中国内陆高原雷暴云底部正电荷区的形成机制

The Formation Mechanism of the Lower Positive Charge Center of Thunderstorm in the Inland Plateau of China

为了进一步了解中国内陆高原雷暴的特殊性,基于以往高原雷暴存在范围深厚的底部正电荷区的观测及模拟事实,利用三维完全可压缩非静力(WRF)模式对2017年6月20日一次内陆高原雷暴过程进行模拟,分析高原雷暴成熟阶段的底部正电荷结构特征;并从微物理和动力角度对其形成机制进行讨论。模拟结果表明,内陆高原地区雷暴云成熟阶段主要呈倾斜的三级性电荷结构;其中底部正电荷区的范围和电荷密度均较大。底部正电荷区主要是由霰和冰雹等固态大粒子与冰晶、雪晶等固态小粒子非感应碰撞起电携带的正电荷以及霰粒子与云滴之间的感应碰撞起电携带正电荷组成;此外霰粒子与雹粒子降落过程中融化成携带正电荷的雨滴也对深厚的底部正电荷区存在一定的作用。

In order to further understand the characteristics of thunderstorm over inland plateau of China,the weather research and forecasting(WRF)model was used to analysis the lower positive charge center(LPCC)characteristics of the thunderstorm occurred on 20 June 2017 and discussed the formation mechanism from the view of microphysics and dynamic,based on the previous observation and simulation facts.The results indicate that the plateau thunderstorm in the mature stage mainly displays an inclined tripole charge structure,which has a larger range of LPCC and larger charge density than the typical one.The LPCC is mainly composed of the positive charge carried by the non-inductive collisional separation between ice-phase microphysics and the inductive collision separation between graupel and cloud drop.In addition,the melting of the graupel and hail particles into raindrops carrying positives charges has a certain effect on the formation of the deep LPCC.