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Dynamics of east-west asymmetry of Indian summer monsoon rainfall trends in recent decades

Konwar, M and Parekh, A and Goswami, BN (2012) Dynamics of east-west asymmetry of Indian summer monsoon rainfall trends in recent decades. Geophysical Research Letters, 39 (10).

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Understanding the regional trends in Indian summer monsoon rainfall has important implications in developing appropriate adaptation strategies. Here, we provide a mechanistic explanation of the observed asymmetry in the trends of seasonal mean rainfall during past three decades over the eastern and western parts of the country. This asymmetry in trends of the seasonal mean rainfall is primarily contributed by a similar asymmetry in the trends of low and medium rainfall (R LMR) events explaining 85 of the seasonal mean. As the R LMR generally comes from mesoscale and synoptic systems, it is likely that the observed asymmetry may arise from some asymmetry in changes in large scale dynamic and thermodynamic parameters. We show that increasing vertically integrated moisture transport (VIMT) over the Arabian Sea (AS) is likely reason for the increasing trend of R LMR in the western parts during recent decades. In contrast, over the eastern parts, the R LMR is decreasing due to a decreasing trend of VIMT over the Bay of Bengal (BoB). The increasing trend of VIMT over AS arises primarily due to increasing trends of low level wind speed and moisture content while the decreasing trend of VIMT over the BoB seems to be due to decreasing trends of low level wind speed and moisture content.

Item Type: Article
Additional Information: Copyright of this article belongs to American Geophysical Union.
Uncontrolled Keywords: Adaptation strategies; Arabian sea; Bay of Bengal; Indian summer monsoon rainfall; Large-scale dynamics; Low-level winds; Mesoscale; Regional trends; Seasonal mean; Seasonal mean rainfall; Synoptic systems; Thermodynamic parameter; Vertically integrated moisture transports, Moisture determination; Wind effects, Rain, adaptive management; asymmetry; mesoscale meteorology; moisture content; moisture transfer; monsoon; precipitation intensity; regional climate; synoptic meteorology; thermodynamics; trend analysis; wind velocity, Bay of Bengal; India; Indian Ocean
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 27 Dec 2013 20:45
Last Modified: 27 Dec 2013 20:45

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