Microphysical characteristics of clouds and precipitation during pre-monsoon and monsoon period over a tropical Indian station

Characteristics of clouds and precipitation during the pre-monsoon (PM) and monsoon months (MM) have been examined in the present study over the tropical station Kolkata (22.65 degrees N, 88.45 degrees E), which is located in the eastern part of India. Satellite data of clouds for the years 2005-2007 and raindrop size distributions (DSD) derived from ground-based Disdrometer for the years 2005 and 2006 for PM and MM has been considered here. Results shows that lower and middle level clouds dominate in the pre-monsoon season and the higher-level clouds are predominant in the monsoon season over the mentioned region. Correspondingly the cloud effective radius value also increases from the pre-monsoon to the monsoon months. The impact of aerosols and moisture plays a vital role in such changes. The characteristics of raindrop size distribution for the two seasons also showed that larger drops are more prevalent during pre-monsoon season whereas the smaller drops are present in larger number in the monsoon months. This is mainly due to the convective nature of rainfall in the pre-monsoon months, where intense convection, accompanied by strong updrafts modifies the raindrops. Thus pre-monsoon (monsoon) season over Kolkata region is characterized by lower/middle level (higher level) clouds, smaller (larger) cloud drop size and larger (smaller) raindrop size at the surface. (C) 2013 Elsevier Ltd. All rights reserved.