Information about lightning properties is important in order to advance the current understanding of lightning, whereby the characteristics of ground strike points (GSPs) are in particular helpful to improving the risk estimation for lightning protection. Lightning properties of a total of 1174 negative downward lightning flashes are analyzed. The high-speed video recordings are taken in different regions, including Austria, Brazil, South Africa and the USA, and are analyzed in terms of flash multiplicity, duration, interstroke intervals and ground strike point properties. According to our knowledge this is the first simultaneous analysis of GSP properties in different regions of the world applying a common methodology. Although the results vary among the data sets, the analysis reveals that a third of the flashes are single-stroke events, while the overall mean number of strokes per flash equals 3.67. From the video imagery an average of 1.56 GSPs per flash is derived, with about 60 % of the multiple-stroke flashes striking the ground in more than one place. It follows that a ground contact point is struck 2.35 times on average. Multiple-stroke flashes last on average 371 ms, whereas the geometric mean (GM) interstroke interval value preceding strokes producing a new GSP is about 18 % greater than the GM value preceding subsequent strokes following a pre-existing lightning channel. In addition, a positive correlation between the duration and multiplicity of the flash is presented. The characteristics of the subset of flashes exhibiting multiple GSPs is further examined. It follows that strokes with a stroke order of 2 create a new GSP in 60 % of the cases, while this percentage quickly drops for higher-order strokes. Further, the possibility of forming a new lightning channel to ground in terms of the number of strokes that conditioned the previous lightning channel shows that approximately 88 % developed after the occurrence of only one stroke. Investigating the time intervals in the other 12 % of the cases when two or more strokes re-used the previous lightning channel showed that the average interstroke time interval preceding a new lightning channel is found to be more than twice the time difference between strokes that follow the previous lightning channel.

中文翻译：

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负向下闪电中的全球地面雷击点特征——第 1 部分：观察

有关闪电特性的信息对于促进当前对闪电的理解非常重要，因此接地点 (GSP) 的特征特别有助于改进闪电保护的风险评估。共分析了 1174 次负向下闪电的闪电特性。高速视频记录是在不同地区拍摄的，包括奥地利、巴西、南非和美国，并根据闪光多重性、持续时间、中风间隔和地面打击点属性进行分析。据我们所知，这是第一次使用通用方法同时分析世界不同地区的 GSP 属性。尽管不同数据集的结果各不相同，但分析表明，三分之一的闪光是单次中风事件，而每次闪光的总平均笔画数等于 3.67。从视频图像中，每个闪光平均产生 1.56 个 GSP，其中大约 60% 的多冲程闪光在一个以上的地方撞击地面。因此，地面接触点平均被击中 2.35 次。多次雷击平均持续 371 毫秒，而产生新 GSP 的雷击前的几何平均 (GM) 间隔值比预先存在的闪电通道之后的后续雷击前的 GM 值大约 18%。此外，还呈现了闪光的持续时间和多重性之间的正相关关系。进一步检查了显示多个 GSP 的闪光子集的特征。因此，笔画顺序为 2 的笔画在 60% 的情况下会创建新的 GSP，而对于高阶笔画，这个百分比会迅速下降。此外，就调节先前闪电通道的雷击次数而言，形成对地的新雷电通道的可能性表明，大约 88% 是在仅发生一次雷击后形成的。调查其他 12% 的情况下两次或多次雷击重复使用以前的闪电通道的时间间隔表明，发现新闪电通道之前的平均击发间隔时间是随后的雷击之间的时间差的两倍多之前的闪电通道。就调节先前闪电通道的雷击次数而言，形成对地的新雷电通道的可能性表明，大约 88% 是在仅发生一次雷击后形成的。调查其他 12% 的情况下两次或多次雷击重复使用以前的闪电通道的时间间隔表明，发现新闪电通道之前的平均击发间隔时间是随后的雷击之间的时间差的两倍多之前的闪电通道。就调节先前闪电通道的雷击次数而言，形成对地的新雷电通道的可能性表明，大约 88% 是在仅发生一次雷击后形成的。调查其他 12% 的情况下两次或多次雷击重复使用以前的闪电通道的时间间隔表明，发现新闪电通道之前的平均击发间隔时间是随后的雷击之间的时间差的两倍多之前的闪电通道。