内蒙古自治区真实地形和地球曲率对闪电定位影响

Effects of Real Terrain and Earth Curvature on Lightning Location in Inner Mongolia Autonomous Region

利用二维球坐标时域有限差分算法FDTD (Finite Difference Time Domain),首先研究了内蒙古自治区真实地形和地球曲率对地闪回击电磁场传播的影响,然后结合真实地形和地球曲率情况下波形结果,进一步分析了测站数量和布局及脉冲到达时间定义方法对定位精度的影响。结果显示:1)各站本身,相对不考虑曲率的光滑地面情况,真实地形和地球曲率都会引起波形峰值时间额外延迟,范围各自为2.91μs至4.50μs和0.08μs至0.92μs,且地球曲率的影响随电磁场传播距离增大而增大;2)由于地形的反射作用,各站本身考虑真实地形情况得到的磁场脉冲强度大于光滑地面情况,增大范围从24.95%至42.98%;3)使用11个站数据定位时,用10%峰值到达法定位时精度最好,误差仅42.1 m。在到达时间定义方法相同时,随着测站数量减少,实现合理定位精度越依靠定位时选取的测站布局。

Two-dimensional spherical coordinates FDTD(Finite Difference Time Domain) method is used to study the effect of real terrain and earth curvature on the propagation of return stoke electromagnetic field. Then further analysis has been made on the location accuracy basing on the wave calculated combined with the number of stations and their position and the different definitions of arrival time. Results show that: 1) In each station, comparing to the smooth ground without earth curvature, the real terrain and the curvature of the earth both cause the extra delay of return stoke electromagnetic pulse peak arrival time which ranges from 2.91 μs to 4.50 μs and 0.08 μs to 0.92 μs, respectively. The delay caused by the earth curvature increases with the farther propagation. 2) In each station, comparing with the smooth ground, the real terrain increases the peak amplitude, which ranges from 24.95% to 42.98%, due to the reflection of real terrain to electromagnetic field. 3) The definition of 10% peak arrival time method gets the most accurate result when we use waves of 11 stations. The error of which is just 42.1 m. As the number of measurement stations decreases, more accurate location depends on more reasonable stations′ position chosen when the same definition is formed.