青藏高原一次地闪放电过程的分析

利用成像率为1000 幅/s的高速摄像系统和快、慢电场变化仪以及宽带干涉仪系统等探测仪器在青藏高原那曲地区所观测的地闪资料，对一次地闪回击及其之前的持续时间较长的云内放电过程进行了分析.结果表明：地闪先导前的云内放电过程发生于雷暴云下部正电荷区和中部负电荷区之间；云中部负电荷区距离地面的高度为28～45 km；闪电的起始放电发生区域距离地面的高度为10～17 km；初始流光在云外发展时具有很大的水平分量和较多的分支；梯级先导的速度为1×105 m/s，在向地面发展时出现较大的弯曲；首次回击放电过程与低海拔地区没有差异，通道中的峰值电流有241 kA；继后回击相对较弱.

An analysis of discharge processes of one cloud-to-ground lightning flash on the Qinghai-Xizang Plateau

The processes of return_stroke and the intracloud discharge just before the first return stroke have been analyzed by using the data from a high_speed digital camera (1 000 frames/s), slow antenna, fast antenna and VHF wide_band interferometer in Nagqu, the Qinghai_Xizang Plateau. The results suggest that the intracloud process occurred between the lower positive charge region and the middle negativecharge region below the cloud. The negative charge region was located at about 28～45 km above the ground. The region of discharge initiation in the cloud was about 10～17 km above the ground. The initial streamer of discharge showed several horizontal branches when it progressed out of the cloud body. The velocity of stepped leader was estimated to be about 1×105 m/s. During its propagation to the ground, the leader channel showed a bigger curl. The first return stroke of the lightning had no difference with that in the lower altitude regions, and its current peak value was about 241 kA. But the subsequent strokes were quite weak on the Plateau.