Differences in cyclonic raindrop size distribution from southwest to northeast monsoon season and from that of noncyclonic rain

Abstract

The raindrop size distributions (RSDs) measured with an impact-type disdrometer have been utilized to study the differences in cyclonic RSD (1) from southwest monsoon (SWM) to northeast monsoon (NEM), (2) from that of noncyclonic rain, and (3) from cyclonic rain elsewhere. The stratified (based on rainfall rate R) cyclonic RSD exhibits significant seasonal variation, with more large drops and fewer small drops in SWM than in NEM. The big drops are almost absent in cyclonic RSD, whereas the small and medium-sized drops are larger in number than they are in noncyclonic rain. The average cloud effective radius in cyclones is nearly equal in SWM and NEM, suggesting that the nature of the cyclonic cloud may be similar (oceanic) in both seasons. The cyclonic RSD in the Bay of Bengal is consistent qualitatively with that observed elsewhere, but there exist some differences in rainfall bulk parameters. Implications of the observed seasonal and cyclonic to noncyclonic differences in RSD on quantitative rainfall estimation and cloud-modeling studies are also discussed.