Investigating Monsoon Raindrop Sizes in Relation to Associated Atmospheric Parameters over the Indian Region.

The paper investigates the physical phenomena that govern raindrop size distribution and cloud characteristics across the diverse climatic regions of the Indian subcontinent. The study focuses on four locations, Kolkata, Bhopal, Desalpar, and Kavaratti Island, during the monsoon period from 2014 to 2016. It employs various techniques, encompassing ground-based measurements from disdrometers, space-borne observations from MODIS, along with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model, MEERA-2, and ERA-5 reanalysis outputs. The study found that there is a predominance of larger raindrops in Kolkata and Kavaratti Island during the monsoon season. This is due to the high atmospheric instability in these regions, which is expressed through convective available potential energy (CAPE). Locations with noticeable diurnal CAPE variations also exert influence over rainfall rates and the occurrence of raindrop sizes at different times throughout the day. Airflow patterns combined with anthropogenic activities affect aerosol levels in India. Bhopal and Desalpar have high dust levels during monsoon due to airflow from desert regions. In urban centers with significant anthropogenic activity, such as Kolkata and Bhopal, sulfate aerosols dominate, while Desalpar and Kavaratti Islands are characterized by a greater prevalence of sea salt aerosols. The dominance of different aerosol types impacted the cloud features, and, as a result, the occurrence of mean raindrop sizes at the four locations. The investigation also found that regions characterized by the predominance of larger raindrops during the monsoon season exhibit a lower cloud-effective radius normalized by the liquid water path. The variability of the raindrop size distribution impacts the empirical relationships between radar reflectivity (Z) and rain rate (R) , as well as between mass-weighted mean drop diameter (D m) and R , over the four locations. The study emphasizes the importance of considering varying Z-R relationships for accurate estimation of rain rates from radar reflectivity measurements in different climatic regions. • Varied rain microstructure observed over the different geographical locations of the Indian subcontinent. • Drop size occurrence probability is controlled by the prevailing CAPE. • CER/LWP ratio is inversely related to mean drop size. • The aerosol types influence the cloud features and as a result the prevailing DSD in a region. • The aerosol environment is controlled by the airflow pattern, geographical location, and anthropogenic activities. [ABSTRACT FROM AUTHOR]