A study of Precipitation Mechanisms of Asian Monsoon

亚洲季风雨的研究不仅对生活在该地区的人们很重要，而且对更好地了解全球水循环也很重要。然而，由于预计云中过冷水含量高，难以进行飞机观测，因此对降水过程的研究进展缓慢。本课题组开发了一套视频探空系统来研究降水过程。视频探空仪是一种气球载视频探空系统，通过使用两个频闪照明源的视频摄像机获取直径为> ~ 0.5 mm的降水颗粒图像。我们在泰国的观测中，1993年11月4日至25日在宋卡（7*N,101*E）发射了13个视频探空仪，1994年10月23日至11月20日在素叻他尼（9*N,99*E）发射了14个视频探空仪。在后一种情况下，与属于泰国气象局的c波段多普勒雷达密切合作发射了视频探空仪。本研究的重点有：1.研究内容：降雨系统有两种类型：一种是低纬度接近的赤道雨系统，另一种是在延伸到中南半岛的大陆上的强高压下形成的季风雨系统。在每个降雨系统中发现不同的降水过程。在赤道雨系统中，暖雨过程占主导地位，而在季风雨系统中，上层霰形成过程和低层暖雨过程都很活跃。根据多普勒雷达分析，这次季风雨系统的特点是有额外的高空抬升。季风雨系统产生的雨滴比赤道雨系统大，这可能是由于从高空落下的霰与暖雨过程产生的雨滴之间的强烈相互作用。

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.