Numerical Simulation Of The Effects Of Thunderstorm Cloud Charge Structure On Lightning Discharge

This paper use an existing stochastic lightning model and four souding data to perform a2-dimensional thunderstorms numerical simulation experiment which resolution is12.5m. Gives ground flash cases base on different thunderstorm cloud charge structure, and analyzes the relationship between characteristics of electrical environment and ground stroke point. Quantitative estimated the influence of positive charge pile in the bottom of a3-poled thunderstorm on lightning discharge and give rationality evaluated; what’s more, makes discharge simulation experiment through establishing space structure model of thunderstorm cloud charge, besides, analysis the relationships between the space charge distribution of thunderstorm and lightning channel extended range, reveals the difference of lightning fractal characteristics under different charge concentration distribution in thunder cloud. The main research results are as follows:1) Under a3-poled thunderstorm which can generate Negative CG lightning,The size and distribution of positive charge pile in the bottom of a3-poled thunderstorm has significant influence on lightning discharge.; when the bottom positive charge pile is narrowed a certain grade, Lightning will cease; when the bottom positive pile is enlarged a certain magnitude, Reverse polarity of cloud flashes will occur. In a3-poled thunderstorm which can generate IC lightning, when the range of positive charge pile in the bottom is enlarged. Reverse polarity of cloud flashes may occur. In a3-poled thunderstorm which can generate Positive CG lightning, the bottom positive charge pile will exclude the downlink leader, because they have charges of the same polarity. The larger of the quantity and distribution range of charge, The stronger of impact of the bottom positive pile on the downlink leader.2) Ground strike point uncertainty range is limited to3km because of the lightning propagation randomness, Using dynamic clustering method to iterative three locations which differ about1km. The distance between the initial point and ground strike point of negative CG lightning is mainly distributed in the range of0～6km; CG lightning primarily is produced in a pair of charges which close to ground, the higher of lightning starting height, the larger of range of distance between the initial point and ground strike point; some positive CG lightning which are produced in the three stage of charge structure of thunderstorm cloud is initial between upper part of positive charge pile and mid negative charge pile, the distance between the initial point and ground strike point is basically above6km.3) The range of Lightning leader propagates keeps positive correlation with the scale of charge in thunderstorm cloud. Before the channel of IC lightning through the charge accumulation centers, lightning The channel of IC lightning have fractal characteristics, the exponent is about1.757, If charge density changes slowly in some place where near the area of high-density charge, exponential will increase.