Numerical Simulation to Evaluate the Effects of Upward Lightning Discharges on Thunderstorm Electrical Parameters

Abstract

A theoretical discussion of the discharge effects of upward lightning simulated with a fine-resolution 2D thunderstorm model is performed in this paper, and the results reveal that the estimates of the total induced charge on the upward lightning discharge channels range from 0.67 to 118.8 C, and the average value is 19.0 C, while the ratio of the induced charge on the leader channels to the total opposite-polarity charge in the discharge region ranges from 5.9% to 47.3%, with an average value of 14.7%. Moreover, the average value of the space electrostatic energy consumed by upward lightning is 1.06×10⁹ J. The above values are lower than those related to intracloud lightning discharges. The density of the deposited opposite-polarity charge is comparable in magnitude to that of the preexisting charge in the discharge area, and the deposition of these opposite-polarity charges rapidly destroys the original space potential well in the discharge area and greatly reduces the space electric field strength. In addition, these opposite-polarity charges are redistributed with the development of thunderstorms. The space charge redistribution caused by lightning discharges partly accounts for the complexity of the charge structures in a thunderstorm, and the complexity gradually decreases with the charge neutralization process.

摘要

本文采用二维高分辨率的雷暴云模式对上行地闪的放电效应进行理论探讨。结果表明上行闪电放电通道中感应电荷的估值在0.67 C到118.8 C之间,感应电荷平均值为19.0 C,通道中感应电荷与放电区域总电荷的比值在5.9%到47.3%之间,平均值为14.7%。此外,上行闪电消耗的空间静电能的平均值为1.06×109J。上行闪电放电对雷暴电参数的影响要明显小于云闪放电对雷暴电参数的影响。分析上行地闪放电后通道残余电荷及空间电场,电位和静电能的变化后发现,闪电放电后在放电区域植入了与原先区域电荷浓度相当的异极性电荷,这些异极性电荷的植入会迅速摧毁原先放电区域的空间位势井,并且大大减弱空间电场强度。随后这些异极性电荷会随着雷暴的发展重新分布。闪电放电造成的空间电荷的重分配在一定程度上解释了雷暴云电荷分布的复杂性,并且这种复杂度会随着电荷中和而逐步减小。