Numerical Simulation Of Effect Of Distribution Characteristic Of Space Charge In Thunderstorms On Lightning Discharge

Based on the existing stochastic lightning parameterization scheme, different charge structures are assumed to acquire charge background of thunderstorm in this paper, and then2-dimensional fine-resolution lighting discharge simulations are performed to quantitatively investigate the effect of distribution characteristic of space charge in thunderstorms on lightning discharges. The main research results are as follows:(1) The screening charge layer at top of thunderstorm and the lower positive charge region will constrain the vertical propagation range of positive and negative leaders of intra-cloud lightning that are triggered between the main positive and negative charge regions. Thereby, the channels of intra-cloud lightning can only propagate in a certain vertical range and tend to propagate horizontally in the end; the increase of charge density or distribution range of charge region both will increase the channel length of intra-cloud lightning, but in different way. The charge density increases the channel length mainly by increasing the channel branches near high charge density center, and they have a nonlinear relationship, while the distribution range increases it by extending the horizontal propagation range of channels, and they have a linear relationship; the increase of charge density of charge region increases the fractal dimension of intra-cloud lightning channel. The increase of distribution range of charge region will not affect the fractal dimension of intra-cloud lightning channel.(2) The LPC plays a key role in generating negative cloud-to-ground (CG) flashes and inverted intra-cloud (IC) lightning, with the increase of charge density or distribution range of LPC region, lightning type changes from positive polarity IC lightning to negative CG flashes and then to inverted IC lightning; relative to distribution range of charge regions, the magnitude of charge density of the LPC region plays a dominant role in lightning type, only when the maximal charge density value of LPC region within a certain range, can negative CG flashes occur, and the occurrence probability is relatively fixed; the common effect of charge density and distribution range of the LPC region is to change the distribution of positive potential well of bottom part of thunderstorms, and inverted IC lightning occur when the initial reference potential is close to OMV, and negative CG flashes occur when the initial reference potential is far less than OMV.(3) The different distribution forms of charge density in thunderstorm have great effect on the branch of channel of IC and the strike of CG, and different types of lightning may occur under different distribution forms of charge density.