闪电先导发展速度和发光特性的研究

The propagation speed and luminescence characteristics of lightning leaders

基于高速摄像机记录的闪电光学资料,分析了自然闪电先导过程的二维传播速度和通道发光强度随时间的演化.研究结果表明,在地闪和双向闪电的梯级先导传播阶段,先导头部到达的每一个位置都会出现一个亮度脉冲;梯级先导头部通过之后,亮度脉冲消失,通道的发光强度基本保持稳定.当先导传播接近地面时,梯级先导的尖端亮度、二维传播速度以及整个通道亮度随时间的变化趋势归为三种类型:增加、减小和无规律.此外,当通道出现分支时,会引起梯级先导头部亮度或整个通道亮度的增强,且大多数情况下梯级先导的传播速度会略微减小.

The light intensity and 2-D propagation speed for leader channel of natural lightning are obtained by analyzing the optical data captured by a high-speed camera.For the leader channels of cloud-to-ground(CG)lightning and bidirectional leader(BI)lightning,the light intensities present a pulse at the positions where the tip of leader arrived,and the tip passed,the pulse disappear and the light intensities of channel remain stable.As the stepped leaders approach the ground,the tip luminous intensities and two-dimension(2-D)propagation speed of the channels as a whole showed the tendencies of“increased”,“decreased”and“irregular”with time.Moreover,the luminous intensities of the tip or total channel increase when the branch occurred,while the propagation speed of stepped leader decreases in most cases.