WorldWideScience

Sample records for featuring enso 1997-2000

  1. Line shapes investigations in Yugoslavia and Serbia V (1997-2000). (Bibliography and citation index)

    Science.gov (United States)

    Dimitrijević, Milan S.

    2001-05-01

    The first part of the publication contains a review and anylysis of the results of spectral line shapes investigations in Yugoslavia and Serbia for 1997-2000. In the second part, the bibliography of the contributions of Yugoslav and Serbian scientists for 1997-2000 is given, together with the Citation Index for 1997-2000 for articles published 1962-2000.

  2. Feline epitheliotropic intestinal malignant lymphoma: 10 cases (1997-2000).

    Science.gov (United States)

    Carreras, Janet K; Goldschmidt, Micheal; Lamb, Martin; McLear, Robert C; Drobatz, Kenneth J; Sørenmo, Karin U

    2003-01-01

    The clinical, histopathologic, and immunohistochemical features of 10 cats with epitheliotropic intestinal malignant lymphoma (EIL) are described. Intestinal biopsy samples were reviewed by 3 pathologists to confirm the diagnosis of EIL. These samples (n = 10) were compared to the intestinal biopsies of normal cats (n = 11), cats with inflammatory bowel disease (IBD; n = 7), and cats with non-EIL (n = 9) for quantification and immunophenotyping of intraepithelial lymphocytes. Immunophenotypic studies were performed with CD3 and CD79a antibody stains to assess for T- and B-cell immunoreactivity, respectively. EIL biopsies had markedly more intraepithelial lymphocytes than normal intestine (NRL) and samples from cats with IBD. However, no marked difference was observed in the number of intraepithelial lymphocytes in cats with non-EIL compared to cats with EIL. Regardless of the histologic diagnosis, the intraepithelial lymphocytes in all cats were small- to intermediate-sized T cells. Clinical findings and imaging studies in the cats identified minimal or nonspecific findings in affected cats. Most cats fit the typical profile of cats with IBD or alimentary malignant lymphoma. Nine of 10 cats with EIL were treated with prednisone with or without additional chemotherapy. Four cats were refractory to chemotherapy and were euthanized within 3.5 months. The remaining 5 cats had long-term survival times of 11 months or greater. The median survival time was 11 months. Additional studies are warranted to better characterize EIL and its relationship to IBD in cats and non-EIL and to identify optimal treatment strategies for this disease.

  3. The large-scale ENSO event, the El Niño and other important regional features

    Directory of Open Access Journals (Sweden)

    1993-01-01

    anomalously heavy subtropical Chilean rainfall. The high index (anti-ENSO phase of the SO relates on the west side of the «see-saw» to anomalously heavy rainfall over eastern and northern Australia, anomalously heavy east monsoon rainfall over Indonesia, above normal summer monsoon rainfall over India, and an abnormally large supply of water entering the Nile River system as a result of abnormally heavy summer monsoon rainfall over the highlands of Ethiopia. In contrast, on the east side of the «see-saw» it relates to cool anti-El Niño conditions over the northwestern South American coastal region with its cool upwelling waters, an equatorial Pacific dry zone extending far to the west as a result of the underlying cool upwelling sea water caused by strong easterly winds, and anomalously low subtropical Chilean rainfall. Although each individual large-scale ENSO and anti-ENSO phase pattern will display its own unique characteristics, the above-stated generalities will frequently occur, particularly when the events are in the strong and very strong intensity categories. At times the initial onset of these large-scale developments can be noted earlier on the western side of the «see-saw» than they can on the eastern side. There is no better example of this than the very strong 1982-1983 ENSO development. An ultimate goal of all research on the large-scale ENSO, the El Niño, and other associated regional climatic features is to eventually develop the capability to provide reasonably reliable long-range outlooks as to the time of onset, areal extent, duration, and intensity of these recurring SO-related ocean-atmosphere climatic fluctuations. Here some of the background information, data, and records obtained over the historical past are presented and discussed.

  4. Bioloogia : Riigieksam 2000. Riigieksam 2001. Riigieksamite 1997-2000 ülesanded / Riiklik Eksami- ja Kvalifikatsioonikeskus; [koost. Lea Koppel

    Index Scriptorium Estoniae

    2000-01-01

    Bioloogia riigieksamite 1997-2000 ülesannete autorid on: Sirje Aher, Tiina Elvisto, Margus Harak, Imbi henno, Urmas Kokassaar, Lea Koppel, Saima Laos, Rutt Nurk, Anu Parts, Tago Sarapuu, Liina Staub, Asta Tuusti, Liia Varend, Mart Viikmaa

  5. An epidemiological analysis of drunk driving accidents in Kagawa Prefecture - comparison of 1997-2000 and 2003-2006.

    Science.gov (United States)

    Fujita, Yoshitsugu; Inoue, Ken; Sakuta, Akira; Seki, Nobuhiko; Miyazawa, Teruomi; Eguchi, Kenji

    2008-10-01

    In this study, we examined the number of drunk driving accidents and drunk driving accident toll in 1997-2000 and 2003-2006 for Kagawa Prefecture, which had Japan's highest number of traffic accident fatalities per 100,000 population.

  6. Levels of persistent fluorinated, chlorinated and brominated compounds in human blood collected in Sweden in 1997-2000

    Energy Technology Data Exchange (ETDEWEB)

    Lindstroem, G.; Kaerrman, A.; Bavel, B. van [MTM Research Centre, Oerebro Univ. (Sweden); Hardell, L. [Dept. of Oncology, Univ. Hospital, Oerebro (Sweden); Hedlund, B. [Environmental Monitoring Section, Swedish EPA, Stockholm (Sweden)

    2004-09-15

    Levels of persistent fluorinated, chlorinated and brominated compounds in blood collected from the Swedish population have been determined in connection with several exposure and monitoring studies at the MTM Research Centre. A data base with 631 individual congener specific measurements on halogenated POPs such as dioxins, PCBs, HCB, DDE, chlordanes, PBDEs and PFAs including information on residency, age, BMI, diet, occupation, number of children, smoking habits, immunological status etc. has been compiled from samples collected between 1994 and 2004. A brief overview focusing on levels of some persistent chlorinated, brominated and fluorinated, compounds in blood collected in a background population group (n=83) in 1997-2000 is given here.

  7. ENSO Indices and Analyses

    Institute of Scientific and Technical Information of China (English)

    WANG Zhiren; WU Dexing; CHEN Xue'en; QIAO Ran

    2013-01-01

    New ENSO indices were developed and the spatial variability and temporal evolution of ENSO were analyzed based on the new indices and modeling experiments,as well as multiple data resources.The new indices,after being defined,were validated with their good diagnostic characteristics and correlation with wind and SST.In the analysis after the definition and validation of the new indices,ENSO feedbacks from wind,heat fluxes,and precipitation were spatially and temporally examined in order to understand ENSO variability and evolution with some emphasized points such as the interaction among the feedbacks,the role of westerly wind bursts and the transformation between zonal and meridional circulations in an ENSO cycle,and the typical pattern of modern ENSO.

  8. A retrospective study of presentation, treatment, and outcome of free-ranging raptors in Greece (1997-2000).

    Science.gov (United States)

    Komnenou, A Th; Georgopoulou, I; Savvas, I; Dessiris, A

    2005-06-01

    A retrospective study was conducted on free-ranging raptors (n = 402) presented to the Veterinary Medical Teaching Hospital, School of Veterinary Medicine, Aristotle University of Thessaloniki, Greece, during a 3-yr period (1997-2000). Representatives of 19 species were admitted from taxonomic orders Accipitriformes (n = 295), Falconiformes (n = 35), and Strigiformes (n = 72). Traumatic injuries (n = 305, 75.8%) were the most common cause of presentation in all raptors. Starvation (n = 38 birds, 9.4%) was the second most common reason, whereas toxicoses (n = 28, 6.9%) were suspected in a limited number of birds. Orphans (n = 31, 7.7%) were presented during breeding season primarily because of inappropriate human intervention. Surgical and medical treatment was given to all birds when necessary. In total, 229 (56.9%) of the presented raptors were successfully rehabilitated and released, 121 (30%) were rehabilitated but nonreleasable, whereas 52 (12.9%) of them died despite treatment. Human intervention (79.2%) plays the most important role in birds of prey morbidity and mortality.

  9. Tratamento cirúrgico da atresia de vias biliares: a experiência do hospital municipal jesus, 1997-2000 Surgical treatment of biliary atresia: the hospital municipal jesus experience 1997-2000

    Directory of Open Access Journals (Sweden)

    Lisieux Eyer de Jesus

    2001-04-01

    Full Text Available OBJETIVO: Analisar a indicação, resultados e limitações da portoenterostomia para o tratamento da atresia de vias biliares em hospital infantil terciário no Rio de Janeiro-RJ/Brasil. MÉTODO: Foram estudados prospectivamente oito pacientes submetidos à portoenterostomia do tipo Kasai 1, num período de três anos (1997-2000. Todos foram submetidos à antibioticoterapia profilática, uso de colerético, reavaliação médica mensal nos primeiros seis meses de seguimento e reavaliação laboratorial, ultra-sonográfica e através de endoscopia digestiva alta em prazos programados. RESULTADOS: Em cinco pacientes foi possível obter drenagem biliar estável e satisfatória por > 6 meses pós-operatórios. Quatro faleceram no período de observação (um por insuficiência hepática, um por colangite, dois por hemorragias digestivas, inclusive os três pacientes em que não foi obtida drenagem biliar satisfatória. Quatro persistem em bom estado geral, anictéricos, um deles com fibrose hepática residual grave e provável indicação futura de transplante hepático. Detectamos problemas graves com relação ao encaminhamento tardio de doentes para tratamento e para disponibilizar transplante hepático quando necessário. CONCLUSÕES: Os resultados da portoenterostomia são compensadores quando é possível obter bom débito biliar no pós-operatório. Em pacientes em que não é obtida boa drenagem biliar o pós-operatório é tormentoso e o óbito é esperado até o segundo ano de vida sem o uso de transplante hepático. É necessário disponibilizar transplante hepático pediátrico em nosso meio e conscientizar a comunidade médica para o encaminhamento precoce de bebês ictéricos além dos primeiros 15 dias de vida para investigação e tratamento em unidades especializadas.BACKGROUND: Indications, results and limitations of portoenterostomy to treat biliary atresia in a referral pediatric hospital in Rio de Janeiro, Brazil, are discussed

  10. Tratamento cirúrgico da atresia de vias biliares: a experiência do hospital municipal jesus, 1997-2000

    Directory of Open Access Journals (Sweden)

    Lisieux Eyer de Jesus

    Full Text Available OBJETIVO: Analisar a indicação, resultados e limitações da portoenterostomia para o tratamento da atresia de vias biliares em hospital infantil terciário no Rio de Janeiro-RJ/Brasil. MÉTODO: Foram estudados prospectivamente oito pacientes submetidos à portoenterostomia do tipo Kasai 1, num período de três anos (1997-2000. Todos foram submetidos à antibioticoterapia profilática, uso de colerético, reavaliação médica mensal nos primeiros seis meses de seguimento e reavaliação laboratorial, ultra-sonográfica e através de endoscopia digestiva alta em prazos programados. RESULTADOS: Em cinco pacientes foi possível obter drenagem biliar estável e satisfatória por > 6 meses pós-operatórios. Quatro faleceram no período de observação (um por insuficiência hepática, um por colangite, dois por hemorragias digestivas, inclusive os três pacientes em que não foi obtida drenagem biliar satisfatória. Quatro persistem em bom estado geral, anictéricos, um deles com fibrose hepática residual grave e provável indicação futura de transplante hepático. Detectamos problemas graves com relação ao encaminhamento tardio de doentes para tratamento e para disponibilizar transplante hepático quando necessário. CONCLUSÕES: Os resultados da portoenterostomia são compensadores quando é possível obter bom débito biliar no pós-operatório. Em pacientes em que não é obtida boa drenagem biliar o pós-operatório é tormentoso e o óbito é esperado até o segundo ano de vida sem o uso de transplante hepático. É necessário disponibilizar transplante hepático pediátrico em nosso meio e conscientizar a comunidade médica para o encaminhamento precoce de bebês ictéricos além dos primeiros 15 dias de vida para investigação e tratamento em unidades especializadas.

  11. Evaluation of management practices in wetland meadows at Grays Lake National Wildlife Refuge, Idaho, 1997-2000

    Science.gov (United States)

    Austin, J.E.; Pyle, W.H.; Keough, J.R.; Johnson, D.H.

    2002-01-01

    We assessed the relative values of 4 management practices (idle, late season grazing, fall prescribed burning, and rotation of idle and summer grazing) to biotic resources of the grassland-wetland meadow ecosystem at Grays Lake during 1997-2000. Three replicates of each treatment were randomly assigned to 12 experimental units that bordered the deep emergent marsh. Biotic factors examined included the breeding bird community and abundance, nesting activity and nest success, small mammal abundance, plant community, and annual plant biomass production. Fall burns achieved treatment objectives, removing most residual vegetation across a range of cover types. Objectives for grazing treatments were mostly attained; however, vegetation use levels were insufficient for consistent attainment of treatment objectives. Savannah sparrow, American coot, Canada goose, sandhill crane, mallard, and yellow-headed blackbird were the most common bird species present. Densities of 2 bird species (savannah sparrow and red-winged blackbird) were related to year effect only. The effect of unit on densities of redhead, lesser scaup, ruddy duck, sora, long-billed curlew, and common snipe likely reflects habitat differences among units. Densities of 6 species (eared grebe, canvasback, American coot, American avocet, willet, and common yellowthroat) were related to both year and unit effects. Treatment affected densities of 6 of the 29 species examined (mallard, northern shoveler, cinnamon teal, blue-winged teal, American crow, and yellow-headed blackbird); we found no common trend in response to treatments among those species. Overall, idled habitat did not stand out to be a valuable treatment, whereas grazing tended to have positive responses for a number of species. Burning was more likely to result in reduced bird densities than other treatments. We also describe the distribution of species observations among 8 different habitat types. Of the 23 nesting species sampled in the

  12. Sloshing Model for ENSO

    CERN Document Server

    Pukite, Paul R

    2014-01-01

    The El Nino southern oscillation (ENSO) behavior can be effectively modeled as a response to a 2nd-order Mathieu/Hill differential equation with periodic coefficients describing sloshing of a volume of water. The forcing of the equation derives from QBO, angular momentum changes synchronized with the Chandler wobble, and solar insolation variations. One regime change was identified in 1980.

  13. On the ENSO Mechanisms

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The El Nino-Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Paci fic Ocean-atmosphere interactions. The oscillatory nature of ENSO requires both positive and negative ocean-atmosphere feedbacks. The positive feedback is dated back to Bjerknes' hypothesis in the 1960s, and different negative feedbacks have been proposed since the 1980s associated with the delayed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflective oscillator. The de layed oscillator assumes that wave reflection at the western boundary provides a negative feedback for the coupled system to oscillate. The western Pacific oscillator emphasizes equatorial wind in the western Pacific that provides a negative feedback for the coupled system. The recharge-discharge oscillator argues that discharge and recharge of equatorial heat content cause the coupled system to oscillate. The advective-re flective oscillator emphasizes the importance of zonal advection associated with wave reflection at both the western and eastern boundaries. All of these physics are summarized in a unified ENSO oscillator. The de layed oscillator, the western Pacific oscillator, the recharge-discharge oscillator, and the advective-reflec tive oscillator can be extracted as special cases of the unified oscillator. As suggested by this unified oscillator, all of the previous ENSO oscillator mechanisms may be operating in nature.

  14. Distinct persistence barriers in two types of ENSO

    Science.gov (United States)

    Ren, Hong-Li; Jin, Fei-Fei; Tian, Ben; Scaife, Adam A.

    2016-10-01

    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 CP 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.

  15. Persistent ENSO in different climates?

    Science.gov (United States)

    Fedorov, A. V.; Manucharyan, G. E.

    2013-12-01

    Growing evidence suggests that, despite profound changes in tropical climate, ENSO has been active over a vast geological epoch stretching millions of years from the Late Cretaceous through the Holocene. In particular, ENSO persisted during the Pliocene when there occurred a dramatic reduction in the mean east-west temperature gradient in the equatorial Pacific - a key element of tropical dynamics. Here we use a comprehensive climate model to explore the dependence of ENSO on this temperature gradient. We find that in a broad range of climates ENSO remains surprisingly robust. When the east-west temperature gradient is reduced from 6oC to 1oC, the amplitude of ENSO decreases only by 30-40%, its dominant period remains close to 3-4 years, and the spectral peak stays above red noise. To explain these results we assess the magnitude of ocean-atmosphere feedbacks that control the stability of the natural mode of ENSO (the Bjerknes Index). We find that due to reorganization of the atmospheric Walker circulation in response to changes in the mean temperature gradient, the growth/decay rates of the ENSO mode stay nearly constant throughout different climates. This factor explains the persistence of the Southern Oscillation in past geological epochs and reconciles the seemingly contradictory findings of ENSO occurrence and the small east-west temperature gradient during the Pliocene. Finally, our results explain why ENSO in many climate models seems to be controlled by a weakly-damped mode just below neutral stability.

  16. Impact of global warming on ENSO phase change

    Directory of Open Access Journals (Sweden)

    W. Cabos Narvaez

    2006-01-01

    Full Text Available We compare the physical mechanisms involved in the generation and decay of ENSO events in a control (present day conditions and Scenario (Is92a, IPCC 1996 simulations performed with the coupled ocean-atmosphere GCM ECHAM4-OPYC3. A clustering technique which objectively discriminates common features in the evolution of the Tropical Pacific Heat Content anomalies leading to the peak of ENSO events allows us to group into a few classes the ENSO events occurring in 240 years of data in the control and scenario runs. In both simulations, the composites of the groups show differences in the generation and development of ENSO. We present the changes in the statistics of the groups and explore the possible mechanisms involved.

  17. Enso modulations on streamflow characteristics

    OpenAIRE

    Yerdelen Cahit; Marti Ali Ihsan; Kahya Ercan

    2011-01-01

    El Niño Southern Oscillation (ENSO) has been linked to climate and hydrologic anomalies throughout the world. This paperpresents how ENSO modulates the basic statistical characteristics of streamflow time series that is assumed to be affected byENSO. For this we first considered hypothetical series that can be obtained from the original series at each station by assumingnon-occurrence of El Niño events in the past. Instead those data belonging to El Niño years were simulated by the RadialBase...

  18. Obesity, mortality, and life years lost associated with breast cancer in nonsmoking US Women, National Health Interview Survey, 1997-2000.

    Science.gov (United States)

    Chang, Su-Hsin; Pollack, Lisa M; Colditz, Graham A

    2013-11-14

    The relationship between obesity and breast cancer has been extensively investigated. However, how obesity and breast cancer interplay to affect mortality and life expectancy of women in the United States has not been well studied. We used data from the National Health Interview Survey, 1997-2000. Our sample included nonsmoking, nonpregnant women who reported a body mass index of at least 18.5 kg/m(2) and no cancer other than breast cancer at the time of the survey. A survival model with Gamma frailty and Gompertz baseline was used to estimate relative risks of total mortality and project life years lost associated with breast cancer by obesity status and age. Breast cancer increased risk of mortality depending on degree of obesity and decreased life years by 1 to 12 years depending on race, age, and obesity status. Relative risks for death increased with degree of obesity. Obese women under age 50 across all racial groups were predicted to lose the most life years; racial groups other than whites and blacks lost the most life years (11.9 y), followed by whites (9.8 y) and blacks (9.2 y). The number of life years lost associated with breast cancer was more marked for more obese than for less obese women and for women under age 50 and women aged 70 or older than for women aged 50 through 69. Public health initiatives should put more emphasis on the prevention and control of obesity for these target populations.

  19. Feedback process responsible for intermodel diversity of ENSO variability

    Science.gov (United States)

    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.

  20. Winter ENSO teleconnections in a warmer climate

    Energy Technology Data Exchange (ETDEWEB)

    Herceg Bulic, Ivana [Faculty of Science, University of Zagreb, Andrija Mohorovicic Geophysical Institute, Department of Geophysics, Zagreb (Croatia); Brankovic, Cedo [Croatian Meteorological and Hydrological Service (DHMZ), Zagreb (Croatia); Kucharski, Fred [The Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)

    2012-04-15

    Changes in the winter atmospheric response to sea surface temperature (SST) anomalies associated with the El Nino-Southern Oscillation (ENSO) in a warmer climate conditions are estimated from the two 20-member ensembles made by an atmospheric general circulation model of intermediate complexity. Warmer climate is simulated by a modification in the radiation parameterisation that corresponds to the doubled CO{sub 2} concentration, and SST forcing is represented by the same SST anomalies as in current climate (1855-2002) experiment superimposed on the climatological SST that was obtained from a complex atmosphere-ocean general circulation model forced with the doubled CO{sub 2}. SST anomalies in the Nino3.4 region, categorised into five classes, enabled a composite analysis of changes in the Northern Hemisphere tropical/extratropical teleconnections. The main features of the tropical-extratropical teleconnections are maintained in both experiments; for example, irrespective of the sign of SST anomalies, the amplitude of the atmospheric response is positively correlated with the intensity of ENSO event and the El Nino impact is stronger than that of La Nina of the same intensity. The strongest extratropical signal in the warmer climate, particularly significant for strong warm events, is found over the Pacific/North American region; however, this extratropical teleconnections is reduced in a warmer climate relative to the current climate. Over the North Atlantic/European region, a detectable signal linked to ENSO is found; this model response is significantly strengthened in the experiment with the doubled CO{sub 2} concentration. Such an atmospheric response in a warmer climate is found to be associated with changes in the mean state followed as well as in the jet waveguiding effect and stationary wave activity. (orig.)

  1. Teleconnection between ENSO and Vegetation

    Science.gov (United States)

    Kogan, F.

    Since 1980s strong ENSO disturbed weather environment economy and human lives worldwide Total impact of these events on society is estimated in billions of dollars and consequences include famine human health problems loss of life property damage and destruction of the environment Areas sensitive to ENSO have been identified in some world areas from climatic records and recently from 15-year satellite data This presentation examines teleconnection between ENSO and terrestrial ecosystems worldwide using 24-year satellite and in situ data records ENSO events were characterized by monthly sea surface temperature SST anomalies in the tropical Pacific They were collected from the improved SST analysis data set Reynolds and Smith 1994 Average anomalies were calculated for the region 5 r N - 5 r S and 170 r - 120 r E 3 4 area Terrestrial ecosystems were presented by the vegetation health condition indices VHI Kogan 1997 The VHIs derived from AVHRR-based NDVI and 10-11 Phi m thermal radiances were designed to monitor moisture and thermal impacts on vegetation health greenness and vigor Two types of responses were identified In boreal winter ecosystems of northern South America southern Africa and Southeast Asia experienced severe moisture and thermal stress during El Ni n o and favorable conditions during La Ni n a years In central South America and the Horn of Africa regions the response was opposite World ecosystems are less sensitive to SSTs during boreal summer except for the areas in northern Brazil

  2. Decadal amplitude modulation of two types of ENSO and its relationship with the mean state

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jung; An, Soon-Il [Yonsei University, Department of Atmospheric Sciences, Global Environmental Laboratory, Seoul (Korea, Republic of); Yeh, Sang-Wook [Hanyang University, Department of Environmental Marine Science, Ansan (Korea, Republic of)

    2012-06-15

    In this study, we classified two types of El Nino-Southern Oscillation (ENSO) events within the decadal ENSO amplitude modulation cycle using a long-term coupled general circulation model simulation. We defined two climate states - strong and weak ENSO amplitude periods - and separated the characteristics of ENSO that occurred in both periods. There are two major features in the characteristics of ENSO: the first is the asymmetric spatial structure between El Nino and La Nina events; the second is that the El Nino-La Nina asymmetry is reversed during strong and weak ENSO amplitude periods. El Nino events during strong (weak) ENSO amplitude periods resemble the Eastern Pacific (Central Pacific) El Nino in terms of the spatial distribution of sea surface temperature anomalies (SSTA) and physical characteristics based on heat budget analysis. The spatial pattern of the thermocline depth anomaly for strong (weak) El Nino is identical to that for weak (strong) La Nina, but for an opposite sign and slightly different amplitude. The accumulated residuals of these asymmetric anomalies dominated by an east-west contrast structure could feed into the tropical Pacific mean state. Moreover, the residual pattern associated with El Nino-La Nina asymmetry resembles the first principal component analysis (PCA) mode of tropical Pacific decadal variability, indicating that the accumulated residuals could generate the change in climate state. Thus, the intensified ENSO amplitude yields the warm residuals due to strong El Nino and weak La Nina over the eastern tropical Pacific. This linear relationship between ENSO and the mean state is strong during the mature phases of decadal oscillation, but it is weak during the transition phases. Furthermore, the second PCA mode of tropical Pacific decadal variability plays an important role in changing the phase of the first mode. Consequently, the feedback between ENSO and the mean state is positive feedback to amplify the first PCA mode

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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.

  5. ENSO signature in the SMOS sea surface salinity maps

    Science.gov (United States)

    Ballabrera, J.; Umbert, M.; Hoareau, N.; Turiel, A.; Font, J.

    2012-12-01

    derived from the SMOS data do indeed display a positive anomaly. The persistence of the feature, its geographical pattern, and the time modulation of the anomaly amplitude indicate that the SSS fields provided by the SMOS mission do actually contain an ENSO-related signal, despite the shortness of the data gathered by the mission. Although the SMOS time span is still too short to allow any study about the factual impact of these data in the prediction of ENSO (either through data assimilation or statistical predictions), these results provide a clear indication that the novel observational technology that SMOS represents for the observation of the Earth is currently able to capture seasonal and interannual signatures of climate interest.

  6. REDEFINING ENSO EPISODES BASED ON CHANGED CLIMATE REFERENCES

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-yan; ZHAI Pan-mao; REN Fu-min

    2005-01-01

    Through studying changes in ENSO indices relative to change of climate reference from 1961~1990 to 1971~2000, the study generated new standards to define ENSO episodes and their intensities. Then according to the new climate references and new index standards, ENSO episodes and their intensities for the period 1951 -2003 have been classified. Finally, an analysis has been performed comparing the new characteristics with the old ones for ENSO period, peak values and intensities.

  7. ENSO influence on the North Atlantic European climate: a non-linear and non-stationary approach

    Science.gov (United States)

    López-Parages, Jorge; Rodríguez-Fonseca, Belén; Dommenget, Dietmar; Frauen, Claudia

    2016-10-01

    El Niño Southern Oscillation (ENSO) impact on the North Atlantic European sector (NAE) is still under discussion. Recent studies have found a non stationary feature of this teleconnection, suggesting an effective modulating role of the ocean mean state. Nevertheless, physical explanations about the underlying mechanisms have been little studied in the available literature. In addition, ENSO events show different SST spatial patterns, phases, and amplitudes, which can also influence on the related remote impacts. In view of all this, in the present study a set of partially coupled experiments have been performed with a global atmospheric general circulation model in which different SST ENSO patterns are superimposed over distinct Pacific and Atlantic SST mean states. These SST background conditions are constructed according to the observational difference between periods with a distinct impact of ENSO on the leading Euro-Mediterranean rainfall mode in late winter-early spring. Our results point to two distinct mechanisms associated with ENSO that can be modulated by the SST mean state: (1) the thermally driven direct circulation (Walker and Hadley cells) connecting the Atlantic and Pacific basins, and (2) the Rossby wave propagation from the tropical Pacific to the North Atlantic. The former elucidates that the positive NAO-like pattern usually related to La Niña events could be only valid for selected decades. The latter explains a reinforced signature of Eastern Pacific Niños on the Euro-Mediterranean rainfall when the tropical Pacific is warmer than usual and the North Atlantic is colder than usual. This feature is consistent with the changing ENSO impact identified in previous studies and demonstrates how the ENSO teleconnection with the NAE climate at interannual timecales could be modulated by multidecadal changes in the SST. According to our results, the assumption of stationarity which is still common to many studies of ENSO teleconnections clearly has to

  8. Impacts of ENSO on global hydrology

    Science.gov (United States)

    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

  9. Impacts of Two-Type ENSO on Rainfall over Taiwan

    OpenAIRE

    Chen-Chih Lin; Yi-Jiun Liou; Shih-Jen Huang

    2015-01-01

    Impacts of two-type ENSO (El Niño/Southern Oscillation), canonical ENSO and ENSO Modoki, on rainfall over Taiwan are investigated by the monthly mean rainfall data accessed from Taiwan Central Weather Bureau. The periods of the two-type ENSO are distinguished by Niño 3.4 index and ENSO Modoki index (EMI). The rainfall data in variously geographical regions are analyzed with the values of Niño 3.4 and EMI by correlation method. Results show that the seasonal rainfalls over Taiwan are different...

  10. Impacts of Two-Type ENSO on Rainfall over Taiwan

    OpenAIRE

    Chen-Chih Lin; Yi-Jiun Liou; Shih-Jen Huang

    2015-01-01

    Impacts of two-type ENSO (El Niño/Southern Oscillation), canonical ENSO and ENSO Modoki, on rainfall over Taiwan are investigated by the monthly mean rainfall data accessed from Taiwan Central Weather Bureau. The periods of the two-type ENSO are distinguished by Niño 3.4 index and ENSO Modoki index (EMI). The rainfall data in variously geographical regions are analyzed with the values of Niño 3.4 and EMI by correlation method. Results show that the seasonal rainfalls over Taiwan are different...

  11. An ENSO beginning in the year 2000?

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.

    Several models have been developed over the last few decades to predict the advent of new ENSO events several months in advance of the actual event. None of the models have predicted a warm event beginning by the year 2000. Positive SST anomalies...

  12. The vertical and spatial structure of ENSO in the upper troposphere and lower stratosphere from GPS radio occultation measurements

    Science.gov (United States)

    Scherllin-Pirscher, B.; Deser, C.; Ho, S.-P.; Chou, C.; Randel, W.; Kuo, Y.-H.

    2012-10-01

    The vertical and spatial structure of the atmospheric El Niño-Southern Oscillation (ENSO) signal is investigated using radio occultation (RO) data from August 2006 to December 2010. Due to their high vertical resolution and global coverage, RO data are well suited to describe the full 3-dimensional ENSO structure in the troposphere and lower stratosphere. We find that interannual temperature anomalies in the equatorial region show a natural decomposition into zonal-mean and eddy (deviations from the zonal-mean) components that are both related to ENSO. Consistent with previous studies, we find that during the warm phase of ENSO, zonal-mean temperatures increase in the tropical troposphere and decrease in the tropical stratosphere. Maximum warming occurs above 8 km, and the transition between warming and cooling occurs near the tropopause. This zonal-mean response lags sea surface temperature anomalies in the eastern equatorial Pacific by 3 months. The atmospheric eddy component, in contrast, responds rapidly (within 1 month) to ENSO forcing. This signal features a low-latitude dipole between the Indian and Pacific Oceans, with off-equatorial maxima centered around 20° to 30° latitude in both hemispheres. The eddy response pattern attains maximum amplitude in the upper troposphere near 11 km and (with opposite polarity) in a shallow layer near the tropopause at approximately 17 km. The eddy ENSO signal tends to be out-of-phase between low and middle latitudes in both the troposphere and lower stratosphere.

  13. Precipitation, temperature, and moisture transport variations associated with two distinct ENSO flavors during 1979-2014

    Science.gov (United States)

    Gu, Guojun; Adler, Robert F.

    2016-11-01

    Interannual precipitation and temperature variations during 1979-2014 are investigated by examining the effects of two distinct flavors of the El Niño-Southern Oscillation (ENSO), i.e., the tropical eastern Pacific (EP) and central Pacific (CP) ENSO events. Satellite- and ground-based observations with global coverage are applied including the monthly precipitation data from the Global Precipitation Climatology Project (GPCP) and surface temperature anomalies from the NASA-GISS surface temperature anomaly analysis. Related variations in other water-cycle components including atmospheric moisture transport are also examined by using the outputs from the NASA-Modern Era Retrospective-analysis for Research and Applications (MERRA). While the second leading mode from an EOF analysis of sea surface temperature (SST) anomalies between 30°N and 30°S is dominated by interdecadal-scale variability that is not a focus of this study, the first and third leading modes represent well the EP and CP events, respectively. The corresponding principal components (PC1 and PC3) are then applied as indices to estimate the influences of the two ENSO flavors on various physical components through linear regression. Because of their distinct SST configurations in the tropical Pacific, the two ENSO flavors manifest different spatial features of precipitation anomalies as shown in past studies. Differences can also be readily seen in satellite-retrieved tropospheric layered temperatures and oceanic columnar water vapor content. General agreements between observations and MERRA outputs can be obtained as judged by consistent respective anomalies corresponding to the two ENSO flavors, suggesting that MERRA could provide an accurate account of variations on the interannual time scale. Interannual variations in MERRA vertically integrated moisture transport (VIMT) are further examined to explore possible relations between precipitation and tropospheric moisture transport corresponding to the

  14. The influence of moderate ENSO on summer rainfall in eastern China and its comparison with strong ENSO

    Institute of Scientific and Technical Information of China (English)

    XUE Feng; LIU ChangZheng

    2008-01-01

    The 6 major ENSO events since 1979 are classified into the strong and moderate ENSO based on in-tensity. The composite analysis is performed to reveal the influence of ENSO on East Asian summer monsoon (EASM) and summer rainfall in eastern China. It is shown that the influence is changed with the seasonal cycle in summer, with a weaker influence in June and a stronger influence in August, in-dicating a long lagged effect of ENSO on EASM. Besides, the circulation and rainfall anomalies caused by the strong ENSO are also stronger with an earlier starting time, while the influence of the moderate ENSO is evident in August. The composite summer rainfall in eastern China for the moderate ENSO exhibits a northern rainfall pattern, which is totally different from the classical ENSO-type rainfall pat-tern. Based on the composite analysis, two moderate ENSO years with a similar intensity (i.e., 1995 and 2003) are compared, The result shows that, the response of EASM to the moderate ENSO during June and July is, to a certain degree, modulated by the circulation systems in mid-high latitudes of Eurasia and in the Southern Hemisphere, thereby inducing a different rainfall distribution in eastern China. In comparison with the strong ENSO in 1983, it is further revealed that, the strong ENSO plays a dominant role in summer rainfall anomalies in eastern China as well as in controlling the influence of the other factors on EASM. The strong ENSO is therefore different with the moderate ENSO.

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

    Science.gov (United States)

    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

  16. Different coupled atmosphere-recharge oscillator Low Order Models for ENSO: a projection approach.

    Science.gov (United States)

    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.

  17. Landslides as a Delayed Signal of Warm Phase of ENSO in the Aconcagua Park (32 Sl)

    Science.gov (United States)

    Moreiras, S.; Lisboa, M.

    2013-05-01

    The Aconcagua mount (6,929 m asl), the top of the Andes, is characterised by high elevations and abrupt topography that seem to have favoured the occurrence of landslides affecting 25% of the Aconcagua Park (Fig 1). Concerning to triggering mechanism, rainfall are mentioned as the main cause of landslides in historical sources; but this assertion could not be confirmed on the basis of available meteorological data beginning after 1940. The most reliable rainfall threshold value corresponds to a 19 mm (daily precipitation) representing 8.7% of the annual precipitation and 8% of the mean annual precipitation for this region. However, main cause of landslides is related to terrain saturation by snow melting and ice thawing of ice-core moraines or rock glaciers during the warm season (November - February). A delayed link between warm phases of ENSO and slope instability could be established by a relationship found between landslides and local river stream flow (Fig. 2). The typical warm phase of ENSO begins in November of one year, increasing during July—August, and ends in February of the following year. Greater snowfall and positive glacier balance has been linked to the ENSO-warm phase. Consequently, increased stream flows of Andean rivers will be measured the following summer. In fact, ENSO-related features in the tropical Pacific play a major role in regulating the hydrological variability in the region with increased (decreased) summer and annual river discharges following El Niño (La Niña) events.; ;

  18. ENSO cycle and climate anomaly in China

    Institute of Scientific and Technical Information of China (English)

    CHEN Yongli; ZHAO Yongping; FENG Junqiao; WANG Fan

    2012-01-01

    The inter-annual variability of the tropical Pacific Subsurface Ocean Temperature Anomaly (SOTA) and the associated anomalous atmospheric circulation over the Asian North Pacific during the El Ni(n)o-Southern Oscillation (ENSO) were investigated using National Centers for Environmental Prediction/ National Center for Atmospheric Research (NCEP/NCAR) atmospheric reanalysis data and simple ocean data simulation (SODA).The relationship between the ENSO and the climate of China was revealed.The main results indicated the following:1) there are two ENSO modes acting on the subsurface tropical Pacific.The first mode is related to the mature phase of ENSO,which mainly appears during winter.The second mode is associated with a transition stage of the ENSO developing or decaying,which mainly occurs during summer; 2) during the mature phase of El Ni(n)o,the meridionality of the atmosphere in the mid-high latitude increases,the Aleutian low and high pressure ridge over Lake Baikal strengthens,northerly winds prevail in northern China,and precipitation in northern China decreases significantly.The ridge of the Ural High strengthens during the decaying phase of El Ni(n)o,as atmospheric circulation is sustained during winter,and the northerly wind anomaly appears in northern China during summer.Due to the ascending branch of the Walker circulation over the western Pacific,the western Pacific Subtropical High becomes weaker,and south-southeasterly winds prevail over southern China.As a result,less rainfall occurs over northern China and more rainfall over the Changjiang River basin and the southwestern and eastern region of Inner Mongolia.The flood disaster that occurred south of Changjiang River can be attributed to this.The La Ni(n)a event causes an opposite,but weaker effect; 3) the ENSO cycle can influence climate anomalies within China via zonal and meridional heat transport.This is known as the "atmospheric-bridge",where the energy anomaly within the tropical Pacific

  19. Stora Enso Timber rajab Imaverre uue tehase Jaapani turu tarvis / Väinu Rozental

    Index Scriptorium Estoniae

    Rozental, Väinu, 1957-

    2004-01-01

    Metsatööstuskontsern Stora Enso Timber ehitab Imaverre liimpuidutehase, mis hakkab tootma liimpuittalasid peamiselt Jaapani turu jaoks. Diagramm. Lisa: Pankurid peavad Stora Enso sammu Eestile kasulikuks

  20. Unstable ENSO Relationship with Indian regional rainfall

    Science.gov (United States)

    Kane, R. P.

    2006-05-01

    In earlier years, El Niños had a strong association with droughts in India. However, in recent years, this relationship seems to have weakened, and even the strong event of 1997-1998 did not produce the expected effects. In the 133-year data, only about 60% of the El Niño and La Niña are effective, and the magnitudes of the anomalies are not in good correlations with the strength of the ENSO. This weakening of ENSO effects in recent years is known to meteorologists. The Indian Meteorological Department (IMD) scientists have formulated prediction schemes, but these are not fully satisfactory. The public and the press are still swayed only by possible El Niño effects, as happened in 2005 when Pacific warming occurred in February. The meteorologists had to assure the press that this was a case of an aborted El Niño, with quiet conditions expected to return by the end of 2005. Considering the experience of the 1997-1998 El Niño, when a strong El Niño developed suddenly, a prediction of a quiet 2005 can be hazardous. More importantly, even if an El Niño develops in the next few months, the press should be told that the chance of strong El Niño effects (droughts) is only about 60%, and these too may be very different in different regions of India.

  1. ENSO Ocean Energetics and Observational Wind Power

    Science.gov (United States)

    Kodama, K.; Burls, N.

    2016-12-01

    The viability of wind power as a potential predictor for ENSO state has previously only been investigated in models. Here we use satellite data to obtain observational equatorial wind power which is then decomposed into climatological (ucτc), mixed-mean-perturbation (ucτ' and u'τc), and perturbation (u'τ') components to compare with the wind power/SST relationship seen in the models. The observational wind power components are also used to compare predictive skill with that of their dynamical counterparts-heat content and wind stress-which are more widely accepted and studied as ENSO predictors. The wind power decomposition reveals the u'τ' perturbation component primarily acts as a damping term. We find that the most robust relationship between wind power and SST arises from the u'τc component computed from the perturbation surface currents and climatological wind stress. u'τc is significantly correlated with the Nino 3.4 index and leads by as many as six months, capturing the role of ocean memory. The wind power decomposition highlights exactly how surface currents can weight the contribution of the winds to have more or less of an effect on the ocean state depending on the whether currents and wind stress act together or oppose each other, illustrating that not all wind anomalies are created equal.

  2. The role of sea surface salinity in ENSO related water cycle anomaly

    Science.gov (United States)

    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

  3. Impacts of Two-Type ENSO on Rainfall over Taiwan

    Directory of Open Access Journals (Sweden)

    Chen-Chih Lin

    2015-01-01

    Full Text Available Impacts of two-type ENSO (El Niño/Southern Oscillation, canonical ENSO and ENSO Modoki, on rainfall over Taiwan are investigated by the monthly mean rainfall data accessed from Taiwan Central Weather Bureau. The periods of the two-type ENSO are distinguished by Niño 3.4 index and ENSO Modoki index (EMI. The rainfall data in variously geographical regions are analyzed with the values of Niño 3.4 and EMI by correlation method. Results show that the seasonal rainfalls over Taiwan are different depending on the effects of two-type ENSO. In canonical El Niño episode, the rainfall increases in winter and spring while it reduces in summer and autumn. On the contrary, the rainfall increases in summer and autumn but reduces in winter and spring in El Niño Modoki episode. Nevertheless, two types of La Niña cause similar effects on the rainfall over Taiwan. It increases in autumn only. The rainfall variations in different types of ENSO are mainly caused by the monsoon and topography.

  4. The role of atmosphere and ocean physical processes in ENSO

    Directory of Open Access Journals (Sweden)

    S. Y. Philip

    2009-09-01

    Full Text Available We examine the behaviour of the El Niño – Southern Oscillation (ENSO in an ensemble of global climate model simulations with perturbations to parameters in the atmosphere and ocean components respectively. The influence of the uncertainty in these parametrisations on ENSO are investigated systematically. The ensemble exhibits a range of different ENSO behaviour in terms of the amplitude and spatial structure of the SST variability. The nature of the individual feedbacks that operate within the ENSO system are diagnosed using an Intermediate Complexity Model (ICM, which has been used previously to examine the diverse ENSO behaviour of the CMIP3 multi-model ensemble. Unlike in that case, the ENSO in these perturbed physics experiments is not principally controlled by variations in the mean climate state. Rather the parameter perturbations influence the ENSO characteristics by modifying the coupling feedbacks within the cycle. The associated feedbacks that contribute most to the ensemble variations are the response of SST to local wind variability and damping, followed by the response of SST to thermocline anomalies and the response of the zonal wind stress to those SST anomalies. Atmospheric noise amplitudes and oceanic processes play a relatively minor role.

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

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Li [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Now at Department of Earth System Science, University of California, Irvine California USA; Cameron-Smith, Philip [Atmospheric, Earth and Energy Division, Lawrence Livermore National Laboratory, Livermore California USA; Russell, Lynn M. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Ghan, Steven J. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Liu, Ying [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Elliott, Scott [Climate Ocean Sea Ice Modeling, Los Alamos National Laboratory, Los Alamos New Mexico USA; Yang, Yang [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Lou, Sijia [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Lamjiri, Maryam A. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Manizza, Manfredi [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA

    2016-11-16

    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 and 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.

  6. ENSO dynamics: low-dimensional-chaotic or stochastic?

    CERN Document Server

    Zivkovic, Tatjana

    2012-01-01

    We apply a test for low-dimensional, deterministic dynamics to the Nino 3 time series for the El Nino Southern Oscillation (ENSO). The test is negative, indicating that the dynamics is high-dimensional/stochastic. However, application of stochastic forcing to a time-delay equation for equatorial-wave dynamics can reproduce this stochastic dynamics and other important aspects of ENSO. Without such stochastic forcing this model yields low-dimensional, deterministic dynamics, hence these results emphasize the importance of the stochastic nature of the atmosphere-ocean interaction in low-dimensional models of ENSO.

  7. A delay differential model of ENSO variability: parametric instability and the distribution of extremes

    Directory of Open Access Journals (Sweden)

    M. Ghil

    2008-05-01

    Full Text Available 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.

  8. Evolution of Indian Ocean dipole and its forcing mechanisms in the absence of ENSO

    Science.gov (United States)

    Wang, Hui; Murtugudde, Raghu; Kumar, Arun

    2016-10-01

    The evolution of Indian Ocean dipole (IOD) and its forcing mechanisms are examined based on the analysis of coupled model simulations that allow or suppress the El Niño-Southern Oscillation (ENSO) mode of variability. The model can reproduce the most salient observed features of IOD even without ENSO, including the relationships between the eastern and western poles at both the surface and subsurface, as well as their seasonality. This suggests that ENSO is not fundamental for the existence of IOD. It is demonstrated that cold (warm) sea surface temperature (SST) anomalies in the eastern Indian Ocean associated with IOD can be initiated by springtime Indonesian rainfall deficit (surplus) through local surface wind response. The growth of the SST anomalies depends on the initial local subsurface condition. Both the air-sea interaction and surface-subsurface interaction contribute to the development of IOD. The evolution of IOD can be represented by two leading extended empirical orthogonal function (EEOF) modes of tropical surface-subsurface Indian Ocean temperatures; one stationary and the other non-stationary. The onset, growth, and termination of IOD, as well as the transition to an opposite phase, can be interpreted as alternations between the non-propagating mode (EEOF1) and the eastward-propagating Kelvin wave (EEOF2). The evolution of IOD is also accompanied by a westward-propagating Rossby wave which is captured in the EEOF1 of the subtropical surface-subsurface Indian Ocean temperatures. Therefore, both Bjerknes feedback and a delayed oscillator operate during the evolution of IOD in the absence of ENSO also.

  9. Westerly Bursts during the 1982/83 ENSO.

    Science.gov (United States)

    Murakami, Takio; Sumathipala, W. L.

    1989-01-01

    Some of the characteristic features of the 1982/83 ENSO are described in terms of 3-month running mean anomalous winds (u, v) at 850 mb, outgoing longwave radiation (OLR), and sea surface temperature (SST) during the 6 yr period 1980-85 over the Indian and Pacific means. Climatological information on `westerly bursts' is obtained from band-pass filtered winds, which are denoted as us, and vs (1-6 day), um and vm (7-20 day), and ul and vl (30-60 day).Atmospheric interannual u and OLR modes are characterized by typical spatial scales of zonal wavenumbers 1 and 2, and very slow eastward phase propagations of about 0.3 m s1 all the way from the western Indian Ocean to the eastern Pacific. Oceanic interannual SST modes also exhibit a slow eastward movement across the Pacific.Westerly ul bursts are sandwiched between twin cyclonic disturbances which are nearly symmetric with respect to the equator. The east-west extent of ul westerly bursts along the equator is about 10 000 km, while the corresponding extent of um bursts amounts to 6000-7000 km. The (um, vm) wind field is asymmetric with respect to the equator and is characterized by cold equatorward surges from the winter hemisphere midlatitude region. The longitudinal scale of us bursts along the equator is only 3000 km or less. Thus, the structure of westerly bursts varies significantly with different periodicities.The relationship between synoptic-scale westerly bursts on time scales of a few days and the planetary scale interannual modes is first investigated by counting the number of days of westerlies (and/or westerly acceleration) in each season at every 20 deg of longitude from 40°E to 100°W along the equator. There exists an association between u and westerly bursts involving the frequency of events; namely, even though westerly bursts are occurring all the time, the frequency of westerly bursts increases after (not before) the ENSO onset. Furthermore, westerly bursts are not unique to the equatorial western

  10. Decadal variability of the IOD-ENSO relationship

    Institute of Scientific and Technical Information of China (English)

    YUAN Yuan; LI ChongYin

    2008-01-01

    Using three kinds of over 100-year sea surface temperature (SST) datasets as well as three-dimensional wind data from NCEP/NCAR, this paper documents the decadal variability of the Indian Ocean Dipole (IOD)-El Nino/Southern Oscillation (ENSO) relationship. During 1946-1969, positive (negative) IOD and warm (cold) ENSO events were more independent of each other. But after 1970, they tended to occur in the same year. ENSO would influence the whole life span of IOD, and IOD also affects the developing phase of ENSO. Considering the climatological background SST, low-level winds and also equatorial vertical circulations, it is revealed that the decadal variability of the IOD-ENSO relationship may be caused by the enhanced Walker circulation with increased rising motion over the Maritime Continent after 1970. Warmer SST around the Maritime Continent gives rise to anomalous low-level convergence and intensified convection there, which apparently increases the SST linkage between the eastern Indian Ocean and the western Pacific and thereby the interaction between the IOD and ENSO event.

  11. The Response of Lower Atmospheric Ozone to ENSO in Aura Measurements and a Chemistry-Climate Simulation

    Science.gov (United States)

    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.

  12. Towards the Use of HYCOM in Coupled ENSO Prediction: Assessment of ENSO Skill in Forced Global HYCOM

    Science.gov (United States)

    2014-09-30

    atmosphere variability in the tropical Pacific, through El Niño/Southern Oscillation (ENSO), is a major contributor to fluctuations in North American and...between the occurrence of westerly wind events in the western Pacific and the equatorial warming that triggers the Bjerknes feedback has been a major...how well HYCOM depicts the diversity of ENSO events over an extended period. A recent study has shown that most of the El Niño events in the 21st

  13. Analytical Formulation of Equatorial Standing Wave Phenomena: Application to QBO and ENSO

    Science.gov (United States)

    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

  14. On the Bimodality of ENSO Cycle Extremes

    Science.gov (United States)

    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.

  15. ENSO Prediction using Vector Autoregressive Models

    Science.gov (United States)

    Chapman, D. R.; Cane, M. A.; Henderson, N.; Lee, D.; Chen, C.

    2013-12-01

    A recent comparison (Barnston et al, 2012 BAMS) shows the ENSO forecasting skill of dynamical models now exceeds that of statistical models, but the best statistical models are comparable to all but the very best dynamical models. In this comparison the leading statistical model is the one based on the Empirical Model Reduction (EMR) method. Here we report on experiments with multilevel Vector Autoregressive models using only sea surface temperatures (SSTs) as predictors. VAR(L) models generalizes Linear Inverse Models (LIM), which are a VAR(1) method, as well as multilevel univariate autoregressive models. Optimal forecast skill is achieved using 12 to 14 months of prior state information (i.e 12-14 levels), which allows SSTs alone to capture the effects of other variables such as heat content as well as seasonality. The use of multiple levels allows the model advancing one month at a time to perform at least as well for a 6 month forecast as a model constructed to explicitly forecast 6 months ahead. We infer that the multilevel model has fully captured the linear dynamics (cf. Penland and Magorian, 1993 J. Climate). Finally, while VAR(L) is equivalent to L-level EMR, we show in a 150 year cross validated assessment that we can increase forecast skill by improving on the EMR initialization procedure. The greatest benefit of this change is in allowing the prediction to make effective use of information over many more months.

  16. ENSO-related PM10 variability on the Korean Peninsula

    Science.gov (United States)

    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.

  17. ENSO, rotación terrestre, volcanes y sismicidad.

    OpenAIRE

    Mesa Sánchez, Óscar José

    2002-01-01

    El fenómeno de El Niño- Oscilación del Sur (ENSO) integra paradigmáticamente todas las geociencias. La interacción océano-atmósfera se acepta comúnmente como el actor central de esta oscilación interanual del sistema climático. Algo más desconocida es la influencia del ENSO en la rotación terrestre, aunque hay excelente evidencia empírica y sólida explicación teórica. Con respecto a la influencia del ENSO en la sismicidad la situación es bastante polémica, las observaciones son discutibles...

  18. Atmosphere-earth angular momentum exchange and ENSO cycle

    Institute of Scientific and Technical Information of China (English)

    钱维宏; 丑纪范

    1996-01-01

    The time series of the earth’s rotation rate, eastern equatorial Pacific sea surface temperature (Tss), sea level pressure (Psl) and atmospheric angular momentum (Maa) during 1976 -1989 are used to study the relation between atmosphere-earth angular momentum exchange and ENSO cycle. The result shows that (i) there are synergetic relationships among the variations of solid earth’s rotation, eastern equatorial Pacific T,, Psl, different latitude zonal Maa and global Maa; (ii) local atmosphere-ocean interaction over low-latitude area can form ENSO-like cycle through Hadley circulation; (iii) the solid earth and global atmosphere-ocean interaction can form some aperiodic behavior and asynchronous oscillations by mountain torque and earth spin anomalous friction torque acting on each component of solid earth-ocean-atmosphere system; and (iv) actual ENSO cycle is a phenomenon reflecting in Pacific basin through interaction among solid earth, global ocean and the atmosphere.

  19. The ENSO-precipitation teleconnection and its modulation by the interdecadal pacific oscillation

    OpenAIRE

    Westra, S.; B. Renard; Thyer, M.

    2015-01-01

    International audience; This study evaluates the role of the interdecadal Pacific oscillation (IPO) in modulating the El Niño?Southern Oscillation (ENSO)-precipitation relationship. The standard IPO index is described together with several alternatives that were derived using a low-frequency ENSO filter, demonstrating that an equivalent IPO index can be obtained as a low-frequency version of ENSO. Several statistical artifacts that arise from using a combination of raw and smoothed ENSO indic...

  20. Inferring changes in ENSO amplitude from the variance of proxy records

    OpenAIRE

    Russon, Tom; Tudhope, Alexander; Collins, Mat; Hegerl, Gabi

    2015-01-01

    One common approach to investigating past changes in ENSO amplitude is through quantifying the variance of ENSO-influenced proxy records. However, a component of the variance of all such proxies will reflect influences that are unrelated to the instrumental climatic indices from which modern ENSO amplitudes are defined. The unrelated component of proxy variance introduces a fundamental source of uncertainty to all such constraints on past ENSO amplitudes. Based on a simple parametric approach...

  1. On the spatial and temporal variability of ENSO precipitation and drought teleconnection in mainland Southeast Asia

    Science.gov (United States)

    Räsänen, Timo A.; Lindgren, Ville; Guillaume, Joseph H. A.; Buckley, Brendan M.; Kummu, Matti

    2016-09-01

    The variability of the hydroclimate over mainland Southeast Asia is strongly influenced by the El Niño-Southern Oscillation (ENSO), which has been linked to severe droughts and floods that profoundly influence human societies and ecosystems alike. Although the significance of ENSO is well understood, there are still limitations in the understanding of its effects on hydroclimate, particularly with regard to understanding the spatio-temporal characteristics and the long-term variation of its effects. Therefore we analysed the seasonal evolution and spatial variations in the effect of ENSO on precipitation over the period of 1980-2013 and the long-term variation in the ENSO teleconnection using tree-ring-derived Palmer drought severity indices (PDSIs) for the March-May season that span over the time period 1650-2004. The analyses provided an improved understanding of the seasonal evolution of the precipitation anomalies during ENSO events. The effects of ENSO were found to be most consistent and expressed over the largest areal extents during March-May of the year when the ENSO events decay. On a longer timescale, we found that ENSO has affected the region's March-May hydroclimate over the majority (95 %) of the 355-year study period and that during half (52 %) of the time ENSO caused a significant increase in hydroclimatic variability. The majority of the extremely wet and dry March-May seasons also occurred during ENSO events. However, considerable variability in ENSO's influence was revealed: the spatial pattern of precipitation anomalies varied between individual ENSO events, and the strength of ENSO's influence was found to vary through time. Given the high variability in ENSO teleconnection that we described and the limitations of the current understanding of the effects of ENSO, we suggest that the adaptation to ENSO-related extremes in hydroclimate over mainland Southeast Asia needs to recognise uncertainty as an inherent part of adaptation, must go beyond

  2. Changes in Sea Salt Emissions Enhance ENSO Variability

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yang; Russell, Lynn M.; Lou, Sijia; Lamjiri, Maryam A.; Liu, Ying; Singh, Balwinder; Ghan, Steven J.

    2016-11-15

    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 atmosphere 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.

  3. Decadal modulation of East China winter precipitation by ENSO

    Science.gov (United States)

    Liu, Jia; Wang, Hui; Lu, Er; Kumar, Arun

    2016-11-01

    The decadal modulation of East China winter precipitation by the El Niño-Southern Oscillation (ENSO) is examined using both observational data and coupled global climate model simulations. The co-variability between 68-year (1948-2015) observed East China precipitation and tropical Pacific sea surface temperature (SST) is quantified by the singular value decomposition (SVD) method. The first SVD mode relates Southeast China winter pluvial (drought) to the tropical Pacific El Niño (La Niña) SST. A comparison between two 480-year model simulations with and without ENSO suggests that ENSO can modulate both the intensity and frequency of East China winter precipitation. In the presence of ENSO, maximum precipitation anomalies over Southeast China can be increased by 50% and largely on the interannual timescale (3-6 years). It is also demonstrated that there is an asymmetry in the precipitation and circulation responses to warm and cold phases of ENSO. The responses are sensitive to the intensity of SST anomalies during El Niño, but less sensitive to SSTs during La Niña. This sensitivity, together with the decadal variations of ENSO, helps understand the observed decadal changes in the strength of the association between wintertime tropical Pacific SST and East China precipitation. The association is relatively weak during 1948-1977 when La Niña occurred more frequently, but strong during 1978-1999 when El Niño occurred more frequently. In the last 16 years (2000-2015) the association is weakest, likely due to the weakened variability of tropical Pacific SST since 2000.

  4. Stora Enso varub Eestis jõuliselt puitu / Väinu Rozental

    Index Scriptorium Estoniae

    Rozental, Väinu, 1957-

    2003-01-01

    Kuigi Soome metsatööstusgrupi Stora Enso Metsa käive kahanes III kvartalis 4%, on Eesti metsavarumisfirmade väitel märgata Stora Enso Metsa üha suurenevat aktiivsust puiduvarumises. Tabel: Stora Enso Metsa suurim saeveski on Imaveres

  5. Forest Understory Fire in the Brazilian Amazon in ENSO and Non-ENSO Years: Area Burned and Committed Carbon Emissions

    Science.gov (United States)

    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.

  6. Nonlinear Dynamical Modeling and Forecast of ENSO Variability

    Science.gov (United States)

    Feigin, Alexander; Mukhin, Dmitry; Gavrilov, Andrey; Seleznev, Aleksey; Loskutov, Evgeny

    2017-04-01

    New methodology of empirical modeling and forecast of nonlinear dynamical system variability [1] is applied to study of ENSO climate system. The methodology is based on two approaches: (i) nonlinear decomposition of data [2], that provides low-dimensional embedding for further modeling, and (ii) construction of empirical model in the form of low dimensional random dynamical ("stochastic") system [3]. Three monthly data sets are used for ENSO modeling and forecast: global sea surface temperature anomalies, troposphere zonal wind speed, and thermocline depth; all data sets are limited by 30 S, 30 N and have horizontal resolution 10x10 . We compare results of optimal data decomposition as well as prognostic skill of the constructed models for different combinations of involved data sets. We also present comparative analysis of ENSO indices forecasts fulfilled by our models and by IRI/CPC ENSO Predictions Plume. [1] A. Gavrilov, D. Mukhin, E. Loskutov, A. Feigin, 2016: Construction of Optimally Reduced Empirical Model by Spatially Distributed Climate Data. 2016 AGU Fall Meeting, Abstract NG31A-1824. [2] D. Mukhin, A. Gavrilov, E. Loskutov , A.Feigin, J.Kurths, 2015: Principal nonlinear dynamical modes of climate variability, Scientific Reports, rep. 5, 15510; doi: 10.1038/srep15510. [3] Ya. Molkov, D. Mukhin, E. Loskutov, A. Feigin, 2012: Random dynamical models from time series. Phys. Rev. E, Vol. 85, n.3.

  7. Stora Enso teeb panuse Ida-Euroopale / Sirje Rank

    Index Scriptorium Estoniae

    Rank, Sirje, 1966-

    2003-01-01

    Metsanduskontsern Stora Enso soovib lähiajal kahekordistada puiduvarumist Balti riikides ja Venemaal, samas on ka kontserni peamised investeerimisplaanid ja tootmisvõimsuse lisamine kavandatud Ida-Euroopasse, kus toorme hind on soodne. Diagramm: Stora kasvab enim Baltimaades ja Venemaal

  8. ENSO-Modulated Cyclogenesis over the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Felton, C.S.; Subrahmanyam, B.; Murty, V.S.N.

    of ENSO and IOD*. J. Climate, 23, 3563–3576. Kanamitsu, M., W. Ebisuzaki, J. Woollen, S-K. Yang, J. J. Hnilo, M. Fiorino and G. L. Potter, 2002: NCEP–DOE AMIP-II Reanalysis (R-2). Bull. Amer. Meteor. Soc., 83, 1631–1643. Kikuchi, K., B. Wang, and H...

  9. ENSO-Type Signals Recorded in the Late Cretaceous Laminated Sediments of Songliao Basin, Northeast China

    Science.gov (United States)

    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

  10. ENSO impacts on flood risk at the global scale

    Science.gov (United States)

    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

  11. Influence of ENSO on the Pacific decadal oscillation in CMIP models

    Science.gov (United States)

    Nidheesh, A. G.; Lengaigne, Matthieu; Vialard, Jérôme; Izumo, Takeshi; Unnikrishnan, A. S.; Cassou, Christophe

    2017-02-01

    Emerging decadal climate predictions call for an assessment of decadal climate variability in the Coupled Model Intercomparison Project (CMIP) database. In this paper, we evaluate the influence of El Niño Southern Oscillation (ENSO) on Pacific Decadal Oscillation (PDO) in 10 control simulations from the CMIP3 and 22 from the CMIP5 database. All models overestimate the time lag between ENSO forcing and the PDO response. While half of the models exhibit ENSO-PDO correlation which is close to that in observation (>0.5) when the time lag is accounted for, the rest of the models underestimate this relationship. Models with stronger ENSO-PDO correlation tend to exhibit larger PDO-related signals in the equatorial and south Pacific, highlighting the key role of ENSO teleconnection in setting the inter-hemispheric Pacific pattern of the PDO. The strength of the ENSO-PDO relationship is related to both ENSO amplitude and strength of ENSO teleconnection to the North Pacific sea-level pressure variability in the Aleutian Low region. The shape of the PDO spectrum is consistent with that predicted from a combination of direct ENSO forcing, atmospheric stochastic forcing over the North Pacific and the re-emergence process in 27 models out of 32. Given the essential role of ENSO in shaping the Pacific decadal variability, models displaying realistic ENSO amplitude and teleconnections should be preferentially used to perform decadal prediction experiments.

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

    Science.gov (United States)

    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.

  13. The ENSO Events in the Tropical Pacific and Dipole Events in the Indian Ocean

    Institute of Scientific and Technical Information of China (English)

    CHAO Jiping; CHAO Qingchen; LIU Lin

    2006-01-01

    A depth map (close to that of the thermocline as defined by 20℃) of climatically maximum sea-temperature anomaly was created at the subsurface of the tropical Pacific and Indian Ocean, based on which the evolving sea-temperature anomaly at this depth map from 1960 to 2000 was statistically analyzed. It is noted that the evolving sea temperature anomaly at this depth map can be better analyzed than the evolving sea surface one. For example, during the ENSO event in the tropical Pacific, the sea-temperature anomaly signals travel counter-clockwise within the range of 10°S-10°N, and while moving, the signals change in intensity or even type. If Dipole is used in the tropical Indian. Ocean for analyzing the depth map of maximum sea-temperature anomaly, the sea-temperature anomalies of the eastern and western Indian Oceans would be negatively correlated in statistical sense (Dipole in real physical sense), which is unlike the sea surface temperature anomaly based analysis which demonstrates that the inter-annual positive and negative changes only occur on the gradients of the western and eastern temperature anomalies.Further analysis shows that the development of ENSO and Dipole has a time lag features statistically, with the sea-temperature anomaly in the eastern equatorial Pacific changing earlier (by three months or so). And the linkage between these two changes is a pair of coupled evolving Walker circulations that move reversely in the equatorial Pacific and Indian Oceans.

  14. Improving ENSO periodicity simulation by adjusting cumulus entrainment in BCC_CSMs

    Science.gov (United States)

    Lu, Bo; Ren, Hong-Li

    2016-12-01

    The simulation of El Niño-Southern Oscillation (ENSO) phenomenon is a challenging issue for coupled climate models. This study focuses on the ENSO periodicity simulated by Beijing Climate Center Climate System Models (BCC_CSM1.1 and BCC_CSM1.1m) which can reproduce reasonably well ENSO amplitude as observations. However, the major period of ENSO simulated by the BCC_CSMs is around 2.4 years, which is much shorter than that in observations. Compared with other 24 coupled models in Coupled Model Intercomparison Project Phase 5 (CMIP5), BCC_CSMs produce a very unrealistic ENSO peak period. Such a bias in simulating periodicity is suggested as a consequence of the severely underestimated air-sea coupling intensity in BCC_CSMs. To test this hypothesis, a quantitative method is developed to diagnose the linear ENSO frequency. As an effort to improve the ENSO simulation in BCC_CSMs, three experiments are performed with varying entrainment rates in the cumulus convection parameterization scheme of BCC_CSM1.1m. A more realistic ENSO period of about 3.3 years can be generated by the model with an inflated entrainment rate. When the cumulus entrainment is increased by 10%, the ENSO-related convective precipitation will enhance in the equatorial central to eastern Pacific. This anomalous convective heating induces an intensified surface westerly wind stress to the west of the anomalous convection center and as a result, the air-sea coupling intensity becomes larger, which contributes to a longer period of ENSO based on previous theories. In addition, the pronounced eastward extension of ENSO-related surface wind stress could also be the secondary factor to generate a lower frequency of ENSO in BCC_CSMs. Our study proposes a method to reduce the biases in ENSO periodicity simulation and puts more insights into the importance of adjusting atmospheric convection to reproduce ENSO properties in coupled model.

  15. How well do climate models simulate atmospheric teleconnctions over the North Pacific and East Asia associated with ENSO?

    Science.gov (United States)

    Kim, Sunyong; Son, Hye-Young; Kug, Jong-Seong

    2017-02-01

    During the El Niño and La Niña mature phase, atmospheric teleconnections over the North Pacific and East Asia vary considerably on sub-seasonal time scales, and are strongly phase-locked to the sub-seasonal evolution. In this study, we investigate how well climate models that participated in the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulate the sub-seasonal evolution of teleconnections over the North Pacific and East Asia associated with El Niño-Southern Oscillation (ENSO). In the observations, there is a prominent anticyclone anomaly over the Kuroshio extension region (i.e. Kuroshio anticyclone), which significantly affects East Asian climate in the early winter (November-December) of El Niño years. However, in January, the Kuroshio anticyclone suddenly disappears, and a cyclonic flow dominates over the North Pacific. It is found here that the CMIP5 models simulate the overall extratropical teleconnection patterns, but they fail to reproduce some of these sub-seasonally-varying features in atmospheric circulation. For example, the models tend to simulate a weaker Kuroshio anticyclone in the early winter during El Niño phases, and fail to capture the abrupt decay of the Kuroshio anticyclone in the late winter. We demonstrate here that these systematic errors in ENSO teleconnection can be explained by systematic errors in tropical precipitation associated with ENSO. That is, negative precipitation anomalies over the western North Pacific (WNP) are too weak in the models compared to that in the observations, and their amplitude tends to be strengthened from December to the following January, while they are weakened in the observations. In addition, analyses on the inter-model diversity strongly support that relative magnitudes of WNP and central Pacific precipitation anomalies are critical for determining sub-seasonal evolution of ENSO teleconnections over the North Pacific and East Asia.

  16. SOLUTION OF THE ENSO DELAYED OSCILLATOR WITH HOMOTOPY ANALYSIS METHOD

    Institute of Scientific and Technical Information of China (English)

    WU Zi-ku

    2009-01-01

    An ENSO delayed oscillator is considered.The El Nino atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions.The conceptual oscillator model should consider the variations of both the eastern and western Pacific anomaly patterns.Using the homotopy analysis method,the approximate expansions of the solution of corresponding problem are constructed.The method is based on a continuous variation from an initial trial to the exact solution.A Maclaurin series expansion provides a successive approximation of the solution through repeated application of a differential operator with the initial trial as the first term.This approach does not require the use of perturbation parameters and the solution series converges rapidly with the number of terms.Comparing the approximate analytical solution by homotopy analysis method with the exact solution,we can find that the homotopy analysis method is valid for solving the strong nonlinear ENSO delayed oscillator model.

  17. Impacts of ENSO, global warming and vegetation on future droughts

    Science.gov (United States)

    Bonfils, C.; Anderson, G. J.; Santer, B. D.; Phillips, T. J.; Taylor, K. E.; Cuntz, M.; Zelinka, M. D.; Marvel, K.; Cook, B.; Cvijanovic, I.; Durack, P. J.

    2016-12-01

    A "super El Nino" with above-normal precipitation over California has provided some drought relief in the region, but most of the State remains in drought conditions. We argue that ENSO is not always be a source of relief in the future in regions where the mean change in terrestrial aridity/moistening in response to greenhouse warming becomes larger than the expected range of current variability. We use a suite of state-of-the-art climate model simulations to identify the regions where a projected change in aridity exists, and consider whether this change is large enough to overwhelm the effect of local drying/moistening associated with ENSO variability. By the end of the 21st century, warming is expected virtually everywhere, independent of the phase of ENSO. In contrast, expectations regarding the net anomalies in regional precipitation are less evident, because changes in the mean state and variability are governed by a number of different, spatially-complex mechanisms. Here, we provide a comprehensive assessment of the relative contributions to future drought from changes in moisture supply and demand. We also investigate the competing effects of mean changes and ENSO variability in terms of ameliorating or exacerbating drought. Finally, we investigate the sensitivity of our conclusions to the inclusion of the radiative and physiological forcings associated with enhanced CO2. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work is released as LLNL-ABS-697898.

  18. Study of the global and regional climatic impacts of ENSO magnitude using SPEEDY AGCM

    Science.gov (United States)

    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

  19. Study of the global and regional climatic impacts of ENSO magnitude using SPEEDY AGCM

    Indian Academy of Sciences (India)

    Muhammad Mubashar Dogar; Fred Kucharski; Syed Azharuddin

    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 fewdecades 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 teleconnectionpatterns 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 alsorequired 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 ofENSO causes weakening in rainfall activity over African tropical rain belt, parts of South and Southeast Asia, whereas, the La Ni˜na 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

  20. Study of the global and regional climatic impacts of ENSO magnitude using SPEEDY AGCM

    KAUST Repository

    Dogar, Muhammad Mubashar

    2017-03-09

    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

  1. Optimal localized observations for advancing beyond the ENSO predictability barrier

    Directory of Open Access Journals (Sweden)

    W. Kramer

    2013-04-01

    Full Text Available The existing 20-member ensemble of 50 yr ECHAM5/MPI-OM simulations provides a reasonably realistic Monte Carlo sample of the El Niño–Southern Oscillation (ENSO. Localized observations of sea surface temperature (SST, zonal wind speed and thermocline depth are assimilated in the ensemble using sequential importance sampling to adjust the weight of ensemble members. We determine optimal observation locations, for which assimilation yields the minimal ensemble spread. Efficient observation locations for SST lie in the ENSO pattern, with the optimum located in the eastern and western Pacific for minimizing uncertainty in the NINO3 and NINO4 index, respectively. After the assimilation of the observations, we investigate how the weighted ensemble performs as a nine-month probabilistic forecast of the ENSO. Here, we focus on the spring predictability barrier with observation in the January–March (March–May period and assess the remaining predictive power in June (August for NINO3 (NINO4. For the ECHAM5/MPI-OM ensemble, this yields that SST observations around 110° W and 140° W provide the best predictive skill for the NINO3 and NINO4 index, respectively. Forecasts can be improved by additionally measuring the thermocline depth at 150° W.

  2. The relationship between ENSO and Paraná River flow

    Directory of Open Access Journals (Sweden)

    A. O. Cardoso

    2006-01-01

    Full Text Available Several studies indicate that there is a relationship between the climatic variability in the South American continent and alterations of the position and intensity of the heat sources in the equatorial region. The El Niño phenomenon can influence the precipitation over some regions of South America such as the Brazilian Northeast, Amazonia, South of Brazil and Uruguay. Over 80% of Brazil's energy comes from hydropower, and decisions concerning future availability and pricing require forecasts of river flow, ideally several months in advance. In this work the relationship between the Paraná River flow and the ENSO (El Niño/Southern Oscillation mode is investigated and statistical forecasts of river flow are tested. An evaluation of the relationship between the Pacific sea surface temperature and the Paraná River flow indicates an ENSO pattern over the equatorial Pacific. The time series of the ENSO mode obtained by applying principal components analysis on the sea surface temperature (SST were used as predictors for the Paraná River flow forecast. Improvement in the model forecast skill is also obtained by considering the lagged river flow time series as a predictor.

  3. The western Pacific pattern bridging stratospheric sudden warming and ENSO

    Science.gov (United States)

    Dai, Ying; Tan, Benkui

    2016-04-01

    Previous studies show that the stratospheric sudden warmings (SSWs) are closely linked to the low height anomalies (LHAs) over the North Pacific and the presence of the LHAs is independent of the phases of the El Nino-Southern Oscillation (ENSO). Based on the wintertime daily reanalysis data from 1958 to 2013, this study demonstrates that most of the LHAs which are linked to SSWs are the footprints left by the western Pacific patterns (WPs), few of them by the Pacific-North American patterns (PNAs), or by mixed WP-PNA patterns. This study also demonstrates that the WPs' LHAs, and therefore the SSWs, are strongly modulated by ENSO and the modulation effects changed over 1958-2013: before 1980, the WPs' LHAs have stronger intensity and longer duration in El Nino winters (EN) than La Nina winters (LN) and ENSO neutral winters (ENSON), and the SSWs occur twice as often during EN, compared to LN and ENSON. After 1980, the WPs' LHAs have stronger intensity in EN and larger frequency during LN than ENSON. Consistently, the SSWs occur nearly twice as often during both EN and LN for this period, compared to ENSON.

  4. The complex influence of ENSO on droughts in Ecuador

    Science.gov (United States)

    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.

  5. ENSO Amplitude Change in Observation and Coupled Models

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qiong; GUAN Yue; YANG Haijun

    2008-01-01

    Observations show that the tropical El Nino-Southern Oscillation (ENSO) variability, after removing both the long term trend and decadal change of the background climate, has been enhanced by as much as 60% during the past 50 years. This shift in ENSO amplitude can be related to mean state changes in global climate. Past global warming has caused a weakening of the Walker circulation over the equatorial Indo-Pacific oceans, as well as a weakening of the trade winds and a reduction in the equatorial upwelling. These changes in tropical climatology play as stabilizing factors of the tropical coupling system. However, the shallower and strengthening thermocline in the equatorial Pacific increases the SST sensitivity to thermocline and wind stress variabilities and tend to destabilize the tropical coupling system. Observations suggest that the destabilizing factors, such as the strengthening thermocline, may have overwhelmed the stabilizing effects of the atmosphere, and played a deterministic role in the enhanced ENSO variability, at least during the past half century. This is different from the recent assessment of IPCC-AR4 coupled models.

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

    Science.gov (United States)

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

    2017-07-01

    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.

  7. On the spatial and temporal variability of ENSO precipitation and drought teleconnection in mainland Southeast Asia

    OpenAIRE

    T. A. Räsänen; Lindgren, V; Guillaume, J H A; Buckley, B.M.; Kummu, M.

    2015-01-01

    The variability in the hydroclimate over mainland Southeast Asia is strongly influenced by the El Niño–Southern Oscillation (ENSO) phenomenon, which has been linked to severe drought and floods that profoundly influence human societies and ecosystems alike. However, the spatial characteristics and long-term stationarity of ENSO's influence in the region are not well understood. We thus aim to analyse seasonal evolution and spatial variations in the effect of ENSO on precipit...

  8. Stability of ENSO and its tropical Pacific teleconnections over the Last Millennium

    OpenAIRE

    S. C. Lewis; A. N. LeGrande

    2015-01-01

    Determining past changes in the amplitude, frequency and teleconnections of the El Niño-Southern Oscillation (ENSO) is important for understanding its potential sensitivity to future anthropogenic climate change. Palaeo-reconstructions from proxy records can provide long-term information of ENSO interactions with the background climatic state through time. However, it remains unclear how ENSO characteristics have changed on long timescales, and precisely which signals proxie...

  9. Stability of ENSO and its tropical Pacific teleconnections over the Last Millennium

    OpenAIRE

    S. C. Lewis; A. N. LeGrande

    2015-01-01

    Determining past changes in the amplitude, frequency and teleconnections of the El Niño–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 signa...

  10. Time-varying spectral characteristics of ENSO over the Last Millennium

    Science.gov (United States)

    Hope, Pandora; Henley, Benjamin J.; Gergis, Joelle; Brown, Josephine; Ye, Hua

    2016-10-01

    The characteristics of El Nino-Southern Oscillation (ENSO) spectra over the Last Millennium are examined to characterise variability over past centuries. Seven published palaeo-ENSO reconstructions and Nino3.4 from six Coupled Model Intercomparison Project-Phase 5 and Paleoclimate Modelling Intercomparison Project-Phase 3 (CMIP5-PMIP3) Last Millennium simulations were analysed. The corresponding Historical and pre-industrial Control CMIP5-PMIP3 simulations were also considered. The post-1850 spectrum of each modelled or reconstructed ENSO series captures aspects of the observed spectrum to varying degrees. We note that no single model or ENSO reconstruction completely reproduces the instrumental spectral characteristics. The spectral power across the 2-3 years (near biennial), 3-8 years (classical ENSO) and 8-25 years (decadal) periodicity bands was calculated in a sliding 50 year window, revealing temporal variability in the spectra. There was strong temporal variability in the spectral power of each periodicity band in observed Nino3.4 and SOI and for all reconstructions and simulations of ENSO. Significant peaks in spectral power such as observed in recent decades also occur in some of the reconstructed palaeo-ENSO (around 1600, the early 1700s and 1900) and modelled series (around the major volcanic eruptions of 1258 and 1452). While the recent increase in spectral power might be in response to enhanced greenhouse gas levels, the increase lies within the range of variability across the suite of ENSO reconstructions and simulations examined here. This study demonstrates that the analysis of a suite of ENSO reconstructions and model simulations can build a broader understanding of the time-varying nature of ENSO spectra, and how the nature of the past spectra of ENSO is to some extent dependant on the climate model or palaeo-ENSO reconstruction chosen.

  11. Time-varying spectral characteristics of ENSO over the Last Millennium

    Science.gov (United States)

    Hope, Pandora; Henley, Benjamin J.; Gergis, Joelle; Brown, Josephine; Ye, Hua

    2017-09-01

    The characteristics of El Nino-Southern Oscillation (ENSO) spectra over the Last Millennium are examined to characterise variability over past centuries. Seven published palaeo-ENSO reconstructions and Nino3.4 from six Coupled Model Intercomparison Project-Phase 5 and Paleoclimate Modelling Intercomparison Project-Phase 3 (CMIP5-PMIP3) Last Millennium simulations were analysed. The corresponding Historical and pre-industrial Control CMIP5-PMIP3 simulations were also considered. The post-1850 spectrum of each modelled or reconstructed ENSO series captures aspects of the observed spectrum to varying degrees. We note that no single model or ENSO reconstruction completely reproduces the instrumental spectral characteristics. The spectral power across the 2-3 years (near biennial), 3-8 years (classical ENSO) and 8-25 years (decadal) periodicity bands was calculated in a sliding 50 year window, revealing temporal variability in the spectra. There was strong temporal variability in the spectral power of each periodicity band in observed Nino3.4 and SOI and for all reconstructions and simulations of ENSO. Significant peaks in spectral power such as observed in recent decades also occur in some of the reconstructed palaeo-ENSO (around 1600, the early 1700s and 1900) and modelled series (around the major volcanic eruptions of 1258 and 1452). While the recent increase in spectral power might be in response to enhanced greenhouse gas levels, the increase lies within the range of variability across the suite of ENSO reconstructions and simulations examined here. This study demonstrates that the analysis of a suite of ENSO reconstructions and model simulations can build a broader understanding of the time-varying nature of ENSO spectra, and how the nature of the past spectra of ENSO is to some extent dependant on the climate model or palaeo-ENSO reconstruction chosen.

  12. The Relative Influences of ENSO Conventional, ENSO Modoki and Indian Ocean Dipole on Mindanao and Northeastern Borneo Precipitation Anomaly

    Science.gov (United States)

    Tsai, C.; Behera, S. K.; Waseda, T.; Tangang, F.

    2014-12-01

    Since the discovery of El Nino Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), and El Nino Modoki (EM), many had thought that all of these 3 climate phenomena are influencing the precipitation in Mindanao and Northeastern Borneo. However, no study was done to identify the real impact of these three climate phenomena on the precipitation of this area. Based on the situation above, this study intends to investigate the influence of ENSO, IOD and EM to Mindanao and Northeastern Borneo precipitation. Besides that, we are investigating factor other than those dominant climate phenomena that affect the precipitation in the study region. For this study, we used APHRODITE (observation precipitation data) as our primary precipitation data. For analysis, we used 850hPa wind data (JRA-55), 200hPa stream function data (JRA-55) and sea surface temperature data (SST; HadISST) from 1961 to 2007. Correlation, partial correlation and composite analyses are used as the method for this study. We discovered that ENSO during December-February (DJF), March-May and September-November (SON) influence the precipitation in the study region. Further analysis indicated that EM during DJF and SON influences precipitation of those regions. The results show that the ENSO and the EM influence the precipitation of this region through Walker circulation and associated teleconnections. However, IOD influence is not significant in any season. It is also discovered that the precipitation in the region is greatly affected by the local winds northeast of Mindanao during DJF. Those are the regional monsoon winds for the Asian Winter Monsoon. In addition, the winter monsoon rainfall is influenced by the winds that are in turn associated with the variations in Aleutian Low and Siberian High. Further analysis will be done to understand the links among them (SST, regional monsoon winds and 200hPa streamfunction) and consequently the mid-latitude teleconnections that affect the regional monsoon winds.

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

    Science.gov (United States)

    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.

  14. Backbone topology, access, and the commercial Internet, 1997 - 2000

    OpenAIRE

    Morton E O'Kelly; Grubesic, Tony H.

    2002-01-01

    As the Internet grows in popularity, telecommunications infrastructure in the United States continues to increase in capacity and geographic reach to meet market demand. Important components of this infrastructure include the commercial fiber-optic backbones used to transport digital information between locations. The spatial organization of commercial Internet backbones reflects an increasingly competitive privatized market for service provision, in which certain locations are more accessibl...

  15. Gebruikswaarde onderzoek hippeastrum - bollenteelt ; resultaten 1997-2000

    NARCIS (Netherlands)

    Berents, A.J.H.; Brabander, E.; Elgersma, R.

    2001-01-01

    De veredeling van Hippeastrum (amaryllis) zorgt voor een geleidelijke vernieuwing van het sortiment. De opbouw van een partij plantmateriaal gaat langzaam en het duurt jaren voordat de waarde van een nieuw ras bekend is. Het gebruikswaarde-onderzoek is gericht op het beoordelen van rassen op teeltei

  16. Colorado wetlands initiative : 1997-2000 : Protecting Colorado's wetlands resource

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The Colorado Wetlands Initiative is an endeavor to protect wetlands and wetland-dependent wildlife through the use of voluntary, incentive-based mechanisms. It is a...

  17. Non Gaussian and Non stationary characters of ENSO: the role of climate shifts and nonlinearities

    Science.gov (United States)

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

    2009-04-01

    ENSO is the dominant climate mode of variability in the Pacific, having socio-economical impacts on surrounding regions. ENSO exhibits a significant modulation at decadal to multidecadal timescales which is associated to changes of its characteristics (onset, amplitude, frequency, propagation, and predictability). Among these characteristics, some of them are generally ignored in ENSO studies, such as its asymmetry 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, the non-Gaussian nature and asymmetry of ENSO is diagnosed from in situ data and a variety of models (from intermediate complexity models to full physics coupled general circulation models) using robust statistical tools. In particular α-stable laws are used as theoretical background material to quantify the non-Gaussian character of ENSO time series. It is shown that the α-stable character of ENSO may result from the presence of climate shifts inducing non stationnarity in the time series. Also, cool (warm) periods are associated with ENSO statistics having a larger (weaker) tendency towards Gaussianity and a weaker (larger) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through non-linear processes. The relationship between change in mean state and non-linearity is investigated both in the Zebiak and Cane model and the IPCC models, which indicate that the propensity of a model to reproduce extreme events is related to its tendency to emphasize the non-linear interaction between mean state and ENSO variability. More particularly, high statistical moments i.e high order nonlinearities seem to be involved in the feedback between extreme events occurrence and mean state shit triggering through energy cascade, emphasizing the ENSO multifractal nature.

  18. Non Stationary And Non Gaussian Character Of ENSO: The Role Of Climate Shifts And Nonlinearities

    Science.gov (United States)

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

    2008-12-01

    ENSO is the dominant climate mode of variability in the Pacific, having socio-economical impacts on surrounding regions. ENSO exhibits a significant modulation at decadal to interdecadal timescales which is associated to changes of its characteristics (onset, amplitude, frequency, propagation, and predictability). Among these characteristics, some of them are generally ignored in ENSO studies, such as its asymmetry 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, the non-Gaussian nature and asymmetry of ENSO is diagnosed from in situ data and the outputs of a variety of models (from intermediate complexity models to full physics coupled general circulation models) using robust statistical tools. In particular alpha-stable laws are used as theoretical background material to quantify the non-Gaussian character of ENSO time series. It is shown that the Alpha-stable character of ENSO may result from the presence of climate shifts inducing non stationnarity in the time series. Also, cool (warm) periods are associated with ENSO statistics having a larger (weaker) tendency towards Gaussianity and a weaker (larger) asymmetry. This supports the hypothesis of ENSO being rectified by changes in mean state through non-linear processes. The relationship between change in mean state and non-linearity is investigated both in the Zebiak and Cane model and the IPCC models, which indicate that the propensity of a model to reproduce extreme events is related to its tendency to emphasize the non-linear interaction between mean state and ENSO variability. More particularly, high statistical moments i.e. high order nonlinearities seem to be involved in the feedback between extreme events occurrence and mean state shift triggering through inverse energy cascade, emphasizing the ENSO multifractal nature.

  19. Impacts of enhanced central Pacific ENSO on wave climate and headland-bay beach morphology

    Science.gov (United States)

    Mortlock, Thomas R.; Goodwin, Ian D.

    2016-06-01

    Wave climate and Pacific basin coastal behaviour associated with El Niño Southern Oscillation (ENSO) is understood at a reconnaissance level, but the coastal response to different central Pacific (CP) versus eastern Pacific (EP) flavours of ENSO is unknown. We show that CP ENSO events produce different patterns of directional wave power to EP ENSO along the southeast Australian shelf and southwest Pacific region, because of significant variability in trade-wind wave generation. The modulation of the trade wind wave climate during CP ENSO has thus far been neglected in existing coastal process studies. We also show that coastal change between CP and EP ENSO cannot be inferred from shifts in the deepwater wave climate. This is because variability in trade wind wave generation is masked in deepwater by the persistence of high power extra-tropical waves that have reduced impact on nearshore processes due to high wave refraction. Morphodynamic modelling in a headland-bay beach indicates that CP ENSO leads to higher coastal erosion potential and slower post-storm recovery than EP ENSO during an El Niño/La Niña cycle. We show that the alongshore variability in beach morphological type can be used to model the static equilibrium planform response for each ENSO phase. Results indicate that shoreline response to ENSO in most headland-bay beach coasts is not as simple as the existing paradigm that (anti-) clockwise rotation occurs during El Niño (La Niña). Our methods provide a second-order approach to project coastal response and predict the discrete shoreline rotations for ENSO flavours.

  20. Simulating the link between ENSO and summer drought in Southern Africa using regional climate models

    Science.gov (United States)

    Meque, Arlindo; Abiodun, Babatunde J.

    2015-04-01

    This study evaluates the capability of regional climate models (RCMs) in simulating the link between El Niño Southern Oscillation (ENSO) and Southern African droughts. It uses the Standardized Precipitation-Evapotranspiration Index (SPEI, computed using rainfall and temperature data) to identify 3-month drought over Southern Africa, and compares the observed and simulated correlation between ENSO and SPEI. The observation data are from the Climate Research Unit, while the simulation data are from ten RCMs (ARPEGE, CCLM, HIRHAM, RACMO, REMO, PRECIS, RegCM3, RCA, WRF, and CRCM) that participated in the regional climate downscaling experiment (CORDEX) project. The study analysed the rainy season (December-February) data for 19 years (1989-2008). The results show a strong link between ENSO and droughts (SPEI) over Southern Africa. The link is owing to the influence of ENSO on both rainfall and temperature fields, but the correlation between ENSO and temperature is stronger than the correlation between ENSO and rainfall. Hence, using only rainfall to monitor droughts in Southern Africa may underestimate the influence of ENSO on the droughts. Only few CORDEX RCMs simulate the influence of ENSO on Southern African drought as observed. In this regard, the ARPEGE model shows the best simulation, while CRCM shows the worst. The different in the performance may be due to their lateral boundary conditions. The RCA-simulated link between ENSO and Southern African droughts is sensitive to the global dataset used as the lateral boundary conditions. In some cases, using RCA to downscale global circulation models (GCM) simulations adds value to the simulated link between ENSO and the droughts, but in other cases the downscaling adds no value to the link. The added value of RCA to the simulated link decreases as the capability of the GCM to simulate the link increases. This study suggests that downscaling GCM simulations with RCMs over Southern Africa may improve or depreciate the

  1. The pelagic ecosystem of the tropical Pacific Ocean: dynamic spatial modelling and biological consequences of ENSO

    Science.gov (United States)

    Lehodey, Patrick

    A feature of the central equatorial Pacific is a strong divergent equatorial upwelling called the cold tongue, which is favorable to the development of a large zonal band with high levels of primary production. Contiguous to the cold tongue, is the western Pacific warm pool, which is characterized by warmer water with lower levels of primary production. At the top of the food web, the tropical tunas are a major component of the pelagic ecosystem and have their maximum biomass in the warm pool. However, during ENSO (El Niño Southern Oscillation) events, variability is observed in both environmental factors and the spatial distribution of tuna. A Spatial Environmental Population Dynamics Model (SEPODYM) is used to assist in the analysis and interpretation of these fishery oceanographic observations. A modelling approach is described and applied to the population and fisheries of skipjack tuna, one of the top predator species with its greatest biomass in the tropical pelagic ecosystem. Environmental variables are used in the model for delineating the spawning area of skipjack, reproducing the transport of its larvae and juveniles, and simulating tuna forage. The forage production is deduced from a simple ecological transfer based on new primary production with biomass calculated as a single population. The model considers an interaction between predicted tuna density and forage density. A habitat index combining temperature preferences with forage distribution is used to constrain the movement of adult tuna. Results of the simulation allow realistic prediction of the large-scale distribution of the species. There is a remarkable out-of-phase pattern linked to ENSO between the western Pacific region and the cold tongue. This pattern is consistent with the observed movements of skipjack.

  2. ENSO and NAO Influences on the Urmia Lake Basin Meteorology and Hydrology

    Science.gov (United States)

    Abrishamchi, A.; Hazrati, S.; Tajrishy, M.; Marino, M. A.

    2006-12-01

    Urmia Lake Basin located in northwest Iran has an area of 51,876 Km2. The western limits of the Basin overlap the elevations on the border between Iran and Turkey. Mean annual precipitation in the Basin varies from 200 to 690 mm averaging 345 mm. The Urmia Lake located at the center of the closed Urmia Basin and west of the Caspian Sea is one of the most important and valuable ecosystems in the country. It is the largest inland lake in Iran and because of its unique natural and ecological features it has been given national park status and has been designated as a Ramsar site (wetland of international importance) in 1975 and a UNESCO Biosphere Reserve. This paper attempts to explore the influences of the large-scale climate signals of the El Nino, La Nina, and NAO phenomena on temperature, precipitation, and streamflow in Urmia Lake Basin as well as the connection of the Urmia Lake level fluctuations with these signals. Results of this study indicate that variations in Urmia Lake Basin temperature and precipitation reflect the far-field influence of the NAO and ENSO. During high positive (negative) phases of NAOslp the region becomes drier (wetter) and cooler (warmer). Two of the main rivers in the Basin studied in this paper are Ajichai and Siminehrood. The extreme negative phase of NAOslp increases monthly Ajichai streamflow. ENSO has different seasonal influences; the most influence is on autumn streamflow that El Nino (La Nina) increases (decreases). Siminehrood streamflows are significantly correlated with the NAOslp and SOI and the occurrence of El Nino has various effects during the year on Siminehrood streamflow; the most significant effects are on autumn streamflow. Results also indicate that variations in Urmia Lake level reflect the far-field influence of the NAO and El Nino Southern Oscillation such that correlations between the normalized average monthly lake level and NAO and SOI indices of prior months are significant.

  3. North Pacific Decadal Variability: Insights from a Biennial ENSO Environment

    Science.gov (United States)

    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.

  4. The complex influence of ENSO on droughts in Ecuador

    KAUST Repository

    Vicente-Serrano, S. M.

    2016-03-26

    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. © 2016 Springer-Verlag Berlin Heidelberg

  5. Impacts of a Pinatubo-size volcanic eruption on ENSO

    KAUST Repository

    Predybaylo, Evgeniya

    2017-01-16

    Observations and model simulations of the climate responses to strong explosive low-latitude volcanic eruptions suggest a significant increase in the likelihood of El Niño during the eruption and posteruption years, though model results have been inconclusive and have varied in magnitude and even sign. In this study, we test how this spread of responses depends on the initial phase of El Niño-Southern Oscillation (ENSO) in the eruption year and on the eruption\\'s seasonal timing. We employ the Geophysical Fluid Dynamics Laboratory CM2.1 global coupled general circulation model to investigate the impact of the Pinatubo 1991 eruption, assuming that in 1991 ENSO would otherwise be in central or eastern Pacific El Niño, La Niña, or neutral phases. We obtain statistically significant El Niño responses in a year after the eruption for all cases except La Niña, which shows no response in the eastern equatorial Pacific. The eruption has a weaker impact on eastern Pacific El Niños than on central Pacific El Niños. We find that the ocean dynamical thermostat and (to a lesser extent) wind changes due to land-ocean temperature gradients are the main feedbacks affecting El Niño development after the eruption. The El Niño responses to eruptions occurring in summer are more pronounced than for winter and spring eruptions. That the climate response depends on eruption season and initial ENSO phase may help to reconcile apparent inconsistencies among previous studies.

  6. Phenological Responses to ENSO in the Global Oceans

    Science.gov (United States)

    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

  7. Imavere Sawmill is Stora Ensos Jewel in the Region / Seppo Vainio ; interv. Toivo Tänavsuu

    Index Scriptorium Estoniae

    Vainio, Seppo

    2004-01-01

    Skandinaavia metsanduskontserni Stora Enso Timberi tegevuse juht Baltikumis vastab küsimustele, mis puudutavad Eesti suurima metsatööstuse Sylvesteri ostu 2003. aastal, Baltikumi üksuste osa Stora Enso tegevuses, Imavere saeveski valimist aasta välisinvestoriks. Vt. samas: Imavere saeveski eile ja täna. Tabel: "Välisinvestor 2004" nominendid

  8. The perturbed solution of sea-air oscillator for ENSO model

    Institute of Scientific and Technical Information of China (English)

    MO Jiaqi; LIN Wantao; ZHU Jiang

    2004-01-01

    A class of delayed oscillators and coupled systems to oscillation of El Nino-Southern Oscillation (ENSO) models are considered. Using the perturbed theory and other methods, the exact solution or asymptotic expansions of the solution for ENSO models is obtained and the asymptotic behavior of solution of corresponding problem is studied.

  9. Reduced herbivory during simulated ENSO rainy events increases native herbaceous plants in semiarid Chile

    NARCIS (Netherlands)

    Manrique, R.; Gutierrez, J.R.; Holmgren, M.; Squeo, F.A.

    2007-01-01

    El Niño Southern Oscillation (ENSO) events have profound consequences for the dynamics of terrestrial ecosystems. Since increased climate variability is expected to favour the invasive success of exotic species, we conducted a field experiment to study the effects that simulated rainy ENSO events in

  10. Imavere Sawmill is Stora Ensos Jewel in the Region / Seppo Vainio ; interv. Toivo Tänavsuu

    Index Scriptorium Estoniae

    Vainio, Seppo

    2004-01-01

    Skandinaavia metsanduskontserni Stora Enso Timberi tegevuse juht Baltikumis vastab küsimustele, mis puudutavad Eesti suurima metsatööstuse Sylvesteri ostu 2003. aastal, Baltikumi üksuste osa Stora Enso tegevuses, Imavere saeveski valimist aasta välisinvestoriks. Vt. samas: Imavere saeveski eile ja täna. Tabel: "Välisinvestor 2004" nominendid

  11. A synthesis of ENSO effects on drylands in Australia, North America and South America

    NARCIS (Netherlands)

    Holmgren, M.; Stapp, P.; Dickman, C.; Gracia, C.; Graham, S.

    2005-01-01

    Fundamentally, El Niño Southern Oscillation (ENSO) is a climatic and oceanographic phenomenon, but it has profound effects on terrestrial ecosystems. Although the ecological effects of ENSO are becoming increasingly known from a wide range of terrestrial ecosystems (Holmgren et al., 2001), their imp

  12. Revisiting the Indian summer monsoon-ENSO links in the IPCC AR4 projections: A cautionary outlook

    Science.gov (United States)

    Roxy, Mathew; Patil, Nitin; Aparna, K.; Ashok, Karumuri

    2013-05-01

    The climate change experiments under the fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC), namely the twentieth century simulations (20C3M) and Special Report on Emissions Scenarios (SRES) A1B, are revisited to study whether these models can reproduce the ENSO and ENSO Modoki patterns as the two important modes from statistical linear analysis as observed. The capability of the models in simulating realistic ENSO/ENSO Modoki teleconnections with the Indian summer monsoon, and also the implications for the future are also explored. Results from the study indicate that only ~ 1/4th of the models from 20C3M capture either ENSO or ENSO Modoki pattern in JJAS. Of this 1/4th, only two models simulate both ENSO and ENSO Modoki as important modes. Again, out of these two, only one model simulates both ENSO and ENSO Modoki as important modes during both summer and winter. It is also shown that the two models that demonstrate ENSO Modoki as well as ENSO associated variance in both 20C3M and SRESA1B represent the links of the ISMR with ENSO reasonably in 20C3M, but indicate opposite type of impacts in SREA1B. With the limited skills of the models in reproducing the monsoon, the ENSO and ENSO Modoki, it is difficult to reconcile that the teleconnections of a tropical driver can change like that. All these indicate the challenges associated with the limitations of the models in reproducing the variability of the monsoons and ENSO flavors, not to speak of failing in capturing the potential impacts of global warming as they are expected to. More research in improving the current day simulations, improving model capacity to simulate better by improving the Green House Gases (GHG) and aerosols in the models are some of the important and immediate steps that are necessary.

  13. Quantifying the impacts of ENSO and IOD on rain gauge and remotely sensed precipitation products over Australia

    OpenAIRE

    Forootan, Ehsan; Khandu, .; Awange, J.; Schumacher, M; Anyah, R.; A. I. J. M. van Dijk; Kusche, J.

    2015-01-01

    Large-scale ocean-atmospheric phenomena like the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) have significant influence on Australia's precipitation variability. In this study, multi-linear regression (MLR) and complex empirical orthogonal function (CEOF) analyses were applied to isolate (i) the continental precipitation variations likely associated with ENSO and IOD, here referred to as ‘ENSO/IOD mode’, and (ii) the variability not associated with ENSO/IOD (the ‘non-ENS...

  14. On the recent strengthening of the relationship between ENSO and northeast monsoon rainfall over South Asia

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Pankaj; Rupa Kumar, K.; Sahai, A.K. [Indian Institute of Tropical Meteorology, Pune (India); Rajeevan, M. [India Meteorological Department, Pune (India)

    2007-05-15

    The southeastern parts of India and Sri Lanka receive substantial rainfall from the northeast monsoon (NEM) during October through December. The interannual variability in NEM rainfall is known to be significantly influenced by the El-Nino/Southern Oscillation (ENSO). Unlike the southwest monsoon (SWM), the NEM rainfall is enhanced during the warm ENSO events, and vice versa. In the context of the recent weakening of the inverse relationship between Southwest Monsoon (SWM) and ENSO, we examine the secular variations in the positive relationship between ENSO and NEM rainfall over South Asia, showing that their relationship has strengthened over the recent years. Based on the analysis of GISST, IMD/CRU precipitation and NCEP/NCAR reanalysis data, we suggest that this secular variation of the relationship is due to epochal changes in the tropospheric circulation associated with ENSO over the region. (orig.)

  15. ENSO flavors in a tree-ring δ18O record of Tectona grandis from Indonesia

    Science.gov (United States)

    Schollaen, K.; Karamperidou, C.; Krusic, P.; Cook, E.; Helle, G.

    2015-10-01

    Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900-2007) of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific) El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern Pacific) El Niño events. These results are consistent with the distinct impacts of the two ENSO flavors on Javanese precipitation, and illustrate the importance of considering ENSO flavors when interpreting palaeoclimate proxy records in the tropics, as well as the potential of palaeoclimate proxy records from appropriately selected tropical regions for reconstructing past variability of. ENSO flavors.

  16. Shortcomings in climate model simulations of the ENSO-Atlantic hurricane teleconnection

    Energy Technology Data Exchange (ETDEWEB)

    Shaman, Jeffrey [Columbia University, Department of Environmental Health Sciences, Mailman School of Public Health, New York, NY (United States); Columbia University, International Research Institute for Climate and Society, Palisades, NY (United States); Maloney, Eric D. [Colorado State University, Department of Atmospheric Science, Fort Collins, CO (United States)

    2012-05-15

    A number of recent studies have used model projections to investigate how the North Atlantic environment in which tropical storms develop, as well as hurricane activity itself, might change in a warming world. However, accurate projection of the North Atlantic environment in the future requires, at a minimum, accurate representation of its mean state and variability in the current climate. Here we examine one metric of Atlantic basin tropical cyclone variability - its well-documented association with the El Nino-Southern Oscillation (ENSO) - in reanalyses and Intergovernmental Panel of Climate Change (IPCC) 4th Assessment Report (AR4) twentieth century and Atmospheric Model Intercomparison Project simulations. We find that no individual model provides consistently good representation of ENSO-related variability in the North Atlantic for variables relevant to hurricane activity (e.g. vertical wind shear, genesis potential). Model representation of the ENSO influence is biased due to both inaccurate representation of ENSO itself and inaccurate representation of the response to ENSO within the North Atlantic. Among variables examined, ENSO impacts on vertical wind shear and potential intensity were most poorly simulated. The multi-model ensemble mean representation of North Atlantic environmental response to ENSO is better matched with reanalysis than most individual AR4 models; however, this mean response still possesses some considerable bias. A few models do provide comparable or slightly better simulation of these ENSO-North Atlantic teleconnections than the multi-model ensemble average; however, for both the multi-model mean and the well performing models, good simulation of the ENSO-related variability of genesis potential within portions of the North Atlantic does not stem from accurate representation of the ENSO-related variability of the individual environmental variables that comprise genesis potential (e.g. vertical wind shear, potential intensity). (orig.)

  17. Why the twenty-first century tropical Pacific trend pattern cannot significantly influence ENSO amplitude?

    Science.gov (United States)

    An, Soon-Il; Choi, Jung

    2015-01-01

    Although the climate is highly expected to change due to global warming, it is unclear whether the El Nino-Southern Oscillation (ENSO) will be more or less active in the future. One may argue that this uncertainty is due to the intrinsic uncertainties in current climate models or the strong natural long-term modulation of ENSO. Here, we propose that the global warming trend cannot significantly modify ENSO amplitude due to weak feedback between the global warming induced tropical climate change and ENSO. By analyzing Coupled Model Intercomparison Project Phase 5 and observation data, we found that the zonal dipole pattern of sea surface temperature [SST; warming in the eastern Pacific and cooling in the western Pacific or vice versa; `Pacific zonal mode' (PZM)] is highly correlated to change in ENSO amplitude. Additionally, this PZM is commonly identified in control experiments (pre-industrial conditions), twentieth century observations, and twenty-first century scenario experiments [representative concentration pathways 4.5 and 8.5 W m-2 (RCP 4.5, 8.5)]. PZM provides favorable conditions for the intensification of ENSO by strengthening air-sea coupling and modifying ENSO pattern. On the other hand, the twenty-first century SST trend pattern, which is different from PZM, is not favorable towards changing ENSO amplitude. Furthermore, we performed an intermediate ocean-atmosphere coupled model simulations, in which the SST trend pattern and PZM are imposed as an external anomalous heat flux or prescribed as a basic state. It was concluded that the SST trend pattern forcing insignificantly changes ENSO amplitude, and the PZM forcing intensifies ENSO amplitude.

  18. Kawasaki disease and ENSO-driven wind circulation

    Science.gov (United States)

    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.

  19. The importance of ENSO nonlinearities in tropical pacific response to external forcing

    Science.gov (United States)

    Karamperidou, Christina; Jin, Fei-Fei; Conroy, Jessica L.

    2016-12-01

    Tropical Pacific climate varies at interannual, decadal and centennial time scales, and exerts a significant influence on global climate. Climate model projections exhibit a large spread in the magnitude and pattern of tropical Pacific warming in response to greenhouse-gas forcing. Here, we show that part of this spread can be explained by model biases in the simulation of interannual variability, namely the El Niño/Southern Oscillation (ENSO) phenomenon. We show that models that exhibit strong ENSO nonlinearities simulate a more accurate balance of ENSO feedbacks, and their projected tropical Pacific sea surface temperature warming pattern is closely linked to their projected ENSO response. Within this group, models with ENSO nonlinearity close to observed project stronger warming of the cold tongue, whereas models with stronger than observed ENSO nonlinearity project a more uniform warming of the tropical Pacific. These differences are also manifest in the projected changes of precipitation patterns, thereby highlighting that ENSO simulation biases may lead to potentially biased projections in long-term precipitation trends, with great significance for regional climate adaptation strategies.

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

    Science.gov (United States)

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

    2016-10-01

    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.

  1. ENSO anomalies over the Western United States: present and future patterns in regional climate simulations

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yongxin; Qian, Yun; Duliere, Valerie; Salathe, E.; Leung, Lai-Yung R.

    2012-01-03

    Surface temperature, precipitation, specific humidity and wind anomalies associated with the warm and cold phases of ENSO simulated by WRF and HadRM are examined for the present and future decades. WRF is driven by ECHAM5 and CCSM3, respectively, and HadRM is driven by HadCM3. For the current decades, all simulations show some capability in resolving the observed warm-dry and coolwet teleconnection patterns over the PNW and the Southwest U.S. for warm and cold ENSO. Differences in the regional simulations originate primarily from the respective driving fields. For the future decades, the warm-dry and cool-wet teleconnection patterns in association with ENSO are still represented in ECHAM5-WRF and HadRM. However, there are indications of changes in the ENSO teleconnection patterns for CCSM3-WRF in the future, with wet anomalies dominating in the PNW and the Southwest U.S. for both warm and cold ENSO, in contrast to the canonical patterns of precipitation anomalies. Interaction of anomalous wind flow with local terrain plays a critical role in the generation of anomalous precipitation over the western U.S. Anomalous dry conditions are always associated with anomalous airflow that runs parallel to local mountains and wet conditions with airflow that runs perpendicular to local mountains. Future changes in temperature and precipitation associated with the ENSO events in the regional simulations indicate varying responses depending on the variables examined as well as depending on the phase of ENSO.

  2. Drivers of coupled model ENSO error dynamics and the spring predictability barrier

    Science.gov (United States)

    Larson, Sarah M.; Kirtman, Ben P.

    2017-06-01

    Despite recent improvements in ENSO simulations, ENSO predictions ultimately remain limited by error growth and model inadequacies. Determining the accompanying dynamical processes that drive the growth of certain types of errors may help the community better recognize which error sources provide an intrinsic limit to predictability. This study applies a dynamical analysis to previously developed CCSM4 error ensemble experiments that have been used to model noise-driven error growth. Analysis reveals that ENSO-independent error growth is instigated via a coupled instability mechanism. Daily error fields indicate that persistent stochastic zonal wind stress perturbations (τx^' } ) near the equatorial dateline activate the coupled instability, first driving local SST and anomalous zonal current changes that then induce upwelling anomalies and a clear thermocline response. In particular, March presents a window of opportunity for stochastic τx^' } to impose a lasting influence on the evolution of eastern Pacific SST through December, suggesting that stochastic τx^' } is an important contributor to the spring predictability barrier. Stochastic winds occurring in other months only temporarily affect eastern Pacific SST for 2-3 months. Comparison of a control simulation with an ENSO cycle and the ENSO-independent error ensemble experiments reveals that once the instability is initiated, the subsequent error growth is modulated via an ENSO-like mechanism, namely the seasonal strength of the Bjerknes feedback. Furthermore, unlike ENSO events that exhibit growth through the fall, the growth of ENSO-independent SST errors terminates once the seasonal strength of the Bjerknes feedback weakens in fall. Results imply that the heat content supplied by the subsurface precursor preceding the onset of an ENSO event is paramount to maintaining the growth of the instability (or event) through fall.

  3. ENSO influence on the dynamical seasonal prediction of the East Asian Winter Monsoon

    Science.gov (United States)

    Kang, Daehyun; Lee, Myong-In

    2017-03-01

    This study examined the forecast skill for the East Asian Winter Monsoon (EAWM) using the following state-of-the-art dynamical seasonal prediction systems: CanCM3, CanCM4, CFSv2, CM2.1, and GEOS-5. To assess the prediction skills and the associations with ENSO teleconnections of these systems, long-term seasonal hindcast data sets for 28 years (1983-2010) were investigated. Observational data indicated that the ENSO-EAWM connection strengthened in a recent period (1997-2010; r = -0.84) compared with that in an earlier period (1983-1996; r = -0.44). For the recent period, a practical level of prediction skill for the EAWM index was retained by CFSv2 and GEOS-5 for the lead time of 2 months or longer, with these models showing a realistic ENSO-EAWM relationship throughout the Western Pacific Warm Pool with east-west dipole anomalies of precipitation induced by ENSO. The prediction skill of the other models was poor, even for lead times of zero to 1 month, with weak ENSO-EAWM relationships and errant north-south dipole anomalies of precipitation associated with ENSO. A large model spread was also found consistently in the CMIP5 AMIP and the Historical simulations by 14 models of the spatial pattern of equatorial Pacific precipitation anomalies associated with ENSO and the effect on the ENSO-EAWM relationship. Based on this study, the accurate prediction of EAWM should be linked with a realistic representation of the convection response in the equatorial Pacific by ENSO and the teleconnection to EAWM.

  4. Drivers of coupled model ENSO error dynamics and the spring predictability barrier

    Science.gov (United States)

    Larson, Sarah M.; Kirtman, Ben P.

    2016-07-01

    Despite recent improvements in ENSO simulations, ENSO predictions ultimately remain limited by error growth and model inadequacies. Determining the accompanying dynamical processes that drive the growth of certain types of errors may help the community better recognize which error sources provide an intrinsic limit to predictability. This study applies a dynamical analysis to previously developed CCSM4 error ensemble experiments that have been used to model noise-driven error growth. Analysis reveals that ENSO-independent error growth is instigated via a coupled instability mechanism. Daily error fields indicate that persistent stochastic zonal wind stress perturbations (τx^' } ) near the equatorial dateline activate the coupled instability, first driving local SST and anomalous zonal current changes that then induce upwelling anomalies and a clear thermocline response. In particular, March presents a window of opportunity for stochastic τx^' } to impose a lasting influence on the evolution of eastern Pacific SST through December, suggesting that stochastic τx^' } is an important contributor to the spring predictability barrier. Stochastic winds occurring in other months only temporarily affect eastern Pacific SST for 2-3 months. Comparison of a control simulation with an ENSO cycle and the ENSO-independent error ensemble experiments reveals that once the instability is initiated, the subsequent error growth is modulated via an ENSO-like mechanism, namely the seasonal strength of the Bjerknes feedback. Furthermore, unlike ENSO events that exhibit growth through the fall, the growth of ENSO-independent SST errors terminates once the seasonal strength of the Bjerknes feedback weakens in fall. Results imply that the heat content supplied by the subsurface precursor preceding the onset of an ENSO event is paramount to maintaining the growth of the instability (or event) through fall.

  5. A delay differential model of ENSO variability, Part 2: Phase locking, multiple solutions, and dynamics of extrema

    CERN Document Server

    Zaliapin, Ilya

    2010-01-01

    We consider a highly idealized model for El Nino/Southern Oscillation (ENSO) variability, as introduced in an earlier paper. The model is governed by a delay differential equation for sea surface temperature in the Tropical Pacific, and it combines two key mechanisms that participate in ENSO dynamics: delayed negative feedback and seasonal forcing. We perform a theoretical and numerical study of the model in the three-dimensional space of its physically relevant parameters: propagation period of oceanic waves across the Tropical Pacific, atmosphere-ocean coupling, and strength of seasonal forcing. Phase locking of model solutions to the periodic forcing is prevalent: the local maxima and minima of the solutions tend to occur at the same position within the seasonal cycle. Such phase locking is a key feature of the observed El Nino (warm) and La Nina (cold) events. The phasing of the extrema within the seasonal cycle depends sensitively on model parameters when forcing is weak. We also study co-existence of mu...

  6. Tailoring wheat management to ENSO phases for increased wheat production in Paraguay

    OpenAIRE

    Melissa A. Ramirez-Rodrigues; Senthold Asseng; Clyde Fraisse; Lydia Stefanova; Alicia Eisenkolbi

    2014-01-01

    Reported regional wheat yields in Paraguay vary from 1 to 3 t/ha from year to year, but appear not to be correlated with El Niño-Southern Oscillation (ENSO) phases. Historical weather data from two locations in representative wheat-growing regions of Paraguay, Encarnación-Itapúa and Ciudad del Este-Alto Paraná combined with crop modeling, were analyzed to optimize nitrogen (N) fertilizer application rates according to the ENSO phase of a growing season. The ENSO phase of a growing season was ...

  7. Ocean-Atmosphere Interaction in the Lifecycle of ENSO: The Coupled Wave Oscillator

    Institute of Scientific and Technical Information of China (English)

    Jialin LIN

    2009-01-01

    To explain the oscillatory nature of E1 Nino/Southern Oscillation (ENSO), many ENSO theories emphasize the free oceanic equatorial waves propagating/reflecting within the Pacific Ocean, or the discharge/recharge of Pacific-basin-averaged ocean heat content. ENSO signals in the Indian and Atlantic oceans are often considered as remote response to the Pacific SST anomaly through atmospheric teleconnections. This study investigates the ENSO life cycle near the equator using long-term observational datasets. Space-time spectral analysis is used to identify and isolate the dominant interannual oceanic and atmospheric wave modes associated with ENSO. Nino3 SST anomaly is utilized as the ENSO index, and lag-correlation/regression are used to construct the composite ENSO life cycle. The propagation, structure and feedback mechanisms of the dominant wave modes are studied in detail. The results show that the dominant oceanic equatorial wave modes associated with ENSO are not free waves, but are two ocean-atmosphere coupled waves including a coupled Kelvin wave and a coupled equatorial Rossby (ER) wave. These waves are not confined only to the Pacific Ocean, but are of planetary scale with zonal wavenumbers 1-2, and propagate all the way around the equator in more than three years, leading to the longer than 3-year period of ENSO. When passing the continents, they become uncoupled atmospheric waves. The coupled Kelvin wave has larger variance than the coupled ER wave, making the total signals dominated by eastward propagation. Surface zonal wind stress (x) acts to slow down the waves. The two coupled waves interact with each other through boundary reflection and superposition, and they also interact with an off-equatorial Rossby wave in north Pacific along 15N through boundary reflection and wind stress forcing. The precipitation anomalies of the two coupled waves meet in the eastern Pacific shortly after the SST maximum of ENSO and excite a dry atmospheric Kelvin wave which

  8. ENSO effects on primary productivity in Southern Atacama desert

    Directory of Open Access Journals (Sweden)

    F. A. Squeo

    2006-01-01

    Full Text Available In the winter-rain southern Atacama Desert of the Coquimbo Region of Chile, El Niño - Southern Oscillation (ENSO events modulate primary productivity. In this region, there are important changes in water availability between La Niña (dry and El Niño (rainy years. Using inter-annual comparisons of LANDSAT images from 30° to 31° S latitude, we observed changes in primary productivity between dry and rainy years at the regional level. There were also significant, negative correlations between productivity and elevation, with changes occurring first at low elevation during rainy years. The limiting factors to dryland vegetation primary productivity is different in regard to elevation. Rain during an El Niño year is the main factor that explains the increase in primary productivity at low elevation, while lower temperatures reduce and delay the net primary productivity at mid elevation.

  9. Tracking down the ENSO delayed oscillator with an adjoint OGCM

    CERN Document Server

    Van Oldenborgh, G J; Venzke, S; Eckert, C; Giering, R; Oldenborgh, Geert Jan van; Burgers, Gerrit; Venzke, Stephan; Eckert, Christian; Giering, Ralf

    1997-01-01

    The adjoint of an ocean general circulation model is used as a tool for investigating the causes of changes in ENSO SST indices. We identify adjoint Kelvin and Rossby waves in the sensitivities to sea level and wind stress at earlier times, which can be traced back for more than a year through western and weak eastern boundary reflections. Depending on the thermocline depth the first and second baroclinic modes are excited. The sensitivities to the heat flux and SST are local and decay in about a month. The sensitivities to the fluxes are converted into the influence of SST using the adjoint of a statistical atmosphere model. Focusing on SST perturbations in the index region itself, we recover, up to a scale factor, the delayed oscillator concept.

  10. Characterizing unforced multi-decadal variability of ENSO: a case study with the GFDL CM2.1 coupled GCM

    Science.gov (United States)

    Atwood, A. R.; Battisti, D. S.; Wittenberg, A. T.; Roberts, W. H. G.; Vimont, D. J.

    2016-12-01

    Large multi-decadal fluctuations of El Niño-Southern Oscillation (ENSO) variability simulated in a 4000-year pre-industrial control run of GFDL CM2.1 have received considerable attention due to implications for constraining the causes of past and future changes in ENSO. We evaluated the mechanisms of this low-frequency ENSO modulation through analysis of the extreme epochs of CM2.1 as well as through the use of a linearized intermediate-complexity model of the tropical Pacific, which produces reasonable emulations of observed ENSO variability. We demonstrate that the low-frequency ENSO modulation can be represented by the simplest model of a linear, stationary process, even in the highly nonlinear CM2.1. These results indicate that CM2.1's ENSO modulation is driven by transient processes that operate at interannual or shorter time scales. Nonlinearities and/or multiplicative noise in CM2.1 likely exaggerate the ENSO modulation by contributing to the overly active ENSO variability. In contrast, simulations with the linear model suggest that intrinsically-generated tropical Pacific decadal mean state changes do not contribute to the extreme-ENSO epochs in CM2.1. Rather, these decadal mean state changes actually serve to damp the intrinsically-generated ENSO modulation, primarily by stabilizing the ENSO mode during strong-ENSO epochs. Like most coupled General Circulation Models, CM2.1 suffers from large biases in its ENSO simulation, including ENSO variance that is nearly twice that seen in the last 50 years of observations. We find that CM2.1's overly strong ENSO variance directly contributes to its strong multi-decadal modulation through broadening the distribution of epochal variance, which increases like the square of the long-term variance. These results suggest that the true spectrum of unforced ENSO modulation is likely substantially narrower than that in CM2.1. However, relative changes in ENSO modulation are similar between CM2.1, the linear model tuned to

  11. A Note on the Role of Meridional Wind Stress Anomalies and Heat Flux in ENSO Simulations

    Institute of Scientific and Technical Information of China (English)

    ZHU Jieshun; SUN Zhaobo; ZHOU Guangqing

    2007-01-01

    Four comparative experiments and some supplementary experiments were conducted to examine the role of meridional wind stress anomalies and heat flux variability in ENSO simulations by using a highresolution Ocean General Circulation Model (OGCM). The results indicate that changes in the direction and magnitude of meridional wind stress anomalies have little influence on ENSO simulations until meridional wind stress anomalies are unrealistically enlarged by a factor of 5.0. However, evidence of an impact on ENSO simulations due to heat flux variability was found. The simulated Ni(n)o-3 index without the effect of heat flux anomalies tended to be around 1.0° lower than the observed, as well as the control run, during the peak months of ENSO events.

  12. NOAA Climate Prediction Center (CPC) El Nino-Southern Oscillation (ENSO) Diagnostics Discussion

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The ENSO Diagnostics Discussion (EDD) is issued by NOAA Climate Prediction Center each month on the Thursday between the 5th and 11th with few exceptions (major...

  13. Do regions outside the tropical Pacific influence ENSO through atmospheric teleconnections?

    Digital Repository Service at National Institute of Oceanography (India)

    Dayan, H.; Izumo, T.; Vialard, J.; Lengaigne, M.; Masson, S

    This paper aims at identifying oceanic regions outside the tropical Pacific, which may influence the El Ni�o Southern Oscillation (ENSO) through interannual modulation of equatorial Pacific winds An Atmospheric General Circulation Model (AGCM) 7...

  14. Global land carbon sink response to temperature and precipitation varies with ENSO phase

    Science.gov (United States)

    Fang, Yuanyuan; Michalak, Anna M.; Schwalm, Christopher R.; Huntzinger, Deborah N.; Berry, Joseph A.; Ciais, Philippe; Piao, Shilong; Poulter, Benjamin; Fisher, Joshua B.; Cook, Robert B.; Hayes, Daniel; Huang, Maoyi; Ito, Akihiko; Jain, Atul; Lei, Huimin; Lu, Chaoqun; Mao, Jiafu; Parazoo, Nicholas C.; Peng, Shushi; Ricciuto, Daniel M.; Shi, Xiaoying; Tao, Bo; Tian, Hanqin; Wang, Weile; Wei, Yaxing; Yang, Jia

    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. 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 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.

  15. Relationship and its instability of ENSO - Chinese variations in droughts and wet spells

    Institute of Scientific and Technical Information of China (English)

    SU MingFeng; WANG HuiJun

    2007-01-01

    Monthly data of Self-Calibrated Palmer Drought Severity Index (PDSI) from 1951 to 2000 are calculated using historical precipitation and temperature data for Chinese 160 stations. Temporal and spatial patterns of the first empirical orthogonal function (EOF) of the PDSI reveals a fairly linear trend resulting from trends in precipitation and surface temperature, which is similar to the linear PDSI trend during 1951-2000 calculated using all monthly data. The EOF analysis also reveals that the leading mode correlates significantly with ENSO events in time and space. The ENSO EOF shows that during the typical warm phase of ENSO, surface conditions are drier in most regions of China, especially North China, but wetter than normal in the southern regions of Changjiang River, and Northwest China. During the typical cold phase of ENSO, these anomalies reverse sign. From 1951 to 2000, there are large multi-year to decadal variations in droughts and wet spells over China, which are all closely related to strong El Nino events. In other words, when one strong El Nino event happens, there is a possible big variability in droughts and wet spells over China on the multi-year or decadal scale. Studies also suggest that during the last 2-3 decades climate changes over China, especially North China's drying and northwest China's wetting, are closely related to the shift in ENSO towards warmer events and global warming since the late 1970s. The instability of the relationship is also studied. It is revealed that there is a good correlation between ENSO and Chinese variations in droughts and wet spells in the 3-8-year band, but the correlation between ENSO and Chinese variations in droughts and wet spells is instable. Studies suggest that there are decadal changes in the correlation: the wavelet coherency between ENSO and Chinese variations in droughts and wet spells is high during 1951-1962 and 1976-1991, but low during 1963-1975 and 1992-2000.

  16. Forced changes to twentieth century ENSO diversity in a last Millennium context

    Science.gov (United States)

    Stevenson, Samantha; Capotondi, Antonietta; Fasullo, John; Otto-Bliesner, Bette

    2017-03-01

    The El Niño/Southern Oscillation (ENSO) exhibits considerable differences between the evolution of individual El Niño and La Niña events (`ENSO diversity'), with significant implications for impacts studies. However, the degree to which external forcing may affect ENSO diversity is not well understood, due to both internal variability and potentially compensatory contributions from multiple forcings. The Community Earth System Model Last Millennium Ensemble (CESM LME) provides an ideal testbed for studying the sensitivity of twentieth century ENSO to forced climate changes, as it contains many realizations of the 850-2005 period with differing combinations of forcings. Metrics of ENSO amplitude and diversity are compared across LME simulations, and although forced changes to ENSO amplitude are generally small, forced changes to diversity are often detectable. Anthropogenic changes to greenhouse gas and ozone/aerosol emissions modify the persistence of Eastern and Central Pacific El Niño events, through shifts in the upwelling and zonal advective feedbacks; these influences generally cancel one another over the twentieth century. Other forcings can also be quite important: land use changes amplify Eastern Pacific El Niño events via modulating zonal advective heating, and orbital forcing tends to preferentially terminate twentieth century Central Pacific El Niño events due to enhanced eastern Pacific cooling during boreal winter and spring. Our results indicate that multiple anthropogenic and natural forcings can have substantial impacts on ENSO diversity, and suggest that correctly representing the net ENSO diversity response to climate change will depend on the precise balance between all these influences.

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

    Science.gov (United States)

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

    2017-02-01

    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.

  18. Seasonality and Predictability of the Indian Ocean Dipole Mode: ENSO Forcing and Internal Variability

    Science.gov (United States)

    Yang, Y.

    2015-12-01

    This study evaluates the relative contributions to the Indian Ocean Dipole (IOD) mode of interannual variability from the El Niño-Southern Oscillation (ENSO) forcing and ocean-atmosphere feedbacks internal to the Indian Ocean. The ENSO forcing and internal variability is extracted by conducting a 10-member coupled simulation for 1950-2012 where sea surface temperature (SST) is restored to the observed anomalies over the tropical Pacific but interactive with the atmosphere over the rest of the world ocean. In these experiments, the ensemble mean is due to ENSO forcing and the inter-member difference arises from internal variability of the climate system independent of ENSO. These elements contribute one third and two thirds of the total IOD variance, respectively. Both types of IOD variability develop into an east-west dipole pattern due to Bjerknes feedback and peak in September-November. The ENSO forced and internal IOD modes differ in several important ways. The forced IOD mode develops in August with a broad meridional pattern, and eventually evolves into the Indian Ocean Basin mode; while the internal IOD mode grows earlier in June, is more confined to the equator and decays rapidly after October. The internal IOD mode is more skewed than the ENSO forced response. The destructive interference of ENSO forcing and internal variability can explain early-terminating IOD events, referred to IOD-like perturbations that fail to grow during boreal summer. Our results have implications for predictability. Internal variability, as represented by pre-season sea surface height anomalies off Sumatra, contributes to predictability considerably. Including this indicator of internal variability, together with ENSO, improves the predictability of IOD.

  19. A PERTURBED SOLUTION OF SEA-AIR OSCILLATOR FOR THE ENSO MECHANISM

    Institute of Scientific and Technical Information of China (English)

    MO Jiaqi; LIN Wantao; WANG Hui

    2005-01-01

    A class of coupled system of the El Nino/La Nino-Southern Oscillation (ENSO)mechanism is studied. Using the perturbed theory,the asymptotic expansions of the solution for ENSO model are obtained and the asymptotic behavior of the solution for corresponding problem is considered.And it is pointed out that the solution tends to the corresponding attractor as t →∞.

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

    Science.gov (United States)

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

    2017-08-01

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

  1. ENSO-conditioned weather resampling method for seasonal ensemble streamflow prediction

    Science.gov (United States)

    Beckers, Joost V. L.; Weerts, Albrecht H.; Tijdeman, Erik; Welles, Edwin

    2016-08-01

    Oceanic-atmospheric climate modes, such as El Niño-Southern Oscillation (ENSO), are known to affect the local streamflow regime in many rivers around the world. A new method is proposed to incorporate climate mode information into the well-known ensemble streamflow prediction (ESP) method for seasonal forecasting. The ESP is conditioned on an ENSO index in two steps. First, a number of original historical ESP traces are selected based on similarity between the index value in the historical year and the index value at the time of forecast. In the second step, additional ensemble traces are generated by a stochastic ENSO-conditioned weather resampler. These resampled traces compensate for the reduction of ensemble size in the first step and prevent degradation of skill at forecasting stations that are less affected by ENSO. The skill of the ENSO-conditioned ESP is evaluated over 50 years of seasonal hindcasts of streamflows at three test stations in the Columbia River basin in the US Pacific Northwest. An improvement in forecast skill of 5 to 10 % is found for two test stations. The streamflows at the third station are less affected by ENSO and no change in forecast skill is found here.

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

    Science.gov (United States)

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

    2017-02-01

    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.

  3. Evidence of reduced mid-Holocene ENSO variance on the Great Barrier Reef, Australia

    Science.gov (United States)

    Leonard, N. D.; Welsh, K. J.; Lough, J. M.; Feng, Y.-x.; Pandolfi, J. M.; Clark, T. R.; Zhao, J.-x.

    2016-09-01

    Globally, coral reefs are under increasing pressure both through direct anthropogenic influence and increases in climate extremes. Understanding past climate dynamics that negatively affected coral reef growth is imperative for both improving management strategies and for modeling coral reef responses to a changing climate. The El Niño-Southern Oscillation (ENSO) is the primary source of climate variability at interannual timescales on the Great Barrier Reef (GBR), northeastern Australia. Applying continuous wavelet transforms to visually assessed coral luminescence intensity in massive Porites corals from the central GBR we demonstrate that these records reliably reproduce ENSO variance patterns for the period 1880-1985. We then applied this method to three subfossil corals from the same reef to reconstruct ENSO variance from ~5200 to 4300 years before present (yBP). We show that ENSO events were less extreme and less frequent after ~5200 yBP on the GBR compared to modern records. Growth characteristics of the corals are consistent with cooler sea surface temperatures (SSTs) between 5200 and 4300 yBP compared to both the millennia prior (~6000 yBP) and modern records. Understanding ENSO dynamics in response to SST variability at geological timescales will be important for improving predictions of future ENSO response to a rapidly warming climate.

  4. Modulation of the ENSO Teleconnection to the Sahel

    Science.gov (United States)

    Pomposi, C.; Giannini, A.; Kushnir, Y.

    2016-12-01

    The West African Monsoon (WAM) system delivers the majority of annual rainfall for the Sahel region of Africa and its variations have enormous impacts on the millions of inhabitants who live in the region. Throughout the recent past, much of its observed variability, particularly on interannual to decadal timescales, has been tied in large part to global sea surface temperature (SST) forcing. While decadal scale changes are largely driven by the Atlantic and Indian basins, it has been well documented that interannual variability of this monsoon system is fundamentally shaped by the Tropical Pacific, and particularly the El Niño Southern Oscillation (ENSO). During the spring of 2015 as a historic El Niño event was building, various news outlets warned of the potential for dry conditions and subsequent famine that could result from a reduction of rainfall during the summer months in the Sahel. These warnings followed the traditional understanding of ENSO's impacts in sub-Saharan Africa to dynamically force drying in the region due to a reorganization of atmospheric circulation and increased convective thresholds. Yet, by the end of the 2015 rainy season, observations indicated that much of the Sahel experienced anomalously wet conditions rather than dry conditions. This recent conundrum motivates work in which we use 2015 as a case study to ask what additional forcings in the global ocean oppose (or alleviate) drying associated with El Niño in the Sahel? Our approach in answering this question is to utilize observations and complete a composite study of years with similar SST forcing to 2015, identifying similarities in the global ocean that translate to anomalous circulation patterns, moisture convergence, and ultimately, rainfall anomalies. Upon identifying the additional basins' opposing influence on Sahel rainfall variability and atmospheric signatures, we subsequently turn to an idealized modeling approach to precisely address how the superposition of

  5. Dynamics and spatial structure of ENSO from re-analyses versus CMIP5 models

    Science.gov (United States)

    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

  6. ENSO and East Asian winter monsoon relationship modulation associated with the anomalous northwest Pacific anticyclone

    Science.gov (United States)

    Kim, Ji-Won; An, Soon-Il; Jun, Sang-Yoon; Park, Hey-Jin; Yeh, Sang-Wook

    2016-09-01

    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

  7. The early 1990s change in ENSO-PSA-SAM relationships and its impact on Southern Hemisphere climate

    OpenAIRE

    Yu, JY; Paek, H; Saltzman, ES; T. Lee

    2015-01-01

    © 2015 American Meteorological Society. This study uncovers an early 1990s change in the relationships between El Niño-Southern Oscillation (ENSO) and two leading modes of the Southern Hemisphere (SH) atmospheric variability: the southern annular mode (SAM) and the Pacific-South American (PSA) pattern. During austral spring, while the PSA maintained a strong correlation with ENSO throughout the period 1948-2014, the SAM-ENSO correlation changed from being weak before the early 1990s to being ...

  8. Twentieth century ENSO-related precipitation mean states in twentieth century reanalysis, reconstructed precipitation and CMIP5 models

    Science.gov (United States)

    Dai, Ni; Arkin, Phillip A.

    2017-05-01

    El Niño-Southern Oscillation (ENSO)-related precipitation during the entire twentieth century is compared among the twentieth century reanalysis (20CR), a statistically reconstructed precipitation dataset (REC) and 30 Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Empirical orthogonal functions, ENSO-related precipitation composites based on sea surface temperature (SST)-constructed ENSO index and singular value decomposition (SVD) are employed to extract ENSO-related precipitation/SST signals in each dataset. With the background trend being removed in all of the data, our results show that the REC and the 20CR resemble both in their precipitation climatology and ENSO-related precipitation results. The biases in the CMIP5 models precipitation climatology such as dry equator over the Pacific Ocean, "double-intertropical convergence zones (ITCZs)" and overly zonal Southern Pacific convergence zone (SPCZ) are major reasons for lowering spatial correlations with the REC and the 20CR precipitation climatology. Two groups of CMIP5 models are built based on severity of these biases in their precipitation background and the spatial correlations of ENSO-related precipitation with the observations. Compared with the group with more severe biases in its precipitation climatology, the group with smaller biases tends to produce more ENSO-like precipitation patterns, simulate more realistic mean magnitude and seasonal variability of ENSO precipitation signals, as well as generating better ENSO-related SST/precipitation correlation patterns produced in its SVD analysis. The ENSO-related precipitation biases in the CMIP5 models over the western Pacific and Indian Ocean, as well as the equatorial Pacific, are strongly related with their precipitation climatology biases over these regions. The ENSO-related precipitation biases over the off-equator eastern Pacific Ocean are associated with both the "double-ITCZs" biases in the precipitation climatology and the ENSO

  9. Twentieth century ENSO-related precipitation mean states in twentieth century reanalysis, reconstructed precipitation and CMIP5 models

    Science.gov (United States)

    Dai, Ni; Arkin, Phillip A.

    2016-07-01

    El Niño-Southern Oscillation (ENSO)-related precipitation during the entire twentieth century is compared among the twentieth century reanalysis (20CR), a statistically reconstructed precipitation dataset (REC) and 30 Coupled Model Intercomparison Project Phase 5 (CMIP5) models. Empirical orthogonal functions, ENSO-related precipitation composites based on sea surface temperature (SST)-constructed ENSO index and singular value decomposition (SVD) are employed to extract ENSO-related precipitation/SST signals in each dataset. With the background trend being removed in all of the data, our results show that the REC and the 20CR resemble both in their precipitation climatology and ENSO-related precipitation results. The biases in the CMIP5 models precipitation climatology such as dry equator over the Pacific Ocean, "double-intertropical convergence zones (ITCZs)" and overly zonal Southern Pacific convergence zone (SPCZ) are major reasons for lowering spatial correlations with the REC and the 20CR precipitation climatology. Two groups of CMIP5 models are built based on severity of these biases in their precipitation background and the spatial correlations of ENSO-related precipitation with the observations. Compared with the group with more severe biases in its precipitation climatology, the group with smaller biases tends to produce more ENSO-like precipitation patterns, simulate more realistic mean magnitude and seasonal variability of ENSO precipitation signals, as well as generating better ENSO-related SST/precipitation correlation patterns produced in its SVD analysis. The ENSO-related precipitation biases in the CMIP5 models over the western Pacific and Indian Ocean, as well as the equatorial Pacific, are strongly related with their precipitation climatology biases over these regions. The ENSO-related precipitation biases over the off-equator eastern Pacific Ocean are associated with both the "double-ITCZs" biases in the precipitation climatology and the ENSO

  10. ENSO's far reaching connection to Indian cold waves.

    Science.gov (United States)

    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.

  11. Isotopic constraints on methane's global sources and ENSO-dependence

    Science.gov (United States)

    Schaefer, Hinrich; Mikaloff Fletcher, Sara; Veidt, Cora; Lassey, Keith; Brailsford, Gordon; Bromley, Tony; Dlugokencky, Ed; Englund Michel, Sylvia; Miller, John; Levin, Ingeborg; Lowe, Dave; Martin, Ross; Vaughn, Bruce; White, James; Nichol, Sylvia

    2017-04-01

    Atmospheric levels of the potent greenhouse gas methane (CH4) have been rising since the industrial revolution, except for a plateau during the early 2000s. Stable carbon isotopes in methane (delta-13CH4) provide constraints on the budget changes associated with the plateau's onset and its end. We present a reconstruction of annual global delta-13CH4 averages based on a global network of stations, whose trends are indicative of global methane source and sink activity. A box model analysis shows that from the mid-1990s methane emissions with the characteristic thermogenic delta-13CH4 signature reduced, implying persistently lower emissions from fossil fuel productions as the cause of the plateau. However, variations in hydroxyl, the main CH4 sink, provide an equably plausible explanation for the plateau onset that may also account for strong variability in emission-vs-removal rates during the plateau period. In contrast, the renewed CH4 rise since 2006 can only be explained by increasing emissions with a biogenic isotope signature, i.e. agriculture or wetlands. We present correlation studies that test whether ENSO activity controls atmospheric delta-13CH4, and by extension methane levels, through tropical wetland emissions.

  12. ENSO and Indian Ocean dipole mode in three coupled GCMs

    Institute of Scientific and Technical Information of China (English)

    YU Yongqiang; LIU Xiying

    2004-01-01

    The simulated ENSO and Indian Ocean dipole (IOD) mode events from three coupled GCMs with the same oceanic component model, CPM0, CPM1 and FGCM0, are compared. The only difference between the CPM0 and the CPM1 comes from the coupling scheme at the air-sea interface, e.g., flux anomaly coupling scheme for the former and direct coupling scheme for the latter. The FGCM0 is also a directly coupled GCM, but its atmospheric component model is the NCAR CCM3 rather than the NCC T63AGCM as in the other two coupled GCMs CPM0 and CPM1.All three coupled models show El Nino-like interannual variability in the tropic Pacific, but the FGCM0 shows a bit stronger amplitude of El Nino events and both the CPM0 and the CPM1 show much weaker amplitude than the observed one. In the meanwhile, the quasi-biennial variability dominates in the FGCM0 simulations, and 4 a and longer periods are significant in both the CPM0 and CPM1 models. As the El Nino events simulated by the three coupled GCMs, the simulated Indian Ocean dipole mode events are stronger from the coupled model FGCM0 and weaker from both the CPM0 and CPM1 models than those from observation.

  13. INTERDECADAL VARIATION OF THE RELATIONSHIP BETWEEN ENSO AND SUMMER INTERANNUAL CLIMATE VARIABILITY IN CHINA

    Institute of Scientific and Technical Information of China (English)

    ZHU Yimin; YANG Xiu-qun; CHEN Xiao-ying; ZHAO Shan-shan; SUN Xu-guang

    2007-01-01

    Interdecadal variation of the relationships between ENSO and the summer interannual climate variability in China is investigated by using techniques of sliding correlation analysis with the tropical Pacific SSTA and the observed surface air temperature and precipitation from stations in China. The results indicate that there are stable and robust relations that the Northern China is relatively dry during the developing phase of ENSO while the Yangtze River valley is relatively wet during the decaying phase of ENSO. On the other hand, interdecadal variations of the relations are also found in other regions. Over the time both prior to the Pacific decadal climate shift (before the late 1970s) and after it (after the late 1970s),during the developing phases of ENSO the summer precipitation anomaly in South China changed from below to above normal, whereas that in Northeast China changed from above to below normal; the summer surface air temperature anomaly in North and Northeast China changed fiom cooling to warming, whereas that in South China changed to cooling; during the decaying phases of ENSO the North China changed from wetter to dryer while the Huai River valley changed from dryer to normal; North China, Yangtze River valley and South China tend to be warmer. Based on the composite analysis of the NCAR/NCEP reanalyze datasets, significant differences existing in ENSO-related atmospheric circulation anomaly in East Asia during pre- and post-shift periods may be responsible for the interdecadal variation of relationships between ENSO and surface air temperature and precipitation in China.

  14. Solar cycle modulation of the ENSO impact on the winter climate of East Asia

    Science.gov (United States)

    Zhou, Qun; Chen, Wen; Zhou, Wen

    2013-06-01

    This study examines how the East Asian winter climate response to the El Niño-Southern Oscillation (ENSO) varies with the 11-year solar cycle. The results indicate that the ENSO and East Asian climate relationship is robust and significant during winters with low solar (LS) activity, with evident warming in the lower troposphere over East Asia, which can be closely linked to the decreased pressure gradient between the cold Eurasian continent and the warm Pacific. Moreover, during the LS and El Niño winters, there is a typical rainfall response in Southeast Asia, with wet conditions over South China and dry conditions over the Philippines, Borneo, Celebes, and Sulawesi, which can be explained by the anticyclone over the western North Pacific (WNP). However, during high solar activity winters, both the surface temperature and rainfall anomalies are much less closely associated with the ENSO. The possible mechanism for this solar modulation of the ENSO-related East Asian climate anomalies may be the change in the tropospheric circulation with the ENSO in both tropical and extratropical regions. Particularly, in the LS cases, an anomalous WNP anticyclone is intensified and a noticeable cyclone occupies northern Northeast Asia, resulting from the changing location and strength of the large-scale Walker circulation induced by the more pronounced sea surface temperature anomalies associated with the ENSO. Further investigation with long historic data confirms that the relationship between the ENSO and the East Asian winter climate anomalies depends on the phases of 11 year solar cycle, with enhanced East Asian climate variation during the LS winters.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    Manatsa, Desmond; Mushore, Terrence; Lenouo, Andre

    2015-09-01

    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

  17. A meridional dipole in premonsoon Bay of Bengal tropical cyclone activity induced by ENSO: TROPICAL CYCLONES, MONSOON AND ENSO

    Energy Technology Data Exchange (ETDEWEB)

    Balaguru, Karthik [Marine Sciences Laboratory, Pacific Northwest National Laboratory, Seattle Washington USA; Leung, L. Ruby [Atmospheric Sciences and Global Change, Pacific Northwest National Laboratory, Richland Washington USA; Lu, Jian [Atmospheric Sciences and Global Change, Pacific Northwest National Laboratory, Richland Washington USA; Foltz, Gregory R. [Physical Oceanography Division, Atlantic Oceanographic and Meteorological Laboratory, Miami Florida USA

    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 shift 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

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

    Science.gov (United States)

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

    2014-04-01

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

  19. El Niño Southern Oscillation (ENSO and global warming

    Directory of Open Access Journals (Sweden)

    B. Nyenzi

    2006-01-01

    Full Text Available It is widely accepted by the international scientific community that human activities have increased atmospheric concentrations of greenhouse gases (GHG and aerosols since the pre-industrial era. This increase has contributed to most of the warming (0.6±0.2°C observed over the 20th century, land areas warming more than the oceans, with the 1990s very likely to be the warmest decade of the 20th century (IPCC, 2001. How this warming influences the occurrence, severity and frequency of ENSO episodes remains highly uncertain. The IPCC (2001 assessment of the scientific literature found insufficient evidence to suggest any direct attribution between increase in ENSO events that occurred in the last 20 to 30 years of the 20th century and global warming (IPCC, 2001. However, assessments carried out since then (e.g. IPCC Fourth Assessment Report (AR4, in preparations suggest El Niño events have become more frequent, persistent and intense during the last 20 to 30 years compared to the previous 100 years. Attribution to global warming, however, remains highly uncertain. Efforts to simulate and model past, present and future behaviour of ENSO under a warming world due to enhanced GHG concentrations produce conflicting results. Since substantial internally-generated variability of ENSO behaviour on multi-decadal to century timescales occurs in long, unforced atmospheric-oceanic general circulation model (AOGCM simulations, the attribution of past and future changes in ENSO amplitude and frequency to external forcing like GHG concentrations cannot be made with certainty. Such attribution would require extensive use of ensemble climate experiments or long experiments with stabilised GHG forcing. Although there are now better ENSO simulations in AOGCM, further model improvements are needed to simulate a more realistic Pacific climatology and seasonal cycle of the key modes influencing the climate of the region, as well as more realistic ENSO variability

  20. Upper tropospheric and lower stratospheric ENSO signal derived from GPS radio occultation temperature

    Science.gov (United States)

    Scherllin-Pirscher, B.; Deser, C.; Ho, S.-P.; Chou, C.; Randel, W.; Kuo, Y.-W.

    2012-04-01

    We use radio occultation (RO) temperature data from CHAMP, GRACE, and Formosat-3/COSMIC (F3C) to detect the El Niño-Southern Oscillation (ENSO) signal in the troposphere and lower stratosphere. Merging data of all satellites, we calculate monthly mean climatologies with a horizontal resolution of 5° latitude and 5° longitude and a vertical spacing of 100 m from the surface up to 20 km. A sufficient number of profiles (>40000 profiles per month) is available since August 2006, when F3C measurements became available. The investigation of temperature anomalies (anomalies are obtained from subtracting the mean annual cycle) in the equatorial region up to 16 km yields a natural split into zonal-mean and eddy (deviations from the zonal-mean) ENSO components. EOF1 is dominated by the zonally-symmetric component where positive sea-surface temperature anomalies come along with warm tropospheric temperatures. It explains almost 70 % of total variance. The corresponding PC1 is highly correlated with the Nino 3.4 index (correlation equals 0.85 at a lag of 3 months). EOF2, which is dominated by the eddy ENSO signal, explains more than 7 % of total variance. PC2 is almost perfectly correlated with the Nino 3.4 index (correlation equals 0.95 at a lag of 0 months). Due to these findings we separate data into zonal-mean and eddy temperature fields and apply PCA and multiple linear regression analysis separately to both fields. Taking advantage of the high vertical resolution of RO data, we show that the node of the positive and negative zonal-mean ENSO signal occurs around the tropopause. Relative to the surface ENSO signal, the atmospheric zonal-mean signal is lagged by 3 months. At low latitudes equatorwards of about 30°, the eddy ENSO signal is characterized by an east-west dipole centered slightly westward to the date line. The vertical node to a reversed east-west dipole occurs at approximately 14.5 km altitude, which is well below the tropopause. At tropospheric mid

  1. Characteristics of Lake Chad Level Variability and Links to ENSO, Precipitation, and River Discharge

    Directory of Open Access Journals (Sweden)

    Churchill Okonkwo

    2014-01-01

    Full Text Available 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.

  2. A Review of ENSO Influence on the North Atlantic. A Non-Stationary Signal

    Directory of Open Access Journals (Sweden)

    Belén Rodríguez-Fonseca

    2016-06-01

    Full Text Available The atmospheric seasonal cycle of the North Atlantic region is dominated by meridional movements of the circulation systems: from the tropics, where the West African Monsoon and extreme tropical weather events take place, to the extratropics, where the circulation is dominated by seasonal changes in the jetstream and extratropical cyclones. Climate variability over the North Atlantic is controlled by various mechanisms. Atmospheric internal variability plays a crucial role in the mid-latitudes. However, El Niño-Southern Oscillation (ENSO is still the main source of predictability in this region situated far away from the Pacific. Although the ENSO influence over tropical and extra-tropical areas is related to different physical mechanisms, in both regions this teleconnection seems to be non-stationary in time and modulated by multidecadal changes of the mean flow. Nowadays, long observational records (greater than 100 years and modeling projects (e.g., CMIP permit detecting non-stationarities in the influence of ENSO over the Atlantic basin, and further analyzing its potential mechanisms. The present article reviews the ENSO influence over the Atlantic region, paying special attention to the stability of this teleconnection over time and the possible modulators. Evidence is given that the ENSO–Atlantic teleconnection is weak over the North Atlantic. In this regard, the multidecadal ocean variability seems to modulate the presence of teleconnections, which can lead to important impacts of ENSO and to open windows of opportunity for seasonal predictability.

  3. Reduced ENSO variability at the LGM revealed by an isotope-enabled Earth system model

    Science.gov (United States)

    Zhu, Jiang; Liu, Zhengyu; Brady, Esther; Otto-Bliesner, Bette; Zhang, Jiaxu; Noone, David; Tomas, Robert; Nusbaumer, Jesse; Wong, Tony; Jahn, Alexandra; Tabor, Clay

    2017-07-01

    Studying the El Niño-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.

  4. Delayed ENSO impact on spring precipitation over North/Atlantic European region

    Energy Technology Data Exchange (ETDEWEB)

    Herceg Bulic, Ivana [Faculty of Science, University of Zagreb, Andrija Mohorovicic Geophysical Institute, Department of Geophysics, Zagreb (Croatia); Kucharski, Fred [Abdus Salam International Centre for Theoretical Physics, Earth System Physics Section, Trieste (Italy)

    2012-06-15

    The delayed impact of winter sea-surface temperature (SST) anomalies in tropical Pacific on spring precipitation over the North Atlantic/European (NAE) region is examined using both measured and modeled data for the period 1901-2002. In an AMIP-type Atmospheric General Circulation Model (AGCM) ensemble, the observed delayed spring precipitation response in Europe to winter ENSO-related SST anomalies is well reproduced. A series of targeted AGCM/coupled GCM experiments are performed to further investigate the mechanisms for this delayed influence. It is found that late winter ENSO SST anomalies lead to the well-documented Rossby wave train arching from the Pacific into the Atlantic region. A positive (negative) ENSO event leads to a quasi-barotropic trough (ridge) in the North Atlantic region. The resulting wind and cloud changes cause anomalies in the surface heat fluxes that result in negative (positive) SST anomalies in the central North Atlantic and anomalies of the opposite sign further to the south. The SST anomalies persist into spring and the atmospheric response to these anomalies is an extension of the ENSO-induced trough (ridge) into the European region, leading to enhanced (reduced) moisture flux and low-level convergence (divergence) and thus positive (negative) precipitation anomalies. Although the signal is overall relatively weak (correlation coefficients of European spring rainfall with winter ENSO SSTs of about 0.3), a proper representation of the outlined mechanism in seasonal forecasting systems may lead to improved seasonal predictions. (orig.)

  5. ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

    Directory of Open Access Journals (Sweden)

    C. A. Williams

    2010-08-01

    Full Text Available Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO and the Indian Ocean Dipole (IOD. However, the regional-scale implications of sea surface temperature variability for Africa's carbon sources and sinks have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

  6. ENSO and IOD teleconnections for African ecosystems: evidence of destructive interference between climate oscillations

    Directory of Open Access Journals (Sweden)

    C. A. Williams

    2011-01-01

    Full Text Available Rainfall and vegetation across Africa are known to resonate with the coupled ocean-atmosphere phenomena of El Niño Southern Oscillation (ENSO and the Indian Ocean Dipole (IOD. However, the regional-scale implications of sea surface temperature variability for Africa's photosyntheis have received little focused attention, particularly in the case of IOD. Furthermore, studies exploring the interactive effects of ENSO and IOD when coincident are lacking. This analysis uses remotely sensed vegetation change plus a land surface model driven with observed meteorology to investigate how rainfall, vegetation, and photosynthesis across Africa respond to these climate oscillations. In addition to the relatively well-known ENSO forcing, the IOD induces large departures of photosynthesis across much of Africa associated with anomalies in rainfall and vegetation greenness. More importantly, sizeable independent effects can be suppressed or even reversed by destructive interferences during periods of simultaneous ENSO and IOD activity. For example, effects of positive IOD on southeastern Africa tended to dominate those of El Niño during their coincidence spanning 1997–1998, with sign reversal of El Niño's typically strong suppression of photosynthesis in this region. These findings call into question past analyses examining teleconnections to ENSO or IOD in isolation, and indicate the need to consider their simultaneous states when examining influences on hydroclimatic and ecological conditions across Africa.

  7. Global land carbon sink response to temperature and precipitation varies with ENSO phase

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Yuanyuan [Carnegie Inst. of Science, Stanford, CA (United States); Michalak, Anna M. [Carnegie Inst. of Science, Stanford, CA (United States); Schwalm, Christopher R. [Woods Hole Research Center, Falmouth, MA (United States); Huntzinger, Deborah N. [Northern Arizona Univ., Flagstaff, AZ (United States); Berry, Joseph A. [Carnegie Inst. of Science, Stanford, CA (United States); Ciais, Philippe [Alternative Energies and Atomic Energy Commission (CEA), Gif sur Yvette (France); Piao, Shilong [Peking Univ., Beijing (China); Poulter, Benjamin [Montana State Univ., Bozeman, MT (United States); Fisher, Joshua B. [California Inst. of Technology (CalTech), Pasadena, CA (United States); Cook, Robert B. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hayes, Daniel [Univ. of Maine, Orno, ME (United States); Huang, Maoyi [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Ito, Akihiko [National Inst. for Environmental Studies, Tsukuba (Japan); Jain, Atul [Univ. of Illinois, Urbana-Champaign, IL (United States); Lei, Huimin [Tsinghua Univ., Beijing (China); Lu, Chaoqun [Ames Lab. and Iowa State Univ., Ames, IA (United States); Mao, Jiafu [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Parazoo, Nicholas C. [California Inst. of Technology (CalTech), Pasadena, CA (United States); Peng, Shushi [Peking Univ., Beijing (China); Ricciuto, Daniel M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Shi, Xiaoying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tao, Bo [Univ. of Kentucky, Lexington, KY (United States); Tian, Hanqin [Auburn Univ., AL (United States); Wang, Weile [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Wei, Yaxing [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yang, Jia [Auburn Univ., AL (United States)

    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 < 0.01), the post La Niña sink is driven largely by tropical precipitation (r PG,T= -0.46, p = 0.04). This finding points to an ENSO-phase-dependent interplay between water availability and temperature in controlling the carbon uptake response to climate variations in tropical ecosystems. Furthermore, we find that none of a suite of ten contemporary terrestrial biosphere models captures these ENSO-phase-dependent responses, highlighting a key uncertainty in modeling climate impacts on the future of the global land carbon sink.

  8. The Impact of ENSO on Trace Gas Composition in the Upper Troposphere to Lower Stratosphere

    Science.gov (United States)

    Oman, Luke; Douglass, Anne; Ziemke, Jerald; Waugh, Darryn

    2016-04-01

    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 NASA's 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.

  9. Characteristics of Lake Chad level variability and links to ENSO, precipitation, and river discharge.

    Science.gov (United States)

    Okonkwo, Churchill; 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.

  10. Interannual Variability of Sea Surface Temperature in the Northern Indian Ocean Associated with ENSO and IOD

    Institute of Scientific and Technical Information of China (English)

    WU Yan-Ling; DU Yan; ZHANG Yu-Hong; ZHENG Xiao-Tong

    2012-01-01

    The Northern Indian Ocean (NIO) sea surface temperature (SST) warming, associated with the E1 Nifio/Southern Oscillations (ENSO) and the Indian Ocean Dipole (IOD) mode, is investigated using the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) monthly data for the period 1979-2010. Statistical analy- ses are used to identify respective contribution from ENSO and IOD. The results indicate that the first NIO SST warming in September-November is associated with an IOD event, while the second NIO SST warming in spring-summer following the mature phase of ENSO is associated with an ENSO event. In the year that IOD co-occurred with ENSO, NIO SST warms twice, rising in the ENSO developing year and decay year. Both short- wave radiation and latent heat flux contribute to the NIO SST variation. The change in shortwave radiation is due to the change in cloudiness. A cloud-SST feedback plays an important role in NIO SST warming. The latent heat flux is related to the change in monsoonal wind. In the first NIO warming, the SST anomaly is mainly due to the change in the latent heat flux. In the second NIO warming, both factors are important.

  11. Do ENSO and Coastal Development Enhance Coastal Burial of Terrestrial Carbon?

    Science.gov (United States)

    Macreadie, Peter I.; Rolph, Timothy C.; Boyd, Ron; Schröder-Adams, Claudia J.; Skilbeck, Charles G.

    2015-01-01

    Carbon cycling on the east coast of Australia has the potential to be strongly affected by El Niño-Southern Oscillation (ENSO) intensification and coastal development (industrialization and urbanization). We performed paleoreconstructions of estuarine sediments from a seagrass-dominated estuary on the east coast of Australia (Tuggerah Lake, New South Wales) to test the hypothesis that millennial-scale ENSO intensification and European settlement in Australia have increased the transfer of organic carbon from land into coastal waters. Our data show that carbon accumulation rates within coastal sediments increased significantly during periods of maximum millennial-scale ENSO intensity (“super-ENSO”) and coastal development. We suggest that ENSO and coastal development destabilize and liberate terrestrial soil carbon, which, during rainfall events (e.g., La Niña), washes into estuaries and becomes trapped and buried by coastal vegetation (seagrass in this case). Indeed, periods of high carbon burial were generally characterized as having rapid sedimentation rates, higher content of fine-grained sediments, and increased content of wood and charcoal fragments. These results, though preliminary, suggest that coastal development and ENSO intensification—both of which are predicted to increase over the coming century—can enhance capture and burial of terrestrial carbon by coastal ecosystems. These findings have important relevance for current efforts to build an understanding of terrestrial-marine carbon connectivity into global carbon budgets. PMID:26691557

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

    Science.gov (United States)

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

    2017-04-01

    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.

  13. Uncertainty in the ocean-atmosphere feedbacks associated with ENSO in the reanalysis products

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arun; Hu, Zeng-Zhen [NCEP/NWS/NOAA, Climate Prediction Center, Camp Springs, MD (United States)

    2012-08-15

    The evolution of El Nino-Southern Oscillation (ENSO) variability can be characterized by various ocean-atmosphere feedbacks, for example, the influence of ENSO related sea surface temperature (SST) variability on the low-level wind and surface heat fluxes in the equatorial tropical Pacific, which in turn affects the evolution of the SST. An analysis of these feedbacks requires physically consistent observational data sets. Availability of various reanalysis data sets produced during the last 15 years provides such an opportunity. A consolidated estimate of ocean surface fluxes based on multiple reanalyses also helps understand biases in ENSO predictions and simulations from climate models. In this paper, the intensity and the spatial structure of ocean-atmosphere feedback terms (precipitation, surface wind stress, and ocean surface heat flux) associated with ENSO are evaluated for six different reanalysis products. The analysis provides an estimate for the feedback terms that could be used for model validation studies. The analysis includes the robustness of the estimate across different reanalyses. Results show that one of the ''coupled'' reanalysis among the six investigated is closer to the ensemble mean of the results, suggesting that the coupled data assimilation may have the potential to better capture the overall atmosphere-ocean feedback processes associated with ENSO than the uncoupled ones. (orig.)

  14. Dynamical theory driven observational analysis of ENSO modes in the equatorial Pacific

    Science.gov (United States)

    Weare, Bryan C.

    2016-09-01

    The dynamics of tropical Pacific sea surface height changes associated with El Niño/Southern Oscillation (ENSO) have been explored using a melding of a simple dynamical model and maximum covariance analysis (MCA). Two dominant MCA modes, which are degenerate and well correlated at a lag of about 4 months, have a combined time series which is strongly correlated with the Niño3.4 ENSO index. The leading Equatorial Mode shows a strong equatorial signature and is associated with Kelvin wave forcing, Ekman pumping, the wind stress curl, and the Recharge Oscillator hypothesis. The lagging East/West Mode shows a less equatorially trapped east/west pattern of variation and is most associated with zonal wind stress and the Delayed Oscillator hypothesis. The net effect of internal equatorial Rossby waves is dissipative and is not confined to the western boundary. The relevant zonal stress and stress curl fields stretch across the basin. Additional analyses show that both the zonal wind stress and the wind stress curl terms are required for the development of classic ENSO events. Removal of either term gives rise to weaker events, which have properties similar to the central Pacific ENSO events. The seasonal phase-locking of ENSO events is shown to be related to a north to south excursion of wind stress anomalies.

  15. Assessing the Quality of Regional Ocean Reanalysis Data from ENSO Signals

    Institute of Scientific and Technical Information of China (English)

    WANG Lu; ZHOU Tian-Jun

    2012-01-01

    The quality of regional ocean reanalysis data for "the joining area of Asia and the Indian-Pacific Ocean (AIPO)" has been assessed from the perspective of ENSO-related ocean signals. The results derived from the AIPO reanalysis, including SST, sea surface height (SSH), and subsurface ocean temperature and currents, are compared with those of Hadley Center Sea Ice and Sea Surface Temperature (HadlSST) data set and Simple Ocean Data Assimilation (SODA) reanalysis data. Both the spatial pattern and the characteristics of evolution of the ENSO-related ocean temperature anomalies are well reproduced by the AIPO reanalysis data. The physical processes proposed to explain the life cycle of ENSO, including the delayed oscillator mechanism, recharge-discharge mechanism, and the zonal advection feedback, are reasonably represented in this dataset. However, the westward Rossby wave signal in 1992 is not obvious in the AIPO data, and the magnitude of the heat content anomalies is different from that of the SODA data. The reason for the discrepancies may lie in the different mod- els and methods for data assimilation and differences in wind stress forcing. The results demonstrate the high reliability of the AIPO reanalysis data in describing ENSO signals, implying its potential application value in ENSO- related studies.

  16. Robust evidence for forced changes in ENSO: from the mid-Holocene to the 21st century

    Science.gov (United States)

    Grothe, P. R.; Cobb, K. M.; Liguori, G.; Di Lorenzo, E.; Capotondi, A.; Cheng, H.; Edwards, R. L.; Santos, G.; Southon, J. R.; Deocampo, D.; Lynch-Stieglitz, J.; Chen, T.; Sayani, H. R.; Townsend, K. J.; Toth, L. T.; Hagos, M. M.; O'Connor, G.; Thompson, D. M.; Lu, Y.

    2016-12-01

    The El Niño-Southern Oscillation (ENSO) represents the largest source of year-to-year global climate extremes, as evidenced during the record-breaking 2015/16 event. However, its sensitivity to external climate forcing, whether natural or anthropogenic, is difficult to assess with available records. Here, we extend the paleo-ENSO record through the generation of 16 new fossil coral d18O timeseries, averaging 15yrs each, for a total of 233 years of data that greatly augment the available paleo-ENSO archive. Combining this new dataset with published data, we quantify the differences in natural variations in ENSO from the early mid-Holocene to present. Monthly-resolved coral d18O records from the heart of the ENSO region, in the central tropical Pacific, track changes in sea surface temperature with high fidelity and have been used to quantify ENSO variability over the last 7,000 years (Cobb et al., 2013). In this study, we document a significant increase in recent ENSO variance as compared to the last 7,000 years, implying a role for greenhouse gases in driving an intensification of ENSO. We also find a significant reduction in ENSO variance of roughly -20% from 3,000-5,000yr before present, relative to the preceding and subsequent intervals of data. The causes of the late mid-Holocene reduction in ENSO variance may be linked to the influence of fall and/or spring equatorial insolation forcing, which perturbs the seasonal cycle at the critical growth and decay phases of ENSO extremes, respectively. In distinguishing between natural variability and forced changes in ENSO, we assess the significance of our results using a variety of different null hypotheses that includes multi-millennial simulations from both statistical and dynamical models of ENSO variability. Our findings imply that ENSO is sensitive to external forcing, both natural and anthropogenic, although the precise mechanisms for such responses require further study. Our results imply that anthropogenic

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

    Science.gov (United States)

    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.

  18. Advective-reflective conceptual model for the oscillatory nature of the ENSO

    Energy Technology Data Exchange (ETDEWEB)

    Picaut, J.; Masia, F.; Penhoat, Y. du [L`Institut Francais de Recherche Scientifique pour le Developpement en Cooperation-ORSTOM, Noumea (France)

    1997-08-01

    Recent findings about zonal displacements of the Pacific warm pool required a notable modification of the delayed action oscillator theory, the current leading theory for the El Nino-Southern Oscillation (ENSO). Simulations with a linearized coupled ocean-atmosphere model resulted in 3- to 6-year ENSO-like oscillations, with many of the variable model parameters found to be very close to their observed values. This simple model suggests that ocean processes that are ignored or underestimated in the delayed action oscillator theory, such as zonal current convergence, zonal advection of sea surface temperature, and equatorial wave reflection from the eastern ocean boundary, are fundamental to the development of the ENSO, in particular to its manifestations in the central equatorial Pacific.

  19. Imavere saeveski on Stora Enso vääriskivi regioonis / Seppo Vainio ; interv. Toivo Tänavsuu

    Index Scriptorium Estoniae

    Vainio, Seppo

    2004-01-01

    Skandinaavia metsanduskontserni Stora Enso Timberi tegevuse juht Baltikumis vastab küsimustele, mis puudutavad Eesti suurima metsatööstuse Sylvesteri ostu 2003. aastal, Baltikumi üksuste osa Stora Enso tegevuses, Imavere saeveski valimist aasta välisinvestoriks. Vt. samas: Imavere saeveski eile ja täna. Tabel: "Välisinvestor 2004" nominendid

  20. ENSO Forecasts in the North American Multi-Model Ensemble: Composite Analysis and Verification

    Science.gov (United States)

    Chen, L. C.

    2015-12-01

    In this study, we examine precipitation and temperature forecasts during El Nino/Southern Oscillation (ENSO) events in six models in the North American Multi-Model Ensemble (NMME), including the CFSv2, CanCM3, CanCM4, FLOR, GEOS5, and CCSM4 models, by comparing the model-based ENSO composites to the observed. The composite analysis is conducted using the 1982-2010 hindcasts for each of the six models with selected ENSO episodes based on the seasonal Ocean Nino Index (ONI) just prior to the date the forecasts were initiated. Two sets of composites are constructed over the North American continent: one based on precipitation and temperature anomalies, the other based on their probability of occurrence in a tercile-based system. The composites apply to monthly mean conditions in November, December, January, February, and March, respectively, as well as to the five-month aggregates representing the winter conditions. For the anomaly composites, we use the anomaly correlation coefficient and root-mean-square error against the observed composites for evaluation. For the probability composites, unlike conventional probabilistic forecast verification assuming binary outcomes to the observations, both model and observed composites are expressed in probability terms. Performance metrics for such validation are limited. Therefore, we develop a probability anomaly correlation measure and a probability score for assessment, so the results are comparable to the anomaly composite evaluation. We found that all NMME models predict ENSO precipitation patterns well during wintertime; however, some models have large discrepancies between the model temperature composites and the observed. The skill is higher for the multi-model ensemble, as well as the five-month aggregates. Comparing to the anomaly composites, the probability composites have superior skill in predicting ENSO temperature patterns and are less sensitive to the sample used to construct the composites, suggesting that

  1. Reconstruction and analysis of time series of ENSO for the last 500 years

    Institute of Scientific and Technical Information of China (English)

    WANG Shaowu; ZHU Jinhong; CAI Jingning; WEN Xinyu

    2004-01-01

    This paper reports the classification of ENSO into seven categories according to annual (March to February of next year) mean SST of Ni(n)o 3.4 and composite index (ΔI) for the period of 1861~2000. Categories +3, +2, and +1 denote very strong, strong and weak warm episodes (E), -3, -2, and -1 mean very strong, strong and weak cold episodes (A). Absolute SST anomalies are about 1.5 ℃, 1.0 ℃ and 0.5 ℃ respectively for the categories 3, 2, and 1 (or -3, -2, and -1). The normal years are expressed as category 0. Annual categories of ENSO are estimated on the basis of proxy data from AD 1501 to 1860. And a series of ENSO category is established for the period of 1501~2000 in conjunction with the observational data. Comparison of proxy data with observations for 1874~1973 indicates that about 80% of the El Ni(n)o years and La Ni(n)a years can be reconstructed from proxy data, and the reliability of the reconstruction is verified. Analysis of the power spectrum of the reconstructed ENSO series shows significant peaks at QBO, 3~4a (year), 5~6a, and 10a period, the former three are in accordance with the observations for the last 100 years or more. Studies on long term variability of ENSO indicates that ENSO frequency is relatively stationary during the last 500 years, including the Little Ice Age (LIA) (1550~1850) and Modern Warming Period (the 20th century). However, the frequency of E is a little higher in the 20th century and that of A is somewhat higher during the LIA.

  2. ENSO feedbacks and their relationships with the mean state in a flux adjusted ensemble

    Science.gov (United States)

    Ferrett, Samantha; Collins, Matthew

    2016-11-01

    The El Niño Southern Oscillation (ENSO) is governed by a combination of amplifying and damping ocean-atmosphere feedbacks in the equatorial Pacific. Here we quantify these feedbacks in a flux adjusted HadCM3 perturbed physics ensemble under present day conditions and a future emissions scenario using the Bjerknes Stability Index (BJ index). Relationships between feedbacks and both the present day biases and responses under climate change of the mean equatorial Pacific climate are investigated. Despite minimised mean sea surface temperature biases through flux adjustment, the important dominant ENSO feedbacks still show biases with respect to observed feedbacks and inter-ensemble diversity. The dominant positive thermocline and zonal advective feedbacks are found to be weaker in ensemble members with stronger mean zonal advection. This is due to a weaker sensitivity of the thermocline slope and zonal surface ocean currents in the east Pacific to surface wind stress anomalies. A drier west Pacific is also found to be linked to weakened shortwave and latent heat flux damping, suggesting a link between ENSO characteristics and the hydrological cycle. In contrast to previous studies using the BJ index that find positive relationships between the index and ENSO amplitude, here they are weakly or negatively correlated, both for present day conditions and for projected differences. This is caused by strong thermodynamic damping which dominates over positive feedbacks, which alone approximate ENSO amplitude well. While the BJ index proves useful for individual linear feedback analysis, we urge caution in using the total linear BJ index alone to assess the reasons for ENSO amplitude biases and its future change in models.

  3. The link between the Barents Sea and ENSO events simulated by NEMO model

    Directory of Open Access Journals (Sweden)

    V. N. Stepanov

    2012-11-01

    Full Text Available An analysis of observational data in the Barents Sea along a meridian at 33°30' E between 70°30' and 72°30' N has reported a negative correlation between El Niño/La Niña Southern Oscillation (ENSO events and water temperature in the top 200 m: the temperature drops about 0.5 °C during warm ENSO events while during cold ENSO events the top 200 m layer of the Barents Sea is warmer.

    Results from 1 and 1/4-degree global NEMO models show a similar response for the whole Barents Sea. During the strong warm ENSO event in 1997–1998 an anomalous anticyclonic atmospheric circulation over the Barents Sea enhances heat loses, as well as substantially influencing the Barents Sea inflow from the North Atlantic, via changes in ocean currents. Under normal conditions along the Scandinavian peninsula there is a warm current entering the Barents Sea from the North Atlantic, however after the 1997–1998 event this current is weakened.

    During 1997–1998 the model annual mean temperature in the Barents Sea is decreased by about 0.8 °C, also resulting in a higher sea ice volume. In contrast during the cold ENSO events in 1999–2000 and 2007–2008, the model shows a lower sea ice volume, and higher annual mean temperatures in the upper layer of the Barents Sea of about 0.7 °C. An analysis of model data shows that the strength of the Atlantic inflow in the Barents Sea is the main cause of heat content variability, and is forced by changing pressure and winds in the North Atlantic. However, surface heat-exchange with the atmosphere provides the means by which the Barents sea heat budget relaxes to normal in the subsequent year after the ENSO events.

  4. Relationship and its instability of ENSO--Chinese variations in droughts and wet spells

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Monthly data of Self-Calibrated Palmer Drought Severity Index (PDSI) from 1951 to 2000 are calculated using historical precipitation and temperature data for Chinese 160 stations. Temporal and spatial pat-terns of the first empirical orthogonal function (EOF) of the PDSI reveals a fairly linear trend resulting from trends in precipitation and surface temperature, which is similar to the linear PDSI trend during 1951―2000 calculated using all monthly data. The EOF analysis also reveals that the leading mode correlates significantly with ENSO events in time and space. The ENSO EOF shows that during the typical warm phase of ENSO, surface conditions are drier in most regions of China, especially North China, but wetter than normal in the southern regions of Changjiang River, and Northwest China. During the typical cold phase of ENSO, these anomalies reverse sign. From 1951 to 2000, there are large multi-year to decadal variations in droughts and wet spells over China, which are all closely related to strong El Nio events. In other words, when one strong El Nio event happens, there is a possible big variability in droughts and wet spells over China on the multi-year or decadal scale. Studies also sug-gest that during the last 2―3 decades climate changes over China, especially North China’s drying and northwest China’s wetting, are closely related to the shift in ENSO towards warmer events and global warming since the late 1970s. The instability of the relationship is also studied. It is revealed that there is a good correlation between ENSO and Chinese variations in droughts and wet spells in the 3―8-year band, but the correlation between ENSO and Chinese variations in droughts and wet spells is instable. Studies suggest that there are decadal changes in the correlation: the wavelet coherency between ENSO and Chinese variations in droughts and wet spells is high during 1951―1962 and 1976―1991, but low during 1963―1975 and 1992―2000.

  5. ENSO flavors in a tree-ring δ18O record of Tectona grandis from Indonesia

    OpenAIRE

    K. Schollaen; C. Karamperidou; P. Krusic; Cook, E; Helle, G.

    2015-01-01

    Indonesia's climate is dominated by the equatorial monsoon system, and has been linked to El Niño-Southern Oscillation (ENSO) events that often result in extensive droughts and floods over the Indonesian archipelago. In this study we investigate ENSO-related signals in a tree-ring δ18O record (1900–2007) of Javanese teak. Our results reveal a clear influence of Warm Pool (central Pacific) El Niño events on Javanese tree-ring δ18O, and no clear signal of Cold Tongue (eastern ...

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

    Science.gov (United States)

    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

  7. ENSO components of the Atlantic multidecadal oscillation and their relation to North Atlantic interannual coastal sea level anomalies

    Directory of Open Access Journals (Sweden)

    J. Park

    2012-11-01

    Full Text Available The El Niño Southern Oscillation (ENSO and the Atlantic Multidecadal Oscillation (AMO are known to influence coastal water levels along the east coast of the United States. By identifying empirical orthogonal functions (EOFs which coherently contribute from the Multivariate ENSO Index (MEI to the AMO index (AMOI, we characterize both the expression of ENSO in the unsmoothed AMOI, and coherent relationships between these indices and interannual sea level anomalies at six stations in the Gulf of Mexico and Western North Atlantic. Within the ENSO band (2–7 yr periods the total contribution of MEI to unsmoothed AMOI variability is 79%. Cross correlation suggests that the MEI leads expression of the ENSO signature in the AMOI by six months, consistent with the mechanism of an atmospheric bridge. Within the ENSO band, essentially all of the coupling between the unsmoothed AMOI and sea level anomalies is the result of ENSO expression in the AMOI. At longer periods we find decadal components of sea level anomalies linked to the AMOI at three southern stations (Key West, Pensacola, Charleston, but not at the northern stations (Baltimore, Boston, Portland, with values of coherence ranging from 20 to 50%. The coherence of MEI to coastal sea level anomalies has a different structure and is generally weaker than that of the ENSO expressed AMOI influence, suggesting distinct physical mechanisms are influencing sea level anomalies due to a direct ENSO teleconnection when compared to teleconnections based on ENSO expression in the AMOI. It is expected that applying this analysis to extremes of sea level anomalies will reveal additional influences.

  8. 黄河源区降水与径流过程对ENSO 事件的响应特征%On the Characteristics of Response of Precipitation and Runoff to the ENSO Events in the Source Regions of the Yellow River

    Institute of Scientific and Technical Information of China (English)

    王根绪; 沈永平; 刘时银

    2001-01-01

    In the source regions of the Yellow River (above the Tangnag Section), runoff is mainly nourished by precipitation, accounting for 64. 1% of the total. Owing to climate change, variation in precipitation would result in runoff change in the source regions. According to a new ENSO index, which has a seasonal resolving ability, 20 ENSO events are identified from the spring 1952 through the spring 1998. There are 13 warm phase events and 7 cold phase events recognized. The strength and influence duration of each ENSO event is confirmed. Comparing the precipitation and runoff changing processes with the relative ENSO events, a statistical responsive relationship of precipitation and runoff to ENSO events in the source regions of the Yellow River are worked out in this paper. It is found that the annual fluctuation of precipitation and runoff in the source regions are obviously inter related to ENSO events. The interrelationship was associated to the features, strength, occurring season and duration of the event. Generally, a warm phase event occurring in the summer and autumn may decrease the precipitation in the influence duration no matter how the strength of the ENSO event is. A warm phase event with middle strength occurring in the spring season would decrease the precipitation in the occurring duration, but would increase the precipitation in the influence duration. On the contrary, the cold phase event may increase the precipitation in the source regions. A warm phase event would decrease the runoff in the source regions. On the contrary, a cold phase event can increase the runoff. Because the occurring rate of the warm phase event has increased since the 1990s, runoff has a decrease trend in the source regions of the Yellow River.%根据最新季分辨率ENSO指数序列所确认的近40多年来所发生的20次ENSO事件,并确定了每次ENSO事件强度及其影响年,通过对相应年份黄河源区降水与径流距平变化值的对比

  9. Optimal localized observationDsiscfuossrionas dvancing beyond the ENSO predictability barrier

    NARCIS (Netherlands)

    Kramer, W.; Dijkstra, H.A.

    2013-01-01

    The existing 20-member ensemble of 50 yr ECHAM5/MPI-OM simulations provides a reasonably realistic Monte Carlo sample of the El Ni˜no–Southern Oscillation (ENSO). Localized observations of sea surface temperature (SST), zonal wind speed and thermocline depth are assimilated in the ensemble using seq

  10. Analysis of ENSO-based climate variability in modulating drought risks over western Rajasthan in India

    Indian Academy of Sciences (India)

    Poulomi Ganguli; M Janga Reddy

    2013-02-01

    This paper investigates the role of El Niño-Southern Oscillation (ENSO)-based climate variability in modulating multivariate drought risks in the drought-prone region of Western Rajasthan in India. Droughts are multivariate phenomenon, often characterized by severity, duration and peak. By using multivariate ENSO index, annual drought events are partitioned into three climatic states – El Niño, La Niña and neutral phases. For multivariate probabilistic representation of drought characteristics, trivariate copulas are employed, which have the ability to preserve the dependence structure of drought variables under uncertain environment. The first copula model is developed without accounting the climate state information to obtain joint and conditional return periods of drought characteristics. Then, copula-based models are developed for each climate state to estimate the joint and conditional probabilities of drought characteristics under each ENSO state. Results of the study suggest that the inclusion of ENSO-based climate variability is helpful in knowing the associated drought risks, and useful for management of water resources in the region.

  11. Corporate social responsibility as a business strategy: Stora Enso-WWF partnership project

    NARCIS (Netherlands)

    Tysiachniouk, M.S.

    2009-01-01

    The paper analyzes the strategic partnership between transnational corporation Stora-Enso and international nongovernmental organization NGO WWF as a business strategy that helps the company to adopt its business to the turbulent environment of the economy in transition. In this paper I draw from th

  12. ENSO-conditioned weather resampling method for seasonal ensemble streamflow prediction

    NARCIS (Netherlands)

    Beckers, Joost V.L.; Weerts, Albrecht H.; Tijdeman, Erik; Welles, Edwin

    2016-01-01

    Oceanic-atmospheric climate modes, such as El Niño-Southern Oscillation (ENSO), are known to affect the local streamflow regime in many rivers around the world. A new method is proposed to incorporate climate mode information into the well-known ensemble streamflow prediction (ESP) method for sea

  13. Interconnections between the Asian monsoon, ENSO, and high northern latitude climate during the Holocene

    Institute of Scientific and Technical Information of China (English)

    HONG Bing; LIN Qinghua; HONG Yetang

    2006-01-01

    The article emphatically reviews the research progress in interconnections between the East Asian and Indian Ocean summer monsoons, between the Asian monsoon and the El Nino-Southern Oscillation (ENSO) activity, and between the monsoon, ENSO and the changing of the North Atlantic climate during the Holocene. According to the studies of recent years, it is found that the intensity variations of the East Asian and Indian Ocean summer monsoons show an opposite relationship, which may be closely related to the phenomena of ENSO in the equatorial Pacific Ocean and the variation of the deep-water formation of the North Atlantic Ocean on the interannual to orbital time scales. The 4k and 8k events occurring at around 4200 and 8200 a BP, respectively, might be the two in a series of severe paleo-El Nino events during the Holocene, strongly reflecting the interactions and influences of the monsoons, ENSO and the North Atlantic climate. In order to better understand the relationships between these paleoclimatic phenomena, scientists need to strengthen the research work on the Asian monsoon division and the comparison between monsoon proxy records, and the study on the proxy record of sea surface temperature with high time-resolution in the equatorial Pacific Ocean and the simulation research of paleoclimate condition.

  14. Rainfall Variability in the Huangfuchuang Watershed and Its Relationship with ENSO

    Directory of Open Access Journals (Sweden)

    Thelma Dede Baddoo

    2015-06-01

    Full Text Available The impact of the El Niño-Southern Oscillation (ENSO phenomenon within the Huangfuchuan watershed, one of the major first-order sub-basins in the middle region of the Yellow River, has not clearly been established. Consequently, the co-varying relationships between rainfall and El Niño/La Niña spanning the period 1954 to 2010 are investigated. Trends and step changes in annual rainfall are investigated with the Mann-Kendall and the distribution free cumulative sum (CUSUM tests. Wavelet transforms are employed to perform spectral analysis of temporal variations in rainfall rates within the watershed. Cross wavelet and wavelet coherence transforms are used to study localized co-varying relationships between rainfall and ENSO index. Results from statistical tests indicate that rainfall in the Huangfuchuan watershed is declining, although not significantly. In addition, wavelet coherency and cross wavelet analysis, and comparison of the extracted dominant annual rainfall and 2–7 year ENSO signals demonstrate that ENSO events impact Huangfuchuan rainfall with El Niño corresponding to rainfall decline and La Niña to rainfall increment with a semiannual to annual lag.

  15. ENSO-induced inter-annual sea level variability in the Singapore strait

    Digital Repository Service at National Institute of Oceanography (India)

    Soumya, M.; Vethamony, P.; Tkalich, P.

    Sea level data from four tide gauge stations in the SS (Tanjong Pagar, Sultan Shoal, Sembawang and Raffles Lighthouse) for the period 1970-2012 were extracted to study the ENSO-induced interannual sea level variability Sea level during this period...

  16. Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China.

    Science.gov (United States)

    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 IRMsoft-flux represents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRMsoft-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.

  17. Impact of 1990-'95 ENSO/WEPO event on Indian monsoon rainfall

    Digital Repository Service at National Institute of Oceanography (India)

    Gopinathan, C.K.

    years. In case of earlier 11 ENSO events, the Indian South West Monsoon Rainfall (ISWMR) was below normal in 73% cases and above normal only 9% of the cases during the starting year of the negative epoch. The ISWMR was slightly above normal in 1990...

  18. Climate Change and ENSO Effects on Southeastern US Climate Patterns and Maize Yield

    Science.gov (United States)

    Mourtzinis, Spyridon; Ortiz, Brenda V.; Damianidis, Damianos

    2016-07-01

    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-1year-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.

  19. EFFECTS OF ENSO ON THE RELATIONSHIP BETWEEN IOD AND SUMMER RAINFALL IN CHINA

    Institute of Scientific and Technical Information of China (English)

    LIU Xuan-fei; YUAN Hui-zhen; GUAN Zhao-yong

    2009-01-01

    Based on the data of 1950 - 1999 monthly global SST from Hadley Center. NCAR/NCEP reanalysis data and rainfall over 160 weather stations in China,investigation is conducted into the difference of summer rainfall in China (hereafter referred to as the "CS rainfall") between the years with the Indian Ocean Dipole (IOD) occurring independently and those with IOD occurring along with ENSO so as to study the effects of El Ni(n)o - Southern Oscillation (ENSO) on the relationship between IOD and the CS rainfall. It is shown that CS rainfall will be more than normal in South China (centered in Hunan province) in the years of positive IOI) occurring independently; the CS rainfall will be less (more) than normal in North China (Southeast China) in the years of positive IOI) occurring together with ENSO. The effect of ENSO is offsetting (enhancing) the relationship between IOD and summer rainfall in Southwest China,the region joining the Yangtze River basin with the ttuaihe River basin (hereafter referred to as the "Yangtze-Huaihe basin") and North China (Southeast China). The circulation field is also examined for preliminary causes of such an influence.

  20. Tree establishment along an ENSO experimental gradient in the Atacama desert

    NARCIS (Netherlands)

    Squeo, F.A.; Holmgren, M.; Jimenez, L.; Alban, L.; Reyes, J.; Gutierrez, J.R.

    2007-01-01

    Questions: (1) What are the roles of regional climate and plant growth rate for seedling establishment during ENSO rainy pulses along the western coast of South America? (2) What is the water threshold for tree seedling establishment in these arid ecosystems? Location: Atacama Desert, western South

  1. The Response of Tropospheric Ozone to ENSO in Observations and a Chemistry-Climate Simulation

    Science.gov (United States)

    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.

  2. Holocene ENSO-related cyclic storms recorded by magnetic minerals in speleothems of central China

    Science.gov (United States)

    Zhu, Zongmin; Feinberg, Joshua M.; Xie, Shucheng; Bourne, Mark D.; Huang, Chunju; Hu, Chaoyong; Cheng, Hai

    2017-01-01

    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 IRMsoft-flux represents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRMsoft-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.

  3. On ENSO suppression during the mid-Holocene in PMIP3

    Science.gov (United States)

    An, Soon-Il

    2016-04-01

    Using the Paleoclimate Modeling Inter-comparison Project Phase 3 (PMIP3), we investigated change in characteristics of the El Niño-Southern Oscillation (ENSO) during the mid-Holocene period (6,000 years before present; 6ka run) compared to pre-industrial period (0ka run). In 6ka run, the overall cooling over tropical Pacific and the suppressed convection were observed, and the enhanced hemispheric discrepancy in the tropical Pacific surface temperature intensified the cross-equatorial surface winds. The multi-model ensemble of PMIP3 models showed that the ENSO activity in the 6ka run was slightly reduced. In particular, in 6ka run in PMIP3, the intensified damping by the mean currents primarily works for the reduction of ENSO activity, while the thermodynamical damping actually was reduced in 6ka run. Therefore, the two opposite effects are slightly compensated for by each other, which results in a small reduction in the ENSO activity during the 6ka in the PMIP3. Furthermore, details in the feedback processes are addressed as well.

  4. ENSO and annual cycle interaction: the combination mode representation in CMIP5 models

    Science.gov (United States)

    Ren, Hong-Li; Zuo, Jinqing; Jin, Fei-Fei; Stuecker, Malte F.

    2016-06-01

    Recent research demonstrated the existence of a combination mode (C-mode) originating from the atmospheric nonlinear interaction between the El Niño-Southern Oscillation (ENSO) and the Pacific warm pool annual cycle. In this paper, we show that the majority of coupled climate models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) are able to reproduce the observed spatial pattern of the C-mode in terms of surface wind anomalies reasonably well, and about half of the coupled models are able to reproduce spectral power at the combination tone periodicities of about 10 and/or 15 months. Compared to the CMIP5 historical simulations, the CMIP5 Atmospheric Model Intercomparison Project (AMIP) simulations can generally exhibit a more realistic simulation of the C-mode due to prescribed lower boundary forcing. Overall, the multi-model ensemble average of the CMIP5 models tends to capture the C-mode better than the individual models. Furthermore, the models with better performance in simulating the ENSO mode tend to also exhibit a more realistic C-mode with respect to its spatial pattern and amplitude, in both the CMIP5 historical and AMIP simulations. This study shows that the CMIP5 models are able to simulate the proposed combination mode mechanism to some degree, resulting from their reasonable performance in representing the ENSO mode. It is suggested that the main ENSO periods in the current climate models needs to be further improved for making the C-mode better.

  5. Impact of ENSO events on the Kruger National Park’s vegetation

    CSIR Research Space (South Africa)

    Wessels, Konrad J

    2011-01-01

    Full Text Available The El Niño Southern Oscillation (ENSO) is a global coupled ocean-atmosphere phenomenon that is a primary driver of inter-annual variability in the rainfall and consequently the vegetation production of southern African rangelands. Evidence from...

  6. Tree establishment along an ENSO experimental gradient in the Atacama desert

    NARCIS (Netherlands)

    Squeo, F.A.; Holmgren, M.; Jimenez, L.; Alban, L.; Reyes, J.; Gutierrez, J.R.

    2007-01-01

    Questions: (1) What are the roles of regional climate and plant growth rate for seedling establishment during ENSO rainy pulses along the western coast of South America? (2) What is the water threshold for tree seedling establishment in these arid ecosystems? Location: Atacama Desert, western South

  7. Climate Change and ENSO Effects on Southeastern US Climate Patterns and Maize Yield.

    Science.gov (United States)

    Mourtzinis, Spyridon; Ortiz, Brenda V; Damianidis, Damianos

    2016-01-01

    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.

  8. Tailoring wheat management to ENSO phases for increased wheat production in Paraguay

    Directory of Open Access Journals (Sweden)

    Melissa A. Ramirez-Rodrigues

    2014-01-01

    Full Text Available Reported regional wheat yields in Paraguay vary from 1 to 3 t/ha from year to year, but appear not to be correlated with El Niño-Southern Oscillation (ENSO phases. Historical weather data from two locations in representative wheat-growing regions of Paraguay, Encarnación-Itapúa and Ciudad del Este-Alto Paraná combined with crop modeling, were analyzed to optimize nitrogen (N fertilizer application rates according to the ENSO phase of a growing season. The ENSO phase of a growing season was defined based on the average of the sea surface temperature (SST anomalies in the Eastern Equatorial Pacific region for the period June–October using the El Niño region 3.0 index (Niño 3.0. Simulated average yields in Alto Paraná were higher in the drier and cooler La Niña wheat-growing seasons (average of 3.5 t/ha compared to the other phases (average of 3.2 t/ha and in Itapúa, in Neutral seasons (average of 3.8 t/ha compared to the other phases (average of 3.7 t/ha. Accordingly, optimal N fertilizer applications ranged between 20 and 60 kg N/ha between phases depending on the sowing date, soil type and initial amount of soil water content. Applying an ENSO or General Circulation Model (GCM-based forecast for ENSO-season-type specific N fertilizer applications resulted in benefits of >100 US$/ha when compared with current farmers’ practice of consistently low N fertilizer applications in Paraguay. When N management based on forecasts was compared with optimized N application without forecast, the benefits of the forecast was only up to 8 US$/ha. The ENSO-persistence-based forecast showed higher values than the GCM-based forecasts with two lead-times but lower skill. Using climate information can significantly increase current wheat yields and gross margins in Paraguay by tailoring N fertilizer applications to the Niño 3.0-defined ENSO phases, which can be forecasted with moderate skill at the beginning of the growing season.

  9. Wintertime precipitation variability over the Arabian Peninsula and its relationship with ENSO in the CAM4 simulations

    Science.gov (United States)

    Niranjan Kumar, K.; Ouarda, T. B. M. J.; Sandeep, S.; Ajayamohan, R. S.

    2016-10-01

    The climate variability on Earth is strongly influenced by the changes in the Sea Surface Temperature (SST) anomalies in the tropical oceans. More specifically, the inter-annual climate variability in the tropics as well as extra-tropical areas has large impact due to the anomalous SSTs in the tropical Pacific coupled with the El Niño Southern Oscillation (ENSO) through atmospheric teleconnections. However, the effect of ENSO on Middle Eastern region, specifically the Arabian Peninsula (AP) is marginally explored in previous studies. Hence, this study explicitly focuses on the assessment of ENSO variability and its winter climate teleconnections to the AP using the Community Atmospheric Model Version 4.0 (CAM4) simulations and Reanalysis datasets. ENSO teleconnections are also evaluated based on two sensitivity experiments (ENSO-related and ENSO-unrelated) using the CAM4 model. It is observed that during El Niño years the peninsular region receives more rainfall through enhanced moisture transport associated with anomalous westerly winds from adjoining Seas. The Rossby wave energy propagation in the atmosphere underlies important teleconnections involving ENSO. It is also noticed that there exist a distinct change in the phase of the Rossby wave pattern during El Niño and La Niña years which further causes the shift in the position of the jet stream over the Middle East.

  10. A further Study of ENSO Rectification: Results from an OGCM with a Seasonal Cycle

    Science.gov (United States)

    Hua, Lijuan; Yu, Yongqiang; Sun, Dezheng

    2015-04-01

    The potential role that rectification of ENSO plays as a viable mechanism to generate climate anomalies on the decadal and longer time-scales demands a thorough study of this process. In this paper, rectification of ENSO was studied using an Ocean GCM that has a realistic seasonal cycle. In addition to conducting a pair of forced ocean GCM experiments with and without ENSO fluctuations as done in a previous study, we have also conducted a forced experiment with the sign of wind anomalies reversed, with the goal of clarifying the role of the asymmetry in the wind forcing and more generally to better understand the nonlinear dynamics responsible for the rectification. We find that the rectification effect of ENSO is to cool western Pacific warm-pool, warm the eastern equatorial Pacific. We further find that when the sign of the wind stress anomalies is reversed, the impact of the rectification on the mean state remains almost unchanged. This lack of change is further explained by noting that the upper ocean temperature and velocity anomalies (t',u',v',w') are found to respond to the wind stress anomalies linearly except for the strongest El Niño years. Thus the correlation between t' and (u',v',w' ) ( and thus the nonlinear dynamical heating NDH ) remains the same when the sign of the wind stress anomalies is reversed. Indeed, the spatial patterns of nonlinear dynamical heating (NDH) in all four seasons is found to resemble the rectified effect of ENSO in the mean temperature field in the respective seasons, indicating the critical role of NDH in the rectification.

  11. ENSO Bred Vectors in Coupled Ocean-Atmosphere General Circulation Models

    Science.gov (United States)

    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.

  12. ENSO-Based Index Insurance: Approach and Peru Flood Risk Management Application

    Science.gov (United States)

    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

  13. Assessing probabilistic predictions of ENSO phase and intensity from the North American Multimodel Ensemble

    Science.gov (United States)

    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.

  14. ENSO teleconnections with Australian rainfall in coupled model simulations of the last millennium

    Science.gov (United States)

    Brown, Josephine R.; Hope, Pandora; Gergis, Joelle; Henley, Benjamin J.

    2016-07-01

    El Niño-Southern Oscillation is the major source of interannual rainfall variability in the Australian region, with the strongest influence over eastern Australia. The strength of this regional ENSO-rainfall teleconnection varies in the observational record. Climate model simulations of the "last millennium" (850-1850 C.E.) can be used to quantify the natural variability of the relationship between ENSO and Australian rainfall on decadal and longer time scales, providing a baseline for evaluating future projections. In this study, historical and last millennium (LM) simulations from six models were obtained from the Coupled Model Intercomparison Project Phase 5 and Palaeoclimate Modelling Intercomparison Project Phase 3. All models reproduce the observed negative correlation between September to February (SONDJF) eastern Australian rainfall and the NINO3.4 index, with varying skill. In the LM simulations, all models produce decadal-scale cooling over eastern Australia in response to volcanic forcing, as well as a long-term cooling trend. Rainfall variability over the same region is not strongly driven by external forcing, with each model simulating rainfall anomalies of different phase and magnitude. SONDJF eastern Australian rainfall is strongly correlated with ENSO in the LM simulations for all models, although some models simulate periods when the teleconnection weakens substantially for several decades. Changes in ENSO variance play a role in modulating the teleconnection strength, but are not the only factor. The long-term average spatial pattern of the ENSO-Australian rainfall teleconnection is similar in the LM and historical simulations, although the spatial pattern varies over time in the LM simulations.

  15. The weakening of the ENSO-Indian Ocean Dipole (IOD) coupling strength in recent decades

    Science.gov (United States)

    Ham, Yoo-Geun; Choi, Jun-Young; Kug, Jong-Seong

    2016-09-01

    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.

  16. Amplification of ENSO effects on Indian summer monsoon by absorbing aerosols

    Science.gov (United States)

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

    2016-04-01

    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 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. in Clim Dyn 26:855-864, 2006. doi: 10.1007/s00382-006-0114-z). Further analyses from sub-sampling of ENSO years, with normal (1-σ) 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.

  17. Impacts of ENSO on Air-Sea Oxygen Exchange: Observations and Mechanisms

    Science.gov (United States)

    Eddebbar, Y.; Long, M. C.; Resplandy, L.; Manizza, M.; Keeling, R. F.

    2016-12-01

    Dissolved oxygen (O2) is essential to life in the ocean. The oceanic O2 content, however, is expected to decline as warming reduces gas solubility and ocean ventilation. The detection, attribution, and prediction of this decline remain uncertain, particularly in the tropical Pacific where models and observations disagree on both magnitude and sign of subsurface O2 change. These discrepancies arise mainly from: 1) models deficiencies, 2) the influence of natural variability, and 3) limited ocean observations. Here, we assess the effects of ENSO, the dominant mode of natural variability on interannual timescales, on the upper ocean O2 budget in the tropical Pacific using an atmospheric apporach. We combine 25 years of continuous high precision measurements of atmospheric O2 and CO2 from the Global Scripps Flask Network using the Atmospheric Potential Oxygen (APO O2 +1.1*CO2), a powerful tracer of air-sea O2 exchange. These measurements show a positive relation between APO and ENSO, with El Niño events driving an anomalous outgassing of O2 into the atmosphere, whereas La Niña is associated with anomalous uptake of O2 into the ocean. To explore driving mechanisms, we examine a hindcast simulation of the Community Earth System Model (CESM) from the 1960-2008 period. We find that the tropical region dominates the global O2 flux and thus the atmospheric O2 budget variability, and find, similarly to the observations, a positive relation between ENSO and air-sea O2 fluxes. In CESM, the tropical O2 flux response to ENSO represents the net balance of large opposing fluxes, whereby changes in ventilation of low-O2 waters dominate over weaker changes in solubility and biological productivity of O2. The observed APO response to ENSO not only informs process understanding of the coupling between climate and biogeochemical dynamics, but also provides a unique and powerful test for climate models.

  18. ENSO detection and use to inform the operation of large scale water systems

    Science.gov (United States)

    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.

  19. A new method for extracting the ENSO-independent Indian Ocean Dipole: application to Australian region tropical cyclone counts

    Energy Technology Data Exchange (ETDEWEB)

    Werner, Angelika; Maharaj, Angela M. [Macquarie University, Department of Environment and Geography, Sydney, NSW (Australia); Holbrook, Neil J. [University of Tasmania, School of Geography and Environmental Studies, Hobart, TAS (Australia)

    2012-06-15

    We introduce a simple but effective means of removing ENSO-related variations from the Indian Ocean Dipole (IOD) in order to better evaluate the ENSO-independent IOD contribution to Australian climate - specifically here interannual variations in Australian region tropical cyclogensis (TCG) counts. The ENSO time contribution is removed from the Indian Ocean Dipole Mode index (DMI) by first calculating the lagged regression of the DMI on the sea surface temperature anomaly (SSTA) index NINO3.4 to maximum lags of 8 months, and then removing this ENSO portion. The new ENSO-independent time series, DMI{sub NOENSO}, correlates strongly with the original DMI at r = 0.87 (significant at >99% level). Despite the strength of the correlation between these series, the IOD events classified based on DMI{sub NOENSO} provide important differences from previously identified IOD events, which are more closely aligned with ENSO phases. IOD event composite maps of SSTAs regressed on DMI{sub NOENSO} reveal a much greater ENSO-independence than the original DMI-related SSTA pattern. This approach is used to explore relationships between Australian region TCG and IOD from 1968 to 2007. While we show that both the DMI and DMI{sub NOENSO} have significant hindcast skill (on the 95% level) when used as predictors in a multiple linear regression model for Australian region annual TCG counts, the IOD does not add any significant hindcast skill over an ENSO-only predictor model, based on NINO4. Correlations between the time series of annual TCG count observations and ENSO + IOD model cross-validated hindcasts achieve r = 0.68 (significant at the 99% level). (orig.)

  20. Investigating the mechanisms of seasonal ENSO phase locking bias in the ACCESS coupled model

    Science.gov (United States)

    Rashid, Harun A.; Hirst, Anthony C.

    2016-02-01

    The mechanisms of coupled model bias in seasonal ENSO phase locking are investigated using versions 1.0 and 1.3 of the CSIRO-BOM ACCESS coupled model (hereafter, ACCESS1.0 and ACCESS1.3, respectively). The two ACCESS coupled models are mostly similar in construction except for some differences, the most notable of which are in the cloud and land surface schemes used in the models. ACCESS1.0 simulates a realistic seasonal phase locking, with the ENSO variability peaking in December as in observations. On the other hand, the simulated ENSO variability in ACCESS1.3 peaks in March, a bias shown to be shared by many other CMIP5 models. To explore the mechanisms of this model bias, we contrast the atmosphere-ocean feedbacks associated with ENSO in both ACCESS model simulations and also compare the key feedbacks with those in other CMIP5 models. We find evidence that the ENSO phase locking bias in ACCESS1.3 is primarily caused by incorrect simulations of the shortwave feedback and the thermocline feedback in this model. The bias in the shortwave feedback is brought about by unrealistic SST-cloud interactions leading to a positive cloud feedback bias that is largest around March, in contrast to the strongest negative cloud feedback found in ACCESS1.0 simulations and observations at that time. The positive cloud feedback bias in ACCESS1.3 is the result of a dominant role played by the low-level clouds in its modeled SST-cloud interactions in the tropical eastern Pacific. Two factors appear to contribute to the dominance of low-level clouds in ACCESS1.3: the occurrence of a stronger mean descending motion bias and, to a lesser extent, a larger mean SST cold bias during March-April in ACCESS1.3 than in ACCESS1.0. A similar association is found between the positive cloud feedback bias and the biases in spring-time mean descending motion and SST for a group of CMIP5 models that show a seasonal phase locking bias similar to ACCESS1.3. Significant differences are also found

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

    Science.gov (United States)

    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

  2. An ENSO prediction approach based on ocean conditions and ocean-atmosphere coupling

    Science.gov (United States)

    Tseng, Yu-heng; Hu, Zeng-Zhen; Ding, Ruiqiang; Chen, Han-ching

    2016-05-01

    A simple statistical model for the El Niño-Southern Oscillation (ENSO) prediction is derived based on the evolution of the ocean heat condition and the oceanic Kelvin wave propagation associated with westerly wind events (WWEs) and easterly wind surges (EWSs) in the tropical Pacific. The multivariate linear regression model solely relies on the pentad thermocline depth anomaly evolution in 25 days along with the zonal surface wind modulation. It successfully hindcasts all ENSOs except for the 2000/01 La Niña, using the pentad (or monthly) mean tropical atmosphere ocean array data since 1994 with an averaged skill (measured by anomaly correlation) of 0.62 (or 0.67) with a 6-month lead. The exception is mainly due to the long-lasting cold sea surface temperature anomalies in the subtropics resulting from the strong 1998/99 La Niña, even though the tropical warm water volume (WWV) had rebounded and turned phases after 2000. We also note that the hindcast skill is comparable using pentad or monthly mean NCEP global ocean data assimilation system data for the same time period. The hindcast skill of the proposed statistical model is better than that based on the WWV index in terms of the monthly correlation, normalized RMSEs and ENSO occurrences, which suggest that including the evolution of the subsurface ocean temperature anomaly and the WWEs/EWSs in the central tropical Pacific can enhance the ability to predict ENSO. The hindcast skill is also comparable to the predictions using other dynamical and statistical models, indicating that these processes are the keys to ENSO development. The dynamics behind the statistical model are consistent with the physical processes of ENSO development as follows: the tropical WWV resulting from the interannually-varying meridional subtropical cell transport provides a sufficient heat source. When the seasonal phase lock of ocean-atmosphere coupling triggers the positive (negative) zonal wind anomaly in boreal summer and fall, an

  3. An ENSO prediction approach based on ocean conditions and ocean-atmosphere coupling

    Science.gov (United States)

    Tseng, Yu-heng; Hu, Zeng-Zhen; Ding, Ruiqiang; Chen, Han-ching

    2017-03-01

    A simple statistical model for the El Niño-Southern Oscillation (ENSO) prediction is derived based on the evolution of the ocean heat condition and the oceanic Kelvin wave propagation associated with westerly wind events (WWEs) and easterly wind surges (EWSs) in the tropical Pacific. The multivariate linear regression model solely relies on the pentad thermocline depth anomaly evolution in 25 days along with the zonal surface wind modulation. It successfully hindcasts all ENSOs except for the 2000/01 La Niña, using the pentad (or monthly) mean tropical atmosphere ocean array data since 1994 with an averaged skill (measured by anomaly correlation) of 0.62 (or 0.67) with a 6-month lead. The exception is mainly due to the long-lasting cold sea surface temperature anomalies in the subtropics resulting from the strong 1998/99 La Niña, even though the tropical warm water volume (WWV) had rebounded and turned phases after 2000. We also note that the hindcast skill is comparable using pentad or monthly mean NCEP global ocean data assimilation system data for the same time period. The hindcast skill of the proposed statistical model is better than that based on the WWV index in terms of the monthly correlation, normalized RMSEs and ENSO occurrences, which suggest that including the evolution of the subsurface ocean temperature anomaly and the WWEs/EWSs in the central tropical Pacific can enhance the ability to predict ENSO. The hindcast skill is also comparable to the predictions using other dynamical and statistical models, indicating that these processes are the keys to ENSO development. The dynamics behind the statistical model are consistent with the physical processes of ENSO development as follows: the tropical WWV resulting from the interannually-varying meridional subtropical cell transport provides a sufficient heat source. When the seasonal phase lock of ocean-atmosphere coupling triggers the positive (negative) zonal wind anomaly in boreal summer and fall, an

  4. The link between the Barents Sea and ENSO events reproduced by NEMO model

    Directory of Open Access Journals (Sweden)

    V. N. Stepanov

    2012-05-01

    Full Text Available An analysis of observational data in the Barents Sea along a meridian at 33°30´ E between 70°30´ and 72°30´ N has reported a negative correlation between El Niño/La Niña-Southern Oscillation (ENSO events and water temperature in the top 200 m: the temperature drops about 0.5 °C during warm ENSO events while during cold ENSO events the top 200 m layer of the Barents Sea is warmer. Results from 1 and 1/4-degree global NEMO models show a similar response for the whole Barents Sea. During the strong warm ENSO event in 1997–1998 an anticyclonic atmospheric circulation is settled over the Barents Sea instead of a usual cyclonic circulation. This change enhances heat loses in the Barents Sea, as well as substantially influencing the Barents Sea inflow from the North Atlantic, via changes in ocean currents. Under normal conditions along the Scandinavian peninsula there is a warm current entering the Barents sea from the North Atlantic, however after the 1997–1998 event this current is weakened.

    During 1997–1998 the model annual mean temperature in the Barents Sea is decreased by about 0.8 °C, also resulting in a higher sea ice volume. In contrast during the cold ENSO events in 1999–2000 and 2007–2008 the model shows a lower sea ice volume, and higher annual mean temperatures in the upper layer of the Barents Sea of about 0.7 °C.

    An analysis of model data shows that the Barents Sea inflow is the main source for the variability of Barents Sea heat content, and is forced by changing pressure and winds in the North Atlantic. However, surface heat-exchange with atmosphere can also play a dominant role in the Barents Sea annual heat balance, especially for the subsequent year after ENSO events.

  5. Testing a four-dimensional variational data assimilation method using an improved intermediate coupled model for ENSO analysis and prediction

    Science.gov (United States)

    Gao, Chuan; Wu, Xinrong; Zhang, Rong-Hua

    2016-07-01

    A four-dimensional variational (4D-Var) data assimilation method is implemented in an improved intermediate coupled model (ICM) of the tropical Pacific. A twin experiment is designed to evaluate the impact of the 4D-Var data assimilation algorithm on ENSO analysis and prediction based on the ICM. The model error is assumed to arise only from the parameter uncertainty. The "observation" of the SST anomaly, which is sampled from a "truth" model simulation that takes default parameter values and has Gaussian noise added, is directly assimilated into the assimilation model with its parameters set erroneously. Results show that 4D-Var effectively reduces the error of ENSO analysis and therefore improves the prediction skill of ENSO events compared with the non-assimilation case. These results provide a promising way for the ICM to achieve better real-time ENSO prediction.

  6. ENSO components of the Atlantic Multidecadal Oscillation and their relation to North Atlantic interannual coastal sea level anomalies

    Science.gov (United States)

    Park, J. C.; Dusek, G.

    2012-12-01

    The El Niño Southern Oscillation (ENSO) and the Atlantic Multidecadal Oscillation (AMO) are known to influence coastal water levels along the East Coast of the United States. By identifying empirical orthogonal functions (EOFs) which coherently contribute from the Multivariate ENSO Index (MEI) to the AMO index (AMOI), we characterize both the expression of ENSO in the unsmoothed AMOI, and coherent relationships between these indices and interannual sea level anomalies at six stations in the Gulf of Mexico and western North Atlantic. We find that from 1871-2011, 40 to 50% of unsmoothed AMOI variability is coherent with the MEI at periods between 2.5 and 4 years. When integrated over the ENSO band of periods from 2 to 7 years, the total power contributed from the MEI to AMOI is 79%. Further, cross correlation finds that the MEI leads expression of the ENSO signature in the AMOI by six months. Within the ENSO band, essentially all of the forcing identified between the unsmoothed AMOI and sea level anomalies are the result of ENSO expression in the AMOI. Broadband couplings are centered at 3.2, 2.8 and 2.2 years with varying levels of coherence across the six stations. At longer periods we find decadal components of sea level anomalies linked to the AMOI at three southern stations (Key West, Pensacola, Charleston), but not at the northern stations (Baltimore, Boston, Portland). Coherence of MEI with coastal sea level anomalies has a different structure and is generally weaker than that of the ENSO expressed AMOI influence, suggesting distinct physical mechanisms are influencing sea level anomalies due to a direct ENSO teleconnection when compared to teleconnections based on ENSO expression in the AMOI. The analysis is based on linear systems theory, and it is cautioned that this model is likely insufficient to fully characterize the links and feedbacks of the complex dynamics expressed in the analyzed indices. Nonetheless, within the constraints of the model, the

  7. Balances de glaciares y clima en Bolivia y Perú: impacto de los eventos ENSO

    Directory of Open Access Journals (Sweden)

    1995-01-01

    Full Text Available BILANS GLACIAIRES ET CLIMAT EN BOLIVIE ET AU PÉROU : IMPACT DES ÉVÉNEMENTS ENSO. À partir d’une reconstruction faite pour le glacier de Zongo (Cordillère Royale, Bolivie avec des données hydrologiques et de l’application du modèle linéaire (Lliboutry sur les données des glaciers Yanamarey et Uruashraju (Cordillère Blanche, Pérou, on a pu disposer de séries de 15-20 ans de bilans de masse. En analysant parallèlement les données recueillies aux stations météorologiques proches, on met en évidence le rôle des températures dans la détermination de ces bilans. La variabilité des températures dépend de façon étroite des phénomènes ENSO (El Niño Southern Oscillation : pendant ces épisodes, les températures maximales et minimales augmentent sensiblement, ce qui affecte le terme ablation du bilan de masse. On vérifie sur ces séries de 20 ans que toutes les années ENSO sont associées à des bilans négatifs. Pendant la plupart des épisodes ENSO se produit au sud du Pérou et en Bolivie une réduction des précipitations, ce qui contribue à accentuer l’effet ENSO sur les bilans. Ces événements ont une grande influence sur l’évolution actuelle des glaciers andins, caractérisée par un recul rapide. La reconstrucción del balance hidrológico a partir de datos hidrométricos del glaciar de Zongo (Cordillera Real de Bolivia, así como la aplicación del modelo lineal (Lliboutry sobre los datos de balance de los glaciares Yanamarey y Uruashraju (Cordillera Blanca del Perú, ofrecen la posibilidad de disponer de series de 15-20 años de balance de masa. Analizando paralelamente los datos recogidos en estaciones meteorológicas cercanas, se puede evidenciar el rol de las temperaturas en la determinación de estos balances. La variabilidad de las temperaturas depende de una manera estrecha de los eventos ENSO (El Niño Southern Oscillation: durante estos eventos, las temperaturas máximas y mínimas aumentan

  8. Improved ENSO simulation from climate system model FGOALS-g1.0 to FGOALS-g2

    Science.gov (United States)

    Chen, Lin; Yu, Yongqiang; Zheng, Weipeng

    2016-10-01

    This study presents an overview of the improvement in the simulation of El Niño-Southern Oscillation (ENSO) in the latest generation of the Institute of Atmospheric Physics' coupled general circulation model (CGCM), the Flexible Global Ocean-Atmosphere-Land System model Grid-point Version 2 (FGOALS-g2; hereafter referred to as "g2") from its predecessor FGOALS-g1.0 (referred to as "g1"), including the more realistic amplitude, irregularity, and ENSO cycle. The changes have been analyzed quantitatively based on the Bjerknes stability index, which serves as a measure of ENSO growth rate. The improved simulation of ENSO amplitude is mainly due to the reasonable representation of the thermocline and thermodynamic feedbacks: On the one hand, the deeper mean thermocline results in a weakened thermocline response to the zonal wind stress anomaly, and the looser vertical stratification of mean temperature leads to a weakened response of anomalous subsurface temperature to anomalous thermocline depth, both of which cause the reduced thermocline feedback in g2; on the other hand, the alleviated cold bias of mean sea surface temperature leads to more reasonable thermodynamic feedback in g2. The regular oscillation of ENSO in g1 is associated with its unsuccessful representation of the role of atmospheric noise over the western-central equatorial Pacific (WCEP) in triggering ENSO events, which arises from the weak synoptic-intraseasonal variability of zonal winds over the WCEP in g1. The asymmetric transition of ENSO in g1 is attributed to the asymmetric effect of thermocline feedback, which is due to the annual cycle of mean upwelling in the eastern Pacific. This study highlights the great impact of improving the representation of mean states on the improved simulation of air-sea feedback processes and ultimately more reasonable depiction of ENSO behaviors in CGCMs.

  9. ENSO Effect on East Asian Tropical Cyclone Landfall via Changes in Tracks and Genesis in a Statistical Model

    Science.gov (United States)

    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.

  10. Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event

    Science.gov (United States)

    Loick-Wilde, Natalie; Bombar, Deniz; Doan, Hai Nhu; Nguyen, Lam Ngoc; Nguyen-Thi, Anh Mai; Voss, Maren; Dippner, Joachim W.

    2017-04-01

    Investigating microplankton biomass and diversity under different climatological conditions is key to the understanding of cascading effects of climate change on nutrient cycles and biological productivity. Here we have used data collected during two contrasting summers along the coast of Viet Nam to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (ENSO) event and was characterized by weak coastal upwelling, in the second summer during July 2004, upwelling was normal. Very low silicate (SiO4) concentrations and SiO4:DIN ratios characterized the source water mass for upwelling in July 2004, and dynamic SiO4 to dissolved inorganic nitrogen ratios (SiO4:DIN) mainly below the Redfield-Brzezinski ratio and DIN to phosphate ratios (DIN:PO43-) below the Redfield ratio were a common feature off Viet Nam. Much higher particle concentrations and PSi/PC ratios during normal upwelling revealed major changes in the microplankton community structure among summers. Small dinoflagellates (10-20 μm) prevailed ubiquitously during reduced upwelling. During normal upwelling, the diatom Rhizosolenia sp. dominated the cell-carbon biomass in the silicate poor upwelling waters. Trichodesmium erythraeum dominated in the Mekong-influenced and nutrient depleted offshore waters, where it co-occurred with Rhizosolenia sp. Both species were directly associated with the much higher primary production (PP) and N2 fixation rates that were quantified in earlier studies, as well as with much higher diversities at these offshore sites. Along the coast, the correlation between Rhizosolenia sp. and PP rates was less clear and the factors regulating the biomass of Rhizosolenia sp. in the upwelling waters are discussed. The very low silicate concentrations in the source water

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

    Energy Technology Data Exchange (ETDEWEB)

    Bonfils, Celine; Santer, Benjamin D.; Phillips, Thomas J.; Marvel, Kate; Leung, Lai-Yung R.; Doutriaux, Charles; Capotondi, Antonietta

    2015-12-15

    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.

  12. An ENSO-Forecast Independent Statistical Model for the Prediction of Annual Atlantic Tropical Cyclone Frequency in April

    Directory of Open Access Journals (Sweden)

    Kenny Xie

    2014-01-01

    Full Text Available Statistical models for preseason prediction of annual Atlantic tropical cyclone (TC and hurricane counts generally include El Niño/Southern Oscillation (ENSO forecasts as a predictor. As a result, the predictions from such models are often contaminated by the errors in ENSO forecasts. In this study, it is found that the latent heat flux (LHF over Eastern Tropical Pacific (ETP, defined as the region 0°–5°N, 115°–125°W in spring is negatively correlated with the annual Atlantic TC and hurricane counts. By using stepwise backward elimination regression, it is further shown that the March value of ETP LHF is a better predictor than the spring or summer ENSO index for Atlantic TC counts. Leave-one-out cross validation indicates that the annual Atlantic TC counts predicted by this ENSO-independent statistical model show a remarkable correlation with the actual TC counts (R=0.72; P value <0.01. For Atlantic hurricanes, the predictions using March ETP LHF and summer (July–September ENSO indices show only minor differences except in moderate to strong El Niño years. Thus, March ETP LHF is an excellent predictor for seasonal Atlantic TC prediction and a viable alternative to using ENSO index for Atlantic hurricane prediction.

  13. Increase in the potential predictability of the Arctic Oscillation via intensified teleconnection with ENSO after the mid-1990s

    Science.gov (United States)

    Kang, Daehyun; Lee, Myong-In

    2017-09-01

    This study examines why the seasonal prediction skill of the Arctic Oscillation (AO) has increased significantly since the mid-1990s in state-of-the-art seasonal forecasting systems in operation. This skill increase is primarily attributed to variability over the North Atlantic with an enhanced connection between the AO and the El Niño and Southern Oscillation (ENSO). The relationship between ENSO and AO depends primarily on low-frequency variability in the North Pacific driven by the North Pacific Gyre Oscillation, as represented by the Hawaiian sea level pressure (SLPHI) index. When the sign of the SLPHI index and that of the NINO3.4 index are out-of-phase (in-phase) with the variability center of ENSO shifted to the central Pacific (eastern Pacific), more intense (weaker) ENSO-AO teleconnection results. Linear barotropic model experiments with prescribed ENSO forcing and differing phase and intensity of SLPHI support the observed relationship in La Niña years, highlighting the important and independent role of the SLPHI variability as a modulator of the ENSO teleconnection to higher latitudes.

  14. The modeling of the ENSO events with the help of a simple model

    CERN Document Server

    Stepanov, V N

    2007-01-01

    The Southern Oscillation (ENSO) is modelled with the help of a simple model representing a classical damped oscillator forced by external forcing. Eastern Pacific sea surface temperature (SST) and the mean equatorial Pacific thermocline depth correspond to the roles of momentum and position. The external forcing of the system is supplied by short-period meridional mass fluctuations in the Pacific sector of the Southern Ocean due to the joint effect of the atmospheric variability over the Antarctic Circumpolar Current (ACC), bottom topography and coastlines, and also by the variability of westerly winds in the tropics. Under such conditions the ENSO-like oscillations arise as a result of propagation of signals due to both initial signals appeared in the Southern Ocean and the tropical westerly wind anomaly, that propagate then across the equatorial Pacific by means of fast wave processes. The external forcings are the main factor in establishing the oscillation pattern.

  15. Relationship between East Asian winter monsoon, warm pool situation and ENSO cycle

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on the observational data analyses and numerical simulations with the air-sea coupled model (CGCM), a new perspective on the occurrence mechanism of ENSO is advanced in this paper. The continuous strong (weak) East Asian winter monsoon will lead to continuous westerly (easterly) wind anomalies over the equatorial western Pacific region. The anomalous equatorial westerly (easterly) winds can cause eastward propagation of the subsurface ocean temperature anomalies (SOTA) in the warm pool region, the positive (negative) SOTA have been in the warm pool region for quite a long time. The eastward propagating of positive (negative) SOTA along the thermocline will lead to positive (negative) SSTA in the equatorial eastern Pacific and the occurrence of El Ni(n)o (La Ni(n)a) event. After the occurrence of ENSO, the winter monsoon in East Asia will be weak (strong) due to the influence of El Ni(n)o (La Ni(n)a).

  16. NUMERICAL MODELING STUDY OF EFFECTS OF EASTERN PACIFIC WARM POOL ON ENSO

    Institute of Scientific and Technical Information of China (English)

    YUE Cai-jun; LU Wei-song; Xiaofan LI

    2010-01-01

    In this study,sensitivity experiments were conducted with the Zebiak-Cane ocean-atmosphere coupled model forced by the wind stress anomaly from the U.S.National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data to study the impacts of eastern Pacific warm pool on the formation and development of ENSO events.The effects of climatological mean sea surface temperature of the warm pool on forecast skill during the ENSO events of 1982-1999 are more considerable that those of climatological mean meridional winds and ocean currents.The forecast skill for the 1997/1998 E1 Ni(n)o event is characterized by sensitivity to climatological mean sea surface temperature and anomalies of northerly winds and currents.The forecast skill is found insensitive to climatological mean northerly meridional winds and currents.

  17. Rainfall mechanisms for the dominant rainfall mode over Zimbabwe relative to ENSO and/or IODZM.

    Science.gov (United States)

    Manatsa, Desmond; Mukwada, Geoffrey

    2012-01-01

    Zimbabwe's homogeneous precipitation regions are investigated by means of principal component analysis (PCA) with regard to the underlying processes related to ENSO and/or Indian Ocean Dipole zonal mode (IODZM). Station standardized precipitation index rather than direct rainfall values represent the data matrix used in the PCA. The results indicate that the country's rainfall is highly homogeneous and is dominantly described by the first principal mode (PC1). This leading PC can be used to represent the major rainfall patterns affecting the country, both spatially and temporarily. The current practice of subdividing the country into the two seasonal rainfall forecast zones becomes irrelevant. Partial correlation analysis shows that PC1 is linked more to the IODZM than to the traditional ENSO which predominantly demonstrates insignificant association with PC1. The pure IODZM composite is linked to the most intense rainfall suppression mechanisms, while the pure El Niño composite is linked to rainfall enhancing mechanisms.

  18. A continuous 3000-year precipitation record of ENSO variability during LGM from a stalagmite in Nanjing

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A glacial stalagmite chronology from Nanjing has been established by the TIMS-U series dating and annual band counting methods. The annually layering sequence spanning the 3000-year period from 18179 to 14900 calendar years before the present (aBP) was analyzed for evidence of East Asian summer monsoon precipitation variability during the Last Glacial Maximum (LGM). Power spectral analysis of the sequence shows a distinct interannual (2-7 years) band of enhanced variability suggestive of El Nino-Southern Oscillation (ENSO) teleconnections into East China during the LGM when climatic boundary conditions were different from those of today. The lower frequency bands (4-7 years) variability becomes weaker from 18179 to 14900 aBP, supporting the precession forcing model. The reappearance of the ENSO band in the coldest climatic boundary conditions during the Heinrich Event 1, however, suggests the stimulation of the enhanced East Asia winter monsoon to the El Nino events.

  19. On the Impact of Local Feedbacks in the Central Pacific on the ENSO Cycle.

    Science.gov (United States)

    Burgers, Gerrit; van Oldenborgh, Geert Jan

    2003-07-01

    While sea surface temperature (SST) anomalies in the eastern equatorial Pacific are dominated by the thermocline feedback, in the central equatorial Pacific local wind effects, such as zonal advection, are important as well. El Niño-Southern Oscillation (ENSO) simulations with a linear model improve markedly if these effects are included as a local wind stress feedback on SST. An atmosphere model that reacts both to eastern and central Pacific SST anomalies is needed for producing a realistic ENSO cycle.First, simulations are studied of a linear 1.5-layer reduced-gravity ocean model and a linear SST anomaly equation, forced by observed monthly wind stress. If only the thermocline feedback is present in the SST equation, SST can be simulated well in the eastern Pacific, but, contrary to observations, central Pacific SST is out of phase with the eastern Pacific. If a wind stress feedback is added in the SST equation, as a term proportional to the zonal wind stress, correlations between observed and simulated SST are above 0.8 in both the central and eastern Pacific, and the correlation between the Niño-3 (5°S-5°N, 90°-150°W) and Niño-4 (5°S-5°N, 150°W-160°E) indexes is close to the observed value of 0.75.Next, a statistical atmosphere is added to the ocean module that is based on a regression of observed wind stress to the observed Niño-3 and Niño-4 indexes. The coupled system is driven by noise that is inferred from the residues of the fit and has a red component. The observed Niño-3-Niño-4 index correlation can be reproduced only with a wind stress feedback in the central Pacific. Also, the level of SST variability rises and the ENSO period increases to more realistic values.The interplay between the local wind stress and the thermocline feedbacks, therefore, is an important factor in the structure of ENSO in the coupled linear model. In the eastern Pacific, the thermocline feedback dominates SST anomalies; in the central Pacific, the local wind

  20. Evidence of increased tropical moisture in southeast Australian alpine precipitation during ENSO

    Science.gov (United States)

    Theobald, Alison; McGowan, Hamish

    2016-10-01

    An understanding of past atmospheric variability during El Niño-Southern Oscillation (ENSO) events is critical for informing debate on current and future changes in precipitation in a warming world. Here we show that atmospheric moisture content over much of Australia during inflow-generating precipitation days (≥10 mm d-1) associated with La Niña (El Niño) events has increased (decreased) over the period 1958-2015. This is most notable in tropical latitudes which are the source of moisture of most precipitation ≥ 10 mm in southeast Australia (SEA). These trends are consistent with climate model projections and increases in tropical sea surface temperatures since the 1950s. They confirm that enhanced tropical ocean forcing of interannual climate variability through ENSO due to global warming is changing the hydroclimate of midlatitudes and in-turn will require major changes to water resource use and management.

  1. Long-term non-linear predictability of ENSO events over the 20th century

    CERN Document Server

    Astudillo, H F; Borotto, F A

    2015-01-01

    We show that the monthly recorded history (1878-2013) of the Southern Oscillation Index (SOI), a descriptor of the El Ni\\~no Southern Oscillation (ENSO) phenomenon, can be well described as a dynamic system that supports an average nonlinear predictability well beyond the spring barrier. The predictability is strongly linked to a detailed knowledge of the topology of the attractor obtained by embedding the SOI index in a wavelets base state space. Using the state orbits on the attractor we show that the information contained in the Southern Oscillation Index (SOI) is sufficient to provide average nonlinear predictions for time periods of 2, 3 and 4 years in advance throughout the 20th century with an acceptable error. The simplicity of implementation and ease of use makes it suitable for studying non linear predictability in any area where observations are similar to those that describe the ENSO phenomenon.

  2. A delay differential model of ENSO variability: Parametric instability and the distribution of extremes

    CERN Document Server

    Ghil, Michael; Thompson, Sylvester

    2007-01-01

    We consider a delay differential equation (DDE) model for El-Nino Southern Oscillation (ENSO) variability. The model combines two key mechanisms that participate in 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 $\\kappa$, and propagation period $\\tau$ of oceanic waves across the Tropical Pacific. Two regimes of variability, stable and unstable, are separated by a sharp neutral curve in the $(b,\\tau)$ plane at constant $\\kappa$. 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 $\\kappa$ increases. In the unstable regime, spontaneous transitions occur in the mean ``temperature'' ({\\it i.e.}, thermo...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-09-07

    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) exhibit 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

  4. Tropospheric ozone variability in the tropics from ENSO to MJO and shorter timescales

    OpenAIRE

    Ziemke, J. R.; Douglass, A.R.; L. D. Oman; S. E. Strahan; B. N. Duncan

    2015-01-01

    Aura OMI and MLS measurements are combined to produce daily maps of tropospheric ozone beginning October 2004. We show that El Niño-Southern Oscillation (ENSO) related inter-annual change in tropospheric ozone in the tropics is small in relation to combined intra-seasonal/Madden–Julian Oscillation (MJO) and shorter timescale variability by a factor of ~ 3–10 (largest in the Atlantic). Outgoing longwave radiation (OLR), taken as a proxy for convection, suggests that convectio...

  5. Connection between the Eastern Subtropical Mode Water in the South Pacific Ocean and the ENSO cycle

    Science.gov (United States)

    Li, Z.

    2012-12-01

    Water subducted in the subtropics is intimately linked to the circulation in the Tropics through the interior mass communication and/or the western boundary, and could potentially affect climate variability on interannual and decadal time scales (Gu and Philander, 1997). The interior mass communication rate between the subtropical and equatorial ocean can be quantified in different ways. For example, Huang and Wang (2001) proposed a method of using the Sverdrup function to quantify the communication rate. Their method is used here to compute the meridional transport function below the Ekman layer in order to investigate the direct communication from the eastern STMW to the equatorial Pacific, and study the connection between the eastern STMW and the ENSO cycle. The western subtropical mode water, however, is less likely to directly participate in the subtropical-tropical exchange because they are mainly formed and confined to the recirculation region of the western subtropical gyre (Ladd and Thompson, 2000). The variability of the Subtropical Mode Water (STMW) formation in the South Pacific Ocean from 1980 to 2004 is investigated in this study, using a high-resolution numerical model and a 3D Lagrangian trajectory model. Variations of subduction rate in the mode waters are closely linked to the El Niño-Southern Oscillation (ENSO) cycle. The eastern STMW could potentially affect the ENSO cycle through the interior communication window that was identified from the virtual streamfunction. Its location and width closely related to the ENSO cycle. The deep westward penetration of the western edge of the window at the equatorial Pacific is evident during the 1998 La Niña event.; Zonal location of the interior communication window for eastern STMW, when the subducted water parcels reach the equatorial Pacific at 10oS. Solid gray (black) line represents the western (eastern) edge of the window.

  6. Utilizing the state of ENSO as a means for season-ahead predictor selection

    Science.gov (United States)

    Zimmerman, Brian G.; Vimont, Daniel J.; Block, Paul J.

    2016-05-01

    This paper introduces the Nino Index Phase Analysis (NIPA) framework for forecasting hydroclimatic variables on a seasonal time scale. Antecedent Sea Surface Temperatures (SSTs) are commonly used in statistical predictive frameworks for seasonal forecasting, however, the typical approach of evaluating all the years on record in one bin ("phase") does not often provide the level of skill required by decision makers. For many locations around the world, the most influential climate signal on the seasonal time scale is the El Nino Southern Oscillation (ENSO), and there are various indices used to capture the state of ENSO and provide this information. NIPA utilizes the state of ENSO to classify the years of record into four phases, operating under the hypothesis that ENSO itself is affecting the "mean state" of the atmospheric-oceanic system, and relevant teleconnections depend on and must be selected within these mean states. A case study focused on spring precipitation over the Lower Colorado River Basin (LCRB) in Texas is chosen to illustrate NIPA's potential. Results show that correlations between wintertime SST fields and spring precipitation in the LCRB improve from 0.21 to 0.47 for the typical "one phase" and the NIPA "four-phase" approach, respectively. Even greater improvements are seen across tercile-based skill scores such as the Heidke Hit Skill Score and Ranked Probability Skill Score; skill is particularly strong for years exhibiting extreme wet or dry conditions. It also outperforms the North American Multi-Model Ensemble predictions across the LCRB for the selected seasons. This is encouraging as improved predictability through NIPA may translate to better decision-making for water managers.

  7. Inter ENSO variability and its influence over the South American monsoon system

    Directory of Open Access Journals (Sweden)

    A. R. M. Drumond

    2006-01-01

    Full Text Available Previous studies have discussed the interannual variability of a meridional seesaw of dry and wet conditions over South America (SA associated to the modulation of the South Atlantic Convergence Zone (SACZ. However, they did not explore if the variability inter ENSO (El Niño Southern Oscillation can be related to the phase changes of this dipole. To answer this question, an observational work was carried out to explore the atmospheric and Sea Surface Temperature (SST conditions related to the same ENSO signal and to opposite dipole phases. Rotated Empirical Orthogonal Function (REOF analysis was applied over normalized Chen precipitation seasonal anomalies in order to find the dipole mode in the Austral Summer (December to February. The fourth rotated mode, explaining 6.6% of the total variance, consists of positive loading over the SACZ region and negative loading over northern Argentina. Extreme events were selected and enhanced activity of SACZ during the Summer season (SACZ+ was identified in nine years: five during La Niña events (LN and two in El Niño episodes (EN. On the other hand, inhibited manifestations of this system (SACZ- were identified in seven years: four in EN and two during LN. Power spectrum analysis indicated that the interannual variability of the precipitation dipole seems to be related to the low frequency and to the quasi-biennial part of ENSO variability. The ENSO events with the same signal can present opposite phases for the dipole. The results suggest that the displacement of the convection over Indonesia and western Pacific can play an important role to modulate the seesaw pattern.

  8. Measuring past changes in ENSO variance using Mg/Ca measurements on individual planktic foraminifera

    Science.gov (United States)

    Marchitto, T. M.; Grist, H. R.; van Geen, A.

    2013-12-01

    Previous work in Soledad Basin, located off Baja California Sur in the eastern subtropical Pacific, supports a La Niña-like mean-state response to enhanced radiative forcing at both orbital and millennial (solar) timescales during the Holocene. Mg/Ca measurements on the planktic foraminifer Globigerina bulloides indicate cooling when insolation is higher, consistent with an ';ocean dynamical thermostat' response that shoals the thermocline and cools the surface in the eastern tropical Pacific. Some, but not all, numerical models simulate reduced ENSO variance (less frequent and/or less intense events) when the Pacific is driven into a La Niña-like mean state by radiative forcing. Hypothetically the question of ENSO variance can be examined by measuring individual planktic foraminiferal tests from within a sample interval. Koutavas et al. (2006) used d18O on single specimens of Globigerinoides ruber from the eastern equatorial Pacific to demonstrate a 50% reduction in variance at ~6 ka compared to ~2 ka, consistent with the sense of the model predictions at the orbital scale. Here we adapt this approach to Mg/Ca and apply it to the millennial-scale question. We present Mg/Ca measured on single specimens of G. bulloides (cold season) and G. ruber (warm season) from three time slices in Soledad Basin: the 20th century, the warm interval (and solar low) at 9.3 ka, and the cold interval (and solar high) at 9.8 ka. Each interval is uniformly sampled over a ~100-yr (~10-cm or more) window to ensure that our variance estimate is not biased by decadal-scale stochastic variability. Theoretically we can distinguish between changing ENSO variability and changing seasonality: a reduction in ENSO variance would result in narrowing of both the G. bulloides and G. ruber temperature distributions without necessarily changing the distance between their two medians; while a reduction in seasonality would cause the two species' distributions to move closer together.

  9. Impacts of ENSO on air-sea oxygen exchange: Observations and mechanisms

    Science.gov (United States)

    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.

  10. Intrinsic modulation of ENSO predictability viewed through a local Lyapunov lens

    Science.gov (United States)

    Karamperidou, Christina; Cane, Mark A.; Lall, Upmanu; Wittenberg, Andrew T.

    2014-01-01

    The presence of rich ENSO variability in the long unforced simulation of GFDL's CM2.1 motivates the use of tools from dynamical systems theory to study variability in ENSO predictability, and its connections to ENSO magnitude, frequency, and physical evolution. Local Lyapunov exponents (LLEs) estimated from the monthly NINO3 SSTa model output are used to characterize periods of increased or decreased predictability. The LLEs describe the growth of infinitesimal perturbations due to internal variability, and are a measure of the immediate predictive uncertainty at any given point in the system phase-space. The LLE-derived predictability estimates are compared with those obtained from the error growth in a set of re-forecast experiments with CM2.1. It is shown that the LLEs underestimate the error growth for short forecast lead times (less than 8 months), while they overestimate it for longer lead times. The departure of LLE-derived error growth rates from the re-forecast rates is a linear function of forecast lead time, and is also sensitive to the length of the time series used for the LLE calculation. The LLE-derived error growth rate is closer to that estimated from the re-forecasts for a lead time of 4 months. In the 2,000-year long simulation, the LLE-derived predictability at the 4-month lead time varies (multi)decadally only by 9-18 %. Active ENSO periods are more predictable than inactive ones, while epochs with regular periodicity and moderate magnitude are classified as the most predictable by the LLEs. Events with a deeper thermocline in the west Pacific up to five years prior to their peak, along with an earlier deepening of the thermocline in the east Pacific in the months preceding the peak, are classified as more predictable. Also, the GCM is found to be less predictable than nature under this measure of predictability.

  11. ENSO related SST anomalies and relation with surface heat fluxes over south Pacific and Atlantic

    Science.gov (United States)

    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.

  12. Predicting monthly precipitation along coastal Ecuador: ENSO and transfer function models

    Science.gov (United States)

    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.

  13. Individual and coupled influences of AMO and ENSO on regional precipitation characteristics and extremes

    Science.gov (United States)

    Goly, Aneesh; Teegavarapu, Ramesh S. V.

    2014-06-01

    Understanding the influences of Atlantic multidecadal oscillation (AMO) and El Niño southern oscillation (ENSO) on regional precipitation extremes and characteristics in the state of Florida is the focus of this study. Exhaustive evaluations of individual and combined influences of these oscillations using, descriptive indices-based assessment of statistically significant changes in rainfall characteristics, identification of spatially varying influences of oscillations on dry and wet spell transition states, antecedent precipitation prior to extreme events, intraevent temporal distribution of precipitation and changes in temporal occurrences of extremes including dry/wet cycles are carried out. Rain gage and gridded precipitation data analysis using parametric hypothesis tests confirm statistically significant changes in the precipitation characteristics from one phase to another of each oscillation and also in coupled phases. Spatially nonuniform and uniform influences of AMO and ENSO, respectively, on precipitation are evident. AMO influences vary in peninsular and continental parts of Florida and the warm (cool) phase of AMO contributes to increased precipitation extremes during wet (dry) season. The influence of ENSO is confined to dry season with El Niño (La Niña) contributing to increase (decrease) in extremes and total precipitation. Wetter antecedent conditions preceding daily extremes are dominant in AMO warm phase compared to the cool and are likely to impact design floods in the region. AMO influence on dry season precipitation extremes is noted for ENSO neutral years. The two oscillations in different phases modulate each other with seasonal and spatially varying impacts and implications on flood control and water supply in the region.

  14. The seasonally changing cloud feedbacks contribution to the ENSO seasonal phase-locking

    Science.gov (United States)

    Dommenget, Dietmar; Yu, Yanshan

    2016-12-01

    ENSO variability has a seasonal phase-locking, with SST anomalies on average decreasing during the beginning of the year and SST anomalies increasing during the second half of the year. As a result of this, the ENSO SST variability is smallest in April and the so call `spring barrier' exists in the predictability of ENSO. In this study we analysis how the seasonal phase-locking of surface short wave radiation associated with cloud cover feedbacks contribute to this phenomenon. We base our analysis on observations and simplified climate model simulations. At the beginning of the year, the warmer mean SST in the eastern equatorial Pacific leads to deeper clouds whose anomalous variability are positively correlated with the underlying SST anomalies. These observations highlight a strong negative surface short wave radiation feedback at the beginning of the year in the eastern Pacific (NINO3 region). This supports the observed seasonal phase-locking of ENSO SST variability. This relation also exists in model simulations of the linear recharge oscillator and in the slab ocean model coupled to a fully complex atmospheric GCM. The Slab ocean simulation has seasonal phase-locking similar to observed mostly caused by similar seasonal changing cloud feedbacks as observed. In the linear recharge oscillator simulations seasonal phase-locking is also similar to observed, but is not just related to seasonal changing cloud feedbacks, but is also related to changes in the sensitivity of the zonal wind stress and to a lesser extent to seasonally change sensitivities to the thermocline depth. In summary this study has shown that the seasonal phase-locking, as observed and simulated, is linked to seasonally changing cloud feedbacks.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    Joshi, Sneh; Kar, Sarat C.

    2017-02-01

    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.

  17. Ancient Analogs of ENSO-Like Moisture Anomaly Patterns Across North America

    Science.gov (United States)

    Stahle, D. W.; Burnette, D. J.; Cook, E. R.

    2014-12-01

    A tripole-like structure tends to develop in the latitudinal distribution of seasonal drought and wetness across North America during El Nino and La Nina extremes. Composite maps of instrumental and tree-ring reconstructed moisture indices during El Nino extremes nearly mirror the teleconnected moisture patterns during La Nina extremes, but the signs of the regional anomalies are reversed. During El Nino events wetness tends to prevail over the southwestern U.S. and northern Mexico, simultaneously with drought over Central America and the Pacific Northwest. Map congruence analysis was used to measure the similarity between the composite moisture anomaly map during 10 El Nino extremes and the continent-wide pattern of tree-ring reconstructed moisture during each year from 1400 to 2005. Map congruence was also computed using the composite moisture anomalies during La Nina extremes as the target (ENSO extremes defined using the extended Multivariate ENSO Index). The two congruence time series (El Nino vs La Nina-like) are far from the perfect inverse of one another (r = -0.36; p < 0.001; 1400-1979), but sub-decadal smoothing reveals interesting episodes of continental scale structure in the moisture field that may have arisen from multi-year cool and warm ENSO extremes over the past 600-years.

  18. A global analysis of ENSO synchrony: The oceans' biological response to physical forcing

    Science.gov (United States)

    Messié, Monique; Chavez, Francisco P.

    2012-09-01

    A global-scale Empirical Orthogonal Function (EOF) analysis of physical (sea surface temperatures, sea level height anomalies, atmospheric sea level pressure, photosynthetically active radiation, zonal surface currents and wind-driven upwelling velocities) and biological (surface chlorophyll concentrations and primary production) variables shows synchronous variations from 1993 to 2010 in the first mode of variability associated with El Niño Southern Oscillation (ENSO). The first EOF of vertical temperature structure along the equatorial Pacific shows identical temporal patterns. The ENSO-driven biological changes are explained both qualitatively and quantitatively from a subset of the physical variables. During the strong 1997-1998 El Niño a global new production decrease of ˜0.6-0.9 PgC yr-1 is estimated from changes in the depth of the nutricline and wind-driven upwelling. This is consistent with the 3.0 PgC yr-1 decrease in global primary production observed by satellite remote sensing. A simple two-layer model of chlorophyll and primary production driven by changes in nitrate and light reproduces the patterns and magnitude of changes observed by satellite. Changes in the depth of the nutricline are found to be the primary driver of the biological anomalies. The ENSO mode of zonal currents in the equatorial Pacific shows that horizontal advection is responsible for changes in chlorophyll in the central Pacific not explained by the two-layer model.

  19. Does stratosphereic sudden warming occur more frequently during ENSO winters than during normal winters?

    Science.gov (United States)

    Son, Seok-Woo; Song, Kanghyun

    2017-04-01

    Stratospheric sudden warming (SSW) events exhibit pronounced interannual variability. Based on WMO definition of SSW, it has been suggested that SSW events occur more preferably during El Niño-Southern Oscillation (ENSO) winters (both El Niño and La Niña winters) than during normal winters. This nonlinear relationship is re-examined here by considering six different definitions of SSW. For all definitions, SSW events are detected more frequently during El Niño winters than during normal winters, in consistent with an enhanced planetary-scale wave activity. However, a systematic relationship is not found during La Niña winters. While two SSW definitions, including WMO definition, show an increased SSW frequency during La Niña winters, other definitions show no change or even a reduced SSW frequency. This result is insensitive to the choice of reanalysis datasets and ENSO index, indicating that the reported ENSO-SSW relationship is not robust but dependent on the details of SSW definition.

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

    Science.gov (United States)

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

    2014-01-01

    El Nino Southern Oscillation (ENSO) is an important driver of interannual variations in climate and ecosystem productivity in tropical regions. However, detailed information about this important phenomenon of the Indian Ocean is scarce. Consequently, the objective of this study is to improve understanding of the impact of warm event El Nino and cool event La Nina on annual tuna landings from the Indian Ocean from 1980 to 2010. In this study, maximum tuna landings were recorded during a weak El Nino year (1456054 t in 2006) and during a weak La Nina year (1243562 t in 2000), although the lowest tuna catch was followed during the strong El Nino year (1204119 t in 2009) and during a strong La Nina year (706546 t in 1988). Validation of predicted tuna landings and SST were showing a significant positive correlation (p Nino years; landings in Indian Ocean tend to be optimum SST 25 to 26°C in ENSO event. Our results confirm the ENSO impact on climate, tuna abundance and production in the Indian Ocean. However, among the oceanic variables SST explained the highest deviance in generalized additive models and therefore considered the best habitat predictor in the Indian Ocean followed by sea level pressure and Winds (U, V, W).

  1. On the relationship between the QBO/ENSO and atmospheric temperature using COSMIC radio occultation data

    Science.gov (United States)

    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.

  2. Análise da demanda por defensivos pela fruticultura brasileira 1997-2000 Fruit tree demand for chemicals 1997-2000

    Directory of Open Access Journals (Sweden)

    Evaristo Marzabal Neves

    2002-12-01

    Full Text Available Este estudo estima a demanda relativa por defensivos pela fruticultura brasileira, principalmente para banana, laranja, maçã, melão e uva, por dispêndio total e volume de princípio ativo por hectare, para o período de 1997 a 2000. Efetua, também, uma análise comparativa destas demandas com as obtidas para as principais culturas brasileiras (soja, milho, cana-de-açúcar e café, as quais são predominantes em termos de área cultivada e dominantes, em termos absolutos, nos dispêndios totais e volumes demandados por princípio ativo em defensivos no Brasil. Determina, ainda, em termos absolutos, a participação da fruticultura nos dispêndios totais e no consumo de princípio ativo, especialmente em acaricidas e fungicidas. Conclui sobre a importância da estimativa da demanda relativa para a fruticultura, que supera significativamente as principais culturas comerciais do País, fornecendo indicadores para o comportamento de mercado para as diferentes classes de defensivos pela fruticultura brasileira.This study estimates for the Brazilian fruit trees, mainly banana, orange, apple, melon and grape, the relative demand for chemicals, considering total expenses and quantity demanded for active principle per hectare, from 1997 to 2000. It is also established a comparative analysis among this demand with ones made by the main Brazilian crops (soybean, maize, sugar cane and coffee, that are predominating in terms of grown area and dominating, in absolute terms, of chemicals total expenses and consume of active principle volume in Brazil. Yet, determines, in absolute terms, the importance of fruit trees in chemicals total expenses and active principle consume, especially acaricides and fungicides. It concludes, about the importance of estimated relative demand for fruit trees, that it is higher than the ones by the mainly commercial crops in the country, offering indicators for the demand and market behavior to chemicals different classes by the Brazilian fruit trees.

  3. Mid to late Holocene Leeuwin Current variability offshore southern Australia linked to ENSO state changes

    Science.gov (United States)

    Perner, Kerstin; Moros, Matthias; De Deckker, Patrick; Blanz, Thomas; Siegel, Herbert; Wacker, Lukas; Schneider, Ralph; Jansen, Eystein

    2015-04-01

    The El Niño-Southern Oscillation (ENSO), a key aspect of the Earth's climate, drives regional to global oceanic and climate changes on various time-scales. Differences in the temporal coverage of Holocene records for the more general state in El Niño frequency, however, restrict a comprehensive overview. Oceanic variability offshore southern Australia is linked to the Leeuwin Current (LC), an eastern boundary current, transporting tropical waters from the Indo Pacific Warm Pool region towards higher latitudes. Instrumental data, spanning the last few decades, document that ENSO modulates LC variability. Here we present new, well-dated time series from two marine sediment cores (MD03-2611 and SS0206-GC 15)of past LC variability, based on alkenone-derived sea-surface temperatures (SST) and planktonic foraminifera offshore southern Australia, an area affected by recent El Niño and La Niña events. Our reconstructions of ENSO-state changes cover the last 7,400 years. With transition into the mid Holocene [dates], we find clear evidence that oceanic conditions prevailed under the dominant influence of a persistent La Niña mode. A strong LC produces a stratified water column and establishes a permanent thermocline as seen in the high abundance of the 'tropical fauna' (Globoturborotalita rubescens, Globoturborotalita tenella and Globigerinella sacculifer (including G. trilobus)) and maximum SST offshore southern Australia. During this La Niña-state dominated period, we record at c. 5000 years BP the first short period of a strong El Niño-like-state, by a pronounced drop in abundance of the subtropical species Globigerinoides ruber and a reduced SST gradient between the two core sites. The Late Holocene (from 3,500 years BP onwards) period is characterized by centennial to millennial scale variability in the LC strength, which is accompanied by an overall decrease of SSTs offshore southern Australia. We link this LC variability to Late Holocene centennial

  4. Reconstructing the Paleo ENSO records from tropical and subtropical ice cores

    Directory of Open Access Journals (Sweden)

    1993-01-01

    acumula tanto en los glaciares polares como alpinos (alta elevación producen laminaciones que permiten un fechamiento preciso de estas secuencias estratigráficas. Este artículo examina la variabilidad climática interanual en los registros de los núcleos de hielo del Quelccaya (1 sobre los últimos 150 años, en que existe una cantidad limitada de datos documentales con los que se pueden evaluar los datos de los núcleos de hielo y (2 el registro más largo, que cubre los últimos 1,500 años, en que la evaluación independiente se torna más difícil. Los registros de precipitación del Quelccaya, derivados de los núcleos de hielo, se comparan con la historia temprana del hombre en Sudamérica. Existe evidencia arqueológica que, cuando se compara con el registro del balance neto del Quelccaya en los 1,500 años, sugiere que los períodos de florecimiento de culturas de altura aparecen durante períodos en que las montañas fueron más húmedas que el promedio, y que las culturas costeras florecieron cuando las montañas fueron más secas que lo normal. Estos datos sugieren que pueden existir nexos océano/atmósfera de más largo período que producen respuestas de precipitación «tipo El Niño» de largo plazo. Interannual variability in climate is a major feature of the climate system, particularly in subtropical and tropical regions. It is essential to know if the interannual variability signature in the climate record is affected by a change in the mean state of the climate system. This goal can be met only by analyzing long records of interannual climate variability throughout intervals in the past when climate was different from today (e.g., Little Ice Age, Medieval Warm, last glaciation. This task is especially important as man may be inadvertently altering the mean state of global climate. With the exception of the annual cycle, ENSO is the dominant global climate signal on time scales of a few months to a few years. It is associated with major

  5. The Role of Intraseasonal Atmosphere Variability in ENSO Generation in Future Climate

    Science.gov (United States)

    Matveeva, Tatiana; Gushchina, Daria

    2016-04-01

    The intraseasonal tropical variability (ITV) is a general component of the atmospheric circulation in the tropics, particularly, it plays the main role in the formation of El Niño-Southern Oscillation (ENSO). The ENSO is the general mode of interannual climate variability. It appears in two kinds of large-scale sea surface temperature (SST) anomalies in the equatorial Pacific Ocean: East Pacific (EP) El Niño (named also Canonical El Niño) characterized by anomalous warming in the eastern Pacific, and Central Pacific (CP) El Niño (so-called El Niño Modoki) with maximum SST anomalous in the center of the Pacific Ocean [Kao and Yu, 2009; Kug et al., 2009]. The ability of CMIP5 coupled ocean-atmosphere general circulation models (CGCMs) to simulate two flavors of El Niño is estimated using Empirical orthogonal functions (EOFs) analysis of SST anomalies fields (Experiment Pi-Control), in this study we assessed 20 CGCMs. Spatial distribution of the first mode (EOF 1) represents SST anomalies field structure of EP El Niño and the second mode (EOF 2) is analogue of SST anomalies spatial distribution during CP El Niño [Ashok et al., 2007]. To identify intensity and frequency ENSO we also considered both NINO3 and NINO4 SST indices. NINO3 and NINO4 regions have been defined based on EOF-analysis (EOF 1 and EOF 2, resp.). It's shown that only several models were able to simulate two kinds of ENSO. Then we tested chosen CGCMs' ability to correct simulation of ITV components. For identification ITV components in the tropical troposphere we applied double space-time Fourier analysis to zonal wind at 850 hPa (U850), following the method of WK99 [Wheler and Kiladis, 1999]. Then we defined wave activity and analyzed spatial pattern of the waves and relationship between the waves and ENSO. Besides, it is shown that the ITV characteristics are altered during different flavors of ENSO [Gushchina and Dewitte, 2012]. In [Yeh et al., 2009] it has been established that the ratio

  6. Influences of Seaway and CO2 Changes during the Pliocene on Tropical Pacific Sector Climate in the Kiel Climate Model: Mean Sate, Annual Cycle, ENSO, and their Interactions

    Science.gov (United States)

    Song, Zhaoyang; Park, Wonsun; Latif, Mojib; Krebs-Kanzow, Uta; Schneider, Birgit

    2016-04-01

    The opening and closing of seaways can have a profound impact on global and regional climate. The El Niño/Southern Oscillation (ENSO) is the leading mode of tropical Pacific interannual variability in the present-day climate. Available proxy evidence suggests that ENSO also existed during past climates, for example during the Pliocene extending from about 5.3 million to about 2.6 million years BP. We investigate the influences of the Panama Seaway closing and Indonesian Passages narrowing, and of carbon dioxide (CO2) changes during the Pliocene on tropical Pacific mean climate, annual cycle and ENSO. The Kiel Climate Model (KCM) is employed to study the influences of the changing geometry and CO2-concentration. We find that ENSO is sensitive to the closing of the Panama Seaway, with ENSO amplitude being reduced by about 15% - 20%. The narrowing of the Indonesian Passages marginally enhances ENSO strength by about 6%. ENSO period changes are modest in all experiments. Annual cycle changes are prominent. The annual cycle in the eastern tropical Pacific intensifies by about 50% in response to the closing of the Panama Seaway, which is largely attributed to the strengthening of meridional wind stress. Bjerknes stability index (BSI) analysis suggests that the growth rate of the ENSO mode does not significantly change due to compensating changes in ocean-atmosphere feedbacks, especially dynamical damping and thermocline feedback. A robust inverse relationship is found between ENSO strength and the strength of the annual cycle.

  7. Influence of seaway changes during the Pliocene on tropical Pacific climate in the Kiel climate model: mean state, annual cycle, ENSO, and their interactions

    Science.gov (United States)

    Song, Zhaoyang; Latif, Mojib; Park, Wonsun; Krebs-Kanzow, Uta; Schneider, Birgit

    2016-08-01

    The El Niño/Southern Oscillation (ENSO) is the leading mode of tropical Pacific interannual variability in the present-day climate. Available proxy evidence suggests that ENSO also existed during past climates, for example during the Pliocene extending from about 5.3 million to about 2.6 million years BP. Here we investigate the influences of the Panama Seaway closing and Indonesian Passages narrowing, and also of atmospheric carbon dioxide (CO2) on the tropical Pacific mean climate and annual cycle, and their combined impact on ENSO during the Pliocene. To this end the Kiel Climate Model), a global climate model, is employed to study the influences of the changing geometry and CO2-concentration. We find that ENSO is sensitive to the closing of the Panama Seaway, with ENSO amplitude being reduced by about 15-20 %. The narrowing of the Indonesian Passages enhances ENSO strength but only by about 6 %. ENSO period changes are modest and the spectral ENSO peak stays rather broad. Annual cycle changes are more prominent. An intensification of the annual cycle by about 50 % is simulated in response to the closing of the Panama Seaway, which is largely attributed to the strengthening of meridional wind stress. In comparison to the closing of the Panama Seaway, the narrowing of the Indonesian Passages only drives relatively weak changes in the annual cycle. A robust relationship is found such that ENSO amplitude strengthens when the annual cycle amplitude weakens.

  8. Machine Learning Methods for the Understanding and Prediction of Climate Systems: Tropical Pacific Ocean Thermocline and ENSO events

    Science.gov (United States)

    Lima, C. H.; Lall, U.

    2012-12-01

    In this work we explore recently developed methods from the machine learning community for dimensionality reduction and model selection of very large datasets. We apply the nonlinear maximum variance unfolding (MVU) method to find a short dimensional space for the thermocline of the Tropical Pacific Ocean as indicated by the ocean depth of the 200C isotherm from the NOAA/NCEP GODAS dataset. The leading modes are then used as covariates in an ENSO forecast model based on LASSO regression, where parameters are shrunk in order to find the best subset of predictors. A comparison with Principal Component Analysis (PCA) reveals that MVU is able to reduce the thermocline data from 21009 dimensions to three main components that collectively explain 77% of the system variance, whereas the first three PCs respond to 47% of the variance only. The series of the first three leading MVU and PCA based modes and their associated spatial patterns show also different features, including an enhanced monotonic upward trend in the first MVU mode that is hardly detected in the correspondent first PCA mode. Correlation analysis between the MVU components and the NINO3 index shows that each of the modes has peak correlations across different lag times, with statistically significant correlation coefficients up to two years. After combining the three MVU components across several lag times, a forecast model for NINO3 based on LASSO regression was built and tested using the ten-fold cross-validation method. Based on metrics such as the RMSE and correlation scores, the results show appreciable skills for lead times that go beyond ten months, particularly for the December NINO3, which is responsible for several floods and droughts across the globe.; Spatial signature of the first MVU mode. ; First MVU series featuring the upward trend.

  9. 近年来对ENSO的研究进展综述%Review of ENSO Research in Recent Years

    Institute of Scientific and Technical Information of China (English)

    朱海彬

    2014-01-01

    The El Niño Southern Oscillation( ENSO)has been internationally concerned as a global disaster. Based on the research achievements about ENSO at home and abroad in recent years,the article analyzed the lat-est research progress of ENSO in the fields of Atmospheric Physics,Disaster Geography,Medicine and Sociology, though demonstrating the brief history and generating mechanism of ENSO,and introduced several research meth-ods recognized internationally. At last,future work on ENSO were discussed.%ENSO作为一种全球性的灾害事件,一直受到各国科学家的普遍关注。文章在参阅了近年来国内外对ENSO研究的基础上,通过阐述其研究简史和生成机理,探讨了ENSO在大气物理学、灾害地理学、医学和社会学等领域的最新研究进展,并介绍了几种国际认可的最新研究方法。最后对ENSO在将来的研究进行了展望。

  10. Relating large-scale climate variability to local species abundance: ENSO forcing and shrimp in Breton Sound, Louisiana, USA

    Science.gov (United States)

    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.

  11. ENSO Variability during the Little Ice Age from the Perspective of a Long Coral Record from the Western Pacific Warm Pool

    Science.gov (United States)

    Hereid, K. A.; Quinn, T. M.; Taylor, F. W.; Shen, C.; Banner, J. L.

    2010-12-01

    The Little Ice Age (LIA, ~1400-1700 CE) is a period of cool temperatures generally best expressed in records from Northern Hemisphere high latitudes, but which is variably expressed in the tropics. In particular, the nature of short-term tropical variability, such as the El Niño-Southern Oscillation (ENSO), is obscured by contradictory evidence. Although central Pacific corals and some South American sedimentary records indicate an increase in ENSO activity during the LIA, tree ring records from ENSO teleconnected regions are highly variable, and lake records from the Galápagos Islands and Ecuador show reduced ENSO activity in the LIA. However, the differing resolutions, physical means for recording ENSO events, and dynamical connections to the ENSO system complicate efforts to form a coherent interpretation of these conflicting proxy records. This study addresses the need for additional LIA proxy records that resolve individual ENSO events, record climate parameters directly impacted by ENSO, and are located in core ENSO-affected regions. We investigate the nature of ENSO during the LIA by generating high-resolution climate time series from corals from Misima Island, Papua New Guinea (10.6°S, 152.8°E). Misima Island is located at the southern edge of the Western Pacific Warm Pool (WPWP), an important heat and moisture source for the climate system that is highly sensitive to ENSO events. Our monthly resolved fossil coral record of δ18O and Sr/Ca variations spans the interval from ~1414-1645 CE, which we compare with similar variations in a near modern coral record (~1915-1945 CE) from this location. The fossil Misima coral δ18O record, bandpass filtered to highlight ENSO frequencies, contains multidecadal variations in ENSO amplitude, consistent with what is observed in the modern instrumental record of ENSO variability. However, the standard deviation of the fossil δ18O record is significantly reduced relative to that observed in the modern Misima coral

  12. Decoupling of ENSO and fires in insular Southeast Asia from 2001-2010

    Science.gov (United States)

    Fuller, D. O.

    2010-12-01

    Eight-day active fire time series (2001-May 2010) in western, insular Southeast Asia were analyzed to evaluate whether the relationship between the El Niño Southern Oscillation (ENSO) and fires has changed through time consistent with the hypothesis that fires and climate forcings are becoming decoupled as deforestation has continued in the region. The study period was marked by three major fire peaks in 2002, 2006 and 2009-2010 coinciding with three El Niño events. Maximum cross correlation coefficients (MCC) between lagged ENSO sea-surface temperature indices and fire counts (raw and seasonally detrended) were modest (≤ 0.50) and showed a general decrease for most land cover types from 2001-2006 to 2007-May 2010. A notable exception was peat swamp forest where the MCC increased slightly between the two periods for all indices except Niño3. A measure of annual seasonality also revealed that fires in peat swamp forest, lowland forest and secondary formations from 2007-May 2010 were more seasonal than fires during 2001-2006. Overall, the evidence suggests that fires and ENSO are becoming decoupled in the region and that forest types such as peat swamp and lowland forest may be experiencing more seasonal fires. We hypothesize that the decoupling occurs because of a stabilization in land use and establishment of permanent crops. We thus expect that fires will diminish in these areas as permanent plantations (primarily oil palm) are established and incentives to protect valuable crops outweigh incentives to convert land for cultivation.

  13. Influence of ENSO-Related Wind Stress Variability on the Coastal Upwelling off Peru

    Science.gov (United States)

    Huaringa, E. E.; Campos, E. J.; Lentini, C. A.

    2005-05-01

    The Eastern Tropical and Subtropical Pacific, particularly the coastal region off the western South America, is negatively affected by the El Niño-Southern Oscillation (ENSO) events. The rise of coastal sea temperatures due to the weakening of coastal upwelling causes the reduction of important fish stocks and other coastal resources of economical significance, especially the sardine and anchovy populations. Here, variability in the intensity of upwelling along the Peruvian coast is studied using monthly means of the ERS-1 and ERS-2 scatterometer wind stress. In the study area, the Trade Winds blow predominantly parallel to the coast, making the upwelling system highly sensitive to variability in the intensity of the wind stress. On its turn, the wind stress intensity is expected to suffer strong variation during ENSO periods. In our ongoing work we try to understand the relationship between coastal upwelling and different ENSO events in the 1991-2000 decade. In this period, two warm events where observed, the relatively weaker 1991-1994 and the stronger 97-98 El Niños. In both cases we found that in the region from 12°S to 3°S, the intensity of alongshore wind stress is reduced considerably, with the coastal upwelled waters being replaced by warmer waters. On the other hand, in the region between 12°S and 19°S the coastal upwelling maintains its intensity because only the cross-shore component of the wind stress was reduced. With respect to the two cold events, the 1996-1997 and the 1998-2000 La Niñas, the intensity of the alongshore windstress was higher than the climatological values. This resulted in more intense upwelling in the entire region.

  14. Empirical Hydrologic Predictions for Southwestern Poland and Their Relation to Enso Teleconnections

    Science.gov (United States)

    Niedzielski, Tomasz

    2010-01-01

    Recent investigations confirm meaningful but weak teleconnections between the El Niño/Southern Oscillation (ENSO) and hydrology in some European regions. In particular, this finding holds for Polish riverflows in winter and early spring as inferred from integrating numerous geodetic, geophysical and hydrologic time series. The purpose of this study is to examine whether such remote teleconnections may have an influence on hydrologic forecasting. The daily discharge time series from southwestern (SW) Poland spanning the time interval from 1971 to 2006 are examined. A few winter and spring peak flows are considered and the issue of their predictability using empirical forecasting is addressed. Following satisfactory prediction performance reported elsewhere, the multivariate autoregressive method is used and its modification based on the finite impulse response filtering is proposed. The initial phases of peak flows are rather acceptably forecasted but the accuracy of predictions in the vicinity of local maxima of the hydrographs is poorer. It has been hypothesized that ENSO signal slightly influences the predictability of winter and early spring floods in SW Poland. The predictions of flood wave maxima are the most accurate for floods preceded by normal states, less accurate for peak flows after La Niño episodes and highly inaccurate for peak flows preceded by El Niño events. Such a finding can be interpreted in terms of intermittency. Before peak flows preceded by El Niño there are temporarily persistent low flows followed by a consecutive melting leading to a considerable intermittency and hence to difficulties in forecasting. Before peak flows preceded by La Niño episodes there exist ENSO-related positive temperature and precipitation anomalies in SW Poland causing lower, but still considerable, intermittency and thus better, but not entirely correct, predictability of hydrologic time series.

  15. Effects of Changes in ENSO on Seasonal Mean Temperature and Rainfall in Nigeria

    Directory of Open Access Journals (Sweden)

    Opeyemi R. Salau

    2016-01-01

    Full Text Available This study investigates the effects of El Niño/Southern Oscillation (ENSO on temperature and rainfall in Nigeria. The persistent rise in population with more demands for rainfall and water supply in Nigeria requires a better understanding of the impacts of ENSO (La Niña, El Niño induced changes on the precipitation patterns under future climate conditions. Thus, we compared the sea surface temperature (SST from the ENSO regions of the Tropical Pacific Ocean (Niño 3 (150°W–90°W, 5°S–5°N and Niño 4 (160°E–150°W, 5°S–5°N with the observed temperature from Nigeria and the temperature is further compared with the associated rainfall. The results show that an increase or decrease in the Niño 3 and Niño 4 SST is accompanied by a corresponding change in the temperature over Nigeria; however, there is better agreement with the Niño 3 SST compared to the Niño 4 SST. The investigation suggests that a slight northward (southward shift in the mean position of Intertropical Convergence Zone (ITCZ during a La Niña (El Niño event is followed by a reduction (increase in the average temperature within Nigeria while the mean precipitation rises (reduces over the country. These results could aid weather prediction which might improve the economy as well as save lives and property during climate-related hazards like drought, forest fires and floods.

  16. Rocky Mountain hydroclimate: Holocene variability and the role of insolation, ENSO, and the North American Monsoon

    Science.gov (United States)

    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.

  17. Indian Ocean Variability and Its Association with ENSO in a Global Coupled Model.

    Science.gov (United States)

    Zhong, Aihong; Hendon, Harry H.; Alves, Oscar

    2005-09-01

    The evolution of the Indian Ocean during El Niño-Southern Oscillation is investigated in a 100-yr integration of an Australian Bureau of Meteorology coupled seasonal forecast model. During El Niño, easterly anomalies are induced across the eastern equatorial Indian Ocean. These act to suppress the equatorial thermocline to the west and elevate it to the east and initially cool (warm) the sea surface temperature (SST) in the east (west). Subsequently, the entire Indian Ocean basin warms, mainly in response to the reduced latent heat flux and enhanced shortwave radiation that is associated with suppressed rainfall. This evolution can be partially explained by the excitation of an intrinsic coupled mode that involves a feedback between anomalous equatorial easterlies and zonal gradients in SST and rainfall. This positive feedback develops in the boreal summer and autumn seasons when the mean thermocline is shallow in the eastern equatorial Indian Ocean in response to trade southeasterlies. This positive feedback diminishes once the climatological surface winds become westerly at the onset of the Australian summer monsoon.ENSO is the leading mechanism that excites this coupled mode, but not all ENSO events are efficient at exciting it. During the typical El Niño (La Niña) event, easterly (westerly) anomalies are not induced until after boreal autumn, which is too late in the annual cycle to instigate strong dynamical coupling. Only those ENSO events that develop early (i.e., before boreal summer) instigate a strong coupled response in the Indian Ocean. The coupled mode can also be initiated in early boreal summer by an equatorward shift of the subtropical ridge in the southern Indian Ocean, which stems from uncoupled extratropical variability.

  18. Influence of ENSO and PDO on mountain glaciers in the outer tropics: case studies in Bolivia

    Science.gov (United States)

    Veettil, Bijeesh Kozhikkodan; Bremer, Ulisses Franz; de Souza, Sergio Florêncio; Maier, Éder Leandro Bayer; Simões, Jefferson Cardia

    2016-08-01

    This paper emphasize on the observational investigation of an ice-covered volcano and two glaciated mountains in the Central Andes from 1984 to 2011. Annual snowlines of the Nevado Sajama in the Cordillera Occidental and the Nevado Cololo and the Nevado Huanacuni in the Cordillera Apolobamba in Bolivia were calculated using remote sensing data. Landsat TM, Landsat ETM+, and LISS-III images taken during the end of dry season were used in this study. Changes in the highest annual snowline during May-September is used an indirect measure of the changes in the equilibrium line altitude of the glaciers in the outer tropics. We tried to understand the combined influence of the El Niño-Southern Oscillation and the Pacific Decadal Oscillation on the variations in the annual snowline altitude of the selected glaciers. Meteorological data in the form of gridded datasets were used for calculating the anomalies in precipitation and temperature during the study period. It is found that the glaciated areas were fluctuated with the occurrence of warm and cold phase of ENSO but the magnitude of the influence of ENSO is observed to be controlled by the phase changes of PDO. Snowline of the Nevado Sajama fluctuated heavily when cold and warm phases of ENSO occur during the cold and warm regimes of PDO, respectively. Nevado Cololo and Nevado Huanacuni are showing a continuous retreating trend during the same period. This clearly indicates that the changes in the Pacific SST patterns have more influence on glaciers in the Cordillera Occidental compared with those in the Cordillera Oriental of the Bolivian Andes.

  19. ENSO and sandy beach macrobenthos of the tropical East Pacific: some speculations

    Directory of Open Access Journals (Sweden)

    T. Vanagt

    2006-01-01

    Full Text Available The influence of the ENSO cycle on marine fauna and flora has only recently been given the attention it deserves. The very strong 1997–1998 El Niño and its obvious effects on marine biota was a key point in ENSO research, but unfortunately few quantitative data about the 1997–1998 El Niño itself are available. To gather information about the effect of ENSO on the macrobenthos, we performed a bi-weekly transect monitoring on an Ecuadorian sandy beach in 2000–2001, during the strong La Niña following the 1997–1998 El Niño, and in the normal period of 2002–2004. In this paper, intertidal macrofaunal densities at higher taxonomic level are used to compare a La Niña phase with the 'normal' situation. The few existing documents about El Niño and sandy beach macrobenthos, and scattered data from previous and current research, were used to complete the picture. Total macrobenthos densities were 300% lower during the La Niña phase compared with equal months in the normal phase. Especially Crustacea and Mollusca showed a marked increase in densities towards the normal situation (94% and 341% respectively. Polychaeta and Echinodermata, however, showed higher densities during the La Niña phase (22% and 73% respectively. Two possible explanations are proposed. (1 Low densities during the La Niña could be due to the very strong preceding El Niño, suggesting the populations were still recovering. This hypothesis is supported by previous work done in the south of Peru. This is, however, a cold water system, compared to the Ecuadorian warm water system. (2 The second hypothesis states that a La Niña will have a very severe impact on the intertidal macrofauna of a warm water system like the Ecuadorian coast.

  20. Controls of seasonal ENSO phase locking in the Kiel Climate Model

    Science.gov (United States)

    Wengel, Christian; Latif, Mojib; Park, Wonsun; Harlass, Jan

    2016-04-01

    The El Niño/Southern Oscillation (ENSO) is characterized by a seasonal phase locking, with strongest SST anomalies in the eastern and central equatorial Pacific during boreal winter and weakest anomalies during boreal spring. Coupled general circulation models (CGCMs) tend to have strong difficulties in capturing the seasonal phase locking of ENSO. In this study, the Kiel Climate Model is used to identify the key processes that determine the seasonal phase locking in that model. An analysis based on the Bjerknes Stability Index reveals that the zonal advection feedback, the Ekman feedback and the thermocline feedback are strongest towards the end of the calendar year and can thus account for the variability maximum in December/January. Despite also being relatively strong in boreal spring, these feedbacks are damped by air-sea heat fluxes and mean ocean currents, which are strongest at that time of the year. Our findings compare well with those obtained from observations. It is further shown that insufficient simulation of the seasonal phase locking can be attributed to a wrong representation of the Bjerknes feedback. That includes weaker zonal advection, Ekman and thermocline feedback towards the end of the calendar year, which reduces variability in boreal winter, and a weaker air-sea heat flux damping during the beginning of the year. This smaller damping can not balance the relatively strong positive feedback processes during boreal spring and, consequently, contributes to a spurious increased variability in boreal spring/summer. Finally, increasing the model resolution of the atmospheric component of the KCM, horizontally and vertically, generally reduces model bias but does not necessarily improve simulation of seasonal ENSO phase locking. Tuning of model parameters is an alternative option by which a realistic phase locking can be achieved at coarse resolution.

  1. Massive bleaching of coral reefs induced by the 2010 ENSO, Puerto Cabello, Venezuela.

    Science.gov (United States)

    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.

  2. Southern Westerly Winds submit to the ENSO regime: A multiproxy paleohydrology record from Lake Dobson, Tasmania

    Science.gov (United States)

    Rees, Andrew B. H.; Cwynar, Les C.; Fletcher, Michael-Shawn

    2015-10-01

    The El Niño-Southern Oscillation (ENSO) and Southern Westerly Winds (SWW) profoundly influence synoptic-scale climate in the Southern Hemisphere. Although many studies have invoked either phenomenon to explain trends in proxy data, few have demonstrated the transition from a climate dominated by SWW flow to one controlled by El Niño activity, which is postulated to have occurred after 5 cal ka BP in the mid-latitudes of the Southern Hemisphere. Tasmania, southeast Australia, is ideally situated to detect changes in both of these climatic controls. Currently, El Niño and La Niña events result in drier and wetter conditions island-wide, respectively, with the greatest impact in the north. Further, Tasmania houses north-south trending mountain ranges near its western coast. As a result, areas west of the mountains exhibit a positive correlation between SWW flow and precipitation, while eastern regions possess either no or a negative relationship. Here, we present data from chironomid remains, charcoal, and geochemical proxies to investigate the paleohydrological history of Lake Dobson, a site located in Mount Field National Park, Tasmania. The proxies revealed three broad periods: (1) an early Holocene (11.5-8.3 cal kyr BP) characterised by generally high rainfall, the occurrence of irregular fires, and elevated charcoal influx at 11.4 and 10.2 cal ka BP - conditions compatible with attenuated SWW flow over the site; (2) an ambiguous mid-Holocene (8.3-5 cal kyr BP) that marks the transition from a SWW- to ENSO-dominated climate; and (3) a relatively dry and stable late Holocene (5 cal kyr BP to present) that is consistent with the onset of a climate controlled by ENSO activity (i.e., characterised by a more mean El Niño climate state). The proxy record of Lake Dobson highlights the teleconnections between the equatorial Pacific and southern Australasia.

  3. Interannual variability of zonal currents in the equatorial Indian Ocean: respective control of IOD and ENSO

    Science.gov (United States)

    Sachidanandan, Chinnu; Lengaigne, Matthieu; Muraleedharan, Pillathu Moolayil; Mathew, Basil

    2017-07-01

    The observational record is too short to confidently differentiate the relative contributions of Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) on the interannual variability of the equatorial current system in the Indian Ocean because of the strong tendency of these two modes to co-occur. In this study, we analyse a five-decade simulation from an ocean general circulation model forced to describe the main interannual variations of surface and subsurface equatorial zonal currents in the Indian Ocean. This simulation is first shown to accurately capture the surface and subsurface zonal current variations in the equatorial region derived from the available observations. Through an EOF analysis on the model outputs, our results further reveals two main modes of equatorial current interannual variability: a dominant mode with largest amplitude in fall largely describing the variability of the fall Wyrtki jet intensity followed a few months later by a secondary mode maximum in winter largely describing the interannual variability of the subsurface currents in that season. Our analysis further confirms that the IOD is largely responsible for the interannual modulation of fall Wyrtki jet intensity by modulating the equatorial wind intensity during that season. The IOD is also responsible for strong subsurface current variations until December, induced by the delayed effect of the IOD wind signal onto the equatorial thermocline tilt. The equatorial current system response to ENSO is weaker and delayed compared to that of the IOD. The remote and delayed impact of ENSO in the IO indeed induces equatorial wind variations in winter that modulate the winter surface current intensity and the spring equatorial undercurrent intensity through its delayed impact on the thermocline tilt.

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

    Science.gov (United States)

    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

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

    Science.gov (United States)

    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

  6. NONLINEAR ANALYSIS OF EQUATORIAL EASTERN PACIFIC AIR-SEA COUPLING OSCILLATION AND A LIMIT- CYCLE THEORY FOR ENSO CYCLE

    Institute of Scientific and Technical Information of China (English)

    黄思训; 项杰; 韩威

    2004-01-01

    The troposphere and ocean mixed layer were considered as two components of a dynamic system operated by solar radiation as the constant source of energy, where upon an air-sea coupling selfexited coupling oscillation model was based with the aid of a locally averaged thermodynamic climate model, resulting mathematically in a closed self-governed dynamic system, a so-called El Nino-Southern Oscillation (ENSO) system. With the limit cycle solution of the system. It is shown that the essential physics of the coupled system can be described by the ENSO system. Compared with the observations, the theoretical limit cycle orbit matches the observed phase loop qualitatively. The ENSO system provides a useful theoretical framework for study of interannual variation of the tropical climate system.

  7. Quantifying the Multivariate ENSO Index (MEI) coupling to CO2 concentration and to the length of day variations

    CERN Document Server

    Mazzarella, A; Scafetta, N

    2012-01-01

    The El Ni\\~no Southern Oscillation (ENSO) is the Earth's strongest climate fluctuation on inter-annual time-scales and has global impacts although originating in the tropical Pacific. Many point indices have been developed to describe ENSO but the Multivariate ENSO Index (MEI) is considered the most representative since it links six different meteorological parameters measured over the tropical Pacific. Extreme values of MEI are correlated to the extreme values of atmospheric CO2 concentration rate variations and negatively correlated to equivalent scale extreme values of the length of day (LOD) rate variation. We evaluate a first order conversion function between MEI and the other two indexes using their annual rate of variation. The quantification of the strength of the coupling herein evaluated provides a quantitative measure to test the accuracy of theoretical model predictions. Our results further confirm the idea that the major local and global Earth-atmosphere system mechanisms are significantly couple...

  8. Excessive Cold-tongue and Weak ENSO Asymmetry: Are These Two Common Biases in Climate Models Linked?

    Science.gov (United States)

    Sun, D. Z.

    2014-12-01

    Among the biases in the tropical Pacific that are common in the climate models, two stand out. One is the excessive cold-tongue in the mean state---the pool of the cold water that is normally in the eastern tropical Pacific extends too far to the west. The other is the underestimate of the asymmetry of El Nino-Southern Oscillation—the fact that El Nino and La Nina are more or less a mirror image of each other in the models while they are not so in the observations. Results from an analysis from CMIP5 models, forced ocean GCM experiments, as well as an analytical model are presented to suggest that these two common biases in our state-of-the-art models are linked. Specifically, an excessive cold-tongue in the mean climatological state makes the ENSO system more stable and thus leads to a more symmetric ENSO, while a more symmetric ENSO in turn results in less nonlinear heating from the ENSO events to the cental equatorial Pacific which in turn contributes to the development of an excessive cold-tongue. The finding underscores that errors in the mean state and ENSO tend to reinforce each other and thus explains why it has been difficult to simulate the tropical Pacific climate. Further comparison with observations suggests that these two biases are the symptoms of a single structural inadequacy in the models: a weak dynamical coupling between the atmosphere and ocean which puts the ENSO system in the models to a different dynamic regime than the obsereved. Measures that may help push the models closer to the observations are suggested.

  9. Role of the upper ocean structure in the response of ENSO-like SST variability to global warming

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Sang-Wook [Hanyang University, Department of Environmental Marine Science, Ansan (Korea); Dewitte, Boris [Laboratoire d' Etude en Geophysique et Oceanographie Spatiale, Toulouse (France); Yim, Bo Young; Noh, Yign [Yonsei University, Department of Atmospheric Sciences, Global Environmental Laboratory, Seoul (Korea)

    2010-08-15

    The response of El Nino and Southern Oscillation (ENSO)-like variability to global warming varies comparatively between the two different climate system models, i.e., the Meteorological Research Institute (MRI) and Geophysical Fluid Dynamics Laboratory (GFDL) Coupled General Circulation Models (CGCMs). Here, we examine the role of the simulated upper ocean temperature structure in the different sensitivities of the simulated ENSO variability in the models based on the different level of CO{sub 2} concentrations. In the MRI model, the sea surface temperature (SST) undergoes a rather drastic modification, namely a tendency toward a permanent El Nino-like state. This is associated with an enhanced stratification which results in greater ENSO amplitude for the MRI model. On the other hand, the ENSO simulated by GFDL model is hardly modified although the mean temperature in the near surface layer increases. In order to understand the associated mechanisms we carry out a vertical mode decomposition of the mean equatorial stratification and a simplified heat balance analysis using an intermediate tropical Pacific model tuned from the CGCM outputs. It is found that in the MRI model the increased stratification is associated with an enhancement of the zonal advective feedback and the non-linear advection. In the GFDL model, on the other hand, the thermocline variability and associated anomalous vertical advection are reduced in the eastern equatorial Pacific under global warming, which erodes the thermocline feedback and explains why the ENSO amplitude is reduced in a warmer climate in this model. It is suggested that change in stratification associated with global warming impacts the equatorial wave dynamics in a way that enhances the second baroclinic mode over the gravest one, which leads to the change in feedback processes in the CGCMs. Our results illustrate that the upper ocean vertical structure simulated in the CGCMs is a key parameter of the sensitivity of ENSO

  10. ENSO variability during MIS 11 (424-374 ka) from Tridacna gigas at Huon Peninsula, Papua New Guinea

    Science.gov (United States)

    Ayling, Bridget F.; Chappell, John; Gagan, Michael K.; McCulloch, Malcolm T.

    2015-12-01

    Marine Isotope Stage 11 (MIS 11) from ∼424,000 to 374,000 yrs ago included one of the longest and warmest interglacials of the last 800,000 yrs, and is a potential analogue for the Holocene due to the similarity of Earth's orbital configuration at this time. The question of how the El Niño-Southern Oscillation (ENSO) responds to warmer background climates remains unanswered and is critical to understand how the ENSO system will evolve under the influence of anthropogenic warming. In this study, we present a 35 yr-long, high-resolution record of MIS 11 climate variability in the Western Pacific Warm Pool (WPWP) based on coupled measurements of skeletal Mg/Ca and δ18O in giant Tridacna gigas clams from Huon Peninsula, Papua New Guinea. The δ18O of modern T. gigas from Huon Peninsula faithfully records sea surface temperature, salinity/rainfall and regional ENSO variability. The geochemical integrity of the MIS 11 T. gigas for recording paleo-ENSO events was established through trace element screening, detailed petrography and SEM analysis. The fossil T. gigas δ18O record indicates that ENSO was operating during a 35-yr window in MIS 11, but with fewer events of shorter duration compared to those experienced during the last 100 yrs. The suppressed ENSO variability in the MIS 11 T. gigas record corresponds with a reduction in the amplitude of the average annual cycle in δ18O values. Distinctive changes in local insolation seasonality, and T. gigas δ18O, brought about by changes in Earth's orbit, provide an additional geochronological constraint on the timing of reef growth at Huon Peninsula to around 402 ka during the MIS 11.3 sub-stage (∼424-395 ka).

  11. Impacts of ENSO on multi-scale variations in sediment discharge from the Pearl River to the South China Sea

    Science.gov (United States)

    Liu, Feng; Chen, Hui; Cai, Huayang; Luo, Xiangxin; Ou, Suying; Yang, Qingshu

    2017-09-01

    Sediment load delivered by rivers is an important terrestrial factor in the evolution and productivity of coastal ecosystems and coastal morphology. As the strongest interannual climate signal, the El Niño Southern Oscillation (ENSO) is closely related to variations in the hydrological cycle at global and regional scales. However, the influence of ENSO on temporal variations in sediment discharge is poorly understood. In this paper, we examine periodic variations in sediment discharge to the South China Sea from the Pearl River since the 1950s using wavelet transform analysis (WT). Furthermore, we apply cross wavelet spectrum (XWT) and wavelet coherence (WTC) to investigate the linkages between ENSO and sediment variability. The WT results revealed that periodic oscillations in sediment discharge in the Pearl River occurred annually (1 yr) before the 2000s, interannually (2-8 yr) from 1960-2002, and decadally (10-16 yr) from 1975-1995. These periodic variations in the sediment load series had common spectrum power with the water discharge and precipitation series, indicating an important climatic control. The XWT and WTC results revealed significant impacts of ENSO on precipitation, water discharge and sediment load at interannual time scales of 2-4.6 yr from 1960-2002 with a shift of patterns of ENSO on sediment variability after the 1970s. In addition, an in-phase relation between sediment discharge and ENSO at time scales of 10-16 yr from 1975-1995 was detected, indicating that variations at decadal scales could be related to other climatic teleconnections such as the Pacific Decadal Oscillation. Compared with the spectrum structures of periodic variations in precipitation and water discharge and their relationship with ENSO, there was a loss of energy in the sediment load at annual time scales after 2002 that can be attributed to dam construction in the river basin. Our study provides perspectives on the connections between ENSO and sediment variability at

  12. Southern Ocean SST Variability and Its Relationship with ENSO on Inter-Decadal Time Scales

    Institute of Scientific and Technical Information of China (English)

    YAN Li; DU Yan; ZHANG Lan

    2013-01-01

    Empirical orthogonal function (EOF) analysis reveals a co-variability of Sea surface temperatures (SSTs) in the Southern Hemisphere (0°-60°S).In the South Indian and Atlantic Oceans,there is a subtropical dipole pattern slanted in the southwest-northeast direction.In the South Pacific Ocean,a meridional tripole structure emerges,whose middle pole co-varies with the dipoles in the South Indian and Atlantic Oceans and is used in this study to track subtropical Pacific variability.The South Indian and Atlantic Ocean dipoles and the subtropical Pacific variability are phase-locked in austral summer.On the inter-decadal time scales,the dipoles in the South Indian and Atlantic Oceans weaken in amplitude after 1979/1980.No such weakening is found in the subtropical South Pacific Ocean.Interestingly,despite the reduced amplitude,the correlation of the Indian Ocean and Atlantic dipoles with El Ni(n)o and Southern Oscillation (ENSO) are enhanced after 1979/1980.The same increase in correlation is found for subtropical South Pacific variability after 1979/1980.These inter-decadal modulations imply that the Southem Hemisphere participates in part of the climate shift in the late 1970s.The correlation between Southern Hemisphere SST and ENSO reduces after 2000.

  13. Improved ENSO simulation in regional coupled GCM using regressive correction method

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A regressive correction method is presented with the primary goal of improving ENSO simulation in regional coupled GCM. It focuses on the correction of ocean-atmosphere exchanged fluxes. On the basis of numerical experiments and analysis, the method can be described as follows: first, driving the ocean model with heat and momentum flux computed from a long-term observation data set; the pro-duced SST is then applied to force the AGCM as its boundary condition; after that the AGCM’s simula-tion and the corresponding observation can be correlated by a linear regressive formula. Thus the re-gressive correction coefficients for the simulation with spatial and temporal variation could be obtained by linear fitting. Finally the coefficients are applied to redressing the variables used for the calculation of the exchanged air-sea flux in the coupled model when it starts integration. This method together with the anomaly coupling method is tested in a regional coupled model, which is composed of a global grid-point atmospheric general circulation model and a high-resolution tropical Pacific Ocean model. The comparison of the results shows that it is superior to the anomaly coupling both in reducing the coupled model ‘climate drift’ and in improving the ENSO simulation in the tropical Pacific Ocean.

  14. Rainfall Mechanisms for the Dominant Rainfall Mode over Zimbabwe Relative to ENSO and/or IODZM

    Directory of Open Access Journals (Sweden)

    Desmond Manatsa

    2012-01-01

    Full Text Available Zimbabwe’s homogeneous precipitation regions are investigated by means of principal component analysis (PCA with regard to the underlying processes related to ENSO and/or Indian Ocean Dipole zonal mode (IODZM. Station standardized precipitation index rather than direct rainfall values represent the data matrix used in the PCA. The results indicate that the country’s rainfall is highly homogeneous and is dominantly described by the first principal mode (PC1. This leading PC can be used to represent the major rainfall patterns affecting the country, both spatially and temporarily. The current practice of subdividing the country into the two seasonal rainfall forecast zones becomes irrelevant. Partial correlation analysis shows that PC1 is linked more to the IODZM than to the traditional ENSO which predominantly demonstrates insignificant association with PC1. The pure IODZM composite is linked to the most intense rainfall suppression mechanisms, while the pure El Niño composite is linked to rainfall enhancing mechanisms.

  15. Impact of ENSO on seasonal variations of Kelvin Waves and mixed Rossby-Gravity Waves

    Science.gov (United States)

    Rakhman, Saeful; Lubis, Sandro W.; Setiawan, Sonni

    2017-01-01

    Characteristics of atmospheric equatorial Kelvin waves and mixed Rossby-Gravity (MRG) waves as well as their relationship with tropical convective activity associated with El Niño-Southern Oscillation (ENSO) were analyzed. Kelvin waves and MRG waves were identified by using a Space-Time Spectral Analysis (STSA) technique, where the differences in the strength of both waves were quantified by taking the wave spectrum differences for each ENSO phase. Our result showed that Kelvin wave activity is stronger during an El Nino years, whereas the MRG wave activity is stronger during the La Nina years. Seasonal variations of Kelvin wave activity occurs predominantly in MAM over the central to the east Pacific in the El Nino years, while the strongest seasonal variation of MRG wave activity occus in MAM and SON over the northern and southern Pacific during La Nina years. The local variation of Kelvin wave and MRG wave activities are found to be controlled by variation in lower level atmospheric convection induced by sea surface temperature in the tropical Pacific Ocean.

  16. NUMERICAL SIMULATION OF LAG INFLUENCE OF ENSO ON EAST-ASIAN MONSOON

    Institute of Scientific and Technical Information of China (English)

    龙振夏; 李崇银

    2001-01-01

    By prescribing sea surface temperature anomalies (SSTAs) over eastern equatorial Pacific in January-March, the lag influence of ENSO (El Nino and La Nina) on monsoon over East Asia has been studied. The results suggest that, due to the excitation of atmospheric low-frequency oscillation by the SSTA, ENSO has significant lag influence on the monsoon over East Asia.During the summer after El Nino, the subtropical high over western Pacific is intensified and shows the northward and westward displacement, meanwhile, the rainfall over East China is below normal, especially in North China; during the winter after El Nino, both the Asian trough and the winter monsoon over East Asia are strengthened. During the summer after La Nina, the anomalous subtropical high prevails over the lower reaches of Yangtze (Changjiang) River, the rainfall between Yangtze and Huaihe Rivers is below normal; during the winter after La Nina,both the Asian trough and the winter monsoon over East Asia are weaker. Compared with La Nina, the effect of El Nino is stronger, but it is not always opposite to the one of La Nina.

  17. A preliminary study on the global land annual precipitation associated with ENSO during 1948-2000

    Science.gov (United States)

    Shi, N.; Chen, L. W.; Xia, D. D.

    2002-11-01

    The global land monthly precipitation data (PREC / L) are used to investigate the relation between the global land annual precipitation and ENSO during 1948-2000, and the results of composite analysis are tested with Monte Carlo simulations. Results indicate that the global land annual precipitation was significantly reduced in large scale areas in warm event years; the areas were the equatorial West Pacific, North China; equatorial Central America; North Bengal Bay and Nepal; East Australia; West India and South Pakistan; the district east of the Lena River; West Europe; and Wilkes Land of Antarctica. In contrast to this, the areas where precipitation increased in warm event years were less, and mainly in Chile and Argentina of South America; Somali, Kenya, and Tanzania of East Africa; Turkey, Iraq, and Iran of the Middle East; Libya and Nigeria of North Africa; Namibia of Southwest Africa; and Botswana and Zimbabwe of southern Africa. Statistical tests show that in warm event years, the area where the land annual precipitation was reduced was larger than the area where the annual precipitation increased, and the reduction in precipitation was more significant than the increase. The results in this paper are compared with previous studies. It is also pointed out that the interdecadal change of ENSO had no significant effect on the interdecadal variation of precipitation in the above regions. However, the warm events of El Nino affected the droughts in East Australia and North China more after the 1980s than before.

  18. A preliminary study on the global land annual precipitation associated with ENSO during 1948 2000

    Science.gov (United States)

    Neng, Shi; Luwen, Chen; Dongdong, Xia

    2002-11-01

    The global land monthly precipitation data (PREC/L) are used to investigate the relation between the global land annual precipitation and ENSO during 1948 2000, and the results of composite analysis are tested with Monte Carlo simulations. Results indicate that the global land annual precipitation was significantly reduced in large scale areas in warm event years; the areas were the equatorial West Pacific, North China; equatorial Central America; North Bengal Bay and Nepal; East Australia; West India and South Pakistan; the district east of the Lena River; West Europe; and Wilkes Land of Antarctica. In contrast to this, the areas where precipitation increased in warm event years were less, and mainly in Chile and Argentina of South America; Somali, Kenya, and Tanzania of East Africa; Turkey, Iraq, and Iran of the Middle East; Libya and Nigeria of North Africa; Namibia of Southwest Africa; and Botswana and Zimbabwe of southern Africa. Statistical tests show that in warm event years, the area where the land annual precipitation was reduced was larger than the area where the annual precipitation increased, and the reduction in precipitation was more significant than the increase. The results in this paper are compared with previous studies. It is also pointed out that the interdecadal change of ENSO had no significant effect on the interdecadal variation of precipitation in the above regions. However, the warm events of El Nino affected the droughts in East Australia and North China more after the 1980s than before.

  19. Interannual Modulation of Subtropical Atlantic Boreal Summer Dust Variability by ENSO

    Energy Technology Data Exchange (ETDEWEB)

    DeFlorio, Mike; Goodwin, Ian D.; Cayan, Dan; Miller, Arthur J.; Ghan, Steven J.; Pierce, David; Russell, Lynn M.; Singh, Balwinder

    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, one 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.

  20. Differential imprints of different ENSO flavors in global patterns of seasonal precipitation extremes

    Science.gov (United States)

    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

  1. Mechanisms of the global electric circuit and lightning variability on the ENSO time scale

    Science.gov (United States)

    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

  2. Impacts of forest to urban land conversion and ENSO phase on water quality of a public water supply reservoir

    Science.gov (United States)

    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...

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

    Science.gov (United States)

    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 improved seasonal precipitation forecasts at regional scales and subsequent improvements to local water resource management. There is potential for future work objectively comparing these results with output from Earth System Models to improve representation of ENSO's influence on spatiotemporal variance of horizontal moisture transport.

  4. Influence of ENSO and IOD to Variability of Sea Surface Height in the North and South of Java Island

    Science.gov (United States)

    Fadlan, Ahmad; Nugroho Sugianto, Denny; Kunarso; Zainuri, Muhammad

    2017-02-01

    Indonesia is one of the largest archipelagic countries in the world. Besides being in the tropics, these waters are also located between two continents and two oceans that making this area are heavily influenced by the global atmospheric phenomena such as El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). Sea level rise is one of the main threats faced by Indonesia and other island countries in the world. Not only global warming, sea level rise in the tropics also caused by inter annual variability such as ENSO and IOD. This research has been aimed to determine the influence of ENSO and IOD to variability of sea surface height in the north and south of Java. This research used Satellite altimetry data were constructed by multi-mission satellite. These results showed that the sea level anomaly generally inversely related to ENSO and Dipole Mode Index. The phenomenon that most influence a decrease sea level anomaly in the study area is a phenomenon IOD + and the phenomenon that most influenced the increase sea level anomaly is La Niña. South of Java is area that has the large effect of changes in sea levels than north of Java. During La Niña, sea level anomaly can be increase up to 0.3 m and sea level anomaly can be decrease up to -0.28 m during IOD+.

  5. A Tropical Ocean Recharge Mechanism for Climate Variability. Part II: A Unified Theory for Decadal and ENSO Modes.

    Science.gov (United States)

    Wang, Xiaochun; Jin, Fei-Fei; Wang, Yuqing

    2003-11-01

    Decadal to interdecadal timescale variability in the Pacific region, commonly referred to as the Pacific decadal oscillation (PDO), is studied in this research using analytical and numerical models. A coupled analytical model is formulated to analyze the physical mechanism of both the PDO and ENSO. It has the equatorial β-plane dynamics of a reduced-gravity model coupled with the wind stress of fixed spatial patterns. The amplitude of the latter is proportional to the sea surface temperature (SST) anomaly in the eastern equatorial Pacific. The SST anomaly is governed by a simple thermal dynamic equation used for ENSO modeling. It is found that when a warm SST is coupled with cyclonic wind stress patterns in the eastern subtropical Pacific, an oscillation with a timescale of around 10 15 yr could be generated. In contrast, when a warm SST is coupled with only a westerly wind stress in the central equatorial Pacific, an ENSO-like oscillation could be generated with a timescale of around 3 5 yr. Thus the present research is potentially relevant to aspects of the PDO and the mechanism of the PDO may be understood as a weakly coupled decadal recharge oscillator similar to the recharge oscillator dynamics of ENSO. The sensitivity of these two kinds of coupled modes to different parameters is tested. Numerical integrations with the reduced-gravity shallow-water model in a rectangular basin and a similar coupled framework confirm the results of the analytical model.

  6. ENSO and implications on rainfall characteristics with reference to maize production in the Free State Province of South Africa

    CSIR Research Space (South Africa)

    Moeletsi, ME

    2011-08-01

    Full Text Available . The rainy season indices for each agricultural year were further subdivided into El Niño and La Niña years. The differences between mean of the rainy season indices were determined for the negative phase of ENSO versus the overall mean and for the positive...

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

    Science.gov (United States)

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

    2014-01-01

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

  8. Microplankton biomass and diversity in the Vietnamese upwelling area during SW monsoon under normal conditions and after an ENSO event

    DEFF Research Database (Denmark)

    Loick-Wilde, Natalie; Bombar, Deniz; Doan, Hai Nhu

    2017-01-01

    to show how climatological-driven changes can have a significant influence on the distribution of microplankton communities and their biomass via its impact on nutrient concentrations in the water column. The first summer in July 2003 followed a weak El-Nino Southern Oscillation (ENSO) event...

  9. Possible influence of the ENSO phenomenon on the pathoecology of diphyllobothriasis and anisakiasis in ancient Chinchorro populations

    Directory of Open Access Journals (Sweden)

    Bernardo T Arriaza

    2010-02-01

    Full Text Available Current clinical data show a clear relationship between the zoonosis rates of Diphyllobothrium pacificum and Anisakis caused by the El Niño Southern Oscillations (ENSO phenomenon along the Chilean coast. These parasites are endemic to the region and have a specific habitat distribution. D. pacificum prefers the warmer waters in the northern coast, while Anisakis prefers the colder waters of Southern Chile. The ENSO phenomenon causes a drastic inversion in the seawater temperatures in this region, modifying both the cool nutrient-rich seawater and the local ecology. This causes a latitudinal shift in marine parasite distribution and prevalence, as well as drastic environmental changes. The abundance of human mummies and archaeological coastal sites in the Atacama Desert provides an excellent model to test the ENSO impact on antiquity. We review the clinical and archaeological literature debating to what extent these parasites affected the health of the Chinchorros, the earliest settlers of this region. We hypothesise the Chinchorro and their descendants were affected by this natural and cyclical ENSO phenomenon and should therefore present fluctuating rates of D. pacificum and Anisakis infestations.

  10. A Statistical Model of Tropical Cyclone Tracks in the Western North Pacific with ENSO-Dependent Cyclogenesis

    Science.gov (United States)

    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).

  11. PREventie van ZIEkenhuisinfecties door Surveillance. Component infecties op de Intensive Care, 1997-2000

    NARCIS (Netherlands)

    Mannien J; Beaumont MTA; Geubbels ELPE; Wille JC; Boer AS de; deelnemers aan het PREZIES-project; Kwaliteitsinstituut voor de; CIE

    2002-01-01

    In the period from July 1997 to December 2000, 19 hospitals collected data on 3,921 patients in the Intensive Care Unit (ICU) for 41,744 ICU patient-days. Of these patients 1,065 had developed 1,673 infections, including 684 with pneumonia, 354 with sepsis, 353 with urinary tract infections and 282

  12. Introduction to Sociology (SOC 1010) Telecourse Report for Years 1997-2000.

    Science.gov (United States)

    Hammond, Ron J.; Knight, Austin L.

    This report is based on the results of student surveys collected during the years 1997 to 2000 from students who took the Introduction to Sociology telecourse at Utah Valley Community College. With a response rate of 45 percent, 231 students completed the survey. The survey was designed to (1) track enrollments; (2) provide a value-added measure…

  13. The reported incidence of work-related musculoskeletal disease in the UK: MOSS 1997-2000.

    Science.gov (United States)

    Cherry, N M; Meyer, J D; Chen, Y; Holt, D L; McDonald, J C

    2001-10-01

    Consultant rheumatologists participate in surveillance of work-related musculoskeletal conditions under the Musculoskeletal Occupational Surveillance Scheme (MOSS), which has been in operation since 1997. During the first 3 years of the scheme, an estimated total of 8070 cases and 8442 diagnoses were obtained, an average of slightly less than 2700 estimated cases each year. Disorders of the upper limb accounted for approximately 66% (5502) of the total, with hand/wrist/arm conditions (3693 cases) comprising the majority of these. Conditions of the lumbar spine and trunk (13% of cases), the cervical spine (12%) and the shoulder (12%) were also frequently reported. Pain with ill-defined pathology was reported in 35% of cases with hand and forearm disorders. Overall, 82% of cases were related to repetitive rather than single injury. The largest numbers of cases were seen in workers in craft occupations (1659) and in clerical and secretarial workers (1524). High rates of musculoskeletal conditions, particularly of upper limb disorders, are notable in mining. In most occupations, and overall, women were at greater risk than men.

  14. RELATIONSHIP BETWEEN AMBIENT AIR QUALITY AND SELECTED BIRTH DEFECTS, SEVEN COUNTY STUDY, TEXAS, 1997-2000

    Science.gov (United States)

    Background and Objectives: A number of epidemiologic investigations have shown adverse effects of ambient air pollution on reproductive outcomes including spontaneous abortion, fetal growth, preterm delivery, and infant mortality. A southern California, population-based, case-c...

  15. AIR QUALITY AND SELECTED BIRTH DEFECTS, SEVEN COUNTY STUDY, TEXAS, 1997-2000

    Science.gov (United States)

    Introduction: A number of epidemiologic investigations have shown adverse effects of ambient air pollution on reproductive outcomes including spontaneous abortion, fetal growth, preterm delivery, and infant mortality. A southern California study found associations between carbon ...

  16. Surveillance for work-related hearing loss in the UK: OSSA and OPRA 1997-2000

    Energy Technology Data Exchange (ETDEWEB)

    Meyer, J.D.; Chen, Y.; McDonald, J.C.; Cherry, N.M. [University of Manchester, Manchester (United Kingdom)

    2002-03-01

    Surveillance data on occupational audiological disorders have been collected by the Occupational Surveillance Scheme for Audiological Physicians (OSSA) since October 1997 and by the Occupational Physicians Reporting Activity (OPRA) from January 1996. During the 3 years ending in September 2000, a total of 1620 new cases were received from consultant audiological physicians; 988 new cases were estimated from reports by occupational physicians in the period from October 1997 to September 2000. The annual incidence of occupational noise-induced hearing loss (NIHL) was 1.94 and 1.23 per 100 000 workers for the OSSA and OPRA schemes, respectively. The median age at diagnosis with NIHL was 59 years in OSSA reports and 50 years in OPRA; nearly all cases were seen in men (95.6 and 92.5% male cases for OSSA and OPRA, respectively). High incidence rates based on OSSA reports were seen in foundry labourers (64.0 per 100 000 employed), coal gas and coke oven furnace workers (54.6), workers in transport and communication (43.1), metal workers (31.3), and members of the armed forces (28.3). Data from occupational physicians point to high rates in sawyers and woodworking machinists, metal furnace workers, coach and carriage builders, maintenance fitters, and engineering labourers. Among workers aged less than or equal to45 years, those in manufacturing and the armed forces were prominent. The long latency of occupational hearing loss makes surveillance difficult, but consistent patterns in occupational risk suggest targets for preventive efforts.

  17. Projected impact of twenty-first century ENSO changes on rainfall over Central America and northwest South America from CMIP5 AOGCMs

    Science.gov (United States)

    Steinhoff, Daniel F.; Monaghan, Andrew J.; Clark, Martyn P.

    2015-03-01

    Due to the importance that the El Niño-Southern Oscillation (ENSO) has on rainfall over the tropical Americas, future changes in ENSO characteristics and teleconnections are important for regional hydroclimate. Projected changes to the ENSO mean state and characteristics, and the resulting impacts on rainfall anomalies over Central America, Colombia, and Ecuador during the twenty-first century are explored for several forcing scenarios using a suite of coupled atmosphere-ocean global climate models (AOGCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Mean-state warming of eastern tropical Pacific sea surface temperatures, drying of Central America and northern Colombia, and wetting of southwest Colombia and Ecuador are consistent with previous studies that used earlier versions of the AOGCMs. Current and projected future characteristics of ENSO (frequency, duration, amplitude) show a wide range of values across the various AOGCMs. The magnitude of ENSO-related rainfall anomalies are currently underestimated by most of the models, but the model ensembles generally simulate the correct sign of the anomalies across the seasons around the peak ENSO effects. While the models capture the broad present-day ENSO-related rainfall anomalies, there is not a clear sense of projected future changes in the precipitation anomalies.

  18. Linking ENSO and heavy rainfall events over coastal British Columbia through a weather pattern classification

    Directory of Open Access Journals (Sweden)

    P. Brigode

    2013-04-01

    Full Text Available Classifications of atmospheric weather patterns (WPs are widely used for the description of the climate of a given region and are employed for many applications, such as weather forecasting, downscaling of global circulation model outputs and reconstruction of past climates. WP classifications were recently used to improve the statistical characterisation of heavy rainfall. In this context, bottom-up approaches, combining spatial distribution of heavy rainfall observations and geopotential height fields have been used to define WP classifications relevant for heavy rainfall statistical analysis. The definition of WPs at the synoptic scale creates an interesting variable which could be used as a link between the global scale of climate signals and the local scale of precipitation station measurements. We introduce here a new WP classification centred on the British Columbia (BC coastal region (Canada and based on a bottom-up approach. Five contrasted WPs composed this classification, four rainy WPs and one non-rainy WP, the anticyclonic pattern. The four rainy WPs are mainly observed in the winter months (October to March, which is the period of heavy precipitation events in coastal BC and is thus consistent with the local climatology. The combination of this WP classification with the seasonal description of rainfall is shown to be useful for splitting observed precipitation series into more homogeneous sub-samples (i.e. sub-samples constituted by days having similar atmospheric circulation patterns and thus identifying, for each station, the synoptic situations that generate the highest hazard in terms of heavy rainfall events. El Niño-Southern Oscillations (ENSO significantly influence the frequency of occurrence of two coastal BC WPs. Within each WP, ENSO seem to influence only the frequency of rainy events and not the magnitudes of heavy rainfall events. Consequently, heavy rainfall estimations do not show significant evolution of heavy

  19. Flood durations and their response to ENSO at the global scale

    Science.gov (United States)

    Ward, Philip; Lall, Upmanu

    2014-05-01

    The economic losses associated with flooding are huge. In 2012 alone, economic losses from flooding exceeded 19 billion, and these losses are rising rapidly. Hence, in recent years several methods have been developed to assess the influence of climate change, climate variability, and socioeconomic change, on flood hazard and flood loss. To date, most of the studies employ methods that simulate flood hazards based on some measure of instantaneous peak discharge (e.g. peak annual discharge), which is used as a proxy for the severity of an event. However, recent large flood disasters, for example those experienced in Thailand, Pakistan, and Queensland, have shown that for the most disastrous floods, the duration of flooding is also very important. To date, few studies have specifically assessed the impacts of climate change and/or variability on flood durations. In this contribution, we examine relationships between flood durations at the global scale and the El Niño Southern Oscillation (ENSO). At the globally aggregated scale, we found no statistical difference between the number of floods during El Niño and La Niña years, compared to the number of floods during neutral years. However, we found that the durations of floods during both El Niño and La Niña are longer than during neutral years. At the regional scale, we found that ENSO exerts a very large influence on both the number of flood events and the duration of those floods. Statistically significant differences in the average duration of floods between neutral years and El Niño and/or La Niña years were found in Australia and Oceania, Eastern Asia, Eastern Europe and Central Asia, Middle and South Africa, North Africa, and Western Europe. We present maps showing the geographical patterns of these influences at the basin scale. We also provide composite analyses of atmospheric conditions during long duration floods for several case study regions (e.g. Queensland, Chao Phraya). Finally, we discuss how

  20. Linking ENSO and heavy rainfall events over coastal British Columbia through a weather pattern classification

    Science.gov (United States)

    Brigode, P.; Mićović, Z.; Bernardara, P.; Paquet, E.; Garavaglia, F.; Gailhard, J.; Ribstein, P.

    2013-04-01

    Classifications of atmospheric weather patterns (WPs) are widely used for the description of the climate of a given region and are employed for many applications, such as weather forecasting, downscaling of global circulation model outputs and reconstruction of past climates. WP classifications were recently used to improve the statistical characterisation of heavy rainfall. In this context, bottom-up approaches, combining spatial distribution of heavy rainfall observations and geopotential height fields have been used to define WP classifications relevant for heavy rainfall statistical analysis. The definition of WPs at the synoptic scale creates an interesting variable which could be used as a link between the global scale of climate signals and the local scale of precipitation station measurements. We introduce here a new WP classification centred on the British Columbia (BC) coastal region (Canada) and based on a bottom-up approach. Five contrasted WPs composed this classification, four rainy WPs and one non-rainy WP, the anticyclonic pattern. The four rainy WPs are mainly observed in the winter months (October to March), which is the period of heavy precipitation events in coastal BC and is thus consistent with the local climatology. The combination of this WP classification with the seasonal description of rainfall is shown to be useful for splitting observed precipitation series into more homogeneous sub-samples (i.e. sub-samples constituted by days having similar atmospheric circulation patterns) and thus identifying, for each station, the synoptic situations that generate the highest hazard in terms of heavy rainfall events. El Niño-Southern Oscillations (ENSO) significantly influence the frequency of occurrence of two coastal BC WPs. Within each WP, ENSO seem to influence only the frequency of rainy events and not the magnitudes of heavy rainfall events. Consequently, heavy rainfall estimations do not show significant evolution of heavy rainfall

  1. Ice-shelf height variability in Amundsen Sea linked to ENSO

    Science.gov (United States)

    Paolo, Fernando; Fricker, Helen; Padman, Laurie

    2016-04-01

    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 18-year (1994-2012) time series of ice-shelf height derived from satellite radar altimetry 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 in ice-shelf height change are much larger than the range of interannual variability in the AS region, the short-term rate of change dh/dt can vary about the trend by more than 50%. We extract the principal modes of variability (EOFs) based on common spectral properties from a set of 140 height time series. 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. This interannual mode in ice-shelf height, represented by the two leading EOFs, is responsible for about 25% of the variance in the de-trended data set. 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. While we find a correlation between modeled precipitation anomalies and ice-shelf height, we are investigating (a) errors in model precipitation, (b) radar backscatter and firn-density issues, and (c) ocean contribution correlated with atmosphere through wind-stress forcing. We

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

    Science.gov (United States)

    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.

  3. Cloud optical thickness variations during 1983-1991: Solar cycle or ENSO?

    Science.gov (United States)

    Kuang, Zhiming; Jiang, Yibo; Yung, Yuk L.

    Based on a detailed analysis of the cloud data obtained by the International Satellite Cloud Climatology Project (ISCCP) in the years 1983-1991, we show that besides the reported 3% variation in global cloudiness (Svensmark and Friis-Christensen, 1997), the global mean cloud optical thickness (MCOT) also has significant variation which is out of phase with that of the global cloudiness. The combined effect of the two opposing variations may be a null effect on the cloud reflectivity. These results are consistent with the Total Ozone Mapping Spectrometer (TOMS) reflectivity measurements. The MCOT variation is further shown to be correlated with both the solar cycle and the ENSO cycle. Our present analysis cannot distinguish which of the above two provides better correlation, although independent data from the High resolution Infrared Radiation Sounder (HIRS) from 1990 to 1996 favor the solar cycle. Future data are needed to identify the true cause of these changes.

  4. Mixed-layer water oscillations in tropical Pacific for ENSO cycle

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The main modes of interannal variabilities of thermocline and sea surface wind stress in the tropical Pacific and their interactions are investigated, which show the following results. (1) The thermocline anomalies in the tropical Pacific have a zonal dipole pattern with 160°W as its axis and a meridional seesaw pattern with 6-8°N as its transverse axis. The meridional oscillation has a phase lag of about 90° to the zonal oscillation, both oscillations get together to form the El Ni(n)o/La Ni(n)a cycle, which behaves as a mixed layer water oscillates anticlockwise within the tropical Pacific basin between equator and 12°N. (2) There are two main patterns of wind stress anomalies in the tropical Pacific, of which the first component caused by trade wind anomaly is characterized by the zonal wind stress anomalies and its corresponding divergences field in the equatorial Pacific, and the abnormal cross-equatorial flow wind stress and its corresponding divergence field, which has a sign opposite to that of the equatorial region, in the off-equator of the tropical North Pacific, and the second component represents the wind stress anomalies and corresponding divergences caused by the ITCZ anomaly. (3) The trade winds anomaly plays a decisive role in the strength and phase transition of the ENSO cycle, which results in the sea level tilting, provides an initial potential energy to the mixed layer water oscillation, and causes the opposite thermocline displacement between the west side and east side of the equator and also between the equator and 12°N of the North Pacific basin, therefore determines the amplitude and route for ENSO cycle. The ITCZ anomaly has some effects on the phase transition. (4) The thermal anomaly of the tropical western Pacific causes the wind stress anomaly and extends eastward along the equator accompanied with the mixed layer water oscillation in the equatorial Pacific, which causes the trade winds anomaly and produces the anomalous wind

  5. Evidences linking ENSO and coral growth in the Southwestern-South Atlantic

    Energy Technology Data Exchange (ETDEWEB)

    Evangelista, H. [LARAMG, Laboratorio de Radioecologia e Mudancas Globais/DBB/UERJ. Pav. HLC, Subsolo, Maracana, RJ (Brazil); Godiva, D. [LARAMG, Laboratorio de Radioecologia e Mudancas Globais/DBB/UERJ. Pav. HLC, Subsolo, Maracana, RJ (Brazil); Universidade Federal Fluminense, Outeiro Sao Joao Batista, s/n, Centro, Departamento de Geoquimica Ambiental, Niteroi, RJ (Brazil); Sifeddine, A. [IRD, Institut de Recherche Pour le Developpement, UR055 Paleotropique, Bondy (France); Universidade Federal Fluminense, Outeiro Sao Joao Batista, s/n, Centro, Departamento de Geoquimica Ambiental, Niteroi, RJ (Brazil); Leao, Z.M.A.N.; Kikuchi, R.K.P. [UFBA/Instituto de Geociencias. Rua Barao de Geremoabo, s/n, Federacao, Salvador, BA (Brazil); Rigozo, N.R. [LARAMG, Laboratorio de Radioecologia e Mudancas Globais/DBB/UERJ. Pav. HLC, Subsolo, Maracana, RJ (Brazil); FAETEC, Faculdade de Educacao e Tecnologia Thereza Porto Marques, Jacarei, SP (Brazil); Segal, B. [UFRJ/Museu Nacional/Setor de Celenterologia/Departamento de Invertebrados, Quinta da Boa Vista s/n, Sao Cristovao, RJ (Brazil); Ambrizzi, T. [USP/Department of Atmospheric Sciences, Sao Paulo, SP (Brazil); Kampel, M. [INPE/Divisao de Sensoriamento Remoto, Sao Paulo, SP (Brazil); Cornec, F. le [Universidade Federal Fluminense, Outeiro Sao Joao Batista, s/n, Centro, Departamento de Geoquimica Ambiental, Niteroi, RJ (Brazil)

    2007-12-15

    Physical and biological changes in the marine environment, induced by oceanic-atmospheric processes, can be imprinted in massive coral skeletons. Herein, we present an evidence of potential El Nino impacts at the Southwestern South Atlantic Ocean (SWSA) inferred from the sclerochronology of the reef coral Favia leptophylla. The application of spectral analysis (wavelet decomposition and the iterative regression) to coral growth length and to meteorological-oceanographic parameters (air temperature, sea surface temperature and precipitation) as well as to Southern Oscillation Index (SOI) and solar irradiation indicated a major significant inverse relationship between SOI and coral growth length at the 4-8 years frequency band. We propose here that coral growth length from the SWSA could be affected by El Nino Southern Oscillation (ENSO) events through an ''atmospheric bridge'', in contrast to its direct effect at the Pacific Ocean, related to the increase in sea surface temperature. (orig.)

  6. ENSO signals on sea-surface salinity in the eastern tropical pacific ocean

    Directory of Open Access Journals (Sweden)

    1998-01-01

    Full Text Available SIGNAUX DE L’ENSO SUR LA SALINITE DE LA SURFACE DE LA MER DANS L’OCEAN PACIFIQUE TROPICAL ORIENTAL. Nous présentons les variations de la température et de la salinité de surface. Des navires de commerce ont été récemment équipés de thermosalinographes automatiques qui permettent d’échantillonner en continu et de localiser le front de salinité le long de la ligne Panama-Tahiti, séparant les masses d’eaux du golfe de Panama et celles du Pacifique central sud. La variation en latitude de la position du front halin suit la position de la zone de convergence intertropicale des vents du Pacifique. La salinité donne ainsi des informations supplémentaires sur le développement du phénomène El Niño dans le Pacifique tropical. La future transmission par satellite de la salinité de surface permettra de suivre en temps réel la distribution de la salinité de surface qui est étroitement liée aux échanges entre l’océan et l’atmosphère. SEÑALES DEL ENSO SOBRE LA SALINIDAD DE LA SUPERFICIE DEL OCÉANO PACÍFICO ORIENTAL. Presentamos las variaciones de la temperatura y de la salinidad de superficie. Barcos de comercio fueron recientemente equipados con termo-saliógrafos automáticos, los cuales permiten observar un muestreo continuo y ubicar el frente de salinidad en la recta Panamá-Tahiti, la cual separa las masas de agua del golfo de Panamá con las del Pacífico centro Sur. La variación en latitud de la ubicación del frente halino acompaña a la posición de la Zona de Convergencia Intertropical de los vientos del Pacífico. La salinidad proporciona también informaciones adicionales sobre el desarrollo del Fenómeno El Niño en el Pacífico tropical. La futura transmisión por satélite de la salinidad de superficie permitirá el monitoreo en tiempo real de la distribución en tiempo real de la salinidad de superficie, la cual está estrechamente vinculada con los intercambios entre el océano y la atmósfera. Various data

  7. How Well Do Global Climate Models Simulate the Variability of Atlantic Tropical Cyclones Associated with ENSO?

    Science.gov (United States)

    Wang, Hui; Long, Lindsey; Kumar, Arun; Wang, Wanqiu; Schemm, Jae-Kyung E.; Zhao, Ming; Vecchi, Gabriel A.; LaRow, Timorhy E.; Lim, Young-Kwon; Schubert, Siegfried D.; hide

    2013-01-01

    The variability of Atlantic tropical cyclones (TCs) associated with El Nino-Southern Oscillation (ENSO) in model simulations is assessed and compared with observations. The model experiments are 28-yr simulations forced with the observed sea surface temperature from 1982 to 2009. The simulations were coordinated by the U.S. CLIVAR Hurricane Working Group and conducted with five global climate models (GCMs) with a total of 16 ensemble members. The model performance is evaluated based on both individual model ensemble means and multi-model ensemble mean. The latter has the highest anomaly correlation (0.86) for the interannual variability of TCs. Previous observational studies show a strong association between ENSO and Atlantic TC activity, as well as distinctions in the TC activities during eastern Pacific (EP) and central Pacific (CP) El Nino events. The analysis of track density and TC origin indicates that each model has different mean biases. Overall, the GCMs simulate the variability of Atlantic TCs well with weaker activity during EP El Nino and stronger activity during La Nina. For CP El Nino, there is a slight increase in the number of TCs as compared with EP El Nino. However, the spatial distribution of track density and TC origin is less consistent among the models. Particularly, there is no indication of increasing TC activity over the U.S. southeast coastal region as in observations. The difference between the models and observations is likely due to the bias of vertical wind shear in response to the shift of tropical heating associated with CP El Nino, as well as the model bias in the mean circulation.

  8. Asymmetric response in Northeast Asia of summer NDVI to the preceding ENSO cycle

    Science.gov (United States)

    Li, Jing; Fan, Ke; Xu, Zhiqing

    2016-11-01

    The possibility of an asymmetric response of summer (June-July-August; JJA) vegetation vigor over Northeast Asia (NEA), captured by Advanced Very High Resolution Radiometer Normalized Difference Vegetation Index (NDVI), to the preceding spring (February-March-April; FMA) El Niño-Southern Oscillation (ENSO) cycle was investigated. Over the period 1982-2006, negative NDVI anomalies with statistical significance appeared over NEA during El Niño episodes; whereas, during La Niña, only slightly increasing NDVI anomalies appeared, and without statistical significance. Results showed the asymmetric responses of atmospheric circulations to El Niño and La Niña to be the most likely main mechanisms responsible for the asymmetric impacts of the spring (FMA) ENSO cycle on summer (JJA) NDVI over NEA (NEA-NDVI). During El Niño, a meridional teleconnection with an anticyclone-cyclone-anticyclone poleward structure is formed from the Philippine Sea to the Sea of Okhotsk. NEA is located right at the border between the mid-latitude cyclone and the high-latitude anticyclonic anomalies, accompanied by a strong northeasterly wind anomaly and the transport of dry, cold air from Russia and East Siberia to NEA. Therefore, the vegetation vigor is distinctly inhibited during El Niño episodes. However, during La Niña episodes, there is a quasi-meridional teleconnection along the Great Circle Route from the tropical western Pacific to the North Pacific, which is quite different from the meridional teleconnection formed during El Niño episodes. Results showed that the northeastward pattern has little impact on circulation and climate factors over NEA. As a result, during La Niña, only a slightly increasing NDVI anomaly appears over NEA, and without statistical significance.

  9. Merging altimeter data with Argo profiles to improve observation of tropical Pacific thermocline circulation and ENSO

    Science.gov (United States)

    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).

  10. ENSO signals in South America. Rains and floods in the Parana River region during colonial times

    Energy Technology Data Exchange (ETDEWEB)

    Del Rosario Prieto, M. [Unit of Environmental History, Argentine Institute of Snow, Glaciers and Environmental Sciences IANIGLA CRICYT, Ruiz Leal s/n, Parque Gral San Martin, 5500 Mendoza (Argentina)

    2007-07-15

    Several studies show that the El Nino-Southern Oscillation (ENSO) is an important factor in determining interannual rainfall variability in South America. This signal is detected in the region including Northeastern Argentina, Uruguay and part of southern Brazil, in the form of excessive rains and big floods in the regional rivers. To check that this relationship was similar in the past the objectives of this paper were to construct a time series of large floods in the Parana River region from documentary records, during the sixteenth to eighteenth centuries, and to evaluate the relationship between that historical record of extreme floods, the ENSO documentary evidence (Ortlieb, The Documented Historical Record of El Nino Events in Peru: An Update of the Quinn Record (Ortlieb, sixteenth through nineteenth centuries, Diaz and Markgraf, (eds.), El Nino and the southern oscillation. Multiscale variability and global and regional Impacts. Cambridge University Press, pp. 207-295, 2001; Quinn and Neal, The historical record of El Nino events, Bradley and Jones (eds.), Climate since a.d. 1500, Routledges, pp. 623-648, 1992) and the temperature index of the Pacific Ocean (Mann ME et al., Global temperature patterns in past centuries: an interactive presentation, IGBP pages/world data center for paleoclimatology data contribution series no. 2000-075. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA, 2000). Considering that the period 1904-2000, where 11 out of 16 floods occurred during El Nino events, it can be concluded that the proportion of years with exceptional flow volume in the Parana River in years with El Nino events in the seventeenth and eighteenth centuries was relatively lower than that of the twentieth century. The reason for this difference is discussed.

  11. Interdecadal changes in the Asian winter monsoon variability and its relationship with ENSO and AO

    Science.gov (United States)

    Yun, Kyung-Sook; Seo, Ye-Won; Ha, Kyung-Ja; Lee, June-Yi; Kajikawa, Yoshiyuki

    2014-08-01

    Interdecadal changes in the Asian winter monsoon (AWM) variability are investigated using three surface air temperature datasets for the 55-year period of 1958-2012 from (1) the National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis 1 (NCEP), (2) combined datasets from the European Centre for Medium-range Weather Forecasts (ECMWF) 40-yr reanalysis and interim data (ERA), and (3) Japanese 55-year reanalysis (JRA). Particular attention has been paid to the first four empirical orthogonal function (EOF) modes of the AWM temperature variability that together account for 64% of the total variance and have been previously identified as predictable modes. The four modes are characterized as follows: the first mode by a southern warming over the Indo-western Pacific Ocean associated with a gradually increasing basin-wide warming trend; the second mode by northern warming with the interdecadal change after the late 1980s; the third and fourth modes by north-south triple pattern, which reveal a phase shift after the late 1970s. The three reanalyses agree well with each other when producing the first three modes, but show large discrepancy in capturing both spatial and temporal characteristics of the fourth mode. It is therefore considered that the first three leading modes are more reliable than the rest higher modes. Considerable interdecadal changes are found mainly in the first two modes. While the first mode shows gradually decreasing variance, the second mode exhibits larger interannual variance during the recent decade. In addition, after the late 1970s, the first mode has a weakening relationship with the El Niño-Southern Oscillation (ENSO) whereas the second mode has strengthening association with the Artic Oscillation (AO). This indicates an increasing role of AO but decreasing role of ENSO on the AWM variability. A better understanding of the interdecadal change in the dominant modes would contribute toward advancing in

  12. The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking is ex-amined by using a mixed-mode model. The results show that the positive feedback process of the ef-fects of the seasonal variation of the upwelling mean on the Kelvin wave is the mechanism of the locking of the event mature phase to the end of the calendar year. The memory of the Rossby waves for the sign-shifting of the sea surface temperature anomaly from positive to negative 6 months before the cold peak time is the other mechanism of the locking of the La Nia event mature phase to the end of the calendar year. The results here are different from previous ones which suggest that the balance between cold and warm trends of sea surface temperature anomaly is the mechanism involved. The cold trend is caused by the upwelling Kelvin wave from upwelling Rossby wave reflected at the western boundary, excited by the westerly anomaly stress over the central Pacific and amplified by the seasonal variation of the coupled strength in its way propagating westward. The warm trend is caused by the Kelvin wave forced by the western wind stress over the middle and eastern equatorial Pacific. The cause of the differences is due to the opposite phase of the seasonal variation of the upwelling mean to that in the observation and an improper parameterization scheme for the effects of the seasonal varia-tion of the upwelling mean on the ENSO cycle in previous studies.

  13. The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking

    Institute of Scientific and Technical Information of China (English)

    YAN BangLiang

    2007-01-01

    The mechanism of the effects of the upwelling mean on the ENSO event mature phase locking is examined by using a mixed-mode model. The results show that the positive feedback process of the effects of the seasonal variation of the upwelling mean on the Kelvin wave is the mechanism of the locking of the event mature phase to the end of the calendar year. The memory of the Rossby waves for the sign-shifting of the sea surface temperature anomaly from positive to negative 6 months before the cold peak time is the other mechanism of the locking of the La Ni(n)a event mature phase to the end of the calendar year. The results here are different from previous ones which suggest that the balance between cold and warm trends of sea surface temperature anomaly is the mechanism involved. The cold trend is caused by the upwelling Kelvin wave from upwelling Rossby wave reflected at the western boundary, excited by the westerly anomaly stress over the central Pacific and amplified by the seasonal variation of the coupled strength in its way propagating westward. The warm trend is caused by the Kelvin wave forced by the western wind stress over the middle and eastern equatorial Pacific. The cause of the differences is due to the opposite phase of the seasonal variation of the upwelling mean to that in the observation and an improper parameterization scheme for the effects of the seasonal variation of the upwelling mean on the ENSO cycle in previous studies.

  14. Deterministic skill of ENSO predictions from the North American Multimodel Ensemble

    Science.gov (United States)

    Barnston, Anthony G.; Tippett, Michael K.; Ranganathan, Meghana; L'Heureux, Michelle L.

    2017-03-01

    Hindcasts and real-time predictions of the east-central tropical Pacific sea surface temperature (SST) from the North American Multimodel Ensemble (NMME) system are verified for 1982-2015. Skill is examined using two deterministic verification measures: mean squared error skill score (MSESS) and anomaly correlation. Verification of eight individual models shows somewhat differing skills among them, with some models consistently producing more successful predictions than others. The skill levels of MME predictions are approximately the same as the two best performing individual models, and sometimes exceed both of them. A decomposition of the MSESS indicates the presence of calibration errors in some of the models. In particular, the amplitudes of some model predictions are too high when predictability is limited by the northern spring ENSO predictability barrier and/or when the interannual variability of the SST is near its seasonal minimum. The skill of the NMME system is compared to that of the MME from the IRI/CPC ENSO prediction plume, both for a comparable hindcast period and also for a set of real-time predictions spanning 2002-2011. Comparisons are made both between the MME predictions of each model group, and between the average of the skills of the respective individual models in each group. Acknowledging a hindcast versus real-time inconcsistency in the 2002-2012 skill comparison, the skill of the NMME is slightly higher than that of the prediction plume models in all cases. This result reflects well on the NMME system, with its large total ensemble size and opportunity for possible complementary contributions to skill.

  15. 热带太平洋年代际平均气候态变化与ENSO循环%DECADAL CLIMATE CHANGE AND ENSO CYCLE

    Institute of Scientific and Technical Information of China (English)

    张勤; 丁一汇

    2001-01-01

    The observed strongest global climate variation on the interannual timescale is the El Nio - Southern Oscillation (ENSO) phenomenon, which is an irregular interannual oscillation resulting primarily from coupled ocean-atmosphere interaction in the tropical Pacific. Since 1970s the El Nio events have been stronger than the La Nina both on frequency and amplitude. Perhaps it links with the global climate warming. In this paper, sea surface temperature, wind stress and OLR data sets are diagnosed by using wavelet transform. The ENSO cycle (2-7 years ) signal and decadal variability ( 8-20 years ) are filtered out to form the data sets in order to investigate the features of the decadal climate change and its effect on ENSO cycle. Then the numerical experiments are designed to identify the effect by running a hybrid tropical Pacific coupled model.   The main results of the paper can be outlined as follows:   1)For the behavior of SSTA and wind stress in tropical Pacific by wavelet analysis, it is clear that not only the energy density of ENSO cycle ( 2-7 years) gets stronger during 1990s, but also does so the decadal oscillation ( 8-20 years). The long-term linear trend of climate change ( more than 20 years ) can be identified with a catastrophe climate change in 1976 from cold climate state turning to warm state.   2)The main warming regions of the sea surface temperature after 1976 is the east tropical areas and extended westward along the equator with the maximum value up to 0.6℃.The main features of wind stress pattern are the increasing westerly anomaly in west tropical Pacific and easterly anomaly at east tropical Pacific so that low level convection occurs near the date line.   3)However, the average state in the tropical Pacific in the 1990s is warmer than that in 1980s. This climate background change in the 1990s may cause the asymmetry of the warm and cold phases. On the other hand, the decadal oscillation has directly affected the ENSO

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

    Directory of Open Access Journals (Sweden)

    J. D. Carriquiry

    2010-06-01

    Full Text Available 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.

  17. Technical Note: Multi-centennial scale analysis and synthesis of an ensemble mean response of ENSO to solar and volcanic forcings

    Directory of Open Access Journals (Sweden)

    J. Sánchez-Sesma

    2010-10-01

    Full Text Available The response of El Niño Southern Oscillation (ENSO to solar and volcanic radiative forcings over the past millennium is reanalyzed and extrapolated based on historical data and numerical experiments employing the Zebiak–Cane (ZC model of the tropical Pacific coupled ocean–atmosphere system. The results suggest a self-similarity of the centennial scale component of the reconstructed ENSO record with a shift in frequencies around 1700 AD when the frequencies almost double. This shift of regime puts forward the non-linearity of ENSO climate with a possible centennial scale forecast, suggesting an ENSO trend toward La Niña conditions for the next three decades.

  18. Non-stationary and non-linear influence of ENSO and Indian Ocean Dipole on the variability of Indian monsoon rainfall and extreme rain events

    Science.gov (United States)

    Krishnaswamy, Jagdish; Vaidyanathan, Srinivas; Rajagopalan, Balaji; Bonell, Mike; Sankaran, Mahesh; Bhalla, R. S.; Badiger, Shrinivas

    2015-07-01

    The El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are widely recognized as major drivers of inter-annual variability of the Indian monsoon (IM) and extreme rainfall events (EREs). We assess the time-varying strength and non-linearity of these linkages using dynamic linear regression and Generalized Additive Models. Our results suggest that IOD has evolved independently of ENSO, with its influence on IM and EREs strengthening in recent decades when compared to ENSO, whose relationship with IM seems to be weakening and more uncertain. A unit change in IOD currently has a proportionately greater impact on IM. ENSO positively influences EREs only below a threshold of 100 mm day-1. Furthermore, there is a non-linear and positive relationship between IOD and IM totals and the frequency of EREs (>100 mm day-1). Improvements in modeling this complex system can enhance the forecasting accuracy of the IM and EREs.

  19. ENSO signals and their spatial-temporal variation characteristics recorded by the sea-level changes in the northwest Pacific margin during 1965-2005

    Institute of Scientific and Technical Information of China (English)

    YUAN LinWang; YU ZhaoYuan; XIE ZhiRen; SONG ZhiYao; L(U) GuoNian

    2009-01-01

    Sea-level is closely linked to the Earth's climate and its change is important as a metric for global and regional climate change.Identifying,extracting,and revealing such information through detailed analysis is the prerequisite for understanding the mechanisms of sea-level change.The monthly- av-erage tide-change records reported and examined in this paper are from 10 tide gauge stations dis-tributed in the northwest margin of the Pacific Ocean,registered during the period 1965-2005.In particular,we have utilized the Second Order Blind Identification (SOBI) method to identify and the Empirical Mode Decomposition (EMD) method to extract the El Nino-Southern Oscillation (ENSO) sig-nals imprinted in those tide gauge records; and subsequently,we have investigated the spa-tial-temporal characteristics of the extracted ENSO signals using wavelet analysis methods.The fol-lowing results are obtained:(1) the ENSO events recorded by each tide gauge series are of different types and intensity,which show considerable temporal-spatial variation characteristics,with sea-level responses to ENSO signals remarkably stronger in low latitude areas than in medium-high latitude areas; (2) due to the influences of ocean currents,topographical conditions,and other factors,there exist variations in the type of relationship between the sea-level changes and the recorded ENSO events at different latitudes; (3) sea-level changes can also denote scale-variation characteristics of ENSO events,and particularly,since 1980s,all the tide gauges located south of Kanmen show intense responses to ENSO and the timescale of ENSO events extended gradually from around 4 years to 2-8 years,reflecting variations in the intensity and frequency of ENSO events; and (4) reverse changes of certain scale were noted before and after strong ENSO events recorded by sea-level changes,sup-porting the research findings about the interaction (mutual coupling and superimposition) between the probability of occurrence

  20. L'effet ENSO Sur les précipitations et les écoulements au XXème siècle - exemple de l'Equateur

    Directory of Open Access Journals (Sweden)

    1993-01-01

    Full Text Available Sur le littoral équatorien, l'analyse statistique des données pluviométriques disponibles, qui s'étalent sur une cinquantaine d'années, a permis de mettre en évidence deux résultats principaux : 1 -les effets de ENSO ne sont pas tous aussi négatifs qu'on le pense habituellement 2 - la fréquence de retour du ENSO 1982-1983 est supérieure à 1000 ans et son impact sur le milieu morpho-dynamique va au-delà des 100 000 km2. IMPACTO DE ENSO EN LAS PRECIPITACIONES Y ESCURRIMIENTOS DURANTE EL SIGLO XX - EL CASO DEL ECUADOR. En la región litoral del Ecuador, un análisis estadístico de las series pluviométricas disponibles, alrededor de cincuenta años, acarrea dos resultados principales: 1 - los efectos de ENSO no son todos tan negativos como se piensa habitualmente 2 - el período de retorno del ENSO 1982-1983 es mayor de los mil años y su impacto sobre el medio geomorfodinámico abarca más de 100 000 km2. ENSO IMPACT ON RAINFALL AND RUNOFF IN XXth CENTURY - CASE OF ECUADOR. On the Pacific coastal region of Ecuador, a statistical analysis of the largest available pluviometric records, about fifty years, yields two main results: 1 - ENSO effects are not so negative as one usually comments 2 - the return period of ENSO 1982-1983 occurrence is over one thousand years and the geomorphodynamic impact acts upon 100 000 km2.

  1. Features of Interannual Variations In Ozone Vertical Distribution: Analysis of Ozonesonde Data

    Science.gov (United States)

    Gruzdev, A.; Bezverkhny, V.

    Data of ozonesonde measurements of vertical distributions of ozone, temperature, velocity and direction the wind at North-American and West European stations are analysed. High-resolution spectral analysis of the data reveals spectral maxima at fre- quencies corresponding to quasi-biennial and 3-4-year variations. The quasi-biennial signal is usually presented by spectral maxima with periods close to 2 and 2.5 years, which are accompanied by maxima at combination frequencies corresponding to 20 and 8-9 months (due to nonlinear interaction of the two quasi-biennial components with the annual cycle). In spite of presence of these interannual variations in general, spectral features can vary significantly not only within the same geographical region, but also from one parameter to another at the same station. High-resolution cross- spectral analysis and spectral-correlation analysis of ozonesonde data, on the one hand, and equatorial stratospheric wind velocity, North Atlantic Oscillation (NAO) index, El Nino/Southern Oscillation (ENSO) index, West Pacific Oscillation index, and Pacific U North American Teleconnection Pattern index, on the other hand, were made. The analysis shows that the quasi-biennial variations in ozone and meteoparam- eters (temperature, air pressure, zonal and meridional wind velocities) are related to similar variations in the equatorial stratospheric wind, NAO and ENSO indices. The equatorial quasi-biennial oscillation is only responsible for the 2.5-year variations of the analysed parameters in the stratosphere, while the NAO and ENSO can affect the two quasi-biennial components in the stratosphere and troposphere. The biennial variations in all the parameters, both in the troposphere and in the stratosphere, are related to the biennial components in the NAO and ENSO indices, which are not co- herent to each other in general. The NAO and ENSO are also responsible for the lower frequency variations of ozone and meteoparameters, in both the

  2. Massive bleaching of coral reefs induced by the 2010 ENSO, Puerto Cabello, Venezuela

    Directory of Open Access Journals (Sweden)

    Carlos del Mónaco

    2012-06-01

    Full Text Available 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 nonbleached 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 Montastraea faveolata. 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 temperatura reached 31ºC 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. Rev. Biol. Trop. 60 (2

  3. The impact of the warm phase of ENSO (El Niño Southern Oscillation events on water resource availability of tropical catchments in Central Sulawesi, Indonesia

    Directory of Open Access Journals (Sweden)

    C. Leemhuis

    2006-01-01

    Full Text Available Precipitation anomalies caused by the warm phase (El Niño of the ENSO cycle lead to a strong decrease of water resources in South-East Asia. The aim of this work is to study the impact of warm phase ENSO caused precipitation anomalies on the water balance of a mesoscale tropical catchment in Central Sulawesi, Indonesia using a scenario analysis. We applied statistically generated precipitation anomalies caused by warm phase ENSO events on a validated hydrological model of the Palu River catchment (2694 km2 to investigate the implications of the generated ENSO scenarios on the total annual water balance, the annual discharge regime and the discharge variability. Moreover we analysed the influence of various catchment characteristics during warm phase ENSO conditions on the discharge variability through a comparison of different sub-catchment types. The results of the scenario analysis proved a severe decline of the annual discharge rate during warm phase ENSO conditions and an increase of the overall discharge variability.

  4. Assessment of the APCC coupled MME suite in predicting the distinctive climate impacts of two flavors of ENSO during boreal winter

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Hye-In; Lee, Doo Young [APEC Climate Center (APCC), Pusan (Korea, Republic of); Pusan National University, Pusan (Korea, Republic of); Ashok, Karumuri [Indian Institute of Tropical Meteorology, Centre for Climate Change Research, Pune (India); Ahn, Joong-Bae [Pusan National University, Pusan (Korea, Republic of); Lee, June-Yi [University of Hawaii, International Pacific Research Center, Honolulu, HI (United States); Luo, Jing-Jia [Research Institute for Global Change/JAMSTEC, Yokohama (Japan); Schemm, Jae-Kyung E. [NCEP/NOAA Climate Prediction Center, Camp Spring, MD (United States); Hendon, Harry H.; Braganza, Karl [Bureau of Meteorology, Centre for Australian Weather and Climate Research, Melbourne, VIC (Australia); Ham, Yoo-Geun [NASA Goddard Space Flight Center (NASA/GSFC), Global Modeling and Assimilation Office, Greenbelt, MD (United States); Universities Space Research Association, Goddard Earth Sciences Technology and Research Studies and Investigations, Greenbelt, MD (United States)

    2012-07-15

    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 1982-2004, 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. (orig.)

  5. Using the Iterative Input variable Selection (IIS) algorithm to assess the relevance of ENSO teleconnections patterns on hydro-meteorological processes at the catchment scale

    Science.gov (United States)

    Beltrame, Ludovica; Carbonin, Daniele; Galelli, Stefano; Castelletti, Andrea

    2014-05-01

    Population growth, water scarcity and climate change are three major factors making the understanding of variations in water availability increasingly important. Therefore, reliable medium-to-long range forecasts of streamflows are essential to the development of water management policies. To this purpose, recent modelling efforts have been dedicated to seasonal and inter-annual streamflow forecasts based on the teleconnection between "at-site" hydro-meteorological processes and low frequency climate fluctuations, such as El Niño Southern Oscillation (ENSO). This work proposes a novel procedure for first detecting the impact of ENSO on hydro-meteorological processes at the catchment scale, and then assessing the potential of ENSO indicators for building medium-to-long range statistical streamflow prediction models. Core of this procedure is the adoption of the Iterative Input variable Selection (IIS) algorithm that is employed to find the most relevant forcings of streamflow variability and derive predictive models based on the selected inputs. The procedure is tested on the Columbia (USA) and Williams (Australia) Rivers, where ENSO influence has been well-documented, and then adopted on the unexplored Red River basin (Vietnam). Results show that IIS outcomes on the Columbia and Williams Rivers are consistent with the results of previous studies, and that ENSO indicators can be effectively used to enhance the streamflow forecast models capabilities. The experiments on the Red River basin show that the ENSO influence is less pronounced, inducing little effects on the basin hydro-meteorological processes.

  6. Comparative Study of the Effects of ENSO Phenomenon (El Niño, La Niña on Temperature and Precipitation of Mashhad

    Directory of Open Access Journals (Sweden)

    vajiheh mohammadi sabet

    2017-03-01

    Full Text Available Introduction: The Southern Oscillation is a large scale phenomenon that changes the Normal oscillating air pressure on both sides of the Pacific Ocean. It disrupted the normal conditions and the patterns of temperature and precipitation change in the nearby region and other regions of the world. This phenomenon is caused by changing the water slope in the Pacific Ocean between Peru (northwestern South America and Northern Australia (about Indonesia and Malaysia. ENSO phenomenon is formed of Elnino (warm state and La Niña (cold state. There is high pressure system in the East and low pressure system in the West Pacific Ocean in normal conditions (Walker cycle. The trade winds blow from East to West with high intensity. ENSO start when the trade winds and temperature and pressure balance on both sides of the PacificOcean change. High pressure will form in the west and low pressure will form in the East. As a result, west will have high and east will have low rainfall. Temperature will change at these two locations. Enso longs about 6 to 18 months. This research investigated the impact of ENSO on monthly precipitation and temperature of Mashhad.The results showed that temperature and rainfall have a good relation with ENSO.This relation occurs in 0-5 month lag. Materials and Methods: The severity of ENSO phenomenon is known by an index which is called ENSO index. The index is the anomaly of sea surface temperature in the Pacific. The long-term temperature and precipitation data of Mashhad selected and analyzed. The Rainfall has no trend but temperature has trend. The trend of temperature modeled by MARS regression and trend was removed.The rainfall data changed to standard and temperature changed to anomaly for comparison with ENSO index. The 2016 annual and monthly temperature of Mashhad is not available. The 2016 Annual temperature was forecasted by ARMA (1,1 model. Then this forecast disaggregated to monthly temperature. For each period of

  7. What do we need to know to predict ENSO? Student-centered learning in a Master course in Climate Physics

    Science.gov (United States)

    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.

  8. The role of ENSO in understanding changes in Colombia's annual malaria burden by region, 1960–2006

    OpenAIRE

    Oliveros Hugo; Barnston Anthony G; Mantilla Gilma

    2009-01-01

    Abstract 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 cli...

  9. Understanding Legacy Features with Featureous

    DEFF Research Database (Denmark)

    Olszak, Andrzej; Jørgensen, Bo Nørregaard

    2011-01-01

    Feature-centric comprehension of source code is essential during software evolution. However, such comprehension is oftentimes difficult to achieve due the discrepancies between structural and functional units of object-oriented programs. We present a tool for feature-centric analysis of legacy...

  10. Linking ENSO and heavy rainfall events over Coastal British Columbia through a weather pattern classification

    Directory of Open Access Journals (Sweden)

    P. Brigode

    2012-10-01

    Full Text Available Classifications of atmospheric weather patterns (WPs are widely used for the description of the climate of a given region and are employed for many applications, such as weather forecasting, downscaling of global circulation model outputs and reconstruction of past climates. WP classifications were recently used to improve the statistical characterisation of heavy rainfall. In this context, bottom-up approaches, combining spatial distribution of heavy rainfall observations and geopotential height fields have been used to define WP classifications relevant for heavy rainfall statistical analysis. The definition of WPs at the synoptic scale creates an interesting variable which could be used as a link between the global scale of climate signals and the local scale of precipitation station measurements. We introduce here a new WP classification centred on the British Columbia Coastal region (Canada and based on a bottom-up approach. Five contrasted WPs composed this classification, four rainy WPs and one non-rainy WP, the anticyclonic pattern. The four rainy WPs are mainly observed in the winter months (October to March, which is the period of heavy precipitation events in Coastal BC and is thus consistent with the local climatology. The combination of this WP classification with the seasonal description of rainfall is shown to be useful for splitting observed precipitation series into more homogeneous sub-samples and thus identifying, for each station, the synoptic situations that generate the highest hazard in terms of heavy rainfall events. El Niño Southern Oscillations significantly influence the frequency of occurrence of two Coastal BC WPs. Within each WP, ENSO seem to influence only the frequency of rainy events and not the magnitudes of heavy rainfall events. Consequently, MEWP heavy rainfall estimations do not show significant evolution of heavy rainfall behaviour between Niño and Niña winters. However, the WP approach captures the

  11. ENSO-cave drip water hydrochemical relationship: a 7-year dataset from south-eastern Australia

    Science.gov (United States)

    Tadros, Carol V.; Treble, Pauline C.; Baker, Andy; Fairchild, Ian; Hankin, Stuart; Roach, Regina; Markowska, Monika; McDonald, Janece

    2016-11-01

    Speleothems (cave deposits), used for palaeoenvironmental reconstructions, are deposited from cave drip water. Differentiating climate and karst processes within a drip-water signal is fundamental for the correct identification of palaeoenvironmental proxies and ultimately their interpretation within speleothem records. We investigate the potential use of trace element and stable oxygen-isotope (δ18O) variations in cave drip water as palaeorainfall proxies in an Australian alpine karst site. This paper presents the first extensive hydrochemical and δ18O dataset from Harrie Wood Cave, in the Snowy Mountains, south-eastern (SE) Australia. Using a 7-year long rainfall δ18O and drip-water Ca, Cl, Mg / Ca, Sr / Ca and δ18O datasets from three drip sites, we determined that the processes of mixing, dilution, flow path change, carbonate mineral dissolution and prior calcite precipitation (PCP) accounted for the observed variations in the drip-water geochemical composition. We identify that the three monitored drip sites are fed by fracture flow from a well-mixed epikarst storage reservoir, supplied by variable concentrations of dissolved ions from soil and bedrock dissolution. We constrained the influence of multiple processes and controls on drip-water composition in a region dominated by El Niño-Southern Oscillation (ENSO). During the El Niño and dry periods, enhanced PCP, a flow path change and dissolution due to increased soil CO2 production occurred in response to warmer than average temperatures in contrast to the La Niña phase, where dilution dominated and reduced PCP were observed. We present a conceptual model, illustrating the key processes impacting the drip-water chemistry. We identified a robust relationship between ENSO and drip-water trace element concentrations and propose that variations in speleothem Mg / Ca and Sr / Ca ratios may be interpreted to reflect palaeorainfall conditions. These findings inform palaeorainfall reconstruction from

  12. Impacts of Forest to Urban Land Conversion and ENSO Phase on Water Quality of a Public Water Supply Reservoir

    Directory of Open Access Journals (Sweden)

    Emile Elias

    2016-01-01

    Full Text Available We used coupled watershed and reservoir models to evaluate the impacts of deforestation and l Niño Southern Oscillation (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 Fluid Dynamics Code (EFDC reservoir model is used to evaluate the difference between daily pre- and post- urbanization nutrients and TOC concentration. Post-disturbance (future reservoir total nitrogen (TN, total phosphorus (TP, TOC and chlorophyll-a concentrations were found to be higher than pre-urbanization (base concentrations (p < 0.05. Predicted future median TOC concentration was 1.1 mg·L−1 (41% higher than base TOC concentration at the source water intake. Simulations show that prior to urbanization, additional water treatment was necessary on 47% of the days between May and October. However, following simulated urbanization, additional drinking water treatment might be continuously necessary between May and October. One of six ENSO indices is weakly negatively correlated with the measured reservoir TOC indicating there may be higher TOC concentrations in times of lower streamflow (La Niña. There is a positive significant correlation between simulated TN and TP concentrations with ENSO suggesting higher concentrations during El Niño.

  13. Future rainfall variability in Indonesia under different ENSO and IOD composites based on decadal predictions of CMIP5 datasets

    Science.gov (United States)

    Bilhaqqi Qalbi, Harisa; Faqih, Akhmad; Hidayat, Rahmat

    2017-01-01

    El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are amongst important climate drivers that play a significant role in driving rainfall variability in Indonesia, especially on inter-annual timescales. The phenomena are suggested to have an association with interdecadal climate variability through the modulation of their oscillations. This study aims to analyse the characteristics of future rainfall variability in Indonesia during different condition of ENSO and IOD events based on decadal predictions of near-term climate change CMIP5 GCM data outputs up to year 2035. Monthly data of global rainfall data with 5x5 km grid resolutions of CHIRPS dataset is used in this study to represent historical rainfall variability as well to serve as a reference for future rainfall predictions. The current and future rainfall and sea surface temperature data have been bias corrected before performing the analysis. Given the comparison between rainfall composites during El-Nino and positive IOD events, the study showed that the future rainfall conditions in Indonesia will become drier than the historical condition resulted from the same composite approach. In general, this study showed the Indonesian rainfall variability in the future is expected to respond differently to a different combination of ENSO and IOD conditions.

  14. ENSO-correlated fluctuations in ocean bottom pressure and wind-stress curl in the North Pacific

    Directory of Open Access Journals (Sweden)

    D. P. Chambers

    2011-07-01

    Full Text Available We examine the magnitude of ENSO-correlated variations in wind-stress curl and ocean bottom pressure in the North Pacific between 1992 until 2010, using satellite observations and model output. Our analysis indicates that while there are significant fluctuations correlated with some El Niño and La Niña events, the correlation is still relatively low. Moreover, the ENSO-correlated variability explains only 50 % of the non-seasonal, low-frequency variance. There are significant residual fluctuations in both wind-stress curl and ocean bottom pressure in the region with periods of 4-years and longer. One such fluctuation began in late 2002 and has been observed by the Gravity Recovery and Climate Experiment (GRACE. Even after accounting for ENSO variations, there is a significant trend in ocean bottom pressure in the region, equivalent to 0.7 ± 0.3 cm yr−1 of sea level from January 2003 until December 2008, which is confirmed with steric-corrected altimetry. Although this low-frequency fluctuation does not appear in an ocean model, we show that the winds used to force the model have a significantly reduced trend that is inconsistent with satellite observations over the same time period.

  15. ENSO-correlated fluctuations in ocean bottom pressure and wind-stress curl in the North Pacific

    Directory of Open Access Journals (Sweden)

    D. P. Chambers

    2011-10-01

    Full Text Available We examine the output of an ocean model forced by ECMWF winds to study the theoretical relationship between wind-induced changes in ocean bottom pressure in the North Pacific between 1992 until 2010 and ENSO. Our analysis indicates that while there are significant fluctuations correlated with some El Niño and La Niña events, the correlation is still relatively low. Moreover, the ENSO-correlated variability explains only 50 % of the non-seasonal, low-frequency variance. There are significant residual fluctuations in both wind-stress curl and ocean bottom pressure in the region with periods of 4-years and longer. One such fluctuation began in late 2002 and has been observed by the Gravity Recovery and Climate Experiment (GRACE. Even after accounting for possible ENSO-correlated variations, there is a significant trend in ocean bottom pressure in the region, equivalent to 0.7 ± 0.3 cm yr−1 of sea level from January 2003 until December 2008, which is confirmed with steric-corrected altimetry. Although this low-frequency fluctuation does not appear in the ocean model, we show that ECMWF winds have a significantly reduced trend that is inconsistent with satellite observations over the same time period, and so it appears that the difference is due to a forcing error in the model and not an intrinsic error.

  16. Site Features

    Data.gov (United States)

    U.S. Environmental Protection Agency — This dataset consists of various site features from multiple Superfund sites in U.S. EPA Region 8. These data were acquired from multiple sources at different times...

  17. Feature Extraction

    CERN Document Server

    CERN. Geneva

    2015-01-01

    Feature selection and reduction are key to robust multivariate analyses. In this talk I will focus on pros and cons of various variable selection methods and focus on those that are most relevant in the context of HEP.

  18. Solar Features

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Collection includes a variety of solar feature datasets contributed by a number of national and private solar observatories located worldwide.

  19. A Holocene Sediment Record From Lake Elsinore, Southern California: Evidence for Relative Lake Level Change and the Onset of ENSO.

    Science.gov (United States)

    Kirby, M. E.; Lund, S. P.; Poulsen, C. J.

    2003-12-01

    precipitation became more vigorous during the mid-Holocene (i.e., an increase in winter precipitation via an increase in the passage of winter cyclones). Because precipitation amount in coastal southwestern North America is so closely linked to ENSO variability, we further suggest that our observations support the hypothesis that modern ENSO variability and conditions developed during the mid-Holocene. This statement is in concert with recent findings from South America and the western Pacific that suggest a mid-Holocene onset of modern ENSO conditions. Our results are also supported by the recently published isotope data from Santa Barbara Basin (Friddell et al., 2003), which indicate an increase in more frequent "warm" ENSO events during the mid-Holocene. Our findings add to the growing number of terrestrial archives that document ENSO related Holocene variability and its timing of onset.

  20. Extraction of 10–30-Day Stable Components from a Boreal Atmosphere during ENSO Phases

    Directory of Open Access Journals (Sweden)

    Kuo Wang

    2015-01-01

    Full Text Available Distinguishing the predictable 10–30-day stable components (STs in the actual atmosphere has been important in atmospheric science research. In this study, a new method for extracting 10–30-day STs was developed with the use of historical observations. We extracted and analyzed 10–30-day STs via statistical extrapolation tests. The results show that the STs are maintained uniformly at the intraseasonal time scale; the overall trends in the atmospheric motion are revealed. Comparisons between pentad-by-pentad changes in the explained variances of the 10–30-day STs under ENSO phases show that the explained variance transmission attenuation trends for El Niño and La Niña years are weaker and more continuous than those of neutral years. Data for 10–30-day STs can remain continuous and stable from one month to the next. The proposed method and results present a new means of extracting predictable STs from the atmosphere using historical data.

  1. Dynamical effect of the zonal wind anomalies over the tropical western Pacific on ENSO cycles

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The circulation and zonal wind anomalies in the lower troposphere over the equatorial western Pacific and their roles in the developing and decaying processes of the 1982-1983, 1986-1987, 1991-1992 and 1997-1998 El Nino events and the occurrence of La Nina events are analyzed by using the observed data in this paper. The results show that before the developing stage of these El Nino events, there were cyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies brought the westerly anomalies over the Indonesia and the tropical western Pacific. However, when the El Nino events developed to their mature phase, there were anticyclonic circulation anomalies in the lower troposphere over the tropical western Pacific, and the anomalies made the easterly anomalies appear over the tropical western Pacific. A simple, dynamical model of tropical ocean is used to calculate the response of the equatorial oceanic waves to the observed anomalies of wind stress near the sea surface of the equatorial Pacific during the 1997/98 ENSO cycle, which was the strongest one in the 20th century.It is shown that the zonal wind stress anomalies have an important dynamical effect on the development and decay of this El Nino event and the occurrence of the following La Nina event.

  2. Early twentieth century response of the global atmospheric electric circuit to ENSO

    Science.gov (United States)

    Harrison, G.; Joshi, M.

    2012-04-01

    The global atmospheric electric circuit links charge separation in disturbed weather regions with current flow in the fair weather regions elsewhere. Variations in disturbed weather, such as the changes in lightning associated with Pacific ocean temperature anomalies, can be expected in turn to modify currents flowing in the global atmospheric electric circuit. Strengthening and weakening of the global circuit current has been observed* to follow El Niño and La Niña respectively, from northern hemisphere atmospheric electricity data obtained during the 1970s. Extending this relationship quantitatively into the first half of the twentieth century is pursued here, using surface data from multiple atmospheric electricity observatories including measurements from the southern hemisphere. The independent atmospheric electricity time series from the observatories show similar variations, which is a pre-requisite for inferring global circuit variations from surface measurement. Combining the measurements allows the global circuit sensitivity to ENSO sea surface temperature anomalies to be derived during the earlier part of the twentieth century. * R.G. Harrison, M. Joshi, K. Pascoe, Inferring convective responses to El Niño with atmospheric electricity measurements at Shetland Environ Res Lett 6 (2011) 044028 http://iopscience.iop.org/1748-9326/6/4/044028/

  3. The Interannual Variations of Summer Precipitation in the Northern Indian Ocean Associated with ENSO

    Institute of Scientific and Technical Information of China (English)

    YANG Ya-Li; DU Yan; WU Yan-Ling; HUANG Gang; ZHANG Yong-Sheng

    2012-01-01

    Using rainfall data from the Global Precipita- tion Climatology Project (GPCP), NOAA extended reconstruction sea surface temperature (ERSST), and NCEP/NCAR reanalysis, this study investigates the interannual variation of summer rainfall southwest of the Indian Peninsula and the northeastern Bay of Bengal associated with ENSO. The composite study indicates a decreased summer rainfall southwest of the Indian Penin- sula and an increase in the northeastern Bay of Bengal during the developing phase, but vice versa during the decay phase of E1 Nifio. Further regression analysis dem- onstrates that abnormal rainfall in the above two regions is controlled by different mechanisms. Southwest of the Indian Peninsula, the precipitation anomaly is related to local convection and water vapor flux in the decay phase of E1 Nifio. The anomalous cyclone circulation at the lower troposphere helps strengthen rainfall. In the northeastern Bay of Bengal, the anomalous rainfall depends on the strength of the Indian southwest summer monsoon (ISSM). A strong/weak ISSM in the developing/decay phase of E1 Nifio can bring more/less water vapor to strengthen/weaken the local summer precipitation.

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

    Science.gov (United States)

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

    2015-10-21

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

  5. Impact of ENSO on variability of AIRS retrieved CO2 over India

    Science.gov (United States)

    Ravi Kumar, K.; Tiwari, Yogesh K.; Revadekar, J. V.; Vellore, Ramesh; Guha, Tania

    2016-10-01

    This study investigates the impact of ENSO on the CO2 variability over the Indian subcontinent for the period 2003-2011 based on the relationships between NINO indices derived from the sea surface temperature (SST) and AIRS-retrieved mid-tropospheric CO2 concentrations. The NINO4 region exhibits positive influence on the variability of CO2 almost during the entire year except for the post-monsoon/winter months (October through December; OND). Significant positive relationship (correlation coefficient r = +0.68) between NINO4 index and CO2 levels is observed for the month of June, while negative relationship (r = -0.73) for the month of October, and the negative relationship tends to continue till November with decreasing magnitudes (r = -0.41). The spatial distribution of mid-tropospheric CO2 concentrations during El Niño and La Niña periods also indicate large-scale impact over the Indian subcontinent with positive (negative) anomalies of about 1-2 ppm during El Niño (La Niña).

  6. On the Atlantic cold tongue mode and the role of the Pacific ENSO

    Directory of Open Access Journals (Sweden)

    R. A. F. De Almeida

    2012-01-01

    Full Text Available The dominant mode of coupled ocean-atmosphere variability in the Tropical Atlantic is analysed in this work from a melange of datasets, focusing on the seasonal development and evolution of the Bjerknes feedback responsible for the generation of the Atlantic cold tongue mode. The strength, seasonality and interannual variability of this mode is investigated through a joint EOF analysis of the anomalies of zonal wind velocity in the western basin together with sea surface temperature from the easternmost Tropical Atlantic, and analysed in conjunction with the depth of the 20 °C isotherm, representing the three mechanisms responsible for the generation of the Bjerknes feedback. Results from the EOF analyses confirm the robustness and seasonality of the Atlantic cold tongue mode, with a positive feedback phase peaking during boreal summer when the Bjerknes feedback is stronger. Analysis of an event in 2005 shows that the positive feedback is followed by a negative feedback phase triggered by the wind field and driven by oceanic heat advection. More importantly, we investigated the linearized impact of Niño events in the Pacific Ocean over the Atlantic by projecting the NINO 3.4 index over the Atlantic data. The Atlantic cold tongue mode has its variance reduced from 62% to 47% in the projected dataset, revealing that the Pacific ENSO has an inhibiting effect over its Atlantic counterpart.

  7. Inter-decadal variations in the linkages between ENSO, the IOD and south-eastern Australian springtime rainfall in the past 30 years

    Science.gov (United States)

    Lim, Eun-Pa; Hendon, Harry H.; Zhao, Mei; Yin, Yonghong

    2017-07-01

    The 30 year period 1985-2014 experienced a swing of the Inter-decadal Pacific Oscillation (IPO) from the warm phase to the cold phase. Here we investigate variation of the relation between El Niño and the Southern Oscillation (ENSO) and the Indian Ocean Dipole mode (IOD) and resultant changes in the predictability of the IOD and south-eastern Australian (SEA) springtime rainfall associated with this swing in the IPO. Using observational analyses, we show that during the warm phase of the IPO in the 1980s-1990s, the amplitudes of ENSO and the IOD were large, and the correlation between them was high; thus predictability of the IOD was high. Nevertheless, during these decades SEA spring rainfall was only weakly related to ENSO and the IOD, and therefore predictability of SEA rainfall was low. In contrast, during the cold phase of the IPO in the 2000s, the opposite was found: the IOD occurred more independently from ENSO, so the IOD was less predictable. Nonetheless, SEA spring rainfall was more strongly related to ENSO and the IOD, and therefore, SEA rainfall was more predictable in the 2000s than in the 1980s-1990s. The cause of this decadal variation in the relationship of SEA rainfall with ENSO and the IOD between the recent warm and cold states of the IPO appears to be a systematic zonal variation of the rainfall anomalies in the tropical Indo-Pacific associated with the IOD and ENSO and related changes in the Rossby wave train path over Australia.

  8. PRONOSTICANDO EL ÍNDICE ENSO VARIOS PASOS EN ADELANTE MEDIANTE TÉCNICAS DE MODELAMIENTO NO LINEAL FORECASTING ENSO SEVERAL STEPS AHEAD THROUGH NONLINEAR MODELING TECHNIQUES

    Directory of Open Access Journals (Sweden)

    Giovanni Salini Calderón

    2010-12-01

    Full Text Available Se indica cómo manejar una gran base de datos consistente de series temporales no lineales, aplicando distintas técnicas de modelamiento no lineal a estas series. Aunque no existen guías explícitas de manipulación de series temporales no lineales en la profusa bibliografía actual, existen diferentes enfoques que pueden ser tomados en cuenta. Para ello se estudió una base de datos mensual correspondiente a datos del Fenómeno del Niño (ENSO, entre los años 1866 y 2006. Se explica cómo debe manipularse esta base de datos que poseen características de no linealidad, la cual será usada para hacer pronósticos varios pasos en adelante. Se aplicaron dos test estándar: Información Mutua Promedio (AMI y Falsos Vecinos más Cercanos (FNN. Se obtuvo el espaciamiento óptimo de los datos, así como el número de datos hacia atrás necesarios para pronosticar valores hacia el futuro. Luego, se diseñaron varios modelos de redes neuronales artificiales (RNA, con diferentes reglas de aprendizajes, funciones de transferencia, elementos de procesamiento (o neuronas en la capa escondida, etc., que permitieron hacer pronóstico de hasta 20 pasos en adelante. Las mejores redes correspondieron a aquellas que poseían como regla de aprendizaje la Regla Delta y la Regla Extendida, con función de transferencia sigmoide y tangente hiperbólica. El tipo de RNA usada fue una de multicapas alimentada hacia adelante y entrenada mediante la técnica de propagación hacia atrás. Se probaron redes con una, dos capas ocultas y sin ninguna capa. El mejor modelo que se obtuvo resultó ser uno consistente de una capa oculta.We indicate how to handle a large database consisting of nonlinear time series, applying different nonlinear modelling techniques to this kind of times series. Nowadays in the current references there is no explicit guide of how to manipulate data from nonlinear time series; however, there are approaches that can be taken account. To this end

  9. Respuestas del clima de América del Sur a las fases de ENSO

    Directory of Open Access Journals (Sweden)

    1998-01-01

    Full Text Available RÉPONSE DU CLIMAT DE L’AMÉRIQUE DU SUD AUX PHASES DE L’ENSO. Les phases hautes de l’ENSO, El Niño (EN, ou basses, Anti-Niño (AN, ont des répercussions diverses sur la pluviométrie de l’Amérique du sud. Pour caractériser ces diverses réponses, les précipitations annuelles ou saisonnières ont été réunies en trois groupes : celui des années EN, celui des années AN et celui des années normales. Les années qui précèdent les étés australs avec EN, les pluies hivernales dans le centre du Chili et dans les Andes de l’ouest de l’Argentine sont renforcées. Certaines années, on observe des sécheresses dans le Nordeste du Brésil au cours de l’été et de l’automne austral qui précèdent le phénomène El Niño dans le Pacifique Tropical. Au cours des mois de décembre à mars des années EN, il pleut abondamment sur la côte ouest de l’Amérique du Sud, depuis la baie de Tumaco jusqu’à Pacasmayo. À l’intérieur, dans la Sierra et l’Altiplano péruano-bolivien, on observe des sécheresses au cours de cette période alors qu’il pleut abondamment au cours de l’été et de l’automne austral dans les basses terres de l’Est de la Bolivie, du Paraguay et du Sud-Est du Brésil. À mesure que l’on s’avance vers l’automne austral, on observe de fortes précipitations dans la partie basse du bassin du Rio de la Plata et du Sud du Brésil. Dans la partie septentrionale et la partie inférieure du bassin amazonien les pluies sont déficitaires au cours des EN, pour devenir excédentaires au cours des AN. La partie intérieure du bassin amazonien réagit de manière inverse : on y observe des excès pluviométriques certaines années EN. Les régions du Venezuela et de la Colombie, sous l’influence climatique des Caraïbes et de l’Atlantique présentent des anomalies négatives de précipitation au cours des EN et une forte pluviosité au cours des AN. Une partie de la Pampa et de la Patagonie ne réagit pas aux

  10. ENSO response to high-latitude volcanic eruptions: the role of the initial conditions

    Science.gov (United States)

    Pausata, Francesco S. R.; Caballero, Rodrigo; Battisti, David S.

    2016-04-01

    Large volcanic eruptions can have major impacts on global climate affecting both atmospheric and ocean circulation through changes in atmospheric chemical composition and optical properties. The residence time of volcanic aerosol from strong eruptions is around 2-3 years and attention has consequently focused on their short-term impacts, and in particular on tropical eruptions. The long-term, ocean-mediated response has been less studied and large uncertainties remain. Moreover, studies have largely focused on tropical eruptions; high-latitude eruptions have drawn less attention because their impacts have been thought to be merely hemispheric rather than global and no study has hitherto investigated the long-term effects of such eruptions. Here we use a climate model to show that large summer high-latitude eruptions in the Northern Hemisphere could cause an El Niño-like anomaly in the equatorial Pacific during the first 8-9 months after the start of the eruption owing to a strong hemispheric cooling. The hemispherically asymmetric cooling shifts the Inter-Tropical Convergence Zone southwards, triggering a weakening of the trade winds over the western and central equatorial Pacific that leads to an El Niño-like anomaly. However, the El Niño-like anomaly strongly depends on the initial ENSO state: a 3-time larger response is shown when the climate system is going towards a La Niña compared to when is going towards an El Niño. Finally, the eruption also leads to a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in the first twenty-five years after the eruption, followed by a weakening lasting at least 35 years. The long-lived changes in the AMOC strength also alter the variability of El Niño-Southern Oscillation.

  11. Large-scale shifts in phytoplankton groups in the Equatorial Pacific during ENSO cycles

    Directory of Open Access Journals (Sweden)

    I. Masotti

    2011-03-01

    Full Text Available The El Niño Southern Oscillation (ENSO drives important changes in the marine productivity of the Equatorial Pacific, in particular during major El Niño/La Niña transitions. Changes in environmental conditions associated with these climatic events also likely impact phytoplankton composition. In this work, the distribution of four major phytoplankton groups (nanoeucaryotes, Prochlorococcus, Synechococcus, and diatoms was examined between 1996 and 2007 by applying the PHYSAT algorithm to the ocean color data archive from the Ocean Color and Temperature Sensor (OCTS and Sea-viewing Wide Field-of-view Sensor (SeaWiFS. Coincident with the decrease in chlorophyll concentrations, a large-scale shift in the phytoplankton composition of the Equatorial Pacific, that was characterized by a decrease in Synechococcus and an increase in nanoeucaryote dominance, was observed during the early stages of both the strong El Niño of 1997 and the moderate El Niño of 2006. A significant increase in diatoms dominance was observed in the Equatorial Pacific during the 1998 La Niña and was associated with elevated marine productivity. An analysis of the environmental variables using a coupled physical-biogeochemical model (NEMO-PISCES suggests that the Synechococcus dominance decrease during the two El Niño events was associated with an abrupt decline in nutrient availability (−0.9 to −2.5 μM NO3 month−1. Alternatively, increased nutrient availability (3 μM NO3 month−1 during the 1998 La Niña resulted in Equatorial Pacific dominance diatom increase. Despite these phytoplankton community shifts, the mean composition is restored after a few months, which suggests resilience in community structure.

  12. Predictability of US tornado outbreak seasons using ENSO and northern hemisphere geopotential height variability

    Institute of Scientific and Technical Information of China (English)

    Kent H. Sparrow; Andrew E. Mercer

    2016-01-01

    The predictability of dangerous atmospheric phenomena such as tornado outbreaks has generally been limited to a week or less. However, recent work has demonstrated the importance of the Rossby wavetrain phasing over the United States in establishing outbreak-favorable environments. The pre-dictability of Rossby wavetrain phasing is strongly related to numerous climate-scale interannual vari-ability indices, which are predictable many months in advance. To formalize the relationship between interannual variability indices and seasonal tornado outbreak frequency, indices derived from monthly mean Northern Hemisphere 500-hPa and 1000-hPa geopotential height fields and Niño 3.4 indices for ENSO phase were compared to annual tornado outbreak seasonal frequencies. Statistical models pre-dicting seasonal outbreak frequency were established using linear (stepwise multivariate linear regressioneSMLR) and nonlinear (support vector regressioneSVR) statistical modeling techniques. The stepwise methodology revealed predictors that are important in establishing outbreak-favorable environments at long lead times. Additionally, the results of the statistical modeling revealed that the nonlinear SVR technique reduced root mean square errors produced by the control SMLR technique by 28% and provided more consistent forecasts. A preliminary physical analysis revealed that years with high outbreak frequencies were associated with the presence of 500-mb troughs over the central and western US during the peak of outbreak season, while lower frequencies were consistent with ridging over the US or northwest flow over the Plains. These patterns support the results of the statistical modeling, which demonstrate the utility of geopotential height variability as a predictability measure of outbreak frequency.

  13. Impacts of high-latitude volcanic eruptions on ENSO and AMOC.

    Science.gov (United States)

    Pausata, Francesco S R; Chafik, Leon; Caballero, Rodrigo; Battisti, David S

    2015-11-10

    Large volcanic eruptions can have major impacts on global climate, affecting both atmospheric and ocean circulation through changes in atmospheric chemical composition and optical properties. The residence time of volcanic aerosol from strong eruptions is roughly 2-3 y. Attention has consequently focused on their short-term impacts, whereas the long-term, ocean-mediated response has not been well studied. Most studies have focused on tropical eruptions; high-latitude eruptions have drawn less attention because their impacts are thought to be merely hemispheric rather than global. No study to date has investigated the long-term effects of high-latitude eruptions. Here, we use a climate model to show that large summer high-latitude eruptions in the Northern Hemisphere cause strong hemispheric cooling, which could induce an El Niño-like anomaly, in the equatorial Pacific during the first 8-9 mo after the start of the eruption. The hemispherically asymmetric cooling shifts the Intertropical Convergence Zone southward, triggering a weakening of the trade winds over the western and central equatorial Pacific that favors the development of an El Niño-like anomaly. In the model used here, the specified high-latitude eruption also leads to a strengthening of the Atlantic Meridional Overturning Circulation (AMOC) in the first 25 y after the eruption, followed by a weakening lasting at least 35 y. The long-lived changes in the AMOC strength also alter the variability of the El Niño-Southern Oscillation (ENSO).

  14. Indo-western Pacific ocean capacitor and coherent climate anomalies in post-ENSO summer: A review

    Science.gov (United States)

    Xie, Shang-Ping; Kosaka, Yu; Du, Yan; Hu, Kaiming; Chowdary, Jasti S.; Huang, Gang

    2016-04-01

    ENSO induces coherent climate anomalies over the Indo-western Pacific, but these anomalies outlast SST anomalies of the equatorial Pacific by a season, with major effects on the Asian summer monsoon. This review provides historical accounts of major milestones and synthesizes recent advances in the endeavor to understand summer variability over the Indo-Northwest Pacific region. Specifically, a large-scale anomalous anticyclone (AAC) is a recurrent pattern in post-El Ni˜no summers, spanning the tropical Northwest Pacific and North Indian oceans. Regarding the ocean memory that anchors the summer AAC, competing hypotheses emphasize either SST cooling in the easterly trade wind regime of the Northwest Pacific or SST warming in the westerly monsoon regime of the North Indian Ocean. Our synthesis reveals a coupled ocean-atmosphere mode that builds on both mechanisms in a two-stage evolution. In spring, when the northeast trades prevail, the AAC and Northwest Pacific cooling are coupled via wind-evaporation-SST feedback. The Northwest Pacific cooling persists to trigger a summer feedback that arises from the interaction of the AAC and North Indian Ocean warming, enabled by the westerly monsoon wind regime. This Indo-western Pacific ocean capacitor (IPOC) effect explains why El Ni˜no stages its last act over the monsoonal Indo-Northwest Pacific and casts the Indian Ocean warming and AAC in leading roles. The IPOC displays interdecadal modulations by the ENSO variance cycle, significantly correlated with ENSO at the turn of the 20th century and after the 1970s, but not in between. Outstanding issues, including future climate projections, are also discussed.

  15. The Atmospheric Bridge: The Influence of ENSO Teleconnections on Air-Sea Interaction over the Global Oceans.

    Science.gov (United States)

    Alexander, Michael A.; Bladé, Ileana; Newman, Matthew; Lanzante, John R.; Lau, Ngar-Cheung; Scott, James D.

    2002-08-01

    During El Niño-Southern Oscillation (ENSO) events, the atmospheric response to sea surface temperature (SST) anomalies in the equatorial Pacific influences ocean conditions over the remainder of the globe. This connection between ocean basins via the `atmospheric bridge' is reviewed through an examination of previous work augmented by analyses of 50 years of data from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis project and coupled atmospheric general circulation (AGCM)-mixed layer ocean model experiments. Observational and modeling studies have now established a clear link between SST anomalies in the equatorial Pacific with those in the North Pacific, north tropical Atlantic, and Indian Oceans in boreal winter and spring. ENSO-related SST anomalies also appear to be robust in the western North Pacific during summer and in the Indian Ocean during fall. While surface heat fluxes are the key component of the atmospheric bridge driving SST anomalies, Ekman transport also creates SST anomalies in the central North Pacific although the full extent of its impact requires further study. The atmospheric bridge not only influences SSTs on interannual timescales but also affects mixed layer depth (MLD), salinity, the seasonal evolution of upper-ocean temperatures, and North Pacific SST variability at lower frequencies. The model results indicate that a significant fraction of the dominant pattern of low-frequency (>10 yr) SST variability in the North Pacific is associated with tropical forcing. AGCM experiments suggest that the oceanic feedback on the extratropical response to ENSO is complex, but of modest amplitude. Atmosphere-ocean coupling outside of the tropical Pacific slightly modifies the atmospheric circulation anomalies in the Pacific-North America (PNA) region but these modifications appear to depend on the seasonal cycle and air-sea interactions both within and beyond the North Pacific Ocean.

  16. On the effects of ENSO on ocean biogeochemistry in the Northern Humboldt Current System (NHCS): A modeling study

    Science.gov (United States)

    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.

  17. Revisiting Cholera-Climate Teleconnections in the Native Homeland: ENSO and other Extremes through the Regional Hydroclimatic Drivers

    Science.gov (United States)

    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

  18. Influencia del clima local y del ENSO en el crecimiento de abarco (Cariniana pyriformis), Chocó, Colombia

    OpenAIRE

    Moreno Valoyes , Miyer Mersory

    2013-01-01

    Resumen: Éste estudio parte de la hipótesis de que los anillos de crecimiento del abarco (Cariniana pyriformis) son anuales y sensibles a la variabilidad climática del área de estudio, municipio Carmen del Darién, Chocó. Por tanto se planteó como objetivo estudiar la anatomía de los anillos de crecimiento del abarco, su frecuencia de formación y su relación con la temperatura, la precipitación y el fenómeno ENSO (El Niño Southern Oscillation). Los resultados indican que el abarco tiene anillo...

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

    Science.gov (United States)

    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

  20. Impact of ENSO variability on the Pacific Equatorial Undercurrent (EUC) sources: A modeling approach depending on the horizontal resolution

    Science.gov (United States)

    Babonneix, A.; Gourdeau, L.; Durand, F.; Menkes, C. E.; Djath, N.

    2012-04-01

    As the most powerful source of climatic variability in the Pacific Ocean, the El Niño Southern Oscillation (ENSO) deeply impacts the equatorial oceanic currents. The Pacific Equatorial UnderCurrent (EUC) is a powerful jet flowing eastward and shoaling with the thermocline in the eastern Pacific, bringing cold waters in surface that retroact with the atmosphere. Its transport has thus been found to follow significant variations at ENSO timescale, with an increased (decreased) transport in La Niña (El Niño) phases. However, the EUC mean properties also vary more slowly due to extratropical forcing. This process is able to modify the heat and mass transports of the subducted waters that feed the EUC. By changing the mean equatorial oceanic conditions, this is suspected to modulate in return the ENSO signal. The EUC sources have very different origins: contributions come from both hemispheres, in part from the Low-Latitude Western Boundary Currents (LLWBCs) and the remaining from the interior ocean. Each source follows different pathways and is characterized by particular properties which differently influences the properties of the downstream equatorial undercurrent and the cold tongue upwelling. The question of the location of the different EUC sources is thus of crucial importance. In this poster, we investigate the links between the ENSO variability and the partitioning of the EUC sources. For this purpose, we use a set of five simulations made available by the DRAKKAR project ranging from a 2° laminar resolution to a turbulent 1/12° partly resolving the meso-scale processes. Increasing models horizontal resolution is largely thought to improve the quality of the resulting simulated currents, in terms of dynamics as of variability. Results show that if some distinct elements appear in terms of mean transit times, little variations are found in terms of partitioning within the different simulations. However, we show that the partitioning between the EUC sources

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

    Science.gov (United States)

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

    2016-12-01

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

  2. El ciclo anual de la hidrología de Colombia en relación con el ENSO y la NAO

    Directory of Open Access Journals (Sweden)

    1998-01-01

    Full Text Available INFLUENCE DE L’ENSO ET DE LA NAO SUR LE CYCLE ANNUEL DE L’HYDROLOGIE DE COLOMBIE. On évalue l’impact de El Niño-Oscillation du Sud (ENSO et de l’Oscillation de l’Atlantique Nord (NAO sur le cycle annuel hydrologique colombien. Les résultats du Projet de Réanalyse Climatologique NCEP/NCAR ont été utilisés pour identifier les mécanismes de la circulation atmosphérique qui interviennent dans cette région au cours des phases extrêmes de l’ENSO. En particulier, l’affaiblissement du courant jet inférieur d’ouest, qui se propage du Pacifique vers l’intérieur de la Colombie, est l’un des principaux mécanismes de circulation susceptible de nous aider à expliquer les anomalies hydrologiques en situation El Niño. Les résultats confirment l’importance de l’influence de l’ENSO et de la NAO sur les précipitations et les débits de Colombie, en particulier au cours des trimestres de septembre-octobre-novembre et de décembre-janvier-février. Se cuantifica la dependencia del ciclo anual de la hidroclimatología de Colombia con respecto del fenómeno El Niño-Oscilación del Sur (ENSO y la Oscilación del Atlántico Norte (NAO. Se usan los resultados del Proyecto de Reanálisis Climático de NCEP/NCAR para identificar los mecanismos de la circulación involucrados en las anomalías climáticas en la región de Suramérica tropical durante las fases extremas del ENSO (El Niño y La Niña. De particular importancia, el debilitamiento, durante El Niño, de la corriente de chorro superficial del oeste que penetra desde el Océano Pacífico hacia el interior de Colombia es un mecanismo de la circulación que coadyuva para explicar las anomalías hidrológicas. Los resultados confirman la fuerte influencia del ENSO y la NAO sobre las lluvias y los caudales de Colombia, en particular durante los trimestres septiembre-octubre-noviembre y diciembre-enero-febrero. THE ANNUAL CYCLE OF THE HYDROLOGY IN COLOMBIA IN RELATION TO THE ENSO AND NAO

  3. Assessment of hurricane's effect on the upper mixed layer of the southwestern Mexican Pacific during ENSO 1997-1998: in situ and satellite observations

    Directory of Open Access Journals (Sweden)

    Raúl Aguirre-Gómez

    2015-03-01

    Full Text Available Using data from closely spaced CTD profiles and satellite imagery we investigated the effect of hurricane Rick on the sea surface temperature (SST and the upper mixed layer of the southwestern Mexican Pacific coast. Effects of ENSO 1997-1998 in this region are also discussed by analysing SST maps. Coincident hydrographic measurements were carried out during an oceanographic campaign over the area in November 1997. Results revealed an increment of SST between 3 to 4°C above the climatological mean temperature (25° ± 2°C, in the Mexican Tropical Pacific, during ENSO. In situ measurements show instabilities in the upper mixed layer after the pass of the hurricane in oceanic areas. Satellite and historical databases enabled interpretation and analyses of ENSO's effect on the southwest coast of Mexico.

  4. Calcification and growth rate recovery of the reef-building Pocillopora species in the northeast tropical Pacific following an ENSO disturbance

    Directory of Open Access Journals (Sweden)

    Jose de Jesús A. Tortolero-Langarica

    2017-04-01

    Full Text Available Pocilloporids are one of the major reef-building corals in the eastern tropical Pacific (ETP and also the most affected by thermal stress events, mainly those associated with El Niño/Southern Oscillation (ENSO periods. To date, coral growth parameters have been poorly reported in Pocillopora species in the northeastern region of the tropical Pacific. Monthly and annual growth rates of the three most abundant morphospecies (P. cf. verrucosa, P. cf. capitata, and P. cf. damicornis were evaluated during two annual periods at a site on the Pacific coast of Mexico. The first annual period, 2010–2011 was considered a strong ENSO/La Niña period with cool sea surface temperatures, then followed by a non-ENSO period in 2012–2013. The linear extension rate, skeletal density, and calcification rate averaged (±SD were 2.31 ± 0.11 cm yr−1, 1.65 ± 0.18 g cm−3, 5.03 ± 0.84 g cm−2 yr-1 respectively, during the strong ENSO event. In contrast, the respective non-ENSO values were 3.50 ± 0.64 cm yr−1, 1.70 ± 0.18 g cm−3, and 6.02 ± 1.36 g cm−2 yr−1. This corresponds to 52% and 20% faster linear extension and calcification rates, respectively, during non-ENSO period. The evidence suggests that Pocillopora branching species responded positively with faster growth rates following thermal anomalies, which allow them to maintain coral communities in the region.

  5. An ENSO stability analysis. Part II: results from the twentieth and twenty-first century simulations of the CMIP3 models

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seon Tae [University of Hawaii at Manoa, Department of Meteorology, Honolulu, HI (United States); University of California, Department of Earth System Science, Irvine, CA (United States); Jin, Fei-Fei [University of Hawaii at Manoa, Department of Meteorology, Honolulu, HI (United States)

    2011-04-15

    In this study, a Bjerknes stability (BJ) index, proposed by Jin et al. (2006), is adopted to assess the overall stability of El Nino and Southern Oscillation (ENSO) in state-of-the-art coupled models. The twentieth and twenty-first century simulations of 12 coupled models among the coupled model intercomparison project phase 3 models used in the intergovernmental panel on climate change forth assessment report demonstrate a significant positive correlation between ENSO amplitude and ENSO stability as measured by the BJ index. The simulations also show a diversity of behavior regarding the ENSO stability among the coupled models, which can be attributed to different mean state and sensitivity of an oceanic and atmospheric response to wind and SST forcing from model to model. When respective components of the BJ index obtained from the coupled models are compared with those from observations, it is revealed that most coupled models underestimate the thermodynamic damping effect and the positive effect of the zonal advective and thermocline feedback. Under increased CO{sub 2} induced warm climate, changes, relative to the twentieth century simulations, in the damping and feedback terms responsible for the ENSO stability measured by the BJ index can be linked to mean state changes and associated atmospheric and oceanic response sensitivity changes. There is a clear multi-model trend in the damping terms and positive zonal advective feedback, thermocline feedback, and Ekman feedback terms under enhanced greenhouse gas conditions. However, the various behavior among the coupled models in competition between the positive feedback and negative damping terms in the BJ index formula prevent the formation of a definitive conclusion regarding future projections of ENSO stability using the current coupled models. (orig.)

  6. ENSO and interdecadal climate variability over the last century documented by geochemical records of two coral cores from the South West Pacific

    Directory of Open Access Journals (Sweden)

    T. Ourbak

    2006-01-01

    Full Text Available The south west Pacific is affected by climatic phenomena such as ENSO (El Niño Southern Oscillation or the PDO (Pacific Decadal Oscillation. Near-monthly resolution calibrations of Sr/Ca, U/Ca and δ18Oc were made on corals taken from New Caledonia and Wallis Island. These geochemical variations could be linked to SST (sea surface temperature and SSS (sea surface salinity variations over the last two decades, itselves dependent on ENSO occurrences. On the other hand, near-half-yearly resolution over the last century smoothes seasonal and interannual climate signals, but emphasizes low frequency climate variability.

  7. Response of regional climate and glacier ice proxies to El Niño-Southern Oscillation (ENSO in the subtropical Andes

    Directory of Open Access Journals (Sweden)

    E. Dietze

    2008-02-01

    Full Text Available El Niño-Southern Oscillation (ENSO is an important element of earth's ocean-climate system. To further understand its past variability, proxy records from climate archives need to be studied. Ice cores from high alpine glaciers may contain high resolution ENSO proxy information, given the glacier site is climatologically sensitive to ENSO. We investigated signals of ENSO in the climate of the subtropical Andes in the proximity of Cerro Tapado glacier (30°08' S, 69°55' W, 5550 m a.s.l., where a 36 m long ice core was drilled in 1999 (Ginot, 2001. We used annual and semi-annual precipitation and temperature time series from regional meteorological stations and interpolated grids for correlation analyses with ENSO indices and ice core-derived proxies (net accumulation, stable isotope ratio δ18O, major ion concentrations. The total time period investigated here comprises 1900 to 2000, but varies with data sets. Only in the western, i.e. Mediterranean Andes precipitation is higher (lower during El Niño (La Niña events, especially at higher altitudes, due to the latitudinal shift of frontal activity during austral winters. However, the temperature response to ENSO is more stable in space and time, being higher (lower during El Niño (La Niña events in most of the subtropical Andes all year long. From a northwest to southeast teleconnection gradient, we suggest a regional water vapour feedback triggers temperature anomalies as a function of ENSO-related changes in regional pressure systems, Pacific sea surface temperature and tropical moisture input. Tapado glacier ice proxies are found to be predominantly connected to eastern Andean summer rain climate, which contradicts previous studies and the modern mean spatial boundary between subtropical summer and winter rain climate derived from the grid data. The only ice core proxy showing a response to ENSO is the major ion concentrations, via local temperature indicating

  8. Sensitivity of North American agriculture to ENSO-based climate scenarios and their socio-economic consequences: Modeling in an integrated assessment framework

    Energy Technology Data Exchange (ETDEWEB)

    Rosenberg, N.J.; Izaurralde, R.C.; Brown, R.A.; Sands, R.D. [Pacific Northwest National Lab., Richland, WA (United States); Legler, D. [Florida State Univ., Tallahassee, FL (United States). Center for Ocean Atmosphere Prediction Studies; Srinivasan, R. [Texas A and M Univ., College Station, TX (United States). Blacklands Research Center; Tiscareno-Lopez, M.

    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. 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-weather simulator

  9. Featuring animacy

    Directory of Open Access Journals (Sweden)

    Elizabeth Ritter

    2015-01-01

    Full Text Available Algonquian languages are famous for their animacy-based grammatical properties—an animacy based noun classification system and direct/inverse system which gives rise to animacy hierarchy effects in the determination of verb agreement. In this paper I provide new evidence for the proposal that the distinctive properties of these languages is due to the use of participant-based features, rather than spatio-temporal ones, for both nominal and verbal functional categories (Ritter & Wiltschko 2009, 2014. Building on Wiltschko (2012, I develop a formal treatment of the Blackfoot aspectual system that assumes a category Inner Aspect (cf. MacDonald 2008, Travis 1991, 2010. Focusing on lexical aspect in Blackfoot, I demonstrate that the classification of both nouns (Seinsarten and verbs (Aktionsarten is based on animacy, rather than boundedness, resulting in a strikingly different aspectual system for both categories. 

  10. Large-scale shifts in phytoplankton groups in the Equatorial Pacific during ENSO cycles

    Directory of Open Access Journals (Sweden)

    I. Masotti

    2010-04-01

    Full Text Available The El Niño Southern Oscillation (ENSO drives important changes in the marine productivity of the Equatorial Pacific, in particular during major El Niño/La Niña transitions. Changes in environmental conditions associated with these climatic events also likely impact phytoplankton composition. In this work, the distribution of four major phytoplankton groups (nanoeucaryotes, Prochlorococcus, Synechococcus, and diatoms was examined between 1996 and 2007 by applying the PHYSAT algorithm to the ocean color data archive from the Ocean Color and Temperature Sensor (OCTS and Sea-viewing Wide Field-of-view Sensor (SeaWiFS. Coincident with the decrease in chlorophyll concentrations, a large-scale shift in the phytoplankton composition of the Equatorial Pacific, that was characterized by a decrease in Synechococcus and an increase in nanoeucaryotes dominance, was observed during the early stages of both the strong El Niño of 1997 and the moderate El Niño of 2006. A significant increase in diatoms dominance was observed in the Equatorial Pacific during the 1998 La Niña and was associated with elevated marine productivity. An analysis of the environmental variables using a coupled physical-biogeochemical model (NEMO-PISCES suggests that the Synechococcus dominance decrease during the two El Niño events was associated with an abrupt decline in nutrient availability (−0.9 to −2.5 μM NO3 month−1. Alternatively, increased nutrient availability (3 μM NO3 month−1 during the 1998 La Niña resulted in Equatorial Pacific dominance diatom increase. Despite these phytoplankton community shifts, the mean composition is restored after a few months, which suggests resilience in community structure. Such rapid changes to the composition of phytoplankton groups should be considered in future modeling approaches to represent variability of the marine productivity in the Equatorial Pacific and to quantify its

  11. Long equatorial waves in the Tropical Atlantic: The 1996-1997 ENSO-like event.

    Science.gov (United States)

    Illig, S.; Dewitte, B.

    2003-04-01

    In 1995 and 1996, westerly wind events (WWE) occurred in the western equatorial Atlantic region prior the observed 1996 warming in the eastern tropical Atlantic, followed by a cold phase in 1997. The sequence of long equatorial waves associated to these wind bursts is investigated during this ENSO-like event from an high-resolution OGCM simulation and several experiments using an intermediate coupled model of the tropical Atlantic. As a first step, from the results of a vertical mode decomposition of a high-resolution OGCM forced simulation of the tropical Atlantic, a multi-mode model of the tropical Atlantic is tuned in order to reproduce the observed interannual low frequency variability in 1981-2000. A mixed layer model including heat flux forcing is also built in order to best reproduce the change in sea surface temperature (SST) anomalies of the OGCM and then coupled to the ocean linear model. Several experiments are then performed with the linear model: first, the role of the individual WWE is identified by forcing the model with modified wind stress anomalies: In particular, the spatio-temporal structure of specific wind events are extracted using a Local Mode Analysis (Goulet and Duvel, 2000) and removed from the model forcing. Second, wave reflexions are cancelled at the eastern or western boundary in order to determine the role of a specific wave on SST changes. The results indicate that downwelling Kelvin waves, triggered by positive Wind Stress Anomalies (WSA), leads to the warming of 1996. The associated reflected first-meridional Rossby waves lead to competitive effects on SST changes : a cooling through zonal advection and a warming through vertical advection. The resulting effect of the Rossby waves is quantified as an increase in SSTA by about 0.4°C in between 20°W and 0°E along the equator in July 1996. The upwelling Rossby waves forced by the WWE reflect into upwelling Kelvin waves which shallow the thermocline (~10m) in the central and

  12. The Impact of ENSO on Extratropical Low Frequency Noise in Seasonal Forecasts

    Science.gov (United States)

    Schubert, Siegfried D.; Suarez, Max J.; Chang, Yehui; Branstator, Grant

    2000-01-01

    This study examines the uncertainty in forecasts of the January-February-March (JFM) mean extratropical circulation, and how that uncertainty is modulated by the El Nino/Southern Oscillation (ENSO). The analysis is based on ensembles of hindcasts made with an Atmospheric General Circulation Model (AGCM) forced with sea surface temperatures observed during; the 1983 El Nino and 1989 La Nina events. The AGCM produces pronounced interannual differences in the magnitude of the extratropical seasonal mean noise (intra-ensemble variability). The North Pacific, in particular, shows extensive regions where the 1989 seasonal mean noise kinetic energy (SKE), which is dominated by a "PNA-like" spatial structure, is more than twice that of the 1983 forecasts. The larger SKE in 1989 is associated with a larger than normal barotropic conversion of kinetic energy from the mean Pacific jet to the seasonal mean noise. The generation of SKE due to sub-monthly transients also shows substantial interannual differences, though these are much smaller than the differences in the mean flow conversions. An analysis of the Generation of monthly mean noise kinetic energy (NIKE) and its variability suggests that the seasonal mean noise is predominantly a statistical residue of variability resulting from dynamical processes operating on monthly and shorter times scales. A stochastically-forced barotropic model (linearized about the AGCM's 1983 and 1989 base states) is used to further assess the role of the basic state, submonthly transients, and tropical forcing, in modulating the uncertainties in the seasonal AGCM forecasts. When forced globally with spatially-white noise, the linear model generates much larger variance for the 1989 base state, consistent with the AGCM results. The extratropical variability for the 1989 base state is dominanted by a single eigenmode, and is strongly coupled with forcing over tropical western Pacific and the Indian Ocean, again consistent with the AGCM results

  13. The progression of the boreal winter monsoon through the western Maritime Continent as differentiated by ENSO phase

    Science.gov (United States)

    Lee, Shao-Yi; McBride, John L.

    2016-08-01

    The impact of global ENSO on the regional monsoon onset over the Maritime Continent is examined, using satellite-derived scatterometer surface winds over the sea channel from the South China Sea, through the Karimata Strait into the Java Sea. An index of monsoon onset, fracsign, is defined based on a positive dot-product between the monthly wind at each gridpoint and the "basis-wind" or climatological wind at the peak of the relevant monsoon season.Rather than being delayed throughout the Maritime Continent during El Niño years, the monsoon is seen to arrive faster at and remain longer over the western Maritime Continent, and therefore delayed for the eastern Maritime Continent. The wind-based diagnostic can be further decomposed into two components that reflect the monsoon wind strength and the location of the wind convergence zone, respectively. During El Niño years, the monsoon strength post-onset is weaker than normal over the eastern maritime continent. However, there is no ENSO-related differentiation in monsoon strength post-onset over the western Maritime Continent.

  14. RELATIONSHIP BETWEEN WEST PACIFIC SUBTROPICAL HIGH AND ENSO AND ITS INFLUENCE ON RAINFALL DISTRIBUTION OF RAINY SEASON IN FUJIAN

    Institute of Scientific and Technical Information of China (English)

    蔡学湛; 吴滨; 温珍治

    2003-01-01

    Relationship between the variations of West Pacific subtropical high indices in the summer half of the year and preceding SST in North Pacific was examined based on a data set of 1951 - 2000. The correlation between the subtropical high indices and preceding SST in the equatorial East Pacific was the strongest among the others, and has great persistency from last autumn to spring. It is indicated that ENSO events appeared about six months earlier than the change of the subtropical high activities, and the subtropical high intensities enhanced (weakened) and western ridge point was westward (eastward) in the year of El Nino(La Nina) events. It was also observed that there were similar interdecadal oscillation and abrupt variations between Nino3 SST, subtropical high intensities and rainfall of rainy season in Fujian. Therefore, experiments were made on rainfall distribution of rainy season in Fujian. The results showed that the distribution was directly affected by the subtropical high activities, pronouncedly caused by ENSO effect.

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

    Science.gov (United States)

    Ham, Yoo-Geun

    2017-08-01

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

  16. Response of the coral reef benthos and herbivory to fishery closure management and the 1998 ENSO disturbance.

    Science.gov (United States)

    McClanahan, T R

    2008-02-01

    The hypothesis that herbivory is higher in areas without fishing and will increase the rate at which hard coral communities return to pre-disturbance conditions was tested in and out of the marine protected areas (MPA) of Kenya after the 1998 El Niño Southern Oscillation (ENSO). Herbivory was estimated by assay and biomass methods, and both methods indicated higher herbivory in fishery closures. Despite higher herbivory, the effect of the ENSO disturbance was larger within these closures, with reefs undergoing a temporary transition from dominance by hard and soft coral to a temporary dominance of turf and erect algae that ended in the dominance of calcifying algae, massive Porites, Pocillopora and a few faviids six years after the disturbance. The fished reefs changed the least but had a greater cover of turf and erect algae and sponge shortly after the disturbance. Higher herbivory in the fishery closures reduced the abundance and persistence of herbivore-susceptible erect algae and created space and appropriate substratum for recruiting corals. Nonetheless, other post-settlement processes may have had strong influences such that annual rates of coral recovery were low ( approximately 2%) and not different between the management regimes. Recovery, as defined as and measured by the return to pre-disturbance coral cover and the dominant taxa, was slower in fishery closures than unmanaged reefs.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yang [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Now at Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Russell, Lynn M. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Xu, Li [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Lou, Sijia [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Lamjiri, Maryam A. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Somerville, Richard C. J. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Miller, Arthur J. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Cayan, Daniel R. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; DeFlorio, Michael J. [Scripps Institution of Oceanography, University of California, San Diego, La Jolla California USA; Ghan, Steven J. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Liu, Ying [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Singh, Balwinder [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Wang, Hailong [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA; Yoon, Jin-Ho [Gwangju Institute of Science and Technology, Gwangju South Korea; Rasch, Philip J. [Atmospheric Science and Global Change Division, Pacific Northwest National Laboratory, Richland Washington USA

    2016-06-02

    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 is 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 Pacific

  18. AN ANALYSIS ON LARGE-SCALE AIR-SEA INTERACTIVE LINKAGES BETWEEN THE TROPICAL INDIAN OCEAN AND THE PACIFIC OCEAN DURING ENSO EVENTS

    Institute of Scientific and Technical Information of China (English)

    DENG Bei-sheng; LIU Hai-tao; CHOU Ji-fan

    2010-01-01

    By utilizing a 3-D atmospheric circulation resolving method, the authors studied the air-sea interactive linkages between the tropical Indian Ocean and the Pacific Ocean in 1979-2008 El Nino-Southern Oscillation (ENSO) events. Their findings showed that evident 3-D gear-coupling characteristics existed in the 1979-2008 ENSO events. Their resolving analyses also suggested that the general circulation showed stronger and wider sinking motions over the eastern Indian Ocean-western Pacific during the mature phase of 1979-2008 ENSO events, compared with the vertical velocities from the U.S. National Centers for Enviornmental Prediction (NCEP) reanalysis data. With their 3-D analysis method, the vertical velocity was resolved by two components, i.e. zonal and meridional components. It was found that the zonal component of the vertical velocities showed a strong sinking motion while the meridional components showed an upward motion during the prevailing phases of the ENSO events,In the tropics, the zonal component of the vertical velocities was found greater than the meridional component, reflecting the dominant characteristics of the vertical velocity, and the overall outcomes showed a strong sinking motion, although the two components also partially offset each other in the processes. Compared with the vertical velocities from NCEP reanalysis, the vertical motions calculated with the 3-D resolving analysis method demonstrate some advantages.

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

    Science.gov (United States)

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

    2016-04-01

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

  20. Prediction Method of El Nino Southern Oscillation: ENSO by Means of Wavelet Based Data Compression with Appropriate Support Length of Base Function

    Directory of Open Access Journals (Sweden)

    Kohei Arai

    2013-08-01

    Full Text Available Method for El Nino/Southern Oscillation: ENSO by means of wavelet based data compression with appropriate support length of base function is proposed. Through the experiments with observed southern oscillation index, the proposed method is validated. Also a method for determination of appropriate support length is proposed and is validated.

  1. An Application of Advanced Ensemble Streamflow Prediction Methods to Assess Potential Impacts of the 2015 - 2016 ENSO Event over the Colorado River Basin

    Science.gov (United States)

    Miller, W. P.; Lamb, K. W.; Piechota, T. C.; Lakshmi, V.; Santos, N. I.; Tootle, G. A.; Kalra, A.; Fayne, J.

    2015-12-01

    Water resource managers throughout the Western United States have struggled with persistent and severe drought since the early 2000s. In the Colorado River Basin, the National Oceanic and Atmospheric Administration's (NOAA's) Colorado Basin River Forecast Center (CBRFC) provides forecasts of water supply conditions to resource managers throughout the basin using Ensemble Streamflow Prediction (ESP) methods that are largely driven by historical observations of temperature and precipitation. Currently, the CBRFC does not have a way to incorporate information from climatic teleconnections such as the El Niño Southern Oscillation (ENSO). ENSO describes warming sea surface temperatures in the Pacific Ocean that typically correlate with cool and wet winter precipitation events in California and the Lower Colorado River Basin during an El Niño event. Past research indicates the potential to identify analog ENSO events to evaluate the impact to reservoir storage in the Colorado River Basin. Current forecasts indicate the potential for one of the strongest El Niño events on record this winter. In this study, information regarding the upcoming ENSO event is used to inform water supply forecasts over the Upper Colorado River Basin. These forecasts are then compared to traditionally derived water supply forecast in an attempt to evaluate the possible impact of the El Niño event to water supply over the Colorado River Basin.

  2. A simple approach to quantifying the noise-ENSO interaction. Part II: the role of coupling between the warm pool and equatorial zonal wind anomalies

    Science.gov (United States)

    Levine, Aaron F. Z.; Jin, Fei Fei; Stuecker, Malte F.

    2017-01-01

    Stochastic forcing has been used conceptually to explain ENSO irregularity. More recently, the concept of state-dependent (multiplicative) stochastic forcing has been explored as an explanation of a number of ENSO properties. By calculating the state-dependence factor of ENSO zonal wind stress noise forcing on SST, we are able to separate the additive and multiplicative components of the wind stress noise forcing of ENSO. Spatially, the months with large additive or multiplicative components all resemble previous studies on westerly wind bursts. They differ from each other in that the wind stresses are significantly stronger during months with a large multiplicative noise component. It is further shown that when the multiplicative noise component is large, there have been large values of the wind stress noise in the preceding months. This is not true of the months when the additive component is large. The multi-month growth of the wind stress from the multiplicative noise process is shown to be related to an eastward migration of the western Pacific Warm Pool, which is coupled to the wind stress through convection. This process is shown to be significantly weakened in a climate model when the ocean and atmosphere are uncoupled.

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

    Science.gov (United States)

    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

  4. Predictable Modes of Summertime Upper-Tropospheric Circulation in the Northern Hemisphere: Linkage with Global Monsoon and ENSO

    Science.gov (United States)

    Lee, June-Yi; Wang, Bin; Ding, Q.; Ha, K.-J.

    2010-05-01

    The first two leading empirical orthogonal function (EOF) modes of summertime upper-tropospheric circulation in the Northern Hemisphere (NH) are identified as predictable modes using National Centers for Environmental Prediction (NCEP)/department of Energy (DOE) reanalysis II in concert with three coupled models' hindcast data from NCEP, Geophysical Fluid Dynamic Lab (GFDL), and Bureau of Meteorology Research Center (BMRC) for 25 years of 1981-2005. The analysis reveals that prediction skills of individual coupled models and their multi-model ensemble (MME) prediction for JJA 200-hPa geopotential height (GPH) in the NH basically come from the coupled models' capability in predicting the two predictable modes of interannual variability. In observation (the one-month lead MME prediction), the first two EOF modes altogether account for 84 % (90.1%) and 35.4 % (70.5%) of the total variance over the Tropics and the Extratropics, respectively, in the NH, indicating that the MME highly overestimates fractional variance of the predictable modes especially over the Extratropics. The residual higher modes cannot be captured by the current coupled models and their MME prediction. The long-lead predictability of the first EOF mode comes mainly from El Niño-Southern Oscillation (ENSO) since it tends to occur summers after mature phase of ENSO. The MME well predicts both temporal and spatial characteristics of the first mode even at 5-month lead (January initial condition) with a temporal correlation coefficient (TCC) skill for principal component (PC) of 0.62 and a pattern correlation coefficient (PCC) skill for eigenvector of 0.96. The second EOF mode is related to not only developing ENSO on interannual time scale but also SST variability over the North Pacific and Atlantic Ocean on interdecadal time scale. The MME is also capable to capture the second mode even at 5-month lead with a TCC skill of 0.67 and a PCC skill of 0.87. While the MME well predicts the zonally

  5. Verification of SPCZ and ENSO dynamics in the extended reanalysis period using the South Pacific Rainfall Atlas

    Science.gov (United States)

    Lorrey, Andrew; Dalu, Giovanni; Diamond, Howard; Gaetani, Marco; Renwick, James

    2010-05-01

    Ground-based rainfall observations during the pre-satellite era in the South West Pacific were examined for an extreme La Niña event that occurred in 1955-56. The rainfall observations were derived from the South Pacific Rainfall Atlas (SPRAT), a data compilation contributed by the regional meteorological services. The influence of tropical cyclone activity on both monthly and warm season rainfall anomalies were also accounted for using the International Best Tracks Archive for Climate Stewardship (IBTrACS) tropical cyclone database. The rainfall anomalies from more than 60 southwest Pacific Island stations showed a region of enhanced rainfall in the southwest half of the south Pacific encompassing the Southern Cook Islands, Tonga, Fiji, New Caledonia, and Vanuatu. Suppressed rainfall was observed in the northeast corner of the region over the Marquesas, the Northern Cook Islands, Tokelau, and Tuvalu. This pattern is similar to what is expected for La Nina events that occurred during the classic re-analysis period (1958 onward). Elimination of anomalously high historical rainfall totals for individual islands using the IBTrACS data allowed a 'best guess' of the past SPCZ position, suggesting it was probably southwest of the its normal climatological position during the 1955-56 La Nina. A comparison of the 'best guess' SPCZ position fit derived from the rainfall anomalies to the omega velocity furnished by the NOAA-CIRES reanalysis show a remarkably similar position of the SPCZ during the 1955-56 ENSO event. Ground-based rainfall observations that support SPRAT (which extend into the early 1900s and beyond) can therefore confirm the fidelity of the NOAA-CIRES extended 20th century reanalysis and can help to reveal past ENSO and SPCZ dynamics. In addition, the high-resolution daily reanalysis data and IBTrACS information indicate a unique SPCZ control on regional tropical cyclone trajectories into the Southern Hemisphere mid-latitudes during ex-tropical transition

  6. Dynamics of upper tropospheric stationary wave anomalies induced by ENSO during the northern summer: A GCM study

    Science.gov (United States)

    Krishnan, R.; Venkatesan, C.; Keshavamurty, R. N.

    1998-03-01

    Ensemble seasonal integrations are carried out with the COLA GCM, with a view to understand the dynamical connection between warm SST anomalies in the equatorial central-eastern Pacific Ocean and the upper level stationary wave anomalies seen during drought years over the Indian summer monsoon region. In addition, experiments with and without orography are performed in order to examine the role of the Himalayas in modulating the El Niño induced stationary wave anomalies over the summer monsoon region. The GCM simulations show a statistically significant weakening of the summer monsoon activity over India in response to the SST forcing in the equatorial Pacific Ocean. This weakening of the summer monsoon appears to be largely related to modifications of the local Hadley and Walker cells over the summer monsoon region. In addition, it is seen that the anomalous ENSO divergent forcing over the tropical Pacific Ocean can act as a potential source for Rossby wave dispersion. Here one finds the possibility of meridionally propagating Rossby waves, which emanate from the ENSO forcing region, to interact with the subtropical westerlies and generate anomalous highs and lows in the subtropics and extratropics. The quasi-stationary perturbations seen over west Asia, Pakistan and northwest India during drought years, seem to be generated by the above mechanism. An alternate mechanism that could be important for the persistence of the quasi-stationary perturbations seems to be based on the dynamic excitation of middle latitude normal modes which can extract energy from the zonally varying unstable basic flow. It is seen from the GCM simulations, that the Himalayan orography plays a crucial role in anchoring the El Niño induced extratropical westerly troughs far to the west in the high latitude belt. In the absence of orography it is seen that the ENSO induced extra-tropical cyclonic anomalies tend to intrude southward into the monsoon region thereby destroying the regional

  7. ENSO impacts on the South American rainfall during 1980s: Hadley and Walker circulation

    Energy Technology Data Exchange (ETDEWEB)

    De Souza, E.B.; Ambrizzi, T. [Departamento de Ciencias Atmosfericas, Instituto Astronomico y Geofisico, Sao Paulo, SP (Brazil)

    2002-04-01

    The changes in the Hadley and Walter cells and their respective impacts on the South American rainfall during the ENSO episodes observed in the decade of 80, were investigated through cross-sections analyses of the atmospheric circulation in altitude, averaged in the zonal and meridional planes. Such large-scale cells almost inverted their climatological circulation pattern, during El Nino events (1982-83 and 1986-87). In these years, manifestation of the anomalous descending branch of the Hadley and Walker cells affects most of the north-northeast of South America, which inhibited the convective activity associated to the Inter Tropical Convergence Zone (ITCZ) and caused drought conditions in the rainy seasons of the Guyana, Surinam, French Guyana, center-east of the Amazon and most of the Northeast Brazil. On the other hand, conditions of excess of precipitation observed in the south-southeast of South America, were favored by the anomalous ascending branch of the Hadley cell. During La Nina events (1984-85 and 1988-89), it was observed an intensification of the ascending and descending branches associated to the Walker and Hadley cells. The anomalous large-scale ascending movement associated to these cells, was extended to the Northeast of Brazil and equatorial South Atlantic, favoring ITCZ to become more active than the normal, which resulted in an above normal rainy season in these areas. An intense subsidence was noticed in the mid latitudes of South America, which inhibited the large-scale convection in the region, explaining the deficient rainy season observed in most of the south-southeast of South America. [Spanish] Los cambios en las celulas de Hadley y Walker y sus respectivos impactos en Suramerica, en las lluvias, durante los episodios en ENOS, observados en la decada de los 80, son investigados a traves de analisis de reacciones cruzadas de la circulacion atmosferica en altitudes promediadas en planos zonal y meridional. Tales celulas de gran escala

  8. Wavelet analysis of the singular spectral reconstructed time series to study the imprints of solar-ENSO-geomagnetic activity on Indian climate

    Science.gov (United States)

    Lakshmi Sunkara, Sri; Krishna Tiwari, Rama

    2016-09-01

    To study the imprints of the solar-ENSO-geomagnetic activity on the Indian subcontinent, we have applied singular spectral analysis (SSA) and wavelet analysis to the tree-ring temperature variability record from the Western Himalayas. Other data used in the present study are the solar sunspot number (SSN), geomagnetic indices (aa index), and the Southern Oscillation Index (SOI) for the common time period of 1876-2000. Both SSA and wavelet spectral analyses reveal the presence of 5-7-year short-term ENSO variations and the 11-year solar cycle, indicating the possible combined influences of solar-geomagnetic activities and ENSO on the Indian temperature. Another prominent signal corresponding to 33-year periodicity in the tree-ring record suggests the Sun-temperature variability link probably induced by changes in the basic state of the Earth's atmosphere. In order to complement the above findings, we performed a wavelet analysis of SSA reconstructed time series, which agrees well with our earlier results and increases the signal-to-noise ratio, thereby showing the strong influence of solar-geomagnetic activity and ENSO throughout the entire period. The solar flares are considered responsible for causing the atmospheric circulation patterns. The net effect of solar-geomagnetic processes on the temperature record might suggest counteracting influences on shorter (about 5-6-year) and longer (about 11-12-year) timescales. The present analyses suggest that the influence of solar activities on the Indian temperature variability operates in part indirectly through coupling of ENSO on multilateral timescales. The analyses, hence, provide credible evidence of teleconnections of tropical Pacific climatic variability and Indian climate ranging from inter-annual to decadal timescales and also suggest the possible role of exogenic triggering in reorganizing the global Earth-ocean-atmospheric systems.

  9. A response in the ENSO cycle to an extratropical forcing mechanism during the El Niño to La Niña transition

    Directory of Open Access Journals (Sweden)

    Yafei Wang

    2013-12-01

    Full Text Available Current El Niño-Southern oscillation (ENSO theory emphasizes that the forcing that drives the cycle mainly exists within tropical regions. However, these ideas are quite limited in explaining completely the occurrence of ENSO. Here, we examine whether extratropical forcing can affect ENSO cycle, specifically the transition from El Niño to La Niña. Although dispersion of the Okhotsk-Japan (OKJ atmospheric wave train across the mid-latitude North Pacific during June terminates in the subtropics, the associated regime of southward surface wind anomalies could reach Eastern Equatorial Pacific (EEP. The OKJ wave train plays a substantial role in generating a similar underlying sea surface temperature (SST wave train through a barotropic process in air–sea interactions and after September, it is negatively correlated strongly with the SST around EEP. Strong OKJ propagation in the positive (negative phase during June is more (less significantly associated with a subsequent La Niña (El Niño episode that is matured after October. Negative SST anomalies at the southern end of the SST wave train with strong overlying OKJ propagation in the positive phase during June and the associated southward surface wind anomalies retained its strength by the further infusion of energy and gradual southward displacement joining the negative SST anomalies around EEP after the October when La Niña usually matured in-situ. Strong OKJ propagation in the positive phase during June tends to occur during a quick summer and fall transition period from El Niño to La Niña. This study strongly suggests that extratropical forcing plays an ignored role in affecting ENSO cycle especially in the formation of La Niña, which was not included in current ENSO theory.

  10. Changes in biomass burning mark the onset of an ENSO-influenced climate regime at 42°S in southwest Tasmania, Australia

    Science.gov (United States)

    Fletcher, Michael-Shawn; Benson, Alexa; Heijnis, Hendrik; Gadd, Patricia S.; Cwynar, Les C.; Rees, Andrew B. H.

    2015-08-01

    We use macroscopic charcoal and sediment geochemistry analysis of two proximal upper montane lakes located at 42°S in southwest Tasmania, Australia, to test the role of the southern hemisphere westerly winds (SWW) and the El Niño-Southern Oscillation (ENSO) in governing the climate of this sector of the southern mid-to high-latitudes. Inter-annual climate anomalies in the study area are driven by changes in both ENSO and the Southern Annular Mode (SAM - an index that describes seasonal to decadal shifts in the SWW), making it an ideal location to test assumptions about the varying influence of the SWW and ENSO, two important components of the global climate system, through time. We find multi-millennial scale trends in fire activity that are remarkably consistent with trends in hydroclimate reconstructed at the same latitude in southern South America, providing empirical support for the notion of zonally symmetric changes in the SWW governing the climate at this latitude in the Southern Hemisphere between 12 and 5 cal ka BP. A transition from multi-millennial scale to sub-millennial scale trends in fire activity occurs after ca 5 cal ka BP in concert with the onset of high frequency and amplitude ENSO variability in the tropical Pacific Ocean region. We conclude that the onset of sub-millennial scale trends in ENSO drove changes in fire activity in our study region over the last ca 5 cal ka. Geochemical data reveals divergent local impacts at the two study sites in response to these major climate transitions that are related to local topography and geography.

  11. Effects of ENSO and temporal rainfall variation on the dynamics of successional communities in old-field succession of a tropical dry forest.

    Science.gov (United States)

    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 and

  12. Possible effect of ENSO on annual sediment discharge of debris flows in the Jiangjia Ravine based on Morlet wavelet transforms

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The multi-time-scale structures of an annual sediment discharge series of debris flow in the Jiangjia Ravine and the Southern Oscillation index are analysed using the method of Morlet wavelet transformations. The possible effects of El Nino episodes on the annual sediment discharge are discussed by comparing the period variations of ENSO and the discharge. The results show that the annual sediment discharge series of debris flow is related to El Nino episodes. Generally, the annual sediment discharge of debris flow is less than usual during an El Nino episode and debris flow is less active. On the contrary, the annual sediment discharge of debris flows is greater than usual during a La Nina episode and debris flows are more frequent. There is a relationship between the annual sediment discharges of debris flow in the Jiangjia Ravine and the summer Southern Oscillation index, with both having quasi-periodic variations of 2 and 5-6 years.

  13. Simulation of tropical tropospheric ozone variation from 1982 to 2010: The meteorological impact of two types of ENSO event

    Science.gov (United States)

    Hou, Xuewei; Zhu, Bin; Fei, Dongdong; Zhu, Xiaoxin; Kang, Hanqing; Wang, Dongdong

    2016-08-01

    The effects of two types of ENSO events on tropical ozone (O3) variations from 1982 to 2010, and the mechanisms underlying these effects, were analyzed using observations and model simulations. Tropospheric column O3 anomalies (TCOA) during canonical El Niño were different from El Niño Modoki. Absolute TCOA values are larger during canonical El Niño than during El Niño Modoki in most regions. La Niña events were not separated into the different types because of their similarity in terms of sea surface temperature patterns. TCOA in La Niña showed a reversed dipole from canonical El Niño. During canonical El Niño, anomalous downward motion together with suppressed convection weakened O3 outflow from the troposphere, causing an increase in tropospheric O3 over western Pacific. Over central and eastern Pacific, decreased O3 concentrations resulted primarily from a change in net chemical production of O3. The change in net O3 chemical production relates to increased levels of HOx under wetter condition. During El Niño Modoki, transport and chemical fluxes were similar but weaker than during canonical El Niño. During La Niña, O3 anomalies and transport fluxes were the opposite of those during the El Niño Modoki. Stratospheric O3 played a key role in the development of O3 anomaly above 250 hPa during ENSO events, contributing >30% to the O3 anomalies. The change in free tropospheric O3 affected the O3 anomaly from 850 hPa to 200 hPa (60% of O3 anomaly). The contribution of O3 from planetary boundary layer was concentrated at the surface, with a contribution of <15%.

  14. Trends of syphilis in Posadas city (Misiones State, Argentina, 1997-2000 Incidência de sífilis na cidade de Posadas (estado de Misiones, Argentina, 1997-2000

    Directory of Open Access Journals (Sweden)

    Ramón Alberto de Torres

    2001-01-01

    Full Text Available Objectives: Misiones State is situated in the north-east of Argentina. The main objective was to establish the evolution of syphilis in Posadas city (300.000 inhabitants from 1997 to 2000. Methods: Outpatients were studied at the STD clinics during 1997. Records of all pregnant women with babies due to the months of April to June, from 1997 to 2000 (n = 4700, were studied. Syphilis was confirmed by clinic, epidemiological and laboratory tests (VDRL and FTA-ABS. Results: Higher incidence of primary syphilis in outpatients was established among 15-19 year-old women and in 20-24 year-old men. The percentages of pregnant women with syphilis were 2.1% (1997, 2.6% (1998, 4.6% (1999 and 3.7% (2000. The most vulnerable age group was 15 to 19 year-old. Geographical distribution of cases changed from four clusters in 1997 to a wide occurrence in all city quarters with lower socioeconomic level (30% of population. Conclusion: Posadas city had an increase in cases of syphilis in pregnant women from 1997 to 1999. This evolution indicates that traditional STD-Aids programs have had no effect on safe sex practices, specially among adolescents. Home by home visits aimed at improving prenatal control as a priority, started in 1999. The incidence of the disease became stable in 2000, but still at a high rate. It is necessary to continue and improve the outreach activities. A cooperative program in these big "twin" cities: Encarnación (Paraguay and Posadas (Argentina - will be also of great help for syphilis control in the area.Objetivos: O estado de Misiones está situado no noroeste argentino, nas fronteiras oeste e norte com o Brasil e a leste do Paraguai. Este foi o interesse para estabelecer a evolução da sífilis na cidade de Posadas (300.000 habitantes, capital do estado de Misiones, desde 1997 até 2000. Métodos: A sífilis foi analisada por meio da avaliação epidemiológica, clínica e confirmação laboratorial (VDRL e FTA- ABS. Todas as mulheres grávidas no momento da evolução foram consultadas no hospital Madariaga, durante o período de abril a junho, de 1997 até 2000 (n = 4700, as quais foram incluídas nas análises. Resultados: A freqüência da sífilis em mulheres grávidas atendidas em hospital público foi de 2,1% (1997, 2,6% (1998, 4,6% (1999 e 3,7% (2000. A faixa etária de maior vulnerabilidade foi de 15 a 19 anos. A distribuição geográfica de casos originados de quatro grupos isolados em 1997 expandiu-se para uma grande ocorrência em todas as regiões de baixo nível de vida socioeconômico (30% do total da população. A sífilis congênita chegou a uma média de 10,8 casos por 1.000 crianças nascidas vivas nos últimos anos. Conclusão: A cidade de Posadas teve um aumento de sífilis em mulheres grávidas de 1997 até 1999. Esta situação endêmica indica que o programa convencional STD-Aids teve um efeito mínimo ou nulo sobre a prática do sexo, principalmente em grupos de adolescentes. Um programa de intervenção do alvo geográfico (visita casa por casa direcionado para prover controle pré-natal como prioridade teve início em 1999. Uma estabilização da sífilis em mulheres grávidas foi demonstrada em 2000, mas a incidência é ainda demasiadamente alta. Torna-se necessária a discussão de um programa de extensão regional que inclua a população binacional das grandes áreas povoadas.

  15. Un análisis de la estructura termal de la estación costera 'La Libertad' y su relación con los eventos ENSO

    Directory of Open Access Journals (Sweden)

    1998-01-01

    Full Text Available ANALYSE DE LA STRUCTURE THERMIQUE DE L’OCEAN A LA STATION «LA LIBERTAD» ET DE SA RELATION AVEC L’ENSO. L’Institut Océanographique Militaire (INOCAR assure tous les 20 jours, depuis 1990, des mesures dans une colonne d’eau de 100 m de profondeur, à dix milles au large du port équatorien de La Libertad, situé dans la Péninsule de Santa Helena. On y observe des ondes équatoriales qui provoquent une augmentation du niveau moyen de l’eau et un enfoncement des isothermes, ce qui permet de considérer que leur distribution est liée à l’apparition des événements ENSO. Nous avons déterminé par ailleurs la relation entre le niveau moyen de l’océan et la profondeur des isothermes. Pour cela nous avons choisi l’isotherme de 20°C que l’on supposera représentative de la distribution thermique (de l’océan dans cette station côtière. El Instituto Oceanográfico de la Armada (INOCAR mantiene desde 1990 hasta la fecha una estación costera a 10 millas náuticas frente a las costa del puerto de La Libertad (Península de Santa Elena, en la que se efectúa un muestreo de toda la columna de agua desde la superficie hasta los 100 m de profundidad, cada 20 días. Del análisis preliminar se ha podido observar que la distribución de las isotermas responde a la presencia de los eventos ENSO como se conoce, durante un episodio ENSO la costa del Ecuador es visitada por ondas ecuatoriales, las cuales a su paso producen una elevación del nivel medio del mar y una profundización de las isotermas. Por lo que se considera que esta distribución de las isotermas guarda relación con la ocurrencia de los eventos ENSO frente a nuestras costas. Por otro lado se determina la relación existente entre el nivel del mar y la profundización de las isotermas. Para este efecto, se simplificó la distribución térmica de la estación costera de La Libertad, seleccionando la isoterma de 20°C, por considerarla representativa de la distribución t

  16. ENSO forcing of the Northern Hemisphere climate in a large ensemble of model simulations based on a very long SST record

    Energy Technology Data Exchange (ETDEWEB)

    Herceg Bulic, Ivana [University of Zagreb, Andrija Mohorovicic Geophysical Institute, Faculty of Science, Zagreb (Croatia); Brankovic, Cedo [Croatian Meteorological and Hydrological Service, Zagreb (Croatia)

    2007-02-15

    The January-March (JFM) climate response of the Northern Hemisphere atmosphere to observed sea surface temperature (SST) anomalies for the period 1855-2002 is analysed from a 35-member ensemble made with SPEEDY, an atmospheric general circulation model (AGCM) of intermediate complexity. The model was run at the T30-L8 resolution, and initial conditions and the early stage of model runs differ among ensemble members in the definition of tropical diabatic heating. SST anomalies in the Nino3.4 region were categorised into five classes extending from strong cold to strong warm. Composites based on such a categorisation enabled an analysis of the influence of the tropical Pacific SST on the Northern Hemisphere atmospheric circulation with an emphasis on the Pacific-North America (PNA) and the North Atlantic-Europe (NAE) regions. As expected, the strongest signal was detected over the PNA region. An ''asymmetry'' in the model response was found for the opposite polarity of the Nino3.4 index; however, this asymmetry stems mainly from the difference in the amplitude of model response rather than from the phase shift between responses to warm and cold El Nino-Southern Oscillation (ENSO) events. The extratropical signal associated with warm ENSO events was found to be stronger than that related to cold events. The results also reveal that, for the PNA region, the amplitude of the response is positively correlated with the strength of ENSO, irrespective of the sign of ENSO. With almost no phase shift between model responses to El Nino and La Nina, the linear component of the response is much stronger than the non-linear component. Although the model climate response over the NAE region is much weaker than that over the PNA region, some striking similarities with the PNA are found. Both sea level pressure and precipitation responses are positively correlated with the strength of ENSO. This is not true for the 200-hPa geopotential heights, and no plausible

  17. Isolation of myxoviruses from migratory waterfowls in San-in district, western Japan in winters of 1997-2000.

    Science.gov (United States)

    Shengqing, Yu; Shinya, Kyoko; Otsuki, Koichi; Ito, Hiroshi; Ito, Toshihiro

    2002-11-01

    Between November 1997 and February 2000, winter migratory waterfowls of several species staying in San-in district, western Japan were surveyed for influenza A virus and paramyxovirus at four stations. A total of 18 influenza A viruses was isolated from 1,404 fecal samples of whistling swans, pintails, mallards, and white-fronted geese. Five different hemagglutinins and eight neuraminidases were identified in the viruses isolated, in 11 different combinations, including H7N8 related to a subtype of a highly pathogenic chicken virus. In 2000, five lentogenic (non-pathogenic) Newcastle disease viruses were also isolated from white-fronted geese. These results suggested that possible precursor viruses for highly pathogenic avian myxoviruses are still brought into Japan by migratory waterfowls. The results also support the contention that continued surveillance of wild waterfowl population should be an integral part of control policies for these serious poultry diseases.

  18. Volatility and cross correlation across asset markets: Evidence from the French and US markets over the 1997-2000 period

    OpenAIRE

    Laborde, David; Rey, Serge

    2001-01-01

    This paper analyzes the causal relationships between returns and volatilities of assets prices in U.S. and French markets. The period for the study has been taken from January 1997 to December 2000, using daily and weekly data. Initial results show that U.S. stock prices "Granger-cause" French stock prices, while changes in French and American stock prices influence significatively the euro/dollar exchange rate. Moreover, it appears that the volatilities of stock markets are linked (with caus...

  19. Diagnostic value of frozen section study for thyroid nodules in patients referred to Shariati Hospital 1997-2000

    Directory of Open Access Journals (Sweden)

    "Shirzad M

    2001-11-01

    Full Text Available Frozen section is a useful method in the diagnosis of different malignancies including those of thyroid origin. However, there are still controversies about its application, sensitivity and specificity for thyroid neoplasm. In this study, diagnostic value of frozen section (FS was compared with permanent histopathologic and Fine Needle Aspiration (FNA. In this study, which was conducted in process research method, permanent sample, FNA, and frozen section results in 214 patients was compared. All of these 214 patients had been seeking medical evaluation for thyroid nodules between years 1997 and 1999 in Shariati hospital. All pathologic evaluations were performed by pathology staff of this hospital. Permanent pathology was considered as the gold standard; so the specificity, sensitivity and diagnostic precision of FNA and FS were evaluated on the basis of its results. We use Macnemar test for this purpose. The number of patients during this period were 214 (160 women and 54 men. Mean age of our patients was 42.3±5.4 and their age ranged between 12 to 84 years. Pathologic results revealed that 163 of the patients (76 percent had benign lesions, and 51 of them (24 percent had malignant lesions. Thyroid malignancies comparised papillary carcinoma (70 percent, follicular carcinoma (13.5 percent, papilofollicular carcinoma (6 percent, medulary carcinoma (6 percent, Hurtle cell carcinoma (4 percent and anaplastic carcinoma (5 percent. FNA was done in all of the patients before surgery and was able to determine the status of nodules in 150 patients. Sensitivity, specificity and precision of FNA in these 150 patients were 72, 96 and 90 percents respectively. When FNA was unable to determine the status of a nodule (64 remaining patients, FS was applied to do the job. A sensitivity of 36 percent, specificity of 85 percent and precision of 73 percent was found in this group of patients. Macnemar test showed that there is no significant difference between FNA and FS methods. This study showed: when FNA is not conclusive, FS will not bring any further benefit. It seems that only in suspicious cases of papillary, undifferentiated and medulary carcinomas, FS can be useful in certifying the results of FNA and choosing the appropriate surgical plan. We should wait for permanent sample reports in the case of follicular or Hurtle cell carcinoma.

  20. Online feature selection with streaming features.

    Science.gov (United States)

    Wu, Xindong; Yu, Kui; Ding, Wei; Wang, Hao; Zhu, Xingquan

    2013-05-01

    We propose a new online feature selection framework for applications with streaming features where the knowledge of the full feature space is unknown in advance. We define streaming features as features that flow in one by one over time whereas the number of training examples remains fixed. This is in contrast with traditional online learning methods that only deal with sequentially added observations, with little attention being paid to streaming features. The critical challenges for Online Streaming Feature Selection (OSFS) include 1) the continuous growth of feature volumes over time, 2) a large feature space, possibly of unknown or infinite size, and 3) the unavailability of the entire feature set before learning starts. In the paper, we present a novel Online Streaming Feature Selection method to select strongly relevant and nonredundant features on the fly. An efficient Fast-OSFS algorithm is proposed to improve feature selection performance. The proposed algorithms are evaluated extensively on high-dimensional datasets and also with a real-world case study on impact crater detection. Experimental results demonstrate that the algorithms achieve better compactness and higher prediction accuracy than existing streaming feature selection algorithms.

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

    Energy Technology Data Exchange (ETDEWEB)

    Moore, M.D.

    1995-12-31

    The Earth`s largest atmospheric convective center is the Indonesian Low. It generates the Australasian monsoon, drives the zonal tropospheric Walker Circulation, and is implicated in the genesis of the El Nino-Southern Oscillation (ENSO). The long-term variability of the Indonesian Low is poorly characterized, yet such information is crucial for evaluating whether changes in the strength and frequency of ENSO events are a possible manifestation of global warming. Stable oxygen isotope ratios ({delta}{sup 18}O) in shallow-water reef coral skeletons track topical convective activity over hundreds of years because the input of isotopically-depleted rainwater dilutes seawater {delta}{sup 18}O. Corals also impose a temperature-dependent fractionation on {delta}{sup 18}O, but where annual rainfall is high and sea surface temperature (SST) variability is low the freshwater flux effect dominates.

  2. Tropical Ocean Evaporation/SST Sensitivity and It's Link to Water and Energy Budget Variations During ENSO

    Science.gov (United States)

    Robertson, Franklin R.; Marshall, Susan; Oglesby, Robert; Roads, John; Sohn, Byung-Ju; Arnold, James E. (Technical Monitor)

    2001-01-01

    The continuing debate over feedback mechanisms governing tropical sea surface temperatures (SSTs) and tropical climate in general has highlighted the diversity of potential checks and balances within the climate system. Competing feedbacks due to changes in surface evaporation, water vapor, and cloud long- and shortwave radiative properties each may serve critical roles in stabilizing or destabilizing the climate system. It is also intriguing that even those climate variations having origins internal to the climate system - changes in ocean heat transport for example, apparently require complementary equilibrating effects by changes in atmospheric energy fluxes. Perhaps the best observational evidence of this is the relatively invariant nature of tropically averaged net radiation exiting the top-of-atmosphere (TOA) as measured by broadband satellite sensors over the past two decades. Thus, analyzing how these feedback mechanisms are operating within the context of current interannual variability may offer considerable insight for anticipating future climate change. In this paper we focus primarily on interannual variations of ocean evaporative fluxes and their significance for coupled water and energy cycles within the tropical climate system. In particular, we use both the da Silva estimates of surface fluxes (based on the Comprehensive Ocean Atmosphere Data Set, COADS) and numerical simulations from several global climate models to examine evaporation sensitivity to perturbations in SST associated with warm and cold ENSO events. The specific questions we address are as follows: (1) What recurring patterns of surface wind and humidity anomalies are present during ENSO and how do they combine to yield systematic evaporation anomalies?, (2) What is the resulting tropical ocean mean evaporation-SST sensitivity associated with this climate perturbation?, and (3) What role does this evaporation play in tropical heat and water balance over tropical oceanic regions? We

  3. Using CERES-Maize and ENSO as Decision Support Tools to Evaluate Climate-Sensitive Farm Management Practices for Maize Production in the Northern Regions of Ghana

    Science.gov (United States)

    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

  4. Using CERES-Maize and ENSO as Decision Support Tools to Evaluate Climate-Sensitive Farm Management Practices for Maize Production in the Northern Regions of Ghana.

    Science.gov (United States)

    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 R(2) 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.

  5. Changes in El Niño - Southern Oscillation (ENSO) conditions during the Greenland Stadial 1 (GS-1) chronozone revealed by New Zealand tree-rings

    Science.gov (United States)

    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.

  6. Sensitivity of the tropical Pacific seasonal cycle and ENSO to changes in mean state induced by a surface heat flux adjustment in CCSM3

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Xiaohua [Institute of Global Environment and Society, Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); George Mason University, Department of Atmospheric, Oceanic and Earth Sciences, Fairfax, VA (United States); University of Maryland at Baltimore County, Goddard Earth Science Technology Center, Baltimore, MD (United States); NASA GSFC Code 613.3, Greenbelt, MD (United States); Huang, Bohua; Shukla, Jagadish [Institute of Global Environment and Society, Center for Ocean-Land-Atmosphere Studies, Calverton, MD (United States); George Mason University, Department of Atmospheric, Oceanic and Earth Sciences, Fairfax, VA (United States)

    2011-07-15

    The influence of mean climate on the seasonal cycle and the El Nino-Southern Oscillation (ENSO) in the tropical Pacific climate is investigated using the Climate Community System Model Version 3 (CCSM3). An empirical time-independent surface heat flux adjustment over the tropical ocean is applied to the oceanic component of CCSM3. In comparison with the control run, the heat flux-adjusted run simulates a more realistic mean climate not only for the sea surface temperature (SST) but also for wind stress and precipitation. Even though the heat flux adjustment is time-independent, the seasonal cycles of SST, wind stress and precipitation over the equatorial eastern Pacific are more realistic in the flux-adjusted simulation. Improvements in the representation of the ENSO variability in the heat flux-adjusted simulation include that the Nino3.4 SST index is less regular than a strong biennial oscillation in the control run. But some deficiencies also arise. For example, the amplitude of the ENSO variability is reduced in the flux-adjusted run. The impact of the mean climate on ENSO prediction is further examined by performing a series of monthly hindcasts from 1982 to 1998 using CCSM3 with and without the heat flux adjustment. The flux-adjusted hindcasts show slightly higher predictive skill than the unadjusted hindcasts with January initial conditions at lead times of 7-9 months and July initial conditions at lead times of 9-11 months. However, their differences during these months are not statistically significant. (orig.)

  7. Inter-annual precipitation variabiity inferred from late Holocene speleothem records from Fiji: implications for SPCZ localisation and ENSO behaviour

    Science.gov (United States)

    Mattey, D.; Stephens, M.; Hoffmann, D.; Brett, M.

    2015-12-01

    The modern tropical Fiji climate is characterised by seasonal rainfall controlled by the position of the South Pacific Convergence Zone (SPCZ). Interannual rainfall is strongly modulated on decadal timescales by ENSO with higher rainfall associated with La Nina events. Voli Voli cave near Sigatoga (Viti Levu) is a stream passage that has been monitored since 2009. A U-Th dated laminated speleothem spans a 1500 year interval across the transition from the Medieval Warm Period into the Little Ice Age marked by a fabric change from finely laminated calcite with thin clay layers, to white well-laminated calcite. The older record is characterised by rising δ13C values followed by a rapid decrease in δ13C around 1200 AD. Evidence from cave monitoring shows that cave air CO2 levels are strongly seasonal as a result of greater ventilation by winter trade winds and high resolution δ13C record shows regularly spaced peaks correlated with paired laminae and cycles in P and S which provide annual markers driven by rainfall and seasonal ventilation. δ18O values remain relatively unchanged throughout the record but micromilling at sub-annual resolution reveals systematic cycles in δ18O that span groups of paired laminae with an inferred periodicity of 3-7 years i.e. a similar frequency to modern ENSO. The presence of these sub-decadal cycles in δ18O may be a result of a combination of factors. The amplitude of 2-3‰ would be equivalent to an amount-effect related change in annual precipitation of around 50% but an additional smoothing process, perhaps a result of aquifer storage, is required to attenuate interannual variance in precipitation. The Voli Voli record provides evidence of an underlying climatic change to more frequent La Niña conditions from 1200 AD and may be associated with increased conflict, shifts in settlements and changes in subsistence strategies on the island. Coeval speleothem isotope records from tropical Pacific Islands provide a provide a

  8. Coral record of southeast Indian Ocean SST, SSH and salinity and their modulation by ENSO and the Western Pacific temperature gradient

    Science.gov (United States)

    Zinke, Jens; Hoell, Andrew; Lough, Janice M.; Feng, Ming; McCulloch, Malcolm T.

    2016-04-01

    Variability of southeastern Indian Ocean (SEIO) sea surface temperatures (SST), sea surface height (SSH) and salinities off Western Australia is a footprint of interannual and decadal climate variations in the tropical Indo-Pacific. La Niña events often result in a strengthened Leeuwin Current, high coastal sea levels, low salinities and unusually warm SSTs, now termed Ningaloo Niño events. The long-term teleconnections of the southeastern Indian Ocean (SEIO) with ENSO and the West Pacific Warm Pool are poorly understood. Here we demonstrate the role of Indo-Pacific coupling in modulating SST, SSH and salinity in the poorly studied SEIO, through a robust 215 year (1795-2010) geochemical coral proxy sea surface temperature (SST), SSH and salinity record. We show that higher SST and SSH accompanied by lower salinities in the SEIO are linked to the behaviour of ENSO and the Western Pacific Warm Pool on decadal to centennial timescales, and are most pronounced when an anomalously strong zonal SST gradient between the western and central Pacific co-occurs with strong La Niña's. Better understanding of the interplay between the zonal SST gradient in the western Pacific, ENSO phase and intrinsic Indian Ocean variability is expected to improve our ability to better predict unusual marine heat waves, sea level surges and important consequences for marine socio-ecological systems in the Future.

  9. The dependence on atmospheric resolution of ENSO and related East Asian-western North Pacific summer climate variability in a coupled model

    Science.gov (United States)

    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).

  10. A 2000-year leaf wax-based hydrogen isotope record from Southeast Asia suggests low frequency ENSO-like teleconnections on a centennial timescale

    Science.gov (United States)

    Yamoah, Kweku A.; Chabangborn, Akkaneewut; Chawchai, Sakonvan; Schenk, Frederik; Wohlfarth, Barbara; Smittenberg, Rienk H.

    2016-09-01

    Limited understanding of the complex dynamics of the tropical monsoon exists, partly due to inadequate paleo (hydro)-climate proxy data from monsoonal regions. This study presents a 2000-year long record of hydrogen isotope values of leaf wax (δDwax) from a sedimentary sequence recovered from Lake Pa Kho, Northern Thailand. Evaluation of present day rainfall patterns and water isotope data indicates that δDwax reflects the amount of rainfall and is also influenced by El Niño-Southern Oscillation (ENSO) dynamics. Over the last 2000 years, wettest conditions occurred between ca. 700 AD and ca. 1000 AD, whereas the driest intervals lasted from ca. 50 BCE to ca. 700 AD and from ca. 1300 AD to ca. 1500 AD. Further investigations to establish the spatiotemporal variability of ENSO within the wider tropical Asian-Pacific realm over centennial timescales revealed a low-frequency-tripole pattern between mainland SE Asia (MSEA), the tropical West Pacific, and the central-eastern Pacific, with a wetter than normal MSEA during El Niño-like climate conditions. This pattern stands in contrast to the annual event where El Niño cause drier conditions in MSEA. We hypothesize that on centennial timescales the land-sea contrast, which drives monsoon intensity in MSEA, is modulated by the latitudinal shift of the Walker circulation and associated ENSO dynamics.

  11. Holocene climatic variations in the Western Cordillera of Colombia: A multiproxy high-resolution record unravels the dual influence of ENSO and ITCZ

    Science.gov (United States)

    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

  12. The role of the intra-daily SST variability in the Indian monsoon variability and monsoon-ENSO-IOD relationships in a global coupled model

    Energy Technology Data Exchange (ETDEWEB)

    Terray, Pascal; Kamala, Kakitha; Masson, Sebastien; Madec, Gurvan [Universite Pierre et Marie Curie, LOCEAN/IPSL, CNRS/IRD/UPMC/MNHN, Paris Cedex 05 (France); Sahai, A.K. [Indian Institute of Tropical Meteorology, Pune (India); Luo, Jing-Jia; Yamagata, Toshio [RIGC, Yokohama (Japan)

    2012-08-15

    The impact of diurnal SST coupling and vertical oceanic resolution on the simulation of the Indian Summer Monsoon (ISM) and its relationships with El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events are studied through the analysis of four integrations of a high resolution Coupled General Circulation Model (CGCM), but with different configurations. The only differences between the four integrations are the frequency of coupling between the ocean and atmosphere for the Sea Surface Temperature (SST) parameter (2 vs. 24 h coupling) and/or the vertical oceanic resolution (31 vs. 301 levels) in the CGCM. Although the summer mean tropical climate is reasonably well captured with all the configurations of the CGCM and is not significantly modified by changing the frequency of SST coupling from once to twelve per day, the ISM-ENSO teleconnections are rather poorly simulated in the two simulations in which SST is exchanged only once per day, independently of the vertical oceanic resolution used in the CGCM. Surprisingly, when 2 h SST coupling is implemented in the CGCM, the ISM-ENSO teleconnection is better simulated, particularly, the complex lead-lag relationships between the two phenomena, in which a weak ISM occurs during the developing phase of an El Nino event in the Pacific, are closely resembling the observed ones. Evidence is presented to show that these improvements are related to changes in the characteristics of the model's El Nino which has a more realistic evolution in its developing and decaying phases, a stronger amplitude and a shift to lower frequencies when a 2-hourly SST coupling strategy is implemented without any significant changes in the basic state of the CGCM. As a consequence of these improvements in ENSO variability, the lead relationships between Indo-Pacific SSTs and ISM rainfall resemble the observed patterns more closely, the ISM-ENSO teleconnection is strengthened during boreal summer and ISM rainfall power spectrum

  13. Diversity in the representation of large-scale circulation associated with ENSO-Indian summer monsoon teleconnections in CMIP5 models

    Science.gov (United States)

    Ramu, Dandi A.; Chowdary, Jasti S.; Ramakrishna, S. S. V. S.; Kumar, O. S. R. U. B.

    2017-03-01

    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

  14. The impact of ENSO on water vapor isotopologues in the tropical pacific: Evidence for changes in long-range transport and convective activity

    Science.gov (United States)

    Jonson Sutanto, Samuel; Hoffmann, Georg; Scheepmaker, Remco A.; Röckmann, Thomas

    2014-05-01

    ENSO (El Niño-Southern Oscillation) is characterized by quasi-periodic changes of tropical sea surface temperature (SST), near-global atmospheric circulation and associated changes in precipitation patterns. Due to the profound effects of ENSO on the global water cycle and on the associated fractionation processes of the water isotopologues, many isotope-based studies have been carried out to study the ENSO variability in the tropics. These studies conclude that "the isotope amount effect'' is a key factor controlling the isotopic signature of water vapor and precipitation close to the surface. The goal of this study is to investigate the hydrologic processes governing the changes in isotopic composition of water vapor at the surface and at higher altitudes during ENSO events. We used the isotopic composition of water vapor modeled by an isotope-enabled GCM (ECHAM4), and measured by the TES (Tropospheric Emission Spectrometer) instrument onboard the Aura satellite. The isotopic composition of precipitation was modeled by ECHAM4 and observed by the GNIP network (Global Network of Isotopes in Precipitation). The amount of precipitation was modeled by ECHAM4 and ERA-Interim (ECMWF Re-Analysis), and measured by the TRMM (Tropical Rainfall Measuring Mission) satellite. Our results agree with previous studies focusing on the lower atmosphere: rainout processes, less rain re-evaporation of falling droplets, and increase of convective updrafts and diffusive exchange within the convective systems (all these processes contribute to "the isotope amount effect'') isotopically deplete the water vapor during wet conditions (e.g. El Niño in Central Pacific and La Niña in West Pacific). However, we find that the isotope signal of water vapor at higher altitudes (e.g. 500 hPa) associated with ENSO events diverges from the near surface signature. Analysis suggests that at higher altitudes, transport of enriched water vapor from lower atmospheric layers through convective updrafts

  15. Interannual Variability of the Winter Stratospheric Polar Vortex in the Northern Hemisphere and Their Relations to QBO and ENSO

    Institute of Scientific and Technical Information of China (English)

    CHEN Wen; WEI Ke

    2009-01-01

    We investigated the interannual variations of the winter stratospheric polar vortex in this paper.EOF analysis shows that two modes of variability dominate the stratospheric polar vortex on interannual timescales.The leading mode (EOF1) reflects the intensity variation of the polar vortex and is characterized by a geopotential height seesaw between the polar region and the mid-latitudes.The second one (EOF2) exhibits variation in the zonal asymmetric part of the polar vortex,which mainly describes the stationary planetary wave activity.As the strongest interannual variation signal in the atmosphere,the QBO has been shown to influence mainly the strength of the polar vortex.On the other hand,the ENSO cycle,as the strongest interannual variation signal in the ocean,has been shown to be mainly associated with the variation of stationary planetary wave activity in the stratosphere.Possible influences of the stratospheric polar vortex on the tropospheric circulation are also discussed in this paper.

  16. A case study of waste management at the Northern Finnish pulp and paper mill complex of Stora Enso Veitsiluoto Mills.

    Science.gov (United States)

    Nurmesniemi, Hannu; Pöykiö, Risto; Keiski, Riitta Liisa

    2007-01-01

    This work presents the current waste management system at the pulp and paper mill complex of Stora Enso Oyj Veitsiluoto Mills at Kemi, Northern Finland. This paper covers examples of case studies carried out at the mill and describes how the wastes and by-products are utilized as a neutralizing agent for acidic wastewaters (i.e., green liquor dregs from the causticizing process), as a hardener in filling mine cavities (i.e., ash from the fluidized bed boiler), as a landscaping agent (i.e., ash as well as the fibre clay from chemical wastewater treatment plant), as a hydraulic barrier material for landfills (i.e., fibre clay), and as a soil enrichment agent (i.e., calcium carbonate from the precipitated calcium carbonate plant). In addition, the wood waste from the wood-handling plant, sawmill, packaging pallet plant and from the groundwood mill, as well as the biosludge from the biological wastewater treatment plant, are all incinerated in the fluidized bed boiler for energy production. Due to effective utilization of the solid wastes generated at the mills, the annual amount of waste to be disposed of in the landfill has decreased between 1994 and 2004 from 42,990 to 6083 tonn (expressed as wet weight). The paper also gives an overview of the relevant European Union legislation on the forest industry and on waste management, as well as of the pulping process and of the generation of major solid wastes in the pulp and paper mills.

  17. An Analysis of the Energetics of Tropical and Extra-Tropical Regions for Warm ENSO Composite Episodes

    Directory of Open Access Journals (Sweden)

    Zayra Christine Sátyro

    Full Text Available Abstract This study focuses on the quantification and evaluation of the effects of ENSO (El Niño Southern Oscillation warm phases, using a composite of five intense El Niño episodes between 1979 – 2011 on the Energetic Lorenz Cycle for four distinct regions around the globe: 80° S – 5° N (region 1, 50° S – 5° N (region 2, 30° S – 5° N (region 3, and 30° S – 30° N (region 4, using Data from NCEP reanalysis-II. Briefly, the results showed that zonal terms of potential energy and kinetic energy were intensified, except for region 1, where zonal kinetic energy weakened. Through the analysis of the period in which higher energy production is observed, a strong communication between the available zonal potential and the zonal kinetic energy reservoirs can be identified. This communication weakened the modes linked to eddies of potential energy and kinetic energy, as well as in the other two baroclinic conversions terms. Furthermore, the results indicate that for all the regions, the system itself works to regain its stable condition.

  18. The impact of ENSO and the NAO on extreme winter precipitation in North America in observations and regional climate models

    Science.gov (United States)

    Whan, Kirien; Zwiers, Francis

    2017-03-01

    The relationship between winter precipitation in North America and indices of the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) is evaluated using non-stationary generalized extreme value distributions with the indices as covariates. Both covariates have a statistically significant influence on precipitation that is well simulated by two regional climate models (RCMs), CanRCM4 and CRCM5. The observed influence of the NAO on extreme precipitation is largest in eastern North America, with the likelihood of a negative phase extreme rainfall event decreased in the north and increased in the south under the positive phase of the NAO. This pattern is generally well simulated by the RCMs although there are some differences in the extent of influence, particularly south of the Great Lakes. A La Niña-magnitude extreme event is more likely to occur under El Niño conditions in California and the southern United States, and less likely in most of Canada and a region south of the Great Lakes. This broad pattern is also simulated well by the RCMs but they do not capture the increased likelihood in California. In some places the extreme precipitation response in the RCMs to external forcing from a covariate is of the opposite sign, despite use of the same lateral boundary conditions and dynamical core. This demonstrates the importance of model physics for teleconnections to extreme precipitation.

  19. The impact of ENSO and the NAO on extreme winter precipitation in North America in observations and regional climate models

    Science.gov (United States)

    Whan, Kirien; Zwiers, Francis

    2016-05-01

    The relationship between winter precipitation in North America and indices of the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO) is evaluated using non-stationary generalized extreme value distributions with the indices as covariates. Both covariates have a statistically significant influence on precipitation that is well simulated by two regional climate models (RCMs), CanRCM4 and CRCM5. The observed influence of the NAO on extreme precipitation is largest in eastern North America, with the likelihood of a negative phase extreme rainfall event decreased in the north and increased in the south under the positive phase of the NAO. This pattern is generally well simulated by the RCMs although there are some differences in the extent of influence, particularly south of the Great Lakes. A La Niña-magnitude extreme event is more likely to occur under El Niño conditions in California and the southern United States, and less likely in most of Canada and a region south of the Great Lakes. This broad pattern is also simulated well by the RCMs but they do not capture the increased likelihood in California. In some places the extreme precipitation response in the RCMs to external forcing from a covariate is of the opposite sign, despite use of the same lateral boundary conditions and dynamical core. This demonstrates the importance of model physics for teleconnections to extreme precipitation.

  20. Dominance of ENSO-Like Variability in Controlling Tropical Ocean Surface Energy Fluxes in the Satellite Era

    Science.gov (United States)

    Robertson, F. R.; Miller, T. L.; Bosilovich, M. G.

    2008-01-01

    Ocean surface turbulent and radiative fluxes are critical links in the climate system since they mediate energy exchange between the two fluid systems (ocean and atmosphere) whose combined heat transport determines the basic character of Earth's climate. Moreover, interannual to decadal climate variability depends crucially on the nature of these exchange processes. For example, addressing the question of the degree to which the global hydrologic cycle is changing depends on our ability to observe and model these fluxes accurately. In this work we investigate the interannual to decadal variation of fluxes over the global tropics, especially the tropical oceans. Recent versions of satellite-derived fresh water flux estimates as well as some reanalyses (e.g. products from Remote Sensing Systems, the Woods Hole Oceanographic Institute, and Global Precipitation Climatology Project) suggest that increases in evaporation and precipitation over the past 20 years exceed those expected on the basis of climate model projected responses to greenhouse gas forcing. At the same time, it is well known that E1 Nino / Southern Oscillation behavior in the Pacific exhibits significant variability at scales longer than interannual. We examine here the degree to which surface fluxes attending these interannual to decadal fluctuations are related to ENSO. We examine consistency between these data sets and explore relationships between SST variations, flux changes and modulation of tropical Walker and Hadley circulations.

  1. The relationship betwwen ENSO cycle and high and low—flow in the upper Yellow River

    Institute of Scientific and Technical Information of China (English)

    LANYongchao; DINGYongjiang; KANGErsi; MAQuanjie; ZHANGJishi

    2003-01-01

    Firstly,the hydrological and meteorological features of the upper reaches of the Yellow River above Tangnag are analyzed based on observation data,and effects of El Nino and La Nina events on the high and low flow in the upper Yellow River are discussed.The results show El Nino and La Nina events possess consanguineous relationship with runoff in the upper Yellow River.As a whole,the probability of low flow occurrence in the upper Yellow River is relatively great along with the occurrence of El Nino event.Moreover,the flood in the upper Yellow River occurs frequently with the occurrence of La Nina event.Besides,the results also show dissimilarity of El Nino event occurring time exerts greater impact on high flow and low flow in the upper Yellow River,that is,the probability of drought will be greater in the same year if El Nino event occurs in spring,the high-flow may happen in this year if El Nino occurs in summer or autumn;the longer the continuous period of El Nino is,the lower the runoff in the upper Yellow River is.

  2. Designing using manufacturing features

    Science.gov (United States)

    Szecsi, T.; Hoque, A. S. M.

    2012-04-01

    This paper presents a design system that enables the composition of a part using manufacturing features. Features are selected from feature libraries. Upon insertion, the system ensures that the feature does not contradict the design-for-manufacture rules. This helps eliminating costly manufacturing problems. The system is developed as an extension to a commercial CAD/CAM system Pro/Engineer.

  3. Features of the Bible

    Institute of Scientific and Technical Information of China (English)

    刘隽

    2008-01-01

    Every literature has its features in some aspects,so is the Bible,one of the greatest literary works in the world that has great impact on western literature.This paper summarizes two features of the Bible,namely,cultural feature and literary feature.

  4. 厄尔尼诺与广西致洪暴雨的关系%Research on the Relationship Between ENSO Cases and Flash-Flood-Producing Rainstorm in Guangxi

    Institute of Scientific and Technical Information of China (English)

    林开平; 李耀先; 李秀存; 梁隽玫

    2001-01-01

    Based on analyzing the relationship between ENSO cases and the flash-flood-producing rainstorm in Guangxi, the result show that the two of them are close. Most of the flash-flood-producing rainstorms happened during the period of ENSO appearing, or in next year after ENSO cases ended. It was very similar that the variability of occurring frequency during the inter-decade, between ENSO cases and the flash-flood-producing rainstorm in Guangxi. In additional, the causes of the flash-flood-producing rainstorm stimulated by ENSO cases in Guangxi was discussed, as well.%分析了ENSO事件的出现与广西致洪暴雨的关系,结果表明了两者关系密切,广西的致洪暴雨基本上都出现于ENSO事件年或ENSO事件结束后的一年里;ENSO事件的出现频率随年代的变化与广西致洪暴雨出现频率随年代的变化非常吻合。此外,还就厄尔尼诺对广西致洪暴雨形成的可能机制进行探讨。

  5. Feature-Aware Verification

    CERN Document Server

    Apel, Sven; Wendler, Philipp; von Rhein, Alexander; Beyer, Dirk

    2011-01-01

    A software product line is a set of software products that are distinguished in terms of features (i.e., end-user--visible units of behavior). Feature interactions ---situations in which the combination of features leads to emergent and possibly critical behavior--- are a major source of failures in software product lines. We explore how feature-aware verification can improve the automatic detection of feature interactions in software product lines. Feature-aware verification uses product-line verification techniques and supports the specification of feature properties along with the features in separate and composable units. It integrates the technique of variability encoding to verify a product line without generating and checking a possibly exponential number of feature combinations. We developed the tool suite SPLverifier for feature-aware verification, which is based on standard model-checking technology. We applied it to an e-mail system that incorporates domain knowledge of AT&T. We found that feat...

  6. Unsupervised Feature Subset Selection

    DEFF Research Database (Denmark)

    Søndberg-Madsen, Nicolaj; Thomsen, C.; Pena, Jose

    2003-01-01

    This paper studies filter and hybrid filter-wrapper feature subset selection for unsupervised learning (data clustering). We constrain the search for the best feature subset by scoring the dependence of every feature on the rest of the features, conjecturing that these scores discriminate some...... irrelevant features. We report experimental results on artificial and real data for unsupervised learning of naive Bayes models. Both the filter and hybrid approaches perform satisfactorily....

  7. Comparison of a 1500 Year-Long ENSO-Sensitive Ice Core Proxy Record to Modeled Solar Forcing Mechanisms

    Science.gov (United States)

    Osterberg, E.; Mayewski, P.; Kreutz, K.; Fisher, D.; Sneed, S.

    2008-12-01

    A calibrated 1500 year-long glaciochemical proxy record for the strength of the wintertime (November-March) Aleutian Low (ALOW) from the Mt. Logan summit (PR Col; 5300 m a.s.l.) ice core [Na+] time series reveals a strong ALOW from ca. 650-900 A.D., ca. 1300-1550 A.D., and ca. 1700-1998 A.D., and a weaker ALOW from ca. 900-1300 A.D. and ca. 1550-1700 A.D. The proxy record was calibrated to instrumental sea-level pressure data using standard regression techniques, and verified using statistical, spectral, and spatial correlation analyses. This record is consistent with ENSO-sensitive paleoclimate proxies from the Pacific basin that indicate El Niño-like conditions during the Little Ice Age (LIA) and La Niña- like conditions during the so-called Medieval Climate Anomaly (MCA). The Mt. Logan ALOW proxy record is significantly correlated with atmospheric Δ14C records (r = 0.39, p<0.05), supporting an influence of solar forcing on late Holocene North Pacific climate. The increased frequency of El Niño conditions during the LIA relative to the MCA is consistent with the modeled "ocean thermostat" mechanism whereby weak solar irradiance during the LIA promotes El Niño-like conditions, and strong MCA solar irradiance promotes La Niña-like conditions by modifying the east-west SST gradient in the tropical Pacific. We will also discuss the consistency of these paleoproxy records with models invoking solar-induced changes in the north-south temperature gradient at the tropopause. In these model results, weaker solar irradiance causes cooling and weaker westerly winds in the stratosphere, inducing a tropospheric response that includes expansion of the polar cell, contraction of the Hadley cell, and enhanced meridional circulation.

  8. Physical forcing and the dynamics of the pelagic ecosystem in the eastern tropical Pacific: simulations with ENSO-scale and global-warming climate drivers

    Energy Technology Data Exchange (ETDEWEB)

    Watters, G. M.; Olson, R. J. [Inter-American Tropical Tuna Commission, La Jolla, CA (United States); Francis, C.; Aydin, K. Y. [Washington Univ., School of Aquatic and Fisheries Sciences, Seattle, WA (United States); Fiedler, P. C.; Reilley, S. B. [NOAA Fisheries, LaJolla, CA (United States); Polovnia, J. J.; Boggs, C. H.; Essington, T. E. [NOAA Fisheries, Honolulu, HI (United States); Walters, C. J. [British Columbia Univ., Fisheries Centre, Vancouver, BC (Canada); Kitchell, J. F. [Wisconsin Univ., Center for Limnology, Madison, WI (United States)

    2003-09-01

    The effects of climate variation on animals at the middle and upper trophic levels in the eastern tropical Pacific Ocean was investigated at El Nino-Southern Oscillation (ENSO) scales. Objectives of the work were: (1) to explore how a single, ENSO-scale climate pulse might affect middle and upper trophic levels of the pelagic ecosystem in the eastern tropical Pacific Ocean; (2) explore ecosystem response to changes in periodicity of warm and cold events during sustained ENSO-scale cycling; and (3) explore how the greenhouse effect might affect pelagic ecosystem in the eastern tropical Pacific Ocean. Two physical forcing scenarios were used: (1) physical effects on phytoplankton biomass, and (2) simultaneous physical effects on phytoplankton biomass and predator recruitment. The effects of climate anomaly pulses, climatic cycles and global warming were simulated. Pulses caused oscillations to propagate through the ecosystem; cycles affected the shapes of these oscillations; and warming caused trends to develop. These results gave rise to several conclusions: (1) it seems unlikely that biomass trajectories of single populations at middle and upper trophic levels could be used to detect bottom-up effects; (2) under constant fishing mortality, direct physical effects on predator recruitment are the dominant source of interannual variability in pelagic ecosystems; (3) top-down effects of fishing are less able to cascade through the food web if direct effects are the dominant source of physical variability in the system; and (4) predictions about the effects of long-term climate change on animals at middle and upper trophic levels may be misleading if future levels of fishing are not considered. 37 refs., 4 tabs., 7 figs.

  9. Variation characteristics and influences of climate factors on aridity index and its association with AO and ENSO in northern China from 1961 to 2012

    Science.gov (United States)

    Zhang, Kexin; Qian, Xiaoqing; Liu, Puxing; Xu, Yihong; Cao, Liguo; Hao, Yongpei; Dai, Shengpei

    2016-08-01

    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 t