Radiative effect of dust aerosols on cloud microphysics and meso-scale dynamics during monsoon breaks over Arabian sea

Abstract

During monsoon breaks (large scale rainfall below the long term normal), dry air laddened with dust aerosols intrude over central India through Arabian sea (AS) from West Asian desert regions. To understand the effect of these dust aerosols on marine clouds over AS during monsoon breaks, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) and Cloud and the Earth's Radiant Energy System (CERES) data have been analyzed for the period 2007 to 2013. The vertical profile of dust backscatter coefficient (DBS) showed an elevated layer between 2 and 5 km and the maximum heating rate observed is 9 K/Day which is higher by 3 K/day as compared to the heating observed in June to September (JJAS) mean. Semi-direct effect due to the interaction of the long range transported dust with pristine cloud environment is observed in both warm and cold clouds. Significant differences in shortwave and longwave fluxes at the top of the atmosphere (TOA), cloud micro and macrophysical parameters are observed between the clouds with and without dust. Also, the percentage differences are more in cold clouds as compared to warm clouds. Dust induced semi-direct effect is found to be more pronounced in cold clouds, while indirect effect in warm clouds. Zonal anomalies of dynamical parameters due to dust induced heating, affect the circulation patterns in the immediate meso-scale environment, which strengthen/extend the monsoon break situation.