Spatial and seasonal variation of rain profiles over Asia observed by spaceborne Precipitation Radar

摘要

The Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) has made it possible for the first time to evaluate global characteristics of vertical structures of rainfall over monsoon Asia. This study is intended to depict features of seasonal variations of the vertical gradient of rainfall rate using TRMM PR data from 1998 to 2000. The features of downward decreasing (DD) or downward increasing (DI) rainfall rate in the lower part of the vertical profile are focused on. Horizontal mapswere made showing decreasing/increasing characteristics in the vertical gradient of rainfall rate over Asia. The pattern showed a clear land-ocean contrast and had monthly variation as the monsoon progressed in Asia. The DD pattern migrated northward around the monsoon onset and withdrew southward in the retrogressing period. The seasonal march of the DD pattern was clear especially over the India subcontinent. The DD seemed to be bordering monsoon rainfall over India. Seasonal changes in characteristics of the vertical profile were observed and are reflected in the horizontal extent of rain and the storm height. It is inferred that large storm systems tend to have high storm height and DD profiles. Most isolated rain systems with low storm height showa DI profile. The DD profile often appears around the border between dry and wet regions and occurs over the wet land.