北京及其周边地区闪电活动的时空特征

Temporal-spatial characteristics of lightning over Beijing and its circumjacent regions

摘要:

利用具有总闪观测能力的SAFIR3000在2005-2007年对北京及周边地区(天津、唐山、廊坊等)的观测资料,分析了该地区云闪和地闪时空分布特征。结果表明:云闪高发时段在15:00-次日00:00,峰值在19:00,高发月份在6-8月,峰值在7月;云闪空间分布高值区在北京东北部、天津北部、承德西南部一带,约为30次/(km²·a);云闪平均高度(海拔高度)日变化差异不大,季节变化夏季最高,冬季最低;高度在9~10 km的云闪最多,占云闪总次数的10.97%。地闪高发时段、月份、地闪高值区(密度约为5次/(km²·a))与云闪基本相似,不同之处在于云闪日分布多为单峰,而地闪为双峰,云闪高值时段开始与结束时间均比地闪早;云闪空间分布高值区密度约为地闪的6倍。3 a平均正闪占地闪总数百分比为16.44%,夏季该百分比较低,春秋季较高,其月际变化与正闪次数月际变化相反。总闪时空分布特征和云闪更为相似,总闪高值区分布和卫星探测得到的基本一致。

Abstract:

Based on the lightning data observed by SAFIR3000 lightning location system from 2005 to 2007 in Beijing and its circumjacent regions (Tianjin,Tangshan,Langfang,etc.),the temporal and spatial characteristics of intracloud(IC) flash and cloud-to-ground(CG) flash were analyzed.The results show that the time of high-frequency IC mainly occurs from 15:00 BST to 24:00 BST and the peak of the IC frequency appears at 19:00 BST.Most of IC flashes are prone to occur between June and August,and the peak occurs in July.The maximum of spatial density of IC mainly appears in the northeast of Beijing,the north of Tianjin and southwest of Chengde at the value of 30 times/(km²·a).The daily variation of average initiated height(MSL) of IC lightning is not obvious.The initiated height is the highest in summer,whereas it is the lowest in winter.The IC flashes mainly occur at the height of 9-10 km,which account for 10.97% of the total IC flashes.The high frequency time,months and high density area (at about 5 times/(km²·a)) of CG lightning are similar to those of IC lightning.However,a few differences appear between IC lightning and CG lightning.Firstly,the daily variation of IC has a single peak but that of CG has two peaks;secondly,both the beginning and ending time of IC’s high value are earlier than that of CG’s.In addition,the lightning density of the former is 5 times larger than the latter’s.The average percentage of+CG flashes in the total CG for three years is 16.44% and the percentage is lower in summer but higher in spring and autumn.In addition,its monthly variation has an inverse correlation with that of the+CG flashes frequency.The temporal-spatial distribution characteristics of total lightning are more similar to those of IC lightning.The high density areas of total lightning detected by SAFIR3000 are basically consistent with those detected by satellites.