Numerical Simulation Of Electrical Activity In Thunderstorms

In order to further study the charging and discharge in thunderstorm by combining of numerical simulation, recent developments in the area of thunderstorm electrification and lightning discharge are reviewed in this paper. The important problems and major achievements of researches are summarized as the mechanism of electrification and numerical simulation of thundercloud electrification. It introduced the development of the ion, particle and other electrification mechanisms in detail, and reviewed some results and progress of the models of electrification and discharge at home and abroad from non-cloud model and cloud model aspects.The work of thee aspects is put forward in a three-dimensional dynamic electrification coupled model. Firstly, the paper used stepwise regression analysis to obtain empirical equations for the separated non-inductive based on Takahashi’s experiment, and fitness analysis of the equations are made with experiment’s values. Secondly, a parameterization of non-inductive graupel-ice charge separation S91based on the laboratory results of Saunders is introduced into the model. The effective liquid water content and environment temperature in S91are replaced by cloud saturation, to result in the deformation of Saunders. The evolution characteristics of non-inductive charge separation polarity, magnitude, charge structure and their relationships with ice crystal and graupel particle distributions produced by the deformation of S91and original S91in a typical storm before the first discharge are analyzed, respectively. Thirdly, the Bi-directional Stochastic Lightning Parameterization scheme is used in the parameterization of discharge, and The structure of spatial charge and charge distribution effects on the characteristics of discharge are analyzed.The results indicate, the calculated values are very close to the experiment’s data, and the method can be introduced into the parameterization of non-inductive based on Takahashi’s experiment. Before the first discharge, in the supersaturated circumstance, charge separation mainly occurs in the region at high temperature and low effective liquid water content, and the transfer charge become lower. Whereas, in the subsaturated or saturated circumstances, charge separation mainly occurs in the region at low temperature and high effective liquid water content, and the transfer charge continuously increasing. After the first discharge, because of the strength of convection intensity and the high of cloud height, lead to the characteristic of discharge is inverted IC flash in the case of the structure is inverted dipole discharge in the early of thunderstorm. With the further development of convection, the characteristic of discharge is positive IC flash when the number of graupel and ice is increasing and the grauple decrease by the middle and low level, which makes the bottom of electrical region expand in the end of thunderstorm. In addition, the occurrence rate of inverted IC flash and positive IC discharge has related to the convection intensity, the distribution of particle, the electrification region and the distribution of charge density.