%0 Journal Article %1 Yan2018El %A Yan, Xiaolu %A Konopka, Paul %A Ploeger, Felix %A Tao, Mengchu %A Müller, Rolf %A Bian, Jianchun %A Riese, Martin %D 2018 %J Atmospheric Chemistry and Physics Discussions %K stratosphere dynamics eastasianmonsoon ozone ENSO %P 1--25 %R 10.5194/acp-2017-1135 %T El Niño Southern Oscillation influence on the Asian summermonsoon anticyclone %U http://dx.doi.org/10.5194/acp-2017-1135 %X 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.

@article{Yan2018El, abstract = {We analyze the influence of the El Ni\~{n}o 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 Ni\~{n}o and La Ni\~{n}a (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 Ni\~{n}o than after La Ni\~{n}a 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 Ni\~{n}o events due to more zonally symmetric subtropical jets than after La Ni\~{n}a 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 Ni\~{n}o events and even during the formation of the ASM anticyclone. The difference between El Ni\~{n}o and La Ni\~{n}a composites becomes statistically insignificant in late summer.}, added-at = {2018-06-18T21:23:34.000+0200}, author = {Yan, Xiaolu and Konopka, Paul and Ploeger, Felix and Tao, Mengchu and M\"{u}ller, Rolf and Bian, Jianchun and Riese, Martin}, biburl = {https://www.bibsonomy.org/bibtex/21df76120e5983a757cec7ce980bee983/pbett}, citeulike-article-id = {14513856}, citeulike-linkout-0 = {http://dx.doi.org/10.5194/acp-2017-1135}, comment = {(private-note)Might be a nice example of dynamical thinking around these sort of phenomena; but in itself, I'm not sure it shows much interesting/novel (I could be wrong)}, day = 08, doi = {10.5194/acp-2017-1135}, interhash = {c42ba7a0b080aaa0b72f78c123399ad5}, intrahash = {1df76120e5983a757cec7ce980bee983}, issn = {1680-7375}, journal = {Atmospheric Chemistry and Physics Discussions}, keywords = {stratosphere dynamics eastasianmonsoon ozone ENSO}, month = jan, pages = {1--25}, posted-at = {2018-01-09 09:33:04}, priority = {2}, timestamp = {2020-04-15T09:29:49.000+0200}, title = {El Ni\~{n}o Southern Oscillation influence on the Asian summermonsoon anticyclone}, url = {http://dx.doi.org/10.5194/acp-2017-1135}, year = 2018 }