西北地区雷暴的气候特征及其变化规律

Climatic Feature of Thunderstorm in Northwest of China and Its Rule of Changes

利用西北地区171个站1961年～2005年雷暴资料，分析了雷暴活动的时空分布特征，采用二阶正交函数和小波方法分析了雷暴变化趋势和振荡周期．结果表明：高原和高山雷暴最多，平川和盆地最少；各地雷暴的年变化都为单峰型，峰值在7月；雷暴随时间变化为抛物线减少型、反抛物线减少型和线性减少型3种类型；小波分析显示出各地都存在准8a周期振荡．

By using the thunderstorm data of 171 stations in the Northwest of China from 1961 to 2005, a spatial-temporal distribution of thunderstorms was analyzed. With the help of second order orthogonal function and wavelet analysis technique, the tendency and the oscillation period of thunderstorms were analyzed too. The results show that thunderstorm days are most in plateaus and alpines, and least in plains and basins. Yearly variation of thunderstorm day is in an unimodal distribution, and July generally is of the high value period. The tendency of thunderstorm days changes with time. There are 3 types： parabloically reducing type, anti-parabolically reducing type, and linearly reducing type. It has a period of nearly 8 years shown by wavelet analysis.