关键词: 中国区域闪电分布, 闪电频数, 闪电密度, 闪电气候特征

Abstract:

Using lightning data detected by the TRMM satellite between 18~30°N and 74~123°E from 1998 Jan , 1 to 2003 Dec,31, the yearly, seasonal and diurnal lightning number and their change with the longitude and latitude, the lightning density distribution and lightning climatic feature were calculated and analyzed in this paper. Results show that the total mean diurnal lightning number is about 54 600 in Chinese land area, and it is 54.47% of the total number during daytime and 45.53% during night time, and their ratio is 1.2. The yearly variety of the diurnal flash number is a pair of peak value , the flash occurs primarily in April to September, and the number is about 92% of the total lightning number in a year. First peak occurs in mid-April to mid-May and the second in June to August, and the second peak is 43.4% of the total yearly lightning number, the flash number in summer (Jun to Aug) is 60% of the total yearly number , and it is only about 0.4% in November to February of the next year.
Diurnal variation presents the single peak, and its range is large, mean hourly flash number is about 2 275 in a year, it reaches a maximum at 18:00 P.M. and it’s about 9.1% of the diurnal number, it comes to a minimum at 9:00~11:00 A.M. and it’s only 3% of the diurnal number, and the maximum is 12 times of the minimum, these show that lightning occurring frequently in Chinese district is primarily in dusk. Diurnal variation presents the single peak, the range of the peak is broad, mean hourly flash number is about 2 275 in a year, it reaches a maximum at 18:00 P.M. and it’s about 9.1% of the diurnal flash number, it comes to a minimum at 9:00~11:00 A.M. and it’s only 3% of the number, and the maximum is 12 times of the minimum. The yearly mean
flash number change with latitude is bigger than that with longitude in Chinese district, the flash number is more in coastal land area than that in inland area, and it is more in inland area than that in sea area, it is more in eastern region than that in western region. The diurnal changing time of peak value occurring lightning in 4 seasons shows that the time with peak value of flash number during a day is different, in winter it is primarily at noon, in autumn it is in the afternoon, while in spring it is at night and in summer it is at dusk. The different yearly mean flash density distribution in daytime, nighttime and all day in Chinese district show that the density is higher in eastern region than that in western region, the high flash density areas are more concentrated relatively. The high flash density areas in daytime are nearby sea, while they are in inland area during nighttime, and the high density areas in daytime are the low flash density areas during nighttime, and vice versa, but there is no such change in Tibet Plateau. The flash density value and its distribution feature are different in different seasons,in spring the high flash density areas are in south part of China, and the large part of inland are the sub-high flash density area, and the density is relatively low in coastal area . In summer the flash density is
higher and the area is larger, the higher density areas are consist with the areas with high yearly mean flash density and they are near sea, while the density in inland area is relatively low. In autumn, the relatively high flash density areas are more scattered, the areas are smaller too, mainly in south littoral. In winter, the density is low and the areas occurring flash are small,mainly in south part of 30°N and Sichuan basin.

Key words: flash distribution in China region, lightning number, lightning density, lightning climate feature