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Local and remote impacts of direct aerosol forcing on Asian monsoon

Chakraborty, Arindam and Nanjundiah, Ravi S and Srinivasan, J (2014) Local and remote impacts of direct aerosol forcing on Asian monsoon. In: INTERNATIONAL JOURNAL OF CLIMATOLOGY, 34 (6). pp. 2108-2121.

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Official URL: http://dx.doi.org/10.1002/joc.3826


The impact of heating by black carbon aerosols on Indian summer monsoon has remained inconclusive. Some investigators have predicted that black carbon aerosols reduce monsoon rainfall while others have argued that it will increase monsoon rainfall. These conclusions have been based on local influence of aerosols on the radiative fluxes. The impact of aerosol-like heating in one region on the rainfall in a remote region has not been examined in detail. Here, using an atmospheric general circulation model, it has been shown that remote influence of aerosol-like heating can be as important as local influence on Indian summer monsoon. Precipitation in northern Arabian Sea and north-west Indian region increased by 16% in June to July when aerosol-like heating were present globally. The corresponding increase in precipitation due to presence of aerosol-like heating only over South Asia (local impact) and East Asia (remote impact) were 28 and 13%, respectively. This enhancement in precipitation was due to destabilization of the atmosphere in pre-monsoon season that affected subsequent convection. Moreover, pre-monsoon heating of the lower troposphere changed the circulation substantially that enabled influx of more moisture over certain regions and reduced the moist static stability of the atmosphere. It has been shown that regional aerosol heating can have large impact on the phase of upper tropospheric Rossby wave in pre-monsoon season, which acts as a primary mechanism behind teleconnection and leads to the change in precipitation during monsoon season. These results demonstrate that changes in aerosol in one region can influence the precipitation in a remote region through changes in circulation.

Item Type: Journal Article
Additional Information: Copyright for this article belongs to the WILEY-BLACKWELL, 111 RIVER ST, HOBOKEN 07030-5774, NJ USA
Keywords: monsoon; aerosols; remote-impact; GCM; Rossby-wave; radiation; precipitation
Department/Centre: Division of Mechanical Sciences > Divecha Centre for Climate Change
Date Deposited: 25 Jul 2014 04:37
Last Modified: 25 Jul 2014 04:37
URI: http://eprints.iisc.ac.in/id/eprint/49514

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