Dynamics of Asian summer monsoon response to anthropogenic aerosol forcing

TitleDynamics of Asian summer monsoon response to anthropogenic aerosol forcing
Publication TypeJournal Article
Year of Publication2019
AuthorsWang H, Xie SP, Kosaka Y, Liu QY, Du Y.
JournalJournal of Climate
Volume32
Pagination843-858
Date Published2019/02
Type of ArticleArticle
ISBN Number0894-8755
Accession NumberWOS:000455575000003
Keywords20th-century; aerosols; Anthropogenic effects; Atmosphere-ocean interaction; Atmospheric circulation; black carbon; climate response; CMIP5; cycle; greenhouse-gas; hydrological; impacts; Meteorology & Atmospheric Sciences; Monsoons; rainfall; sea; Stratiform clouds; Surface temperature; tropical precipitation
Abstract

Anthropogenic aerosols partially mask the greenhouse warming and cause the reduction in Asian summer monsoon precipitation and circulation. By decomposing the atmospheric change into the direct atmospheric response to radiative forcing and sea surface temperature (SST)-mediated change, the physical mechanisms for anthropogenic-aerosol-induced changes in the East Asian summer monsoon (EASM) and South Asian summer monsoon (SASM) are diagnosed. Using coupled and atmospheric general circulation models, this study shows that the aerosol-induced troposphere cooling over Asian land regions generates anomalous sinking motion between 20 degrees and 40 degrees N and weakens the EASM north of 20 degrees N without SST change. The decreased EASM precipitation and the attendant wind changes are largely due to this direct atmospheric response to radiative forcing, although the aerosol-induced North Pacific SST cooling also contributes. The SST-mediated change dominates the aerosol-induced SASM response, with contributions from both the north-south interhemispheric SST gradient and the local SST cooling pattern over the tropical Indian Ocean. Specifically, with large meridional gradient, the zonal-mean SST cooling pattern is most important for the Asian summer monsoon response to anthropogenic aerosol forcing, resulting in a reorganization of the regional meridional atmospheric overturning circulation. While uncertainty in aerosol radiative forcing has been emphasized in the literature, our results show that the intermodel spread is as large in the SST effect on summer monsoon rainfall, calling for more research into the ocean-atmosphere coupling.

DOI10.1175/jcli-d-18-0386.1
Student Publication: 
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