汛期短历时强降水过程的闪电特征

对2011年3次短历时强降水天气过程的闪电特征分析结果表明:①3次短时强降水都以负闪为主,负闪占总闪电的比例都在92﹪以上;②小时闪电频数峰值超前降雨峰值1h或同相;③5min闪电频数超前雨量峰值5~60min;④负闪电密集区主要发生在40dBZ以上的回波区,偶尔发生的正闪一般在较弱回波处;闪电大部分发生在回波顶高大于5km以上的区域;多分布在速度不均匀场附近;闪电密集区与VIL大值区对应关系不太好;⑤不同云体,闪电特征不尽相同,闪电频数高峰有的发生在强回波阶段,有的并不是回波最强阶段,而是减弱阶段。强回波前沿出现闪电密集区或前方无回波处发生闪电,预示未来强回波移动的方向;有的云体发展、成熟阶段闪电分布密集,负闪电主要集中在强回波中心附近,云体减弱阶段闪电分散,集中在单体的不同部位。

Characteristics of Lightning in three Short Duration Heavy Rains in Flood Season

An analysis is made of lightning flashes during three short duration severe rain events. The results show that: (1) The lightning flashes in three cases were mainly negative, and the ratio of negative lightning flashes to total lightning flashes is over 92%. (2) The lightning frequency peaks were one hour earlier in phase than precipitation peaks. (3) The 5 minute lightning frequency peaks were 5 to 60 minutes earlier than precipitation peaks. (4) The areas with negative lightning flashes concentrated are around the areas with the reflectivity of radar being above 40 dBz; the positive lightning flashes which occurred occasionally distributed in the weak echo areas; lightning flashes occurred mostly in the areas with the echo top being over 5 km and in the wind fields with radial velocity being uneven. The VIL had poor correlation with lightning flashes, and some lighting flashes occur in the areas where VIL is small. (5) Lightning characteristics differ for different clouds; some lightning frequency peaks occurred in the strong echo stage, but some occurred in the weak stage. Sometimes lightning flashes concentrated around or in the front of a strong echo area, which indicates the moving direction of the strong echoes. Some lightning flashes occurred in the developing or mature stage of clouds, and the negative lightning flashes were concentrated near a strong echo area. The lightning flashes were distributed dispersedly in the weakening stage of clouds, concentrated in the different sites.