一次引发台湾地区强降水的锋面及中尺度系统分析研究

Diagnosis Analysis of Severe Heavy Rainfall in Taiwan Region during Heavy Rainfall Experiment in South China

使用1998年海峡两岸及其临近地区暴雨试验(HUAMEX)和南海季风试验(SCSMEX)提供的加密观测资料,对1998年6月6～11日间影响台湾地区的降水系统进行了分析.发现,这段时间内影响台湾地区降水的中尺度系统大部分来自海上,主要由台湾的西南部或东南部进入台湾地区,还有少量影响台湾地区的降水系统来自台湾的西北端,弱冷锋的存在为台湾附近中尺度系统的发生发展提供了有利的背景场;低空急流对水汽输送和低层动力辐合有重要贡献,中尺度地形的影响不可忽视;上述条件形成了有利于此次台湾强降水特有的环境,这与TAMEX期间的某些个例有明显的差异.作者集中对引发6月7～8日台湾地区大暴雨的中尺度系统的特征进行了深入分析,表明:此次强降水过程为一系列β中尺度系统所致,其生命史大约为3～8h,水平尺度为20～150 km;对流层中低层风场扰动是中尺度系统可能的触发机制之一.每小时地面资料的分析表明,强降水发生期间,地面南风分量、地面湿度等均明显增加,表现出明显的β中尺度特征.

During the period of Heavy Rainfall Experiment in South China （HUAMEX） and South China Sea Monsoon Experiment （SCSMEX） in 1998, a very strong heavy rainfall event occurred in Taiwan Region during 24 hours from 1200 UTC 7 June to 1200 UTC 8 June of 1998. The maximum 24-hour precipitation amounts were 370 mm in Taiwan Region. The case study of Taiwan healy rainfall has been done in this paper and the data from satellite, Doppler radar, automatic meteorological stations and conventional observation are used. The following points are concluded： The weak cold front system provided very favorable environment for heavy rainfall formation; The most mesoscale systems causing rainfall events in Taiwan Region come from South China Sea; The low level jet played the very important role in occurrence of severe heavy rainfalls and the influence of terrain lifting can also not he ignored; Probably, the wind disturbances, especially the convergence in the lower and middle troposphere were related with the occurrence and development of the mesoscale convective systems; The heavy rainfall in Taiwan Region was caused by a series of mesoscale-β systems.