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| Titel |
The effect of regional changes in anthropogenic aerosols on rainfall of the East Asian Summer Monsoon |
| VerfasserIn |
L. Guo, E. J. Highwood, L. C. Shaffrey, A. G. Turner |
| 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 ; 13, no. 3 ; Nr. 13, no. 3 (2013-02-06), S.1521-1534 |
| Datensatznummer |
250017644
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| Publikation (Nr.) |
 copernicus.org/acp-13-1521-2013.pdf |
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| Zusammenfassung |
| The response of East Asian Summer Monsoon (EASM) precipitation to long term
changes in regional anthropogenic aerosols (sulphate and black carbon) is
explored in an atmospheric general circulation model, the atmospheric
component of the UK High-Resolution Global Environment Model v1.2 (HiGAM).
Separately, sulphur dioxide (SO2) and black carbon (BC) emissions in 1950
and 2000 over East Asia are used to drive model simulations, while emissions
are kept constant at year 2000 level outside this region. The response of the
EASM is examined by comparing simulations driven by aerosol emissions
representative of 1950 and 2000. The aerosol radiative effects are also
determined using an off-line radiative transfer model. During June, July and
August, the EASM was not significantly changed as either SO2 or BC
emissions increased from 1950 to 2000 levels. However, in September,
precipitation is significantly decreased by 26.4% for sulphate aerosol and
14.6% for black carbon when emissions are at the 2000 level. Over 80% of
the decrease is attributed to changes in convective precipitation. The cooler
land surface temperature over China in September (0.8 °C for sulphate
and 0.5 °C for black carbon) due to increased aerosols reduces the
surface thermal contrast that supports the EASM circulation. However,
mechanisms causing the surface temperature decrease in September are
different between sulphate and BC experiments. In the sulphate experiment,
the sulphate direct and the 1st indirect radiative effects
contribute to the surface cooling. In the BC experiment, the BC direct effect
is the main driver of the surface cooling, however, a decrease in low cloud
cover due to the increased heating by BC absorption partially counteracts the
direct effect. This results in a weaker land surface temperature response to
BC changes than to sulphate changes. The resulting precipitation response is
also weaker, and the responses of the monsoon circulation are different for
sulphate and black carbon experiments. This study demonstrates a mechanism
that links regional aerosol emission changes to the precipitation changes of
the EASM, and it could be applied to help understand the future changes in
EASM precipitation in CMIP5 simulations. |
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