We gridded 11 years of cloud-to-ground (CG) flashes detected by the U.S. National Lightning Detection Network during the warm season in 15 km × 15 km × 15 min grid cells to identify storms with substantial CG flash rates clearly dominated by flashes lowering one polarity of charge to the ground or the other (+CG flashes vs. −CG flashes). Previous studies in the central United States had found that the gross charge distribution of storms dominated by +CG flashes included a large upper negative charge over a large middle level positive charge, a reversal of the usual polarities. In each of seven regions spanning the contiguous United States (CONUS), we compared 17 environmental parameters of storms dominated by +CG flashes with those of storms dominated by –CG flashes. These parameters were chosen based on their expected roles in modulating supercooled liquid water content (SLWC) in the updraft because laboratory experiments have shown that SLWC affects the polarity of charge exchanged during rebounding collisions between riming graupel and small ice particles in the mixed phase region. This, in turn, would affect the vertical polarity of a storm's charge distribution and the dominant polarity of CG flashes. Our results suggest that the combination of parameters conducive to dominant +CG flash activity and, by inference, to anomalous storm charge structure varies widely from region to region, the lack of a favorable value of any particular parameter in a given region being offset by favorable values of one or more other parameters.

中文翻译：

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暴雨的近风暴环境的区域内比较，这些暴雨以频繁的正向与负向的云对地闪光为主

我们将美国国家闪电探测网在暖季期间在15 km×15 km×15分钟的网格中对11年的云对地面（CG）闪光进行了网格划分，以识别出明显以CG下降为主的暴风雨。一种电荷是对地极性，另一种是（+ CG闪烁对比-CG闪烁）。在美国中部的先前研究发现，以+ CG闪光为主的风暴的总电荷分布包括较大的上层负电荷，而不是较大的中层正电荷，这与通常的极性相反。在横跨美国（CONUS）的七个地区中，我们分别比较了以+ CG为主的风暴和以–CG为主导的风暴的17个环境参数。选择这些参数是根据它们在调节上升气流中的过冷液态水含量（SLWC）中的预期作用来选择的，因为实验室实验表明，SLWC会影响混合相和边缘冰砾和小冰粒之间的回弹碰撞过程中交换的电荷极性。反过来，这将影响风暴的电荷分布的垂直极性和CG闪烁的主要极性。我们的结果表明，有利于主导+ CG闪光活动的参数组合以及通过推断得出的异常风暴电荷结构在各个区域之间差异很大，给定区域中任何特定参数的有利值不足都会被有利条件所抵消。一个或多个其他参数的值。