Modeling of Rain Drop Size Distribution in Association With Convective and Cloud Parameter Over a Tropical Location

The difference in rain drop size distribution (DSD) characteristics between convective and stratiform rain and in monsoon and premonsoon season have been investigated over a tropical location, Kolkata, using seven years of data collected from a Joss–Waldvogel disdrometer (JWD). During the Indian summer monsoon (ISM) and the premonsoon season, Kolkata gets substantial rain. Interannual variability of DSD has been evident. The normalized drop size distributions of DSD show a double peak at 20–50 mm/h rain rate due to drop break up and coalescence process. For convective rain, the concentration of higher drops (
$>$
3 mm) is more significant compared to stratiform rain. In the premonsoon period, a significant contribution of normalized DSD in the afternoon to late evening has been evident due to nor’westers. The contribution of normalized DSD of higher drops (
$>$
3 mm) is more in the premonsoon convective rain compared to monsoon convective rain. The larger slope of
$\mu $
–
$\Lambda $
relationship has been observed in the premonsoon convective period which corresponds to higher
$D_{m}$
values. The relationship between radar reflectivity (
$Z$
) and rain rate (
$R$
) distinguishes the monsoon and premonsoon seasons. Radiometric measurements have been used to examine the effects of the atmospheric instability parameter convective available potential energy (CAPE) and cloud base height (CBH) on the formation of larger drop sizes. This study will be useful for understanding precipitation microphysics and improving the quantitative precipitation estimation (QPE) algorithm.