地形地表的不规则起伏对雷电电磁场传输的影响  

Effect of irregular terrain on propagation of lightning electromagnetic field

作　　者：张其林[1,2] 张源源[1,2] 李东帅[1,2] 樊艳峰[1,2] 高金阁[1,2] 

机构地区：[1]气象灾害省部共建教育部重点实验室,南京信息工程大学,南京210044 [2]南京信息工程大学大气物理学院,南京210044

出　　处：《气象学报》2013年第2期357-365,共9页Acta Meteorologica Sinica

基　　金：国家自然科学基金项目(40975002)

摘　　要：为了研究地形地表的不规则起伏(简称粗糙地表)对雷电电磁场传播的影响,首先利用二维分形方法模拟了粗糙地表,然后利用Barrick表面阻抗理论和Wait近似算法研究了粗糙地表对雷电电磁场传播的影响。结果表明,粗糙地表对地闪首次回击垂直电场的影响较小,但对继后回击存在明显的影响。随着粗糙度的增加,继后回击垂直电场峰值的衰减程度明显增加,且时域脉冲波形上升沿时间增大。如继后回击电磁场传播100 km,均方高为30 m的粗糙地表(电导率σ=0.1 S/m)引起时域电磁场波形上升沿时间额外增约1.5μs,电场峰值额外减小约12%,且其影响随着地面电导率的减小而增大。因此,在实际工作中应考虑复杂地形地表对闪电定位系统探测精度和效率的可能影响。A two-dimensional fractional Brown motion（fBm） model is presented for describing the rough ground surface,and we have analyzed the propagation effects of a fractal rough ground surface on the lightning-radiated electromagnetic field by using Barrick＇s theory and Wait＇s approximates. The results show that the rough land surface has no or little effect on the vertical electric field generated by the lightning first return stroke,however it has obvious effect on the field generated by the lightning suhsequent return stroke. The rise time of the field waveform increases with the increasing of the roughness,and the field peak decreases obviously. For example,when the ground conductivity is 0.1 S/m,the extra attenuation of the field peak and the extra risetime of the waveform caused by the roughness with a mean square height of 30 m are about 12% and 1.5 μs in its propagating 100 km,respectively. Therefore,we should take into account the errors in the accuracy and efficiency of the lightning location system detection caused by the rough propagation paths of the lightning field.

关 键 词：分形粗糙地表 雷电回击 垂直电场 传播误差 

分 类 号：P427.321[天文地球—大气科学及气象学]