Fine-resolution simulation of cloud-to-ground lightning and thundercloud charge transfer
Fine-resolution simulation of cloud-to-ground lightning and thundercloud charge transfer
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DOI：
10.1016/j.atmosres.2008.05.012
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发表时间：
2009-02
影响因子：
5.5
通讯作者：
Shanchang Tao;Yongbo Tan;Baoyou Zhu;M. Ma;Weitao Lu
中科院分区：
文献类型：
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作者：
Shanchang Tao;Yongbo Tan;Baoyou Zhu;M. Ma;Weitao Lu
利用改进的随机闪电模型，对雷暴云带电过程中产生的偶极子、三极、双偶极子和多层电荷结构等不同类型的云电荷分布进行了二维12.5 m分辨率的云地闪电放电过程模拟。模拟结果给出了地闪的精细分支通道结构，并说明了地闪通道传播与云电荷分布的关系。地闪的模拟特征与观测结果相吻合。模拟研究是必要的，在我们的理解复杂的电荷转移过程所造成的CG闪电在雷暴云。相反极性的感应电荷沉积或嵌入在局部体积的双向领导人通过在CG闪电放电期间。虽然嵌入影响电荷结构只在一对显着的正，负电荷区域最接近地面，电场强度急剧减弱和雷暴云的静电能量显着消耗时，放电终止。除了模拟初始先导对地的向上和向下击穿以及随后的回程（RS）之外，模拟还假设电流继续在通道中流向地面，并确定向上击穿直到放电结束。对于随后的放电子过程，向上的先导通道倾向于转移与RS极性相同的电荷，而向下的先导通道有利于将相反的电荷转移到地。在一些CG闪光模拟的子过程中，来自向下先导的相反电荷的大小超过来自向上先导的具有相同极性的电荷的大小，使得转移到地面的净电荷具有与RS相反的极性。模拟呈现出与现实双极地闪相似的地闪特征。
2-D 12.5 m-resolution simulations of cloud-to-ground (CG) lightning discharge processes have been performed using an improved stochastic lightning model for different types of cloud charge distributions, such as dipole, tripole, bi-dipole and multi-layer charge structures produced from the numerical simulation of thundercloud electrification. The modelling produced the fine branched channel structure of CG lightning and the results illustrate the relations between CG lightning channel propagation and cloud charge distribution. The simulated features of CG lightning are associated with the observed results. The simulation studies are essential in our understanding of complex charge transfer processes caused by CG lightning discharges in thunderclouds. The induced charges of opposite polarity are deposited or embedded in the local volumes where the bidirectional leaders passed during a CG lightning discharge. Although the embedding affects charge structure only in a pair of significant positive and negative charge regions closest to the ground, the electric field strength acutely weakens and electrostatic energy in thunderclouds is significantly consumed when the discharge terminates. In addition to simulating the upward and downward breakdown of the initial leader to ground and the ensuing return stroke (RS), the simulation assumes that current continues to flow in the channel to ground and determines the upward breakdown until the end of the discharge. For the subsequent discharge sub-process, the upward leader channel tends to transfer the charges with the same polarity as the RS, while the downward leader channel favors transfer of opposite charge to ground. In the sub-processes of a few CG flash simulations, the magnitude of the opposite charges from the downward leader exceeds that of charges with the same polarity from the upward leader so that the net charges transferred to the ground have a reversed polarity to the RS. The simulation presents similar features of CG lightning as those observed in realistic bipolar CG lightning.