Asymmetry in summertime atmospheric circulation anomalies over the northwest Pacific during decaying phase of El Niño and La Niña

2016 ◽  
Vol 49 (5-6) ◽  
pp. 2007-2023 ◽  
Author(s):  
Weichen Tao ◽  
Gang Huang ◽  
Renguang Wu ◽  
Kaiming Hu ◽  
Pengfei Wang ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Northwest Pacific ◽  
La Nina ◽  
Circulation Anomalies ◽  
Atmospheric Circulation Anomalies

Asymmetry of Atmospheric Circulation Anomalies over the Western North Pacific between El Niño and La Niña*

2010 ◽  
Vol 23 (18) ◽  
pp. 4807-4822 ◽  
Author(s):  
Bo Wu ◽  
Tim Li ◽  
Tianjun Zhou
Keyword(s):  
Atmospheric Circulation ◽  
El Niño ◽  
North Pacific ◽  
Western North Pacific ◽  
El Nino ◽  
Precipitation Anomaly ◽  
La Niña ◽  
La Nina ◽  
The Asymmetry ◽  
Atmospheric Circulation Anomalies

Abstract The asymmetry of the western North Pacific (WNP) low-level atmospheric circulation anomalies between the El Niño and La Niña mature winter is examined. An anomalous WNP cyclone (WNPC) center during La Niña tends to shift westward relative to an anomalous WNP anticyclone (WNPAC) center during El Niño. Two factors may contribute to this asymmetric response. The first factor is the longitudinal shifting of El Niño and La Niña anomalous heating. The composite negative precipitation anomaly center during La Niña is located farther to the west of the composite positive precipitation anomaly center during El Niño. The westward shift of the heating may further push the WNPC westward relative to the position of the WNPAC. The second factor is the amplitude asymmetry of sea surface temperature anomalies (SSTAs) in the WNP, namely, the amplitude of local cold SSTA during El Niño is greater than that of warm SSTA during La Niña. The asymmetry of SSTA is originated from the asymmetric SSTA tendencies during the ENSO developing summer. Although both precipitation and surface wind anomalies are approximately symmetric, the surface latent heat flux anomalies are highly asymmetric over the key WNP region, where the climate mean zonal wind speed is small. Both the anomalous westerly during El Niño and the anomalous easterly during La Niña in the region lead to an enhanced surface evaporation, strengthening (weakening) the enhancement of the cold (warm) SSTA in situ during El Niño (La Niña). The asymmetry of the SSTA in the WNP is further amplified due to anomalous wind differences between El Niño and La Niña in their mature winter. Atmospheric general circulation model experiments demonstrate that both factors contribute to the asymmetry between the WNPAC and WNPC. The asymmetric circulation in the WNP contributes to the asymmetry of temporal evolutions between El Niño and La Niña.

scholarly journals El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone

2018 ◽  
Author(s):  
Xiaolu Yan ◽  
Paul Konopka ◽  
Felix Ploeger ◽  
Mengchu Tao ◽  
Rolf Müller ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
La Niña ◽  
Tropical Tropopause ◽  
La Nina ◽  
Asian Summer ◽  
The Impact

Abstract. We analyze the influence of the El Niño Southern Oscillation (ENSO) on the atmospheric circulation and the mean ozone distribution in the tropical and sub-tropical UTLS region. In particular, we focus on the impact of ENSO on the onset of the Asian summer monsoon (ASM) anticyclone. Using the Multivariate ENSO Index, we define climatologies (composites) of atmospheric circulation and composition in the months following El Niño and La Niña (boreal) winters and investigate how ENSO-related flow anomalies propagate into spring and summer. To quantify differences in the divergent and non-divergent part of the flow, the velocity potential (VP) and the stream function (SF) respectively, are calculated from the ERA-Interim reanalysis around the tropical tropopause (potential temperature level θ=380 K). While VP quantifies the well-known ENSO anomalies of the Walker circulation, SF can be used to study the impact of ENSO on the formation of the ASM anticyclone which turns out to be slightly weaker after El Niño than after La Niña winters. In addition, stratospheric intrusions around the eastern flank of the anticyclone into the Tropical Tropopause Layer (TTL) are weaker in the months after strong El Niño events due to more zonally symmetric subtropical jets than after La Niña winters. By using satellite (MLS), in-situ (SHADOZ) observations and model simulations (CLaMS) of ozone, we discuss ENSO-induced differences around the tropical tropopause. Ozone composites show more zonally symmetric features with less in-mixed ozone from the stratosphere into the TTL during and after strong El Niño events and even during the formation of the ASM anticyclone. The difference between El Niño and La Niña composites becomes statistically insignificant in late summer.

scholarly journals Asymmetry of Atmospheric Responses to Two-Type El Niño and La Niña over Northwest Pacific

2019 ◽  
Vol 33 (5) ◽  
pp. 826-836
Author(s):  
Mingcheng Chen ◽  
Tim Li ◽  
Xiaohui Wang
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
Northwest Pacific ◽  
La Nina

scholarly journals Contribution of Synoptic Transients to the Potential Predictability of PNA Circulation Anomalies: El Niño versus La Niña

2015 ◽  
Vol 28 (21) ◽  
pp. 8347-8362 ◽  
Author(s):  
Muhammad Adnan Abid ◽  
In-Sik Kang ◽  
Mansour Almazroui ◽  
Fred Kucharski
Keyword(s):  
El Niño ◽  
El Nino ◽  
Signal To Noise Ratio ◽  
Tropical Pacific ◽  
La Niña ◽  
Potential Predictability ◽  
La Nina ◽  
The Pacific ◽  
Circulation Anomalies ◽  
Sst Anomalies

Abstract The potential predictability (PP) of seasonal-mean 200-hPa geopotential height (Z200) anomalies in the Pacific–North American (PNA) region is examined for El Niño and La Niña separately by using 50 ensemble members of twentieth-century AGCM simulations. Observed sea surface temperature (SST) is prescribed for the period 1870–2009, and 14 El Niño and La Niña years after 1900 are selected for the present study. The domain-averaged value of PP for Z200 in the PNA region, as measured by the signal-to-noise ratio, for El Niño is about 60% larger than that of La Niña. Such a large PP is mainly due to a larger signal and partly to less noise during El Niño compared to that during La Niña . The transient eddy feedback to the PNA circulation anomalies is stronger during El Niño events (about 50%) than that during La Niña, and this difference in the transients contributes significantly to the different Z200 signals in the PNA region. The noise variance of the transients during El Niño is about 17% smaller than during La Niña, and thus transients play an important role in the reduction of Z200 noise during El Niño. Idealized experiments with the same spatial pattern but different signs of SST anomalies confirm the results mentioned above. Moreover, these experiments with several different amplitudes of positive and negative phases of tropical Pacific SST anomalies show that signals of Z200 and transients are proportional to precipitation anomalies in the tropical Pacific, and noises of Z200 for El Niño cases are somewhat smaller than the corresponding values of La Niña.

scholarly journals El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone

2018 ◽  
Vol 18 (11) ◽  
pp. 8079-8096 ◽  
Author(s):  
Xiaolu Yan ◽  
Paul Konopka ◽  
Felix Ploeger ◽  
Mengchu Tao ◽  
Rolf Müller ◽  
...  
Keyword(s):  
Atmospheric Circulation ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Asian Summer Monsoon ◽  
La Niña ◽  
Tropical Tropopause ◽  
La Nina ◽  
Asian Summer ◽  
The Impact

Abstract. We analyse the influence of the El Niño Southern Oscillation (ENSO) on the atmospheric circulation and the mean ozone distribution in the tropical and subtropical UTLS region. In particular, we focus on the impact of ENSO on the onset of the Asian summer monsoon (ASM) anticyclone. Using the Multivariate ENSO Index (MEI), we define climatologies (composites) of atmospheric circulation and composition in the months following El Niño and La Niña (boreal) winters and investigate how ENSO-related flow anomalies propagate into spring and summer. To quantify differences in the divergent and non-divergent parts of the flow, the velocity potential (VP) and the stream function (SF) are respectively calculated from the ERA-Interim reanalysis in the vicinity of the tropical tropopause at potential temperature level θ=380 K. While VP quantifies the well-known ENSO anomalies of the Walker circulation, SF can be used to study the impact of ENSO on the formation of the ASM anticyclone, which turns out to be slightly weaker after El Niño winters than after La Niña winters. In addition, stratospheric intrusions around the eastern flank of the anticyclone into the tropical tropopause layer (TTL) are weaker in the months after strong El Niño events due to more zonally symmetric subtropical jets than after La Niña winters. By using satellite (MLS) and in situ (SHADOZ) observations and model simulations (CLaMS) of ozone, we discuss ENSO-induced differences around the tropical tropopause. Ozone composites show more zonally symmetric features with less in-mixed ozone from the stratosphere into the TTL during and after strong El Niño events and even during the formation of the ASM anticyclone. These isentropic anomalies are overlaid with the well-known anomalies of the faster (slower) Hadley and Brewer–Dobson circulations after El Niño (La Niña) winter. The duration and intensity of El Niño-related anomalies may be reinforced through late summer and autumn if the El Niño conditions last until the following winter.

ANALISIS DAERAH RAWAN KEKERINGAN LAHAN JAGUNG BERDASARKAN IKLIM OLDEMAN DAN KETERSEDIAN AIR TANAH DI NUSA TENGGARA TIMUR SAAT PERIODE EL NINO DAN LA NINA

2019 ◽  
Vol 3 ◽  
pp. 1219
Author(s):  
Oki Adrianto ◽  
Sudirman Sudirman ◽  
Suwandi Suwandi
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
La Nina

Perekonomian Provinsi Nusa Tenggara Timur secara sektoral masih didominasi sektor pertanian.Tanaman jagung menjadi salah satu produksi tanaman pangan terbesar berdasarkan data dari Dinas Pertanian dan Perkebunan Provinsi Nusa Tenggara Timur tahun 2015. Peningkatan produksi pertanian dapat dilakukan melalui berbagai strategi adaptasi dan upaya penanganan bencana, salah satu upaya tersebut adalah dengan penyediaan informasi iklim terkait penentuan daerah-daerah rawan kekeringan. Tujuan dari penelitian ini adalah untuk mengetahui sebaran wilayah rawan kekeringan lahan jagung bulanan di Provinsi Nusa Tenggara Timur saat kondisi El Nino dan La Nina dengan periodeisasi bulanan januari hingga desember. Data yang digunakan dalam penelitian ini adalah data curah hujan rata rata bulanan di 19 pos hujan di Provinsi Nusa Tenggara Timur dan suhu udara rata-rata bulanan dihitung menggunakan pendekatan teori Brack dengan titik referensi Stasiun Klimatologi Lasiana Kupang. Periode dari masing-masing data yang digunakan adalah dari tahun 1991 dan 1997 digunakan sebagai tahun El Nino dan tahun 1999 dan 2010 digunakan sebagai tahun La Nina. Metode yang digunakan untuk menentukan tingkat rawan kekeringan dengan menggunakan pembobotan berdasarkan penjumlahan bobot tipe iklim Oldeman dan bobot ketersediaan air tanah. Hasil penelitian menunjukkan sebaran daerah kekeringan di Provinsi Nusa Tenggara Timurpada tahun el nino lebih luas dibandingkan tahun la nina.

A Influência dos fenômenos El Niño e La Niña sobre a dinâmica climática da região Amazônica

2018 ◽  
Vol 1 ◽  
pp. e2018014
Author(s):  
Samya de Freitas MOREIRA ◽  
Cleiciane Silva da CONCEIÇÃO ◽  
Milla Cristina Santos da CRUZ ◽  
Antônio PEREIRA JÚNIOR
Keyword(s):  
El Niño ◽  
El Nino ◽  
La Niña ◽  
La Nina

Caracterização climática da temperatura do ar em Veranópolis, Rio Grande do Sul

Agrometeoros ◽  
2020 ◽  
Vol 26 (2) ◽  
Author(s):  
Amanda Heemann Junges
Keyword(s):  
El Niño ◽  
El Nino ◽  
Rio Grande ◽  
La Niña ◽  
Rio Grande Do Sul ◽  
La Nina

Estudos locais de caraterização e variabilidade climática são fundamentais para geração de informações mais adaptadas às atividades agrícolas desenvolvidas em um município ou região. O objetivo desse trabalho foi caracterizar climaticamente e analisar a influência de eventos El Niño Oscilação Sul (ENOS) na série 1956-2015 de temperatura do ar de Veranópolis, RS. Para caracterização climática foram estabelecidas estatísticas descritivas das temperaturas do ar máximas, mínimas e médias mensais, estacional e anual na série e normal climatológica padrão 1961- 1990. Para identificação de diferenças entre estações e influência de eventos ENOS, os dados foram submetidos à análise de variância e teste de Duncan. Os resultados indicaram que a temperatura média anual é de 17,3ºC, variando entre 12,7ºC (julho) e 21,8ºC (janeiro). O clima é do tipo Cfb, de acordo com a classificação climática de Köppen e TE (temperado) na classificação climática do Estado. Temperaturas mínimas médias mensais inferiores a 10ºC ocorrem de maio a setembro, período de maior variabilidade interanual das temperaturas máximas (desvio padrão entre 1,5º e 1,8ºC), mínimas (1,6-1,8ºC) e médias mensais (1,4-1,7ºC). Anos de La Niña possuem temperaturas médias estacionais inferiores as de El Niño, embora diferenciação em relação a neutros ocorra somente para temperaturas mínimas na primavera e máximas no outono.

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.

Atmospheric teleconnection patterns associated with severe and mild ice cover on the Great Lakes, 1963–2011

2012 ◽  
Vol 47 (3-4) ◽  
pp. 421-435 ◽  
Author(s):  
Xuezhi Bai ◽  
Jia Wang
Keyword(s):  
North America ◽  
Great Lakes ◽  
El Niño ◽  
El Nino ◽  
Ice Cover ◽  
Reanalysis Data ◽  
Teleconnection Pattern ◽  
La Niña ◽  
Atmospheric Teleconnection ◽  
La Nina

Atmospheric teleconnection circulation patterns associated with severe and mild ice cover over the Great Lakes are investigated using the composite analysis of lake ice data and National Center of Environmental Prediction (NCEP) reanalysis data for the period 1963–2011. The teleconnection pattern associated with the severe ice cover is the combination of a negative North Atlantic Oscillation (NAO) or Arctic Oscillation (AO) and negative phase of Pacific/North America (PNA) pattern, while the pattern associated with the mild ice cover is the combination of a positive PNA (or an El Niño) and a positive phase of the NAO/AO. These two extreme ice conditions are associated with the North American ridge–trough variations. The intensified ridge–trough system produces a strong northwest-to-southeast tilted ridge and trough and increases the anomalous northwesterly wind, advecting cold, dry Arctic air to the Great Lakes. The weakened ridge–trough system produces a flattened ridge and trough, and promotes a climatological westerly wind, advecting warm, dry air from western North America to the Great Lakes. Although ice cover for all the individual lakes responds roughly linearly and symmetrically to both phases of the NAO/AO, and roughly nonlinearly and asymmetrically to El Niño and La Niña events, the overall ice cover response to individual NAO/AO or Niño3.4 index is not statistically significant. The combined NAO/AO and Niño3.4 indices can be used to reliably project severe ice cover during the simultaneous –NAO/AO and La Niña events, and mild ice cover during the simultaneous +NAO/AO and El Niño events.

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