高建筑物上未连接上行先导的特征统计分析(英文)
作者单位：Laboratory of Lightning Physics and Protection EngineeringChinese Academy of Meteorological Sciences
会议名称：《强化科技基础 推进气象现代化——第29届中国气象学会年会》
会议日期：2012年
学科分类：081405[工学-防灾减灾工程及防护工程] 08[工学] 0837[工学-安全科学与工程] 0814[工学-土木工程]
基 金：国家自然科学基金项目(批准号:41075003、41175003和 41030960)资助
关 键 词：Cloud-to-ground lightning Unconnected upward leader Tall structure High-speed photography
摘 要：The characteristics of 45 unconnected upward leaders(UULs) occurred in 19 downward negative flashes observed in Guangzhou during 2009-2011 are *** of the 45 UULs is an upward positive leader initiated by a downward negative stepped leader before a new strike point is *** each UUL,several parameters are determined when possible mainly by using high-speed images:inception height,inception time prior to return stroke(RS),horizontal distance between the strike point and the UUL’s inception point,two-dimensional(2D) distance between the nearest tip of the downward leader branches and the UUL’s inception point when the UUL is initiated,2D length,and 2D average propagation velocity,whose values range from 40 m to 503 m(number of samples:45),less than 0.1 ms to 1.32 ms(38),20 m to 1.3 km(38),99 m to 578 m(21),0.48 m to 399 m(45),and 5.79 to 33.8 × 10 4 m s-1(22),*** analysis of the UULs’ characteristics shows the following:(1) No UUL with an inception time prior to RS larger than 0.5 ms is initiated at a height lower than 300 m.(2) Those UULs with inception heights lower than 300 m seldom exhibit 2D lengths longer than 50 m,and most(22/27,81%) of them have 2D lengths of shorter than 20 ***(12/14,86%) of those UULs with 2D lengths longer than 50 m exhibit inception heights higher than 300 m.(3) Six of the 22 2D average propagation velocities are on the order of 10 4 m s-1 and 19(86%) of them are smaller than 2.0 × 10 5 m s-1.(4) Those UULs with inception heights lower than 300 m only can be initiated by those lightning flashes within approximately 600 m,while those with inception heights higher than 400 m can even be initiated by flashes over 1 km away.(5) The maximum distances for the downward leaders to attract the initiation of the UULs with inception heights from 100 m to 200,200 m to 300 m,and over 400 m are approximately 350 m,450 m,and 600 m,respectively.