青藏高原闪电活动的时空分布特征

利用卫星上携带的闪电探测仪所获取的8年闪电资料(1995～2002)对青藏高原闪电活动的时空分布以及高原季风期间闪电活动对地面热力学特征的响应进行了研究.结果表明，高原上的平均闪电密度为3fl·a-1·km-2，并在高原中部（32°N, 88°E）出现闪电密度峰值5.1fl·a-1·km-2.闪电活动主要发生在6～8月，并在6月下旬至7月中旬最为活跃.大部分地区的闪电活动日变化峰值出现在14:00～16:00 LT，在中西部的显著高山地区早于这一时刻，而在显著低海拔的塔里木和柴达木盆地晚于这一时刻.夏季季风期间高原上的闪电活动明显依赖于地表的热力学特征，并与地表鲍恩比和感热通量呈明显的线性正相关，相关系数分别为0.7和0.6，鲍恩比有可能作为调整闪电产生效率的量度.

SPATIAL AND TEMPORAL DISTRIBUTION OF LIGHTNING ACTIVITIES OVER THE TIBETAN PLATEAU

We study the spatial and temporal distribution of lightning flash activity and its response to the thermodynamic characteristics over the Tibetan plateau by using the composite gridded lightning data from 1995 to 2002 observed by the satellite based sensors, provided by NASA LIS/OTD Science Team in Marshall Space Flight Center. Our results show that the mean flash density over the Tibetan plateau is 3 fl·a-1·km-2, and the maximum flash activity is over the Central Plateau around (32°N, 88°E) with a peak value of 5.1 fl·a-1·km-2. The flash activity on the Plateau exhibited a seasonal variation and mainly occurs from June to August with a maximum flash activity period from late June to middle July. The diurnal variation of the maximum flash rate peaked during 14:00～16:00 LT with exceptions of the prominent high mountain region, which peaked earlier, and prominent low basins, which peaked later. The flash activity on the Plateau strongly depends on the ground thermodynamic characteristics, and positive correlations between lightning activity and Bowen ratio and ground sensitive heat flux are found during plateau monsoon season. Their correlation coefficients are 0.7 and 0.6, respectively, and the Bowen ratio could be an indicator of lightning producing efficiency.