Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 5 8 2005 10.5194/acp-5-2181-2005 http://www.atmos-chem-phys.net/5/2181/2005/ http://www.atmos-chem-phys.net/5/2181/2005/acp-5-2181-2005.html http://www.atmos-chem-phys.net/5/2181/2005/acp-5-2181-2005.pdf 2181 2188 2005-08-12 The Indian summer monsoon rainfall: interplay of coupled dynamics, radiation and cloud microphysics P. K. Patra S. K. Behera J. R. Herman S. Maksyutov H. Akimoto Y. Yamagata Frontier Research Center for Global Change/JAMSTEC, Yokohama 2360001, Japan NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA Dept. Earth and Planetary Science, University of Tokyo, Tokyo 113-0033, Japan The Indian summer monsoon rainfall (ISMR), which has a strong connection to agricultural food production, has been less predictable by conventional models in recent times. Two distinct years 2002 and 2003 with lower and higher July rainfall, respectively, are selected to help understand the natural and anthropogenic influences on ISMR. We show that heating gradients along the meridional monsoon circulation are reduced due to aerosol radiative forcing and the Indian Ocean Dipole in 2002. An increase in the dust and biomass-burning component of the aerosols through the zonal monsoon circulation resulted in reduction of cloud droplet growth in July 2002. These conditions were opposite to those in July 2003 which led to an above average ISMR. In this study, we have utilized NCEP/NCAR reanalyses for meteorological data (e.g. sea-surface temperature, horizontal winds, and precipitable water), NOAA interpolated outgoing long-wave radiation, IITM constructed all-India rainfall amounts, aerosol parameters as observed from the TOMS and MODIS satellites, and ATSR fire count maps. Based on this analysis, we suggest that monsoon rainfall prediction models should include synoptic as well as interannual variability in both atmospheric dynamics and chemical composition.