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This paper presents an investigation into cloud-to-ground lightning activity data collected by a lightning detection system in the Guang-Dong Province, the southernmost in China. Annual lightning days are acquired and ground flash density maps are constructed from the database, which contains the information of more than one million flashes. The lightning days are compared with annual thunderstorm days collected by the Guang-Dong Meteorological Agency, and a weak correlation is noted. The correlation between ground flash density and thunderstorm day is studied, and an empirical formula is presented. The relationship between transmission line faults and ground flash density is discussed in this paper too. It is noted that the correlation with the faults caused by lightning is relatively high. The correlation coefficient does not significantly vary with the threshold of discharge current set for constructing the map of revised ground flash density.

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Most lightning location networks obtain the position results by optimizing the goodness of fit to determine that all combinatorial time differences of arrivals (TDOAs) are due to a common discharge. This paper proposes a three-dimensional (3D) lightning location method based on range difference (RD) space projection. The proposed method projects all the measurements into the RD space, which has the space-invariant feature of the equivalence cell and can be partitioned soundly. Aiming at the problem of computational cost of the procedure of the projection, the hierarchical strategy is proposed to improve computational efficiency. The performance of the RD space projection based on the hierarchical strategy is analyzed via Monte-Carlo simulations. The results show that the proposed method can locate lightning sources in real time with high accuracy. The results also show that the location accuracy is limited by the level of the inherent time uncertainty, the layout, and the size of the receiver network. Under the fixed layout and size of the receiver network, and the fixed measurement noise uncertainty, the positioning precision cannot be improved more even if the grid step is small enough or the number of receivers is large enough.