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

The ENSO Impact on Predicting World Cocoa Prices

OpenAIRE

Ubilava, David; Helmers, Claes Gustav

2011-01-01

Cocoa beans are produced in equatorial and sub-equatorial regions of West Africa, Southeast Asia and South America. These are also the regions most affected by El Nino Southern Oscillation (ENSO) -- a climatic anomaly affecting temperature and precipitation in many parts of the world. Thus, ENSO, has a potential of affecting cocoa production and, subsequently, prices on the world market. This study investigates the benefits of using a measure of ENSO variable in world cocoa price forecasting ...

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

Science.gov (United States)

Krauskopf, Bernd; Sieber, Jan

2014-09-08

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

A non-stationary relationship between global climate phenomena and human plague incidence in Madagascar.

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Kreppel, Katharina S; Caminade, Cyril; Telfer, Sandra; Rajerison, Minoarison; Rahalison, Lila; Morse, Andy; Baylis, Matthew

2014-10-01

Plague, a zoonosis caused by Yersinia pestis, is found in Asia and the Americas, but predominantly in Africa, with the island of Madagascar reporting almost one third of human cases worldwide. Plague's occurrence is affected by local climate factors which in turn are influenced by large-scale climate phenomena such as the El Niño Southern Oscillation (ENSO). The effects of ENSO on regional climate are often enhanced or reduced by a second large-scale climate phenomenon, the Indian Ocean Dipole (IOD). It is known that ENSO and the IOD interact as drivers of disease. Yet the impacts of these phenomena in driving plague dynamics via their effect on regional climate, and specifically contributing to the foci of transmission on Madagascar, are unknown. Here we present the first analysis of the effects of ENSO and IOD on plague in Madagascar. We use a forty-eight year monthly time-series of reported human plague cases from 1960 to 2008. Using wavelet analysis, we show that over the last fifty years there have been complex non-stationary associations between ENSO/IOD and the dynamics of plague in Madagascar. We demonstrate that ENSO and IOD influence temperature in Madagascar and that temperature and plague cycles are associated. The effects on plague appear to be mediated more by temperature, but precipitation also undoubtedly influences plague in Madagascar. Our results confirm a relationship between plague anomalies and an increase in the intensity of ENSO events and precipitation. This work widens the understanding of how climate factors acting over different temporal scales can combine to drive local disease dynamics. Given the association of increasing ENSO strength and plague anomalies in Madagascar it may in future be possible to forecast plague outbreaks in Madagascar. The study gives insight into the complex and changing relationship between climate factors and plague in Madagascar.

A non-stationary relationship between global climate phenomena and human plague incidence in Madagascar.

Directory of Open Access Journals (Sweden)

Katharina S Kreppel

2014-10-01

Full Text Available Plague, a zoonosis caused by Yersinia pestis, is found in Asia and the Americas, but predominantly in Africa, with the island of Madagascar reporting almost one third of human cases worldwide. Plague's occurrence is affected by local climate factors which in turn are influenced by large-scale climate phenomena such as the El Niño Southern Oscillation (ENSO. The effects of ENSO on regional climate are often enhanced or reduced by a second large-scale climate phenomenon, the Indian Ocean Dipole (IOD. It is known that ENSO and the IOD interact as drivers of disease. Yet the impacts of these phenomena in driving plague dynamics via their effect on regional climate, and specifically contributing to the foci of transmission on Madagascar, are unknown. Here we present the first analysis of the effects of ENSO and IOD on plague in Madagascar.We use a forty-eight year monthly time-series of reported human plague cases from 1960 to 2008. Using wavelet analysis, we show that over the last fifty years there have been complex non-stationary associations between ENSO/IOD and the dynamics of plague in Madagascar. We demonstrate that ENSO and IOD influence temperature in Madagascar and that temperature and plague cycles are associated. The effects on plague appear to be mediated more by temperature, but precipitation also undoubtedly influences plague in Madagascar. Our results confirm a relationship between plague anomalies and an increase in the intensity of ENSO events and precipitation.This work widens the understanding of how climate factors acting over different temporal scales can combine to drive local disease dynamics. Given the association of increasing ENSO strength and plague anomalies in Madagascar it may in future be possible to forecast plague outbreaks in Madagascar. The study gives insight into the complex and changing relationship between climate factors and plague in Madagascar.

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

Science.gov (United States)

Clark, Austin; Cecil, Daniel J.

2018-01-01

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

Disturbed solution of the El Niño-southern oscillation sea—air delayed oscillator

International Nuclear Information System (INIS)

Xie Feng; Lin Wan-Tao; Lin Yi-Hua; Mo Jia-Qi

2011-01-01

A class of delayed oscillators of El Niño-southern oscillation (ENSO) models is considered. Using the delayed theory, the perturbed theory and other methods, the asymptotic expansions of the solutions for ENSO models are obtained and the asymptotic behaviour of solution of corresponding problem is studied. (general)

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

Science.gov (United States)

MAO, J.; WU, X.

2017-12-01

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

Phase-locking phenomena and excitation of damped and driven nonlinear oscillators

DEFF Research Database (Denmark)

Shagalov, A.G.; Juul Rasmussen, Jens; Naulin, Volker

2009-01-01

Resonant phase-locking phenomena ('autoresonance') in the van der Pol Duffing oscillator forced by a small amplitude periodic driving with slowly varying frequency have been studied. We show that autoresonance occurs for oscillators with sufficiently small damping, when the system may have bi-stable...

Homotopic mapping solution of an oscillator for the El Niño/La Niña-southern oscillation

International Nuclear Information System (INIS)

Xian-Chun, Zhou; Yi-Hua, Lin; Wan-Tao, Lin; Jia-Qi, Mo

2009-01-01

This paper considers a class of oscillator for the El Niño/La Niña-southern oscillation (ENSO) model. By using the homotopic mapping method, it obtains approximations of the solution for the ENSO model. (general)

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

Science.gov (United States)

Clark, Austin; Cecil, Daniel

2018-01-01

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

Is ENSO related to 2015 Easter Star Capsized on the Yangtze River of China?

Science.gov (United States)

Xie, P.

2015-12-01

Natural disasters have profound effects on community security and economic damage of China's Hubei province. In June 1st, 2015, a cruise ship, Easter Star, capsized on Yangtze River in Hubei province with 442 died. What reason gives rise to such strong convection causing ship sunk? Based on the wind disasters of Hubei province happened in 1963-2015, this study analyzes their features bytime-series regression, and correlates them to global El Niño/Southern Oscillation (ENSO) events. The compared results demonstrated that the wind disasters shown an increasing tendency. There are two peaks corresponding to the strongest ENSO peaks during the past 50 years; each peak lasts two-three years. The facts demonstrated an essential linear relation between the ENSO phenomena and wind disasters in Hubei province. 2015 Easter Star capsized happened at current El Niño event in 2014-2015. We also observed that the historical wind disasters appeared in seasonal variation. Over 90% events concentrated in spring and summer; very few events happened in autumn and winter. Moreover, the disasters depend on the geographic conditions. Most disasters concentrated in four zones, named as Xingshan-Baokang, Xuanen, Wufeng-Yichang, Jingzhou-Gongan, in which Xingshan and Changyang are the two most density of zones. Yangtze River provides an air flowing conduct for strong convective winds. It can be concluded that the strong convection causing 2015 Easter Star capsized is related to current global ENSO phenomenon.Keywords: ENSO, wind disaster, time-series regression analysis, Easter Star, Yangtze River, Hubei Province,

Evaluation of the effects of ENSO teleconnection on climatic parameters fluctuations in Khorasan Province I.R. of Iran

International Nuclear Information System (INIS)

Ehteramian, Kourosh; Shahabfar, Alireza; Gharaei, Sohrab M.; Jamali, Javad B.

2004-01-01

The long term forecasting and monitoring of climatological parameters depends on identification of all effective factors, which are affects on this phenomena. One of these parameters is the weather signal. These signals are determinable and specific pattern and occurs in the distinguished regions in the world, but it's effects are world wide. One of the famous signals is ENSO phenomenon, which have two phases. In this paper with using annual and seasonal correlations between southern oscillation index (SOI) and precipitation and temperature data the effective amounts of ENSO phases on the differences of these factors was studied in the all regions of Khorasan province in Iran, then for more comprehensive study the classification maps in relation of ENSO and variability of precipitation and temperature were drown. It was concluded that the mentioned parameters in the whole of the province especially in central and north strip have shown significant action to ENSO, in other word the average of precipitation and temperature correlation indices are negative annually and seasonally, it means when SOI amounts are increased the precipitation and temperature in Khorasan will be decreased. With regard to increasing the above weather parameters in all regions of Khorasan at the time of ENSO negative phases (El Nino condition) variations of precipitation and temperature could be related to the changes of the pattern of occurrence this phenomenon (ENSO) due to climatic change around the world. (Author)

Analysis of graphic representation ability in oscillation phenomena

Science.gov (United States)

Dewi, A. R. C.; Putra, N. M. D.; Susilo

2018-03-01

This study aims to investigates how the ability of students to representation graphs of linear function and harmonic function in understanding of oscillation phenomena. Method of this research used mix methods with concurrent embedded design. The subjects were 35 students of class X MIA 3 SMA 1 Bae Kudus. Data collection through giving essays and interviews that lead to the ability to read and draw graphs in material of Hooke's law and oscillation characteristics. The results of study showed that most of the students had difficulty in drawing graph of linear function and harmonic function of deviation with time. Students’ difficulties in drawing the graph of linear function is the difficulty of analyzing the variable data needed in graph making, confusing the placement of variable data on the coordinate axis, the difficulty of determining the scale interval on each coordinate, and the variation of how to connect the dots forming the graph. Students’ difficulties in representing the graph of harmonic function is to determine the time interval of sine harmonic function, the difficulty to determine the initial deviation point of the drawing, the difficulty of finding the deviation equation of the case of oscillation characteristics and the confusion to different among the maximum deviation (amplitude) with the length of the spring caused the load.Complexity of the characteristic attributes of the oscillation phenomena graphs, students tend to show less well the ability of graphical representation of harmonic functions than the performance of the graphical representation of linear functions.

Influences of the ENSO event on the rainfall of dry Sudan

International Development Research Centre (IDRC) Digital Library (Canada)

One third of the world's population live in places where medium to high water stress is compounded by pollution, climate change, inefficient management approaches and governance issues. This study detects the El Nino Southern Oscillation (ENSO) events and signals, and the influences of the different ENSO stages in the ...

Perturbation method of studying the EI Niño oscillation with two parameters by using the delay sea-air oscillator model

International Nuclear Information System (INIS)

Du Zeng-Ji; Lin Wan-Tao; Mo Jia-Qi

2012-01-01

The EI Niño-southern oscillation (ENSO) is an interannual phenomenon involved in tropical Pacific ocean-atmosphere interactions. In this paper, we develop an asymptotic method of solving the nonlinear equation using the ENSO model. Based on a class of the oscillator of the ENSO model, a approximate solution of the corresponding problem is studied employing the perturbation method

The Relationship between El nino Southern Oscillation (ENSO) Phenomenon and Seasonal Precipitation Variability in Eastern Kenya with Special Reference to Katumani: Its Implication to Crop Production

International Nuclear Information System (INIS)

Kitheka, S.K

1999-01-01

Climatic variability has been defined as a major limitation to agricultural production in semi arid Kenya. The major difficulty to both farmers and research community, has been the inability to to predict seasonal rainfall prior to the season onset. Although several researches have attempted and made advances in predicting rainfall amount, solutions to the problem have not been achieved. This study has examined and related rainfall at Katumani with the El Nino-Southern Oscillation (ENSO) phenomenon. Rainfall variations during different phases of ENSO were established. Some advances in the early prediction of March-May and October -January rains for, both, the warm and cold phases of ENSO have been made. Crop production is closely related to the rainfall and therefore a need for revision of agronomic recommendation to tie them with rainfall variation

ENSO related decadal scale climate variability from the Indo-Pacific Warm Pool

NARCIS (Netherlands)

Brijker, J.M.; Jung, S.J.A.; Ganssen, G.M.; Bickert, T.; Kroon, D.

2006-01-01

The El Niño-Southern Oscillation (ENSO) is a climatic phenomenon that affects socio-economical welfare in vast areas in the world. A continuous record of Holocene ENSO related climate variability of the Indo-Pacific Warm pool (IPWP) is constructed on the basis of stable oxygen isotopes in shells of

Interannual hydroclimatic variability and the 2009-2011 extreme ENSO phases in Colombia: from Andean glaciers to Caribbean lowlands

Science.gov (United States)

Bedoya-Soto, Juan Mauricio; Poveda, Germán; Trenberth, Kevin E.; Vélez-Upegui, Jorge Julián

2018-03-01

During 2009-2011, Colombia experienced extreme hydroclimatic events associated with the extreme phases of El Niño-Southern Oscillation (ENSO). Here, we study the dynamics of diverse land-atmosphere phenomena involved in such anomalous events at continental, regional, and local scales. Standardized anomalies of precipitation, 2-m temperature, total column water (TCW), volumetric soil water (VSW), temperature at 925 hPa, surface sensible heat (SSH), latent heat (SLH), evaporation (EVP), and liquid water equivalent thickness (LWET) are analyzed to assess atmosphere-land controls and relationships over tropical South America (TropSA) during 1986-2013 (long term) and 2009-2011 (ENSO extreme phases). An assessment of the interannual covariability between precipitation and 2-m temperature is performed using singular value decomposition (SVD) to identify the dominant spatiotemporal modes of hydroclimatic variability over the region's largest river basins (Amazon, Orinoco, Tocantins, Magdalena-Cauca, and Essequibo). ENSO, its evolution in time, and strong and consistent spatial structures emerge as the dominant mode of variability. In situ anomalies during both extreme phases of ENSO 2009-2011 over the Magdalena-Cauca River basins are linked at the continental scale. The ENSO-driven hydroclimatic effects extend from the diurnal cycle to interannual timescales, as reflected in temperature data from tropical glaciers and the rain-snow boundary in the highest peaks of the Central Andes of Colombia to river levels along the Caribbean lowlands of the Magdalena-Cauca River basin.

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

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

Mean Bias in Seasonal Forecast Model and ENSO Prediction Error.

Science.gov (United States)

Kim, Seon Tae; Jeong, Hye-In; Jin, Fei-Fei

2017-07-20

This study uses retrospective forecasts made using an APEC Climate Center seasonal forecast model to investigate the cause of errors in predicting the amplitude of El Niño Southern Oscillation (ENSO)-driven sea surface temperature variability. When utilizing Bjerknes coupled stability (BJ) index analysis, enhanced errors in ENSO amplitude with forecast lead times are found to be well represented by those in the growth rate estimated by the BJ index. ENSO amplitude forecast errors are most strongly associated with the errors in both the thermocline slope response and surface wind response to forcing over the tropical Pacific, leading to errors in thermocline feedback. This study concludes that upper ocean temperature bias in the equatorial Pacific, which becomes more intense with increasing lead times, is a possible cause of forecast errors in the thermocline feedback and thus in ENSO amplitude.

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

Coastal upwelling along the southwest coast of India – ENSO modulation

Directory of Open Access Journals (Sweden)

K. Muni Krishna

2008-06-01

Full Text Available An index of El Niño Southern Oscillation (ENSO in the Pacific during pre monsoon season is shown to account for a significant part of the variability of coastal Sea Surface Temperature (SST anomalies measured a few months later within the wind driven southwest coast of India coastal upwelling region 7° N–14° N. This teleconnection is thought to result from an atmospheric bridge between the Pacific and north Indian Oceans, leading to warm (cold ENSO events being associated with relaxation (intensification of the Indian trade winds and of the wind-induced coastal upwelling. This ENSO related modulation of the wind-driven coastal upwelling appears to contribute to the connection observed at the basin-scale between ENSO and SST in the Arabian Sea. The ability to use this teleconnection to give warning of large changes in the southwest coast of India coastal upwelling few months in advance is successfully tested using data from 1998 and 1999 ENSO events.

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

Directory of Open Access Journals (Sweden)

1995-01-01

sensiblemente y esto afecta el término ablación del balance de masa. Se verifica en estas series de 20 años que todos los años ENSO estén asociados a balances negativos. Durante la mayoría de los eventos ENSO, en el sur de Perú y en Bolivia, se produce una reducción de las precipitaciones, lo que contribuye a acentuar el efecto ENSO sobre los balances. Estos acontecimientos tienen una influencia importante sobre la evolución actual de los glaciares andinos, caracterizada por un retroceso rápido. GLACIER BALANCE AND CLIMATE IN BOLIVIA AND PERU: EFFECTS OF ENSO EVENTS. Mass balance of Zongo Glacier (Cordillera Real, Bolivia was reconstructed by using hydrological data. Moreover, the “linear model” (Llliboutry was applied on the balance measurements from Yanamarey and Uruashraju ablation zone (Cordillera Blanca, Peru. Compared with temperature and precipitation data from reliable meteorological stations, these 15-20 yr time series of glacier balances allow us to point out temperature as the principal factor controlling mass balance evolution. Temperature variability strongly depends on ENSO (El Niño Southern Oscillation events: a clear positive deviation of maxima and minima is generally observed during these events, which strongly increases the ablation. Consequently, a systematical negative mass balance is associated with ENSO events. In Southern Peru and in Bolivia, this tendance is enhanced by a frequent decrease in the precipitation, which modifies the accumulation term at high altitude. So, it is demonstrated that ENSO phenomena closely control the glacier mass balance variability and have a great influence in the rapid glacier retreat observed in this area of Tropical Andes.

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

Interdecadal variations of ENSO around 1999/2000

Science.gov (United States)

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

2017-02-01

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

The homotopic method of travelling wave solution for El Niño tropic sea–air coupled oscillator

International Nuclear Information System (INIS)

Mo Jiaqi; Lin Wantao

2008-01-01

The EI Niño and Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Pacific sea–air interactions. In this paper, an asymptotic method of solving nonlinear equations for the ENSO model is proposed. And based on a class of oscillator of the ENSO model and by employing the method of homotopic mapping, the approximate solution of equations for the corresponding ENSO model is studied. It is proved from the results that homotopic method can be used for analysing the sea surface temperature anomaly in the equatorial Pacific of the sea–air oscillator for the ENSO model

Das El Niño/Southern Oscillation-Phänomen / The El Niño/Southern Oscillation Phenomenon

OpenAIRE

Latif, Mojib

2006-01-01

Zusammenfassung Das El Niño/Southern Oscillation (ENSO)-Phänomen ist die stärkste kurzfristige natürliche Klimaschwankung auf Zeitskalen von einigen Monaten bis zu mehreren Jahren. Obwohl ENSO seinen Ursprung im äquatorialen Pazifik hat, wirkt es sich dennoch auf das globale Klima aus. ENSO resultiert aus der Wechselwirkung zwischen Ozean und Atmosphäre und ist einige Monate im voraus vorhersagbar. Es besteht die Möglichkeit, dass der anthropogene Klimawandel die ENSO-Statistik...

ENSO activity during the last climate cycle using Individual Foraminifera Analysis

Science.gov (United States)

Leduc, G.; Vidal, L.; Thirumalai, K.

2017-12-01

The El Niño / Southern Oscillation (ENSO) is the principal mode of interannual climate variability and affects key climate parameters such as low-latitude rainfall variability. Recent climate modeling experiments tend to suggest an increase in the frequency of both El Niño and La Niña events in the future, but these results remain model-dependent and require to be validated by paleodata-model comparisons. Fossil corals indicate that the ENSO variance during the 20th century is particularly high as compared to other time periods of the Holocene. Beyond the Holocene, however, little is known on past ENSO changes, which makes difficult to test paleoclimate model simulations that are used to study the ENSO sensitivity to various types of forcings. We have expanded an Individual Foraminifera Analysis (IFA) dataset using the thermocline-dwelling N. dutertrei on a marine core collected in the Panama Basin (Leduc et al., 2009), that has proven to be a skillful way to reconstruct the ENSO (Thirumalai et al., 2013). Our new IFA dataset comprehensively covers the Holocene, allowing to verify how the IFA method compares with ENSO reconstructions using corals. The dataset then extends back in time to Marine Isotope Stage 6 (MIS), with a special focus the last deglaciation and Termination II (MIS5/6) time windows, as well as key time periods to tests the sensitivity of ENSO to ice volume and orbital parameters. The new dataset confirms variable ENSO activity during the Holocene and weaker activity during LGM than during the Holocene, as a recent isotope-enabled climate model simulations of the LGM suggests (Zhu et al., 2017). Such pattern is reproduced for the Termination II. Leduc, G., L. Vidal, O. Cartapanis, and E. Bard (2009), Modes of eastern equatorial Pacific thermocline variability: Implications for ENSO dynamics over the last glacial period, Paleoceanography, 24, PA3202, doi:10.1029/2008PA001701. Thirumalai, K., J. W. Partin, C. S. Jackson, and T. M. Quinn (2013

ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing

Science.gov (United States)

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

2018-03-01

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

An exploratory modeling study on bio-physical processes associated with ENSO

Science.gov (United States)

Park, Jong-Yeon; Kug, Jong-Seong; Park, Young-Gyu

2014-05-01

Variability of marine phytoplankton associated with El Niño-Southern Oscillation (ENSO) and potential biological feedbacks onto ENSO are investigated by performing coupled ocean/biogeochemical model experiments forced by realistic surface winds from 1951 to 2010. The ocean model used in this study is the MOM4, which is coupled to a biogeochemical model, called TOPAZ (Tracers in the Ocean with Allometric Zooplankton). In general, it is shown that MOM4-TOPAZ mimics the observed main features of phytoplankton variability associated with ENSO. By comparing the actively coupled MOM4-TOPAZ experiment with the ocean model experiments using prescribed chlorophyll concentrations, potential impacts of phytoplankton on ENSO are evaluated. We found that chlorophyll generally increases mean sea surface temperature (SST) and decreases subsurface temperature by altering the penetration of solar radiation. However, as the chlorophyll concentration increases, the equatorial Pacific SST decreases due to the enhanced upwelling of the cooler subsurface water with shoaling of mixed layer and thermocline. The presence of chlorophyll generally intensifies ENSO amplitude by changing the ocean basic state. On the other hand, interactively varying chlorophyll associated with the ENSO tends to reduce ENSO amplitude. Therefore, the two biological effects on SST are competing against each other regarding the SST variance in the equatorial Pacific.

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

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.

The 1950-1998 warm ENSO events and regional implications to ...

African Journals Online (AJOL)

1998 seasonal El Niño/Southern Oscillation (ENSO) is investigated in 502 rivers gauged in 9 countries of the Southern African region. We found some evidence of possible links between available surface water resources in terms of mean annual ...

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...

ENSO Dynamics and Trends, AN Alternate View

Science.gov (United States)

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

2017-12-01

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

Source of low frequency modulation of ENSO amplitude in a CGCM

Energy Technology Data Exchange (ETDEWEB)

Moon, Byung-Kwon [Chonbuk National University, Division of Science Education/Institute of Science Education, Jeonju (Korea); Yeh, Sang-Wook [Korea Ocean Research and Development Institute, Ansan (Korea); Dewitte, Boris [Laboratoire d' Etude en Geophysique et Oceanographie Spatiale, Toulouse (France); Jhun, Jong-Ghap [Seoul National University, School of Earth and Environmental Sciences, Seoul (Korea); Kang, In-Sik [Seoul National University, Climate Environment System Research Center (CES), Seoul (Korea)

2007-07-15

We study the relationship between changes in equatorial stratification and low frequency El Nino/Southern Oscillation (ENSO) amplitude modulation in a coupled general circulation model (CGCM) that uses an anomaly coupling strategy to prevent climate drifts in the mean state. The stratification is intensified at upper levels in the western and central equatorial Pacific during periods of high ENSO amplitude. Furthermore, changes in equatorial stratification are connected with subsurface temperature anomalies originating from the central south tropical Pacific. The correlation analysis of ocean temperature anomalies against an index for the ENSO modulation supports the hypothesis of the existence of an oceanic ''tunnel'' that connects the south tropical Pacific to the equatorial wave guide. Further analysis of the wind stress projection coefficient onto the oceanic baroclinic modes suggests that the low frequency modulation of ENSO amplitude is associated with a significant contribution of higher-order modes in the western and central equatorial Pacific. In the light of these results, we suggest that, in the CGCM, change in the baroclinic mode energy distribution associated with low frequency ENSO amplitude modulation have its source in the central south tropical Pacific. (orig.)

ENSO variations and drought occurrence in Indonesia and the Philippines

Science.gov (United States)

Harger, J. R. E.

The "El Nino-Southern Oscillation" (ENSO) consists of a sympathetic movement involving the Pacific ocean and associated atmosphere in an essentially chaotic manner along the equator. The system oscillates between extremes of the so-called "warm events" usually lasting 1 or 2 yr 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. Information drawn from meteorological records in southeast Asia clearly indicates that each event is unique in terms of the signature which it imposes on the rainfall and temperature from location to location. Nevertheless, a strong underlying pattern within the context of each event, itself apparently initiated or molded by the character of the preceding years, can be detected. This pattern permits relatively circumscribed predictions of forward conditions (drought intensity) for 2-3 yr, to be made once the event "locks in" for the duration of the warm event and at least 1 yr beyond. The character of the intervening non-ENSO years can also be projected but in a more tenuous, though fairly regular manner. When the non-ENSO years leading up to a warm event are scored in terms of the extent to which they depart from the secular warming trend for the warmest month using data from Jakarta and Semarang on the north coast of Java, the cumulative temperature deviations signal the character of the upcoming ENSO event. This signal does not, however, allow an exact determination to be made with respect to whether or not an ENSO event will occur in the next year. For the available historical instrumental data, all markedly upward-moving traces eventually delivered a hot dry season in east Indonesia. This sort of tendency within non-ENSO blocks can thus serve as a caution in the sense that a very hot ENSO event is likely in the offing. The

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.

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

Directory of Open Access Journals (Sweden)

M. Holmgren

2006-01-01

Full Text Available 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 impacts have been more intensively studied in arid and semiarid systems. In this brief communication, we summarize the main conclusions of a recent symposium on the effects of ENSO in these ecosystems, which was convened as part of the First Alexander von Humboldt International Conference on the El Niño Phenomenon and its Global Impact, in Guayaquil, Ecuador, from 16–20 May 2005. Participants in the symposium shared results and perspectives from research conducted in North and South America and Australia, regions where the ecological effects of ENSO have been studied in depth. Although the reports covered a wide array of organisms and ecological systems (Fig. 1, a recurring theme was the strong increase in rainfall associated with ENSO events in dry ecosystems (during the El Niño phase of the oscillation in the Americas and the La Niña phase in Australia. Because inter-annual variability in precipitation is such a strong determinant of productivity in arid and semiarid ecosystems, increased ENSO rainfall is crucial for plant recruitment, productivity and diversity in these ecosystems. Several long-term studies show that this pulse in primary productivity causes a subsequent increase in herbivores, followed by an increase in carnivores, with consequences for changes in ecosystem structure and functioning that can be quite complex.

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.

2017-12-01

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

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

Digital Repository Service at National Institute of Oceanography (India)

Gopinathan, C.K.

The negative phase of the 1990-'95 El Nino-Southern Oscillation (ENSO) and the associated Warming of the Equatorial Pacific Ocean (WEPO) was the longest observed in the 113 years of its recorded history, compared to its normal duration of 1 to 2...

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

2017-04-28

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

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;

Ocean Chlorophyll as a Precursor of ENSO: An Earth System Modeling Study

Science.gov (United States)

Park, Jong-Yeon; Dunne, John P.; Stock, Charles A.

2018-02-01

Ocean chlorophyll concentration, a proxy for phytoplankton, is strongly influenced by internal ocean dynamics such as those associated with El Niño-Southern Oscillation (ENSO). Observations show that ocean chlorophyll responses to ENSO generally lead sea surface temperature (SST) responses in the equatorial Pacific. A long-term global Earth system model simulation incorporating marine biogeochemical processes also exhibits a preceding chlorophyll response. In contrast to simulated SST anomalies, which significantly lag the wind-driven subsurface heat response to ENSO, chlorophyll anomalies respond rapidly. Iron was found to be the key factor connecting the simulated surface chlorophyll anomalies to the subsurface ocean response. Westerly wind bursts decrease central Pacific chlorophyll by reducing iron supply through wind-driven thermocline deepening but increase western Pacific chlorophyll by enhancing the influx of coastal iron from the maritime continent. Our results mechanistically support the potential for chlorophyll-based indices to inform seasonal ENSO forecasts beyond previously identified SST-based indices.

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.

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

Science.gov (United States)

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

2016-12-01

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

Marine lake ecosystem dynamics illustrate ENSO variation in the tropical western Pacific

OpenAIRE

Martin, Laura E; Dawson, Michael N; Bell, Lori J; Colin, Patrick L

2005-01-01

Understanding El Niño/Southern Oscillation (ENSO) and its biological consequences is hindered by a lack of high-resolution, long-term data from the tropical western Pacific. We describe a preliminary, 6 year dataset that shows tightly coupled ENSO-related bio-physical dynamics in a seawater lake in Palau, Micronesia. The lake is more strongly stratified during La Niña than El Niño conditions, temperature anomalies in the lake co-vary strongly with the Niño 3.4 climate index, and the abundance...

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.

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

Science.gov (United States)

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

2017-09-01

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

Identification of symmetric and asymmetric responses in seasonal streamflow globally to ENSO phase

Science.gov (United States)

Lee, Donghoon; Ward, Philip J.; Block, Paul

2018-04-01

The phase of the El Niño Southern Oscillation (ENSO) has large-ranging effects on streamflow and hydrologic conditions globally. While many studies have evaluated this relationship through correlation analysis between annual streamflow and ENSO indices, an assessment of potential asymmetric relationships between ENSO and streamflow is lacking. Here, we evaluate seasonal variations in streamflow by ENSO phase to identify asymmetric (AR) and symmetric (SR) spatial pattern responses globally and further corroborate with local precipitation and hydrological condition. The AR and SR patterns between seasonal precipitation and streamflow are identified at many locations for the first time. Our results identify strong SR patterns in particular regions including northwestern and southern US, northeastern and southeastern South America, northeastern and southern Africa, southwestern Europe, and central-south Russia. The seasonally lagged anomalous streamflow patterns are also identified and attributed to snowmelt, soil moisture, and/or cumulative hydrological processes across river basins. These findings may be useful in water resources management and natural hazards planning by better characterizing the propensity of flood or drought conditions by ENSO phase.

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

Science.gov (United States)

Rice, Joshua S.; Emanuel, Ryan E.

2017-05-01

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

Analysis of Roanoke Region Weather Patterns Under Global Teleconnections

OpenAIRE

LaRocque, Eric John

2006-01-01

This work attempts to relate global teleconnections, through physical phenomena such as the El Nino-Southern Oscillation (ENSO), Artic Oscillation (AO), North Atlantic Oscillation (NAO), and the Pacific North American (PNA) pattern to synoptic-scale weather patterns and precipitation in the Roanoke, Virginia region. The first chapter describes the behavior of the El Nino-Southern Oscillation (ENSO) by implementing non-homogeneous and homogeneous Markov Chain models on a monthly time series o...

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

Science.gov (United States)

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

2017-04-01

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

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.

Change of ENSO characteristics in response to global warming

Science.gov (United States)

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

2017-12-01

the frequency of ENSO events greatly increases due to global warming, and many more extreme El Niño and La Niña events appear under the El Niño-like and the La Niña-like background warmings, respectively. This study reconciles the phenomena and mechanisms of different characteristics of ENSO changes in observations and models.

Waves of El Nino-southern Oscillation and Influenza Pandemics

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Olusegun Steven Ayodele Oluwole

2016-04-01

Full Text Available Influenza pandemics have occurred at irregular intervals for over 500 years, unlike seasonal influenza epidemics which occur annually. Although the risk factors are known, the basis for the timing of influenza pandemic waves are unknown. Coherence of peaks of El Niño and influenza pandemic in 2009–2010, however, suggests that both waves are coupled. This study was done to determine the relation of influenza pandemics to the peaks and waveforms of El Niño southern oscillation (ENSO. ENSO cycles from 1871–2015 which had El Niño phases were windowed from Multivariate El Niño Index. Influenza pandemic peaks were mapped to ENSO monthly time series. ENSO waveforms were compared graphically, and fitted to nonstationary cosinor models. Second order polynomial regression model was fitted to the peak and duration of El Niño. Agglomerative hierarchical cluster of ENSO waveforms was performed. All influenza pandemic peaks mapped to El Niño peaks, with lags of 0–5 months. ENSO waveforms during influenza pandemics share parameters of oscillation. Nonstationary cosinor models showed that ENSO cycles are complex waves. There was second order polynomial relationship between peak and duration of El Niños, p < 0.0001. ENSO waveforms clustered into four distinct groups. ENSO waveforms during influenza pandemics of 1889–1900, 1957–1958, and 1968–1969 linked closely. ENSO indices were significantly high from 7–16 months after onset of cycles, p < 0.0001. Surveillance for El Niño events to forecast periods of maximal transmission and survival of influenza A viruses is, therefore, crucial for public health control strategies.

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...

ENSO Modulations due to Interannual Variability of Freshwater Forcing and Ocean Biology-induced Heating in the Tropical Pacific.

Science.gov (United States)

Zhang, Rong-Hua; Gao, Chuan; Kang, Xianbiao; Zhi, Hai; Wang, Zhanggui; Feng, Licheng

2015-12-18

Recent studies have identified clear climate feedbacks associated with interannual variations in freshwater forcing (FWF) and ocean biology-induced heating (OBH) in the tropical Pacific. The interrelationships among the related anomaly fields are analyzed using hybrid coupled model (HCM) simulations to illustrate their combined roles in modulating the El Niño-Southern Oscillation (ENSO). The HCM-based supporting experiments are performed to isolate the related feedbacks, with interannually varying FWF and OBH being represented individually or collectively, which allows their effects to be examined in a clear way. It is demonstrated that the interannual freshwater forcing enhances ENSO variability and slightly prolongs the simulated ENSO period, while the interannual OBH reduces ENSO variability and slightly shortens the ENSO period, with their feedback effects tending to counteract each other.

Vegetation anomalies associated with the ENSO phenomenon in the Cauca river valley, Colombia

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J. M. Valencia

2017-12-01

Full Text Available The main factors affecting the production and yield of sugarcane are variety, agronomic management, soil type and climate, of which the first three there is some control, while the climate is one factor of which you cannot have any control, therefore, it should be monitored. Colombia, being located in the equatorial pacific, is affected by two atmospheric oceanic phenomena known as “El Niño” and “La Niña”, which make up the climatic phenomenon of ENSO (El Niño-Southern Oscillation and affect the quantity and the number of days with rainfall and influences the production of sugarcane. The objective of this work is to identify spatially and temporally the zones with greater and lower impact of the ENSO phenomenon in the cultivation of sugarcane in Colombia through the use of the Standard Vegetation Index (SVI and the Rainfall Anomally Index (RAI using EVI/MODIS images and precipitation data from meteorological stations on a quarterly basis for the period 2000-2015. A similar trend was found between both indices in the “El Niño” and “Neutral” seasons, while in the “La Niña” season the RAI tended to rise while the SVI decreased when the RAI was very high, this tendency being much more marked in areas with floods caused by the overflow of the main rivers. In addition, a comparison was made between the SVI index and a productivity anomaly index (IAP, finding a direct correlation between both (R2 = 0.4, p<0.001. This work showed that through the use of vegetation indexes, a temporal analysis of the impact of climate on an agricultural crop can be carried out, especially with ENSO conditions.

La pluviométrie au Pérou pendant les phases ENSO et LNSO

Directory of Open Access Journals (Sweden)

1998-01-01

Full Text Available Les données mensuelles (1960-1990 de précipitations de 21 stations situées dans les trois domaines physiques du Pérou (côte, Andes et plaine amazonienne sont analysées lors des phases ENSO et LNSO de l’Oscillation Australe du Pacifique. Ce n’est qu’à Piura, dans la région côtière du Nord, que les excédents sont significatifs en phase ENSO (test de Kolmogorov-Smirnov mais les volumes précipités sont très différents d’un événement à l’autre. Ailleurs, n’apparaît pas de différence significative entre les pluies des phases ENSO (ou LNSO et celles des périodes normales. Toutefois, la pluviométrie est souvent déficitaire dans les Andes en phase ENSO en période LNSO, elle est également déficitaire au Sud des Andes, mais plus souvent excédentaire au Nord. Dans la plaine amazonienne, la variabilité spatio-temporelle est trop importante lors des deux phases pour que soit esquissé un comportement général. LA PLUVIOMETRÍA EN EL PERÚ DURANTE LAS FASES ENSO Y LNSO. Los datos mensuales (1960-1990 de precipitación de 21 estaciones ubicadas en la Costa, la Sierra y la Selva de Perú son estudiados durante las fases ENSO y LNSO de la Oscilación del Sur del Pacífico. Las lluvias de Piura, en el norte de la Costa, son las únicas que presentan excesos significativos (test de Kolmogorov-Smirnov durante la fase ENSO pero los volúmenes cambian mucho de un evento a otro. No hay, en otros lugares, diferencia significativa entre las lluvias de las fases ENSO (o LNSO y las lluvias de años normales. Pero, muchas veces, la pluviosidad es deficitaria en los Andes durante los ENSO durante los eventos LNSO, las lluvias son también deficitarias en los Andes del Sur, pero más veces hay excesos en el Norte. En la Selva Amazónica, la variabilidad espacio-temporal es demasiado grande para dibujar un comportamiento general. RAINFALL IN PERU DURING THE ENSO AND LNSO PHASES. Monthly rainfall data (1960-1990 taken from 21 stations in three

The ENSO-pandemic influenza connection: coincident or causal?

Science.gov (United States)

Shaman, J. L.; Lipsitch, M.

2011-12-01

The El Niño-Southern Oscillation (ENSO) is a coupled ocean-atmosphere system in the tropical Pacific, which affects weather conditions, including temperatures, precipitation, winds and storm activity, across the planet. ENSO has two extreme phases marked by either warmer (El Niño) or cooler (La Niña) than average sea surface temperatures in the central equatorial Pacific. We find that the 4 most recent human influenza pandemics (1918, 1957, 1968, 2009), all of which were first identified in boreal spring or summer, were preceded by La Niña conditions in the equatorial Pacific. Changes in ENSO have been shown to alter the migration, stopover time, fitness and interspecies mixing of migratory birds, and consequently likely affect their mixing with domestic animals. We hypothesize that La Niña conditions bring divergent influenza subtypes together in some parts of the world and favor the reassortment of influenza through simultaneous multiple infection of individual hosts and the generation of novel pandemic strains. We propose approaches to test this hypothesis using influenza population genetics, virus prevalence in various host species, and avian migration patterns.

Tropical cyclone prediction skills - MJO and ENSO dependence in S2S data sets

Science.gov (United States)

Lee, C. Y.; Camargo, S.; Vitart, F.; Sobel, A. H.; Tippett, M.

2017-12-01

The El Niño-Southern Oscillation (ENSO) and the Madden-Julian Oscillation (MJO) are two important climate controls on tropical cyclone (TC) activity. The seasonal prediction skill of dynamical models is determined in large part by their accurate representations of the ENSO-TC relationship. Regarding intraseasonal TC variability, observations suggest MJO to be the primary control. Given the ongoing effort to develop dynamical seasonal-to-subseasonal (S2S) TC predictions, it is important to examine whether the global models, running on S2S timescales, are able to reproduce these known ENSO-TC and MJO-TC relationships, and how this ability affects forecasting skill. Results from the S2S project (from F. Vitart) suggest that global models have skill in predicting MJO phase with up to two weeks of lead time (four weeks for ECMWF). Meanwhile, our results show that, qualitatively speaking, the MJO-TC relationship in storm genesis is reasonably captured, with some models (e.g., ECMWF, BoM, NCEP, MetFr) performing better than the others. However, we also find that model skill in predicting basin-wide genesis and accumulated cyclone energy (ACE) are mainly due to the models' ability to capture the climatological seasonality. Removing the seasonality significantly reduces the models' skill; even the best model (ECMWF) in the most reliable basin (western north Pacific and Atlantic) has very little skill (close to 0.1 in Brier skill score for genesis and close to 0 in rank probability skill score for ACE). This brings up the question: do any factors contribute to intraseasonal TC prediction skill other than seasonality? Is the low skill, after removing the seasonality, due to poor MJO and ENSO simulations, or to poor representation of other ENSO-TC or MJO-TC relationships, such as ENSO's impact on the storm tracks? We will quantitatively discuss the dependence of the TC prediction skill on ENSO and MJO, focusing on Western North Pacific and Atlantic, where we have sufficient

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

Science.gov (United States)

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

2017-12-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-05-01

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<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. We further find that none of a suite of ten contemporary terrestrial biosphere models captures these ENSO-phase-dependent responses, highlighting a key uncertainty in modeling climate impacts on the future of the global land carbon sink.

El Niño-Southern Oscillation effect on quasi-biennial oscillations of temperature diurnal tides in the mesosphere and lower thermosphere

Science.gov (United States)

Sun, Yang-Yi; Liu, Huixin; Miyoshi, Yasunobu; Liu, Libo; Chang, Loren C.

2018-05-01

In this study, we evaluate the El Niño-Southern Oscillation (ENSO) signals in the two dominant temperature diurnal tides, diurnal westward wavenumber 1 (DW1) and diurnal eastward wavenumber 3 (DE3) on the quasi-biennial oscillation (QBO) scale (18-34 months) from 50 to 100 km altitudes. The tides are derived from the 21-year (January 1996-February 2017) Ground-to-Topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) temperature simulations and 15-year (February 2002-February 2017) Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature observations. The results show that ENSO warm phases shorten the period ( 2 years) of the QBO in DW1 amplitude near the equator and DE3 amplitude at low latitudes of the Northern Hemisphere. In contrast, the QBO period lengthens ( 2.5 years) during the ENSO neutral and cold phases. Correlation analysis shows the long-lasting effect of ENSO on the tidal QBO in the mesosphere and lower thermosphere.[Figure not available: see fulltext.

ENSO-driven nutrient variability recorded by central equatorial Pacific corals

Science.gov (United States)

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

2012-12-01

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

Cyclic Markov chains with an application to an intermediate ENSO model

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R. A. Pasmanter

2003-01-01

Full Text Available We develop the theory of cyclic Markov chains and apply it to the El Niño-Southern Oscillation (ENSO predictability problem. At the core of Markov chain modelling is a partition of the state space such that the transition rates between different state space cells can be computed and used most efficiently. We apply a partition technique, which divides the state space into multidimensional cells containing an equal number of data points. This partition leads to mathematical properties of the transition matrices which can be exploited further such as to establish connections with the dynamical theory of unstable periodic orbits. We introduce the concept of most and least predictable states. The data basis of our analysis consists of a multicentury-long data set obtained from an intermediate coupled atmosphere-ocean model of the tropical Pacific. This cyclostationary Markov chain approach captures the spring barrier in ENSO predictability and gives insight also into the dependence of ENSO predictability on the climatic state.

Linear dynamical modes as new variables for data-driven ENSO forecast

Science.gov (United States)

Gavrilov, Andrey; Seleznev, Aleksei; Mukhin, Dmitry; Loskutov, Evgeny; Feigin, Alexander; Kurths, Juergen

2018-05-01

A new data-driven model for analysis and prediction of spatially distributed time series is proposed. The model is based on a linear dynamical mode (LDM) decomposition of the observed data which is derived from a recently developed nonlinear dimensionality reduction approach. The key point of this approach is its ability to take into account simple dynamical properties of the observed system by means of revealing the system's dominant time scales. The LDMs are used as new variables for empirical construction of a nonlinear stochastic evolution operator. The method is applied to the sea surface temperature anomaly field in the tropical belt where the El Nino Southern Oscillation (ENSO) is the main mode of variability. The advantage of LDMs versus traditionally used empirical orthogonal function decomposition is demonstrated for this data. Specifically, it is shown that the new model has a competitive ENSO forecast skill in comparison with the other existing ENSO models.

Present El Niño-ENSO events and past Super-ENSO events

Directory of Open Access Journals (Sweden)

1993-01-01

Full Text Available LES ÉVÉNEMENTS ENSO ACTUELS ET LES ANCIENS ÉVÉNEMENTS SUPER-ENSO. Les événements ENSO actuels et les anciens événements Super-ENSO représentent la redistribution d’énergie et de masse dans le système terrestre, due à l’échange de momentum angulaire entre la Terre “solide” et l’hydrosphère. Les événements El Niño-ENSO actuels montrent une corrélation claire avec des décélérations interannuelles de la vitesse de rotation de la Terre: la durée du jour (LOD augmente. Bien qu’il soit généralement considéré que ces changements de rotation sont causés par l’échange de momentum angulaire avec l’atmosphère, nous démontrons ici qu’une grande partie, peut-être la majeure partie, des variations du LOD sont causées en réalité par l’échange du momentum angulaire entre la terre “solide” et l’hydrosphère dans un systéme couplé de régénération. Ce mécanisme agit aussi sur des échelles de temps qui vont de la décennie au siècle, provoquant des événements Super-ENSO. Plusieurs de ces événements ont été identifiés au cours de l’Holocène. Un événement de plus grande envergure a eu lieu à l’ère médiévale. Au cours de la période qui va de 13.5 à 9.5 Ka, les changements importants peuvent représenter des événements Mega-ENSO. Au cours des âges glaciaires, avec une vitesse de rotation plus grande, il est probable que les événements ENSO-El Niño furent absents. Dans les enregistrements du passé, de courte durée, les empreintes d’événements Super-ENSO doivent étre beaucoup plus fréquents que ceux de véritables ENSO interannuels, simplement parce que ces derniers sont trop brefs et généralement trop légers. ACTUALES EVENTOS EL NIÑO-ENSO Y ANTIGUOS EVENTOS SUPER-ENSO. Los actuales eventos ENSO y los antiguos eventos Super-ENSO representan la redistribución de energía y masa en el sistema terrestre, debido al intercambio de momento angular entre la Tierra “sólida” y la

Indian Ocean and Indian summer monsoon: relationships without ENSO in ocean-atmosphere coupled simulations

Science.gov (United States)

Crétat, Julien; Terray, Pascal; Masson, Sébastien; Sooraj, K. P.; Roxy, Mathew Koll

2017-08-01

The relationship between the Indian Ocean and the Indian summer monsoon (ISM) and their respective influence over the Indo-Western North Pacific (WNP) region are examined in the absence of El Niño Southern Oscillation (ENSO) in two partially decoupled global experiments. ENSO is removed by nudging the tropical Pacific simulated sea surface temperature (SST) toward SST climatology from either observations or a fully coupled control run. The control reasonably captures the observed relationships between ENSO, ISM and the Indian Ocean Dipole (IOD). Despite weaker amplitude, IODs do exist in the absence of ENSO and are triggered by a boreal spring ocean-atmosphere coupled mode over the South-East Indian Ocean similar to that found in the presence of ENSO. These pure IODs significantly affect the tropical Indian Ocean throughout boreal summer, inducing a significant modulation of both the local Walker and Hadley cells. This meridional circulation is masked in the presence of ENSO. However, these pure IODs do not significantly influence the Indian subcontinent rainfall despite overestimated SST variability in the eastern equatorial Indian Ocean compared to observations. On the other hand, they promote a late summer cross-equatorial quadrupole rainfall pattern linking the tropical Indian Ocean with the WNP, inducing important zonal shifts of the Walker circulation despite the absence of ENSO. Surprisingly, the interannual ISM rainfall variability is barely modified and the Indian Ocean does not force the monsoon circulation when ENSO is removed. On the contrary, the monsoon circulation significantly forces the Arabian Sea and Bay of Bengal SSTs, while its connection with the western tropical Indian Ocean is clearly driven by ENSO in our numerical framework. Convection and diabatic heating associated with above-normal ISM induce a strong response over the WNP, even in the absence of ENSO, favoring moisture convergence over India.

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.)

ENSO, IOD and Indian Summer Monsoon in NCEP climate forecast system

Energy Technology Data Exchange (ETDEWEB)

Pokhrel, Samir; Chaudhari, H.S.; Saha, Subodh K.; Dhakate, Ashish; Yadav, R.K.; Salunke, Kiran; Mahapatra, S.; Rao, Suryachandra A. [Indian Institute of Tropical Meteorology, Pashan, Pune (India)

2012-11-15

El Nino-Southern Oscillation (ENSO), Indian Ocean Dipole (IOD) and Indian Summer Monsoon rainfall features are explored statistically and dynamically using National Centers for Environment Prediction (NCEP) Climate Forecast System (CFSv1) freerun in relation to observations. The 100 years of freerun provides a sufficiently long homogeneous data set to find out the mean state, periodicity, coherence among these climatic events and also the influence of ENSO and IOD on the Indian monsoon. Differences in the occurrence of seasonal precipitation between the observations and CFS freerun are examined as a coupled ocean-atmosphere system. CFS simulated ENSO and IOD patterns and their associated tropical Walker and regional Hadley circulation in pure ENSO (PEN), pure IOD (PIO) and coexisting ENSO-IOD (PEI) events have some similarity to the observations. PEN composites are much closer to the observation as compared to PIO and PEI composites, which suggest a better ENSO prediction and its associated teleconnections as compared to IOD and combined phenomenon. Similar to the observation, the model simulation also show that the decrease in the Indian summer monsoon rainfall during ENSO phases is associated with a descending motion of anomalous Walker circulation and the increase in the Indian summer monsoon rainfall during IOD phase is associated with the ascending branch of anomalous regional Hadley circulation. During co-existing ENSO and IOD years, however, the fate of Indian summer monsoon is dictated by the combined influence of both of them. The shift in the anomalous descending and ascending branches of the Walker and Hadley circulation may be somewhat attributed to the cold (warm) bias over eastern (western) equatorial Indian Ocean basin, respectively in the model. This study will be useful for identifying some of the limitations of the CFS model and consequently it will be helpful in improving the model to unravel the realistic coupled ocean-atmosphere interactions

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

A 600 k.y. record of El Niño-Southern Oscillation (ENSO): Evidence for persisting teleconnections during the Middle Eocene greenhouse climate of Central Europe

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Lenz, Olaf K.; Wilde, Volker; Riegel, Walter; Harms, Franz-Juergen

2010-07-01

The El Niño-Southern Oscillation (ENSO) is a globally important factor in today's climate dynamics. Annually laminated oil shales from the maar lake of Messel (Germany) provide high-resolution sedimentological and paleoenvironmental data of a time interval of ˜600 k.y. during the Eocene greenhouse phase. Individual laminae consist of a light spring and summer algal layer (Tetraedron minimum layer) and a dark winter layer composed of terrigenous background sediment. Four sections were selected from the core of the Messel 2001 well in order to count varves and to measure total varve thickness and the thickess of light and dark laminae. Spectral analyses were done in order to detect possible cyclic fluctuations in varve thickness. Fluctuations are significant in the quasi-biennial (2.1-2.5 yr) and low-frequency band (2.8-3.5 yr, 4.9-5.6 yr), thus showing that algal growth as well as the background sedimentation were controlled by ENSO effects at least over a time interval of 600 k.y. This confirms the existence of a previously postulated robust Eocene ENSO. Significant peaks within a quasi-decadal (10-11 yr), interdecadal (17-26 yr), and multidecadal band (˜52 yr, ˜82 yr) show either the enduring influence of more or less cyclic instabilities or the influence of solar cycles.

Excitation and damping of transversal oscillation in coronal loops by wake phenomena

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A abedini

2018-02-01

Full Text Available Transversal oscillation of coronal loops that are interpreted as signatures of magneto hydrodynamics (MHD waves are observed frequently in active region corona loops. The amplitude of this oscillation has been found to be strongly attenuated. The damping of transverse oscillation may be produced by the dissipation mechanism and the wake of the traveling disturbance. The damping of transversal loop oscillations with wake phenomena is not related to any dissipation mechanism. Also, these kinds of coronal loop oscillations are not related to the kink mode, although this mode can be occurred after the attenuation process by the energy of the wave packet deposited in the loop.  In this paper the excitation and damping of transversal coronal loop oscillations with wake of traveling wave packet is discussed in detail, both theoretically and observationally. Here, the transversal coronal loop oscillations is modeled with a one dimensional simple line-tied. The dynamics of the loop and the coronal is governed by the Klein–Gordon differential equation. A localized disturbance that can be generated by nearby flare produces a perturbation that undergoes dispersion as it propagates toward the loop. As a consequence, the amplitudes of oscillates decay with time roughly t-1/2 at the external cutoff frequency. These observed data on 2016-Dec-4 by Atmospheric Imaging Assembly (AIA onboard Solar Dynamic Observatory (SDO observations data, consisting of 560 images with an interval of 24 seconds in the 171 A0 pass band is analyzed for evidence of excitation and damping of transverse oscillations of coronal loop that is situated near a flare. In this analyzed signatures of transverse oscillations that are damped rapidly were found, with periods in the range of P=18.5-23.85 minutes. Furthermore, oscillation of loop segments attenuate with time roughly as t-α that average values of α for 4 different loops change form 0.65-0.80. The magnitude values of α are in

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

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

2009-07-01

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

Fossil Coral Records of ENSO during the Last Glacial Period

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Partin, J. W.; Taylor, F. W.; Shen, C. C.; Edwards, R. L.; Quinn, T. M.; DiNezro, P.

2017-12-01

Only a handful of paleoclimate records exist that can resolve interannual changes, and hence El Nino/Southern Oscillation (ENSO) variability, during the last glacial period, a time of altered mean climate. The few existing data suggest reduced ENSO variability compared to the Holocene, possibly due to a weaker zonal sea surface temperature gradient across the tropical Pacific and/or a deeper thermocline in the eastern tropical Pacific. Our goal is to add crucial data to this extremely limited subset using sub-annually resolved fossil corals that grew during this time period to reconstruct ENSO. We seek to recover fossil corals from Vanuatu, SW Pacific (16°S, 167°E) with the objective of using coral δ18O to reconstruct changes in the ENSO during and near the Last Glacial Maximum (LGM). Modern δ18O coral records from Vanuatu show a high degree of skill in capturing ENSO variability, making it a suitable site for reconstructing ENSO variability. We have custom designed and are building a drill system that can rapidly core many 0-25 m holes resulting in much more meters of penetration than achieved by previous land-based reef drilling. As the new drill system is extremely portable and can be quickly relocated by workers without landing craft or vehicles, it is time and cost efficient. Because the proposed drilling sites have uplifted extremely fast, 7 mm/year, the LGM shoreline has been raised from 120-140 m depth to within a depth range of 10 below to 20 m above present sea level. This enables all the drilling to be within the time range of interest ( 15-25 ka). A last advantage is that the LGM corals either are still submersed in seawater or emerged only within the last 2000 years at the uplift rate of 7 mm/yr. This greatly reduces the chances of disruption of the original climate signal because sea water is less diagenetically damaging than meteoric water in the mixed, phreatic, or vadose zones. LGM coral records will enable us to compare the proxy variability

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

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

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

A New ENSO Index Derived from Satellite Measurements of Column Ozone

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Ziemke, J. R.; Chandra, S.; Oman, L. D.; Bhartia, P. K.

2010-01-01

Column Ozone measured in tropical latitudes from Nimbus 7 total ozone mapping spectrometer (TOMS), Earth Probe TOMS, solar backscatter ultraviolet (SBUV), and Aura ozone monitoring instrument (OMI) are used to derive an El Nino-Southern Oscillation (ENSO) index. This index, which covers a time period from 1979 to the present, is defined as the Ozone ENSO Index (OEI) and is the first developed from atmospheric trace gas measurements. The OEI is constructed by first averaging monthly mean column ozone over two broad regions in the western and eastern Pacific and then taking their difference. This differencing yields a self-calibrating ENSO index which is independent of individual instrument calibration offsets and drifts in measurements over the long record. The combined Aura OMI and MLS ozone data confirm that zonal variability in total column ozone in the tropics caused by ENSO events lies almost entirely in the troposphere. As a result, the OEI can be derived directly from total column ozone instead of tropospheric column ozone. For clear-sky ozone measurements a +1K change in Nino 3.4 index corresponds to +2.9 Dobson Unit (DU) change in the OEI, while a +1 hPa change in SOI coincides with a -1.7DU change in the OEI. For ozone measurements under all cloud conditions these numbers are +2.4DU and -1.4 DU, respectively. As an ENSO index based upon ozone, it is potentially useful in evaluating climate models predicting long term changes in ozone and other trace gases.

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

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Lemmon, Danielle E.; Karnauskas, Kristopher B.

2018-04-01

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

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

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

2017-12-01

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

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

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

2011-12-01

One of the most important modes of interannual variability from ocean-atmosphere system is the El Niño/Southern Oscillation - ENSO. The Brazil southern region belongs to the Southeast of South America, where there is a strong signal of ENSO, especially over the precipitation. This phenomenon can be modulated by low frequency climate patterns, especially the dominant pattern of North Pacific, called Pacific Decadal Oscillation (PDO). Attempting to better understand these interactions, the objective of this study was to investigate the seasonal impact of ENSO events over the Southern Brazil precipitation, taking into account the PDO phases. The dataset used in this study, consist of monthly precipitation records of six well distributed stations from southern Brazil (Rio Grande do Sul state). From these series it was calculated a unique index, which was categorized in three classes, in order to obtain the extremes: very below normal precipitation (below the percentile 10), normal precipitation (between percentile 10 and 90) and very above normal precipitation (above the percentile 90). To characterize the ENSO events, it was applied the Trenberth (1997) criteria in the index proposed by Bunge and Clarke (2009), which corrects the inconsistencies between the conventional SST index for Niño 3.4 region and the Southern Oscillation Index before 1950, going beyond the incoherence for decadal scale. For PDO, it was used the index proposed by Mantua et al. (1997). Contingency tables were constructed to analyze the seasonal, simultaneous, and 3, 6, 9 and 12 months lagged relationships between ENSO events (El Niño, neutral, La Niña), and extreme precipitation anomalies (categories), also considering the PDO phases during the 1913-1999 period. Moreover, a wavelet analysis was used to check the coherency and phase among these 3 times series during the 1913-2006 period. The Contingency Tables analysis showed that, generally, there were more positive (negative) precipitation

On the physical causes of ENSO events and the ITCZ's extreme latitudinal displacements

International Nuclear Information System (INIS)

Njau, E.C.

1988-08-01

We predict the maximum latitudinal shifts of the Inter-Tropical convergence zone (ITCZ) over land masses due to variations in the surface or near-surface temperature fields. We also predict the mean locations of the ITCZ over oceans during northern hemisphere (NH) and southern hemisphere (SH) summers. All our predictions are shown to agree well with observations. Finally, on the basis of the association between the latitudinal location of the eastern pacific portion of the ITCZ and El Nino-Southern Oscillation (ENSO) events as well as some previous related work (Njau, 1985a; 1985b; 1986; 1987; 1988), we suggest possible physical causes of the ENSO events. (author). 39 refs, 1 fig., 2 tabs

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-12-01

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

Some considerations about mixing, oscillation phenomena and CP violation of different mass eigenstates

International Nuclear Information System (INIS)

Malace, Simona; Lucaci-Timoce, Angela; Lazanu, I.

2003-01-01

In the last twenty years there have been made many experimental and theoretical efforts to measure and verify the prediction of the Standard Model, as well as to put in evidence small deviation from these values. In the present paper, we discuss some aspects of possible regularities of the formalism of mixing and oscillation phenomena of the mass eigenstates in particle physics and possible consequences of hidden proprieties of the systems. In the literature representations of lepton flavour mixing with different parametrisation are used for three generations of leptons and quarks. Although these are mathematically equivalent, only one of them are likely to describe the underlying physics in a more transparent way, and particularly convenient in the analysis of experimental data or is able to establish a concordance with these ones. Flavour permutational symmetry of the mixing matrix, 'maximal democracy' and maximal CP violation give a simple and efficient way to understand the essential characteristics of the phenomena, with a minimum number of parameters. The deviations of the experimental data of these predicted values represent a simple clue to study phenomenologically the breaking of symmetries. The interplay of gravitation and linear superposition of different mass eigenstates, and their consequences on the oscillation clocks, phases and the physical observability are also briefly discussed. (authors)

Interhemispheric temperature difference as a predictor of boreal winter ENSO

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Piskozub, Jacek; Gutowska, Dorota

2013-04-01

winter ENSO variability. In, fact, we did not expect a high value for a phenomenon which is a self-regulated ocean-atmosphere oscillation with timing partly triggered by stochastic atmospheric forcing, especially as we predict ENSO with (semi)global parameters. It is possible that further research may identify smaller regions of both hemispheres which temperature differences explain a larger part of ENSO variability. However in our opinion, the importance of this result is that it may not only improve ENSO prediction but also help in better understanding of ENSO variability in different time scales.

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

2018-06-01

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

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.

Phenological patterns of Spodoptera Guenée, 1852 (Lepidoptera: Noctuidae) is more affected by ENSO than seasonal factors and host plant availability in a Brazilian Savanna

Science.gov (United States)

Piovesan, Mônica; Specht, Alexandre; Carneiro, Eduardo; Paula-Moraes, Silvana Vieira; Casagrande, Mirna Martins

2018-03-01

The identification of factors responsible for the population dynamics is fundamental for pest management, since losses can reach 18% of annual production. Besides regular seasonal environmental factors and crop managements, additional supra-annual meteorological phenomena can also affect population dynamics, although its relevance has been rarely investigated. Among crop pests, Spodoptera stands out due to its worldwide distribution, high degree of polyphagy, thus causing damages in several crops in the world. Aiming to distinguish the relevance of different factors shaping population dynamics of Spodoptera in an ecosystem constituted of dry and rainy seasons, the current study used circular statistics to identify phenological patterns and test if its population fluctuation is driven by El Niño-Southern Oscillation (ENSO) effect, seasonal meteorological parameters, and/or host plant availability. Samplings were done in an intercropping system, in the Brazilian Savanna, during the new moon cycles between July/2013 and June/2016. Species were recorded all year round, but demonstrated differently non-uniform distribution, being concentrated in different seasons of the year. Population fluctuations were mostly affected by the ENSO intensity, despite the contrasting seasonal meteorological variation or host plant availability in a 400-m radius. Studies involving the observation of supra-annual phenomena, although rare, reach similar conclusions in relation to Neotropical insect fauna. Therefore, it is paramount to have long-term sampling studies to obtain a more precise response of the pest populations towards the agroecosystem conditions.

Effect of AMOC collapse on ENSO in a high resolution general circulation model

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Williamson, Mark S.; Collins, Mat; Drijfhout, Sybren S.; Kahana, Ron; Mecking, Jennifer V.; Lenton, Timothy M.

2018-04-01

We look at changes in the El Niño Southern Oscillation (ENSO) in a high-resolution eddy-permitting climate model experiment in which the Atlantic Meridional Circulation (AMOC) is switched off using freshwater hosing. The ENSO mode is shifted eastward and its period becomes longer and more regular when the AMOC is off. The eastward shift can be attributed to an anomalous eastern Ekman transport in the mean equatorial Pacific ocean state. Convergence of this transport deepens the thermocline in the eastern tropical Pacific and increases the temperature anomaly relaxation time, causing increased ENSO period. The anomalous Ekman transport is caused by a surface northerly wind anomaly in response to the meridional sea surface temperature dipole that results from switching the AMOC off. In contrast to a previous study with an earlier version of the model, which showed an increase in ENSO amplitude in an AMOC off experiment, here the amplitude remains the same as in the AMOC on control state. We attribute this difference to variations in the response of decreased stochastic forcing in the different models, which competes with the reduced damping of temperature anomalies. In the new high-resolution model, these effects approximately cancel resulting in no change in amplitude.

Marine lake ecosystem dynamics illustrate ENSO variation in the tropical western Pacific.

Science.gov (United States)

Martin, Laura E; Dawson, Michael N; Bell, Lori J; Colin, Patrick L

2006-03-22

Understanding El Niño/Southern Oscillation (ENSO) and its biological consequences is hindered by a lack of high-resolution, long-term data from the tropical western Pacific. We describe a preliminary, 6 year dataset that shows tightly coupled ENSO-related bio-physical dynamics in a seawater lake in Palau, Micronesia. The lake is more strongly stratified during La Niña than El Niño conditions, temperature anomalies in the lake co-vary strongly with the Niño 3.4 climate index, and the abundance of the dominant member of the pelagic community, an endemic subspecies of zooxanthellate jellyfish, is temperature associated. These results have broad relevance because the lake: (i) illustrates an ENSO signal that is partly obscured in surrounding semi-enclosed lagoon waters and, therefore, (ii) may provide a model system for studying the effects of climate change on community evolution and cnidarian-zooxanthellae symbioses, which (iii) should be traceable throughout the Holocene because the lake harbours a high quality sediment record; the sediment record should (iv) provide a sensitive and regionally unique record of Holocene climate relevant to predicting ENSO responses to future global climate change and, finally, (v) seawater lake ecosystems elsewhere in the Pacific may hold similar potential for past, present, and predictive measurements of climate variation and ecosystem response.

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

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J.D. Wolfe; C.J. Ralph

2009-01-01

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

Comparison of Forced ENSO-Like Hydrological Expressions in Simulations of the Preindustrial and Mid-Holocene

Science.gov (United States)

Lewis, Sophie C.; LeGrande, Allegra N.; Schmidt, Gavin A.; Kelley, Maxwell

2014-01-01

Using the water isotope- and vapor source distribution (VSD) tracer-enabled Goddard Institute for Space Studies ModelE-R, we examine changing El Nino-Southern Oscillation (ENSO)-like expressions in the hydrological cycle in a suite of model experiments. We apply strong surface temperature anomalies associated with composite observed El Nino and La Nina events as surface boundary conditions to preindustrial and mid-Holocene model experiments in order to investigate ENSO-like expressions in the hydrological cycle under varying boundary conditions. We find distinct simulated hydrological anomalies associated with El Nino-like ("ENSOWARM") and La Nina-like ("ENSOCOOL") conditions, and the region-specific VSD tracers show hydrological differences across the Pacific basin between El Nino-like and La Nina-like events. The application of ENSOCOOL forcings does not produce climatological anomalies that represent the equal but opposite impacts of the ENSOWARM experiment, as the isotopic anomalies associated with ENSOWARM conditions are generally stronger than with ENSOCOOL and the spatial patterns of change distinct. Also, when the same ENSO-like surface temperature anomalies are imposed on the mid-Holocene, the hydrological response is muted, relative to the preindustrial. Mid-Holocene changes in moisture sources to the analyzed regions across the Pacific reveal potentially complex relationships between ENSO-like conditions and boundary conditions. Given the complex impacts of ENSO-like conditions on various aspects of the hydrological cycle, we suggest that proxy record insights into paleo-ENSO variability are most likely to be robust when synthesized from a network of many spatially diverse archives, which can account for the potential nonstationarity of ENSO teleconnections under different boundary conditions.

An Ensemble Approach to Understanding the ENSO Response to Climate Change

Science.gov (United States)

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

2017-12-01

The dynamics of the El Nino/Southern Oscillation (ENSO) are known to be sensitive to changes in background climate conditions, as well as atmosphere/ocean feedbacks. However, the degree to which shifts in ENSO characteristics can be robustly attributed to external climate forcings remains unknown. Efforts to assess these changes in a multi-model framework are subject to uncertainties due to both differing model physics and internal ENSO variability. New community ensembles created at the National Center for Atmospheric Research and the NOAA Geophysical Fluid Dynamics Laboratory are ideally suited to addressing this problem, providing many realizations of the climate of the 850-2100 period with a combination of both natural and anthropogenic climate forcing factors. Here we analyze the impacts of external forcing on El Nino and La Nina evolution using four sets of simulations: the CESM Last Millennium Ensemble (CESM-LME), which covers the 850-2005 period and provides long-term context for forced responses; the Large Ensemble (CESM-LE), which includes 20th century and 21st century (RCP8.5) projections; the Medium Ensemble (CESM-ME), which is composed of 21st century RCP4.5 projections; and a large ensemble with the GFDL ESM2M, which includes 20th century and RCP8.5 projections. In the CESM, ENSO variance increases slightly over the 20th century in all ensembles, with the effects becoming much larger during the 21st. The slower increase in variance over the 20th century is shown to arise from compensating influences from greenhouse gas (GHG) and anthropogenic aerosol emissions, which give way to GHG-dominated effects by 2100. However, the 21st century variance increase is not robust: CESM and the ESM2M differ drastically in their ENSO projections. The mechanisms for these inter-model differences are discussed, as are the implications for the design of future multi-model ENSO projection experiments.

The multidecadal variations of the interannual relationship between the East Asian summer monsoon and ENSO in a coupled model

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Liu, Bo; Huang, Gang; Hu, Kaiming; Wu, Renguang; Gong, Hainan; Wang, Pengfei; Zhao, Guijie

2017-10-01

This study investigates the multidecadal variations of the interannual relationship between the East Asian summer monsoon (EASM) and El Niño-Southern Oscillation (ENSO) in 1000-year simulation of a coupled climate model. The interannual relationship between ENSO and EASM has experienced pronounced changes throughout the 1000-year simulation. During the periods with significant ENSO-EASM relationship, the ENSO-related circulation anomalies show a Pacific-Japan (PJ)-like pattern with significant wave-activity flux propagating from the tropics to the north in lower troposphere and from the mid-latitudes to the south in upper troposphere. The resultant ENSO-related precipitation anomalies are more (less) than normal over the East Asia (western North Pacific) in the decaying summers of El Niño events. In contrast, the circulation and precipitation anomalies are weak over East Asia-western North Pacific during the periods with weak ENSO-EASM relationship. Based on the energy conversion analysis, the related anomalies achieve barotropic and baroclinic energy from the mean flow during the periods with strong ENSO-EASM relationship. On the contrary, during the low-correlation periods, the energy conversion is too weak to form the link between the tropics and mid-latitudes. The main reason for the multidecadal variations of ENSO-EASM relationship is the amplitude discrepancy of SST anomalies over the Indo-western Pacific Ocean which, in turn, leads to the intensity difference of the western North Pacific anomalous anticyclone (WPAC) and related climate anomalies.

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

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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.

El Niño-Southern Oscillation and water resources in the headwaters region of the Yellow River: links and potential for forecasting

Directory of Open Access Journals (Sweden)

A. Lü

2011-04-01

Full Text Available This research explores the rainfall-El Niño-Southern Oscillation (ENSO and runoff-ENSO relationships and examines the potential for water resource forecasting using these relationships. The Southern Oscillation Index (SOI, Niño1.2, Niño3, Niño4, and Niño3.4 were selected as ENSO indicators for cross-correlation analyses of precipitation and runoff. There was a significant correlation (95% confidence level between precipitation and ENSO indicators during three periods: January, March, and from September to November. In addition, monthly streamflow and monthly ENSO indictors were significantly correlated during three periods: from January to March, June, and from October to December (OND, with lag periods between one and twelve months. Because ENSO events can be accurately predicted one to two years in advance using physical modeling of the coupled ocean-atmosphere system, the lead time for forecasting runoff using ENSO indicators in the Headwaters Region of the Yellow River could extend from one to 36 months. Therefore, ENSO may have potential as a powerful forecasting tool for water resources in the headwater regions of Yellow River.

Where was ENSO strongest?

Science.gov (United States)

Cane, M. A.; Chen, D.; Kaplan, A.

2008-12-01

Mark A. Cane, Dake Chen, Alexey Kaplan The description of this session begins: "Historical SST records suggest that for the past three decades, ENSO has been anomalously strong" and goes on to ask why. In this talk we dispute this interpretation of the historical record from within the historical record. In particular, we suggest that the most "anomalously strong" period in the historical ENSO record is the late nineteenth century. This claim requires a discussion of how we measure "ENSO strength". We also speculate on possible reasons for the strength of ENSO in this earlier period. Finally, we consult the models, and in reiteration of the collective conclusion of all speakers at this session, find that the riddles the models provide are inelegant and disobliging, lacking the cryptic wisdom of the classical oracles.

ENSO impacts on flood risk at the global scale

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Ward, Philip; Dettinger, Michael; Jongman, Brenden; Kummu, Matti; Winsemius, Hessel

2014-05-01

We present the impacts of El Niño Southern Oscillation (ENSO) on society and the economy, via relationships between ENSO and the hydrological cycle. We also discuss ways in which this knowledge can be used in disaster risk management and risk reduction. This contribution provides the most recent results of an ongoing 4-year collaborative research initiative to assess and map the impacts of large scale interannual climate variability on flood hazard and risk at the global scale. We have examined anomalies in flood risk between ENSO phases, whereby flood risk is expressed in terms of indicators such as: annual expected damage; annual expected affected population; annual expected affected Gross Domestic Product (GDP). We show that large anomalies in flood risk occur during El Niño or La Niña years in basins covering large parts of the Earth's surface. These anomalies reach statistical significance river basins covering almost two-thirds of the Earth's surface. Particularly strong anomalies exist in southern Africa, parts of western Africa, Australia, parts of Central Eurasia (especially for El Niño), the western USA (especially La Niña anomalies), and parts of South America. We relate these anomalies to possible causal relationships between ENSO and flood hazard, using both modelled and observed data on flood occurrence and extremity. The implications for flood risk management are many-fold. In those regions where disaster risk is strongly influenced by ENSO, the potential predictably of ENSO could be used to develop probabilistic flood risk projections with lead times up to several seasons. Such data could be used by the insurance industry in managing risk portfolios and by multinational companies for assessing the robustness of their supply chains to potential flood-related interruptions. Seasonal forecasts of ENSO influence of peak flows could also allow for improved flood early warning and regulation by dam operators, which could also reduce overall risks

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

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

2017-12-01

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

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

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

2014-09-01

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

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

The interdecadal changes of south pacific sea surface temperature in the mid-1990s and their connections with ENSO

Science.gov (United States)

Li, Gang; Li, Chongyin; Tan, Yanke; Bai, Tao

2014-01-01

The characteristic changes of South Pacific sea surface temperature anomalies (SSTAs) for the period January 1979 to December 2011, during which the 1990s Pacific pan-decadal variability (PDV) interdecadal regime shifts occurred, were examined. Empirical Orthogonal Function (EOF) analysis was applied to the monthly mean SSTA for two sub-periods: January 1979 to December 1994 (P1) and January 1996 to December 2011 (P2). Both the spatial and temporal features of the leading EOF mode for P1 and P2 showed a remarkable difference. The spatial structure of the leading EOF changed from a tripolar pattern for P1 (EOF-P1) to a dipole-like pattern for P2 (EOF-P2). Besides, EOF-P1 (EOF-P2) had significant spectral peaks at 4.6 yr (2.7 yr). EOF-P2 not only had a closer association with El Niño-Southern Oscillation (ENSO), but also showed a faster response to ENSO than EOF-P1 based on their lead-lag relationships with ENSO. During the development of ENSO, the South Pacific SSTA associated with ENSO for both P1 and P2 showed a significant eastward propagation. However, after the peak of ENSO, EOF-P1 showed a stronger persistence than EOF-P2, which still showed eastward propagation. The variability of the SSTA associated with the whole process of ENSO evolution during P1 and the SSTA associated with the development of ENSO during P2 support the existence of ocean-to-atmosphere forcing, but the SSTA associated with the decay of ENSO shows the phenomenon of atmosphere-to-ocean forcing.

El Nino/Southern Oscillation response to global warming.

Science.gov (United States)

Latif, M; Keenlyside, N S

2009-12-08

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

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

Science.gov (United States)

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

2016-12-01

A set of ensemble seasonal reforecasts for 1958-2014 is conducted using the National Centers for Environmental Prediction (NCEP) Climate Forecast System, version 2 (CFSv2), initialized with observation-based ocean, atmosphere, land and sea ice reanalyses, including the Eu­ropean Centre for Medium-Range Weather Forecasts (ECMWF) global ocean reanalysis version 4, the ERA-40 atmospheric reanalysis, the NCEP CFS Reanalysis for atmosphere, land and sea ice, and the NASA Global Land Data Assimilation System reanalysis version 2.0 for land. The purpose is to examine a long and continuous seasonal reforecast dataset from a modern seasonal forecast system to be used by the research community. In comparison with other current reforecasts, this dataset allows us to evaluate the degree to which El Niño and Southern Oscillation (ENSO) events can be predicted, using a larger sample of events. Furthermore, we can directly compare the predictability of the ENSO events in 1960s-70s with the more widely studied ENSO events occurring since the 1980s to examine the state-of-the-art seasonal forecast system's capability at different phases of global climate change and multidecadal variability. A major concern is whether the seasonal reforecasts before 1979 have useful skill when there were fewer ocean observations. Our preliminary examination of the reforecasts shows that, although the reforecasts have lower skill in predicting the SST anomalies in the North Pacific and North Atlantic before 1979, the prediction skill of the ENSO onset and development for 1958-1978 is comparable to that for 1979-2014. The skill of the earlier predictions declines faster in the ENSO decaying phase because the reforecasts initialized after the summer season persistently predict lingering wind and SST anomalies in the eastern equatorial Pacific during the decaying phase of several major ENSO events in the 1960s-70s. Since the 1980s, the reforecasts initialized in fall overestimate the peak SST

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.

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

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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

ENSO Diversity Changes Due To Global Warming In CESM-LE

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

2017-12-01

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

Biennial-Aligned Lunisolar-Forcing of ENSO: Implications for Simplified Climate Models

Science.gov (United States)

Pukite, P. R.

2017-12-01

By solving Laplace's tidal equations along the equatorial Pacific thermocline, assuming a delayed-differential effective gravity forcing due to a combined lunar+solar (lunisolar) stimulus, we are able to precisely match ENSO periodic variations over wide intervals. The underlying pattern is difficult to decode by conventional means such as spectral analysis, which is why it has remained hidden for so long, despite the excellent agreement in the time-domain. What occurs is that a non-linear seasonal modulation with monthly and fortnightly lunar impulses along with a biennially-aligned "see-saw" is enough to cause a physical aliasing and thus multiple folding in the frequency spectrum. So, instead of a conventional spectral tidal decomposition, we opted for a time-domain cross-validating approach to calibrate the amplitude and phasing of the lunisolar cycles. As the lunar forcing consists of three fundamental periods (draconic, anomalistic, synodic), we used the measured Earth's length-of-day (LOD) decomposed and resolved at a monthly time-scale [1] to align the amplitude and phase precisely. Even slight variations from the known values of the long-period tides will degrade the fit, so a high-resolution calibration is possible. Moreover, a narrow training segment from 1880-1920 using NINO34/SOI data is adequate to extrapolate the cycles of the past 100 years (see attached figure). To further understand the biennial impact of a yearly differential-delay, we were able to also decompose using difference equations the historical sea-level-height readings at Sydney harbor to clearly expose the ENSO behavior. Finally, the ENSO lunisolar model was validated by back-extrapolating to Unified ENSO coral proxy (UEP) records dating to 1650. The quasi-biennial oscillation (QBO) behavior of equatorial stratospheric winds derives following a similar pattern to ENSO via the tidal equations, but with an emphasis on draconic forcing. This improvement in ENSO and QBO understanding has

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.

The Influence of ENSO to the Rainfall Variability in North Sumatra Province

Science.gov (United States)

Irwandi, H.; Pusparini, N.; Ariantono, J. Y.; Kurniawan, R.; Tari, C. A.; Sudrajat, A.

2018-04-01

The El Niño Southern Oscillation (ENSO) is a global phenomenon that affects the variability of rainfall in North Sumatra. The influence of ENSO will be different for each region. This review will analyse the influence of ENSO activity on seasonal and annual rainfall variability. In this research, North Sumatra Province will be divided into 4 (four) regions based on topographical conditions, such as: East Coast (EC), East Slope (ES), Mountains (MT), and West Coast (WC). The method used was statistical and descriptive analysis. Data used in this research were rainfall data from 15 stations / climate observation posts which spread in North Sumatera region and also anomaly data of Nino 3.4 region from period 1981-2016. The results showed that the active El Niño had an effect on the decreasing the rainfall during the period of DJF, JJA and SON in East Coast, East Slope, and Mountains with the decreasing of average percentage of annual rainfall up to 7%. On the contrary, the active La Nina had an effect on the addition of rainfall during the period DJF and JJA in the East Coast and Mountains with the increasing of average percentage of annual rainfall up to 6%.

Atmosphere-Ocean Variations in the Indo-Pacific Sector during ENSO Episodes.

Science.gov (United States)

Lau, Ngar-Cheung; Nath, Mary Jo

2003-01-01

The influences of El Niño-Southern Oscillation (ENSO) events on air-sea interaction in the Indian-western Pacific (IWP) Oceans have been investigated using a general circulation model. Observed monthly sea surface temperature (SST) variations in the deep tropical eastern/central Pacific (DTEP) have been inserted in the lower boundary of this model through the 1950-99 period. At all maritime grid points outside of DTEP, the model atmosphere has been coupled with an oceanic mixed layer model with variable depth. Altogether 16 independent model runs have been conducted.Composite analysis of selected ENSO episodes illustrates that the prescribed SST anomalies in DTEP affect the surface atmospheric circulation and precipitation patterns in IWP through displacements of the near-equatorial Walker circulation and generation of Rossby wave modes in the subtropics. Such atmospheric responses modulate the surface fluxes as well as the oceanic mixed layer depth, and thereby establish a well-defined SST anomaly pattern in the IWP sector several months after the peak in ENSO forcing in DTEP. In most parts of the IWP region, the net SST tendency induced by atmospheric changes has the same polarity as the local composite SST anomaly, thus indicating that the atmospheric forcing acts to reinforce the underlying SST signal.By analyzing the output from a suite of auxiliary experiments, it is demonstrated that the SST perturbations in IWP (which are primarily generated by ENSO-related atmospheric changes) can, in turn, exert notable influences on the atmospheric conditions over that region. This feedback mechanism also plays an important role in the eastward migration of the subtropical anticyclones over the western Pacific in both hemispheres.

Atmospheric QBO and ENSO indices with high vertical resolution from GNSS radio occultation temperature measurements

Science.gov (United States)

Wilhelmsen, Hallgeir; Ladstädter, Florian; Scherllin-Pirscher, Barbara; Steiner, Andrea K.

2018-03-01

We provide atmospheric temperature variability indices for the tropical troposphere and stratosphere based on global navigation satellite system (GNSS) radio occultation (RO) temperature measurements. By exploiting the high vertical resolution and the uniform distribution of the GNSS RO temperature soundings we introduce two approaches, both based on an empirical orthogonal function (EOF) analysis. The first method utilizes the whole vertical and horizontal RO temperature field from 30° S to 30° N and from 2 to 35 km altitude. The resulting indices, the leading principal components, resemble the well-known patterns of the Quasi-Biennial Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO) in the tropics. They provide some information on the vertical structure; however, they are not vertically resolved. The second method applies the EOF analysis on each altitude level separately and the resulting indices contain information on the horizontal variability at each densely available altitude level. They capture more variability than the indices from the first method and present a mixture of all variability modes contributing at the respective altitude level, including the QBO and ENSO. Compared to commonly used variability indices from QBO winds or ENSO sea surface temperature, these new indices cover the vertical details of the atmospheric variability. Using them as proxies for temperature variability is also of advantage because there is no further need to account for response time lags. Atmospheric variability indices as novel products from RO are expected to be of great benefit for studies on atmospheric dynamics and variability, for climate trend analysis, as well as for climate model evaluation.

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.

Influence of ENSO on coastal flood hazard and exposure at the global-scale

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Muis, S.; Haigh, I. D.; Guimarães Nobre, G.; Aerts, J.; Ward, P.

2017-12-01

The El Niño-Southern Oscillation (ENSO) is the dominant signal of interannual climate variability. The unusually warm (El Niño) and cold (La Niña) oceanic and atmospheric conditions in the tropical Pacific drives interannual variability in both mean and extreme sea levels, which in turn may influence the probabilities and impacts of coastal flooding. We assess the influence of ENSO on coastal flood hazard and exposure using daily timeseries from the Global Time and Surge Reanalysis (GTSR) dataset (Muis et al., 2016). As the GTSR timeseries do not include steric effects (i.e. density differences), we improve the GTSR timeseries by adding steric sea levels. Evaluation against observed sea levels shows that the including steric sea levels leads to a much better representation of the seasonal and interannual variability. We show that sea level anomalies occur during ENSO years with higher sea levels during La Niña in the South-Atlantic, Indian Ocean and the West Pacific, whereas sea levels are lower in the east Pacific. The pattern is generally inversed for El Niño. We also find an effect of ENSO in the number of people exposed to coastal flooding. Although the effect is minor at the global-scale, it may be important for flood risk management to consider at the national or sub national levels. Previous studies at the global-scale have used tide gauge observation to assess the influence of ENSO on extreme sea levels. The advantage of our approach over observations is that GTSR provides a consistent dataset with a full global coverage for the period 1979-2014. This allows us to assess ENSO's influence on sea level extremes anywhere in the world. Furthermore, it enables us to also calculate the impacts of extreme sea levels in terms of coastal flooding and exposed population. ReferencesMuis et al (2016) A global reanalysis of storm surges and extreme sea levels. Nature Communications.7:11969. doi:10.1038/ncomms11969.

Perspective on the northwestward shift of autumn tropical cyclogenesis locations over the western North Pacific from shifting ENSO

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Hu, Chundi; Zhang, Chengyang; Yang, Song; Chen, Dake; He, Shengping

2017-11-01

During the recent decades of satellite era, more tropical cyclogenesis locations (TCLs) were observed over the northwestern part of the western North Pacific (WNP), relative to the southeastern part, during the boreal autumn. This increase in TCLs over the northwestern WNP is largely attributed to the synergy of shifting El Niño-Southern Oscillation (ENSO) and the 1998 Pacific climate regime shift. Both central Pacific (CP) La Niña and CP El Niño have occurred more frequently since 1998, with only one eastern Pacific El Niño observed in autumn 2015. The change in the mean longitude of TCLs is closely linked to the ENSO diversity, whereas the change in the mean latitude is dominated by the warming of the WNP induced by an interdecadal tendency of CP La Niña-like events. The physical mechanisms responsible for this shifting ENSO-TCL linkage can be potentially explained by the tacit-and-mutual configurations between tropical upper-tropospheric trough and monsoon trough, on both interannual and interdecadal timescales, which is mainly due to the ENSO-related large-scale environment changes in ocean and atmosphere that modulate the WNP TCL.

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

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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

Variability modes of precipitation along a Central Mediterranean area and their relations with ENSO, NAO, and other climatic patterns

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Kalimeris, Anastasios; Ranieri, Ezio; Founda, Dimitra; Norrant, Caroline

2017-12-01

This study analyses a century-long set of precipitation time series in the Central Mediterranean (encompassing the Greek Ionian and the Italian Puglia regions) and investigates the statistically significant modes of the interannual precipitation variability using efficient methods of spectral decomposition. The statistical relations and the possible physical couplings between the detected modes and the global or hemispheric patterns of climatic variability (the El Niño Southern Oscillation or ENSO, the North Atlantic Oscillation or NAO, the East Atlantic or EA, the Scandinavian or SCAND, and others) were examined in the time-frequency domain and low-order synchronization events were sought. Significant modes of precipitation variability were detected in the Taranto Gulf and the southern part of the Greek Ionian region at the sub-decadal scales (mostly driven by the SCAND pattern) and particularly at the decadal and quasi-decadal scales, where strong relations found with the ENSO activity (under complex implications of EA and NAO) prior to the 1930s or after the early-1970s. The precipitation variations in the Adriatic stations of Puglia are dominated by significant bi-decadal modes which found to be coherent with the ENSO activity and also weakly related with the Atlantic Ocean sea surface temperature intrinsic variability. Additionally, important discontinuities characterize the evolution of precipitation in certain stations of the Taranto Gulf and the Greek Ionian region during the early-1960s and particularly during the early-1970s, followed by significant reductions in the mean annual precipitation. These discontinuities seem to be associated with regional effects of NAO and SCAND, probably combined with the impact of the 1970s climatic shift in the Pacific and the ENSO variability.

The association between El Niño/Southern Oscillation events and typhoons in the Marshall Islands.

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Spennemann, D H; Marschner, I C

1995-09-01

An analysis of the historic record of typhoons in the Marshall Islands has identified a significant association between the occurrence of the El Niño/Southern Oscillation phenomenon (ENSO) and the occurrence of typhoons in the Marshall Islands. Whilst typhoons normally occur further to the east, the warming of the ocean waters around the Marshall Islands, as part of the ENSO phenomenon, generates typhoons further to the west. The results suggest that typhoons are 2.6 times more likely to occur during ENSO years, with a 71 per cent chance of a typhoon striking during an ENSO year, and only a 26 per cent chance of one happening during a non-ENSO year. This has implications for planning and public safety, which the relevant authorities may wish to take note of.

El Niño/Southern Oscillation response to global warming

Science.gov (United States)

Latif, M.; Keenlyside, N. S.

2009-01-01

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

Assessment of the APCC Coupled MME Suite in Predicting the Distinctive Climate Impacts of Two Flavors of ENSO during Boreal Winter

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Jeong, Hye-In; Lee, Doo Young; Karumuri, Ashok; Ahn, Joong-Bae; Lee, June-Yi; Luo, Jing-Jia; Schemm, Jae-Kyung E.; Hendon, Harry H.; Braganza, Karl; Ham, Yoo-Geun

2012-01-01

Forecast skill of the APEC Climate Center (APCC) Multi-Model Ensemble (MME) seasonal forecast system in predicting two main types of El Nino-Southern Oscillation (ENSO), namely canonical (or cold tongue) and Modoki ENSO, and their regional climate impacts is assessed for boreal winter. The APCC MME is constructed by simple composite of ensemble forecasts from five independent coupled ocean-atmosphere climate models. Based on a hindcast set targeting boreal winter prediction for the period 19822004, we show that the MME can predict and discern the important differences in the patterns of tropical Pacific sea surface temperature anomaly between the canonical and Modoki ENSO one and four month ahead. Importantly, the four month lead MME beats the persistent forecast. The MME reasonably predicts the distinct impacts of the canonical ENSO, including the strong winter monsoon rainfall over East Asia, the below normal rainfall and above normal temperature over Australia, the anomalously wet conditions across the south and cold conditions over the whole area of USA, and the anomalously dry conditions over South America. However, there are some limitations in capturing its regional impacts, especially, over Australasia and tropical South America at a lead time of one and four months. Nonetheless, forecast skills for rainfall and temperature over East Asia and North America during ENSO Modoki are comparable to or slightly higher than those during canonical ENSO events.

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

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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.

Dynamics of the Indian monsoon and ENSO relationships in the SINTEX global coupled model

Energy Technology Data Exchange (ETDEWEB)

Terray, P. [LODYC, Paris (France); Universite Paris 7, Paris (France); Guilyardi, E. [LSCE, Gif-sur-Yvette (France); CGAM, Reading (United Kingdom); Fischer, A.S. [LODYC, Paris (France); Delecluse, P. [LODYC, Paris (France); LSCE, Gif-sur-Yvette (France)

2005-02-01

This paper uses recent gridded climatological data and a coupled general circulation model (GCM) simulation in order to assess the relationships between the interannual variability of the Indian summer monsoon (ISM) and the El Nino-Southern Oscillation (ENSO). The focus is on the dynamics of the ISM-ENSO relationships and the ability of the state-of-the-art coupled GCM to reproduce the complex lead-lag relationships between the ISM and the ENSO. The coupled GCM is successful in reproducing the ISM circulation and rainfall climatology in the Indian areas even though the entire ISM circulation is weaker relative to that observed. In both observations and in the simulation, the ISM rainfall anomalies are significantly associated with fluctuations of the Hadley circulation and the 200 hPa zonal wind anomalies over the Indian Ocean. A quasi-biennial time scale is found to structure the ISM dynamical and rainfall indices in both cases. Moreover, ISM indices have a similar interannual variability in the simulation and observations. The coupled model is less successful in simulating the annual cycle in the tropical Pacific. Despite some problems in simulation of the annual cycle and the Southern Oscillation, the coupled model captures some aspects of the interannual variability in the tropical Pacific. ENSO events are phase-locked with the annual cycle as observed, but are of reduced amplitude relative to the observations. Wavelet analysis of the model Nino34 time series shows enhanced power in the 2-4 year band, as compared to the 2-8 year range for observations during the 1950-2000 period. The ISM circulation is weakened during ENSO years in both the simulation and the observations. However, the model fails to reproduce the lead-lag relationship between the ISM and Nino34 sea surface temperatures (SSTs). Furthermore, lag correlations show that the delayed response of the wind stress over the central Pacific to ISM variability is insignificant in the simulation. These

ENSO surface shortwave radiation forcing over the tropical Pacific

Directory of Open Access Journals (Sweden)

K. G. Pavlakis

2008-09-01

Full Text Available We have studied the spatial and temporal variation of the downward shortwave radiation (DSR at the surface of the Earth during ENSO events for a 21-year period over the tropical and subtropical Pacific Ocean (40° S–40° N, 90° E–75° W. The fluxes were computed using a deterministic model for atmospheric radiation transfer, along with satellite data from the ISCCP-D2 database, reanalysis data from NCEP/NCAR for the key atmospheric and surface input parameters, and aerosol parameters from GADS (acronyms explained in main text. A clear anti-correlation was found between the downward shortwave radiation anomaly (DSR-A time-series, in the region 7° S–5° N 160° E–160° W located west of the Niño-3.4 region, and the Niño-3.4 index time-series. In this region where the highest in absolute value DSR anomalies are observed, the mean DSR anomaly values range from −45 Wm⁻² during El Niño episodes to +40 Wm⁻² during La Niña events. Within the Niño-3.4 region no significant DSR anomalies are observed during the cold ENSO phase in contrast to the warm ENSO phase. A high correlation was also found over the western Pacific (10° S–5° N, 120–140° E, where the mean DSR anomaly values range from +20 Wm⁻² to −20 Wm⁻² during El Niño and La Niña episodes, respectively. There is also convincing evidence that the time series of the mean downward shortwave radiation anomaly in the off-equatorial western Pacific region 7–15° N 150–170° E, precedes the Niño-3.4 index time-series by about 7 months and the pattern of this anomaly is indicative of ENSO operating through the mechanism of the western Pacific oscillator. Thus, the downward shortwave radiation anomaly is a complementary index to the SST anomaly for the study of ENSO events and can be used to assess whether or not El Niño or La Niña conditions prevail.

Interdecadal modulation of the relationship between ENSO, IPO and precipitation: insights from tree rings in Australia

Energy Technology Data Exchange (ETDEWEB)

Heinrich, Ingo [School of Resources, Environment and Society, Australian National University, Canberra, ACT (Australia); Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Climate Dynamics and Landscape Evolution, Potsdam (Germany); Weidner, Kathrin [Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Climate Dynamics and Landscape Evolution, Potsdam (Germany); Forschungszentrum Juelich GmbH, Institute for Chemistry and Dynamics of the Geosphere, Juelich (Germany); Helle, Gerhard [Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Climate Dynamics and Landscape Evolution, Potsdam (Germany); Vos, Heinz [Forschungszentrum Juelich GmbH, Institute for Chemistry and Dynamics of the Geosphere, Juelich (Germany); Lindesay, Janette; Banks, John C.G. [School of Resources, Environment and Society, Australian National University, Canberra, ACT (Australia)

2009-07-15

Australian climate-proxy reconstructions based on tree rings from tropical and subtropical forests have not been achieved so far due to the rarity of species producing anatomically distinct annual growth rings. Our study identifies the Australian Red Cedar (Toona ciliata) as one of the most promising tree species for tree-ring research in Australasia because this species exhibits distinct annual tree rings, a prerequisite for high quality tropical dendroclimatology. Based on these preliminary studies, we were able, for the first time in subtropical and tropical Australia, to develop a statistically robust, precisely dated and annually resolved chronology back to AD1854. We show that the variability in ring widths of T. ciliata is mainly dependent on annual precipitation. The developed proxy data series contains both high- and low-frequency climate signals which can be associated with the El Nino Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). A comparison of different data sets (Brisbane precipitation, tree rings, coral luminescence record from the Great Barrier Reef, ENSO and IPO) revealed non-stationary correlation patterns throughout the twentieth century but little instability between the new tree-ring chronology and Brisbane precipitation. (orig.)

Internal variability in a 1000-yr control simulation with the coupled climate model ECHO-G - II. El Nino Southern Oscillation and North Atlantic Oscillation

Energy Technology Data Exchange (ETDEWEB)

Min, Seung-Ki; Hense, Andreas [Univ. of Bonn (Germany). Meteorological Inst.; Legutke, Stephanie [Max Planck Inst. for Meteorology, Hamburg (Germany); Kwon, Won-Tae [Meteorological Research Inst., Seoul (Korea, Republic of)

2005-08-01

A 1000-yr control simulation (CTL) performed with the atmosphere-ocean global climate model ECHO-G is analysed with regard to the El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO), the two major natural climatic variabilities, in comparison with observations and other model simulations. The ENSO-related sea surface temperature climate and its seasonal cycle in the tropical Pacific and a single Intertropical Convergence Zone in the eastern tropical Pacific are simulated reasonably, and the ENSO phase-locking to the annual cycle and the subsurface ocean behaviour related to equatorial wave dynamics are also reproduced well. The simulated amplitude of the ENSO signal is however too large and its occurrence is too regular and frequent. Also, the observed westward propagation of zonal wind stress over the equatorial Pacific is not captured by the model. Nevertheless, the ENSO-related teleconnection patterns of near-surface temperature (T2m), precipitation (PCP) and mean sea level pressure (MSLP) are reproduced realistically. The NAO index, defined as the MSLP difference between Gibraltar and Iceland, has a 'white' noise spectrum similar to that of the detrended index obtained from observed data. The correlation and regression patterns of T2m, PCP and MSLP with the NAO index are also successfully simulated. However, the model overestimates the warming over the North Pacific in the high index phase of the NAO, a feature it shares with other coupled models. This might be associated with an enhanced Atlantic/Pacific teleconnection, which is hardly seen in the observations. A detection analysis of the NAO index shows that the observed recent 4060 yr trend cannot be explained by the model's internal variability while the recent 2030 yr trend occurs with a more than 1% chance in ECHO-G CTL.

Regional characteristics of the effects of the El Niño-Southern Oscillation on the sea level in the China Sea

Science.gov (United States)

Wang, Hui; Liu, Kexiu; Wang, Aimei; Feng, Jianlong; Fan, Wenjing; Liu, Qiulin; Xu, Yao; Zhang, Zengjian

2018-05-01

Based on coastal tide level, satellite altimetry, and sea surface temperature (SST) data of offshore areas of China's coast and the equatorial Pacific Ocean, the regional characteristics of the effects of the El Niño-Southern Oscillation (ENSO) on the sea level in the China Sea were investigated. Singular value decomposition results show a significant teleconnection between the sea level in the China Sea and the SST of the tropical Pacific Ocean; the correlation coefficient decreases from south to north. Data from tide gauges along China's coast show that the seasonal sea-level variations are significantly correlated with the ENSO. In addition, China's coast was divided into three regions based on distinctive regional characteristics. Results obtained show that the annual amplitude of sea level was low during El Niño developing years, and especially so during the El Niño year. The ENSO intensity determined the response intensity of the annual amplitude of the sea level. The response region (amplitude) was relatively large for strong ENSO intensities. Significant oscillation periods at a timescale of 4-7 years existed in the sea level of the three regions. The largest amplitude of oscillation was 1.5 cm, which was the fluctuation with the 7-year period in the South China Sea. The largest amplitude of oscillation in the East China Sea was about 1.3 cm. The amplitude of oscillation with the 6-year period in the Bohai Sea and Yellow Sea was the smallest (less than 1 cm).

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

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

2017-12-01

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

Future changes in rainfall associated with ENSO, IOD and changes in the mean state over Eastern Africa

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Endris, Hussen Seid; Lennard, Christopher; Hewitson, Bruce; Dosio, Alessandro; Nikulin, Grigory; Artan, Guleid A.

2018-05-01

This study examines the projected changes in the characteristics of the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) in terms of mean state, intensity and frequency, and associated rainfall anomalies over eastern Africa. Two regional climate models driven by the same four global climate models (GCMs) and the corresponding GCM simulations are used to investigate projected changes in teleconnection patterns and East African rainfall. The period 1976-2005 is taken as the reference for present climate and the far-future climate (2070-2099) under Representative Concentration Pathway 8.5 (RCP8.5) is analyzed for projected change. Analyses of projections based on GCMs indicate an El Niño-like (positive IOD-like) warming pattern over the tropical Pacific (Indian) Ocean. However, large uncertainties remain in the projected future changes in ENSO/IOD frequency and intensity with some GCMs show increase of ENSO/IOD frequency and intensity, and others a decrease or no/small change. Projected changes in mean rainfall over eastern Africa based on the GCM and RCM data indicate a decrease in rainfall over most parts of the region during JJAS and MAM seasons, and an increase in rainfall over equatorial and southern part of the region during OND, with the greatest changes in equatorial region. During ENSO and IOD years, important changes in the strength of the teleconnections are found. During JJAS, when ENSO is an important driver of rainfall variability over the region, both GCM and RCM projections show an enhanced La Niña-related rainfall anomaly compared to the present period. Although the long rains (MAM) have little association with ENSO in the reference period, both GCMs and RCMs project stronger ENSO teleconnections in the future. On the other hand, during the short rains (OND), a dipole future change in rainfall teleconnection associated with ENSO and IOD is found, with a stronger ENSO/IOD related rainfall anomaly over the eastern part of the domain

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.

Impacts of winter NPO on subsequent winter ENSO: sensitivity to the definition of NPO index

Science.gov (United States)

Chen, Shangfeng; Wu, Renguang

2018-01-01

This study investigates the linkage between boreal winter North Pacific Oscillation (NPO) and subsequent winter El Niño-Southern Oscillation (ENSO) based on seven different NPO indices. Results show that the influence of winter NPO on the subsequent winter El Niño is sensitive to how the NPO is defined. A significant NPO-El Niño connection is obtained when the NPO-related anomalous cyclone over the subtropical North Pacific extends to near-equatorial regions. The anomalous cyclone induces warm sea surface temperature (SST) anomalies through modulating surface heat fluxes. These warm SST anomalies are able to maintain into the following spring and summer through an air-sea coupled process and in turn induce significant westerly wind anomalies over the tropical western Pacific. In contrast, the NPO-El Niño relationship is unclear when the NPO-related anomalous cyclone over the subtropical North Pacific is confined to off-equatorial regions and cannot induce significant warm SST anomalies over the subtropical North Pacific. The present study suggests that definitions of NPO should be taken into account when using NPO to predict ENSO. In particular, we recommend defining the NPO index based on the empirical orthogonal function technique over appropriate region that does not extend too far north.

The role of the intra-daily SST variability in the Indian monsoon variability and monsoon-ENSO-IOD relationships in a global coupled model

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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

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.

Pengaruh ENSO (El Niño and Southern Oscillation terhadap transpor massa air laut di Selat Malaka

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Muhammad

2012-04-01

Full Text Available Abstrak. Penelitian ini mengkaji pengaruh ENSO (El Niño and Southern Oscillation di Selat Malaka dengan memakai indek osilasi selatan Samudera Pasifik dalam menentukan kondisi Normal, El Niño dan La Nina sebagai analisis transpor massa air laut, elevasi muka laut dan densitas laut. Metode penelitian menggunakan persamaan Navier-Stokes dengan gaya pembangkit pasang surut, angin dari National Centers for Environmental Prediction (NCEP Tahun 1980-2007, Salinitas (Levitus dan Boyer, 1994a dan Temperatur (Levitus dan Boyer, 1994b. Persamaan gerak air laut tersebut dimodelkan dengan model Hamburg Shelf Ocean Model (HAMSOM. Hasil-hasil menunjukkan bahwa transpor di bagian barat laut Selat Malaka pergerakannya melemah dan transpor di bagian tenggara pergerakannya menguat dibandingkan pada kondisi tahun Normal dan La Nina. Sedangkan elevasi muka air di Selat Malaka pada kondisi tahun El Niño lebih rendah dibandingkan pada kondisi Normal dan La Nina. Selanjutnya densitas permukaan laut di Selat Malaka pada kondisi tahun Normal, El Niño dan La Nina berkisar 18,5 s/d 20,5 kg/m3. Densitas laut lapisan 30-50 m di Selat Malaka pada kondisi tahun Normal, El Niño dan La Nina berkisar 19 s/d 21 kg/m3. Densitas permukaan laut dan densitas laut kedalaman 30-50 m di bagian tenggara Selat Malaka pada kondisi El Niño lebih besar dibandingkan pada tahun Normal maupun tahun La Nina.

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

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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

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.)

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

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Trismidianto; Satyawardhana, H.

2018-05-01

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

Effects of climate oscillations on wildland fire potential in the continental United States

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Shelby A. Mason; Peter E. Hamlington; Benjamin D. Hamlington; W. Matt Jolly; Chad M. Hoffman

2017-01-01

The effects of climate oscillations on spatial and temporal variations in wildland fire potential in the continental U.S. are examined from 1979 to 2015 using cyclostationary empirical orthogonal functions (CSEOFs). The CSEOF analysis isolates effects associated with the modulated annual cycle and the El Niño–Southern Oscillation (ENSO). The results show that, in early...

Effects of ocean initial perturbation on developing phase of ENSO in a coupled seasonal prediction model

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Lee, Hyun-Chul; Kumar, Arun; Wang, Wanqiu

2018-03-01

Coupled prediction systems for seasonal and inter-annual variability in the tropical Pacific are initialized from ocean analyses. In ocean initial states, small scale perturbations are inevitably smoothed or distorted by the observational limits and data assimilation procedures, which tends to induce potential ocean initial errors for the El Nino-Southern Oscillation (ENSO) prediction. Here, the evolution and effects of ocean initial errors from the small scale perturbation on the developing phase of ENSO are investigated by an ensemble of coupled model predictions. Results show that the ocean initial errors at the thermocline in the western tropical Pacific grow rapidly to project on the first mode of equatorial Kelvin wave and propagate to the east along the thermocline. In boreal spring when the surface buoyancy flux weakens in the eastern tropical Pacific, the subsurface errors influence sea surface temperature variability and would account for the seasonal dependence of prediction skill in the NINO3 region. It is concluded that the ENSO prediction in the eastern tropical Pacific after boreal spring can be improved by increasing the observational accuracy of subsurface ocean initial states in the western tropical Pacific.

Teleconnections in Groundwater of U.S. Principal Aquifers to the Non-Stationarity of ENSO, NAO, PDO, and AMO

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Gurdak, J. J.; Kuss, A. M.

2012-12-01

Groundwater will play an important role in society's adaptation to climate variability and change. Therefore, it is particularly important to detect and quantify teleconnections in groundwater with non-stationarity in climate variability on interannual to multidecadal timescales because of the tangible and near-term implications for water-resource management. Interannual to multidecadal climate variability partially controls precipitation distribution in space and time, drought frequency and severity, snowmelt runoff, streamflow, and other hydrologic processes that profoundly affects surface-water resources. However, the effects of interannual to multidecadal climate variability on recharge rates and mechanisms and other subsurface hydrologic processes that affect groundwater quantity and quality are largely unknown in most aquifers of the United States (U.S.) and other regions of the world. Here we use singular spectrum analysis (SSA), wavelet coherence analysis, and lag correlation to quantify the effects of the El Niño Southern Oscillation (ENSO) (2-7 year cycle), North Atlantic Oscillation (NAO) (3-6 year cycle), Pacific Decadal Oscillation (PDO) (10-25 year cycle), and Atlantic Multidecadal Oscillation (AMO) (50-70 year cycle) on precipitation, groundwater levels, simulated groundwater pumping, and climate varying recharge rates across the regionally extensive Central Valley (52,000 km2), Basin and Range (700,000 km2), High Plains (450,000 km2), and North Atlantic Coastal Plain (130,000 km2) Principal Aquifers (PAs) of the U.S. The results indicate that precipitation, recharge, and groundwater levels are partially affected by interannual to multidecadal climate variability and groundwater-level fluctuations are not solely a function of temporal patterns in pumping. ENSO and PDO have a greater control than NAO and AMO on variability in precipitation and groundwater levels across the U.S., particularly in the western and central PAs. At many locations, recharge

Distribution of black flies (Diptera: Simuliidae) along an elevational gradient in the Andes Mountains of Colombia during the El Niño Southern Oscillation.

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Mantilla, Juan S; Moncada, Ligia I; Matta, Nubia E; Adler, Peter H

2018-07-01

Vector ecology is a key factor in understanding the transmission of disease agents, with each species having an optimal range of environmental requirements. Scarce data, however, are available for how interactions of local and broad-scale climate phenomena, such as seasonality and the El Niño Southern Oscillation (ENSO), affect simuliids. We, therefore, conducted an exploratory study to examine distribution patterns of species of Simuliidae along an elevational gradient of the Otún River in the Colombian Andes, encompassing four ecoregions. Larval and pupal simuliids were sampled at 52 sites ranging from 1800 to 4750 m above sea level in dry and wet seasons and during the La Niña phase (2011-2012) and the El Niño phase (2015-2016) of the ENSO; physicochemical measurements were taken during the El Niño phase. Twenty-seven species in two genera (Gigantodax and Simulium) were collected. Species richness and occurrence in each ecoregion were influenced by elevation, seasonality, and primarily the warm El Niño and cool La Niña phases of the ENSO. The degree of change differed among ecoregions and was related to physicochemical factors, mainly with stream discharge. Some putative simuliid vectors of Leucocytozoon, such as G. misitu and S. muiscorum, markedly changed in distribution and occurrence, potentially influencing parasite transmission. Copyright © 2018 Elsevier B.V. All rights reserved.

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

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MacMartin, Douglas G; Tziperman, Eli

2014-09-08

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

Salinity anomaly as a trigger for ENSO events.

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

2014-10-29

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

Impact of atmospheric model resolution on simulation of ENSO feedback processes: a coupled model study

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Hua, Lijuan; Chen, Lin; Rong, Xinyao; Su, Jingzhi; Wang, Lu; Li, Tim; Yu, Yongqiang

2018-03-01

This study examines El Niño-Southern Oscillation (ENSO)-related air-sea feedback processes in a coupled general circulation model (CGCM) to gauge model errors and pin down their sources in ENSO simulation. Three horizontal resolutions of the atmospheric component (T42, T63 and T106) of the CGCM are used to investigate how the simulated ENSO behaviors are affected by the resolution. We find that air-sea feedback processes in the three experiments mainly differ in terms of both thermodynamic and dynamic feedbacks. We also find that these processes are simulated more reasonably in the highest resolution version than in the other two lower resolution versions. The difference in the thermodynamic feedback arises from the difference in the shortwave-radiation (SW) feedback. Due to the severely (mildly) excessive cold tongue in the lower (higher) resolution version, the SW feedback is severely (mildly) underestimated. The main difference in the dynamic feedback processes lies in the thermocline feedback and the zonal-advection feedback, both of which are caused by the difference in the anomalous thermocline response to anomalous zonal wind stress. The difference in representing the anomalous thermocline response is attributed to the difference in meridional structure of zonal wind stress anomaly in the three simulations, which is linked to meridional resolution.

Relationship between annual precipitation variability and ENSO in Southern California for the Common Era (last 2,000 years)

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DU, X.; Hendy, I. L.; Hinnov, L.; Brown, E. T.; Schimmelmann, A.; Pak, D. K.

2017-12-01

The El Niño-Southern Oscillation (ENSO) has a major influence on Southern California's hydroclimate as demonstrated by both historical observations and model simulations. Santa Barbara Basin (SBB) off Southern California preserves a unique varved (i.e. annually laminated) marine sedimentary archive of modern and Holocene hydroclimate variability, notably including the transition from the regionally dry Medieval Climate Anomaly (MCA) to the wetter Little Ice Age (LIA). Here we present sub-annually resolved scanning XRF elemental counts for the last 2,000 years in SBB from core SPR0901-03KC. Titanium (associated with silicate minerals) is delivered more efficiently to SBB sediments during times of enhanced river flow and in the Mediterranean climate of Southern California, river flow only occurs after precipitation. The Ti record suggests that the precipitation frequency was reduced during the MCA except for a pluvial episode at CE 1075-1121, but increased during the LIA. Time series analysis of Ti counts indicates ENSO variability robustly increased during the intervals CE 450-520, 650-720, 980-1150, 1380-1550 and 1720-1750, and experienced relatively quiescent intervals between CE 50-150, 250-400, 550-650, 750-950, 1150-1280 and 1580-1620. Generally the LIA in Southern California is characterized by more active ENSO variability with long periodicities (4-7 yr) and multi-decadal variability (54 yr). MCA drought episodes were associated with less active ENSO. Active ENSO variability in Southern California during the last 2,000 years coincided with reconstructed southward migration of the Intertropical Convergence Zone (ITCZ) suggesting the ITCZ may play a role in the waxing and waning of ENSO teleconnections between the central Pacific and the west coast of North America.

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

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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 hourly resolution before taking the density weighted vertical average. Long term means (LTM; 1979-2015) were quantified and the influence of strong ENSO events was assessed by quantifying deviations from the LTM for each respective covariance property during months associated with the selected ENSO events. Results reveal regions of statistically significant (CI = 0.05) differences from the LTM for the vertically integrated HMF and each covariance quantity. Broader implications of this work include potential for improved seasonal precipitation forecasts at regional scales and subsequent improvements to local water resource management. There is potential for future work objectively comparing these results with output from Earth System Models to improve

Long term changes in flooding and heavy rainfall associated with North Atlantic tropical cyclones: Roles of the North Atlantic Oscillation and El Niño-Southern Oscillation

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Aryal, Yog N.; Villarini, Gabriele; Zhang, Wei; Vecchi, Gabriel A.

2018-04-01

The aim of this study is to examine the contribution of North Atlantic tropical cyclones (TCs) to flooding and heavy rainfall across the continental United States. Analyses highlight the spatial variability in these hazards, their temporal changes in terms of frequency and magnitude, and their connection to large-scale climate, in particular to the North Atlantic Oscillation (NAO) and El Niño-Southern Oscillation (ENSO). We use long-term stream and rain gage measurements, and our analyses are based on annual maxima (AMs) and peaks-over-threshold (POTs). TCs contribute to ∼20-30% of AMs and POTs over Florida and coastal areas of the eastern United States, and the contribution decreases as we move inland. We do not detect statistically significant trends in the magnitude or frequency of TC floods. Regarding the role of climate, NAO and ENSO do not play a large role in controlling the frequency and magnitude of TC flooding. The connection between heavy rainfall and TCs is comparable to what observed in terms of flooding. Unlike flooding, NAO plays a significant role in TC-related extreme rainfall along the U.S. East Coast, while ENSO is most strongly linked to the TC precipitation in Texas.

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

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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

Simulation of Relationship between ENSO and winter precipitation over Western Himalayas: Application of Regional climate model (RegT-Band)

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Tiwari, P. R.; Mohanty, U. C.; Dey, S.; Acharaya, N.; Sinha, P.

2012-12-01

Precipitation over the Western Himalayas region during winter is mainly associated with the passage of midlatitude synoptic systems known as western disturbances (WDs). Recently, many observational and modeling studies reported that the relationship of the Indian southwest monsoon rainfall with El Niño- Southern Oscillation (ENSO) has weakened since around 1980. But, in contrast, only very few observational studies are reported so far to examine the relationship between ENSO and the winter precipitation over the Western Himalayas region from December to February (DJF). But there is a huge gap of modeling this phenomenon. So keeping in view of the absence of modeling studies, an attempt is made to simulate the relationship between wintertime precipitations associated with large scale global forcing of ENSO over the Western Himalayas. In the present study, RegT-Band, a tropical band version of the regional climate model RegCM4 is integrated for a set of 5 El Niño (1986-87, 1991-92, 1997-98, 2002-03, 2009-10) and 4 La Niña (1984-85, 1988-89, 1999-2000, 2007-08) years with the observed sea-surface temperature and lateral boundary condition. The domain extends from 50° S to 50° N and covers the entire tropics at a grid spacing of about 45 km, i.e. it includes lateral boundary forcing only at the southern and northern boundaries. The performance evaluation of the model in capturing the large scale fields followed by ENSO response with wintertime precipitation over the Western Himalayas region has been carried out by using National Center for Environmental Prediction (NCEP)-Department of Energy (DOE) reanalysis 2 (NNRP2) data (2.5° x 2.5°) and Aphrodite precipitation data (0.25° x 0.25°). The model is able to delineate the mean circulation associated with ENSO over the region during DJF reasonably well and shows strong southwesterly to northwesterly wind flow, which is there in verification analysis also. The vertical structure of the low as well as upper level

Asymptotic solution for the El Niño time delay sea—air oscillator model

International Nuclear Information System (INIS)

Mo Jia-Qi; Lin Wan-Tao; Lin Yi-Hua

2011-01-01

A sea—air oscillator model is studied using the time delay theory. The aim is to find an asymptotic solving method for the El Niño-southern oscillation (ENSO) model. Employing the perturbed method, an asymptotic solution of the corresponding problem is obtained. Thus we can obtain the prognoses of the sea surface temperature (SST) anomaly and the related physical quantities. (general)

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

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Joshi, Sneh; Kar, Sarat C.

2018-02-01

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

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

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

2015-11-05

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

Seasonal to Interannual Variability of Satellite-Based Precipitation Estimates in the Pacific Ocean Associated with ENSO from 1998 to 2014

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Xueyan Hou

2016-10-01

Full Text Available Based on a widely used satellite precipitation product (TRMM Multi-satellite Precipitation Analysis 3B43, we analyzed the spatiotemporal variability of precipitation over the Pacific Ocean for 1998–2014 at seasonal and interannual timescales, separately, using the conventional empirical orthogonal function (EOF and investigated the seasonal patterns associated with El Niño–Southern Oscillation (ENSO cycles using season-reliant empirical orthogonal function (SEOF analysis. Lagged correlation analysis was also applied to derive the lead/lag correlations of the first two SEOF modes for precipitation with Pacific Decadal Oscillation (PDO and two types of El Niño, i.e., central Pacific (CP El Niño and eastern Pacific (EP El Niño. We found that: (1 The first two seasonal EOF modes for precipitation represent the annual cycle of precipitation variations for the Pacific Ocean and the first interannual EOF mode shows the spatiotemporal variability associated with ENSO; (2 The first SEOF mode for precipitation is simultaneously associated with the development of El Niño and most likely coincides with CP El Niño. The second SEOF mode lagged behind ENSO by one year and is associated with post-El Niño years. PDO modulates precipitation variability significantly only when ENSO occurs by strengthening and prolonging the impacts of ENSO; (3 Seasonally evolving patterns of the first two SEOF modes represent the consecutive precipitation patterns associated with the entire development of EP El Niño and the following recovery year. The most significant variation occurs over the tropical Pacific, especially in the Intertropical Convergence Zone (ITCZ and South Pacific Convergence Zone (SPCZ; (4 Dry conditions in the western basin of the warm pool and wet conditions along the ITCZ and SPCZ bands during the mature phase of El Niño are associated with warm sea surface temperatures in the central tropical Pacific, and a subtropical anticyclone dominating

Precipitation in Santa Barbara, CA on varying timescales and the relationships with the El Niño Southern Oscillation, the Madden-Julian Oscillation, and atmospheric rivers

Science.gov (United States)

Harris, S. M.; Carvalho, L. V.; Jones, C.

2013-12-01

This study aimed to understand the patterns and variations of extreme precipitation events that occur in Santa Barbara County and determine the relationships with various phenomena that affect the region. Santa Barbara, CA is an area with complex topography that is disposed to numerous hazard events including landslides and flooding, particularly during the region's rainy season (Nov.-Apr.). These incidents are especially frequent in the seasons after fire-events, another hazard common to the region. In addition, Santa Barbara is affected by several tropical phenomena that influence precipitation on varying timescales including the El Niño Southern Oscillation (ENSO), the Madden-Julian Oscillation (MJO), and atmospheric rivers (ARs). It is well known that ENSO and the MJO influence storms that occur in southern California through processes such as the modulation of the upper level jet and the low level moisture flux. ARs have been revealed to be responsible for the movement of large quantities of water vapor from tropical areas to the midlatitudes and have been linked to high-intensity storms throughout the western coast of North America. We examined rainy season (Nov.-Apr.) precipitation within Santa Barbara County using hourly rainfall data spanning approximately forty years (~1971-2010) from seven, local, rain gauge stations. The distributions as well as totals of precipitation on varying timescales (hourly, daily, seasonal, and yearly) were defined for specified intensities of rainfall based upon the 75th, 90th, 95th, and 99th percentiles. Persistence, expressed as the number of consecutive hours (or days) including intense precipitation defined according to the percentiles, was investigated on the hourly and daily timescales. In addition, specified storm episodes identified in this study were examined with data from the Tropical Rainfall Measurement Mission in order to assess the spatial features of high-intensity storms. Results from this analysis will be

Climate Prediction Center - The ENSO Cycle

Science.gov (United States)

Weather Service NWS logo - Click to go to the NWS home page Climate Prediction Center Home Site Map News Web resources and services. HOME > El Niño/La Niña > The ENSO Cycle ENSO Cycle Banner Climate for Weather and Climate Prediction Climate Prediction Center 5830 University Research Court College

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

A High-Resolution ENSO-Driven Rainfall Record Derived From an Exceptionally Fast Growing Stalagmite From Niue Island (South Pacific)

Science.gov (United States)

Troy, S.; Aharon, P.; Lambert, W. J.

2012-12-01

El Niño-Southern Oscillation's (ENSO) dominant control over the present global climate and its unpredictable response to a global warming makes the study of paleo-ENSO important. So far corals, spanning the Tropical Pacific Ocean, are the most commonly used geological archives of paleo-ENSO. This is because corals typically exhibit high growth rates (>1 cm/yr), and reproduce reliably surface water temperatures at sub-annual resolution. However there are limitations to coral archives because their time span is relatively brief (in the order of centuries), thus far making a long and continuous ENSO record difficult to achieve. On the other hand stalagmites from island settings can offer long and continuous records of ENSO-driven rainfall. Niue Island caves offer an unusual opportunity to investigate ENSO-driven paleo-rainfall because the island is isolated from other large land masses, making it untainted by continental climate artifacts, and its geographical location is within the Tropical Pacific "rain pool" (South Pacific Convergence Zone; SPCZ) that makes the rainfall variability particularly sensitive to the ENSO phase switches. We present here a δ18O and δ13C time series from a stalagmite sampled on Niue Island (19°00' S, 169°50' W) that exhibits exceptionally high growth rates (~1.2 mm/yr) thus affording a resolution comparable to corals but for much longer time spans. A precise chronology, dating back to several millennia, was achieved by U/Th dating of the stalagmite. The stalagmite was sampled using a Computer Automated Mill (CAM) at 300 μm increments in order to receive sub-annual resolution (every 3 months) and calcite powders of 50-100 μg weight were analyzed for δ18O and δ13C using a Continuous Flow Isotope Ratio Mass Spectrometer (CF-IRMS). The isotope time series contains variable shifts at seasonal, inter-annual, and inter-decadal periodicities. The δ13C and δ18O yield ranges of -3.0 to -13.0 (‰ VPDB) and -3.2 to -6.2 (‰ VPDB

Suppression and revival of oscillation in indirectly coupled limit cycle oscillators

International Nuclear Information System (INIS)

Sharma, P.R.; Kamal, N.K.; Verma, U.K.; Suresh, K.; Thamilmaran, K.; Shrimali, M.D.

2016-01-01

Highlights: • The phenomena of suppression and revival of oscillations are studied in indirectly coupled nonlinear oscillators. • The decay parameter and a feedback factor play a crucial role in emergent dynamical behavior of oscillators. • The critical curves for different dynamical regions are obtained analytically using linear stability analysis. • Electronic circuit experiments demonstrate these emergent dynamical states. - Abstract: We study the phenomena of suppression and revival of oscillations in a system of limit cycle oscillators coupled indirectly via a dynamic local environment. The dynamics of the environment is assumed to decay exponentially with time. We show that for appropriate coupling strength, the decay parameter of the environment plays a crucial role in the emergent dynamics such as amplitude death (AD) and oscillation death (OD). We also show that introducing a feedback factor in the diffusion term revives the oscillations in this system. The critical curves for the regions of different emergent states as a function of coupling strength, decay parameter of the environment and feedback factor in the coupling are obtained analytically using linear stability analysis. These results are found to be consistent with the numerics and are also observed experimentally.

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

Science.gov (United States)

Codron, Francis; Vintzileos, Augustin; Sadourny, Robert

2001-03-01

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

Solar cycle modulation of ENSO variability

Science.gov (United States)

Kodera, Kunihiko; Thiéblemont, Rémi

2016-04-01

Inspired by the work of Labitzke and van Loon on solar/QBO modulation in the stratosphere, Barnett (1989) conducted an investigation on the relationship between the the biannual component of the sea surface temperature (SST) in the equatorial eastern Pacific and the solar activity. He found that the amplitude of biannual component of the SST (BO) is modulated by the 11-year solar cycle: the amplitude of the BO is large during a period of low solar activity, but small during high solar activity. More than 25-years or two solar cycle has passed since his finding, but the relationship still holds. In order to get an insight into the mechanism of the solar modulation of the El Niño Southern Oscillation (ENSO), here we have revisited this problem. Solar cycle modulation of the BO in the tropical SST is discernible since the end of the 19th centuries, but the amplitude modulation is particularly clear after 1960's. The composite analysis of the SST based on the amplitude of the BO during 1958-2012, indicates that the amplitude of BO is larger when the equatorial Pacific temperature anomalies are high in the central Pacific, but low in the eastern Pacific. Central Pacific anomalies extend to the northern hemisphere, while those in the central Pacific spread toward the southern hemisphere. In short, this anomalous SST pattern is similar to the El Niño modoki. In this connection, it should be noted that the solar signal in the tropical SST also exhibits a similar pattern. This suggests that the modulation of the ENSO variability by the solar cycle originates through a modulation of the El Niño Modoki rather than the canonical El Nino.

Wavelet analysis of interannual LOD, AAM, and ENSO: 1997-98 El Niño and 1998-99 La Niña signals

Science.gov (United States)

Zhou, Y. H.; Zheng, D. W.; Liao, X. H.

2001-05-01

On the basis of the data series of the length of day (LOD), the atmospheric angular momentum (AAM) and the Southern Oscillation Index (SOI) for January 1970-June 1999, the relationship among Interannual LOD, AAM, and the EL Niño/Southern Oscillation (ENSO) is analyzed by the wavelet transform method. The results suggest that they have similar time-varying spectral structures. The signals of 1997-98 El Niño and 1998-99 La Niña events can be detected from the LOD or AAM data.

Homoclinic phenomena in the gravitational collapse

International Nuclear Information System (INIS)

Koiller, J.; Mello Neto, J.R.T. de; Soares, I.D.

1984-01-01

A class of Bianchi IX cosmological models is shown to have chaotic gravitational collapse, due to Poincare's homoclinic phenomena. Such models can be programmed so that for any given positive integer N (N=infinity included) the universe undergoes N non-periodic oscillations (each oscillation requiring a long time) before collapsing. For N=infinity the universe undergoes periodic oscillations. (Author) [pt

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.

An idealized study of the impact of extratropical climate change on El Nino-Southern Oscillation

Energy Technology Data Exchange (ETDEWEB)

Zhang, Qiong [Chinese Academy of Sciences, LASG, Institute of Atmospheric Science, Beijing (China); Yang, Haijun [Peking University, Department of Atmospheric Science and Laboratory for Severe Storm and Flood Disasters, Beijing (China); Zhong, Yafang [University of Wisconsin-Madison, Center for Climatic Research and Department of Atmospheric and Oceanic Sciences, Madison, WI (United States); Wang, Dongxiao [Chinese Academy of Sciences, Laboratory of Tropical Marine Environmental Dynamics, Guangzhou (China); South China Sea Institute of Oceanology, Guangzhou (China)

2005-12-01

Extratropical impacts on the tropical El Nino-Southern Oscillation (ENSO) are studied in a coupled climate model. Idealized experiments show that the remote impact of the extratropics on the equatorial thermocline through oceanic tunnel can substantially modulate the ENSO in both magnitude and frequency. First of all, an extratropical warming can be conveyed to the equator by the mean subduction current, resulting in a warming of the equatorial thermocline. Second, the extratropical warming can weaken the Hadley cells, which in turn slow down the mean shallow meridional overturning circulations in the upper Pacific, reducing the equatorward cold water supply and the equatorial upwelling. These oceanic dynamic processes would weaken the stratification of the equatorial thermocline and retard a buildup (purge) of excess heat content along the equator, and finally result in a weaker and longer ENSO cycle. This study highlights a nonlocal mechanism in which ENSO behavior is related to the extratropical climate conditions. (orig.)

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

Science.gov (United States)

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

2007-01-01

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

Reconstruction of El Niño - Southern oscillation variability during the Holocene

NARCIS (Netherlands)

Donders, T.H.

2005-01-01

The El Niño – Southern Oscillation (ENSO) in the tropical Pacific constitutes the largest source of global climate variability on interannual timescales. Every 2-7 year the El Niño phenomenon causes altered Pacific circulation, leading to widespread droughts and floods. However, the exact mechanisms

The Solar and Southern Oscillation Components in the Satellite Altimetry Data

DEFF Research Database (Denmark)

Howard, Daniel; Shaviv, Nir J.; Svensmark, Henrik

2015-01-01

altimetry data can be explained as the combined effect of both the solar forcing and the El Niño-Southern Oscillation (ENSO). The phase of the solar component can be used to derive the different steric and eustatic contributions. We find that the peak to peak radiative forcing associated with the solar...

The El Niño Southern Oscillation index and wildfire prediction in British Columbia

NARCIS (Netherlands)

Xu, Zhen; Kooten, van G.C.

2014-01-01

This study investigates the potential to predict monthly wildfires and area burned in British Columbia's interior using El Niño Southern Oscillation (ENSO). The zero-inflated negative binomial (ZINB) and the generalized Pareto (GP) distributions are used, respectively, to account for uncertainty in

Hydrological cycle effects on the aquatic community in a Neotropical stream of the Andean piedmont during the 2007-2010 ENSO events.

Science.gov (United States)

Ríos-Pulgarín, M I; Barletta, M; Mancera-Rodriguez, N J

2016-07-01

The seasonal and interannual changes in the fish, macroinvertebrates and phycoperiphyton assemblages of the Guarinó River were examined in relation to the physical and chemical environmental changes associated with the hydrological cycle and the El Niño-Niña/Southern Oscillation (ENSO) between 2007 and 2010. Four samplings (in dry and rainy seasons) were performed per year. Environmental variables (temperature, pH, conductivity, turbidity, oxygen, total nitrogen, orthophosphate, depth and flow rate) were measured. The temporal patterns of the taxonomic compositions for the three assemblages and the functional composition of fish and macroinvertebrate assemblages with respect to environmental variables were examined through canonical discriminant analysis, multidimensional scaling and multiple correlations. The presence and abundance of fishes, macroinvertebrates and algae species were regulated by environmental variables associated with extreme hydrological events, which derived from the natural torrential regimen of the basin and larger-scale phenomena, such as El Niño and La Niña. Fish abundance and richness were significantly correlated with algal density and pH, the macroinvertebrate density was negatively related to the flow rate and the richness was positively correlated with algal density. The algae richness was positively correlated with pH and negatively correlated with the flow rate and nitrogen. The algal density was positively correlated with pH and temperature and negatively correlated with river flow. The phycoperiphyton assemblage exhibited more direct responses in its density and richness to the hydrological changes (r(2) = 0·743 and 0·800, respectively). In functional terms, the El Niño phenomenon was defined by a greater abundance of omnivorous and insectivorous fishes, as well as filter feeders, scrapers and macroinvertebrate predators. During La Niña, a greater abundance of benthic fishes (both detritivorous and insectivorous) and

An MJO-Mediated Mechanism to Explain ENSO and IOD Impacts on East African Short Rains

Science.gov (United States)

Zaitchik, B. F.; Berhane, F.; Gnanadesikan, A.

2015-12-01

Previous studies have found that the El Nino Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) have significant impacts on rainfall over East Africa (EA) during the short rains (Oct-Dec). However, not all ENSO and IOD events are associated with significant precipitation anomalies over EA. Our analysis shows that the IOD and ENSO influence EA rainfall by modifying the MJO. Composite analysis of rainfall and outgoing longwave radiation data show that the MJO over the Indian Ocean (phases 2 and 3 of the Wheeler and Hendon index) is associated with significant increase in precipitation over EA during El Niño. In La Niña and non-ENSO years, the MJO over the Indian Ocean has very weak impacts on EA convection and precipitation. Although previous studies have found that El Niño / La Niña events are associated with anomalous wetness/dryness over EA, the associations are not evident in the absence of the MJO. Similarly, the IOD exhibits strong associations with EA precipitation when there is MJO activity over the Indian Ocean. During the positive phase of the IOD, the MJO over the Indian Ocean has impacts that extend to EA. In the absence of the MJO, however, the IOD shows weak associations with EA precipitation. Furthermore, there are more MJO days in the Indian Ocean during El Niño and positive IOD events, which implies stronger impacts on EA. During La Niña events more MJO days are observed in the Pacific Ocean, favoring subsidence over the western Indian Ocean and dry anomalies over EA. These observations suggest two critical MJO-related questions that must be addressed in order to explain EA short rain variability typically attributed to ENSO or IOD: first, how do ENSO and IOD modify background conditions in a way that causes Indian Ocean MJO activity to be more strongly connected to EA under El Niño and IOD positive conditions, and second, why is it that El Niño and IOD positive states slow MJO propagation over the Indian Ocean and speed it over

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

Non-linear phenomena in electronic systems consisting of coupled single-electron oscillators

International Nuclear Information System (INIS)

Kikombo, Andrew Kilinga; Hirose, Tetsuya; Asai, Tetsuya; Amemiya, Yoshihito

2008-01-01

This paper describes non-linear dynamics of electronic systems consisting of single-electron oscillators. A single-electron oscillator is a circuit made up of a tunneling junction and a resistor, and produces simple relaxation oscillation. Coupled with another, single electron oscillators exhibit complex behavior described by a combination of continuous differential equations and discrete difference equations. Computer simulation shows that a double-oscillator system consisting of two coupled oscillators produces multi-periodic oscillation with a single attractor, and that a quadruple-oscillator system consisting of four oscillators also produces multi-periodic oscillation but has a number of possible attractors and takes one of them determined by initial conditions

Analysis of the Effects of ENSO and Atmospheric Rivers on Precipitation in Los Angeles County

Science.gov (United States)

Santacruz, A.; Lamb, K.

2017-12-01

The Winter 2016-2017 season in California was marked by substantial amounts of precipitation; this resulted in critically-low reservoirs filling up and the removal of most of California from drought status. The year prior was characterized by one of the strongest El Nino-Southern Oscillation (ENSO) events, though it did not produce nearly enough precipitation as the 2016-2017 season. The major contributors to the increased rainfall during the 2016-2017 season were climactic phenomenon known as atmospheric rivers (ARs), which transport water vapor through the atmosphere in narrow bands, and are known to produce extreme rain events. Determining the exact timing, landfall areas, and total precipitation amounts of ARs is currently of great interest; a recent study showed that extreme weather events are likely to increase in California in the coming years, which motivates research into how phenomenon such as ENSO and ARs play a role. Using long-term daily rain gauge data provided by the Los Angeles County Department of Public Works, we compute the precipitation volume and storm count for various locations in Los Angeles County and identify anomalies. These data will then be compared with the occurrence and intensity of AR and ENSO events by using NOAA's NOI and ESRL AR data. The results can be used to provide a better grasp of extreme climactic patterns and their effects on the amount of precipitation in the region.

Investigation of hydrological variability in the Korean Peninsula with the ENSO teleconnections

Directory of Open Access Journals (Sweden)

S. Yoon

2016-10-01

Full Text Available This study analyzes nonlinear behavior links with atmospheric teleconnections between hydrologic variables and climate indices using statistical models during warm season (June to September over the Korean Peninsula (KP. The ocean-related major climate factor, which is the El Niño-Southern Oscillation (ENSO was used to analyze the atmospheric teleconnections by principal component analysis (PCA and a singular spectrum analysis (SSA. The nonlinear lag time correlations between climate indices and hydrologic variables are calculated by Mutual Information (MI technique. The nonlinear correlation coefficients (CCs by MI were higher than linear CCs, and ENSO shows a few months of lag time correlation. The warm season hydrologic variables in KP shows a significant increasing tendency during the warm pool (WP, and the cold tongue (CT El Niño decaying years shows a significant decreasing tendency, while the La Niña year shows slightly above normal conditions, respectively. A better understanding of the relationship between climate indices and streamflow, and their local impacts can help to prepare for the river discharge management by water managers and scientists. Furthermore, these results provide useful data for policy makers and end-users to support long-range water resources prediction and water-related policy.

Interaction between Tropical Atlantic Variability and El Niño-Southern Oscillation.

Science.gov (United States)

Saravanan, R.; Chang, Ping

2000-07-01

The interaction between tropical Atlantic variability and El Niño-Southern Oscillation (ENSO) is investigated using three ensembles of atmospheric general circulation model integrations. The integrations are forced by specifying observed sea surface temperature (SST) variability over a forcing domain. The forcing domain is the global ocean for the first ensemble, limited to the tropical ocean for the second ensemble, and further limited to the tropical Atlantic region for the third ensemble. The ensemble integrations show that extratropical SST anomalies have little impact on tropical variability, but the effect of ENSO is pervasive in the Tropics. Consistent with previous studies, the most significant influence of ENSO is found during the boreal spring season and is associated with an anomalous Walker circulation. Two important aspects of ENSO's influence on tropical Atlantic variability are noted. First, the ENSO signal contributes significantly to the `dipole' correlation structure between tropical Atlantic SST and rainfall in the Nordeste Brazil region. In the absence of the ENSO signal, the correlations are dominated by SST variability in the southern tropical Atlantic, resulting in less of a dipole structure. Second, the remote influence of ENSO also contributes to positive correlations between SST anomalies and downward surface heat flux in the tropical Atlantic during the boreal spring season. However, even when ENSO forcing is absent, the model integrations provide evidence for a positive surface heat flux feedback in the deep Tropics, which is analyzed in a companion study by Chang et al. The analysis of model simulations shows that interannual atmospheric variability in the tropical Pacific-Atlantic system is dominated by the interaction between two distinct sources of tropical heating: (i) an equatorial heat source in the eastern Pacific associated with ENSO and (ii) an off-equatorial heat source associated with SST anomalies near the Caribbean

Non-stationary influence of El Niño-Southern Oscillation and winter temperature on oak latewood growth in NW Iberian Peninsula.

Science.gov (United States)

Rozas, Vicente; García-González, Ignacio

2012-09-01

The properties of El Niño-Southern Oscillation (ENSO), such as period, amplitude, and teleconnection strength to extratropical regions, have changed since the mid-1970s. ENSO affects the regional climatic regime in SW Europe, thus tree performance in the Iberian Peninsula could be affected by recent ENSO dynamics. We established four Quercus robur chronologies of earlywood and latewood widths in the NW Iberian Peninsula. The relationship between tree growth and the Southern Oscillation Index (SOI), the atmospheric expression of ENSO, showed that only latewood growth was correlated negatively with the SOI of the previous summer-autumn-winter. This relationship was non-stationary, with significant correlations only during the period 1952-1980; and also non-linear, with enhanced latewood growth only in La Niña years, i.e. years with a negative SOI index for the previous autumn. Non-linear relationship between latewood and SOI indicates an asymmetric influence of ENSO on tree performance, biassed towards negative SOI phases. During La Niña years, climate in the study area was warmer and wetter than during positive years, but only for 1952-1980. Winter temperatures became the most limiting factor for latewood growth since 1980, when mean regional temperatures increased by 1°C in comparison to previous periods. As a result, higher winter respiration rates, and the extension of the growing season, would probably cause an additional consumption of stored carbohydrates. The influence of ENSO and winter temperatures proved to be of great importance for tree growth, even at lower altitudes and under mild Atlantic climate in the NW Iberian Peninsula.

A study of Solar-Enso correlation with southern Brazil tree ring index (1955- 1991)

Science.gov (United States)

Rigozo, N.; Nordemann, D.; Vieira, L.; Echer, E.

The effects of solar activity and El Niño-Southern Oscillation on tree growth in Southern Brazil were studied by correlation analysis. Trees for this study were native Araucaria (Araucaria Angustifolia)from four locations in Rio Grande do Sul State, in Southern Brazil: Canela (29o18`S, 50o51`W, 790 m asl), Nova Petropolis (29o2`S, 51o10`W, 579 m asl), Sao Francisco de Paula (29o25`S, 50o24`W, 930 m asl) and Sao Martinho da Serra (29o30`S, 53o53`W, 484 m asl). From these four sites, an average tree ring Index for this region was derived, for the period 1955-1991. Linear correlations were made on annual and 10 year running averages of this tree ring Index, of sunspot number Rz and SOI. For annual averages, the correlation coefficients were low, and the multiple regression between tree ring and SOI and Rz indicates that 20% of the variance in tree rings was explained by solar activity and ENSO variability. However, when the 10 year running averages correlations were made, the coefficient correlations were much higher. A clear anticorrelation is observed between SOI and Index (r=-0.81) whereas Rz and Index show a positive correlation (r=0.67). The multiple regression of 10 year running averages indicates that 76% of the variance in tree ring INdex was explained by solar activity and ENSO. These results indicate that the effects of solar activity and ENSO on tree rings are better seen on long timescales.

Oscillator phenomena in the solar atmosphere and radiation modulation in microwaves

International Nuclear Information System (INIS)

Vaz, A.M.Z.

1983-05-01

An overview of the principal known descriptions of oscillations in the solar atmosphere at different ranges of periods was developed. Particular attention was given to oscillations with time scale of seconds, associated to active regions or bursts. 1.5 quasi-periodic oscillations were detected by the first time at more than one microwave frequency simultaneously (22 GHz and 44 GHz), with high sensitivity and high time resolution, superimposed on a burst on Dec. 15, 1980. An advance phase of 0,3s between the oscillations in the frequencies of 22 GHz and 44 GHz was discovered. The proposed mechanism to explain such oscillations is based on oscillations of the magnetic field at the source. These oscillations modulate the gyro-synchrotron emission from high energy electrons trapped in the magnetic structure. The phase difference is attributed to the influence of the optical thickness of the gyro-synchrotron emission at 22 GHz. (Author) [pt

The influence of ENSO on an oceanic eddy pair in the South China Sea

Science.gov (United States)

Chu, Xiaoqing; Dong, Changming; Qi, Yiquan

2017-03-01

An eddy pair off the Vietnam coast is one of the most important features of the summertime South China Sea circulation. Its variability is of interest due to its profound impact on regional climate, ecosystems, biological processes, and fisheries. This study examines the influence of the El Niño-Southern Oscillation (ENSO), a basin-scale climatic mode, on the interannual variability of this regional eddy pair using satellite observational data and historical hydrographic measurements. Over the last three decades, the eddy pair strengthened in 1994 and 2002, and weakened in 2006, 2007, and 2008. It was absent in 1988, 1995, 1998, and 2010, coinciding with strong El Nino-to-La Nina transitions. Composite analyses showed that the strong transition events of ENSO led to radical changes in the summer monsoon, through the forcing of a unique sea surface temperature anomaly structure over the tropical Indo-Pacific basin. With weaker zonal wind, a more northward wind direction, and the disappearance of a pair of positive and negative wind stress curls, the eastward current jet turns northward along the Vietnam coast and the eddy pair disappears.

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.

Role of the Indian Ocean on the southern oscillation, atmospheric circulation indices and monsoon rainfall over India

Digital Repository Service at National Institute of Oceanography (India)

Sadhuram, Y.; Wells, N.C.

Oscillation and ENSO is also examined. Indian monsoon rainfall is strongly and positively correlated with the SST of November month (0.77; statistically significant at 99% level) of the preceding calendar year. Monsoon indices (M1, U200) are strongly...

Relationships between the Antarctic oscillation, the Madden-Julian oscillation, and ENSO, and consequences for rainfall analysis

CSIR Research Space (South Africa)

Pohl, B

2010-01-01

Full Text Available range, it is not unambiguously related to the global-scale Madden–Julian oscillation (MJO) activity, with in particular no coherent phase relationship with the MJO index. Moreover, in the high southern latitudes, the MJO-associated anomaly fields do...

Sawtooth phenomena in tokamaks

International Nuclear Information System (INIS)

Kuvshinov, B.N.; Savrukhin, P.V.

1989-01-01

A review of experimental and theoretical investigaions of sawtooth phenomena in tokamaks is presented. Different types of sawtooth oscillations, scaling laws and methods of interanl disruption stabilization are described. Theoretical models of the sawtooth instability are discussed. 122 refs.; 4 tabs

Neutrino oscillations at proton accelerators

International Nuclear Information System (INIS)

Michael, Douglas

2002-01-01

Data from many different experiments have started to build a first glimpse of the phenomenology associated with neutrino oscillations. Results on atmospheric and solar neutrinos are particularly clear while a third result from LSND suggests a possibly very complex oscillation phenomenology. As impressive as the results from current experiments are, it is clear that we are just getting started on a long-term experimental program to understand neutrino masses, mixings and the physics which produce them. A number of exciting fundamental physics possibilities exist, including that neutrino oscillations could demonstrate CP or CPT violation and could be tied to exotic high-energy phenomena including strings and extra dimensions. A complete exploration of oscillation phenomena demands many experiments, including those possible using neutrino beams produced at high energy proton accelerators. Most existing neutrino experiments are statistics limited even though they use gigantic detectors. High intensity proton beams are essential for producing the intense neutrino beams which we need for next generation neutrino oscillation experiments

Neutrino Oscillations at Proton Accelerators

Science.gov (United States)

Michael, Douglas

2002-12-01

Data from many different experiments have started to build a first glimpse of the phenomenology associated with neutrino oscillations. Results on atmospheric and solar neutrinos are particularly clear while a third result from LSND suggests a possibly very complex oscillation phenomenology. As impressive as the results from current experiments are, it is clear that we are just getting started on a long-term experimental program to understand neutrino masses, mixings and the physics which produce them. A number of exciting fundamental physics possibilities exist, including that neutrino oscillations could demonstrate CP or CPT violation and could be tied to exotic high-energy phenomena including strings and extra dimensions. A complete exploration of oscillation phenomena demands many experiments, including those possible using neutrino beams produced at high energy proton accelerators. Most existing neutrino experiments are statistics limited even though they use gigantic detectors. High intensity proton beams are essential for producing the intense neutrino beams which we need for next generation neutrino oscillation experiments.

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

NARCIS (Netherlands)

Ward, P.J.; Jongman, B.; Kummu, M.S.; Dettinger, M.D.; Sperna Weiland, F.C.; Winsemius, H.C.

2014-01-01

El Niño Southern Oscillation (ENSO) is the most dominant interannual signal of climate variability and has a strong influence on climate over large parts of the world. In turn, it strongly influences many natural hazards (such as hurricanes and droughts) and their resulting socioeconomic impacts,

Tree-ring analysis of winter climate variability and ENSO in Mediterranean California

International Nuclear Information System (INIS)

Woodhouse, C.A.; Univ. of Colorado, Boulder

2006-01-01

The feasibility of using tree-ring data as a proxy for regional precipitation and ENSO events in the Mediterranean region of California is explored. A transect of moisture-sensitive tree-ring sites, extending from southwestern to north-central California, documents regional patterns of winter precipitation and replicates the regional response to ENSO events in the 20. century. Proxy records of ENSO were used with the tree-ring data to examine precipitation/ENSO patterns in the 18. and 19. centuries. Results suggest some temporal and spatial variability in the regional precipitation response to ENSO over the last three centuries

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

2017-10-01

Analyses of the variation characteristics for aridity index (AI) can further enhance the understanding of climate change and have effect on hydrology and agriculture. In this paper, based on the data of 283 standard meteorological stations, the temporal-spatial variations and the influences of climate factors on AI were investigated and the relationship between AI and two climate indices (the Arctic Oscillation (AO); El Nino-Southern Oscillation (ENSO)) were also assessed in northern China (NC) during the period from 1961 to 2012. The results revealed that the annual mean AI decreased at the rate of -0.031 per decade in the past 52 years and the trend was statistically significant at the 0.01 level. The Mann-Kendall (M-K) test presented that the percentages of stations with positive trends and negative trends for AI were 10 and 81.9 % (22.6 % statistically significant), respectively. Spatially, in the western part of 100° E, the extremely dry area declined and the climate tended to become wet obviously. In the eastern part of 100° E, dry area moved toward the east and the south, which resulted in the enhancement of semiarid area and the shrinkage of subhumid area. The contributions of sunshine duration and precipitation to the decline of AI are more than those of other meteorological variables in NC. Moreover, the average temperature has risen significantly and AI decreased in NC, which indicated the existence of "paradox." Relationship between climate indices (AO and ENSO) and AI demonstrated that the influence of ENSO on AI overweight the AO on AI in NC.

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

Science.gov (United States)

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

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

Science.gov (United States)

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

2000-01-01

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

An Ocean Biology-induced Negative Feedback on ENSO in the Tropical Pacific Climate System

Science.gov (United States)

Zhang, R. H.

2016-02-01

Biological conditions in the tropical Pacific Ocean (e.g., phytoplankton biomass) are strongly regulated by physical changes associated with the El Niño-Southern Oscillation (ENSO). The existence and variation of phytoplankton biomass, in turn, act to modulate the vertical penetration of the incoming sunlight in the upper ocean, presenting an ocean biology-induced heating (OBH) effect on the climate system. Previously, a penetration depth of solar radiation in the upper ocean (Hp) is defined to describe the related bio-climate connections. Parameterized in terms of its relationship with the sea surface temperature (SST) in the tropical Pacific, an empirical model for interannual Hp variability has been derived from remotely sensed ocean color data, which is incorporated into a hybrid coupled model (HCM) to represent OBH effects. In this paper, various HCM experiments are performed to demonstrate the bio-feedback onto ENSO, including a climatological Hp run (in which Hp is prescribed as seasonally varying only), interannual Hp runs (with different intensities of interannually varying OBH effects), and a run in which the sign of the OBH effect is artificially reversed. Significant modulating impacts on interannual variability are found in the HCM, characterized by a negative feedback between ocean biology and the climate system in the tropical Pacific: the stronger the OBH feedback, the weaker the interannual variability. Processes involved in the feedback are analyzed; it is illustrated that the SST is modulated indirectly by ocean dynamical processes induced by OBH. The significance and implication of the OBH effects are discussed for their roles in ENSO variability and model biases in the tropical Pacific.

A pan-tropical cascade of fire driven by El Niño/Southern Oscillation

NARCIS (Netherlands)

Chen, Yang; Morton, Douglas C.; Andela, Niels; Van Der Werf, Guido R.; Giglio, Louis; Randerson, James T.

2017-01-01

The El Niño/Southern Oscillation (ENSO) has a pronounced influence on year-to-year variations in climate 1 . The response of fires to this forcing 2 is complex and has not been evaluated systematically across different continents. Here we use satellite data to create a climatology of burned-area and

Southern Hemisphere Extratropical Cyclones and their Relationship with ENSO in springtime

Science.gov (United States)

Reboita, M. S.; Ambrizzi, T.; Da Rocha, R.

2013-05-01

Extratropical cyclones occurrence is associated with the teleconnection mechanisms that produce climate variability. Among these mechanisms we have El Niño-Southern Oscillation (ENSO). Some works have indicated that during the ENSO positive phase there are more cyclogenetic conditions in some parts of the globe as the southwest of South Atlantic Ocean. Therefore, the purpose of this study is to verify if the extratropical cyclones number and location are altered in the different ENSO phases in the austral spring over the Southern Hemisphere (SH). The Melbourne University automatic tracking scheme was used to determine the cyclone climatology from 1980 to 2012. All cyclones that appear with lifetime higher or equal to 24 hours in the sea level pressure data from National Centers for Environment Prediction reanalysis I were included in the climatology. El Niño (EN), La Niña (LN) and Neutral (N) years were identified through the Oceanic Niño Index (ONI) from Climate Prediction Center/NOAA. The average number of cyclones in the spring over the SH is similar in the EN (200), N (184) and LN (197) episodes. By latitude bands, during EN episodes the cyclones occurrence reduces in 16% between 70-60 degrees and increases in ~15% between 80-70 and 50-40 degrees. On the other hand, during the LN episodes, the cyclones are 17% more frequent in 50-60 degrees and 22% less frequent in 30-20 degrees. One more detailed analysis of the cyclones trajectory density (that is a statistic product of the tracking algorithm) shows that in the South Atlantic Ocean, near the southeast of South America, the number of cyclones in EN years is higher than in the neutral period and lower than in the LN years. In the Indian Ocean, the EN year is characterized by a cyclones reduction in the west and east sector, near the continents. In the Pacific Ocean, the region southward the New Zealand presents more cyclones occurrence in EN years.

Impacto de los eventos de El Niño Southern oscillation (ENSO sobre la leishmaniosis cutánea en Sucre, Venezuela, a través del uso de información satelital, 1994 - 2003

Directory of Open Access Journals (Sweden)

Gilberto Cabaniel S

2005-03-01

Full Text Available Objetivos: Describir los posibles impactos de El Niño Southern Oscillation (ENSO sobre la leishmaniosis cutánea (LC en Sucre, Venezuela en el período 1994-2003. Materiales y Métodos: La data climática se obtuvo de sistemas remotos y fue clasificada de acuerdo con la National Oceanographic and Atmospheric Administration (NOAA en periodos El Niño, Neutral o La Niña, usando el Southern Oscillation Index (SOI como indicador de variabilidad. Los datos de LC fueron obtenidos de la Gerencia de Saneamiento Ambiental en Sucre. Se realizaron comparaciones de las variaciones anuales y desviaciones de las tendencias medias, entre la incidencia de LC y variabilidad climática, así como modelos de regresión. Resultados: Se registraron entre 1994 -2003 en Sucre 2212 casos de LC. Se observaron tres fases importantes de El Niño: 1994-1995, 1997-1998 y 2001-2003, la más relevante correspondió a 1997-1998, que fue seguido de un periodo frío y lluvioso en 1999 (La Niña. Durante 1999/2000, se registraron 360 casos de LC en Sucre, con importante variabilidad intraanual, se observó un incremento en 66,7% de los casos de LC (F=10,06, p=0,0051 asociado a la presencia de La Niña débil (poco frío y lluvioso. Los modelos mostraron que a mayores valores del SOI menor incidencia de LC (r 2 =0,3308, p=0,0504. El incremento sobre la tendencia media de las precipitaciones se asoció con incrementos sobre las tendencias de la LC durante 1994-2003 (p=0,0358. Conclusiones: Estos datos reflejan la importancia del ENSO sobre la incidencia de la LC, abriendo una nueva línea de investigación con posible impacto en la predicción y monitoreo con relevancia en salud pública.

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.

ENSO variability reflected in precipitation oxygen isotopes across the Asian Summer Monsoon region

Science.gov (United States)

Cai, Zhongyin; Tian, Lide; Bowen, Gabriel J.

2017-10-01

Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.

Global atmospheric response to specific linear combinations of the main SST modes. Part I: numerical experiments and preliminary results

Directory of Open Access Journals (Sweden)

S. Trzaska

1996-10-01

Full Text Available This article investigates through numerical experiments the controversial question of the impact of El Niño-Southern Oscillation (ENSO phenomena on climate according to large-scale and regional-scale interhemispheric thermal contrast. Eight experiments (two considering only inversed Atlantic thermal anomalies and six combining ENSO warm phase with large-scale interhemispheric contrast and Atlantic anomaly patterns were performed with the Météo-France atmospheric general circulation model. The definition of boundary conditions from observed composites and principal components is presented and preliminary results concerning the month of August, especially over West Africa and the equatorial Atlantic are discussed. Results are coherent with observations and show that interhemispheric and regional scale sea-surface-temperature anomaly (SST patterns could significantly modulate the impact of ENSO phenomena: the impact of warm-phase ENSO, relative to the atmospheric model intercomparison project (AMIP climatology, seems stronger when embedded in global and regional SSTA patterns representative of the post-1970 conditions [i.e. with temperatures warmer (colder than the long-term mean in the southern hemisphere (northern hemisphere]. Atlantic SSTAs may also play a significant role.

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

Science.gov (United States)

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

2016-02-01

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

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.

2015-01-01

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

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

KAUST Repository

Dogar, Muhammad Mubashar; Kucharski, Fred; Azharuddin, Syed

2017-01-01

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

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

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.

Water table depth fluctuations during ENSO phenomenon on different tropical peat swamp forest land covers in Katingan, Indonesia

Science.gov (United States)

Rossita, A.; Witono, A.; Darusman, T.; Lestari, D. P.; Risdiyanto, I.

2018-03-01

As it is the main role to maintain hydrological function, peatland has been a limelight since drainage construction for agriculture evolved. Drainage construction will decrease water table depth (WTD) and result in CO2 emission release to the atmosphere. Regardless of human intervention, WTD fluctuations can be affected by seasonal climate and climate variability, foremost El Niño Southern Oscillation (ENSO). This study aims to determine the correlation between rainfall in Katingan and ENSO index, analyze the pattern of WTD fluctuation of open area and forest area in 2015 (during very strong El Niño) and 2016 (during weak La Niña), calculate the WTD trendline slope during the dry season, and rainfall and WTD correlation. The result showed that open area has a sharper slope of decreasing or increasing WTD when entering the dry, compared to the forest area. Also, it is found that very strong El Niño in 2015 generated a pattern of more extreme decreasing WTD during the dry season than weak La Niña in 2016.

Gamma oscillations: precise temporal coordination without a metronome.

Science.gov (United States)

Nikolić, Danko; Fries, Pascal; Singer, Wolf

2013-02-01

Gamma oscillations in the brain should not be conceptualized as a sine wave with constant oscillation frequency. Rather, these oscillations serve to concentrate neuronal discharges to particular phases of the oscillation cycle and thereby provide the substrate for various, functionally relevant synchronization phenomena. Copyright © 2012 Elsevier Ltd. All rights reserved.

The influence of El Niño-Southern Oscillation regimes on eastern African vegetation and its future implications under the RCP8.5 warming scenario

Science.gov (United States)

Fer, Istem; Tietjen, Britta; Jeltsch, Florian; Wolff, Christian

2017-09-01

The El Niño-Southern Oscillation (ENSO) is the main driver of the interannual variability in eastern African rainfall, with a significant impact on vegetation and agriculture and dire consequences for food and social security. In this study, we identify and quantify the ENSO contribution to the eastern African rainfall variability to forecast future eastern African vegetation response to rainfall variability related to a predicted intensified ENSO. To differentiate the vegetation variability due to ENSO, we removed the ENSO signal from the climate data using empirical orthogonal teleconnection (EOT) analysis. Then, we simulated the ecosystem carbon and water fluxes under the historical climate without components related to ENSO teleconnections. We found ENSO-driven patterns in vegetation response and confirmed that EOT analysis can successfully produce coupled tropical Pacific sea surface temperature-eastern African rainfall teleconnection from observed datasets. We further simulated eastern African vegetation response under future climate change as it is projected by climate models and under future climate change combined with a predicted increased ENSO intensity. Our EOT analysis highlights that climate simulations are still not good at capturing rainfall variability due to ENSO, and as we show here the future vegetation would be different from what is simulated under these climate model outputs lacking accurate ENSO contribution. We simulated considerable differences in eastern African vegetation growth under the influence of an intensified ENSO regime which will bring further environmental stress to a region with a reduced capacity to adapt effects of global climate change and food security.

The Anticipation of the ENSO: What Resonantly Forced Baroclinic Waves Can Teach Us (Part II

Directory of Open Access Journals (Sweden)

Jean-Louis Pinault

2018-06-01

Full Text Available The purpose of the paper is to take advantage of recent work on the study of resonantly forced baroclinic waves in the tropical Pacific to significantly reduce systematic and random forecasting errors resulting from the current statistical models intended to predict El Niño. Their major drawback is that sea surface temperature (SST, which is widely used, is very difficult to decipher because of the extreme complexity of exchanges at the ocean-atmosphere interface. In contrast, El Niño-Southern Oscillation (ENSO forecasting can be performed between 7 and 8 months in advance precisely and very simply from (1 the subsurface water temperature at particular locations and (2 the time lag of the events (their expected date of occurrence compared to a regular 4-year cycle. Discrimination of precursor signals from objective criteria prevents the anticipation of wrong events, as occurred in 2012 and 2014. The amplitude of the events, their date of appearance, as well as their potential impact on the involved regions are estimated. Three types of ENSO events characterize their climate impact according to whether they are (1 unlagged or weakly lagged, (2 strongly lagged, or (3 out of phase with the annual quasi-stationary wave (QSW (Central Pacific El Niño events. This substantial progress is based on the analysis of baroclinic QSWs in the tropical basin and the resulting genesis of ENSO events. As for cold events, the amplification of La Niña can be seen a few months before the maturation phase of an El Niño event, as occurred in 1998 and 2016.

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

Science.gov (United States)

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

2014-01-01

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

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

Science.gov (United States)

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

2014-01-01

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

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

Science.gov (United States)

Potts, K. A.

2017-12-01

ENSO events are the most significant perturbation of the climate system. Previous attempts to link ENSO with volcanic eruptions typically failed because only large eruptions across the globe which eject tephra into the stratosphere were considered. I analyse all volcanic eruptions in South Eastern (SE) Asia (10ºS to 10ºN and from 90ºE to 160ºE) the most volcanically active area in the world with over 23% of all eruptions in the Global Volcanism Program database occurring here and with 5 volcanoes stated to have erupted nearly continuously for 30 years. SE Asia is also the region where the convective arm of the thermally direct Walker Circulation occurs driven by the intense equatorial solar radiation which creates the high surface temperature. The volcanic tephra plume intercepts some of the solar radiation by absorption/reflection which cools the surface and heats the atmosphere creating a temperature inversion compared to periods without the plume. This reduces convection and causes the Walker Cell and Trade Winds to weaken. This reduced wind speed causes the central Pacific Ocean to warm which creates convection there which further weakens the Walker Cell. With the reduced wind stress the western Pacific warm pool migrates east. This creates an ENSO event which continues until the tephra plume reduces, typically when the SE Asian monsoon commences, and convection is re-established over SE Asia and the Pacific warm pool migrates back to the west. Correlations of SE Asian tephra and the ENSO indices are typically over 0.80 at p indices. If two events A and B correlate 5 options are available: 1. A causes B; 2. B causes A; 3. C, another event, causes A &B simultaneously; 4. It's a coincidence; and 5. The relationship is complex with feedback. The volcanic correlations only allow options 1 or 4 as ENSO cannot cause volcanoes to erupt and are backed up by several independent satellite datasets. I conclude volcanic and anthropogenic aerosols over SE Asia are the

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

Directory of Open Access Journals (Sweden)

1993-01-01

Full Text Available L'EVENEMENT ENSO A GRANDE ECHELLE, EL NIÑO ET AUTRES CARACTERISTIQUES REGIONALES IMPORTANTES. En ce qui concerne cette activité, on a ramassé - et on continue de le faire - une information coordonnée et améliorée. Cependant, les informations année après année sur les changements climatiques en lien avec l’Oscillation du Sud (SO sont limitées de façon primaire à la période comprise entre l’année 622 et nos jours. La fluctuation océano-atmosphérique récurrente et à grande échelle, El Niño/ Oscillation du Sud (ENSO, qui se présente sous les basses latitudes depuis l’Afrique orientale vers l’est jusqu’aux Amériques, se manifeste en gros comme une «balançoire» dans les conditions océano-atmosphériques entre la zone de l’Océan Indien tropical et celles de l’Océan Pacifique tropical. L’ENSO est en lien avec une phase de bas indice de la SO et est associé, du côté occidental de la «balançoire», à une sécheresse en Australie occidentale et septentrionale, une sècheresse par l’est de la mousson en Indonésie, une pluie déficiente de la mousson-est d’été en Inde et une pluie déficiente de la mousson d’été dans la montagne éthiopienne (qui débouche sur une faible contribution au système du Nil. Par opposition, du côté oriental de la «balançoire», celle-ci est en lien avec El Niño, avec des températures superficielles de la mer (TSM anormalement hautes, des pluies au-dessus de la normale dans le Pacifique équatorial central et oriental et des pluies anormalement fortes dans le Chili sub-tropical. Le haut indice (phase anti-Niño de la SO est en lien, du côté occidental de la «balançoire», avec des pluies anormalement fortes en Australe orientale et septentrionale, des pluies de mousson de l’est anormalement fortes en Indonésie, des pluies de mousson d’été au-dessus de la normale en Inde, et une quantité d’eau anormalement grande qui se déverse dans le Nil, suite aux pluies de

Zonally resolved impact of ENSO on the stratospheric circulation and water vapor entry values

Science.gov (United States)

Konopka, Paul; Ploeger, Felix; Tao, Mengchu; Riese, Martin

2016-10-01

Based on simulations with the Chemical Lagrangian Model of the Stratosphere (CLaMS) for the period 1979-2013, with model transport driven by the ECMWF ERA-Interim reanalysis, we discuss the impact of the El Niño Southern Oscillation (ENSO) on the variability of the dynamics, water vapor, ozone, and mean age of air (AoA) in the tropical lower stratosphere during boreal winter. Our zonally resolved analysis at the 390 K potential temperature level reveals that not only (deseasonalized) ENSO-related temperature anomalies are confined to the tropical Pacific (180-300°E) but also anomalous wave propagation and breaking, as quantified in terms of the Eliassen-Palm (EP) flux divergence, with strongest local contribution during the La Niña phase. This anomaly is coherent with respective anomalies of water vapor (±0.5 ppmv) and ozone (±100 ppbv) derived from CLaMS being in excellent agreement with the Aura Microwave Limb Sounder observations. Thus, during El Niño a more zonally symmetric wave forcing drives a deep branch of the Brewer-Dobson (BD) circulation. During La Niña this forcing increases at lower levels (≈390 K) over the tropical Pacific, likely influencing the shallow branch of the BD circulation. In agreement with previous studies, wet (dry) and young (old) tape recorder anomalies propagate upward in the subsequent months following El Niño (La Niña). Using CLaMS, these anomalies are found to be around +0.3 (-0.2) ppmv and -4 (+4) months for water vapor and AoA, respectively. The AoA ENSO anomaly is more strongly affected by the residual circulation (≈2/3) than by eddy mixing (≈1/3).

Targeted Energy Transfer Phenomena in Vibro-Impact Oscillators

International Nuclear Information System (INIS)

Lee, Young S.; McFarland, D. Michael; Bergman, Lawrence A.; Nucera, Francesco; Vakakis, Alexander F.

2008-01-01

We study targeted energy transfer (TET) in a coupled oscillator, consisting of a single-degree-of-freedom primary linear oscillator coupled to a vibro-impact nonlinear energy sink (VI NES). For this purpose, we first compute the VI periodic orbits of the underlying hamiltonian VI system, and construct the corresponding frequency-energy plot (FEP). Then, considering inelastic impacts and viscous dissipation, we examine VI damped transitions on the FEP to identify a TET phenomenon by exciting a VI impulsive orbit, which is the most efficient mechanism for TET. Not only can the VI TET involve passive absorption and local dissipation of significant portions of the energy from the primary systems, but it occurs at sufficiently fast time scales. This renders VI NESs suitable for applications, like seismic mitigation, where shock elimination in the early, highly energetic regime of the motion is a critical requirement

Verification of an ENSO-Based Long-Range Prediction of Anomalous Weather Conditions During the Vancouver 2010 Olympics and Paralympics

Science.gov (United States)

Mo, Ruping; Joe, Paul I.; Doyle, Chris; Whitfield, Paul H.

2014-01-01

A brief review of the anomalous weather conditions during the Vancouver 2010 Winter Olympic and Paralympic Games and the efforts to predict these anomalies based on some preceding El Niño-Southern Oscillation (ENSO) signals are presented. It is shown that the Olympic Games were held under extraordinarily warm conditions in February 2010, with monthly mean temperature anomalies of +2.2 °C in Vancouver and +2.8 °C in Whistler, ranking respectively as the highest and the second highest in the past 30 years (1981-2010). The warm conditions continued, but became less anomalous, in March 2010 for the Paralympic Games. While the precipitation amounts in the area remained near normal through this winter, the lack of snow due to warm conditions created numerous media headlines and practical problems for the alpine competitions. A statistical model was developed on the premise that February and March temperatures in the Vancouver area could be predicted using an ENSO signal with considerable lead time. This model successfully predicted the warmer-than-normal, lower-snowfall conditions for the Vancouver 2010 Winter Olympics and Paralympics.

Interannual variation in methane emissions from tropical wetlands triggered by repeated El Niño Southern Oscillation

Science.gov (United States)

Zhu, Qiuan; Peng, Changhui; Ciais, Philippe; Jiang, Hong; Liu, Jinxun; Bousquet, Philippe; Li, Shiqin; Chang, Jie; Fang, Xiuqin; Zhou, Xiaolu; Chen, Huai; Liu, Shirong; Lin, Guanghui; Gong, Peng; Wang, Meng; Wang, Han; Xiang, Wenhua; Chen, Jing

2017-01-01

Methane (CH4) emissions from tropical wetlands contribute 60%–80% of global natural wetland CH4 emissions. Decreased wetland CH4 emissions can act as a negative feedback mechanism for future climate warming and vice versa. The impact of the El Niño–Southern Oscillation (ENSO) on CH4 emissions from wetlands remains poorly quantified at both regional and global scales, and El Niño events are expected to become more severe based on climate models’ projections. We use a process-based model of global wetland CH4 emissions to investigate the impacts of the ENSO on CH4 emissions in tropical wetlands for the period from 1950 to 2012. The results show that CH4 emissions from tropical wetlands respond strongly to repeated ENSO events, with negative anomalies occurring during El Niño periods and with positive anomalies occurring during La Niña periods. An approximately 8-month time lag was detected between tropical wetland CH4 emissions and ENSO events, which was caused by the combined time lag effects of ENSO events on precipitation and temperature over tropical wetlands. The ENSO can explain 49% of interannual variations for tropical wetland CH4 emissions. Furthermore, relative to neutral years, changes in temperature have much stronger effects on tropical wetland CH4 emissions than the changes in precipitation during ENSO periods. The occurrence of several El Niño events contributed to a lower decadal mean growth rate in atmospheric CH4 concentrations throughout the 1980s and 1990s and to stable atmospheric CH4 concentrations from 1999 to 2006, resulting in negative feedback to global warming.

An improved ENSO simulation by representing chlorophyll-induced climate feedback in the NCAR Community Earth System Model.

Science.gov (United States)

Kang, Xianbiao; Zhang, Rong-Hua; Gao, Chuan; Zhu, Jieshun

2017-12-07

The El Niño-Southern oscillation (ENSO) simulated in the Community Earth System Model of the National Center for Atmospheric Research (NCAR CESM) is much stronger than in reality. Here, satellite data are used to derive a statistical relationship between interannual variations in oceanic chlorophyll (CHL) and sea surface temperature (SST), which is then incorporated into the CESM to represent oceanic chlorophyll -induced climate feedback in the tropical Pacific. Numerical runs with and without the feedback (referred to as feedback and non-feedback runs) are performed and compared with each other. The ENSO amplitude simulated in the feedback run is more accurate than that in the non-feedback run; quantitatively, the Niño3 SST index is reduced by 35% when the feedback is included. The underlying processes are analyzed and the results show that interannual CHL anomalies exert a systematic modulating effect on the solar radiation penetrating into the subsurface layers, which induces differential heating in the upper ocean that affects vertical mixing and thus SST. The statistical modeling approach proposed in this work offers an effective and economical way for improving climate simulations.

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

Science.gov (United States)

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

2017-12-01

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

Asian Summer Monsoon Rainfall associated with ENSO and its Predictability

Science.gov (United States)

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

2015-12-01

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

Influence of El Niño Southern Oscillation on global hydropower production

Science.gov (United States)

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

2016-04-01

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

Nonlinear oscillations

CERN Document Server

Nayfeh, Ali Hasan

1995-01-01

Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim

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

Science.gov (United States)

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

2012-01-01

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

Precipitation and ice core isotopes from the Asian Summer Monsoon region reflect coherent ENSO variability

Science.gov (United States)

Cai, Z.; Tian, L.; Bowen, G. J.

2017-12-01

Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.

ENSO influence on the interannual variability of the Red Sea convergence zone and associated rainfall

KAUST Repository

Dasari, Hari Prasad

2017-07-18

The Red Sea convergence zone (RSCZ) is formed by opposite surface winds blowing from northwest to southeast directions at around 18°-19°N between October and January. A reverse-oriented, low-level monsoon trough at 850hPa, known as the Red Sea trough (RST), transfers moisture from the southern Red Sea to RSCZ. The positions of the RSCZ and RST and the intensity of the RST have been identified as important factors in modulating weather and climatic conditions across the Middle East. Here, we investigate the influence of the El Niño southern oscillation (ENSO) on the interannual variability of RSCZ, RST, and regional rainfall during winter months. Our results indicate that El Niño (warm ENSO phase) favours a shift of the RSCZ to the north and a strengthening of the RST in the same direction. Conversely, during November and December of La Niña periods (cold ENSO phase), the RSCZ shift to the south and the RST strengthens in the same direction. During El Niño periods, southeasterly wind speeds increase (20-30%) over the southern Red Sea and northwesterly wind speeds decrease (10-15%) over the northern Red Sea. Noticeable increases in the number of rainy days and the intensity of rain events are observed during El Niño phases. These increases are associated with colder than normal air intrusion at lower levels from the north combined with warm air intrusion from the south over the RSCZ. Our analysis suggests that during El Niño winters, warmer sea surface temperatures and higher convective instability over the Red Sea favour local storms conditions and increase rainfall over the Red Sea and adjoining regions.

Oscillation phenomena and operating limits of the closed two-phase thermosyphon

International Nuclear Information System (INIS)

Fukano, T.; Kadoguchi, K.; Tien, C.L.

1986-01-01

In a vertical thermosyphon an up-going vapor flow prevents a liquid film from flowing downward and causes flooding if the heat input exceeds a certain value. Then the evaporator wall partially dries out. The wall temperature in the evaporator and the system pressure are measured and their post-dryout behavior is classified into three types: (1) the periodic oscillation, and transient variations going asymptotically to (2) the higher and (3) the lower than the initial system pressure setting. The occurrence of the first type, periodic oscillation, is limited to when the amount of working fluid, methanol, is about one-third of the evaporator volume. To explain these changes in the system pressure and wall temperature a physical model, based on the alternating flooding and deflooding concept is proposed. In this work the effect of the tube diameter, amount of working fluid, and system pressure on these oscillations and the flow and heat transfer characteristics during the oscillations are also experimentally investigated

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

Science.gov (United States)

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

2016-04-01

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

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

Science.gov (United States)

Gutierrez, Luciano

2017-01-01

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

Oscillating and rotating sine-Gordon system

DEFF Research Database (Denmark)

Olsen, O. H.; Samuelsen, Mogens Rugholm

1986-01-01

The interaction between a 2π kink and the background or vacuum is investigated in the pure sine-Gordon system. For an oscillating background (i.e., the k=0 part of the phonon spectrum) the 2π kink oscillates, while for increasing or decreasing vacuum two phenomena have been observed, depending...

Tracking ENSO with tropical trees: Progress in stable isotope dendroclimatology

Science.gov (United States)

Evans, M. N.; Poussart, P. F.; Saleska, S. R.; Schrag, D. P.

2002-12-01

The terrestrial tropics remain an important gap in the growing proxy network used to characterize past ENSO behavior. Here we describe a strategy for development of proxy estimates of paleo-ENSO, via proxy rainfall estimates derived from stable isotope (δ18O) measurements made on tropical trees. The approach applies a new model of oxygen isotopic composition of alpha-cellulose (Roden et al., 2000), a rapid method for cellulose extraction from raw wood (Brendel et al., 2000), and continuous flow isotope ratio mass spectrometry (Brand, 1996) to develop proxy chronological, rainfall and growth rate estimates from tropical trees, even those lacking annual rings. The promise and pitfalls of the approach are illustrated in pilot datasets from the US, Costa Rica, Brazil, and Peru, which show isotopic cycles of 4-6 per mil, and interannual anomalies of up to 8 per mil. Together with the mature ENSO proxies (corals, extratropical tree-rings, varved sediments, and ice cores), replicated and well-dated stable isotope chronologies from tropical trees may eventually improve our understanding of ENSO history over the past several hundred years.

Association of Taiwan’s Rainfall Patterns with Large-Scale Oceanic and Atmospheric Phenomena

Directory of Open Access Journals (Sweden)

Yi-Chun Kuo

2016-01-01

Full Text Available A 50-year (1960–2009 monthly rainfall gridded dataset produced by the Taiwan Climate Change Projection and Information Platform Project was presented in this study. The gridded data (5 × 5 km displayed influence of topography on spatial variability of rainfall, and the results of the empirical orthogonal functions (EOFs analysis revealed the patterns associated with the large-scale sea surface temperature variability over Pacific. The first mode (65% revealed the annual peaks of large rainfall in the southwestern mountainous area, which is associated with southwest monsoons and typhoons during summertime. The second temporal EOF mode (16% revealed the rainfall variance associated with the monsoon and its interaction with the slopes of the mountain range. This pattern is the major contributor to spatial variance of rainfall in Taiwan, as indicated by the first mode (40% of spatial variance EOF analysis. The second temporal EOF mode correlated with the El Niño Southern Oscillation (ENSO. In particular, during the autumn of the La Niña years following the strong El Niño years, the time-varying amplitude was substantially greater than that of normal years. The third temporal EOF mode (7% revealed a north-south out-of-phase rainfall pattern, the slowly evolving variations of which were in phase with the Pacific Decadal Oscillation. Because of Taiwan’s geographic location and the effect of local terrestrial structures, climate variability related to ENSO differed markedly from other regions in East Asia.

Harmonic oscillations, chaos and synchronization in systems consisting of Van der Pol oscillator coupled to a linear oscillator

International Nuclear Information System (INIS)

Woafo, P.

1999-12-01

This paper deals with the dynamics of a model describing systems consisting of the classical Van der Pol oscillator coupled gyroscopically to a linear oscillator. Both the forced and autonomous cases are considered. Harmonic response is investigated along with its stability boundaries. Condition for quenching phenomena in the autonomous case is derived. Neimark bifurcation is observed and it is found that our model shows period doubling and period-m sudden transitions to chaos. Synchronization of two and more systems in their chaotic regime is presented. (author)

Using Remote Sensing Products to Identify Marine Association Patterns in Factors Relating to ENSO in the Pacific Ocean

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Cunjin Xue

2017-01-01

Full Text Available El Niño–Southern Oscillation (ENSO and its relationships with marine environmental parameters comprise a very complicated and interrelated system. Traditional spatiotemporal techniques face great challenges in dealing with which, how, and where the marine environmental parameters in different zones help to drive, and respond to, ENSO events. Remote sensing products covering a 15-year period from 1998 to 2012 were used to quantitatively explore these patterns in the Pacific Ocean (PO by a prevail quantitative association rule mining algorithm, that is, a priori, within a mining framework. The marine environmental parameters considered were monthly anomaly of sea surface chlorophyll-a (CHLA, monthly anomaly of sea surface temperature (SSTA, monthly anomaly of sea level anomaly (SLAA, monthly anomaly of sea surface precipitation (SSPA, and monthly anomaly of sea surface wind speed (WSA. Four significant discoveries are found, namely: (1 Association patterns among marine environmental parameters and ENSO events were found primarily in five sub-regions of the PO: the western PO, the central and eastern tropical PO, the middle of the northern subtropical PO, offshore of the California coast, and the southern PO; (2 In the western and the middle and east of the equatorial PO, the association patterns are more complicated than other regions; (3 The following factors were found to be predicators of and responses to La Niña events: abnormal decrease of SLAA and WSA in the east of the equatorial PO, abnormal decrease of SSPA and WSA in the middle of the equatorial PO, abnormal decrease of SSTA in the eastern and central tropical PO, and abnormal increase of SLAA in the western PO; (4 Only abnormal decrease of CHLA in the middle of the equatorial PO was found to be a predicator of and response to El Niño events. These findings will help to improve our abilities to identify the marine association patterns in factors relating to ENSO events.

On the unstable ENSO-Western North Pacific Monsoon relation during the 20th Century

Science.gov (United States)

Vega Martín, Inmaculada; Gallego Puyol, David; Ribera Rodriguez, Pedro; Gómez Delgado, Francisco de Paula; Peña-Ortiz, Cristina

2017-04-01

The concept of the Western North Pacific Summer Monsoon (WNPSM) appeared for the first time in 1987. Unlike the Indian Summer Monsoon and the East Asian summer monsoon, the WNPSM is an oceanic monsoon driven essentially by the meridional gradient of sea surface temperature. Its circulation is characterized by a northwest-southeast oriented monsoon trough with intense precipitation and low-level southwesterlies and upper-tropospheric easterlies in the region [100°-130° E, 5°-15°N]. Although this monsoon is mainly oceanic, it modulates the precipitation of densely populated areas such as the Philippines. To date, the WNPSM has been quantified by the so-called Western North Pacific Monsoon Index (WNPMI), an index based on wind anomalies over large domains of the Western Pacific. The requirement of continuous observed wind over remote oceanic areas to compute the WNPMI has limited its availability to the 1949-2014 period. In this work we have extended the index by almost 100 years by using historical observations of wind direction taken aboard ships. Our Western North Pacific Directional Index (WNPDI), is defined as the sum of the persistence of the low-level westerly winds in [5°-15°N, 100°-130°E] and easterly winds in [20°-30°N, 110°-140°E]. The new WNPDI index is highly correlated to the existent WNPMI for the concurrent period (1948-2014). (r=+0.88, p<0.01), indicating that the new approach based in the use of wind direction alone (a variable that can be considered instrumental even before the 20th Century), captures most of the monsoonal signal. Previous studies found that, during the second part of the 20th Century the WNPSM exhibited two basic characteristics: first a large interannual variability and second, a significant relation between the WNPSM and the El Niño/Southern Oscillation (ENSO) in a way in which a strong (weak) WNPSM tends to occur during the El Niño (La Niña) developing year or/and La Niña (El Niño) decaying year. The analysis of

Understanding ENSO dynamics through the exploration of past climates

International Nuclear Information System (INIS)

Phipps, Steven J; Brown, Jaclyn N

2010-01-01

The palaeoclimate record shows that significant changes in ENSO characteristics took place during the Holocene. Exploring these changes, using both data and models, provides a means of understanding ENSO dynamics. Previous modelling studies have suggested a mechanism whereby changes in the Earth's orbital geometry explain the strengthening of ENSO over the Holocene. Decreasing summer insolation over the Asian landmass resulted in a weakening of the Asian monsoon system. This led to a weakening of the easterly trade winds in the western Pacific, creating conditions more favourable for El Nino development. To explore this hypothesised forcing mechanism, we use a climate system model to conduct a suite of simulations of the climate of the past 8,000 years. In the early Holocene, we find that the Asian summer monsoon system is intensified, resulting in an amplification of the easterly trade winds in the western Pacific. The stronger trade winds represent a barrier to the eastward propagation of westerly wind bursts, therefore inhibiting the onset of El Nino events. The fundamental behaviour of ENSO remains unchanged, with the major change over the Holocene being the influence of the background state of the Pacific on the susceptibility of the ocean to the initiation of El Nino events.

Changing characteristics of streamflow in the Midwest and its relation to oceanic-atmospheric oscillations

Science.gov (United States)

Thakur, B.; Pathak, P.; Kalra, A.; Ahmad, S.

2016-12-01

The identification of primary drivers of streamflow may prove beneficial in forecasting streamflow in the Midwestern U.S. In the past researches, streamflow in the region have been strongly correlated with El Niño-Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO). The present study takes in to account the pre-defined Pacific and Atlantic Ocean regions (e.g., ENSO, PDO, AMO) along with new regions with an intent to identify new significantly correlated regions. This study assesses the interrelationship between sea surface temperatures (SST) anomalies in the Pacific and Atlantic Ocean and seasonal streamflow in the Midwestern U.S. Average Pacific and Atlantic Ocean SST anomalies, were calculated for 2 different 3 month series: September-November and December-February so as to create a lead time varying from 3 to 9 months. Streamflow were averaged for three seasons: spring (April-June), spring-summer (April-August) and summer (June-August). The correlation between streamflow and SST is analyzed using singular value decomposition for a period of 1960-2013. The result of the study showed several regions-other than the known Pacific and Atlantic Ocean regions- that were significantly correlated with streamflow stations. Higher correlation between the climate indices and streamflow were observed as the lead time decreased. The identification of the associations between SST and streamflow and significant SST regions in the Pacific and Atlantic Ocean may enhance the skill of streamflow predictability and water management in the region.

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

Science.gov (United States)

Kohyama, T.; Hartmann, D. L.

2017-12-01

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

Influencia del fenómeno ENSO sobre la precipitación nival en el sector andino de Chile central durante el invierno

Directory of Open Access Journals (Sweden)

1998-01-01

Full Text Available INFLUENCE DU PHÉNOMÈNE ENSO SUR LES PRÉCIPITATIONS NEIGEUSES DANS LE CENTRE DU CHILI ANDIN AU COURS DE L’HIVER AUSTRAL. On analyse l’influence du phénomène El Niño/Oscillation du Sud (ENSO sur les précipitations nivales dans les Andes du Chili central au cours de l’hiver. Pour cela, on a utilisé l’information obtenue sur des sites spécifiques (routes de neige situées entre 30° et 38° S et les anomalies de Température de Surface de la Mer (TSM du bloc Niño 3, comme indicateur de l’importance des événements chauds ou froids dans le Pacifique équatorial central. Au nord de 35°S, l’accumulation de neige tend à être supérieure à la normale quand l’anomalie moyenne de TSM dépasse +1°C au cours de la période mai-août. Dans ce même secteur, on enregistre une précipitation inférieure à la normale les hivers caractérisés par une anomalie de TSM inférieure à -0,5°C. Dans la zone située au sud de 35° S, l’influence du phénomène ENSO sur l’accumulation de neige n’est plus significative. Se analiza la influencia del fenómeno El Niño/Oscilación del Sur (ENSO sobre la precipitación nival en los Andes de Chile central durante el invierno. Para esto, se utiliza información de rutas de nieve localizadas entre 30° y 38° S, y de anomalías de temperatura superficial del mar (TSM en la región Niño 3 como un indicador de la magnitud de los eventos cálidos y fríos en el Pacífico ecuatorial central. En la región al norte de 35° S, la acumulación de nieve durante el invierno tiende a ser superior a lo normal cuando la magnitud de la anomalía media de TSM en el periodo mayo-agosto supera +1,0° C. En este mismo sector se verifica que durante los inviernos caracterizados por una anomalía de TSM inferior a -0,5° C, suele registrarse una precipitación nival inferior a lo normal. En el sector al sur de los 35° S, la influencia del fenómeno ENSO sobre la acumulación de nieve durante el invierno no es

Tropospheric Column Ozone Response to ENSO in GEOS-5 Assimilation of OMI and MLS Ozone Data

Science.gov (United States)

Olsen, Mark A.; Wargan, Krzysztof; Pawson, Steven

2016-01-01

We use GEOS-5 analyses of Ozone Monitoring Instrument (OMI) and Microwave Limb Sounder (MLS) ozone observations to investigate the magnitude and spatial distribution of the El Nino Southern Oscillation (ENSO) influence on tropospheric column ozone (TCO) into the middle latitudes. This study provides the first explicit spatially resolved characterization of the ENSO influence and demonstrates coherent patterns and teleconnections impacting the TCO in the extratropics. The response is evaluated and characterized by both the variance explained and sensitivity of TCO to the Nino 3.4 index. The tropospheric response in the tropics agrees well with previous studies and verifies the analyses. A two-lobed response symmetric about the Equator in the western Pacific/Indonesian region seen in some prior studies and not in others is confirmed here. This two-lobed response is consistent with the large-scale vertical transport. We also find that the large-scale transport in the tropics dominates the response compared to the small-scale convective transport. The ozone response is weaker in the middle latitudes, but a significant explained variance of the TCO is found over several small regions, including the central United States. However, the sensitivity of TCO to the Nino 3.4 index is statistically significant over a large area of the middle latitudes. The sensitivity maxima and minima coincide with anomalous anti-cyclonic and cyclonic circulations where the associated vertical transport is consistent with the sign of the sensitivity. Also, ENSO related changes to the mean tropopause height can contribute significantly to the midlatitude response. Comparisons to a 22-year chemical transport model simulation demonstrate that these results from the 9- year assimilation are representative of the longer term. This investigation brings insight to several seemingly disparate prior studies of the El Nino influence on tropospheric ozone in the middle latitudes.

Tropospheric column ozone response to ENSO in GEOS-5 assimilation of OMI and MLS ozone data

Directory of Open Access Journals (Sweden)

M. A. Olsen

2016-06-01

Full Text Available We use GEOS-5 analyses of Ozone Monitoring Instrument (OMI and Microwave Limb Sounder (MLS ozone observations to investigate the magnitude and spatial distribution of the El Niño Southern Oscillation (ENSO influence on tropospheric column ozone (TCO into the middle latitudes. This study provides the first explicit spatially resolved characterization of the ENSO influence and demonstrates coherent patterns and teleconnections impacting the TCO in the extratropics. The response is evaluated and characterized by both the variance explained and sensitivity of TCO to the Niño 3.4 index. The tropospheric response in the tropics agrees well with previous studies and verifies the analyses. A two-lobed response symmetric about the Equator in the western Pacific/Indonesian region seen in some prior studies and not in others is confirmed here. This two-lobed response is consistent with the large-scale vertical transport. We also find that the large-scale transport in the tropics dominates the response compared to the small-scale convective transport. The ozone response is weaker in the middle latitudes, but a significant explained variance of the TCO is found over several small regions, including the central United States. However, the sensitivity of TCO to the Niño 3.4 index is statistically significant over a large area of the middle latitudes. The sensitivity maxima and minima coincide with anomalous anti-cyclonic and cyclonic circulations where the associated vertical transport is consistent with the sign of the sensitivity. Also, ENSO related changes to the mean tropopause height can contribute significantly to the midlatitude response. Comparisons to a 22-year chemical transport model simulation demonstrate that these results from the 9-year assimilation are representative of the longer term. This investigation brings insight to several seemingly disparate prior studies of the El Niño influence on tropospheric ozone in the middle latitudes.

Impacts of the ENSO Modoki and other Tropical Indo-Pacific Climate-Drivers on African Rainfall.

Science.gov (United States)

Preethi, B; Sabin, T P; Adedoyin, J A; Ashok, K

2015-11-16

The study diagnoses the relative impacts of the four known tropical Indo-Pacific drivers, namely, El Niño Southern Oscillation (ENSO), ENSO Modoki, Indian Ocean Dipole (IOD), and Indian Ocean Basin-wide mode (IOBM) on African seasonal rainfall variability. The canonical El Niño and El Niño Modoki are in general associated with anomalous reduction (enhancement) of rainfall in southern (northern) hemispheric regions during March-May season. However, both the El Niño flavours anomalously reduce the northern hemispheric rainfall during June-September. Interestingly, during boreal spring and summer, in many regions, the Indian Ocean drivers have influences opposite to those from tropical Pacific drivers. On the other hand, during the October-December season, the canonical El Niño and/or positive IOD are associated with an anomalous enhancement of rainfall in the Eastern Africa, while the El Niño Modoki events are associated with an opposite impact. In addition to the Walker circulation changes, the Indo-Pacific drivers influence the African rainfall through modulating jet streams. During boreal summer, the El Niño Modoki and canonical El Niño (positive IOD) tend to weaken (strengthen) the tropical easterly jet, and result in strengthening (weakening) and southward shift of African easterly jet. This anomalously reduces (enhances) rainfall in the tropical north, including Sahelian Africa.

Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America

Science.gov (United States)

Münnich, M.; Neelin, J. D.

2005-11-01

In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

Hydro-climatic variability over the Andes of Colombia associated with ENSO: a review of climatic processes and their impact on one of the Earth's most important biodiversity hotspots

Science.gov (United States)

Poveda, Germán; Álvarez, Diana M.; Rueda, Óscar A.

2011-06-01

The hydro-climatic variability of the Colombian Andes associated with El Niño-Southern Oscillation (ENSO) is reviewed using records of rainfall, river discharges, soil moisture, and a vegetation index (NDVI) as a surrogate for evapotranspiration. Anomalies in the components of the surface water balance during both phases of ENSO are quantified in terms of their sign, timing, and magnitude. During El Niño (La Niña), the region experiences negative (positive) anomalies in rainfall, river discharges (average and extremes), soil moisture, and NDVI. ENSO's effects are phase-locked to the seasonal cycle, being stronger during December-February, and weaker during March-May. Besides, rainfall and river discharges anomalies show that the ENSO signal exhibits a westerly wave-like propagation, being stronger (weaker) and earlier (later) over the western (eastern) Andes. Soil moisture anomalies are land-cover type dependant, but overall they are enhanced by ENSO, showing very low values during El Niño (mainly during dry seasons), but saturation values during La Niña. A suite of large-scale and regional mechanisms cooperating at the ocean-atmosphere-land system are reviewed to explaining the identified hydro-climatic anomalies. This review contributes to an understanding of the hydro-climatic framework of a region identified as the most critical hotspot for biodiversity on Earth, and constitutes a wake-up call for scientists and policy-makers alike, to take actions and mobilize resources and minds to prevent the further destruction of the region's valuable hydrologic and biodiversity resources and ecosystems. It also sheds lights towards the implementation of strategies and adaptation plans to coping with threats from global environmental change.

Anti-synchronization of chaotic oscillators

International Nuclear Information System (INIS)

Kim, Chil-Min; Rim, Sunghwan; Kye, Won-Ho; Ryu, Jung-Wan; Park, Young-Jai

2003-01-01

We have observed anti-synchronization phenomena in coupled identical chaotic oscillators. Anti-synchronization can be characterized by the vanishing of the sum of relevant variables. We have qualitatively analyzed its base mechanism by using the dynamics of the difference and the sum of the relevant variables in coupled chaotic oscillators. Near the threshold of the synchronization and anti-synchronization transition, we have obtained the novel characteristic relation

Oscillator circuits frontiers in design, analysis and applications

CERN Document Server

2016-01-01

This book surveys recent developments in the design, analysis and applications of oscillator circuit design. It highlights developments in the analysis of synchronization and wave phenomena, new analytical and design methods and their application, and novel engineering applications of oscillator circuits.

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

Interannual sea level variability in the Pearl River Estuary and its response to El Niño-Southern Oscillation

Science.gov (United States)

Wang, Linlin; Li, Qiang; Mao, Xian-zhong; Bi, Hongsheng; Yin, Peng

2018-03-01

The South China coast, especially the Pearl River Estuary (PRE) region, is prosperous and densely populated, but vulnerable to sea level changes. Sea level anomalies (SLA) during 1954-2012 from tide gauge station data and regional SLAs during 1993-2012 from satellite altimetry are analyzed and compare to the El Niño-Southern Oscillation (ENSO). Results show that sea level declines during El Niño events and rises during La Niña. Sea level in the PRE responds to ENSO with 3-month lag. The ENSO can cause sea level in the PRE to fluctuate from -8.70 to 8.11 cm. Sea level cycles of 3 and 5 years are related to ENSO. The ENSO mechanism affecting sea level in the PRE was analyzed by identifying dominant regional and local forces. Weak/strong SLAs in most El Niño/La Niña events may be attributed to less/more seawater transport driven by anomalously weak/strong north winds and local anomalously high/low sea level pressure. Wind-driven coastal current is the predominant factor. It generated coastal seawater volume transport along a 160 km wide cross section to decrease by 21.07% in a typical El Niño period (January 2010) and increase by 44.03% in a typical La Niña period (January 2011) as compared to an ENSO neutral situation (January 2013). Results of sea level rise and its potential mechanism provide insight for disaster protection during extreme El Niño/La Niña events.

Role of tropical Indian and Atlantic Oceans variability on ENSO

Science.gov (United States)

Prodhomme, Chloé; Terray, Pascal; Masson, Sebastien; Boschat, Ghyslaine

2014-05-01

There are strong evidences of an interaction between tropical Indian, Atlantic and Pacific Oceans. Nevertheless, these interactions remain deeply controversial. While some authors claim the tropical Indian and Atlantic oceans only play a passive role with respect to ENSO, others suggest a driving role for these two basins on ENSO. The mecanisms underlying these relations are not fully understood and, in the Indian Ocean, the possible role of both modes of tropical variability (the Indian Ocean Dipole (IOD) and the Indian Ocean Basin mode (IOB)) remain unclear. To better quantify and understand how the variability of the tropical Indian and Atlantic Oceans impact ENSO variability, we performed two sensitivity experiments using the SINTEX-F2 coupled model. For each experiment, we suppressed the variability of SST and the air-sea coupling in either the tropical Indian Ocean or tropical Atlantic Ocean by applying a strong nudging of the SST to the observed SST climatology. In both experiments, the ENSO periodicity increases. In the Atlantic experiment, our understanding of this increased periodicity is drastically limited by the strongly biased mean state in this region. Conversely, in the Indian Ocean experiment, the increase of ENSO periodicity is related to the absence of the IOB following the El Niño peak, which leads to a decrease of westerly winds in the western Pacific during late winter and spring after the peak. These weaker westerlies hinders the transition to a La Niña phase and thus increase the duration and periodicity of the event.

How do the multiple large-scale climate oscillations trigger extreme precipitation?

Science.gov (United States)

Shi, Pengfei; Yang, Tao; Xu, Chong-Yu; Yong, Bin; Shao, Quanxi; Li, Zhenya; Wang, Xiaoyan; Zhou, Xudong; Li, Shu

2017-10-01

Identifying the links between variations in large-scale climate patterns and precipitation is of tremendous assistance in characterizing surplus or deficit of precipitation, which is especially important for evaluation of local water resources and ecosystems in semi-humid and semi-arid regions. Restricted by current limited knowledge on underlying mechanisms, statistical correlation methods are often used rather than physical based model to characterize the connections. Nevertheless, available correlation methods are generally unable to reveal the interactions among a wide range of climate oscillations and associated effects on precipitation, especially on extreme precipitation. In this work, a probabilistic analysis approach by means of a state-of-the-art Copula-based joint probability distribution is developed to characterize the aggregated behaviors for large-scale climate patterns and their connections to precipitation. This method is employed to identify the complex connections between climate patterns (Atlantic Multidecadal Oscillation (AMO), El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) and seasonal precipitation over a typical semi-humid and semi-arid region, the Haihe River Basin in China. Results show that the interactions among multiple climate oscillations are non-uniform in most seasons and phases. Certain joint extreme phases can significantly trigger extreme precipitation (flood and drought) owing to the amplification effect among climate oscillations.

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

Science.gov (United States)

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

2013-10-29

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

Truly neutral microobjects and oscillations in particle physics

International Nuclear Information System (INIS)

Bilenky, S.M.; Pontecorvo, B.

1982-01-01

Oscillation phenomena between different states of neutral elementary particles are discussed. The known kaon oscillation and the proposed neutrino, neutron and other kinds of oscillations are analysed. The proper bound states of neutral objects (neutrinos, neutrons, hydrogen atoms) are investigated in the case of small and strong violation of CP symmetry. Consequences concerning the observable masses and quantum numbers of such neutral objects are drawn. (D.Gy.)

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.

2018-04-01

Realistic simulation of large-scale circulation patterns associated with El Niño-Southern Oscillation (ENSO) is vital in coupled models in order to represent teleconnections to different regions of globe. The diversity in representing large-scale circulation patterns associated with ENSO-Indian summer monsoon (ISM) teleconnections in 23 Coupled Model Intercomparison Project Phase 5 (CMIP5) models is examined. CMIP5 models have been classified into three groups based on the correlation between Niño3.4 sea surface temperature (SST) index and ISM rainfall anomalies, models in group 1 (G1) overestimated El Niño-ISM teleconections and group 3 (G3) models underestimated it, whereas these teleconnections are better represented in group 2 (G2) models. Results show that in G1 models, El Niño-induced Tropical Indian Ocean (TIO) SST anomalies are not well represented. Anomalous low-level anticyclonic circulation anomalies over the southeastern TIO and western subtropical northwest Pacific (WSNP) cyclonic circulation are shifted too far west to 60° E and 120° E, respectively. This bias in circulation patterns implies dry wind advection from extratropics/midlatitudes to Indian subcontinent. In addition to this, large-scale upper level convergence together with lower level divergence over ISM region corresponding to El Niño are stronger in G1 models than in observations. Thus, unrealistic shift in low-level circulation centers corroborated by upper level circulation changes are responsible for overestimation of ENSO-ISM teleconnections in G1 models. Warm Pacific SST anomalies associated with El Niño are shifted too far west in many G3 models unlike in the observations. Further large-scale circulation anomalies over the Pacific and ISM region are misrepresented during El Niño years in G3 models. Too strong upper-level convergence away from Indian subcontinent and too weak WSNP cyclonic circulation are prominent in most of G3 models in which ENSO-ISM teleconnections are

Hydro-climatic variability over the Andes of Colombia associated with ENSO: a review of climatic processes and their impact on one of the Earth's most important biodiversity hotspots

Energy Technology Data Exchange (ETDEWEB)

Poveda, German; Alvarez, Diana M. [Universidad Nacional de Colombia, School of Geosciences and Environment, Medellin (Colombia); Rueda, Oscar A. [Universidad Nacional de Colombia, School of Geosciences and Environment, Medellin (Colombia); Grupo HTM, Medellin (Colombia)

2011-06-15

The hydro-climatic variability of the Colombian Andes associated with El Nino-Southern Oscillation (ENSO) is reviewed using records of rainfall, river discharges, soil moisture, and a vegetation index (NDVI) as a surrogate for evapotranspiration. Anomalies in the components of the surface water balance during both phases of ENSO are quantified in terms of their sign, timing, and magnitude. During El Nino (La Nina), the region experiences negative (positive) anomalies in rainfall, river discharges (average and extremes), soil moisture, and NDVI. ENSO's effects are phase-locked to the seasonal cycle, being stronger during December-February, and weaker during March-May. Besides, rainfall and river discharges anomalies show that the ENSO signal exhibits a westerly wave-like propagation, being stronger (weaker) and earlier (later) over the western (eastern) Andes. Soil moisture anomalies are land-cover type dependant, but overall they are enhanced by ENSO, showing very low values during El Nino (mainly during dry seasons), but saturation values during La Nina. A suite of large-scale and regional mechanisms cooperating at the ocean-atmosphere-land system are reviewed to explaining the identified hydro-climatic anomalies. This review contributes to an understanding of the hydro-climatic framework of a region identified as the most critical hotspot for biodiversity on Earth, and constitutes a wake-up call for scientists and policy-makers alike, to take actions and mobilize resources and minds to prevent the further destruction of the region's valuable hydrologic and biodiversity resources and ecosystems. It also sheds lights towards the implementation of strategies and adaptation plans to coping with threats from global environmental change. (orig.)

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

Science.gov (United States)

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

2018-01-01

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

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

Science.gov (United States)

McGowan, Hamish; Theobald, Alison

2017-10-01

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

Rabi oscillations in bidimensional photonic crystals

International Nuclear Information System (INIS)

Centeno, E.; Felbacq, D.

2000-01-01

We theoretically and numerically investigate transient phenomena in finite two-dimensional photonic crystals doped by single-mode microcavities. We show that for antisymmetric defect modes, there are Rabi oscillations between the microcavities. We develop a spectral analysis which permits us to compute the Rabi frequencies of these oscillations as well as the Q factor of the microcavities. We present a method allowing the computation of the coupling factor between localized modes

On the mechanism of oscillations in neutrophils

DEFF Research Database (Denmark)

Brasen, Jens Christian; Barington, Torben; Olsen, Lars Folke

2010-01-01

We have investigated the regulation of the oscillatory generation of H(2)O(2) and oscillations in shape and size in neutrophils in suspension. The oscillations are independent of cell density and hence do not represent a collective phenomena. Furthermore, the oscillations are independent...... of the external glucose concentration and the oscillations in H(2)O(2) production are 180 degrees out of phase with the oscillations in NAD(P)H. Cytochalasin B blocked the oscillations in shape and size whereas it increased the period of the oscillations in H(2)O(2) production. 1- and 2-butanol also blocked...... the oscillations in shape and size, but only 1-butanol inhibited the oscillations in H(2)O(2) production. We conjecture that the oscillations are likely to be due to feedback regulations in the signal transduction cascade involving phosphoinositide 3-kinases (PI3K). We have tested this using a simple mathematical...

Multi-year assimilation of IASI and MLS ozone retrievals: variability of tropospheric ozone over the tropics in response to ENSO

Science.gov (United States)

Peiro, Hélène; Emili, Emanuele; Cariolle, Daniel; Barret, Brice; Le Flochmoën, Eric

2018-05-01

The Infrared Atmospheric Sounder Instrument (IASI) allows global coverage with very high spatial resolution and its measurements are promising for long-term ozone monitoring. In this study, Microwave Limb Sounder (MLS) O3 profiles and IASI O3 partial columns (1013.25-345 hPa) are assimilated in a chemistry transport model to produce 6-hourly analyses of tropospheric ozone for 6 years (2008-2013). We have compared and evaluated the IASI-MLS analysis and the MLS analysis to assess the added value of IASI measurements. The global chemical transport model MOCAGE (MOdèle de Chimie Atmosphérique à Grande Echelle) has been used with a linear ozone chemistry scheme and meteorological forcing fields from ERA-Interim (ECMWF global reanalysis) with a horizontal resolution of 2° × 2° and 60 vertical levels. The MLS and IASI O3 retrievals have been assimilated with a 4-D variational algorithm to constrain stratospheric and tropospheric ozone respectively. The ozone analyses are validated against ozone soundings and tropospheric column ozone (TCO) from the OMI-MLS residual method. In addition, an Ozone ENSO Index (OEI) is computed from the analysis to validate the TCO variability during the ENSO events. We show that the assimilation of IASI reproduces the variability of tropospheric ozone well during the period under study. The variability deduced from the IASI-MLS analysis and the OMI-MLS measurements are similar for the period of study. The IASI-MLS analysis can reproduce the extreme oscillation of tropospheric ozone caused by ENSO events over the tropical Pacific Ocean, although a correction is required to reduce a constant bias present in the IASI-MLS analysis.

Quenching phenomena in natural circulation loop

International Nuclear Information System (INIS)

Umekawa, Hisashi; Ozawa, Mamoru; Ishida, Naoki

1995-01-01

Quenching phenomena has been investigated experimentally using circulation loop of liquid nitrogen. During the quenching under natural circulation, the heat transfer mode changes from film boiling to nucleate boiling, and at the same time flux changes with time depending on the vapor generation rate and related two-phase flow characteristics. Moreover, density wave oscillations occur under a certain operating condition, which is closely related to the dynamic behavior of the cooling curve. The experimental results indicates that the occurrence of the density wave oscillation induces the deterioration of effective cooling of the heat surface in the film and the transition boiling regions, which results in the decrease in the quenching velocity

Quenching phenomena in natural circulation loop

Energy Technology Data Exchange (ETDEWEB)

Umekawa, Hisashi; Ozawa, Mamoru [Kansai Univ., Osaka (Japan); Ishida, Naoki [Daihatsu Motor Company, Osaka (Japan)

1995-09-01

Quenching phenomena has been investigated experimentally using circulation loop of liquid nitrogen. During the quenching under natural circulation, the heat transfer mode changes from film boiling to nucleate boiling, and at the same time flux changes with time depending on the vapor generation rate and related two-phase flow characteristics. Moreover, density wave oscillations occur under a certain operating condition, which is closely related to the dynamic behavior of the cooling curve. The experimental results indicates that the occurrence of the density wave oscillation induces the deterioration of effective cooling of the heat surface in the film and the transition boiling regions, which results in the decrease in the quenching velocity.

Eventos de tiempo severo inducidos por el ENSO en la temporada invernal cubana

Directory of Open Access Journals (Sweden)

1998-01-01

THE CUBAN WINTER SEASON. The Cuban winter season frames the dry season of the year in the country, in which, differently from summer tropical systems, severe weather phenomena are hardly on record. However, in winter seasons under ENSO influence, meteorological systems are anomalously activated in latitudes farther south than normal. Severe weather events lasting from 24 to 48 hours are then relatively frequent and accounts for the formation of severe squall lines, intense rains, tornadoes, hail and coastal floods. These events cause death and great destruction, mainly in agriculture and the sugar cane industry. Climatologists recognize ENSO as the major cause of interannual climatic variability on the Planet. From this point of view, they describe and forecast ENSO seasonal effects as positive or negative deviations from normal meteorological variables such as precipitation and temperature. Nevertheless, a more detailed approach can only be achieved from the study of ENSO inducing synoptic systems, which cause severe weather. This becomes entirely necessary to design an Early Warning System for the interests of Civil Defense and economy. In the present paper the role of Subtropical Jet Stream is identified as the prime cause for the formation of severe weather events in Cuba. Besides, from the study of winter seasons with moderate or strong ENSO presence since 1957-58 through 1996-97, several synoptic patterns were obtained from surface and upper air charts, as well as their association with ENSO inducing severe weather events. Examples of impact of these events in the Country are shown. Using these techniques, an early forecast system used by Civil Defense was created.

Isotopic changes due to convective moistening of the lower troposphere associated with variations in the ENSO and IOD from 2005 to 2006

Directory of Open Access Journals (Sweden)

Jeonghoon Lee

2015-04-01

Full Text Available We use the tropospheric emission spectrometer measurements of the isotopic composition of water vapour (δD in the lower troposphere to examine how changes in the distribution of convection and precipitation control water vapour amount and its isotope over the Indian Ocean. Measurements of the outgoing longwave radiation and vertical velocity from NCEP/NCAR Reanalysis and cloud ice water content from the Microwave Limb Sounder show distinct variations in convection due to a phase shift of both El Niño – Southern Oscillation (ENSO and Indian Ocean Dipole (IOD. These variations in convection are associated with changes in precipitation and water amount over the Western Indian Ocean (WIO and Eastern Indian Ocean (EIO, depending on the phases of ENSO and/or the IOD. Over the EIO in 2006, induced by the interplay of both positive ENSO and IOD, it is drier and less isotopically depleted due to less frequent and/or weaker deep convective activity and subsequent precipitation compared to 2005. By contrast, over the WIO in 2006, an increase in water vapour and precipitation but little isotopic fractionation in water vapour of clear sky compared to 2005 is likely associated with an increase in both enhanced deep and shallow convection, caused by the positive IOD. Therefore, paleoarchives of water isotopes near Africa will be more difficult to relate to a single process because changes in convective activity result in changes in precipitation but do not have a significant impact on the isotopic composition of the source vapour based on this case analysis.

The role of the hydrological cycle on the temporal patterns of macroinvertebrate assemblages in an Andean foothill stream in Colombia

Directory of Open Access Journals (Sweden)

María I. Ríos-Pulgarín

2016-03-01

Full Text Available The seasonal and interannual changes in the structure, composition and functional feeding groups of the macroinvertebrate assemblage of the Guarinó River, a torrential system located in the Colombian Andean foothills, were examined in relation to the physical and chemical environmental changes associated with the hydrological cycle and the El Niño-Niña/Southern Oscillation (ENSO between 2007 and 2010. Benthic samples were collected at three sites in the lower sections of the river. A total of 127 taxa were collected in the study, with the total taxonomic richness per site ranging from 82 to 96 taxa and benthos density averaging 5.41 ind. m-2. The density showed a tendency to decrease in periods of maximum river level and flow, particularly during La Niña phenomena, and to increase in dry periods, especially in the third year (2009-2010 during El Niño phenomena. The presence and abundance of taxa, functional feeding groups and life habits were regulated by environmental parameters associated with hydrological variability, derived of ENSO phenomena, especially flow rate values. The assemblage showed high taxonomic and functional diversity, which is characteristic of ecosystems affected by recurrent hydrological disturbances, exhibiting differentiated responses based on adaptive strategies against the local hydrologic regime that allow fast recovery under conditions like ENSO phenomena. Such responses include composition changes according to adaptations to different hydrological scenarios, the predominance of generalist trophic guilds and taxa with plasticity in their habits and range of environmental tolerance.

Rhythmic components in renal autoregulation: Nonlinear modulation phenomena

International Nuclear Information System (INIS)

Pavlov, A.N.; Sosnovtseva, O.V.; Pavlova, O.N.; Mosekilde, E.; Holstein-Rathlou, N.-H.

2009-01-01

Autoregulation of nephron blood flow involves two oscillatory processes: the tubular-flow sensitive tubuloglomerular feedback (TGF) mechanism and the blood-pressure sensitive myogenic mechanism. Both act to regulate the diameter of the afferent arteriole, which carries blood to the nephron. In this paper, we apply wavelet analysis to time series of the proximal tubular pressure obtained from normotensive and hypertensive rats to study how the TGF-mediated oscillations modulate both the frequency and the amplitude of the myogenic oscillations. The tubular pressure oscillations are nearly periodic for normotensive rats, but irregular (or chaotic) for rats with hypertension. Modulation phenomena are clearly observed in both types of rats, but the effect is stronger in those with hypertension.

Reactor Neutrino Oscillations: KamLAND and KASKA

International Nuclear Information System (INIS)

Suekane, F.

2006-01-01

Nuclear reactors generate a huge number of low energy ν-bar e 's. The reactor neutrinos have been used to study properties of neutrinos since its discovery a half century ago. Recently, KamLAND group finally discovered reactor neutrino oscillation with average baseline 180 km. According to the 3 flavor scheme of standard theory and measured oscillation parameters so far, the reactor neutrino is expected to perform another type of small oscillation at a baseline 1.8 km. KASKA experiment is a project to detect this small oscillation and to measure the last neutrino mixing angle θ 13 by using the world most powerful reactor complex, Kashiwazaki-Kariwa nuclear power station. In this proceedings, phenomena of neutrino oscillation and the two reactor oscillation experiments, KamLAND and KASKA, are introduced

Changes in ENSO amplitude under climate warming and cooling

Science.gov (United States)

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

2018-05-01

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

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...

Nonlinear resonance in Duffing oscillator with fixed and integrative ...

Indian Academy of Sciences (India)

We study the nonlinear resonance, one of the fundamental phenomena in nonlinear oscillators, in a damped and periodically-driven Duffing oscillator with two types of time-delayed feedbacks, namely, fixed and integrative. Particularly, we analyse the effect of the time-delay parameter and the strength of the ...

Nonlinear resonance in Duffing oscillator with fixed and integrative ...

Indian Academy of Sciences (India)

2012-03-02

Mar 2, 2012 ... Abstract. We study the nonlinear resonance, one of the fundamental phenomena in nonlinear oscillators, in a damped and periodically-driven Duffing oscillator with two types of time-delayed feedbacks, namely, fixed and integrative. Particularly, we analyse the effect of the time-delay parameter α and the ...

Power oscillations in BWR reactors

International Nuclear Information System (INIS)

Espinosa P, G.

2002-01-01

One of the main problems in the operation of BWR type reactors is the instability in power that these could present. One type of oscillations and that is the objective of this work is the named density wave, which is attributed to the thermohydraulic processes that take place in the reactor core. From the beginnings of the development of BWR reactors, the stability of these has been an important aspect in their design, due to its possible consequences on the fuel integrity. The reactor core operates in two phase flow conditions and it is observed that under certain power and flow conditions, power instabilities appear. Studying this type of phenomena is complex, due to that a reactor core is constituted approximately by 27,000 fuel bars with different distributions of power and flow. The phenomena that cause the instability in BWR reactors continue being matter of scientific study. In the literature mainly in nuclear subject, it can be observed that exist different methods and approximations for studying this type of phenomena, nevertheless, their results are focused to establish safety limits in the reactor operation, instead of studying in depth of the knowledge about. Also in this line sense of the reactor data analysis, the oscillations characteristic frequencies are obtained for trying to establish if the power is growing or decreasing. In addition to that before mentioned in this paper it is presented a rigorous study applying the volumetric average method, for obtaining the vacuum waves propagation velocities and its possible connection with the power oscillations. (Author)

Density wave oscillations of a boiling natural circulation loop induced by flashing

Energy Technology Data Exchange (ETDEWEB)

Furuya, Masahiro; Inada, Fumio; Yasuo, Akira [Central Research Institute of Electric Power Industry, Tokyo (Japan)

1995-09-01

Experiments are conducted to investigate two-phase flow instabilities in a boiling natural circulation loop with a chimney due to flashing in the chimney at lower pressure. The test facility used in this experiment is designed to have non-dimensional values which are nearly equal to those of natural circulation BWR. Stability maps in reference to the heat flux, the inlet subcooling, the system pressure are presented. This instability is suggested to be density wave oscillations due to flashing in the chimney, and the differences from other phenomena such as flow pattern oscillations and geysering phenomena are discussed by investigating the dynamic characteristics, the oscillation period, and the transient flow pattern.

The influence of El Niño-Southern Oscillation (ENSO) cycles on wave-driven sea-floor sediment mobility along the central California continental margin

Science.gov (United States)

Storlazzi, Curt D.; Reid, Jane A.

2010-01-01

Ocean surface waves are the dominant temporally and spatially variable process influencing sea floor sediment resuspension along most continental shelves. Wave-induced sediment mobility on the continental shelf and upper continental slope off central California for different phases of El Niño-Southern Oscillation (ENSO) events was modeled using monthly statistics derived from more than 14 years of concurrent hourly oceanographic and meteorologic data as boundary input for the Delft SWAN wave model, gridded sea floor grain-size data from the usSEABED database, and regional bathymetry. Differences as small as 0.5 m in wave height, 1 s in wave period, and 10° in wave direction, in conjunction with the spatially heterogeneous unconsolidated sea-floor sedimentary cover, result in significant changes in the predicted mobility of continental shelf surficial sediment in the study area. El Niño events result in more frequent mobilization on the inner shelf in the summer and winter than during La Niña events and on the outer shelf and upper slope in the winter months, while La Niña events result in more frequent mobilization on the mid-shelf during spring and summer months than during El Niño events. The timing and patterns of seabed mobility are addressed in context of geologic and biologic processes. By understanding the spatial and temporal variability in the disturbance of the sea floor, scientists can better interpret sedimentary patterns and ecosystem structure, while providing managers and planners an understanding of natural impacts when considering the permitting of offshore activities that disturb the sea floor such as trawling, dredging, and the emplacement of sea-floor engineering structures.

Mixed-Mode Oscillations in Complex-Plasma Instabilities

International Nuclear Information System (INIS)

Mikikian, Maxime; Cavarroc, Marjorie; Coueedel, Lenaiec; Tessier, Yves; Boufendi, Laiefa

2008-01-01

Instabilities in dusty plasmas are frequent phenomena. We show that some instabilities can be described by mixed-mode oscillations often encountered in chemical systems or neuronal dynamics and studied through dynamical system theories. The time evolution of these instabilities is studied through the change in the associated waveform. Frequency and interspike interval are analyzed and compared to results obtained in other scientific fields concerned by mixed-mode oscillations

O impacto do ENSO e do dipolo do Atlântico no nordeste do Brasil

Directory of Open Access Journals (Sweden)

1998-01-01

íos, conduciendo a lluvias torrenciales con inundaciones en el Sudeste y Sur de Brasil. IMPACT OF ENSO AND ATLANTIC DIPOLE IN NORTH-EASTERN BRAZIL. A brief review of the El Niño/Southern Oscillation and Atlantic Dipole phenomena has been made with relation to their impacts on Brazil, especially in the northern North-east Brazil (NEB. Anomalies in rainfall are mainly caused by the SST variations in the tropical Atlantic and equatorial Pacific oceans. The atmospheric tropical response is shown as changes in the meridional (Hadley and zonal circulation (Walker with anomalous subsidence in the drought years and accelerated vertical motion during the years with excess rainfall. In the extra-tropical latitudes, blocking phenomenon associated with a train of Rossby waves from the Pacific changes the magnitude and trajectory of the jet streams in both hemispheres, also changing the trajectory and intensity of the cold front systems, leading to torrential rains with floods in Southeast and South of Brazil.

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

Science.gov (United States)

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

2016-12-01

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

Inter-decadal modulation of ENSO teleconnections to the Indian Ocean in a coupled model: Special emphasis on decay phase of El Niño

Science.gov (United States)

Chowdary, J. S.; Parekh, Anant; Gnanaseelan, C.; Sreenivas, P.

2014-01-01

Inter-decadal modulation of El Niño-Southern Oscillation (ENSO) teleconnections to tropical Indian Ocean (TIO) is investigated in the coupled general circulation model Climate Forecast System (CFS) using a hundred year integration. The model is able to capture the periodicity of El Niño variability, which is similar to that of the observations. The maximum TIO/north Indian Ocean (NIO) SST warming (during spring following the decay phase of El Niño) associated with El Niño is well captured by the model. Detailed analysis reveals that the surface heat flux variations mainly contribute to the El Niño forced TIO SST variations both in observations and model. However, spring warming is nearly stationary throughout the model integration period, indicating poor inter-decadal El Niño teleconnections. The observations on the other hand displayed maximum SST warming with strong seasonality from epoch to epoch. The model El Niño decay delayed by more than two seasons, results in persistent TIO/NIO SST warming through the following December unlike in the observations. The ocean wave adjustments and persistent westerly wind anomalies over the equatorial Pacific are responsible for late decay of El Niño in the model. Consistent late decay of El Niño, throughout the model integration period (low variance), is mainly responsible for the poor inter-decadal ENSO teleconnections to TIO/NIO. This study deciphers that the model needs to produce El Niño decay phase variability correctly to obtain decadal-modulations in ENSO teleconnection.

RELAP5-3D code validation for RBMK phenomena

International Nuclear Information System (INIS)

Fisher, J.E.

1999-01-01

The RELAP5-3D thermal-hydraulic code was assessed against Japanese Safety Experiment Loop (SEL) and Heat Transfer Loop (HTL) tests. These tests were chosen because the phenomena present are applicable to analyses of Russian RBMK reactor designs. The assessment cases included parallel channel flow fluctuation tests at reduced and normal water levels, a channel inlet pipe rupture test, and a high power, density wave oscillation test. The results showed that RELAP5-3D has the capability to adequately represent these RBMK-related phenomena

Quantum dynamical phenomena of independent electrons in semiconductor superlattices subject to a uniform electric field

International Nuclear Information System (INIS)

Bouchard, A.M.

1994-01-01

This report discusses the following topics: Bloch oscillations and other dynamical phenomena of electrons in semiconductor superlattices; solvable dynamical model of an electron in a one-dimensional aperiodic lattice subject to a uniform electric field; and quantum dynamical phenomena of electrons in aperiodic semiconductor superlattices

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

Directory of Open Access Journals (Sweden)

1998-01-01

types collected in the tropical Pacific are analyzed to assess the regional impacts of past (1972-1996 El Niño Southern Oscillation (ENSO events. Focus is made on the regional changes in sea-surface temperature and salinity. Commercial vessels were recently equipped with automated thermosalinographs which allows to monitor the location of salinity front along the Panama-Tahiti line, separating the Panama Gulf from the South Pacific water masses. The latitudinal change of the salinity front is well correlated with the latitudinal change of the ITCZ. Salinity distribution gives additional information on El-Niño development. How future real time SSS data might provide interesting information on the development of ENSO phenomenon in the eastern tropical Pacific area will be discussed.

Self-induced free surface oscillations caused by water jet

International Nuclear Information System (INIS)

Fukaya, M.; Madarame, H.; Okamoto, K.; Iida, M.; Someya, S.

1995-01-01

The interaction between the high speed flow and the free surfaces could induced surface oscillations. Recently, some kinds of self-induced free surface oscillations caused by water jet were discovered, e.g., a self-induced sloshing, 'Jet-Flutter' and a self-induced manometer oscillation. These oscillations have many different characteristics with each other. In this study, the similarities and differences of these oscillations are examined, and the geometrical effects on the phenomena are experimentally investigated. The self-induced sloshing and the Jet-Flutter have different dimensionless traveling times, which suggests a difference in the energy supply mechanism. When the distance between the inlet and the outlet is small in a vessel, the self-induced manometer oscillation could occur in the multi-free-surface system. (author)

Sub-seasonal prediction of significant wave heights over the Western Pacific and Indian Oceans, part II: The impact of ENSO and MJO

Science.gov (United States)

Shukla, Ravi P.; Kinter, James L.; Shin, Chul-Su

2018-03-01

This study evaluates the effect of El Niño and the Southern Oscillation (ENSO) and Madden Julian Oscillation (MJO) events on 14-day mean significant wave height (SWH) at 3 weeks lead time (Wk34) over the Western Pacific and Indian Oceans using the National Centers for Environmental Prediction (NCEP) Climate Forecast System, version 2 (CFSv2). The WAVEWATCH-3 (WW3) model is forced with daily 10m-winds predicted by a modified version of CFSv2 that is initialized with multiple ocean analyses in both January and May for 1979-2008. A significant anomaly correlation of predicted and observed SWH anomalies (SWHA) at Wk34 lead-time is found over portions of the domain, including the central western Pacific, South China Sea (SCS), Bay of Bengal (BOB) and southern Indian Ocean (IO) in January cases, and over BOB, equatorial western Pacific, the Maritime Continent and southern IO in May cases. The model successfully predicts almost all the important features of the observed composite SWHA during El Niño events in January, including negative SWHA in the central IO where westerly wind anomalies act on an easterly mean state, and positive SWHA over the southern Ocean (SO) where westerly wind anomalies act on a westerly mean state. The model successfully predicts the sign and magnitude of SWHA at Wk34 lead-time in May over the BOB and SCS in composites of combined phases-2-3 and phases-6-7 of MJO. The observed leading mode of SWHA in May and the third mode of SWHA in January are influenced by the combined effects of ENSO and MJO. Based on spatial and temporal correlations, the spatial patterns of SWHA in the model at Wk34 in both January and May are in good agreement with the observations over the equatorial western Pacific, equatorial and southern IO, and SO.

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

Phase locking between Josephson soliton oscillators

DEFF Research Database (Denmark)

Holst, T.; Hansen, Jørn Bindslev; Grønbech-Jensen, N.

1990-01-01

We report observations of phase-locking phenomena between two Josephson soliton (fluxon) oscillators biased in self-resonant modes. The locking strength was measured as a function of bias conditions. A frequency tunability of the phase-locked oscillators up to 7% at 10 GHz was observed. Two coupled...... perturbed sine-Gordon equations were derived from an equivalent circuit consisting of inductively coupled, nonlinear, lossy transmission lines. These equations were solved numerically to find the locking regions. Good qualitative agreement was found between the experimental results and the calculations...

Flashing oscillation in pool water

International Nuclear Information System (INIS)

Takamasa, Tomoji; Kondo, Koichi; Hazuku, Tatsuya

1996-01-01

This paper presents an experimental study of high-pressure saturated water discharging into the pool water. The purpose of the experiment is to clarify the phenomena that occur in blow-down of high-pressure saturated water from the pressure vessel into the water-filled containment in the case of a wall-crack accident or a LOCA in an advanced reactor. The results revealed that a flashing oscillation (FO) occurs when high-pressure saturated water discharges into the pool water, under specified experimental settings. The range of the flashing oscillates between a point very close to and some distance from the vent hole. The pressures in the vent tube and pool water vary according to the flashing oscillation. The pressure oscillation and frequency of flashing position might be caused by the balancing action between the supply of saturated water, flashing at the control volume and its condensation on the steam-water interface. A linear analysis was conducted using a spherical flashing bubble model. The period of the flashing oscillation in the experiments can be explained by theoretical analysis

Paleoclimate Records from New Zealand Maar Lakes, Insights into ENSO Teleconnections and Climatic Events in the South (West) Pacific.

Science.gov (United States)

Shulmeister, J.; Nobes, D. C.; Striewski, B.

2008-05-01

The maar craters of the New Zealand Auckland Volcanic Field (36.5°S, 174.5°E) contain some of the highest resolution late-Quaternary paleoclimate records in the Southern Hemisphere. Here we integrate laminae count results from recent drilling in the Hopua Crater with existing records from the nearby Onepoto Crater (Pepper et al., 2004). In total these records cover many thousands of years between the onset of the last glaciation maximum and the early mid-Holocene. The cores are strongly laminated. Individual laminae in both craters are very fine (sub-mm to mm scale) and form couplets which comprise a darker mineralogenic rich layer and a lighter diatomaceous layer. In places these couplets are annual, and may reflect seasonal algal blooms, but in other sections of the record, notably through the late-Glacial and Holocene, the couplets are deposited at inter-annual time scales. Spectral analyses of couplet thickness counts using a fast Fourier transform (FFT) with 64 to 256-year running windows, and a 50 per cent overlap indicate strong spectral power during the LGM and markedly weaker power during both the deglaciation and early Holocene. In fact there is no spectral strength for most of these periods. Three brief (centennial duration) events punctuate this extended period of low spectral power. These occur at c. 16 ka, c. 14.8 ka and during the early Holocene. They display spectral power in the 5-7yr ENSO window and also at longer time intervals that may be consistent with the Pacific Decadal Oscillation. We infer the local switching on (or up) of ENSO and PDO teleconnections and suspect these are embedded in circum-polar circulation changes. In addition to these spectral power episodes, there is a general increase in the number of couplet cycles per century between the deglaciation and the early mid-Holocene. This matches observations from Equador and Peru and suggests that trans-Pacific ENSO responses are in phase between western tropical South America and New

Seasonality in ENSO-related precipitation, river discharges, soil moisture, and vegetation index in Colombia

Science.gov (United States)

Poveda, GermáN.; Jaramillo, Alvaro; Gil, Marta MaríA.; Quiceno, Natalia; Mantilla, Ricardo I.

2001-08-01

An analysis of hydrologic variability in Colombia shows different seasonal effects associated with El Niño/Southern Oscillation (ENSO) phenomenon. Spectral and cross-correlation analyses are developed between climatic indices of the tropical Pacific Ocean and the annual cycle of Colombia's hydrology: precipitation, river flows, soil moisture, and the Normalized Difference Vegetation Index (NDVI). Our findings indicate stronger anomalies during December-February and weaker during March-May. The effects of ENSO are stronger for streamflow than for precipitation, owing to concomitant effects on soil moisture and evapotranspiration. We studied time variability of 10-day average volumetric soil moisture, collected at the tropical Andes of central Colombia at depths of 20 and 40 cm, in coffee growing areas characterized by shading vegetation ("shaded coffee"), forest, and sunlit coffee. The annual and interannual variability of soil moisture are highly intertwined for the period 1997-1999, during strong El Niño and La Niña events. Soil moisture exhibited greater negative anomalies during 1997-1998 El Niño, being strongest during the two dry seasons that normally occur in central Colombia. Soil moisture deficits were more drastic at zones covered by sunlit coffee than at those covered by forest and shaded coffee. Soil moisture responds to wetter than normal precipitation conditions during La Niña 1998-1999, reaching maximum levels throughout that period. The probability density function of soil moisture records is highly skewed and exhibits different kinds of multimodality depending upon land cover type. NDVI exhibits strong negative anomalies throughout the year during El Niños, in particular during September-November (year 0) and June-August (year 0). The strong negative relation between NDVI and El Niño has enormous implications for carbon, water, and energy budgets over the region, including the tropical Andes and Amazon River basin.

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

Directory of Open Access Journals (Sweden)

J. C. Currie

2013-10-01

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

Understanding oscillatory phenomena in molecular hydrogen generation via sodium borohydride hydrolysis.

Science.gov (United States)

Budroni, M A; Biosa, E; Garroni, S; Mulas, G R C; Marchettini, N; Culeddu, N; Rustici, M

2013-11-14

The hydrolysis of borohydride salts represents one of the most promising processes for the generation of high purity molecular hydrogen under mild conditions. In this work we show that the sodium borohydride hydrolysis exhibits a fingerprinting periodic oscillatory transient in the hydrogen flow over a wide range of experimental conditions. We disproved the possibility that flow oscillations are driven by supersaturation phenomena of gaseous bubbles in the reactive mixture or by a nonlinear thermal feedback according to a thermokinetic model. Our experimental results indicate that the NaBH4 hydrolysis is a spontaneous inorganic oscillator, in which the hydrogen flow oscillations are coupled to an "oscillophor" in the reactive solution. The discovery of this original oscillator paves the way for a new class of chemical oscillators, with fundamental implications not only for testing the general theory on oscillations, but also with a view to chemical control of borohydride systems used as a source of hydrogen based green fuel.

El Nino, La Nina and the Colombian hydrology prediction and forecast

International Nuclear Information System (INIS)

Poveda J, G.; Mesa S, O.J.

1995-01-01

The climatic phenomenon known as El Nino-Southern Oscillation (ENSO) Phenomenon has two phases: El Nino (Warm Phase) and La Nina (Cold phase). Both phases (Warm and cold) insult the Earth Planet hydrology and climatology and particularly the South America tropical zone, something which includes Colombia. This oscillation (Warm and cold) occurs in monthly time scale to multi - annual (until 6 years) time scale. As a rule, El Nino produces stronger and extended dry periods, while La Nina increases rains frequency and produces maximum wealth in water currents. A quantitative analysis of both phases (warm and cold) influence in Colombian rivers wealth measured in 50 different stations is presented. Also the frequency histograms, the average and the typical deviation of wealth monthly average for El Nino years and La Nina years, as well as for the evaluated total period are presented. With the objective of confirming the strong influence that exercise the oceanic- atmospherical phenomena that occur in South Pacific Ocean on Colombian hydrology, correlation analysis with Southern Oscillation Index (SOI) and temperatures variation on Indian and Pacific Ocean is presented. The topic ENSO phenomenon Predictions and Forecasts with relation to planning of hydraulics resources managing projects at Colombia is discussed

Tree Carbohydrate Dynamics Across a Rainfall Gradient in Panama During the 2016 ENSO

Science.gov (United States)

Dickman, L. T.; Xu, C.; Behar, H.; McDowell, N.

2017-12-01

Non-structural carbohydrates (NSC) provide a measure of the carbon supply available to support respiration, growth, and defense. Support for a role of carbon starvation - or depletion of NSC stores - in drought induced tree mortality is varied without consensus for the tropics. The 2016 ENSO drought provided a unique opportunity to capture drought impacts on tropical forest carbohydrate dynamics. To quantify these impacts, we collected monthly NSC samples across a rainfall gradient in Panama for the duration of the ENSO. We observed high variability in foliar NSC among species within sites. Foliage contained very little starch, indicating that total NSC dynamics are driven by soluble sugars. Foliar NSC depletion did not progress with drought duration as predicted, but showed little variation over course of the ENSO. Foliar NSC did, however, increase with rainfall, suggesting NSC depletion may occur with longer-term drought. These results suggest that, while short-term droughts like the 2016 ENSO may not have a significant impact on carbon dynamics, we may observe greater impacts as drought progresses over longer timescales. These results will be used to evaluate whether the current implementation of carbon starvation in climate models are capturing observed trends in tropical forest carbon allocation and mortality, and to tune model parameters for improved predictive capability.

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

Science.gov (United States)

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

2018-05-01

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

'Oscillator-wave' model: properties and heuristic instances

International Nuclear Information System (INIS)

Damgov, Vladimir; Trenchev, Plamen; Sheiretsky, Kostadin

2003-01-01

The article considers a generalized model of an oscillator, subjected to the influence of an external wave. It is shown that the systems of diverse physical background, which this model encompasses by their nature, should belong to the broader, proposed in previous works class of 'kick-excited self-adaptive dynamical systems'. The theoretical treatment includes an analytic approach to the conditions for emergence of small and large amplitudes, i.e. weak and strong non-linearity of the system. Derived also are generalized conditions for the transition of systems of this 'oscillator-wave' type to non-regular and chaotic behaviour. For the purpose of demonstrating the heuristic properties of the generalized oscillator-wave model from this point of view are considered the relevant systems and phenomena of the quantized cyclotron resonance and the megaquantum resonance-wave model of the Solar System. We point to a number of other natural and scientific phenomena, which can be effectively analyzed from the point of view of the developed approach. In particular we stress on the possibility for development and the wide applicability of specific wave influences, for example for the improvement and the speeding up of technological processes

Forced convective boiling of water inside helically coiled tube. Characteristics of oscillation of dryout point

International Nuclear Information System (INIS)

Nagai, Niro; Sugiyama, Kenta; Takeuchi, Masanori; Yoshikawa, Shinji; Yamamoto, Fujio

2006-01-01

The helically coiled tube of heat exchanger is used for the evaporator of prototype fast breeder reactor 'Monju'. This paper aims at the grasp of two-phase flow phenomena of forced convective boiling of water inside helical coiled tube, especially focusing on oscillation phenomena of dryout point. A glass-made helically coiled tube was used to observe the inside water boiling behavior flowing upward, which was heated by high temperature oil outside the tube. This oil was also circulated through a glass made tank to provide the heat source for water evaporation. The criterion for oscillation of dryout point was found to be a function of inlet liquid velocity and hot oil temperature. The observation results suggest the mechanism of dryout point oscillation mainly consists of intensive nucleate boiling near the dryout point and evaporation of thin liquid film flowing along the helical tube. In addition, the oscillation characteristics were experimentally confirmed. As inlet liquid velocity increases, oscillation amplitude also increases but oscillation cycle does not change so much. As hot oil temperature increases, oscillation amplitude and cycle gradually decreases. (author)

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

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.

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...... (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......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...

Quantum coherence phenomena in semiconductor quantum dots: quantum interference, decoherence and Rabi oscillation

International Nuclear Information System (INIS)

Htoon, H.; Shih, C.K.; Takagahara, T.

2003-01-01

We performed extensive studies on quantum decoherence processes of excitons trapped in the various excited states of SAQDs. Energy level structure and dephasing times of excited states were first determined by conducting photoluminescence excitation spectroscopy and wave-packet interferometry on a large number of individual SAQDs. This large statistical basis allows us to extract the correlation between the energy level structure and dephasing times. The major decoherence mechanisms and their active regime were identified from this correlation. A significant suppression of decoherence was also observed in some of the energetically isolated excited states, providing an experimental evidence for the theoretical prediction, known as 'phonon bottleneck effect'. Furthermore, we observed the direct experimental evidence of Rabi oscillation in these excited states with long decoherence times. In addition, a new type of quantum interference (QI) phenomenon was discovered in the wave-packet interferometry experiments performed in the strong excitation regime where the non-linear effects of Rabi oscillation become important. Detailed theoretical investigations attribute this phenomenon to the coherent dynamics resulting from the interplay of Rabi oscillation and QI

Synchronization as Aggregation: Cluster Kinetics of Pulse-Coupled Oscillators.

Science.gov (United States)

O'Keeffe, Kevin P; Krapivsky, P L; Strogatz, Steven H

2015-08-07

We consider models of identical pulse-coupled oscillators with global interactions. Previous work showed that under certain conditions such systems always end up in sync, but did not quantify how small clusters of synchronized oscillators progressively coalesce into larger ones. Using tools from the study of aggregation phenomena, we obtain exact results for the time-dependent distribution of cluster sizes as the system evolves from disorder to synchrony.

Mid-late Holocene changes in the El Niño Southern Oscillation and Hadley Cell intensity; their effect on sea-surface conditions in the mid-latitude southeast Pacific Ocean (41°S)

OpenAIRE

Verleye, T.

2010-01-01

The study focuses on the observed effects of changes in the El Niño Southern Oscillation (ENSO) and Hadley Cell intensity on sea-surface water conditions in the SE Pacific (41°S; Site ODP1233) during the last 8.000 years. Recent studies suggest that periods characterised by a negative Southern Oscillation Index (SOI; El Niño) cause positive precipitation anomalies during austral winter (and annually) in Mid-South Chile, while austral summer periods are rather drier. This because El Niño weake...

Nonstationary behavior in a delayed feedback traveling wave tube folded waveguide oscillator

International Nuclear Information System (INIS)

Ryskin, N.M.; Titov, V.N.; Han, S.T.; So, J.K.; Jang, K.H.; Kang, Y.B.; Park, G.S.

2004-01-01

Folded waveguide traveling-wave tubes (FW TWT) are among the most promising candidates for powerful compact amplifiers and oscillators in millimeter and submillimeter wave bands. In this paper, the nonstationary behavior of a FW TWT oscillator with delayed feedback is investigated. Starting conditions of the oscillations are derived analytically. Results of numerical simulation of single-frequency, self-modulation (multifrequency) and chaotic generation regimes are presented. Mode competition phenomena, multistability and hysteresis are discussed

Design of Self-Oscillating Gels and Application to Biomimetic Actuators

Directory of Open Access Journals (Sweden)

Ryo Yoshida

2010-03-01

Full Text Available As a novel biomimetic polymer, we have developed polymer gels with an autonomous self-oscillating function. This was achieved by utilizing oscillating chemical reactions, called the Belousov-Zhabotinsky (BZ reaction, which is recognized as a chemical model for understanding several autonomous phenomena in biological systems. Under the coexistence of the reactants, the polymer gel undergoes spontaneous swelling-deswelling changes without any on-off switching by external stimuli. In this review, our recent studies on the self-oscillating polymer gels and application to biomimetic actuators are summarized.

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

Science.gov (United States)

Yudawati Cahyarini, Sri; Henrizan, Marfasran

2018-02-01

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

The complex influence of ENSO on droughts in Ecuador

KAUST Repository

Vicente-Serrano, S. M.; Aguilar, E.; Martí nez, R.; Martí n-Herná ndez, N.; Azorin-Molina, C.; Sanchez-Lorenzo, A.; El Kenawy, Ahmed M.; Tomá s-Burguera, M.; Moran-Tejeda, E.; Ló pez-Moreno, J. I.; Revuelto, J.; Beguerí a, S.; Nieto, J. J.; Drumond, A.; Gimeno, L.; Nieto, R.

2016-01-01

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

The effect of El-Niño on South Asian Monsoon and agricultural production

Science.gov (United States)

Mukherjee, A.

2015-12-01

Mukherjee A, Wang S.Y.Abstract:The South Asian Monsoon has a prominent and significant impact on South Asian countries like India, Bangladesh, Nepal, Pakistan, Sri Lanka and it is one of the most studied phenomena in the world. The monsoon is historically known to be influenced by El Niño-Southern Oscillation (ENSO). The inter-annual and inter-decadal variability of seasonal precipitation over India strongly depends upon the ENSO phasing. The average southwest monsoon rainfall received during the years with El Niño was found to be less compared to normal years and the average rainfall during the northeast monsoon is higher in coastal Andhra Pradesh. ENSO is anti-correlated with Indian summer monsoon (ISM). The last prominent effect of ENSO on India's monsoon occurred in 2009 with 23% reduction in annual rainfall, reducing summer sown crops such as rice, sugar cane etc. and pushing up food prices. Climatic resources endowment plays a major role in planning agricultural production in tropical and sub-tropical environment especially under rain-fed agriculture, and so contingent crop planning drawn on this relationship would help to mitigate the effects of ENSO episodes in the region. The unexplored area in this domain of research is the changes in the frequency and intensity of ENSO due to global warming and its impact on ENSO prediction and agricultural management practices. We analyze the last 30 years datasets of Pacific SST, and precipitation and air temperature over Southeast Asia to examine the evolution of ENSO teleconnections with ISM, as well as making estimates of drought indices such as Palmer Drought Severity Index. This research can lead toward better crop management strategies in the South Asian monsoon region.

Three-Dimensional Dirac Oscillator with Minimal Length: Novel Phenomena for Quantized Energy

Directory of Open Access Journals (Sweden)

Malika Betrouche

2013-01-01

Full Text Available We study quantum features of the Dirac oscillator under the condition that the position and the momentum operators obey generalized commutationrelations that lead to the appearance of minimal length with the order of the Planck length, ∆xmin=ℏ3β+β′, where β and β′ are two positive small parameters. Wave functions of the system and the corresponding energy spectrum are derived rigorously. The presence of the minimal length accompanies a quadratic dependence of the energy spectrum on quantum number n, implying the property of hard confinement of the system. It is shown that the infinite degeneracy of energy levels appearing in the usual Dirac oscillator is vanished by the presence of the minimal length so long as β≠0. Not only in the nonrelativistic limit but also in the limit of the standard case (β=β′=0, our results reduce to well known usual ones.

El Niño revisited: the influence of El Niño Southern Oscillation on the world's largest tuna fisheries.

Science.gov (United States)

Receveur, A.; Simon, N.; Menkes, C.; Tremblay-Boyer, L.; Senina, I.; Lehodey, P.

2016-12-01

El Niño Southern Oscillation (ENSO) drives global climate on inter-annual scales and impacts the ecosystem structure in the warm-pool and cold-tongue of the Pacific Ocean. During the El Niño phase of ENSO, the warm-pool can stretch from the western equatorial Pacific to the eastern Pacific allowing species associated with the warm-pool to correspondingly spread eastwards. Conversely, during the la Niña phase the warm-pool is pushed to the far western equatorial Pacific by the cold-tongue allowing species associated with this ecosystem to spread westwards. Consequently, ENSO dynamics are likely to be critical for understanding the ecological processes supporting fisheries in the equatorial Pacific Ocean. Surface inhabiting tuna, such as skipjack, are thought to track the convergence of the warm-pool and cold-tongue with fishing vessels tracking this tuna behavior. Given the reliance of Pacific Island economies on tuna fisheries, knowing when tunas are more likely to be present in high density in their territorial waters is beneficial for harvest control policies such as effort trading between nations. We use the SEAPODYM model to investigate the response of bigeye and skipjack tuna species to the phases of ENSO. SEAPODYM is an age structured model that integrates fisheries dependent and independent data with environmental data. We analyze the outputs of SEAPODYM using wavelets to assess the impact of environmental and biotic variables on the abundance and distribution of adult and juvenile age classes and to study time series cycle and temporal lags to ENSO. The main result for skipjack is the eastward or westward movement of the biomass pattern which is significantly lagged with the warm pool ENSO displacement. That lag ranges from 8 months for juvenile up to 18 months for adults. Such delayed response, can be traced in the model. Higher temperature in the central Pacific during El Niño leads to better recruitment which leads to lagged increase of juvenile

ENSO Simulation in CGCMs and the Associated Errors in Atmospheric Response

International Nuclear Information System (INIS)

AchutaRao, K.; Sperber, K.R.

2000-01-01

Tropical Pacific variability, and specifically the simulation of ENSO in coupled ocean-atmosphere general circulation models (CGCMs) has previously been assessed in many studies (McCreary and Anderson[1991], Neelin et al.[1992], Mechoso et al.[1995], Latif et al.[2000], and Davey et al.[2000]). These studies have concentrated on SST variations in the tropical Pacific, and discussions of the atmospheric response have been limited to east-west movements of the convergence zone. In this paper we discuss the large-scale atmospheric response to simulated ENSO events. Control simulations from 17 global CGCMs from CMIP (Meehl et al.[2000]) are studied. The web site http:// www-pcmdi.llnl.gov/cmip/modeldoc provides documentation of the configurations of the models

Synchronization of an ensemble of oscillators regulated by their spatial movement.

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Sarkar, Sumantra; Parmananda, P

2010-12-01

Synchronization for a collection of oscillators residing in a finite two dimensional plane is explored. The coupling between any two oscillators in this array is unidirectional, viz., master-slave configuration. Initially the oscillators are distributed randomly in space and their autonomous time-periods follow a Gaussian distribution. The duty cycles of these oscillators, which work under an on-off scenario, are normally distributed as well. It is realized that random hopping of oscillators is a necessary condition for observing global synchronization in this ensemble of oscillators. Global synchronization in the context of the present work is defined as the state in which all the oscillators are rendered identical. Furthermore, there exists an optimal amplitude of random hopping for which the attainment of this global synchronization is the fastest. The present work is deemed to be of relevance to the synchronization phenomena exhibited by pulse coupled oscillators such as a collection of fireflies. © 2010 American Institute of Physics.

Do our reconstructions of ENSO have too much low-frequency variability?

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Loope, G. R.; Overpeck, J. T.

2017-12-01

Reconstructing the spectrum of Pacific SST variability has proven to be difficult both because of complications with proxy systems such as tree rings and the relatively small number of records from the tropical Pacific. We show that the small number of long coral δ18O and Sr/Ca records has caused a bias towards having too much low-frequency variability in PCR, CPS, and RegEM reconstructions of Pacific variability. This occurs because the individual coral records used in the reconstructions have redder spectra than the shared signal (e.g. ENSO). This causes some of the unshared, low-frequency signal from local climate, salinity and possibly coral biology to bleed into the reconstruction. With enough chronologies in a reconstruction, this unshared noise cancels out but the problem is exacerbated in our longest reconstructions where fewer records are available. Coral proxies tend to have more low-frequency variability than SST observations so this problem is smaller but can still be seen in pseudoproxy experiments using observations and reanalysis data. The identification of this low-frequency bias in coral reconstructions helps bring the spectra of ENSO reconstructions back into line with both models and observations. Although our analysis is mostly constrained to the 20th century due to lack of sufficient data, we expect that as more long chronologies are developed, the low-frequency signal in ENSO reconstructions will be greatly reduced.

ANALISIS CURAH HUJAN PANTAI BARAT SUMATERA BAGIAN UTARA PERIODE 1994-2007

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Indra Gustari

2009-07-01

Full Text Available Dari data curah hujan di pantai barat Sumatera bagian utara dilakukan analisis spektrum daya untuk mengetahui pola curah hujan di daerah tersebut, selanjut dilihat hubungannya dengan intensitas monsun,  Indian Ocean Dipole Mode (IODM dan El-Nino Southern Oscillation (ENSO. Hasil analisis menunjukkan bahwa pola curah hujan di pantai barat Sumatera bagian utara memiliki dua puncak dan sangat dipengaruhi oleh faktor cuaca dengan dengan osilasi satu tahunan (annual oscillation, dan setengah tahunan (semi-annual oscillation dan ditemukan hubungan yang kuat antara variabilitas monsun dan IODM. Pola hujan didaerah ini tidak memperlihatkan pengaruh ENSO.   The data of Rainfall in the west coast of northern Sumatera were analyzed through power spectrum analyzer to find out the rainfall pattern in that area and to look at the relationship between rainfall pattern and monsoon intensity, Indian Ocean Dipole Mode (IODM and El-Nino Southern Oscillation (ENSO. The result of this analysis shows that the main rainfall pattern in the west coast of northern Sumatera has two peaks and is very much influenced by the factor of weather with annual oscillation and semi-annual oscillation, there is a strong relationship between monsoon variability and IODM, and the influence of ENSO on the rainfall in this region is not significant.

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

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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).

Emergence of a super-synchronized mobbing state in a large population of coupled chemical oscillators

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Ghoshal, Gourab; Muñuzuri, Alberto P.; Pérez-Mercader, Juan

2016-01-01

Oscillatory phenomena are ubiquitous in Nature. The ability of a large population of coupled oscillators to synchronize constitutes an important mechanism to express information and establish communication among members. To understand such phenomena, models and experimental realizations of globally coupled oscillators have proven to be invaluable in settings as varied as chemical, biological and physical systems. A variety of rich dynamical behavior has been uncovered, although usually in the context of a single state of synchronization or lack thereof. Through the experimental and numerical study of a large population of discrete chemical oscillators, here we report on the unexpected discovery of a new phenomenon revealing the existence of dynamically distinct synchronized states reflecting different degrees of communication. Specifically, we discover a novel large-amplitude super-synchronized state separated from the conventionally reported synchronized and quiescent states through an unusual sharp jump transition when sampling the strong coupling limit. Our results assume significance for further elucidating globally coherent phenomena, such as in neuropathologies, bacterial cell colonies, social systems and semiconductor lasers.

Influence of ENSO on Regional Indian Summer Monsoon Precipitation—Local Atmospheric Influences or Remote Influence from Pacific

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Indrani Roy

2016-02-01

Full Text Available Using CMIP5 model outputs in different El Niño-Southern Oscillation (ENSO phases, this work investigates the indicator that could be used as an Index to characterise regional Indian Summer Monsoon (ISM precipitation. Dividing the Indian subcontinent into five arbitrarily chosen regions, viz. Central North East (CNE (18°N–31°N, 86°E–75°E, Hilly (H (28°N–38°N, 85°E–70°E, North West (NW (21°N–31°N, 79°E–67°E, North East (NE (21°N–31°N, 86°E–97°E and Southern India (S (18°N–7°N, 73°E–85°E, local wind field and remote influences from the tropical Pacific are considered to improve understanding of regional monsoon rainfall. Results are also compared with observations/reanalysis data to pinpoint areas of shortcomings and agreements. Model results suggest that regional wind velocity, viz. meridional wind component (V at 850 mb level (V850 and zonal component at 200 mb (U200 and 850 mb (U850 can yield better estimation of local precipitation in regions CNE, H and NW, agreeing well with earlier proposed monsoon Indices. Such observations are independent of different subcategories of ENSO phases and models show good correspondence with observations. Analyses with V at 200 mb (V200 indicate circulation of the upper branch of Hadley cells in regions CNE and S, though suggest the best agreement among models in comparison with other fields, but there are some deviations from observations, indicating a missing mechanism in the models. Using models, this study identified the best parameter in different regions that could be used for the regional monsoon Index, irrespective of various ENSO subcategories; for CNE it is the U200, for H it is U200 and U850, and for NW it is U850. The current analysis, however, fails to indicate anything clearly about the NE region. When focusing on the remote influence from the eastern Pacific region, it is found that atmospheric contribution to regional ISM precipitation fails to indicate

Precipitation response to the current ENSO variability in a warming world

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

2013-12-01

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

Equatorial Precession Drove Mid-Latitude Changes in ENSO-Scale Variation in the Earliest Miocene

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Fox, B.; D'Andrea, W. J.; Lee, D. E.; Wilson, G. S.

2014-12-01

Foulden Maar is an annually laminated lacustrine diatomite deposit from the South Island of New Zealand. The deposit was laid down over ~100 kyr of the latest Oligocene and earliest Miocene, during the peak and deglaciation phase of the Mi-1 Antarctic glaciation event. At this time, New Zealand was located at approximately the same latitude as today (~45°S). Evidence from organic geochemical proxies (δD, δ13C) and physical properties (density, colour) indicates the presence of an 11-kyr cycle at the site. Although it is known that 11-kyr insolation (half-precession) cycles occur between the Tropics, this cycle is rarely seen in sedimentary archives deposited outside the immediate vicinity of the Equator. Records from Foulden Maar correlate well with the amplitude and phase of the modelled equatorial half-precession cycle for the earliest Miocene. High-resolution (50 µm) colour intensity measurements and lamina thickness measurements both indicate the presence of significant ENSO-like (2-8 year) variation in the Foulden Maar sediments. Early results from targeted lamina thickness measurements suggest that ENSO-band variation is modulated by the 11-kyr cycle, with power in the ENSO band increasing during periods of increased insolation at the Equator. This implies that equatorial half-precession had a significant effect on ENSO-like variation in the early Miocene, and that this effect was felt as far afield as the mid-latitudes of the Southern Hemisphere.

Influence of surface nudging on climatological mean and ENSO feedbacks in a coupled model

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Zhu, Jieshun; Kumar, Arun

2018-01-01

Studies have suggested that surface nudging could be an efficient way to reconstruct the subsurface ocean variability, and thus a useful method for initializing climate predictions (e.g., seasonal and decadal predictions). Surface nudging is also the basis for climate models with flux adjustments. In this study, however, some negative aspects of surface nudging on climate simulations in a coupled model are identified. Specifically, a low-resolution version of the NCEP Climate Forecast System, version 2 (CFSv2L) is used to examine the influence of nudging on simulations of climatological mean and on the coupled feedbacks during ENSO. The effect on ENSO feedbacks is diagnosed following a heat budget analysis of mixed layer temperature anomalies. Diagnostics of the climatological mean state indicates that, even though SST biases in all ocean basins, as expected, are eliminated, the fidelity of climatological precipitation, surface winds and subsurface temperature (or the thermocline depth) could be highly ocean basin dependent. This is exemplified by improvements in the climatology of these variables in the tropical Atlantic, but degradations in the tropical Pacific. Furthermore, surface nudging also distorts the dynamical feedbacks during ENSO. For example, while the thermocline feedback played a critical role during the evolution of ENSO in a free simulation, it only played a minor role in the nudged simulation. These results imply that, even though the simulation of surface temperature could be improved in a climate model with surface nudging, the physics behind might be unrealistic.

Modelling of density limit phenomena in toroidal helical plasmas

International Nuclear Information System (INIS)

Itoh, Kimitaka; Itoh, Sanae-I.

2001-01-01

The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the Wendelstein 7-AS (W7-AS) stellarator. (author)

Modelling of density limit phenomena in toroidal helical plasmas

International Nuclear Information System (INIS)

Itoh, K.; Itoh, S.-I.

2000-03-01

The physics of density limit phenomena in toroidal helical plasmas based on an analytic point model of toroidal plasmas is discussed. The combined mechanism of the transport and radiation loss of energy is analyzed, and the achievable density is derived. A scaling law of the density limit is discussed. The dependence of the critical density on the heating power, magnetic field, plasma size and safety factor in the case of L-mode energy confinement is explained. The dynamic evolution of the plasma energy and radiation loss is discussed. Assuming a simple model of density evolution, of a sudden loss of density if the temperature becomes lower than critical value, then a limit cycle oscillation is shown to occur. A condition that divides the limit cycle oscillation and the complete radiation collapse is discussed. This model seems to explain the density limit oscillation that has been observed on the W7-AS stellarator. (author)

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

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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

Roles of tropical SST patterns during two types of ENSO in modulating wintertime rainfall over southern China

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Xu, Kang; Huang, Qing-Lan; Tam, Chi-Yung; Wang, Weiqiang; Chen, Sheng; Zhu, Congwen

2018-03-01

The impacts of the eastern-Pacific (EP) and central-Pacific (CP) El Niño-Southern Oscillation (ENSO) on the southern China wintertime rainfall (SCWR) have been investigated. Results show that wintertime rainfall over most stations in southern China is enhanced (suppressed) during the EP (CP) El Niño, which are attributed to different atmospheric responses in the western North Pacific (WNP) and South China Sea (SCS) during two types of ENSO. When EP El Niño occurs, an anomalous low-level anticyclone is present over WNP/the Philippines region, resulting in stronger-than-normal southwesterlies over SCS. Such a wind branch acts to suppress East Asian winter monsoon (EAWM) and enhance moisture supply, implying surplus SCWR. During CP El Niño, however, anomalous sinking and low-level anticyclonic flow are found to cover a broad region in SCS. These circulation features are associated with moisture divergence over the northern part of SCS and suppressed SCWR. General circulation model experiments have also been conducted to study influence of various tropical sea surface temperature (SST) patterns on the EAWM atmospheric circulation. For EP El Niño, formation of anomalous low-level WNP anticyclone is jointly attributed to positive/negative SST anomalies (SSTA) over the central-to-eastern/ western equatorial Pacific. However, both positive and negative CP Niño-related-SSTA, located respectively over the central Pacific and WNP/SCS, offset each other and contribute a weak but broad-scale anticyclone centered at SCS. These results suggest that, besides the vital role of SST warming, SST cooling over SCS/WNP during two types of El Niño should be considered carefully for understanding the El Niño-EAWM relationship.

Nonlinear dynamics of drops and bubbles and chaotic phenomena

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Trinh, Eugene H.; Leal, L. G.; Feng, Z. C.; Holt, R. G.

1994-01-01

Nonlinear phenomena associated with the dynamics of free drops and bubbles are investigated analytically, numerically and experimentally. Although newly developed levitation and measurement techniques have been implemented, the full experimental validation of theoretical predictions has been hindered by interfering artifacts associated with levitation in the Earth gravitational field. The low gravity environment of orbital space flight has been shown to provide a more quiescent environment which can be utilized to better match the idealized theoretical conditions. The research effort described in this paper is a closely coupled collaboration between predictive and guiding theoretical activities and a unique experimental program involving the ultrasonic and electrostatic levitation of single droplets and bubbles. The goal is to develop and to validate methods based on nonlinear dynamics for the understanding of the large amplitude oscillatory response of single drops and bubbles to both isotropic and asymmetric pressure stimuli. The first specific area on interest has been the resonant coupling between volume and shape oscillatory modes isolated gas or vapor bubbles in a liquid host. The result of multiple time-scale asymptotic treatment, combined with domain perturbation and bifurcation methods, has been the prediction of resonant and near-resonant coupling between volume and shape modes leading to stable as well as chaotic oscillations. Experimental investigations of the large amplitude shape oscillation modes of centimeter-size single bubbles trapped in water at 1 G and under reduced hydrostatic pressure, have suggested the possibility of a low gravity experiment to study the direct coupling between these low frequency shape modes and the volume pulsation, sound-radiating mode. The second subject of interest has involved numerical modeling, using the boundary integral method, of the large amplitude shape oscillations of charged and uncharged drops in the presence

Temperature oscillations in methanol partial oxidation reactor for the production of hydrogen

Energy Technology Data Exchange (ETDEWEB)

Kim, Jinsu; Byeon, Jeonguk; Seo, Il Gyu; Lee, Hyun Chan; Kim, Dong Hyun; Lee, Jietae [Kyungpook National University, Daegu (Korea, Republic of)

2013-04-15

Methanol partial oxidation (POX) is a well-known reforming reaction for the production of hydrogen from methanol. Since POX is relatively fast and highly exothermic, this reforming method will be efficient for the fast start-up and load-following operation. However, POX generates hot spots around catalyst and even oscillations in the reactor temperature. These should be relieved for longer operations of the reactor without catalyst degradations. For this, temperature oscillations in a POX reactor are investigated experimentally. Various patterns of temperature oscillations according to feed flow rates of reactants and reactor temperatures are obtained. The bifurcation phenomena from regular oscillations to chaotic oscillations are found as the methanol flow rate increases. These experimental results can be used for theoretical analyses of oscillations and for designing safe reforming reactors.

Temperature oscillations in methanol partial oxidation reactor for the production of hydrogen

International Nuclear Information System (INIS)

Kim, Jinsu; Byeon, Jeonguk; Seo, Il Gyu; Lee, Hyun Chan; Kim, Dong Hyun; Lee, Jietae

2013-01-01

Methanol partial oxidation (POX) is a well-known reforming reaction for the production of hydrogen from methanol. Since POX is relatively fast and highly exothermic, this reforming method will be efficient for the fast start-up and load-following operation. However, POX generates hot spots around catalyst and even oscillations in the reactor temperature. These should be relieved for longer operations of the reactor without catalyst degradations. For this, temperature oscillations in a POX reactor are investigated experimentally. Various patterns of temperature oscillations according to feed flow rates of reactants and reactor temperatures are obtained. The bifurcation phenomena from regular oscillations to chaotic oscillations are found as the methanol flow rate increases. These experimental results can be used for theoretical analyses of oscillations and for designing safe reforming reactors

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

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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.

Antagonistic Phenomena in Network Dynamics

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Motter, Adilson E.; Timme, Marc

2018-03-01

Recent research on the network modeling of complex systems has led to a convenient representation of numerous natural, social, and engineered systems that are now recognized as networks of interacting parts. Such systems can exhibit a wealth of phenomena that not only cannot be anticipated from merely examining their parts, as per the textbook definition of complexity, but also challenge intuition even when considered in the context of what is now known in network science. Here, we review the recent literature on two major classes of such phenomena that have far-reaching implications: (a) antagonistic responses to changes of states or parameters and (b) coexistence of seemingly incongruous behaviors or properties - both deriving from the collective and inherently decentralized nature of the dynamics. They include effects as diverse as negative compressibility in engineered materials, rescue interactions in biological networks, negative resistance in fluid networks, and the Braess paradox occurring across transport and supply networks. They also include remote synchronization, chimera states, and the converse of symmetry breaking in brain, power-grid, and oscillator networks as well as remote control in biological and bioinspired systems. By offering a unified view of these various scenarios, we suggest that they are representative of a yet broader class of unprecedented network phenomena that ought to be revealed and explained by future research.

Nonlinear transient waves in coupled phase oscillators with inertia.

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Jörg, David J

2015-05-01

Like the inertia of a physical body describes its tendency to resist changes of its state of motion, inertia of an oscillator describes its tendency to resist changes of its frequency. Here, we show that finite inertia of individual oscillators enables nonlinear phase waves in spatially extended coupled systems. Using a discrete model of coupled phase oscillators with inertia, we investigate these wave phenomena numerically, complemented by a continuum approximation that permits the analytical description of the key features of wave propagation in the long-wavelength limit. The ability to exhibit traveling waves is a generic feature of systems with finite inertia and is independent of the details of the coupling function.

Fractional Bateman—Feshbach Tikochinsky Oscillator

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Dumitru, Baleanu; Jihad, H. Asad; Ivo, Petras

2014-02-01

In the last few years the numerical methods for solving the fractional differential equations started to be applied intensively to real world phenomena. Having these things in mind in this manuscript we focus on the fractional Lagrangian and Hamiltonian of the complex Bateman—Feshbach Tikochinsky oscillator. The numerical analysis of the corresponding fractional Euler-Lagrange equations is given within the Grünwald—Letnikov approach, which is power series expansion of the generating function.

Basin stability measure of different steady states in coupled oscillators

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Rakshit, Sarbendu; Bera, Bidesh K.; Majhi, Soumen; Hens, Chittaranjan; Ghosh, Dibakar

2017-04-01

In this report, we investigate the stabilization of saddle fixed points in coupled oscillators where individual oscillators exhibit the saddle fixed points. The coupled oscillators may have two structurally different types of suppressed states, namely amplitude death and oscillation death. The stabilization of saddle equilibrium point refers to the amplitude death state where oscillations are ceased and all the oscillators converge to the single stable steady state via inverse pitchfork bifurcation. Due to multistability features of oscillation death states, linear stability theory fails to analyze the stability of such states analytically, so we quantify all the states by basin stability measurement which is an universal nonlocal nonlinear concept and it interplays with the volume of basins of attractions. We also observe multi-clustered oscillation death states in a random network and measure them using basin stability framework. To explore such phenomena we choose a network of coupled Duffing-Holmes and Lorenz oscillators which are interacting through mean-field coupling. We investigate how basin stability for different steady states depends on mean-field density and coupling strength. We also analytically derive stability conditions for different steady states and confirm by rigorous bifurcation analysis.

Unsteady phenomena in the edge tone

International Nuclear Information System (INIS)

Paal, G.; Vaik, I.

2007-01-01

Despite its geometrical simplicity, the edge tone displays a remarkably complex behaviour. A plane jet oscillates around the wedge-shaped object with a relatively stable frequency and under certain circumstances emits an audible tone. This configuration plays a central role in the sound production of several wind instruments but occurs in industrial situations too. The flow exhibits various interesting nonlinear phenomena reported in the literature which are not entirely explained. In this paper, detailed high precision numerical simulations of the flow are reported under various conditions. Several phenomena are reproduced in agreement with the literature such as the existence of 'stages', the dependence of oscillation frequency on the outflow velocity and the orifice-edge distance within one stage, the pressure distribution on the edge surface, etc. A criterion for the appropriate time step for constant accuracy has been derived. The location of force action is surprisingly stable; it remains in a very narrow region of the wedge surface independently of the Reynolds number and the orifice-edge distance but it is much further behind the edge tip than reported in the literature. The various stages can coexist in different ways: jumping back and forth between stages or being superposed on each other. Regardless of the form, the first stage continues to be dominant even when the second and third stage appears. The question of disturbance propagation velocity and disturbance wavelength is also investigated. The development of higher harmonics of a single stage along the orifice-edge tip distance is presented

Phase-shift and spin-rotation phenomena in neutron interferometry

International Nuclear Information System (INIS)

Badurek, G.; Rauch, H.; Zeilinger, A.; Bauspiess, W.; Bonse, U.

1976-01-01

The perfect-crystal neutron interferometer was used to study characteristic phenomena arising from simultaneous phase shift and spin rotation of neutron waves. In accordance with theoretical predictions, the beams leaving the interferometer became partially polarized, even with unpolarized incident neutrons. The intensity and the polarization as a function of phase shift and spin rotation have been found to oscillate with the same period, displaying a mutual beat pattern

Emergence of dynamical order synchronization phenomena in complex systems

CERN Document Server

Manrubia, Susanna C; Zanette, Damián H

2004-01-01

Synchronization processes bring about dynamical order and lead tospontaneous development of structural organization in complex systemsof various origins, from chemical oscillators and biological cells tohuman societies and the brain. This book provides a review and adetailed theoretical analysis of synchronization phenomena in complexsystems with different architectures, composed of elements withperiodic or chaotic individual dynamics. Special attention is paid tostatistical concepts, such as nonequilibrium phase transitions, orderparameters and dynamical glasses.

Simultaneous excitation of the snake-like oscillations and the m/n = 1/1 resistive interchange modes around the iota = 1 rational surface just after hydrogen pellet injections in LHD plasmas

Science.gov (United States)

Bando, T.; Ohdachi, S.; Suzuki, Y.; Sakamoto, R.; Narushima, Y.; Takemura, Y.; Watanabe, K. Y.; Sakakibara, S.; Du, X. D.; Motojima, G.; Tanaka, K.; Morisaki, T.; LHD Experiment Group

2018-01-01

Two types of oscillation phenomena are found just after hydrogen ice pellet injections in the Large Helical Device (LHD). Oscillation phenomena appear when the deposition profile of a hydrogen ice pellet is localized around the rotational transform ι = 1 rational surface. At first, damping oscillations (type-I) appear only in the soft X-ray (SX) emission. They are followed by the second type of oscillations (type-II) where the magnetic fluctuations and density fluctuations synchronized to the SX fluctuations are observed. Both oscillations have poloidal/toroidal mode number, m/n = 1/1. Since the type-II oscillations appear when the local pressure is large and/or the local magnetic Reynold's number is small, it is reasonable that type-II oscillations are caused by the resistive interchange modes. Because both types of oscillations appear simultaneously at slightly different locations and with slightly different frequencies, it is certain that type-I oscillations are different from type-II oscillations, which we believe is the MHD instability. It is possible that type-I oscillations are caused by the asymmetric concentration of the impurities. The type-I oscillations are similar to the impurity snake phenomena observed in tokamaks though type-I oscillations survive only several tens of milliseconds in LHD.

WATER HAMMER OSCILLATIONS IN THE IRRIGATION FACILITIES

Science.gov (United States)

Kurata, Kouichi; Sasaki, Katsuhito; Makihata, Toshiaki

In case a gate installed at the end of discharge conduit is vibrating during discharge, or an air valve is vibrating during water-filling operation into the conduit pipe between main gate and auxiliary gate, and vibration period tv is larger than tc (water hammer propagation time) that is equivalent to the phenomenon of slow closure, there is a possibility that water hammer oscillation in the discharge conduit could be induced. In this paper, by using two case examples, vibration phenomena transmitted to each part are analyzed, on the basis of water pressure fluctuation and pressure wave propagation due to occurrence of water hammer oscillation.

Vibration phenomena in large scale pressure suppression tests

International Nuclear Information System (INIS)

Aust, E.; Boettcher, G.; Kolb, M.; Sattler, P.; Vollbrandt, J.

1982-01-01

Structure und fluid vibration phenomena (acceleration, strain; pressure, level) were observed during blow-down experiments simulating a LOCA in the GKSS full scale multivent pressure suppression test facility. The paper describes first the source related excitations during the two regimes of condensation oscillation and of chugging, and deals then with the response vibrations of the facility's wetwell. Modal analyses of the wetwell were run using excitation by hammer and by shaker in order to separate phenomena that are particular to the GKSS facility from more general ones, i.e. phenomena specific to the fluid related parameters of blowdown and to the geometry of the vent pipes only. The lowest periodicities at about 12 and 16 Hz stem from the vent acoustics. A frequency of about 36 to 38 Hz prominent during chugging seems to result from the lowest local models of two of the wetwell's walls when coupled by the wetwell pool. Further peaks found during blowdown in the spectra of signals at higher frequencies correspond to global vibration modes of the wetwell. (orig.)

Exchange magnon induced resistance asymmetry in permalloy spin-Hall oscillators

Energy Technology Data Exchange (ETDEWEB)

Langenfeld, S. [Microelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE (United Kingdom); Walter Schottky Institut and Physik-Department, Technische Universität München, 85748 Garching (Germany); Tshitoyan, V.; Fang, Z.; Ferguson, A. J., E-mail: ajf1006@cam.ac.uk [Microelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE (United Kingdom); Wells, A.; Moore, T. A. [School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT (United Kingdom)

2016-05-09

We investigate magnetization dynamics in a spin-Hall oscillator using a direct current measurement as well as conventional microwave spectrum analysis. When the current applies an anti-damping spin-transfer torque, we observe a change in resistance which we ascribe mainly to the excitation of incoherent exchange magnons. A simple model is developed based on the reduction of the effective saturation magnetization, quantitatively explaining the data. The observed phenomena highlight the importance of exchange magnons on the operation of spin-Hall oscillators.

Neutrino oscillations and the seesaw origin of neutrino mass

Energy Technology Data Exchange (ETDEWEB)

Miranda, O.G., E-mail: omr@fis.cinvestav.mx [Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, Apdo. Postal 14-740, 07000 Mexico, Distrito Federal (Mexico); Valle, J.W.F. [AHEP Group, Institut de Física Corpuscular – C.S.I.C./Universitat de València, Parc Cientific de Paterna, C/Catedratico José Beltrán, 2, E-46980 Paterna (València) (Spain)

2016-07-15

The historical discovery of neutrino oscillations using solar and atmospheric neutrinos, and subsequent accelerator and reactor studies, has brought neutrino physics to the precision era. We note that CP effects in oscillation phenomena could be difficult to extract in the presence of unitarity violation. As a result upcoming dedicated leptonic CP violation studies should take into account the non-unitarity of the lepton mixing matrix. Restricting non-unitarity will shed light on the seesaw scale, and thereby guide us towards the new physics responsible for neutrino mass generation.

Analyzing Elevator Oscillation with the Smartphone Acceleration Sensors

Science.gov (United States)

Kuhn, Jochen; Vogt, Patrik; Müller, Andreas

2014-01-01

It has often been reported in this column that smartphones are very suitable tools for exploring the physical properties of everyday phenomena. A very good example of this is an elevator ride. In addition to the acceleration processes, oscillations of the cabin are interesting. The present work responds to the second aspect.

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

Collective three-flavor oscillations of supernova neutrinos

Science.gov (United States)

Dasgupta, Basudeb; Dighe, Amol

2008-06-01

Neutrinos and antineutrinos emitted from a core collapse supernova interact among themselves, giving rise to collective flavor conversion effects that are significant near the neutrinosphere. We develop a formalism to analyze these collective effects in the complete three-flavor framework. It naturally generalizes the spin-precession analogy to three flavors and is capable of analytically describing phenomena like vacuum/Mikheyev-Smirnov-Wolfenstein (MSW) oscillations, synchronized oscillations, bipolar oscillations, and spectral split. Using the formalism, we demonstrate that the flavor conversions may be “factorized” into two-flavor oscillations with hierarchical frequencies. We explicitly show how the three-flavor solution may be constructed by combining two-flavor solutions. For a typical supernova density profile, we identify an approximate separation of regions where distinctly different flavor conversion mechanisms operate, and demonstrate the interplay between collective and MSW effects. We pictorialize our results in terms of the “e3-e8 triangle” diagram, which is a tool that can be used to visualize three-neutrino flavor conversions in general, and offers insights into the analysis of the collective effects in particular.

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...

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

Science.gov (United States)

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

2017-04-01

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

Remote ENSO forcing versus local air-sea interaction in QTCM: a sensitivity study to intraseasonal variability

Directory of Open Access Journals (Sweden)

D. Gushchina

2006-01-01

Full Text Available The skill of a newly designed global atmospheric model of intermediate complexity - QTCM (for quasi-equilibrium tropical circulation model in simulating the teleconnections is investigated. The role of the ENSO remote forcing over the Pacific surrounding regions is emphasized from sensitivity experiments to critical parameters of the model. The role of the tropical intraseasonal variability (ITV on the simulated ENSO teleconnection pattern is estimated using the methodology proposed by Lin et al. (2000 allowing to damp the energy of ITV in the model. The reduction of intraseasonal variability allows emphasizing the forced response of the atmosphere and eases the detection of local coupled atmosphere-ocean patterns. It was shown that the simulated ITV has an impact on the ENSO teleconnection pattern both in the mid-latitudes and in regions of ascending and descending branches of Walker circulation cells in the tropics.

Geographical distribution of the association between El Niño South Oscillation and dengue fever in the Americas: a continental analysis using geographical information system-based techniques

Directory of Open Access Journals (Sweden)

Marcos C. Ferreira

2014-11-01

Full Text Available El Niño South Oscillation (ENSO is one climatic phenomenon related to the inter-annual variability of global meteorological patterns influencing sea surface temperature and rainfall variability. It influences human health indirectly through extreme temperature and moisture conditions that may accelerate the spread of some vector-borne viral diseases, like dengue fever (DF. This work examines the spatial distribution of association between ENSO and DF in the countries of the Americas during 1995-2004, which includes the 1997-1998 El Niño, one of the most important climatic events of 20th century. Data regarding the South Oscillation index (SOI, indicating El Niño-La Niña activity, were obtained from Australian Bureau of Meteorology. The annual DF incidence (AIy by country was computed using Pan-American Health Association data. SOI and AIy values were standardised as deviations from the mean and plotted in bars-line graphics. The regression coefficient values between SOI and AIy (rSOI,AI were calculated and spatially interpolated by an inverse distance weighted algorithm. The results indicate that among the five years registering high number of cases (1998, 2002, 2001, 2003 and 1997, four had El Niño activity. In the southern hemisphere, the annual spatial weighted mean centre of epidemics moved southward, from 6° 31' S in 1995 to 21° 12' S in 1999 and the rSOI,AI values were negative in Cuba, Belize, Guyana and Costa Rica, indicating a synchrony between higher DF incidence rates and a higher El Niño activity. The rSOI,AI map allows visualisation of a graded surface with higher values of ENSO-DF associations for Mexico, Central America, northern Caribbean islands and the extreme north-northwest of South America.

Response of O2 and pH to ENSO in the California Current System in a high-resolution global climate model

Science.gov (United States)

Turi, Giuliana; Alexander, Michael; Lovenduski, Nicole S.; Capotondi, Antonietta; Scott, James; Stock, Charles; Dunne, John; John, Jasmin; Jacox, Michael

2018-02-01

Coastal upwelling systems, such as the California Current System (CalCS), naturally experience a wide range of O2 concentrations and pH values due to the seasonality of upwelling. Nonetheless, changes in the El Niño-Southern Oscillation (ENSO) have been shown to measurably affect the biogeochemical and physical properties of coastal upwelling regions. In this study, we use a novel, high-resolution global climate model (GFDL-ESM2.6) to investigate the influence of warm and cold ENSO events on variations in the O2 concentration and the pH of the CalCS coastal waters. An assessment of the CalCS response to six El Niño and seven La Niña events in ESM2.6 reveals significant variations in the response between events. However, these variations overlay a consistent physical and biogeochemical (O2 and pH) response in the composite mean. Focusing on the mean response, our results demonstrate that O2 and pH are affected rather differently in the euphotic zone above ˜ 100 m. The strongest O2 response reaches up to several hundreds of kilometers offshore, whereas the pH signal occurs only within a ˜ 100 km wide band along the coast. By splitting the changes in O2 and pH into individual physical and biogeochemical components that are affected by ENSO variability, we found that O2 variability in the surface ocean is primarily driven by changes in surface temperature that affect the O2 solubility. In contrast, surface pH changes are predominantly driven by changes in dissolved inorganic carbon (DIC), which in turn is affected by upwelling, explaining the confined nature of the pH signal close to the coast. Below ˜ 100 m, we find conditions with anomalously low O2 and pH, and by extension also anomalously low aragonite saturation, during La Niña. This result is consistent with findings from previous studies and highlights the stress that the CalCS ecosystem could periodically undergo in addition to impacts due to climate change.

Critical Power Response to Power Oscillations in Boiling Water Reactors

International Nuclear Information System (INIS)

Farawila, Yousef M.; Pruitt, Douglas W.

2003-01-01

The response of the critical power ratio to boiling water reactor (BWR) power oscillations is essential to the methods and practice of mitigating the effects of unstable density waves. Previous methods for calculating generic critical power response utilized direct time-domain simulations of unstable reactors. In this paper, advances in understanding the nature of the BWR oscillations and critical power phenomena are combined to develop a new method for calculating the critical power response. As the constraint of the reactor state - being at or slightly beyond the instability threshold - is removed, the new method allows the calculation of sensitivities to different operation and design parameters separately, and thus allows tighter safety margins to be used. The sensitivity to flow rate and the resulting oscillation frequency change are given special attention to evaluate the extension of the oscillation 'detect-and-suppress' methods to internal pump plants where the flow rate at natural circulation and oscillation frequency are much lower than jet pump plants

Comments on microscopic mechanics, generalizations of classical mechanics and Planck's oscillators

International Nuclear Information System (INIS)

Yussouff, M.

1983-05-01

The new microscopic mechanics removes the dichotomy of physics into classical and quantum phenomena. Its physical picture and connections with generalizations of classical mechanics are discussed. It gives a new meaning to Bohr's frequency relation and Planck's oscillators. (author)

Time-averaged second-order pressure and velocity measurements in a pressurized oscillating flow prime mover

Energy Technology Data Exchange (ETDEWEB)

Paridaens, Richard [DynFluid, Arts et Metiers, 151 boulevard de l' Hopital, Paris (France); Kouidri, Smaine [LIMSI-CNRS, Orsay Cedex (France)

2016-11-15

Nonlinear phenomena in oscillating flow devices cause the appearance of a relatively minor secondary flow known as acoustic streaming, which is superimposed on the primary oscillating flow. Knowledge of control parameters, such as the time-averaged second-order velocity and pressure, would elucidate the non-linear phenomena responsible for this part of the decrease in the system's energetic efficiency. This paper focuses on the characterization of a travelling wave oscillating flow engine by measuring the time-averaged second order pressure and velocity. Laser Doppler velocimetry technique was used to measure the time-averaged second-order velocity. As streaming is a second-order phenomenon, its measurement requires specific settings especially in a pressurized device. Difficulties in obtaining the proper settings are highlighted in this study. The experiments were performed for mean pressures varying from 10 bars to 22 bars. Non-linear effect does not constantly increase with pressure.

Time Series Decomposition into Oscillation Components and Phase Estimation.

Science.gov (United States)

Matsuda, Takeru; Komaki, Fumiyasu

2017-02-01

Many time series are naturally considered as a superposition of several oscillation components. For example, electroencephalogram (EEG) time series include oscillation components such as alpha, beta, and gamma. We propose a method for decomposing time series into such oscillation components using state-space models. Based on the concept of random frequency modulation, gaussian linear state-space models for oscillation components are developed. In this model, the frequency of an oscillator fluctuates by noise. Time series decomposition is accomplished by this model like the Bayesian seasonal adjustment method. Since the model parameters are estimated from data by the empirical Bayes' method, the amplitudes and the frequencies of oscillation components are determined in a data-driven manner. Also, the appropriate number of oscillation components is determined with the Akaike information criterion (AIC). In this way, the proposed method provides a natural decomposition of the given time series into oscillation components. In neuroscience, the phase of neural time series plays an important role in neural information processing. The proposed method can be used to estimate the phase of each oscillation component and has several advantages over a conventional method based on the Hilbert transform. Thus, the proposed method enables an investigation of the phase dynamics of time series. Numerical results show that the proposed method succeeds in extracting intermittent oscillations like ripples and detecting the phase reset phenomena. We apply the proposed method to real data from various fields such as astronomy, ecology, tidology, and neuroscience.

Fractional Bateman—Feshbach Tikochinsky Oscillator

International Nuclear Information System (INIS)

Baleanu, Dumitru; Asad, Jihad H.; Petras Ivo

2014-01-01

In the last few years the numerical methods for solving the fractional differential equations started to be applied intensively to real world phenomena. Having these things in mind in this manuscript we focus on the fractional Lagrangian and Hamiltonian of the complex Bateman—Feshbach Tikochinsky oscillator. The numerical analysis of the corresponding fractional Euler-Lagrange equations is given within the Grünwald—Letnikov approach, which is power series expansion of the generating function. (physics of elementary particles and fields)

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.

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

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 Kruger National Park shows the strong relationship between the ENSO episodes (droughts during El Niño and high rainfall during La Niña episodes), rainfall, grass production and satellite time-series data of vegetation activity. El Niño conditions have...

Evolution of ENSO-related rainfall anomalies in Southeast Asia region and its relationship with atmosphere-ocean variations in Indo-Pacific sector

Energy Technology Data Exchange (ETDEWEB)

Juneng, Liew; Tangang, Fredolin T. [Technology National University of Malaysia, Marine Science Program, School of Environmental and Natural Resource Sciences, Bangi Selangor (Malaysia)

2005-09-01

The Southeast Asia rainfall (SEAR) anomalies depend strongly on phases of El Nino (La Nina). Using an extended empirical orthogonal function (EEOF) analysis, it is shown that the dominant EEOF mode of SEAR anomalies evolves northeastward throughout a period from the summer when El Nino develops to spring the following year when the event weakens. This evolution is consistent with northeastward migration of the ENSO-related anomalous out going radiation field. During boreal summer (winter), the strong ENSO-related anomaly tends to reside in regions south (north) of the equator. The evolution of dominant mode of SEAR anomalies is in tandem with the evolution of ENSO-related sea surface temperature (SST) anomalies. The strengthening and weakening of ''boomerang-shaped'' SST in western Pacific, the changing sign of anomalous SST in Java Sea and the warming in Indian Ocean and South China Sea are all part of ENSO-related changes and all are linked to SEAR anomaly. The anomalous low-level circulation associated with ENSO-related SEAR anomaly indicates the strengthening and weakening of two off-equatorial anticyclones, one over the Southern Indian Ocean and the other over the western North Pacific. Together with patterns of El Nino minus La Nina composites of various fields, it is proposed that the northeastward evolution of SEAR anomaly is basically part of the large-scale eastward evolution of ENSO-related signal in the Indo-Pacific sector. The atmosphere-ocean interaction plays an important role in this evolution. (orig.)

El Niño-Southern Oscillation-based index insurance for floods: Statistical risk analyses and application to Peru

Science.gov (United States)

Khalil, Abedalrazq F.; Kwon, Hyun-Han; Lall, Upmanu; Miranda, Mario J.; Skees, Jerry

2007-10-01

Index insurance has recently been advocated as a useful risk transfer tool for disaster management situations where rapid fiscal relief is desirable and where estimating insured losses may be difficult, time consuming, or subject to manipulation and falsification. For climate-related hazards, a rainfall or temperature index may be proposed. However, rainfall may be highly spatially variable relative to the gauge network, and in many locations, data are inadequate to develop an index because of short time series and the spatial dispersion of stations. In such cases, it may be helpful to consider a climate proxy index as a regional rainfall index. This is particularly useful if a long record is available for the climate index through an independent source and it is well correlated with the regional rainfall hazard. Here El Niño-Southern Oscillation (ENSO) related climate indices are explored for use as a proxy to extreme rainfall in one of the districts of Peru, Piura. The ENSO index insurance product may be purchased by banks or microfinance institutions to aid agricultural damage relief in Peru. Crop losses in the region are highly correlated with floods but are difficult to assess directly. Beyond agriculture, many other sectors suffer as well. Basic infrastructure is destroyed during the most severe events. This disrupts trade for many microenterprises. The reliability and quality of the local rainfall data are variable. Averaging the financial risk across the region is desirable. Some issues with the implementation of the proxy ENSO index are identified and discussed. Specifically, we explore (1) the reliability of the index at different levels of probability of exceedance of maximum seasonal rainfall, (2) the effect of sampling uncertainties and the strength of the proxy's association to local outcome, (3) the potential for clustering of payoffs, (4) the potential that the index could be predicted with some lead time prior to the flood season, and (5) evidence

Plasma and oscillations with contributions in memoriam including a complete bibliography of his works

CERN Document Server

Suits, C Guy

1961-01-01

The Collected Works of Irving Langmuir, Volume 5: Plasma and Oscillations is an 11-chapter text covers the extensive research study of Langmuir in the field of gas discharges. This book specifically tackles oscillations in ionized gases. The opening chapters describe the plasma-boundary phenomena and the use of a probe to separate the primary electron beam from the scattered electrons. The succeeding chapters deal with the collisions between electrons and gas molecules, oscillations in ionized gases, and the interaction of electron and positive ion space charges in cathode sheaths. These t

A Possible Minimum Toy Model with Negative Differential Capacitance for Self-sustained Current Oscillation

International Nuclear Information System (INIS)

Xiong Gang; Sun Zhouzhou; Wang Xiangrong

2007-01-01

We generalize a simple model for superlattices to include the effect of differential capacitance. It is shown that the model always has a stable steady-state solution (SSS) if all differential capacitances are positive. On the other hand, when negative differential capacitance is included, the model can have no stable SSS and be in a self-sustained current oscillation behavior. Therefore, we find a possible minimum toy model with both negative differential resistance and negative differential capacitance which can include the phenomena of both self-sustained current oscillation and I-V oscillation of stable SSSs.

Analysis of diffusivity of the oscillating reaction components in a microreactor system

Directory of Open Access Journals (Sweden)

Martina Šafranko

2017-01-01

Full Text Available When performing oscillating reactions, periodical changes in the concentrations of reactants, intermediaries, and products take place. Due to the mentioned periodical changes of the concentrations, the information about the diffusivity of the components included into oscillating reactions is very important for the control of the oscillating reactions. Non-linear dynamics makes oscillating reactions very interesting for analysis in different reactor systems. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor, with the aim of identifying the limiting component. The geometry of the microreactor microchannel and a well defined flow profile ensure optimal conditions for the diffusion phenomena analysis, because diffusion profiles in a microreactor depend only on the residence time. In this paper, the analysis of diffusivity of the oscillating reaction components was performed in a microreactor equipped with 2 Y-shape inlets and 2 Y-shape outlets, with active volume of V = 4 μL at different residence times.

Effects of Atlantic warm pool variability over climate of South America tropical transition zone

Science.gov (United States)

Ricaurte Villota, Constanza; Romero-Rodríguez, Deisy; Andrés Ordoñez-Zuñiga, Silvio; Murcia-Riaño, Magnolia; Coca-Domínguez, Oswaldo

2016-04-01

Colombia is located in the northwestern corner of South America in a climatically complex region due to the influence processes modulators of climate both the Pacific and Atlantic region, becoming in a transition zone between phenomena of northern and southern hemisphere. Variations in the climatic conditions of this region, especially rainfall, have been attributed to the influence of the El Nino Southern Oscillation (ENSO), but little is known about the interaction within Atlantic Ocean and specifically Caribbean Sea with the environmental conditions of this region. In this work We studied the influence of the Atlantic Warm Pool (AWP) on the Colombian Caribbean (CC) climate using data of Sea Surface Temperature (SST) between 1900 - 2014 from ERSST V4, compared with in situ data SIMAC (National System for Coral Reef Monitoring in Colombia - INVEMAR), rainfall between 1953-2013 of meteorological stations located at main airports in the Colombian Caribbean zone, administered by IDEAM, and winds data between 2003 - 2014 from WindSat sensor. The parameters analyzed showed spatial differences throughout the study area. SST anomalies, representing the variability of the AWP, showed to be associated with Multidecadal Atlantic Oscillation (AMO) and with the index of sea surface temperature of the North-tropical Atlantic (NTA), the variations was on 3 to 5 years on the ENSO scale and of approximately 11 years possibly related to solar cycles. Rainfall anomalies in the central and northern CC respond to changes in SST, while in the south zone these are not fully engage and show a high relationship with the ENSO. Finally, the winds also respond to changes in SST and showed a signal approximately 90 days possibly related to the Madden-Julian Oscillation, whose intensity depends on the CC region being analyzed. The results confirm that region is a transition zone in which operate several forcing, the variability of climate conditions is difficult to attribute only one, as ENSO

Dynamics of chiral oscillations: a comparative analysis with spin flipping

International Nuclear Information System (INIS)

Bernardini, A E

2006-01-01

Chiral oscillation as well as spin flipping effects correspond to quantum phenomena of fundamental importance in the context of particle physics and, in particular, of neutrino physics. From the point of view of first quantized theories, we are specifically interested in pointing out the differences between chirality and helicity by obtaining their dynamic equations for a fermionic Dirac-type particle (neutrino). We also identify both effects when the non-minimal coupling with an external (electro)magnetic field in the neutrino interacting Lagrangian is taken into account. We demonstrate that, however, there is no constraint between chiral oscillations, when it takes place in vacuum, and the process of spin flipping related to the helicity quantum number, which does not take place in vacuum. To conclude, we show that the origin of chiral oscillations (in vacuum) can be interpreted as projections of very rapid oscillations of position onto the longitudinal direction of momentum

TGF-mediated oscillations in the proximal intratubular pressure: differences between spontaneously hypertensive rats and Wistar-Kyoto rats

DEFF Research Database (Denmark)

Holstein-Rathlou, N H; Leyssac, P P

1986-01-01

fluid (ATF). When furosemide was added to the ATF in a concentration of 0.1 mM, the oscillations were abolished in both strains of rats. It is concluded that, in both strains of rats the oscillatory phenomena depend upon TGF activity. It is suggested that the irregular pattern of the oscillations...

Asymptotic representation of relaxation oscillations in lasers

CERN Document Server

Grigorieva, Elena V

2017-01-01

In this book we analyze relaxation oscillations in models of lasers with nonlinear elements controlling light dynamics. The models are based on rate equations taking into account periodic modulation of parameters, optoelectronic delayed feedback, mutual coupling between lasers, intermodal interaction and other factors. With the aim to study relaxation oscillations we present the special asymptotic method of integration for ordinary differential equations and differential-difference equations. As a result, they are reduced to discrete maps. Analyzing the maps we describe analytically such nonlinear phenomena in lasers as multistability of large-amplitude relaxation cycles, bifurcations of cycles, controlled switching of regimes, phase synchronization in an ensemble of coupled systems and others. The book can be fruitful for students and technicians in nonlinear laser dynamics and in differential equations.

Climate variability from isotope records in precipitation

International Nuclear Information System (INIS)

Grassl, H.; Latif, M.; Schotterer, U.; Gourcy, L.

2002-01-01

Selected time series from the Global Network for Isotopes in Precipitation (GNIP) revealed a close relationship to climate variability phenomena like El Nino - Southern Oscillation (ENSO) or the North Atlantic Oscillation (NAO) although the precipitation anomaly in the case studies of Manaus (Brazil) and Groningen (The Netherlands) is rather weak. For a sound understanding of this relationship especially in the case of Manaus, the data should include major events like the 1997/98 El Nino, however, the time series are interrupted frequently or important stations are even closed. Improvements are only possible if existing key stations and new ones (placed at 'hot spots' derived from model experiments) are supported continuously. A close link of GNIP to important scientific programmes like CLIVAR, the Climate Variability and Predictability Programme seems to be indispensable for a successful continuation. (author)

Periodic Solutions of the Duffing Harmonic Oscillator by He's Energy Balance Method

Directory of Open Access Journals (Sweden)

A. M. El-Naggar

2015-11-01

Full Text Available Duffing harmonic oscillator is a common model for nonlinear phenomena in science and engineering. This paper presents He´s Energy Balance Method (EBM for solving nonlinear differential equations. Two strong nonlinear cases have been studied analytically. Analytical results of the EBM are compared with the solutions obtained by using He´s Frequency Amplitude Formulation (FAF and numerical solutions using Runge-Kutta method. The results show the presented method is potentially to solve high nonlinear oscillator equations.

Parametric and scaling studies of condensation oscillation in subcooled water of the in-containment refueling water storage tank

International Nuclear Information System (INIS)

Lee, Jun Hyung; No, Hee Cheon

1999-01-01

Condensation oscillation by jetting the steam into subcooled water through spargers is studied. To provide a suitable guideline for oscillation phenomena in the IRWST of the next generation reactor, scaling methodology is introduced. Through scaling methodology and subsequent tests, it shows that the volume of steam cavity determines the dynamic characteristics of condensation oscillation. The second-order linear differential equation for frequency analysis is derived and its results are compared with those from the test data. Two types of condensation phenomena exist according to steam flow rates. At subsonic jet, condensation interface becomes irregular in shape and upper system volumes affect the dynamic characteristics of condensation oscillation. At sonic jet, a regular steam cavity forms at the exit of discharge holes. Parametric effects and subsequent dynamic responses of the pool tank are investigated through experiments in applicable test ranges. When the temperature of pool water becomes lower, the amplitude becomes larger. Critical parameters are derived from the scaling methodology and are system volume, cavity volume, discharge hole area, and density ration. It is found that system friction factors affect frequency components of condensation oscillation. Oscillations of a steam cavity occur mainly on the face of the axial direction and pressure amplitudes become larger than that of the lateral direction

Re-evaluating the resource potential of lomas fog oasis environments for Preceramic hunter-gatherers under past ENSO modes on the south coast of Peru

Science.gov (United States)

Beresford-Jones, David; Pullen, Alexander G.; Whaley, Oliver Q.; Moat, Justin; Chauca, George; Cadwallader, Lauren; Arce, Susana; Orellana, Alfonso; Alarcón, Carmela; Gorriti, Manuel; Maita, Patricia K.; Sturt, Fraser; Dupeyron, Agathe; Huaman, Oliver; Lane, Kevin J.; French, Charles

2015-12-01

Lomas - ephemeral seasonal oases sustained by ocean fogs - were critical to ancient human ecology on the desert Pacific coast of Peru: one of humanity's few independent hearths of agriculture and "pristine" civilisation. The role of climate change since the Late Pleistocene in determining productivity and extent of past lomas ecosystems has been much debated. Here we reassess the resource potential of the poorly studied lomas of the south coast of Peru during the long Middle Pre-ceramic period (c. 8000-4500 BP): a period critical in the transition to agriculture, the onset of modern El Niño Southern Oscillation ('ENSO') conditions, and eustatic sea-level rise and stabilisation and beach progradation. Our method combines vegetation survey and herbarium collection with archaeological survey and excavation to make inferences about both Preceramic hunter-gatherer ecology and the changed palaeoenvironments in which it took place. Our analysis of newly discovered archaeological sites - and their resource context - show how lomas formations defined human ecology until the end of the Middle Preceramic Period, thereby corroborating recent reconstructions of ENSO history based on other data. Together, these suggest that a five millennia period of significantly colder seas on the south coast induced conditions of abundance and seasonal predictability in lomas and maritime ecosystems, that enabled Middle Preceramic hunter-gatherers to reduce mobility by settling in strategic locations at the confluence of multiple eco-zones at the river estuaries. Here the foundations of agriculture lay in a Broad Spectrum Revolution that unfolded, not through population pressure in deteriorating environments, but rather as an outcome of resource abundance.

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

Excitation of solar and stellar oscillations

International Nuclear Information System (INIS)

Baudin, Frederic

2009-01-01

In this report for an Accreditation to Supervise Research (HDR), and after an introduction which outlines the potential of helio-seismology, the author addresses the problem of excitation and amplitude of stellar oscillations with respect to their most important aspects, i.e. the theoretical framework of the present understanding of excitation mechanisms, and instrumental influences on measurements which are used to assess excitation rates, the difficulty to perform these measurements, and their analysis in some various cases. Thus, the author addresses excitation mechanisms of stellar oscillation (stochastic excitation, opacity- related excitation, and other excitation mechanisms), the excitation of solar modes (observation and theoretical predictions, influence of magnetic phenomena, solar g modes), and the excitation of modes in other stars (solar-type pulsators, red giants, and not so conventional pulsators such as HD180642 and Be stars like HD49330)

Interannual variability of summertime aerosol optical depth over East Asia during 2000–2011: a potential influence from El Niño Southern Oscillation

International Nuclear Information System (INIS)

Liu, Yikun; Liu, Junfeng; Tao, Shu

2013-01-01

Aerosols degrade air quality, perturb atmospheric radiation, and impact regional and global climate. Due to the rapid increase in anthropogenic emissions, aerosol loading over East Asia (EA) is markedly higher than other industrialized regions, which motivates a need to characterize the evolution of aerosols and understand the associated drivers. Based on the MISR satellite data during 2000–2011, a wave-like interannual variation of summertime aerosol optical depth (SAOD) is observed over the highly populated North China Plain (NCP) in East Asia. Specifically, the peak-to-trough ratio of SAOD ranges from 1.4 to 1.6, with a period of 3–4 years. This variation pattern differs apparently from what has been seen in EA emissions, indicating a periodic change in regional climate pattern during the past decade. Investigations of meteorological fields over the region reveal that the high SAOD is generally associated with the enhanced Philippine Sea Anticyclone Anomaly (PSAA) which weakens southeasterlies over northeastern EA and depresses air ventilation. Alternatively, higher temperature and lower relative humidity are found to be coincident with reduced SAOD. The behavior of PSAA has been found previously to be modulated by the El Niño Southern Oscillations (ENSO), therefore ENSO could disturb the EA SAOD as well. Rather than changing coherently with the ENSO activity, the SAOD peaks over NCP are found to be accompanied by the rapid transition of El Niño warm to cold phases developed four months ahead. An index measuring the development of ENSO during January–April is able to capture the interannual variability of SAOD over NCP during 2000–2011. This finding indicates a need to integrate the large-scale periodic climate variability in the design of regional air quality policy. (letter)

Stimulus-dependent modulation of spontaneous low-frequency oscillations in the rat visual cortex.

Science.gov (United States)

Huang, Liangming; Liu, Yadong; Gui, Jianjun; Li, Ming; Hu, Dewen

2014-08-06

Research on spontaneous low-frequency oscillations is important to reveal underlying regulatory mechanisms in the brain. The mechanism for the stimulus modulation of low-frequency oscillations is not known. Here, we used the intrinsic optical imaging technique to examine stimulus-modulated low-frequency oscillation signals in the rat visual cortex. The stimulation was presented monocularly as a flashing light with different frequencies and intensities. The phases of low-frequency oscillations in different regions tended to be synchronized and the rhythms typically accelerated within a 30-s period after stimulation. These phenomena were confined to visual stimuli with specific flashing frequencies (12.5-17.5 Hz) and intensities (5-10 mA). The acceleration and synchronization induced by the flashing frequency were more marked than those induced by the intensity. These results show that spontaneous low-frequency oscillations can be modulated by parameter-dependent flashing lights and indicate the potential utility of the visual stimulus paradigm in exploring the origin and function of low-frequency oscillations.

A real-time ocean reanalyses intercomparison project in the context of tropical pacific observing system and ENSO monitoring

Science.gov (United States)

Xue, Yan; Wen, C.; Kumar, A.; Balmaseda, M.; Fujii, Y.; Alves, O.; Martin, M.; Yang, X.; Vernieres, G.; Desportes, C.; Lee, T.; Ascione, I.; Gudgel, R.; Ishikawa, I.

2017-12-01

An ensemble of nine operational ocean reanalyses (ORAs) is now routinely collected, and is used to monitor the consistency across the tropical Pacific temperature analyses in real-time in support of ENSO monitoring, diagnostics, and prediction. The ensemble approach allows a more reliable estimate of the signal as well as an estimation of the noise among analyses. The real-time estimation of signal-to-noise ratio assists the prediction of ENSO. The ensemble approach also enables us to estimate the impact of the Tropical Pacific Observing System (TPOS) on the estimation of ENSO-related oceanic indicators. The ensemble mean is shown to have a better accuracy than individual ORAs, suggesting the ensemble approach is an effective tool to reduce uncertainties in temperature analysis for ENSO. The ensemble spread, as a measure of uncertainties in ORAs, is shown to be partially linked to the data counts of in situ observations. Despite the constraints by TPOS data, uncertainties in ORAs are still large in the northwestern tropical Pacific, in the SPCZ region, as well as in the central and northeastern tropical Pacific. The uncertainties in total temperature reduced significantly in 2015 due to the recovery of the TAO/TRITON array to approach the value before the TAO crisis in 2012. However, the uncertainties in anomalous temperature remained much higher than the pre-2012 value, probably due to uncertainties in the reference climatology. This highlights the importance of the long-term stability of the observing system for anomaly monitoring. The current data assimilation systems tend to constrain the solution very locally near the buoy sites, potentially damaging the larger-scale dynamical consistency. So there is an urgent need to improve data assimilation systems so that they can optimize the observation information from TPOS and contribute to improved ENSO prediction.

Mechanical Properties of Laminate Materials: From Surface Waves to Bloch Oscillations

DEFF Research Database (Denmark)

Liang, Z.; Willatzen, Morten; Christensen, Johan

2015-01-01

for designing Bloch oscillations in classical plate structures and show how mechanical Bloch oscillations can be generated in arrays of solid plates when the modal wavelength is gradually reduced. The design recipe describes how Bloch oscillations in classical structures of arbitrary dimensions can be generated......We propose hitherto unexplored and fully analytical insights into laminate elastic materials in a true condensed-matter-physics spirit. Pure mechanical surface waves that decay as evanescent waves from the interface are discussed, and we demonstrate how these designer Scholte waves are controlled......, and we demonstrate this numerically for structures with millimeter and centimeter dimensions in the kilohertz to megahertz range. Analytical predictions agree entirely with full wave simulations showing how elastodynamics can mimic quantum-mechanical condensed-matter phenomena....

Global oscillations of the Sun: observed as oscillations in the apparent solar limb darkening function

International Nuclear Information System (INIS)

Hill, H.A.; Caudell, T.P.

1979-01-01

Analysis of the 1973 solar oblateness observations made at SCLERA has indicated that most of the oscillatory power found in observations of the apparent solar diameter is statistically significant and that it is produced by fluctuations in the limb darkening function rather than by a simple displacement of the solar limb. The differential refractive effects in the Earth's atmosphere may be ruled out as operative mechanisms for generating the observed oscillations. Solar and non-solar mechanisms for producing changes in the apparent limb darkening function are considered as possible sources of the observed oscillatory effects; it is concluded that acoustic and gravity modes of oscillation are the only viable mechanisms capable of producing these phenomena. This interpretation necessitates the imposition of certain constraints on modelling of the solar interior and on solar pulsation theory. The conclusion that the oscillations are detected through changes in the limb darkening function leads to a new constraint on the photospheric boundary conditions used in pulsation theory. The identification of two of the oscillations as being high-order gravity modes also necessitates the formulation of a new constraint on the Brunt-Vaisalai frequency in the solar interior and, in addition, may place a constraint depth on the convection zone. Application of the constraint on the Brunt-Vaisalai frequency permits discrimination between current models while the first constraint, if correct, may further complicate studies of the outer envelope of the Sun. (author)

Leading El-Niño SST Oscillations around the Southern South American Continent

Directory of Open Access Journals (Sweden)

Yu-Chen Hsu

2018-05-01

Full Text Available The inter-annual variations in the sea surface temperatures (SSTs of the tropical and subtropical Pacific Ocean have been widely investigated, largely due to their importance in achieving the sustainable development of marine ecosystems under a changing climate. The El Niño-Southern Oscillation (ENSO is a widely recognized variability. In the subpolar region in the southern hemisphere, the Antarctic Circumpolar Current (ACC is one of the main sources of the Peru Current. A change in the SST in the Southern Ocean may change the physical properties of the seawater in the tropical and subtropical Pacific Ocean. However, the variations in the SST in the Southern Ocean have rarely been addressed. This study uses a 147-year (1870–2016 dataset from the Met Office Hadley Centre to show that the SST anomalies (SSTAs in the oceans west and east of South America and the Antarctic Peninsula have strong positive (R = 0.56 and negative (R = −0.67 correlations with the Niño 3.4 SSTA, respectively. Such correlations are likely related to the changes in circulations of the ACC. We further show that, statistically, the temporal variations in the SSTAs of the ACC lead the Niño 3.4 SSTA by four to six months. Such findings imply that change in the strength of ENSO or circulation under the changing climate could change the climate in regions at higher latitudes as well.

High-Resolution Modeling of ENSO-Induced Precipitation in the Tropical Andes: Implications for Proxy Interpretation.

Science.gov (United States)

Kiefer, J.; Karamperidou, C.

2017-12-01

Clastic sediment flux into high-elevation Andean lakes is controlled by glacial processes and soil erosion caused by high precipitation events, making these lakes suitable archives of past climate. To wit, sediment records from Laguna Pallcacocha in Ecuador have been interpreted as proxies of ENSO variability, owing to increased precipitation in the greater region during El Niño events. However, the location of the lake's watershed, the presence of glaciers, and the different impacts of ENSO on precipitation in the eastern vs western Andes have challenged the suitability of the Pallcacocha record as an ENSO proxy. Here, we employ WRF, a high-resolution regional mesoscale weather prediction model, to investigate the circulation dynamics, sources of moisture, and resulting precipitation response in the L. Pallcacocha region during different flavors of El Niño and La Niña events, and in the presence or absence of ice caps. In patricular, we investigate Eastern Pacific (EP), Central Pacific (CP), coastal El Niño, and La Niña events. We validate the model simulations against spatially interpolated station measurements and reanalysis data. We find that during EP events, moisture is primarily advected from the Pacific, whereas during CP events, moisture primarily originates from the Atlantic. More moisture is available during EP events, which implies higher precipitation rates. Furthermore, we find that precipitation during EP events is mostly non-convective in contrast to primarily convective precipitation during CP events. Finally, a synthesis of the sedimentary record and the EP:CP ratio of accumulated precipitation and specific humidity in the L. Pallcacocha region allows us to assess whether past changes in the relative frequency of the two ENSO flavors may have been recorded in paleoclimate archives in this region.

48{sup th} Annual meeting on nuclear technology (AMNT 2017). Key topic / Outstanding know-how and sustainable innovations. Technical session: Reactor physics, thermo and fluid dynamics. Neutron flux oscillations phenomena

Energy Technology Data Exchange (ETDEWEB)

Herb, Joachim [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH, Garching (Germany). Abt. Kuehlkreislauf

2018-01-15

The Technical Session about Neutron Flux Oscillation Phenomena was chaired by Joachim Herb (Gesellschaft fuer Anlagen und Reaktorsicherheit (GRS) GmbH) and well attended by approx. 50 listeners. It comprised of three keynotes and two technical presentations. The main topics were the significant changes of the neutron flux noise levels in different German and foreign pressurized water reactors (PWRs). For about ten years an increase in neutron noise levels has been observed in German PWRs. During the following five years the noise levels have been decreasing again. In principle, a correlation of the neutron noise levels to the use of certain fuel element types was observed and the phenomenon of neutron flux oscillations had been known since decades. Nevertheless, no self-consistent physical theory exists so far, which can explain the observed changes and the absolute levels of the observed neutron flux noise levels. Therefore, safety authorities, technical support organizations (TSO), utilities as well as research organizations showed increased interest in this topic during the last years. The results of the corresponding work as well as an outlook into soon-starting research projects were given in this session.

Synchronization in Complex Oscillator Networks and Smart Grids

Energy Technology Data Exchange (ETDEWEB)

Dorfler, Florian [Los Alamos National Laboratory; Chertkov, Michael [Los Alamos National Laboratory; Bullo, Francesco [Center for Control, Dynamical Systems and Computation, University of California at Santa Babara, Santa Barbara CA

2012-07-24

The emergence of synchronization in a network of coupled oscillators is a fascinating topic in various scientific disciplines. A coupled oscillator network is characterized by a population of heterogeneous oscillators and a graph describing the interaction among them. It is known that a strongly coupled and sufficiently homogeneous network synchronizes, but the exact threshold from incoherence to synchrony is unknown. Here we present a novel, concise, and closed-form condition for synchronization of the fully nonlinear, non-equilibrium, and dynamic network. Our synchronization condition can be stated elegantly in terms of the network topology and parameters, or equivalently in terms of an intuitive, linear, and static auxiliary system. Our results significantly improve upon the existing conditions advocated thus far, they are provably exact for various interesting network topologies and parameters, they are statistically correct for almost all networks, and they can be applied equally to synchronization phenomena arising in physics and biology as well as in engineered oscillator networks such as electric power networks. We illustrate the validity, the accuracy, and the practical applicability of our results in complex networks scenarios and in smart grid applications.

Neutrino mass and oscillation angle phenomena within the asymmetric left-right models

International Nuclear Information System (INIS)

Boyarkin, O.; Rein, D.

1994-07-01

The light and heavy Majorana neutrinos which appear naturally in SU(2) L x SU(2) R x U(1) B-L model are investigated. The exact solutions are presented for the system of two neutrinos with multipole moments propagating through magnetic and matter fields. The cross section of the reaction e - e - → W - k W - n calculated and its dependence on the mass of the right-handed neutrino and the oscillation angle is investigated. The process e + e - → W + k W - n is also included in our analysis. (author). 26 refs, 9 figs

United States streamflow probabilities based on forecasted La Nina, winter-spring 2000

Science.gov (United States)

Dettinger, M.D.; Cayan, D.R.; Redmond, K.T.

1999-01-01

Although for the last 5 months the TahitiDarwin Southern Oscillation Index (SOI) has hovered close to normal, the “equatorial” SOI has remained in the La Niña category and predictions are calling for La Niña conditions this winter. In view of these predictions of continuing La Niña and as a direct extension of previous studies of the relations between El NiñoSouthern Oscil-lation (ENSO) conditions and streamflow in the United States (e.g., Redmond and Koch, 1991; Cayan and Webb, 1992; Redmond and Cayan, 1994; Dettinger et al., 1998; Garen, 1998; Cayan et al., 1999; Dettinger et al., in press), the probabilities that United States streamflows from December 1999 through July 2000 will be in upper and lower thirds (terciles) of the historical records are estimated here. The processes that link ENSO to North American streamflow are discussed in detail in these diagnostics studies. Our justification for generating this forecast is threefold: (1) Cayan et al. (1999) recently have shown that ENSO influences on streamflow variations and extremes are proportionately larger than the corresponding precipitation teleconnections. (2) Redmond and Cayan (1994) and Dettinger et al. (in press) also have shown that the low-frequency evolution of ENSO conditions support long-lead correlations between ENSO and streamflow in many rivers of the conterminous United States. (3) In many rivers, significant (weeks-to-months) delays between precipitation and the release to streams of snowmelt or ground-water discharge can support even longer term forecasts of streamflow than is possible for precipitation. The relatively slow, orderly evolution of El Niño-Southern Oscillation episodes, the accentuated dependence of streamflow upon ENSO, and the long lags between precipitation and flow encourage us to provide the following analysis as a simple prediction of this year’s river flows.

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

Science.gov (United States)

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

2016-12-01

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

Tropical cyclone genesis in the Southern Hemisphere and its relationship with the ENSO

Energy Technology Data Exchange (ETDEWEB)

Kuleshov, Y.; Qi, L. [Australian Bureau of Meteorology, Melbourne, VIC (Australia). National Climate Centre; Chane Ming, F.; Chouaibou, I.; Hoareau, C. [UMR CNRS-Meteo-France-Univ. de la Reunion, La Reunion (France). Lab. de l' Atmosphere et des Cyclones; Roux, F. [Paul Sabatier Univ., CNRS, Toulouse (France). Lab. d' Aerologie

2009-07-01

Tropical cyclogenesis climatology over the South Indian and South Pacific Oceans has been developed using a new tropical cyclone (TC) archive for the Southern Hemisphere, and changes in geographical distribution of areas favourable for TC genesis related to changes in the El Nino-Southern Oscillation (ENSO) phases have been investigated. To explain these changes, large-scale environmental variables which influence TC genesis and development such as sea surface temperatures (SSTs), relative humidity in mid-troposphere, vertical wind shear and lower tropospheric vorticity have been examined. In the South Indian Ocean, reduction of TC genesis in the western part of the basin and its increase in the eastern part as well as displacement of the area favourable for TC genesis further away from the equator during La Nina events compared to El Nino events can be explained by changes in geographical distribution of relative humidity and vorticity across the basin as primary contributors; positive anomalies of SSTs observed during La Nina seasons in the eastern part of the basin additionally contribute to enhanced cyclogenesis near the Western Australia. In the South Pacific Ocean, changes in geographical distribution of relative humidity and vorticity appear to be the key large-scale environmental factors responsible for enhanced TC genesis in the eastern (western) part of the basin as well as for the northeast (southwest) shift of points of cyclogenesis during El Nino (La Nina) events, with vertical wind shear and SSTs as additional contributing large-scale environmental variables. (orig.)

Different types of bursting calcium oscillations in non-excitable cells

International Nuclear Information System (INIS)

Perc, Matjaz; Marhl, Marko

2003-01-01

In the paper different types of bursting Ca 2+ oscillations are presented. We analyse bursting behaviour in four recent mathematical models for Ca 2+ oscillations in non-excitable cells. Separately, regular, quasi-periodic, and chaotic bursting Ca 2+ oscillations are classified into several subtypes. The classification is based on the dynamics of separated fast and slow subsystems, the so-called fast-slow burster analysis. For regular bursting Ca 2+ oscillations two types of bursting are specified: Point-Point and Point-Cycle bursting. In particular, the slow passage effect, important for the Hopf-Hopf and SubHopf-SubHopf bursting subtypes, is explained by local divergence calculated for the fast subsystem. Quasi-periodic bursting Ca 2+ oscillations can be found in only one of the four studied mathematical models and appear via a homoclinic bifurcation with a homoclinic torus structure. For chaotic bursting Ca 2+ oscillations, we found that bursting patterns resulting from the period doubling root to chaos considerably differ from those appearing via intermittency and have to be treated separately. The analysis and classification of different types of bursting Ca 2+ oscillations provides better insight into mechanisms of complex intra- and intercellular Ca 2+ signalling. This improves our understanding of several important biological phenomena in cellular signalling like complex frequency-amplitude signal encoding and synchronisation of intercellular signal transduction between coupled cells in tissue

J-PARC Press Release: Electron neutrino oscillation detected at T2K

CERN Multimedia

T2K Press Office

2011-01-01

Tsukuba, Japan, June 15, 2011. The T2K experiment, whose primary purpose is to study neutrino interactions at a large distance from their source, has detected 6 electron neutrino candidate events based on the data collected before March 11, 2011. For the first time, it was possible to observe an indication that muon neutrinos are able to transform into electron neutrinos over a distance of 295 km through the quantum mechanical phenomena of neutrino flavor oscillations.   The Super-Kamiokande detector, in Japan. © 2011, High Energy Accelerator Research Organization, KEK. The T2K experiment is searching for the neutrino oscillation phenomena, where particular types of neutrinos transform into other types of neutrinos. These observations help determine neutrino masses, as well elucidating the uncharted nature of neutrinos, such as the relationship among three neutrino generations (types). T2K aims at the world’s best sensitivity by detecting neutrinos with the Super-Kamiokande d...

Study of the atmospheric neutrino oscillations in the Frejus experiment

International Nuclear Information System (INIS)

Perdereau, O.

1989-05-01

The behavior of atmospheric neutrinos is investigated. It is a zero mass, zero charge and weak interacting particle. The aim of the investigation is to search for non standard phenomena, such as neutrino oscillations. The neutrino theoretical properties are discussed and the physical parameters experimental limits are recalled. The analysis of the approximately 200 events from atmospheric neutrinos observed in Frejus detector is carried out. The results and simulation of neutrino interactions are presented. The data analysis induces to the exclusion of neutrino oscillation hypothesis from some models. Three cases of oscillations involving two neutrino flavors are analyzed. The effect of a third flavor is also taken into account. The present data and those from IMB and Kamiokande experiments are compared. Topics involving investigations on the superposition of a signal and the atmospheric neutrinos are included [fr

How will the impact of El Nino and La Nina on Australia change under global warming?

International Nuclear Information System (INIS)

Power, Scott; Morgan, Adam; Moise, Aurel; Grainger, Simon; Smith, Ian; Reeder, Michael

2007-01-01

Full text: The El Nino-Southern Oscillation (ENSO) has a profound influence on Australia. How will this influence change under global warming? Will El Nino droughts become more frequent or more intense? Will La Nina events tend to produce more or less rainfall over Australia than they have in the past? Has ENSO already changed? Has ENSO's impact on Australia already changed? Will global warming be 'El Nino-like'? How well do current models simulate ENSO and how reliable are their projections for ENSO? Here we will provide answers to these questions drawing on the IPCC (2007) report and recent research conducted here in Australia. We will see that: ENSO and its impact on Australia varied substantially on decadal and longer time-scales over the past century; The frequency of El Nino events appeared to increase; The Walker Circulation, which is one of the most prominent and important atmospheric circulations in the world, is centred in the Pacific Ocean and is strongly modulated by ENSO. The Southern Oscillation Index (SOI) - which is used to track ENSO and the strength of the Walker Circulation -has trended down over the past century. The tropical Pacific - the engine room for ENSO - has warmed to unprecedented levels. The Walker Circulation weakens in some models in response to global warming. The relationship between Australian rainfall, temperature and the SOI has changed. The IPCC WG1 Report (2007) concluded that'... there is no consistent indication at this time of discernable changes in ENSO amplitude or frequency in the 21st century'. Even if ENSO variability in the tropical Pacific does not change, ENSO's impact on Australia might. Evidence supporting this hypothesis will be provided. Finally, we will discuss what this all means for Australia

Sea level oscillations over minute timescales: a global perspective

Science.gov (United States)

Vilibic, Ivica; Sepic, Jadranka

2016-04-01

Sea level oscillations occurring over minutes to a few hours are an important contributor to sea level extremes, and a knowledge on their behaviour is essential for proper quantification of coastal marine hazards. Tsunamis, meteotsunamis, infra-gravity waves and harbour oscillations may even dominate sea level extremes in certain areas and thus pose a great danger for humans and coastal infrastructure. Aside for tsunamis, which are, due to their enormous impact to the coastlines, a well-researched phenomena, the importance of other high-frequency oscillations to the sea level extremes is still underrated, as no systematic long-term measurements have been carried out at a minute timescales. Recently, Intergovernmental Oceanographic Commission (IOC) established Sea Level Monitoring Facility portal (http://www.ioc-sealevelmonitoring.org), making 1-min sea level data publicly available for several hundred tide gauge sites in the World Ocean. Thereafter, a global assessment of oscillations over tsunami timescales become possible; however, the portal contains raw sea level data only, being unchecked for spikes, shifts, drifts and other malfunctions of instruments. We present a quality assessment of these data, estimates of sea level variances and contributions of high-frequency processes to the extremes throughout the World Ocean. This is accompanied with assessment of atmospheric conditions and processes which generate intense high-frequency oscillations.

A pan-tropical cascade of fire driven by El Niño/Southern Oscillation

Science.gov (United States)

Chen, Yang; Morton, Douglas C.; Andela, Niels; van der Werf, Guido R.; Giglio, Louis; Randerson, James T.

2017-12-01

The El Niño/Southern Oscillation (ENSO) has a pronounced influence on year-to-year variations in climate1. The response of fires to this forcing2 is complex and has not been evaluated systematically across different continents. Here we use satellite data to create a climatology of burned-area and fire-emissions responses, drawing on six El Niño and six La Niña events during 1997-2016. On average, reductions in precipitation and terrestrial water storage increased fire emissions in pan-tropical forests by 133% during and following El Niño as compared with La Niña. Fires peaked in equatorial Asia early in the ENSO cycle when El Niño was strengthening (Aug-Oct), before moving to southeast Asia and northern South America (Jan-Apr), Central America (Mar-May) and the southern Amazon (Jul-Oct) during the following year. Large decreases in fire occurred across northern Australia during Sep-Oct of the second year from a reduced fuel availability. Satellite observations of aerosols and carbon monoxide provided independent confirmation of the spatiotemporal evolution of fire anomalies. The predictable cascade of fire across different tropical continents described here highlights an important time delay in the Earth system's response to precipitation redistribution. These observations help to explain why the growth rate of atmospheric CO2 increases during El Niño3 and may contribute to improved seasonal fire forecasts.

Rainfall Patterns Analysis over Ampangan Muda, Kedah from 2007 - 2016

Science.gov (United States)

Chooi Tan, Kok

2018-04-01

The scientific knowledge about climate change and climate variability over Malaysia pertaining to the extreme water-related disaster such as drought and flood. A deficit or increment in precipitation occurred over the past century becomes a useful tool to understand the climate change in Malaysia. The purpose of this work is to examine the rainfall patterns over Ampangan Muda, Kedah. Daily rainfall data is acquired from Malaysian Meteorological Department to analyse the temporal and trends of the monthly and annual rainfall over the study area from 2007 to 2016. The obtained results show that the temporal and patterns of the rainfall over Ampangan Muda, Kedah is largely affected by the regional phenomena such as monsoon, El Niño Southern Oscillation (ENSO), and the Madden-Julian Oscillation. In addition, backward trajectories analysis is also used to identify the patterns for long-range of synoptic circulation over the region.

Effects of hurricanes and climate oscillations on annual variation in reproduction in wet forest, Puerto Rico.

Science.gov (United States)

Zimmerman, Jess K; Hogan, James Aaron; Nytch, Christopher J; Bithorn, John E

2018-06-01

Interannual changes in global climate and weather disturbances may influence reproduction in tropical forests. Phenomena such as the El Niño Southern Oscillation (ENSO) are known to produce interannual variation in reproduction, as do severe storms such as hurricanes. Using stationary trap-based phenology data collected fortnightly from 1993 to 2014 from a hurricane-affected (1989 Hugo, 1998 Georges) subtropical wet forest in northeastern Puerto Rico, we conducted a time series analysis of flowering and seed production. We addressed (1) the degree to which interannual variation in flower and seed production was influenced by global climate drivers and time since hurricane disturbance, and (2) how long-term trends in reproduction varied with plant lifeform. The seasonally de-trended number of species in flower fluctuated over time while the number of species producing seed exhibited a declining trend, one that was particularly evident during the second half of the study period. Lagged El Niño indices and time series hurricane disturbance jointly influenced the trends in numbers of flowering and fruiting species, suggesting complex global influences on tropical forest reproduction with variable periodicities. Lag times affecting flowering tended to be longer than those affecting fruiting. Long-term patterns of reproduction in individual lifeforms paralleled the community-wide patterns, with most groups of lifeform exhibiting a long-term decline in seed but not flower production. Exceptions were found for hemiepiphytes, small trees, and lianas whose seed reproduction increased and then declined over time. There was no long-term increase in flower production as reported in other Neotropical sites. © 2018 by the Ecological Society of America.

Neutrino oscillations in dense neutrino gases

International Nuclear Information System (INIS)

Samuel, S.

1993-01-01

We consider oscillations of neutrinos under conditions in which the neutrino density is sufficiently large that neutrino-neutrino interactions cannot be neglected. A formalism is developed to treat this highly nonlinear system. Numerical analysis reveals a rich array of phenomena. In certain gases, a self-induced Mikheyev-Smirnov-Wolfenstein effect occurs in which electron neutrinos are resonantly converted into muon neutrinos. In another relatively low-density gas, an unexpected parametric resonant conversion takes place. Finally, neutrino-neutrino interactions maintain coherence in one system for which a priori one expected decoherence

Dissipative neutrino oscillations in randomly fluctuating matter

International Nuclear Information System (INIS)

Benatti, F.; Floreanini, R.

2005-01-01

The generalized dynamics describing the propagation of neutrinos in randomly fluctuating media is analyzed: It takes into account matter-induced, decoherence phenomena that go beyond the standard Mikheyev-Smirnov-Wolfenstein (MSW) effect. A widely adopted density fluctuation pattern is found to be physically untenable: A more general model needs to be instead considered, leading to flavor changing effective neutrino-matter interactions. They induce new, dissipative effects that modify the neutrino oscillation pattern in a way amenable to a direct experimental analysis

Dissipative neutrino oscillations in randomly fluctuating matter

Science.gov (United States)

Benatti, F.; Floreanini, R.

2005-01-01

The generalized dynamics describing the propagation of neutrinos in randomly fluctuating media is analyzed: It takes into account matter-induced, decoherence phenomena that go beyond the standard Mikheyev-Smirnov-Wolfenstein (MSW) effect. A widely adopted density fluctuation pattern is found to be physically untenable: A more general model needs to be instead considered, leading to flavor changing effective neutrino-matter interactions. They induce new, dissipative effects that modify the neutrino oscillation pattern in a way amenable to a direct experimental analysis.

The NOW regional coupled model: Application to the tropical Indian Ocean climate and tropical cyclone activity

Digital Repository Service at National Institute of Oceanography (India)

Samson, G.; Masson, S.; Lengaigne, M.; Keerthi, M.G.; Vialard, J.; Pous, S.; Madec, G.; Jourdain, N.C.; Jullien, S.; Menkes, C.; Marchesiello, P.

with the Indian Ocean Dipole (IOD) and the delayed basin-wide warming/cooling induced by the El Nino Southern Oscillation (ENSO). The timing of IOD occurrence in the ~ model generally matches that of the observed events, confirming the influence of ENSO on the IOD...

El Niño effects on the dynamics of terrestrial ecosystems

NARCIS (Netherlands)

Holmgren, M.; Scheffer, M.; Ezcurra, E.; Gutiérrez, J.R.; Mohren, G.M.J.

2001-01-01

New studies are showing that the El Niño Southern Oscillation (ENSO) has major implications for the functioning of different ecosystems, ranging from deserts to tropical rain forests. ENSO-induced pulses of enhanced plant productivity can cascade upward through the food web invoking unforeseen

Climate, ENSO and 'Black Swans' over the Last Millennium

Science.gov (United States)

Thompson, L. G.; Mosley-Thompson, E.; Davis, M. E.; Kenny, D. V.; Lin, P. N.

2014-12-01

Tropical rainfall patterns influence the lives of billions of people both north and south of the Equator. Evidence of major ENSO events such as droughts is often recorded in the oxygen isotopic ratios and aerosol concentrations in tropical ice cores. Here we examine unusual events recorded in three ice cores, two (Quelccaya and Coropuna) in the Southern Hemisphere on the Peruvian Altiplano and the third (Dasuopu) located 22,000 km away on the southern edge of the Tibetan Plateau at the top of the Himalayas. These records suggest that the unique lower and middle tropospheric air flow over chloride (Cl-) and fluoride (F-) enriched areas upwind of the sites during ENSO events leads to enhanced deposition of these species on these glaciers. Linkages are demonstrated between ice-core chemistry and drought indicators, changes in lake levels, and ENSO and monsoon indices. Two unusual events, in the late 18th and mid-14th Centuries, are marked by abnormally high concentrations of F- and Cl- in at least two of the ice core records. All three records document a drought from 1789 to 1800 CE in which increases in these anionic concentrations reflect the abundance of continental atmospheric dust derived from arid regions upwind of the core sites. The earlier event, apparent only in the Quelccaya and Dasuopu ice cores, begins abruptly in 1343 and tapers off by 1375. The interaction between high frequency El Niños and low frequency shifts in the inter-tropical convergence zone may have resulted in these unusually severe and extended droughts. These "Black Swan" events correspond to historically documented, devastating population disruptions that were in part climate related. The 1789 to 1800 CE event was concurrent with the Doji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive climate disruptions are documented in Central and South America. The mid-14th Century drought is concomitant with major monsoon

Fast Soft X-ray Images of MHD Phenomena in NSTX

International Nuclear Information System (INIS)

Bush, C.E.; Stratton, B.C.; Robinson, J.; Zakharov, L.E.; Fredrickson, E.D.; Stutman, D.; Tritz, K.

2008-01-01

A variety of magnetohydrodynamic (MHD) phenomena have been observed on the National Spherical Torus Experiment (NSTX). Many of these affect fast particle losses, which are of major concern for future burning plasma experiments. Usual diagnostics for studying these phenomena are arrays of Mirnov coils for magnetic oscillations and PIN diode arrays for soft x-ray emission from the plasma core. Data reported here are from an unique fast soft x-ray imaging camera (FSXIC) with a wide-angle (pinhole) tangential view of the entire plasma minor cross section. The camera provides a 64x64 pixel image, on a CCD chip, of light resulting from conversion of soft x-rays incident on a phosphor to the visible. We have acquired plasma images at frame rates of 1-500 kHz (300 frames/shot), and have observed a variety of MHD phenomena: disruptions, sawteeth, fishbones, tearing modes, and ELMs. New data including modes with frequency > 90 kHz are also presented. Data analysis and modeling techniques used to interpret the FSXIC data are described and compared, and FSXIC results are compared to Mirnov and PIN diode array results.

Measuring and characterizing beat phenomena with a smartphone

Science.gov (United States)

Osorio, M.; Pereyra, C. J.; Gau, D. L.; Laguarda, A.

2018-03-01

Nowadays, smartphones are in everyone’s life. Apart from being excellent tools for work and communication, they can also be used to perform several measurements of simple physical magnitudes, serving as a mobile and inexpensive laboratory, ideal for use physics lectures in high schools or universities. In this article, we use a smartphone to analyse the acoustic beat phenomena by using a simple experimental setup, which can complement lessons in the classroom. The beats were created by the superposition of the waves generated by two tuning forks, with their natural frequencies previously characterized using different applications. After the characterization, we recorded the beats and analysed the oscillations in time and frequency.

BWR power oscillation evaluation methodologies in core design

International Nuclear Information System (INIS)

Hotta, Akitoshi

1995-01-01

At the initial stage of BWR development, the power oscillation due to the nuclear-thermal interaction originated in random boiling phenomena and nuclear void feedback was feared. But it was shown that under the high pressure condition in the normal operation of recent commercial BWRs, the core is in very stable state. However, power oscillation events have been observed in actual machines, and it is necessary to do the stability evaluation that sufficiently reflects the detailed operation conditions of actual plants. As the cause of power oscillation events, the instability of control system and nuclear-thermal coupling instability are important, and their mechanisms are explained. As the model for analyzing the stability of BWR core, the nuclear-thermal coupling model in frequency domain is the central existence. As the information for the design, the parameters of fuel assemblies, and the nuclear parameters and the thermohydraulic parameters of cores are enumerated. LAPUR-TSI is a nuclear-thermal coupling model. The analysis system in the software of Tokyo Electric Power Co. is outlined, and the analysis model was verified. (K.I.)

Complex dynamics of an archetypal self-excited SD oscillator driven by moving belt friction

International Nuclear Information System (INIS)

Li Zhi-Xin; Cao Qing-Jie; Alain, Léger

2016-01-01

We propose an archetypal self-excited system driven by moving belt friction, which is constructed with the smooth and discontinuous (SD) oscillator proposed by the Cao et al. and the classical moving belt. The moving belt friction is modeled as the Coulomb friction to formulate the mathematical model of the proposed self-excited SD oscillator. The equilibrium states of the unperturbed system are obtained to show the complex equilibrium bifurcations. Phase portraits are depicted to present the hyperbolic structure transition, the multiple stick regions, and the friction-induced asymmetry phenomena. The numerical simulations are carried out to demonstrate the friction-induced vibration of multiple stick-slip phenomena and the stick-slip chaos in the perturbed self-excited system. The results presented here provide an opportunity for us to get insight into the mechanism of the complex friction-induced nonlinear dynamics in mechanical engineering and geography. (paper)

Lagrangian analysis of two-phase hydrodynamic and nuclear-coupled density-wave oscillations

International Nuclear Information System (INIS)

Lahey, R.T. Jr.; Yadigaroglu, G.

1974-01-01

The mathematical technique known as the ''method of characteristics'' has been used to construct an exact, analytical solution to predict the onset of density-wave oscillations in diabatic two-phase systems, such as Boiling Water Nuclear Reactors (BWR's). Specifically, heater wall dynamics, boiling boundary dynamics and nuclear kinetics have been accounted for in this analysis. Emphasis is placed on giving the reader a clear physical understanding of the phenomena of two-phase density-wave oscillations. Explanations are presented in terms of block diagram logic, and phasor representations of the various pressure drop perturbations are given. (U.S.)

Interference phenomena at backscattering by ice crystals of cirrus clouds.

Science.gov (United States)

Borovoi, Anatoli; Kustova, Natalia; Konoshonkin, Alexander

2015-09-21

It is shown that light backscattering by hexagonal ice crystals of cirrus clouds is formed within the physical-optics approximation by both diffraction and interference phenomena. Diffraction determines the angular width of the backscattering peak and interference produces the interference rings inside the peak. By use of a simple model for distortion of the pristine hexagonal shape, we show that the shape distortion leads to both oscillations of the scattering (Mueller) matrix within the backscattering peak and to a strong increase of the depolarization, color, and lidar ratios needed for interpretation of lidar signals.

A simple model of intraseasonal oscillations

Science.gov (United States)

Fuchs, Željka; Raymond, David J.

2017-06-01

The intraseasonal oscillations and in particular the MJO have been and still remain a "holy grail" of today's atmospheric science research. Why does the MJO propagate eastward? What makes it unstable? What is the scaling for the MJO, i.e., why does it prefer long wavelengths or planetary wave numbers 1-3? What is the westward moving component of the intraseasonal oscillation? Though linear WISHE has long been discounted as a plausible model for intraseasonal oscillations and the MJO, the version we have developed explains many of the observed features of those phenomena, in particular, the preference for large zonal scale. In this model version, the moisture budget and the increase of precipitation with tropospheric humidity lead to a "moisture mode." The destabilization of the large-scale moisture mode occurs via WISHE only and there is no need to postulate large-scale radiatively induced instability or negative effective gross moist stability. Our WISHE-moisture theory leads to a large-scale unstable eastward propagating mode in n = -1 case and a large-scale unstable westward propagating mode in n = 1 case. We suggest that the n = -1 case might be connected to the MJO and the observed westward moving disturbance to the observed equatorial Rossby mode.

CPC - Climate Weather Linkage: El Niño Southern Oscillation

Science.gov (United States)

Teleconnections AO NAO PNA AAO Blocking Storm Tracks Climate Glossary Outreach About Us Our Mission Who We Are . P., and A. Kumar, 2000: Understanding and predicting extratropical teleconnections related to ENSO extratropical circulation anomalies during the 1986-1989 ENSO cycle. J. Climate, 6, 595-616. Ropelewski, C. F

Evidences of the association among epidemic of malaria buds in Colombia and the phenomenon El Nino - oscillation of the south

International Nuclear Information System (INIS)

Poveda J, German; Rojas M, William

1997-01-01

The El Nino-Southern Oscillation (ENSO) phenomenon is the main forcing mechanism of climatic variability in tropical South America from seasons to decades. Colombia experience below normal dry periods and above normal air temperatures during the warm phase of ENSO (El Nino), and the converse for the cold phase (La Nina). We analyze records of the annual parasitary incidence (A.P.I) index of malaria in Colombia (Plasmodium vivax and Plasmodium falciparum) for the 1959-1994 period we conclude that: (1) during the occurrence of the El Nino event there is a remarkable increase in the number of cases of malaria in Colombia, with a correlation coefficient of 0.62 (statistically significant at the 95% level) between the malaria 8eries and the sea surface temperature series at the nino-4 region (5 degrades N-5 degrades S, 160 degrades E-150 degrades O); and (2) there is an increasing trend in the number of cases for the aforementioned period these statistically related correlations and modeling results may be used for developing health early warning systems (hews) of climate conditions conducive to outbreaks, facilitating early, environmentally-sound public health interventions to control and mitigate the incidence of diseases related with climate variability

Rhythmical Phenomena in Dermal Perfusion - Proved Assesment Strategies and new Discoveries

Directory of Open Access Journals (Sweden)

Markus Huelsbusch

2005-01-01

Full Text Available The phenomena of rhythm fluctuation of arterial blood pressure were discovered already in the first continuous recordings in the 18th century. However the formation of such rhythms hasn’t been explained until now. This work presents two concepts which could aid in bringing new insights into the understanding of these rhythms. One development is a multisensor system capable to acquire multiple PPG channels, ECG and additionally breathing signals to correlate local and central driven oscillations. The second new development is Photoplethysmography Imaging which allows contactless measurements of cutaneous perfusion with spatial resolution. Together with the necessary mathematical analysis tools like the Wavelet Transform a sound basis for assessment and evaluation of rhythm fluctuations in human hemodynamics is provided. Using the presented framework new, previously unreported phenomena of distributed blood volume movements in dermal perfusion could be observed.

Enhanced biennial variability in the Pacific due to Atlantic capacitor effect.

Science.gov (United States)

Wang, Lei; Yu, Jin-Yi; Paek, Houk

2017-03-20

The El Niño-Southern Oscillation (ENSO) and the variability in the Pacific subtropical highs (PSHs) have major impacts on social and ecological systems. Here we present an Atlantic capacitor effect mechanism to suggest that the Atlantic is a key pacemaker of the biennial variability in the Pacific including that in ENSO and the PSHs during recent decades. The 'charging' (that is, ENSO imprinting the North Tropical Atlantic (NTA) sea surface temperature (SST) via an atmospheric bridge mechanism) and 'discharging' (that is, the NTA SST triggering the following ENSO via a subtropical teleconnection mechanism) processes alternate, generating the biennial rhythmic changes in the Pacific. Since the early 1990s, a warmer Atlantic due to the positive phase of Atlantic multidecadal oscillation and global warming trend has provided more favourable background state for the Atlantic capacitor effect, giving rise to enhanced biennial variability in the Pacific that may increase the occurrence frequency of severe natural hazard events.

Midwest agriculture and ENSO: A comparison of AVHRR NDVI3g data and crop yields in the United States Corn Belt from 1982 to 2014

Science.gov (United States)

Glennie, Erin; Anyamba, Assaf

2018-06-01

A time series of Advanced Very High Resolution Radiometer (AVHRR) derived normalized difference vegetation index (NDVI) data were compared to National Agricultural Statistics Service (NASS) corn yield data in the United States Corn Belt from 1982 to 2014. The main objectives of the comparison were to assess 1) the consistency of regional Corn Belt responses to El Niño/Southern Oscillation (ENSO) teleconnection signals, and 2) the reliability of using NDVI as an indicator of crop yield. Regional NDVI values were used to model a seasonal curve and to define the growing season - May to October. Seasonal conditions in each county were represented by NDVI and land surface temperature (LST) composites, and corn yield was represented by average annual bushels produced per acre. Correlation analysis between the NDVI, LST, corn yield, and equatorial Pacific sea surface temperature anomalies revealed patterns in land surface dynamics and corn yield, as well as typical impacts of ENSO episodes. It was observed from the study that growing seasons coincident with La Niña events were consistently warmer, but El Niño events did not consistently impact NDVI, temperature, or corn yield data. Moreover, the El Niño and La Niña composite images suggest that impacts vary spatially across the Corn Belt. While corn is the dominant crop in the region, some inconsistencies between corn yield and NDVI may be attributed to soy crops and other background interference. The overall correlation between the total growing season NDVI anomaly and detrended corn yield was 0.61(p = 0.00013), though the strength of the relationship varies across the Corn Belt.

Aspects of extratropical synoptic-scale processes in opposing ENSO phases

Science.gov (United States)

Schwierz, C.; Wernli, H.; Hess, D.

2003-04-01

Energy and momentum provided by anomalous tropical heating/cooling affect the circulation on the global scale. Pacific Sea surface temperature anomalies strongly force local conditions in the equatorial Pacific, but are also known to change the climate in the extratropics, particularly over the American continent. The impact on more remote areas such as the Atlantic-European region is less clear. There the observed effects in both analyses and model studies show dependence on the resolution of the model/data, as well as on the time scales under consideration (Merkel and Latif, 2002; Compo et al., 2001). Most of the previous studies focus on larger-scale processes and seasonal time scales (or longer). Here we concentrate on the impact of opposing ENSO phases on extratropical synoptic-scale dynamics. The investigation is undertaken for the Niño/Niña events of 1972/3 and 1973/4 respectively, for 5 winter months (NDJFM) using ECMWF ERA40 data with 1o× 1o horizontal resolution and 60 vertical levels. The examination of the resulting differences in terms of standard dynamical fields (temperature, sea level pressure, precipitation, geopotential) is complemented with additional diagnostic fields (e.g. potential vorticity (PV), anti-/cyclone tracks and frequencies, PV streamers/cut-offs, blocking) in an attempt to gain more insight into aspects of extratropical synoptic-scale dynamical processes associated with ENSO SST anomalies.

Entanglement in Quantum Field Theory: particle mixing and oscillations

International Nuclear Information System (INIS)

Blasone, M; Dell'Anno, F; De Siena, S; Illuminati, F

2013-01-01

The phenomena of particle mixing and flavor oscillations in elementary particle physics are associated with multi-mode entanglement of single-particle states. We show that, in the framework of quantum field theory, these phenomena exhibit a fine structure of quantum correlations, as multi-mode multi-particle entanglement appears. Indeed, the presence of anti-particles adds further degrees of freedom, thus providing nontrivial contributions both to flavor entanglement and, more generally, to multi-partite entanglement. By using the global entanglement measure, based on the linear entropies associated with all the possible bipartitions, we analyze the entanglement in the multiparticle states of two-flavor neutrinos and anti-neutrinos. A direct comparison with the instance of the quantum mechanical Pontecorvo single-particle states is also performed.

Improvements of ENSO-monsoon relationship in CMIP5 models through statistical downscaling over India.

Science.gov (United States)

Akhter, J.; Das, L.; Deb, A.

2017-12-01

Present study has assessed the skills of global climate models (GCMS) from coupled model inter-comparison project phase five (CMIP5) in simulating ENSO-monsoon relationships over seven homogeneous zones of India. Observational sea surface temperature (SST) data has revealed that there has been a significant negative correlation between zonal precipitation and Nino 3.4 index over North Mountainous India, North West India, North Central India, West Peninsular India and South Peninsular India. First and third principal component (PC) of zonal precipitation explaining 44.4% and 14.2% variance respectively has also shown significant anti-correlation with Nino 3.4. Analysis with CMIP5 models revealed that majority of GCMs have failed to reproduce both magnitude and phase of such relationships mainly due to poor simulation of Nino 3.4 index. Therefore, an attempt has been made to improve the results through empirical orthogonal function (EOF) based statistical downscaling of CMIP5 GCMs. To downscale Nino 3.4 index, an optimal predictor combination of PCs extracted from EOF fields of large scale GCM predictors like Geo-potential height, u and v wind, Specific and relative humidity and air temperature at pressure levels 500, 850 and 1000 hpa, mean sea level pressure and atmospheric vapor content has been utilized. Results indicated improvements of downscaled CMIP5 models in simulating ENSO-monsoon relationship for zone wise precipitation. Multi-model ensemble (MME) of downscaled GCMs has better skill than individuals GCM. Therefore, downscaled MME may be used more reliably to investigate future ENSO-monsoon relationship under various warming scenarios

Instabilities in the coupled equatorial ocean atmosphere system

NARCIS (Netherlands)

Dijkstra, H.A.; Vaart, P.C.F. van der

1999-01-01

The large-scale interaction between the ocean and atmosphere is one of the impor- tant factors of natural climate variability.The El-Niño/Southern Oscillation (ENSO) phenomenon in the Tropical Pacific is one of the most prominent examples of climate variability on interannual time scales.ENSO has

Influence of climatic teleconnections on the temporal isotopic ...

Indian Academy of Sciences (India)

a close relation to the El Ni˜no Southern Oscillation (ENSO) variability. The ENSO indices ... record seems to have been caused through an atmospheric mechanism. ... temperature prior and subsequent to the year 1997. ... in the reconstruction of past climate change and suggests possible influence of climatic teleconnec-.

Tropical cyclone genesis in the Southern Hemisphere and its relationship with the ENSO

Directory of Open Access Journals (Sweden)

Y. Kuleshov

2009-06-01

Full Text Available Tropical cyclogenesis climatology over the South Indian and South Pacific Oceans has been developed using a new tropical cyclone (TC archive for the Southern Hemisphere, and changes in geographical distribution of areas favourable for TC genesis related to changes in the El Niño-Southern Oscillation (ENSO phases have been investigated. To explain these changes, large-scale environmental variables which influence TC genesis and development such as sea surface temperatures (SSTs, relative humidity in mid-troposphere, vertical wind shear and lower tropospheric vorticity have been examined. In the South Indian Ocean, reduction of TC genesis in the western part of the basin and its increase in the eastern part as well as displacement of the area favourable for TC genesis further away from the equator during La Niña events compared to El Niño events can be explained by changes in geographical distribution of relative humidity and vorticity across the basin as primary contributors; positive anomalies of SSTs observed during La Niña seasons in the eastern part of the basin additionally contribute to enhanced cyclogenesis near the Western Australia. In the South Pacific Ocean, changes in geographical distribution of relative humidity and vorticity appear to be the key large-scale environmental factors responsible for enhanced TC genesis in the eastern (western part of the basin as well as for the northeast (southwest shift of points of cyclogenesis during El Niño (La Niña events, with vertical wind shear and SSTs as additional contributing large-scale environmental variables.

Quantum field-theoretical description of neutrino and neutral kaon oscillations

Science.gov (United States)

Volobuev, Igor P.

2018-05-01

It is shown that the neutrino and neutral kaon oscillation processes can be consistently described in quantum field theory using only plane waves of the mass eigenstates of neutrinos and neutral kaons. To this end, the standard perturbative S-matrix formalism is modified so that it can be used for calculating the amplitudes of the processes passing at finite distances and finite time intervals. The distance-dependent and time-dependent parts of the amplitudes of the neutrino and neutral kaon oscillation processes are calculated and the results turn out to be in accordance with those of the standard quantum mechanical description of these processes based on the notion of neutrino flavor states and neutral kaon states with definite strangeness. However, the physical picture of the phenomena changes radically: now, there are no oscillations of flavor or definite strangeness states, but, instead of it, there is interference of amplitudes due to different virtual mass eigenstates.

A Data Gathering Scheme in Wireless Sensor Networks Based on Synchronization of Chaotic Spiking Oscillator Networks

International Nuclear Information System (INIS)

Nakano, Hidehiro; Utani, Akihide; Miyauchi, Arata; Yamamoto, Hisao

2011-01-01

This paper studies chaos-based data gathering scheme in multiple sink wireless sensor networks. In the proposed scheme, each wireless sensor node has a simple chaotic oscillator. The oscillators generate spike signals with chaotic interspike intervals, and are impulsively coupled by the signals via wireless communication. Each wireless sensor node transmits and receives sensor information only in the timing of the couplings. The proposed scheme can exhibit various chaos synchronous phenomena and their breakdown phenomena, and can effectively gather sensor information with the significantly small number of transmissions and receptions compared with the conventional scheme. Also, the proposed scheme can flexibly adapt various wireless sensor networks not only with a single sink node but also with multiple sink nodes. This paper introduces our previous works. Through simulation experiments, we show effectiveness of the proposed scheme and discuss its development potential.

Storm surge evolution and its relationship to climate oscillations at Duck, NC

Science.gov (United States)

Munroe, Robert; Curtis, Scott

2017-07-01

Coastal communities experience increased vulnerability during storm surge events through the risk of damage to coastal infrastructure, erosion/deposition, and the endangerment of human life. Policy and planning measures attempt to avoid or mitigate storm surge consequences through building codes and setbacks, beach stabilization, insurance rates, and coastal zoning. The coastal emergency management community and public react and respond on shorter time scales, through temporary protection, emergency stockpiling, and evacuation. This study utilizes time series analysis, the Kolmogorov-Smirnov (K-S) test, Pearson's correlation, and the generalized extreme value (GEV) theorem to make the connection between climate oscillation indices and storm surge characteristics intra-seasonally to inter-annually. Results indicate that an El Niño (+ENSO), negative phase of the NAO, and positive phase of the PNA pattern all support longer duration and hence more powerful surge events, especially in winter. Increased surge duration increases the likelihood of extensive erosion, inland inundation, among other undesirable effects of the surge hazard.

Modeling of termokinetic oscillations at partial oxidation of methane

Science.gov (United States)

Arutyunov, A. V.; Belyaev, A. A.; Inovenkov, I. N.; Nefedov, V. V.

2017-12-01

Partial oxidation of natural gas at moderate temperatures below 1500 K has significant interest for a number of industrial applications. But such processes can proceed at different unstable regimes including oscillating modes. Nonlinear phenomena at partial oxidation of methane were observed at different conditions. The investigation of the complex nonlinear system of equations that describes this process is a real method to insure its stability at industrial conditions and, at the same time, is an effective tool for its further enhancement. Numerical analysis of methane oxidation kinetics in the continuous stirred-tank reactor, with the use of detailed kinetic model has shown the possibility of the appearance of oscillating modes in the appropriate range of reaction parameters that characterize the composition, pressure, reagents flow, thermophysical features of the system, and geometry of the reactor. The appearance of oscillating modes is connected both with the reaction kinetics, heat release and sink and reagents introduction and removing. At that, oscillations appear only at a limited range of parameters, but can be accompanied by significant change in the yield of products. We have determined the range of initial temperature and pressure at which oscillations can be observed, if all other parameters remained fixed. The boundaries of existence of oscillations on the phase plane were calculated. It was shown that depending on the position inside the oscillation region the oscillations have different frequency and amplitude. It was reviled the role of heat exchange with the environment: at the absence of heat exchange the oscillating modes are impossible. In the vicinity of the boundary of phase range, where oscillations exist, significant change of concentration of some products were observed, for example, that of CO2, which in this case one of the principal products is. At that, insignificant increase in pressure not only change the character of CO2 behaving

The impact of combined ENSO and PDO on the PNA climate: a 1,000-year climate modeling study

Energy Technology Data Exchange (ETDEWEB)

Yu, B. [Environment Canada, Climate Data and Analysis Section, Climate Research Division, Toronto, ON (Canada); Zwiers, F.W. [Environment Canada, Canadian Centre for Climate Modelling and Analysis, Climate Research Division, Victoria (Canada)

2007-12-15

This study analyzes the atmospheric response to the combined Pacific interannual ENSO and decadal-interdecadal PDO variability, with a focus on the Pacific-North American (PNA) sector, using a 1,000-year long integration of the Canadian Center for Climate Modelling and Analysis (CCCma) coupled climate model. Both the tropospheric circulation and the North American temperature suggest an enhanced PNA-like climate response and impacts on North America when ENSO and PDO variability are in phase. The anomalies of the centers of action for the PNA-like pattern are significantly different from zero and the anomaly pattern is field significant. In association with the stationary wave anomalies, large stationary wave activity fluxes appear in the mid-high latitudes originating from the North Pacific and flowing downstream toward North America. There are significant Rossby wave source anomalies in the extratropical North Pacific and in the subtropical North Pacific. In addition, the axis of the Pacific storm track shifts southward with the positive PNA. Atmospheric heating anomalies associated with ENSO variability are confined primarily to the tropics. There is an anomalous heating center over the northeast Pacific, together with anomalies with the same polarity in the tropical Pacific, for the PDO variability. The in-phase combination of ENSO and PDO would in turn provide anomalous atmospheric energy transports towards North America from both the Tropical Pacific and the North Pacific, which tends to favor the occurrence of stationary wave anomalies and would lead to a PNA-like wave anomaly structure. The modeling results also confirm our analysis based on the observational record in the twentieth century. (orig.)

Two ENSO episodes with reversed impacts on the regional precipitation of the northeastern South America Dos eventos ENSO con impactos opuestos sobre la precipitación regional en el noreste de Sudamérica

Directory of Open Access Journals (Sweden)

Everaldo B. de Souza

2004-12-01

Full Text Available Diagnostic analyses of two ENSO episodes observed during 1954-55 (La Niña and 1972-73 (El Niño over tropical Pacific Ocean are reported. These years were marked by reversed impact on the regional precipitation observed over the northeastern South America. The observational results showed that, in the Pacific Ocean, the La Niña stayed well configured during both summer and autumn of 1954-55, however the El Niño presented its mature phase during summer of 1972-73 and an abrupt decline during autumn of 1973. On the other hand, the large-scale oceanic and atmospheric patterns related to the intertropical Atlantic SST gradient, created dynamic conditions that modulated the positioning of ITCZ in the equatorial Atlantic and regulated significantly the rainfall anomalies observed in the northeastern South America, overcoming the effect of the ENSO mode observed in the tropical Pacific.En el presente trabajo se realiza un estudio de diagnóstico de los eventos ENSO ocurridos en 1954-55 (La Niña y 1972-73 (El Niño. Durante 1954-55 (1972-73, se observaron anomalías de temperaturas de la superficie del mar (TSM positivas (negativas en el Atlántico Norte y negativas (positivas en el Atlántico Sur, lo que define la fase positiva (negativa del dipolo Atlántico. Los resultados obtenidos muestran que pese a la ocurrencia del evento La Niña (El Niño en el Pacífico, la configuración del dipolo positivo (negativo en el Atlántico creó las condiciones favorables para mantener la ITCZ al norte (sur del Ecuador. En consecuencia, se encontró un déficit (exceso de precipitación en el nor-noreste brasileño durante DEF y MAM de 1954-55 (1972-73. Por lo tanto, durante estos años la configuración anómala de TSM en el Atlántico moduló las anomalías de lluvia observadas en el Amazonas y noreste de Brasil, superando el efecto del ENSO.

Heteroclinic Bifurcation Behaviors of a Duffing Oscillator with Delayed Feedback

Directory of Open Access Journals (Sweden)

Shao-Fang Wen

2018-01-01

Full Text Available The heteroclinic bifurcation and chaos of a Duffing oscillator with forcing excitation under both delayed displacement feedback and delayed velocity feedback are studied by Melnikov method. The Melnikov function is analytically established to detect the necessary conditions for generating chaos. Through the analysis of the analytical necessary conditions, we find that the influences of the delayed displacement feedback and delayed velocity feedback are separable. Then the influences of the displacement and velocity feedback parameters on heteroclinic bifurcation and threshold value of chaotic motion are investigated individually. In order to verify the correctness of the analytical conditions, the Duffing oscillator is also investigated by numerical iterative method. The bifurcation curves and the largest Lyapunov exponents are provided and compared. From the analysis of the numerical simulation results, it could be found that two types of period-doubling bifurcations occur in the Duffing oscillator, so that there are two paths leading to the chaos in this oscillator. The typical dynamical responses, including time histories, phase portraits, and Poincare maps, are all carried out to verify the conclusions. The results reveal some new phenomena, which is useful to design or control this kind of system.

Violation of the Leggett-Garg Inequality in neutrino oscillations

Science.gov (United States)

Weiss, T. E.; Formaggio, J. A.; Kaiser, D. I.; Murskyj, M. M.

2017-09-01

The Leggett-Garg inequality, an analogue of Bell’s inequality involving correlations of measurements on a system at different times, stands as one of the hallmark tests of quantum mechanics against classical predictions. The phenomenon of neutrino oscillations should adhere to quantum-mechanical predictions and provide an observable violation of the Leggett-Garg inequality. We demonstrate how oscillation phenomena can be used to test for violations of the classical bound by performing measurements on an ensemble of neutrinos at distinct energies, as opposed to a single neutrino at distinct times. A study of the MINOS experiment’s data shows a greater than 6σ violation over a distance of 735 km, representing the longest distance over which either the Leggett-Garg inequality or Bell’s inequality has been tested.

Predictability of a Coupled Model of ENSO Using Singular Vector Analysis: Optimal Growth and Forecast Skill.

Science.gov (United States)

Xue, Yan

The optimal growth and its relationship with the forecast skill of the Zebiak and Cane model are studied using a simple statistical model best fit to the original nonlinear model and local linear tangent models about idealized climatic states (the mean background and ENSO cycles in a long model run), and the actual forecast states, including two sets of runs using two different initialization procedures. The seasonally varying Markov model best fit to a suite of 3-year forecasts in a reduced EOF space (18 EOFs) fits the original nonlinear model reasonably well and has comparable or better forecast skill. The initial error growth in a linear evolution operator A is governed by the eigenvalues of A^{T}A, and the square roots of eigenvalues and eigenvectors of A^{T}A are named singular values and singular vectors. One dominant growing singular vector is found, and the optimal 6 month growth rate is largest for a (boreal) spring start and smallest for a fall start. Most of the variation in the optimal growth rate of the two forecasts is seasonal, attributable to the seasonal variations in the mean background, except that in the cold events it is substantially suppressed. It is found that the mean background (zero anomaly) is the most unstable state, and the "forecast IC states" are more unstable than the "coupled model states". One dominant growing singular vector is found, characterized by north-south and east -west dipoles, convergent winds on the equator in the eastern Pacific and a deepened thermocline in the whole equatorial belt. This singular vector is insensitive to initial time and optimization time, but its final pattern is a strong function of initial states. The ENSO system is inherently unpredictable for the dominant singular vector can amplify 5-fold to 24-fold in 6 months and evolve into the large scales characteristic of ENSO. However, the inherent ENSO predictability is only a secondary factor, while the mismatches between the model and data is a

Regular and irregular patterns of self-localized excitation in arrays of coupled phase oscillators

Energy Technology Data Exchange (ETDEWEB)

Wolfrum, Matthias; Omel' chenko, Oleh E. [Weierstrass Institute, Mohrenstrasse 39, Berlin 10117 (Germany); Sieber, Jan [College of Engineering, Mathematics and Physical Sciences, University of Exeter, North Park Road, Exeter EX4 4QF (United Kingdom)

2015-05-15

We study a system of phase oscillators with nonlocal coupling in a ring that supports self-organized patterns of coherence and incoherence, called chimera states. Introducing a global feedback loop, connecting the phase lag to the order parameter, we can observe chimera states also for systems with a small number of oscillators. Numerical simulations show a huge variety of regular and irregular patterns composed of localized phase slipping events of single oscillators. Using methods of classical finite dimensional chaos and bifurcation theory, we can identify the emergence of chaotic chimera states as a result of transitions to chaos via period doubling cascades, torus breakup, and intermittency. We can explain the observed phenomena by a mechanism of self-modulated excitability in a discrete excitable medium.

Neutrino Oscillation Parameter Sensitivity in Future Long-Baseline Experiments

Energy Technology Data Exchange (ETDEWEB)

Bass, Matthew [Colorado State Univ., Fort Collins, CO (United States)

2014-01-01

The study of neutrino interactions and propagation has produced evidence for physics beyond the standard model and promises to continue to shed light on rare phenomena. Since the discovery of neutrino oscillations in the late 1990s there have been rapid advances in establishing the three flavor paradigm of neutrino oscillations. The 2012 discovery of a large value for the last unmeasured missing angle has opened the way for future experiments to search for charge-parity symmetry violation in the lepton sector. This thesis presents an analysis of the future sensitivity to neutrino oscillations in the three flavor paradigm for the T2K, NO A, LBNE, and T2HK experiments. The theory of the three flavor paradigm is explained and the methods to use these theoretical predictions to design long baseline neutrino experiments are described. The sensitivity to the oscillation parameters for each experiment is presented with a particular focus on the search for CP violation and the measurement of the neutrino mass hierarchy. The variations of these sensitivities with statistical considerations and experimental design optimizations taken into account are explored. The effects of systematic uncertainties in the neutrino flux, interaction, and detection predictions are also considered by incorporating more advanced simulations inputs from the LBNE experiment.

Modification of shape oscillations of an attached bubble by surfactants

Directory of Open Access Journals (Sweden)

Tihon J.

2013-04-01

Full Text Available Surface-active agents (surfactants, e.g. washing agents strongly modifies properties of gas-liquid interface. We have carried out extensive experiments, in which we study effect of surfactants on the shape oscillations of a bubble, which is attached at a tip of a capillary. In the experiments, shape oscillations of a bubble are invoked by a motion of a capillary, to which the bubble is injected. Decaying oscillations are recorded and their frequency and damping are evaluated. By changing the excitation frequency, three lowest oscillation modes are studied. Experiments were repeated in aqueous solution of several surfactants (terpineol, SDS, CTAB, Triton X-100, Triton X-45 at various concentrations. Generally, these features are observed: Initially a surfactant addition leads to an increase of the oscillation frequency (though surface tension is decreasing; this effect can be attributed to the increasing interfacial elasticity. The decay time of oscillation is strongly decreasing, as a consequence of energy dissipation linked with Marangoni stresses. At a certain critical concentration, frequency decreases abruptly and the decay time passes by a minimum. With further addition of surfactant, frequency decreases, and the decay time slightly lengthens. Above critical micelle concentration, all these parameters stabilize. Interestingly, the critical concentration, at which frequency drop occurs, depends on mode order. This clearly shows that the frequency drop and minimum decay time are not a consequence of some abrupt change of interfacial properties, but are a consequence of some phenomena, which still need to be explained.

The role of inhibition in generating and controlling Parkinson's disease oscillations in the basal ganglia

Directory of Open Access Journals (Sweden)

Arvind eKumar

2011-10-01

Full Text Available Movement disorders in Parkinson's disease (PD are commonly associated with slow oscillations and increased synchrony of neuronal activity in the basal ganglia. The neural mechanisms underlying this dynamic network dysfunction, however, are only poorly understood. Here, we show that the strength of inhibitory inputs from striatum to globus pallidus external (GPe is a key parameter controlling oscillations in the basal ganglia. Specifically, the increase in striatal activity observed in PD is sufficient to unleash the oscillations in the basal ganglia. This finding allows us to propose a unified explanation for different phenomena: absence of oscillation in the healthy state of the basal ganglia, oscillations in dopamine-depleted state and quenching of oscillations under deep brain stimulation (DBS. These novel insights help us to better understand and optimize the function of DBS protocols. Furthermore, studying the model behaviour under transient increase of activity of the striatal neurons projecting to the indirect pathway, we are able to account for both motor impairment in PD patients and for reduced response inhibition in DBS implanted patients.

Recharge beneath low-impact design rain gardens and the influence of El Niño Southern Oscillation on urban, coastal groundwater resources

Science.gov (United States)

Newcomer, M. E.; Gurdak, J. J.

2011-12-01

Groundwater resources in urban, coastal environments are highly vulnerable to increased human pressures and climate variability. Impervious surfaces, such as buildings, roads, and parking lots prevent infiltration, reduce recharge to underlying aquifers, and increase contaminants in surface runoff that often overflow sewage systems. To mitigate these effects, cities worldwide are adopting low impact design (LID) approaches that direct runoff into natural vegetated systems, such as rain gardens that reduce, filter, and slow stormwater runoff, and are hypothesized to increase infiltration and recharge rates to aquifers. The effects of LID on recharge rates and quality is unknown, particularly during intense precipitation events for cities along the Pacific coast in response to interannual variability of the El Niño Southern Oscillation (ENSO). Using vadose zone monitoring sensors and instruments, I collected and monitored soil, hydraulic, and geochemical data to quantify the rates and quality of infiltration and recharge to the California Coastal aquifer system beneath a LID rain garden and traditional turf-lawn setting in San Francisco, CA. The data were used to calibrate a HYDRUS-3D model to simulate recharge rates under historical and future variability of ENSO. Understanding these processes has important implications for managing groundwater resources in urban, coastal environments.

Computer simulation of phenomena in plasma via particles

International Nuclear Information System (INIS)

Alves, M.V.; Bittencourt, J.A.

1988-06-01

The method of plasma computer simulation via particles has become an efficient tool to investigate the time and spatial evolution of various physical phenomena in plasmas. This method is based on the study of the individual plasma particle motions interacting with one another and with the externally applied fields. Although fairly simple, it allows a non-linear analysis of complex plasma physical phenomena and to obtain diagnostics even for regions of the system where experimental measurements would be difficult to make. In this report, a general view of the electrostatic one-dimensional computer code ES1, originally developed by A. Bruce Langdon, is presented. The main mathematical artifice in this code is the use of a spatial grid in which various plasma particles are represented by ''superparticles'', using a given shape function. The principal characteristics of the model, the approximations made and the mathematical methods used to solve the equations involved, are described. The specification of the input parameters which characterize the system, the initial conditions and the graphic diagnostics which can be utilized, are also described. Results are presented illustrating graphically the behavior of the plasma oscillations, the two-stream instability and the beam-plasma instability. (author) [pt

The El Niño - La Niña cycle and recent trends in supply and demand of net primary productivity in African drylands

NARCIS (Netherlands)

Abdi, A.M.; Vrieling, A.; Yengoh, G.T.; Anyamba, A.; Seaquist, J.W.; Ummenhofer, C.C.; Ardö, J.

2016-01-01

Inter-annual climatic variability over a large portion of sub-Saharan Africa is under the influence of the El Niño-Southern Oscillation (ENSO). Extreme variability in climate is a threat to rural livelihoods in sub-Saharan Africa, yet the role of ENSO in the balance between supply and demand of net

Entanglement in a QFT Model of Neutrino Oscillations

International Nuclear Information System (INIS)

Illuminati, F.; Blasone, M.; Dell’Anno, F.; De Siena, S.

2014-01-01

Tools of quantum information theory can be exploited to provide a convenient description of the phenomena of particle mixing and flavor oscillations in terms of entanglement, a fundamental quantum resource. We extend such a picture to the domain of quantum field theory where, due to the nontrivial nature of flavor neutrino states, the presence of antiparticles provides additional contributions to flavor entanglement. We use a suitable entanglement measure, the concurrence, that allows extracting the two-mode (flavor) entanglement from the full multimode, multiparticle flavor neutrino states

Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought

Science.gov (United States)

Pervez, M. S.; Henebry, G. M.

2014-02-01

We evaluated the spatial and temporal responses of precipitation in the basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean (IO) dipole modes using observed precipitation records at 43 stations across the Ganges and Brahmaputra basins from 1982 to 2010. Daily observed precipitation records were extracted from Global Surface Summary of the Day dataset and spatial and monthly anomalies were computed. The anomalies were averaged for the years influenced by climate modes combinations. Occurrences of El Niño alone significantly reduced (60% and 88% of baseline in the Ganges and Brahmaputra basins, respectively) precipitation during the monsoon months in the northwestern and central Ganges basin and across the Brahmaputra basin. In contrast, co-occurrence of La Niña and a positive IO dipole mode significantly enhanced (135% and 160% of baseline, respectively) precipitation across both basins. During the co-occurrence of neutral phases in both climate modes (occurring 13 out of 28 yr), precipitation remained below average to average in the agriculturally extensive areas of Haryana, Uttar Pradesh, Bihar, eastern Nepal, and the Rajshahi district in Bangladesh in the Ganges basin and northern Bangladesh, Meghalaya, Assam, and Arunachal Pradesh in the Brahmaputra basin. This pattern implies that a regular water deficit is likely in these areas with implications for the agriculture sector due to its reliance on consistent rainfall for successful production. Major flooding and drought occurred as a consequence of the interactive effects of the ENSO and IO dipole modes, with the sole exception of extreme precipitation and flooding during El Niño events. This observational analysis will facilitate well informed decision making in minimizing natural hazard risks and climate impacts on agriculture, and supports development of strategies ensuring optimized use of water resources in best management practice under changing climate.

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.

Journal of Earth System Science | Indian Academy of Sciences

Indian Academy of Sciences (India)

The annual 18O profile of the core shows a close relation to the El Niño Southern Oscillation (ENSO) variability. The ENSO indices show significant correlation with the surface air temperatures and 18O values of this region during the austral summer season and support an additional influence related to the Southern ...

Analysis of vortex phenomena in PWRs at reduced inventory conditions

International Nuclear Information System (INIS)

Waldrep, G.W.; Field, R.W.

1990-01-01

Several recent events have occurred in pressurized water reactors in which shutdown cooling flow has been lost. This has resulted in considerable concern in the industry with operation at or near mid-loop conditions during shutdown operations. Although operation at mid-loop conditions can be minimized, it cannot be totally eliminated without fully off-loading the core. The primary concern is that at reduced inventory conditions and with high flow rates [>15 m 3 /min (4,000 gal/min)], air entrainment due to vortexing can occur. Although the Palo Verde Nuclear Generating Station (PVNGS) (operated by Arizona Public Service) never experienced an actual loss of shutdown cooling, several instances occurred in which evidence of air entrainment was observed. These indications include pump amp oscillations, flow noises, bubbles in the tygon-level monitoring system, and discharge flow/pressure oscillations. These occurrences as well as the NRC's concerns heightened Arizona Public Service's desire to thoroughly understand the actual flow characteristics and vortex phenomena in a Combustion Engineering System 80 pressurized water reactor

A New Technique to Observe ENSO Activity via Ground-Based GPS Receivers

Science.gov (United States)

Suparta, Wayan; Iskandar, Ahmad; Singh, Mandeep Singh Jit

In an attempt to study the effects of global climate change in the tropics for improving global climate model, this paper aims to detect the ENSO events, especially El Nino phase by using ground-based GPS receivers. Precipitable water vapor (PWV) obtained from the Global Positioning System (GPS) Meteorology measurements in line with the sea surface temperature anomaly (SSTa) are used to connect their response to El Niño activity. The data gathered from four selected stations over the Southeast Asia, namely PIMO (Philippines), KUAL (Malaysia), NTUS (Singapore) and BAKO (Indonesia) for the year of 2009/2010 were processed. A strong correlation was observed for PIMO station with a correlation coefficient of -0.90, significantly at the 99 % confidence level. In general, the relationship between GPS PWV and SSTa at all stations on a weekly basis showed with a negative correlation. The negative correlation indicates that during the El Niño event, the PWV variation was in decreased trend. Decreased trend of PWV value is caused by a dry season that affected the GPS signals in the ocean-atmospheric coupling. Based on these promising results, we can propose that the ground-based GPS receiver is capable used to monitor ENSO activity and this is a new prospective method that previously unexplored.

A case study of the intraseasonal oscillation traversing the TOGA-COARE LSD. [large-scale domain

Science.gov (United States)

Vincent, Dayton G.; Schrage, Jon M.; Sliwinski, L. D.

1993-01-01

The paper presents examination of tree intraseasonal (30-60 day) oscillations (ISOs) that occurred during the southern summer season (December 1, 1985 - February 28, 1986) traversing the Large-Scale Domain (LSD) TOGA-COARE, the region which also plays an important role in ENSO, Australian monsoon, and extratropical circulations. Data presented include Hovmoeller diagrams of 5-day running means of 250-mb velocity potential anomalies and OLR anomalies; graphs of five-day running means of OLR in precipitable water (W) per sq m, averaged over 10 x 10 deg boxes centered on 5 S and (1) 145 E, (2) 155 E, (3) 165 E, and (4) 165 D, indicating the midpoint of each ISO; and vertical profiles of zonal wind in m/s averaged over the time period that each ISO spends in the 10 x 10 deg box centered at 5 S, and 175 E and 145 E.

El Niño-Southern Oscillation and dengue early warning in Ecuador

Science.gov (United States)

Stewart, A. M.; Lowe, R.

2012-04-01

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

A memristor-based third-order oscillator: beyond oscillation

KAUST Repository

Talukdar, Abdul Hafiz Ibne

2012-10-06

This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

A memristor-based third-order oscillator: beyond oscillation

KAUST Repository

Talukdar, Abdul Hafiz Ibne; Radwan, Ahmed G.; Salama, Khaled N.

2012-01-01

This paper demonstrates the first third-order autonomous linear time variant circuit realization that enhances parametric oscillation through the usage of memristor in conventional oscillators. Although the output has sustained oscillation, the linear features of the conventional oscillators become time dependent. The poles oscillate in nonlinear behavior due to the oscillation of memristor resistance. The mathematical formulas as well as SPICE simulations are introduced for the memristor-based phase shift oscillator showing a great matching.

Spatiotemporal change of intraseasonal oscillation intensity over the tropical Indo-Pacific Ocean associated with El Niño and La Niña events

Science.gov (United States)

Wu, Renguang; Song, Lei

2018-02-01

The present study analyzes the intraseasonal oscillation (ISO) intensity change over the tropical Indo-Pacific associated with the El Niño-Southern Oscillation (ENSO) and compares the intensity change between El Niño and La Niña years and between the 10-20-day and 30-60-day ISOs. The ISO intensity change tends to be opposite between El Niño and La Niña years in the developing and mature phases. The intensity change features a contrast between the tropical southeastern Indian Ocean and the tropical western North Pacific (WNP) in the developing phases and between the Maritime Continent and the tropical central Pacific in the mature phase. In the decaying phases, the intensity change shows notable differences between El Niño and La Niña events and between fast and slow decaying El Niño events. Large intensity change is observed over the tropical WNP in the developing summer, over the tropical southeastern Indian Ocean in the developing fall, and over the tropical WNP in the fast decaying El Niño summer due to a combined effect of vertical shear, vertical motion, and lower-level moisture. In the ENSO developing summer and in the El Niño decaying summer, the 10-20-day ISO intensity change displays a northwest-southeast tilted distribution over the tropical WNP, whereas the large 30-60-day ISO intensity change is confined to the off-equatorial WNP. In the La Niña decaying summer, the 30-60-day ISO intensity change features a large zonal contrast across the Philippines, whereas the 10-20-day ISO intensity anomaly is characterized by a north-south contrast over the tropical WNP.

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

OpenAIRE

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 the theory of institutional sociology to explain complex interaction between transnational actors and actors in localities that jointly form a governance generating network in order to implement the ...

Numerical study on the characteristics of air bubble oscillation in water

International Nuclear Information System (INIS)

Kim, Hwan Yeol; Bae, Yoon Yeong

2003-01-01

In both a boiling water reactor and an advanced type of pressurized water reactor under construction in Korea named APR1400, when a pressure relieving system is in operation, water, air and steam discharge successively into a sub-cooled water pool through spargers. Among the phenomena occurring during the discharging processes, the air bubble clouds with a low-frequency and high-amplitude oscillation may result in significant damage to the submerged structures if the resonance between the bubble clouds and structures occur. The phenomena involved are so complicated that most predictions of frequency and pressure loads have resorted to experimental work and computational approach has been precluded. This study deals with a numerical prediction of the pressure field generated by the oscillation of air bubble. The analysis was performed by using a commercial thermal hydraulic analysis code, FLUENT, version 4.5. The multiphase flows of water, air and steam were simulated by the VOF (Volume Of Fluid) model contained in the code. Unlike the author's previous study, the LRR (Load Reduction Ring) of the sparger is artificially blocked for the investigation of LRR effects on the pressure field. It also includes the effect of air mass and inlet pressure in the piping on the pressure field. (author)

Four-cluster chimera state in non-locally coupled phase oscillator systems with an external potential

International Nuclear Information System (INIS)

Zhu Yun; Zheng Zhi-Gang; Yang Jun-Zhong

2013-01-01

Dynamics of a one-dimensional array of non-locally coupled Kuramoto phase oscillators with an external potential is studied. A four-cluster chimera state is observed for the moderate strength of the external potential. Different from the clustered chimera states studied before, the instantaneous frequencies of the oscillators in a synchronized cluster are different in the presence of the external potential. As the strength of the external potential increases, a bifurcation from the two-cluster chimera state to the four-cluster chimera states can be found. These phenomena are well predicted analytically with the help of the Ott—Antonsen ansatz. (general)

Strong links between teleconnections and ecosystem exchange found at a Pacific Northwest old-growth forest from flux tower and MODIS EVI data