Understanding the role of cloud microphysical processes behind the Indian summer monsoon rainfall.

Cloud microphysical processes and rainfall over the Indian summer monsoon (ISM) region are unique because of the strong interaction among clouds, thermodynamics, and dynamics. The heating and presence of water vapor during ISM help for the formation of cloud particles in stratiform and convective clouds. In this study, we have analyzed the role of cloud microphysical processes behind the ISM rainfall (ISMR) and their inter-annual and sub-seasonal variability from the Goddard Earth Observing System (GEOS) model data (i.e., MERRA reanalysis). The spatial distribution of microphysical process rates (e.g., auto-conversion, freezing, accretion of rain and snow) over the Indian subcontinent are in line with the rainfall distribution. Besides, the interannual variability of these cloud microphysical process rates is coupled to that of the ISMR. It is revealed that these microphysical processes are in line with the spatial distribution of more (less) rainfall over the Indian subcontinent during active (break) spells. They also have significant sub-seasonal variability like ISMR over the ISM region. The variance is more in the synoptic scale than in quasi-biweekly mode (QBM) and monsoon intraseasonal oscillation (MISO) scales. Further, the sub-seasonal variances of microphysical process rates are well correlated with the mean ISMR. Results also reveal the teleconnection of cloud microphysical processes over the ISM region with the ENSO phenomena. We hope that the understanding of detailed microphysical processes during ISM will help the development of a climate model for depicting the mean monsoon. It may then enhance the skill of seasonal prediction. [ABSTRACT FROM AUTHOR]