我国中部五省雷暴日时空分布特征

Thunderstorm Days of the Five Provinces in Central China

为研究中部五省雷暴日时空分布特征,利用1961―2010年中部五省85个气象台站雷暴日资料,采用小波分析和EOF分析等数理统计方法,对其雷暴日时空分布特征进行了统计分析。结果表明:近50年来,中部五省初雷日期和终雷日期没有表现出提前或推迟的趋势,年平均雷暴日整体呈下降趋势,夏季雷暴日的减少是影响年雷暴日减少的主要原因。中部五省年平均雷暴日为41d,其中春季占全年雷暴日的30.3%,夏季占57.6%,秋季占8.5%,冬季占3.6%;五省平均初雷日期在3月1日或2日,从南至北初雷日期依次推迟,南北最大相差近3个月;终雷日期在10月4日或5日,终雷日期是南晚北早,南北最大相差近2个月;雷暴日月变化曲线呈双峰型,主峰在7月或8月,次峰在4月;通过小波分析,年平均雷暴日主要呈11a、17a和6a、4a左右的振荡周期;长江以北地区,20d<年平均雷暴日≤40d,属多雷暴地区;长江以南地区,年平均雷暴日>40d,属于高雷区或强雷区,其中赣南和湘南少部分地区年平均雷暴日>60d,属强雷区。根据EOF分析,将五省年平均雷暴日空间分布划分为:一致型、南北反相型、梅雨型和局地型等4种类型。年平均雷暴日整体呈下降趋势的原因,可能与夏季风的强弱和大气环流突变有关。

The spatial and temporal distribution characteristics of thunderstorm days of the five provinces in Central China were researched with the 1961-2010 data from 85 central meteorological stations, and were analyzed by using mathematical statistics methods, such as the wavelet analysis and the EOF analysis. The results showed that： in the past 50 years of the five provinces, the average date of the first thunderstorm and the last thunderstorm did not have a tendency of advance or delay, but the number of annual mean thunderstorm days showed a whole trend of decline because of the reducing of thunderstorm days during summer. The average annual number of thunderstorm days was 41, of which spring thunderstorm days accounted for 30.3%, summer 57.6%, autumn 8.5%, and winter 3.6%.The average date of the first thunderstorm occurred on March 1st or March 2nd, and postponed from South to North in turn, and the greatest disparity could be nearly 3 months. The last thunderstorm occurred on October 4th or the 5th, the average date of the last thunderstorm in South ended later than in North, and the maximum time difference could be up to 2 months. The monthly variation of thunderstorms took on a bimodal curve, whose main peak appeared in July and the secondary peak in April. The wavelet analysis showed that the average annual thunderstorm days had the cycles of ii years, 17 years, 6 years, and 4 years, respectively. The areas located north of the Yangtze River were the frequently occurring thunderstorm region. where the average annual number of thunderstorm days were between 20 and 40. The areas located south of the Yangtze were the more frequently occurring thunderstorm region, where the average thunderstorm days were more than 40. In some areas of South Jiangxi and Hunan, the average thunderstorm days more than 60, those were the most frequently occurring thunderstorm region. According to the EOF analysis, the spatial distribution of the average number of thunderstorm days could be classified into 4 types： the consistent type, the North and South inverting type, the plum rain type, and the local type. The reasons causing the whole decline trend of the annual mean thunderstorm days, might be associated with the strength of the summer monsoon and the mutation of atmospheric circulation.