【作者】 孙京；

【导师】 郭凤霞；

【作者基本信息】 南京信息工程大学 ， 雷电科学与技术， 2012， 硕士

【摘要】 本论文的主要目的是为了利用数值模拟手段对雷暴云内起电和放电做进一步研究。首先,对国内外有关雷暴云起电机制的试验结果和起/放电的非云模式和云模式的研究结果进行了回顾,总结了这两方面研究的主要发展历程、现状及所涉及的重要问题。然后,在一个三维强风暴动力-电耦合数值模式的基础上,主要做了三方面的工作：(1)采用多项式回归分析法,给出了基于Takahashi实验数据的非感应转移电荷量的数学公式,并与实验值进行了比较；(2)在模式中引入基于Saunders实验结果的非感应起电参数化方案S91,并利用云水饱和度替代环境温度和有效液水含量,将S91方案变形。对比分析了一次雷暴单体首次放电前,变形后的S91方案和原S91方案模拟得到的非感应转移电荷的极性、量级、电荷结构以及与霰和冰晶粒子分布之间的关系；(3)采用固定电场阈值触发、双向随机发展的放电参数化方案,通过一次雷暴过程的模拟,分析了空间电荷结构和电荷分布对闪电放电特征的影响。结果表明,在温度高于-10℃,液水含量介于0.08～8g/cm3的情况下,由数学公式得到的非感应转移电荷量与实验结果一致性较好,但在温度低于-25℃,液水含量介于0.5～2g/cm3的情况下,两者的一致性不是很好。因此,可以在模式中引入基于Takahashi的非感应起电参数化方案时,直接应用此公式,而替代以前较繁琐的查表法；首次放电前,当云水环境趋于过饱和状态时,转移电荷产生的主要区域位于高温、低有效液态水区,且转移电荷数目也较少。当云水环境趋于亚饱和或饱和状态时,转移电荷主要产生于低温、高有效液态水区域,且转移电荷数目不断增加。放电后,雷暴云初期和中期,由于对流强度较强,云层高度较高,在反偶极性电荷结构出现的情况下,云内闪电起始于上部负电荷和中部正电荷区之间,且正、负电荷区中心浓度较大,闪电主要为反极性云闪。随着对流的进一步发展,在雷暴云末期,当云内粒子增多、增大,大部分霰粒子逐渐降落到中低层,使上部负电荷中心浓度减小,底部的起电区域增大,这种情况下云内闪电多发生在中部正电荷和底部负电荷区之间,闪电主要为正常极性的云闪。关键词雷暴云数值模式非感应起电机制放电电荷结构更多还原

【Abstract】 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.更多还原