annual resolution. The δ18 O of Borneo rainfall is a robust proxy of regional convective intensity and precipitation amount, both of which are directly influenced by ENSO activity. Our estimates of stalagmite δ18 O variance at ENSO periods (2-7 yr) show a significant reduction in interannual variability during the mid-Holocene (3240-3380 and 5160-5230 yr BP) relative to both the late Holocene (2390-2590 yr BP) and early Holocene (6590-6730 yr BP). The Borneo results are therefore inconsistent with lacustrine records of ENSO from the eastern equatorial Pacific that show little or no ENSO variance during the early Holocene. Instead, our results support coral, mollusc and foraminiferal records from the central and eastern equatorial Pacific that show a mid-Holocene minimum in ENSO variance. Reduced mid-Holocene interannual δ18 O variability in Borneo coincides with an overall minimum in mean δ18 O from 3.5 to 5.5 kyr BP. Persistent warm pool convection would tend to enhance the Walker circulation during the mid-Holocene, which likely contributed to reduced ENSO variance during this period. This finding implies that both convective intensity and interannual variability in Borneo are driven by
A possible explanation for the divergent projection of ENSO amplitude change under global warming
NASA Astrophysics Data System (ADS)
Chen, Lin; Li, Tim; Yu, Yongqiang; Behera, Swadhin K.
2017-12-01
The El Niño-Southern Oscillation (ENSO) is the greatest climate variability on interannual time scale, yet what controls ENSO amplitude changes under global warming (GW) is uncertain. Here we show that the fundamental factor that controls the divergent projections of ENSO amplitude change within 20 coupled general circulation models that participated in the Coupled Model Intercomparison Project phase-5 is the change of climatologic mean Pacific subtropical cell (STC), whose strength determines the meridional structure of ENSO perturbations and thus the anomalous thermocline response to the wind forcing. The change of the thermocline response is a key factor regulating the strength of Bjerknes thermocline and zonal advective feedbacks, which ultimately lead to the divergent changes in ENSO amplitude. Furthermore, by forcing an ocean general circulation mode with the change of zonal mean zonal wind stress estimated by a simple theoretical model, a weakening of the STC in future is obtained. Such a change implies that ENSO variability might strengthen under GW, which could have a profound socio-economic consequence.
ENSO impacts on flood risk at the global scale
NASA Astrophysics Data System (ADS)
Ward, Philip; Dettinger, Michael; Jongman, Brenden; Kummu, Matti; Winsemius, Hessel
2014-05-01
We present the impacts of El Niño Southern Oscillation (ENSO) on society and the economy, via relationships between ENSO and the hydrological cycle. We also discuss ways in which this knowledge can be used in disaster risk management and risk reduction. This contribution provides the most recent results of an ongoing 4-year collaborative research initiative to assess and map the impacts of large scale interannual climate variability on flood hazard and risk at the global scale. We have examined anomalies in flood risk between ENSO phases, whereby flood risk is expressed in terms of indicators such as: annual expected damage; annual expected affected population; annual expected affected Gross Domestic Product (GDP). We show that large anomalies in flood risk occur during El Niño or La Niña years in basins covering large parts of the Earth's surface. These anomalies reach statistical significance river basins covering almost two-thirds of the Earth's surface. Particularly strong anomalies exist in southern Africa, parts of western Africa, Australia, parts of Central Eurasia (especially for El Niño), the western USA (especially La Niña anomalies), and parts of South America. We relate these anomalies to possible causal relationships between ENSO and flood hazard, using both modelled and observed data on flood occurrence and extremity. The implications for flood risk management are many-fold. In those regions where disaster risk is strongly influenced by ENSO, the potential predictably of ENSO could be used to develop probabilistic flood risk projections with lead times up to several seasons. Such data could be used by the insurance industry in managing risk portfolios and by multinational companies for assessing the robustness of their supply chains to potential flood-related interruptions. Seasonal forecasts of ENSO influence of peak flows could also allow for improved flood early warning and regulation by dam operators, which could also reduce overall risks
The role of Indonesian convection in the interaction between the Indian Ocean and ENSO
NASA Astrophysics Data System (ADS)
Wieners, Claudia; Dijkstra, Henk; de Ruijter, Will
2017-04-01
In recent years it has been discussed whether a cool West Indian Ocean (WIO) or negative Indian Ocean Dipole (IOD) in boreal autumn favours El Niño at a lead time of 15 months (Izumo et al, 2010; Wieners et al, 2016). Observational evidence suggests that a cool WIO or negative IOD might be accompanied by easterlies over the West Pacific, though it is hard to disentangle influences of the Indian Ocean and ENSO through data analysis. Such easterlies can enhance the West Pacific Warm Water Volume, thus favouring El Niño development from the following boreal spring onward. However, the Gill response to a cool WIO (negative IOD) forcing would lead to westerly (nearly zero) winds over the WPO. We hypothesise that a cool WIO or negative IOD leads to low-level air convergence and hence enhanced convectional heating over the Maritime Continent (MC), which in turn amplifies the wind convergence such as to cause easterly winds over the West Pacific. This hypothesis is tested by adding a simplified Indian Ocean and a simple convective feedback over the MC to a Zebiak-Cane model. We confirm that for a sufficiently strong convection feedback a cool WIO or negative IOD indeed leads to easterlies over the WPO. The response IO cooling over the whole zonal width of the basin (negative Indian Ocean Basinwide warming / IOB) is still westerly, with the direct Gill response dominating over convection-induced winds. Positive (negative) IOB events typically occur a few months after El Niño (La Niña) - observed correlations are about 0.9 - and cause easterlies (westerlies) over the Pacific, facilitating the switch to the opposite ENSO phase, hence IOB variability dampens the ENSO mode and reduces its period. The IOD, on the other hand, tends to be positive (negative) a few months prior to El Niño (La Niña) and trigger westerlies (easterlies) favouring ENSO development. However, the observed correlation between IOD and ENSO is only about 0.6, i.e. the IOD is less closely liked to the
Recent Status Scores for Version 6 of the Addiction Severity Index (ASI-6)
Cacciola, John S.; Alterman, Arthur I; Habing, Brian; McLellan, A. Thomas
2012-01-01
Aims To describe the derivation of Recent Status Scores (RSSs) for Version 6 of the Addiction Severity Index (ASI-6). Design 118 ASI-6 recent status items were subjected to nonparametric item response theory (NIRT) analyses followed by confirmatory factor analysis (CFA). Generalizability and concurrent validity of the derived scores were determined. Setting and Participants 607 recent admissions to variety of substance abuse treatment programs constituted the derivation sample; a subset (N = 254) comprised the validity sample. Measurements The ASI-6 interview and a validity battery of primarily self-report questionnaires that included at least one measure corresponding to each of the seven ASI domains were administered. Findings Nine summary scales describing recent status that achieved or approached both high scalability and reliability were derived; one scale for each of six areas (medical, employment/finances, alcohol, drug, legal, psychiatric), and three scales for the family/social area. Intercorrelations among the RSSs also supported the multidimensionality of the ASI-6. Concurrent validity analyses yielded strong evidence supporting the validity of the six of the RSSs (Medical, Alcohol, Drug, Employment, Family/Social Problems, Psychiatric). Evidence was weaker for the Legal, Family/Social Support and Child Problems RSSs. Generalizability analyses of the scales to males versus females and whites versus blacks supported the comparability of the findings with slight exceptions. Conclusions The psychometric analyses to derive Addiction Severity Index-6 Recent Status Scores (RSSs) support the multidimensionality of the ASI-6 (i.e., the relative independence of different life functioning areas), consistent with research on earlier editions of the instrument. In general, the ASI-6 scales demonstrate acceptable scalability, reliability and concurrent validity. While questions remain about the generalizability of some scales to population subgroups, the overall
Role of tropical Indian and Atlantic Oceans variability on ENSO
NASA Astrophysics Data System (ADS)
Prodhomme, Chloé; Terray, Pascal; Masson, Sebastien; Boschat, Ghyslaine
2014-05-01
There are strong evidences of an interaction between tropical Indian, Atlantic and Pacific Oceans. Nevertheless, these interactions remain deeply controversial. While some authors claim the tropical Indian and Atlantic oceans only play a passive role with respect to ENSO, others suggest a driving role for these two basins on ENSO. The mecanisms underlying these relations are not fully understood and, in the Indian Ocean, the possible role of both modes of tropical variability (the Indian Ocean Dipole (IOD) and the Indian Ocean Basin mode (IOB)) remain unclear. To better quantify and understand how the variability of the tropical Indian and Atlantic Oceans impact ENSO variability, we performed two sensitivity experiments using the SINTEX-F2 coupled model. For each experiment, we suppressed the variability of SST and the air-sea coupling in either the tropical Indian Ocean or tropical Atlantic Ocean by applying a strong nudging of the SST to the observed SST climatology. In both experiments, the ENSO periodicity increases. In the Atlantic experiment, our understanding of this increased periodicity is drastically limited by the strongly biased mean state in this region. Conversely, in the Indian Ocean experiment, the increase of ENSO periodicity is related to the absence of the IOB following the El Niño peak, which leads to a decrease of westerly winds in the western Pacific during late winter and spring after the peak. These weaker westerlies hinders the transition to a La Niña phase and thus increase the duration and periodicity of the event.
ENSO Bred Vectors in Coupled Ocean-Atmosphere General Circulation Models
NASA Technical Reports Server (NTRS)
Yang, S. C.; Cai, Ming; Kalnay, E.; Rienecker, M.; Yuan, G.; Toth, ZA.
2004-01-01
The breeding method has been implemented in the NASA Seasonal-to-Interannual Prediction Project (NSIPP) Coupled General Circulation Model (CGCM) with the goal of improving operational seasonal to interannual climate predictions through ensemble forecasting and data assimilation. The coupled instability as cap'tured by the breeding method is the first attempt to isolate the evolving ENSO instability and its corresponding global atmospheric response in a fully coupled ocean-atmosphere GCM. Our results show that the growth rate of the coupled bred vectors (BV) peaks at about 3 months before a background ENSO event. The dominant growing BV modes are reminiscent of the background ENSO anomalies and show a strong tropical response with wind/SST/thermocline interrelated in a manner similar to the background ENSO mode. They exhibit larger amplitudes in the eastern tropical Pacific, reflecting the natural dynamical sensitivity associated with the presence of the shallow thermocline. Moreover, the extratropical perturbations associated with these coupled BV modes reveal the variations related to the atmospheric teleconnection patterns associated with background ENSO variability, e.g. over the North Pacific and North America. A similar experiment was carried out with the NCEP/CFS03 CGCM. Comparisons between bred vectors from the NSIPP CGCM and NCEP/CFS03 CGCM demonstrate the robustness of the results. Our results strongly suggest that the breeding method can serve as a natural filter to identify the slowly varying, coupled instabilities in a coupled GCM, which can be used to construct ensemble perturbations for ensemble forecasts and to estimate the coupled background error covariance for coupled data assimilation.
Discriminative and Criterion Validity of the Autism Spectrum Identity Scale (ASIS)
ERIC Educational Resources Information Center
McDonald, T. A. M.
2017-01-01
Individuals on the autism spectrum face stigma that can influence identity development. Previous research on the 22-item Autism Spectrum Identity Scale (ASIS) reported a four-factor structure with strong split-sample cross-validation and good internal consistency. This study reports the discriminative and criterion validity of the ASIS with other…
Identification of symmetric and asymmetric responses in seasonal streamflow globally to ENSO phase
NASA Astrophysics Data System (ADS)
Lee, Donghoon; Ward, Philip J.; Block, Paul
2018-04-01
The phase of the El Niño Southern Oscillation (ENSO) has large-ranging effects on streamflow and hydrologic conditions globally. While many studies have evaluated this relationship through correlation analysis between annual streamflow and ENSO indices, an assessment of potential asymmetric relationships between ENSO and streamflow is lacking. Here, we evaluate seasonal variations in streamflow by ENSO phase to identify asymmetric (AR) and symmetric (SR) spatial pattern responses globally and further corroborate with local precipitation and hydrological condition. The AR and SR patterns between seasonal precipitation and streamflow are identified at many locations for the first time. Our results identify strong SR patterns in particular regions including northwestern and southern US, northeastern and southeastern South America, northeastern and southern Africa, southwestern Europe, and central-south Russia. The seasonally lagged anomalous streamflow patterns are also identified and attributed to snowmelt, soil moisture, and/or cumulative hydrological processes across river basins. These findings may be useful in water resources management and natural hazards planning by better characterizing the propensity of flood or drought conditions by ENSO phase.
Reduced ENSO Variability at the LGM Revealed by an Isotope-enabled Earth System Model
NASA Astrophysics Data System (ADS)
Zhu, J.; Liu, Z.; Otto-Bliesner, B. L.; Brady, E. C.; Noone, D.; Zhang, J.; Tomas, R. A.; Jahn, A.; Nusbaumer, J. M.; Wong, T. E.
2016-12-01
El Nino-Southern Oscillation (ENSO) is the most important climate variability at interannual timescale, greatly affecting the weather and climate worldwide. Studying the ENSO at the Last Glacial Maximum (LGM, 21 kyrs before present) can help us better understand its dynamics and improve its projections under anthropogenic global warming. However, both numerical simulations and paleoclimate reconstructions show contradicting results among themselves, e.g., using the Individual Foraminifera Analysis (IFA) approach, some paleo-records suggest an amplified ENSO at the LGM relative to present day; while others indicate a weakened ENSO. These contradictions are hard to explore using traditional climate models due to the indirect nature of model-data comparison: numerical models usually simulate variations in climate state variables (e.g., temperature); while reconstructions can only use proxies (e.g., water isotopes) to infer changes in these state variables. Here we employ the recently developed isotope-enabled Community Earth System Model (iCESM) to study the ENSO strength at the LGM and attempt to provide a consistent picture between climate model and different reconstructions. We find that ENSO at the LGM is about 30% weaker than that of the preindustrial in iCESM, primarily attributable to the weakened atmosphere-ocean coupled feedbacks in a colder climate with a deeper thermocline. With the capability of simulating water isotopes, our model demonstrates that total variance recorded by the IFA water-isotope records in the eastern equatorial Pacific (e.g., Core CD21-30) could actually increase because of an intensified annual cycle, instead of an amplified ENSO. Furthermore, our isotope-enabled simulations suggest that caution should be applied when interpreting the subsurface IFA water-isotope records (e.g., Cores CD38-17P and MD02-2529) due to the wide spread of habitat depth of thermocline-dwelling foraminifera and their possible migration with temporally varying
NASA Astrophysics Data System (ADS)
Kim, Ji-Won; An, Soon-Il; Jun, Sang-Yoon; Park, Hey-Jin; Yeh, Sang-Wook
2017-08-01
Using observational datasets and numerical model experiments, the mechanism on the slowly varying change in the relationship between the El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) is investigated. The decadal-window (11-, 15-, and 21-year) moving correlations show a significant change in the boreal wintertime ENSO-EAWM relationship between two sub-periods of 1976‒1992 and 1997‒2013. Such recent change in ENSO-EAWM relationship is mainly attributed to the changes in the intensity and zonal location of the anomalous lower-tropospheric northwest Pacific anticyclone (NWP-AC). NWP-AC commonly develops near the region of the Philippine Sea during the ENSO's peak phase and plays an important role of bridging the tropical convection and mid-latitude teleconnection. On one hand, the intensity of the NWP-AC is influenced by the interdecadal variation in a linkage between ENSO and the Indian Ocean sea surface temperature (SST) variability, referring that a strong connection between the Pacific and Indian Oceans results in the strengthening of NWP-AC response to ENSO. On the other hand, the zonal displacement of the NWP-AC is associated with the Pacific Decadal Oscillation (PDO) and the Atlantic Multidecadal Oscillation (AMO). That is, the tropical Pacific mean state (i.e., zonal SST gradient between climatologically warm western Pacific and cold eastern Pacific)—strengthened by either the negative PDO phase or the positive AMO phase—drives the anomalous ENSO-induced convection to be shifted to the west. With this westward shift, the zonal center of the NWP-AC also migrates westward over the Philippine Islands and exerts stronger connection between ENSO and EAWM. In contrast, the relaxed zonal SST contrast associated with either the positive PDO phase or the negative AMO phase tends to exhibit weaker ENSO-EAWM relationship via both of eastward shifted zonal centers of the anomalous ENSO-induced convection and the NWP-AC. Finally, a
Modulation of ENSO evolution by strong tropical volcanic eruptions
NASA Astrophysics Data System (ADS)
Wang, Tao; Guo, Dong; Gao, Yongqi; Wang, Huijun; Zheng, Fei; Zhu, Yali; Miao, Jiapeng; Hu, Yongyun
2017-11-01
The simulated responses of the El Niño-Southern Oscillation (ENSO) to volcanic forcings are controversial, and some mechanisms of these responses are not clear. We investigate the impacts of volcanic forcing on the ENSO using a long-term simulation covering 1400-1999 as simulated by the Bergen Climate Model (BCM) and a group of simulations performed with the Community Atmosphere Model version 4.0 (CAM4) and the BCM's ocean component Miami Isopycanic Coordinated Ocean Model (MICOM). The analysis of the long-term BCM simulation indicates that ENSO has a negative-positive-negative response to strong tropical volcanic eruptions (SVEs), which corresponds to the different stages of volcanic forcing. In the initial forcing stage, a brief and weak La Niña-like response is caused by the cooling along the west coast of the South American continent and associated enhancement of the trade winds. In the peak forcing stage, westerly wind anomalies are excited by both reduced east-west sea level pressure gradients and weakened and equatorward shifted tropical convergence zones. These westerly wind anomalies extend to the equatorial eastern Pacific, leading to an El Niño-like response. At the same time, easterly wind anomalies west of 120°E and strong cooling effects can promote a discharged thermocline state and excite an upwelling Kelvin wave in the western Pacific. In the declining forcing stage, forced by the recovered trade winds, the upwelling Kelvin wave propagates eastward and reaches the equatorial eastern Pacific. Through the Bjerknes feedback, a strong and temporally extended La Niña-like response forms. Additional CAM4 simulations suggest a more important role of the surface cooling over the Maritime Continent and surrounding ocean in shaping the westerly wind anomalies over the equatorial central-eastern Pacific and the easterly wind anomalies west of 120° E, which are key to causing the El Niño-like responses and subsequent La Niña-like responses
Structural properties of a-Si films and their effect on aluminum induced crystallization
DOE Office of Scientific and Technical Information (OSTI.GOV)
Tankut, Aydin; Ozkol, Engin; Karaman, Mehmet
2015-10-15
In this paper, we report the influence of the structural properties of amorphous silicon (a-Si) on its subsequent crystallization behavior via the aluminum induced crystallization (AIC) method. Two distinct a-Si deposition techniques, electron beam evaporation and plasma enhanced chemical vapor deposition (PECVD), are compared for their effect on the overall AIC kinetics as well as the properties of the final poly-crystalline (poly-Si) silicon film. Raman and FTIR spectroscopy results indicate that the PECVD grown a-Si films has higher intermediate-range order, which is enhanced for increased hydrogen dilution during deposition. With increasing intermediate-range order of the a-Si, the rate of AICmore » is diminished, leading larger poly-Si grain size.« less
Reduced ENSO Variability at the LGM Revealed by an Isotope-Enabled Earth System Model
NASA Technical Reports Server (NTRS)
Zhu, Jiang; Liu, Zhengyu; Brady, Esther; Otto-Bliesner, Bette; Zhang, Jiaxu; Noone, David; Tomas, Robert; Nusbaumer, Jesse; Wong, Tony; Jahn, Alexandra;
2017-01-01
Studying the El Nino Southern Oscillation (ENSO) in the past can help us better understand its dynamics and improve its future projections. However, both paleoclimate reconstructions and model simulations of ENSO strength at the Last Glacial Maximum (LGM; 21 ka B.P.) have led to contradicting results. Here we perform model simulations using the recently developed water isotope-enabled Community Earth System Model (iCESM). For the first time, model-simulated oxygen isotopes are directly compared with those from ENSO reconstructions using the individual foraminifera analysis (IFA). We find that the LGM ENSO is most likely weaker comparing with the preindustrial. The iCESM suggests that total variance of the IFA records may only reflect changes in the annual cycle instead of ENSO variability as previously assumed. Furthermore, the interpretation of subsurface IFA records can be substantially complicated by the habitat depth of thermocline-dwelling foraminifera and their vertical migration with a temporally varying thermocline.
On the role of ozone feedback in the ENSO amplitude response under global warming.
Nowack, Peer J; Braesicke, Peter; Luke Abraham, N; Pyle, John A
2017-04-28
The El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean is of key importance to global climate and weather. However, state-of-the-art climate models still disagree on the ENSO's response under climate change. The potential role of atmospheric ozone changes in this context has not been explored before. Here we show that differences between typical model representations of ozone can have a first-order impact on ENSO amplitude projections in climate sensitivity simulations. The vertical temperature gradient of the tropical middle-to-upper troposphere adjusts to ozone changes in the upper troposphere and lower stratosphere, modifying the Walker circulation and consequently tropical Pacific surface temperature gradients. We show that neglecting ozone changes thus results in a significant increase in the number of extreme ENSO events in our model. Climate modeling studies of the ENSO often neglect changes in ozone. We therefore highlight the need to understand better the coupling between ozone, the tropospheric circulation, and climate variability.
On the role of ozone feedback in the ENSO amplitude response under global warming
NASA Astrophysics Data System (ADS)
Nowack, P. J.; Braesicke, P.; Abraham, N. L.; Pyle, J. A.
2017-12-01
The El Niño-Southern Oscillation (ENSO) in the tropical Pacific is of key importance to global climate and weather. However, climate models still disagree on the ENSO's response under climate change. Here we show that typical model representations of ozone can have a first-order impact on ENSO amplitude projections in climate sensitivity simulations (i.e. standard abrupt 4xCO2). We mainly explain this effect by the lapse rate adjustment of the tropical troposphere to ozone changes in the upper troposphere and lower stratosphere (UTLS) under 4xCO2. The ozone-induced lapse rate changes modify the Walker circulation response to the CO2 forcing and consequently tropical Pacific surface temperature gradients. Therefore, not including ozone feedbacks increases the number of extreme ENSO events in our model. In addition, we demonstrate that even if ozone changes in the tropical UTLS are included in the simulations, the neglect of the ozone response in the middle-upper stratosphere still leads to significantly larger ENSO amplitudes (compared to simulations run with a fully interactive atmospheric chemistry scheme). Climate modeling studies of the ENSO often neglect changes in ozone. Our results imply that this could affect the inter-model spread found in ENSO projections and, more generally, surface climate change simulations. We discuss the additional complexity in quantifying such ozone-related effects that arises from the apparent model dependency of chemistry-climate feedbacks and, possibly, their range of surface climate impacts. In conclusion, we highlight the need to understand better the coupling between ozone, the tropospheric circulation, and climate variability. Reference: Nowack PJ, Braesicke P, Abraham NL, and Pyle JA (2017), On the role of ozone feedback in the ENSO amplitude response under global warming, Geophys. Res. Lett. 44, 3858-3866, doi:10.1002/2016GL072418.
The ENSO-pandemic influenza connection: coincident or causal?
NASA Astrophysics Data System (ADS)
Shaman, J. L.; Lipsitch, M.
2011-12-01
The El Niño-Southern Oscillation (ENSO) is a coupled ocean-atmosphere system in the tropical Pacific, which affects weather conditions, including temperatures, precipitation, winds and storm activity, across the planet. ENSO has two extreme phases marked by either warmer (El Niño) or cooler (La Niña) than average sea surface temperatures in the central equatorial Pacific. We find that the 4 most recent human influenza pandemics (1918, 1957, 1968, 2009), all of which were first identified in boreal spring or summer, were preceded by La Niña conditions in the equatorial Pacific. Changes in ENSO 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.
Ocean Chlorophyll as a Precursor of ENSO: An Earth System Modeling Study
NASA Astrophysics Data System (ADS)
Park, Jong-Yeon; Dunne, John P.; Stock, Charles A.
2018-02-01
Ocean chlorophyll concentration, a proxy for phytoplankton, is strongly influenced by internal ocean dynamics such as those associated with El Niño-Southern Oscillation (ENSO). Observations show that ocean chlorophyll responses to ENSO generally lead sea surface temperature (SST) responses in the equatorial Pacific. A long-term global Earth system model simulation incorporating marine biogeochemical processes also exhibits a preceding chlorophyll response. In contrast to simulated SST anomalies, which significantly lag the wind-driven subsurface heat response to ENSO, chlorophyll anomalies respond rapidly. Iron was found to be the key factor connecting the simulated surface chlorophyll anomalies to the subsurface ocean response. Westerly wind bursts decrease central Pacific chlorophyll by reducing iron supply through wind-driven thermocline deepening but increase western Pacific chlorophyll by enhancing the influx of coastal iron from the maritime continent. Our results mechanistically support the potential for chlorophyll-based indices to inform seasonal ENSO forecasts beyond previously identified SST-based indices.
NASA Astrophysics Data System (ADS)
Ren, Rongcai; Rao, Jian; Wu, Guoxiong; Cai, Ming
2017-05-01
The concurrent effects of the El Niño-Southern Oscillation (ENSO) on the northern winter stratosphere have been widely recognized; however, the delayed effects of ENSO in the next winter after mature ENSO have yet to be confirmed in multi reanalyses and model simulations. This study uses three reanalysis datasets, a long-term fully coupled model simulation, and a high-top general circulation model to examine ENSO's delayed effects in the stratosphere. The warm-minus-cold composite analyses consistently showed that, except those quick-decaying quasi-biennial ENSO events that reverse signs during July-August-September (JAS) in their decay years, ENSO events particularly those quasi-quadrennial (QQ) that persist through JAS, always have a significant effect on the extratropical stratosphere in both the concurrent winter and the next winter following mature ENSO. During the concurrent winter, the QQ ENSO-induced Pacific-North American (PNA) pattern corresponds to an anomalous wavenumber-1 from the upper troposphere to the stratosphere, which acts to intensify/weaken the climatological wave pattern during warm/cold ENSO. Associated with the zonally quasi-homogeneous tropical forcing in spring of the QQ ENSO decay years, there appear persistent and zonally quasi-homogeneous temperature anomalies in the midlatitudes from the upper troposphere to the lower stratosphere until summer. With the reduction in ENSO forcing and the PNA responses in the following winter, an anomalous wavenumber-2 prevails in the extratropics. Although the anomalous wave flux divergence in the upper stratospheric layer is still dominated by wavenumber-1, it is mainly caused by wavenumber-2 in the lower stratosphere. However, the wavenumber-2 activity in the next winter is always underestimated in the model simulations, and wavenumber-1 activity dominates in both winters.
El Nino, La Nina, ENSO | National Oceanic and Atmospheric Administration
your local weather Enter your ZIP code GO Enter Search Terms El Nino, La Nina, ENSO Content La Nina is gone, for now May 10, 2018 More On El Nino, La Nina, ENSO Ocean surface temperatures in April 2018 compared to the 1981-2010 average. What's going on with La Niña? March 22, 2018 More On El Nino, La Nina
Global land carbon sink response to temperature and precipitation varies with ENSO phase
Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.; ...
2017-06-01
Climate variability associated with the El Niño-Southern Oscillation (ENSO) and its consequent impacts on land carbon sink interannual variability have been used as a basis for investigating carbon cycle responses to climate variability more broadly, and to inform the sensitivity of the tropical carbon budget to climate change. Past studies have presented opposing views about whether temperature or precipitation is the primary factor driving the response of the land carbon sink to ENSO. We show that the dominant driver varies with ENSO phase. And whereas tropical temperature explains sink dynamics following El Niño conditions (r TG,P = 0.59, p
Global land carbon sink response to temperature and precipitation varies with ENSO phase
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.
Climate variability associated with the El Niño-Southern Oscillation (ENSO) and its consequent impacts on land carbon sink interannual variability have been used as a basis for investigating carbon cycle responses to climate variability more broadly, and to inform the sensitivity of the tropical carbon budget to climate change. Past studies have presented opposing views about whether temperature or precipitation is the primary factor driving the response of the land carbon sink to ENSO. Here, we show that the dominant driver varies with ENSO phase. Whereas tropical temperature explains sink dynamics following El Niño conditions (r TG,P=0.59, p<0.01), the post Lamore » Niña sink is driven largely by tropical precipitation (r PG,T=-0.46, p=0.04). This finding points to an ENSO-phase-dependent interplay between water availability and temperature in controlling the carbon uptake response to climate variations in tropical ecosystems. We further find that none of a suite of ten contemporary terrestrial biosphere models captures these ENSO-phase-dependent responses, highlighting a key uncertainty in modeling climate impacts on the future of the global land carbon sink.« less
Global land carbon sink response to temperature and precipitation varies with ENSO phase
DOE Office of Scientific and Technical Information (OSTI.GOV)
Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.
Climate variability associated with the El Niño-Southern Oscillation (ENSO) and its consequent impacts on land carbon sink interannual variability have been used as a basis for investigating carbon cycle responses to climate variability more broadly, and to inform the sensitivity of the tropical carbon budget to climate change. Past studies have presented opposing views about whether temperature or precipitation is the primary factor driving the response of the land carbon sink to ENSO. We show that the dominant driver varies with ENSO phase. And whereas tropical temperature explains sink dynamics following El Niño conditions (r TG,P = 0.59, p
Potential role of salinity in ENSO and MJO predictions
NASA Astrophysics Data System (ADS)
Zhu, J.; Kumar, A.; Murtugudde, R. G.; Xie, P.
2017-12-01
Studies have suggested that ocean salinity can vary in response to ENSO and MJO. For example, during an El Niño event, sea surface salinity decreases in the western and central equatorial Pacific, as a result of zonal advection of low salinity water by anomalous eastward surface currents, and to a lesser extent as a result of a rainfall excess associated with atmospheric convection and warm water displacements. However, the effect of salinity on ENSO and MJO evolutions and their forecasts has been less explored. In this analysis, we explored the potential role of salinity in ENSO and MJO predictions by conducting sensitivity experiments with NCEP CFSv2. Firstly, two forecasts experiments are conducted to explore its effect on ENSO predictions, in which the interannual variability of salinity in the ocean initial states is either included or excluded. Comparisons suggested that the salinity variability is essential to correctly forecast the 2007/08 La Niña starting from April 2007. With realistic salinity initial states, the tendency to decay of the subsurface cold condition during the spring and early summer 2007 was interrupted by positive salinity anomalies in the upper central Pacific, which working together with the Bjerknes positive feedback, contributed to the development of the La Niña event. Our study suggests that ENSO forecasts will benefit from more accurate sustained salinity observations having large-scale spatial coverage. We also assessed the potential role of salinity in MJO by evaluating a long coupled free run that has a relatively realistic MJO simulation and a set of predictability experiment, both based on CFSv2. Diagnostics of the free run suggest that, while the intraseasonal SST variations lead convections by a quarter cycle, they are almost in phase only with changes in barrier layer thickness, thereby suggesting an active role of salinity on SST. Its effect on MJO predictions is further explored by controlling the surface salinity
ENSO Diversity Changes Due To Global Warming In CESM-LE
NASA Astrophysics Data System (ADS)
Carreric, A.; Dewitte, B.; Guemas, V.
2017-12-01
The El Niño Southern Oscillation (ENSO) is predicted to be modified due to global warming based on the CMIP3 and CMIP5 data bases. In particular the frequency of occurrence of extreme Eastern Pacific El Niño events is to double in the future in response to the increase in green-house gazes. Such forecast relies however on state-of-the-art models that still present mean state biases and do not simulate realistically key features of El Niño events such as its diversity which is related to the existence of at least two types of El Niño events, the Eastern Pacific (EP) El Nino and the Central Pacific (CP) El Niño events. Here we take advantage of the Community Earth System Model (CESM) Large Ensemble (LE) that provides 35 realizations of the climate of the 1920-2100 period with a combination of both natural and anthropogenic climate forcing factors, to explore on the one hand methods to detect changes in ENSO statistics and on the other hand to investigate changes in thermodynamical processes associated to the increase oceanic stratification owed to global warming. The CESM simulates realistically many aspects of the ENSO diversity, in particular the non-linear evolution of the phase space of the first two EOF modes of Sea Surface Temperature (SST) anomalies in the tropical Pacific. Based on indices accounting for the two ENSO regimes used in the literature, we show that, although there is no statistically significant (i.e. confidence level > 95%) changes in the occurrence of El Niño types from the present to the future climate, the estimate of the changes is sensitive to the definition of ENSO indices that is used. CESM simulates in particular an increase occurrence of extreme El Niño events that can vary by 28% from one method to the other. It is shown that the seasonal evolution of EP El Niño events is modified from the present to the future climate, with in particular a larger occurrence of events taking place in Austral summer in the warmer climate
A metric for quantifying El Niño pattern diversity with implications for ENSO-mean state interaction
NASA Astrophysics Data System (ADS)
Lemmon, Danielle E.; Karnauskas, Kristopher B.
2018-04-01
Recent research on the El Niño-Southern Oscillation (ENSO) phenomenon increasingly reveals the highly complex and diverse nature of ENSO variability. A method of quantifying ENSO spatial pattern uniqueness and diversity is presented, which enables (1) formally distinguishing between unique and "canonical" El Niño events, (2) testing whether historical model simulations aptly capture ENSO diversity by comparing with instrumental observations, (3) projecting future ENSO diversity using future model simulations, (4) understanding the dynamics that give rise to ENSO diversity, and (5) analyzing the associated diversity of ENSO-related atmospheric teleconnection patterns. Here we develop a framework for measuring El Niño spatial SST pattern uniqueness and diversity for a given set of El Niño events using two indices, the El Niño Pattern Uniqueness (EPU) index and El Niño Pattern Diversity (EPD) index, respectively. By applying this framework to instrumental records, we independently confirm a recent regime shift in El Niño pattern diversity with an increase in unique El Niño event sea surface temperature patterns. However, the same regime shift is not observed in historical CMIP5 model simulations; moreover, a comparison between historical and future CMIP5 model scenarios shows no robust change in future ENSO diversity. Finally, we support recent work that asserts a link between the background cooling of the eastern tropical Pacific and changes in ENSO diversity. This robust link between an eastern Pacific cooling mode and ENSO diversity is observed not only in instrumental reconstructions and reanalysis, but also in historical and future CMIP5 model simulations.
ASIS v1.0: an adaptive solver for the simulation of atmospheric chemistry
NASA Astrophysics Data System (ADS)
Cariolle, Daniel; Moinat, Philippe; Teyssèdre, Hubert; Giraud, Luc; Josse, Béatrice; Lefèvre, Franck
2017-04-01
This article reports on the development and tests of the adaptive semi-implicit scheme (ASIS) solver for the simulation of atmospheric chemistry. To solve the ordinary differential equation systems associated with the time evolution of the species concentrations, ASIS adopts a one-step linearized implicit scheme with specific treatments of the Jacobian of the chemical fluxes. It conserves mass and has a time-stepping module to control the accuracy of the numerical solution. In idealized box-model simulations, ASIS gives results similar to the higher-order implicit schemes derived from the Rosenbrock's and Gear's methods and requires less computation and run time at the moderate precision required for atmospheric applications. When implemented in the MOCAGE chemical transport model and the Laboratoire de Météorologie Dynamique Mars general circulation model, the ASIS solver performs well and reveals weaknesses and limitations of the original semi-implicit solvers used by these two models. ASIS can be easily adapted to various chemical schemes and further developments are foreseen to increase its computational efficiency, and to include the computation of the concentrations of the species in aqueous-phase in addition to gas-phase chemistry.
An Ensemble Approach to Understanding the ENSO Response to Climate Change
NASA Astrophysics Data System (ADS)
Stevenson, S.; Capotondi, A.; Fasullo, J.; Otto-Bliesner, B. L.
2017-12-01
The dynamics of the El Nino/Southern Oscillation (ENSO) are known to be sensitive to changes in background climate conditions, as well as atmosphere/ocean feedbacks. However, the degree to which shifts in ENSO characteristics can be robustly attributed to external climate forcings remains unknown. Efforts to assess these changes in a multi-model framework are subject to uncertainties due to both differing model physics and internal ENSO variability. New community ensembles created at the National Center for Atmospheric Research and the NOAA Geophysical Fluid Dynamics Laboratory are ideally suited to addressing this problem, providing many realizations of the climate of the 850-2100 period with a combination of both natural and anthropogenic climate forcing factors. Here we analyze the impacts of external forcing on El Nino and La Nina evolution using four sets of simulations: the CESM Last Millennium Ensemble (CESM-LME), which covers the 850-2005 period and provides long-term context for forced responses; the Large Ensemble (CESM-LE), which includes 20th century and 21st century (RCP8.5) projections; the Medium Ensemble (CESM-ME), which is composed of 21st century RCP4.5 projections; and a large ensemble with the GFDL ESM2M, which includes 20th century and RCP8.5 projections. In the CESM, ENSO variance increases slightly over the 20th century in all ensembles, with the effects becoming much larger during the 21st. The slower increase in variance over the 20th century is shown to arise from compensating influences from greenhouse gas (GHG) and anthropogenic aerosol emissions, which give way to GHG-dominated effects by 2100. However, the 21st century variance increase is not robust: CESM and the ESM2M differ drastically in their ENSO projections. The mechanisms for these inter-model differences are discussed, as are the implications for the design of future multi-model ENSO projection experiments.
Can solar cycle modulate the ENSO effect on the Pacific/North American pattern?
NASA Astrophysics Data System (ADS)
Li, Delin; Xiao, Ziniu
2018-01-01
The ENSO effect on the Pacific/North American pattern (PNA) is well-known robust. Recent studies from observations and model simulations have reported that some important atmospheric circulation systems of extratropics are markedly modulated by the 11-year solar cycle. But less effort has been devoted to revealing the solar influence on the PNA. We thus hypothesize that the instability and uncertainty in the relationship between solar activity and PNA could be due to the ENSO impacts. In this study, solar cycle modulation of the ENSO effect on the PNA has been statistically examined by the observations from NOAA and NCEP/NCAR for the period of 1950-2014. Results indicate that during the high solar activity (HS) years, the PNA has stronger relevance to the ENSO, and the response of tropospheric geopotential height to ENSO variability is broadly similar to the typical positive PNA pattern. However, in the case of low solar activity (LS) years, the correlation between ENSO and PNA decreases relatively and the response has some resemblance to the negative phase of Arctic Oscillation (AO). Also, we find the impacts of solar activity on the middle troposphere are asymmetric during the different solar cycle phases, and the weak PNA-like response to solar activity only presents in the HS years. Closer inspection suggests that the higher solar activity has a much more remarkable modulation on the PNA-like response to the warm ENSO (WE) than that to the cold ENSO (CE), particularly over the Northeast Pacific region. The possible cause of the different responses might be the solar influence on the subtropical westerlies of upper troposphere. When the sea surface temperature (SST) of east-central tropical Pacific is anomalously warm, the upper tropospheric westerlies are significantly modulated by the higher solar activity, resulting in the acceleration and eastward shift of the North Pacific subtropical jet, which favors the propagation of WE signal from the tropical Pacific
ENSO-based probabilistic forecasts of March-May U.S. tornado and hail activity
NASA Astrophysics Data System (ADS)
Lepore, Chiara; Tippett, Michael K.; Allen, John T.
2017-09-01
Extended logistic regression is used to predict March-May severe convective storm (SCS) activity based on the preceding December-February (DJF) El Niño-Southern Oscillation (ENSO) state. The spatially resolved probabilistic forecasts are verified against U.S. tornado counts, hail events, and two environmental indices for severe convection. The cross-validated skill is positive for roughly a quarter of the U.S. Overall, indices are predicted with more skill than are storm reports, and hail events are predicted with more skill than tornado counts. Skill is higher in the cool phase of ENSO (La Niña like) when overall SCS activity is higher. SCS forecasts based on the predicted DJF ENSO state from coupled dynamical models initialized in October of the previous year extend the lead time with only a modest reduction in skill compared to forecasts based on the observed DJF ENSO state.
A-Si Photoreceptors At The Threshold Of Industrial Application
NASA Astrophysics Data System (ADS)
Senske, W.; Marschall, N.
1986-03-01
A-Si has become an attractive alternative for conventional electrophotographic photoreceptors. A-Si photoreceptors have been prepared by other laboratories by plasma deposition with blocking and protection layers. These photoreceptors are highly photosensitive and show low fatigue. Using sputtering we have shown that this technique is capable of produc-ing films with high charge acceptance. The increase of the deposition rate is presently un-der intensive investigation. High rates can be achieved by a higher degree of silane decomposition or by magnetron sputtering together with a higher power level. Deposition rates of more than 20 pm/h have been obtained by both techniques.
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.
Importance of convective parameterization in ENSO predictions
NASA Astrophysics Data System (ADS)
Zhu, Jieshun; Kumar, Arun; Wang, Wanqiu; Hu, Zeng-Zhen; Huang, Bohua; Balmaseda, Magdalena A.
2017-06-01
This letter explored the influence of atmospheric convection scheme on El Niño-Southern Oscillation (ENSO) predictions using a set of hindcast experiments. Specifically, a low-resolution version of the Climate Forecast System version 2 is used for 12 month hindcasts starting from each April during 1982-2011. The hindcast experiments are repeated with three atmospheric convection schemes. All three hindcasts apply the identical initialization with ocean initial conditions taken from the European Centre for Medium-Range Weather Forecasts and atmosphere/land initial states from the National Centers for Environmental Prediction. Assessments indicate a substantial sensitivity of the sea surface temperature prediction skill to the different convection schemes, particularly over the eastern tropical Pacific. For the Niño 3.4 index, the anomaly correlation skill can differ by 0.1-0.2 at lead times longer than 2 months. Long-term simulations are further conducted with the three convection schemes to understand the differences in prediction skill. By conducting heat budget analyses for the mixed-layer temperature anomalies, it is suggested that the convection scheme having the highest skill simulates stronger and more realistic coupled feedbacks related to ENSO. Particularly, the strength of the Ekman pumping feedback is better represented, which is traced to more realistic simulation of surface wind stress. Our results imply that improving the mean state simulations in coupled (ocean-atmosphere) general circulation model (e.g., ameliorating the Intertropical Convergence Zone simulation) might further improve our ENSO prediction capability.
Reforecasting the ENSO Events in the Past Fifty-Seven Years (1958-2014)
NASA Astrophysics Data System (ADS)
Huang, B.; Shin, C. S.; Shukla, J.; Marx, L.; Balmaseda, M.; Halder, S.; Dirmeyer, P.; Kinter, J. L.
2016-12-01
A set of ensemble seasonal reforecasts for 1958-2014 is conducted using the National Centers for Environmental Prediction (NCEP) Climate Forecast System, version 2 (CFSv2), initialized with observation-based ocean, atmosphere, land and sea ice reanalyses, including the European Centre for Medium-Range Weather Forecasts (ECMWF) global ocean reanalysis version 4, the ERA-40 atmospheric reanalysis, the NCEP CFS Reanalysis for atmosphere, land and sea ice, and the NASA Global Land Data Assimilation System reanalysis version 2.0 for land. The purpose is to examine a long and continuous seasonal reforecast dataset from a modern seasonal forecast system to be used by the research community. In comparison with other current reforecasts, this dataset allows us to evaluate the degree to which El Niño and Southern Oscillation (ENSO) events can be predicted, using a larger sample of events. Furthermore, we can directly compare the predictability of the ENSO events in 1960s-70s with the more widely studied ENSO events occurring since the 1980s to examine the state-of-the-art seasonal forecast system's capability at different phases of global climate change and multidecadal variability. A major concern is whether the seasonal reforecasts before 1979 have useful skill when there were fewer ocean observations. Our preliminary examination of the reforecasts shows that, although the reforecasts have lower skill in predicting the SST anomalies in the North Pacific and North Atlantic before 1979, the prediction skill of the ENSO onset and development for 1958-1978 is comparable to that for 1979-2014. The skill of the earlier predictions declines faster in the ENSO decaying phase because the reforecasts initialized after the summer season persistently predict lingering wind and SST anomalies in the eastern equatorial Pacific during the decaying phase of several major ENSO events in the 1960s-70s. Since the 1980s, the reforecasts initialized in fall overestimate the peak SST
Modeling and Observations of the Response of Tropical Tropospheric Ozone to ENSO
NASA Technical Reports Server (NTRS)
Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Waugh, D. W.; Lang, C.; Rodriquez, J. M.; Nielsen, J. E.
2012-01-01
The El Nino-Southern Oscillation (ENSO) is the dominant mode of tropical variability on interannual time scales. ENSO appears to extend its influence into the chemical composition of the tropical troposphere, Recent results have revealed an ENSO induced wave-1 anomaly in observed tropical tropospheric column ozone, This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this result using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years, An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region, We will show targeted comparisons with SHADOZ ozonesondes over these regions to provide insight into the vertical structure. Also, comparisons with NASA's Aura satellite Microwave Limb Sounder (MLS) and Tropospheric Emissions Spectrometer (TES) instruments and other appropriate data sets will be shown. In addition, the water vapor response to ENSO will be compared to help illuminate its role relative to dynamics in impacting ozone concentrations. These results indicate that the tropospheric ozone response to ENSO is potentially a very useful chemistry-climate diagnostic and should be considered in future modeling assessments.
Amplification of ENSO Effects on Indian Summer Monsoon by Absorbing Aerosols
NASA Technical Reports Server (NTRS)
Kim, Maeng-Ki; Lau, William K. M.; Kim, Kyu-Myong; Sang, Jeong; Kim, Yeon-Hee; Lee, Woo-Seop
2015-01-01
In this study, we present observational evidence, based on satellite aerosol measurements and MERRA reanalysis data for the period 1979-2011, indicating that absorbing aerosols can have strong influence on seasonal-to-interannual variability of the Indian summer monsoon rainfall, including amplification of ENSO effects. We find a significant correlation between ENSO (El Nino Southern Oscillation) and aerosol loading in April-May, with La Nina (El Nino) conditions favoring increased (decreased) aerosol accumulation over northern India, with maximum aerosol optical depth (AOD) over the Arabian Sea and Northwestern India, indicative of strong concentration of dust aerosols transported from West Asia and Middle East deserts. Composite analyses based on a normalized aerosol index (NAI) show that high concentration of aerosol over northern India in April-May is associated with increased moisture transport, enhanced dynamically induced warming of the upper troposphere over the Tibetan Plateau, and enhanced rainfall over northern India and the Himalayan foothills during May-June, followed by a subsequent suppressed monsoon rainfall over all India,consistent with the Elevated Heat Pump (EHP) hypothesis (Lau et al. 2006). Further analyses from sub-sampling of ENSO years, with normal (less than 1 sigma), and abnormal (greater than 1 sigma)) NAI over northern India respectively show that the EHP may lead to an amplification of the Indian summer monsoon response to ENSO forcing, particularly with respect to the increased rainfall over the Himalayan foothills, and the warming of the upper troposphere over the Tibetan Plateau. Our results suggest that absorbing aerosol, particular desert dusts can strongly modulate ENSO influence, and possibly play important roles as a feedback agent in climate change in Asian monsoon regions.
NASA Astrophysics Data System (ADS)
Giannini, A.; Saravanan, R.; Chang, P.
A comparison of rainfall variability in the semi-arid Brazilian Nordeste in observations and in two sets of model simulations leads to the conclusion that the evolving interaction between Tropical Atlantic Variability (TAV) and the El Niño-Southern Oscillation (ENSO) phenomenon can explain two puzzling features of ENSO's impact on the Nordeste: (1) the event-to-event unpredictability of ENSO's impact; (2) the greater impact of cold rather than warm ENSO events during the past 50 years. The explanation is in the `preconditioning' role of Tropical Atlantic Variability. When, in seasons prior to the mature phase of ENSO, the tropical Atlantic happens to be evolving consistently with the development expected of the ENSO teleconnection, ENSO and TAV add up to force large anomalies in Nordeste rainfall. When it happens to be evolving in opposition to the canonical development of ENSO, then the net outcome is less obvious, but also less anomalous. The more frequent occurrence of tropical Atlantic conditions consistent with those that develop during a cold ENSO event, i.e. of a negative meridional sea surface temperature gradient, explains the weaker warm ENSO and stronger cold ENSO anomalies in Nordeste rainfall of the latter part of the twentieth century. Close monitoring of the evolution of the tropical Atlantic in seasons prior to the mature phase of ENSO should lead to an enhanced forecast potential.
Tropical cyclone prediction skills - MJO and ENSO dependence in S2S data sets
NASA Astrophysics Data System (ADS)
Lee, C. Y.; Camargo, S.; Vitart, F.; Sobel, A. H.; Tippett, M.
2017-12-01
The El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO) are two important climate controls on tropical cyclone (TC) activity. The seasonal prediction skill of dynamical models is determined in large part by their accurate representations of the ENSO-TC relationship. Regarding intraseasonal TC variability, observations suggest MJO to be the primary control. Given the ongoing effort to develop dynamical seasonal-to-subseasonal (S2S) TC predictions, it is important to examine whether the global models, running on S2S timescales, are able to reproduce these known ENSO-TC and MJO-TC relationships, and how this ability affects forecasting skill. Results from the S2S project (from F. Vitart) suggest that global models have skill in predicting MJO phase with up to two weeks of lead time (four weeks for ECMWF). Meanwhile, our results show that, qualitatively speaking, the MJO-TC relationship in storm genesis is reasonably captured, with some models (e.g., ECMWF, BoM, NCEP, MetFr) performing better than the others. However, we also find that model skill in predicting basin-wide genesis and accumulated cyclone energy (ACE) are mainly due to the models' ability to capture the climatological seasonality. Removing the seasonality significantly reduces the models' skill; even the best model (ECMWF) in the most reliable basin (western north Pacific and Atlantic) has very little skill (close to 0.1 in Brier skill score for genesis and close to 0 in rank probability skill score for ACE). This brings up the question: do any factors contribute to intraseasonal TC prediction skill other than seasonality? Is the low skill, after removing the seasonality, due to poor MJO and ENSO simulations, or to poor representation of other ENSO-TC or MJO-TC relationships, such as ENSO's impact on the storm tracks? We will quantitatively discuss the dependence of the TC prediction skill on ENSO and MJO, focusing on Western North Pacific and Atlantic, where we have sufficient
Räsänen, Okko; Metsäranta, Marjo; Vanhatalo, Sampsa
2013-04-01
The degree of interhemispheric synchrony in the neonatal EEG assessment refers to the co-occurrence of activity bouts during quiet sleep or burst suppression, and it has been widely considered as a key component in assessing background activity. However, no objective measures have been published for measuring it, and all conventionally used visual criteria suffer from significant ambiguities. Our present study aimed to develop such a quantitative measure of (a)synchrony, called activation synchrony index (ASI). We developed the ASI paradigm based on the testing of statistical independence between two quantized amplitude envelopes of wideband-filtered signals where higher frequencies had been pre-emphasized. The core parameter settings of ASI paradigm were defined using a smaller EEG dataset, and the final ASI paradigm was tested using a visually classified dataset of EEG records from 33 fullterm and 25 preterm babies, which showed varying grades of asynchrony. Our findings show that ASI could distinguish all EEG recordings with normal synchrony from those with modest or severe asynchrony at individual level, and there was a highly significant correlation (p<0.001) between ASI and the visually assessed grade of asynchrony. In addition, we showed that i) ASI is stable in recordings over several hours in duration, such as the typical neonatal brain monitoring, that ii) ASI values are sensitive to sleep stage, and that iii) they correlate with age in the preterm babies. Comparison of ASI to other three potential paradigms demonstrated a significant competitive advantage. Finally, ASI was found to be remarkably resistant to common artefacts as tested by adding significant level of real EEG artefacts from noisy recordings. An objective and reliable measure of (a)synchrony may open novel avenues for using ASI as a putative early functional biomarker in the neonatal brain, as well as for building proper automated classifiers of neonatal EEG background. Notably, the
Changes in ENSO amplitude under climate warming and cooling
NASA Astrophysics Data System (ADS)
Wang, Yingying; Luo, Yiyong; Lu, Jian; Liu, Fukai
2018-05-01
The response of ENSO amplitude to climate warming and cooling is investigated using the Community Earth System Model (CESM), in which the warming and cooling scenarios are designed by adding heat fluxes of equal amplitude but opposite sign onto the ocean surface, respectively. Results show that the warming induces an increase of the ENSO amplitude but the cooling gives rise to a decrease of the ENSO amplitude, and these changes are robust in statistics. A mixed layer heat budget analysis finds that the increasing (decreasing) SST tendency under climate warming (cooling) is mainly due to an enhancement (weakening) of dynamical feedback processes over the equatorial Pacific, including zonal advective (ZA) feedback, meridional advective (MA) feedback, thermocline (TH) feedback, and Ekman (EK) feedback. As the climate warms, a wind anomaly of the same magnitude across the equatorial Pacific can induce a stronger zonal current change in the east (i.e., a stronger ZA feedback), which in turn produces a greater weakening of upwelling (i.e., a stronger EK feedback) and thus a larger thermocline change (i.e., a stronger TH feedback). In response to the climate warming, in addition, the MA feedback is also strengthened due to an enhancement of the meridional SST gradient around the equator resulting from a weakening of the subtropical cells (STCs). It should be noted that the weakened STCs itself has a negative contribution to the change of the MA feedback which, however, appears to be secondary. And vice versa for the cooling case. Bjerknes linear stability (BJ) index is also evaluated for the linear stability of ENSO, with remarkably larger (smaller) BJ index found for the warming (cooling) case.
ENSO Related Inter-Annual Lightning Variability from the Full TRMM LIS Lightning Climatology
NASA Technical Reports Server (NTRS)
Clark, Austin; Cecil, Daniel
2018-01-01
The El Nino/Southern Oscillation (ENSO) contributes to inter-annual variability of lightning production more than any other atmospheric oscillation. This study further investigated how ENSO phase affects lightning production in the tropics and subtropics using the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS). Lightning data were averaged into mean annual warm, cold, and neutral 'years' for analysis of the different phases and compared to model reanalysis data. An examination of the regional sensitivities and preliminary analysis of three locations was conducted using model reanalysis data to determine the leading convective mechanisms in these areas and how they might respond to the ENSO phases
The Angola Low: relationship with southern African rainfall and ENSO
NASA Astrophysics Data System (ADS)
Crétat, Julien; Pohl, Benjamin; Dieppois, Bastien; Berthou, Ségolène; Pergaud, Julien
2018-05-01
The main states of the Angola Low (AL) are identified using clustering analysis applied to daily anomalous patterns of 700-hPa wind vorticity over Angola and adjacent countries from November to March for the 1980/81-2014/15 period. At the daily timescale, we examine the extent to which the main states of the AL modulate daily rainfall over southern Africa. At the interannual timescale, we assess both the relationship between the occurrence of these AL states and El Niño southern oscillation (ENSO) and the role of the AL in explaining ENSO's failure in driving southern African rainfall at times. Three reanalyses are considered to account for uncertainties induced by the scarcity of data available for assimilation over southern Africa. Three preferential states of the Angola Low are identified: AL state close to its seasonal climatology with slight zonal displacements, anomalously weak AL state and anomalously strong AL state with meridional displacements. These different states all significantly modulate daily southern African rainfall. Near-climatological AL state promotes wet rainfall anomalies over eastern subtropical southern Africa and dry rainfall anomalies over its western part. A slight westward shift in the near-climatological position of the AL leads to reversed zonal gradient in rainfall. The remaining regimes significantly modulate the meridional gradient in southern African rainfall. Anomalously weak and anomalously northward AL states promote wet rainfall anomalies over tropical southern Africa and dry rainfall anomalies over subtropical southern Africa. The reverse prevails for anomalously southward AL. At the interannual timescale, ENSO significantly modulates the seasonal occurrence of most AL states in the three reanalyses. Anomalously weak and southward AL states are more strongly correlated with regional rainfall than ENSO in all reanalyses, suggesting that accounting for AL variability may improve seasonal forecasts. Case study analysis of the
Biennial-Aligned Lunisolar-Forcing of ENSO: Implications for Simplified Climate Models
NASA Astrophysics Data System (ADS)
Pukite, P. R.
2017-12-01
By solving Laplace's tidal equations along the equatorial Pacific thermocline, assuming a delayed-differential effective gravity forcing due to a combined lunar+solar (lunisolar) stimulus, we are able to precisely match ENSO periodic variations over wide intervals. The underlying pattern is difficult to decode by conventional means such as spectral analysis, which is why it has remained hidden for so long, despite the excellent agreement in the time-domain. What occurs is that a non-linear seasonal modulation with monthly and fortnightly lunar impulses along with a biennially-aligned "see-saw" is enough to cause a physical aliasing and thus multiple folding in the frequency spectrum. So, instead of a conventional spectral tidal decomposition, we opted for a time-domain cross-validating approach to calibrate the amplitude and phasing of the lunisolar cycles. As the lunar forcing consists of three fundamental periods (draconic, anomalistic, synodic), we used the measured Earth's length-of-day (LOD) decomposed and resolved at a monthly time-scale [1] to align the amplitude and phase precisely. Even slight variations from the known values of the long-period tides will degrade the fit, so a high-resolution calibration is possible. Moreover, a narrow training segment from 1880-1920 using NINO34/SOI data is adequate to extrapolate the cycles of the past 100 years (see attached figure). To further understand the biennial impact of a yearly differential-delay, we were able to also decompose using difference equations the historical sea-level-height readings at Sydney harbor to clearly expose the ENSO behavior. Finally, the ENSO lunisolar model was validated by back-extrapolating to Unified ENSO coral proxy (UEP) records dating to 1650. The quasi-biennial oscillation (QBO) behavior of equatorial stratospheric winds derives following a similar pattern to ENSO via the tidal equations, but with an emphasis on draconic forcing. This improvement in ENSO and QBO understanding has
Suppression of ENSO in a coupled model without water vapor feedback
NASA Astrophysics Data System (ADS)
Hall, A.; Manabe, S.
We examine 800-year time series of internally generated variability in both a coupled ocean-atmosphere model where water vapor anomalies are not allowed to interact with longwave radiation and one where they are. The ENSO-like phenomenon in the experiment without water vapor feedback is drastically suppressed both in amplitude and geographic extent relative to the experiment with water vapor feedback. Surprisingly, the reduced amplitude of ENSO-related sea surface temperature anomalies in the model without water vapor feedback cannot be attributed to greater longwave damping of sea surface temperature. (Differences between the two experiments in radiative feedback due to clouds counterbalance almost perfectly the differences in radiative feedback due to water vapor.) Rather, the interaction between water vapor anomalies and longwave radiation affects the ENSO-like phenomenon through its influence on the vertical structure of radiative heating: Because of the changes in water vapor associated with it, a given warm equatorial Pacific sea surface temperature anomaly is associated with a radiative heating profile that is much more gravitationally unstable when water vapor feedback is present. The warm sea surface temperature anomaly therefore results in more convection in the experiment with water vapor feedback. The increased convection, in turn, is related to a larger westerly wind-stress anomaly, which creates a larger decrease in upwelling of cold water, thereby enhancing the magnitude of the original warm sea surface temperature anomaly. In this manner, the interaction between water vapor anomalies and longwave radiation magnifies the air-sea interactions at the heart of the ENSO phenomenon; without this interaction, the coupling between sea surface temperature and wind stress is effectively reduced, resulting in smaller amplitude ENSO episodes with a more limited geographical extent.
NASA Technical Reports Server (NTRS)
Lewis, Sophie C.; LeGrande, Allegra N.; Schmidt, Gavin A.; Kelley, Maxwell
2014-01-01
Using the water isotope- and vapor source distribution (VSD) tracer-enabled Goddard Institute for Space Studies ModelE-R, we examine changing El Nino-Southern Oscillation (ENSO)-like expressions in the hydrological cycle in a suite of model experiments. We apply strong surface temperature anomalies associated with composite observed El Nino and La Nina events as surface boundary conditions to preindustrial and mid-Holocene model experiments in order to investigate ENSO-like expressions in the hydrological cycle under varying boundary conditions. We find distinct simulated hydrological anomalies associated with El Nino-like ("ENSOWARM") and La Nina-like ("ENSOCOOL") conditions, and the region-specific VSD tracers show hydrological differences across the Pacific basin between El Nino-like and La Nina-like events. The application of ENSOCOOL forcings does not produce climatological anomalies that represent the equal but opposite impacts of the ENSOWARM experiment, as the isotopic anomalies associated with ENSOWARM conditions are generally stronger than with ENSOCOOL and the spatial patterns of change distinct. Also, when the same ENSO-like surface temperature anomalies are imposed on the mid-Holocene, the hydrological response is muted, relative to the preindustrial. Mid-Holocene changes in moisture sources to the analyzed regions across the Pacific reveal potentially complex relationships between ENSO-like conditions and boundary conditions. Given the complex impacts of ENSO-like conditions on various aspects of the hydrological cycle, we suggest that proxy record insights into paleo-ENSO variability are most likely to be robust when synthesized from a network of many spatially diverse archives, which can account for the potential nonstationarity of ENSO teleconnections under different boundary conditions.
NASA Astrophysics Data System (ADS)
Giannakis, D.; Slawinska, J. M.
2016-12-01
The variability of the Indo-Pacific Ocean on interannual to multidecadal timescales is investigated in a millennial control run of CCSM4 and in observations using a recently introduced technique called Nonlinear Laplacian Spectral Analysis (NLSA). Through this technique, drawbacks associated with ad hoc pre-filtering of the input data are avoided, enabling recovery of low-frequency and intermittent modes not accessible previously via classical approaches. Here, a multiscale hierarchy of modes is identified for Indo-Pacific SST and numerous linkages between these patterns are revealed. On interannual timescales, a mode with spatiotemporal pattern corresponding to the fundamental component of ENSO emerges, along with modulations of the annual cycle by ENSO in agreement with ENSO combination mode theory. In spatiotemporal reconstructions, these patterns capture the seasonal southward migration of SST and zonal wind anomalies associated with termination of El Niño and La Niña events. Notably, this family of modes explains a significant portion of SST variance in Eastern Indian Ocean regions employed in the definition of Indian Ocean dipole (IOD) indices, suggesting that it should be useful for understanding the linkage of these indices with ENSO and the interaction of the Indian and Pacific Oceans. In model data, we find that the ENSO and ENSO combination modes are modulated on multidecadal timescales by a mode predominantly active in the western tropical Pacific - we call this mode West Pacific Multidecadal Oscillation (WPMO). Despite the relatively low variance explained by this mode, its dynamical role appears to be significant as it has clear sign-dependent modulating relationships with the interannual modes carrying most of the variance. In particular, cold WPMO events are associated with anomalous Central Pacific westerlies favoring stronger ENSO events, while warm WPMO events suppress ENSO activity. Moreover, the WPMO has significant climatic impacts as
Phenological Responses to ENSO in the Global Oceans
NASA Astrophysics Data System (ADS)
Racault, M.-F.; Sathyendranath, S.; Menon, N.; Platt, T.
2017-01-01
Phenology relates to the study of timing of periodic events in the life cycle of plants or animals as influenced by environmental conditions and climatic forcing. Phenological metrics provide information essential to quantify variations in the life cycle of these organisms. The metrics also allow us to estimate the speed at which living organisms respond to environmental changes. At the surface of the oceans, microscopic plant cells, so-called phytoplankton, grow and sometimes form blooms, with concentrations reaching up to 100 million cells per litre and extending over many square kilometres. These blooms can have a huge collective impact on ocean colour, because they contain chlorophyll and other auxiliary pigments, making them visible from space. Phytoplankton populations have a high turnover rate and can respond within hours to days to environmental perturbations. This makes them ideal indicators to study the first-level biological response to environmental changes. In the Earth's climate system, the El Niño-Southern Oscillation (ENSO) dominates large-scale inter-annual variations in environmental conditions. It serves as a natural experiment to study and understand how phytoplankton in the ocean (and hence the organisms at higher trophic levels) respond to climate variability. Here, the ENSO influence on phytoplankton is estimated through variations in chlorophyll concentration, primary production and timings of initiation, peak, termination and duration of the growing period. The phenological variabilities are used to characterise phytoplankton responses to changes in some physical variables: sea surface temperature, sea surface height and wind. It is reported that in oceanic regions experiencing high annual variations in the solar cycle, such as in high latitudes, the influence of ENSO may be readily measured using annual mean anomalies of physical variables. In contrast, in oceanic regions where ENSO modulates a climate system characterised by a seasonal
The natural oscillation of two types of ENSO events based on analyses of CMIP5 model control runs
NASA Astrophysics Data System (ADS)
Xu, Kang; Su, Jingzhi; Zhu, Congwen
2014-07-01
The eastern- and central-Pacific El Niño-Southern Oscillation (EP- and CP-ENSO) have been found to be dominant in the tropical Pacific Ocean, and are characterized by interannual and decadal oscillation, respectively. In the present study, we defined the EP- and CP-ENSO modes by singular value decomposition (SVD) between SST and sea level pressure (SLP) anomalous fields. We evaluated the natural features of these two types of ENSO modes as simulated by the pre-industrial control runs of 20 models involved in phase five of the Coupled Model Intercomparison Project (CMIP5). The results suggested that all the models show good skill in simulating the SST and SLP anomaly dipolar structures for the EP-ENSO mode, but only 12 exhibit good performance in simulating the tripolar CP-ENSO modes. Wavelet analysis suggested that the ensemble principal components in these 12 models exhibit an interannual and multi-decadal oscillation related to the EP- and CP-ENSO, respectively. Since there are no changes in external forcing in the pre-industrial control runs, such a result implies that the decadal oscillation of CP-ENSO is possibly a result of natural climate variability rather than external forcing.
The crucial role of the Green Sahara in damping ENSO variability during the Holocene
NASA Astrophysics Data System (ADS)
Pausata, Francesco S. R.; Zhang, Qiong; Muschitiello, Francesco; Stager, Curt
2016-04-01
Several paleoclimate records show that the ENSO variability may have been remarkably smaller during the mid Holocene (MH) relative to today; however, MH model simulations in which only the orbital forcing is taken into account are not able to fully capture the magnitude of this change. We use a fully coupled simulation for 6000 yr BP (MH) in which we prescribed not only the MH orbital forcing but also Saharan vegetation and reduced dust concentrations. By performing a set of idealized experiments in which each forcing is changed in turn, we show that when accounting for both vegetated Sahara and reduced dust concentrations, the amplitude of the ENSO cycle and its variability are remarkably reduced (~25%) compared to case when only the orbital forcing is prescribed (only 7%). The changes in ENSO behavior are accompanied by damping of the Atlantic El Niño variability (almost 50%). The simulated changes in equatorial variability are connected to the momentous strengthening of the WAM monsoon, which extents all the way to the northernmost part of the Sahara desert. Such changes in the WAM and in the atmospheric circulation over the equatorial Atlantic led to a reduction of the Atlantic El Niño variability and affect ENSO behavior through the atmospheric circulation bridge between the Atlantic and the Pacific. Hence, our results suggest orbital forcing is likely not the only forcing at play behind the changes in ENSO behavior and point to the changes over equatorial Atlantic connected to the Sahara greening as a crucial factor in altering the ENSO spatiotemporal characteristic during the MH.
Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; ...
2015-12-18
The El Niño–Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with coupled general circulation models (CGCMs) to investigate how regional precipitation in the twenty-first century may be affected by changes in both ENSO-driven precipitation variability and slowly evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of twentieth-century climate change.more » Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in twenty-first-century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with twentieth-century observations and more stationary during the twenty-first century. Finally, the model-predicted twenty-first-century rainfall response to cENSO is decomposed into the sum of three terms: 1) the twenty-first-century change in the mean state of precipitation, 2) the historical precipitation response to the cENSO pattern, and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. Lastly, by examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.« less
NASA Technical Reports Server (NTRS)
Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, L. Ruby; Doutriaux, Charles; Capotondi, Antonietta
2015-01-01
El Niño-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with coupled general circulation models (CGCMs) to investigate how regional precipitation in the twenty-first century may be affected by changes in both ENSO-driven precipitation variability and slowly evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of twentieth-century climate change. Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in twenty-first-century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with twentieth-century observations and more stationary during the twenty-first century. Finally, the model-predicted twenty-first-century rainfall response to cENSO is decomposed into the sum of three terms: 1) the twenty-first-century change in the mean state of precipitation, 2) the historical precipitation response to the cENSO pattern, and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. By examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.
NASA Technical Reports Server (NTRS)
Bonfils, Celine J. W.; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, L. Ruby; Doutriaux, Charles; Capotondi, Antonietta
2015-01-01
The El Nino-Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with Coupled General Circulation Models (CGCMs) to investigate how regional precipitation in the 21st century may be affected by changes in both ENSO-driven precipitation variability and slowly-evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of 20th century climate change. Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in 21st century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with 20th century observations and more stationary during the 21st century. Finally, the model-predicted 21st century rainfall response to cENSO is decomposed into the sum of three terms: 1) the 21st century change in the mean state of precipitation; 2) the historical precipitation response to the cENSO pattern; and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. By examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.
NASA Astrophysics Data System (ADS)
Sun, Qiaohong; Miao, Chiyuan; Qiao, Yuanyuan; Duan, Qingyun
2017-12-01
The El Niño-Southern Oscillation (ENSO) and local temperature are important drivers of extreme precipitation. Understanding the impact of ENSO and temperature on the risk of extreme precipitation over global land will provide a foundation for risk assessment and climate-adaptive design of infrastructure in a changing climate. In this study, nonstationary generalized extreme value distributions were used to model extreme precipitation over global land for the period 1979-2015, with ENSO indicator and temperature as covariates. Risk factors were estimated to quantify the contrast between the influence of different ENSO phases and temperature. The results show that extreme precipitation is dominated by ENSO over 22% of global land and by temperature over 26% of global land. With a warming climate, the risk of high-intensity daily extreme precipitation increases at high latitudes but decreases in tropical regions. For ENSO, large parts of North America, southern South America, and southeastern and northeastern China are shown to suffer greater risk in El Niño years, with more than double the chance of intense extreme precipitation in El Niño years compared with La Niña years. Moreover, regions with more intense precipitation are more sensitive to ENSO. Global climate models were used to investigate the changing relationship between extreme precipitation and the covariates. The risk of extreme, high-intensity precipitation increases across high latitudes of the Northern Hemisphere but decreases in middle and lower latitudes under a warming climate scenario, and will likely trigger increases in severe flooding and droughts across the globe. However, there is some uncertainties associated with the influence of ENSO on predictions of future extreme precipitation, with the spatial extent and risk varying among the different models.
Influence of ENSO on Gulf Stream cyclogenesis and the North Atlantic storm track
NASA Astrophysics Data System (ADS)
Li, C.; Schemm, S.; Ciasto, L.; Kvamsto, N. G.
2015-12-01
There is emerging evidence that climate in the North Atlantic-European sector is sensitive to vacillations of tropical Pacific sea surface temperatures, in particular, the central Pacific flavour of the El Nino Southern Oscillation (ENSO) and concomitant trends in atmospheric heating. The frequency of central Pacific ENSOs appears to have increased over the last decades and some studies suggest it may continue increasing in the future, but the precise mechanisms by which these events affect the North Atlantic synoptic scale circulation are poorly understood. Here, we show that central Pacific ENSOs influence where midlatitude cyclogenesis occurs over the Gulf Stream, producing more cyclogenesis in the jet exit region rather than in the climatologically preferred jet entrance region. The cyclones forming over the Gulf Stream in central Pacific ENSO seasons tend to veer north, penetrating deeper into the Arctic rather than into continental Europe. The shift in cyclogenesis is linked to changes in the large scale circulation, namely, the upper-level trough formed in the lee of the Rocky Mountains.
Characteristics of Lake Chad Level Variability and Links to ENSO, Precipitation, and River Discharge
Demoz, Belay; Gebremariam, Sium
2014-01-01
This study used trend, correlation, and wavelet analysis to characterize Lake Chad (LC) level fluctuations, river discharge, El Niño Southern Oscillation (ENSO), and precipitation regimes and their interrelationships. Linear correlation results indicate a negative association between ENSO and LC level, river discharge and precipitation. Trend analysis shows increasing precipitation in the Lake Chad Basin (LCB) but decreasing LC level. The mode of interannual variability in LC level, rainfall, and ENSO analyzed using wavelet analysis is dominated by 3-4-year periods. Results show that variability in ENSO could explain only 31% and 13% of variations in LC level at Kindjeria and precipitation in the northern LCB, respectively. The wavelet transform coherency (WTC) between LC level of the southern pool at Kalom and ENSO is statistically significant at the 95% confidence level and phase-locked, implying a cause-and-effect association. These strong coherencies coincide with the La Niña years with the exception of 1997-1998 El Niño events. The WTC shows strong covariance between increasing precipitation and LC level in the northern pool at a 2- to 4-year band and 3- to 4-year band localized from 1996 to 2010. Implications for water resource planning and management are discussed. PMID:25538946
Chen, Shangfeng; Chen, Wen; Yu, Bin
2018-05-02
Previous studies indicated that the spring Arctic Oscillation (AO) exerts significant influences on the subsequent winter El Niño-Southern Oscillation (ENSO). This analysis suggests that the spring AO-ENSO linkage is highly modulated by its preceding November AO. When November and the subsequent spring AO indices are in phase, the spring AO has a pronounced influence on ENSO. However, when the November and spring AO indices are out of phase, the spring AO-ENSO connection disappears. Modulation of the November AO on the spring AO-ENSO connection is mainly through the constructive and destructive superposition of the November and spring AO associated sea surface temperature (SST) anomalies in the tropical central-eastern Pacific in spring and summer, as well as the SST anomalies developed further in the tropical Pacific via the positive air-sea feedback.
NASA Astrophysics Data System (ADS)
Qin, Jianhuang; Ding, Ruiqiang; Wu, Zhiwei; Li, Jianping; Zhao, Sen
2017-03-01
Previous studies suggest that the atmospheric precursor of El Niño-Southern Oscillation (ENSO) in the extratropical Southern Hemisphere (SH) might trigger a quadrapole sea surface temperature anomaly (SSTA) in the South Pacific and subsequently influence the following ENSO. Such a quadrapole SSTA is referred to as the South Pacific quadrapole (SPQ). The present study investigated the relationships between the atmospheric precursor signal of ENSO and leading modes of atmospheric variability in the extratropical SH [including the SH annular mode (SAM), the first Pacific-South America (PSA1) mode, and the second Pacific-South America (PSA2) mode]. The results showed that the atmospheric precursor signal in the extratropical SH basically exhibits a barotropic wavenumber-3 structure over the South Pacific and is significantly correlated with the SAM and the PSA2 mode during austral summer. Nevertheless, only the PSA2 mode was found to be a precursor for the following ENSO. It leads the SPQ-like SSTA by around one month, while the SAM and the PSA1 mode do not show any obvious linkage with either ENSO or the SPQ. This suggests that the PSA2 mode may provide a bridge between the preceding circulation anomalies over the extratropical SH and the following ENSO through the SPQ-like SSTA.
NASA Astrophysics Data System (ADS)
Ding, Ruiqiang; Li, Jianping; Tseng, Yu-heng; Sun, Cheng; Xie, Fei
2017-01-01
Previous studies have indicated that boreal winter subtropical and extratropical sea surface pressure (SLP) anomalies over both the North and South Pacific are significantly related to the El Niño-Southern Oscillation (ENSO) state in the following boreal winter. Here we use observational data and model simulations to show that the ability of the boreal winter North Pacific SLP anomalies to initiate ENSO events a year later may strongly depend on the state of the simultaneous South Pacific SLP anomalies and vice versa. When the boreal winter North Pacific SLP anomalies are of the opposite sign to the simultaneous South Pacific anomalies, the correlation of the North or South Pacific anomalies with the following ENSO state becomes much weaker, and the strength of the ENSO events also tends to be weaker. One possible reason for this is that when the boreal winter North and South Pacific SLP anomalies have the opposite sign, the westerly anomalies over the western-central equatorial Pacific during the following boreal summer are greatly reduced by the interference between the antecedent North and South Pacific SLP anomalies, thereby not favoring the development of ENSO events. Further analysis indicates that a combination of North and South Pacific precursor signals may serve to enhance the ENSO prediction skill.
Kawasaki disease and ENSO-driven wind circulation
NASA Astrophysics Data System (ADS)
Ballester, Joan; Burns, Jane C.; Cayan, Dan; Nakamura, Yosikazu; Uehara, Ritei; Rodó, Xavier
2013-05-01
disease (KD) is the most common cause of acquired heart disease in children worldwide. Recently, a climatological study suggested that KD may be triggered by a windborne agent traveling across the north Pacific through the westerly wind flow prevailing at midlatitudes. Here we use KD records to describe the association between enhanced disease activity on opposite sides of the basin and different phases of the El Niño-Southern Oscillation (ENSO) phenomenon, via the linkage to these tropospheric winds. Results show that years with higher-than-normal KD cases in Japan preferentially occur during either El Niño Modoki or La Niña conditions, while in San Diego during the mature phase of El Niño or La Niña events. Given that ENSO offers a degree of predictability at lead times of 6 months, these modulations suggest that seasonal predictions of KD could be used to alert clinicians to periods of increased disease activity.
Linear dynamical modes as new variables for data-driven ENSO forecast
NASA Astrophysics Data System (ADS)
Gavrilov, Andrey; Seleznev, Aleksei; Mukhin, Dmitry; Loskutov, Evgeny; Feigin, Alexander; Kurths, Juergen
2018-05-01
A new data-driven model for analysis and prediction of spatially distributed time series is proposed. The model is based on a linear dynamical mode (LDM) decomposition of the observed data which is derived from a recently developed nonlinear dimensionality reduction approach. The key point of this approach is its ability to take into account simple dynamical properties of the observed system by means of revealing the system's dominant time scales. The LDMs are used as new variables for empirical construction of a nonlinear stochastic evolution operator. The method is applied to the sea surface temperature anomaly field in the tropical belt where the El Nino Southern Oscillation (ENSO) is the main mode of variability. The advantage of LDMs versus traditionally used empirical orthogonal function decomposition is demonstrated for this data. Specifically, it is shown that the new model has a competitive ENSO forecast skill in comparison with the other existing ENSO models.
NASA Astrophysics Data System (ADS)
Van de Casteele, Elke; Parizel, Paul; Sijbers, Jan
2012-03-01
Adaptive statistical iterative reconstruction (ASiR) is a new reconstruction algorithm used in the field of medical X-ray imaging. This new reconstruction method combines the idealized system representation, as we know it from the standard Filtered Back Projection (FBP) algorithm, and the strength of iterative reconstruction by including a noise model in the reconstruction scheme. It studies how noise propagates through the reconstruction steps, feeds this model back into the loop and iteratively reduces noise in the reconstructed image without affecting spatial resolution. In this paper the effect of ASiR on the contrast to noise ratio is studied using the low contrast module of the Catphan phantom. The experiments were done on a GE LightSpeed VCT system at different voltages and currents. The results show reduced noise and increased contrast for the ASiR reconstructions compared to the standard FBP method. For the same contrast to noise ratio the images from ASiR can be obtained using 60% less current, leading to a reduction in dose of the same amount.
NASA Astrophysics Data System (ADS)
Manatsa, Desmond; Mushore, Terrence; Lenouo, Andre
2017-01-01
The provision of timely and reliable climate information on which to base management decisions remains a critical component in drought planning for southern Africa. In this observational study, we have not only proposed a forecasting scheme which caters for timeliness and reliability but improved relevance of the climate information by using a novel drought index called the standardised precipitation evapotranspiration index (SPEI), instead of the traditional precipitation only based index, the standardised precipitation index (SPI). The SPEI which includes temperature and other climatic factors in its construction has a more robust connection to ENSO than the SPI. Consequently, the developed ENSO-SPEI prediction scheme can provide quantitative information about the spatial extent and severity of predicted drought conditions in a way that reflects more closely the level of risk in the global warming context of the sub region. However, it is established that the ENSO significant regional impact is restricted only to the period December-March, implying a revisit to the traditional ENSO-based forecast scheme which essentially divides the rainfall season into the two periods, October to December and January to March. Although the prediction of ENSO events has increased with the refinement of numerical models, this work has demonstrated that the prediction of drought impacts related to ENSO is also a reality based only on observations. A large temporal lag is observed between the development of ENSO phenomena (typically in May of the previous year) and the identification of regional SPEI defined drought conditions. It has been shown that using the Southern Africa Regional Climate Outlook Forum's (SARCOF) traditional 3-month averaged Nino 3.4 SST index (June to August) as a predictor does not have an added advantage over using only the May SST index values. In this regard, the extended lead time and improved skill demonstrated in this study could immensely benefit
The role of ENSO in understanding changes in Colombia's annual malaria burden by region, 1960–2006
Mantilla, Gilma; Oliveros, Hugo; Barnston, Anthony G
2009-01-01
Background Malaria remains a serious problem in Colombia. The number of malaria cases is governed by multiple climatic and non-climatic factors. Malaria control policies, and climate controls such as rainfall and temperature variations associated with the El Niño/Southern Oscillation (ENSO), have been associated with malaria case numbers. Using historical climate data and annual malaria case number data from 1960 to 2006, statistical models are developed to isolate the effects of climate in each of Colombia's five contrasting geographical regions. Methods Because year to year climate variability associated with ENSO causes interannual variability in malaria case numbers, while changes in population and institutional control policy result in more gradual trends, the chosen predictors in the models are annual indices of the ENSO state (sea surface temperature [SST] in the tropical Pacific Ocean) and time reference indices keyed to two major malaria trends during the study period. Two models were used: a Poisson and a Negative Binomial regression model. Two ENSO indices, two time reference indices, and one dummy variable are chosen as candidate predictors. The analysis was conducted using the five geographical regions to match the similar aggregation used by the National Institute of Health for its official reports. Results The Negative Binomial regression model is found better suited to the malaria cases in Colombia. Both the trend variables and the ENSO measures are significant predictors of malaria case numbers in Colombia as a whole, and in two of the five regions. A one degree Celsius change in SST (indicating a weak to moderate ENSO event) is seen to translate to an approximate 20% increase in malaria cases, holding other variables constant. Conclusion Regional differentiation in the role of ENSO in understanding changes in Colombia's annual malaria burden during 1960–2006 was found, constituting a new approach to use ENSO as a significant predictor of the
The Impact of ENSO on Trace Gas Composition in the Upper Troposphere to Lower Stratosphere
NASA Technical Reports Server (NTRS)
Oman, Luke; Douglass, Anne; Ziemke, Jerry; Waugh, Darryn Warwick
2016-01-01
The El Nino-Southern Oscillation (ENSO) is the dominant mode of interannual variability in the tropical troposphere and its effects extend well into the stratosphere. Its impact on atmospheric dynamics and chemistry cause important changes to trace gas constituent distributions. A comprehensive suite of satellite observations, reanalyses, and chemistry climate model simulations are illuminating our understanding of processes like ENSO. Analyses of more than a decade of observations from NASAs Aura and Aqua satellites, combined with simulations from the Goddard Earth Observing System Chemistry-Climate Model (GEOSCCM) and other Chemistry Climate Modeling Initiative (CCMI) models, and the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) reanalysis have provided key insights into the response of atmospheric composition to ENSO. While we will primarily focus on ozone and water vapor responses in the upper troposphere to lower stratosphere, the effects of ENSO ripple through many important trace gas species throughout the atmosphere. The very large 2015-2016 El Nino event provides an opportunity to closely examine these impacts with unprecedented observational breadth. An improved quantification of natural climate variations, like those from ENSO, is needed to detect and quantify anthropogenic climate changes.
NASA Astrophysics Data System (ADS)
Perez Arango, J. D.; Lintner, B. R.; Lyon, B.
2016-12-01
Although many aspects of the tropical response to ENSO are well-known, the spatial characteristics of the rainfall response to ENSO remain relatively unexplored. Moreover, in current generation climate models, the spatial signatures of the ENSO tropical teleconnection are more uncertain than other aspects of ENSO variability, such as the amplitude of rainfall anomalies. Following the approach of Lyon (2004) and Lyon and Barnston (2005), we analyze here integrated measures of the spatial extent of drought and pluvial conditions in the tropics and their relationship to ENSO in observations as well as simulations of Phase 5 of the Coupled Model Intercomparison Project (CMIP5) with prescribed SST forcing. We compute diagnostics including the model ensemble-means and standard deviations of moderate, intermediate, and severe droughts and pluvials and the lagged correlations with respect to ENSO-based SST indices like NINO3. Overall, in a tropics-wide sense, the models generally capture the areal extent of observed droughts and pluvials and their phasing with respect to ENSO. However, at more local scales, e.g., tropical South America, the simulated metrics agree less strongly with observations, underscoring the role of errors in the spatial patterns of ENSO-induced rainfall anomalies.
Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng
2015-01-01
Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other. PMID:26678931
The enso signal in the lower stratosphere: propagation via rossby waves.
NASA Astrophysics Data System (ADS)
Calvo, N.; Garcia Herrera, R.; Garcia, R.; Gallego, D.; Gimeno, L.; Hernandez, E.; Ribera, P.
2003-04-01
The ENSO signal on the lower stratosphere has been analyzed through the study of the relationship between SST in the Tropical Pacific and lower stratospheric temperatures from the Microwave Sounding Unit (MSU) using the t4 channel, which is sensitive to lower stratospheric temperature. Lagged point correlations have been calculated between the Niño3.4 index and MSU t4 monthly anomaly series at each grid point for the whole globe from January 1979 through December 2000. Correlation values are very similar in both tropics and extratropics, but their signs are opposite: positive in extratropical regions and negative in the tropics. Moreover, the significant correlation signal is longer lasting at middle latitudes, from lag 9 to lag 6, and much shorter in the Tropics, where it is significant only at lags 0 and 3. In the extratropical area, four regions are significant: Eurasia, the Southern Indian Ocean, and the North and South Pacific Oceans. The signal in Eurasia is the first to be observed (at lag 9) and it could be considered as a predictor of extreme ENSO events. The Pacific Ocean shows the PNA and PSA patterns. There, the signal appears earlier in the Southern Hemisphere (lag 6) because wind conditions at boreal summer (usually lag 6) do not favour the propagation of Rossby waves into the stratosphere. Further, the shape of the correlation patterns suggests that only planetary waves are able to propagate the ENSO signal into the stratosphere. In the tropics, the ENSO signal takes the form of a pair of Rossby gyres, observed in the Pacific Ocean at lags 0 and 3 as two regions of significant correlation located symmetricaly north and south of the Equator. The same analysis has been carried out for a period without any extreme events (SST anomalies in the Niño3.4 region smaller than 1 standard desviation), in which case no signal is observed in the lower stratosphere. This suggests that only strong ENSO (defined by anomalies larger than 1 standard desviation in
A Further Extension of the Tahiti-Darwin SOI, Early ENSO Events and Darwin Pressure.
NASA Astrophysics Data System (ADS)
Allan, Robert J.; Nicholls, Neville; Jones, Phil D.; Butterworth, Ian J.
1991-07-01
An extension of the Tahiti minus Darwin Southern Oscillation Index (SOI) from 1882 back to 1876 is reported following the recovery of early Darwin mean sea-level pressure data spanning the period 1865-81. As a result, we are able to compare, for the first time, the major 1877-78 and 1982-83 ENSO events on the basis of this commonly used index. Early Darwin and Jakarta data are also examined in terms of a measure of the Australian response to documented El Niño and/or ENSO events in 1866, 1868, 1871, 1873, 1874 and 1875.The SOI during the 1877-78 ENSO event has a similar temporal response to that in 1982-83, but the index is slightly weaker than in the recent event. Examination of documentary evidence confirms the severity of the drought conditions that affected the Australian continent during the 1877-78 ENSO, and shows that this response is in line with the wider Indo-Pacific impacts reported in the literature. Earlier El Niño phases in 1868 and 1873 are not resolved distinctly in either the Darwin or Jakarta pressure data. This appears to illustrate that El Niño event histories do not always indicate wider ENSO influences in the Indo-Pacific basin, particularly during weak to moderate phases.
NASA Astrophysics Data System (ADS)
Zheng, Xiao-Tong; Hui, Chang; Yeh, Sang-Wook
2018-06-01
El Niño-Southern Oscillation (ENSO) is the dominant mode of variability in the coupled ocean-atmospheric system. Future projections of ENSO change under global warming are highly uncertain among models. In this study, the effect of internal variability on ENSO amplitude change in future climate projections is investigated based on a 40-member ensemble from the Community Earth System Model Large Ensemble (CESM-LE) project. A large uncertainty is identified among ensemble members due to internal variability. The inter-member diversity is associated with a zonal dipole pattern of sea surface temperature (SST) change in the mean along the equator, which is similar to the second empirical orthogonal function (EOF) mode of tropical Pacific decadal variability (TPDV) in the unforced control simulation. The uncertainty in CESM-LE is comparable in magnitude to that among models of the Coupled Model Intercomparison Project phase 5 (CMIP5), suggesting the contribution of internal variability to the intermodel uncertainty in ENSO amplitude change. However, the causations between changes in ENSO amplitude and the mean state are distinct between CESM-LE and CMIP5 ensemble. The CESM-LE results indicate that a large ensemble of 15 members is needed to separate the relative contributions to ENSO amplitude change over the twenty-first century between forced response and internal variability.
NASA Technical Reports Server (NTRS)
Yonekura, Emmi; Hall, Timothy M.
2014-01-01
Improvements on a statistical tropical cyclone (TC) track model in the western North Pacific Ocean are described. The goal of the model is to study the effect of El Nino-Southern Oscillation (ENSO) on East Asian TC landfall. The model is based on the International Best-Track Archive for Climate Stewardship (IBTrACS) database of TC observations for 1945-2007 and employs local regression of TC formation rates and track increments on the Nino-3.4 index and seasonally varying climate parameters. The main improvements are the inclusion of ENSO dependence in the track propagation and accounting for seasonality in both genesis and tracks. A comparison of simulations of the 1945-2007 period with observations concludes that the model updates improve the skill of this model in simulating TCs. Changes in TC genesis and tracks are analyzed separately and cumulatively in simulations of stationary extreme ENSO states. ENSO effects on regional (100-km scale) landfall are attributed to changes in genesis and tracks. The effect of ENSO on genesis is predominantly a shift in genesis location from the southeast in El Nino years to the northwest in La Nina years, resulting in higher landfall rates for the East Asian coast during La Nina. The effect of ENSO on track propagation varies seasonally and spatially. In the peak activity season (July-October), there are significant changes in mean tracks with ENSO. Landfall-rate changes from genesis- and track-ENSO effects in the Philippines cancel out, while coastal segments of Vietnam, China, the Korean Peninsula, and Japan show enhanced La Nina-year increases.
The impact of ENSO on regional chlorophyll-a anomaly in the Arafura Sea
NASA Astrophysics Data System (ADS)
Dewi, D. M. P. R.; Fatmasari, D.; Kurniawan, A.; Munandar, M. A.
2018-03-01
The El Niño-Southern Oscillation (ENSO) is a naturally occurring phenomenon that involves fluctuating ocean temperature in the equatorial Pacific. ENSO influences ocean climate variability in Indonesia including the Arafura Sea. The relationship between oceanic chlorophyll-a and ENSO has been the focus of study over the past decade. Here we examine the impact of ENSO on regional chlorophyll-a anomaly in the Papua waters using 14 years of chlorophyll-a and sea surface temperature (SST) data from AQUA MODIS and sea level anomaly data from AVISO. It is found that when El Niño events occur the negative SST anomaly in the Papua waters as well as the enhanced upwelling cause the increase of chlorophyll-a concentration. The highest chlorophyll-a concentration (> 1 mg–cm-3) occured during El Niño and observed around the Aru archipelago. In contrast during La Niña event, the positive SST anomaly in Papua waters and the suppressed upwelling cause the decrease of chlorophyll-a concentration. Our results suggest that during El Niño (La Niña), the enhanced (suppressed) upwelling related to the significant decreasing (increasing) of sea level anomaly.
Development of a global Agricultural Stress Index System (ASIS) based on remote sensing data
NASA Astrophysics Data System (ADS)
Van Hoolst, R.
2016-12-01
According to the 2012 IPCC SREX report, extreme drought events are projected to become more frequent and intense in several regions of the world. Wide and timely monitoring systems are required to mitigate the impact of agricultural drought. Therefore, FAO's Global Information and Early Warning System (GIEWS) and the Climate, Energy and Tenure Division (NRC) have established the `Agricultural Stress Index System' (ASIS). The ASIS is a remote sensing application that provides early warnings of agricultural drought at a global scale. The ASIS has first been designed and described by Rojas et al. (2011). This study focused on the African continent and was based on the back processing of low resolution data of the NOAA-satellites. In the current setup, developed by VITO (Flemish Institute for Technological Research), the system operates in Near Real Time using data from the METOP-AVHRR sensor. The Agricultural Stress Index (ASI) is the percentage of agricultural area affected by drought in the course of the growing season within a given administrative unit. The start and end of the growing season are derived per pixel from the long term NDVI average of SPOT-VEGETATION. The Global Administrative Unit Layer (GAUL) defines the administrative boundaries at level 0, 1 and 2. A global cropland and grassland map eliminates non-agricultural areas. Temperature and NDVI anomalies are used as drought indicators and calculated at a per pixel base. The ASIS aggregates this information and produces every dekad global maps to highlight hotspots of drought stress. New developments are ongoing to strengthen the ASIS to produce country specific outputs, improve existing drought indicators and estimate production deficits using a probabilistic approach.
Connection between ENSO and Asian Summer Monsoon Precipitation Oxygen Isotope
NASA Astrophysics Data System (ADS)
Cai, Z.; Tian, L.
2016-12-01
In an effort to understand the connection between El Niño Southern Oscillation (ENSO) and Asian Summer Monsoon (ASM) precipitation oxygen isotope, this study investigates the spatial and interannual patterns in summer (JJAS) monsoon precipitation δ18O and satellite water vapor isotope retrievals, especially those patterns associated with convection and vapor transport. Both precipitation and vapor isotope values exhibit a "V" shaped longitudinal pattern in their spatial variations, reflecting the gradual rainout and increase in convective intensity along vapor transport routes. In order to understand interannual variations, an ASM precipitation δ18O index (ASMOI) is introduced to measure the temporal variations in regional precipitation δ18O; and these variations are consistent with central Indo-Pacific convection and cloud-top height. The counter variations in the ASMOI in El Niño and La Niña years confirm the existence of a positive isotope- ENSO response (e.g., high values corresponding to warm phases) over the eastern Indian Ocean and southeastern Asia (80°E-120°E/10°S-30°N) as a response to changes in convection. However, JJAS vapor δD over the western Pacific (roughly east of 120oE) varies in opposition, due to the influence of water vapor transport. This opposite variation does not support the interpretation of precipitation isotope-ENSO relationship as changing proportion of vapor transported from different regions, but rather condensation processes associated with convection. These findings are important for studying past ASM and ENSO activity from various isotopic archives and have implications for the study of the atmospheric water cycle.
The role of sea surface salinity in ENSO related water cycle anomaly
NASA Astrophysics Data System (ADS)
Tang, Wenqing; Yueh, Simon
2017-04-01
This study investigates the role of sea surface salinity (SSS) in the water cycle anomaly associated with El Niño Southern Oscillation (ENSO). The 2015-16 El Niño, one of the strongest ENSO events observed in centuries, coincident with unprecedented coverage of spacebased remote sensing of SSS over global oceans. We analyze three SSS data sets: from the NASA's missions of SMAP and Aquarius, and the ESA's Soil Moisture and Ocean Salinity (SMOS). One typical characteristics of an ENSO event is the zonal displacement of the Western equatorial Pacific Fresh Pool (WPFP). The edge of the pool extends eastward during El Niño, retreats westward during La Niña. For super El Niño, the eastern edge of WPFP extends much more east across the equatorial Pacific. Indeed, SSS from SMAP reveals much stronger eastward migration of WPFP starting in April 2015. The eastern edge of WPFP reached 140°W in March 2016, about 40° more eastward extension than Aquarius observed in previous years. In the following months from March to June 2016, WPFP retreated westward, coincident with the ending of this strong El Niño event [WMO, El Nino/La Nina update, 2016]. SMOS data shows similar feature, confirming that there is no systematic biases between SMAP and Aquarius retrievals. We examine the linkage between the observed SSS variation and ENSO related water cycle anomaly by integrated analysis of SSS data sets in conjunction with other satellite and in situ measurements on rain, wind, evaporation and ocean currents. Based on the governing equation of the mixed layer salt budget, the freshwater exchange between air-sea interfaces is estimated as residual of the mixed-layer salinity (MLS) temporal change and advection (Focean), as an alternative to evaporation minus precipitation (FE-P). We analyzed the spatial and temporal variation of Focean and FE-P to explore the anomalous signature in the oceanic and atmospheric branches of the water cycle associated with 2015/16 ENSO. The maximum
ENSO-Based Index Insurance: Approach and Peru Flood Risk Management Application
NASA Astrophysics Data System (ADS)
Khalil, A. F.; Kwon, H.; Lall, U.; Miranda, M. J.; Skees, J. R.
2006-12-01
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 due to short time-series and the spatial dispersion of stations. In such cases, it may be helpful to consider a climate proxy index as a regional rainfall index. This is particularly useful if a long record is available for the climate index through an independent source and it is well correlated with the regional rainfall hazard. Here, ENSO related climate indices are explored for use as a proxy to extreme rainfall in one of the departments of Peru -- Piura. The ENSO index insurance product may be purchased by banks or microfinance institutions (MFIs) to aid agricultural damage relief in Peru. Crop losses in the region are highly correlated with floods, but are difficult to assess directly. Beyond agriculture, many other sectors suffer as well. Basic infrastructure is destroyed during the most severe events. This disrupts trade for many micro-enterprises. The reliability and quality of the local rainfall data is variable. Averaging the financial risk across the region is desirable. Some issues with the implementation of the proxy ENSO index are identified and discussed. Specifically, we explore (a) the reliability of the index at different levels of probability of exceedance of maximum seasonal rainfall; (b) the potential for clustering of payoffs; (c) the potential that the index could be predicted with some lead time prior to the flood season; and (d) evidence for climate change or non-stationarity in the flood exceedance probability from the long ENSO record. Finally, prospects for
NASA Astrophysics Data System (ADS)
Li, Gang; Li, Chongyin; Tan, Yanke; Bai, Tao
2014-01-01
The characteristic changes of South Pacific sea surface temperature anomalies (SSTAs) for the period January 1979 to December 2011, during which the 1990s Pacific pan-decadal variability (PDV) interdecadal regime shifts occurred, were examined. Empirical Orthogonal Function (EOF) analysis was applied to the monthly mean SSTA for two sub-periods: January 1979 to December 1994 (P1) and January 1996 to December 2011 (P2). Both the spatial and temporal features of the leading EOF mode for P1 and P2 showed a remarkable difference. The spatial structure of the leading EOF changed from a tripolar pattern for P1 (EOF-P1) to a dipole-like pattern for P2 (EOF-P2). Besides, EOF-P1 (EOF-P2) had significant spectral peaks at 4.6 yr (2.7 yr). EOF-P2 not only had a closer association with El Niño-Southern Oscillation (ENSO), but also showed a faster response to ENSO than EOF-P1 based on their lead-lag relationships with ENSO. During the development of ENSO, the South Pacific SSTA associated with ENSO for both P1 and P2 showed a significant eastward propagation. However, after the peak of ENSO, EOF-P1 showed a stronger persistence than EOF-P2, which still showed eastward propagation. The variability of the SSTA associated with the whole process of ENSO evolution during P1 and the SSTA associated with the development of ENSO during P2 support the existence of ocean-to-atmosphere forcing, but the SSTA associated with the decay of ENSO shows the phenomenon of atmosphere-to-ocean forcing.
Influence of ENSO on coastal flood hazard and exposure at the global-scale
NASA Astrophysics Data System (ADS)
Muis, S.; Haigh, I. D.; Guimarães Nobre, G.; Aerts, J.; Ward, P.
2017-12-01
The El Niño-Southern Oscillation (ENSO) is the dominant signal of interannual climate variability. The unusually warm (El Niño) and cold (La Niña) oceanic and atmospheric conditions in the tropical Pacific drives interannual variability in both mean and extreme sea levels, which in turn may influence the probabilities and impacts of coastal flooding. We assess the influence of ENSO on coastal flood hazard and exposure using daily timeseries from the Global Time and Surge Reanalysis (GTSR) dataset (Muis et al., 2016). As the GTSR timeseries do not include steric effects (i.e. density differences), we improve the GTSR timeseries by adding steric sea levels. Evaluation against observed sea levels shows that the including steric sea levels leads to a much better representation of the seasonal and interannual variability. We show that sea level anomalies occur during ENSO years with higher sea levels during La Niña in the South-Atlantic, Indian Ocean and the West Pacific, whereas sea levels are lower in the east Pacific. The pattern is generally inversed for El Niño. We also find an effect of ENSO in the number of people exposed to coastal flooding. Although the effect is minor at the global-scale, it may be important for flood risk management to consider at the national or sub national levels. Previous studies at the global-scale have used tide gauge observation to assess the influence of ENSO on extreme sea levels. The advantage of our approach over observations is that GTSR provides a consistent dataset with a full global coverage for the period 1979-2014. This allows us to assess ENSO's influence on sea level extremes anywhere in the world. Furthermore, it enables us to also calculate the impacts of extreme sea levels in terms of coastal flooding and exposed population. ReferencesMuis et al (2016) A global reanalysis of storm surges and extreme sea levels. Nature Communications.7:11969. doi:10.1038/ncomms11969.
HadCM3 Simulations of ENSO behaviour during the Mid-Pliocene Warm Period
NASA Astrophysics Data System (ADS)
Bonham, S. G.; Haywood, A. M.; Lunt, D. J.
2009-04-01
It has been suggested that a permanent El Niño state existed during the mid-Pliocene (ca. 3.3 - 3.0 Ma BP), with a west-to-east temperature gradient in the tropical Pacific considerably weaker than today. This is based upon a number of palaeoceanographic studies which have examined the development of the thermocline and SST gradient in the tropical Pacific over the last five million years. This state is now being referred to as El Padre in recognition of the fact that a mean state warming in EEP SSTs does not necessarily imply the presence of a permanent El Niño. Recent results from mid-Pliocene coupled ocean-atmosphere model simulations have shown clear ENSO variability whilst maintaining the warming in the EEP. This research expands on this study, using the UK Met Office GCM (HadCM3), to examine the behaviour and characteristics of ENSO in two mid-Pliocene simulations (with an open and closed Central American Seaway, CAS) compared with a control pre-industrial run, as well as produce a detailed profile of the mean state climates. The results shown include timescales of ENSO variability across four regions in the Pacific, as well as frequency, EOF and wavelet analysis. We have also looked at the interaction of ENSO with the annual cycle and the onset of ENSO events, and the interdecadal variability in the simulations. The initial timeseries produced have shown a greater variability of ENSO during the closed CAS mid-Pliocene simulation where the system oscillates between events much more frequently than seen in the pre-industrial run. The EOF and wavelet analyses quantify this behaviour, showing that the variability is approximately 15% higher over the central and eastern equatorial Pacific, with a period of oscillation of 2-5 years compared with 4-8 years for the pre-industrial simulation. These results will be compared with those obtained from the second mid-Pliocene simulation (open CAS).
NASA Astrophysics Data System (ADS)
Adnan Abid, Mohammad; Almazroui, Mansour; Kucharski, Fred
2017-04-01
Summer seasonal rainfall falls mainly over the south and southwestern parts of the Arabian Peninsula (AP). The relationship between this mean summer seasonal rainfall pattern and El Niño Southern Oscillation (ENSO) is analyzed with the aid of a 15-member ensemble of simulations using the King Abdulaziz University (KAU) Atmospheric Global Climate Model (AGCM). Each simulation is forced with Hadley Sea Surface Temperature (SST) for the period 1980-2015. The southwestern peninsula rainfall is linked towith the SST anomalies in the central-eastern pacific region. This relation is established through an atmospheric teleconnection which shows an upper-level convergence (divergence) anomalies over the southern Arabian Peninsula compensating the central-eastern Pacific region upper-level divergence (convergence) anomalies for the warm (cold) El Niño Southern Oscillaton (ENSO) phase. The upper-level convergence (divergence) over the southern Arabian Peninsula leads to sinking (rising) motion, low-level divergence (convergence) and consequently to reduced (enhanced) rainfall. The correlation coefficient between the observed area-averged Niño3.4 index and athe South Arabian Rainfall Index (SARI) is -0.54. This indicates that AP receives less rainfall during the warm (El Niño) phase, while the opposite happens in the cold (La Niña) El Niño Southern Oscillaton (ENSO) phase. The lower tropospheric cyclonic circulation anomalies strongly modulate the ENSO-related rainfall in the region. Overall, the model shows a 43% potential predictability (PP) for the Southern Arabian Peninsula Rainfall Index (SARI). Further, the predictability during the warm ENSO (El Niño) events is higher than during cold ENSO (La Niña) events. This is not only because of a stronger signal, but also noise reduction contributes to the increase of the regional PP in El Niño compared to that of La Niña years.
Dual Use of Packaging on the Moon: Logistics-2-Living
NASA Technical Reports Server (NTRS)
Howe, A. Scott; Howard, Robert
2010-01-01
This paper describes a modular packaging system for logistics that can be reconfigured into internal outfitting for a lunar outpost, including desks, chairs, partitions, cabinets, and radiation shielding. Logistics include clothes, equipment, food, and other consumables needed to sustain the crew for the duration of the mission. A significant mass penalty is required for the packaging and handling of logistics for re-supply of short to long-term space missions that must be brought out of the gravity well on a launch vehicle. Once the supplies have been exhausted, the packaging material is typically of no further use and is discarded. If a scheme can be developed that reuses the logistics packaging, the mass penalty can be reduced. In this research, a modular packaging system has been devised as a kit-of-parts that can be used for both handling logistics supplies, and then reconfigured into desks, chairs, partitions, cabinets, and radiation shielding. The system is derived from a standard International Space Station (ISS)-type Cargo Transfer Bag (CTB), using soft, unfoldable box-like containers with stiff metal inserts. The empty hydrogen-impregnated CTBs can be used as-is for cabinets, opened up for use as partitions, or draped over the habitat as layers of radiation shielding. Stiff metal inserts can be reconfigured into desks and other useful outfitting.
NASA Astrophysics Data System (ADS)
Endris, Hussen Seid; Lennard, Christopher; Hewitson, Bruce; Dosio, Alessandro; Nikulin, Grigory; Artan, Guleid A.
2018-05-01
This study examines the projected changes in the characteristics of the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) in terms of mean state, intensity and frequency, and associated rainfall anomalies over eastern Africa. Two regional climate models driven by the same four global climate models (GCMs) and the corresponding GCM simulations are used to investigate projected changes in teleconnection patterns and East African rainfall. The period 1976-2005 is taken as the reference for present climate and the far-future climate (2070-2099) under Representative Concentration Pathway 8.5 (RCP8.5) is analyzed for projected change. Analyses of projections based on GCMs indicate an El Niño-like (positive IOD-like) warming pattern over the tropical Pacific (Indian) Ocean. However, large uncertainties remain in the projected future changes in ENSO/IOD frequency and intensity with some GCMs show increase of ENSO/IOD frequency and intensity, and others a decrease or no/small change. Projected changes in mean rainfall over eastern Africa based on the GCM and RCM data indicate a decrease in rainfall over most parts of the region during JJAS and MAM seasons, and an increase in rainfall over equatorial and southern part of the region during OND, with the greatest changes in equatorial region. During ENSO and IOD years, important changes in the strength of the teleconnections are found. During JJAS, when ENSO is an important driver of rainfall variability over the region, both GCM and RCM projections show an enhanced La Niña-related rainfall anomaly compared to the present period. Although the long rains (MAM) have little association with ENSO in the reference period, both GCMs and RCMs project stronger ENSO teleconnections in the future. On the other hand, during the short rains (OND), a dipole future change in rainfall teleconnection associated with ENSO and IOD is found, with a stronger ENSO/IOD related rainfall anomaly over the eastern part of the domain
Marine lake ecosystem dynamics illustrate ENSO variation in the tropical western Pacific
Martin, Laura E; Dawson, Michael N; Bell, Lori J; Colin, Patrick L
2005-01-01
Understanding El Niño/Southern Oscillation (ENSO) and its biological consequences is hindered by a lack of high-resolution, long-term data from the tropical western Pacific. We describe a preliminary, 6 year dataset that shows tightly coupled ENSO-related bio-physical dynamics in a seawater lake in Palau, Micronesia. The lake is more strongly stratified during La Niña than El Niño conditions, temperature anomalies in the lake co-vary strongly with the Niño 3.4 climate index, and the abundance of the dominant member of the pelagic community, an endemic subspecies of zooxanthellate jellyfish, is temperature associated. These results have broad relevance because the lake: (i) illustrates an ENSO signal that is partly obscured in surrounding semi-enclosed lagoon waters and, therefore, (ii) may provide a model system for studying the effects of climate change on community evolution and cnidarian–zooxanthellae symbioses, which (iii) should be traceable throughout the Holocene because the lake harbours a high quality sediment record; the sediment record should (iv) provide a sensitive and regionally unique record of Holocene climate relevant to predicting ENSO responses to future global climate change and, finally, (v) seawater lake ecosystems elsewhere in the Pacific may hold similar potential for past, present, and predictive measurements of climate variation and ecosystem response. PMID:17148349
Marine lake ecosystem dynamics illustrate ENSO variation in the tropical western Pacific.
Martin, Laura E; Dawson, Michael N; Bell, Lori J; Colin, Patrick L
2006-03-22
Understanding El Niño/Southern Oscillation (ENSO) and its biological consequences is hindered by a lack of high-resolution, long-term data from the tropical western Pacific. We describe a preliminary, 6 year dataset that shows tightly coupled ENSO-related bio-physical dynamics in a seawater lake in Palau, Micronesia. The lake is more strongly stratified during La Niña than El Niño conditions, temperature anomalies in the lake co-vary strongly with the Niño 3.4 climate index, and the abundance of the dominant member of the pelagic community, an endemic subspecies of zooxanthellate jellyfish, is temperature associated. These results have broad relevance because the lake: (i) illustrates an ENSO signal that is partly obscured in surrounding semi-enclosed lagoon waters and, therefore, (ii) may provide a model system for studying the effects of climate change on community evolution and cnidarian-zooxanthellae symbioses, which (iii) should be traceable throughout the Holocene because the lake harbours a high quality sediment record; the sediment record should (iv) provide a sensitive and regionally unique record of Holocene climate relevant to predicting ENSO responses to future global climate change and, finally, (v) seawater lake ecosystems elsewhere in the Pacific may hold similar potential for past, present, and predictive measurements of climate variation and ecosystem response.
NASA Astrophysics Data System (ADS)
Ohdaira, Keisuke; Matsumura, Hideki
2013-01-01
We succeed in the formation of micrometer-order-thick polycrystalline silicon (poly-Si) films through the flash-lamp-induced liquid-phase explosive crystallization (EC) of precursor a-Si films prepared by electron-beam (EB) evaporation. The velocity of the explosive crystallization (vEC) is estimated to be ˜14 m/s, which is close to the velocity of the liquid-phase epitaxy (LPE) of Si at a temperature around the melting point of a-Si of 1418 K. Poly-Si films formed have micrometer-order-long grains stretched along a lateral crystallization direction, and X-ray diffraction (XRD) and electron diffraction pattern measurements reveal that grains in poly-Si films tend to have a particular orientation. These features are significantly different from our previous results: the formation of poly-Si films containing randomly-oriented 10-nm-sized fine grains formed from a-Si films prepared by catalytic chemical vapor deposition (Cat-CVD) or sputtering. One possible reason for the emergence of a different EC mode in EB-evaporated a-Si films is the suppression of solid-phase nucleation (SPN) during Flash Lamp Annealing (FLA) due to tensile stress which precursor a-Si films originally hold. Poly-Si films formed from EB-evaporated a-Si films would contribute to the realization of high-efficiency thin-film poly-Si solar cells because of large and oriented grains.
SchemaOnRead: A Package for Schema-on-Read in R
DOE Office of Scientific and Technical Information (OSTI.GOV)
North, Michael J.
Schema-on-read is an agile approach to data storage and retrieval that defers investments in data organization until production queries need to be run by working with data directly in native form. Schema-on-read functions have been implemented in a wide range of analytical systems, most notably Hadoop. SchemaOnRead is a CRAN package that uses R’s flexible data representations to provide transparent and convenient support for the schema-on-read paradigm in R. The schema-on- read tools within the package include a single function call that recursively reads folders with text, comma separated value, raster image, R data, HDF5, NetCDF, spreadsheet, Weka, Epi Info,more » Pajek network, R network, HTML, SPSS, Systat, and Stata files. The provided tools can be used as-is or easily adapted to implement customized schema-on-read tool chains in R. This paper’s contribution is that it introduces and describes SchemaOnRead, the first R package specifically focused on providing explicit schema-on-read support in R.« less
Role of 20th tropical precipitation on ENSO amplitude changes due to greenhouse warming in CMIP5
NASA Astrophysics Data System (ADS)
Ham, Yoo-Geun; Kug, Jong-Seong
2016-04-01
This study examines the relationship between the intermodel diversities of the present-climate climatology and those of ENSO amplitude change under global warming in the Coupled Model Intercomparison Project phase 5 (CMIP5) models. The models with increased ENSO amplitude under greenhouse warming (i.e., 'ENSO-amplified models') tend to simulate a 20th century stronger climatological ITCZ and SPCZ over the central-eastern Pacific that are located further away from the equator during boreal spring. Moisture budget analysis indicates that those climatological differences lead to stronger positive climatological precipitation change over the off-equatorial central-eastern Pacific under greenhouse warming. The stronger positive climatological precipitation change enhances the air-sea coupling strength over the central-eastern Pacific, which leads to increase the ENSO amplitude.
Modulation of Winter Precipitation Dynamics Over the Arabian Gulf by ENSO
NASA Astrophysics Data System (ADS)
Sandeep, S.; Ajayamohan, R. S.
2018-01-01
The Arabian Gulf (Gulf) and the surrounding regions are centers of intense economic activity. The precipitating weather systems that form over the Gulf are important for this predominantly arid region. It is suggested that El Niño-Southern Oscillation (ENSO) influences the Middle East precipitation variability through an equatorward shift of the subtropical jet. Here we present compelling evidence to illustrate the role of ENSO in modulating the local dynamics and moisture transport in initiating precipitation during different ENSO phases using satellite and reanalysis data. It is found that the moisture transport from the Red and Arabian Seas toward the Gulf is stronger during El Niño years. The pattern and strength of moisture transport toward the Gulf is weakened during La Niña and neutral years, with most of the transport directed toward the northern Gulf. Using a 120 h back trajectory analysis, it is found that while the air parcels coming toward the Gulf from the Arabian and Red Seas side originate at lower tropospheric levels, the air parcels from the Mediterranean originate at middle and upper tropospheric levels during El Niño years. In contrast, upper tropospheric air parcels originating over the southern Arabian Sea plays a dominant role on Gulf precipitation during La Niña and neutral years. The seasonal mean transients of zonal winds show a robust ENSO signature over the Gulf, indicating a favorable (less favorable) condition for the penetration of midlatitude eddies over the region during El Niño (La Niña) winters.
ENSO detection and use to inform the operation of large scale water systems
NASA Astrophysics Data System (ADS)
Pham, Vuong; Giuliani, Matteo; Castelletti, Andrea
2016-04-01
El Nino Southern Oscillation (ENSO) is a large-scale, coupled ocean-atmosphere phenomenon occurring in the tropical Pacific Ocean, and is considered one of the most significant factors causing hydro-climatic anomalies throughout the world. Water systems operations could benefit from a better understanding of this global phenomenon, which has the potential for enhancing the accuracy and lead-time of long-range streamflow predictions. In turn, these are key to design interannual water transfers in large scale water systems to contrast increasingly frequent extremes induced by changing climate. Despite the ENSO teleconnection is well defined in some locations such as Western USA and Australia, there is no consensus on how it can be detected and used in other river basins, particularly in Europe, Africa, and Asia. In this work, we contribute a general framework relying on Input Variable Selection techniques for detecting ENSO teleconnection and using this information for improving water reservoir operations. Core of our procedure is the Iterative Input variable Selection (IIS) algorithm, which is employed to find the most relevant determinants of streamflow variability for deriving predictive models based on the selected inputs as well as to find the most valuable information for conditioning operating decisions. Our framework is applied to the multipurpose operations of the Hoa Binh reservoir in the Red River basin (Vietnam), taking into account hydropower production, water supply for irrigation, and flood mitigation during the monsoon season. Numerical results show that our framework is able to quantify the relationship between the ENSO fluctuations and the Red River basin hydrology. Moreover, we demonstrate that such ENSO teleconnection represents valuable information for improving the operations of Hoa Binh reservoir.
Effect of AMOC collapse on ENSO in a high resolution general circulation model
NASA Astrophysics Data System (ADS)
Williamson, Mark S.; Collins, Mat; Drijfhout, Sybren S.; Kahana, Ron; Mecking, Jennifer V.; Lenton, Timothy M.
2018-04-01
We look at changes in the El Niño Southern Oscillation (ENSO) in a high-resolution eddy-permitting climate model experiment in which the Atlantic Meridional Circulation (AMOC) is switched off using freshwater hosing. The ENSO mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased ENSO period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the meridional sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in ENSO amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude.
ENSO shifts and their link to Southern Africa surface air temperature in summer
NASA Astrophysics Data System (ADS)
Manatsa, D.; Mukwada, G.; Makaba, L.
2018-05-01
ENSO has been known to influence the trends of summer warming over Southern Africa. In this work, we used observational and reanalysis data to analyze the relationship between ENSO and maximum surface air temperature (SATmax) trends during the three epochs created by the ENSO phase shifts around 1977 and 1997 for the period 1960 to 2014. We observed that while ENSO and cloud cover remains the dominant factor controlling SATmax variability, the first two epochs had the predominant La Niña (El Niño)-like events connected to robust positive (negative) trends in cloud fraction. However, this established relationship reversed in the post-1997 La Niña-like dominated epoch which coincided with a falling cloud cover trend. It is established that this deviation from the previously established link within the previous epochs could be due to the post-1998 era in which SATmin was suppressed while SATmax was enhanced. The resulting increase in diurnal temperature range (DTR) could have discouraged the formation of low-level clouds which have relatively more extensive areal coverage and hence allowing more solar energy to reach the surface to boost daytime SATmax. It is noted that these relationships are more pronounced from December to March.
Tree Carbohydrate Dynamics Across a Rainfall Gradient in Panama During the 2016 ENSO
NASA Astrophysics Data System (ADS)
Dickman, L. T.; Xu, C.; Behar, H.; McDowell, N.
2017-12-01
Non-structural carbohydrates (NSC) provide a measure of the carbon supply available to support respiration, growth, and defense. Support for a role of carbon starvation - or depletion of NSC stores - in drought induced tree mortality is varied without consensus for the tropics. The 2016 ENSO drought provided a unique opportunity to capture drought impacts on tropical forest carbohydrate dynamics. To quantify these impacts, we collected monthly NSC samples across a rainfall gradient in Panama for the duration of the ENSO. We observed high variability in foliar NSC among species within sites. Foliage contained very little starch, indicating that total NSC dynamics are driven by soluble sugars. Foliar NSC depletion did not progress with drought duration as predicted, but showed little variation over course of the ENSO. Foliar NSC did, however, increase with rainfall, suggesting NSC depletion may occur with longer-term drought. These results suggest that, while short-term droughts like the 2016 ENSO may not have a significant impact on carbon dynamics, we may observe greater impacts as drought progresses over longer timescales. These results will be used to evaluate whether the current implementation of carbon starvation in climate models are capturing observed trends in tropical forest carbon allocation and mortality, and to tune model parameters for improved predictive capability.
Empirical modeling ENSO dynamics with complex-valued artificial neural networks
NASA Astrophysics Data System (ADS)
Seleznev, Aleksei; Gavrilov, Andrey; Mukhin, Dmitry
2016-04-01
The main difficulty in empirical reconstructing the distributed dynamical systems (e.g. regional climate systems, such as El-Nino-Southern Oscillation - ENSO) is a huge amount of observational data comprising time-varying spatial fields of several variables. An efficient reduction of system's dimensionality thereby is essential for inferring an evolution operator (EO) for a low-dimensional subsystem that determines the key properties of the observed dynamics. In this work, to efficient reduction of observational data sets we use complex-valued (Hilbert) empirical orthogonal functions which are appropriate, by their nature, for describing propagating structures unlike traditional empirical orthogonal functions. For the approximation of the EO, a universal model in the form of complex-valued artificial neural network is suggested. The effectiveness of this approach is demonstrated by predicting both the Jin-Neelin-Ghil ENSO model [1] behavior and real ENSO variability from sea surface temperature anomalies data [2]. The study is supported by Government of Russian Federation (agreement #14.Z50.31.0033 with the Institute of Applied Physics of RAS). 1. Jin, F.-F., J. D. Neelin, and M. Ghil, 1996: El Ni˜no/Southern Oscillation and the annual cycle: subharmonic frequency locking and aperiodicity. Physica D, 98, 442-465. 2. http://iridl.ldeo.columbia.edu/SOURCES/.KAPLAN/.EXTENDED/.v2/.ssta/
NASA Astrophysics Data System (ADS)
Geng, Xin; Zhang, Wenjun; Jin, Fei-Fei; Stuecker, Malte F.
2018-01-01
We here propose a new statistical method to interpret nonstationary running correlations by decomposing them into a stationary part and a first-order Taylor expansion approximation for the nonstationary part. Then, this method is applied to investigate the nonstationary behavior of the El Niño-Southern Oscillation (ENSO)-East Asian winter monsoon (EAWM) relationship, which exhibits prominent multidecadal variations. It is demonstrated that the first-order approximation of the nonstationary part can be expressed to a large extent by the impact of the nonlinear interaction between the Atlantic Multidecadal Oscillation (AMO) and ENSO (AMO*Niño3.4) on the EAWM. Therefore, the nonstationarity in the ENSO-EAWM relationship comes predominantly from the impact of an AMO modulation on the ENSO-EAWM teleconnection via this key nonlinear interaction. This general method can be applied to investigate nonstationary relationships that are often observed between various different climate phenomena.
The Response of Tropospheric Ozone to ENSO in Observations and a Chemistry-Climate Simulation
NASA Technical Reports Server (NTRS)
Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Waugh, D. W.; Rodriguez, J. M.; Nielsen, J. E.
2012-01-01
The El Nino-Southern Oscillation (ENSO) is the dominant mode of tropical variability on interannual time scales. ENSO appears to extend its influence into the chemical composition of the tropical troposphere. Recent results have revealed an ENSO induced wave-l anomaly in observed tropical tropospheric column ozone. This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this result using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years. An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region. We will show targeted comparisons with observations from NASA's Aura satellite Microwave Limb Sounder (MLS), and the Tropospheric Emissions Spectrometer (TES) to provide insight into the vertical structure of ozone changes. The tropospheric ozone response to ENSO could be a useful chemistry-climate model evaluation tool and should be considered in future modeling assessments.
Simulating Eastern- and Central-Pacific Type ENSO Using a Simple Coupled Model
NASA Astrophysics Data System (ADS)
Fang, Xianghui; Zheng, Fei
2018-06-01
Severe biases exist in state-of-the-art general circulation models (GCMs) in capturing realistic central-Pacific (CP) El Niño structures. At the same time, many observational analyses have emphasized that thermocline (TH) feedback and zonal advective (ZA) feedback play dominant roles in the development of eastern-Pacific (EP) and CP El Niño-Southern Oscillation (ENSO), respectively. In this work, a simple linear air-sea coupled model, which can accurately depict the strength distribution of the TH and ZA feedbacks in the equatorial Pacific, is used to investigate these two types of El Niño. The results indicate that the model can reproduce the main characteristics of CP ENSO if the TH feedback is switched off and the ZA feedback is retained as the only positive feedback, confirming the dominant role played by ZA feedback in the development of CP ENSO. Further experiments indicate that, through a simple nonlinear control approach, many ENSO characteristics, including the existence of both CP and EP El Niño and the asymmetries between El Niño and La Niña, can be successfully captured using the simple linear air-sea coupled model. These analyses indicate that an accurate depiction of the climatological sea surface temperature distribution and the related ZA feedback, which are the subject of severe biases in GCMs, is very important in simulating a realistic CP El Niño.
The weakening of the ENSO-Indian Ocean Dipole (IOD) coupling strength in recent decades
NASA Astrophysics Data System (ADS)
Ham, Yoo-Geun; Choi, Jun-Young; Kug, Jong-Seong
2017-07-01
This study examines a recent weakening of the coupling between the El Nino-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) mode after the 2000s and 2010s compared to the previous two decades (1980s and 1990s). The correlation between the IOD during the September-November season and the Nino3.4 index during the December-February season is 0.21 for 1999-2014, while for the previous two decades (1979-1998) it is 0.64. It is found that this weakening of the ENSO-IOD coupling during the 2000s and 2010s is associated with different spatial patterns in ENSO evolution during the boreal spring and summer seasons. During the boreal spring season of the El Nino developing phase, positive precipitation anomalies over the northern off-equatorial western Pacific is systematically weakened during the 2000s and 2010s. This also weakens the low-level cross-equatorial southerly flow, which can cause local negative precipitation anomalies over the maritime continent through increased evaporation and cold and dry moist energy advection. The weakened negative precipitation anomalies over the maritime continent reduces the amplitude of the equatorial easterly over the IO, therefore, suppresses a ENSO-related IOD variability. An analysis using climate models that participated in the Coupled Model Intercomparison Project phase 5 (CMIP5) supports this observational findings that the amplitude of the cross-equatorial southerly flow and associated suppressed convective activities over the maritime continent during the El Nino developing season are critical for determining the ENSO-IOD coupling strength in climate models.
Is ENSO related to 2015 Easter Star Capsized on the Yangtze River of China?
NASA Astrophysics Data System (ADS)
Xie, P.
2015-12-01
Natural disasters have profound effects on community security and economic damage of China's Hubei province. In June 1st, 2015, a cruise ship, Easter Star, capsized on Yangtze River in Hubei province with 442 died. What reason gives rise to such strong convection causing ship sunk? Based on the wind disasters of Hubei province happened in 1963-2015, this study analyzes their features bytime-series regression, and correlates them to global El Niño/Southern Oscillation (ENSO) events. The compared results demonstrated that the wind disasters shown an increasing tendency. There are two peaks corresponding to the strongest ENSO peaks during the past 50 years; each peak lasts two-three years. The facts demonstrated an essential linear relation between the ENSO phenomena and wind disasters in Hubei province. 2015 Easter Star capsized happened at current El Niño event in 2014-2015. We also observed that the historical wind disasters appeared in seasonal variation. Over 90% events concentrated in spring and summer; very few events happened in autumn and winter. Moreover, the disasters depend on the geographic conditions. Most disasters concentrated in four zones, named as Xingshan-Baokang, Xuanen, Wufeng-Yichang, Jingzhou-Gongan, in which Xingshan and Changyang are the two most density of zones. Yangtze River provides an air flowing conduct for strong convective winds. It can be concluded that the strong convection causing 2015 Easter Star capsized is related to current global ENSO phenomenon.Keywords: ENSO, wind disaster, time-series regression analysis, Easter Star, Yangtze River, Hubei Province,
NASA Astrophysics Data System (ADS)
Tippett, Michael K.; Ranganathan, Meghana; L'Heureux, Michelle; Barnston, Anthony G.; DelSole, Timothy
2017-05-01
Here we examine the skill of three, five, and seven-category monthly ENSO probability forecasts (1982-2015) from single and multi-model ensemble integrations of the North American Multimodel Ensemble (NMME) project. Three-category forecasts are typical and provide probabilities for the ENSO phase (El Niño, La Niña or neutral). Additional forecast categories indicate the likelihood of ENSO conditions being weak, moderate or strong. The level of skill observed for differing numbers of forecast categories can help to determine the appropriate degree of forecast precision. However, the dependence of the skill score itself on the number of forecast categories must be taken into account. For reliable forecasts with same quality, the ranked probability skill score (RPSS) is fairly insensitive to the number of categories, while the logarithmic skill score (LSS) is an information measure and increases as categories are added. The ignorance skill score decreases to zero as forecast categories are added, regardless of skill level. For all models, forecast formats and skill scores, the northern spring predictability barrier explains much of the dependence of skill on target month and forecast lead. RPSS values for monthly ENSO forecasts show little dependence on the number of categories. However, the LSS of multimodel ensemble forecasts with five and seven categories show statistically significant advantages over the three-category forecasts for the targets and leads that are least affected by the spring predictability barrier. These findings indicate that current prediction systems are capable of providing more detailed probabilistic forecasts of ENSO phase and amplitude than are typically provided.
Characteristics of the East Asian Winter Climate Associated with the Westerly Jet Stream and ENSO
NASA Technical Reports Server (NTRS)
Yang, Song; Lau, K.-M.; Kim, K.-M.; Einaudi, Franco (Technical Monitor)
2000-01-01
In this study, the influences of the East Asian jet stream (EAJS) and El Nino/Southern Oscillation (ENSO) on the interannual variability of the East Asian winter climate are examined with a focus on the relative climate impacts of the two phenomena. Although the variations of the East Asian winter monsoon and the temperature and precipitation of China, Japan, and Korea are emphasized, the associated changes in the broad-scale atmospheric circulation patterns over Asia and the Pacific and in the extratropical North Pacific sea surface temperature (SST) are also investigated. It is demonstrated that there is no apparent relationship between ENSO and the interannual variability of EAJS core. The EAJS and ENSO are associated with distinctly different patterns of atmospheric circulation and SST in the Asian-Pacific regions. While ENSO causes major climate signals in the Tropics and over the North Pacific east of the dateline, the EAJS produces significant changes in the atmospheric circulation over East Asia and western Pacific. In particular, the EAJS explains larger variance of the interannual signals of the East Asian trough, the Asian continental high, the Aleutian low, and the East Asian winter monsoon. When the EAJS is strong, all these atmospheric systems intensify significantly. The response of surface temperature and precipitation to EAJS variability and ENSO is more complex. In general, the East Asian winter climate is cold (warm) and dry (wet) when the EAJS is strong (weak) and it is warm during El Nino years. However, different climate signals are found during different La Nina years. In terms of linear correlation, both the temperature and precipitation of northern China, Korea, and central Japan are more significantly associated with the EAJS than with ENSO.
Coral Cd/Ca and Mn/Ca records of ENSO variability in the Gulf of California
NASA Astrophysics Data System (ADS)
Carriquiry, J. D.; Villaescusa, J. A.
2010-06-01
We analyzed the trace element ratios Cd/Ca and Mn/Ca in three coral colonies (Porites panamensis (1967-1989), Pavona clivosa (1967-1989) and Pavona gigantea (1979-1989)) from Cabo Pulmo reef, Southern Gulf of California, Mexico, to assess the oceanographic changes caused by El Niño - Southern Oscillation (ENSO) events in the Eastern Tropical North Pacific (ETNP). Interannual variations in the coral Cd/Ca and Mn/Ca ratios showed clear evidence that incorporation of Cd and Mn in the coral skeleton was influenced by ENSO conditions, but the response for each metal was controlled by different processes. The Mn/Ca ratios were significantly higher during ENSO years (p<0.05) relative to non-ENSO years for the three species of coral. In contrast, the Cd/Ca was systematically lower during ENSO years, but the difference was significant (p<0.05) only in Pavona gigantea. A decrease in the incorporation of Cd and a marked increase in Mn indicated strongly reduced vertical mixing in the Gulf of California during the mature phase of El Niño. The oceanic warming during El Niño events produces a relaxation of upwelling and a stabilization of the thermocline, which may act as a physical barrier limiting the transport of Cd from deeper waters into the surface layer. In turn, this oceanic condition can increase the residence time of particulate-Mn in surface waters, allowing an increase in the photo-reduction of particulate-Mn and the release of available Mn into the dissolved phase. These results support the use of Mn/Ca and Cd/Ca ratios in biogenic carbonates as tracers of increases in ocean stratification and trade wind weakening and/or collapse in the ETNP during ENSO episodes.
ENSO effects on MLT diurnal tides: A 21 year reanalysis data-driven GAIA model simulation
NASA Astrophysics Data System (ADS)
Liu, Huixin; Sun, Yang-Yi; Miyoshi, Yasunobu; Jin, Hidekatsu
2017-05-01
Tidal responses to El Niño-Southern Oscillation (ENSO) in the mesosphere and lower thermosphere (MLT) are investigated for the first time using reanalysis data-driven simulations covering 21 years. The simulation is carried out with the Ground-to-topside Atmosphere-Ionosphere model for Aeronomy (GAIA) during 1996-2016, which covers nine ENSO events. ENSO impacts on diurnal tides at 100 km altitude are analyzed and cross-compared among temperature (T), zonal wind (U), and meridional wind (V), which reveals the following salient features: (1) Tidal response can differ significantly among T, U, and V in terms of magnitude and latitudinal structure, making detection of ENSO effects sensitive to the parameter used and the location of a ground station; (2) the nonmigrating DE3 tide in T and U shows a prominent hemisphere asymmetric response to La Niña, with an increase between 0° and 30°N and a decrease between 30° and 0°S. In contrast, DE3 in V exhibits no significant response; (3) the migrating DW1 enhances during El Niño in equatorial regions for T and U but in off-equatorial regions for V. As the first ENSO study based on reanalysis-driven simulations, GAIA's full set of tidal responses in T, U, and V provides us with a necessary global context to better understand and cross-compare observations during ENSO events. Comparisons with observations during the 1997-98 El Niño and 2010-11 La Niña reveal good agreement in both magnitude and timing. Comparisons with "free-run" WACCM simulations (T) show consistent results in nonmigrating tides DE2 and DE3 but differences in the migrating DW1 tide.
Microprocessing of ITO and a-Si thin films using ns laser sources
NASA Astrophysics Data System (ADS)
Molpeceres, C.; Lauzurica, S.; Ocaña, J. L.; Gandía, J. J.; Urbina, L.; Cárabe, J.
2005-06-01
Selective ablation of thin films for the development of new photovoltaic panels and sensoring devices based on amorphous silicon (a-Si) is an emerging field, in which laser micromachining systems appear as appropriate tools for process development and device fabrication. In particular, a promising application is the development of purely photovoltaic position sensors. Standard p-i-n or Schottky configurations using transparent conductive oxides (TCO), a-Si and metals are especially well suited for these applications, appearing selective laser ablation as an ideal process for controlled material patterning and isolation. In this work a detailed study of laser ablation of a widely used TCO, indium-tin-oxide (ITO), and a-Si thin films of different thicknesses is presented, with special emphasis on the morphological analysis of the generated grooves. Excimer (KrF, λ = 248 nm) and DPSS lasers (λ = 355 and λ = 1064 nm) with nanosecond pulse duration have been used for material patterning. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) techniques have been applied for the characterization of the ablated grooves. Additionally, process parametric windows have been determined in order to assess this technology as potentially competitive to standard photolithographic processes. The encouraging results obtained, with well-defined ablation grooves having thicknesses in the order of 10 µm both in ITO and in a-Si, open up the possibility of developing a high-performance double Schottky photovoltaic matrix position sensor.
The complex influence of ENSO on droughts in Ecuador
NASA Astrophysics Data System (ADS)
Vicente-Serrano, S. M.; Aguilar, E.; Martínez, R.; Martín-Hernández, N.; Azorin-Molina, C.; Sanchez-Lorenzo, A.; El Kenawy, A.; Tomás-Burguera, M.; Moran-Tejeda, E.; López-Moreno, J. I.; Revuelto, J.; Beguería, S.; Nieto, J. J.; Drumond, A.; Gimeno, L.; Nieto, R.
2017-01-01
In this study, we analyzed the influence of El Niño-Southern Oscillation (ENSO) on the spatio-temporal variability of droughts in Ecuador for a 48-year period (1965-2012). Droughts were quantified from 22 high-quality and homogenized time series of precipitation and air temperature by means of the Standardized Precipitation Evapotranspiration Index. In addition, the propagation of two different ENSO indices (El Niño 3.4 and El Niño 1 + 2 indices) and other atmospheric circulation processes (e.g., vertical velocity) on different time-scales of drought severity were investigated. The results showed a very complex influence of ENSO on drought behavior across Ecuador, with two regional patterns in the evolution of droughts: (1) the Andean chain with no changes in drought severity, and (2) the Western plains with less severe and frequent droughts. We also detected that drought variability in the Andes mountains is explained by the El Niño 3.4 index [sea surface temperature (SST) anomalies in the central Pacific], whereas the Western plains are much more driven by El Niño 1 + 2 index (SST anomalies in the eastern Pacific). Moreover, it was also observed that El Niño and La Niña phases enhance droughts in the Andes and Western plains regions, respectively. The results of this work could be crucial for predicting and monitoring drought variability and intensity in Ecuador.
Holocene ITCZ and ENSO-driven climate variability from the Panama isthmus
NASA Astrophysics Data System (ADS)
Urrego, D. H.; Aronson, R. B.; Bush, M. B.
2009-12-01
Holocene climate has previously been considered relatively stable compared to Pleistocene fluctuations. Recent paleoclimatic reconstructions have shown, however, that Holocene climatic variability is large and that the key to understanding and predicting responses to current climate change could lie in Holocene climatic history. In tropical regions, one of the most important oceanic-atmospheric systems regulating present and past interannual climatic fluctuations is the InterTropical Convergence Zone (ITCZ). Several hypotheses have been postulated to explain Holocene climate oscillations and their impacts in Northern South America. One of these hypotheses is that reduced precipitation during the mid-Holocene in the Caribbean and off the coast of Venezuela resulted from a southward migration of the ITCZ’s mean annual position (1, 2). In turn, this southward movement was associated with changes in the location of warm pools and insolation maxima regions in the tropical Atlantic. However, oscillations in Pacific warm pools should be expected to influence the annual ITCZ cycle as well. The latitudinal positions of these warm pools in the Pacific are directly influenced by ENSO (El Niño Southern Oscillation), and are predicted to move south during El Niño (warm-ENSO) years. A mid-Holocene increase in the frequency of warm ENSO events is reported in the eastern Pacific after 6 ka (3, 4), and although this change occurred more than a thousand years earlier than the southward migrations of the ITCZ reconstructed from tropical Atlantic systems, we hypothesize that there must be a link between these two apparently separate events. Reconciling the roles of Atlantic versus Pacific ocean-atmosphere interactions, and the effect of Pacific phenomena like ENSO on the annual position of the ITCZ are therefore crucial to understand climatic variability in tropical America. Lago La Yeguada is located in the Isthmus of Panama and its climate is determined mainly by the ITCZ, ENSO
Atmosphere-Ocean Variations in the Indo-Pacific Sector during ENSO Episodes.
NASA Astrophysics Data System (ADS)
Lau, Ngar-Cheung; Nath, Mary Jo
2003-01-01
The influences of El Niño-Southern Oscillation (ENSO) events on air-sea interaction in the Indian-western Pacific (IWP) Oceans have been investigated using a general circulation model. Observed monthly sea surface temperature (SST) variations in the deep tropical eastern/central Pacific (DTEP) have been inserted in the lower boundary of this model through the 1950-99 period. At all maritime grid points outside of DTEP, the model atmosphere has been coupled with an oceanic mixed layer model with variable depth. Altogether 16 independent model runs have been conducted.Composite analysis of selected ENSO episodes illustrates that the prescribed SST anomalies in DTEP affect the surface atmospheric circulation and precipitation patterns in IWP through displacements of the near-equatorial Walker circulation and generation of Rossby wave modes in the subtropics. Such atmospheric responses modulate the surface fluxes as well as the oceanic mixed layer depth, and thereby establish a well-defined SST anomaly pattern in the IWP sector several months after the peak in ENSO forcing in DTEP. In most parts of the IWP region, the net SST tendency induced by atmospheric changes has the same polarity as the local composite SST anomaly, thus indicating that the atmospheric forcing acts to reinforce the underlying SST signal.By analyzing the output from a suite of auxiliary experiments, it is demonstrated that the SST perturbations in IWP (which are primarily generated by ENSO-related atmospheric changes) can, in turn, exert notable influences on the atmospheric conditions over that region. This feedback mechanism also plays an important role in the eastward migration of the subtropical anticyclones over the western Pacific in both hemispheres.
NASA Astrophysics Data System (ADS)
Zheng, Dawei; Ding, Xiaoli; Zhou, Yonghong; Chen, Yongqi
2003-03-01
Time series of the length of day characterizing the rate of Earth rotation, the atmospheric angular momentum and the Southern Oscillation Index from 1962 to 2000 are used to reexamine the relationships between the ENSO events and the changes in the length of day, as well as the global atmospheric angular momentum. Particular attention is given to the different effects of the 1982-1983 and 1997-1998 ENSO events on the variations of Earth rotation. The combined effects of multiscale atmospheric oscillations (seasonal, quasi-biennial and ENSO time scales) on the anomalous variations of the interannual rates of Earth rotation are revealed in this paper by studying the wavelet spectra of the data series.
Yim, Bo; Yeh, Sang -Wook; Sohn, Byung -Ju
2016-01-29
Observational evidence shows that the Walker circulation (WC) in the tropical Pacific has strengthened in recent decades. In this study, we examine the WC trend for 1979–2005 and its relationship with the precipitation associated with the El Niño Southern Oscillation (ENSO) using the sea surface temperature (SST)-constrained Atmospheric Model Intercomparison Project (AMIP) simulations of the Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. All of the 29 models show a strengthening of the WC trend in response to an increase in the SST zonal gradient along the equator. Despite the same SST-constrained AMIP simulations, however, a large diversity ismore » found among the CMIP5 climate models in the magnitude of the WC trend. The relationship between the WC trend and precipitation anomalies (PRCPAs) associated with ENSO (ENSO-related PRCPAs) shows that the longitudinal position of the ENSO-related PRCPAs in the western tropical Pacific is closely related to the magnitude of the WC trend. Specifically, it is found that the strengthening of the WC trend is large (small) in the CMIP5 AMIP simulations in which the ENSO-related PRCPAs are located relatively westward (eastward) in the western tropical Pacific. Furthermore, the zonal shift of the ENSO-related precipitation in the western tropical Pacific, which is associated with the climatological mean precipitation in the tropical Pacific, could play an important role in modifying the WC trend in the CMIP5 climate models.« less
Using a 4D-Variational Method to Optimize Model Parameters in an Intermediate Coupled Model of ENSO
NASA Astrophysics Data System (ADS)
Gao, C.; Zhang, R. H.
2017-12-01
Large biases exist in real-time ENSO prediction, which is attributed to uncertainties in initial conditions and model parameters. Previously, a four dimentional variational (4D-Var) data assimilation system was developed for an intermediate coupled model (ICM) and used to improve ENSO modeling through optimized initial conditions. In this paper, this system is further applied to optimize model parameters. In the ICM used, one important process for ENSO is related to the anomalous temperature of subsurface water entrained into the mixed layer (Te), which is empirically and explicitly related to sea level (SL) variation, written as Te=αTe×FTe (SL). The introduced parameter, αTe, represents the strength of the thermocline effect on sea surface temperature (SST; referred as the thermocline effect). A numerical procedure is developed to optimize this model parameter through the 4D-Var assimilation of SST data in a twin experiment context with an idealized setting. Experiments having initial condition optimized only and having initial condition plus this additional model parameter optimized both are compared. It is shown that ENSO evolution can be more effectively recovered by including the additional optimization of this parameter in ENSO modeling. The demonstrated feasibility of optimizing model parameter and initial condition together through the 4D-Var method provides a modeling platform for ENSO studies. Further applications of the 4D-Var data assimilation system implemented in the ICM are also discussed.
Response of Global Lightning Activity Observed by the TRMM/LIS During Warm and Cold ENSO Phases
NASA Technical Reports Server (NTRS)
Chronis, Themis G.; Cecil, Dan; Goodman, Steven J.; Buechler, Dennis
2007-01-01
This paper investigates the response of global lightning activity to the transition from the warm (January February March-JFM 1998) to the cold (JFM 1999) ENSO phase. The nine-year global lightning climatology for these months from the Tropical Rainfall Measuring Mission (TRMM) Lightning Imaging Sensor (LIS) provides the observational baseline. Flash rate density is computed on a 5.0x5.0 degree lat/lon grid within the LIS coverage area (between approx.37.5 N and S) for each three month period. The flash rate density anomalies from this climatology are examined for these months in 1998 and 1999. The observed lightning anomalies spatially match the documented general circulation features that accompany the warm and cold ENSO events. During the warm ENSO phase the dominant positive lightning anomalies are located mostly over the Western Hemisphere and more specifically over Gulf of Mexico, Caribbean and Northern Mid-Atlantic. We further investigate specifically the Northern Mid-Atlantic related anomaly features since these show strong relation to the North Atlantic Oscillation (NAO). Furthermore these observed anomaly patterns show strong spatial agreement with anomalous upper level (200 mb) cold core cyclonic circulations. Positive sea surface temperature anomalies during the warm ENSO phase also affect the lightning activity, but this is mostly observed near coastal environments. Over the open tropical oceans, there is climatologically less lightning and the anomalies are less pronounced. Warm ENSO related anomalies over the Eastern Hemisphere are most prominent over the South China coast. The transition to the cold ENSO phase illustrates the detected lightning anomalies to be more pronounced over East and West Pacific. A comparison of total global lightning between warm and cold ENSO phase reveals no significant difference, although prominent regional anomalies are located over mostly oceanic environments. All three tropical "chimneys" (Maritime Continent, Central
Climate Change and ENSO Effects on Southeastern US Climate Patterns and Maize Yield.
Mourtzinis, Spyridon; Ortiz, Brenda V; Damianidis, Damianos
2016-07-19
Climate change has a strong influence on weather patterns and significantly affects crop yields globally. El Niño Southern Oscillation (ENSO) has a strong influence on the U.S. climate and is related to agricultural production variability. ENSO effects are location-specific and in southeastern U.S. strongly connect with climate variability. When combined with climate change, the effects on growing season climate patterns and crop yields might be greater than expected. In our study, historical monthly precipitation and temperature data were coupled with non-irrigated maize yield data (33-43 years depending on the location) to show a potential yield suppression of ~15% for one °C increase in southeastern U.S. growing season maximum temperature. Yield suppression ranged between -25 and -2% among locations suppressing the southeastern U.S. average yield trend since 1981 by 17 kg ha(-1)year(-1) (~25%), mainly due to year-to-year June temperature anomalies. Yields varied among ENSO phases from 1971-2013, with greater yields observed during El Niño phase. During La Niña years, maximum June temperatures were higher than Neutral and El Niño, whereas June precipitation was lower than El Niño years. Our data highlight the importance of developing location-specific adaptation strategies quantifying both, climate change and ENSO effects on month-specific growing season climate conditions.
Forecasting of Seasonal Rainfall using ENSO and IOD teleconnection with Classification Models
NASA Astrophysics Data System (ADS)
De Silva, T.; Hornberger, G. M.
2017-12-01
Seasonal to annual forecasts of precipitation patterns are very important for water infrastructure management. In particular, such forecasts can be used to inform decisions about the operation of multipurpose reservoir systems in the face of changing climate conditions. Success in making useful forecasts often is achieved by considering climate teleconnections such as the El-Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) as related to sea surface temperature variations. We present an analysis to explore the utility of using rainfall relationships in Sri Lanka with ENSO and IOD to predict rainfall to the Mahaweli, river basin. Forecasting of rainfall as classes - above normal, normal, and below normal - can be useful for water resource management decision making. Quadratic discrimination analysis (QDA) and random forest models are used to identify the patterns of rainfall classes with respect to ENSO and IOD indices. These models can be used to forecast the likelihood of areal rainfall anomalies using predicted climate indices. Results can be used for decisions regarding allocation of water for agriculture and electricity generation within the Mahaweli project of Sri Lanka.
A delay differential model of ENSO variability: Extreme values and stability analysis
NASA Astrophysics Data System (ADS)
Zaliapin, I.; Ghil, M.
2009-04-01
We consider a delay differential equation (DDE) model for El-Niño Southern Oscillation (ENSO) variability [Ghil et al. (2008), Nonlin. Proc. Geophys., 15, 417-433.] The model combines two key mechanisms that participate in ENSO dynamics: delayed negative feedback and seasonal forcing. Toy models of this type were shown to capture major features of the ENSO phenomenon [Jin et al., Science (1994); Tziperman et al., Science (1994)]; they provide a convenient paradigm for explaining interannual ENSO variability and shed new light on its dynamical properties. So far, though, DDE model studies of ENSO have been limited to linear stability analysis of steady-state solutions, which are not typical in forced systems, case studies of particular trajectories, or one-dimensional scenarios of transition to chaos, varying a single parameter while the others are kept fixed. In this work we take several steps toward a comprehensive analysis of DDE models relevant for ENSO phenomenology and illustrate the complexity of phase-parameter space structure for even such a simple model of climate dynamics. We formulate an initial value problem for our model and prove the existence, uniqueness, and continuous dependence theorem. We then use this theoretical result to perform detailed numerical stability analyses of the model in the three-dimensional space of its physically relevant parameters: strength of seasonal forcing b, atmosphere-ocean coupling ΰ, and propagation period ? of oceanic waves across the Tropical Pacific. Two regimes of variability, stable and unstable, are reported; they are separated by a sharp neutral curve in the (b,?) plane at constant ΰ. The detailed structure of the neutral curve becomes very irregular and possibly fractal, while individual trajectories within the unstable region become highly complex and possibly chaotic, as the atmosphere-ocean coupling ΰ increases. In the unstable regime, spontaneous transitions occur in the mean temperature (i
The QBO, Gravity Waves Forced by Tropical Convection, and ENSO.
NASA Technical Reports Server (NTRS)
Geller, Marvin A.; Zhou, Tiehan; Yuan, Wei
2016-01-01
By means of theory, a simplified cartoon illustrating wave forcing of the stratospheric quasi-biennial oscillation (QBO), and general circulation modeling of the QBO, it is argued that the period of the QBO is mainly controlled by the magnitude of the gravity wave (GW) vertical fluxes of horizontal momentum (GWMF) forcing the QBO, while the QBO amplitude is mainly determined by the phase speeds of the GWs that make up this momentum flux. It is furthermore argued that it is the zonally averaged GWMF that principally determines the QBO period irrespective of the longitudinal distribution of this GW momentum flux. These concepts are used to develop a hypothesis for the cause of a previously reported El Nino- Southern Oscillation (ENSO) modulation of QBO periods and amplitudes. Some observational evidence is reported for the ENSO modulation of QBO amplitudes to have been different before the 1980s than after about 1990. A hypothesis is also given to explain this in terms of the different ENSO modulation of tropical deep convection that took place before the 1980s from that which occurred after about 1990. The observational evidence, while consistent with our hypotheses, does not prove that our hypotheses are correct given the small number of El Ninos and La Ninas that occurred in the early and later periods. Further research is needed to support or refute our hypotheses
δ 18O in the Tropical Conifer Agathis robusta Records ENSO-Related Precipitation Variations
Boysen, Bjorn M. M.; Evans, Michael N.; Baker, Patrick J.
2014-01-01
Long-lived trees from tropical Australasia are a potential source of information about internal variability of the El Niño-Southern Oscillation (ENSO), because they occur in a region where precipitation variability is closely associated with ENSO activity. We measured tree-ring width and oxygen isotopic composition (O) of -cellulose from Agathis robusta (Queensland Kauri) samples collected in the Atherton Tablelands, Queensland, Australia. Standard ring-width chronologies yielded low internal consistency due to the frequent presence of false ring-like anatomical features. However, in a detailed examination of the most recent 15 years of growth (1995–2010), we found significant correlation between O and local precipitation, the latter associated with ENSO activity. The results are consistent with process-based forward modeling of the oxygen isotopic composition of -cellulose. The O record also enabled us to confirm the presence of a false growth ring in one of the three samples in the composite record, and to determine that it occurred as a consequence of anomalously low rainfall in the middle of the 2004/5 rainy season. The combination of incremental growth and isotopic measures may be a powerful approach to development of long-term (150+ year) ENSO reconstructions from the terrestrial tropics of Australasia. PMID:25062034
Predicting monthly precipitation along coastal Ecuador: ENSO and transfer function models
NASA Astrophysics Data System (ADS)
de Guenni, Lelys B.; García, Mariangel; Muñoz, Ángel G.; Santos, José L.; Cedeño, Alexandra; Perugachi, Carlos; Castillo, José
2017-08-01
It is well known that El Niño-Southern Oscillation (ENSO) modifies precipitation patterns in several parts of the world. One of the most impacted areas is the western coast of South America, where Ecuador is located. El Niño events that occurred in 1982-1983, 1987-1988, 1991-1992, and 1997-1998 produced important positive rainfall anomalies in the coastal zone of Ecuador, bringing considerable damage to livelihoods, agriculture, and infrastructure. Operational climate forecasts in the region provide only seasonal scale (e.g., 3-month averages) information, but during ENSO events it is key for decision-makers to use reliable sub-seasonal scale forecasts, which at the present time are still non-existent in most parts of the world. This study analyzes the potential predictability of coastal Ecuador rainfall at monthly scale. Instead of the discrete approach that considers training models using only particular seasons, continuous (i.e., all available months are used) transfer function models are built using standard ENSO indices to explore rainfall forecast skill along the Ecuadorian coast and Galápagos Islands. The modeling approach considers a large-scale contribution, represented by the role of a sea-surface temperature index, and a local-scale contribution represented here via the use of previous precipitation observed in the same station. The study found that the Niño3 index is the best ENSO predictor of monthly coastal rainfall, with a lagged response varying from 0 months (simultaneous) for Galápagos up to 3 months for the continental locations considered. Model validation indicates that the skill is similar to the one obtained using principal component regression models for the same kind of experiments. It is suggested that the proposed approach could provide skillful rainfall forecasts at monthly scale for up to a few months in advance.
Coral based-ENSO/IOD related climate variability in Indonesia: a review
NASA Astrophysics Data System (ADS)
Yudawati Cahyarini, Sri; Henrizan, Marfasran
2018-02-01
Indonesia is located in the prominent site to study climate variability as it lies between Pacific and Indian Ocean. It has consequences to the regional climate in Indonesia that its climate variability is influenced by the climate events in the Pacific oceans (e.g. ENSO) and in the Indian ocean (e.g. IOD), and monsoon as well as Indonesian Throughflow (ITF). Northwestern monsoon causes rainfall in the region of Indonesia, while reversely Southwestern monsoon causes dry season around Indonesia. The ENSO warm phase called El Nino causes several droughts in Indonesian region, reversely the La Nina causes flooding in some regions in Indonesia. However, the impact of ENSO in Indonesia is different from one place to the others. Having better understanding on the climate phenomenon and its impact to the region requires long time series climate data. Paleoclimate study which provides climate data back into hundreds to thousands even to million years overcome this requirement. Coral Sr/Ca can provide information on past sea surface temperature (SST) and paired Sr/Ca and δ18O may be used to reconstruct variations in the precipitation balance (salinity) at monthly to annual interannual resolution. Several climate studies based on coral geochemical records in Indonesia show that coral Sr/Ca and δ18O from Indonesian records SST and salinity respectively. Coral Sr/Ca from inshore Seribu islands complex shows more air temperature rather than SST. Modern coral from Timor shows the impact of ENSO and IOD to the saliniy and SST is different at Timor sea. This result should be taken into account when interpreting Paleoclimate records over Indonesia. Timor coral also shows more pronounced low frequency SST variability compared to the SST reanalysis (model). The longer data of low frequency variability will improve the understanding of warming trend in this climatically important region.
Impacts of ENSO on air-sea oxygen exchange: Observations and mechanisms
NASA Astrophysics Data System (ADS)
Eddebbar, Yassir A.; Long, Matthew C.; Resplandy, Laure; Rödenbeck, Christian; Rodgers, Keith B.; Manizza, Manfredi; Keeling, Ralph F.
2017-05-01
Models and observations of atmospheric potential oxygen (APO ≃ O2 + 1.1 * CO2) are used to investigate the influence of El Niño-Southern Oscillation (ENSO) on air-sea O2 exchange. An atmospheric transport inversion of APO data from the Scripps flask network shows significant interannual variability in tropical APO fluxes that is positively correlated with the Niño3.4 index, indicating anomalous ocean outgassing of APO during El Niño. Hindcast simulations of the Community Earth System Model (CESM) and the Institut Pierre-Simon Laplace model show similar APO sensitivity to ENSO, differing from the Geophysical Fluid Dynamics Laboratory model, which shows an opposite APO response. In all models, O2 accounts for most APO flux variations. Detailed analysis in CESM shows that the O2 response is driven primarily by ENSO modulation of the source and rate of equatorial upwelling, which moderates the intensity of O2 uptake due to vertical transport of low-O2 waters. These upwelling changes dominate over counteracting effects of biological productivity and thermally driven O2 exchange. During El Niño, shallower and weaker upwelling leads to anomalous O2 outgassing, whereas deeper and intensified upwelling during La Niña drives enhanced O2 uptake. This response is strongly localized along the central and eastern equatorial Pacific, leading to an equatorial zonal dipole in atmospheric anomalies of APO. This dipole is further intensified by ENSO-related changes in winds, reconciling apparently conflicting APO observations in the tropical Pacific. These findings suggest a substantial and complex response of the oceanic O2 cycle to climate variability that is significantly (>50%) underestimated in magnitude by ocean models.
McCabe, G.J.; Dettinger, M.D.
1999-01-01
Changing patterns of correlations between the historical average June-November Southern Oscillation Index (SOI) and October-March precipitation totals for 84 climate divisions in the western US indicate a large amount of variability in SOI/precipitation relations on decadal time scales. Correlations of western US precipitation with SOI and other indices of tropical El Nino-Southern Oscillation (ENSO) processes were much weaker from 1920 to 1950 than during recent decades. This variability in teleconnections is associated with the character of tropical air-sea interactions as indexed by the number of out-of-phase SOI/tropical sea surface temperature (SST) episodes, and with decadal variability in the North Pacific Ocean as indexed by the Pacific Decadal Oscillation (PDO). ENSO teleconnections with precipitation in the western US are strong when SOI and NINO3 are out-of-phase and PDO is negative. ENSO teleconnections are weak when SOI and NINO3 are weakly correlated and PDO is positive. Decadal modes of tropical and North Pacific Ocean climate variability are important indicators of periods when ENSO indices, like SOI, can be used as reliable predictors of winter precipitation in the US.
NASA Technical Reports Server (NTRS)
Yonekura, Emmi; Hall, Timothy M.
2011-01-01
A new statistical model for western North Pacific Ocean tropical cyclone genesis and tracks is developed and applied to estimate regionally resolved tropical cyclone landfall rates along the coasts of the Asian mainland, Japan, and the Philippines. The model is constructed on International Best Track Archive for Climate Stewardship (IBTrACS) 1945-2007 historical data for the western North Pacific. The model is evaluated in several ways, including comparing the stochastic spread in simulated landfall rates with historic landfall rates. Although certain biases have been detected, overall the model performs well on the diagnostic tests, for example, reproducing well the geographic distribution of landfall rates. Western North Pacific cyclogenesis is influenced by El Nino-Southern Oscillation (ENSO). This dependence is incorporated in the model s genesis component to project the ENSO-genesis dependence onto landfall rates. There is a pronounced shift southeastward in cyclogenesis and a small but significant reduction in basinwide annual counts with increasing ENSO index value. On almost all regions of coast, landfall rates are significantly higher in a negative ENSO state (La Nina).
NASA Astrophysics Data System (ADS)
Rustic, G. T.; Polissar, P. J.; Ravelo, A. C.; White, S. M.
2017-12-01
The El Niño Southern Oscillation (ENSO) plays a dominant role in Earth's climate variability. Paleoceanographic evidence suggests that ENSO has changed in the past, and these changes have been linked to large-scale climatic shifts. While a close relationship between ENSO evolution and climate boundary conditions has been predicted, testing these predictions remains challenging. These climate boundary conditions, including insolation, the mean surface temperature gradient of the tropical Pacific, global ice volume, and tropical thermocline depth, often co-vary and may work together to suppress or enhance the ocean-atmosphere feedbacks that drive ENSO variability. Furthermore, suitable paleo-archives spanning multiple climate states are sparse. We have aimed to test ENSO response to changing climate boundary conditions by generating new reconstructions of mixed-layer variability from sedimentary archives spanning the last three glacial-interglacial cycles from the Central Tropical Pacific Line Islands, where El Niño is strongly expressed. We analyzed Mg/Ca ratios from individual foraminifera to reconstruct mixed-layer variability at discrete time intervals representing combinations of climatic boundary conditions from the middle Holocene to Marine Isotope Stage (MIS) 8. We observe changes in the mixed-layer temperature variability during MIS 5 and during the previous interglacial (MIS 7) showing significant reductions in ENSO amplitude. Differences in variability during glacial and interglacial intervals are also observed. Additionally, we reconstructed mixed-layer and thermocline conditions using multi-species Mg/Ca and stable isotope measurements to more fully characterize the state of the Central Tropical Pacific during these intervals. These reconstructions provide us with a unique view of Central Tropical Pacific variability and water-column structure at discrete intervals under varying boundary climate conditions with which to assess factors that shape ENSO
ASI's space automation and robotics programs: The second step
NASA Technical Reports Server (NTRS)
Dipippo, Simonetta
1994-01-01
The strategic decisions taken by ASI in the last few years in building up the overall A&R program, represent the technological drivers for other applications (i.e., internal automation of the Columbus Orbital Facility in the ESA Manned Space program, applications to mobile robots both in space and non-space environments, etc...). In this context, the main area of application now emerging is the scientific missions domain. Due to the broad range of applications of the developed technologies, both in the in-orbit servicing and maintenance of space structures and scientific missions, ASI foresaw the need to have a common technological development path, mainly focusing on: (1) control; (2) manipulation; (3) on-board computing; (4) sensors; and (5) teleoperation. Before entering into new applications in the scientific missions field, a brief overview of the status of the SPIDER related projects is given, underlining also the possible new applications for the LEO/GEO space structures.
Sensitivity of Water Scarcity Events to ENSO-Driven Climate Variability at the Global Scale
NASA Technical Reports Server (NTRS)
Veldkamp, T. I. E.; Eisner, S.; Wada, Y.; Aerts, J. C. J. H.; Ward, P. J.
2015-01-01
Globally, freshwater shortage is one of the most dangerous risks for society. Changing hydro-climatic and socioeconomic conditions have aggravated water scarcity over the past decades. A wide range of studies show that water scarcity will intensify in the future, as a result of both increased consumptive water use and, in some regions, climate change. Although it is well-known that El Niño- Southern Oscillation (ENSO) affects patterns of precipitation and drought at global and regional scales, little attention has yet been paid to the impacts of climate variability on water scarcity conditions, despite its importance for adaptation planning. Therefore, we present the first global-scale sensitivity assessment of water scarcity to ENSO, the most dominant signal of climate variability. We show that over the time period 1961-2010, both water availability and water scarcity conditions are significantly correlated with ENSO-driven climate variability over a large proportion of the global land area (> 28.1 %); an area inhabited by more than 31.4% of the global population. We also found, however, that climate variability alone is often not enough to trigger the actual incidence of water scarcity events. The sensitivity of a region to water scarcity events, expressed in terms of land area or population exposed, is determined by both hydro-climatic and socioeconomic conditions. Currently, the population actually impacted by water scarcity events consists of 39.6% (CTA: consumption-to-availability ratio) and 41.1% (WCI: water crowding index) of the global population, whilst only 11.4% (CTA) and 15.9% (WCI) of the global population is at the same time living in areas sensitive to ENSO-driven climate variability. These results are contrasted, however, by differences in growth rates found under changing socioeconomic conditions, which are relatively high in regions exposed to water scarcity events. Given the correlations found between ENSO and water availability and scarcity
NASA Astrophysics Data System (ADS)
Shin, So-Jung; An, Soon-Il
2018-02-01
Two leading but independent modes of Northern Pacific atmospheric circulation: the North Pacific Oscillation (NPO) and the Pacific Meridional Mode (PMM), are known external triggers of the El Niño-Southern Oscillation (ENSO) by the sequential migration of sea surface temperature (SST) anomalies into the tropics possibly by means of wind-evaporation-SST (WES) feedbacks. Because of the similar roles of NPO and PMM, most previous studies have explored them with no separation. Here, we investigate their independent and combined effects in triggering ENSO, and find that when the NPO and PMM occur simultaneously during spring, ENSO or ENSO-like SST anomalies are generated during the following winter; whereas when either the NPO or PMM occur alone, ENSO events rarely occur. Furthermore, the relationship between NPO and PMM shows noticeable interdecadal variability, which is related to decadal changes in the mean upper-level jet stream over the North Pacific. Changes in the upper-level jet stream modify the location of the center of the Aleutian Low, which plays a role in bridging the NPO and PMM processes, especially when it migrates to the southwest. The period when NPO and PMM are well correlated coincides somewhat with the active ENSO period, and vice versa, indicating that a more efficient trigger due to combined NPO-PMM processes results in a higher variation of ENSO. Finally, analysis of the coupled model control simulations strongly supports our observational analysis results.
NASA Astrophysics Data System (ADS)
Parton, W. J.; Del Grosso, S. J.; Smith, W. K.; Chen, M.
2017-12-01
The El Nino Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) are multi-annual to multi-decadal climate patterns defined by ocean temperature anomalies that can strongly modulate climate variability. Here we evaluated the impacts of PDO and ENSO sea surface temperature (SST) anomalies on observed grassland above ground plant production (ANPP; 1940 to 2015), spring (April to July) cumulative actual evapotranspiration (iAET; 1900 to 2015) , and satellite-derived growing season (April to October) cumulative normalized difference vegetation index (iNDVI 1982 to 2015) across the United States Great Plains. The results showed that grassland ANPP is well correlated to iAET (r2=0.69) and iNDVI (r2=0.50 to 0.70) for the Cheyenne Wyoming and Northeastern Colorado long-term ANPP sites. At the site scale, during the negative phase of the PDO, we find ANPP is much lower (25%) and that variability of iAET, iNDVI, and ANPP are much higher (2 to 3 times) compared to the warm phase PDO. Further, we find there is a high frequency of below normal iAET when PDO and ENSO SST's are both negative, while there is a high frequency of above normal iAET when PDO and ENSO values are positive. At the regional scale, iAET, iNDVI, and modeled ANPP data sets show that plant production and iAET values are high in the southern Great Plains and low in the northern Great Plains when spring PDO and ENSO are both in the positive phase, while the opposite pattern is observed when both PDO and ENSO are both in the negative phase. Variability of iAET, iNDVI, and modeled ANPP are much higher in the central Great Plains during the negative phase PDO. We demonstrate clearly that the PDO and ENSO SST anomalies have large impacts on mean and variability of grassland plant production across the Great Plains.
NASA Astrophysics Data System (ADS)
Frederiksen, Carsten; Grainger, Simon; Zheng, Xiaogu; Sisson, Janice
2013-04-01
ENSO variability is an important driver of the Southern Hemisphere (SH) atmospheric circulation. Understanding the observed and projected changes in ENSO variability is therefore important to understanding changes in Australian surface climate. Using a recently developed methodology (Zheng et al., 2009), the coherent patterns, or modes, of ENSO-related variability in the SH atmospheric circulation can be separated from modes that are related to intraseasonal variability or to changes in radiative forcings. Under this methodology, the seasonal mean SH 500 hPa geopotential height is considered to consist of three components. These are: (1) an intraseasonal component related to internal dynamics on intraseasonal time scales; (2) a slow-internal component related to internal dynamics on slowly varying (interannual or longer) time scales, including ENSO; and (3) a slow-external component related to external (i.e. radiative) forcings. Empirical Orthogonal Functions (EOFs) are used to represent the modes of variability of the interannual covariance of the three components. An assessment is first made of the modes in models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) dataset for the SH summer and winter seasons in the 20th century. In reanalysis data, two EOFs of the slow component (which includes the slow-internal and slow-external components) have been found to be related to ENSO variability (Frederiksen and Zheng, 2007). In SH summer, the CMIP5 models reproduce the leading ENSO mode very well when the structures of the EOF and the associated SST, and associated variance are considered. There is substantial improvement in this mode when compared with the CMIP3 models shown in Grainger et al. (2012). However, the second ENSO mode in SH summer has a poorly reproduced EOF structure in the CMIP5 models, and the associated variance is generally underestimated. In SH winter, the performance of the CMIP5 models in reproducing the structure and variance is
Tropical Pacific Mean State and ENSO Variability across Marine Isotope Stage 3
NASA Astrophysics Data System (ADS)
Hertzberg, J. E.; Schmidt, M. W.; Marcantonio, F.; Bianchi, T. S.
2017-12-01
The El Niño/Southern Oscillation (ENSO) phenomenon is the largest natural interannual signal in the Earth's climate system and has widespread effects on global climate that impact millions of people worldwide. A series of recent research studies predict an increase in the frequency of extreme El Niño and La Niña events as Earth's climate continues to warm. In order for climate scientists to forecast how ENSO will evolve in response to global warming, it is necessary to have accurate, comprehensive records of how the system has naturally changed in the past, especially across past abrupt warming events. Nevertheless, there remains significant uncertainty about past changes in tropical Pacific climate and how ENSO variability relates to the millennial-scale warming events of the last ice age. This study aims to reconstruct changes in the tropical Pacific mean state and ENSO variability across Marine Isotope Stage 3 from a sediment core recovered from the Eastern Equatorial Pacific cold tongue (MV1014-02-17JC, 0°10.8' S, 85°52.0' W, 2846 m water depth). In this region, thermocline temperatures are significantly correlated to ENSO variability - thus, we analyzed Mg/Ca ratios in the thermocline dwelling foraminifera Neogloboquadrina dutertrei as a proxy for thermocline temperatures in the past. Bulk ( 50 tests/sample) foraminifera Mg/Ca temperatures are used to reconstruct long-term variability in the mean state, while single shell ( 1 test/sample, 60 samples) Mg/Ca analyses are used to assess thermocline temperature variance. Based on our refined age model, we find that thermocline temperature increases of up to 3.5°C occur in-step with interstadial warming events recorded in Greenland ice cores. Cooler thermocline temperatures prevail during stadial intervals and Heinrich Events. This suggests that interstadials were more El-Niño like, while stadials and Heinrich Events were more La-Niña like. These temperature changes are compared to new records of dust flux
Analytical Formulation of Equatorial Standing Wave Phenomena: Application to QBO and ENSO
NASA Astrophysics Data System (ADS)
Pukite, P. R.
2016-12-01
Key equatorial climate phenomena such as QBO and ENSO have never been adequately explained as deterministic processes. This in spite of recent research showing growing evidence of predictable behavior. This study applies the fundamental Laplace tidal equations with simplifying assumptions along the equator — i.e. no Coriolis force and a small angle approximation. To connect the analytical Sturm-Liouville results to observations, a first-order forcing consistent with a seasonally aliased Draconic or nodal lunar period (27.21d aliased into 2.36y) is applied. This has a plausible rationale as it ties a latitudinal forcing cycle via a cross-product to the longitudinal terms in the Laplace formulation. The fitted results match the features of QBO both qualitatively and quantitatively; adding second-order terms due to other seasonally aliased lunar periods provides finer detail while remaining consistent with the physical model. Further, running symbolic regression machine learning experiments on the data provided a validation to the approach, as it discovered the same analytical form and fitted values as the first principles Laplace model. These results conflict with Lindzen's QBO model, in that his original formulation fell short of making the lunar connection, even though Lindzen himself asserted "it is unlikely that lunar periods could be produced by anything other than the lunar tidal potential".By applying a similar analytical approach to ENSO, we find that the tidal equations need to be replaced with a Mathieu-equation formulation consistent with describing a sloshing process in the thermocline depth. Adapting the hydrodynamic math of sloshing, we find a biennial modulation coupled with angular momentum forcing variations matching the Chandler wobble gives an impressive match over the measured ENSO range of 1880 until the present. Lunar tidal periods and an additional triaxial nutation of 14 year period provide additional fidelity. The caveat is a phase
NASA Astrophysics Data System (ADS)
Gao, Chuan; Zhang, Rong-Hua; Wu, Xinrong; Sun, Jichang
2018-04-01
Large biases exist in real-time ENSO prediction, which can be attributed to uncertainties in initial conditions and model parameters. Previously, a 4D variational (4D-Var) data assimilation system was developed for an intermediate coupled model (ICM) and used to improve ENSO modeling through optimized initial conditions. In this paper, this system is further applied to optimize model parameters. In the ICM used, one important process for ENSO is related to the anomalous temperature of subsurface water entrained into the mixed layer ( T e), which is empirically and explicitly related to sea level (SL) variation. The strength of the thermocline effect on SST (referred to simply as "the thermocline effect") is represented by an introduced parameter, α Te. A numerical procedure is developed to optimize this model parameter through the 4D-Var assimilation of SST data in a twin experiment context with an idealized setting. Experiments having their initial condition optimized only, and having their initial condition plus this additional model parameter optimized, are compared. It is shown that ENSO evolution can be more effectively recovered by including the additional optimization of this parameter in ENSO modeling. The demonstrated feasibility of optimizing model parameters and initial conditions together through the 4D-Var method provides a modeling platform for ENSO studies. Further applications of the 4D-Var data assimilation system implemented in the ICM are also discussed.
NASA Astrophysics Data System (ADS)
Rongstad, B.; Marchitto, T. M., Jr.; Koutavas, A.; Mekik, F.
2017-12-01
El Niño Southern Oscillation (ENSO) is Earth's dominant mode of interannual climate variability, and is responsible for widespread climatic, ecological and societal impacts, such as reduced upwelling and fishery collapse in the eastern equatorial Pacific during El Niño events. While corals offer high resolution records of paleo-ENSO, continuous and gap-free records for the tropical Pacific are rare. Individual foraminifera analyses provide an opportunity to create continuous down-core records of ENSO through the construction and comparison of species-specific sea surface temperature (SST) distributions at different time periods; however, there has been little focus on calibrating this technique to modern ENSO conditions. Here, we present data from a core-top calibration of individual Mg/Ca measurements in planktic foraminifera in the eastern tropical Pacific, using surface dweller G. ruber and thermocline dweller N. dutertrei. We convert the individual Mg/Ca measurements to inferred temperature distributions for each species, and then compare the distributions to modern day temperature characteristics including vertical structure, annual mean, seasonality, and interannual variability. ENSO variance is theoretically inferred from the tails of the distributions: El Niño events affect the warm tail and La Niña events affect the cool tail. Finally, we discuss the utility of individual measurements of Mg/Ca in planktic foraminifera to reconstruct ENSO in down-core sections.
Interannual Variability in Amundsen Sea Ice-Shelf Height Change Linked to ENSO
NASA Astrophysics Data System (ADS)
Paolo, F. S.; Fricker, H. A.; Padman, L.
2015-12-01
Atmospheric and sea-ice conditions around Antarctica, particularly in the Amundsen and Bellingshausen seas, respond to climate dynamics in the tropical Pacific Ocean on interannual time scales including the El Nino-Southern Oscillation (ENSO). It has been hypothesized that the mass balance of the Antarctic Ice Sheet, including its floating ice shelves, also responds to this climate signal; however, this has not yet been unambiguously demonstrated. We apply multivariate singular spectrum analysis (MSSA) to our 18-year (1994-2012) time series of ice-shelf height in the Amundsen Sea (AS) region. This advanced spectral method distinguishes between regular deterministic behavior ("cycles") at sub-decadal time scale and irregular behavior ("noise") at shorter time scales. Although the long-term trends of AS ice-shelf height changes are much larger than the range of interannual variability, the short-term rate of change dh/dt can vary about the trend by more than 50%. The mode of interannual variability in the AS ice-shelf height is strongly correlated with the low-frequency mode of ENSO (periodicity of ~4.5 years) as represented by the Southern Oscillation Index. The ice-shelf height in the AS is expected to respond to changes in precipitation and inflows of warm subsurface Circumpolar Deep Water (CDW) into the ocean cavities under the ice shelves, altering basal melt rates. Since both of these processes affecting ice-shelf mass balance respond to changes in wind fields for different ENSO states, we expect some correlation between them. We will describe the spatial structure of AS ice-shelf height response to ENSO, and attempt to distinguish the precipitation signal from basal mass balance due to changing CDW inflows.
Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China.
Zhu, Zongmin; Feinberg, Joshua M; Xie, Shucheng; Bourne, Mark D; Huang, Chunju; Hu, Chaoyong; Cheng, Hai
2017-01-31
Extreme hydrologic events such as storms and floods have the potential to severely impact modern human society. However, the frequency of storms and their underlying mechanisms are limited by a paucity of suitable proxies, especially in inland areas. Here we present a record of speleothem magnetic minerals to reconstruct paleoprecipitation, including storms, in the eastern Asian monsoon area over the last 8.6 ky. The geophysical parameter IRM soft-flux represents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRM soft-flux exhibits relatively higher values before 6.7 ky and after 3.4 ky and lower values in the intervening period, consistent with regional hydrological changes observed in independent records. Abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial El Niño-Southern Oscillation (ENSO) patterns, documenting the occurrence of ENSO-related storms in the Holocene. Spectral power analyses reveal that the storms occur on a significant 500-y cycle, coincident with periodic solar activity and ENSO variance, showing that reinforced (subdued) storms in central China correspond to reduced (increased) solar activity and amplified (damped) ENSO. Thus, the magnetic minerals in speleothem HS4 preserve a record of the cyclic storms controlled by the coupled atmosphere-oceanic circulation driven by solar activity.
Recent status scores for version 6 of the Addiction Severity Index (ASI-6).
Cacciola, John S; Alterman, Arthur I; Habing, Brian; McLellan, A Thomas
2011-09-01
To describe the derivation of recent status scores (RSSs) for version 6 of the Addiction Severity Index (ASI-6). 118 ASI-6 recent status items were subjected to nonparametric item response theory (NIRT) analyses followed by confirmatory factor analysis (CFA). Generalizability and concurrent validity of the derived scores were determined. A total of 607 recent admissions to variety of substance abuse treatment programs constituted the derivation sample; a subset (n = 252) comprised the validity sample. The ASI-6 interview and a validity battery of primarily self-report questionnaires that included at least one measure corresponding to each of the seven ASI domains were administered. Nine summary scales describing recent status that achieved or approached both high scalability and reliability were derived; one scale for each of six areas (medical, employment/finances, alcohol, drug, legal, psychiatric) and three scales for the family/social area. Intercorrelations among the RSSs also supported the multi-dimensionality of the ASI-6. Concurrent validity analyses yielded strong evidence supporting the validity of six of the RSSs (medical, alcohol, drug, employment, family/social problems, psychiatric). Evidence was weaker for the legal, family/social support and child problems RSSs. Generalizability analyses of the scales to males versus females and whites versus blacks supported the comparability of the findings, with slight exceptions. The psychometric analyses to derive Addiction Severity Index version 6 recent status scores support the multi-dimensionality of the Addiction Severity Index version 6 (i.e. the relative independence of different life functioning areas), consistent with research on earlier editions of the instrument. In general, the Addiction Severity Index version 6 scales demonstrate acceptable scalability, reliability and concurrent validity. While questions remain about the generalizability of some scales to population subgroups, the overall findings
NASA Astrophysics Data System (ADS)
Aharon, P.; Rasbury, M. S.; Lambert, W. J.; Ghaleb, B.; Lambert, L.
2005-12-01
Improved understanding of ocean-atmosphere interactions that control interdecadal ENSO variability prompted recently a renewed interest in the acquisition of highly resolved proxy ENSO records. Corals possessing annual growth increments have extended the ENSO archive several centuries beyond the existing instrumental data but much longer records are needed to constrain the interdecadal periodicities and unravel their underlying causes. To this end, paleoclimate proxies archived in stalagmites from tropical Pacific settings have not been harnessed to the task of ENSO paleo-reconstructions although stalagmites elsewhere have offered valuable paleoclimate insights. Here we report the results of an investigation of stalagmites from a water-table cave on Niue Island in the South Pacific (19o 00' S; 169o 50' W) located at the epicenter of oceanic ENSO. Century-long instrumental records on Niue provide a frame of reference and indicate that the interannual and interdecadal air temperature variability is negligible but the rainfall is fully engaged in the wheels of ENSO such that El-Niño and La-Niña events correspond with droughts and abundant rainfall, respectively. Seasonal monsoon and trade rainfalls exhibit a marked contrast in their oxygen isotope compositions. Rainfall amount governs microbial soil activities resulting in convergent 18O and 13C depletions and enrichments in the drips that are transferred to the calcite stalagmites in the Niuean caves. A detailed study of four actively growing stalagmites whose chronology overlaps with the instrumental records confirms that interannual and decadal-scale ENSO variability is clearly expressed in the annual couplets widths and stable oxygen and carbon isotope time-series records of continuous layered stalagmites. Acquisition of a chronology for USM1 stalagmite posed radiometric dating challenges. The U concentration, in the range of 44.2 to 97.5 ppb, is relatively low by comparison with typical stalagmite values
NASA Astrophysics Data System (ADS)
Firpo, M. A.; Sansigolo, C. A.
2011-12-01
One of the most important modes of interannual variability from ocean-atmosphere system is the El Niño/Southern Oscillation - ENSO. The Brazil southern region belongs to the Southeast of South America, where there is a strong signal of ENSO, especially over the precipitation. This phenomenon can be modulated by low frequency climate patterns, especially the dominant pattern of North Pacific, called Pacific Decadal Oscillation (PDO). Attempting to better understand these interactions, the objective of this study was to investigate the seasonal impact of ENSO events over the Southern Brazil precipitation, taking into account the PDO phases. The dataset used in this study, consist of monthly precipitation records of six well distributed stations from southern Brazil (Rio Grande do Sul state). From these series it was calculated a unique index, which was categorized in three classes, in order to obtain the extremes: very below normal precipitation (below the percentile 10), normal precipitation (between percentile 10 and 90) and very above normal precipitation (above the percentile 90). To characterize the ENSO events, it was applied the Trenberth (1997) criteria in the index proposed by Bunge and Clarke (2009), which corrects the inconsistencies between the conventional SST index for Niño 3.4 region and the Southern Oscillation Index before 1950, going beyond the incoherence for decadal scale. For PDO, it was used the index proposed by Mantua et al. (1997). Contingency tables were constructed to analyze the seasonal, simultaneous, and 3, 6, 9 and 12 months lagged relationships between ENSO events (El Niño, neutral, La Niña), and extreme precipitation anomalies (categories), also considering the PDO phases during the 1913-1999 period. Moreover, a wavelet analysis was used to check the coherency and phase among these 3 times series during the 1913-2006 period. The Contingency Tables analysis showed that, generally, there were more positive (negative) precipitation
NASA Astrophysics Data System (ADS)
Bracco, Annalisa; Kucharski, Fred; Molteni, Franco; Hazeleger, Wilco; Severijns, Camiel
2007-04-01
This study investigates how accurately the interannual variability over the Indian Ocean basin and the relationship between the Indian summer monsoon and the El Niño Southern Oscillation (ENSO) can be simulated by different modelling strategies. With a hierarchy of models, from an atmospherical general circulation model (AGCM) forced by observed SST, to a coupled model with the ocean component limited to the tropical Pacific and Indian Oceans, the role of heat fluxes and of interactive coupling is analyzed. Whenever sea surface temperature anomalies in the Indian basin are created by the coupled model, the inverse relationship between the ENSO index and the Indian summer monsoon rainfall is recovered, and it is preserved if the atmospherical model is forced by the SSTs created by the coupled model. If the ocean model domain is limited to the Indian Ocean, changes in the Walker circulation over the Pacific during El-Niño years induce a decrease of rainfall over the Indian subcontinent. However, the observed correlation between ENSO and the Indian Ocean zonal mode (IOZM) is not properly modelled and the two indices are not significantly correlated, independently on season. Whenever the ocean domain extends to the Pacific, and ENSO can impact both the atmospheric circulation and the ocean subsurface in the equatorial Eastern Indian Ocean, modelled precipitation patterns associated both to ENSO and to the IOZM closely resemble the observations.
The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño
NASA Astrophysics Data System (ADS)
Santoso, Agus; Mcphaden, Michael J.; Cai, Wenju
2017-12-01
The year 2015 was special for climate scientists, particularly for the El Niño Southern Oscillation (ENSO) research community, as a major El Niño finally materialized after a long pause since the 1997/1998 extreme El Niño. It was scientifically exciting since, due to the short observational record, our knowledge of an extreme El Niño has been based only on the 1982/1983 and 1997/1998 events. The 2015/2016 El Niño was marked by many environmental disasters that are consistent with what is expected for an extreme El Niño. Considering the dramatic impacts of extreme El Niño, and the risk of a potential increase in frequency of ENSO extremes under greenhouse warming, it is timely to evaluate how the recent event fits into our understanding of ENSO extremes. Here we provide a review of ENSO, its nature and dynamics, and through analysis of various observed key variables, we outline the processes that characterize its extremes. The 2015/2016 El Niño brings a useful perspective into the state of understanding of these events and highlights areas for future research. While the 2015/2016 El Niño is characteristically distinct from the 1982/1983 and 1997/1998 events, it still can be considered as the first extreme El Niño of the 21st century. Its extremity can be attributed in part to unusually warm condition in 2014 and to long-term background warming. In effect, this study provides a list of physically meaningful indices that are straightforward to compute for identifying and tracking extreme ENSO events in observations and climate models.
Different coupled atmosphere-recharge oscillator Low Order Models for ENSO: a projection approach.
NASA Astrophysics Data System (ADS)
Bianucci, Marco; Mannella, Riccardo; Merlino, Silvia; Olivieri, Andrea
2016-04-01
El Ninõ-Southern Oscillation (ENSO) is a large scale geophysical phenomenon where, according to the celebrated recharge oscillator model (ROM), the Ocean slow variables given by the East Pacific Sea Surface Temperature (SST) and the average thermocline depth (h), interact with some fast "irrelevant" ones, representing mostly the atmosphere (the westerly wind burst and the Madden-Julian Oscillation). The fast variables are usually inserted in the model as an external stochastic forcing. In a recent work (M. Bianucci, "Analytical probability density function for the statistics of the ENSO phenomenon: asymmetry and power law tail" Geophysical Research Letters, under press) the author, using a projection approach applied to general deterministic coupled systems, gives a physically reasonable explanation for the use of stochastic models for mimicking the apparent random features of the ENSO phenomenon. Moreover, in the same paper, assuming that the interaction between the ROM and the fast atmosphere is of multiplicative type, i.e., it depends on the SST variable, an analytical expression for the equilibrium density function of the anomaly SST is obtained. This expression fits well the data from observations, reproducing the asymmetry and the power law tail of the histograms of the NINÕ3 index. Here, using the same theoretical approach, we consider and discuss different kind of interactions between the ROM and the other perturbing variables, and we take into account also non linear ROM as a low order model for ENSO. The theoretical and numerical results are then compared with data from observations.
Simulation of different types of ENSO impacts on South Asian Monsoon in CCSM4
NASA Astrophysics Data System (ADS)
Islam, Siraj ul; Tang, Youmin
2017-02-01
It has been found in observation that there are different types of influences of El Nino Southern Oscillation (ENSO) on the South Asian Monsoon (SAM). A correct description and representation of these teleconnections is critical for climate models to simulate and predict SAM. In this study, we examine these teleconnections in NCAR CAM4 and CCSM4 models, including the strength and weakness of these models in preserving different types of ENSO-SAM relationships. By using observational and simulation dataset, the composite analysis, based on specific selection criteria, is performed for both SAM rainfall and the eastern equatorial Pacific sea surface temperature (SST) anomalies. Anomalous SAM rainfall is characterized in three different types i.e. the indirect influence of the SST anomalies of preceding winter (DJF-only), direct influence of the SST anomalies of concurrent summer (JJAS-only) and the combined influence of both preceding winter and concurrent summer (DJF&JJAS). The analysis reveals that CAM4 uncoupled simulation can reasonably well reproduce the anomalous SAM rainfall in DJF-only and DJF&JJAS types whereas the model fails to simulate the anomalous rainfall in the JJAS-only type. The better performance of CAM4, particularly in DJF&JJAS type, comes from its realistic simulation of moisture content and thermal contrast. Its failure to preserve the ENSO-SAM relationship of JJAS-only type is due to the absence of ENSO induced warming in Northern Indian Ocean via atmospheric circulation which is indirectly linked to the lack of air-sea coupling. The role of Indian Ocean in controlling the ENSO-SAM teleconnections of the DJF&JJAS type is further investigated using CAM4 sensitivity experiments. It is found that in absence of Indian Ocean SST, the anomalous SAM summer rainfall suppresses in the DJF&JJAS type, suggesting the important modulation by Indian Ocean SST probably through the preceding winter equatorial Pacific SST forcing and the atmospheric
Do our reconstructions of ENSO have too much low-frequency variability?
NASA Astrophysics Data System (ADS)
Loope, G. R.; Overpeck, J. T.
2017-12-01
Reconstructing the spectrum of Pacific SST variability has proven to be difficult both because of complications with proxy systems such as tree rings and the relatively small number of records from the tropical Pacific. We show that the small number of long coral δ18O and Sr/Ca records has caused a bias towards having too much low-frequency variability in PCR, CPS, and RegEM reconstructions of Pacific variability. This occurs because the individual coral records used in the reconstructions have redder spectra than the shared signal (e.g. ENSO). This causes some of the unshared, low-frequency signal from local climate, salinity and possibly coral biology to bleed into the reconstruction. With enough chronologies in a reconstruction, this unshared noise cancels out but the problem is exacerbated in our longest reconstructions where fewer records are available. Coral proxies tend to have more low-frequency variability than SST observations so this problem is smaller but can still be seen in pseudoproxy experiments using observations and reanalysis data. The identification of this low-frequency bias in coral reconstructions helps bring the spectra of ENSO reconstructions back into line with both models and observations. Although our analysis is mostly constrained to the 20th century due to lack of sufficient data, we expect that as more long chronologies are developed, the low-frequency signal in ENSO reconstructions will be greatly reduced.
2015-16 ENSO Drove Tropical Soil Moisture Dynamics and Methane Fluxes
NASA Astrophysics Data System (ADS)
Aronson, E. L.; Dierick, D.; Botthoff, J.; Swanson, A. C.; Johnson, R. F.; Allen, M. F.
2017-12-01
The El Niño/Southern Oscillation Event (ENSO) cycle drives large-scale climatic trends globally. Within the new world tropics, El Niño brings dryer weather than the counterpart La Niña. Atmospheric methane growth rates have shown extreme variability over the past three decades. One proposed driver is the proportion of tropical land surface saturated, affecting methane production or consumption. We measured methane flux bimonthly through the transition of 2015-16 ENSO. The date of measurement, across El Niño and La Niña within the typical "rainy" and "dry" seasons, to be the most significant driver of methane flux. Soil moisture varied across this time period, and regulated methane flux. During the strong El Niño, extreme dry soil conditions occurred in a typical "rainy" season month reducing soil moisture. Wetter than usual soil conditions appeared during the "rainy" season month of the moderate La Niña. The dry El Niño soils corresponded to greater methane consumption by tropical forest soils, and a reduced local atmospheric column methane concentration. Conversely, the wet La Niña soils had lower methane consumption and higher local atmospheric column methane concentrations. The ENSO cycle is a strong driver of tropical terrestrial and wetland soil moisture conditions, and can regulate global atmospheric methane dynamics.
Assessment of laser ablation techniques in a-si technologies for position-sensor development
NASA Astrophysics Data System (ADS)
Molpeceres, C.; Lauzurica, S.; Ocana, J. L.; Gandia, J. J.; Urbina, L.; Carabe, J.
2005-07-01
Laser micromachining of semiconductor and Transparent Conductive Oxides (TCO) materials is very important for the practical applications in photovoltaic industry. In particular, a problem of controlled ablation of those materials with minimum of debris and small heat affected zone is one of the most vital for the successful implementation of laser micromachining. In particular, selective ablation of thin films for the development of new photovoltaic panels and sensoring devices based on amorphous silicon (a-Si) is an emerging field, in which laser micromachining systems appear as appropriate tools for process development and device fabrication. In particular, a promising application is the development of purely photovoltaic position sensors. Standard p-i-n or Schottky configurations using Transparent Conductive Oxides (TCO), a-Si and metals are especially well suited for these applications, appearing selective laser ablation as an ideal process for controlled material patterning and isolation. In this work a detailed study of laser ablation of a widely used TCO, Indium-tin-oxide (ITO), and a-Si thin films of different thicknesses is presented, with special emphasis on the morphological analysis of the generated grooves. The profiles of ablated grooves have been studied in order to determine the best processing conditions, i.e. laser pulse energy and wavelength, and to asses this technology as potentially competitive to standard photolithographic processes. The encouraging results obtained, with well defined ablation grooves having thicknesses in the order of 10 μm both in ITO and a-Si, open up the possibility of developing a high-performance double Schottky photovoltaic matrix position sensor.
South Asian Summer Monsoon and Its Relationship with ENSO in the IPCC AR4 Simulations
DOE Office of Scientific and Technical Information (OSTI.GOV)
Annamalai, H; Hamilton, K; Sperber, K R
In this paper we use the extensive integrations produced for the IPCC Fourth Assessment Report (AR4) to examine the relationship between ENSO and the monsoon at interannual and decadal timescales. We begin with an analysis of the monsoon simulation in the 20th century integrations. Six of the 18 models were found to have a reasonably realistic representation of monsoon precipitation climatology. For each of these six models SST and anomalous precipitation evolution along the equatorial Pacific during El Nino events display considerable differences when compared to observations. Out of these six models only four (GFDL{_}CM{_}2.0, GFDL{_}CM{_}2.1, MRI, and MPI{_}ECHAM5) exhibitmore » a robust ENSO-monsoon contemporaneous teleconnection, including the known inverse relationship between ENSO and rainfall variations over India. Lagged correlations between the all-India rainfall (AIR) index and Nino3.4 SST reveal that three models represent the timing of the teleconnection, including the spring predictability barrier which is manifested as the transition from positive to negative correlations prior to the monsoon onset. Furthermore, only one of these three models (GFDL{_}CM{_}2.1) captures the observed phase lag with the strongest anticorrelation of SST peaking 2-3 months after the summer monsoon, which is partially attributable to the intensity of simulated El Nino itself. We find that the models that best capture the ENSO-monsoon teleconnection are those that correctly simulate the timing and location of SST and diabatic heating anomalies in the equatorial Pacific, and the associated changes to the equatorial Walker Circulation during El Nino events. The strength of the AIR-Nino3.4 SST correlation in the model runs waxes and wanes to some degree on decadal timescales. The overall magnitude and timescale for this decadal modulation in most of the models is similar to that seen in observations. However, there is little consistency in the phase among the realizations
Precipitation response to the current ENSO variability in a warming world
NASA Astrophysics Data System (ADS)
Bonfils, C.; Santer, B. D.; Phillips, T. J.; Marvel, K.; Leung, L.
2013-12-01
The major triggers of past and recent droughts include large modes of variability, such as ENSO, as well as specific and persistent patterns of sea surface temperature anomalies (SSTAs; Hoerling and Kumar, 2003, Shin et al. 2010, Schubert et al. 2009). However, alternative drought initiators are also anticipated in response to increasing greenhouse gases, potentially changing the relative contribution of ocean variability as drought initiator. They include the intensification of the current zonal wet-dry patterns (the thermodynamic mechanism, Held and Soden, 2006), a latitudinal redistribution of global precipitation (the dynamical mechanism, Seager et al. 2007, Seidel et al. 2008, Scheff and Frierson 2008) and a reduction of local soil moisture and precipitation recycling (the land-atmosphere argument). Our ultimate goal is to investigate whether the relative contribution of those mechanisms change over time in response to global warming. In this study, we first perform an EOF analysis of the 1900-1999 time series of observed global SST field and identify a simple ENSO-like (ENSOL) mode of SST variability. We show that this mode is well spatially and temporally correlated with observed worldwide regional precipitation and drought variability. We then develop concise metrics to examine the fidelity with which the CMIP5 coupled global climate models (CGCMs) capture this particular ENSO-like mode in the current climate, and their ability to replicate the observed teleconnections with precipitation. Based on the CMIP5 model projections of future climate change, we finally analyze the potential temporal variations in ENSOL to be anticipated under further global warming, as well as their associated teleconnections with precipitation (pattern, amplitude, and total response). Overall, our approach allows us to determine what will be the effect of the current ENSO-like variability (i.e., as measured with instrumental observations) on precipitation in a warming world. This
NASA Astrophysics Data System (ADS)
Zaliapin, I.; Ghil, M.; Thompson, S.
2007-12-01
We consider a Delay Differential Equation (DDE) model for El-Nino Southern Oscillation (ENSO) variability. The model combines two key mechanisms that participate in the ENSO dynamics: delayed negative feedback and seasonal forcing. Descriptive and metric stability analyses of the model are performed in a complete 3D space of its physically relevant parameters. Existence of two regimes --- stable and unstable --- is reported. The domains of the regimes are separated by a sharp neutral curve in the parameter space. The detailed structure of the neutral curve become very complicated (possibly fractal), and individual trajectories within the unstable region become highly complex (possibly chaotic) as the atmosphere-ocean coupling increases. In the unstable regime, spontaneous transitions in the mean "temperature" (i.e., thermocline depth), period, and extreme annual values occur, for purely periodic, seasonal forcing. This indicates (via the continuous dependence theorem) the existence of numerous unstable solutions responsible for the complex dynamics of the system. In the stable regime, only periodic solutions are found. Our results illustrate the role of the distinct parameters of ENSO variability, such as strength of seasonal forcing vs. atmosphere ocean coupling and propagation period of oceanic waves across the Tropical Pacific. The model reproduces, among other phenomena, the Devil's bleachers (caused by period locking) documented in other ENSO models, such as nonlinear PDEs and GCMs, as well as in certain observations. We expect such behavior in much more detailed and realistic models, where it is harder to describe its causes as completely.
Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene
NASA Astrophysics Data System (ADS)
Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.
2014-12-01
Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.
Influence of surface nudging on climatological mean and ENSO feedbacks in a coupled model
NASA Astrophysics Data System (ADS)
Zhu, Jieshun; Kumar, Arun
2018-01-01
Studies have suggested that surface nudging could be an efficient way to reconstruct the subsurface ocean variability, and thus a useful method for initializing climate predictions (e.g., seasonal and decadal predictions). Surface nudging is also the basis for climate models with flux adjustments. In this study, however, some negative aspects of surface nudging on climate simulations in a coupled model are identified. Specifically, a low-resolution version of the NCEP Climate Forecast System, version 2 (CFSv2L) is used to examine the influence of nudging on simulations of climatological mean and on the coupled feedbacks during ENSO. The effect on ENSO feedbacks is diagnosed following a heat budget analysis of mixed layer temperature anomalies. Diagnostics of the climatological mean state indicates that, even though SST biases in all ocean basins, as expected, are eliminated, the fidelity of climatological precipitation, surface winds and subsurface temperature (or the thermocline depth) could be highly ocean basin dependent. This is exemplified by improvements in the climatology of these variables in the tropical Atlantic, but degradations in the tropical Pacific. Furthermore, surface nudging also distorts the dynamical feedbacks during ENSO. For example, while the thermocline feedback played a critical role during the evolution of ENSO in a free simulation, it only played a minor role in the nudged simulation. These results imply that, even though the simulation of surface temperature could be improved in a climate model with surface nudging, the physics behind might be unrealistic.
Dynamical excitation of the tropical Pacific Ocean and ENSO variability by Little Ice Age cooling.
Rustic, Gerald T; Koutavas, Athanasios; Marchitto, Thomas M; Linsley, Braddock K
2015-12-18
Tropical Pacific Ocean dynamics during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are poorly characterized due to a lack of evidence from the eastern equatorial Pacific. We reconstructed sea surface temperature, El Niño-Southern Oscillation (ENSO) activity, and the tropical Pacific zonal gradient for the past millennium from Galápagos ocean sediments. We document a mid-millennium shift (MMS) in ocean-atmosphere circulation around 1500-1650 CE, from a state with dampened ENSO and strong zonal gradient to one with amplified ENSO and weak gradient. The MMS coincided with the deepest LIA cooling and was probably caused by a southward shift of the intertropical convergence zone. The peak of the MCA (900-1150 CE) was a warm period in the eastern Pacific, contradicting the paradigm of a persistent La Niña pattern. Copyright © 2015, American Association for the Advancement of Science.
The Influence of ENSO to the Rainfall Variability in North Sumatra Province
NASA Astrophysics Data System (ADS)
Irwandi, H.; Pusparini, N.; Ariantono, J. Y.; Kurniawan, R.; Tari, C. A.; Sudrajat, A.
2018-04-01
The El Niño Southern Oscillation (ENSO) is a global phenomenon that affects the variability of rainfall in North Sumatra. The influence of ENSO will be different for each region. This review will analyse the influence of ENSO activity on seasonal and annual rainfall variability. In this research, North Sumatra Province will be divided into 4 (four) regions based on topographical conditions, such as: East Coast (EC), East Slope (ES), Mountains (MT), and West Coast (WC). The method used was statistical and descriptive analysis. Data used in this research were rainfall data from 15 stations / climate observation posts which spread in North Sumatera region and also anomaly data of Nino 3.4 region from period 1981-2016. The results showed that the active El Niño had an effect on the decreasing the rainfall during the period of DJF, JJA and SON in East Coast, East Slope, and Mountains with the decreasing of average percentage of annual rainfall up to 7%. On the contrary, the active La Nina had an effect on the addition of rainfall during the period DJF and JJA in the East Coast and Mountains with the increasing of average percentage of annual rainfall up to 6%.
Prediction of ENSO episodes using canonical correlation analysis
DOE Office of Scientific and Technical Information (OSTI.GOV)
Barnston, A.G.; Ropelewski, C.F.
Canonical correlation analysis (CCA) is explored as a multivariate linear statistical methodology with which to forecast fluctuations of the El Nino/Southern Oscillation (ENSO) in real time. CCA is capable of identifying critical sequences of predictor patterns that tend to evolve into subsequent pattern that can be used to form a forecast. The CCA model is used to forecast the 3-month mean sea surface temperature (SST) in several regions of the tropical Pacific and Indian oceans for projection times of 0 to 4 seasons beyond the immediately forthcoming season. The predictor variables, representing the climate situation in the four consecutive 3-monthmore » periods ending at the time of the forecast, are (1) quasi-global seasonal mean sea level pressure (SLP) and (2) SST in the predicted regions themselves. Forecast skill is estimated using cross-validation, and persistence is used as the primary skill control measure. Results indicate that a large region in the eastern equatorial Pacific (120[degrees]-170[degrees] W longitude) has the highest overall predictability, with excellent skill realized for winter forecasts made at the end of summer. CCA outperforms persistence in this region under most conditions, and does noticeably better with the SST included as a predictor in addition to the SLP. It is demonstrated that better forecast performance at the longer lead times would be obtained if some significantly earlier (i.e., up to 4 years) predictor data were included, because the ability to predict the lower-frequency ENSO phase changes would increase. The good performance of the current system at shorter lead times appears to be based largely on the ability to predict ENSO evolution for events already in progress. The forecasting of the eastern tropical Pacific SST using CCA is now done routinely on a monthly basis for a O-, 1-, and 2-season lead at the Climate Analysis Center.« less
NASA Astrophysics Data System (ADS)
Troy, S.; Aharon, P.; Lambert, W. J.
2012-12-01
El Niño-Southern Oscillation's (ENSO) dominant control over the present global climate and its unpredictable response to a global warming makes the study of paleo-ENSO important. So far corals, spanning the Tropical Pacific Ocean, are the most commonly used geological archives of paleo-ENSO. This is because corals typically exhibit high growth rates (>1 cm/yr), and reproduce reliably surface water temperatures at sub-annual resolution. However there are limitations to coral archives because their time span is relatively brief (in the order of centuries), thus far making a long and continuous ENSO record difficult to achieve. On the other hand stalagmites from island settings can offer long and continuous records of ENSO-driven rainfall. Niue Island caves offer an unusual opportunity to investigate ENSO-driven paleo-rainfall because the island is isolated from other large land masses, making it untainted by continental climate artifacts, and its geographical location is within the Tropical Pacific "rain pool" (South Pacific Convergence Zone; SPCZ) that makes the rainfall variability particularly sensitive to the ENSO phase switches. We present here a δ18O and δ13C time series from a stalagmite sampled on Niue Island (19°00' S, 169°50' W) that exhibits exceptionally high growth rates (~1.2 mm/yr) thus affording a resolution comparable to corals but for much longer time spans. A precise chronology, dating back to several millennia, was achieved by U/Th dating of the stalagmite. The stalagmite was sampled using a Computer Automated Mill (CAM) at 300 μm increments in order to receive sub-annual resolution (every 3 months) and calcite powders of 50-100 μg weight were analyzed for δ18O and δ13C using a Continuous Flow Isotope Ratio Mass Spectrometer (CF-IRMS). The isotope time series contains variable shifts at seasonal, inter-annual, and inter-decadal periodicities. The δ13C and δ18O yield ranges of -3.0 to -13.0 (‰ VPDB) and -3.2 to -6.2 (‰ VPDB
On The Bimodality of ENSO Cycle Extremes
NASA Technical Reports Server (NTRS)
Wilson, Robert M.
2000-01-01
On the basis of sea surface temperature in the El Nino 3.4 region (5N.-5S., 120-170W.) during the interval of 1950-1997, Kevin Trenberth previously has identified some 16 El Nino and 10 La Nina, these 26 events representing the extremes of the quasi-periodic El Nino-Southern Oscillation (ENSO) cycle. Runs testing shows that the duration, recurrence period, and sequencing of these extremes vary randomly. Hence, the decade of the 1990's, especially for El Nino, is not significantly different from that of previous decadal epochs, at least, on the basis of the frequency of onsets of ENSO extremes. Additionally, the distribution of duration for both El Nino and La Nina looks strikingly bimodal, each consisting of two preferred modes, about 8- and 16-months long for El Nino and about 9- and 18-months long for La Nina, as does the distribution of the recurrence period for El Nino, consisting of two preferred modes about 21- and 50- mo long. Scatterplots of the recurrence period versus duration for El Nino are found to be statistically important, displaying preferential associations that link shorter (longer) duration with shorter (longer) recurrence periods. Because the last onset of El Nino occurred in April 1997 and the event was of longer than average duration, onset of the next anticipated El Nino is not expected until February 2000 or later.
ERIC Educational Resources Information Center
Kraft, Donald H., Ed.
The 2000 ASIS (American Society for Information Science) conference explored knowledge innovation. The tracks in the conference program included knowledge discovery, capture, and creation; classification and representation; information retrieval; knowledge dissemination; and social, behavioral, ethical, and legal aspects. This proceedings is…
NASA Technical Reports Server (NTRS)
Yu, Jin-Yi; Lau, K. M.
2004-01-01
In this study, we perform experiments with a coupled atmosphere-ocean general circulation model (CGCM) to examine ENSO's influence on the interannual sea surface temperature (SST) variability of the tropical Indian Ocean. The control experiment includes both the Indian and Pacific Oceans in the ocean model component of the CGCM (the Indo-Pacific Run). The anomaly experiment excludes ENSOs influence by including only the Indian Ocean while prescribing monthly-varying climatological SSTs for the Pacific Ocean (the Indian-Ocean Run). In the Indo-Pacific Run, an oscillatory mode of the Indian Ocean SST variability is identified by a multi-channel singular spectral analysis (MSSA). The oscillatory mode comprises two patterns that can be identified with the Indian Ocean Zonal Mode (IOZM) and a basin-wide warming/cooling mode respectively. In the model, the IOZM peaks about 3-5 months after ENSO reaches its maximum intensity. The basin mode peaks 8 months after the IOZM. The timing and associated SST patterns suggests that the IOZM is related to ENSO, and the basin- wide warming/cooling develops as a result of the decay of the IOZM spreading SST anomalies from western Indian Ocean to the eastern Indian Ocean. In contrast, in the Indian-Ocean Run, no oscillatory modes can be identified by the MSSA, even though the Indian Ocean SST variability is characterized by east-west SST contrast patterns similar to the IOZM. In both control and anomaly runs, IOZM-like SST variability appears to be associated with forcings from fluctuations of the Indian monsoon. Our modeling results suggest that the oscillatory feature of the IOZM is primarily forced by ENSO.
NASA Astrophysics Data System (ADS)
Wengel, C.; Latif, M.; Park, W.; Harlaß, J.; Bayr, T.
2018-02-01
The El Niño/Southern Oscillation (ENSO) is characterized by a seasonal phase locking, with strongest eastern and central equatorial Pacific sea surface temperature (SST) anomalies during boreal winter and weakest SST anomalies during boreal spring. In this study, key feedbacks controlling seasonal ENSO phase locking in the Kiel Climate Model (KCM) are identified by employing Bjerknes index stability analysis. A large ensemble of simulations with the KCM is analyzed, where the individual runs differ in either the number of vertical atmospheric levels or coefficients used in selected atmospheric parameterizations. All integrations use the identical ocean model. The ensemble-mean features realistic seasonal ENSO phase locking. ENSO phase locking is very sensitive to changes in the mean-state realized by the modifications described above. An excessive equatorial cold tongue leads to weak phase locking by reducing the Ekman feedback and thermocline feedback in late boreal fall and early boreal winter. Seasonal ENSO phase locking also is sensitive to the shortwave feedback as part of the thermal damping in early boreal spring, which strongly depends on eastern and central equatorial Pacific SST. The results obtained from the KCM are consistent with those from models participating in the Coupled Model Intercomparison Project phase 5 (CMIP5).
NASA Technical Reports Server (NTRS)
Oman, L. D.; Douglass, A. R.; Ziemke, J. R.; Rodriquez, J. M.; Waugh, D. W.; Nielsen, J. E.
2012-01-01
The El Nino-Southern Oscillation (ENSO) is the dominant mode of tropical variability on interannual time scales. ENSO appears to extend its influence into the chemical composition of the tropical troposphere. Recent work has revealed an ENSO-induced wave-1 anomaly in observed tropical tropospheric column ozone. This results in a dipole over the western and eastern tropical Pacific, whereby differencing the two regions produces an ozone anomaly with an extremely high correlation to the Nino 3.4 Index. We have successfully reproduced this feature using the Goddard Earth Observing System Version 5 (GEOS-5) general circulation model coupled to a comprehensive stratospheric and tropospheric chemical mechanism forced with observed sea surface temperatures over the past 25 years. An examination of the modeled ozone field reveals the vertical contributions of tropospheric ozone to the column over the western and eastern Pacific region. We will show composition sensitivity in observations from NASA s Aura satellite Microwave Limb Sounder (MLS) and the Tropospheric Emissions Spectrometer (TES) and a simulation to provide insight into the vertical structure of these ENSO-induced ozone changes. The ozone changes due to the Quasi-Biennial Oscillation (QBO) in the extra-polar upper troposphere and lower stratosphere in MLS measurements will also be discussed.
NASA Astrophysics Data System (ADS)
DU, X.; Hendy, I. L.; Hinnov, L.; Brown, E. T.; Schimmelmann, A.; Pak, D. K.
2017-12-01
The El Niño-Southern Oscillation (ENSO) has a major influence on Southern California's hydroclimate as demonstrated by both historical observations and model simulations. Santa Barbara Basin (SBB) off Southern California preserves a unique varved (i.e. annually laminated) marine sedimentary archive of modern and Holocene hydroclimate variability, notably including the transition from the regionally dry Medieval Climate Anomaly (MCA) to the wetter Little Ice Age (LIA). Here we present sub-annually resolved scanning XRF elemental counts for the last 2,000 years in SBB from core SPR0901-03KC. Titanium (associated with silicate minerals) is delivered more efficiently to SBB sediments during times of enhanced river flow and in the Mediterranean climate of Southern California, river flow only occurs after precipitation. The Ti record suggests that the precipitation frequency was reduced during the MCA except for a pluvial episode at CE 1075-1121, but increased during the LIA. Time series analysis of Ti counts indicates ENSO variability robustly increased during the intervals CE 450-520, 650-720, 980-1150, 1380-1550 and 1720-1750, and experienced relatively quiescent intervals between CE 50-150, 250-400, 550-650, 750-950, 1150-1280 and 1580-1620. Generally the LIA in Southern California is characterized by more active ENSO variability with long periodicities (4-7 yr) and multi-decadal variability (54 yr). MCA drought episodes were associated with less active ENSO. Active ENSO variability in Southern California during the last 2,000 years coincided with reconstructed southward migration of the Intertropical Convergence Zone (ITCZ) suggesting the ITCZ may play a role in the waxing and waning of ENSO teleconnections between the central Pacific and the west coast of North America.
NASA Technical Reports Server (NTRS)
Jeong, Hye-In; Lee, Doo Young; Karumuri, Ashok; Ahn, Joong-Bae; Lee, June-Yi; Luo, Jing-Jia; Schemm, Jae-Kyung E.; Hendon, Harry H.; Braganza, Karl; Ham, Yoo-Geun
2012-01-01
Forecast skill of the APEC Climate Center (APCC) Multi-Model Ensemble (MME) seasonal forecast system in predicting two main types of El Nino-Southern Oscillation (ENSO), namely canonical (or cold tongue) and Modoki ENSO, and their regional climate impacts is assessed for boreal winter. The APCC MME is constructed by simple composite of ensemble forecasts from five independent coupled ocean-atmosphere climate models. Based on a hindcast set targeting boreal winter prediction for the period 19822004, we show that the MME can predict and discern the important differences in the patterns of tropical Pacific sea surface temperature anomaly between the canonical and Modoki ENSO one and four month ahead. Importantly, the four month lead MME beats the persistent forecast. The MME reasonably predicts the distinct impacts of the canonical ENSO, including the strong winter monsoon rainfall over East Asia, the below normal rainfall and above normal temperature over Australia, the anomalously wet conditions across the south and cold conditions over the whole area of USA, and the anomalously dry conditions over South America. However, there are some limitations in capturing its regional impacts, especially, over Australasia and tropical South America at a lead time of one and four months. Nonetheless, forecast skills for rainfall and temperature over East Asia and North America during ENSO Modoki are comparable to or slightly higher than those during canonical ENSO events.
NASA Astrophysics Data System (ADS)
Zhao, Haikun; Wang, Chunzai
2018-02-01
The present paper uses the satellite era data from 1979 to 2015 to examine the relationship between El Niño-Southern Oscillation (ENSO) and tropical cyclones (TCs) in the western North Pacific (WNP) during the boreal summer from June to August. It is found that WNP TC variability is characterized by two major feature changes: (1) a significant reduction of the TC number since 1998 and (2) a stronger interannual relationship between ENSO and TCs since 1998. Results suggested that such changes are largely due to the synergy effects of a shifting ENSO and the Pacific climate regime shift. Since 1998 with a cool Pacific decadal oscillation phase switching from a warm phase, more La Niña and central Pacific (CP) El Niño events occur. The decreased low-level relative vorticity and increased vertical wind shear during 1998-2015 compared to 1979-1997 are responsible for the TC reduction. The stronger interannual relationship between ENSO and TCs since 1998 is closely associated the change of CP sea surface temperature. It enhances the associations of environmental factors including vertical wind shear and mid-level relative humidity with TCs and thus increases the interannual relationship between ENSO and TCs. These two feature changes also manifest in the mean TC genesis location, with a northwestward shift of the TC genesis location during 1998-2015 and an increased relation to El Niño Modoki index since 1998. This study has an important implication for TC outlooks in the WNP based on climate predictions and projections.
NASA Astrophysics Data System (ADS)
Feng, Juan; Chen, Wen
2014-03-01
The variability of the East Asian winter monsoon (EAWM) can be divided into an ENSO-related part (EAWMEN) and an ENSO-unrelated part (EAWMres). The influence of EAWMres on the ENSO-East Asian summer monsoon (EASM) relationship in the decaying stages of ENSO is investigated in the present study. To achieve this, ENSO is divided into four groups based on the EAWMres: (1) weak EAWMres-El Niño (WEAWMres-EN); (2) strong EAWMres-El Niño (SEAWMres- EN); (3) weak EAWMres-La Niña (WEAWMres-LN); (4) strong EAWMres-La Niña (SEAWMres-LN). Composite results demonstrate that the EAWMres may enhance the atmospheric responses over East Asia to ENSO for WEAWMres-EN and SEAWMres-LN. The corresponding low-level anticyclonic (cyclonic) anomalies over the western North Pacific (WNP) associated with El Niño (La Niña) tend to be strong. Importantly, this feature may persist into the following summer, causing abundant rainfall in northern China for WEAWMres-EN cases and in southwestern China for SEAWMres-LN cases. In contrast, for the SEAWMres-EN and WEAWMres-LN groups, the EAWMres tends to weaken the atmospheric circulation anomalies associated with El Niño or La Niña. In these cases, the anomalous WNP anticyclone or cyclone tend to be reduced and confined to lower latitudes, which results in deficient summer rainfall in northern China for SEAWMres-EN and in southwestern China for WEAWMres-LN. Further study suggests that anomalous EAWMres may have an effect on the extra-tropical sea surface temperature anomaly, which persists into the ensuing summer and may interfere with the influences of ENSO.
NASA Technical Reports Server (NTRS)
Lau, K.-M.; Wu, H. T.
2000-01-01
Using global rainfall and sea surface temperature (SST) data for the past two decades (1979-1998), we have investigated the intrinsic modes of Asian summer monsoon (ASM) and ENSO co-variability. Three recurring ASM rainfall-SST coupled modes were identified. The first is a basin scale mode that features SST and rainfall variability over the entire tropics (including the ASM region), identifiable with those occurring during El Nino or La Nina. This mode is further characterized by a pronounced biennial variation in ASM rainfall and SST associated with fluctuations of the anomalous Walker circulation that occur during El Nino/La Nina transitions. The second mode comprises mixed regional and basin-scale rainfall and SST signals, with pronounced intraseasonal and interannual variabilities. This mode features a SST pattern associated with a developing La Nina, with a pronounced low level anticyclone in the subtropics of the western Pacific off the coast of East Asia. The third mode depicts an east-west rainfall and SST dipole across the southern equatorial Indian Ocean, most likely stemming from coupled ocean-atmosphere processes within the ASM region. This mode also possesses a decadal time scale and a linear trend, which are not associated with El Nino/La Nina variability. Possible causes of year-to-year rainfall variability over the ASM and sub-regions have been evaluated from a reconstruction of the observed rainfall from singular eigenvectors of the coupled modes. It is found that while basin-scale SST can account for portions of ASM rainfall variability during ENSO events (up to 60% in 1998), regional processes can accounts up to 20-25% of the rainfall variability in typical non-ENSO years. Stronger monsoon-ENSO relationship tends to occur in the boreal summer immediately preceding a pronounced La Nina, i.e., 1998, 1988 and 1983. Based on these results, we discuss the possible impacts of the ASM on ENSO variability via the west Pacific anticyclone and articulate a
North Pacific decadal variability: insights from a biennial ENSO environment
NASA Astrophysics Data System (ADS)
Achuthavarier, Deepthi; Schubert, Siegfried D.; Vikhliaev, Yury V.
2017-08-01
This study examines the mechanisms of the Pacific decadal oscillation (PDO) in the NASA GEOS-5 general circulation model (GCM). Similar to several other state-of-the-art GCMs, the El Niño-Southern Oscillation (ENSO) simulated by the GEOS-5 has a strong biennial periodicity. Since this is a model bias that precludes a strong role of ENSO, it provides a unique environment to assess the other leading mechanisms of North Pacific decadal variability. Despite the biennial ENSO periodicity, the model simulates a realistic PDO pattern in the North Pacific that is resolved as the first empirical orthogonal function (EOF) of winter mean sea surface temperature (SST). The spectrum of the PDO indicates no preferred periodicity. The SST anomalies associated with the PDO, particularly its basin wide structure, are primarily forced by the Aleutian low through Ekman transport. The slow geostrophic transport in association with the meridional adjustment of the subtropical gyre is limited to a narrow region in the Kuroshio-Oyashio extension, north of 40°N. The atmosphere's response to the PDO, while weak, projects onto the North Pacific Oscillation (NPO), a meridional dipole in sea level pressure. Both the lack of preferred periodicity and the weak atmospheric response indicate an air-sea coupled oscillation is an unlikely mechanism in this model. In agreement with recent studies, the NPO is correlated with the North Pacific Gyre Oscillation, which is another leading EOF of North Pacific SST variability. The results emphasize the role of atmospheric variability in the North Pacific SST modes, thereby bringing into question the potential for their predictability.
North Pacific Decadal Variability: Insights from a Biennial ENSO Environment
NASA Technical Reports Server (NTRS)
Achuthavarier, Deepthi; Schubert, Siegfried D.; Vikhliaev, Yury V.
2016-01-01
This study examines the mechanisms of the Pacific decadal oscillation (PDO) in the NASA GEOS-5 general circulation model (GCM). Similar to several other state-of-the-art GCMs, the El Niño-Southern Oscillation (ENSO) simulated by the GEOS-5 has a strong biennial periodicity. Since this is a model bias that precludes a strong role of ENSO, it provides a unique environment to assess the other leading mechanisms of North Pacific decadal variability. Despite the biennial ENSO periodicity, the model simulates a realistic PDO pattern in the North Pacific that is resolved as the first empirical orthogonal function (EOF) of winter mean sea surface temperature (SST). The spectrum of the PDO indicates no preferred periodicity. The SST anomalies associated with the PDO, particularly its basin wide structure, are primarily forced by the Aleutian low through Ekman transport. The slow geostrophic transport in association with the meridional adjustment of the subtropical gyre is limited to a narrow region in the Kuroshio-Oyashio extension, north of 40degN. The atmosphere's response to the PDO, while weak, projects onto the North Pacific Oscillation (NPO), a meridional dipole in sea level pressure. Both the lack of preferred periodicity and the weak atmospheric response indicate an air-sea coupled oscillation is an unlikely mechanism in this model. In agreement with recent studies, the NPO is correlated with the North Pacific Gyre Oscillation, which is another leading EOF of North Pacific SST variability. The results emphasize the role of atmospheric variability in the North Pacific SST modes, thereby bringing into question the potential for their predictability.
An MJO-Mediated Mechanism to Explain ENSO and IOD Impacts on East African Short Rains
NASA Astrophysics Data System (ADS)
Zaitchik, B. F.; Berhane, F.; Gnanadesikan, A.
2015-12-01
Previous studies have found that the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) have significant impacts on rainfall over East Africa (EA) during the short rains (Oct-Dec). However, not all ENSO and IOD events are associated with significant precipitation anomalies over EA. Our analysis shows that the IOD and ENSO influence EA rainfall by modifying the MJO. Composite analysis of rainfall and outgoing longwave radiation data show that the MJO over the Indian Ocean (phases 2 and 3 of the Wheeler and Hendon index) is associated with significant increase in precipitation over EA during El Niño. In La Niña and non-ENSO years, the MJO over the Indian Ocean has very weak impacts on EA convection and precipitation. Although previous studies have found that El Niño / La Niña events are associated with anomalous wetness/dryness over EA, the associations are not evident in the absence of the MJO. Similarly, the IOD exhibits strong associations with EA precipitation when there is MJO activity over the Indian Ocean. During the positive phase of the IOD, the MJO over the Indian Ocean has impacts that extend to EA. In the absence of the MJO, however, the IOD shows weak associations with EA precipitation. Furthermore, there are more MJO days in the Indian Ocean during El Niño and positive IOD events, which implies stronger impacts on EA. During La Niña events more MJO days are observed in the Pacific Ocean, favoring subsidence over the western Indian Ocean and dry anomalies over EA. These observations suggest two critical MJO-related questions that must be addressed in order to explain EA short rain variability typically attributed to ENSO or IOD: first, how do ENSO and IOD modify background conditions in a way that causes Indian Ocean MJO activity to be more strongly connected to EA under El Niño and IOD positive conditions, and second, why is it that El Niño and IOD positive states slow MJO propagation over the Indian Ocean and speed it over
Oceanic Channel of the IOD-ENSO teleconnection over the Indo-Pacific Ocean
NASA Astrophysics Data System (ADS)
Yuan, Dongliang; Wang, Jing; Zhao, Xia; Zhou, Hui; Xu, Tengfei; Xu, Peng
2017-04-01
The lag correlations of observations and model simulated data that participate the Coupled Model Intercomparison Project phase-5 (CMIP5) are used to study the precursory teleconnection between the Indian Ocean Dipole (IOD) and the Pacific ENSO one year later through the Indonesian seas. The results suggest that Indonesian Throughflow (ITF) play an important role in the IOD-ENSO teleconnection. Numerical simulations using a hierarchy of ocean models and climate coupled models have shown that the interannual sea level depressions in the southeastern Indian Ocean during IOD force enhanced ITF to transport warm water of the Pacific warm pool to the Indian Ocean, producing cold subsurface temperature anomalies, which propagate to the eastern equatorial Pacific and induce significant coupled ocean-atmosphere evolution. The teleconnection is found to have decadal variability. Similar decadal variability has also been identified in the historical simulations of the CMIP5 models. The dynamics of the inter-basin teleconnection during the positive phases of the decadal variability are diagnosed to be the interannual variations of the ITF associated with the Indian Ocean Dipole (IOD). During the negative phases, the thermocline in the eastern equatorial Pacific is anomalously deeper so that the sea surface temperature anomalies in the cold tongue are not sensitive to the thermocline depth changes. The IOD-ENSO teleconnection is found not affected significantly by the anthropogenic forcing.
NASA Astrophysics Data System (ADS)
Bedoya-Soto, Juan Mauricio; Poveda, Germán; Trenberth, Kevin E.; Vélez-Upegui, Jorge Julián
2018-03-01
During 2009-2011, Colombia experienced extreme hydroclimatic events associated with the extreme phases of El Niño-Southern Oscillation (ENSO). Here, we study the dynamics of diverse land-atmosphere phenomena involved in such anomalous events at continental, regional, and local scales. Standardized anomalies of precipitation, 2-m temperature, total column water (TCW), volumetric soil water (VSW), temperature at 925 hPa, surface sensible heat (SSH), latent heat (SLH), evaporation (EVP), and liquid water equivalent thickness (LWET) are analyzed to assess atmosphere-land controls and relationships over tropical South America (TropSA) during 1986-2013 (long term) and 2009-2011 (ENSO extreme phases). An assessment of the interannual covariability between precipitation and 2-m temperature is performed using singular value decomposition (SVD) to identify the dominant spatiotemporal modes of hydroclimatic variability over the region's largest river basins (Amazon, Orinoco, Tocantins, Magdalena-Cauca, and Essequibo). ENSO, its evolution in time, and strong and consistent spatial structures emerge as the dominant mode of variability. In situ anomalies during both extreme phases of ENSO 2009-2011 over the Magdalena-Cauca River basins are linked at the continental scale. The ENSO-driven hydroclimatic effects extend from the diurnal cycle to interannual timescales, as reflected in temperature data from tropical glaciers and the rain-snow boundary in the highest peaks of the Central Andes of Colombia to river levels along the Caribbean lowlands of the Magdalena-Cauca River basin.
Piazza, Bryan P.; LaPeyre, Megan K.; Keim, B.D.
2010-01-01
Climate creates environmental constraints (filters) that affect the abundance and distribution of species. In estuaries, these constraints often result from variability in water flow properties and environmental conditions (i.e. water flow, salinity, water temperature) and can have significant effects on the abundance and distribution of commercially important nekton species. We investigated links between large-scale climate variability and juvenile brown shrimp Farfantepenaeus aztecus abundance in Breton Sound estuary, Louisiana (USA). Our goals were to (1) determine if a teleconnection exists between local juvenile brown shrimp abundance and the El Niño Southern Oscillation (ENSO) and (2) relate that linkage to environmental constraints that may affect juvenile brown shrimp recruitment to, and survival in, the estuary. Our results identified a teleconnection between winter ENSO conditions and juvenile brown shrimp abundance in Breton Sound estuary the following spring. The physical connection results from the impact of ENSO on winter weather conditions in Breton Sound (air pressure, temperature, and precipitation). Juvenile brown shrimp abundance effects lagged ENSO by 3 mo: lower than average abundances of juvenile brown shrimp were caught in springs following winter El Niño events, and higher than average abundances of brown shrimp were caught in springs following La Niña winters. Salinity was the dominant ENSO-forced environmental filter for juvenile brown shrimp. Spring salinity was cumulatively forced by winter river discharge, winter wind forcing, and spring precipitation. Thus, predicting brown shrimp abundance requires incorporating climate variability into models.
NASA Astrophysics Data System (ADS)
Sachse, D.; Romero, L.; Kienel, U.; Haug, G. H.
2016-12-01
ENSO is one of the major drivers of inter-annual climate variability and its effects extend far beyond the Tropical Pacific. However, our knowledge about the stability and linearity of ENSO teleconnections is limited due to the short temporal coverage of observational data, in particular of well dated paleo-ENSO records. Here we present a high-resolution record of rainfall variability on the Pacific coast of Mexico, which today is significantly correlated to ENSO variability (NINO 3.4 index), with dryer conditions during an El Niño phase and wetter conditions during a La Niña phase. The lake, situated in a volcanic crater on Isabel Island, is strongly influenced by rainfall intensity, i.e. freshwater and saline sea water input. A halophile bacterial community dominates during dry phases and an algal community dominates in a freshwater lens which develops during the wet season. Specific lipid biomarkers in the sediments indicate the dominant bacterial community (tetrahymanol and long-chain diols, respectively) in an annually laminated sediment core and record the timing and direction of ENSO mean state changes. We find the region was dry before 825 AD, indicating dominant El Niño. Between 825 and 950 AD, wetter conditions provide evidence for a dominating La Niña like pattern. During the early Medieval Climate Anomaly (MCA, 925-1100 AD) we reconstruct a dryer (El Niño like) environment, changing into a La Niña dominated pattern, prevailing until 1700 AD. The late Little Ice Age (LIA, 1700-1850AD) was initially dry and changed into a wetter climate at 1750 AD. Afterwards El Niño dominated in the region. The overall pattern of these changes agrees with other paleoclimate records from the Pacific region. However, our well dated (±20 years) high-resolution record identifies a number of short-lived episodes of deviations from this pattern, in particular during the MCA and the LIA. We also find strong similarities in the timing of these episodes with North Pacific
NASA Astrophysics Data System (ADS)
Park, Jungjae; Shin, Young Ho; Byrne, Roger
2016-12-01
Several recent studies suggest the hypothesis that the El Niño-Southern Oscillation (ENSO) is an important factor controlling the Holocene East Asian Monsoon (EAM). However, the mechanism underlying this influence remains unclear due to the lack of high-resolution paleoclimate records from the coast of East Asia. Here, we provide a new record of late Holocene climate change in coastal East Asia based on multi-proxy evidence (pollen, organic content, magnetic susceptibility, grain size) obtained from a sediment core from Jeju Island, South Korea. As Jeju Island is strongly influenced by the Kuroshio flow, our sediment proxy records contain ENSO signals from the tropical Pacific. The study area was affected by dry/cool conditions in the western tropical Pacific (WTP) between 4350 and 1920 cal yr BP when El Niños were frequent, and by rapid warming/wetting and forestation since 1920 cal yr BP when La Niñas were more common. Jeju Island was relatively dry/cool between 2100 and 1600, 1300-1200, 1100-1000, 800-650, and 300-50 cal yr BP, as opposed to the Galápagos Islands, which were relatively wet/warm, reflecting the ENSO-related negative correlation between eastern and western margins of Pacific. Wet conditions may have prevailed during the early Little Ice Age (LIA) (620-280 cal yr BP) despite consistent cooling. This period of high precipitation may have been associated with the increased landfall of typhoons and with warmer Kuroshio currents under La Niña-like conditions. According to our results, EAM on the East Asian coastal margin was predominantly driven by ENSO activity, rather than by the precession effect. Paleoclimatic data from Jeju Island, with its insular position and closeness to warm Kuroshio currents, provide clear evidence of these ENSO influences.
Global Complexity: Information, Chaos, and Control at ASIS 1996 Annual Meeting.
ERIC Educational Resources Information Center
Jacob, M. E. L.
1996-01-01
Discusses proceedings of the 1996 ASIS (American Society for Information Science) annual meeting in Baltimore (Maryland), including chaos theory; electronic universities; distance education; intellectual property, including information privacy on the Internet; the need for leadership in libraries and information centers; information warfare and…
PDO modulation of the ENSO impact on the summer South Asian high
NASA Astrophysics Data System (ADS)
Xue, Xu; Chen, Wen; Chen, Shangfeng; Feng, Juan
2018-02-01
This study investigates modulation effects of the Pacific decadal oscillation (PDO) on the impact of boreal winter El Niño-Southern Oscillation (ENSO) on the South Asian high (SAH) variability in the following summer. In the El Niño together with positive PDO (EL/+PDO) or the La Niña together with negative PDO (LA/-PDO) years, boreal winter ENSO can influence the following summer SAH activity significantly. The SAH tends to be obviously strengthened (weakened) and located further south (north) during EL/+PDO (LA/-PDO). However, in the El Niño together with negative PDO (EL/-PDO) or the La Niña together with positive PDO (LA/+PDO) years, the influence of ENSO on the SAH tends to be weak. The strength and location of SAH are close to those in the climatology of 1950-2011 during the EL/-PDO or the LA/+PDO. Further analysis indicates that the PDO could exert pronounced influence on the ENSO-SAH connection via modulating the anomalous Walker circulation and charge effect over the tropical Indian Ocean (TIO). During the EL/+PDO or LA/-PDO, the anomalous Walker circulation associated with El Niño or La Niña is stronger and lasts for a longer time than those during the EL/-PDO or LA/+PDO. This leads to stronger descending (ascending) motion over the Maritime Continent and easterly (westerly) wind anomalies over the eastern Indian Ocean in the EL/+PDO (LA/-PDO), which further exert larger effects on the surface heat fluxes and subsurface ocean dynamical heating process over the Indian Ocean. As such, the induced warm (cold) sea surface temperature anomalies over the Indian Ocean are more significant and larger in the EL/+PDO (LA/-PDO). These larger sea surface temperature anomalies over the TIO could exert a more significant influence on the tropospheric temperature via moisture adjustment, which subsequently results in stronger SAH variability in the EL/+PDO or the LA/-PDO.
On the Bimodality of ENSO Cycle Extremes
NASA Technical Reports Server (NTRS)
Wilson, Robert M.
2000-01-01
On the basis of sea surface temperature in the El Nino 3.4 region (5 deg. N.,-5 deg. S., 120-170 deg. W.) during the interval of 1950-1997, Kevin Trenberth previously has identified some 16 El Nino and 10 La Nina, these 26 events representing the extremes of the quasi-periodic El Nino-Southern Oscillation (ENSO) cycle. Runs testing shows that the duration, recurrence period, and sequencing of these extremes vary randomly. Hence, the decade of the 1990's, especially for El Nino, is not significantly different from that of previous decadal epochs, at least, on the basis of the frequency of onsets of ENSO extremes. Additionally, the distribution of duration for both El Nino and La Nina looks strikingly bimodal, each consisting of two preferred modes, about 8- and 16-mo long for El Nino and about 9- and 18-mo long for La Nina, as does the distribution of the recurrence period for El Nino, consisting of two preferred modes about 21- and 50-mo long. Scatterplots of the recurrence period versus duration for El Nino are found to be statistically important, displaying preferential associations that link shorter (longer) duration with shorter (longer) recurrence periods. Because the last onset of El Nino occurred in April 1997 and the event was of longer than average duration, onset of the next anticipated El Nino is not expected until February 2000 or later.
The ceremonial transfer of Leonardo, the first MPLM, from ASI to NASA
NASA Technical Reports Server (NTRS)
1998-01-01
Participants pose for a photo at the Space Station Processing Facility ceremony transferring the 'Leonardo' Multipurpose Logistics Module (MPLM) from the Italian Space Agency, Agenzia Spaziale Italiana (ASI), to NASA. From left, they are astronaut Jim Voss, European Space Agency astronauts Umberto Guidoni of Italy and Christer Fuglesang of Sweden, NASA International Space Station Program Manager Randy Brinkley, NASA Administrator Daniel S. Goldin, ASI President Sergio De Julio and Stephen Francois, director, International Space Station Launch Site Support at KSC. The MPLM, a reusable logistics carrier, will be the primary delivery system used to resupply and return International Space Station cargo requiring a pressurized environment. Leonardo is the first of three MPLM carriers for the International Space Station. It is scheduled to be launched on Space Shuttle Mission STS-100, targeted for April 2000.
Association of surgeons in training 40th anniversary conference: Liverpool #ASiT2016.
Harries, Rhiannon L; Williams, Adam P; McElnay, Philip J; Gokani, Vimal J
2016-11-01
The Association of Surgeons in Training (ASiT) is a professional body and registered charity working to promote excellence in surgical training for the benefit of junior doctors and patient alike. ASiT is independent of the National Health Service (NHS), Surgical Royal Colleges and specialty associations, and represents trainees in all ten surgical specialities. We were delighted to be celebrating our 40th Anniversary Conference in the fantastic city of Liverpool with over 700 delegates in attendance and in the company of many ASiT Past Presidents. The conference programme focused on how to overcome threats to training in light of the recent turbulent events associated with the junior doctor contract dispute with inspiring talks from Professor Sir Bruce Keogh, NHS Medical Director and Rt Hon Heidi Alexander MP, Shadow Health Secretary. The other central topic to the conference was 'celebrating excellence in surgical training' and we were thankful to many other high profile speakers who attended to help in this celebration. In addition, over £4000 was distributed between more than 30 prizes and was awarded by the incoming President, Mr Adam Williams, to delegates who presented the highest scoring academic work from over 1200 submitted abstracts. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.
NASA Astrophysics Data System (ADS)
Xu, M.; Hoffman, F. M.
2016-12-01
The El Niño Southern Oscillation (ENSO) is an important interannual climate variability and has significant consequences and impacts on the global biosphere. The responses of vegetation to ENSO are highly heterogeneous and generally depend on the biophysical and biochemical characteristics associated with model plant functional types (PFTs). The modeled biogeochemical variables from Earth System Models (ESMs) are generally grid averages consisting of several PFTs within a gridcell, which will lead to difficulties in directly comparing them with site observations and large uncertainties in studying their responses to large scale climate variability. In this study, we conducted a transient ENSO simulation for the previoustwo decades from 1995 to 2020 using the DOE ACME v0.3 model. It has a comprehensive terrestrial biogeochemistry model that is fully coupled with a sophisticated atmospheric model with an advanced spectral element dynamical core. The model was driven by the NOAA optimum interpolation sea surface temperature (SST) for contemporary years and CFS v2 nine-month seasonal predicted and reconstructed SST for future years till to 2020. We saved the key biogeochemical variables in the subgrid PFT patches and compared them with site observations directly. Furthermore, we studied the biogeochemical responses of terrestrial vegetation to two largest ENSO events (1997-1998 and 2015-2016) for different PFTs. Our results show that it is useful and meaningful to compare and analyze model simulations in subgrid patches. The comparison and analysis not only gave us the details of responses of terrestrial ecosystem to global climate variability under changing climate, but also the insightful view on the model performance on the PFT level.
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.
ENSO Transition Asymmetry: Internal and External Causes and Intermodel Diversity
NASA Astrophysics Data System (ADS)
An, Soon-Il; Kim, Ji-Won
2018-05-01
El Niño is frequently followed by La Niña, but the opposite case rarely happens. Here we explore a mechanism for such an asymmetrical transition and its future changes. Internally, the asymmetrical response of upper ocean waves against surface wind stress anomaly exerts a primary cause of El Niño-Southern Oscillation (ENSO) transition asymmetry. Externally, the asymmetrical capacitor effects of both Indian and Atlantic Oceans play some roles in driving the ENSO transition asymmetry via the interbasin interactions. The historical runs of Coupled Model Intercomparison Project Phase 5 show that the intermodel transition asymmetry is significantly correlated with the intermodel asymmetry in ocean wave response to surface wind forcing but not with that in the interbasin interactions. In addition, the El Niño-to-La Niña transition tendency was weaker in moderate global warming scenario runs (Representative Concentration Pathway 4.5) while slightly enhanced in strong warming scenario runs (Representative Concentration Pathway 8.5). Similar changes also appeared in the asymmetrical response of ocean waves against the surface wind forcing.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Rosenberg, N.J.; Izaurralde, R.C.; Brown, R.A.
1997-09-01
A group of Canadian, US and Mexican natural resource specialists, organized by the Pacific Northwest National Laboratory (PNNL) under its North American Energy, Environment and Economy (NA3E) Program, has applied a simulation modeling approach to estimating the impact of ENSO-driven climatic variations on the productivity of major crops grown in the three countries. Methodological development is described and results of the simulations presented in this report. EPIC (the Erosion Productivity Impact Calculator) was the agro-ecosystem model selected-for this study. EPIC uses a daily time step to simulate crop growth and yield, water use, runoff and soil erosion among other variables.more » The model was applied to a set of so-called representative farms parameterized through a specially-assembled Geographic Information System (GIS) to reflect the soils, topography, crop management and weather typical of the regions represented. Fifty one representative farms were developed for Canada, 66 for the US and 23 for Mexico. El Nino-Southern Oscillation (ENSO) scenarios for the EPIC simulations were created using the historic record of sea-surface temperature (SST) prevailing in the eastern tropical Pacific for the period October 1--September 30. Each year between 1960 and 1989 was thus assigned to an ENSO category or state. The ENSO states were defined as El Nino (EN, SST warmer than the long-term mean), Strong El Nino (SEN, much warmer), El Viejo (EV, cooler) and Neutral (within {+-}0.5 C of the long-term mean). Monthly means of temperature and precipitation were then calculated at each farm for the period 1960--1989 and the differences (or anomalies) between the means in Neutral years and EN, SEN and EV years determined. The average monthly anomalies for each ENSO state were then used to create new monthly statistics for each farm and ENSO-state combination. The adjusted monthly statistics characteristic of each ENSO state were then used to drive a stochastic
NASA Astrophysics Data System (ADS)
Kutta, E. J.; Hubbart, J. A.; Svoma, B. M.; Eichler, T. P.; Lupo, A. R.
2016-12-01
El Nino-Southern Oscillation (ENSO) is well documented as a leading source of seasonal to inter-annual variations in global weather and climate. Strong ENSO events have been shown to alter the location and magnitude of Hadley and Walker circulations that maintain equilibrium at tropical latitudes and regulate moisture transport into mid-latitude storm tracks. Broad impacts associated with ENSO events include anomalous regional precipitation (ARP) and temperature patterns and subsequent impacts to socioeconomic and human health systems. Potential socioeconomic and human health impacts range from regional changes in water resources and agricultural productivity to local storm water management, particularly in rapidly urbanizing watersheds. Evidence is mounting to suggest that anthropogenic climate change will increase the frequency of heavy precipitation events, which compounds impacts of ARP patterns associated with strong El Nino events. Therefore, the need exists to identify common regional patterns of spatiotemporal variance of horizontal moisture flux (HMF) during months (Oct-Feb) associated with the peak intensity (Oceanic Nino Index [ONI]) of the three strongest El Nino (ONI > µ + 2σ) and La Nina (ONI < µ - σ) events occurring between January 1979 and June 2016. ERA-Interim reanalysis output on model levels was used to quantify spatial and temporal covariance of HMF at 6-hourly resolution before taking the density weighted vertical average. Long term means (LTM; 1979-2015) were quantified and the influence of strong ENSO events was assessed by quantifying deviations from the LTM for each respective covariance property during months associated with the selected ENSO events. Results reveal regions of statistically significant (CI = 0.05) differences from the LTM for the vertically integrated HMF and each covariance quantity. Broader implications of this work include potential for improved seasonal precipitation forecasts at regional scales and subsequent
NASA Astrophysics Data System (ADS)
Barros, G. P.; Marques, W. C.
2013-05-01
The aim of this study is to investigate the influence and importance of ENSO events on the control of the freshwater discharge pattern at Patos Lagoon, in timescales longer than one year. For this study it was used freshwater discharge, water levels and South Oscillation Index (SOI) data sets. The Southern Oscillation Index, or SOI, gives an indication of the development and intensity of El Niño or La Niña events in the Pacific Ocean. Sustained negative values of the SOI greater than -8 often indicate El Niño episodes. Sustained positive values of the SOI greater than +8 are typical of a La Niña episode. Cross wavelet technique is applied to examine the coherence and phase between interannual time-series (South Oscillation Index, freshwater discharge and water levels). Over synoptic time scales, wind action is the most effective forcing in Patos Lagoon's circulation. However, at longer time scales (over one year), freshwater discharge becomes the most important forcing, controling the water levels, circulation and other processes. At longer time scales, South America is affected by ENSO's influence. El Niño is the South Oscillation phase where the trade winds are weak, the pressure is low over the eastern Tropical Pacific and high on the west side. The south region of Brazil shows precipitation anomalies associated with the ENSO occurrence. The most significant ENSO events show a high temporal variability, which may occur in near biannual scales (1.5 - 3 years) or in lower frequencies (3 years - 7 years). The freshwater discharge of the main tributaries and water levels in Patos Lagoon are influenced by ENSO on interannual scales (cycles between 3.8 and 6 years). Therefore, El Niño events are associated with high mean values of freshwater discharge and water levels above the mean. On the other hand, La Niña events are associated with low mean values of freshwater discharge and water levels below the mean. These results are consistent with analysis related to
The INAF contribution to the ASI Space Debris program: observational activities.
NASA Astrophysics Data System (ADS)
Pupillo, G.; Salerno, E.; Bartolini, M.; Di Martino, M.; Mattana, A.; Montebugnoli, S.; Portelli, C.; Pluchino, S.; Schillirò, F.; Konovalenko, A.; Nabatov, A.; Nechaeva, M.
Space debris are man made objects orbiting around Earth that pose a serious hazard for both present and future human activities in space. Since 2007 the Istituto Nazionale di Astrofisica (INAF) carried out a number of radar campaigns in the framework of the ASI ``Space Debris'' program. The observations were performed by using bi- and multi-static radars, composed of the INAF 32-m Italian radiotelescopes located at Medicina and Noto (used as receivers) and the 70-m parabolic antenna at Evpatoria (Ukraine) used as transmitter. The 32 m Ventspils antenna in Latvia also participated in the last campaign at the end of June 2010. Several kinds of objects in various orbital regions (radar calibrators, rocket upper stages, debris of different sizes) were observed and successfully detected. Some unknown objects were also discovered in LEO during the beam-park sessions. In this paper we describe some results of the INAF-ASI space debris research activity.
ERIC Educational Resources Information Center
Carise, Deni; McLellan, A. Thomas
The Addiction Severity Index (ASI), used throughout the United States and other countries, is the most widely used assessment tool in the addictions field. It is a semi-structured assessment instrument designed for use with clients for substance abuse treatment. The ASI gathers information in seven important areas of a patient's life: medical,…
A 300-year Vietnam hydroclimate and ENSO variability record reconstructed from tree ring δ18O
NASA Astrophysics Data System (ADS)
Sano, Masaki; Xu, Chenxi; Nakatsuka, Takeshi
2012-06-01
A tree ring δ18O chronology is developed for the past 300 years (1705-2004) using 6 cypress trees from northern Vietnam to reconstruct long-term hydroclimatic variations in the summer monsoon season. To the best of our knowledge, this is the first well-replicated tree ringδ18O chronology from Southeast Asia, as well as the longest yet produced. Response analyses reveal that tree ring δ18O is significantly correlated with temperature, precipitation, and the Palmer Drought Severity Index (PDSI) during the period May-October, with highest correlation to the PDSI. Our δ18O chronology accounts for 44% of the PDSI variance, and is in good agreement with a 52-year tree ringδ18O chronology from northern Laos (r = 0.77), indicating that regional hydroclimatic signals are well recorded in the δ18O data. Spatial correlation analyses with global sea surface temperatures suggest that the tropical Pacific plays an important role in modulating hydroclimate over the study region. Further, the δ18O chronology correlates significantly with El Niño-Southern Oscillation (ENSO)-related indices, and is therefore used to reconstruct the annual Multivariate ENSO Index. Because previously published ENSO reconstructions are based mainly on proxy records originating from North America and/or the tropical Pacific, the future development of a tree ringδ18O network from mainland Southeast Asia could lead to an independent and more robust reconstruction of ENSO variability.
NASA Astrophysics Data System (ADS)
Tiwari, P. R.; Mohanty, U. C.; Dey, S.; Acharaya, N.; Sinha, P.
2012-12-01
Precipitation over the Western Himalayas region during winter is mainly associated with the passage of midlatitude synoptic systems known as western disturbances (WDs). Recently, many observational and modeling studies reported that the relationship of the Indian southwest monsoon rainfall with El Niño- Southern Oscillation (ENSO) has weakened since around 1980. But, in contrast, only very few observational studies are reported so far to examine the relationship between ENSO and the winter precipitation over the Western Himalayas region from December to February (DJF). But there is a huge gap of modeling this phenomenon. So keeping in view of the absence of modeling studies, an attempt is made to simulate the relationship between wintertime precipitations associated with large scale global forcing of ENSO over the Western Himalayas. In the present study, RegT-Band, a tropical band version of the regional climate model RegCM4 is integrated for a set of 5 El Niño (1986-87, 1991-92, 1997-98, 2002-03, 2009-10) and 4 La Niña (1984-85, 1988-89, 1999-2000, 2007-08) years with the observed sea-surface temperature and lateral boundary condition. The domain extends from 50° S to 50° N and covers the entire tropics at a grid spacing of about 45 km, i.e. it includes lateral boundary forcing only at the southern and northern boundaries. The performance evaluation of the model in capturing the large scale fields followed by ENSO response with wintertime precipitation over the Western Himalayas region has been carried out by using National Center for Environmental Prediction (NCEP)-Department of Energy (DOE) reanalysis 2 (NNRP2) data (2.5° x 2.5°) and Aphrodite precipitation data (0.25° x 0.25°). The model is able to delineate the mean circulation associated with ENSO over the region during DJF reasonably well and shows strong southwesterly to northwesterly wind flow, which is there in verification analysis also. The vertical structure of the low as well as upper level
Mesoscale Convective Complexes (MCCs) over the Indonesian Maritime Continent during the ENSO events
NASA Astrophysics Data System (ADS)
Trismidianto; Satyawardhana, H.
2018-05-01
This study analyzed the mesoscale convective complexes (MCCs) over the Indonesian Maritime Continent (IMC) during the El Niño/Southern Oscillation (ENSO) events for the the15-year period from 2001 to 2015. The MCCs identified by infrared satellite imagery that obtained from the Himawari generation satellite data. This study has reported that the frequencies of the MCC occurrences at the El Niño and La Niña were higher than that of neutral conditions during DJF. Peak of MCC occurrences during DJF at La Niña and neutral condition is in February, while El Niño is in January. ENSO strongly affects the occurrence of MCC during the DJF season. The existences of the MCC were also accompanied by increased rainfall intensity at the locations of the MCC occurrences for all ENSO events. During JJA seasons, the MCC occurrences are always found during neutral conditions, El Niño and La Niña in Indian Ocean. MCC occurring during the JJA season on El Niño and neutral conditions averaged much longer than during the DJF season. In contrast, MCCs occurring in La Niña conditions during the JJA season are more rapidly extinct than during the DJF. It indicates that the influence of MCC during La Niña during the DJF season is stronger than during the JJA season.
ERIC Educational Resources Information Center
Woods, Larry, Ed.
The 1999 American Society for Information Science (ASIS) conference explored current knowledge creation, acquisition, navigation, correlation, retrieval, management, and dissemination practicalities and potentialities, their implementation and impact, and the theories behind the developments. Speakers reviewed processes, technologies, and tools,…
French, Michael T; Salomé, Helena J; Sindelar, Jody L; McLellan, A Thomas
2002-04-01
To provide detailed methodological guidelines for using the Drug Abuse Treatment Cost Analysis Program (DATCAP) and Addiction Severity Index (ASI) in a benefit-cost analysis of addiction treatment. A representative benefit-cost analysis of three outpatient programs was conducted to demonstrate the feasibility and value of the methodological guidelines. Procedures are outlined for using resource use and cost data collected with the DATCAP. Techniques are described for converting outcome measures from the ASI to economic (dollar) benefits of treatment. Finally, principles are advanced for conducting a benefit-cost analysis and a sensitivity analysis of the estimates. The DATCAP was administered at three outpatient drug-free programs in Philadelphia, PA, for 2 consecutive fiscal years (1996 and 1997). The ASI was administered to a sample of 178 treatment clients at treatment entry and at 7-months postadmission. The DATCAP and ASI appear to have significant potential for contributing to an economic evaluation of addiction treatment. The benefit-cost analysis and subsequent sensitivity analysis all showed that total economic benefit was greater than total economic cost at the three outpatient programs, but this representative application is meant to stimulate future economic research rather than justifying treatment per se. This study used previously validated, research-proven instruments and methods to perform a practical benefit-cost analysis of real-world treatment programs. The study demonstrates one way to combine economic and clinical data and offers a methodological foundation for future economic evaluations of addiction treatment.
NASA Astrophysics Data System (ADS)
O'Hara, Patrick D.; Haase, Ben J. M.; Elner, Robert W.; Smith, Barry D.; Kenyon, Jamie K.
2007-08-01
Declines in avian populations are a global concern, particularly for species that migrate between Arctic-temperate and tropical locations. Long-term population studies offer opportunities to detect and document ecological effects attributable to long-term climatic cycles such as the El Niño/Southern Oscillation (ENSO). In this study, we report possible population-level effects of such climatic cycles on shorebird species that use two non-breeding season sites in Ecuador (Santa Elena peninsula area, near La Libertad). During our 9-year study period (1991/1992-1999/2000), there was a particularly strong ENSO warm phase event during 1997/1998. Population trend data for three species of shorebird, Western Sandpipers ( Calidris mauri), Semipalmated Sandpipers ( C. pusilla), and Least Sandpipers ( C. minutilla), indicated abundances generally declined during the 1990s, but there was an increase in the proportion of first-year birds and their abundance in the years following the 1997/1998 ENSO warm phase. There was some support for variation in apparent survivorship associated with the onset of the ENSO warm phase event in our population models, based on capture-mark-recapture data. Following the 1997/1998 ENSO event onset, individuals for all three species were significantly lighter during the non-breeding season ( F1,3789 = 6.6, p = 0.01). Least-squares mean mass (controlling for size, sex and day of capture) for first-year birds dropped significantly more than for adults following ENSO (first-year mass loss = 0.69 ± 0.12 g; adult mass loss = 0.34 ± 0.11 g, F1,3789 = 5.31, p = 0.021), and least-squares mean mass dropped most during the period when sandpipers prepare for northward migration by gaining mass and moulting into breeding plumage. Least Sandpipers may have declined the most in mean mass following ENSO (0.76 ± 0.19 g), whereas Semipalmated Sandpipers were 0.52 ± 0.12 g lighter, and Western Sandpipers 0.40 ± 0.13 g lighter, but overall variation among
Effect of ENSO on the variability of SST and Chlorophyll-a in Java Sea
NASA Astrophysics Data System (ADS)
Wirasatriya, Anindya; Prasetyawan, Indra B.; Triyono, Chandra D.; Muslim; Maslukah, Lilik
2018-02-01
Sea surface temperature (SST) and chlorophyll-a (Chl-a) are two parameters often used for identifying the marine productivity. Located at the maritime continent, the variability of SST and Chl-a in the Indonesian seas is influenced by El Niño Southern Oscillation (ENSO). The previous studies showed that the effect of El Niño tend to decrease SST and increase Chl-a in the areas within the Indonesian seas. Using long time observation of satellite data (2003-2016), it was found different result in Java Sea. Since Java Sea has strong seasonal variability influenced by monsoon wind, the effect of ENSO depend on the season. During southeast monsoon season, El Niño (La Niña) tend to increase (decrease) the speed of southeasterly wind cause the decrease or increase of SST. On the contrary, during northwest monsoon season, El Niño (La Niña) tend to decrease (increase) the speed of northwesterly wind cause the increase (decrease) of SST. The dependence of Chl-a on wind speed is only observed in the off shore which exhibit the strong seasonal variation. However, the effect of ENSO on the variability of Chl-a is not robust since the effected amplitude is less than the RMSE of Chl-a data.
NASA Astrophysics Data System (ADS)
Ham, Yoo-Geun; Kug, Jong-Seong
2017-04-01
The relationship between the present-climate climatology and those of ENSO amplitude change under global warming in the CMIP5 models is examined. The models with increased ENSO amplitude under greenhouse warming tend to simulate a 20th century stronger climatological ITCZ and SPCZ over the central-eastern Pacific that are located further away from the equator during boreal spring. The budget analysis using moisture equation indicates that those climatological differences lead to stronger positive climatological precipitation change over the off-equatorial central-eastern Pacific under greenhouse warming. The stronger positive climatological precipitation change enhances the air-sea coupling strength over the central-eastern Pacific, which results in the increase of the ENSO amplitude.
Possible shift in the ENSO-Indian monsoon rainfall relationship under future global warming
Azad, Sarita; Rajeevan, M.
2016-01-01
EI Nino-Southern Oscillation (ENSO) and Indian monsoon rainfall are known to have an inverse relationship, which we have observed in the rainfall spectrum exhibiting a spectral dip in 3–5 y period band. It is well documented that El Nino events are known to be associated with deficit rainfall. Our analysis reveals that this spectral dip (3–5 y) is likely to shift to shorter periods (2.5–3 y) in future, suggesting a possible shift in the relationship between ENSO and monsoon rainfall. Spectral analysis of future climate projections by 20 Coupled Model Intercomparison project 5 (CMIP5) models are employed in order to corroborate our findings. Change in spectral dip speculates early occurrence of drought events in future due to multiple factors of global warming. PMID:26837459
Influence of Mean State Changes on the Structure of ENSO in a Tropical Coupled GCM.
NASA Astrophysics Data System (ADS)
Codron, Francis; Vintzileos, Augustin; Sadourny, Robert
2001-03-01
This study examines the response of the climate simulated by the Institut Pierre Simon Laplace tropical Pacific coupled general circulation model to two changes in parameterization: an improved coupling scheme at the coast, and the introduction of a saturation mixing ratio limiter in the water vapor advection scheme, which improves the rainfall distribution over and around orography. The main effect of these modifications is the suppression of spurious upwelling off the South American coast in Northern Hemisphere summer. Coupled feedbacks then extend this warming over the whole basin in an El Niño-like structure, with a maximum at the equator and in the eastern part of the basin. The mean precipitation pattern widens and moves equatorward as the trade winds weaken.This warmer mean state leads to a doubling of the standard deviation of interannual SST anomalies, and to a longer ENSO period. The structure of the ENSO cycle also shifts from westward propagation in the original simulation to a standing oscillation. The simulation of El Niño thus improves when compared to recent observed events. The study of ENSO spatial structure and lagged correlations shows that these changes of El Niño characteristics are caused by both the increase of amplitude and the modification of the spatial structure of the wind stress response to SST anomalies.These results show that both the mean state and variability of the tropical ocean can be very sensitive to biases or forcings, even geographically localized. They may also give some insight into the mechanisms responsible for the changes in ENSO characteristics due to decadal variability or climate change.
Weakening of the relationship between the Indian Ocean Dipole and the ENSO in recent decades
NASA Astrophysics Data System (ADS)
Choi, Jun-Young; Ham, Yoo-Geun; Kug, Jong-Seong
2016-04-01
This study reports, on the 20th century the relationship between the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) was weaker then late 1990s. We shows that 15-yr moving correlation between the Nino3.4 index during the December to February (DJF) and IOD index during the September to November (SON) season. At this results we divided previous decades (1979 to 1998) and late decades (1999 to 2014). The correlation coefficient was 0.64 in the previous decades and 0.21 in the late decades. Late decades was suddenly weaker then previous decades. Because, there is a big difference between previous decades and late decades in the ENSO regressed precipitation anomaly spatial distribution during the El Nino developing the MAM season. There was existed positive precipitation anomalies over the off-equatorial western Pacific. It was induced the cross-equatorial southerly flow over the eastern Indian Ocean and maritime continent. It means cross-equatorial southerly flow was key point to understanding ENSO-IOD coupling system. In addition, using the climate models participated in Coupled Model Intercomparison Project phase 5 (CMIP5) supports the observational results.
The role of the basic state in the ENSO-monsoon relationship and implications for predictability
NASA Astrophysics Data System (ADS)
Turner, A. G.; Inness, P. M.; Slingo, J. M.
2005-04-01
The impact of systematic model errors on a coupled simulation of the Asian summer monsoon and its interannual variability is studied. Although the mean monsoon climate is reasonably well captured, systematic errors in the equatorial Pacific mean that the monsoon-ENSO teleconnection is rather poorly represented in the general-circulation model. A system of ocean-surface heat flux adjustments is implemented in the tropical Pacific and Indian Oceans in order to reduce the systematic biases. In this version of the general-circulation model, the monsoon-ENSO teleconnection is better simulated, particularly the lag-lead relationships in which weak monsoons precede the peak of El Niño. In part this is related to changes in the characteristics of El Niño, which has a more realistic evolution in its developing phase. A stronger ENSO amplitude in the new model version also feeds back to further strengthen the teleconnection. These results have important implications for the use of coupled models for seasonal prediction of systems such as the monsoon, and suggest that some form of flux correction may have significant benefits where model systematic error compromises important teleconnections and modes of interannual variability.
NASA Astrophysics Data System (ADS)
Zheng, Fei; Li, Jianping; Ding, Ruiqiang
2017-11-01
There is increasing evidence of the possible role of extratropical forcing in the evolution of ENSO. The Southern Hemisphere Annular Mode (SAM) is the dominant mode of atmospheric circulation in the Southern Hemisphere extratropics. This study shows that the austral summer (December-January-February; DJF) SAM may also influence the amplitude of ENSO decay during austral autumn (March-April-May; MAM). The mechanisms associated with this SAM-ENSO relationship can be briefly summarized as follows: The SAM is positively (negatively) correlated with SST in the Southern Hemisphere middle (high) latitudes. This dipole-like SST anomaly pattern is referred to as the Southern Ocean Dipole (SOD). The DJF SOD, caused by the DJF SAM, could persist until MAM and then influence atmospheric circulation, including trade winds, over the Niño3.4 area. Anomalous trade winds and SST anomalies over the Niño3.4 area related to the DJF SAM are further developed through the Bjerkness feedback, which eventually results in a cooling (warming) over the Niño3.4 area followed by the positive (negative) DJF SAM.
NASA Astrophysics Data System (ADS)
Xue, Yan; Wen, C.; Kumar, A.; Balmaseda, M.; Fujii, Y.; Alves, O.; Martin, M.; Yang, X.; Vernieres, G.; Desportes, C.; Lee, T.; Ascione, I.; Gudgel, R.; Ishikawa, I.
2017-12-01
An ensemble of nine operational ocean reanalyses (ORAs) is now routinely collected, and is used to monitor the consistency across the tropical Pacific temperature analyses in real-time in support of ENSO monitoring, diagnostics, and prediction. The ensemble approach allows a more reliable estimate of the signal as well as an estimation of the noise among analyses. The real-time estimation of signal-to-noise ratio assists the prediction of ENSO. The ensemble approach also enables us to estimate the impact of the Tropical Pacific Observing System (TPOS) on the estimation of ENSO-related oceanic indicators. The ensemble mean is shown to have a better accuracy than individual ORAs, suggesting the ensemble approach is an effective tool to reduce uncertainties in temperature analysis for ENSO. The ensemble spread, as a measure of uncertainties in ORAs, is shown to be partially linked to the data counts of in situ observations. Despite the constraints by TPOS data, uncertainties in ORAs are still large in the northwestern tropical Pacific, in the SPCZ region, as well as in the central and northeastern tropical Pacific. The uncertainties in total temperature reduced significantly in 2015 due to the recovery of the TAO/TRITON array to approach the value before the TAO crisis in 2012. However, the uncertainties in anomalous temperature remained much higher than the pre-2012 value, probably due to uncertainties in the reference climatology. This highlights the importance of the long-term stability of the observing system for anomaly monitoring. The current data assimilation systems tend to constrain the solution very locally near the buoy sites, potentially damaging the larger-scale dynamical consistency. So there is an urgent need to improve data assimilation systems so that they can optimize the observation information from TPOS and contribute to improved ENSO prediction.
Analysis of the 1877-78 ENSO episode and comparison with 1982-83
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kiladis, G.N.; Diaz, H.F.
A comparison of the 1877-78 and 1982-83 El Nino/Southern Oscillation (ENSO) events was made using monthly and seasonal values of sea surface temperature (SST) and station pressure in the tropics, sea level pressure (SLP) in North America and the North Atlantic, temperature in North America and precipitation in several key areas around the globe. SST anomalies in the eastern tropical Pacific, heavy rains in coastal Peru and extreme pressure anomalies across the Pacific and Indian Oceans during 1877-78 indicate an ENSO event of comparable magnitude to that during 1982-83. Both events were also associated with drought conditions in the Indonesianmore » region, India, South Africa, northeastern Brazil and Hawaii. Wintertime teleconnections in the midlatitudes of the Northern Hemisphere were similar in terms of SLP from the North Pacific to Europe, resulting in significantly higher than normal temperatures over most of the US and extreme rains in California.« less
Sharma, Umender K; Chatterji, Dipankar
2008-05-01
Anti-sigma factors Escherichia coli Rsd and bacteriophage T4 AsiA bind to the essential housekeeping sigma factor, sigma(70), of E. coli. Though both factors are known to interact with the C-terminal region of sigma(70), the physiological consequences of these interactions are very different. This study was undertaken for the purpose of deciphering the mechanisms by which E. coli Rsd and bacteriophage T4 AsiA inhibit or modulate the activity of E. coli RNA polymerase, which leads to the inhibition of E. coli cell growth to different amounts. It was found that AsiA is the more potent inhibitor of in vivo transcription and thus causes higher inhibition of E. coli cell growth. Measurements of affinity constants by surface plasmon resonance experiments showed that Rsd and AsiA bind to sigma(70) with similar affinity. Data obtained from in vivo and in vitro binding experiments clearly demonstrated that the major difference between AsiA and Rsd is the ability of AsiA to form a stable ternary complex with RNA polymerase. The binding patterns of AsiA and Rsd with sigma(70) studied by using the yeast two-hybrid system revealed that region 4 of sigma(70) is involved in binding to both of these anti-sigma factors; however, Rsd interacts with other regions of sigma(70) as well. Taken together, these results suggest that the higher inhibition of E. coli growth by AsiA expression is probably due to the ability of the AsiA protein to trap the holoenzyme RNA polymerase rather than its higher binding affinity to sigma(70).
Sharma, Umender K.; Chatterji, Dipankar
2008-01-01
Anti-sigma factors Escherichia coli Rsd and bacteriophage T4 AsiA bind to the essential housekeeping sigma factor, σ70, of E. coli. Though both factors are known to interact with the C-terminal region of σ70, the physiological consequences of these interactions are very different. This study was undertaken for the purpose of deciphering the mechanisms by which E. coli Rsd and bacteriophage T4 AsiA inhibit or modulate the activity of E. coli RNA polymerase, which leads to the inhibition of E. coli cell growth to different amounts. It was found that AsiA is the more potent inhibitor of in vivo transcription and thus causes higher inhibition of E. coli cell growth. Measurements of affinity constants by surface plasmon resonance experiments showed that Rsd and AsiA bind to σ70 with similar affinity. Data obtained from in vivo and in vitro binding experiments clearly demonstrated that the major difference between AsiA and Rsd is the ability of AsiA to form a stable ternary complex with RNA polymerase. The binding patterns of AsiA and Rsd with σ70 studied by using the yeast two-hybrid system revealed that region 4 of σ70 is involved in binding to both of these anti-sigma factors; however, Rsd interacts with other regions of σ70 as well. Taken together, these results suggest that the higher inhibition of E. coli growth by AsiA expression is probably due to the ability of the AsiA protein to trap the holoenzyme RNA polymerase rather than its higher binding affinity to σ70. PMID:18359804
NASA Astrophysics Data System (ADS)
Kiefer, J.; Karamperidou, C.
2017-12-01
Clastic sediment flux into high-elevation Andean lakes is controlled by glacial processes and soil erosion caused by high precipitation events, making these lakes suitable archives of past climate. To wit, sediment records from Laguna Pallcacocha in Ecuador have been interpreted as proxies of ENSO variability, owing to increased precipitation in the greater region during El Niño events. However, the location of the lake's watershed, the presence of glaciers, and the different impacts of ENSO on precipitation in the eastern vs western Andes have challenged the suitability of the Pallcacocha record as an ENSO proxy. Here, we employ WRF, a high-resolution regional mesoscale weather prediction model, to investigate the circulation dynamics, sources of moisture, and resulting precipitation response in the L. Pallcacocha region during different flavors of El Niño and La Niña events, and in the presence or absence of ice caps. In patricular, we investigate Eastern Pacific (EP), Central Pacific (CP), coastal El Niño, and La Niña events. We validate the model simulations against spatially interpolated station measurements and reanalysis data. We find that during EP events, moisture is primarily advected from the Pacific, whereas during CP events, moisture primarily originates from the Atlantic. More moisture is available during EP events, which implies higher precipitation rates. Furthermore, we find that precipitation during EP events is mostly non-convective in contrast to primarily convective precipitation during CP events. Finally, a synthesis of the sedimentary record and the EP:CP ratio of accumulated precipitation and specific humidity in the L. Pallcacocha region allows us to assess whether past changes in the relative frequency of the two ENSO flavors may have been recorded in paleoclimate archives in this region.
NASA Astrophysics Data System (ADS)
Geng, Xin; Zhang, Wenjun; Stuecker, Malte F.; Liu, Peng; Jin, Fei-Fei; Tan, Guirong
2017-10-01
This work investigates the decadal modulation of the El Niño-Southern Oscillation (ENSO)-East Asian winter monsoon (EAWM) relationship by the Atlantic Multidecadal Oscillation (AMO). A stable ENSO-EAWM relationship is found during the positive AMO phase but not during the negative phase. While the impact of El Niño events on the EAWM does not depend on the AMO phase, a different picture is observed for La Niña events. The La Niña boreal winter season coincides with a strengthened EAWM during a positive AMO phase and a weakened EAWM during a negative AMO phase. We suggest that the AMO's modulating effect mainly comprises two pathways that influence ENSO's impact on the EAWM. On one hand, when La Niña coincides with a positive AMO, the warm SST anomalies over the western North Pacific (WNP) are amplified both in intensity and spatial extent, which favors strengthened WNP cyclonic anomalies and an enhanced EAWM. During La Niña with a negative AMO, only very weak SST anomalies occur over the WNP with reduced WNP cyclonic anomalies that are confined to the tropics, thus having little effect on the EAWM. On the other hand, an eastward-propagating Rossby wavetrain across the mid-high latitudes of Eurasia during a warm AMO phase strengthens the Siberian high and thus leads to a strengthened EAWM, while during a cold AMO phase the Siberian high is weakened, leading to a reduced EAWM. In contrast, El Niño and its associated atmospheric responses are relatively strong and stable, independent of the AMO phase. These results carry important implications to the seasonal-to-interannual predictability associated with ENSO.
Linkages between ENSO/PDO signals and precipitation, streamflow in China during the last 100 years
NASA Astrophysics Data System (ADS)
Ouyang, R.; Liu, W.; Fu, G.; Liu, C.; Hu, L.; Wang, H.
2014-09-01
This paper investigates the single and combined impacts of El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) on precipitation and streamflow in China over the last century. Results indicate that the precipitation and streamflow overall decrease during El Niño/PDO warm phase periods and increase during La Niña/PDO cool phase periods in the majority of China, although there are regional and seasonal differences. Precipitation and streamflow in the Yellow River basin, Yangtze River basin and Pearl River basin are more significantly influenced by El Niño and La Niña events than is precipitation and streamflow in the Songhua River basin, especially in October and November. Moreover, significant influence of ENSO on streamflow in the Yangtze River mainly occurs in summer and autumn while in the Pearl River influence primarily occurs in the winter and spring. The precipitation and streamflow are relatively greater in the warm PDO phase in the Songhua River basin and several parts of the Yellow River basin and relatively less in the Pearl River basin and most parts of Northwest China compared to those in the cool PDO phase, though there is little significance detected by Wilcoxon signed-rank test. When considering the combined influence of ENSO and PDO, the responses of precipitation/streamflow are shown to be opposite in northern China and southern China, with ENSO-related precipitation/streamflow enhanced in northern China and decreased in southern China during the warm PDO phases, and enhanced in southern China and decreased in northern China during the cool PDO phases. It is hoped that this study will be beneficial for understanding the precipitation/streamflow responses to the changing climate and will correspondingly provide valuable reference for water resources prediction and management across China.
ENSO related SST anomalies and relation with surface heat fluxes over south Pacific and Atlantic
NASA Astrophysics Data System (ADS)
Chatterjee, S.; Nuncio, M.; Satheesan, K.
2017-07-01
The role of surface heat fluxes in Southern Pacific and Atlantic Ocean SST anomalies associated with El Nino Southern Oscillation (ENSO) is studied using observation and ocean reanalysis products. A prominent dipole structure in SST anomaly is found with a positive (negative) anomaly center over south Pacific (65S-45S, 120W-70W) and negative (positive) one over south Atlantic (50S-30S, 30W-0E) during austral summer (DJF) of El Nino (LaNina). During late austral spring-early summer (OND) of El Nino (LaNina), anomalous northerly (southerly) meridional moisture transport and a positive (negative) sea level pressure anomaly induces a suppressed (enhanced) latent heat flux from the ocean surface over south Pacific. This in turn results in a shallower than normal mixed layer depth which further helps in development of the SST anomaly. Mixed layer thins further due to anomalous shortwave radiation during summer and a well developed SST anomaly evolves. The south Atlantic pole exhibits exactly opposite characteristics at the same time. The contribution from the surface heat fluxes to mixed layer temperature change is found to be dominant over the advective processes over both the basins. Net surface heat fluxes anomaly is also found to be maximum during late austral spring-early summer period, with latent heat flux having a major contribution to it. The anomalous latent heat fluxes between atmosphere and ocean surface play important role in the growth of observed summertime SST anomaly. Sea-surface height also shows similar out-of-phase signatures over the two basins and are well correlated with the ENSO related SST anomalies. It is also observed that the magnitude of ENSO related anomalies over the southern ocean are weaker in LaNina years than in El Nino years, suggesting an intensified tropics-high latitude tele-connection during warm phases of ENSO.
Re-reading the IPCC Report: Aerosols, Droughts and ENSO Events
NASA Astrophysics Data System (ADS)
Potts, K. A.
2008-12-01
The Technical Summary of Working Group One in the IPCC Fourth Assessment Report states that "changes in aerosols may have affected precipitation and other aspects of the hydrologic cycle more strongly than other anthropogenic forcing agents" and that "Simulations also suggest that absorbing aerosols, particularly black carbon, can reduce the solar radiation reaching the surface and can warm the atmosphere at regional scales, affecting the vertical temperature profile and the large-scale atmospheric circulation". Taking these two statements at face value I first identify eight seasonal, anthropogenic, regional scale, aerosol plumes which now occur each year and then report the correlation of the aerosol optical depth (AOD) of some of these plumes with climate anomalies in the higher latitudes and with ENSO events. The eight identified aerosol plumes vary significantly in extent and AOD inter annually. They have also increased in geographic extent and AOD over recent decades as the population in the tropics, the origin of the majority of these plumes, has increased dramatically requiring increased levels of agriculture and commercial activity. I show that: the AOD of the South East Asian Plume, occurring from late July to November, correlates with four characteristics of drought in south eastern Australia; the aerosol index of the Middle East Plume correlates negatively with rainfall in Darfur; and the volume of tephra ejected by volcanoes in south east Asia correlates: negatively with rainfall and water inflows into the Murray River in south eastern Australia; and positively with ENSO events over the period 1890/91 to 2006. I conclude that aerosol plumes over south eastern Asia are the cause of drought in south eastern Australia and ENSO events and confirm the statements made in the IPCC Report with respect to these aerosol plumes. I propose a new component of surface aerosol radiative forcing, Regional Dimming, which interferes with the seasonal movement of the
NASA Astrophysics Data System (ADS)
Ghil, M.; Zaliapin, I.; Thompson, S.
2008-05-01
We consider a delay differential equation (DDE) model for El-Niño Southern Oscillation (ENSO) variability. The model combines two key mechanisms that participate in ENSO dynamics: delayed negative feedback and seasonal forcing. We perform stability analyses of the model in the three-dimensional space of its physically relevant parameters. Our results illustrate the role of these three parameters: strength of seasonal forcing b, atmosphere-ocean coupling κ, and propagation period τ of oceanic waves across the Tropical Pacific. Two regimes of variability, stable and unstable, are separated by a sharp neutral curve in the (b, τ) plane at constant κ. The detailed structure of the neutral curve becomes very irregular and possibly fractal, while individual trajectories within the unstable region become highly complex and possibly chaotic, as the atmosphere-ocean coupling κ increases. In the unstable regime, spontaneous transitions occur in the mean "temperature" (i.e., thermocline depth), period, and extreme annual values, for purely periodic, seasonal forcing. The model reproduces the Devil's bleachers characterizing other ENSO models, such as nonlinear, coupled systems of partial differential equations; some of the features of this behavior have been documented in general circulation models, as well as in observations. We expect, therefore, similar behavior in much more detailed and realistic models, where it is harder to describe its causes as completely.
Mechanism of ENSO influence on the South Asian monsoon rainfall in global model simulations
NASA Astrophysics Data System (ADS)
Joshi, Sneh; Kar, Sarat C.
2018-02-01
Coupled ocean atmosphere global climate models are increasingly being used for seasonal scale simulation of the South Asian monsoon. In these models, sea surface temperatures (SSTs) evolve as coupled air-sea interaction process. However, sensitivity experiments with various SST forcing can only be done in an atmosphere-only model. In this study, the Global Forecast System (GFS) model at T126 horizontal resolution has been used to examine the mechanism of El Niño-Southern Oscillation (ENSO) forcing on the monsoon circulation and rainfall. The model has been integrated (ensemble) with observed, climatological and ENSO SST forcing to document the mechanism on how the South Asian monsoon responds to basin-wide SST variations in the Indian and Pacific Oceans. The model simulations indicate that the internal variability gets modulated by the SSTs with warming in the Pacific enhancing the ensemble spread over the monsoon region as compared to cooling conditions. Anomalous easterly wind anomalies cover the Indian region both at 850 and 200 hPa levels during El Niño years. The locations and intensity of Walker and Hadley circulations are altered due to ENSO SST forcing. These lead to reduction of monsoon rainfall over most parts of India during El Niño events compared to La Niña conditions. However, internally generated variability is a major source of uncertainty in the model-simulated climate.
Interaction between the ENSO and the Asian monsoon in a coral record of tropical climate
DOE Office of Scientific and Technical Information (OSTI.GOV)
Charles, C.D.; Hunter, D.E.; Fairbanks, R.G.
1997-08-15
The oxygen isotopic composition of a banded coral from the western equatorial Indian Ocean provides a 150-year-long history of the relation between the El Nino-Southern Oscillation (ENSO) phenomenon and the Asian monsoon. Interannual cycles in the coral time series were found to correlate with Pacific coral and instrumental climate records, suggesting a consistent linkage across ocean basins, despite the changing frequency and amplitude of the ENSO. However, decadal variability that is characteristic of the monsoon system also dominates the coral record, which implies important interactions between tropical and midlatitude climate variability. One prominent manifestation of this interaction is the strongmore » amplitude modulation of the quasi-biennial cycle. 26 refs., 4 figs.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wang, S-Y; Hipps, Lawrence; Gillies, Robert R.
2014-05-16
The 2013-14 California drought was accompanied by an anomalous high-amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer, and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either ENSO or Pacific Decadal Oscillation; instead it is correlated with a typemore » of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased GHG loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013-14, the associated drought and its intensity.« less
NASA Astrophysics Data System (ADS)
Wang, S.-Y.; Hipps, Lawrence; Gillies, Robert R.; Yoon, Jin-Ho
2014-05-01
The 2013-2014 California drought was initiated by an anomalous high-amplitude ridge system. The anomalous ridge was investigated using reanalysis data and the Community Earth System Model (CESM). It was found that the ridge emerged from continual sources of Rossby wave energy in the western North Pacific starting in late summer and subsequently intensified into winter. The ridge generated a surge of wave energy downwind and deepened further the trough over the northeast U.S., forming a dipole. The dipole and associated circulation pattern is not linked directly with either El Niño-Southern Oscillation (ENSO) or Pacific Decadal Oscillation; instead, it is correlated with a type of ENSO precursor. The connection between the dipole and ENSO precursor has become stronger since the 1970s, and this is attributed to increased greenhouse gas loading as simulated by the CESM. Therefore, there is a traceable anthropogenic warming footprint in the enormous intensity of the anomalous ridge during winter 2013-2014 and the associated drought.
NASA Astrophysics Data System (ADS)
Lee, Hyun-Chul; Kumar, Arun; Wang, Wanqiu
2018-03-01
Coupled prediction systems for seasonal and inter-annual variability in the tropical Pacific are initialized from ocean analyses. In ocean initial states, small scale perturbations are inevitably smoothed or distorted by the observational limits and data assimilation procedures, which tends to induce potential ocean initial errors for the El Nino-Southern Oscillation (ENSO) prediction. Here, the evolution and effects of ocean initial errors from the small scale perturbation on the developing phase of ENSO are investigated by an ensemble of coupled model predictions. Results show that the ocean initial errors at the thermocline in the western tropical Pacific grow rapidly to project on the first mode of equatorial Kelvin wave and propagate to the east along the thermocline. In boreal spring when the surface buoyancy flux weakens in the eastern tropical Pacific, the subsurface errors influence sea surface temperature variability and would account for the seasonal dependence of prediction skill in the NINO3 region. It is concluded that the ENSO prediction in the eastern tropical Pacific after boreal spring can be improved by increasing the observational accuracy of subsurface ocean initial states in the western tropical Pacific.
Reforecasting the 1972-73 ENSO Event and the Monsoon Drought Over India
NASA Astrophysics Data System (ADS)
Shukla, J.; Huang, B.; Shin, C. S.
2016-12-01
This paper presents the results of reforcasting the 1972-73 ENSO event and the Indian summer monsoon drought using the National Centers for Environmental Prediction (NCEP) Climate Forecast System, version 2 (CFSv2), initialized with the European Centre for Medium-Range Weather Forecasts (ECMWF) global ocean reanalysis version 4, and observation-based land and atmosphere reanalyses. The results of this paper demonstrate that if the modern day climate models were available during the 1970's, even with the limited observations at that time, it should have been possible to predict the 1972-73 ENSO event and the associated monsoon drought. These results further suggest the necessity of continuing to develop realistic models of the climate system for accurate and reliable seasonal predictions. This paper also presents a comparison of the 1972-73 El Niño reforecast with the 1997-98 case. As the strongest event during 1958-78, the 1972-73 El Niño is distinguished from the 1997-98 one by its early termination. Initialized in the spring season, the forecast system predicted the onset and development of both events reasonably well, although the reforecasts underestimate the ENSO peaking magnitudes. On the other hand, the reforecasts initialized in spring and fall of 1972 persistently predicted lingering wind and SST anomalies in the eastern equatorial Pacific during the spring of 1973. Initialized in fall of 1997, the reforecast also grossly overestimates the peaking westerly wind and warm SST anomalies in the 1997-98 El Niño.In 1972-73, both the Eastern Pacific SST anomalies (for example Nino 3 Index) and the summer monsoon drought over India and the adjoining areas were predicted remarkably well. In contrast, the Eastern Pacific SST anomalies for the 1997-98 event were predicted well, but the normal summer monsoon rainfall over India of 1997 was not predicted by the model. This case study of the 1972-73 event is part of a larger, comprehensive reforecast project
Historical series and Near Real Time data analysis produced within ASI-SRV project infrastructures
NASA Astrophysics Data System (ADS)
Silvestri, M.; Musacchio, M.; Buongiorno, M.; Corradini, S.; Lombardo, V.; Merucci, L.; Spinetti, C.; Sansosti, E.; Pugnaghi, S.; Teggi, S.; Vignoli, S.; Amodio, A.; Dini, L.
2009-12-01
ASI-Sistema Rischio Vulcanico (SRV) project is devoted to the development of a pre-operative integrated system managing different Earth Observation (EO) and Non EO data to respond to specific needs of the Italian Civil Protection Department (DPC) and improve the monitoring of Italian active volcanoes. The project provides the capability to maintain a repository where the acquired data are stored and generates products offering a support to risk managers during the different volcanic activity phases. All the products are obtained considering technical choices and developments of ASI-SRV based on flexible and scalable modules which take into account also the new coming space sensors and new processing algorithms. An important step of the project development regards the technical and scientific feasibility of the provided products that depends on the data availability, accuracy algorithms and models used in the processing and of course the possibility to validate the results by means of comparison with non-EO independent measurements. The ASI-SRV infrastrucutre is based on a distributed client/server architecture which implies that different processors need to ingest data set characterized by a constant and common structure. ASI-SRV will develop, in its final version, a centralized HW-SW system located at INGV which will control two complete processing chains, one located at INGV for Optical data, and the other located at IREA for SAR data. The produced results will be disseminated through a WEB-GIS interface which will allow the DPC to overview and assimilate the products in a compatible format respect to their local monitoring system in order to have an immediate use of the provided information. In this paper the first results producing ground deformation measurement via Differential Interferometric SAR (DInSAR) techniques by using SAR data and via the application of the Small BAseline Subset (SBAS) technique developed at IREA, are reported. Moreover different
Modulation of the SSTA decadal variation on ENSO events and relationships of SSTA With LOD,SOI, etc
NASA Astrophysics Data System (ADS)
Liao, D. C.; Zhou, Y. H.; Liao, X. H.
2007-01-01
Interannual and decadal components of the length of day (LOD), Southern Oscillation Index (SOI) and Sea Surface Temperature anomaly (SSTA) in Nino regions are extracted by band-pass filtering, and used for research of the modulation of the SSTA on the ENSO events. Results show that besides the interannual components, the decadal components in SSTA have strong impacts on monitoring and representing of the ENSO events. When the ENSO events are strong, the modulation of the decadal components of the SSTA tends to prolong the life-time of the events and enlarge the extreme anomalies of the SST, while the ENSO events, which are so weak that they can not be detected by the interannual components of the SSTA, can also be detected with the help of the modulation of the SSTA decadal components. The study further draws attention to the relationships of the SSTA interannual and decadal components with those of LOD, SOI, both of the sea level pressure anomalies (SLPA) and the trade wind anomalies (TWA) in tropic Pacific, and also with those of the axial components of the atmospheric angular momentum (AAM) and oceanic angular momentum (OAM). Results of the squared coherence and coherent phases among them reveal close connections with the SSTA and almost all of the parameters mentioned above on the interannual time scales, while on the decadal time scale significant connections are among the SSTA and SOI, SLPA, TWA, ?3w and ?3w+v as well, and slight weaker connections between the SSTA and LOD, ?3pib and ?3bp
DOE Office of Scientific and Technical Information (OSTI.GOV)
Tomita, Tomohiko; Yanai, Michio
The link between the Asian monsoon and the El Nino/Southern Oscillation (ENSO) has been demonstrated by a number of studies. This study examines two ENSO withdrawal periods and discusses if the Asian monsoon played a role in the differences between them. The 1986 event occurred in the later half of 1986 and retreated in 1988. The 1951 and 1991 events were similar to each other and seemed to continue to the second year after onset and not to have the clear La Nina phase after the events. In the central and eastern Pacific, three variables progress in phase as themore » ENSO cycle: sea surface temperature (SST), heat source (Q1), and divergence. Correlation coefficients were calculated and examined with the mean SST on the equator and with the standard deviation of the interannual components of SST. In the central and eastern Pacific, the standard deviation is large and three correlation coefficients are large (over 0.6). Strong air-sea interaction associated with ENSO cycle is deduced. In the Indian Ocean and the western Pacific, the correlation coefficients with SST become small rapidly, while the correlation coefficient between Q1 and the divergence is still large. The interannual variability of SSt may not be crucial for those of Q1 and of the divergence in this region because of the potential to generate well organized convection through the high mean SST. This suggests that various factors, such as effects from mid-latitudes, may modify the interannual variability in the region. To examine the effects of the Asian winter monsoon, the anomalous wind field at 850 hPa was investigated. The conditions of the Asian winter monsoon were quite different between the withdrawal periods in the 1986 and 1991 ENSO events. The Asian winter monsoon seems to be a factor to modify the ENSO cycle, especially in the retreat periods. In addition, the SST from the tropical Indian Ocean to western Pacific may be important for the modulation of the ENSO/monsoon system. 9 refs., 10
DOE Office of Scientific and Technical Information (OSTI.GOV)
Zhang, Huijun; Ren, Jiadong, E-mail: jdren@ysu.edu.cn; Wu, Lailei
The structural, elastic and electronic properties of LiSi{sub 2}N{sub 3} and its substitutions by Na, K and Rb were investigated through first-principles computations. The expansion of lattice parameters of ASi{sub 2}N{sub 3} from Li, Na, K to Rb is found to be determined by the bond angle of Si–N1–Si, which suggests a possible way to improve the lithium ionic conductivity by substitutions. ASi{sub 2}N{sub 3} (A=Li, Na, K and Rb) shows the similar elastic behaviors, while the electronic band gap gradually decreases from 5.1 to 3.4 eV from LiSi{sub 2}N{sub 3} to RbSi{sub 2}N{sub 3}. Interestingly, the analysis of electronicmore » structure, crystal orbital Hamiltonian populations and Bader charges shows that the covalence of Si–N bonding is critical for the stability of ASi{sub 2}N{sub 3} phase. Among ASi{sub 2}N{sub 3} phases, there is a relatively high ionicity in NaSi{sub 2}N{sub 3}; the Si–N bond strength in [Si{sub 2}N{sub 3}]{sup −} net for KSi{sub 2}N{sub 3} and RbSi{sub 2}N{sub 3} is comparable to LiSi{sub 2}N{sub 3}, but stronger than NaSi{sub 2}N{sub 3}. - Graphic abstract: Universal trend of structural and electronic properties in alkaline metal silicon nitrides, ASi{sub 2}N{sub 3}, A=Li, Na, K and Rb. - Highlights: • Trend in structure, electronic and mechanical properties of ASi{sub 2}N{sub 3} (A=Li-Rb) were predicted. • Lattice expansion of ASi{sub 2}N{sub 3} induced by the bond angle of Si–N1–Si was found. • Calculated band gap decreases from 5.1 to 3.4 eV from LiSi{sub 2}N{sub 3} to RbSi{sub 2}N{sub 3}. • Covalent Si–N bonding is critical for the stability of ASi{sub 2}N{sub 3}.« less
NASA Astrophysics Data System (ADS)
Potts, K. A.
2017-12-01
ENSO events are the most significant perturbation of the climate system. Previous attempts to link ENSO with volcanic eruptions typically failed because only large eruptions across the globe which eject tephra into the stratosphere were considered. I analyse all volcanic eruptions in South Eastern (SE) Asia (10ºS to 10ºN and from 90ºE to 160ºE) the most volcanically active area in the world with over 23% of all eruptions in the Global Volcanism Program database occurring here and with 5 volcanoes stated to have erupted nearly continuously for 30 years. SE Asia is also the region where the convective arm of the thermally direct Walker Circulation occurs driven by the intense equatorial solar radiation which creates the high surface temperature. The volcanic tephra plume intercepts some of the solar radiation by absorption/reflection which cools the surface and heats the atmosphere creating a temperature inversion compared to periods without the plume. This reduces convection and causes the Walker Cell and Trade Winds to weaken. This reduced wind speed causes the central Pacific Ocean to warm which creates convection there which further weakens the Walker Cell. With the reduced wind stress the western Pacific warm pool migrates east. This creates an ENSO event which continues until the tephra plume reduces, typically when the SE Asian monsoon commences, and convection is re-established over SE Asia and the Pacific warm pool migrates back to the west. Correlations of SE Asian tephra and the ENSO indices are typically over 0.80 at p < 0.01 In recent decades the anthropogenic SE Asian aerosol Plume (SEAP) has intensified the volcanic plume in some years from August to November. Using NASA satellite data from 1978 and the NASA MERRA 2 reanalysis dataset I show correlation coefficients typically over 0.70 and up to 0.97 at p < 0.01 between the aerosol optical depth or index and the ENSO indices. If two events A and B correlate 5 options are available: 1. A causes B; 2
NASA Astrophysics Data System (ADS)
Changnon, David; Creech, Tamara; Marsili, Nathan; Murrell, William; Saxinger, Michael
1999-06-01
During the 1997/98 El Niño event, a Northern Illinois University (NIU) faculty member and a group of undergraduate meteorology students interacted with the university's heating plant manager to determine whether climate information and forecast tools could assist him with NIU's natural gas purchase decisions each fall. Based on the El Niño-driven temperature forecasts and information developed by the faculty-directed student group, which indicated that northern Illinois would experience a warmer than average winter (December through March), the manager chose the option to ride the market on a continuous basis, buying incrementally to reduce total natural gas expenditures, rather than lock into a fixed price.To aid this annual decision process, winter El Niño-Southern Oscillation (ENSO) classifications, based on sea surface temperature (SST) data measured in the Niño-3 region, were analyzed to determine whether relationships existed between local mean winter temperature and the ENSO phenomena during the 1951-97 period. An SST ENSO model, which uses the past winter's ENSO state along with the SST trends from April through September, was developed to predict the upcoming winter's temperatures (above, near, or below average). The model predicted an 83% chance of a winter experiencing average to below-average temperatures following an El Niño winter, regardless of trend. Those winters following a non-ENSO winter with steady or increasing SST trends experienced average or above-average temperatures 79% of the time. These results supported the manager's natural gas decision, which in turn saved NIU approximately $500,000 and aided in the university's decision to hire a full-time applied meteorologist to provide advice on a continuing basis.
Notohamiprodjo, S; Deak, Z; Meurer, F; Maertz, F; Mueck, F G; Geyer, L L; Wirth, S
2015-01-01
The purpose of this study was to compare cranial CT (CCT) image quality (IQ) of the MBIR algorithm with standard iterative reconstruction (ASiR). In this institutional review board (IRB)-approved study, raw data sets of 100 unenhanced CCT examinations (120 kV, 50-260 mAs, 20 mm collimation, 0.984 pitch) were reconstructed with both ASiR and MBIR. Signal-to-noise (SNR) and contrast-to-noise (CNR) were calculated from attenuation values measured in caudate nucleus, frontal white matter, anterior ventricle horn, fourth ventricle, and pons. Two radiologists, who were blinded to the reconstruction algorithms, evaluated anonymized multiplanar reformations of 2.5 mm with respect to depiction of different parenchymal structures and impact of artefacts on IQ with a five-point scale (0: unacceptable, 1: less than average, 2: average, 3: above average, 4: excellent). MBIR decreased artefacts more effectively than ASiR (p < 0.01). The median depiction score for MBIR was 3, whereas the median value for ASiR was 2 (p < 0.01). SNR and CNR were significantly higher in MBIR than ASiR (p < 0.01). MBIR showed significant improvement of IQ parameters compared to ASiR. As CCT is an examination that is frequently required, the use of MBIR may allow for substantial reduction of radiation exposure caused by medical diagnostics. • Model-Based iterative reconstruction (MBIR) effectively decreased artefacts in cranial CT. • MBIR reconstructed images were rated with significantly higher scores for image quality. • Model-Based iterative reconstruction may allow reduced-dose diagnostic examination protocols.
ENSO Simulation in Coupled Ocean-Atmosphere Models: Are the Current Models Better?
DOE Office of Scientific and Technical Information (OSTI.GOV)
AchutaRao, K; Sperber, K R
Maintaining a multi-model database over a generation or more of model development provides an important framework for assessing model improvement. Using control integrations, we compare the simulation of the El Nino/Southern Oscillation (ENSO), and its extratropical impact, in models developed for the 2007 Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report with models developed in the late 1990's (the so-called Coupled Model Intercomparison Project-2 [CMIP2] models). The IPCC models tend to be more realistic in representing the frequency with which ENSO occurs, and they are better at locating enhanced temperature variability over the eastern Pacific Ocean. When compared withmore » reanalyses, the IPCC models have larger pattern correlations of tropical surface air temperature than do the CMIP2 models during the boreal winter peak phase of El Nino. However, for sea-level pressure and precipitation rate anomalies, a clear separation in performance between the two vintages of models is not as apparent. The strongest improvement occurs for the modeling groups whose CMIP2 model tended to have the lowest pattern correlations with observations. This has been checked by subsampling the multi-century IPCC simulations in a manner to be consistent with the single 80-year time segment available from CMIP2. Our results suggest that multi-century integrations may be required to statistically assess model improvement of ENSO. The quality of the El Nino precipitation composite is directly related to the fidelity of the boreal winter precipitation climatology, highlighting the importance of reducing systematic model error. Over North America distinct improvement of El Nino forced boreal winter surface air temperature, sea-level pressure, and precipitation rate anomalies in the IPCC models occurs. This improvement, is directly proportional to the skill of the tropical El Nino forced precipitation anomalies.« less
Use of ENSO forecasts to select nitrogen fertilizer application strategies for winter
USDA-ARS?s Scientific Manuscript database
El Niño Southern Oscillation (ENSO) has a strong impact on winter crops in Alabama (AL). Wheat is basically grown during winter as cash crop and sometimes also as fodder or grain crop in AL. Thus, it is very necessary to understand the impact of variability in climate factors due to the different ph...
Climate, ENSO and 'Black Swans' over the Last Millennium
NASA Astrophysics Data System (ADS)
Thompson, L. G.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.
2014-12-01
Tropical rainfall patterns influence the lives of billions of people both north and south of the Equator. Evidence of major ENSO events such as droughts is often recorded in the oxygen isotopic ratios and aerosol concentrations in tropical ice cores. Here we examine unusual events recorded in three ice cores, two (Quelccaya and Coropuna) in the Southern Hemisphere on the Peruvian Altiplano and the third (Dasuopu) located 22,000 km away on the southern edge of the Tibetan Plateau at the top of the Himalayas. These records suggest that the unique lower and middle tropospheric air flow over chloride (Cl-) and fluoride (F-) enriched areas upwind of the sites during ENSO events leads to enhanced deposition of these species on these glaciers. Linkages are demonstrated between ice-core chemistry and drought indicators, changes in lake levels, and ENSO and monsoon indices. Two unusual events, in the late 18th and mid-14th Centuries, are marked by abnormally high concentrations of F- and Cl- in at least two of the ice core records. All three records document a drought from 1789 to 1800 CE in which increases in these anionic concentrations reflect the abundance of continental atmospheric dust derived from arid regions upwind of the core sites. The earlier event, apparent only in the Quelccaya and Dasuopu ice cores, begins abruptly in 1343 and tapers off by 1375. The interaction between high frequency El Niños and low frequency shifts in the inter-tropical convergence zone may have resulted in these unusually severe and extended droughts. These "Black Swan" events correspond to historically documented, devastating population disruptions that were in part climate related. The 1789 to 1800 CE event was concurrent with the Doji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive climate disruptions are documented in Central and South America. The mid-14th Century drought is concomitant with major monsoon
NASA Astrophysics Data System (ADS)
Gao, Pan; Xu, Xiaohua; Zhang, Xiaohong
2017-04-01
In this paper, the spatial patterns and vertical structure of atmospheric temperature anomalies, in both the tropics and the extratropical latitudes, associated with the El Niño-Southern Oscillation (ENSO) and quasi-biennial oscillation (QBO) in the upper troposphere and stratosphere are investigated using global positioning system (GPS) radio occultation (RO) measurements from the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) Formosa Satellite Mission 3 mission from July 2006 to February 2014. We find that negative correlations between the atmospheric temperature in the tropics and ENSO are observed at 17-30 km in the lower stratosphere at a lag of 1-4 months and at a lead of 1 month. Out-of-phase temperature variation is observed in the troposphere over the mid-latitude band and in-phase behaviour is observed in the lower stratosphere. Interestingly, we also find that there is a significant negative correlation at a lag of 1-3 months from 32 km to 40 km in the mid-latitude region of the Northern Hemisphere. The atmospheric temperature variations over mid-latitude regions in both hemispheres are closely related to the QBO. There are also two narrow zones over the subtropical jet zone where the QBO signals are strong in both hemispheres, approximately parallel to the equator. Finally, we develop a new robust index to describe the strength of the ENSO and QBO signal.
Forecasting ENSO events: A neural network-extended EOF approach
DOE Office of Scientific and Technical Information (OSTI.GOV)
Tangang, F.T.; Tang, B.; Monahan, A.H.
The authors constructed neural network models to forecast the sea surface temperature anomalies (SSTA) for three regions: Nino 4. Nino 3.5, and Nino 3, representing the western-central, the central, and the eastern-central parts of the equatorial Pacific Ocean, respectively. The inputs were the extended empirical orthogonal functions (EEOF) of the sea level pressure (SLP) field that covered the tropical Indian and Pacific Oceans and evolved for a duration of 1 yr. The EEOFs greatly reduced the size of the neural networks from those of the authors` earlier papers using EOFs. The Nino 4 region appeared to be the best forecastedmore » region, with useful skills up to a year lead time for the 1982-93 forecast period. By network pruning analysis and spectral analysis, four important inputs were identified: modes 1, 2, and 6 of the SLP EEOFs and the SSTA persistence. Mode 1 characterized the low-frequency oscillation (LFO, with 4-5-yr period), and was seen as the typical ENSO signal, while mode 2, with a period of 2-5 yr, characterized the quasi-biennial oscillation (QBO) plus the LFO. Mode 6 was dominated by decadal and interdecadal variations. Thus, forecasting ENSO required information from the QBO, and the decadal-interdecadal oscillations. The nonlinearity of the networks tended to increase with lead time and to become stronger for the eastern regions of the equatorial Pacific Ocean. 35 refs., 14 figs., 4 tabs.« less
NASA Astrophysics Data System (ADS)
Gomez, F. A.; Lee, S. K.; Liu, Y.; Hernandez, F., Jr.; Lamkin, J. T.
2017-12-01
Previous studies have suggested that El Nino-Southern Oscillation (ENSO) plays a role in modulating phytoplankton biomass and the reproductive success of marine species in the Gulf of Mexico (GoM). However, characterizations of ENSO-related ecosystem responses such as plankton production have not been fully addressed for the region. Here we examine ENSO impacts on biogeochemical processes within coastal and open ocean domains in the GoM, using a three dimensional high-resolution ocean-biogeochemical model, forced with historical surface fluxes and river run-off for 1979 - 2014. Enhanced precipitation across southern US during El Nino winter increases freshwater discharge and nutrient load into the GoM mainly via the Mississippi-Atchafalaya River. Those anomalies lead to reduced salinity and greater concentration of dissolved inorganic nitrogen and plankton production in the northern shelf especially during winter. In addition, the frequency of northerly wind anomalies that cool the upper ocean increases during El Nino. The negative surface heat flux anomalies further decrease vertical thermal stratification and thus increase phytoplankton production during early spring in the northern deep GoM.
NASA Astrophysics Data System (ADS)
Wiedermann, Marc; Siegmund, Jonatan F.; Donges, Jonathan F.; Donner, Reik V.
2017-04-01
The El Nino Southern Oscillation (ENSO) with its positive (El Nino) and negative (La Nina) phases is known to trigger climatic responses in various parts of the Earth, an effect commonly attributed to teleconnectivity. A series of studies has demonstrated that El Nino periods exhibits a relatively broad variety of spatial patterns, which can be classified into two main flavors termed East Pacific (EP, canonical) and Central Pacific (CP, Modoki) El Nino, and that both subtypes can trigger distinct climatic responses like droughts vs. precipitation increases at the regional level. More recently, a similar discrimination of La Nina periods into two different flavors has been reported, and it is reasonable to assume that these different expressions are equally accompanied by differential responses of regional climate variability in particularly affected regions. In this work, we study in great detail the imprints of both types of El Nino and La Nina periods in extremal seasonal precipitation sums during fall (SON), winter (DJF) and spring (MAM) around the peak time of the corresponding ENSO phase. For this purpose, we employ a recently developed objective classification of El Nino and La Nina periods into their two respective flavors based on global teleconnectivity patterns in daily surface air temperature anomalies as captured by the associated climate network representations (Wiedermann et al., 2016). In order to study the statistical relevance of the timing of different El Nino and La Nina types on that of seasonal precipitation extremes around the globe (according to the GPCC data set as a reference), we utilize event coincidence analysis (Donges et al., 2016), a new powerful yet conceptually simple and intuitive statistical tool that allows quantifying the degree of simultaneity of distinct events in pairs of time series. Our results provide a comprehensive overview on ENSO related imprints in regional seasonal precipitation extremes. We demonstrate that key
Southern Hemisphere Extratropical Cyclones and their Relationship with ENSO in springtime
NASA Astrophysics Data System (ADS)
Reboita, M. S.; Ambrizzi, T.; Da Rocha, R.
2013-05-01
Extratropical cyclones occurrence is associated with the teleconnection mechanisms that produce climate variability. Among these mechanisms we have El Niño-Southern Oscillation (ENSO). Some works have indicated that during the ENSO positive phase there are more cyclogenetic conditions in some parts of the globe as the southwest of South Atlantic Ocean. Therefore, the purpose of this study is to verify if the extratropical cyclones number and location are altered in the different ENSO phases in the austral spring over the Southern Hemisphere (SH). The Melbourne University automatic tracking scheme was used to determine the cyclone climatology from 1980 to 2012. All cyclones that appear with lifetime higher or equal to 24 hours in the sea level pressure data from National Centers for Environment Prediction reanalysis I were included in the climatology. El Niño (EN), La Niña (LN) and Neutral (N) years were identified through the Oceanic Niño Index (ONI) from Climate Prediction Center/NOAA. The average number of cyclones in the spring over the SH is similar in the EN (200), N (184) and LN (197) episodes. By latitude bands, during EN episodes the cyclones occurrence reduces in 16% between 70-60 degrees and increases in ~15% between 80-70 and 50-40 degrees. On the other hand, during the LN episodes, the cyclones are 17% more frequent in 50-60 degrees and 22% less frequent in 30-20 degrees. One more detailed analysis of the cyclones trajectory density (that is a statistic product of the tracking algorithm) shows that in the South Atlantic Ocean, near the southeast of South America, the number of cyclones in EN years is higher than in the neutral period and lower than in the LN years. In the Indian Ocean, the EN year is characterized by a cyclones reduction in the west and east sector, near the continents. In the Pacific Ocean, the region southward the New Zealand presents more cyclones occurrence in EN years.
NASA Astrophysics Data System (ADS)
Yu, E.; Wang, C.; Hinnov, L. A.; Wu, H.
2014-12-01
The quasi-periodic, ca. 2-7 year El Niño Southern Oscillation (ENSO) phenomenon globally influences the inter-annual variability of temperature and precipitation. Global warming may increase the frequency of extreme ENSO events. Although the Cretaceous plate tectonic configuration was different from today, the sedimentary record suggests that ENSO-type oscillations had existed at the time of Cretaceous greenhouse conditions. Cored Cretaceous lacustrine sediments from the Songliao Basin in Northeast China (SK-1 cores from the International Continental Drilling Program) potentially offer a partially varved record of Cretaceous paleoclimate. Fourteen polished thin sections from the depth interval 1096.12-1096.53 m with an age of 84.4 Ma were analyzed by optical and scanning electron microscopy (SEM). ImageJ software was applied to extract gray scale curves from optical images at pixel resolution. We tracked minimum values of the gray scale curves to estimate the thickness of each lamina. Five sedimentary structures were recognized: flaser bedding, wavy bedding, lenticular bedding, horizontal bedding, and massive layers. The mean layer thicknesses with different sedimentary structures range from 116 to 162mm, very close to the mean sedimentation rate estimated for this sampled interval, 135mm/year, indicating that the layers bounded by pure clay lamina with the minimum gray values are varves. SEM images indicate that a varve is composed, in succession, of one lamina rich in coarse silt, one lamina rich in fine silt, one clay-rich lamina with some silt, and one clay-rich lamina. This suggests that a Cretaceous year featured four distinct depositional seasons, two of which were rainy and the others were lacking precipitation. Spectral analysis of extended intervals of the tuned gray scale curve indicates the presence of inter-annual periodicities of 2.2-2.7 yr, 3.5-6.1 year, and 10.1-14.5 year consistent with those of modern ENSO cycles and solar cycles, as well as
On the unstable ENSO-Western North Pacific Monsoon relation during the 20th Century
NASA Astrophysics Data System (ADS)
Vega Martín, Inmaculada; Gallego Puyol, David; Ribera Rodriguez, Pedro; Gómez Delgado, Francisco de Paula; Peña-Ortiz, Cristina
2017-04-01
The concept of the Western North Pacific Summer Monsoon (WNPSM) appeared for the first time in 1987. Unlike the Indian Summer Monsoon and the East Asian summer monsoon, the WNPSM is an oceanic monsoon driven essentially by the meridional gradient of sea surface temperature. Its circulation is characterized by a northwest-southeast oriented monsoon trough with intense precipitation and low-level southwesterlies and upper-tropospheric easterlies in the region [100°-130° E, 5°-15°N]. Although this monsoon is mainly oceanic, it modulates the precipitation of densely populated areas such as the Philippines. To date, the WNPSM has been quantified by the so-called Western North Pacific Monsoon Index (WNPMI), an index based on wind anomalies over large domains of the Western Pacific. The requirement of continuous observed wind over remote oceanic areas to compute the WNPMI has limited its availability to the 1949-2014 period. In this work we have extended the index by almost 100 years by using historical observations of wind direction taken aboard ships. Our Western North Pacific Directional Index (WNPDI), is defined as the sum of the persistence of the low-level westerly winds in [5°-15°N, 100°-130°E] and easterly winds in [20°-30°N, 110°-140°E]. The new WNPDI index is highly correlated to the existent WNPMI for the concurrent period (1948-2014). (r=+0.88, p<0.01), indicating that the new approach based in the use of wind direction alone (a variable that can be considered instrumental even before the 20th Century), captures most of the monsoonal signal. Previous studies found that, during the second part of the 20th Century the WNPSM exhibited two basic characteristics: first a large interannual variability and second, a significant relation between the WNPSM and the El Niño/Southern Oscillation (ENSO) in a way in which a strong (weak) WNPSM tends to occur during the El Niño (La Niña) developing year or/and La Niña (El Niño) decaying year. The analysis of
Guziński, Maciej; Waszczuk, Łukasz; Sąsiadek, Marek J
2016-10-01
To evaluate head CT protocol developed to improve visibility of the brainstem and cerebellum, lower bone-related artefacts in the posterior fossa and maintain patient radioprotection. A paired comparison of head CT performed without Adaptive Statistical Iterative Reconstruction (ASiR) and a clinically indicated follow-up with 40 % ASiR was acquired in one group of 55 patients. Patients were scanned in the axial mode with different scanner settings for the brain and the posterior fossa. Objective image quality analysis was performed with signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Subjective image quality analysis was based on brain structure visibility and evaluation of the artefacts. We achieved 19 % reduction of total DLP and significantly better image quality of posterior fossa structures. SNR for white and grey matter in the cerebellum were 34 % to 36 % higher, respectively, CNR was improved by 142 % and subjective analyses were better for images with ASiR. When imaging parameters are set independently for the brain and the posterior fossa imaging, ASiR has a great potential to improve CT performance: image quality of the brainstem and cerebellum is improved, and radiation dose for the brain as well as total radiation dose are reduced. •With ASiR it is possible to lower radiation dose or improve image quality •Sequentional imaging allows setting scan parameters for brain and posterior-fossa independently •We improved visibility of brainstem structures and decreased radiation dose •Total radiation dose (DLP) was decreased by 19.
NASA Astrophysics Data System (ADS)
Tao, Ling-Jiang; Gao, Chuan; Zhang, Rong-Hua
2018-07-01
Previous studies indicate that ENSO predictions are particularly sensitive to the initial conditions in some key areas (socalled "sensitive areas"). And yet, few studies have quantified improvements in prediction skill in the context of an optimal observing system. In this study, the impact on prediction skill is explored using an intermediate coupled model in which errors in initial conditions formed to make ENSO predictions are removed in certain areas. Based on ideal observing system simulation experiments, the importance of various observational networks on improvement of El Niño prediction skill is examined. The results indicate that the initial states in the central and eastern equatorial Pacific are important to improve El Ni˜no prediction skill effectively. When removing the initial condition errors in the central equatorial Pacific, ENSO prediction errors can be reduced by 25%. Furthermore, combinations of various subregions are considered to demonstrate the efficiency on ENSO prediction skill. Particularly, seasonally varying observational networks are suggested to improve the prediction skill more effectively. For example, in addition to observing in the central equatorial Pacific and its north throughout the year, increasing observations in the eastern equatorial Pacific during April to October is crucially important, which can improve the prediction accuracy by 62%. These results also demonstrate the effectiveness of the conditional nonlinear optimal perturbation approach on detecting sensitive areas for target observations.
Aspects of extratropical synoptic-scale processes in opposing ENSO phases
NASA Astrophysics Data System (ADS)
Schwierz, C.; Wernli, H.; Hess, D.
2003-04-01
Energy and momentum provided by anomalous tropical heating/cooling affect the circulation on the global scale. Pacific Sea surface temperature anomalies strongly force local conditions in the equatorial Pacific, but are also known to change the climate in the extratropics, particularly over the American continent. The impact on more remote areas such as the Atlantic-European region is less clear. There the observed effects in both analyses and model studies show dependence on the resolution of the model/data, as well as on the time scales under consideration (Merkel and Latif, 2002; Compo et al., 2001). Most of the previous studies focus on larger-scale processes and seasonal time scales (or longer). Here we concentrate on the impact of opposing ENSO phases on extratropical synoptic-scale dynamics. The investigation is undertaken for the Niño/Niña events of 1972/3 and 1973/4 respectively, for 5 winter months (NDJFM) using ECMWF ERA40 data with 1o× 1o horizontal resolution and 60 vertical levels. The examination of the resulting differences in terms of standard dynamical fields (temperature, sea level pressure, precipitation, geopotential) is complemented with additional diagnostic fields (e.g. potential vorticity (PV), anti-/cyclone tracks and frequencies, PV streamers/cut-offs, blocking) in an attempt to gain more insight into aspects of extratropical synoptic-scale dynamical processes associated with ENSO SST anomalies.
Effects of ENSO on weather-type frequencies and properties at New Orleans, Louisiana, USA
McCabe, G.J.; Muller, R.A.
2002-01-01
Examination of historical climate records indicates a significant relation between the El Nin??o/Southern Oscillation (ENSO) and seasonal temperature and precipitation in Louisiana. In this study, a 40 yr record of twice daily (06:00 and 15:00 h local time) weather types are used to study the effects of ENSO variability on the local climate at New Orleans, Louisiana. Tropical Pacific sea-surface temperatures (SSTs) for the NINO3.4 region are used to define ENSO events (i.e. El Nin??o and La Nin??a events), and daily precipitation and temperature data for New Orleans are used to define weather-type precipitation and temperature properties. Data for winters (December through February) 1962-2000 are analyzed. The 39 winters are divided into 3 categories; winters with NINO3.4 SST anomalies 1??C (El Nin??o events), and neutral conditions (all other years). For each category, weather-type frequencies and properties (i.e. precipitation and temperature) are determined and analyzed. Results indicate that El Nin??o events primarily affect precipitation characteristics of weather types at New Orleans, whereas the effects of La Nin??a events are most apparent in weather-type frequencies. During El Nin??o events, precipitation for some of the weather types is greater than during neutral and La Nin??a conditions and is related to increased water vapor transport from the Tropics to the Gulf of Mexico. The changes in weather-type frequencies during La Nin??a events are indicative of a northward shift in storm tracks and/or a decrease in storm frequency in southern Louisiana.
A study of Solar-Enso correlation with southern Brazil tree ring index (1955- 1991)
NASA Astrophysics Data System (ADS)
Rigozo, N.; Nordemann, D.; Vieira, L.; Echer, E.
The effects of solar activity and El Niño-Southern Oscillation on tree growth in Southern Brazil were studied by correlation analysis. Trees for this study were native Araucaria (Araucaria Angustifolia)from four locations in Rio Grande do Sul State, in Southern Brazil: Canela (29o18`S, 50o51`W, 790 m asl), Nova Petropolis (29o2`S, 51o10`W, 579 m asl), Sao Francisco de Paula (29o25`S, 50o24`W, 930 m asl) and Sao Martinho da Serra (29o30`S, 53o53`W, 484 m asl). From these four sites, an average tree ring Index for this region was derived, for the period 1955-1991. Linear correlations were made on annual and 10 year running averages of this tree ring Index, of sunspot number Rz and SOI. For annual averages, the correlation coefficients were low, and the multiple regression between tree ring and SOI and Rz indicates that 20% of the variance in tree rings was explained by solar activity and ENSO variability. However, when the 10 year running averages correlations were made, the coefficient correlations were much higher. A clear anticorrelation is observed between SOI and Index (r=-0.81) whereas Rz and Index show a positive correlation (r=0.67). The multiple regression of 10 year running averages indicates that 76% of the variance in tree ring INdex was explained by solar activity and ENSO. These results indicate that the effects of solar activity and ENSO on tree rings are better seen on long timescales.
NASA Astrophysics Data System (ADS)
Feng, Juan; Chen, Wen; Li, Yanjie
2017-04-01
Asymmetric atmospheric responses to ENSO are revisited after dividing it into two types: eastern-Pacific (EP) and central-Pacific (CP) ENSO. The EP ENSO triggers two obvious asymmetric atmospheric teleconnections: One is the Pacific-North American-like teleconnection. Its asymmetry is characterized by weaker amplitudes during the EP La Niña than EP El Niño, which is caused by a much weaker EP La Niña tropical forcing and the resultant weaker extra-tropical vorticity forcing. The other is the Atlantic-Eurasian teleconnection with negative height anomalies in the subtropical Atlantic and Eurasia and positive anomalies in the high-latitude Atlantic and northeast Asia, which appears during the EP La Niña but not during the EP El Niño. The background state plays a vital role in this asymmetry. The EP La Niña-type basic state is more conducive to propagation of the wave rays into the Atlantic-Eurasian region compared to EP El Niño situation. In contrast, the CP ENSO yields an Arctic Oscillation-like teleconnection, presenting an appreciable asymmetry in the subtropical amplitudes that are stronger during the CP El Niño than during the CP La Niña. In this case, the distinct effects of the different background state on the equatorward wave rays are responsible for this asymmetry. Under the CP El Niño-type background state, the equatorward wave rays tend to be reflected at the latitudes where the zonal wind equals zero (U = 0), and then successfully captured by the subtropical westerly jet. However, under the CP La Niña-type background state, the equatorward wave rays disappear at U = 0 latitudes.
Analysis of the Effects of ENSO and Atmospheric Rivers on Precipitation in Los Angeles County
NASA Astrophysics Data System (ADS)
Santacruz, A.; Lamb, K.
2017-12-01
The Winter 2016-2017 season in California was marked by substantial amounts of precipitation; this resulted in critically-low reservoirs filling up and the removal of most of California from drought status. The year prior was characterized by one of the strongest El Nino-Southern Oscillation (ENSO) events, though it did not produce nearly enough precipitation as the 2016-2017 season. The major contributors to the increased rainfall during the 2016-2017 season were climactic phenomenon known as atmospheric rivers (ARs), which transport water vapor through the atmosphere in narrow bands, and are known to produce extreme rain events. Determining the exact timing, landfall areas, and total precipitation amounts of ARs is currently of great interest; a recent study showed that extreme weather events are likely to increase in California in the coming years, which motivates research into how phenomenon such as ENSO and ARs play a role. Using long-term daily rain gauge data provided by the Los Angeles County Department of Public Works, we compute the precipitation volume and storm count for various locations in Los Angeles County and identify anomalies. These data will then be compared with the occurrence and intensity of AR and ENSO events by using NOAA's NOI and ESRL AR data. The results can be used to provide a better grasp of extreme climactic patterns and their effects on the amount of precipitation in the region.
NASA Astrophysics Data System (ADS)
Yan, Xiaolu; Konopka, Paul; Ploeger, Felix; Tao, Mengchu; Bian, Jianchun; Mueller, Rolf
2017-04-01
El Nino and La Nina are opposite phases of El Nino-Southern Oscillation (ENSO). The extremes of ENSO patterns have impacts not only on ocean processes, but also on global weather and climate. The ENSO activities typically show pronounced features in boreal winter time, but some prolonged events may last for months or years. In this study we analyze the influence of ENSO on the atmospheric composition in the tropical and extra-tropical UTLS region in the months following strong ENSO events. In particular, we are interested in the impact of ENSO on the Asian summer monsoon (ASM) anticyclone. Using the Multivariate ENSO Index (MEI), we define two composites starting from strong El Nino and La Nina winters (|MEI|>0.9) and analyze the anomalies caused by them in the following months. To quantify the differences in dynamics, the velocity potential (VP) and the stream function (SF) are calculated based on ERA-Interim reanalysis from 1979 to 2015. SF shows that during winter the horizontal flow in the tropical UTLS is dominated by two equatorially symmetric anticyclones resembling the well-known Matsuno-Gill solution. In summer, the anticyclone in the North Hemisphere is shifted to the ASM region. VP shows that the centers of the divergent part of the flow lie in the West Tropical Pacific and Central Pacific for La Nina and El Nino winters, respectively. These centers move northwestwards during spring and summer. The anticyclone, subtropical jet and the divergent part of the flow after La Nina winters are significantly stronger than after El Nino winters. Based on the MLS measurements of CO, H2O and O3 from 2004 to 2015, we also discuss the respective anomalies at the tropopause level for the El Nino/La Nina composites. EL Nino composite of CO shows higher values in the tropical region not only during winter but also during spring and summer. La Nina composite of H2O shows low anomaly over Maritime Continent which spread over the whole tropics until summer. The H2O
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.
Larsson, Joel; Båth, Magnus; Ledenius, Kerstin; Caisander, Håkan; Thilander-Klang, Anne
2016-06-01
The purpose of this study was to investigate the effect of different combinations of convolution kernel and the level of Adaptive Statistical iterative Reconstruction (ASiR™) on diagnostic image quality as well as visualisation of anatomical structures in paediatric abdominal computed tomography (CT) examinations. Thirty-five paediatric patients with abdominal pain with non-specified pathology undergoing abdominal CT were included in the study. Transaxial stacks of 5-mm-thick images were retrospectively reconstructed at various ASiR levels, in combination with three convolution kernels. Four paediatric radiologists rated the diagnostic image quality and the delineation of six anatomical structures in a blinded randomised visual grading study. Image quality at a given ASiR level was found to be dependent on the kernel, and a more edge-enhancing kernel benefitted from a higher ASiR level. An ASiR level of 70 % together with the Soft™ or Standard™ kernel was suggested to be the optimal combination for paediatric abdominal CT examinations. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Slocum, Matthew G; Orzell, Steve L
2013-01-01
Seasonality drives ecological processes through networks of forcings, and the resultant complexity requires creative approaches for modeling to be successful. Recently ecologists and climatologists have developed sophisticated methods for fully describing seasons. However, to date the relationships among the variables produced by these methods have not been analyzed as networks, but rather with simple univariate statistics. In this manuscript we used structural equation modeling (SEM) to analyze a proposed causal network describing seasonality of rainfall for a site in south-central Florida. We also described how this network was influenced by the El Niño-Southern Oscillation (ENSO), and how the network in turn affected the site's wildfire regime. Our models indicated that wet and dry seasons starting later in the year (or ending earlier) were shorter and had less rainfall. El Niño conditions increased dry season rainfall, and via this effect decreased the consistency of that season's drying trend. El Niño conditions also negatively influenced how consistent the moistening trend was during the wet season, but in this case the effect was direct and did not route through rainfall. In modeling wildfires, our models showed that area burned was indirectly influenced by ENSO via its effect on dry season rainfall. Area burned was also indirectly reduced when the wet season had consistent rainfall, as such wet seasons allowed fewer wildfires in subsequent fire seasons. Overall area burned at the study site was estimated with high accuracy (R (2) score = 0.63). In summary, we found that by using SEMs, we were able to clearly describe causal patterns involving seasonal climate, ENSO and wildfire. We propose that similar approaches could be effectively applied to other sites where seasonality exerts strong and complex forcings on ecological processes.
Massive bleaching of coral reefs induced by the 2010 ENSO, Puerto Cabello, Venezuela.
del Mónaco, Carlos; Haiek, Gerard; Narciso, Samuel; Galindo, Miguel
2012-06-01
El Niño Southern Oscillation (ENSO) has generated global coral massive bleaching. The aim of this work was to evaluate the massive bleaching of coral reefs in Puerto Cabello, Venezuela derived from ENSO 2010. We evaluated the bleaching of reefs at five localities both at three and five meter depth. The coral cover and densities of colonies were estimated. We recorded living coral cover, number and diameter of bleached and non-bleached colonies of each coral species. The colonies were classified according to the proportion of bleached area. Satellite images (Modis Scar) were analyzed for chlorophyll-a concentration and temperature in August, September, October and November from 2008-2010. Precipitation, wind speed and air temperature information was evaluated in meteorological data for 2009 and 2010. A total of 58.3% of colonies, belonging to 11 hexacoral species, were affected and the greatest responses were observed in Colpophyllia natans, Montastraea annularis and Montastraeafaveolata. The most affected localities were closer to the mainland and had a bleached proportion up to 62.73+/-36.55%, with the highest proportion of affected colonies, whereas the farthest locality showed 20.25+/-14.00% bleached and the smallest proportion. The salinity in situ varied between 30 and 33ppm and high levels of turbidity were observed. According to the satellite images, in 2010 the surface water temperature reached 31 degree C in August, September and October, and resulted higher than those registered in 2008 and 2009. Regionally, chlorophyll values were higher in 2010 than in 2008 and 2009. The meteorological data indicated that precipitation in November 2010 was three times higher than in November 2009. Massive coral bleaching occurred due to a three month period of high temperatures followed by one month of intense ENSO-associated precipitation. However, this latter factor was likely the trigger because of the bleaching gradient observed.
A Structural Equation Model Analysis of Relationships among ENSO, Seasonal Descriptors and Wildfires
Slocum, Matthew G.; Orzell, Steve L.
2013-01-01
Seasonality drives ecological processes through networks of forcings, and the resultant complexity requires creative approaches for modeling to be successful. Recently ecologists and climatologists have developed sophisticated methods for fully describing seasons. However, to date the relationships among the variables produced by these methods have not been analyzed as networks, but rather with simple univariate statistics. In this manuscript we used structural equation modeling (SEM) to analyze a proposed causal network describing seasonality of rainfall for a site in south-central Florida. We also described how this network was influenced by the El Niño-Southern Oscillation (ENSO), and how the network in turn affected the site’s wildfire regime. Our models indicated that wet and dry seasons starting later in the year (or ending earlier) were shorter and had less rainfall. El Niño conditions increased dry season rainfall, and via this effect decreased the consistency of that season’s drying trend. El Niño conditions also negatively influenced how consistent the moistening trend was during the wet season, but in this case the effect was direct and did not route through rainfall. In modeling wildfires, our models showed that area burned was indirectly influenced by ENSO via its effect on dry season rainfall. Area burned was also indirectly reduced when the wet season had consistent rainfall, as such wet seasons allowed fewer wildfires in subsequent fire seasons. Overall area burned at the study site was estimated with high accuracy (R 2 score = 0.63). In summary, we found that by using SEMs, we were able to clearly describe causal patterns involving seasonal climate, ENSO and wildfire. We propose that similar approaches could be effectively applied to other sites where seasonality exerts strong and complex forcings on ecological processes. PMID:24086670
ENSO variability reflected in precipitation oxygen isotopes across the Asian Summer Monsoon region
NASA Astrophysics Data System (ADS)
Cai, Zhongyin; Tian, Lide; Bowen, Gabriel J.
2017-10-01
Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.
ENSO related variability in the Southern Hemisphere, 1948-2000
NASA Astrophysics Data System (ADS)
Ribera, Pedro; Mann, Michael E.
2003-01-01
The spatiotemporal evolution of Southern Hemisphere climate variability is diagnosed based on the use of the NCEP reanalysis (1948-2000) dataset. Using the MTM-SVD analysis method, significant narrowband variability is isolated from the multi-variate dataset. It is found that the ENSO signal exhibits statistically significant behavior at quasiquadrennial (3-6 yr) timescales for the full time-period. A significant quasibiennial (2-3 yr) timescales emerges only for the latter half of period. Analyses of the spatial evolution of the two reconstructed signals shed additional light on linkages between low and high-latitude Southern Hemisphere climate anomalies.
The energy gap in a-Si 1 - xC g: H alloys
NASA Astrophysics Data System (ADS)
Valladares, Ariel A.; Valladares, Alexander; Enrique Sansores, L.; Nelis, Mary Ann Me
1997-02-01
The electronic structure of amorphous tetrahedral clusters of the type a-Si 1 - xC g: H are studied using the pseudopotential SCF Hartree-Fock approximation. The reduced energy gap isgiven by Egr( x) - 1 + 0.84 x for x ⩽ 0.5, whereas experimentally Egr( x) = 1 + 0.96 x. For x ⩾ 0.5 the dip in the gap value reported experimentally is verified.
El Niño Southern Oscillation (ENSO) and dysentery in Shandong province, China.
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.
NASA Astrophysics Data System (ADS)
Xue, Yan
The optimal growth and its relationship with the forecast skill of the Zebiak and Cane model are studied using a simple statistical model best fit to the original nonlinear model and local linear tangent models about idealized climatic states (the mean background and ENSO cycles in a long model run), and the actual forecast states, including two sets of runs using two different initialization procedures. The seasonally varying Markov model best fit to a suite of 3-year forecasts in a reduced EOF space (18 EOFs) fits the original nonlinear model reasonably well and has comparable or better forecast skill. The initial error growth in a linear evolution operator A is governed by the eigenvalues of A^{T}A, and the square roots of eigenvalues and eigenvectors of A^{T}A are named singular values and singular vectors. One dominant growing singular vector is found, and the optimal 6 month growth rate is largest for a (boreal) spring start and smallest for a fall start. Most of the variation in the optimal growth rate of the two forecasts is seasonal, attributable to the seasonal variations in the mean background, except that in the cold events it is substantially suppressed. It is found that the mean background (zero anomaly) is the most unstable state, and the "forecast IC states" are more unstable than the "coupled model states". One dominant growing singular vector is found, characterized by north-south and east -west dipoles, convergent winds on the equator in the eastern Pacific and a deepened thermocline in the whole equatorial belt. This singular vector is insensitive to initial time and optimization time, but its final pattern is a strong function of initial states. The ENSO system is inherently unpredictable for the dominant singular vector can amplify 5-fold to 24-fold in 6 months and evolve into the large scales characteristic of ENSO. However, the inherent ENSO predictability is only a secondary factor, while the mismatches between the model and data is a
NASA Technical Reports Server (NTRS)
Curtis, Scott; Adler, Robert
2000-01-01
The ENSO phenomenon is characterized by fluctuations in the climate system of the tropical Pacific. Quantifying changes in the precipitation component of this system is important in understanding the distribution of heating in the atmosphere which drives the large-scale circulation and affects the weather patterns in the mid-latitudes. Monitoring precipitation anomalies in the Pacific is also an important component for tracking the evolution of ENSO. The most timely and complete observations of the earth come from satellite instruments. In this study, the state of the art satellite-gauge merged monthly precipitation data set from the Global Precipitation Climatology Project (GPCP) is used to depict tropical rainfall patterns during ENSO events over the past two decades and quantify these patterns using indices. This analysis will be complemented by daily precipitation data which can resolve the Madden-Julian Oscillation and westerly wind burst events. The 1997-98 El Nino and 1998-2000 La Nina were the best observed ENSO cycle in the historic record. Prior to the El Nino (in terms of anomalous warming of the east Pacific) dry anomalies over the Maritime Continent were observed in February 1997 as a westerly wind burst advected convection to the east. The largest SST anomalies occurred around November-December 1997, which were followed by the largest precipitation anomalies in the beginning of 1998. The largest precipitation departures from normal were not colocated with the SST anomalies, but were further west, In the spring of 1998 negative precipitation anomalies to the north of the equator intensified, signaling the mature phase of the El Nino. A rapid increase in the precipitation-based La Nina index from December-January 1998 to March-April 1998 signaled the coming La Nina. The 1982-1983 El Nino was comparable in strength (according to several indices) and the precipitation patterns evolved in a similar fashion. For the 1998-2000 La Nina, the coldest anomalies
GaInAsP/InP lateral-current-injection distributed feedback laser with a-Si surface grating.
Shindo, Takahiko; Okumura, Tadashi; Ito, Hitomi; Koguchi, Takayuki; Takahashi, Daisuke; Atsumi, Yuki; Kang, Joonhyun; Osabe, Ryo; Amemiya, Tomohiro; Nishiyama, Nobuhiko; Arai, Shigehisa
2011-01-31
We fabricated a novel lateral-current-injection-type distributed feedback (DFB) laser with amorphous-Si (a-Si) surface grating as a step to realize membrane lasers. This laser consists of a thin GaInAsP core layer grown on a semi-insulating InP substrate and a 30-nm-thick a-Si surface layer for DFB grating. Under a room-temperature continuous-wave condition, a low threshold current of 7.0 mA and high efficiency of 43% from the front facet were obtained for a 2.0-μm stripe width and 300-μm cavity length. A small-signal modulation bandwidth of 4.8 GHz was obtained at a bias current of 30 mA.
Long-Term ENSO Variation Over the Last 20,000 Years From the Peru Continental Margin
NASA Astrophysics Data System (ADS)
Skilbeck, G.; Fink, D.; Gagan, M.; Rein, B.
2006-12-01
Three ODP Leg 201 cores from the Peru continental margin comprise highly laminated diatomaceous ooze spanning Last Glacial Maximum to present. Geochemical proxy data, layer counting and spectral analysis of red color variation suggest the layers represent interannual accumulation under the influence tropical ENSO conditions, with darker layers representing El Niño events. AMS 14-C dating (Skilbeck &Fink, 2006) of bulk sediment from Sites 201-1228 and -1229 (~11°S) and comparison with Rein et al. (2005) Core SO147-106KL (~12°S) show that where the shelf is narrow south of ~10.5°S, regionally consistent rates of sediment accumulation have occurred over the late Deglaciation and Holocene, with high rates characterising the late (0-2.0 kyrBP, ~100 cm/ka) and the early (8.5-10 kyrBP, ~80 cm/ka) Holocene. Over these intervals laminae are of interannual resolution. Further north where the shelf is broader, Holocene-Late Deglaciation sediments are thin or absent, but the Early Deglaciation is well represented. In a core from ODP Site 201-1227 (~9°S, 427m water depth), the period 15.5-17.5 kyrBP is characterised by sediment accumulation rates in excess of 300 cm/ka, and interannual laminations are again present. Spectral analysis of the instrumental record of ENSO, the SOI, shows a relative stable mode of variation with an average frequency of about 5.5 yr for the past 130 years. Analysis of our ODP cores shows that the ENSO mode appears to be relatively stable for periods of 300-500 years throughout the Holocene with frequencies varying mostly between 5 and 8 years and relatively sudden mode switches, suggesting inter alia that the instrumental record is not long enough to test predictive models of ENSO variation. Throughout the Holocene, this pattern of variation transcends the sedimentation-rate zones identified above, with the inference that changes in the rate of sedimentation have not influenced the temporal pattern. The later part of the deglaciation period (10
NASA Astrophysics Data System (ADS)
Xu, J.
2013-12-01
The Indonesian Throughflow (ITF) links upper ocean waters of the west Pacific and Indian Ocean, modulates heat and fresh water budgets between these oceans and in turn plays an important role in global climate change. It was suggested that East Asian monsoon and El Niño-Southern Oscillation (ENSO) exert a strong influence on flux, water properties and vertical stratification of the modern ITF. Possible link of the ITF to ENSO is also supported by significant linear correlation (R2=0.43) between thermocline temperature (TT) of the ITF outflow and NINO3.4 index over the past 50 years. In this work, seawater temperatures and salinity and vertical thermal structure of the ITF outflow since the last glacial were reconstructed from Core SO18462 that was retrieved from exit of the ITF to the Timor Sea (TS) (Holbourn et al., 2011). The records of Core SO18462 were then compared with records of Core 3cBX that were considered to reveal ENSO-like conditions in the center of the western Pacific warm pool (WPWP) (Sagawa et al., 2012). The results show that surface waters were comparable in the TS and the WPWP prior to ~16ka, and then diverged with much freshening in the TS. On the contrary, thermocline waters were largely diverged, warmer and more saline in the TS than in the WPWP, and then started to converge from ~16ka. Sea surface temperature (SST) remained over 28°C (the temperature defining range of modern WPWP) in both of the regions during 11.5-6ka. SST then slightly decreased below 28°C in the TS when it kept all the way above 28°C in the WPWP towards the late Holocene. In contrast, TT and thermocline depth remained overall unchanged in the WPWP, concurring with decreasing of TT and shoaling of thermocline in the TS during 11.5-6ka. After 6ka, thermocline continued shoaling in the TS, when TT remained decreasing and thermocline salinity approached to be similar in both of the regions. Comparison of TS and WPWP records conspicuously disclose two categories of
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
A forward bias method for lag correction of an a-Si flat panel detector
DOE Office of Scientific and Technical Information (OSTI.GOV)
Starman, Jared; Tognina, Carlo; Partain, Larry
2012-01-15
Purpose: Digital a-Si flat panel (FP) x-ray detectors can exhibit detector lag, or residual signal, of several percent that can cause ghosting in projection images or severe shading artifacts, known as the radar artifact, in cone-beam computed tomography (CBCT) reconstructions. A major contributor to detector lag is believed to be defect states, or traps, in the a-Si layer of the FP. Software methods to characterize and correct for the detector lag exist, but they may make assumptions such as system linearity and time invariance, which may not be true. The purpose of this work is to investigate a new hardwaremore » based method to reduce lag in an a-Si FP and to evaluate its effectiveness at removing shading artifacts in CBCT reconstructions. The feasibility of a novel, partially hardware based solution is also examined. Methods: The proposed hardware solution for lag reduction requires only a minor change to the FP. For pulsed irradiation, the proposed method inserts a new operation step between the readout and data collection stages. During this new stage the photodiode is operated in a forward bias mode, which fills the defect states with charge. A Varian 4030CB panel was modified to allow for operation in the forward bias mode. The contrast of residual lag ghosts was measured for lag frames 2 and 100 after irradiation ceased for standard and forward bias modes. Detector step response, lag, SNR, modulation transfer function (MTF), and detective quantum efficiency (DQE) measurements were made with standard and forward bias firmware. CBCT data of pelvic and head phantoms were also collected. Results: Overall, the 2nd and 100th detector lag frame residual signals were reduced 70%-88% using the new method. SNR, MTF, and DQE measurements show a small decrease in collected signal and a small increase in noise. The forward bias hardware successfully reduced the radar artifact in the CBCT reconstruction of the pelvic and head phantoms by 48%-81%. Conclusions: Overall
NASA Astrophysics Data System (ADS)
Wilhelmsen, Hallgeir; Ladstädter, Florian; Scherllin-Pirscher, Barbara; Steiner, Andrea K.
2018-03-01
We provide atmospheric temperature variability indices for the tropical troposphere and stratosphere based on global navigation satellite system (GNSS) radio occultation (RO) temperature measurements. By exploiting the high vertical resolution and the uniform distribution of the GNSS RO temperature soundings we introduce two approaches, both based on an empirical orthogonal function (EOF) analysis. The first method utilizes the whole vertical and horizontal RO temperature field from 30° S to 30° N and from 2 to 35 km altitude. The resulting indices, the leading principal components, resemble the well-known patterns of the Quasi-Biennial Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO) in the tropics. They provide some information on the vertical structure; however, they are not vertically resolved. The second method applies the EOF analysis on each altitude level separately and the resulting indices contain information on the horizontal variability at each densely available altitude level. They capture more variability than the indices from the first method and present a mixture of all variability modes contributing at the respective altitude level, including the QBO and ENSO. Compared to commonly used variability indices from QBO winds or ENSO sea surface temperature, these new indices cover the vertical details of the atmospheric variability. Using them as proxies for temperature variability is also of advantage because there is no further need to account for response time lags. Atmospheric variability indices as novel products from RO are expected to be of great benefit for studies on atmospheric dynamics and variability, for climate trend analysis, as well as for climate model evaluation.
NASA Astrophysics Data System (ADS)
Kalimeris, Anastasios; Ranieri, Ezio; Founda, Dimitra; Norrant, Caroline
2017-12-01
This study analyses a century-long set of precipitation time series in the Central Mediterranean (encompassing the Greek Ionian and the Italian Puglia regions) and investigates the statistically significant modes of the interannual precipitation variability using efficient methods of spectral decomposition. The statistical relations and the possible physical couplings between the detected modes and the global or hemispheric patterns of climatic variability (the El Niño Southern Oscillation or ENSO, the North Atlantic Oscillation or NAO, the East Atlantic or EA, the Scandinavian or SCAND, and others) were examined in the time-frequency domain and low-order synchronization events were sought. Significant modes of precipitation variability were detected in the Taranto Gulf and the southern part of the Greek Ionian region at the sub-decadal scales (mostly driven by the SCAND pattern) and particularly at the decadal and quasi-decadal scales, where strong relations found with the ENSO activity (under complex implications of EA and NAO) prior to the 1930s or after the early-1970s. The precipitation variations in the Adriatic stations of Puglia are dominated by significant bi-decadal modes which found to be coherent with the ENSO activity and also weakly related with the Atlantic Ocean sea surface temperature intrinsic variability. Additionally, important discontinuities characterize the evolution of precipitation in certain stations of the Taranto Gulf and the Greek Ionian region during the early-1960s and particularly during the early-1970s, followed by significant reductions in the mean annual precipitation. These discontinuities seem to be associated with regional effects of NAO and SCAND, probably combined with the impact of the 1970s climatic shift in the Pacific and the ENSO variability.
NASA Astrophysics Data System (ADS)
Li, Xin; Babovic, Vladan
2016-04-01
Flood and drought are hydrologic extreme events that have significant impact on human and natural systems. Characterization of flood and drought in terms of their start, duration and strength, and investigation of the impact of natural climate variability (i.e., ENSO) and anthropogenic climate change on them can help decision makers to facilitate adaptions to mitigate potential enormous economic costs. To date, numerous studies in this area have been conducted, however, they are primarily focused on extra-tropical regions. Therefore, this study presented a detailed framework to characterize flood and drought events in a tropical urban city-state (i.e., Singapore), based on daily data from 26 precipitation stations. Flood and drought events are extracted from standardized precipitation anomalies from monthly to seasonal time scales. Frequency, duration and magnitude of flood and drought at all the stations are analyzed based on crossing theory. In addition, spatial variation of flood and drought characteristics in Singapore is investigated using ordinary kriging method. Lastly, the impact of ENSO condition on flood and drought characteristics is analyzed using regional regression method. The results show that Singapore can be prone to extreme flood and drought events at both monthly and seasonal time scales. ENSO has significant influence on flood and drought characteristics in Singapore, but mainly during the South West Monsoon season. During the El Niño phase, drought can become more extreme. The results have implications for water management practices in Singapore.
Anderson, Lesleigh
2012-01-01
Over the period of instrumental records, precipitation maximum in the headwaters of the Colorado Rocky Mountains has been dominated by winter snow, with a substantial degree of interannual variability linked to Pacific ocean–atmosphere dynamics. High-elevation snowpack is an important water storage that is carefully observed in order to meet increasing water demands in the greater semi-arid region. The purpose here is to consider Rocky Mountain water trends during the Holocene when known changes in earth's energy balance were caused by precession-driven insolation variability. Changes in solar insolation are thought to have influenced the variability and intensity of the El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and North American Monsoon and the seasonal precipitation balance between rain and snow at upper elevations. Holocene records are presented from two high elevation lakes located in northwest Colorado that document decade-to-century scale precipitation seasonality for the past ~ 7000 years. Comparisons with sub-tropical records of ENSO indicate that the snowfall-dominated precipitation maxima developed ~ 3000 and 4000 years ago, coincident with evidence for enhanced ENSO/PDO dynamics. During the early-to-mid Holocene the records suggest a more monsoon affected precipitation regime with reduced snowpack, more rainfall, and net moisture deficits that were more severe than recent droughts. The Holocene perspective of precipitation indicates a far broader range of variability than that of the past century and highlights the non-linear character of hydroclimate in the U.S. west.
DOT National Transportation Integrated Search
1996-08-01
THIS DOCUMENT, STATEWIDE ITS AS-IS AGENCY REPORTS FOR MINNESOTA, CONSISTS OF A COLLECTION OF INDIVIDUAL SYSTEM SURVEY REPORTS RELATED TO TRANSPORTATION SYSTEMS. THE POLARIS PROJECT WILL USE THE SURVEY INFORMATION COLLECTED TO DERIVE THE EXISTING ARCH...
NASA Astrophysics Data System (ADS)
Beaufort, Luc; Grelaud, Michaël
2017-12-01
The El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) account for a large part of modern climate variability. Over the last decades, understanding of these modes of climate variability has increased but prediction in the context of global warming has proven difficult because of the lack of pertinent and reproducible paleodata. Here, we infer the dynamics of these oscillations from fossil assemblage and calcification state of coccolithophore in the Californian margin because El Niño has a strong impact on phytoplankton ecology and PDO on the upwelling intensity and hence on the ocean chemistry. Intense Californian upwelling brings water rich in CO2 and poor in carbonate ions and coccolithophores secrete lower calcified coccoliths. Seasonally laminated sediments of the Santa Barbara Basin are used to document ENSO variability and PDO index for the last 2700 years at a temporal resolution of 3 years. The records present the same characteristics as other PDO or ENSO records from the same area spanning the last centuries. We are therefore confident on the value produced here for the last 2.7 millennia. The records show important centennial variability that is equivalent to solar cycles.
NASA Astrophysics Data System (ADS)
Stiegler, Christian; Meijide, Ana; June, Tania; Knohl, Alexander
2017-04-01
The 2015-2016 El Niño-Southern Oscillation (ENSO) event was one of the strongest observed in the last 20 years. Oil palm plantations cover a large fraction of tropical lowlands in Southeast Asia but despite their growing areal extent, measurements and observations of greenhouse gas exchange and surface energy balance are still scarce. In addition, the effects of extreme events such as ENSO on carbon sequestration and the partitioning of surface energy balance components are widely unknown. In this study, we use micrometeorological measurements located in commercial oil palm plantations in the Jambi province (Sumatra, Indonesia) to assess the impact of the 2015-2016 ENSO event and severe forest fires on greenhouse gas exchange and surface energy budget. Continuous measurements are in operation since July 2013 and we assess turbulent fluxes of carbon dioxide (CO2), water vapour and sensible heat using the eddy covariance technique before, during and after the 2015-2016 ENSO event. In the beginning of the ENSO event, the area experienced a strong drought with decreasing soil moisture, increasing air and surface temperatures, and strong atmospheric vapour pressure deficit. During the peak of the drought from August to October 2015, hundreds of forest fires in the area resulted in strong smoke production, decreasing incoming solar radiation by 35% compared to pre-ENSO values and diffuse radiation became almost the sole shortwave radiation flux. During the beginning of the drought, carbon uptake of the oil palm plantation was around 2.1 gC m-2 d-1 and initially increased by 50% due to clear-sky conditions and high incoming photosynthetically active radiation (PAR) but increasing density of smoke turned the oil palm plantation into a source of carbon. The turbulent heat fluxes experienced an increase in sensible heat fluxes due to drought conditions at the cost of latent heat fluxes resulting in an increase in the midday Bowen-ratio from 0.17 to 0.40. Strong smoke
NASA Astrophysics Data System (ADS)
Chen, Zhiping; Luo, Jia
2017-04-01
The specific humidity and the temperature response of El Niño-Southern Oscillation in the troposphere and lower stratosphere (TLS) over different areas i.e., Niño 3.4 (N3.4); -5˚ S-5˚ N, 180˚ W-180˚ E (G5); -30˚ S-30˚ N, 180˚ W-180˚ E (G30); -60˚ S-60˚ N, 180˚ W-180˚ E (G60); -90˚ S-90˚ N, 180˚ W-180˚ E (G90) were investigated using Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Positioning System (GPS) radio occultation (RO) data from June 2006 to June 2014. The empirical orthogonal functions (EOFs) and band-pass filtering with different filtering ranges at different altitudes were used to extract the ENSO-related signals of the specific humidity and the temperature over different altitude levels in the TLS. The time series that has the maximum correlation coefficient between the ENSO-related signals and the ONI were regarded as the strongest response to ENSO. The results confirmed that the ENSO was originated from tropical Pacific Ocean. The lag time and the phase of the maximum specific humidity or temperature response to ENSO event does not show a uniform patern at different altitudes in the troposphere over different areas, but the 1-2 seasons lag ONI was found and consistent with previous study results. The maximum correlation coefficient between the specific humidity and the ONI was about 0.94 at a lag time of 3 months at about 225 hpa altitude over the statistical areas while the maximum correlation coefficients (0.91) between the temperature and the ONI was found at ˜325 hpa altitude level at a lag time of 1 month in the TLS. The well agreement between the ENSO-related signals in the troposphere and the ONI indicates that the specific humidity and temperature derived from COSMIC GPS RO observations are significant for monitoring the ENSO events.
NASA Astrophysics Data System (ADS)
Liu, Zhiyong; Zhang, Xin; Fang, Ruihong
2018-02-01
Understanding the potential connections between climate indices such as the El Niño-Southern Oscillation (ENSO) and Arctic Oscillation (AO) and drought variability will be beneficial for making reasonable predictions or assumptions about future regional droughts, and provide valuable information to improve water resources planning and design for specific regions of interest. This study is to examine the multi-scale relationships between winter drought variability over Shaanxi (North China) and both ENSO and AO during the period 1960-2009. To accomplish this, we first estimated winter dryness/wetness conditions over Shaanxi based on the self-calibrating Palmer drought severity index (PDSI). Then, we identified the spatiotemporal variability of winter dryness/wetness conditions in the study area by using the empirical orthogonal function (EOF). Two primary sub-regions of winter dryness/wetness conditions across Shaanxi were identified. We further examined the periodical oscillations of dryness/wetness conditions and the multi-scale relationships between dryness/wetness conditions and both ENSO and AO in winter using wavelet analysis. The results indicate that there are inverse multi-scale relations between winter dryness/wetness conditions and ENSO (according to the wavelet coherence) for most of the study area. Moreover, positive multi-scale relations between winter dryness/wetness conditions and AO are mainly observed. The results could be beneficial for making reasonable predictions or assumptions about future regional droughts and provide valuable information to improve water resources planning and design within this study area. In addition to the current study area, this study may also offer a useful reference for other regions worldwide with similar climate conditions.
ENSO modulation of tropical Indian Ocean subseasonal variability
NASA Astrophysics Data System (ADS)
Jung, Eunsil; Kirtman, Ben P.
2016-12-01
In this study, we use 30 years of retrospective climate model forecasts and observational estimates to show that El Niño/Southern Oscillation (ENSO) affects the amplitude of subseasonal variability of sea surface temperature (SST) in the southwest Indian Ocean, an important Tropical Intraseasonal Oscillation (TISO) onset region. The analysis shows that deeper background mixed-layer depths and warmer upper ocean conditions during El Niño reduce the amplitude of the subseasonal SST variability over Seychelles-Chagos Thermocline Ridge (SCTR), which may reduce SST-wind coupling and the amplitude of TISO variability. The opposite holds for La Niña where the shallower mixed-layer depth enhances SST variability over SCTR, which may increase SST-wind coupling and the amplitude of TISO variability.
ENSO-driven climate variability promotes periodic major outbreaks of dengue in Venezuela.
Vincenti-Gonzalez, M F; Tami, A; Lizarazo, E F; Grillet, M E
2018-04-10
Dengue is a mosquito-borne viral disease of global impact. In Venezuela, dengue has emerged as one of the most important public health problems of urban areas with frequent epidemics since 2001. The long-term pattern of this disease has involved not only a general upward trend in cases but also a dramatic increase in the size and frequency of epidemic outbreaks. By assuming that climate variability has a relevant influence on these changes in time, we quantified the periodicity of dengue incidence in time-series of data from two northern regions of Venezuela. Disease cycles of 1 and 3-4 years (p < 0.05) were detected. We determined that dengue cycles corresponded with local climate and the El Niño Southern Oscillation (ENSO) variation at both seasonal and inter-annual scales (every 2-3 years). Dengue incidence peaks were more prevalent during the warmer and dryer years of El Niño confirming that ENSO is a regional climatic driver of such long-term periodicity through local changes in temperature and rainfall. Our findings support the evidence of the effect of climate on dengue dynamics and advocate the incorporation of climate information in the surveillance and prediction of this arboviral disease in Venezuela.
A New Technique to Observe ENSO Activity via Ground-Based GPS Receivers
NASA Astrophysics Data System (ADS)
Suparta, Wayan; Iskandar, Ahmad; Singh, Mandeep Singh Jit
In an attempt to study the effects of global climate change in the tropics for improving global climate model, this paper aims to detect the ENSO events, especially El Nino phase by using ground-based GPS receivers. Precipitable water vapor (PWV) obtained from the Global Positioning System (GPS) Meteorology measurements in line with the sea surface temperature anomaly (SSTa) are used to connect their response to El Niño activity. The data gathered from four selected stations over the Southeast Asia, namely PIMO (Philippines), KUAL (Malaysia), NTUS (Singapore) and BAKO (Indonesia) for the year of 2009/2010 were processed. A strong correlation was observed for PIMO station with a correlation coefficient of -0.90, significantly at the 99 % confidence level. In general, the relationship between GPS PWV and SSTa at all stations on a weekly basis showed with a negative correlation. The negative correlation indicates that during the El Niño event, the PWV variation was in decreased trend. Decreased trend of PWV value is caused by a dry season that affected the GPS signals in the ocean-atmospheric coupling. Based on these promising results, we can propose that the ground-based GPS receiver is capable used to monitor ENSO activity and this is a new prospective method that previously unexplored.
ENSO variability of Quelccaya Ice Cap δ18O driven by monsoon control of vapor isotope ratios
NASA Astrophysics Data System (ADS)
Hurley, J. V.; Vuille, M. F.; Hardy, D. R.
2016-12-01
The δ18O from the Quelccaya Ice Cap (QIC), Peru corresponds with and has been used to reconstruct Nino region SSTs but the physical mechanisms that tie ENSO-variable equatorial Pacific SSTs to snow δ18O at 5680 m in the Andes have not been fully described. We use a proxy system forward model to simulate and explore ENSO variable snow δ18O at the QIC, which is observed and accurately simulated with our model to be respectively higher and lower than average during El Nino and La Nina. We then explore the relative roles of ENSO-forcing on components of the forward model: the seasonality of snowfall at the QIC, vapor initial δ18O values, and temperature. The local hydrologic cycle is characterized by earlier onset and reduced duration of peak snowfall during El Nino, and more snow accumulation during La Nina. When we isolate the influence of the local hydrologic cycle in the forward model, El Nino and La Nina snowfall seasonalities yield respectively higher and lower snow δ18O values, compared with the control simulation. The South American summer monsoon (SASM) is characterized by enhanced convection over the Amazon during La Nina and as a consequence, lower vapor δ18O values over the western Amazon Basin. When we isolate the influence of the vapor initial delta-value in the forward model, higher initial delta-values during El Nino yield higher snow δ18O at the QIC. The seasonality of temeratures over the western Amazon Basin and near Quelccaya is amplified during El Nino when there are higher and lower temperatures respectively during austral summer and winter. When we isolate the temperature influence in the forward model, the warmer summer El Nino conditions require a more humid initial vapor and result in lower snow δ18O values. Most (more than two-thirds) of the ENSO variability in QIC δ18O can be accounted for by SASM activity and its influence on the vapor initial delta-value.
aSi EPIDs for the in-vivo dosimetry of static and dynamic beams
NASA Astrophysics Data System (ADS)
Piermattei, A.; Cilla, S.; Azario, L.; Greco, F.; Russo, M.; Grusio, M.; Orlandini, L.; Fidanzio, A.
2015-10-01
Portal imaging by amorphous silicon (aSi) photodiode is currently the most applied technology for in-vivo dosimetry (IVD) of static and dynamic radiotherapy beams. The strategy, adopted in this work to perform the IVD procedure by aSi EPID, is based on: in patient reconstruction of the isocenter dose and day to day comparison between 2D-portal images to verify the reproducibility of treatment delivery. About 20.000 tests have been carried out in this last 3 years in 8 radiotherapy centers using the SOFTDISO program. The IVD results show that: (i) the procedure can be implemented for linacs of different manufacturer, (ii) the IVD analysis can be obtained on a computer screen, in quasi real time (about 2 min after the treatment delivery) and (iii) once the causes of the discrepancies were eliminated, all the global IVD tests for single patient were within the acceptance criteria defined by: ±5% for the isocenter dose, and Pγ<1≥90% of the checked points for the 2D portal image γ-analysis. This work is the result of a project supported by the Istituto Nazionale di Fisica Nucleare (INFN) and Università Cattolica del S.Cuore (UCSC).
Zonally resolved impact of ENSO on the stratospheric circulation and water vapor entry values
NASA Astrophysics Data System (ADS)
Konopka, Paul; Ploeger, Felix; Tao, Mengchu; Riese, Martin
2016-10-01
Based on simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the period 1979-2013, with model transport driven by the ECMWF ERA-Interim reanalysis, we discuss the impact of the El Niño Southern Oscillation (ENSO) on the variability of the dynamics, water vapor, ozone, and mean age of air (AoA) in the tropical lower stratosphere during boreal winter. Our zonally resolved analysis at the 390 K potential temperature level reveals that not only (deseasonalized) ENSO-related temperature anomalies are confined to the tropical Pacific (180-300°E) but also anomalous wave propagation and breaking, as quantified in terms of the Eliassen-Palm (EP) flux divergence, with strongest local contribution during the La Niña phase. This anomaly is coherent with respective anomalies of water vapor (±0.5 ppmv) and ozone (±100 ppbv) derived from CLaMS being in excellent agreement with the Aura Microwave Limb Sounder observations. Thus, during El Niño a more zonally symmetric wave forcing drives a deep branch of the Brewer-Dobson (BD) circulation. During La Niña this forcing increases at lower levels (≈390 K) over the tropical Pacific, likely influencing the shallow branch of the BD circulation. In agreement with previous studies, wet (dry) and young (old) tape recorder anomalies propagate upward in the subsequent months following El Niño (La Niña). Using CLaMS, these anomalies are found to be around +0.3 (-0.2) ppmv and -4 (+4) months for water vapor and AoA, respectively. The AoA ENSO anomaly is more strongly affected by the residual circulation (≈2/3) than by eddy mixing (≈1/3).
Evolution of Tropical and Extratropical Precipitation Anomalies During the 1997 to 1999 ENSO Cycle
NASA Technical Reports Server (NTRS)
Curtis, Scott; Adler, Robert; Huffman, George; Nelkin, Eric; Bolvin, David; Einaudi, Franco (Technical Monitor)
2000-01-01
The 1997-1999 ENSO period was very powerful, but also well observed. Multiple satellite rainfall estimates combined with gauge observations allow for a quantitative analysis of precipitation anomalies in the tropics and elsewhere accompanying the 1997-99 ENSO cycle. An examination of the evolution of the El Nino and accompanying precipitation anomalies revealed that a dry Maritime Continent preceded the formation of positive SST anomalies in the eastern Pacific Ocean. 30-60 day oscillations in the winter of 1996/97 may have contributed to this lag relationship. Furthermore, westerly wind burst events may have maintained the drought over the Maritime Continent. The warming of the equatorial Pacific was then followed by an increase in convection. A rapid transition from El Nino to La Nina occurred in May 1998, but as early as October-November 1997 precipitation indices captured substantial changes in Pacific rainfall anomalies. The global precipitation patterns for this event were in good agreement with the strong consistent ENSO-related precipitation signals identified in earlier studies. Differences included a shift in precipitation anomalies over Africa during the 1997-98 El Nino and unusually wet conditions over northeast Australia during the later stages of the El Nino. Also, the typically wet region in the north tropical Pacific was mostly dry during the 1998-99 La Nina. Reanalysis precipitation was compared to observations during this time period and substantial differences were noted. In particular, the model had a bias towards positive precipitation anomalies and the magnitudes of the anomalies in the equatorial Pacific were small compared to the observations. Also, the evolution of the precipitation field, including the drying of the Maritime Continent and eastward progression of rainfall in the equatorial Pacific was less pronounced for the model compared to the observations.
NASA Astrophysics Data System (ADS)
Smittenberg, R. H.; Sachs, J. P.; Dawson, M. N.
2004-12-01
There is still much uncertainty whether the El Niño Southern Oscillation (ENSO) will become stronger or more frequent in a warming global climate. A principal reason for this uncertainty stems from a glaring lack of paleoclimate data in the equatorial Pacific, which hampers model validation. To partly resolve this data deficiency, sediments of three marine anoxic lakes were cored in Palau, an island group that lies in the heart of the West Pacific Warm Pool. The lakes contain seawater that seeps through fissures in the surrounding karst, and they are permanently stratified due to fresh water input provided by the year-round wet climate (map 1970-2000 = 3.7m). During ENSO events, however, the islands suffer from drought. The surface water hydrogen isotopic compositions in the lakes are sensitive to the relative proportions of D-depleted rainwater and D-enriched seawater, and are therefore sensitive to ENSO events. The lake surface water H/D values are recorded by algal and bacterial biomarkers that are preserved well in the highly organic and anoxic sediments, which accumulate relatively fast (mean 1 mm/yr). Ongoing down core measurement will eventually result in a precipitation proxy record of the islands. To obtain endmember D/H values, a comprehensive set of water samples from sea, lakes and rain water was obtained, as well as suspended particulate matter. Higher plant biomarker D/H values derived from the jungle vegetation surrounding the lakes may render supporting climatic proxy data, being influenced by evapotranspiration. Some lakes are inhabited by millions of jellyfish (Mastigias) that live in symbiosis with zooxanthellae. The jellyfish of one of the investigated lakes disappeared completely after the last large ENSO event in 1998 (returning in 2000-01), and a correlation is suggested. To reconstruct the history of jellyfish occurrence, jellyfish and sedimentary lipids were extracted and compared. In addition to a possible ENSO proxy record, this
Sheikh, Adnan
2016-01-01
Objective: The aim of this study was to evaluate the impact of adaptive statistical iterative reconstruction (ASiR) technique on the image quality and radiation dose reduction. The comparison was made with the traditional filtered back projection (FBP) technique. Methods: We retrospectively reviewed 78 patients, who underwent cervical spine CT for blunt cervical trauma between 1 June 2010 and 30 November 2010. 48 patients were imaged using traditional FBP technique and the remaining 30 patients were imaged using the ASiR technique. The patient demographics, radiation dose, objective image signal and noise were recorded; while subjective noise, sharpness, diagnostic acceptability and artefacts were graded by two radiologists blinded to the techniques. Results: We found that the ASiR technique was able to reduce the volume CT dose index, dose–length product and effective dose by 36%, 36.5% and 36.5%, respectively, compared with the FBP technique. There was no significant difference in the image noise (p = 0.39), signal (p = 0.82) and signal-to-noise ratio (p = 0.56) between the groups. The subjective image quality was minimally better in the ASiR group but not statistically significant. There was excellent interobserver agreement on the subjective image quality and diagnostic acceptability for both groups. Conclusion: The use of ASiR technique allowed approximately 36% radiation dose reduction in the evaluation of cervical spine without degrading the image quality. Advances in knowledge: The present study highlights that the ASiR technique is extremely helpful in reducing the patient radiation exposure while maintaining the image quality. It is highly recommended to utilize this novel technique in CT imaging of different body regions. PMID:26882825
Patro, Satya N; Chakraborty, Santanu; Sheikh, Adnan
2016-01-01
The aim of this study was to evaluate the impact of adaptive statistical iterative reconstruction (ASiR) technique on the image quality and radiation dose reduction. The comparison was made with the traditional filtered back projection (FBP) technique. We retrospectively reviewed 78 patients, who underwent cervical spine CT for blunt cervical trauma between 1 June 2010 and 30 November 2010. 48 patients were imaged using traditional FBP technique and the remaining 30 patients were imaged using the ASiR technique. The patient demographics, radiation dose, objective image signal and noise were recorded; while subjective noise, sharpness, diagnostic acceptability and artefacts were graded by two radiologists blinded to the techniques. We found that the ASiR technique was able to reduce the volume CT dose index, dose-length product and effective dose by 36%, 36.5% and 36.5%, respectively, compared with the FBP technique. There was no significant difference in the image noise (p = 0.39), signal (p = 0.82) and signal-to-noise ratio (p = 0.56) between the groups. The subjective image quality was minimally better in the ASiR group but not statistically significant. There was excellent interobserver agreement on the subjective image quality and diagnostic acceptability for both groups. The use of ASiR technique allowed approximately 36% radiation dose reduction in the evaluation of cervical spine without degrading the image quality. The present study highlights that the ASiR technique is extremely helpful in reducing the patient radiation exposure while maintaining the image quality. It is highly recommended to utilize this novel technique in CT imaging of different body regions.
Contrasting ENSO types with novel satellite derived ocean phytoplankton biomass
NASA Astrophysics Data System (ADS)
Sharma, P.; Singh, A. M.; Marinov, I.; Kostadinov, T. S.
2016-12-01
Observed variations in community structure and biogeochemical processes in the tropics and the North Atlantic have been linked, in the first order, to the El Niño Southern Oscillation phenomenon (e.g., Bates, 2001; Karl et al., 2001; Di Lorenzo et al., 2010; Di Lorenzo et al., 2013). Current significant technical advances have allowed for the retrieval of biological data from the optical properties of the water via satellite ocean color remote sensing, providing an opportunity for quantifying the relationships between biological and climate indices. Studies have focused in-depth on contrasting flavors of the ENSO types with various physical (e.g., Singh et al. 2011; Turk et al. 2011) and biological (e.g., Radenac et al. 2012) indices. Here, we analyze the impact of different ENSO types on biology via analysis of recently-derived backscattering-based biomass separated into size-groups (Kostadinov et al. 2010, 2016) over the 17-year (1997-2013). We further contrast the responses of biomass with those of chlorophyll (Chl) and particulate inorganic carbon (PIC). We analyze the complex spatial differences in both physical (SST, mixed layer depth, winds) and biological (Chl, total and size-partitioned biomass) variability across the Pacific warm pool and equatorial tongue via simple EOF, combined regression-EOF and Agglomerative Hierarchical Clustering (AHC) analysis. The interannual variability in the physical and biological fields show clear signatures of the Niño cold-tongue (NCT) and Niño warm pool (NWP). Possible mechanisms responsible for these signatures are discussed.
NASA Astrophysics Data System (ADS)
Singh, S.; Abebe, A.; Srivastava, P.; Chaubey, I.
2017-12-01
Evaluation of the influences of individual and coupled oceanic-atmospheric oscillations on streamflow at a regional scale in the United States is the focus of this study. The main climatic oscillations considered in this study are: El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and North Atlantic Oscillation (NAO). Unimpacted or minimally impacted by water management streamflow data from the Model Parameter Estimation Experiment (MOPEX) were used in this study. Two robust and novel non-parametric tests, namely, the rank based partial least square (PLS) and the Joint Rank Fit (JRFit) procedures were used to identify the individual and coupled effect of oscillations on streamflow across continental U.S. (CONUS), respectively. Moreover, the interactive effects of ENSO with decadal and multidecadal cycles were tested and quantified using the JRFit interaction test. The analysis of ENSO indicated higher streamflows during La Niña phase compared to the El Niño phase in Northwest, Northeast and the lower part of Ohio Valley while the opposite occurs for rest of the climatic regions in US. Two distinct climate regions (Northwest and Southeast) were identified from the PDO analysis where PDO negative phase results in increased streamflow than PDO positive phase. Consistent negative and positive correlated regions around the CONUS were identified for AMO and NAO, respectively. The interaction test of ENSO with decadal and multidecadal oscillations showed that El Niño is modulated by the negative phase of PDO and NAO, and the positive phase of AMO, respectively, in the Upper Midwest. However, La Niña is modulated by the positive phase of AMO and PDO in Ohio Valley and Northeast while in Southeast and the South it is modulated by AMO negative phase. Results of this study will assist water managers to understand the streamflow change patterns across the CONUS at decadal and multi-decadal time scales. The
McCann, L; Maguire, R; Miller, M; Kearney, N
2009-03-01
Chemotherapy forms a core component of treatment for the majority patients with cancer. Recent changes in cancer services mean patients frequently receive such treatment as outpatients and are often required to manage side effects at home without direct support from oncology health professionals. Information technology continues to develop to support patients in the community; this study evaluated the impact of a mobile phone-based advanced symptom management system (ASyMS) on chemotherapy related toxicity in patients with lung, breast or colorectal cancer. One hundred and twelve patients were randomized from seven clinical sites across the UK; 56 patients used the mobile phone to record their symptoms, sending their reports directly to the nurses at their clinical site; 56 control group patients received standard care. Health professionals were alerted about any severe or life-threatening symptoms through the development of a chemotherapy symptom risk model. Patients' perceptions of ASyMS were evaluated pre and post participation. Patients reported many benefits of using ASyMS including improved communication with health professionals, improvements in the management of their symptoms, and feeling reassured their symptoms were being monitored while at home. ASyMS has the potential to positively impact on the management of symptoms in patients receiving chemotherapy treatment.
NASA Astrophysics Data System (ADS)
Lübbecke, Joke; Glessmer, Mirjam
2017-04-01
An important learning outcome of a Master of Sciences program is to empower students to understand which information they need, how they can gain the required knowledge and skills, and how to apply those to solve a given scientific problem. In designing a class on the El-Nino-Southern-Oscillation (ENSO) for students in the Climate Physics program at Kiel University, Germany, we have implemented various active learning strategies to meet this goal. The course is guided by an overarching question, embedded in a short story: What would we need to know to successfully predict ENSO? The students identify desired learning outcomes and collaboratively construct a concept map which then serves as a structure for the 12 weeks of the course, where each individual topic is situated in the larger context of the students' own concept map. Each learning outcome of the course is therefore directly motivated by a need to know expressed by the students themselves. During each session, students are actively involved in the learning process. They work individually or in small groups, for example testing different index definitions, analyzing data sets, setting up simple numerical models and planning and constructing hands-on experiments to demonstrate physical processes involved in the formation of El Niño events. The instructor's role is to provide the necessary background information and guide the students where it is needed. Insights are shared between groups as students present their findings to each other and combine the information, for example by cooperatively constructing a world map displaying the impacts of ENSO or by exchanging experts on different ENSO oscillator theories between groups. Development of this course was supported by the PerLe Fonds for teaching innovations at Kiel University. A preliminary evaluation has been very positive with students in particular appreciating their active involvement in the class.
NASA Astrophysics Data System (ADS)
Hurst, D. F.; Davis, S. M.; Rosenlof, K. H.; Lambert, A.; Read, W. G.; Hall, E.; Jordan, A. F.
2017-12-01
Variations in tropical lower stratospheric water vapor are generally attributable to annual cycles in the Brewer-Dobson circulation and inter-annual phenomenon like the quasi-biennial oscillation (QBO) and the El Niño Southern Oscillation (ENSO). Extremes in tropical lower stratospheric water vapor (SWV) occur when these annual and inter-annual changes are constructively superimposed. The atypical progression of the 2015-16 QBO led to a strong and rapid cooling of the tropical lower stratosphere during 2016. From December 2015 to November 2016, monthly tropical mean (15°S-15°N) coldpoint temperature (CPT) anomalies decreased 3.2°C, from 1.1 to -2.1°C. Accordingly, monthly tropical mean SWV anomalies at 83 hPa dropped 1.9 ppm, from 0.85 to -1.05 ppm. This decline in SWV anomalies is equivalent to 40% of the long-term December average tropical abundance of SWV at 83 hPa. The 2016 decreases in tropical anomalies of both CPTs and SWV were not zonally uniform, with average Eastern Hemisphere reductions greater by 2°C and 0.9 ppm (50%), respectively. Since the QBO typically has a zonally uniform effect on tropical CPTs, this implies a zonally non-uniform mechanism like ENSO also influenced CPTs during 2016. The transition of ENSO from strong El Niño to weak La Niña conditions in 2016 would induce this zonal non-uniformity by shifting convective activity from the Eastern Pacific to the Western Pacific and Indian Ocean regions. Evidence indicates the simultaneous cooling of tropical CPTs by both the QBO and ENSO during 2016 rapidly dried the tropical lower stratosphere with anomalous strength, especially in the Eastern Hemisphere.
Comparative performance evaluation of a new a-Si EPID that exceeds quad high-definition resolution.
McConnell, Kristen A; Alexandrian, Ara; Papanikolaou, Niko; Stathakis, Sotiri
2018-01-01
Electronic portal imaging devices (EPIDs) are an integral part of the radiation oncology workflow for treatment setup verification. Several commercial EPID implementations are currently available, each with varying capabilities. To standardize performance evaluation, Task Group Report 58 (TG-58) and TG-142 outline specific image quality metrics to be measured. A LinaTech Image Viewing System (IVS), with the highest commercially available pixel matrix (2688x2688 pixels), was independently evaluated and compared to an Elekta iViewGT (1024x1024 pixels) and a Varian aSi-1000 (1024x768 pixels) using a PTW EPID QC Phantom. The IVS, iViewGT, and aSi-1000 were each used to acquire 20 images of the PTW QC Phantom. The QC phantom was placed on the couch and aligned at isocenter. The images were exported and analyzed using the epidSoft image quality assurance (QA) software. The reported metrics were signal linearity, isotropy of signal linearity, signal-tonoise ratio (SNR), low contrast resolution, and high-contrast resolution. These values were compared between the three EPID solutions. Computed metrics demonstrated comparable results between the EPID solutions with the IVS outperforming the aSi-1000 and iViewGT in the low and high-contrast resolution analysis. The performance of three commercial EPID solutions have been quantified, evaluated, and compared using results from the PTW QC Phantom. The IVS outperformed the other panels in low and high-contrast resolution, but to fully realize the benefits of the IVS, the selection of the monitor on which to view the high-resolution images is important to prevent down sampling and visual of resolution.
ENSO related sea surface salinity variability in the equatorial Pacific
NASA Astrophysics Data System (ADS)
Qu, T.
2016-12-01
Recently available satellite and Argo data have shown coherent, large-scale sea surface salinity (SSS) variability in the equatorial Pacific. Based on this variability, several SSS indices of El Nino have been introduced by previous studies. Combining results from an ocean general circulation model with available satellite and in-situ observations, this study investigates the SSS variability and its associated SSS indices in the equatorial Pacific. The ocean's role and in particular the vertical entrainment of subtropical waters in this variability are discussed, which suggests that the SSS variability in the equatorial Pacific may play some active role in ENSO evolution.
NASA Astrophysics Data System (ADS)
Huang, Wenyu; Chen, Ruyan; Yang, Zifan; Wang, Bin; Ma, Wenqian
2017-09-01
To examine the combined effects of the different spatial patterns of the Arctic Oscillation (AO)-related sea level pressure (SLP) anomalies and the El Niño-Southern Oscillation (ENSO)-related sea surface temperature (SST) anomalies on the wintertime surface temperature anomalies over East Asia, a nonlinear method based on self-organizing maps is employed. Investigation of identified regimes reveals that the AO can affect East Asian temperature anomalies when there are significant SLP anomalies over the Arctic Ocean and northern parts of Eurasian continent. Analogously, ENSO is found to affect East Asian temperature anomalies when significant SST anomalies are present over the tropical central Pacific. The regimes with the warmest and coldest temperature anomalies over East Asia are both associated with the negative phase of the AO. The ENSO-activated, Pacific-East Asian teleconnection pattern could affect the higher latitude continental regions when the impact of the AO is switched off. When the spatial patterns of the AO and ENSO have significant, but opposite, impacts on the coastal winds, no obvious temperature anomalies can be observed over south China. Further, the circulation state with nearly the same AO and Niño3 indices may drive rather different responses in surface temperature over East Asia. The well-known continuous weakening (recovery) of the East Asian winter monsoon that occurred around 1988 (2009) can be attributed to the transitions of the spatial patterns of the SLP anomalies over the Arctic Ocean and Eurasian continent, through their modulation on the occurrences of the Ural and central Siberian blocking events.
NASA Astrophysics Data System (ADS)
Ramu, Dandi A.; Chowdary, Jasti S.; Ramakrishna, S. S. V. S.; Kumar, O. S. R. U. B.
2018-04-01
Realistic simulation of large-scale circulation patterns associated with El Niño-Southern Oscillation (ENSO) is vital in coupled models in order to represent teleconnections to different regions of globe. The diversity in representing large-scale circulation patterns associated with ENSO-Indian summer monsoon (ISM) teleconnections in 23 Coupled Model Intercomparison Project Phase 5 (CMIP5) models is examined. CMIP5 models have been classified into three groups based on the correlation between Niño3.4 sea surface temperature (SST) index and ISM rainfall anomalies, models in group 1 (G1) overestimated El Niño-ISM teleconections and group 3 (G3) models underestimated it, whereas these teleconnections are better represented in group 2 (G2) models. Results show that in G1 models, El Niño-induced Tropical Indian Ocean (TIO) SST anomalies are not well represented. Anomalous low-level anticyclonic circulation anomalies over the southeastern TIO and western subtropical northwest Pacific (WSNP) cyclonic circulation are shifted too far west to 60° E and 120° E, respectively. This bias in circulation patterns implies dry wind advection from extratropics/midlatitudes to Indian subcontinent. In addition to this, large-scale upper level convergence together with lower level divergence over ISM region corresponding to El Niño are stronger in G1 models than in observations. Thus, unrealistic shift in low-level circulation centers corroborated by upper level circulation changes are responsible for overestimation of ENSO-ISM teleconnections in G1 models. Warm Pacific SST anomalies associated with El Niño are shifted too far west in many G3 models unlike in the observations. Further large-scale circulation anomalies over the Pacific and ISM region are misrepresented during El Niño years in G3 models. Too strong upper-level convergence away from Indian subcontinent and too weak WSNP cyclonic circulation are prominent in most of G3 models in which ENSO-ISM teleconnections are
Maza-Villalobos, Susana; Poorter, Lourens; Martínez-Ramos, Miguel
2013-01-01
The effects of temporal variation of rainfall on secondary succession of tropical dry ecosystems are poorly understood. We studied effects of inter-seasonal and inter-year rainfall variation on the dynamics of regenerative successional communities of a tropical dry forest in Mexico. We emphasized the effects caused by the severe El Niño Southern Oscillation (ENSO) occurred in 2005. We established permanent plots in sites representing a chronosequence of Pasture (abandoned pastures, 0–1 years fallow age), Early (3–5), Intermediate (8–12), and Old-Growth Forest categories (n = 3 per category). In total, 8210 shrubs and trees 10 to 100-cm height were identified, measured, and monitored over four years. Rates of plant recruitment, growth and mortality, and gain and loss of species were quantified per season (dry vs. rainy), year, and successional category, considering whole communities and separating seedlings from sprouts and shrubs from trees. Community rates changed with rainfall variation without almost any effect of successional stage. Mortality and species loss rates peaked during the ENSO year and the following year; however, after two rainy years mortality peaked in the rainy season. Such changes could result from the severe drought in the ENSO year, and of the outbreak of biotic agents during the following rainy years. Growth, recruitment and species gain rates were higher in the rainy season but they were significantly reduced after the ENSO year. Seedlings exhibited higher recruitment and mortality rate than sprouts, and shrubs showed higher recruitment than trees. ENSO strongly impacted both the dynamics and trajectory of succession, creating transient fluctuations in the abundance and species richness of the communities. Overall, there was a net decline in plant and species density in most successional stages along the years. Therefore, strong drought events have critical consequences for regeneration dynamics, delaying the successional process
Relationships of the symmetric and asymmetric components of ENSO to US extreme precipitation
Lejiang Yu; Warren E. Heilman; Shiyuan Zhong; Xindi Bian
2017-01-01
We used 35-year (1979â2013) hourly rainfall data from theNorth American LandData Assimilation System (NLDAS-2) to examine the relationships of the symmetric and asymmetric components of two types of El Niño-Southern Oscillation (ENSO) (El Niño and ElNiño Modoki) episodes with occurrences of extreme precipitation events across the United States. During the cold season,...
Mechanisms of the global electric circuit and lightning variability on the ENSO time scale
NASA Astrophysics Data System (ADS)
Mareev, Evgeny; Volodin, Evgeny; Slyunyaev, Nikolay
2017-04-01
Many studies of lightning activity on the El Niño-Southern Oscillation (ENSO) time scale show increased activity over tropical land areas during the warm El Niño phase (e.g., Satori et al., 2009; Price, 2009). The mechanisms of this variability—particularly in terms of its role in the global electric circuit (GEC)—are still under debate (e.g., Williams and Mareev, 2014). In this study a general circulation model of the atmosphere and ocean INMCM4.0 (Institute of Numerical Mathematics Coupled Model) is used for modelling the GEC variability on the ENSO time scale. The ionospheric potential (IP) and the lightning flash rate are calculated to study regional peculiarities and possible mechanisms of lightning variation. The IP parameterisation is used (Mareev and Volodin, 2014) which takes into account quasi-stationary currents of electrified clouds (including thunderstorms) as principal contributors into the DC global circuit. The account of conductivity variation in the IP parameterisation is suggested based on the approach realised in (Slyunyaev et al., 2014). Comparison of simulation results with the observational data on lightning activity on the ENSO time scale is discussed. Numerical simulations suggest that the inter-annual IP variability is low and does not exceed 1% of the mean value, being tightly correlated with the mean sea surface temperature (SST) in the Pacific Ocean (180W-100W, 5S-5N—El Niño area). The IP maximum corresponds to the SST minimum. This result can be explained taking into account that during El Niño (positive temperature anomaly) precipitations in the equatorial part of the Pacific increase while in other tropic zones including the land areas they decrease. Comparison of simulation results with the observational data on lightning activity on the ENSO time scale is discussed. During the El Niño period in the model, the mean aerosol content in the atmosphere decrease, which is caused by the weakening of the winds over Sahara and
Subregional precipitation climate of the Caribbean and relationships with ENSO and NAO
NASA Astrophysics Data System (ADS)
Jury, Mark; Malmgren, BjöRn A.; Winter, Amos
2007-08-01
Thirty-five meteorological stations encompassing the Caribbean region (Cuba, Bahamas, Jamaica, Dominican Republic, Puerto Rico, US Virgin Islands, St. Maarten, and Barbados) were analyzed over the time interval 1951-1981 to assess regional precipitation patterns and their relationships with the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO). Application of factor analysis to these series revealed the existence of four geographically distinct precipitation regions, (C1) western Cuba and northwestern Bahamas, (C2) Jamaica, eastern Cuba, and southeastern Bahamas, (C3) Dominican Republic and northwestern Puerto Rico, and (C4) eastern Puerto Rico, US Virgin Islands, St. Maarten, and Barbados. This regionalization is related to different annual cycles and interannual fluctuations of rainfall. The annual cycle is more unimodal and largest in the northwest Caribbean (C1) and becomes increasingly bimodal toward lower latitudes (C4) as expected. Year-to-year variations of precipitation are compared with two well-known climatic indices. The ENSO relationship, represented by Niño 3.4 sea surface temperatures (SST), is positive and stable at all lags, but tends to reverse over the SE Caribbean (C4) in late summer. The NAO influence is weak and seasonally dependent. Early summer rainfall in the northwest Caribbean (C1) increases under El Niño conditions. Clusters 2 and 3 are less influenced by the global predictors and more regional in character.
Kearney, N; McCann, L; Norrie, J; Taylor, L; Gray, P; McGee-Lennon, M; Sage, M; Miller, M; Maguire, R
2009-04-01
To evaluate the impact of a mobile phone-based, remote monitoring, advanced symptom management system (ASyMS) on the incidence, severity and distress of six chemotherapy-related symptoms (nausea, vomiting, fatigue, mucositis, hand-foot syndrome and diarrhoea) in patients with lung, breast or colorectal cancer. A two group (intervention and control) by five time points (baseline, pre-cycle 2, pre-cycle 3, pre-cycle 4 and pre-cycle 5) randomised controlled trial. Seven clinical sites in the UK; five specialist cancer centres and two local district hospitals. One hundred and twelve people with breast, lung or colorectal cancer receiving outpatient chemotherapy. A mobile phone-based, remote monitoring, advanced symptom management system (ASyMS). Chemotherapy-related morbidity of six common chemotherapy-related symptoms (nausea, vomiting, fatigue, mucositis, hand-foot syndrome and diarrhoea). There were significantly higher reports of fatigue in the control group compared to the intervention group (odds ratio = 2.29, 95%CI = 1.04 to 5.05, P = 0.040) and reports of hand-foot syndrome were on average lower in the control group (odds ratio control/intervention = 0.39, 95%CI = 0.17 to 0.92, P = 0.031). The study demonstrates that ASyMS can support the management of symptoms in patients with lung, breast and colorectal cancer receiving chemotherapy.
NASA Astrophysics Data System (ADS)
Stiegler, C.; Meijide, A.; June, T.; Knohl, A.
2016-12-01
Oil palm plantations cover a large fraction of tropical lowlands in Southeast Asia. However, despite their growing areal extent, measurements and observations of greenhouse gas exchange and surface energy balance are still scarce. In addition, the effects of extreme events such as El Niño-Southern Oscillation (ENSO) on carbon sequestration and the partitioning of surface energy balance components are widely unknown. In this study, we use micrometeorological measurements located in commercial oil palm plantations in the Jambi province (Sumatra, Indonesia) to assess the impact of the 2015-2016 ENSO event on greenhouse gas exchange and surface energy budget. Measurements are in operation since July 2013 and we assess continuously turbulent fluxes of carbon dioxide (CO2), water vapour and sensible heat using the eddy covariance technique before, during and after the 2015-2016 ENSO event. The full surface energy budget is completed by measurements of radiative components, ground heat fluxes, and soil thermal and hydrological properties. The study is part of a large interdisciplinary project focussing on the ecological and socioeconomic functions of lowland rainforest transformation systems (EFForTS). During the ENSO event, the area experienced a strong drought with decreasing soil moisture and increasing air and surface temperatures. During the peak in September and October 2015, hundreds of fires in the area resulted in strong smoke production decreasing incoming solar radiation and increasing the diffuse fraction. Compared to regular years, the carbon uptake of the oil palm plantation decreased during the ENSO event. The turbulent heat fluxes experienced an increase in sensible heat fluxes due to drought conditions at the cost of latent heat fluxes resulting in an increase in the Bowen-ratio. Overall, the ENSO event resulted in a major anomaly of exchange processes between the oil palm plantation and the atmosphere.
NASA Astrophysics Data System (ADS)
Cai, Z.; Tian, L.; Bowen, G. J.
2017-12-01
Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.
Gershunov, A.; Barnett, T.P.; Cayan, D.R.; Tubbs, T.; Goddard, L.
2000-01-01
Three long-range forecasting methods have been evaluated for prediction and downscaling of seasonal and intraseasonal precipitation statistics in California. Full-statistical, hybrid-dynamical - statistical and full-dynamical approaches have been used to forecast El Nin??o - Southern Oscillation (ENSO) - related total precipitation, daily precipitation frequency, and average intensity anomalies during the January - March season. For El Nin??o winters, the hybrid approach emerges as the best performer, while La Nin??a forecasting skill is poor. The full-statistical forecasting method features reasonable forecasting skill for both La Nin??a and El Nin??o winters. The performance of the full-dynamical approach could not be evaluated as rigorously as that of the other two forecasting schemes. Although the full-dynamical forecasting approach is expected to outperform simpler forecasting schemes in the long run, evidence is presented to conclude that, at present, the full-dynamical forecasting approach is the least viable of the three, at least in California. The authors suggest that operational forecasting of any intraseasonal temperature, precipitation, or streamflow statistic derivable from the available records is possible now for ENSO-extreme years.
Teleconnections of ENSO and IOD to summer monsoon and rice production potential of India
NASA Astrophysics Data System (ADS)
Jha, Somnath; Sehgal, Vinay Kumar; Raghava, Ramesh; Sinha, Mourani
2016-12-01
Regional trend of summer monsoon precipitation has been analyzed for broad physical regions of India namely, (i) Indo-Gangetic plain, (ii) Central and East India, (iii) Coastal and Peninsular India and (iv) Western India. A significantly drying trend has been found in the two regions namely, Indo-Gangetic plain and Central and East India with comparative seasonal rate of drying higher in the latter region. A complex relation between the regional trend of summer monsoon precipitation, global teleconnection parameters and rice production of the regions have been studied. El Niño-Southern Oscillation (ENSO) and Indian Ocean dipole (IOD) have a significant role in the precipitation anomaly of Indo-Gangetic plain unlike Central and East India where the ENSO only plays role as global teleconnection parameter. Rice production of Central and East India has been found to be affected adversely during the El Nino years. Central and East India is found to be the worst affected region compared to the Indo-Gangetic plain with respect to its fragile rainfed rice production potential and strong adverse teleconnection of El Nino on the rice production in this zone.
The influence of ENSO on an oceanic eddy pair in the South China Sea
NASA Astrophysics Data System (ADS)
Chu, Xiaoqing; Dong, Changming; Qi, Yiquan
2017-03-01
An eddy pair off the Vietnam coast is one of the most important features of the summertime South China Sea circulation. Its variability is of interest due to its profound impact on regional climate, ecosystems, biological processes, and fisheries. This study examines the influence of the El Niño-Southern Oscillation (ENSO), a basin-scale climatic mode, on the interannual variability of this regional eddy pair using satellite observational data and historical hydrographic measurements. Over the last three decades, the eddy pair strengthened in 1994 and 2002, and weakened in 2006, 2007, and 2008. It was absent in 1988, 1995, 1998, and 2010, coinciding with strong El Nino-to-La Nina transitions. Composite analyses showed that the strong transition events of ENSO led to radical changes in the summer monsoon, through the forcing of a unique sea surface temperature anomaly structure over the tropical Indo-Pacific basin. With weaker zonal wind, a more northward wind direction, and the disappearance of a pair of positive and negative wind stress curls, the eastward current jet turns northward along the Vietnam coast and the eddy pair disappears.
Feelemyer, Jonathan P; Jarlais, Don C Des; Arasteh, Kamyar; Phillips, Benjamin W; Hagan, Holly
2014-01-01
Opioid substitution treatment (OST) can increase quality of life (WHOQOL-BREF) and reduce addiction severity index (ASI) scores among participants over time. OST program participants have noted that improvement in quality of life is one of the most important variables to their reduction in drug use. However, there is little systematic understanding of WHOQOL-BREF and ASI domain changes among OST participants in low and middle-income countries (LMIC). Utilizing PRISMA guidelines we conducted a systematic literature search to identify OST program studies documenting changes in WHOQOL-BREF or ASI domains for participants in buprenorphine or methadone programs in LMIC. Standardized mean differences for baseline and follow-up domain scores were compared along with relationships between domain scores, OST dosage, and length of follow-up. There were 13 OST program studies with 1801 participants from five countries eligible for inclusion in the review. Overall, statistically significant changes were noted in all four WHOQOL-BREF domain and four of the seven ASI domain scores (drug, psychological, legal, and family) documented in studies. Dosage of pharmacologic medication and length of follow-up did not affect changes in domain scores. WHOQOL-BREF and ASI domain scoring is a useful tool in measuring overall quality of life and levels of addiction among OST participants. Coupled with measurements of blood-borne infection, drug use, relapse, and overdose, WHOQOL-BREF and ASI represent equally important tools for evaluating the effects of OST over time and should be further developed as integrated tools in the evaluation of participants in LMIC. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
ASI/CGS products and services in support of GNSS-meteorology
NASA Astrophysics Data System (ADS)
Pacione, Rosa; Pace, Brigida; Bianco, Giuseppe
2013-04-01
For more than a decade, ASI/CGS has supported ground-based GNSS meteorology in Europe participating in various projects such as MAGIC, COST-716, TOUGH, E-GVAP (phase I and II) and providing Zenith Tropospheric path Delays (ZTD) derived from a European network of GNSS stations covering mainly the central Mediterranean area. Working in close cooperation with the meteorological community, GNSS data are analyzed in order to provide ZTD with different latencies ranging from post-processing, useful for climate studies, to near-real time, for hourly assimilation into Numerical Weather Prediction (NWP) model. However advancements in NWP models (such as the Met Office UKV 1.5km model) with rapid update cycles require observations with improved timeliness and with greater spatial and temporal resolution than is currently available. To fulfil this requirement a sub-hourly PPP processing has been set-up, and is under evaluation, thanks to the availability of the IGS RT orbit and clock corrections. Moreover ZTD estimates are the input data for developing new and enhanced products: ZTD residuals fields and Integrated Water Vapour (IWV) maps. The former will be helpful in augmenting empirical tropospheric models for positioning applications. The latter are useful for nowcasting and severe weather monitoring since they let to follow IWV time evolution. We present an overview of the developed products and services; the new directions in support of NWP applications and the nowcasting and forecasting of severe weather events that emerge within E-GVAP phase III and the EU COST Action "Advanced Global Navigation Satellite Systems tropospheric products for monitoring Severe Weather Events and Climate" (GNSS4SWEC). Acknowledgements. This work has been carried out under ASI contract I-014-10-0.
Cleary, Daniel F R
2003-04-01
The impact of disturbance on species diversity may be related to the spatial scales over which it occurs. Here I assess the impact of logging and ENSO (El Niño Southern Oscillation) -induced burning and forest isolation on the species richness (477 species out of more than 28,000 individuals) and community composition of butterflies and butterfly guilds using small (0.9 ha) plots nested within large (450 ha) landscapes. The landscapes were located in three habitat classes: (1) continuous, unburned forest; (2) unburned isolates surrounded by burned forest; and (3) burned forest. Plots with different logging histories were sampled within the two unburned habitat classes, allowing for independent assessment of the two disturbance factors (logging and burning). Disturbance within habitat classes (logging) had a very different impact on butterfly diversity than disturbance among habitat classes (due to ENSO-induced burning and isolation). Logging increased species richness, increased evenness, and lowered dominance. Among guilds based on larval food plants, the species richness of tree and herb specialists was higher in logged areas but their abundance was lower. Both generalist species richness and abundance was higher in logged areas. Among habitat classes, species richness was lower in burned forest and isolates than continuous forest but there was no overall difference in evenness or dominance. Among guilds, generalist species richness was significantly lower in burned forest and isolates than continuous forest. Generalist abundance was also very low in the isolates. There was no difference among disturbance classes in herb specialist species richness but abundance was significantly higher in the isolates and burned forest than in continuous forest. Tree specialist species richness was lower in burned forest than continuous forest but did not differ between continuous forest and isolates. The scale of assessment proved important in estimating the impact of
Significant influences of global mean temperature and ENSO on extreme rainfall over Southeast Asia
NASA Astrophysics Data System (ADS)
Villafuerte, Marcelino, II; Matsumoto, Jun
2014-05-01
Along with the increasing concerns on the consequences of global warming, and the accumulating records of disaster related to heavy rainfall events in Southeast Asia, this study investigates whether a direct link can be detected between the rising global mean temperature, as well as the El Niño-Southern Oscillation (ENSO), and extreme rainfall over the region. The maximum likelihood modeling that allows incorporating covariates on the location parameter of the generalized extreme value (GEV) distribution is employed. The GEV model is fitted to annual and seasonal rainfall extremes, which were taken from a high-resolution gauge-based gridded daily precipitation data covering a span of 57 years (1951-2007). Nonstationarities in extreme rainfall are detected over the central parts of Indochina Peninsula, eastern coasts of central Vietnam, northwest of the Sumatra Island, inland portions of Borneo Island, and on the northeastern and southwestern coasts of the Philippines. These nonstationarities in extreme rainfall are directly linked to near-surface global mean temperature and ENSO. In particular, the study reveals that a kelvin increase in global mean temperature anomaly can lead to an increase of 30% to even greater than 45% in annual maximum 1-day rainfall, which were observed pronouncedly over central Vietnam, southern coast of Myanmar, northwestern sections of Thailand, northwestern tip of Sumatra, central portions of Malaysia, and the Visayas island in central Philippines. Furthermore, a pronounced ENSO influence manifested on the seasonal maximum 1-day rainfall; a northward progression of 10%-15% drier condition over Southeast Asia as the El Niño develops from summer to winter is revealed. It is important therefore, to consider the results obtained here for water resources management as well as for adaptation planning to minimize the potential adverse impact of global warming, particularly on extreme rainfall and its associated flood risk over the region
Interannual Modulation of Subtropical Atlantic Boreal Summer Dust Variability by ENSO
DOE Office of Scientific and Technical Information (OSTI.GOV)
DeFlorio, Mike; Goodwin, Ian D.; Cayan, Dan
2016-01-01
Dust variability in the climate system has been studied for several decades, yet there remains an incomplete understanding of the dynamical mechanisms controlling interannual and decadal variations in dust transport. The sparseness of multi-year observational datasets has limited our understanding of the relationship between climate variations and atmospheric dust. We use available observations and a century-length fully coupled Community Earth System Model (CESM) simulation to show that the El Niño- Southern Oscillation (ENSO) exerts a control on North African dust transport during boreal summer. In CESM, this relationship is stronger over the dusty tropical North Atlantic than near Barbados, onemore » of the few sites having a multi-decadal observed record. During strong La Niña summers in CESM, a statistically significant increase in lower tropospheric easterly wind is associated with an increase in North African dust transport over the Atlantic. Barbados dust and Pacific SST variability are only weakly correlated in both observations and CESM, suggesting that other processes are controlling the crossbasin variability of dust. We also use our CESM simulation to show that the relationship between downstream North African dust transport and ENSO fluctuates on multidecadal timescales and may be modulated by the North Atlantic Oscillation (NAO). Our findings indicate that existing observations of dust over the tropical North Atlantic are not extensive enough to completely describe the variability of dust and dust transport, and demonstrate the importance of global models to supplement and interpret observational records.« less
Biological effects of the 1997/98 ENSO in Cook Inlet, Alaska
Piatt, John F.; Drew, Gary S.; van Pelt, Thomas I.; Abookire, Alisa A.; Nielsen, April; Shultz, Michael T.; Kitaysky, Alexander S.
1999-01-01
We have been conducting detailed studies of the biology of seabirds in relation to oceanography and forage fish ecology in lower Cook Inlet, Alaska, since 1995. This fortuitously allowed us to document biological effects of the 1997/98 ENSO in this region. Anomalously warm sea surface temperatures (SSTs) were observed in the Gulf of Alaska (GOA) beginning in June of 1997, but not in Cook Inlet until September, 1997. Warm temperature anomalies at the surface and at depth persisted until May of 1998, when temperatures returned to average in the GOA and Cook Inlet. Thus, temperature anomalies occurred outside the core window of productivity (June–August) for forage fish and seabirds in both 1997 and 1998. Abundance or production of phytoplankton, zooplankton, fish, and seabirds in lower Cook Inlet varied among years, and overall appeared to be depressed in 1998. We observed a few biological anomalies that might be attributed to ENSO effects: (1) a significant die-off of Common Murres occurred in March–May of 1998, (2) murres and Black-legged Kittiwakes were physiologically stressed during the 1998 breeding season, (3) murres failed to reproduce at one colony in 1998, (4) kittiwake breeding success was lower than usual at colonies in 1998, and (5) phenology of breeding was later in 1998 for both murres and kittiwakes. We presume that seabird die-offs, reduced productivity and delayed phenology were linked to a reduction or delay in food availability, but the mechanism by which anomalously warm water temperatures in winter reduce forage fish availability during the summer breeding season for seabirds is not known.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Pern, F. J.; Watson, G. L.; Glick, S. H.
2001-10-01
Presented at the 2001 NCPV Program Review Meeting: Study of photothermal stability of special EVA encapsulant by accelerated exposure testing and analysis of causes of performance degradation on a-Si modules.
Ocean Thermal and Color Evolution During the 1997/1998 ENSO Event
NASA Technical Reports Server (NTRS)
Rienecker, Michele
1998-01-01
A reduced gravity primitive equation modeling and assimilation system is used to study the evolution of the tropical Pacific during the 1997/1998 ENSO cycle. The modeling/assimilation scheme ingests satellite altimeter data and TAO temperature profiles and uses SSM/I satellite derived winds as surface boundary forcing. The four-dimensional structure of the upper ocean circulation structure will be compared against available in situ observations across the Pacific basin. In particular, variability near the Galapagos Islands will be highlighted during the spring of 1998 when phytoplankton concentrations were observed to increase a hundred-fold over a two week period.
NASA Astrophysics Data System (ADS)
McCurdy, B. M. C.
2013-06-01
An overview is provided of the use of amorphous silicon electronic portal imaging devices (EPIDs) for dosimetric purposes in radiation therapy, focusing on 3D patient dose estimation. EPIDs were originally developed to provide on-treatment radiological imaging to assist with patient setup, but there has also been a natural interest in using them as dosimeters since they use the megavoltage therapy beam to form images. The current generation of clinically available EPID technology, amorphous-silicon (a-Si) flat panel imagers, possess many characteristics that make them much better suited to dosimetric applications than earlier EPID technologies. Features such as linearity with dose/dose rate, high spatial resolution, realtime capability, minimal optical glare, and digital operation combine with the convenience of a compact, retractable detector system directly mounted on the linear accelerator to provide a system that is well-suited to dosimetric applications. This review will discuss clinically available a-Si EPID systems, highlighting dosimetric characteristics and remaining limitations. Methods for using EPIDs in dosimetry applications will be discussed. Dosimetric applications using a-Si EPIDs to estimate three-dimensional dose in the patient during treatment will be overviewed. Clinics throughout the world are implementing increasingly complex treatments such as dynamic intensity modulated radiation therapy and volumetric modulated arc therapy, as well as specialized treatment techniques using large doses per fraction and short treatment courses (ie. hypofractionation and stereotactic radiosurgery). These factors drive the continued strong interest in using EPIDs as dosimeters for patient treatment verification.
NASA Astrophysics Data System (ADS)
Gillies, D. M.; Knudsen, D. J.; Donovan, E.; Jackel, B. J.; Gillies, R.; Spanswick, E.
2017-12-01
We compare field-aligned currents (FACs) measured by the Swarm constellation of satellites with the location of red-line (630 nm) auroral arcs observed by all-sky imagers (ASIs) to derive a characteristic emission height for the optical emissions. In our 10 events we find that an altitude of 200 km applied to the ASI maps gives optimal agreement between the two observations. We also compare the new FAC method against the traditional triangulation method using pairs of all-sky imagers (ASIs), and against electron density profiles obtained from the Resolute Bay Incoherent Scatter Radar-Canadian radar (RISR-C), both of which are consistent with a characteristic emission height of 200 km. We also present the spatial error associated with georeferencing REdline Geospace Observatory (REGO) and THEMIS all-sky imagers (ASIs) and how it applies to altitude projections of the mapped image. Utilizing this error we validate the estimated altitude of redline aurora using two methods: triangulation between ASIs and field-aligned current profiles derived from magnetometers on-board the Swarm satellites.
Tropospheric Column Ozone Response to ENSO in GEOS-5 Assimilation of OMI and MLS Ozone Data
NASA Technical Reports Server (NTRS)
Olsen, Mark A.; Wargan, Krzysztof; Pawson, Steven
2016-01-01
We use GEOS-5 analyses of Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone observations to investigate the magnitude and spatial distribution of the El Nino Southern Oscillation (ENSO) influence on tropospheric column ozone (TCO) into the middle latitudes. This study provides the first explicit spatially resolved characterization of the ENSO influence and demonstrates coherent patterns and teleconnections impacting the TCO in the extratropics. The response is evaluated and characterized by both the variance explained and sensitivity of TCO to the Nino 3.4 index. The tropospheric response in the tropics agrees well with previous studies and verifies the analyses. A two-lobed response symmetric about the Equator in the western Pacific/Indonesian region seen in some prior studies and not in others is confirmed here. This two-lobed response is consistent with the large-scale vertical transport. We also find that the large-scale transport in the tropics dominates the response compared to the small-scale convective transport. The ozone response is weaker in the middle latitudes, but a significant explained variance of the TCO is found over several small regions, including the central United States. However, the sensitivity of TCO to the Nino 3.4 index is statistically significant over a large area of the middle latitudes. The sensitivity maxima and minima coincide with anomalous anti-cyclonic and cyclonic circulations where the associated vertical transport is consistent with the sign of the sensitivity. Also, ENSO related changes to the mean tropopause height can contribute significantly to the midlatitude response. Comparisons to a 22-year chemical transport model simulation demonstrate that these results from the 9- year assimilation are representative of the longer term. This investigation brings insight to several seemingly disparate prior studies of the El Nino influence on tropospheric ozone in the middle latitudes.
NASA Astrophysics Data System (ADS)
Liu, Bo; Zhao, Guijie; Huang, Gang; Wang, Pengfei; Yan, Bangliang
2017-08-01
The authors present results for El Niño-Southern Oscillation (ENSO) and East Asian-western North Pacific climate variability simulated in a new version high-resolution coupled model (ICM.V2) developed at the Center for Monsoon System Research of the Institute of Atmospheric Physics (CMSR, IAP), Chinese Academy of Sciences. The analyses are based on the last 100-year output of a 1000-year simulation. Results are compared to an earlier version of the same coupled model (ICM.V1), reanalysis, and observations. The two versions of ICM have similar physics but different atmospheric resolution. The simulated climatological mean states show marked improvement over many regions, especially the tropics in ICM.V2 compared to those in ICM.V1. The common bias in the cold tongue has reduced, and the warm biases along the ocean boundaries have improved as well. With improved simulation of ENSO, including its period and strength, the ENSO-related western North Pacific summer climate variability becomes more realistic compared to the observations. The simulated East Asian summer monsoon anomalies in the El Niño decaying summer are substantially more realistic in ICM.V2, which might be related to a better simulation of the Indo-Pacific Ocean capacitor (IPOC) effect and Pacific decadal oscillation (PDO).
The ENSO Effects on Tropical Clouds and Top-of-Atmosphere Cloud Radiative Effects in CMIP5 Models
NASA Technical Reports Server (NTRS)
Su, Wenying; Wang, Hailan
2015-01-01
The El Nino-Southern Oscillation (ENSO) effects on tropical clouds and top-of-atmosphere (TOA) cloud radiative effects (CREs) in Coupled Model Intercomparison Project Phase5 (CMIP5) models are evaluated using satellite-based observations and International Satellite Cloud Climatology Project satellite simulator output. Climatologically, most CMIP5 models produce considerably less total cloud amount with higher cloud top and notably larger reflectivity than observations in tropical Indo-Pacific (60 degrees East - 200 degrees East; 10 degrees South - 10 degrees North). During ENSO, most CMIP5 models considerably underestimate TOA CRE and cloud changes over western tropical Pacific. Over central tropical Pacific, while the multi-model mean resembles observations in TOA CRE and cloud amount anomalies, it notably overestimates cloud top pressure (CTP) decreases; there are also substantial inter-model variations. The relative effects of changes in cloud properties, temperature and humidity on TOA CRE anomalies during ENSO in the CMIP5 models are assessed using cloud radiative kernels. The CMIP5 models agree with observations in that their TOA shortwave CRE anomalies are primarily contributed by total cloud amount changes, and their TOA longwave CRE anomalies are mostly contributed by changes in both total cloud amount and CTP. The model biases in TOA CRE anomalies particularly the strong underestimations over western tropical Pacific are, however, mainly explained by model biases in CTP and cloud optical thickness (tau) changes. Despite the distinct model cloud biases particularly in tau regime, the TOA CRE anomalies from cloud amount changes are comparable between the CMIP5 models and observations, because of the strong compensations between model underestimation of TOA CRE anomalies from thin clouds and overestimation from medium and thick clouds.
Herwiningsih, Sri; Hanlon, Peta; Fielding, Andrew
2014-12-01
A Monte Carlo model of an Elekta iViewGT amorphous silicon electronic portal imaging device (a-Si EPID) has been validated for pre-treatment verification of clinical IMRT treatment plans. The simulations involved the use of the BEAMnrc and DOSXYZnrc Monte Carlo codes to predict the response of the iViewGT a-Si EPID model. The predicted EPID images were compared to the measured images obtained from the experiment. The measured EPID images were obtained by delivering a photon beam from an Elekta Synergy linac to the Elekta iViewGT a-Si EPID. The a-Si EPID was used with no additional build-up material. Frame averaged EPID images were acquired and processed using in-house software. The agreement between the predicted and measured images was analyzed using the gamma analysis technique with acceptance criteria of 3 %/3 mm. The results show that the predicted EPID images for four clinical IMRT treatment plans have a good agreement with the measured EPID signal. Three prostate IMRT plans were found to have an average gamma pass rate of more than 95.0 % and a spinal IMRT plan has the average gamma pass rate of 94.3 %. During the period of performing this work a routine MLC calibration was performed and one of the IMRT treatments re-measured with the EPID. A change in the gamma pass rate for one field was observed. This was the motivation for a series of experiments to investigate the sensitivity of the method by introducing delivery errors, MLC position and dosimetric overshoot, into the simulated EPID images. The method was found to be sensitive to 1 mm leaf position errors and 10 % overshoot errors.
Hoell, Andrew; Funk, Christopher C.
2013-01-01
The temporal evolution and distribution of Pacific SST as well as the near-surface tropical Pacific zonal wind, tropical divergence and vertical velocity are considerably different during ENSO events partitioned according to the strength of the WPG. Modifications to the tropical circulation result in changes to the Indo-west Pacific precipitation and vertically integrated energy budgets and are linked to strong and consistent circulation and precipitation modifications throughout the Northern Hemisphere during winter.
NASA Astrophysics Data System (ADS)
Poveda, Germán; Álvarez, Diana M.; Rueda, Óscar A.
2011-06-01
The hydro-climatic variability of the Colombian Andes associated with El Niño-Southern Oscillation (ENSO) is reviewed using records of rainfall, river discharges, soil moisture, and a vegetation index (NDVI) as a surrogate for evapotranspiration. Anomalies in the components of the surface water balance during both phases of ENSO are quantified in terms of their sign, timing, and magnitude. During El Niño (La Niña), the region experiences negative (positive) anomalies in rainfall, river discharges (average and extremes), soil moisture, and NDVI. ENSO's effects are phase-locked to the seasonal cycle, being stronger during December-February, and weaker during March-May. Besides, rainfall and river discharges anomalies show that the ENSO signal exhibits a westerly wave-like propagation, being stronger (weaker) and earlier (later) over the western (eastern) Andes. Soil moisture anomalies are land-cover type dependant, but overall they are enhanced by ENSO, showing very low values during El Niño (mainly during dry seasons), but saturation values during La Niña. A suite of large-scale and regional mechanisms cooperating at the ocean-atmosphere-land system are reviewed to explaining the identified hydro-climatic anomalies. This review contributes to an understanding of the hydro-climatic framework of a region identified as the most critical hotspot for biodiversity on Earth, and constitutes a wake-up call for scientists and policy-makers alike, to take actions and mobilize resources and minds to prevent the further destruction of the region's valuable hydrologic and biodiversity resources and ecosystems. It also sheds lights towards the implementation of strategies and adaptation plans to coping with threats from global environmental change.
ASI aurora search: an attempt of intelligent image processing for circular fisheye lens.
Yang, Xi; Gao, Xinbo; Song, Bin; Wang, Nannan; Yang, Dong
2018-04-02
The circular fisheye lens exhibits an approximately 180° angular field-of-view (FOV), which is much larger than that of an ordinary lens. Thus, images captured with a circular fisheye lens are distributed non-uniformly with spherical deformation. Along with the fast development of deep neural networks for normal images, how to apply it to achieve intelligent image processing for a circular fisheye lens is a new task of significant importance. In this paper, we take the aurora images captured with all-sky-imagers (ASI) as a typical example. By analyzing the imaging principle of ASI and the magnetic characteristics of the aurora, a deformed region division (DRD) scheme is proposed to replace the region proposals network (RPN) in the advanced mask regional convolutional neural network (Mask R-CNN) framework. Thus, each image can be regarded as a "bag" of deformed regions represented with CNN features. After clustering all CNN features to generate a vocabulary, each deformed region is quantified to its nearest center for indexing. On the stage of an online search, a similarity score is computed by measuring the distances between regions in the query image and all regions in the data set, and the image with the highest value is outputted as the top rank search result. Experimental results show that the proposed method greatly improves the search accuracy and efficiency, demonstrating that it is a valuable attempt of intelligent image processing for circular fisheye lenses.
Maguire, R; McCann, L; Miller, M; Kearney, N
2008-09-01
Many people diagnosed with cancer will receive chemotherapy as a core component of their care. Recent changes in the delivery of cancer services mean that patients frequently receive care on an out-patient basis and are therefore often required to manage related side effects at home without direct support from oncology health professionals. The use of information and communications technology may be seen as a means of supporting patients receiving chemotherapy in the home care setting. This mixed methods study, reports on the perceptions of nurses (n=35) who participated in a randomised controlled trial of a mobile phone based, Advanced Symptom Management System (ASyMS), in the management of chemotherapy-related toxicity in patients with breast, lung and colorectal cancer. Nurses' perceptions of ASyMS were evaluated at the start and the end of the study. Overall, they could see the benefits of ASyMS in the remote monitoring of chemotherapy toxicity and its role in facilitating early intervention and subsequent management, demonstrating the potential utility of the system within clinical practice.
USDA-ARS?s Scientific Manuscript database
We used coupled watershed and reservoir models to evaluate the impacts of deforestation and ENSO phase on drinking water quality. Source water total organic carbon (TOC) is especially important due to the potential for production of carcinogenic disinfection byproducts (DBPs). The Environmental Flui...
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yang, Yang; Russell, Lynn M.; Xu, Li
The impacts of the El Niño–Southern Oscillation (ENSO) events on shortwave and longwave cloud radiative effects (CRESW and CRELW) and the underlying changes in cloud fraction as well as aerosol emissions, wet scavenging and transport are quantified using three 150-year simulations in preindustrial conditions by the CESM model. Compared to recent observations from Clouds and the Earth’s Radiant Energy System (CERES), the model simulation successfully reproduced larger variations of CRESW over the tropical western and central Pacific, Indonesian regions, and the eastern Pacific Ocean, as well as large variations of CRELW located mainly within the tropics. The ENSO cycle ismore » found to dominate interannual variations of cloud radiative effects, especially over the tropics. Relative to those during La Niña events, simulated cooling (warming) effects from CRESW (CRELW) during El Niño events are stronger over the tropical western and central Pacific Ocean, with the largest difference exceeding 40 Wm–2 (30 Wm–2), with weaker effects of 10–30 Wm–2 over Indonesian regions and the subtropical Pacific Ocean. Sensitivity tests show that variations of cloud radiative effects are mainly driven by ENSO-related changes in cloud fraction. The variations in medium and high cloud fractions each account for about 20–50% of the interannual variations of CRESW over the tropics and almost all of the variations of CRELW between 60°S and 60°N. The variation of low cloud fraction contributes most interannual variations of CRESW over the mid-latitude oceans. Variations in natural aerosol concentrations considering emissions, wet scavenging and transport explained 10–30% of the interannual variations of both CRESW and CRELW over the tropical Pacific, Indonesian regions and the tropical Indian Ocean. Changes in wet scavenging of natural aerosol modulate the variations of cloud radiative effects. Because of increased (decreased) precipitation over the tropical western
NASA Astrophysics Data System (ADS)
Fehr, M.; Schnegg, A.; Rech, B.; Astakhov, O.; Finger, F.; Bittl, R.; Teutloff, C.; Lips, K.
2014-02-01
Light-induced degradation of hydrogenated amorphous silicon (a-Si :H), known as the Staebler-Wronski effect, has been studied by time-domain pulsed electron-paramagnetic resonance. Electron-spin echo relaxation measurements in the annealed and light-soaked state revealed two types of defects (termed type I and II), which can be discerned by their electron-spin echo relaxation. Type I exhibits a monoexponential decay related to indirect flip-flop processes between dipolar coupled electron spins in defect clusters, while the phase relaxation of type II is dominated by H1 nuclear spin dynamics and is indicative for isolated spins. We propose that defects are either located at internal surfaces of microvoids (type I) or are isolated and uniformly distributed in the bulk (type II). The concentration of both defect type I and II is significantly higher in the light-soaked state compared to the annealed state. Our results indicate that in addition to isolated defects, defects on internal surfaces of microvoids play a role in light-induced degradation of device-quality a-Si :H.
NASA Astrophysics Data System (ADS)
Lee, Sang-Ki; Wittenberg, Andrew T.; Enfield, David B.; Weaver, Scott J.; Wang, Chunzai; Atlas, Robert
2016-04-01
Recent violent and widespread tornado outbreaks in the US, such as occurred in the spring of 2011, have caused devastating societal impact with significant loss of life and property. At present, our capacity to predict US tornado and other severe weather risk does not extend beyond seven days. In an effort to advance our capability for developing a skillful long-range outlook for US tornado outbreaks, here we investigate the spring probability patterns of US regional tornado outbreaks during 1950-2014. We show that the four dominant springtime El Niño-Southern Oscillation (ENSO) phases (persistent versus early-terminating El Niño and resurgent versus transitioning La Niña) and the North Atlantic sea surface temperature tripole variability are linked to distinct and significant US regional patterns of outbreak probability. These changes in the probability of outbreaks are shown to be largely consistent with remotely forced regional changes in the large-scale atmospheric processes conducive to tornado outbreaks. An implication of these findings is that the springtime ENSO phases and the North Atlantic SST tripole variability may provide seasonal predictability of US regional tornado outbreaks.
NASA Astrophysics Data System (ADS)
Rebenack, C.; Willoughby, H. E.; Anderson, W. T.; Cherubini, P.
2013-12-01
The South Florida coastal ecosystem is among the world's subtropical coastlines which are threatened by the potential effects of climate change. A well-developed localized paleohistory is essential in the understanding of the role climate variability/change has on both hydrological dynamics and disturbance event frequency and intensity; this understanding can then aid in the development of better predictive models. High resolution paleoclimate proxies, such as those developed from tree-ring archives, may be useful tools for extrapolating actual climate trends over time from the overlapping long-term and short-term climate cycles, such as the Atlantic Multidecadal Oscillation (AMO) and the El Niño-Southern Oscillation (ENSO). In South Florida, both the AMO and ENSO strongly influence seasonal precipitation, and a more complete grasp of how these cycles have affected the region in the past could be applied to future freshwater management practices. Dendrochronology records for the terrestrial subtropics, including South Florida, are sparse because seasonality for this region is precipitation driven; this is in contrast to the drastic temperature changes experienced in the temperate latitudes. Subtropical seasonality may lead to the complete lack of visible rings or to the formation of ring structures that may or may not represent annual growth. Fortunately, it has recently been demonstrated that Pinus elliottii trees in South Florida produce distinct annual growth rings; however ring width was not found to significantly correlate with either the AMO or ENSO. Dendrochronology studies may be taken a step beyond the physical tree-ring proxies by using the carbon isotope ratios to infer information about physiological controls and environmental factors that affect the distribution of isotopes within the plant. It has been well established that the stable isotope composition of cellulose can be related to precipitation, drought, large-scale ocean/atmospheric oscillations
Impacts of winter NPO on subsequent winter ENSO: sensitivity to the definition of NPO index
NASA Astrophysics Data System (ADS)
Chen, Shangfeng; Wu, Renguang
2018-01-01
This study investigates the linkage between boreal winter North Pacific Oscillation (NPO) and subsequent winter El Niño-Southern Oscillation (ENSO) based on seven different NPO indices. Results show that the influence of winter NPO on the subsequent winter El Niño is sensitive to how the NPO is defined. A significant NPO-El Niño connection is obtained when the NPO-related anomalous cyclone over the subtropical North Pacific extends to near-equatorial regions. The anomalous cyclone induces warm sea surface temperature (SST) anomalies through modulating surface heat fluxes. These warm SST anomalies are able to maintain into the following spring and summer through an air-sea coupled process and in turn induce significant westerly wind anomalies over the tropical western Pacific. In contrast, the NPO-El Niño relationship is unclear when the NPO-related anomalous cyclone over the subtropical North Pacific is confined to off-equatorial regions and cannot induce significant warm SST anomalies over the subtropical North Pacific. The present study suggests that definitions of NPO should be taken into account when using NPO to predict ENSO. In particular, we recommend defining the NPO index based on the empirical orthogonal function technique over appropriate region that does not extend too far north.
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.
NASA Astrophysics Data System (ADS)
Coloma Ribera, R.; van de Kruijs, R. W. E.; Sturm, J. M.; Yakshin, A. E.; Bijkerk, F.
2017-03-01
The initial growth of DC sputtered ZrO2 on top of a-Si, SiN, and SiO2 layers has been studied by in vacuo high-sensitivity low energy ion scattering for two gas deposition conditions with different oxygen contents (high-O and low-O conditions). This unique surface sensitive technique allowed the determination of surface composition and thicknesses required to close the ZrO2 layer on all three substrates for both conditions. The ZrO2 layer closes similarly on all substrates due to more favorable enthalpies of formation for ZrO2 and ZrSiO4, resulting in passivation of the Si from the substrate. However, this layer closes at about half of the thickness (˜1.7 nm) for low-O conditions due to less oxidative conditions and less energetic particles arriving at the sample, which leads to less intermixing via silicate formation. In contrast, for high-O conditions, there is more ZrSiO4 and/or SiOx formation, giving more intermixing (˜3.4 nm). In vacuo X-ray photoelectron spectroscopy (XPS) measurements revealed similar stoichiometric ZrO2 layers deposited by both conditions and a higher interaction of the ZrO2 layer with the underlying a-Si for high-O conditions. In addition, oxygen diffusion through low-O ZrO2 films on a-Si has been investigated by ex situ angular-resolved XPS of samples annealed in atmospheric oxygen. For temperatures below 400 °C, no additional oxidation of the underlying a-Si was observed. This, together with the amorphous nature and smoothness of these samples, makes ZrO2 a good candidate as an oxidation protective layer on top of a-Si.
SU-E-T-164: Clinical Implementation of ASi EPID Panels for QA of IMRT/VMAT Plans.
Hosier, K; Wu, C; Beck, K; Radevic, M; Asche, D; Bareng, J; Kroner, A; Lehmann, J; Logsdon, M; Dutton, S; Rosenthal, S
2012-06-01
To investigate various issues for clinical implementation of aSi EPID panels for IMRT/VMAT QA. Six linacs are used in our clinic for EPID-based plan QA; two Varian Truebeams, two Varian 2100 series, two Elekta Infiniti series. Multiple corrections must be accounted for in the calibration of each panel for dosimetric use. Varian aSi panels are calibrated with standard dark field, flood field, and 40×40 diagonal profile for beam profile correction. Additional corrections to account for off-axis and support arm backscatter are needed for larger field sizes. Since Elekta iViewGT system does not export gantry angle with images, a third-party inclinometer must be physically mounted to back of linac gantry and synchronized with data acquisition via iViewGT PC clock. A T/2 offset correctly correlates image and gantry angle for arc plans due to iView image time stamp at the end of data acquisition for each image. For both Varian and Elekta panels, a 5 MU 10×10 calibration field is used to account for the nonlinear MU to dose response at higher energies. Acquired EPID images are deconvolved via a high pass filter in Fourier space and resultant fluence maps are used to reconstruct a 3D dose 'delivered' to patient using DosimetryCheck. Results are compared to patient 3D dose computed by TPS using a 3D-gamma analysis. 120 IMRT and 100 VMAT cases are reported. Two 3D gamma quantities (Gamma(V10) and Gamma(PTV)) are proposed for evaluating QA results. The Gamma(PTV) is sensitive to MLC offsets while Gamma(V10) is sensitive to gantry rotations. When a 3mm/3% criteria and 90% or higher 3D gamma pass rate is used, all IMRT and 90% of VMAT QA pass QA. After appropriate calibration of aSi panels and setup of image acquisition systems, EPID based 3D dose reconstruction method is found clinically feasible. © 2012 American Association of Physicists in Medicine.
Initialization and Predictability of a Coupled ENSO Forecast Model
NASA Technical Reports Server (NTRS)
Chen, Dake; Zebiak, Stephen E.; Cane, Mark A.; Busalacchi, Antonio J.
1997-01-01
The skill of a coupled ocean-atmosphere model in predicting ENSO has recently been improved using a new initialization procedure in which initial conditions are obtained from the coupled model, nudged toward observations of wind stress. The previous procedure involved direct insertion of wind stress observations, ignoring model feedback from ocean to atmosphere. The success of the new scheme is attributed to its explicit consideration of ocean-atmosphere coupling and the associated reduction of "initialization shock" and random noise. The so-called spring predictability barrier is eliminated, suggesting that such a barrier is not intrinsic to the real climate system. Initial attempts to generalize the nudging procedure to include SST were not successful; possible explanations are offered. In all experiments forecast skill is found to be much higher for the 1980s than for the 1970s and 1990s, suggesting decadal variations in predictability.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Yoon, Jin-Ho; Leung, Lai-Yung R.
This study assesses the relative influence of soil moisture memory and tropical sea surface temperature (SST) in seasonal rainfall over the contiguous United States. Using observed precipitation, the NINO3.4 index and soil moisture and evapotranspiration simulated by a land surface model for 61 years, analysis was performed using partial correlations to evaluate to what extent land surface and SST anomaly of El Niño and Southern Oscillation (ENSO) can affect seasonal precipitation over different regions and seasons. Results show that antecedent soil moisture is as important as concurrent ENSO condition in controlling rainfall anomalies over the U.S., but they generally dominatemore » in different seasons with SST providing more predictability during winter while soil moisture, through its linkages to evapotranspiration and snow water, has larger influence in spring and early summer. The proposed methodology is applicable to climate model outputs to evaluate the intensity of land-atmosphere coupling and its relative importance.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Balaguru, Karthik; Leung, L. Ruby; Lu, Jian
2016-06-27
Analysis of Bay of Bengal tropical cyclone (TC) track data for the month of May during 1980-2013 reveals a meridional dipole in TC intensification: TC intensification rates increased in the northern Bay and decreased in the southern Bay. The dipole was driven by an increase in low-level vorticity and atmospheric humidity in the northern Bay, making the environment more favorable for TC intensification, and enhanced vertical wind shear in the southern Bay, tending to reduce TC development. These environmental changes were associated with a strengthening of the monsoon circulation for the month of May, driven by a La Nin˜a-like shiftmore » in tropical Pacific SSTs andassociated tropical wave dynamics. Analysis of a suite of climate models fromthe CMIP5 archive for the 150-year historical period shows that most models correctly reproduce the link between ENSO and Bay of Bengal TC activity through the monsoon at interannual timescales. Under the RCP 8.5 scenario the same CMIP5 models produce an El Nin˜o like warming trend in the equatorial Pacific, tending to weaken the monsoon circulation. These results suggest« less
NASA Astrophysics Data System (ADS)
Emerton, R.; Cloke, H. L.; Stephens, L.; Woolnough, S. J.; Zsoter, E.; Pappenberger, F.
2016-12-01
El Niño Southern Oscillation (ENSO), a mode of variability which sees fluctuations between anomalously high or low sea surface temperatures in the Pacific, is known to influence river flow and flooding at the global scale. The anticipation and forecasting of floods is crucial for flood preparedness, and this link, alongside the predictive skill of ENSO up to seasons ahead, may provide an early indication of upcoming severe flood events. Information is readily available indicating the likely impacts of El Niño and La Niña on precipitation across the globe, which is often used as a proxy for flood hazard. However, the nonlinearity between precipitation and flood magnitude and frequency means that it is important to assess the impact of ENSO events not only on precipitation, but also on river flow and flooding. Historical probabilities provide key information regarding the likely impacts of ENSO events. We estimate, for the first time, the historical probability of increased flood hazard during El Niño and La Niña through a global hydrological analysis, using a new 20thCentury ensemble river flow reanalysis for the global river network. This dataset was produced by running the ECMWF ERA-20CM atmospheric reanalysis through a research set-up of the Global Flood Awareness System (GloFAS) using the CaMa-Flood hydrodynamic model, to produce a 110-year global reanalysis of river flow. We further evaluate the added benefit of the hydrological analysis over the use of precipitation as a proxy for flood hazard. For example, providing information regarding regions that are likely to experience a lagged influence on river flow compared to the influence on precipitation. Our results map, at the global scale, the probability of abnormally high river flow during any given month during an El Niño or La Niña; information such as this is key for organisations that work at the global scale, such as humanitarian aid organisations, providing a seasons-ahead indicator of potential
The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET) experiment.
Schofield, J T; Barnes, J R; Crisp, D; Haberle, R M; Larsen, S; Magalhães, J A; Murphy, J R; Seiff, A; Wilson, G
1997-12-05
The Mars Pathfinder atmospheric structure investigation/meteorology (ASI/MET) experiment measured the vertical density, pressure, and temperature structure of the martian atmosphere from the surface to 160 km, and monitored surface meteorology and climate for 83 sols (1 sol = 1 martian day = 24.7 hours). The atmospheric structure and the weather record are similar to those observed by the Viking 1 lander (VL-1) at the same latitude, altitude, and season 21 years ago, but there are differences related to diurnal effects and the surface properties of the landing site. These include a cold nighttime upper atmosphere; atmospheric temperatures that are 10 to 12 degrees kelvin warmer near the surface; light slope-controlled winds; and dust devils, identified by their pressure, wind, and temperature signatures. The results are consistent with the warm, moderately dusty atmosphere seen by VL-1.
Butler, Stephen F; Black, Ryan A; Severtson, Stevan Geoffrey; Dart, Richard C; Green, Jody L
2018-01-01
The objectives were to examine the abuse prevalence and route-of-administration (ROA) profiles of sublingual buprenorphine/naloxone combination (BNX) film in comparison with the BNX tablet and to identify clinically-relevant subgroups of patients or geographic patterns. Between Q1 2015 through Q3 2015, data were collected from two major surveillance systems: (1) assessment of individuals in substance use disorder (SUD) treatment collected from the National Addictions Vigilance Intervention and Prevention Program (NAVIPPRO®) ASI-MV® system and (2) intentional abuse/misuse exposures in the RADARS® System Poison Center Program. Poisson regression models were tailored to each system's data characteristics by population (all SUD treatment patients, US census) and adjusted for prescription volume. Effects of gender, race, age and US region as well as ROA profile were examined. For the ASI-MV study, 45,695 assessments of unique adults evaluated for substance use problems were collected. The abuse rate unadjusted for prescription volume of BNX tablet formulation was 2.64 cases/100 ASI-MV respondents versus 7.01 cases for the film formulation (RR=0.390, p<0.001). Prescription-adjusted abuse, however, was greater for the tablet version (0.47 abuse cases/100 ASI-MV respondents/100,000 dosage units compared with 0.38 for the film) (RR=1.25, p<0.001). Results among the US population from the RADARS System Poison Center Program data revealed a similar pattern; population rates for film abuse (0.0364) were greater than for tablet (0.0161), while prescription-adjusted rates were greater for tablet (0.2114) than for film (0.1703) per 100,000 prescriptions. ASI-MV ROA analyses indicated less abuse of the film by any alternate route, insufflation or injection than the tablet. Poison center data found more injection of tablets than film, although insufflation was not significantly different. On a prescription-adjusted basis, overall abuse of the BNX tablet is greater than that of
NASA Astrophysics Data System (ADS)
Shim, Kyurhee
2013-11-01
A theoretical model utilizing a universal tight binding method and a correlated function expansion technique is presented to calculate the valence band maximum (VBM) and the conduction band minimum (CBM) of the binary (GaAs, InAS, GaSb, and InSb) and quaternary alloy GaxIn1-xAsySb1-y systems. By organizing the relative positions of the VBM and CBM between semiconductors, the band alignments and band types in the heterojunctions are determined. A straddling (type-I) band alignment in InAs/GaAs, InSb/GaAs, and GaSb/InSb, staggered (type-II) band alignment in GaSb/GaAs, and broken (type-III) band alignment in InSb/InAs and InAs/GaSb are found respectively. In addition, the compositional variations of VBM, CBM, valence band offset, conduction band offset, and band type for the alloy GaxIn1-xAsySb1-y lattice matched on GaSb and InAs are obtained as increasing the composition x. A pronounced upward bowing for the VBM and a very slight upward bowing (almost linear) for CBM are found, respectively. By controlling the compositions (x, y), band type transitions occur. The GaxIn1-xAsySb1-y heterojunctions lattice matched to GaSb changes their band types from type-III at x ˜0→ to type-II at x = 0.07, and → to type-I at x = 0.38. In contrast, the GaxIn1-xAsySb1-y heterojunctions lattice matched to InAs changes their band types from type-II x ˜0→ to type-III at x = 0.32. Reasonable agreement is obtained between our theoretical results and existing experimental data.
NASA Astrophysics Data System (ADS)
Mogollón, Rodrigo; Calil, Paulo H. R.
2017-08-01
The response of the ocean biogeochemistry to intense El Niño Southern Oscillation (ENSO) events in the Northern Humboldt Current System (NHCS) is assessed with an eddy-resolving coupled physical-biogeochemical model. El Niño (EN) 1997-1998 and La Niña (LN) 1999-2000 are well reproduced, inducing large spatial and temporal variability of biogeochemical properties at three coastal upwelling centers along the Peruvian coast (Chimbote 9.4°S, Callao 12.1°S, and Pisco 14°S). During EN, the upper limit of the Oxygen Minimum Zone (OMZ) experiences an offshore displacement of, approximately, 60 km and a deepening of, approximately, 150 m when compared to neutral-ENSO conditions, thus ventilating the upper 100 m of the water column. In contrast, during LN, the OMZ tongue outcrops over the continental shelf deoxygenating the water column at all locations. During LN, at the southernmost location, enhanced Eddy Kinetic Energy (EKE) induces a leaking of the coastal nutrient inventory by horizontally advecting nitrogen from the nearshore region into the oligotrophic ocean. This leads to a reduction of biological production in the coastal zone. During EN, nitrification is an order of magnitude larger than denitrification in supplying the nitrite coastal pool. During LN peak, nitrification is reduced by 80%, while denitrification becomes equally important, evidencing a coupling between these two oxygen-dependent processes. The nitrogen removal due to suboxic activity is mostly controlled by the Anaerobic Ammonium Oxidation (Anammox) in the southern domain during neutral-ENSO conditions. Our results show that during EN, denitrification contributes with 60% of the total nitrogen removal. In contrast, Anammox contributes with 70% during LN. The outgassing of nitrous oxide (N2O), an intermediate product of denitrification, is reduced and enhanced during EN and LN, respectively, and it is strongly modulated by the spatiotemporal variability of oxygen in the environment.
NASA Astrophysics Data System (ADS)
MAO, J.; WU, X.
2017-12-01
The spatio-temporal variations of eastern China spring rainfall are identified via empirical orthogonal function (EOF) analysis of rain-gauge (gridded) precipitation datasets for the period 1958-2013 (1920-2013). The interannual variations of the first two leading EOF modes are linked with the El Niño-Southern Oscillation (ENSO), with this linkage being modulated by the Pacific Decadal Oscillation (PDO). The EOF1 mode, characterized by predominant rainfall anomalies from the Yangtze River to North China (YNC), is more likely associated with out-of-phase PDO-ENSO events [i.e., El Niño during cold PDO (EN_CPDO) and La Niña during warm PDO (LN_WPDO)]. The sea surface temperature anomaly (SSTA) distributions of EN_CPDO (LN_WPDO) events induce a significant anomalous anticyclone (cyclone) over the western North Pacific stretching northwards to the Korean Peninsula and southern Japan, resulting in anomalous southwesterlies (northeasterlies) prevailing over eastern China and above-normal (below-normal) rainfall over YNC. In contrast, EOF2 exhibits a dipole pattern with predominantly positive rainfall anomalies over southern China along with negative anomalies over YNC, which is more likely connected to in-phase PDO-ENSO events [i.e., El Niño during warm PDO (EN_WPDO) and La Niña during cold PDO (LN_CPDO)]. EN_WPDO (LN_CPDO) events force a southwest-northeast oriented dipole-like circulation pattern leading to significant anomalous southwesterlies (northeasterlies) and above-normal (below-normal) rainfall over southern China. Numerical experiments with the CAM5 model forced by the SSTA patterns of EN_WPDO and EN_CPDO events reproduce reasonably well the corresponding anomalous atmospheric circulation patterns and spring rainfall modes over eastern China, validating the related mechanisms.
Sub-regional Precipitation Climate of the Caribbean and Relationships With ENSO and NAO
NASA Astrophysics Data System (ADS)
Winter, A.; Jury, M.; Malmgren, B.
2006-12-01
Thirty-five meteorological stations encompassing the Caribbean region (Cuba, Bahamas, Jamaica, Dominican Republic, Puerto Rico, U.S. Virgin Islands, St. Maarten, and Barbados) were analyzed over the time interval 1951-1981 to assess regional precipitation patterns and their relationships with the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO). Application of factor analysis to these series revealed the existence of four geographically distinct precipitation regions: (1) western Cuba and northwestern Bahamas, (2) Jamaica, eastern Cuba, and southeastern Bahamas, (3) Dominican Republic and northwestern Puerto Rico, and (4) eastern Puerto Rico, U.S. Virgin Islands, St. Marteen, and Barbados. This regionalization is related to different annual cycles and interannual fluctuations of rainfall. The annual cycle is unimodal and largest in the northwest Caribbean (1), and becomes increasingly bimodal toward lower latitudes (4) as expected. Year-to-year variations of precipitation are compared with two well known climatic indices. The ENSO relationship, represented by Niño3.4 SST, is positive and stable at all lags, but tends to reverse over the SE Caribbean (4) in late summer. The NAO influence is weak and seasonally dependent. Early summer rainfall in the northwest Caribbean (1) increases under El Niño conditions. Clusters 2 and 3 are less influenced by the global predictors and more regional in character. Previous related work sub-divided the Caribbean into two to three regions. Our work also shows that the main Caribbean basin should be divided into two clusters and not one homogeneous region as has previously been reported.
NASA Astrophysics Data System (ADS)
Rossita, A.; Witono, A.; Darusman, T.; Lestari, D. P.; Risdiyanto, I.
2018-03-01
As it is the main role to maintain hydrological function, peatland has been a limelight since drainage construction for agriculture evolved. Drainage construction will decrease water table depth (WTD) and result in CO2 emission release to the atmosphere. Regardless of human intervention, WTD fluctuations can be affected by seasonal climate and climate variability, foremost El Niño Southern Oscillation (ENSO). This study aims to determine the correlation between rainfall in Katingan and ENSO index, analyze the pattern of WTD fluctuation of open area and forest area in 2015 (during very strong El Niño) and 2016 (during weak La Niña), calculate the WTD trendline slope during the dry season, and rainfall and WTD correlation. The result showed that open area has a sharper slope of decreasing or increasing WTD when entering the dry, compared to the forest area. Also, it is found that very strong El Niño in 2015 generated a pattern of more extreme decreasing WTD during the dry season than weak La Niña in 2016.
NASA Astrophysics Data System (ADS)
Yuan, Dongliang; Hu, Xiaoyue; Xu, Peng; Zhao, Xia; Masumoto, Yukio; Han, Weiqing
2018-01-01
The dynamics of the teleconnection between the Indian Ocean Dipole (IOD) in the tropical Indian Ocean and El Niño-Southern Oscillation (ENSO) in the tropical Pacific Ocean at the time lag of one year are investigated using lag correlations between the oceanic anomalies in the southeastern tropical Indian Ocean in fall and those in the tropical Indo-Pacific Ocean in the following winter-fall seasons in the observations and in high-resolution global ocean model simulations. The lag correlations suggest that the IOD-forced interannual transport anomalies of the Indonesian Throughflow generate thermocline anomalies in the western equatorial Pacific Ocean, which propagate to the east to induce ocean-atmosphere coupled evolution leading to ENSO. In comparison, lag correlations between the surface zonal wind anomalies over the western equatorial Pacific in fall and the Indo-Pacific oceanic anomalies at time lags longer than a season are all insignificant, suggesting the short memory of the atmospheric bridge. A linear continuously stratified model is used to investigate the dynamics of the oceanic connection between the tropical Indian and Pacific Oceans. The experiments suggest that interannual equatorial Kelvin waves from the Indian Ocean propagate into the equatorial Pacific Ocean through the Makassar Strait and the eastern Indonesian seas with a penetration rate of about 10%-15% depending on the baroclinic modes. The IOD-ENSO teleconnection is found to get stronger in the past century or so. Diagnoses of the CMIP5 model simulations suggest that the increased teleconnection is associated with decreased Indonesian Throughflow transports in the recent century, which is found sensitive to the global warming forcing.
NASA Astrophysics Data System (ADS)
Muñoz, Paula; Gorin, Georges; Parra, Norberto; Velásquez, Cesar; Lemus, Diego; Monsalve-M., Carlos; Jojoa, Marcela
2017-01-01
The Páramo de Frontino (3460 m elevation) in Colombia is located approximately halfway between the Pacific and Atlantic oceans. It contains a 17 kyr long, stratigraphically continuous sedimentary sequence dated by 30 AMS 14C ages. Our study covers the last 11,500 cal yr and focuses on the biotic (pollen) and abiotic (microfluorescence-X or μXRF) components of this high mountain ecosystem. The pollen record provides a proxy for temperature and humidity with a resolution of 20-35 yr, and μXRF of Ti and Fe is a proxy for rainfall with a sub-annual (ca. 6-month) resolution. Temperature and humidity display rapid and significant changes over the Holocene. The rapid transition from a cold (mean annual temperature (MAT) 3.5 °C lower than today) and wet Younger Dryas to a warm and dry early Holocene is dated at 11,410 cal yr BP. During the Holocene, MAT varied from ca. 2.5 °C below to 3.5° above present-day temperature. Warm periods (11,410-10,700, 9700-6900, 4000-2400 cal yr BP) were separated by colder intervals. The last 2.4 kyr of the record is affected by human impact. The Holocene remained dry until 7500 cal yr BP. Then, precipitations increased to reach a maximum between 5000 and 4500 cal yr BP. A rapid decrease occurred until 3500 cal yr BP and the late Holocene was dry. Spectral analysis of μXRF data show rainfall cyclicity at millennial scale throughout the Holocene, and at centennial down to ENSO scale in more specific time intervals. The highest rainfall intervals correlate with the highest activity of ENSO. Variability in solar output is possibly the main cause for this millennial to decadal cyclicity. We interpret ENSO and ITCZ as the main climate change-driving mechanisms in Frontino. Comparison with high-resolution XRF data from the Caribbean Cariaco Basin (a proxy for rainfall in the coastal Venezuelian cordilleras) demonstrates that climate in Frontino was Pacific-driven (ENSO-dominated) during the YD and early Holocene, whereas it was Atlantic
NASA Astrophysics Data System (ADS)
Shulmeister, J.; Nobes, D. C.; Striewski, B.
2008-05-01
The maar craters of the New Zealand Auckland Volcanic Field (36.5°S, 174.5°E) contain some of the highest resolution late-Quaternary paleoclimate records in the Southern Hemisphere. Here we integrate laminae count results from recent drilling in the Hopua Crater with existing records from the nearby Onepoto Crater (Pepper et al., 2004). In total these records cover many thousands of years between the onset of the last glaciation maximum and the early mid-Holocene. The cores are strongly laminated. Individual laminae in both craters are very fine (sub-mm to mm scale) and form couplets which comprise a darker mineralogenic rich layer and a lighter diatomaceous layer. In places these couplets are annual, and may reflect seasonal algal blooms, but in other sections of the record, notably through the late-Glacial and Holocene, the couplets are deposited at inter-annual time scales. Spectral analyses of couplet thickness counts using a fast Fourier transform (FFT) with 64 to 256-year running windows, and a 50 per cent overlap indicate strong spectral power during the LGM and markedly weaker power during both the deglaciation and early Holocene. In fact there is no spectral strength for most of these periods. Three brief (centennial duration) events punctuate this extended period of low spectral power. These occur at c. 16 ka, c. 14.8 ka and during the early Holocene. They display spectral power in the 5-7yr ENSO window and also at longer time intervals that may be consistent with the Pacific Decadal Oscillation. We infer the local switching on (or up) of ENSO and PDO teleconnections and suspect these are embedded in circum-polar circulation changes. In addition to these spectral power episodes, there is a general increase in the number of couplet cycles per century between the deglaciation and the early mid-Holocene. This matches observations from Equador and Peru and suggests that trans-Pacific ENSO responses are in phase between western tropical South America and New
Kang, Xianbiao; Zhang, Rong-Hua; Gao, Chuan; Zhu, Jieshun
2017-12-07
The El Niño-Southern oscillation (ENSO) simulated in the Community Earth System Model of the National Center for Atmospheric Research (NCAR CESM) is much stronger than in reality. Here, satellite data are used to derive a statistical relationship between interannual variations in oceanic chlorophyll (CHL) and sea surface temperature (SST), which is then incorporated into the CESM to represent oceanic chlorophyll -induced climate feedback in the tropical Pacific. Numerical runs with and without the feedback (referred to as feedback and non-feedback runs) are performed and compared with each other. The ENSO amplitude simulated in the feedback run is more accurate than that in the non-feedback run; quantitatively, the Niño3 SST index is reduced by 35% when the feedback is included. The underlying processes are analyzed and the results show that interannual CHL anomalies exert a systematic modulating effect on the solar radiation penetrating into the subsurface layers, which induces differential heating in the upper ocean that affects vertical mixing and thus SST. The statistical modeling approach proposed in this work offers an effective and economical way for improving climate simulations.
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 (2009â2013) from two freshwater marsh sites located in Everglades National Park that differ...
Impacts of the ENSO Modoki and other Tropical Indo-Pacific Climate-Drivers on African Rainfall
Preethi, B.; Sabin, T. P.; Adedoyin, J. A.; Ashok, K.
2015-01-01
The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (ENSO), ENSO Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (enhancement) of rainfall in southern (northern) hemispheric regions during March-May season. However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September. Interestingly, during boreal spring and summer, in many regions, the Indian Ocean drivers have influences opposite to those from tropical Pacific drivers. On the other hand, during the October-December season, the canonical El Niño and/or positive IOD are associated with an anomalous enhancement of rainfall in the Eastern Africa, while the El Niño Modoki events are associated with an opposite impact. In addition to the Walker circulation changes, the Indo-Pacific drivers influence the African rainfall through modulating jet streams. During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet. This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa. PMID:26567458
Impacts of the ENSO Modoki and other Tropical Indo-Pacific Climate-Drivers on African Rainfall.
Preethi, B; Sabin, T P; Adedoyin, J A; Ashok, K
2015-11-16
The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (ENSO), ENSO Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (enhancement) of rainfall in southern (northern) hemispheric regions during March-May season. However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September. Interestingly, during boreal spring and summer, in many regions, the Indian Ocean drivers have influences opposite to those from tropical Pacific drivers. On the other hand, during the October-December season, the canonical El Niño and/or positive IOD are associated with an anomalous enhancement of rainfall in the Eastern Africa, while the El Niño Modoki events are associated with an opposite impact. In addition to the Walker circulation changes, the Indo-Pacific drivers influence the African rainfall through modulating jet streams. During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet. This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa.
NASA Astrophysics Data System (ADS)
Akanda, A. S.; Jutla, A.; Huq, A.; Colwell, R. R.
2014-12-01
Cholera is a global disease, with significantly large outbreaks occurring since the 1990s, notably in Sub-Saharan Africa and South Asia and recently in Haiti, in the Caribbean. Critical knowledge gaps remain in the understanding of the annual recurrence in endemic areas and the nature of epidemic outbreaks, especially those that follow extreme hydroclimatic events. Teleconnections with large-scale climate phenomena affecting regional scale hydroclimatic drivers of cholera dynamics remain largely unexplained. For centuries, the Bengal delta region has been strongly influenced by the asymmetric availability of water in the rivers Ganges and the Brahmaputra. As these two major rivers are known to have strong contrasting affects on local cholera dynamics in the region, we argue that the role of El Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), or other phenomena needs to be interpreted in the context of the seasonal role of individual rivers and subsequent impact on local environmental processes, not as a teleconnection having a remote and unified effect. We present a modified hypothesis that the influences of large-scale climate phenomena such as ENSO and IOD on Bengal cholera can be explicitly identified and incorporated through regional scale hydroclimatic drivers. Here, we provide an analytical review of the literature addressing cholera and climate linkages and present hypotheses, based on recent evidence, and quantification on the role of regional scale hydroclimatic drivers of cholera. We argue that the seasonal changes in precipitation and temperature, and resulting river discharge in the GBM basin region during ENSO and IOD events have a dominant combined effect on the endemic persistence and the epidemic vulnerability to cholera outbreaks in spring and fall seasons, respectively, that is stronger than the effect of localized hydrological and socio-economic sensitivities in Bangladesh. In addition, systematic identification of underlying seasonal
MacCarthy, Dilys S.; Adiku, Samuel G. K.; Freduah, Bright S.; Gbefo, Francis; Kamara, Alpha Y.
2017-01-01
Maize (Zea mays) has traditionally been a major cereal staple in southern Ghana. Through breeding and other crop improvement efforts, the zone of cultivation of maize has now extended to the northern regions of Ghana which, hitherto, were the home to sorghum and millet as the major cereals. Maize yield in the northern Ghana is hampered by three major biophysical constraints, namely, poor soil fertility, low soil water storage capacity and climate variability. In this study we used the DSSAT crop model to assess integrated water and soil management strategies that combined the pre-season El-Niño-Southern Oscillation (ENSO)-based weather forecasting in selecting optimal planting time, at four locations in the northern regions of Ghana. It could be shown that the optimum planting date for a given year was predictable based on February-to-April (FMA) Sea Surface Temperature (SST) anomaly for the locations with R2 ranging from 0.52 to 0.71. For three out of four locations, the ENSO-predicted optimum planting dates resulted in significantly higher maize yields than the conventional farmer selected planting dates. In Wa for instance, early optimum planting dates were associated with La Nina and El Niño (Julian Days 130-150; early May to late May) whereas late planting (mid June to early July) was associated with the Neutral ENSO phase. It was also observed that the addition of manure and fertilizer improved soil water and nitrogen use efficiency, respectively, and minimized yield variability, especially when combined with weather forecast. The use of ENSO-based targeted planting date choice together with modest fertilizer and manure application has the potential to improve maize yields and also ensure sustainable maize production in parts of northern Ghana. PMID:28184227
NASA Astrophysics Data System (ADS)
Peiro, Hélène; Emili, Emanuele; Cariolle, Daniel; Barret, Brice; Le Flochmoën, Eric
2018-05-01
The Infrared Atmospheric Sounder Instrument (IASI) allows global coverage with very high spatial resolution and its measurements are promising for long-term ozone monitoring. In this study, Microwave Limb Sounder (MLS) O3 profiles and IASI O3 partial columns (1013.25-345 hPa) are assimilated in a chemistry transport model to produce 6-hourly analyses of tropospheric ozone for 6 years (2008-2013). We have compared and evaluated the IASI-MLS analysis and the MLS analysis to assess the added value of IASI measurements. The global chemical transport model MOCAGE (MOdèle de Chimie Atmosphérique à Grande Echelle) has been used with a linear ozone chemistry scheme and meteorological forcing fields from ERA-Interim (ECMWF global reanalysis) with a horizontal resolution of 2° × 2° and 60 vertical levels. The MLS and IASI O3 retrievals have been assimilated with a 4-D variational algorithm to constrain stratospheric and tropospheric ozone respectively. The ozone analyses are validated against ozone soundings and tropospheric column ozone (TCO) from the OMI-MLS residual method. In addition, an Ozone ENSO Index (OEI) is computed from the analysis to validate the TCO variability during the ENSO events. We show that the assimilation of IASI reproduces the variability of tropospheric ozone well during the period under study. The variability deduced from the IASI-MLS analysis and the OMI-MLS measurements are similar for the period of study. The IASI-MLS analysis can reproduce the extreme oscillation of tropospheric ozone caused by ENSO events over the tropical Pacific Ocean, although a correction is required to reduce a constant bias present in the IASI-MLS analysis.
NASA Astrophysics Data System (ADS)
Mo, Ruping; Joe, Paul I.; Doyle, Chris; Whitfield, Paul H.
2014-01-01
A brief review of the anomalous weather conditions during the Vancouver 2010 Winter Olympic and Paralympic Games and the efforts to predict these anomalies based on some preceding El Niño-Southern Oscillation (ENSO) signals are presented. It is shown that the Olympic Games were held under extraordinarily warm conditions in February 2010, with monthly mean temperature anomalies of +2.2 °C in Vancouver and +2.8 °C in Whistler, ranking respectively as the highest and the second highest in the past 30 years (1981-2010). The warm conditions continued, but became less anomalous, in March 2010 for the Paralympic Games. While the precipitation amounts in the area remained near normal through this winter, the lack of snow due to warm conditions created numerous media headlines and practical problems for the alpine competitions. A statistical model was developed on the premise that February and March temperatures in the Vancouver area could be predicted using an ENSO signal with considerable lead time. This model successfully predicted the warmer-than-normal, lower-snowfall conditions for the Vancouver 2010 Winter Olympics and Paralympics.
49 CFR 173.24 - General requirements for packagings and packages.
Code of Federal Regulations, 2011 CFR
2011-10-01
...) New packagings and packagings which are reused; and (3) Specification and non-specification packagings..., sufficient ullage (outage) must be left to ensure that neither leakage nor permanent distortion of the...
Fresh New Air in Space? `MoMa' on the A.S.I. Launch Pad
NASA Astrophysics Data System (ADS)
Ambesi Impiombato, Francesco Saverio; Curcio, Francesco; Meli, Antonella; Zambito, Anna Maria
2006-12-01
The present project has been developed because of the desire to unify the research lines in the A.S.I. ‘Medicine & Biotechnology’ area into one research line that could satisfy the interests of all of the collaborative groups and at the same time could pursue a relevant social goal. A 6 month feasibility study (SF) called MoMa was carried out in the ASI framework. During the SF the know-how and the tools already available in the national scientific community have been assessed, selected and evaluated even with the important contribution of Small and Medium-size Enterprises (SME) and of Italian industries already involved in Space Research. As result of the SF MoMa, all of the participants decided to combine all the efforts together and define, with all the know-how and the available technologies, one strategic topic, the “Aging” with a special attention to the Quality of Life (QoL). The space environment is a unique laboratory to study the reaction of living organisms (especially humans) to microgravity and cosmic radiation. The study of the effects of these two variables at the molecular and cellular levels will shed light on the response of cells and living organisms to adverse stimulations that are always present even on Earth and will help us able to develop the best strategies to protect the organisms from the progressive structural and functional decline related to Aging. Relevant spin-offs on Earth and also relevant industrial applications are the expected outputs of this project.
The influence of ENSO, PDO and PNA on secular rainfall variations in Hawai`i
NASA Astrophysics Data System (ADS)
Frazier, Abby G.; Elison Timm, Oliver; Giambelluca, Thomas W.; Diaz, Henry F.
2017-11-01
Over the last century, significant declines in rainfall across the state of Hawai`i have been observed, and it is unknown whether these declines are due to natural variations in climate, or manifestations of human-induced climate change. Here, a statistical analysis of the observed rainfall variability was applied as first step towards better understanding causes for these long-term trends. Gridded seasonal rainfall from 1920 to 2012 is used to perform an empirical orthogonal function (EOF) analysis. The leading EOF components are correlated with three indices of natural climate variations (El Niño-Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Pacific North American (PNA)), and multiple linear regression (MLR) is used to model the leading components with climate indices. PNA is the dominant mode of wet season (November-April) variability, while ENSO is most significant in the dry season (May-October). To assess whether there is an anthropogenic influence on rainfall, two methods are used: a linear trend term is included in the MLR, and pattern correlation coefficients (PCC) are calculated between recent rainfall trends and future changes in rainfall projected by downscaling methods. PCC results indicate that recent observed rainfall trends in the wet season are positively correlated with future expected changes in rainfall, while dry season PCC results do not show a clear pattern. The MLR results, however, show that the trend term adds significantly to model skill only in the dry season. Overall, MLR and PCC results give weak and inconclusive evidence for detection of anthropogenic signals in the observed rainfall trends.
ENSO/PDO-Like Variability of Tropical Ocean Surface Energy Fluxes Over the Satellite Era
NASA Technical Reports Server (NTRS)
Robertson, F. R.; Miller, Tim L.
2008-01-01
Recent variations of tropical climate on interannual to near-decadal scales have provided a useful target for studying the nature of climate feedback processes. A strong warm / cold ENSO couplet (e.g. 1997-2000) along with several subsequent weaker events are prominent interannual signals that are part of an apparent longer term strengthening of the Walker circulation during the mid to late 1990's with some weakening thereafter. Decadal scale changes in tropical SST structure during the 1990s are accompanied by focusing of precipitation over the Indo-Pacific warm pool and an increase in tropical ocean evaporation of order 1.0 % /decade. Associated with ENSO and PDO-like tropical SST changes are surface freshwater and radiative fluxes which have important implications for heat and energy transport variations. In this study we examine how surface fluxes attending interannual to decadal SST fluctuations, e.g. precipitation (GPCP, TRMM), turbulent fluxes (OAFlux), and radiative fluxes (ERBE/CERES, SRB) are coupled. Using these data we analyze vertically-integrated divergence of moist static energy, divMSE, and its dry static energy and latent energy components. We examine consistency between these data sets and explore relationships between SST variations, flux changes and modulation of tropical Walker and Hadley circulations. Strong signatures ofMSE flux transport linking ascending and descending regions of tropical circulations are found. Relative strengths of these fluxes and transports are interpreted as a measure of efficiency in the overall process of tropical heat balance during episodes of warm or cold tropical SST.
NASA Astrophysics Data System (ADS)
Ham, Yoo-Geun
2017-08-01
This study analyzes a reduction in the asymmetry of El Niño Southern-Oscillation (ENSO) amplitude due to global warming in Coupled Model Intercomparison Project Phase 5 models. The multimodel-averaged Niño3 skewness during December-February season decreased approximately 40% in the RCP4.5 scenario compared to that in the historical simulation. The change in the nonlinear relationship between sea surface temperature (SST) and precipitation is a key factor for understanding the reduction in ENSO asymmetry due to global warming. In the historical simulations, the background SST leading to the greatest precipitation sensitivity (SST for Maximum Precipitation Sensitivity, SST_MPS) occurs when the positive SST anomaly is located over the equatorial central Pacific. Therefore, an increase in climatological SST due to global warming weakens the atmospheric response during El Niño over the central Pacific. However, the climatological SST over this region in the historical simulation is still lower than the SST_MPS for the negative SST anomaly; therefore, a background SST increase due to global warming can further increase precipitation sensitivity. The atmospheric feedbacks during La Niña are enhanced and increase the La Niña amplitude due to global warming.
Advancements in meat packaging.
McMillin, Kenneth W
2017-10-01
Packaging of meat provides the same or similar benefits for raw chilled and processed meats as other types of food packaging. Although air-permeable packaging is most prevalent for raw chilled red meat, vacuum and modified atmosphere packaging offer longer shelf life. The major advancements in meat packaging have been in the widely used plastic polymers while biobased materials and their integration into composite packaging are receiving much attention for functionality and sustainability. At this time, active and intelligent packaging are not widely used for antioxidant, antimicrobial, and other functions to stabilize and enhance meat properties although many options are being developed and investigated. The advances being made in nanotechnology will be incorporated into food packaging and presumably into meat packaging when appropriate and useful. Intelligent packaging using sensors for transmission of desired information and prompting of subsequent changes in packaging materials, environments or the products to maintain safety and quality are still in developmental stages. Copyright © 2017 Elsevier Ltd. All rights reserved.
Potential role of resurfacing Subtropical Underwater in ENSO evolution
NASA Astrophysics Data System (ADS)
Qu, T.; Chi, J.
2017-12-01
Results from a model of the Estimating the Circulation and Climate of the Ocean (ECCO) have shown that the resurfacing of high salinity Subtropical Underwater contributes to the sea surface salinity variability in the equatorial Pacific. On interannual time scale, this contribution can account for as much as 25% of the surface freshwater flux anomalies and is believed to play a role in ENSO evolution. Having these results in mind, this study investigates the surface salinity budget and its primary controls in the equatorial Pacific using ECCO output for the period 1993-2016. Particular attention is paid to 2014/2015 and 2015/2016. Preliminary analyses of the model results suggest that enhanced subsurface processes and in particular enhanced entrainment of Subtropical Underwater are primarily responsible for the positive sea surface salinity anomalies in the central equatorial Pacific during 2014/2015, which represents an opposite phase of El Niño. These subsurface processes weakened during 2015/2016, diretly contributing to the development of the 2015/2016 El Niño. The mechanisms controlling these subsurface processes are discussed.
GenASiS Basics: Object-oriented utilitarian functionality for large-scale physics simulations
Cardall, Christian Y.; Budiardja, Reuben D.
2015-06-11
Aside from numerical algorithms and problem setup, large-scale physics simulations on distributed-memory supercomputers require more basic utilitarian functionality, such as physical units and constants; display to the screen or standard output device; message passing; I/O to disk; and runtime parameter management and usage statistics. Here we describe and make available Fortran 2003 classes furnishing extensible object-oriented implementations of this sort of rudimentary functionality, along with individual `unit test' programs and larger example problems demonstrating their use. Lastly, these classes compose the Basics division of our developing astrophysics simulation code GenASiS (General Astrophysical Simulation System), but their fundamental nature makes themmore » useful for physics simulations in many fields.« less
Packaging Your Training Materials
ERIC Educational Resources Information Center
Espeland, Pamela
1977-01-01
The types of packaging and packaging materials to use for training materials should be determined during the planning of the training programs, according to the packaging market. Five steps to follow in shopping for packaging are presented, along with a list of packaging manufacturers. (MF)
Janjarasskul, Theeranun; Krochta, John M
2010-01-01
Research groups and the food and pharmaceutical industries recognize edible packaging as a useful alternative or addition to conventional packaging to reduce waste and to create novel applications for improving product stability, quality, safety, variety, and convenience for consumers. Recent studies have explored the ability of biopolymer-based food packaging materials to carry and control-release active compounds. As diverse edible packaging materials derived from various by-products or waste from food industry are being developed, the dry thermoplastic process is advancing rapidly as a feasible commercial edible packaging manufacturing process. The employment of nanocomposite concepts to edible packaging materials promises to improve barrier and mechanical properties and facilitate effective incorporation of bioactive ingredients and other designed functions. In addition to the need for a more fundamental understanding to enable design to desired specifications, edible packaging has to overcome challenges such as regulatory requirements, consumer acceptance, and scaling-up research concepts to commercial applications.
Influence of Decadal Variability of Global Oceans on South Asian Monsoon and ENSO-Monsoon Relation
NASA Astrophysics Data System (ADS)
Krishnamurthy, Lakshmi
This study has investigated the influence of the decadal variability associated with global oceans on South Asian monsoon and El Nino-Southern Oscillation (ENSO)-monsoon relation. The results are based on observational analysis using long records of monsoon rainfall and circulation and coupled general circulation model experiments using the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM) version 4 model. The multi-channel singular spectrum analysis (MSSA) of the observed rainfall over India yields three decadal modes. The first mode (52 year period) is associated with the Atlantic Multidecadal Oscillation (AMO), the second one (21 year) with the Pacific Decadal Oscillation (PDO) and the third mode (13 year) with the Atlantic tripole. The existence of these decadal modes in the monsoon was also found in the control simulation of NCAR CCSM4. The regionally de-coupled model experiments performed to isolate the influence of North Pacific and North Atlantic also substantiate the above results. The relation between the decadal modes in the monsoon rainfall with the known decadal modes in global SST is examined. The PDO has significant negative correlation with the Indian Monsoon Rainfall (IMR). The mechanism for PDO-monsoon relation is hypothesized through the seasonal footprinting mechanism and further through Walker and Hadley circulations. The model results also confirm the negative correlation between PDO and IMR and the mechanism through which PDO influences monsoon. Both observational and model analysis show that droughts (floods) are more likely over India than floods (droughts) when ENSO and PDO are in their warm (cold) phase. This study emphasizes the importance of carefully distinguishing the different decadal modes in the SST in the North Atlantic Ocean as they have different impacts on the monsoon. The AMO exhibits significant positive correlation with the IMR while the Atlantic tripole has significant negative
NASA Astrophysics Data System (ADS)
Kholodnov, Viacheslav; Drugova, Albina; Nikitin, Mikhail; Chekanova, Galina
2012-10-01
Technology of infrared (IR) avalanche photodiodes (APDs) gradually moves from simple single element APD to 2D focal plane arrays (FPA). Spectral covering of APDs is expanded continuously from classic 1.3 μm to longer wavelengths due to using of narrow-gap semiconductor materials like Hg1-xCdxTe. APDs are of great interest to developers and manufacturers of different optical communication, measuring and 3D reconstruction thermal imaging systems. Major IR detector materials for manufacturing of high-performance APDs became heteroepitaxial structures InxGa1-xAsyP1-y and Hg1-xCdxTe. Progress in IR APD technology was achieved through serious improvement in material growing techniques enabling forming of multilayer heterostuctures with separate absorption and multiplication regions (SAM). Today SAM-APD design can be implemented both on InxGa1-xAsyP1-y and Hg1-xCdxTe multilayer heteroepitaxial structures. To create the best performance optimal design avalanche heterophotodiode (AHPD) it is necessary to carry out a detailed theoretical analysis of basic features of generation, avalanche breakdown and multiplication of charge carriers in proper heterostructure. Optimization of AHPD properties requires comprehensive estimation of AHPD's pixel performance depending on pixel's multi-layer structure design, layers doping, distribution of electric field in the structure and operating temperature. Objective of the present article is to compare some features of 1.55 μm SAM-AHPDs based on InxGa1-xAsyP1-y and Hg1-xCdxTe.
Spielberger, Richard; Ohme, Bruce Walker; Jensen, Ronald J.
2011-06-21
A heater for heating packaged die for burn-in and heat testing is described. The heater may be a ceramic-type heater with a metal filament. The heater may be incorporated into the integrated circuit package as an additional ceramic layer of the package, or may be an external heater placed in contact with the package to heat the die. Many different types of integrated circuit packages may be accommodated. The method provides increased energy efficiency for heating the die while reducing temperature stresses on testing equipment. The method allows the use of multiple heaters to heat die to different temperatures. Faulty die may be heated to weaken die attach material to facilitate removal of the die. The heater filament or a separate temperature thermistor located in the package may be used to accurately measure die temperature.
NASA Technical Reports Server (NTRS)
Robertson, Franklin R.; Fitzjarrald, Dan; Marshall, Susan; Oglesby, Robert; Roads, John; Arnold, James E. (Technical Monitor)
2001-01-01
This paper focuses on how fresh water and radiative fluxes over the tropical oceans change during ENSO warm and cold events and how these changes affect the tropical energy balance. At present, ENSO remains the most prominent known mode of natural variability at interannual time scales. While this natural perturbation to climate is quite distinct from possible anthropogenic changes in climate, adjustments in the tropical water and energy budgets during ENSO may give insight into feedback processes involving water vapor and cloud feedbacks. Although great advances have been made in understanding this phenomenon and realizing prediction skill over the past decade, our ability to document the coupled water and energy changes observationally and to represent them in climate models seems far from settled (Soden, 2000 J Climate). In a companion paper we have presented observational analyses, based principally on space-based measurements which document systematic changes in rainfall, evaporation, and surface and top-of-atmosphere (TOA) radiative fluxes. Here we analyze several contemporary climate models run with observed SSTs over recent decades and compare SST-induced changes in radiation, precipitation, evaporation, and energy transport to observational results. Among these are the NASA / NCAR Finite Volume Model, the NCAR Community Climate Model, the NCEP Global Spectral Model, and the NASA NSIPP Model. Key disagreements between model and observational results noted in the recent literature are shown to be due predominantly to observational shortcomings. A reexamination of the Langley 8-Year Surface Radiation Budget data reveals errors in the SST surface longwave emission due to biased SSTs. Subsequent correction allows use of this data set along with ERBE TOA fluxes to infer net atmospheric radiative heating. Further analysis of recent rainfall algorithms provides new estimates for precipitation variability in line with interannual evaporation changes inferred from
DOE Office of Scientific and Technical Information (OSTI.GOV)
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 amore » temperature-dependent fractionation on {delta}{sup 18}O, but where annual rainfall is high and sea surface temperature (SST) variability is low the freshwater flux effect dominates.« less
Tessé, Sophie; Bourbon, Henri-Marc; Debuchy, Robert; Budin, Karine; Dubois, Emeline; Liangran, Zhang; Antoine, Romain; Piolot, Tristan; Kleckner, Nancy; Zickler, Denise; Espagne, Eric
2017-01-01
Meiosis is the cellular program by which a diploid cell gives rise to haploid gametes for sexual reproduction. Meiotic progression depends on tight physical and functional coupling of recombination steps at the DNA level with specific organizational features of meiotic-prophase chromosomes. The present study reveals that every step of this coupling is mediated by a single molecule: Asy2/Mer2. We show that Mer2, identified so far only in budding and fission yeasts, is in fact evolutionarily conserved from fungi (Mer2/Rec15/Asy2/Bad42) to plants (PRD3/PAIR1) and mammals (IHO1). In yeasts, Mer2 mediates assembly of recombination–initiation complexes and double-strand breaks (DSBs). This role is conserved in the fungus Sordaria. However, functional analysis of 13 mer2 mutants and successive localization of Mer2 to axis, synaptonemal complex (SC), and chromatin revealed, in addition, three further important functions. First, after DSB formation, Mer2 is required for pairing by mediating homolog spatial juxtaposition, with implications for crossover (CO) patterning/interference. Second, Mer2 participates in the transfer/maintenance and release of recombination complexes to/from the SC central region. Third, after completion of recombination, potentially dependent on SUMOylation, Mer2 mediates global chromosome compaction and post-recombination chiasma development. Thus, beyond its role as a recombinosome–axis/SC linker molecule, Mer2 has important functions in relation to basic chromosome structure. PMID:29021238
ENSO's far reaching connection to Indian cold waves.
Ratnam, J V; Behera, Swadhin K; Annamalai, H; Ratna, Satyaban B; Rajeevan, M; Yamagata, Toshio
2016-11-23
During boreal winters, cold waves over India are primarily due to transport of cold air from higher latitudes. However, the processes associated with these cold waves are not yet clearly understood. Here by diagnosing a suite of datasets, we explore the mechanisms leading to the development and maintenance of these cold waves. Two types of cold waves are identified based on observed minimum surface temperature and statistical analysis. The first type (TYPE1), also the dominant one, depicts colder than normal temperatures covering most parts of the country while the second type (TYPE2) is more regional, with significant cold temperatures only noticeable over northwest India. Quite interestingly the first (second) type is associated with La Niña (El Niño) like conditions, suggesting that both phases of ENSO provide a favorable background for the occurrence of cold waves over India. During TYPE1 cold wave events, a low-level cyclonic anomaly generated over the Indian region as an atmospheric response to the equatorial convective anomalies is seen advecting cold temperatures into India and maintaining the cold waves. In TYPE2 cold waves, a cyclonic anomaly generated over west India anomalously brings cold winds to northwest India causing cold waves only in those parts.
NASA Astrophysics Data System (ADS)
Wang, Chunxue; Ma, Zhenfeng
2018-04-01
The rainy season precipitation in Tibet (RSPT) is a direct cause for local floods/droughts. It also indirectly affects the thermal conditions of the Tibetan Plateau, which can result in anomalous patterns of atmospheric circulation over East Asia. The interannual variability of the RSPT is often linked with the El Niño-Southern Oscillation (ENSO), but the relevant mechanisms are far from being understood, particularly for different types of ENSO events. We investigated the interannual variation of the RSPT in association with different types of ENSO. A quasi-3-yr period of the RSPT (less-more-more precipitation) was significant at the 95% confidence level. A joint multi-taper method with singular value decomposition analysis of the coupled field between the RSPT and the sea surface temperature (SST) revealed that the developing eastern Pacific type El Niño was accompanied by a decrease in the RSPT. The shift from the central Pacific type El Niño to the eastern Pacific La Niña was accompanied by an increase in the RSPT. Weakening of the central Pacific La Niña was accompanied by an increase in the RSPT. Analysis of the mechanism of this coupling, using the same analysis method but other climatic factors, indicated that the gradually strengthening eastern Pacific El Niño can inhibit the Walker circulation, weakening the South Asian summer monsoon, and resulting in transport of less water vapor from the Bay of Bengal to Tibet. The change from the central Pacific El Niño to the eastern Pacific La Niña led to continued strengthening of the Walker circulation with westward movement of the ascending area. This enhanced the South Asian summer monsoon over the Arabian Sea and transported more water vapor to Tibet. The decreasing central Pacific La Niña accompanied by persistent cooling of SSTs in the equatorial Pacific led to a strong eastern North Pacific summer monsoon, causing an anomaly in the easterly transport of water vapor from the Sea of Japan to Tibet and
49 CFR 173.24a - Additional general requirements for non-bulk packagings and packages.
Code of Federal Regulations, 2010 CFR
2010-10-01
... subchapter. (b) Non-bulk packaging filling limits. (1) A single or composite non-bulk packaging may be filled... gross mass marked on the packaging. (3) A single or composite non-bulk packaging which is tested and... marked on the packaging, or 1.2 if not marked. In addition: (i) A single or composite non-bulk packaging...
49 CFR 173.24a - Additional general requirements for non-bulk packagings and packages.
Code of Federal Regulations, 2012 CFR
2012-10-01
... subchapter. (b) Non-bulk packaging filling limits. (1) A single or composite non-bulk packaging may be filled... gross mass marked on the packaging. (3) A single or composite non-bulk packaging which is tested and... marked on the packaging, or 1.2 if not marked. In addition: (i) A single or composite non-bulk packaging...
49 CFR 173.24a - Additional general requirements for non-bulk packagings and packages.
Code of Federal Regulations, 2013 CFR
2013-10-01
... subchapter. (b) Non-bulk packaging filling limits. (1) A single or composite non-bulk packaging may be filled... gross mass marked on the packaging. (3) A single or composite non-bulk packaging which is tested and... marked on the packaging, or 1.2 if not marked. In addition: (i) A single or composite non-bulk packaging...
Optimization of imprintable nanostructured a-Si solar cells: FDTD study.
Fisker, Christian; Pedersen, Thomas Garm
2013-03-11
We present a finite-difference time-domain (FDTD) study of an amorphous silicon (a-Si) thin film solar cell, with nano scale patterns on the substrate surface. The patterns, based on the geometry of anisotropically etched silicon gratings, are optimized with respect to the period and anti-reflection (AR) coating thickness for maximal absorption in the range of the solar spectrum. The structure is shown to increase the cell efficiency by 10.2% compared to a similar flat solar cell with an optimized AR coating thickness. An increased back reflection can be obtained with a 50 nm zinc oxide layer on the back reflector, which gives an additional efficiency increase, leading to a total of 14.9%. In addition, the patterned cells are shown to be up to 3.8% more efficient than an optimized textured reference cell based on the Asahi U-type glass surface. The effects of variations of the optimized solar cell structure due to the manufacturing process are investigated, and shown to be negligible for variations below ±10%.
NASA Technical Reports Server (NTRS)
Klumpp, A. R.
1994-01-01
Ten families of subprograms are bundled together for the General-Purpose Ada Packages. The families bring to Ada many features from HAL/S, PL/I, FORTRAN, and other languages. These families are: string subprograms (INDEX, TRIM, LOAD, etc.); scalar subprograms (MAX, MIN, REM, etc.); array subprograms (MAX, MIN, PROD, SUM, GET, and PUT); numerical subprograms (EXP, CUBIC, etc.); service subprograms (DATE_TIME function, etc.); Linear Algebra II; Runge-Kutta integrators; and three text I/O families of packages. In two cases, a family consists of a single non-generic package. In all other cases, a family comprises a generic package and its instances for a selected group of scalar types. All generic packages are designed to be easily instantiated for the types declared in the user facility. The linear algebra package is LINRAG2. This package includes subprograms supplementing those in NPO-17985, An Ada Linear Algebra Package Modeled After HAL/S (LINRAG). Please note that LINRAG2 cannot be compiled without LINRAG. Most packages have widespread applicability, although some are oriented for avionics applications. All are designed to facilitate writing new software in Ada. Several of the packages use conventions introduced by other programming languages. A package of string subprograms is based on HAL/S (a language designed for the avionics software in the Space Shuttle) and PL/I. Packages of scalar and array subprograms are taken from HAL/S or generalized current Ada subprograms. A package of Runge-Kutta integrators is patterned after a built-in MAC (MIT Algebraic Compiler) integrator. Those packages modeled after HAL/S make it easy to translate existing HAL/S software to Ada. The General-Purpose Ada Packages program source code is available on two 360K 5.25" MS-DOS format diskettes. The software was developed using VAX Ada v1.5 under DEC VMS v4.5. It should be portable to any validated Ada compiler and it should execute either interactively or in batch. The largest package
Detecting small holes in packages
Kronberg, James W.; Cadieux, James R.
1996-01-01
A package containing a tracer gas, and a method for determining the presence of a hole in the package by sensing the presence of the gas outside the package. The preferred tracer gas, especially for food packaging, is sulfur hexafluoride. A quantity of the gas is added to the package and the package is closed. The concentration of the gas in the atmosphere outside the package is measured and compared to a predetermined value of the concentration of the gas in the absence of the package. A measured concentration greater than the predetermined value indicates the presence of a hole in the package. Measuring may be done in a chamber having a lower pressure than that in the package.
NASA Technical Reports Server (NTRS)
Stilwell, E. J.
1985-01-01
Most of the key areas of concern in packaging the three principle food forms for the space station were covered. It can be generally concluded that there are no significant voids in packaging materials availability or in current packaging technology. However, it must also be concluded that the process by which packaging decisions are made for the space station feeding program will be very synergistic. Packaging selection will depend heavily on the preparation mechanics, the preferred presentation and the achievable disposal systems. It will be important that packaging be considered as an integral part of each decision as these systems are developed.
Detecting small holes in packages
Kronberg, J.W.; Cadieux, J.R.
1996-03-19
A package containing a tracer gas, and a method for determining the presence of a hole in the package by sensing the presence of the gas outside the package are disclosed. The preferred tracer gas, especially for food packaging, is sulfur hexafluoride. A quantity of the gas is added to the package and the package is closed. The concentration of the gas in the atmosphere outside the package is measured and compared to a predetermined value of the concentration of the gas in the absence of the package. A measured concentration greater than the predetermined value indicates the presence of a hole in the package. Measuring may be done in a chamber having a lower pressure than that in the package. 3 figs.
On the Bimodality of ENSO Cycle Extremes
NASA Technical Reports Server (NTRS)
Wilson, Robert M.
1999-01-01
On the basis of sea surface temperature in the Nino 3.4 region (5 deg N-5 deg S, 120 deg- 170 deg W) during the interval of 1950-1997, Kevin Trenberth previously has identified some 16 El Nino and 10 La Nina, these 26 events representing the extremes of the quasi-periodic El Nino-Southern Oscillation (ENSO) cycle. Runs testing shows that the duration and recurrence period associated with these extremes vary randomly, as does the sequencing of the extremes. Hence, the frequency of occurrence of these events during the 1990s, especially, for El Nino should not be construed as being significantly different from that of previous epochs. Additionally, the distribution of duration for both El Nino and La Nina looks bimodal, consisting of two preferred modes - about 8 and 16 months in length for El Nino and about 9 and 18 months in length for La Nina. Likewise, the distribution of recurrence period, especially, for El Nino looks bimodal, consisting of two preferred modes - about 21 and 50 months in length. Scatter plots of the recurrence period versus duration for El Nino strongly suggest preferential associations between them, linking shorter (longer) duration with shorter (longer) recurrence period. Because the last known onset of El Nino occurred in April 1997 and the event was of longer than average duration, one infers that the onset of the next expected El Nino will not occur until February 2000 or later.
Anhydrous Ammonia Training Module. Trainer's Package. Participant's Package.
ERIC Educational Resources Information Center
Beaudin, Bart; And Others
This document contains a trainer's and a participant's package for teaching employees on site safe handling procedures for working with anhydrous ammonia, especially on farms. The trainer's package includes the following: a description of the module; a competency; objectives; suggested instructional aids; a training outline (or lesson plan) for…
Different types of drifts in two seasonal forecast systems and their dependence on ENSO
NASA Astrophysics Data System (ADS)
Hermanson, L.; Ren, H.-L.; Vellinga, M.; Dunstone, N. D.; Hyder, P.; Ineson, S.; Scaife, A. A.; Smith, D. M.; Thompson, V.; Tian, B.; Williams, K. D.
2017-11-01
Seasonal forecasts using coupled ocean-atmosphere climate models are increasingly employed to provide regional climate predictions. For the quality of forecasts to improve, regional biases in climate models must be diagnosed and reduced. The evolution of biases as initialized forecasts drift away from the observations is poorly understood, making it difficult to diagnose the causes of climate model biases. This study uses two seasonal forecast systems to examine drifts in sea surface temperature (SST) and precipitation, and compares them to the long-term bias in the free-running version of each model. Drifts are considered from daily to multi-annual time scales. We define three types of drift according to their relation with the long-term bias in the free-running model: asymptoting, overshooting and inverse drift. We find that precipitation almost always has an asymptoting drift. SST drifts on the other hand, vary between forecasting systems, where one often overshoots and the other often has an inverse drift. We find that some drifts evolve too slowly to have an impact on seasonal forecasts, even though they are important for climate projections. The bias found over the first few days can be very different from that in the free-running model, so although daily weather predictions can sometimes provide useful information on the causes of climate biases, this is not always the case. We also find that the magnitude of equatorial SST drifts, both in the Pacific and other ocean basins, depends on the El Niño Southern Oscillation (ENSO) phase. Averaging over all hindcast years can therefore hide the details of ENSO state dependent drifts and obscure the underlying physical causes. Our results highlight the need to consider biases across a range of timescales in order to understand their causes and develop improved climate models.
NASA Astrophysics Data System (ADS)
Poveda, GermáN.; Jaramillo, Alvaro; Gil, Marta MaríA.; Quiceno, Natalia; Mantilla, Ricardo I.
2001-08-01
An analysis of hydrologic variability in Colombia shows different seasonal effects associated with El Niño/Southern Oscillation (ENSO) phenomenon. Spectral and cross-correlation analyses are developed between climatic indices of the tropical Pacific Ocean and the annual cycle of Colombia's hydrology: precipitation, river flows, soil moisture, and the Normalized Difference Vegetation Index (NDVI). Our findings indicate stronger anomalies during December-February and weaker during March-May. The effects of ENSO are stronger for streamflow than for precipitation, owing to concomitant effects on soil moisture and evapotranspiration. We studied time variability of 10-day average volumetric soil moisture, collected at the tropical Andes of central Colombia at depths of 20 and 40 cm, in coffee growing areas characterized by shading vegetation ("shaded coffee"), forest, and sunlit coffee. The annual and interannual variability of soil moisture are highly intertwined for the period 1997-1999, during strong El Niño and La Niña events. Soil moisture exhibited greater negative anomalies during 1997-1998 El Niño, being strongest during the two dry seasons that normally occur in central Colombia. Soil moisture deficits were more drastic at zones covered by sunlit coffee than at those covered by forest and shaded coffee. Soil moisture responds to wetter than normal precipitation conditions during La Niña 1998-1999, reaching maximum levels throughout that period. The probability density function of soil moisture records is highly skewed and exhibits different kinds of multimodality depending upon land cover type. NDVI exhibits strong negative anomalies throughout the year during El Niños, in particular during September-November (year 0) and June-August (year 0). The strong negative relation between NDVI and El Niño has enormous implications for carbon, water, and energy budgets over the region, including the tropical Andes and Amazon River basin.
IN-PACKAGE CHEMISTRY ABSTRACTION
DOE Office of Scientific and Technical Information (OSTI.GOV)
E. Thomas
2005-07-14
This report was developed in accordance with the requirements in ''Technical Work Plan for Postclosure Waste Form Modeling'' (BSC 2005 [DIRS 173246]). The purpose of the in-package chemistry model is to predict the bulk chemistry inside of a breached waste package and to provide simplified expressions of that chemistry as a function of time after breach to Total Systems Performance Assessment for the License Application (TSPA-LA). The scope of this report is to describe the development and validation of the in-package chemistry model. The in-package model is a combination of two models, a batch reactor model, which uses the EQ3/6more » geochemistry-modeling tool, and a surface complexation model, which is applied to the results of the batch reactor model. The batch reactor model considers chemical interactions of water with the waste package materials, and the waste form for commercial spent nuclear fuel (CSNF) waste packages and codisposed (CDSP) waste packages containing high-level waste glass (HLWG) and DOE spent fuel. The surface complexation model includes the impact of fluid-surface interactions (i.e., surface complexation) on the resulting fluid composition. The model examines two types of water influx: (1) the condensation of water vapor diffusing into the waste package, and (2) seepage water entering the waste package as a liquid from the drift. (1) Vapor-Influx Case: The condensation of vapor onto the waste package internals is simulated as pure H{sub 2}O and enters at a rate determined by the water vapor pressure for representative temperature and relative humidity conditions. (2) Liquid-Influx Case: The water entering a waste package from the drift is simulated as typical groundwater and enters at a rate determined by the amount of seepage available to flow through openings in a breached waste package.« less
Performance Study of an aSi Flat Panel Detector for Fast Neutron Imaging of Nuclear Waste
DOE Office of Scientific and Technical Information (OSTI.GOV)
Schumann, M.; Mauerhofer, E.; Engels, R.
Radioactive waste must be characterized to check its conformance for intermediate storage and final disposal according to national regulations. For the determination of radio-toxic and chemo-toxic contents of radioactive waste packages non-destructive analytical techniques are preferentially used. Fast neutron imaging is a promising technique to assay large and dense items providing, in complementarity to photon imaging, additional information on the presence of structures in radioactive waste packages. Therefore the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA) using 14 MeV neutrons is studied in a cooperation framework of Forschungszentrum Juelich GmbH, RWTH Aachen University and Siemensmore » AG. However due to the low neutron emission of neutron generators in comparison to research reactors the challenging task resides in the development of an imaging detector with a high efficiency, a low sensitivity to gamma radiation and a resolution sufficient for the purpose. The setup is composed of a commercial D-T neutron generator (Genie16GT, Sodern) with a surrounding shielding made of polyethylene, which acts as a collimator and an amorphous silicon flat panel detector (aSi, 40 x 40 cm{sup 2}, XRD-1642, Perkin Elmer). Neutron detection is achieved using a general propose plastic scintillator (EJ-260, Eljen Technology) linked to the detector. The thermal noise of the photodiodes is reduced by employing an entrance window made of aluminium. Optimal gain and integration time for data acquisition are set by measuring the response of the detector to the radiation of a 500 MBq {sup 241}Am-source. Detector performance was studied by recording neutron radiography images of materials with various, but well known, chemical compositions, densities and dimensions (Al, C, Fe, Pb, W, concrete, polyethylene, 5 x 8 x 10 cm{sup 3}). To simulate gamma-ray emitting waste radiographs in presence of a gamma-ray sources ({sup 60}Co, {sup 137}Cs
NASA Astrophysics Data System (ADS)
Chowdary, J. S.; Parekh, Anant; Gnanaseelan, C.; Sreenivas, P.
2014-01-01
Inter-decadal modulation of El Niño-Southern Oscillation (ENSO) teleconnections to tropical Indian Ocean (TIO) is investigated in the coupled general circulation model Climate Forecast System (CFS) using a hundred year integration. The model is able to capture the periodicity of El Niño variability, which is similar to that of the observations. The maximum TIO/north Indian Ocean (NIO) SST warming (during spring following the decay phase of El Niño) associated with El Niño is well captured by the model. Detailed analysis reveals that the surface heat flux variations mainly contribute to the El Niño forced TIO SST variations both in observations and model. However, spring warming is nearly stationary throughout the model integration period, indicating poor inter-decadal El Niño teleconnections. The observations on the other hand displayed maximum SST warming with strong seasonality from epoch to epoch. The model El Niño decay delayed by more than two seasons, results in persistent TIO/NIO SST warming through the following December unlike in the observations. The ocean wave adjustments and persistent westerly wind anomalies over the equatorial Pacific are responsible for late decay of El Niño in the model. Consistent late decay of El Niño, throughout the model integration period (low variance), is mainly responsible for the poor inter-decadal ENSO teleconnections to TIO/NIO. This study deciphers that the model needs to produce El Niño decay phase variability correctly to obtain decadal-modulations in ENSO teleconnection.
NASA Astrophysics Data System (ADS)
Zhang, Kexin; Qian, Xiaoqing; Liu, Puxing; Xu, Yihong; Cao, Liguo; Hao, Yongpei; Dai, Shengpei
2017-10-01
Analyses of the variation characteristics for aridity index (AI) can further enhance the understanding of climate change and have effect on hydrology and agriculture. In this paper, based on the data of 283 standard meteorological stations, the temporal-spatial variations and the influences of climate factors on AI were investigated and the relationship between AI and two climate indices (the Arctic Oscillation (AO); El Nino-Southern Oscillation (ENSO)) were also assessed in northern China (NC) during the period from 1961 to 2012. The results revealed that the annual mean AI decreased at the rate of -0.031 per decade in the past 52 years and the trend was statistically significant at the 0.01 level. The Mann-Kendall (M-K) test presented that the percentages of stations with positive trends and negative trends for AI were 10 and 81.9 % (22.6 % statistically significant), respectively. Spatially, in the western part of 100° E, the extremely dry area declined and the climate tended to become wet obviously. In the eastern part of 100° E, dry area moved toward the east and the south, which resulted in the enhancement of semiarid area and the shrinkage of subhumid area. The contributions of sunshine duration and precipitation to the decline of AI are more than those of other meteorological variables in NC. Moreover, the average temperature has risen significantly and AI decreased in NC, which indicated the existence of "paradox." Relationship between climate indices (AO and ENSO) and AI demonstrated that the influence of ENSO on AI overweight the AO on AI in NC.
Jo, Catherine L; Ambs, Anita; Dresler, Carolyn M; Backinger, Cathy L
2017-02-01
We aimed to investigate the effects of special packaging (child-resistant, adult-friendly) and tamper-resistant packaging on health and behavioral outcomes in order to identify research gaps and implications for packaging standards for tobacco products. We searched seven databases for keywords related to special and tamper-resistant packaging, consulted experts, and reviewed citations of potentially relevant studies. 733 unique papers were identified. Two coders independently screened each title and abstract for eligibility. They then reviewed the full text of the remaining papers for a second round of eligibility screening. Included studies investigated a causal relationship between type of packaging or packaging regulation and behavioral or health outcomes and had a study population composed of consumers. Studies were excluded on the basis of publication type, if they were not peer-reviewed, and if they had low external validity. Two reviewers independently coded each paper for study and methodological characteristics and limitations. Discrepancies were discussed and resolved. The review included eight studies: four assessing people's ability to access the contents of different packaging types and four evaluating the impact of packaging requirements on health-related outcomes. Child-resistant packaging was generally more difficult to open than non-child-resistant packaging. Child-resistant packaging requirements have been associated with reductions in child mortality. Child-resistant packaging holds the expectation to reduce tobacco product poisonings among children under six. Published by Elsevier Inc.
National Institute of Standards and Technology Data Gateway
NIST Scoring Package (PC database for purchase) The NIST Scoring Package (Special Database 1) is a reference implementation of the draft Standard Method for Evaluating the Performance of Systems Intended to Recognize Hand-printed Characters from Image Data Scanned from Forms.
Package Up Your Troubles--An Introduction to Package Libraries
ERIC Educational Resources Information Center
Frank, Colin
1978-01-01
Discusses a "package deal" library--a prefabricated building including interior furnishing--in terms of costs, fitness for purpose, and interior design, i.e., shelving, flooring, heating, lighting, and humidity. Advantages and disadvantages of the package library are also considered. (Author/MBR)
Antony, Bhavna Josephine; Kim, Byung-Jin; Lang, Andrew; Carass, Aaron; Prince, Jerry L; Zack, Donald J
2017-01-01
The use of spectral-domain optical coherence tomography (SD-OCT) is becoming commonplace for the in vivo longitudinal study of murine models of ophthalmic disease. Longitudinal studies, however, generate large quantities of data, the manual analysis of which is very challenging due to the time-consuming nature of generating delineations. Thus, it is of importance that automated algorithms be developed to facilitate accurate and timely analysis of these large datasets. Furthermore, as the models target a variety of diseases, the associated structural changes can also be extremely disparate. For instance, in the light damage (LD) model, which is frequently used to study photoreceptor degeneration, the outer retina appears dramatically different from the normal retina. To address these concerns, we have developed a flexible graph-based algorithm for the automated segmentation of mouse OCT volumes (ASiMOV). This approach incorporates a machine-learning component that can be easily trained for different disease models. To validate ASiMOV, the automated results were compared to manual delineations obtained from three raters on healthy and BALB/cJ mice post LD. It was also used to study a longitudinal LD model, where five control and five LD mice were imaged at four timepoints post LD. The total retinal thickness and the outer retina (comprising the outer nuclear layer, and inner and outer segments of the photoreceptors) were unchanged the day after the LD, but subsequently thinned significantly (p < 0.01). The retinal nerve fiber-ganglion cell complex and the inner plexiform layers, however, remained unchanged for the duration of the study.
Lang, Andrew; Carass, Aaron; Prince, Jerry L.; Zack, Donald J.
2017-01-01
The use of spectral-domain optical coherence tomography (SD-OCT) is becoming commonplace for the in vivo longitudinal study of murine models of ophthalmic disease. Longitudinal studies, however, generate large quantities of data, the manual analysis of which is very challenging due to the time-consuming nature of generating delineations. Thus, it is of importance that automated algorithms be developed to facilitate accurate and timely analysis of these large datasets. Furthermore, as the models target a variety of diseases, the associated structural changes can also be extremely disparate. For instance, in the light damage (LD) model, which is frequently used to study photoreceptor degeneration, the outer retina appears dramatically different from the normal retina. To address these concerns, we have developed a flexible graph-based algorithm for the automated segmentation of mouse OCT volumes (ASiMOV). This approach incorporates a machine-learning component that can be easily trained for different disease models. To validate ASiMOV, the automated results were compared to manual delineations obtained from three raters on healthy and BALB/cJ mice post LD. It was also used to study a longitudinal LD model, where five control and five LD mice were imaged at four timepoints post LD. The total retinal thickness and the outer retina (comprising the outer nuclear layer, and inner and outer segments of the photoreceptors) were unchanged the day after the LD, but subsequently thinned significantly (p < 0.01). The retinal nerve fiber-ganglion cell complex and the inner plexiform layers, however, remained unchanged for the duration of the study. PMID:28817571
Tessé, Sophie; Bourbon, Henri-Marc; Debuchy, Robert; Budin, Karine; Dubois, Emeline; Liangran, Zhang; Antoine, Romain; Piolot, Tristan; Kleckner, Nancy; Zickler, Denise; Espagne, Eric
2017-09-15
Meiosis is the cellular program by which a diploid cell gives rise to haploid gametes for sexual reproduction. Meiotic progression depends on tight physical and functional coupling of recombination steps at the DNA level with specific organizational features of meiotic-prophase chromosomes. The present study reveals that every step of this coupling is mediated by a single molecule: Asy2/Mer2. We show that Mer2, identified so far only in budding and fission yeasts, is in fact evolutionarily conserved from fungi (Mer2/Rec15/Asy2/Bad42) to plants (PRD3/PAIR1) and mammals (IHO1). In yeasts, Mer2 mediates assembly of recombination-initiation complexes and double-strand breaks (DSBs). This role is conserved in the fungus Sordaria However, functional analysis of 13 mer2 mutants and successive localization of Mer2 to axis, synaptonemal complex (SC), and chromatin revealed, in addition, three further important functions. First, after DSB formation, Mer2 is required for pairing by mediating homolog spatial juxtaposition, with implications for crossover (CO) patterning/interference. Second, Mer2 participates in the transfer/maintenance and release of recombination complexes to/from the SC central region. Third, after completion of recombination, potentially dependent on SUMOylation, Mer2 mediates global chromosome compaction and post-recombination chiasma development. Thus, beyond its role as a recombinosome-axis/SC linker molecule, Mer2 has important functions in relation to basic chromosome structure. © 2017 Tessé et al.; Published by Cold Spring Harbor Laboratory Press.
Jo, Catherine L.; Ambs, Anita; Dresler, Carolyn M.; Backinger, Cathy L.
2017-01-01
Objective We aimed to investigate the effects of special packaging (child-resistant, adult-friendly) and tamper-resistant packaging on health and behavioral outcomes in order to identify research gaps and implications for packaging standards for tobacco products. Methods We searched seven databases for keywords related to special and tamper-resistant packaging, consulted experts, and reviewed citations of potentially relevant studies. 733 unique papers were identified. Two coders independently screened each title and abstract for eligibility. They then reviewed the full text of the remaining papers for a second round of eligibility screening. Included studies investigated a causal relationship between type of packaging or packaging regulation and behavioral or health outcomes and had a study population composed of consumers. Studies were excluded on the basis of publication type, if they were not peer-reviewed, and if they had low external validity. Two reviewers independently coded each paper for study and methodological characteristics and limitations. Discrepancies were discussed and resolved. Results The review included eight studies: four assessing people’s ability to access the contents of different packaging types and four evaluating the impact of packaging requirements on health-related outcomes. Child-resistant packaging was generally more difficult to open than non-child-resistant packaging. Child-resistant packaging requirements have been associated with reductions in child mortality. Conclusions Child-resistant packaging holds the expectation to reduce tobacco product poisonings among children under six. PMID:27939602
NASA Astrophysics Data System (ADS)
Zhang, D.; Lee, T.; Wang, F.; McPhaden, M. J.; Kessler, W. S.
2016-12-01
Meridional thermocline currents play an important role in the recharge and discharge of tropical Pacific warm water during the development and transition of ENSO cycles. Previous analyses have shown large variations of the equatorward meridional thermocline convergence/divergence on ENSO and decadal time scales in the interior ocean. The total convergence/divergence is however unknown due to the lack of long term observation in the western boundary currents. Numerical modelling studies suggested a tendency of compensation between the interior and western boundary currents, but the exact compensation is model dependent. While Argo floats provide reasonable data coverage in the interior ocean, few floats are in the western boundary currents. Recent multi-mission satellite altimeter data and advanced processing techniques have resulted in higher resolution sea surface height anomaly (SSHA) products with better accuracy closer to the coasts. This study utilizes the statistical relationship between Argo dynamic height profiles and altimeter SSHA to calculate geostrophic thermocline currents in both the interior ocean and the western boundary of the tropical Pacific. The derived thermocline currents in the western boundary are validated by a 3.5-year moored Acoustic Doppler Current Profiler (ADCP) measurement in the Mindanao Current and by a series of glider surveys (Davis et al. 2012) in the Solomon Sea. The meridional transport timeseries of the interior and western boundary currents in the thermocline show different lead-lag relationships to the Nino 3.4 index. Results will be discussed in the context of recent 2014-2015 El Nino development and the potential contribution to the Tropical Pacific Observing System (TPOS).
Butler, Stephen F.; Black, Ryan A.; McCaffrey, Stacey A.; Ainscough, Jessica; Doucette, Ann M.
2017-01-01
The purpose of this study was to develop and validate a computer adaptive testing (CAT) version of the Addiction Severity Index-Multimedia Version (ASI-MV®), the Addiction Severity CAT. This goal was accomplished in four steps. First, new candidate items for Addiction Severity CAT domains were evaluated after brainstorming sessions with experts in substance abuse treatment. Next, this new item bank was psychometrically evaluated on a large non-clinical (n =4419) and substance abuse treatment sample (n =845). Based on these results, final items were selected and calibrated for the creation of the Addiction Severity CAT algorithms. Once the algorithms were developed for the entire assessment, a fully functioning prototype of an Addiction Severity CAT was created. CAT simulations were conducted and optimal termination criteria were selected for the Addiction Severity CAT algorithms. Finally, construct validity of the CAT algorithms was evaluated by examining convergent/discriminant validity and sensitivity to change. The Addiction Severity CAT was determined to be valid, sensitive to change, and reliable. Further, the Addiction Severity CAT’s time of administration was found to be significantly less than the average time of administration for the ASI-MV composite scores. This study represents the initial validation of an IRT-based Addiction Severity CAT, and further exploration of the Addiction Severity CAT is needed. PMID:28230387
Butler, Stephen F; Black, Ryan A; McCaffrey, Stacey A; Ainscough, Jessica; Doucette, Ann M
2017-05-01
The purpose of this study was to develop and validate a computer adaptive testing (CAT) version of the Addiction Severity Index-Multimedia Version (ASI-MV), the Addiction Severity CAT. This goal was accomplished in 4 steps. First, new candidate items for Addiction Severity CAT domains were evaluated after brainstorming sessions with experts in substance abuse treatment. Next, this new item bank was psychometrically evaluated on a large nonclinical (n = 4,419) and substance abuse treatment (n = 845) sample. Based on these results, final items were selected and calibrated for the creation of the Addiction Severity CAT algorithms. Once the algorithms were developed for the entire assessment, a fully functioning prototype of an Addiction Severity CAT was created. CAT simulations were conducted, and optimal termination criteria were selected for the Addiction Severity CAT algorithms. Finally, construct validity of the CAT algorithms was evaluated by examining convergent and discriminant validity and sensitivity to change. The Addiction Severity CAT was determined to be valid, sensitive to change, and reliable. Further, the Addiction Severity CAT's time of completion was found to be significantly less than the average time of completion for the ASI-MV composite scores. This study represents the initial validation of an Addiction Severity CAT based on item response theory, and further exploration of the Addiction Severity CAT is needed. (PsycINFO Database Record (c) 2017 APA, all rights reserved).