云凝结核浓度对北京一次降水过程影响的数值模拟

Simulation study on the effects of aerosol concentration upon a precipitation event in Beijing

利用WRF v3.6.1模式,采用Thompson云微物理参数化方案对北京奥运会期间的一次降水过程进行了模拟,通过3组数值试验对比分析了高、中、低云凝结核浓度对降水的影响。数值试验结果显示:(1)在云凝结核浓度较低的情况下,云凝结核浓度增加使24 h累积降水量增加,且增加的幅度相对较低;在云凝结浓度较高的情况下,云凝结核浓度增加使24 h累积降水量减少,且减少的幅度相对较高。(2)从地面雨强分布来看,不同的云凝结核浓度对暴雨、大雨、中雨、小雨的影响均体现在降水强度上,对降水位相的影响不显著。(3)云凝结核浓度的变化对低云量的影响与其对降水的影响相一致,故低云量是影响降水的一个重要因素。

A precipitation process occurring during the opening ceremony of Olympic Games in Bei- jing was simulated by WRF v3.6.1 model coupled with Thompson cloud microphysical scheme, moreover, the effects of high, median and low Cloud Condensation Nucleus（CCN） concentration on rainfall were an- alyzed by comparing three groups of simulations. It was found that ： （ 1 ） In the case of low concentration of CCN, the increasing of CCN concentration results in the enhanced amount of 24 h accumulated precip itation with a relative low extent, while in the case of high concentration of CCN, it is to the contrary. （2） From the distribution of rainfall intensity, the effects of CCN concentration variation on hard, heavy, moderate, light rain are both reflected in rainfall intensity, but not in precipitation phase. （3） The effects of CCN concentration on low cloud fraction are the same with the effects of it on rainfall, so the low cloud fraction is a key cause of the precipitation variation.