中文摘要：

利用天气学、卫星云图和物理诊断方法，对2004年2月20日发生在陕西省的一次暴雨过程进行分析。结果发现：其环流演变是一次纬向型朝径向型环流快速调整的过程；暴雨区的主要水汽输送分别由700hPa孟加拉湾的西南暖湿急流和低纬度热带低气压西侧的850hPa的偏南气流提供，热带低压西侧的偏南急流直伸到陕西的位置决定了强降水的落区；云图分析显示暴雨期间在菲律宾附近有一个热带低气压云系存在并维持，与夏季出现大范围暴雨时的云图特征较为相似。结论表明对陕西春季的暴雨预报除考虑环流演变外，还应关注低纬地区的水汽和能量输送及热带低压云系活动状况。

英文摘要：

Using synoptic principles, satellite imagery and diagnosed physical quantities, this paper gives a comprehensive analysis of a torrential rain event that occurred in Shanxi province on Feb. 20, 2004. The results indicate the followings. （1） Its latitudinal circulation evolves quickly to a longitudinal one. （2） The water vapor in the rainstorm area is supplied mostly by a warm moist southwest jet stream in Bay of Bengal on the 700 hPa level and an 850 hPa southerly generated west of tropical low pressures in lower latitudes, and the location of the torrential rain is governed by the part of Shanxi where the southerly jet stream has extended to. （3） As shown in an analysis of the cloud imagery, there is a persistent cloud system of tropical low pressure near the Philippines during the torrential rain, which resembles cloud image features characteristic of large scale summer torrential rains. It is concluded that for the forecast of spring torrential rains in Shanxi, the water vapor and energy transport over lower latitude areas and movements of tropical low pressure cloud systems should be paid attention to besides circulation evolution.