El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone
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 Mult...
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doaj-d298c1c319b44ed89f1df466476e823f2020-11-25T00:03:39ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-06-01188079809610.5194/acp-18-8079-2018El Niño Southern Oscillation influence on the Asian summer monsoon anticycloneX. Yan0X. Yan1P. Konopka2F. Ploeger3M. Tao4R. Müller5M. L. Santee6J. Bian7J. Bian8M. Riese9Forschungszentrum Jülich (IEK-7: Stratosphere), Jülich, GermanyKey Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, ChinaForschungszentrum Jülich (IEK-7: Stratosphere), Jülich, GermanyForschungszentrum Jülich (IEK-7: Stratosphere), Jülich, GermanyForschungszentrum Jülich (IEK-7: Stratosphere), Jülich, GermanyForschungszentrum Jülich (IEK-7: Stratosphere), Jülich, GermanyJet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USAKey Laboratory of Middle Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, ChinaCollege of Earth Science, University of Chinese Academy of Sciences, Beijing, ChinaForschungszentrum Jülich (IEK-7: Stratosphere), Jülich, GermanyWe 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 <i>θ</i> = 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.https://www.atmos-chem-phys.net/18/8079/2018/acp-18-8079-2018.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
X. Yan X. Yan P. Konopka F. Ploeger M. Tao R. Müller M. L. Santee J. Bian J. Bian M. Riese |
spellingShingle |
X. Yan X. Yan P. Konopka F. Ploeger M. Tao R. Müller M. L. Santee J. Bian J. Bian M. Riese El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone Atmospheric Chemistry and Physics |
author_facet |
X. Yan X. Yan P. Konopka F. Ploeger M. Tao R. Müller M. L. Santee J. Bian J. Bian M. Riese |
author_sort |
X. Yan |
title |
El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone |
title_short |
El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone |
title_full |
El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone |
title_fullStr |
El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone |
title_full_unstemmed |
El Niño Southern Oscillation influence on the Asian summer monsoon anticyclone |
title_sort |
el niño southern oscillation influence on the asian summer monsoon anticyclone |
publisher |
Copernicus Publications |
series |
Atmospheric Chemistry and Physics |
issn |
1680-7316 1680-7324 |
publishDate |
2018-06-01 |
description |
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 <i>θ</i> = 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. |
url |
https://www.atmos-chem-phys.net/18/8079/2018/acp-18-8079-2018.pdf |
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