# Inversion of a Thunderstorm Cloud Charging Model Based on a 3D Atmospheric Electric Field
## 4 Discussion and Conclusions  
The three-dimensional electric field meter we developed overcomes the shortcomings of a traditional electric field meter that can only measure the vertical electric field components at the ground. Observational experiments have confirmed that thunderstorm clouds produce horizontal electric field components that cannot be ignored near the ground. This provides more comprehensive electric field information for the tracking, warning, and charge structure of thunderstorm clouds. By establishing an observation model of the three-dimensional electric field, it was proven that the orientation information of the thunderstorm cloud can be determined by the ratio of the three-dimensional electric field values of the observation points. Therefore, the three-dimensional electric field data can be used to continuously monitor the movement trajectory of the thunderstorm cloud, which can be used as a useful supplement to radar data. Lightning warning is an important application of atmospheric electric field meters. The traditional atmospheric electric field meter has a certain leakage alarm because it only measures the vertical atmospheric electric field and ignores the horizontal component. For example, when the three-dimensional electric field meter in the experiment measured the thunderstorm cloud in the second stage (15:50 p.m.-16:20 p.m.), the horizontal component electric fields \(E_{x}\) and \(E_{y}\) were obviously stronger than the vertical electric field \(E_{z}\). The amplitude gave a lightning warning. However, if it was measured by a conventional electric field meter, it will be impossible to give an early warning because the electric field \(E_{z}\) in the vertical direction is weak. The amount of electric field information measured by traditional electric field meters is too small, and it is difficult to invert the structural parameters of the thunderstorm cloud. Multiple networking electric field meters must be used to calculate the positional relationship of each electric field meter and the measured vertical electric field. However, the installation environment of each electric field meter in the grid including the terrain, surrounding buildings, etc., will cause distortion of the atmospheric electric field, resulting in poor consistency of the measurement data, and it is difficult to correct. Based on incorrect electric field data, the inversion of atmospheric electric fields is difficult to carry out. The three-dimensional electric field and the charged structure parameters are nonlinear, and the particle swarm optimization algorithm is suitable for nonlinear inversion problems. However, in the process of finding the optimal solution in the inversion iteration, the position of the particle must be limited according to the typical thunderstorm cloud charge structure parameter. The inversion method assumes that the thunderstorm cloud is a multi-layer structure, and the charge center of the thunderstorm cloud is treated as a point charge. The thunderstorm cloud-charged structure of the experimental inversion observation site (Nanjing) was evenly polar, which was consistent with the results of the comprehensive analysis of the electric field and radar data in the literature [21]. \begin{table}
\begin{tabular}{c c c c} \hline
**Station** & **Distance (Km)** & **Official Data (KV/m)** & **3D AEFM (KV/m)** \\ \hline Pukou & 18.91 & \(-\)1.6 & \(-\)1.583 \\ Nanjing Meteorological & 18.40 & \(-\)1.4 & \(-\)1.367 \\ Bureau & 16.49 & \(-\)1.9 & \(-\)1.931 \\ Luhe & 22.14 & \(-\)0.8 & \(-\)0.830 \\ \hline \end{tabular}
\end{table} 
Table 2: Comparisons between official data and 3D AEFM (the three-dimensional electric field meter) measurements. The measurement of three-dimensional atmospheric electric field provides more comprehensive data for the study of lightning structure and lightning warning of thunderstorm clouds.