湘北地区不同地理环境雷暴活动特征

Characteristics of Thunderstorm Activity in Different Geographical Environments in Northern Hunan

利用1977—2011年湘北地区岳阳、常德和石门3个国家气象观测站雷暴观测资料,采用核密度估计、线性倾向方法和Mann-Kendall趋势检验分析3种不同地理环境雷暴基本规律与变化情况。结果表明:湘北地区处于不同地理环境的岳阳、常德和石门三地雷暴日数春、夏季多而秋、冬季少,其中石门春、夏、秋季平均雷暴日数最多,岳阳在四季平均雷暴日数最少;三地雷暴日数皆呈减少趋势,其中石门减少最慢且不显著;三地初雷日平均日期在2月中旬,终雷日平均日期在10月中下旬,其中石门平均初雷日最早,终雷日最迟,雷暴期最长,而岳阳雷暴期最短,1977—2011年三地初雷日皆有推后,终雷日皆有提前,雷暴期都在缩短;三地雷暴主要起止于午后至凌晨,岳阳相对均匀,石门与常德相对集中;三地雷暴主要起止于偏西偏南方向,岳阳雷暴起止方位有显著的昼夜差异,尤其是洞庭湖湖面以及湖面与城区交界处雷暴活动昼夜差异显著,石门和常德昼夜差异较小;三地雷暴的起止时间、持续时间和起止方位皆有明显的季节变化。

Thunderstorm observation data of three national meteorological stations of Yueyang, Changde and Shimen from 1977 to 2011 were adopted to analyze the basic laws and changes of thunderstorms in three different geographical areas in Northern Hunan by methods of kernel density estimation, linear tendency method and Mann-Kendall trend test. The results show that thunderstorm days in Yueyang, Changde and Shimen are more in spring and summer while less in autumn and winter. Among them, Shimen has the most thunderstorm days in spring, summer and autumn, and Yueyang has the least thunderstorm days in four seasons. The number of thunderstorm days in the three places shows a downward trend, the most slowly and not significantly trend is showed in Shimen. The average date of the first and the last thunderstorms in the three places appears in mid-February and mid-to late October separately. The earliest average date of first thunderstorm, the latest average date of final thunderstorm and the longest thunderstorm period all appear in Shimen, while the shortest thunderstorm period appears in Yueyang. Thunderstorms in the three areas mainly start and end in the afternoon to early morning, relatively uniform in Yueyang but concentrated in Shimen and Changde. The thunderstorms in the three areas mainly start and end in the direction of west and south, and notable difference between day and night in the starting and ending direction presents in Yueyang, especially on the lake surface and the junction between the lake surface and the city, little difference in Shimen and Changde. The starting and ending time, duration and starting and ending directions of the thunderstorms in three areas all show obvious seasonal change.