摘要
我们应用改进的随机闪电参数化方案,对两次雷暴的起、放电过程进行了二维12.5m和250m分辨率云闪模拟试验,分析表明高分辨率模拟的云闪通道几何结构、延伸范围和最大垂直电场变化等特征与观测结果更为一致,并且揭示了云闪放电重新配置云内电荷分布和空间电荷中和过程的一种新的物理图像:(1)云闪的直接物理效应是在已有的空间电荷区内沿着放电通道沉积异极性电荷、形成复杂的空间电荷分布,有效地导致云中电位和场强绝对值及静电场能量剧烈下降,使放电终止.其中:放电后在闪电通道经过主要区域,电位降到±30MV之间,垂直电场强度也降到±20kV.m-1之间,一次正或负云闪估计消耗掉107～1010J静电能;(2)云中电荷中和不是正、负空间电荷简单地直接相互抵消的瞬态过程,而是广泛分布的云中空间电荷与通道沉积的异极性电荷通过湍流交换、平流输送、重力沉降以及起电等多种因素逐渐混合并部分被中和的一个后续慢过程,其弛豫时间典型值在14～44s之间,在此期间通道感应电荷总量下降到50%以下.并残余部分电荷参与后续放电前高空间电荷密度和强电场的重建过程.
This paper extends the use of Stochastic Lightning Model in a simulation experiment, in which 12.5 and 250 m resolution simulations of intra-cloud （IC） lightning discharges within a two dimensional numerical thunderstorm model have been performed, and gives the comparing analyses of the simulated results with the observed data. The results show ： （ 1 ） During an IC flash discharge, more complex distribution of the space charges in thundercloud is caused by the induced charges along the channels, and lead to a sudden decrease in the maxima of electrostatic potential and potential gradient as well as consume of electrostatic energy of thundercloud. The ratio of induced charges to surrounding space charges varies from 0.2% to 70.8% , the electrostatic potential and field strength drop down respectively to ± 30 MV and ± 20 kV·m^- 1 where the flash channels passed, and consumed electrostatic energy of thunderstorm for a positive or negative IC flash is about 10^7 - 10^10 J. （2） As contrasted with transient IC discharges, the charge neutralization in thundercloud is a slow process with a relaxation time of about one minute or less. The dispersed space charges in thundercloud and opposite charges deposited in the flash channels are mixed slowly and neutralized partially by turbulence exchanging, advection transporting and gravitational sedimentation etc.. There are 15% -40% excess of induced channel charges to be not neutralized, which contributes to rebuilding new distribution of space charges and electrostatic potential.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2007年第4期1053-1065,共13页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(40205002
40475004)资助.
关键词
云闪
感应电荷
电位分布变化
静电能量变化
电荷中和
Intra-cloud flash, Induced charge, Variation of potential distribution, Variation of electrostatic energy, Charge neutralization
