北京及周边城市气溶胶污染对城市降水的影响  

Impacts of aerosols from Beijing and the surrounding areas on urban precipitation

作　　者：陈卫东[1,2,3] 付丹红[4] 苗世光[1] 张亦洲[1] 

机构地区：[1]中国气象局北京城市气象研究所,北京100089 [2]中国气象科学研究院,北京100081 [3]中国电力科学研究院,南京210003 [4]中国科学院大气物理研究所,北京100029

出　　处：《科学通报》2015年第22期2124-2135,共12页Chinese Science Bulletin

基　　金：国家自然科学基金(41175015,41175122)资助

摘　　要：利用中尺度可分辨云模式(Weather Research and Forecasting,WRF)研究了北京及周边城市气溶胶污染对城市降水的影响.结果表明:2011年8月14日北京地区一次强降水过程中,城市气溶胶污染对区域平均降水量均有一定的增加作用,城市轻度污染型区域平均降水量增加39.42%,城市污染型降水增加15.63%,城市重度污染型降水增加12.28%.城市污染背景下,区域平均降水量随气溶胶浓度增加而逐渐减小,城市污染型相对于城市轻度污染型区域平均降水量减少约17%.这主要是由于城市污染气溶胶增多使得云凝结核(CCN)增多,云滴数浓度增加,云滴有效半径减小,零度层以下云滴碰并效率降低,抑制云水向雨水的转化,雨滴数浓度减少,雨滴蒸发过程减弱,不利于零度层以下强下沉气流的发展和维持,地面冷池和最大风速减弱,低层辐合抬升减弱,不利于水汽垂直输送和降水的转化,地面降水减小.城市污染气溶胶通过云微物理过程影响热力场和动力场影响地面降水过程.The aerosol properties and possible impacts on a convective precipitation case on 14 August 2008 over the Beijing region are investigated by using Weather Research and Forecasting Model （WRF）. The results show that the domain-averaged precipitation amount can be increased up to 39.42%, 15.63% and 12.28% under slightly, moderately and heavily polluted conditions, respectively. Under polluted conditions, the increase of aerosols can lead to the decrease of the domain-averaged precipitation amount over the Beijing region. The domain-averaged precipitation amount can be reduced about 17% between light polluted and polluted conditions, which is mainly caused by the increase of the number of cloud condensation nuclei and cloud droplets and the decrease of cloud droplet effective radius. Many small cloud droplets nucleating from high aerosol concentrations may not grow larger, and coalesce very inefficiently into raindrops, and the cooling processes of the raindrops weaken, which is not favorable to the development and maintain of downdrafts and lead to the decreases of the surface outflow wind speed and cold pool near the surface, and the low-level convergence produced by the interactions between low-level cold outflows and large-scale low-level airflow weakens, which is not favorable to the vertical transport of water vapor and conversion of precipitation, and leads to the decrease of precipitation. Therefore, the mainly mechanism is the effects of the cloud and microphysical processes on the thermal and dynamic fields under polluted conditions.

关 键 词：气溶胶 降水 数值模拟 

分 类 号：X513[环境科学与工程—环境工程] P426.6[天文地球—大气科学及气象学]