Abstract:

To master the law of lightning activity in Chongqing, the ADTD lightning location data from 2008 to 2019 were analyzed in detail by using the mathematical statistics method and ArcGIS software.The temporal and spatial distribution characteristics of lightning frequency in Chongqing, the distribution characteristics of lightning current amplitude and steepness, and the cumulative probability distribution function were obtained.The results showed that the average annual occurrence of ground lightning in Chongqing is 208000 times, of which negative ground lightning accounts for 95.7%.The inter-annual variation of ground lightning frequency is large, with a maximum of 3.04×10⁵ times per year and a minimum of 1.27×10⁵ times per year.The monthly distribution is unimodal, and the high incidence period of lightning is from July to August, accounting for 57.9% of the whole year.The diurnal variation is bimodal, the negative lightning reaches the peak at 03:00 and 17:00.The peak time of positive lightning appears 1-2 hours later than that of negative lightning, and the peak value in the afternoon is much smaller than that at night.The spatial distribution of lightning density is closely related to topography, and the high-value area is mainly located at the intersection of mountains and the transition zone from the plateau hills to mountains.From the north of Jiangjin to the central urban area of Chongqing, the south of Kaizhou to the north of Wanzhou, the south of Zhongxian to the west of Shizhu, the south of Yongchuan, and from Rongchang to the west of Dazu are the areas with high ground flash density.The density is generally greater than 3 times·km^-2·a^-1, and locally greater than 6 times·km^-2·a^-1.The average lightning current amplitude of total lightning is 37.9 kA, of which the part of 10-50 kA accounts for 80.1%, and the probability peak value appears at 28 kA.The average steepness of total lightning is 10.1 kA·μs^-1, of which 5-20 kA·μs^-1 accounts for 92%, and the probability peak value appears at 8 kA·μs^-1.The cumulative probability distribution function of the total flash amplitude and steepness was obtained by regression fitting with the least square method.The observed value and fitted value were basically consistent, and the fitting effect was good.

Key words: Lightning location data, Ground flash density, Lightning current amplitude, Lightning current steepness, Probability distributions