卫星观测的西南地区闪电的时空分布

Temporal and Spatial Distributions of Lightning Activity in Southwest China Based on Satellite Observations

利用TRMM卫星上携带的闪电探测仪(LIS)所获取的10 a闪电资料(1998—2007年)对西南地区闪电活动的时空分布特征进行了分析。结果表明:该地区闪电次数的年差异较大,最多年份是最少年份的2倍多,闪电活动季节性特征非常明显,闪电主要集中在春末仲夏发生,呈现单峰值特征,4—8月是闪电高发期(约占全年总闪电活动的84.83%)。闪电活动的日变化表明,闪电峰值区集中在傍晚、午夜前后两个时段,闪电谷值区出现在09:00—12:00,夜雷暴多,这是与其他地区闪电日变化显著不同的地方。在对闪电次数进行了探测效率订正后,根据LIS注视时间,计算了闪电密度。西南地区闪电密度分布大体呈现:东部高,西部低;南部高,北部低。闪电密度较高、面积较大的高值中心位于中越交界的老山一带,非常明显的大片低发区主要位于西南西部地区。研究表明:西南地区闪电时空分布与当地的地形地势、水汽和地理环境条件等诸多因素有关。

The temporal and spatial distributions of lightning activities in Southwest China are studied by using the ten years＇（from 1998 to 2007） observation data from the Lightning Imaging Sensor（LIS） boarded on the Tropical Rainfall Measurement Mission（TRMM） satellite.The result indicates that the number of lightning flashes observed through LIS varies from year to year and the maximum is about twice as many as the minimum.The lightning activities clearly show seasonal variations in Southwest China and the late spring and midsummer are the main lightning activity seasons.The seasonal variation of the flash number presents a single peak value and about 84.83% of the lightning flashes of a year occur between April and August.It is showed that lightning activities primarily occur not only in early evening but also at midnight and the lightning activities comes to the minimum between 09：00—12：00 BST and the thunderstorm occurs more at night than in the daytime,which is obviously different from the situation in other regions.With the corrected number of lightning flashes efficiency,according to the detecting time by LIS,lightning flash density value is calculated.Lightning flash density in Southwest China is higher in eastern region than that in western region and it is high in southern region than that in northern region.Lightning flash density centers are found mainly in Laoshan areas between China and Vietnam.Fewer lighting flashes are found in the west of Southwest China.Results show that the temporal and spatial distributions of lightning activities in Southwest China are closely related to the topography and terrain,water vapor and environmental condition and so on.