基于ADTD资料的浙江地区多回击地闪特征分析

Characteristic Analysis of Multi-return Strokes of Cloud-to-Ground Lightning in Zhejiang Based on ADTD Data

利用2007—2018年浙江省ADTD闪电定位资料,分析了该地区多回击地闪分布及相关参数特征。结果表明:浙江省多回击地闪占总地闪的26.74%,其中正闪以单回击地闪为主;正、负闪平均回击数分别为1.04次和1.65次,最大回击数分别为5次和21次。回击数和地闪数存在较为一致的年际变化,正、负多回击地闪日变化分别呈多峰和单峰分布。正、负多回击地闪电流强度算术平均值分别为72.06kA和-36.89kA,回击平均强度随回击数的增加而下降,约40%的地闪过程中至少有1次继后回击强度比首次回击强;首次回击和继后回击的强度分布呈对数正态分布,集中在15~45kA之间。正、负地闪回击间隔时间算术平均值分别为125.47ms和138.14ms,几何平均值分别为56.73ms和98.95ms,回击间隔时间呈对数正态分布,平均回击间隔时间随回击数的增大而减小。多回击地闪继后回击与首次回击之间距离与回击数呈准正态分布,集中在距离为1km范围内。

Based on the lightning location data of ADTD in Zhejiang Province from 2007 to 2018,the distribution and related parameters of multiple return strokes of cloud-to-ground(CG)lightning are analyzed.The results show that the number of multiple return stroke flashes accounts for 26.79%of the total CG number.The positive flashes are dominated by single-return stroke CG lightning flashes.The mean stroke number of positive CG and negative CG is 1.04 and 1.65,and the maximum stroke number is5 and 21,respectively.The inter-annul variation features of multiple stroke CG lightning flashes and total CG lightning flashes are consistent.The daily changes of positive CG and negative CG show multimodal and unimodal distributions,respectively.The arithmetic mean current intensity of the positive multiple stroke lightning is 72.06 kA,and that of the negative is-36.89 kA.The average current for CG flashes of particular multiplicity has a tendency of decreasing with the stroke order.Furthermore,about 40%of multiple stroke CG flashes have at least one subsequent stroke,with the initial peak electric field stronger than that of the first return stroke.The current intensities of the first return stroke and flowing stroke of CG show a log-normal distribution,in which the stroke frequency is the highest when the current intensity is from 15 kA to 45 kA.The arithmetic mean interval stroke of positive CG lightning is 125.47 ms,and the negative is 138.14 ms.The geometric mean interval stroke of positive CG lightning is 56.73 ms,and the negative is 98.95 ms.The interval of stroke lightning also shows a log-normal distribution.The mean interval has a tendency of decreasing with the stroke order.The distribution of interval distance between first return stroke and flowing stroke shows a quasi-normal distribution,and the strokes mostly occur within the range of 1 km.