陕西榆林地区正地闪分布特征

Distribution Characteristics of Positive Cloud-to-ground Lightning in Yulin Area of Shaanxi

利用闪电定位资料,对陕西榆林地区正地闪发生的时间、强度、区域进行分析。结果表明:榆林地区正地闪占闪电总数的9.01%,年平均比例为8.68%;正地闪在6—8月频次较高,占全年正地闪频次的67.54%,3—4月和10—11月频次较低,占全年正地闪频次的15.07%;正地闪与负地闪、总地闪的日变化规律相似,变化曲线近似呈单谷双峰型;正地闪的日分布主要集中在高发期的主峰时间段,在总闪频次较低的时间段正地闪所占的比例大;各年正闪电流强度各范围的频次分布曲线大致相同,电流强度主要分布在11~30 kA;正闪电流强度<50 kA时,正闪频次随电流强度的增大而增大,>50 kA时,正闪频次随电流强度的增大而减小;府谷地区正闪电流强度的年平均值最大,达到109.92 kA;正地闪主要发生在靖边、横山、神木、榆林4县,占正地闪年平均次数的55.90%,最大频次出现在神木县,年平均频次207次;最小频次出现在吴堡县,年平均频次28次。

Based on the lightning location data,the occurrence time,intensity and area of positive ground lightning in Yulin area of Shaanxi Province were analyzed.The results showed that the positive ground lightning accounted for 9.01%of the total lightning in Yulin area,and the annual average proportion was 8.68%.The frequency of positive ground flash was higher from June to August,accounting for 67.54%of the annual positive ground flash frequency,while the frequency was lower from March to April and October to November,accounting for 15.07%of the annual positive ground flash frequency.The diurnal variation of positive,negative and total lightning is similar,and the variation curve is approximately single valley and double peak type.The diurnal distribution of positive ground flash mainly concentrated in the main peak period of the high occurrence period,and the proportion of positive ground flash was large in the period of the low total flash frequency.The frequency distribution curves of each range of positive lightning current intensity in each year are roughly the same,and the current intensity is mainly distributed in the range of 11~30 kA.When the current intensity is less than 50 kA,the positive flash frequency increases with the current intensity,and when the current intensity is less than 50 kA,the positive flash frequency decreases with the current intensity.The annual mean value of positive lightning current intensity in Fugu area is the highest,reaching 109.92 kA.Positive ground flash mainly occurred in Jingbian,Hengshan,Shenmu and Yulin counties,accounting for 55.90%of the average annual frequency of positive ground flash.The maximum frequency was 207 times in Shenmu county.The lowest frequency was found in Wubao County,with an average annual frequency of 28.