安徽闪电分布特征和不稳定条件分析

利用安徽2008—2011年LD-Ⅱ型闪电定位系统资料,以统计方法分析安徽闪电分布特征,发现安徽闪电的发生较为集中在7—8月,闪电极性以负闪为主(约占总闪的93%以上),同时存在南北差异。南部的闪电数和平均电流强度比北部大,但北部正闪比例略高于南部。进一步结合2008—2011年阜阳、安庆两站探空资料,选取了抬升指数、对流有效位能、700~400 hPa平均相对湿度、700 hPa假相当位温、850~500 hPa温差、沙氏指数与K指数7个大气不稳定参数,以两站为中心的0.5个纬距范围内,分析了探空放球时间后6 h内,大气不稳定参数与闪电活动的关系,确定了闪电活动的不稳定参数阀值,为闪电活动预报奠定基础。

Analysis on the distributions and instabilities of lightning in Anhui

With the data from lightning location system in Anhui province from 2008 to 2011, this paper mainly analyzes the distribution features of lightning in Anhui. Findings can be summarized as follow: (1) Most of lightnings in Anhui province mainly occurrs in July and August, whose polarity is almost negative(93%). (2) A difference exists between the northern and southern Anhui. Lightning frequency and current strength in the south is higher than those in the north, whereas the proportion of positive lightning in the north is higher than that in the south. Combined with the sounding data in Fuyang and Anqing, seven atmospheric instability parameters are selected for the further analysis:such as lifted index, convective available potential energy, average relative humidity from 700 to 400 hPa, pseudo-equivalent potential temperature at 700 hPa, temperature range between 850 and 500 hPa, Showalter index and K-index. The relationship between these atmospheric instability parameters and lightning activities is analyzed and the instable threshold of lightning is confirmed within 6 h after the releasing of the sounding balloon (within 0.5° latitude range around Fuyang and Anqing stations),which all provide a foundation for lightning forecasting.