Abstract:

By using the lightning data in 2000 and 2002 around Lanzhou，lightning characteristics such as daily variation，spatial density，intensity and polarity of lightning are analyzed and also compared with those in Shandong province.The results indicate that major cloud-to-ground（CG）flashes of lightning are negative.The mean intensity of positive flashes is stronger than that of negative flashes and their ratio is over average during 12：00 to 00：00.Daily variety of the CGand negative flashes is bimodalundulance，other than positive flashes unimodal.The biggest flashes frequency center locates in Weiyuan and Longxi county，and accord with the location of hail source are aand hail affecting zone. Furthermore，the spatial distribution of lightning is closely related to the topography and under lying surface and synoptic climatic background

Key words: cloud-to-ground lightning, distribution characteristics, hail

摘要：

利用2000年和2002年设在兰州的闪电定位仪资料，分析了兰州周边地区地闪的日频次变化、强度谱分布和累计百分数、日均月变化、闪电密度、极性等特征，并与山东地区的分布做了比较。结果表明，兰州周边地区的云—地闪电中负闪占绝大多数，正闪的平均强度大于负闪，正负闪的比值在午后至次日凌晨大于其均值；总地闪和负闪的日变化呈典型的双峰变化，正闪的双峰特征不明显；兰州西南偏南的渭源和陇西县是闪电频发的中心地带，闪电空间分布中心与冰雹发生源地和影响区对应一致；闪电多发区与地形和气候背景有很大关系。

关键词: 云—地闪电, 分布特征, 冰雹