西藏高原闪电特性时空分布特征

Spatial and Temporal Distribution Characteristics of Lightning over Tibetan Plateau

利用2009年6月至2011年5月西藏高原闪电监测系统的闪电监测资料,分析了高原闪电分布的时空特征,结果表明:高原的闪电平均强度为61.89kA,负闪占闪电总数的78.2%,平均强度55.97kA,正闪占21.8%,平均强度83.14kA;雨季前的闪电中主要为正闪,正闪占73%;而雨季期间的闪电中,正闪仅占闪电总数的9%;闪电频次的日变化特征呈单峰型分布,主要集中在15:00—21:00这段午后至夜间的时段内,且在17:00达到峰值,与午后至夜间这段时间为强对流发生条件较好的时段相一致,03:00至12:00左右是高原闪电低发时段;闪电的高发地区为那曲地区中东部、昌都地区西部、日喀则地区东部及山南地区,其中负闪有两个强中心,分别位于那曲地区的嘉黎县和山南地区的朗卡子县,而在南部的错那县也为正闪强中心;闪电强度表现为冬季高、夏季低,各月的闪电平均强度均在50kA以上;拟合出高原地区的总闪、正闪和负闪的雷电流强度累积概率方程,拟合率均达0.99以上。

Based on the data from June 2009 to May 2011 over the Tibetan plateau, the temporal and spatial distribution of lightning is analyzed. Results show that the average value of lightning intensity was 61.89 kA; the negative ground flash took up 78.2% of the total; and the average of negative ground flash intensity was 55.97 kA. The positive ground flash took up 21.8% of the total, and the average of negative ground flash intensity was 83.14 kA. The lightning flashes were mainly positive ground flashes, which took up 73% before rainy season. The positive ground flashes took only 9~ during the rainy season. The daily variation of lightning frequency showed the obvious single peak pattern, with the high-frequency period in 15：00-- 21：00 （the peak at about 17 ： 00） and the low-frequency period in 03：00-- 12 ： 00. The lightning density distribution had obvious regional difference. The high density areas of lightning were the mid-eastern Naqu, western Changdu, eastern Rikaze, and Shannan. The negative flashes had two high density centers： Jiali and Langkazi. The Cuona was also a positive high density center. The lightning intensity was higher in winter and lower in summer. The monthly average intensity was greater than 50 kA. A probability equation is set up according to the lightning intensity, the positive and the negative flash lightning inter^sity, and the corresponding cumulative frequency. The fitting rate between the measured values and the calculated is higher than 0.99.