强风暴个例电荷结构及云闪放电差异的数值模拟

利用耦合电过程的冰粒子分档模式对长春地区两个降雹型和非降雹型强风暴个例的闪电特征进行了模拟和对比分析。结果表明,在雷暴云的初始发展期,由于上升气流较弱,两者电荷分布相似,均表现为弱的正偶极结构。随着云体不断发展,两者电荷分布开始表现出差异:降雹型个例中的上升气流较强,风切变较大,过冷水能被携带到较高的高度,冰相粒子也能被带到较高处或在较高处继续增长,使得不同区域均存在冰相粒子含量中心。因此,冰相粒子的发生范围不同、环境参数不同及荷电符号不同的非感应起电过程,形成多个电荷中心,电荷结构易出现多层分布。在不同的发展时期电荷结构均呈现出不同的形态,放电既可能在上升气流区触发,也可能在气流辐散区触发。相对而言,非降雹型个例中的上升气流较弱,风切变较小,冰相粒子的分布较规则,非感应起电过程较均匀,从而导致电荷分布始终较均匀。不同发展时期的电荷结构都相对有规则,满足放电条件的位置具有一定的相似性。

Numerical Simulation of Difference of Electric Structure and Discharge of Cloud Flash for Two Severe Thunderstorm Cases

The electric structure and discharge of cloud flash between two severe thunderstorm cases(one is with hail shooting process and the other is without hail shooting process,expressed by H case and NH case,respectively) in Changchun city,Jilin Provence was simulated and comparatively analyzedby a three-dimensional hail-category cloud model coupled with electrification process.Results show that the electric structures of the two cases caused by the weak updraft at the initial stage of severe thunderstorm are similar and both have a weak positive-pole distribution.With the development of thunderstorm,the difference of the electric structure occurs.Stronger updraft and wind shear in H case make super-cooled water and ice phase particle be carried to higher level in different regions in where the ice phase particle grow,which produces several content center of ice phase particle so that the non-inductive processes at different regions with different environmentparameters and sign of charge in ice phase particles occur and several charge centers develop.And the charge is apt to show a multi-layered distribution. The different distributions of charge at differentstages could be initiated at both updraft zones and divergence zone.With relatively weaker updraft and wind shear,the distribution of the ice phase particle in NH case is more regular,so is the non-inductive process.And the distribution of charge is well-distributed and more regular at different stages.Therefore,the position where lightning flashe might is similar to some extent.