关键词: 三峡库区, 雷暴, 趋势, 变化特征

Abstract: Based on daily observations of thunderstorm data for 38 stations in the regions of the Three Gorges during 1961～2001, the characteristics of spatial and temporal distribution of thunderstorm are analyzed, such as annual and seasonal variability, as well as first and last dates of thunderstorm over the Three Gorges area .The results show that the mean annual number of thunderstorm days are 34～45d, and interannual thunderstorm variability is large, the difference between the maximum and minimum of annual thunderstorm days is 27～61d. For the region as a whole ,the annual number of thunderstorm days have a decreasing trend with trend ratios reaching 1～7d/10a. The obvious seasonal variation of thunderstorm can also be detected in the Three Gorges region, and the period of April to August is the most frequent season for thunderstorm, in which the total number of thunderstorm days is comparatively high. The first dates of thunderstorm in the Three Gorges region are early in the east and late in the west, but the last dates seem relatively identical. The average duration of thunderstorm is 195～239 d, longer period can be observed in the east than that in the west. The first date of thunderstorm has a tendency of delaying, and its trend ratio is 2～6 d/10 a; The variation tendency of the last date is ahead of time, and its trend is 2～4 d/10 a; The duration of thunderstorm become short during the 40 years , its trend ratios are 2～8 d/10 a.

Key words: the Three Gorges area, thunderstorm, variation, trend, change feature