首次回击具有双接地点的地闪光学和电学特征的个例分析

Optical and Electrical Characteristics of the Cloud-to-Ground Lightning Flash with Two-Striking-Point in the First Return-Stroke

利用成像率为1000幅/s的数字化高速摄像系统和时间分辨率为1μs的快、慢天线闪电电场变化测量仪在广州附近观测到一次首次回击具有两个接地点的负极性地闪。两个分支到达地面的时间间隔约为30μs;在发生回击R2时,其中一个分支的直窜先导发展成为企图先导。观测发现M-分量的发光要比梯级先导强;回击间的K-变化与云中的在击穿和通道的延伸有关,但不引起云地间通道的发光。光学和电场变化的同步观测证实了直窜-梯级先导的发展速度与前一次回击的时间间隔有关,较快的先导发展速度对应于较短的回击时间间隔,较慢的发展速度对应于较长的回击时间间隔。另外,本文在资料分析的基础上,提出了产生双接地点的四种可能原因。

Cloud\|to\|ground lightning flash with two\|striking\|point has been studied by using the simultaneous observation of the high\|speed video camera system with 1000 frame s-1resolution, slow and fast antenna systems with 1 μs time resolution. The time interval of the two channels reached at the ground is 30 μs. One of the leaders became an attempt leader just before the return\|stroke R2.The \%M\%\|components were found to be significantly brighter than the stepped leaders.The \%K\%\|events were caused by intracloud breakdown and channel extension, which were usually accompanied by the luminescence within the cloud. In addition, the simultaneously optical and electrical observation confirmed that the speed of the dart\|step leader was related to the time interval between it and the former return\|stroke. The higher leader speed was associated with the shortertime interval between return strokes, and vice versa. Four possible causations were proposed for the formation of two\|striking\|point flash.