Characteristics of a negative lightning with multiple‐ground terminations observed by a VHF lightning location system
Characteristics of a negative lightning with multiple‐ground terminations observed by a VHF lightning location system
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DOI：
10.1002/2015jd023702
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发表时间：
2016-01
期刊：
影响因子：
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通讯作者：
Zhuling Sun;X. Qie;Mingyuan Liu;R. Jiang;Zhichao Wang;Hongbo Zhang
中科院分区：
文献类型：
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作者：
Zhuling Sun;X. Qie;Mingyuan Liu;R. Jiang;Zhichao Wang;Hongbo Zhang
利用VHF频段闪电辐射源的二维测绘系统，结合宽带电场变化记录，分析了一次具有四个地面终止的四个前导回击序列的负云地闪电的传播特性。4个阶梯式引导-笔划序列分别来自云内初始击穿过程的两个不同分支，每个相邻的两个引导-笔划序列之间的时间间隔分别为82.9ms、81.4ms和152.2 ms。前两个卒中序列是多个终止卒中(MTS)，每个MTS显示由两个前导分支引起的两个不同的地面终止。对应的电场变化呈现两个快速上升的波形，间隔分别为1.5ms和2.7ms，第二个峰值比第一个峰值小3-4倍。每个MTS的第二个接地支路发生在其通道与主冲程通道的连接条件较差时。第三和第四引线-行程序列通过第二MT的不同接地通道之一连接到地面。在这两次击打之前，省道先导者表现出混沌的脉冲串(CPT)，伴随着强烈和连续的VHF辐射，电场变化显著缓慢。先导阶段仅发生在先导阶段，先导阶段的传播速度约为107m/S。与先导不同的是，先导尝试阶段伴随有规则的脉冲串，沿前一航道以106m/S的速度传播。
Propagation characteristics of a negative cloud‐to‐ground lightning with four leader‐return stroke sequences exhibiting four ground terminations, referred to as multiple termination flash, are analyzed using a two‐dimensional mapping system of lightning radiation sources in VHF band along with broadband electric field change records. The four stepped leader‐stroke sequences were produced from two different branches of the preliminary breakdown process inside the cloud, and the time intervals between each adjacent two leader‐stroke sequences were 82.9 ms, 81.4 ms, and 152.2 ms, respectively. The first two stroke sequences were multiple termination strokes (MTSs), and each MTS showed two different ground terminations induced by two leader branches. The corresponding electric field changes exhibited two fast‐rising waveforms separated by 1.5 ms and 2.7 ms, respectively, and the second peak was 3–4 times smaller than the first. The second grounding branch in each MTS occurred when its channel was in poor connection conditions to the main stroke channel. The third and fourth leader‐stroke sequences connected to the ground with one of the different grounded channels of the second MTS. The dart leaders before these two strokes exhibited chaotic pulse trains (CPTs) with significant slow electric field variations accompanying strong and continuous VHF radiations. The CPTs only occurred in the dart leader stage which propagated with a speed in an order of 107 m/s. Different from dart leader, attempted leader was associated with regular pulse trains and propagated at a speed order of 106 m/s along the previous channel.