Three‐dimensional imaging of upward positive leaders in triggered lightning using VHF broadband digital interferometers
Three‐dimensional imaging of upward positive leaders in triggered lightning using VHF broadband digital interferometers
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DOI：
10.1029/2009gl042065
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发表时间：
2010-03
影响因子：
5.2
通讯作者：
S. Yoshida;C. Biagi;V. Rakov;J. D. Hill;M. V. Stapleton;D. Jordan;M. Uman;T. Morimoto;T. Ushio;Z. Kawasaki
中科院分区：
文献类型：
--
作者：
S. Yoshida;C. Biagi;V. Rakov;J. D. Hill;M. V. Stapleton;D. Jordan;M. Uman;T. Morimoto;T. Ushio;Z. Kawasaki
使用VHF宽带数字干涉仪和高速摄像机对两次人工引发的闪电中的向上正先导（UPL）进行了三维成像，并进行了时间同步通道基电流测量。两个UPL的可定位VHF源分别从1.1公里和1.5公里开始，在UPL开始后几毫秒，分别上升到2.4公里和3.7公里，平均三维速度约为106 ms−1。两次闪光的初始阶段电流异常大，峰值分别为6 kA和18 kA。当平均电流高于3 kA且具有显著脉冲活动时，定位与正先导传播相关的VHF源。源高度和通道基电流表明，在2至4公里的高度可能有一个显著的负电荷区域，这低于佛罗里达典型雷暴的冻结水平。
Upward positive leaders (UPLs) in two artificially‐initiated lightning flashes were imaged in three dimensions using VHF broadband digital interferometers and a high‐speed video camera with time‐synchronized channel‐base current measurements. Locatable VHF sources of the two UPLs began at 1.1 km and 1.5 km, a few milliseconds after the UPL inception, and ascended to 2.4 km and 3.7 km, respectively, with average 3‐D speeds on the order of 106 ms−1. The initial stage currents for both flashes were unusually large and had peak values of 6 kA and 18 kA. VHF sources associated with positive leader propagation were located when the average current was higher than 3 kA and had significant pulse activity. The source altitudes and channel‐base currents suggest that there might have been a region of significant negative charge at altitudes from 2 to 4 km, which is below the freezing level of typical thunderstorms in Florida.