scholarly journals The Asymmetric Influence of the Two Types of El Niño and La Niña on Summer Rainfall over Southeast China

2013 ◽  
Vol 26 (13) ◽  
pp. 4567-4582 ◽  
Author(s):  
Muhammad Afzaal Karori ◽  
Jianping Li ◽  
Fei-Fei Jin
Keyword(s):  
El Niño ◽  
El Nino ◽  
Summer Rainfall ◽  
La Niña ◽  
Positive Phase ◽  
Negative Phase ◽  
Boreal Summer ◽  
La Nina ◽  
Asymmetric Response ◽  
The Relationship

Abstract In this study, the authors demonstrate that the two types of El Niño–Southern Oscillation (ENSO) have asymmetric features with respect to the impact of their positive and negative phases on boreal summer rainfall over the Yangtze River Valley (YRV) and South China (SC). The relationship between rainfall over the YRV and the warm pool (WP) La Niña is positive and significant, whereas the relationship with the WP El Niño is not. In the case of the cold tongue (CT) ENSO, its positive phase has a positive influence, while there is no significant relationship with the negative phase. In contrast, rainfall over SC has a significant positive relationship with WP El Niño, but a nonsignificant relationship with WP La Niña. The positive phase of the CT ENSO has a significant negative influence on SC rainfall, while the negative phase has a nonsignificant impact. An asymmetric atmospheric response to the asymmetric sea surface temperature anomalies (SSTAs) was also observed in the lower troposphere. The location of the center of the anomalous circulations over the study region differs during the opposite phases of the two types of ENSO. This asymmetric response is likely to be linked to the different spatial patterns of the two types of El Niño and La Niña. Atmospheric general circulation models confirm the authors' analysis of the observed data. Numerical simulations show that the asymmetric response of the lower atmosphere is driven mainly by differing SSTA patterns in the equatorial Pacific Ocean.

scholarly journals The asymmetric response of Yangtze river basin summer rainfall to El Niño/La Niña

2018 ◽  
Vol 13 (2) ◽  
pp. 024015 ◽  
Author(s):  
Steven C Hardiman ◽  
Nick J Dunstone ◽  
Adam A Scaife ◽  
Philip E Bett ◽  
Chaofan Li ◽  
...  
Keyword(s):  
River Basin ◽  
El Niño ◽  
Yangtze River ◽  
El Nino ◽  
Yangtze River Basin ◽  
Summer Rainfall ◽  
La Niña ◽  
La Nina ◽  
Asymmetric Response

Rendimento de grãos de soja e de milho, no Rio Grande do Sul, não difere entre eventos El Niño Oscilação Sul

Agrometeoros ◽  
2018 ◽  
Vol 26 (1) ◽  
Author(s):  
Ronaldo Matzenauer ◽  
Bernadete Radin ◽  
Alberto Cargnelutti Filho
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Rio Grande ◽  
La Niña ◽  
Rio Grande Do Sul ◽  
La Nina ◽  
Significant Difference ◽  
Income Data ◽  
The Relationship

O objetivo deste trabalho foi avaliar a relação entre o fenômeno El Niño Oscilação Sul - ENOS e o rendimento de grãos de soja e de milho no Rio Grande do Sul e verificar a hipótese de que os eventos El Niño são favoráveis e os eventos La Niña são prejudiciais ao rendimento de grãos das culturas. Foram utilizados dados de rendimento de grãos dos anos agrícolas de 1974/75 a 2016/17, e relacionados com as ocorrências de eventos ENOS. Foram analisados os dados de rendimento observados na colheita e os dados estimados com a remoção da tendência tecnológica. Os resultados mostraram que não houve diferença significativa do rendimento médio de grãos de soja e de milho na comparação entre os eventos ENOS. Palavras-chave: El Niño, La Niña, safras agrícolas. Abstract – The objective of this work was to evaluate the relationship between the El Niño Southern Oscillation (ENSO) phenomenon with the grain yield of soybean and maize in Rio Grande do Sul state, Brazil and to verify the hypothesis that the El Niño events are favorable and the La Niña events are harmful to the culture’s grain yields. Were used data from the agricultural years of 1974/75 to 2016/17, and related to the occurrence of ENOS events. We analyzed income data observed at harvest and estimated data with technological tendency was removed. The results showed that there was no significant difference in the average yield of soybeans and corn in the comparison between events.

scholarly journals Changes in Spread and Predictability Associated with ENSO in an Ensemble Coupled GCM

2006 ◽  
Vol 19 (17) ◽  
pp. 4378-4396 ◽  
Author(s):  
Renguang Wu ◽  
Ben P. Kirtman
Keyword(s):  
Surface Pressure ◽  
El Niño ◽  
El Nino ◽  
Tropical Pacific ◽  
La Niña ◽  
Boreal Summer ◽  
Boreal Winter ◽  
Central Pacific ◽  
La Nina ◽  
Signal Change

Abstract The present study documents the influence of El Niño and La Niña events on the spread and predictability of rainfall, surface pressure, and 500-hPa geopotential height, and contrasts the relative contribution of signal and noise changes to the predictability change based on a long-term integration of an interactive ensemble coupled general circulation model. It is found that the pattern of the El Niño–Southern Oscillation (ENSO)-induced noise change for rainfall follows closely that of the corresponding signal change in most of the tropical regions. The noise for tropical Pacific surface pressure is larger (smaller) in regions of lower (higher) mean pressure. The ENSO-induced noise change for 500-hPa height displays smaller spatial scales compared to and has no systematic relationship with the signal change. The predictability for tropical rainfall and surface pressure displays obvious contrasts between the summer and winter over the Bay of Bengal, the western North Pacific, and the tropical southwestern Indian Ocean. The predictability for tropical 500-hPa height is higher in boreal summer than in boreal winter. In the equatorial central Pacific, the predictability for rainfall is much higher in La Niña years than in El Niño years. This occurs because of a larger percent reduction in the amplitude of noise compared to the percent decrease in the magnitude of signal from El Niño to La Niña years. A consistent change is seen in the predictability for surface pressure near the date line. In the western North and South Pacific, the predictability for boreal winter rainfall is higher in El Niño years than in La Niña years. This is mainly due to a stronger signal in El Niño years compared to La Niña years. The predictability for 500-hPa height increases over most of the Tropics in El Niño years. Over western tropical Pacific–Australia and East Asia, the predictability for boreal winter surface pressure and 500-hPa height is higher in El Niño years than in La Niña years. The predictability change for 500-hPa height is primarily due to the signal change.

scholarly journals Diversity of East China Summer Rainfall Change in Post-El Niño Summers

2020 ◽  
Vol 8 ◽  
Author(s):  
Wen Zhang ◽  
Xiaoye Zhou ◽  
Pang-Chi Hsu ◽  
Fei Liu
Keyword(s):  
El Niño ◽  
North China ◽  
El Nino ◽  
Summer Rainfall ◽  
La Niña ◽  
East China ◽  
La Nina ◽  
Huaihe River Valley ◽  
Precipitation Anomalies ◽  
Cluster 2

East China has experienced positive precipitation anomalies in post-El Niño summers, mainly in the Yangtze-Huaihe River Valley. This kind of monsoonal rainfall change induced by El Niño, however, is not always the same due to El Niño diversity and mean state change. Here, we use cluster analysis on the post-El Niño (PE) East China summer precipitation anomalies to identify the diversity of this El Niño-induced monsoon change. The result shows that PE East China summer rainfall anomalies mainly display three different modes for all selected 20 El Niño events from 1957 to 2016. Cluster 1 shows the middle and lower reaches of the Yangtze River demonstrate strong wet anomalies, while South and North China are dominated by dry anomalies, similar to a sandwich mode. Cluster 2 is distinguished by dry anomalies over South China and wet anomalies over North China, exhibiting a dipole mode. Compared with Cluster 1, the change caused by Cluster 3 is different, showing negative anomalies over the Yangtze-Huaihe River Valley. The three clusters are correlated with successive events of El Niño, a quick transfer to a strong La Niña and a quick transfer to a weak La Niña respectively. The associated anomalous anticyclone (AAC) focuses on (120°E, 20°N) in Cluster 1, which expands southward for Cluster 2 and moves eastward for Cluster 3. The feedback of AAC-sea surface temperature (SST) mainly works for supporting the AAC in Cluster 1, but it is weak for Cluster 2; the strong easterly anomalies related to La Niña contribute to the AAC location change for Cluster 2. Both AAC-SST feedback and easterly anomalies support the AAC of Cluster 3. The CMIP5 output can capture these diverse responses in circulation except that their simulated AAC for Cluster 1 is significant to the east of the observed.

scholarly journals Impacts of Different Types of ENSO on the Interannual Seesaw between the Somali and the Maritime Continent Cross-Equatorial Flows

2017 ◽  
Vol 30 (7) ◽  
pp. 2621-2638 ◽  
Author(s):  
Chen Li ◽  
Jing-Jia Luo ◽  
Shuanglin Li
Keyword(s):  
Negative Correlation ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Boreal Summer ◽  
Maritime Continent ◽  
La Nina ◽  
Different Types ◽  
Ep El Niño ◽  
Sst Gradient

The impacts of different types of El Niño–Southern Oscillation (ENSO) on the interannual negative correlation (seesaw) between the Somali cross-equatorial flow (CEF) and the Maritime Continent (MC) CEF during boreal summer (June–August) are investigated using the ECMWF twentieth-century reanalysis (ERA-20C) dataset and numerical experiments with a global atmospheric model [the Met Office Unified Model global atmosphere, version 6 (UM-GA6)]. The results suggest that ENSO plays a prominent role in governing the CEF-seesaw relation. A high positive correlation (0.86) exists between the MC CEF and Niño-3.4 index and also in the case of eastern Pacific (EP) El Niño, central Pacific (CP) El Niño, EP La Niña, and CP La Niña events. In contrast, a negative correlation (−0.35) exists between the Somali CEF and Niño-3.4 index, and this negative relation is significant only in the EP El Niño years. Further, the variation of the MC CEF is highly correlated with the local north–south sea surface temperature (SST) gradient, while the variation of the Somali CEF displays little relation with the local SST gradient. The Somali CEF may be remotely influenced by ENSO. The model results confirm that the EP El Niño plays a major role in causing the weakened Somali CEF via modifying the Walker cell. However, the impact of the EP El Niño on the Somali CEF differs with different seasonal background. It is also found that the interannual CEF seesaw displays a multidecadal change before and after the 1950s, which is linked with the multidecadal strengthening of the intensity of the EP ENSO.

scholarly journals The ENSO–Asian Monsoon Interaction in a Coupled Ocean–Atmosphere GCM

2007 ◽  
Vol 20 (20) ◽  
pp. 5164-5177 ◽  
Author(s):  
Ying Li ◽  
Riyu Lu ◽  
Buwen Dong
Keyword(s):  
El Niño ◽  
Asian Monsoon ◽  
El Nino ◽  
Southern Oscillation ◽  
La Niña ◽  
Enso Cycle ◽  
Central Pacific ◽  
La Nina ◽  
Ocean Atmosphere ◽  
The Relationship

Abstract In this study, the authors evaluate the (El Niño–Southern Oscillation) ENSO–Asian monsoon interaction in a version of the Hadley Centre coupled ocean–atmosphere general circulation model (CGCM) known as HadCM3. The main focus is on two evolving anomalous anticyclones: one located over the south Indian Ocean (SIO) and the other over the western North Pacific (WNP). These two anomalous anticyclones are closely related to the developing and decaying phases of the ENSO and play a crucial role in linking the Asian monsoon to ENSO. It is found that the HadCM3 can well simulate the main features of the evolution of both anomalous anticyclones and the related SST dipoles, in association with the different phases of the ENSO cycle. By using the simulated results, the authors examine the relationship between the WNP/SIO anomalous anticyclones and the ENSO cycle, in particular the biennial component of the relationship. It is found that a strong El Niño event tends to be followed by a more rapid decay and is much more likely to become a La Niña event in the subsequent winter. The twin anomalous anticyclones in the western Pacific in the summer of a decaying El Niño are crucial for the transition from an El Niño into a La Niña. The El Niño (La Niña) events, especially the strong ones, strengthen significantly the correspondence between the SIO anticyclonic (cyclonic) anomaly in the preceding autumn and WNP anticyclonic (cyclonic) anomaly in the subsequent spring, and favor the persistence of the WNP anomaly from spring to summer. The present results suggest that both El Niño (La Niña) and the SIO/WNP anticyclonic (cyclonic) anomalies are closely tied with the tropospheric biennial oscillation (TBO). In addition, variability in the East Asian summer monsoon, which is dominated by the internal atmospheric variability, seems to be responsible for the appearance of the WNP anticyclonic anomaly through an upper-tropospheric meridional teleconnection pattern over the western and central Pacific.

Composite Analysis of the Effects of ENSO Events on Antarctica

2016 ◽  
Vol 29 (5) ◽  
pp. 1797-1808 ◽  
Author(s):  
Lee J. Welhouse ◽  
Matthew A. Lazzara ◽  
Linda M. Keller ◽  
Gregory J. Tripoli ◽  
Matthew H. Hitchman
Keyword(s):  
El Niño ◽  
Geopotential Height ◽  
El Nino ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
La Niña ◽  
Austral Spring ◽  
Enso Events ◽  
La Nina ◽  
The Relationship

Abstract Previous investigations of the relationship between El Niño–Southern Oscillation (ENSO) and the Antarctic climate have focused on regions that are impacted by both El Niño and La Niña, which favors analysis over the Amundsen and Bellingshausen Seas (ABS). Here, 35 yr (1979–2013) of European Centre for Medium-Range Weather Forecasts interim reanalysis (ERA-Interim) data are analyzed to investigate the relationship between ENSO and Antarctica for each season using a compositing method that includes nine El Niño and nine La Niña periods. Composites of 2-m temperature (T2m), sea level pressure (SLP), 500-hPa geopotential height, sea surface temperatures (SST), and 300-hPa geopotential height anomalies were calculated separately for El Niño minus neutral and La Niña minus neutral conditions, to provide an analysis of features associated with each phase of ENSO. These anomaly patterns can differ in important ways from El Niño minus La Niña composites, which may be expected from the geographical shift in tropical deep convection and associated pattern of planetary wave propagation into the Southern Hemisphere. The primary new result is the robust signal, during La Niña, of cooling over East Antarctica. This cooling is found from December to August. The link between the southern annular mode (SAM) and this cooling is explored. Both El Niño and La Niña experience the weakest signal during austral autumn. The peak signal for La Niña occurs during austral summer, while El Niño is found to peak during austral spring.

scholarly journals Dynamics of Late Spring Rainfall Reduction in Recent Decades over Southeastern China

2009 ◽  
Vol 22 (8) ◽  
pp. 2240-2247 ◽  
Author(s):  
Yun Qiu ◽  
Wenju Cai ◽  
Xiaogang Guo ◽  
Aijun Pan
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Late Spring ◽  
La Niña ◽  
Boreal Summer ◽  
Necessary Condition ◽  
Southeastern China ◽  
Sea Level Pressure ◽  
La Nina

Abstract Since 1951, late spring (May) rainfall over southeastern China (SEC) has decreased by more than 30% from its long-term average, in contrast to a rainfall increase in boreal summer. The dynamics have yet to be fully determined. This paper shows that as the Indo-Pacific enters into a La Niña phase, significant negative mean sea level pressure (MSLP) anomalies grow over the Indian Ocean and the western Pacific sector. The associated large-scale southwesterly anomalies transport moisture to the nearby South China Sea and the SEC region, contributing to a higher rainfall. A presence of a Philippine Sea anticyclonic (PSAC) pattern, arising from a decaying El Niño, strengthens the rain-conducive flow to SEC, but it is not a necessary condition. During the past decades, an increase in protracted El Niño events accompanied by a reduction in La Niña episodes has contributed to the May rainfall decline. The extent to which climate change is contributing is discussed.

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