2010-2019年杭州地闪变化特征及其与海拔高度的关系

Characteristics of ground flash and its relationship with altitude in Hangzhou from 2010 to 2019

利用2010—2019年杭州闪电定位资料,通过数理统计、线性回归等方法分析了杭州市雷电活动时空变化特征及其与海拔的关系。结果表明:杭州地闪活动呈东多西少、南多北少的分布,密度高值区出现在西南部,低海拔地区的地闪频次较高海拔地区的地闪频次高。夏季地闪活动最为频繁,主要集中在7月和8月,春、秋季地闪频次差别不大,冬季地闪频次较其他三个季节少一个量级。夏季和秋季的地闪活动多发生在午后至傍晚,春季地闪活动在凌晨发生较为频繁,这可能与具有夜发性特征中尺度对流系统持续时间长有关。地闪强度绝对值主要集中在10—60 kA,正地闪均值随着海拔高度增加而增大,负地闪和总地闪的雷电流均值随海拔高度的上升呈“V”形变化。正地闪、负地闪和总地闪≤16 kA比例和≥100 kA的比例均随海拔高度增加而减小。在100—200 m的丘陵和200—500 m的小起伏山地,绕击率较高,超过1500 m的山区,≤16 kA的雷电流造成的绕击风险小;400 m及以下地区,≥100 kA的雷电流造成的反击概率大,高于1600 m的大起伏山地基本不会发生反击现象。

Based on lightning location data from 2010 to 2019 in Hangzhou,the characteristics of ground flash and its relationship with altitude were analyzed using mathematical statistics and linear regression methods.The results show that the number of ground flashes in the east is greater than that in the west of Hangzhou and the number of ground flashes in the south is greater than that in the north.The region with a high density of ground flash is southwest of Hangzhou and the frequency of ground flash in the low altitude area is higher than that in the high altitude areas.The season with the highest frequency of ground flash is summer and ground flash mainly occurs in July and August.The frequencies of ground flashes in spring and autumn are similar,while the frequency in winter is one order of magnitude less than that in the other three seasons.In summer and autumn,the ground flash usually occurs from mid-afternoon to late-afternoon,while in spring,it occurs frequently in the early morning,which may be related to the long duration of nocturnal medium size convective system.The absolute value of ground flash intensity mainly concentrates from 10 to 60 kA.The average value of the positive ground flash increases with the altitude,and the average value of the negative ground flash and the total lightning current show a"V"shape along with the elevation.The proportions of positive,negative and the total ground flash current≤16 kA and≥100 kA decrease with the increase of altitude.The shielding failure rate is higher for hills′elevation from 100 to 200 meters and small mountains′elevation from 200 to 500 meters.The shielding failure risk caused by lightning current≤16 kA and mountains′elevation higher than 1500 meters is low.The probability of shielding failure caused by lightning current≥100 kA and mountains′elevation less than 400 meters is high.There are virtually no counterattacks at mountains′elevation above 1600 meters.