传播效应对远距离雷电电磁场的影响  

Propagation Effect on the Lightning-radiated Electromagnetic Field at Far Distances

作　　者：侯文豪 王尧钧 王洪生 崔逊 焦雪 张其林[2] HOU Wen-hao;WANG Yao-jun;WANG Hong-sheng;CUI Xun;JIAO Xue;ZHANG Qi-lin(Jiangsu Meteorological Disaster Prevention Technology Center, Nanjing 210041, China;Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disaster (CIC-FEMD)/Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing 210044, China)

机构地区：[1]江苏省气象灾害防御技术中心,南京210041 [2]南京信息工程大学气象灾害预报预警与评估协同创新中心/中国气象局气溶胶与云降水重点开放实验室,南京210044

出　　处：《科学技术与工程》2022年第7期2601-2608,共8页Science Technology and Engineering

基　　金：江苏省气象局青年基金(KQ202112);国家重点研发计划(2017YFC1501505);国家自然科学基金面上项目(41775006)。

摘　　要：雷电电磁波沿着地球表面传播时,受传播效应影响波形会发生畸变,进而影响雷电定位系统的精度。采用Wait解析算法研究了地面有限电导率与地球曲率对1000 km以内雷电电磁场波形的影响,对不同回击电流波形和不同电导率情况下的远场衰减系数进行了拟合,修正了现有的回击电流峰值反演公式,并对传播效应带来的远场波形到达时间延迟量进行了统计分析。结果表明:当观测距离大于200 km时地球曲率对场的衰减不容忽略;和平坦地面相比,弯曲的地表使得200、500、1000 km处的远场峰值分别额外衰减了约9.6%、29.4%和55.5%。考虑传播效应后远场峰值与理想场的峰值之比随着观测距离d的增加以exp(-d/α)的指数函数大幅递减,指数衰减距离常数α的平均值为1000 km。回击电流波形陡度越大,包含的高频分量越多,远场的衰减越大。雷电电磁波沿陆地表面传播时,传播距离每增加100 km波形初始到达时间平均延迟0.36μs,峰值到达时间平均延迟0.96μs。由此可见,远距离雷电定位和参数反演应充分考虑地球曲率带来的传播效应。When the lightning electromagnetic wave propagates along the ground surface,the far field will be distorted due to the propagation effect,which will affect the accuracy of the lightning locating system.The Wait’s analytical method was used to investigate the propagation effect of the finite ground conductivity and the earth’s curvature on the lightning-radiated electromagnetic field.The far-field attenuation factors for different return stroke current waveforms and different conductivities were fitted,and the field-to-current conversion factor had been revised.The delay in arrival time of the far-field waveform caused by the propagation effect had been statistically analyzed.The results show that the effect of earth curvature cannot be ignored when the observation distance is larger than 200 km.Comparing with the case of flat ground,earth’s curvature causes an additional attenuation of 9.6%,29.4%and 55.5%of the field peak at observation distances of 200 km,500 km and 1000 km,respectively.The ratio of the attenuated field peak to the ideal field peak decreases exponentially with the increase of the propagation distance,and the average value of the exponential decay constant is 1000 km.The steeper of the current wavefront,the more high frequency it contains,and the greater of the attenuation.When lightning-radiated electromagnetic field propagates along the land surface,with an increase of the propagation distance by 100 km,the delay in arrival time of the far-field waveform and the field peak is increased by 0.36μs and 0.96μs on average,respectively.It is concluded that,the propagation effect of the earth curvature needs to be considered for the long-range lightning locating and the measure of the lightning current parameters.

关 键 词：雷电电磁场 传播效应 地球曲率 雷电流峰值反演 闪电定位 

分 类 号：P427.3[天文地球—大气科学及气象学]