Precipitation Microphysics in Intensifying and Weakening Tropical Cyclones Over the Western North Pacific: Insights From GPM DPR

Abstract

Shear‐relative, quadrant‐scale differences in precipitation microphysics between intensifying tropical cyclones (ITCs) and weakening tropical cyclones (WTCs) are investigated using Ku/Ka‐band observations from the Global Precipitation Measurement (GPM) Dual‐frequency Precipitation Radar (DPR) over the western North Pacific during 2014–2024. The results indicate that ITCs exhibit a higher fraction of convective pixels and statistically significantly larger near‐surface drop sizes compared with WTCs, despite their weaker instantaneous storm intensities. Notably, the downshear right (DR) quadrant of ITCs acts as a convective initiation zone, exhibiting the highest convective fraction yet the lowest mean storm echo top height, with microphysical signatures of more active drop breakup. In contrast, the downshear left (DL) quadrant emerges as particularly critical for intensification, showing the greatest enhancement in precipitation properties, especially in rain rate and storm echo top height, while the corresponding enhancement for WTCs is comparatively subdued. Additionally, the presence of significantly greater Z _e and larger drop sizes observed above the melting layer in the DL quadrant of ITCs indicates vigorous ice‐phase processes (e.g., riming and aggregation), while in WTCs, rapid Z _e increases are confined to a shallow layer, consistent with weaker updrafts that limit vertical ice growth. These results suggest that monitoring storm echo top heights and drop‐size evolution, particularly within the DR and DL quadrants, likely provide valuable insight towards early‐warning indicators of TC intensification and offer observational constraints for improving TC intensity forecasting.