Importance of Taking Into Account the Soil Stratification in Reproducing the Late-Time Features of Distant Fields Radiated by Lightning

In this paper, we present an analysis of the propagation effect along a lossy ground on the characteristics of lightning-generated electric fields, using simultaneous observations of lightning currents and radiated fields measured at nine different distances associated with rocket-triggered lightning. The triggered-lightning site is located in Conghua (Guangdong, China). The electric field waveforms were measured using the sensors belonging to the Foshan three-dimensional lightning location system that are located at distances from the triggered-lightning site ranging from 69 to 126 km. The propagation path was over land and mainly over flat ground. The field sensors used had an overall bandwidth from 160 Hz to 1 MHz. It is shown that even though the early response of the field can be reproduced reasonably well by adjusting the ground electrical conductivity, the subsidiary peaks, and the late-time response of the fields cannot be satisfactorily reproduced assuming a homogeneous ground model. However, a two-layer soil model allows obtaining very good agreement between computed and measured waveforms for all the considered distances and events. Compared to the homogeneous ground case, the computed early-, intermediate-, and late-time response follows to a much better extent the experimental waveforms. We also provide a discussion on the influence of the computational model and parameters on the simulated results.