Long-term Seasonal Characteristics of Raindrop Microphysics During Different Rain Events Over the Western Ghats of India

The microphysics behind the formation of rain droplets is an important feature influencing orographic precipitation at any location. The raindrop microphysics were determined for the precipitation in Mahabaleshwar, the orographic region of the Western Ghats in the Indian subcontinent, using Joss-Waldvogel Disdrometer (JWD) observational data for the period from 2013 to 2019. Smaller (< 1 mm) rain droplets were found to be dominant in monsoon seasons, while in the pre-monsoon and post-monsoon, a higher concentration of medium-sized (1-3 mm) and larger (> 3 mm) rain droplets were observed. In each season, the peak rain droplet concentration moved toward giant rain droplets with increasing rain rate. The probability density function of mass-weighted mean diameter (D-m), normalized-intercept parameter (log(10)N(w)), rain rate (log(10)R), liquid water content (log(10)W), shape parameter (mu), and slope parameter (?) indicate a clear distinction in all three seasons. High D-m and lower log(10)N(w) mean values were observed during the convective precipitation, while the opposite was observed during the stratiform rainfall of each season, except for the post-monsoon convective precipitation. Monsoon rainfall of both convective and stratiform nature had the lowest D-m and highest log(10)N(w) compared to the respective cloud structure of pre-monsoon and post-monsoon. The D-m and log(10)N(w) values in post-monsoon stratiform rain lay between the values observed in the monsoon and post-monsoon seasons. At the same time, the convective precipitation in the post-monsoon had the highest D-m value, with a larger log(10)N(w) than the pre-monsoon convective precipitation. A unique mu-? quadratic equation was also determined for the pre-monsoon, monsoon, and post-monsoon season rain events.