Raindrop size distribution of monsoon and tropical cyclone events over South China

The rainy season in South China is predominantly influenced by monsoon and tropical cyclone (TC) weather systems. However, due to the lack of long-term observational data, the microphysical characteristics of raindrop size distributions (DSDs) associated with these systems remain insufficiently understood. This study utilizes five years (2016–2020) of 2DVD observations to analyze the differences in DSD characteristics of monsoon and TC rainfall. The results indicate that monsoon rainfall exhibits higher concentrations of medium to large raindrops (diameter > 2.1 mm), along with larger mean rainfall rates ( R ) and mass-weighted mean diameters ( D m ), but lower normalized intercept parameters ( N w ) compared to TC rainfall. Distinct differences in the mean normalized DSDs are observed between monsoon and TC rainfall. Convective rain under both systems shows the characteristics of maritime convective rain. Additionally, the relationships between kinetic energy (KE) and R , KE and D m , as well as radar reflectivity ( Z ) and R , differ between monsoon and TC rainfall. TC events have relatively humid atmospheric conditions and higher wind speeds, resulting in the presence of a large number of small raindrops. These findings enhance understanding of the DSD characteristics under different synoptic regimes and provide valuable implications for improving rainfall KE estimation, DSD retrieval, and quantitative precipitation estimation over South China. • Monsoon rainfall shows larger drops; tropical cyclone rainfall shows higher concentrations in South China. • Both monsoon and tropical cyclone convective rainfall show maritime convective rainfall features. • Raindrop size distributions vary in response to differing dynamic and thermodynamic conditions.