Characteristics of seasonal scale convective and stratiform precipita tion in Asia based on measurements by TRMM Precipitation Radar

The frequency, intensity and vertical structure of convective and stratiform precipitation at seasonal scale in Asia are investigated based on measurements by TRMM Precipitation radar (PR) in the latest ten years (1998 to 2007). Results indicate a nearly banded distribution of seasonal mean precipitation with rain rate no more than 10 mm/d in East Asia around the subtropical anticyclone in the western Pacific in spring, autumn and winter. However, heavy rain areas of more than 12 mm/d occur in the wide spread Asian summer monsoon region from the Bay of Bengal, southwestern China, eastern China to Japan during summer. Generally, rain intensity of both convective and stratiform precipitation is weaker over land than over ocean. It is the topographic forcing effect in Asia that produces windward heavy rain bands on about 1000 km scale at high frequencies, while weak precipitation usually appears less frequently in the leeward mountain regions. Results also show a convective precipitation frequency less than 3% in most parts of Asia. For stratiform precipitation, however, its frequency exceeds 3% with a maximum of about 10% in Asia. The frequency distributions for both convective and stratiform precipitation in Asia display higher percentages in the tropical region to the south and southwest of the subtropical anticyclone than in the mid-latitude region to the north and northwest of the subtropical anticyclone. Furthermore, the convective precipitation frequency in spring is higher in the Indochina Peninsula, southern China and south China sea than that in the Indian subcontinent. The seasonal variability of precipitation profiles for both convective and stratiform precipitation is best demonstrated by the changes of the storm top height, i.e. the depth of precipitating clouds, which are stronger in the extratropical regions than in the tropics, stronger over land than over ocean in the same latitude, stronger in the Bay of Bengal than South China Sea. No such a seasonal variability is found in South China Sea and the warm pool in the western Pacific. Results also expose a four-layer structure for the convective precipitation, and a three-layer structure for the stratiform precipitation.