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| Titel |
Impact of different Asian source regions on the composition of the Asian monsoon anticyclone and of the extratropical lowermost stratosphere |
| VerfasserIn |
B. Vogel, G. Günther, R. Müller, J.-U. Grooß, M. Riese |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 23 ; Nr. 15, no. 23 (2015-12-10), S.13699-13716 |
| Datensatznummer |
250120220
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| Publikation (Nr.) |
 copernicus.org/acp-15-13699-2015.pdf |
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| Zusammenfassung |
The impact of different boundary
layer source regions in Asia on the chemical composition of the Asian monsoon
anticyclone, considering its intraseasonal variability in 2012, is analysed
by simulations of the Chemical Lagrangian Model of the Stratosphere (CLaMS)
using artificial emission tracers. The horizontal distribution of simulated
CO, O3, and artificial emission tracers for India/China are in good
agreement with patterns found in satellite measurements of O3 and CO by
the Aura Microwave Limb Sounder (MLS). Using in addition, correlations of
artificial emission tracers with potential vorticity demonstrates that
the emission tracer for India/China is a very good proxy for spatial
distribution of trace gases within the Asian monsoon anticyclone. The Asian
monsoon anticyclone constitutes a horizontal transport barrier for emission
tracers and is highly variable in location and shape. From the end of June to
early August, a northward movement of the anticyclone and, during September, a
strong broadening of the spatial distribution of the emission tracer for
India/China towards the tropics are found. In addition to the change of the
location of the anticyclone, the contribution of different boundary source
regions to the composition of the Asian monsoon anticyclone in the upper
troposphere strongly depends on its intraseasonal variability and is
therefore more complex than hitherto believed. The largest contributions to
the composition of the air mass in the anticyclone are found from northern
India and Southeast Asia at a potential temperature of 380 K. In the early
(mid-June to mid-July) and late (September) period of the
2012 monsoon season, contributions of emissions from Southeast Asia are highest; in the
intervening period (early August), emissions from northern India have the largest
impact. Our findings show that the temporal variation of the contribution of
different convective regions is imprinted in the chemical composition of the
Asian monsoon anticyclone.
Air masses originating in Southeast Asia are found both within and outside of
the Asian monsoon anticyclone because these air masses experience, in addition
to transport within the anticyclone, upward transport at the southeastern
flank of the anticyclone and in the tropics. Subsequently, isentropic poleward
transport of these air masses occurs at around 380 K with the result that
the extratropical lowermost stratosphere in the Northern Hemisphere is
flooded by the end of September with air masses originating in Southeast Asia.
Even after the breakup of the anticyclonic circulation (around the
end of September), significant contributions of air masses originating in
India/China are still found in the upper troposphere over Asia. Our results
demonstrate that emissions from India, China, and Southeast Asia have
a significant impact on the chemical composition of the lowermost
stratosphere of the Northern Hemisphere, in particular at the end of the
monsoon season in September/October 2012. |
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