关键词: 甘肃, 雷暴, 气候特征, 小波分析

Abstract:

Based on thunderstorm data collected at 63 meteorological stations in Gansu province during 1961-2011, we analyxed the climate characteristics of thunderstorm with the climate trend coefficient and wavelet mathods. The results showed that the spatial distribution of average annual thunderstorm days presented significant trend from northeast to southwest while thunderstorms more likely happened in northeast than southwest, and the provincial average thunderstorm days were 24 d. There were three high thunderstorm centers, and topography was the main factor affecting the spatial distribution of thunderstorm in Gansu. The average annual thunderstorm days had an obviously decreasing linear trend during the last 51 years, among them the 1961-1990 period was high incidence of thunderstorms and the 1990-2011 period was opposite. It demonstrated that the Gannan Plateau had the fastest reduce speed which reduced 4 d approximately every decade, this may be related to the decline of cape and 700 hPa relative humidity. The most obvious decreasing trend was in summer which reduced 3.4 d every decade, especially in June.The first and last thunderstorm days for different areas in Gansu were various. The first thunderstorm day appeared earliest and the last thunderstorm day appeared latest in the Gannan Plateau, but in the Hexi Corridor the first thunderstorm day appeared latest and the last thunderstorm day appeared earliest. So the Gannan Plateau has the longest number of thunderstorm days which reached 204 d and the Hexi Corridor has the shortest one which reached 105 d. Reason for the shortened thunderstorm period is that the first thunderstorm day was back up obviously and the last thunderstorm day was brought forward in the last 51 years. Wavelet Analysis shows that thunderstorm days had two oscillation periods in Gansu which were 24 a and 8 a.The current number of thunderstorm days is in a less period.

Key words: Gansu, thunderstorm, climate characteristics, wavelets analysis