青藏高原闪电和降水气候特征及时空对应关系

Climatological Characteristics and Spatio-temporal Correspondence of Lightning and Precipitation over the Tibetan Plateau

基于1998 2013年的TRMM(t ropical rainfall measuring mission)数据,分析青藏高原闪电活动与降水气候特征及时空对应关系,结果表明:青藏高原(简称高原)的闪电活动中心在高原中部和东北部,中部最大闪电密度达到6.2 fl·km^(-2)·a^(-1);但高原降水最活跃的区域是东南部,年降水量超过800 mm。闪电活动和降水随月份均呈现出先西进再东退的特征,但高原东北部强闪电活动区位置几乎不变化。在固定区域闪电和降水月变化具有一致性,活跃期出现在5—9月,呈单峰结构,除西部和东南部外,闪电与降水峰值月份吻合。结合TRMM降水特征(简称PFs)资料研究单个闪电表征降水量(rainyield per flash,RPF)的空间分布特征表明,闪电活动可以作为高原深对流的指示因子,而RPF可以有效表征深对流系统在整个降水系统中的比例。高原中西部和东北部深对流系统在整个降水系统中的比例最大,而在高原东南部最小,高原东南部的降水更多由暖云降水系统贡献。

Based on the analysis of TRMM data from 1998 to 2013,climatological characteristics of lightning activities,precipitation and their relationships over the Tibetan Plateau are investigated.The largest densities of lightning are over the central and northeast parts of the Plateau,with the maximum lightning density over the central Plateau reaching 6.2 fl · km^-2 · a^-1.Nevertheless,the strongest precipitation occurs over the southeast part of the Plateau where the value is above 800 mm · a^-1.Both the lightning activity and precipition move westward in May and then retreat in September over the most parts of the Plateau,while the strong lightning activity over the northeast of the Plateau barely moves.Unlike the lightning activity,the precipitation shows a cascade change from southeast to northwest.In chosen specified areas,the lightning and precipitation show parallel changes,including their active periods from May to September and single peak patterns.Except for the west and southeast parts of the Plateau,the peak months of lightning and precipitation in other areas are the same.The geographic distribtuion of the rainfall per flash（RPF） is then investigated and exhibits that the minimum RPF appears over the central and west parts of the Plateau,ranging from 5×10~7 to 7 × 10~7 kg · fl^-1.The maximum RPF reaches above 1 × 10~9 kg · fl^-1over the area along the Himalayas,stretching to the southeast part of the Plateau,and over the northern Plateau near the Kunlun Mountains.Combined with the analysis of TRMM precipitation features（PFs）,it is exposed that the lightning can be the proxy of deep convective activity over the plateau,while RPF can effectively represent the percentage of deep convective systems in all precipitation systems.In this way,the mid-west and northeast parts of the Plateau account for the largest percentage of deep convective activities in the whole precipitation system,while the southeast parts of the Plateau account for the smallest percentage,indicating that most of the precipitation over the southeast parts of the Plateau might be contributed by warm clouds.