Parameters of triggered-lightning flashes in Florida and Alabama
Parameters of triggered-lightning flashes in Florida and Alabama
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DOI：
10.1029/93jd02293
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发表时间：
1993-12
影响因子：
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通讯作者：
R. Fisher;G. Schnetzer;R. Thottappillil;V. Rakov;M. Uman;J. D. Goldberg
中科院分区：
文献类型：
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作者：
R. Fisher;G. Schnetzer;R. Thottappillil;V. Rakov;M. Uman;J. D. Goldberg
1990年夏天在佛罗里达州的NASA肯尼迪航天中心和1991年夏天在阿拉巴马州的麦克莱兰堡分别测量了触发闪电的通道基流。此外，获得了所有闪光灯的3或5毫秒分辨率的16毫米电影记录，并获得了佛罗里达州的三次闪光灯的条纹相机记录。这里分析的17次闪光包含69次冲程，都是从云层到地面的负电荷降低。给出了冲程间隔、无电流冲程间隔、总冲程持续时间、总冲程充注量、总冲程动作积分(∫i2dt)、回程电流波前特性、半峰时间和回程峰值电流的统计数据。回击电流脉冲的特征是上升时间在几微秒或更短的数量级并且峰值在4到38kA的范围内，被发现直到闪电通道底部的任何先前电流降到小于2的噪声电平之后才发生。与M分量相关的电流脉冲发生在建立的几十到几百安培的通道电流流动期间，其特征是上升时间较慢(通常是几十微秒到几百微秒)，并且峰值通常小于回击脉冲的上升时间。回击电流平均上升速率与电流峰值之间存在较强的正相关关系。回击电流峰值与10-90%上升时间之间、回击峰值与峰值一半处的电流波形宽度之间基本没有相关性。佛罗里达州和阿拉巴马州触发闪电的参数彼此相似，但与1981年雷暴研究国际计划期间新墨西哥州记录的触发闪电不同。跟随回击电流峰值并持续超过10毫秒的持续电流呈现出各种波形，我们将其细分为四类。所有这样的连续电流似乎都是从一个可能与M分量相关的电流脉冲开始的。以便于实际使用的形式，在附录中简要总结了对雷电保护重要的雷电参数。
Channel base currents from triggered lightning were measured at the NASA Kennedy Space Center, Florida, during summer 1990 and at Fort McClellan, Alabama, during summer 1991. Additionally, 16-mm cinematic records with 3- or 5-ms resolution were obtained for all flashes, and streak camera records were obtained for three of the Florida flashes. The 17 flashes analyzed here contained 69 strokes, all lowering negative charge from cloud to ground. Statistics on interstroke interval, no-current interstroke interval, total stroke duration, total stroke charge, total stroke action integral (∫ i2dt), return stroke current wave front characteristics, time to half peak value, and return stroke peak current are presented. Return stroke current pulses, characterized by rise times of the order of a few microseconds or less and peak values in the range of 4 to 38 kA, were found not to occur until after any preceding current at the bottom of the lightning channel fell below the noise level of less than 2 A. Current pulses associated with M components, characterized by slower rise times (typically tens to hundreds of microseconds) and peak values generally smaller than those of the return stroke pulses, occurred during established channel current flow of some tens to some hundreds of amperes. A relatively strong positive correlation was found between return stroke current average rate of rise and current peak. There was essentially no correlation between return stroke current peak and 10–90% rise time or between return stroke peak and the width of the current waveform at half of its peak value. Parameters of the lightning flashes triggered in Florida and Alabama are similar to each other but are different from those of triggered lightning recorded in New Mexico during the 1981 Thunderstorm Research International Program. Continuing currents that follow return stroke current peaks and last for more than 10 ms exhibit a variety of wave shapes that we have subdivided into four categories. All such continuing currents appear to start with a current pulse presumably associated with an M component. A brief summary of lightning parameters important for lightning protection, in a form convenient for practical use, is presented in an appendix.