北京地区城市环境对云和降水影响的个例数值模拟研究

Numerical simulation of urban environment impacts on clouds and precipitation in Beijing

本文利用中尺度可分辨云模式(WRF,Weather Research and Forecasting)对2011年8月14日北京地区一次强降水过程进行了数值模拟和敏感性试验,研究了城市环境(包括城市气溶胶和城市地表)对北京地区云和降水的影响.研究结果表明:城市气溶胶污染增强和城市地表使得北京地区(城区和周边)降水量减少,对城区平均累积降水量的影响作用分别为-38.92%和-3.4%.降水系统向北京主城区移动过程中,城市气溶胶在城市环境影响降水过程中的作用逐渐减小为85.13%,城市地表的作用增加到14.87%.城市污染气溶胶增强,使得非降水性粒子增多,而降水性粒子减少,这不利于对流的发展增强,使得水汽的垂直输送减弱,导致区域降水量减小.城市地表对强对流的发展也表现为减弱作用,这使得水汽的垂直输送减小,区域降水量减小.

A heavy rainfall on August 14, 2011 were simulated and sensitively tested by using Weather Research and Forecasting Model （WRF） to study the urban environment （including urban aerosol and urban surface） on the influence of clouds and precipitation in Beijing. Results show that, the pollution of aerosols and urban surface reduce the precipitation of Beiiing （urban area and surrounding）, the effect of average cumulative rainfall in urban areas were —38. 92% and —3. 4% respectively. Precipitation system in the process of moving to main urban area of Beijing, the role of urban aerosols decrease to 85. 13＆, the role of urban surface increases to 14. 87% in the urban environment affecting precipitation process. The pollution of aerosols increasing non-precipitation particles and reducing precipitation particles, which is not conducive to the development of enhanced convection, so that the vertical transport of water vapor weakened, resulting in regional precipitation decreases. Urban surface also has a weakening effect on the development of enhanced convection and vertically transport of water vapor, and therefore reduce regional precipitation.