A study of Precipitation Mechanisms of Asian Monsoon

点击翻译按钮获取中文摘要

The study of Asian Monsoon rain is important not only for people living in the area but also for a better understanding of global water circulation. However, because it is difficult to conduct aircraft observations due to the expected high content of supercooled water in cloud, the study of precipitation processes has been slow in progress.Our research group has developed videosonde system to study the precipitation processes. The videosonde is a balloon-borne videosonde system from which images of precipitation particles > 0.5 mm in diameter are acquired by a video camera using two sources of stroboscopic illumination.In our observations in Thailand, thirteen videosondes were launched in Songkhla (7*N,101*E)during the period from November 4 to 25,1993, and fourteen videosondes were launched in Surat Thani (9*N,99*E)during the period from October 23 to November 20,1994. In the latter case, videosondes were launched in close collaboration with the C-band doppler radar which belongs to Thai Meteorological Agency.Highlights of the research are :1. There are two types of rain system : One is the equatorial rain system approached from lower latitude, and the second is the monsoon rain system which developed under intence high pressure over the continent extending over the Indo-China Peninsula.2. Different precipitation processes is found in each rain system. In the equatorial rain system, warm rain process dominates, while upper-level graupel formation process as well as low-level warm rain process is active in the monsoon rain system.3. According to the doppler radar analysis, the monsoon rain system is characterized by additional upper-level lifting.4. Larger raindrops are produced in the monsoon rain system than in the equatorial rain system probably because of the strong interaction between graupel falling from above and raindrops grown by warm rain process.