摘要
本文将非感应起电机制耦合到WRF中尺度模式中,选取Morrison双参数微物理方案,采用整体放电参数化方案,改变初始云凝结核(CCN)浓度(浓度变化从500 cm-3到4000 cm-3),共模拟15组试验,讨论了CCN浓度(nCCN)对雷暴云起电强度的影响。通过研究发现:随nCCN增加,霰粒子数浓度减少,混合比增加,导致霰粒子平均尺度增加;冰晶粒子数浓度增加,混合比基本不变,导致冰晶粒子平均尺度减小。此外,霰粒子平均尺度增大,下落末速度增大,冰晶粒子平均尺度减小,下落末速度减小,二者末速度差值增加,导致单次碰撞电荷分离量增加。综上所述,气溶胶浓度增加使霰粒子与冰晶粒子碰撞分离过程增强,单次碰撞电荷分离量增加,正负电荷密度平均值增加,从而增强雷暴起电强度。
In this paper, the Weather Research and Forecasting（WRF） model coupled with a non-inductive electrification mechanism and Morrison two-moment bulk microphysics scheme has been used to investigate the effect of cloud condensation nuclei（CCN） concentration on the development of thunderstorm electrification. Meanwhile, a bulk lightning parameterization scheme is incorporated into the WRF model. Fifteen examples with the initial CCN concentration changing from 500 cm^（-3） to 4000 cm^（-3） have been conducted. The results show that increasing CCN concentration decreases the number concentration of graupels but increases their mass content, leading to a greater mean size of graupels. On the contrary, with the increase in CCN concentration, the number concentration of ice crystals increases, while the mass content remains almost unchanged, resulting in a smaller mean size of ice crystals. In addition, the relative differences in falling speed between graupels and ice crystals increase mainly because of the changes in their size. This leads to an increase in the mean charge separation per rebounding collision. In summary, due to more ice crystals participating in the rebounding collision process and a larger mean charge separation per rebounding collision, increasing CCN concentration results in an enhancement in the electrification intensity, which leads to increases in the mean charge density.
出处
《大气科学》
CSCD
北大核心
2017年第1期106-120,共15页
Chinese Journal of Atmospheric Sciences
基金
国家重点基础研究发展计划(973计划)项目2014CB441403
江苏高校优势学科建设工程资助项目(PAPD)~~
