Temporal and Spatial Characteristics of Preliminary Breakdown Pulses in Intracloud Lightning Flashes
Temporal and Spatial Characteristics of Preliminary Breakdown Pulses in Intracloud Lightning Flashes
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DOI：
10.1029/2019jd031130
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发表时间：
2019-12
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影响因子：
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通讯作者：
D. Shi;Daohong Wang;Ting Wu;N. Takagi
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作者：
D. Shi;Daohong Wang;Ting Wu;N. Takagi
利用快速天线闪电测绘阵列（Fast Antenna Lightning Mapping Array）系统，研究了32次正常云内闪电的初始击穿（PB）脉冲的时空特征。发现PB过程开始于初步孤立脉冲（PIP）阶段，随后是经典PB脉冲（PBP）簇。一个典型的PIP级由两个或三个PIP组成，平均持续时间约为129 μs。一个典型的PBP簇由几个窄脉冲（NPs）和一个经典PBP组成，平均持续时间约为193 μs。在一个PIP阶段中，较晚出现的脉冲通常具有较低的高度，这表明相对于PB过程的总体向上进展而言是一种向后延伸。平均而言，PIP阶段涉及的水平和垂直延伸分别为60和216米。在每个PBP簇中，PBP总是位于最低高度，并在其前面的NP之后，而这些NP的位置可以有不同的模式，在扩展方面。平均而言，在一个典型的PBP集群涉及的总体水平和垂直延伸分别为161和515米。对于PIP阶段和PBP集群，它们的垂直延伸明显长于它们的水平延伸，反映了PB过程的主要垂直通道。基于PB脉冲的时间和空间特性，我们提出了一个模型来解释PIP，NP和PBPs是如何产生的。
We have studied the temporal and spatial characteristics of preliminary breakdown (PB) pulses in 32 normal intracloud flashes recorded by a fast antenna lightning mapping array system called Fast Antenna Lightning Mapping Array. It was found that PB processes started with a stage of preliminary isolated pulses (PIPs) and followed by classic PB pulse (PBP) clusters. A typical PIP stage consists of two or three PIPs and on average lasts about 129 μs. A typical PBP cluster consists of several narrow pulses (NPs) and one classic PBP and on average lasts about 193 μs. During one PIP stage, the pulses occurring later usually have a lower altitude, indicating a kind of backward extension relative to the overall upward progression of PB process. On average, the horizontal and vertical extensions involved in a PIP stage are 60 and 216 m, respectively. In each PBP cluster, PBP is always located at the lowest height and behind its preceding NPs, while these NP locations could have various patterns in term of extension. On average, the overall horizontal and vertical extensions involved in a typical PBP cluster are 161 and 515 m, respectively. For both the PIP stage and PBP cluster, their vertical extensions are apparently longer than their horizontal extensions, reflecting a predominantly vertical channel of PB process. Based on the temporal and spatial characteristics of PB pulses, we have proposed a model to interpret how the PIPs, NPs, and PBPs are produced.