三峡库区雷暴气候变化特征分析

利用长江三峡库区及其周边地区38个气象站1961～2001年的逐日雷暴资料，统计、分析了三峡库区雷暴日数及其初、终日的时空分布特征。结果表明：41年来，长江三峡库区年平均雷暴日数较多,一般为34～45 d,其中库区西北部和中南部为多雷区；年际变化大，最多年比最少年一般偏多27～61 d；整个库区年雷暴日数的变化均存在不同程度的减少趋势，气候倾向率为 1～7 d/10 a；雷暴出现的季节变化很明显，4～8月为多发时段；雷暴初日库区东部早于西部，终日东西段差别不大；雷暴持续期普遍在195～239 d之间,其中西部持续时间短，东部长；大部地区雷暴初日有推后的变化趋势，推迟速率约2～6 d/10 a；终日有提前的变化趋势，且提前速率为2～4 d/10 a；库区大部雷暴期呈缩短的变化趋势，缩短速率为2～8 d/10 a。

FEATURES OF CLIMATE CHANGE IN THUNDERSTORM OVER THE THREE GORGES AREA

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.