一次飑线过程的闪电活动特征

Analysis of Lightning Characteristics of a Squall Line System

结合地闪定位资料和TRMM卫星LIS观测的总闪电资料对一次飑线过程闪电活动进行分析,结果如下:这次飑线过程的正地闪超过了负地闪,占地闪的54.7%。在系统发展的初始阶段全部为正地闪;在系统的快速发展阶段地闪频数明显增大,正地闪比例很高,均在75%以上。在系统成熟至减弱阶段,地闪频数开始下降,而正地闪比例下降,负地闪的比例却越来越大,并占据支配地位。正地闪发生在线对流区(即强回波区内或附近),负地闪发生在层状云区。正地闪并不对应于主上升气流区而是紧邻上升气流区的后部。该雷暴云内闪电活动非常频繁,云地闪比例高达26.1:1。降雹和地面大风区位于正地闪密集区内,地闪频数峰值对应于地面大风阶段。

The characteristics of cloud-to-ground lightning （CG） in a squall line were studied in detail by combining the data from ground-based CG location network and Lightning Imaging Sensor on TRMM satellite. Results show that positive CG flashes accounted for 54.7% of the total CG flashes. During the initial developing stage, most of the CG flashes were positive. CG flash rate increased significantly along with the rapid development of the squall line, and the percentage of positive CG was more than 75% during this period. The CG flash rate began to decrease but the percentage of negative CG flash increased gradually and exceeded that of positive CG during the mature and dissipating stages. Almost all positive CG flashes occurred near the strong radar echo regions, in the front parts of the squall line. However, the negative CG flashes almost exclusively occurred in the regions with weak and uniform radar echoes. Dense positive CG flashes corresponded to updraft regions, they didn＇t fall in the core of the updraft, but just behind and close to the main updraft instead. The total flash rate in the storm was very high, and its ratio of intracloud flashes （IC） to CG flashes was 26.1：1. Hailfalling and strong wind at surface occurred in or near the regions with dense positive CG flashes. The CG flash rate peak corresponded to the period of strong surface wind.