Application of the 2σ Lightning Jump Algorithm Based on DBSCAN Cluster
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摘要: 针对业务运行中雷达观测存在遮挡和雷达产品延迟,提出利用带噪声基于密度的空间聚类(density-based spatial clustering of applications with noise,DBSCAN)算法对闪电数据的聚类结果替代雷达产品,并分别利用北京三维闪电定位网(Beijing Total Lightning System,BJTLS)和升级后的国家闪电定位网(DDW1)总闪数据,应用2σ闪电跃增算法对北京2022年6月4日和12日两次强对流致灾过程进行临近预警,对比强对流单体识别法和DBSCAN聚类法的预警效果。结果表明:两种算法和两种闪电数据均能有效预警北京地区的灾害性天气,基于BJTLS总闪数据的预警效果较优;对于BJTLS总闪数据,两种方法的预警效果相当,预警命中率、误报率、临近成功指数和平均预警提前时间依次分别为100%,11.9%,88.1%,38.9 min和100%,13.3%,86.7%,42.8 min;仅利用闪电数据并应用2σ闪电跃增算法可对灾害性天气进行临近预警,摆脱对雷达产品的依赖。
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关键词:
- 闪电定位;
- 闪电跃增;
- DBSCAN聚类算法;
- 灾害性天气;
- 临近预警
Abstract: A DBSCAN (density-based spatial clustering of applications with noise) cluster of lightning data is proposed as the substitute for radar products to solve the problem of beam blockage in radar observation and the delay of radar products in service operations. Two lightning data, BJTLS (Beijing Total Lightning System) and upgraded National Lightning Positioning Network (DDW1), are used and the 2σ lightning jump algorithm is applied to perform severe weather nowcasting on 4 June and 12 June in 2022. The nowcasting effects of the strong convective cell identification method and the DBSCAN clustering method are further compared and analyzed. Based on a determined search radius (R) for neighboring lightning data and a determined minimum number of location results (number of minimum points) in R, the DBSCAN's clustering effect on lightning location data corresponds well with the strong convective radar echo. The ideal parameter combinations for BJTLS, R is 0.05, number of minimum points is 5; and for DDW1 data R is 0.22 and number of minimum points is 3. The results show that both methods and two kinds of data could effectively be used in severe weather nowcast. For BJTLS data, the effects of two methods are equivalent. The probability of detection, false alarm rate, critical success index and lead time of two methods are 100% and 100%, 11.9% and 13.3%, 88.1% and 86.7%, 38.9 min and 42.8 min, respectively. The 2σ lightning jump algorithm can be applied for nowcasting with lightning data, reducing the dependence on radar products. For DDW1 lightning data, compared with the identification method, the start time of the clustering method delays, leading to missing alarms. Since the flash rate of the DDW1 lightning data is low, there will be more missed cases if the flash rate threshold is set to trigger the lightning jump. But without the threshold, there will be more false alarms in operation. Therefore, BJTLS data is more suitable than DDW1 data for applying the 2σ lightning jump algorithm in the service operation. The detection efficiency of BJTLS in Beijing is high and it is necessary to further improve the detection efficiency of DDW1. In conclusion, the DBSCAN clustering method provides a new idea for the service operation of the 2σ lightning jump algorithm. -
图 2 2022年6月12日强对流单体的识别
(·代表云闪,×表示负地闪, +表示正地闪,蓝色曲线为识别的单体范围,下同)
(a)19:20 BJTLS总闪数据与识别的强对流单体,(b)19:20 BJTLS总闪数据的DBSCAN聚类结果,(c)19:50 DDW1总闪数据与识别的强对流单体,(d)19:50 DDW1总闪数据的DBSCAN聚类结果Fig. 2 Identified strong convective cells on 12 Jun 2022
(· denotes an intracloud(IC) flash, × denotes a negative cloud-to-ground(CG) flash, + denotes a positive CG flash, the blue irregular circle denotes the range of an identified cell, similarly hereinafter)
(a)total flashes of BJTLS and the identified strong convective cells at 1920 BT, (b)DBSCAN clustering of total flashes of BJTLS at 1920 BT, (c)total flashes of DDW1 and the identified strong convective cells at 1950 BT, (d)DBSCAN clustering of total flashes of DDW1 at 1950 BT图 5 2022年6月4日超级对流单体的强对流单体识别法和DBSCAN聚类法对BJTLS总闪数据和DDW1总闪数据的2σ闪电跃增预警效果对比
(a)强对流单体识别法和BJTLS总闪数据, (b)DBSCAN聚类法和BJTLS总闪数据, (c)强对流单体识别法和DDW1总闪数据, (d)DBSCAN聚类法和DDW1总闪数据
Fig. 5 Comparison in nowcasting effect of the 2σ lightning jump algorithm between identification method and DBSCAN method using total flash data of BJTLS and DDW1 for the supercell on 4 Jun 2022
(a)identification method and BJTLS data, (b)DBSCAN method and BJTLS data, (c)identification method and DDW1 data, (d)DBSCAN method and DDW1 data
图 10 2022年6月12—13日强对流单体识别法和DBSCAN聚类法对BJTLS总闪数据和DDW1总闪数据的2σ闪电跃增预警效果对比
(a)强对流单体识别法和BJTLS总闪数据, (b)DBSCAN聚类法和BJTLS总闪数据, (c)强对流单体识别法和DDW1总闪数据, (d)DBSCAN聚类法和DDW1总闪数据
Fig. 10 Comparison in nowcasting effect of the 2σ lightning jump algorithm between identification method and DBSCAN method using total flash data of BJTLS and DDW1 for disastrous weather cell on 12-13 Jun 2022
(a)identification method and BJTLS data, (b)DBSCAN method and BJTLS data, (c)identification method and DDW1 data, (d)DBSCAN method and DDW1 data
表 1 2022年6月4日和12日北京地区灾害性天气记录
Table 1 Records of disastrous weather in Beijing on 4 Jun and 12 Jun in 2022
日期 起始时刻 灾害类型 代表符号 发生位置 强度或最大直径 产生单体 4日 18:18 大风 W1 怀柔杏树台 17.2 m·s-1 18:20单体1 19:00 冰雹 H2 怀柔城区 20 mm 19:02单体1 19:02 大风 W3 怀柔桥梓镇 18.1 m·s-1 19:02单体1 19:10 大风 W4 顺义兴农天力 24.2 m·s-1 19:08单体1 19:17 冰雹 H5 顺义木林 10 mm 19:20单体1 19:18 大风 W6 顺义牛栏山 17.4 m·s-1 19:20单体1 19:19 大风 W7 奥林匹克水上公园 24.9 m·s-1 19:20单体1 19:21 冰雹 H8 顺义北小营 10 mm 19:20单体1 19:29 强降水 R9 顺义牛栏山 20 mm·h-1 19:26单体1 19:49 冰雹 H10 顺义杨镇 10 mm 19:50单体1 20:05 大风 W11 通州小邓各庄村 25.2 m·s-1 20:02单体1 20:06 大风 W12 通州北刘各庄村 22.6 m·s-1 20:08单体1 20:08 大风 W13 通州副中心办公楼 14.1 m·s-1 20:08单体1 20:15 冰雹, 大风 H14, W15 通州潞城镇, 中农富通 40 mm, 24.4 m·s-1 20:14单体1 20:17 大风 W16 通州大豆各庄小学 20.2 m·s-1 20:14单体1 20:20 大风 W17 通州西定环卫所 19.7 m·s-1 20:20单体1 20:22 大风 W18 通州马坊村 17.4 m·s-1 20:20单体1 20:23 大风 W19 通州漷县村 18.6 m·s-1 20:20单体1 20:28 大风 W20 通州101农场 29.9 m·s-1 20:26单体1 20:31 大风 W21 通州永乐店二村 20.3 m·s-1 20:32单体1 20:34 大风 W22 通州曹庄村 26.7 m·s-1 20:32单体1 20:35 大风 W23 通州老槐庄 19.3 m·s-1 20:38单体1 20:40 强降水 R24 通州101农场 30 mm·h-1 20:38单体1 12日 19:53 强降水, 大风 R10, W11 顺义北小营 30 mm·h-1, 17.2 m·s-1 19:56单体4 19:55 冰雹 H12 密云不老屯 8 mm 19:56单体4 20:25 冰雹 H13 怀柔北房 8 mm 20:26单体3 20:36 强降水 R14 顺义北小营 50 mm·h-1 20:38单体3 20:38 冰雹 H15, H16 顺义李遂, 龙屯湾 10 mm, 25 mm 20:38单体3 20:58 冰雹 H17 朝阳常营 5 mm 21:02单体3 21:04 冰雹,大风 H18, W19 通州永顺, 通州气象局 30 mm, 17.2 m·s-1 21:02单体3 21:10 强降水 R20 朝阳楼梓庄 20 mm·h-1 21:08单体5 21:37 冰雹 H21 朝阳气象局 8 mm 21:44单体2 21:38 冰雹 H22 北京市观象台 20 mm 21:44单体2 21:45 冰雹 H23 丰台木樨园 30 mm 21:44单体2 22:48 冰雹 H25 朝阳小红门 60 mm 21:50单体6 22:55 冰雹 H26 大兴瀛海 5 mm 21:50单体6 23:02 强降水 R27 大兴瀛海 20 mm·h-1 23:02单体2 23:21 冰雹 H28 大兴气象局 10 mm 23:20单体2 表 2 基于两种数据和两种方法的灾害性天气预警对比
Table 2 Comparison in disastrous weather nowcasting of identification method and DBSCAN method using total flash data of BJTLS and DDW1
统计量 BJTLS DDW1 强对流单体识别法 DBSCAN聚类法 强对流单体识别法 DBSCAN聚类法 预警命中次数 52 52 48 49 预警误报次数 7 8 3 8 预警漏报次数 0 0 4 3 命中率/% 100 100 92.3 94.2 误报率/% 11.9 13.3 5.8 14.0 临界成功指数/% 88.1 86.7 87.3 81.7 预警提前时间/min 38.9 42.8 35.8 28.9 -
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