Numerical Simulation on the Effects of the Horizontal Charge Distribution on Lightning Types and Behaviors

Previous studies have generally acknowledged that lightning propagation behaviors and lightning types are closely related to the unbalanced charge amount and vertical stratification of charge structure. In this study, the total charge amount remains nearly balanced (±5%) between the adjacent charge regions where discharges initiate to avoid the interference of a total charge imbalance. Significant influences on the leader propagation tendency and lightning type are revealed by investigating different horizontal charge distribution features emphasizing on the effects of the charge distribution uniformity and the relative position of the high‐density charge center. Sensitivity experiments are performed with a two‐dimensional stochastic discharge model and demonstrate the following. Under a symmetric charge distribution, the more uniform charge distribution is conducive for leaders propagate horizontally; the charge being more compact in the central zone is favorable for vertical extension of leaders. Under an asymmetric charge distribution, a horizontal shift of high‐density charge center is conducive to the extension of leaders in the offset direction. Different charge distributions will change the electrical energy of charge regions resulting in various lightning behaviors. Various charge distributions provide favorable conditions for some lightning flashes (including positive cloud‐to‐ground flashes [PCG], “bolt‐from‐the‐blue” [BFB] flashes and gigantic jets). PCGs are favorably triggered with the more compact upper positive charge (P) and more uniform middle negative charge (N), and BFB discharges can be triggered between the P and N regions when the high‐density charge center in the P region is horizontally shifted. A possible method is provided to explain various lightning behaviors.