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Global warming shifts the monsoon circulation, drying South Asia

Annamalai, H and Hafner, J and Sooraj, KP and Pillai, P (2013) Global warming shifts the monsoon circulation, drying South Asia. Journal of Climate, 26 (9). pp. 2701-2718.

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Monsoon rainfall over South Asia has decreased during the last 5 to 6 decades according to several sets of observations. Although sea surface temperature (SST) has risen across the Indo-Pacific warm pool during this period, the expected accompanying increased rainfall has occurred only in the tropical western Pacific. The above changes noted in observations are also seen in a coupled climate model, but only when the model includes the recent increase in greenhouse gas concentration. The hypothesis that the robust rise in SST over the warm pool, perhaps anchored by an increase in greenhouse gas concentrations, is instrumental in the east- west shift in monsoon rainfall (enhanced rainfall over tropical western Pacific and decreased rainfall over South Asia) is proposed.Asuite of controlled experiments with an atmospheric general circulation model has been performed to isolate the impact of regional SST warming trends on the dryness over South Asia. Model experiments support the hypothesis that the rising SST trend over the tropical western Pacific has changed the atmospheric circulation: over the Bay of Bengal more dry and cool air is advected from the northeast than previously. Moist static energy budget diagnostics on the model solutions identify the sources for this east- west shift. SST warming over the warm pool has accelerated in recent decades. Therefore, a close monitoring of that warming is important for long-term variations of monsoon rainfall. The inconsistency in the amplitude of drying over South Asia among the various land-based rainfall observations and lack of sustained rainfall observations over the open oceans, however, poses constraints in the results.

Item Type: Article
Additional Information: Copyright of this article belongs to American Meteorological Society.
Uncontrolled Keywords: Atmospheric circulation; Atmospheric general circulation models; Controlled experiment; Coupled climate model; Long-term variations; Monsoon circulations; Sea surface temperature (SST); Tropical Western Pacific, Atmospheric temperature; Atmospheric thermodynamics; Climatology; Experiments; Global warming; Greenhouse gases; Lakes; Tropics, Rain, atmospheric circulation; atmospheric general circulation model; climate modeling; drought; energy budget; global warming; greenhouse gas; monsoon; sea surface temperature, Bay of Bengal; Indian Ocean; Pacific Ocean; Pacific Ocean (West); South Asia
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 12 Jun 2014 10:07
Last Modified: 12 Jun 2014 10:07

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