4-year Climatology of Global Drop Size Distribution and its Seasonal Variability Observed by Spaceborne Dual-frequency Precipitation Radar

Abstract

This study investigates the global drop size distribution (DSD) of rainfall and its relationship to large-scale precipitation characteristics using the Dual-frequency Precipitation Radar (DPR) onboard the Global Precipitation Measurement (GPM) Core Observatory. This study focuses on seasonal variations in the dominant precipitation systems regarding variations in DSD. A mass-weighted mean diameter (Dm), which is estimated based on the dualfrequency information derived from the GPM/DPR, is statistically analyzed as a typical parameter of the DSD. Values of the annual mean Dm, in general, are larger over land than over the oceans, and the relationship between Dm and precipitation rate (R) is not a simple one-to-one relationship. Furthermore, Dm exhibits statistically significant seasonal variations, specifically over the northwest Pacific Ocean, whereas R shows insignificant variations, indicating the variations in R cannot explain the distinct seasonal changes in Dm. Focusing on the seasonal variation in Dm over the northwest Pacific Ocean, the results indicate that the variation in Dm is related to the seasonal change in the dominant precipitation systems. In the summer over the northwest Pacific Ocean, Dm is related to the organized precipitation systems associated with the Baiu front over the mid-latitudes and tropical disturbances over the subtropical region, with relatively higher precipitation top heights, composed of both stratiform and convective precipitations. Contrary to the summer, larger Dm over the mid-latitudes in winter is related to extraCorresponding author: Moeka Yamaji, Earth Observation Research Center, Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki, 305-8505, Japan E-mail: yamaji.moeka@jaxa.jp J-stage Advance Published Date: 27 May 2020 Journal of the Meteorological Society of Japan Vol. 98, No. 4 756