Abstract
The dominant microphysical processes responsible for differences in mass-weighted-mean-diameter (Dm) of deep and shallow rain during wet and dry spells of southwest monsoon (SWM) and northeast Monsoon (NEM) over continental, oceanic, and orographic regions of India are inferred from GPM (Global Precipitation Measurement) DPR (Dual-frequency Precipitation Radar) measurements made between 2014 and 2022. The deep precipitating systems Dm shows oceanic and continental nature during wet and dry spells of SWM and NEM. The dry spells of SWM over northwest India, all the spells except the wet spells of NEM over southeast Peninsular India, dry spells of NEM over northeast India show continental rain clusters and others show maritime rain characteristics. Mean Dm of deep systems at various rain rate intervals show marked intraseasonal variations over northwest India, central India, and foothills of the Himalayas during SWM and over the Western Ghats, southeast peninsular India, and northeast India during the NEM. Though Dm is larger in SWM than in NEM at seasonal scale, the dry spells of NEM show largest Dm than in other spells in SWM and NEM. The observed near surface Dm differences between the wet and dry spells of SWM and NEM are seen from 1.5 km below the melting layer and are magnified during the descent of raindrops by the microphysical processes over all the regions except for southeast peninsular India and Myanmar coast during the SWM dry spells. Below the melting layer, collision-coalescence and breakup processes are considerable in the deep precipitating systems, and only the collision-coalescence process (> 95%) dominates in shallow rain over all regions.
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