1961—2011年甘肃雷暴气候分布特征及变化趋势

Climate Distribution Characteristics and Trends of Thunderstorm During 1961-2011 in Gansu,China

利用1961—2011年甘肃省63个测站的雷暴观测资料,采用气候倾向率趋势系数和小波分析方法,研究了甘肃省雷暴气候变化特征。结果表明:年平均雷暴日数呈东北—西南走向,东北少、西南多,全省平均为24d,有3个雷暴高发中心,地形是影响甘肃雷暴空间分布的主要因子。近51年中,1961—1990年为多雷暴期,1991—2011年为少雷暴期,雷暴日数总体呈减少趋势,其中甘南高原减少速率最快,每10年约减少4d,这可能与对流有效位能和700hPa相对湿度的下降有关。在春、夏、秋三季中,夏季雷暴日数减少的趋势最为明显,每10年减少3.4d,尤以6月最甚。初、终雷暴日的地区差异较大,甘南高原初雷暴日出现最早,终雷暴日结束最晚,河西走廊初雷暴日出现最晚,终雷暴日结束最早,因此甘南高原是甘肃雷暴期最长的地区,达204d,河西走廊则最短,为105d。近51年来甘肃雷暴期的缩短主要是初雷暴日的显著推后和终雷暴日的提前所致。小波分析表明甘肃雷暴日数存在24a和8a的周期震荡,当前雷暴的发生正处在一个偏少的周期内。

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 reached204 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.