Detection Results of Guangdong-Hongkong-Macao Lightning Location System for Tall-object Lightning
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摘要: 基于2016—2017年广州高建筑物雷电观测站获取的资料对粤港澳闪电定位系统(简称定位系统)的性能进行评估,并根据2014—2018年定位系统历史资料对广州高建筑物区域的雷电活动特征进行初步分析,结果表明:定位系统对闪电的探测效率为93%(214/229),对回击的探测效率为93%(449/481),对下行闪电首次回击、继后回击及上行闪电回击的定位误差的平均值(中值)分别为361 m(188 m)、252 m(167 m)和294 m(173 m);当接地点高度低于200 m(不低于200 m)时,定位系统对下行负极性闪电首次和继后回击的云闪/地闪识别正确率分别为99%(80%)和93%(35%),有83%的上行负地闪回击被定位系统误判为云闪,广州高建筑物区域内绝大部分负云闪定位记录实际是高建筑物地闪;对定位系统得到的孤立高建筑物闪电密度中心进行分析后发现,广州塔(600 m)闪电密度中心200 m半径范围内年均回击次数约为中信广场(390 m)和广发证券大厦(308 m)的5倍,推测广州塔闪电的主要类型为上行闪电,而中信广场和广发证券大厦则为下行闪电。Abstract: Tall-object lightning is one hot topic in the field of atmospheric electricity. In order to explore the application of Guangdong-Hong Kong-Macao Lightning Location System (GHMLLS) data on tall-object lightning, the performance of GHMLLS is evaluated based on the observation obtained at the Tall-Object Lightning Observatory in Guangzhou (TOLOG) during 2016 to 2017, and a preliminary comparative analysis on characteristics of lightning activities in the tall-object area in Guangzhou are made. Results show that the flash detection and the stroke detection of GHMLLS is about 93% (214/229) and 93% (449/481). The arithmetic mean (median) value of the location error is about 361 m(188 m), 252 m(167 m) and 294 m(173 m) for downward first negative strokes, downward subsequent negative strokes and upward negative strokes respectively. It is found that the cloud-to-ground (CG) lightning with higher grounding points are more likely to be misidentified as intro-cloud (IC) lightning by the GHMLLS. When the grounding point is (is not) lower than 200 m, the identification accuracy of the IC/CG classification is 99% (80%) and 93% (35%), respectively, for downward first negative strokes and the subsequent negative strokes. The accuracy of the IC/CG classification for upward negative strokes is found to be only 17%. According to statistical results of GHMLLS dataset from 2014 to 2018, negative IC records in tall-object area in Guangzhou are found to be more prominently gathered near buildings with height over 300 m than CG records, indicating that most negative IC records are actually tall-object strokes but just misjudged by GHMLLS. Mean shift algorithm is used to identify the lightning density centers of three relatively isolated tall buildings, namely the Canton Tower (600 m), the CITIC Plaza (390 m) and the GF Securities Headquarters (308 m). It's found that the number of strokes within the radius of 200 m in the lightning density center of the Canton Tower is about 5 times as much as that of the CITIC Plaza or the GF Securities Headquarters. It is speculated that most lightning occurred on the Canton Tower belonging to upward type, while those hitting the CITIC Plaza and the GF Securities Headquarters are mainly downward type.
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图 4 2014—2018年广州高建筑物区域S1(a)、S2(b)、S3(c)和S4(d)类型回击的频次分布
(网格尺寸100 m×100 m,字母A到E代表高度不低于350 m的建筑,实心三角、空心三角和交叉号分别代表高度在300~349 m,250~299 m以及200~249 m的建筑)
Fig. 4 Frequency distribution of strokes of type S1(a), S2(b), S3(c) and S4(d) in Guangzhou tall-object area
(the cell size is 100 m×100 m, A-E denote buildings with heights no less than 350 m, the solid triangle, hollow triangle and the cross symbols denote buildings with heights within ranges of 300-349 m, 250-299 m and 200-249 m, respectively)
图 5 2014—2018年广州塔(a)、中信广场(b)和2016—2018年广发证券大厦(c)附近闪电密度中心周围200 m和500 m半径范围内的定位记录
(实心圆、空心圆、实心倒三角和交叉号分别代表S1,S2,S3,S4类回击)
Fig. 5 Lightning location plots within a radius of 200 m and 500 m around the lightning density center produced by the Canton Tower(a), the CITIC Plaza(b) during 2014-2018, and the GF Securities Headquarters during 2016-2018(c)
(the solid circle, hollow circle, solid inverted triangle and the cross symbols denote the stroke records belonging to class S1, S2, S3, S4)
表 1 基于2016—2017广州高建筑物地闪个例的粤港澳闪电定位系统探测效率评估
Table 1 Evaluation of the detection efficiency of GHMLLS based on the tall-object lightning flashes observed in Guangzhou during 2016-2017
地闪类别 闪电次数 探测到的闪电次数 闪电探测效率/% 能确认的回击次数 探测到的回击次数 回击探测效率/% 下行负极性闪电 195 185 95 385 360 93 下行正极性闪电 9 5 56 9 5 56 上行负极性闪电 25 24 96 87 84 97 表 2 基于2016—2017广州高建筑物地闪个例的粤港澳闪电定位系统云闪/地闪识别正确率的评估
Table 2 Evaluation of intra-cloud and cloud-to-groud lightnings classification based on tall-object strokes observed in Guangzhou during 2016-2017
地闪回击类别 接地点高度低于200 m 接地点高度不低于200 m 总次数 误判次数 识别正确率/% 总次数 误判次数 识别正确率/% 下行负闪电首次回击 84 1 99 41 8 80 下行负闪电继后回击 126 9 93 54 35 35 上行负闪电回击 94 78 17 表 3 广州塔、中信广场和广发证券大厦附近闪电定位记录密度中心周围不同距离范围内年平均回击次数对比
Table 3 Comparison of annual number of strokes within different distance ranges around the stroke records center near the Canton Tower, the CITIC Plaza and the GF Securities Headquarters
高建筑物 距离闪电密度中心的半径d/m 年平均回击次数 S1 S2 S3 S4 合计 广州塔 d < 200 12.4 7.2 23.0 88.4 131.0 200≤d < 500 12.6 3.0 3.8 9.2 28.6 中信广场 d < 200 8.0 8.4 1.4 8.4 26.2 200≤d < 500 14.0 4.6 0.6 0.2 19.4 广发证券大厦 d < 200 6.0 7.0 1.7 9.0 23.3 200≤d < 500 6.7 3.7 0.0 2.7 13.0 -
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