雷暴非感应起电机制的模拟研究Ⅰ．云内因子影响

A SIMULATION STUDY OF NON-INDUCTIVE CHARGING MECHANISM IN THUNDERSTORM Ⅰ AFFECT OF CLOUD FACTOR

利用一个二维时变积云动力－电数值模式模拟了非感应起电过程，讨论了流场、降水以及冰晶谱分布对起电的影响。结果指出：只有在强上升气流穿过－２０℃高度层时才会产生强起电，且发生在达到最大上升速度后出现降落的时段。随着电荷浓度的增加，主负电荷区中心高度也随之降落并稳定在一个高度上。冰晶谱分布能够改变冰相粒子的垂直结构，从而也就改变了起电率和电荷的时空分布。模拟试验中还得到了持续时间较短的云下部次正电荷区，并讨论了与流场的关系，指出在上升气流初始降落时段若能继续维持相对较强的上升气流，则可增长次正电荷区的持续时间。

In this paper,an axisymmetric,time-dependent numerical cloud model has been applied to study non-inductive charging,and to discuss affect of convection,rainfall and ice crystal size distribution on the charging The results show that there are intensive charging in the cloud when intensive updraft centre passes -20℃ temperature layer,and one appear during the updraft velocity just begins to decrease after acquiring maximal updraft velocity After,with as increasing of space charge concentration,with as droping of height of main negative charge center and that there is a stable height The ice crystal size distribution can change vertical structure of ice particles,and also can change charging rate and time-space charge distribution The simulated positive charge center in the lower part of the cloud has shorter duration The results also show that if just weaken updraft can maintain relatively intensive velocity,the duration of the lower positive charge center also can increase This perhaps is a reason of different characteristic in lower positive charge center for southern and northern thunderstorms