2007年5～8月云南省雷电活动特点和致灾因子分析

Analysis of Characteristics and Causes of Lightning Activity in May to August of 2007 in Yunnan

对2007年5～8月雷电活动及其灾害成因进行了分析，结果表明：云南雷电活动频繁，但空间分布不均匀；雷电活动的时间分布基本呈一峰一谷变化，峰值出现在17～18时，谷值出现在10～11时；雷击灾害发生的可能性不但与闪电频数有关，还与闪电强度有关，闪电一般发生在回波强度≥40dBz、组合反射率≥45dBz、回波顶高≥12km的具有典型强对流特征的区域；回波强度越强、顶高越高，发生雷电的可能性越大，出现的雷电灾害越严重；低槽切变、两高辐合型北方系统以及南海低压、热带辐合带型、西行台风型南方热带系统为雷电的发生发展提供了有利的环流背景以及动力、热力或者水汽条件；雷电发生在SI〈0℃和θse850-θse500〉6℃的强烈对流不稳定区域内。

The lightning activity and the causes of lightning disaster from May to August of 2007 are analyzed The results show that lightning activity is frequent, but spatial distribution is uneven. The changes of temporal distribution of lightning activity show a peak-low pattern. The peak appears between 17：00 and 18：00 PM and valley appears between 10：00 and 11：00AM. The probability of lightning disaster is not only related to lightning frequency, but also related to lightning intensity. Lightning strikes always takes place in the strong convective region where echo intensity is equal to or greater than 40 dBz, composite reflectivity is equal to or greater than 45 dBz and Echo Top-ET is equal to or greater than 12 km. If the echo intensity is strong and the Echo Top-ET is high, there will be more possibility of lightning occurrence and lightening disaster will become more serious. Yunnan lightning activity occur in the unstable field where SI is bellow 0 and θse850-θse500 is above 6 ℃ by the favorable weather background, such as north systems of trough-shear and two high-pressure convergence, and south tropical systems of Nanhai trough, tropical convergence and typhoon which moves to the east.