一次中尺度对流系统的闪电演变特征

A Case Study on Characteristics of Lightning Activity in a Mesoscale Convective System

利用地面雷电探测网资料、多普勒雷达和卫星资料对一次典型的MCS过程的地闪变化特征进行了分析,结果表明,在系统发展的最初阶段全为负地闪;在MCS的成熟阶段地闪频数一直较高,在10次/min以上,负地闪占绝对优势;在消散阶段,地闪频数急剧下降,同时正地闪所占比例越来越大,甚至超过负地闪。地闪基本出现在<-50℃的云区和前部大的温度梯度区内,集中发生于<-60℃的云区。负地闪主要发生在强对流区(>40 dBz),其持续时间和强对流的维持时间几乎相当,说明负地闪可以很好地指示或有助于识别强对流区;密集的正地闪也与强回波区相对应,而稀疏的正地闪则多发生在系统后部的稳定性降水或云砧部位。同时,在MCS成熟阶段出现高正地闪频数的瞬间突增有可能对应着地面强天气的发生,在强对流天气的临近预报中应予以关注。

The evolution of cloud-to-ground （CG） lightning in a typical mesoscale convective system （MCS） was analyzed by using the data from lightning detection system, Doppler radar and satellite. The result shows that almost all the CG flashes are negative at the first developing stage. The CG flash rate is high （more than 10 min 1） and negative CG flash predominates along the mature stage of the storm. The CG flash rate declines rapidly with the increase of positive CG lightning ratio at dissipating stage. The CG flashes mainly occur in the region with the temperature less than -50℃ and high temperature gradient in the front of MCS, but there is no CG flash in the cloud with temperature higher than -30℃. Negative CG flashes cluster in the intense echo （〉40 dBz） region and its duration coincidences with the strong convection, which suggests that the negative CG flash could be used to indicate the strong convective region. Moreover, the dense positive CG flashes can also be observed in the strong echo region, while sparse ones are in the weak and stable echo region or cloud anvil in the rear MCS. The data analysis also shows that the high positive CG flash rate could correspond to a damaging weather. The advent of high positive CG flash rate should he paid more attention in nowcasting of severe convective weather.