Abstract:
Numerous observation-based studies have proposed that the extension scale of lightning channels is closely related to charge distribution patterns. They have also proposed that in areas with strong convection, small and frequent lightning is likely to form with the pattern of charge pockets. Herein, the lightning discharge parameterization scheme was coupled with the double-layer uniform pocket charge model, and a large number of random simulation tests were conducted to verify that such cloud flashes can be formed against the background of pocket charge and provide the general law of lightning initiation and discharge with this charge distribution pattern. The total dimension of the charge region was fixed, whereas the pairs of the charge region in the simulation were varied to discuss the similarities and differences of lightning initiation and discharge behavior against each charge background. Simulation results indicate that (1) with the increase in charge pairs, the charge concentration and total charge quantity for lightning startup increase. (2) The axial ratio of each small charge region is the key factor affecting lightning initiation behavior. In addition, the spatial configuration relationship of multiple pairs of charges and the runaway breakdown threshold cause the lightning starting position and probability in the horizontal and vertical directions to differ in each case. (3) The spatial characteristics of lightning are limited by the geometric characteristics of the small charge region. (4) The distribution of the charge region considerably affects the development shape of lightning. Against each charge background, the distribution range and concentration area of initial leader angles differ. The variation range of the initial leader angle and number of horizontal development cases are considerably higher in the case wherein the vertical and horizontal radii of the small charge region are equal to those in the case of the previous charge structure (flat ellipse).