Asymmetric impacts of El Niño and La Niña on the Pacific–South America teleconnection pattern

2021 ◽  
pp. 1-50
Keyword(s):  
El Niño ◽  
El Nino ◽  
Wave Train ◽  
La Niña ◽  
Convective Precipitation ◽  
Eastern Region ◽  
Mean Flow ◽  
Amundsen Sea ◽  
La Nina ◽  
The Pacific

Abstract El Niño–Southern Oscillation (ENSO) has a huge influence on Antarctic climate variability via Rossby wave trains. In this study, the asymmetry of the ENSO teleconnection in the Southern Hemisphere, as along with the mechanisms involved, is systematically investigated. In four reanalysis datasets, the composite atmospheric circulation anomaly in austral winter over the Amundsen Sea during La Niña is situated more to the west than during El Niño. This asymmetric feature is reproduced by ECHAM5.3.2 forced with both composite and idealized symmetric sea surface temperature anomalies. Utilizing a linear baroclinic model, we find that ENSO-triggered circulation anomalies in the subtropics can readily extract kinetic energy from the climatological mean flow and develop efficiently at the exit of the subtropical jet stream (STJ). The discrepancy in the location of the STJ between El Niño and La Niña causes asymmetric circulation responses by affecting the energy conversion. During El Niño years, anomalous tropical convective precipitation increases the meridional temperature gradient, which in turn leads to the strengthening of the STJ and the eastward movement of the jet core and jet exit in the Pacific. With the movement of the STJ exit, the wave train tends to develop over the eastern region. The opposite is the case during La Niña when the westward shift of the jet exit favors the development of the wave train in the western region. Our findings expand the current understanding regarding ENSO teleconnection.

scholarly journals A New Perspective on the Excitation of Low-Tropospheric Mixed Rossby–Gravity Waves in Association with Energy Dispersion

2012 ◽  
Vol 69 (4) ◽  
pp. 1397-1403 ◽  
Author(s):  
Guanghua Chen ◽  
Chi-Yung Tam
Keyword(s):  
El Niño ◽  
El Nino ◽  
Wave Train ◽  
La Niña ◽  
Boreal Summer ◽  
Mean Flow ◽  
Energy Dispersion ◽  
Low Level ◽  
La Nina ◽  
Equatorial Wave

Abstract This study investigates the synoptic-scale equatorial response to Rossby wave energy dispersion associated with off-equatorial wave activity sources and proposes a new mechanism for triggering low-level mixed Rossby–gravity (MRG) waves. A case study based on observations in boreal summer 2002 reveals that a vortex related to tropical cyclogenesis generated a coherent wave train through southeastward energy dispersion. The southeastward-propagating energy packet gave rise to the equatorial atmospheric response with a temporal scale similar to the wave train and with a structure consistent with the equatorially trapped MRG wave. A baroclinic multilevel anomaly model is employed to verify the excitation of MRG associated with the energy dispersion originating outside of the equatorial region and to explore the discrepancy in the equatorial responses under the different background flows corresponding to El Niño and La Niña. The results show that the prevalence of the low-level westerly flow, the associated zonal wind convergence, and the easterly vertical wind shear can be more favorable for the enhancement of southeastward-propagating energy dispersion and equatorial MRG response in the low troposphere during El Niño than those during La Niña. In addition, the strength of the mean flow can strongly affect the extent of equatorial wave response and modulate its phase and group velocity due to the Doppler shift effect.

scholarly journals Role of the Indo-Pacific Interbasin Coupling in Predicting Asymmetric ENSO Transition and Duration

2012 ◽  
Vol 25 (9) ◽  
pp. 3321-3335 ◽  
Author(s):  
Masamichi Ohba ◽  
Masahiro Watanabe
Keyword(s):  
El Niño ◽  
General Circulation ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
La Nina ◽  
The Pacific ◽  
Enso Asymmetry ◽  
Sst Anomalies

Warm and cold phases of El Niño–Southern Oscillation (ENSO) exhibit a significant asymmetry in their transition/duration such that El Niño tends to shift rapidly to La Niña after the mature phase, whereas La Niña tends to persist for up to 2 yr. The possible role of sea surface temperature (SST) anomalies in the Indian Ocean (IO) in this ENSO asymmetry is investigated using a coupled general circulation model (CGCM). Decoupled-IO experiments are conducted to assess asymmetric IO feedbacks to the ongoing ENSO evolution in the Pacific. Identical-twin forecast experiments show that a coupling of the IO extends the skillful prediction of the ENSO warm phase by about one year, which was about 8 months in the absence of the IO coupling, in which a significant drop of the prediction skill around the boreal spring (known as the spring prediction barrier) is found. The effect of IO coupling on the predictability of the Pacific SST is significantly weaker in the decay phase of La Niña. Warm IO SST anomalies associated with El Niño enhance surface easterlies over the equatorial western Pacific and hence facilitate the El Niño decay. However, this mechanism cannot be applied to cold IO SST anomalies during La Niña. The result of these CGCM experiments estimates that approximately one-half of the ENSO asymmetry arises from the phase-dependent nature of the Indo-Pacific interbasin coupling.

scholarly journals ENSO Modulation of the QBO: Results from MIROC Models with and without Nonorographic Gravity Wave Parameterization

2019 ◽  
Vol 76 (12) ◽  
pp. 3893-3917 ◽  
Author(s):  
Yoshio Kawatani ◽  
Kevin Hamilton ◽  
Kaoru Sato ◽  
Timothy J. Dunkerton ◽  
Shingo Watanabe ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
El Niño ◽  
El Nino ◽  
Horizontal Resolution ◽  
La Niña ◽  
Mean Flow ◽  
Quasi Biennial Oscillation ◽  
La Nina ◽  
Zonal Wavenumber

Abstract Observational studies have shown that, on average, the quasi-biennial oscillation (QBO) exhibits a faster phase progression and shorter period during El Niño than during La Niña. Here, the possible mechanism of QBO modulation associated with ENSO is investigated using the MIROC-AGCM with T106 (~1.125°) horizontal resolution. The MIROC-AGCM simulates QBO-like oscillations without any nonorographic gravity wave parameterizations. A 100-yr integration was conducted during which annually repeating sea surface temperatures based on the composite observed El Niño conditions were imposed. A similar 100-yr La Niña integration was also conducted. The MIROC-AGCM simulates realistic differences between El Niño and La Niña, notably shorter QBO periods, a weaker Walker circulation, and more equatorial precipitation during El Niño than during La Niña. Near the equator, vertical wave fluxes of zonal momentum in the uppermost troposphere are larger and the stratospheric QBO forcing due to interaction of the mean flow with resolved gravity waves (particularly for zonal wavenumber ≥43) is much larger during El Niño. The tropical upwelling associated with the Brewer–Dobson circulation is also stronger in the El Niño simulation. The effects of the enhanced tropical upwelling during El Niño are evidently overcome by enhanced wave driving, resulting in the shorter QBO period. The integrations were repeated with another model version (MIROC-ECM with T42 horizontal resolution) that employs a parameterization of nonorographic gravity waves in order to simulate a QBO. In the MIROC-ECM the average QBO periods are nearly identical in the El Niño and La Niña simulations.

scholarly journals Multi-model assessment of the late-winter stratospheric response to El Niño and La Niña

2021 ◽  
Author(s):  
Bianca Mezzina ◽  
Froila M. Palmeiro ◽  
Javier García-Serrano ◽  
Ileana Bladé ◽  
Lauriane Batté ◽  
...  
Keyword(s):  
Rossby Wave ◽  
El Niño ◽  
Lower Stratosphere ◽  
El Nino ◽  
Wave Train ◽  
La Niña ◽  
Late Winter ◽  
Polar Cap ◽  
La Nina ◽  
Rossby Wave Train

AbstractThe impact of El Niño-Southern Oscillation (ENSO) on the late-winter extra-tropical stratosphere (January–March) is assessed in a multi-model framework. Three state-of-the-art atmospheric models are run with prescribed SST anomalies representative of a strong ENSO event, with symmetric patterns for El Niño and La Niña. The well-known temperature perturbation in the lower stratosphere during El Niño is captured by two models, in which the anomalous warming at polar latitudes is accompanied by a positive geopotential height anomaly that extends over the polar cap. In the third model, which shows a lack of temperature anomalies over the pole, the anomalous anticyclone is confined over Canada and does not expand to the polar cap. This anomalous center of action emerges from the large-scale tropospheric Rossby wave train forced by ENSO, and shrinking/stretching around the polar vortex is invoked to link it to the temperature response. No disagreement across models is found in the lower stratosphere for La Niña, whose teleconnection is opposite in sign but weaker. In the middle-upper stratosphere (above 50 hPa) the geopotential height anomalies project on a wavenumber-1 (WN1) pattern for both El Niño and, more weakly, La Niña, and show a westward tilt with height up to the stratopause. It is suggested that this WN1 pattern arises from the high-latitude lower-stratospheric anomalies, and that the ENSO teleconnection to the polar stratosphere can be interpreted in terms of upward propagation of the stationary Rossby wave train and quasi-geostrophic balance, instead of wave breaking.

scholarly journals PDO–ENSO Effects in the Climate of Mexico

2006 ◽  
Vol 19 (24) ◽  
pp. 6433-6438 ◽  
Author(s):  
Edgar G. Pavia ◽  
Federico Graef ◽  
Jorge Reyes
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Climate Anomalies ◽  
Enso Events ◽  
La Nina ◽  
Mean Temperature ◽  
The Pacific

Abstract The role of the Pacific decadal oscillation (PDO) in El Niño–Southern Oscillation (ENSO)-related Mexican climate anomalies during winter and summer is investigated. The precipitation and mean temperature data of approximately 1000 stations throughout Mexico are considered. After sorting ENSO events by warm phase (El Niño) and cold phase (La Niña) and prevailing PDO phase: warm or high (HiPDO) and cold or low (LoPDO), the authors found the following: 1) For precipitation, El Niño favors wet conditions during summers of LoPDO and during winters of HiPDO. 2) For mean temperature, cooler conditions are favored during La Niña summers and during El Niño winters, regardless of the PDO phase; however, warmer conditions are favored by the HiPDO during El Niño summers.

Impacts of El Niño and La Niña Cycles: Systems and Sectors

2008 ◽  
Author(s):  
Cynthia Rosenzweig ◽  
Daniel Hillel
Keyword(s):  
Pacific Ocean ◽  
El Niño ◽  
El Nino ◽  
Terrestrial Ecosystem ◽  
Terrestrial Ecosystems ◽  
La Niña ◽  
Enso Events ◽  
La Nina ◽  
The Pacific ◽  
The Pacific Ocean

Perturbations of the climate system caused by El Niño and La Niña events affect natural and managed systems in vast areas of the Pacific Ocean and far beyond it. (Other oscillations affect systems and sectors in wide swaths of the world as well.)1 El Niño–Southern Oscillation (ENSO) events have been associated with ecosystem disruptions and forest fires, crop failures and famines, disease epidemics, and even market fluctuations in various regions. The forms and degrees of impact depend not only on the strength and duration of an El Niño or La Niña event and its associated teleconnections, but also on the state, sensitivity, and vulnerability of the affected system and its biotic community, as well as its human population. The underlying characteristics of ecosystems and human societies in each region are important factors in their susceptibility to ENSO-related damages. Variation may be enhanced as ENSO effects ripple through natural and managed ecosystems. The underlying health of the affected biota, interrelationships among different biotic associations, and pressure by humans all affect marine as well as terrestrial ecosystem responses to ENSO events. Impacts on human systems can be both direct and indirect. Some ENSO phenomena, such as severe storms, affect human lives and infrastructures directly. Other impacts occur through alterations in the marine and terrestrial ecosystems and water supplies upon which human populations ultimately depend. In this chapter we consider some of the impacts that ENSO and other oscillations (described with their teleconnections in chapter 1) have on marine and terrestrial ecosystems and on human-managed systems apart from agriculture. The significant and geographically widespread changes that El Niño events induce in the Pacific Ocean alter conditions for various marine communities. These alterations include dramatic changes in the abundance and distribution of organisms, associated collapses of commercial fisheries, and ensuing consequences affecting human livelihood (Glantz, 2004; Lehodey et al., 2006). Some of the effects are well documented. Reductions in primary production of up to 95% were measured in the eastern equatorial Pacific in 1982–83 (Barber and Chavez, 1983.) Large changes in ecosystem structure and productivity have also been recorded in other parts of the Pacific Ocean, including the western Pacific and in the North Pacific subtropical gyre (north of the Hawaiian Islands) (Karl et al., 1995).

scholarly journals The Collective Contribution of Atmospheric and Oceanic Components to ENSO Asymmetry

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 469
Author(s):  
Yanli Tang ◽  
Lijuan Li ◽  
Bin Wang ◽  
Pengfei Lin ◽  
Wenjie Dong ◽  
...  
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Convective Precipitation ◽  
Coupled Models ◽  
Atmospheric Component ◽  
Bj Index ◽  
La Nina ◽  
Sst Anomalies

Four cross-coupled models were used to investigate the relative contributions of atmospheric and oceanic components to the asymmetry of the El Niño–Southern Oscillation (ENSO). Strong El Niño and La Niña events related to the negative heat flux feedbacks were found to be determined mainly by the atmospheric component, and the stronger sea surface temperature (SST) anomalies in the warm phase did not lead to an increased SST asymmetry. The skewness of the four models could be affected by both atmospheric and oceanic components; the atmospheric component determines the strength of positive and negative SST anomalies, and the oceanic component affects the strength of the negative SST anomalies in the cold phase under the same atmospheric component group. The Bjerknes stability index (BJ index) of warm and cold phases contributed to the El Niño–La Niña SSTA asymmetries in observation, but the BJ index did not necessarily explain the El Niño–La Niña SSTA asymmetries in climate model simulations. The SST asymmetries in these four models were closely associated with convective precipitation and wind stress asymmetries, which are also determined by both the atmospheric and oceanic components.

scholarly journals Influência do el niño e la niña no número de dias de precipitação pluviométrica do estado do Mato Grosso do Sul

2016 ◽  
Vol 10 (1) ◽  
pp. 73
Author(s):  
Nayhara De Lima Oliveira ◽  
Francisco Fernando Noronha Marcuzzo
Keyword(s):  
El Niño ◽  
Direct Relationship ◽  
El Nino ◽  
La Niña ◽  
Mato Grosso ◽  
La Nina ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Mato Grosso Do Sul ◽  
Key Words Temperature

ResumoUm melhor detalhamento do comportamento da precipitação pluvial pode ser obtido com o estudo do NDC (Número de Dias de Chuva) e a sua correlação com fenômenos climáticos. O presente trabalho teve como objetivo correlacionar a variação do NDC no Estado do Mato Grosso do Sul com a intensidade do Índice Oceânico Niño(a) (ION). Utilizaram-se dados de 37 estações pluviométricas com 30 anos de dados e 55 estações com dados variando de 20 a 29 anos, sendo que toda série histórica está entre os anos de 1977 a 2006. No período de 1977 a 2006 o ION mensal médio variou entre -1,1°C e 1,3°C, variações consideradas moderadas, com algumas variações consideradas fortes nos anos de 1982 (2,3°C), 1983 (2,3°C). 1988 (-1,9°C), 1991 (1,6°C), 1992 (1,8°C), 1997 (2,5°C), 1998 (2,3°C), 1999/2000 (-1,6°C) e 2002 (1,5°C). Observa-se que o NDC de cada ano do período não tem uma relação direta com os fenômenos El Niño e La Niña, já que a linha de tendência polinomial de segunda ordem pouco variou.Palavras-chave: Temperatura do Oceano Pacífico, ENOS, Número de Dias de Chuva, Climatologia. AbstractA more detailed behavior of rainfall can be obtained from the study of Number of Days Rain (NDC) and its correlation with weather phenomena. This study aimed to correlate the variation of the NDC in the state of Mato Grosso do Sul with the intensity Niño Index (a). We used data from 37 rainfall stations with 30 years of data and 55 stations with data ranging from 20 to 29 years, and throughout this series between the years 1977 to 2006. In the period 1977 to 2006 the average monthly Niño índex ranged between -1,1°C and 1,3°C, variations considered moderate, with some variations considered strong in the years 1982 (2.3°C), 1983 (2.3°C), 1988(-1.9°C), 1991 (1.6°C), 1992 (1,8°C), 1997 (2.5°C), 1998 (2.3°C), 1999/2000 (-1.6°C) and 2002 (1.5°C). It is observed that in general the NDC for each year of the period has a direct relationship with El Niño and La Niña, since the polynomial trendline second order changed little. Key-words: Temperature of the Pacific Ocean, ENSO, Number of Days of Rain, Climatology ResumenUn comportamiento más detallado de la precipitación se pueden obtener a partir del estudio de Número de días de lluvia (NDL) y su correlación con los fenómenos meteorológicos. Este estudio tuvo como objetivo relacionar la variación de lo NDL en el estado de Mato Grosso do Sul, con la intensidad de El Niño Index (a). Se utilizaron los datos de 37 estaciones pluviométricas con 30 años de datos y 55 estaciones con datos de entre 20 y 29 años (1977 y 2006). En el período de 1977 a 2006, el índice de El Niño (a) promedio mensual osciló entre -1,1°C y 1,3° C, las variaciones considera moderado, con algunas variaciones consideradas fuerte en 1982 (2,3°C), 1983 (2,3°C). 1988 (-1,9°C), 1991 (1,6°C), 1992 (1,8°C), 1997 (2,5°C), 1998 (2,3°C), 1999/2000 (-1,6°C) y 2002 (1,5°C). Se observa que, en general, el NDC para cada año del período tiene una relación directa con El Niño y La Niña, ya que la línea de tendencia polinómica de segundo orden ha cambiado poco.Palabras clave: Temperatura del Océano Pacífico, ENSO, número de días de lluvia, Climatologia. 

scholarly journals Identificação das causas climáticas dos eventos extremos e dos impactos dos ENOS Canônico e Modoki nas macrorregiões de Alagoas

2021 ◽  
Vol 14 (4) ◽  
pp. 1880-1897
Author(s):  
Djane Fonseca Da Silva ◽  
Pedro Fernandes de Souza Neto ◽  
Silvania Donato da Silva ◽  
Maria José da Silva Lima ◽  
Iara Bezerra da Silva Cavalcante ◽  
...  
Keyword(s):  
Extreme Events ◽  
El Niño ◽  
Daily Precipitation ◽  
El Nino ◽  
The State ◽  
La Niña ◽  
Eastern Region ◽  
Equatorial Pacific Ocean ◽  
La Nina ◽  
Daily Precipitation Data

Anomalies of sea surface temperature that occur in some regions of the Equatorial Pacific Ocean are being studied because their cause different impacts and originate in different ways, are the ENOS, Modoki and Canonical. The objective of this work is to identify the climatic causes of the extreme events that occurred in the macro-regions of Alagoas, and at the same time, to compare the effects of ENOS Canonical and Modoki and their classes on the macro-regions of Alagoas. The daily precipitation data for 21 municipalities in the State of Alagoas were obtained through the National Water Agency from 1963 to 2014. EN Modoki and low promoted an increase in rainfall in the Eastern region. EN Fortes, on the other hand, caused a decrease in rainfall in the Sertão. Canonical LN events caused a significant increase in rainfall in the three macro-regions, but the effect was better in LN Forte. During the phases of the Atlantic Dipole, the negative phase generated positive SPI across the state, and in the positive phase, there was a decrease in SPI in the East, and a negative SPI record in Sertão and Agreste. The climatic causes of the extreme events were the combination of semiannual, interannual scales, scale between 1-2 years of ENOS, scale of ENOS extended and scale of 11 years (Dipole and sunspots), potentiating the local total rainfall, and for cases of drought , your absence. It was found, through cluster analysis, similarity between the SPIs of La Niña low and La Niña Canonical, and between El Niño Canonical is linked to El Niño Forte. Mathematically, the categories of El Niño and La Niña strong and weak showed better correlations with ENOS Modoki and Canonical, suggesting a pattern for Alagoas.

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