关键词: 云地闪, 地闪密度, 雷暴日

Abstract: Based on the cloud-to-ground lightning data from the detecting station during 1997 to 2011 and the observational data from the national basic weather station at Shenzhen during 1953 to 2011, the temporal and spatial distributions of cloud-to-ground lightning flashes (hereafter abbreviated as lightning flashes) and the trends of thunderstorm days in Shenzhen were analyzed. The results show that the annual thunderstorm day is in a descending trend in recent 59 years, and it is a 5 years main cycle and a 10-15 years sub-cycle by a wavelet analysis. The significant peak values of the monthly thunderstorm days occur in June and August, especially in August. There is a close relation between activity of thunderstorm and solar radiation. The frequency of lightning flashes is highest from 14:00 to 18:00 at Shenzhen. Many lightning flashes are recorded in the northwestern area and inland area, while the few are in the southeastern area and coastal or riverside area in Shenzhen. The spatial distribution of lightning flashes is significantly influenced by the land-sea distribution and the topography. The analysis of the lightning intensity shows that the positive and negative peak values of mean monthly lightning intensity appear in February and June respectively, and the intensity of the negative lightning is lower than that of positive lightning flashes. Neither the positive lightning nor the negative lightning flashes, they never occur in the time period that the frequency of lightning flashes is the highest.

Key words: Cloud-to-ground lightning flash, Lightning flash density, Thunderstorm day