45a来宁夏雷暴气候统计特征及趋势分析

Statistic Climate Characteristics and Thunderstorm Weather Tendency in Ningxia during the Last 45 Years

利用1961--2005年宁夏逐日雷暴资料，利用数理统计、小波分析等方法，揭示出了宁夏雷暴天气气候统计特征和演变趋势。结果表明，宁夏总体上属中雷区，年平均出现雷暴日为86．62d，年际变化幅度大，多、少雷暴年均有7a，雷暴日最多年为118d，最少年为65d；45a来雷暴的发生有逐渐减少的趋势，并以3．072d／10a的气候倾向率递减，且存在3～4a的较短周期和8a左右的较长周期振荡；雷暴多发生在3～10月，主要集中出现在夏季，尤以7月突出，有明显的季、月变化，冬季雷暴出现的概率非常低；初雷日平均出现在4月中旬，终雷日平均出现在9月中旬，全区平均雷暴初终日间日数为139d左右；雷暴发生有明显的日变化特征，有双峰型和单峰型之分，集中出现在11：00-22：00时，其中，15：00时前后为雷暴发生高频时；雷暴的发生与地形、地势有密切关系。

The daily thunderstorm data of Ningxia during 1961-2005 are used to analyze the climatic change characteristics by methods of mathematical statistics, linear analysis, and wavelet analysis and so on. Some conclusions are drawn as follows： Ningxia is located in the region with middle thunderstorm frequency, and the number of annual mean thunderstorm days is 86.62 days. During the last 45 years, there were 7 years with more thunderstorm days and 7 years with less thunderstorm days; the number of the most annual thunderstorm days was 118 and the least was 65; the inter-annual change range was large. There was a decreasing trend of thunderstorm weather frequency in these 45 years, with a decreasing rate of 3. 072 d/10a, and a 3-4 years relatively short period and a 8 years relatively long period viration. Thunderstorm events mainly occurred in March to October, mostly in summer, and especially in July, it has obviously seasonal and monthly change, and the probability was extremely low in winter. The first thunderstorm occurred in mid- April and the last occurred in mid-September by mean; the mean duration between the first and the last in the whole region was about 139 days. There was obvious diurnal variation in thunderstorms occurrence, showing bimodal or unimodal types; most occurred during 11：00--22：00, with high frequency before or after 15：00. The occurrence of thunderstorms has close relationship with the terrain and topography.