基于LLS的雷电流波头时间分布特征

Temporal Characteristics of Lightning Current Wave-Front Time Based on LLS

利用湖北省2007—2013年雷电定位系统（Lightning Location System,LLS）监测的雷电流相关参数资料,采用数理统计方法,对雷电流波头时间的年、季、月、日变化以及累积概率和概率密度分布进行了统计分析。结果表明,正闪电平均波头时间为4.8μs,负闪和总闪电为3.6μs;一年中,正闪电7月波头时间最短,月变化特征大致呈＂V＂形;负闪和总闪电5—7月波头时间比其他月份短,月变化特征大致呈＂U＂形。正闪电波头时间季节、日变化明显,负闪和总闪电季节、日变化不明显。波头时间小于等于10μs时,正闪、负闪和总闪电的波头时间累积概率分别为95.5%、99.7%和99.6%,总闪电95%的波头时间大于1.5μs,50%的大于3.1μs,5%的大于6.0μs。波头时间在2-3μs时,正闪、负闪和总闪电的概率密度最大。气温较低月份,波头时间相对较长,反之,波头时间相对较短,其原因可能与雷电流幅值大小有关,具体原因有待进一步研究。

For a further study on the temporal characteristics of lightning current wave-front time and the demands of lightning protection engineering design, lightning risks management, and the lightning disaster prevention, the lightning current data observed by LLS （Lightning Location System） from 2007 to 2013 are used to analyze the annual, seasonal, monthly, and daily variation of lightning current wave-front time, its cumulative probability, and cumulative probability density by the mathematical statistics method. The results show that the mean wave-front time of positive lightning is 4.8 μs; the wave-front time of negative lightning and the total number of lightning is 3.6 μs; in the whole year, the shortest wave-front time for positive lightning is in July, and its monthly variation presents a V-shaped variation. On the other hand, the wave-front time for negative lightning and the total one is shorter between May and July than in any other months, and its variation appears to be an U-shaped style. The wave-front time of positive lightning changes obviously in different seasons and days, but those of negative lightning and the total one stay stable. When the wave-front time is less than or equal to 10μs, the cumulative probabilities of wave- front time are 95.5%, 99.7%, and 99.6% for positive lightning, negative lightning, and the total one, respectively. The wave-front time of longer than 1.5 μs occupies 95% of the total lightning, and 50% for that of longer than 3.1μs, only 5% for that of longer than 6.0μs. When the wave-front time is 2 to 3μs, the cumulative probability density of wave-front time is the greatest for these three kinds of lightning. The months with low temperatures have longer wave-front time, and on the contrary, the wave-front time will be shorter. The reason seems to be connected with the amplitude of lightning current, whose specific reasons need to be further investigated.