Analysis of monthly cloud climatology of the Indian subcontinent as observed by TRMM precipitation radar

Abstract

ABSTRACTTropical Rainfall Measuring Mission Precipitation Radar data (2A23 V7), for a period of 9 years (2002–2010), is used to analyse the evolution of the monthly cloud climatology over the Indian subcontinent (lat. 6.5°–38.5°N, long. 66.5°–100.5°E). The analysis of the cloud data suggests that over most regions and seasons, the stratiform cloud fraction is associated with outflows from and remnants of convective cells. However, the stratiform cloud cover over the North Indian subcontinent during winter season is not accompanied by any convective cloud maximum zone, indicating minimal role of ground processes in the growth of cloud cover over the region during this season. Mesoscale factors and land surface processes play a major role in the development of cloud maxima during March to May over the Indian subcontinent, over the eastern Himalayas and adjoining plains, as well as southwest peninsular India. As the summer monsoon season approaches, the spatial spread and growth of both cloud fractions gradually increase (stratiform fraction of cloud cover increases rapidly, while the convective fraction rises gradually) over east India, Bay of Bengal and over south Arabian Sea, indicating increased organization of the cloud systems with longer lasting stratiform outflows with the advancement of the season. The largest cloud maxima during the monsoon season are observed at the windward side of hills along the west coast of peninsular India and the west coast of Myanmar. The respective values of convective and stratiform cloud fractions indicate that the cloud cover over Myanmar is associated with more organized cloud systems with larger stratiform outflows, as compared with clouds along the west coast of peninsular India. Similarly, during October to December, the increasing stratiform cloud fractions over southeast peninsular India indicate increasing organization of clouds, compared with values during the monsoon season over this region.