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首页> 外文期刊>Journal of Geophysical Research, D. Atmospheres: JGR >Analysis of lightning electromagnetic field propagation in mountainous terrain and its effects on ToA-based lightning location systems
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Analysis of lightning electromagnetic field propagation in mountainous terrain and its effects on ToA-based lightning location systems

机译：雷电电磁场在山区地形中的传播及其对基于ToA的雷电定位系统的影响分析

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摘要

In this paper, we analyze the propagation effects on lightning-radiated electromagnetic fields over mountainous terrain by using a three-dimensional (3-D) finite difference time domain (FDTD) method. We also discuss the time delay error in the time-of-arrival (ToA) technique currently used to locate lightning in detection networks, specifically. Furthermore, the accuracy of different approximate methods presented in the literature is discussed and tested by using our 3-D FDTD method. It is found that (1) the time delays and amplitudes of the lightning-radiated electromagnetic fields can be significantly affected by the presence of a mountainous terrain and associated diffraction phenomena; (2) for a finitely conducting ground, the time delay shows a slight increase with the increase of the observation distance, but the time delay resulting from the finite ground conductivity appears to be smaller than that caused by the mountainous terrain; and (3) the timing error associated with the ToA technique depends on the threshold times. Threshold times of 10% and 20% of the peak provide very similar results compared to those corresponding to the peak of the first derivative of the magnetic field, and the threshold time exceeds 50% of the initial rising amplitude of the signal. Furthermore, we have assessed the accuracy of two simplified methods (terrain-envelope method and tight-terrain fit method) to account for the time delays resulting from the propagation in a mountainous terrain. It is found that both methods result in time delays that are in reasonable agreement but always overestimating the results obtained using the full-wave 3-D FDTD approach for the perfectly conducting ground. These two methods represent interesting alternatives to account for the time delay over a nonflat terrain using the terrain model.
机译：在本文中，我们使用三维（3-D）时差有限域（FDTD）方法分析了山地地形对雷电电磁场的传播效应。我们还将在当前用于在检测网络中定位雷电的到达时间（ToA）技术中讨论时间延迟误差。此外，使用我们的3-D FDTD方法讨论并测试了文献中提出的不同近似方法的准确性。结果发现：（1）山区地形的存在和相关的衍射现象会严重影响雷电辐射电磁场的时间延迟和幅度。 （2）对于有限导电的地面，时延随观察距离的增加而略有增加，但由有限的地面电导率引起的时延似乎小于由山区引起的时延。 （3）与ToA技术相关的定时误差取决于阈值时间。与对应于磁场一阶导数的峰值的阈值时间相比，峰值的10％和20％的阈值时间提供了非常相似的结果，并且阈值时间超过了信号初始上升幅度的50％。此外，我们评估了两种简化方法（地形包络法和紧密地形拟合法）的准确性，以解决在山区地形中传播所造成的时间延迟。发现这两种方法都会导致时间延迟，这些时间延迟在合理的范围内，但总是高估了使用全波3-D FDTD方法获得的理想导电地面的结果。这两种方法代表了使用地形模型解决非平坦地形上的时间延迟的有趣替代方法。

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