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Compact Lightning Strokes in Winter Thunderstorms
Journal of Geophysical Research: Atmospheres ( IF 4.4 ) Pub Date : 2021-07-21 , DOI: 10.1029/2021jd034932
Ting Wu 1 , Daohong Wang 1 , Nobuyuki Takagi 1
Affiliation  

With the observation of a 14-site Fast Antenna Lightning Mapping Array in the Hokuriku region of Japan, we identified a special type of lightning stroke called “compact stroke” in winter thunderstorms. A compact stroke starts with a fast downward negative leader followed by a “compact return stroke.” Compact strokes have the following characteristics that are not seen in normal lightning strokes: (a) Durations of preceding discharges (defined as the time difference between the return stroke and the start of the flash) are generally smaller than 200 μs. (b) Most compact strokes are inferred to be produced in small gaps between mountain tops and negative charge regions in winter thunderstorms. (c) Channel lengths of compact strokes are estimated to be shorter than 600 m with an average of about 300 m. (d) Characteristics of electric field change waveforms of compact return strokes are closely related with durations of preceding discharges. (e) Peak currents of compact return strokes increase with increasing channel lengths. It seems that elevations of mountain surfaces where compact strokes occur are comparable to the altitude of the lower positive charge region, so we speculate that the mountain surface and the near-surface space carry positive charges when a storm is overhead and are virtually the lower positive charge region of a normal tripole structure. As a result, compact strokes are confined between the main negative and lower positive charge regions, and small pulses with short durations preceding compact return strokes are produced by downward negative leaders corresponding to the preliminary breakdown stage.

中文翻译:

冬季雷暴中的紧凑型雷击

通过对日本北陆地区 14 个站点的快速天线闪电映射阵列的观察,我们在冬季雷暴中发现了一种特殊类型的雷击,称为“紧凑型雷击”。紧凑型冲程以快速向下的负先导开始,然后是“紧凑型返回冲程”。紧凑型雷击具有以下在正常雷击中不常见的特征: (a) 先前放电的持续时间(定义为回击和闪光开始之间的时间差)通常小于 200 μs。(b) 据推测,冬季雷暴中,大多数致密中风是在山顶和负电荷区之间的小间隙中产生的。(c) 紧凑行程的通道长度估计短于 600 m,平均约为 300 m。(d) 紧凑回程的电场变化波形特征与前次放电的持续时间密切相关。(e) 紧凑回程的峰值电流随着通道长度的增加而增加。似乎发生致密笔划的山地表面的海拔与较低正电荷区域的高度相当,因此我们推测,当风暴在头顶上空时,山地表面和近地表空间带有正电荷,实际上是较低的正电荷正常三极结构的电荷区。因此,
更新日期:2021-08-09
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