中文摘要：

利用地面常规观测资料和NCEP再分析资料，把我国西南地区春季出现的热低压分为本地生成型热低压和北方移入型热低压两种类型，定义了热低压的位置指数和强度指数，并以此讨论两种类型热低压的时空分布特征，对西南热低压进行定量描述以及研究其形成规律和机理，以提高天气预报的准确率。研究结果表明：西南地区热低压具有明显的地域性，较少移动；春季我国西南地区近1／4时间受热低压影响，4月份热低压出现频率最高，而5月份的热低压最强，热低压存在明显的日变化且其强度有逐年增强的趋势。热低压主要形成于地形鞍型场附近，是导致我国西南地区春季高温天气和贵州春季暴雨的主要天气系统，有70％的热低压天气过程会带来35℃以上的高温天气，在贵州分别有69％、50％的热低压在填塞过程中会产生大雨、暴雨以上的降水。

英文摘要：

Using the surface observation data and NCEP reanalysis data, spring thermal depressions in the southwest of China are classified into a local type and north-intruding type. Then the position and strength indexes are defined, the space-time distribution and numeral characteristic are analyze and their formation rules and mechanisms are studied for improving the accuracy of weather forecast. The results indicate that the thermal depressions are mostly regional and stationary. The effect of the spring thermal depression generally holds for almost a quarter of a year in the region, and the highest frequency and intensity respectively occur in April and May. It has an obvious diurnal variation pattern and gets stronger year by year. The southwest thermal depressions, mostly forming in the regions close to a saddle-back-shaped field, are the main synoptic systems which cause high temperature weathers in the southwest of China and rain storms in Guizhou province, and 70% of which bring about high temperature weathers over 35 ℃, 69% and 50% heavy rain and rainstorm, respectively.