Inferences on upward leader characteristics from measured currents
Inferences on upward leader characteristics from measured currents
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DOI：
10.1016/j.atmosres.2020.105420
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发表时间：
2021-04
影响因子：
5.5
通讯作者：
A. Nag;K. Cummins;K. Cummins;M. Plaisir;Jennifer G. Wilson;D. E. Crawford;Robert G. Brown;R. Noggle;H. Rassoul
中科院分区：
文献类型：
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作者：
A. Nag;K. Cummins;K. Cummins;M. Plaisir;Jennifer G. Wilson;D. E. Crawford;Robert G. Brown;R. Noggle;H. Rassoul
我们详细分析了与肯尼迪航天中心（KSC）工业区塔（IAT）发起的向上未连接的领导者（UULs）相关的电流。在自然闪电中的UUL的电流测量是相对罕见的，并提供了重要的见解向上领导者的发展和传播。在2018年8月1日至2019年11月15日期间，从KSC-IAT发起了8个UUL。所有的UUL都是积极的，因为它们发生在响应向下的负先导，附着在塔附近的地面。KSC中尺度东部范围闪电信息系统（MERLIN）将这些附近的闪电定位在距离塔185至783米的范围内，中位数为538米。这些中风的峰值电流范围为13至69.3 kA，中位数为26.7 kA。从电荷转移的角度来看，这些UUL可以被认为是一种双极闪电现象;它们在电流开始和电流极性反转之间将负电荷转移到地面，随后，它们有效地将正电荷转移到地面。我们将前一个时间段标记为UUL发展阶段，后者标记为崩溃阶段。发展阶段的中位持续时间和电荷转移分别为789 μs和− 6.4 mC，崩溃阶段分别为388 μs和4.7 mC。总的来说，UUL转移到地面的净电荷是负的。在发育阶段，UUL电流由覆盖在较慢（毫秒级）“背景”电流上的较快（总持续时间约为10 μs）脉冲组成。背景-峰值UUL电流脉冲幅度范围为3.4-289.2 A，中位数为30.1 A。中位脉冲总持续时间和半高宽分别为14.1 μs和4.9 μs。中位背景至峰值和10-90%上升时间分别为3.2和2.0 μs。脉冲间期范围为4.2-132.8 μs，中位数为20 μs。一般来说，脉冲幅度较大，背景电流较高，脉冲间隔较短，在后期的UUL。与较低电流的UUL相比，在较晚时间具有较高背景电流的UUL更接近于向下先导分支。
We analyzed in detail currents associated with upward unconnected leaders (UULs) initiated from the Kennedy Space Center (KSC) Industrial Area Tower (IAT). Current measurements of UULs in natural lightning are relatively rare and provide important insights into the development and propagation of upward leaders. Eight UULs were initiated from the KSC-IAT between August 1, 2018 and November 15, 2019. All UULs were positive as they occurred in response to downward negative leaders that attached to ground near the tower. The KSC Mesoscale Eastern Range Lightning Information System (MERLIN) located these nearby strokes at distances ranging from 185 to 783 m from the tower, with the median being 538 m. The peak current for these strokes ranged from 13 to 69.3 kA, with the median being 26.7 kA. From the perspective of charge transferred, these UULs can be considered to be a bipolar lightning phenomenon; they transferred negative charge to ground between the inception of their current and the current-polarity reversal, following which, they effectively transferred positive charge to ground. We labeled the former time-period as the UUL development phase and the latter as the collapse phase. The median duration and charge transferred for the development phase were 789 μs and − 6.4 mC, respectively, and for the collapse phase were 388 μs and 4.7 mC, respectively. Overall, the net charge transferred to ground by UULs was negative. During the development phase, UUL-currents consisted of faster (total durations of the order of 10 μs) impulses overlaid on slower (millisecond-scale) “background” current. The background-to-peak UUL current-pulse amplitudes ranged from 3.4–289.2 A with the median being 30.1 A. The median pulse total duration and full-width at half-maximum (FWHM) were 14.1 μs and 4.9 μs, respectively. The median background-to-peak and 10-to-90% risetimes were 3.2 and 2.0 μs, respectively. Interpulse intervals ranged from 4.2–132.8 μs, with the median being 20 μs. Generally speaking, pulse amplitudes were larger, background currents were higher, and interpulse intervals were shorter at later times during UULs. It is likely that the UULs with higher background currents at later times were more closely approached by a downward leader branch versus the lower-current UULs.