城市化发展对苏州灰霾影响的数值模拟

Numerical simulation of the impact of urban growth on Suzhou's urban haze

城市面积扩张、建筑密度加大等城市化特征会影响城市气象环境,导致城市污染物扩散能力减弱,这可能对中国城市灰霾有一定贡献.本文利用南京大学空气质量预报模式（NJU-CAQPS）研究了苏州城市化发展对灰霾的影响.本文利用苏州地区1986年、1996年、2006年三个年代的地表类型资料对苏州地区2010年1、4、7、10月中旬共18d灰霾状况进行数值模拟,同时进行了建筑高度和建筑密度对灰霾影响的敏感性试验.结果表明：近20年的城市面积扩张可导致城区PM2.5平均浓度增加3～4μg·m^-3,城市部分地区PM2.5增加可达25～32μg·m^-3;使城区平均能见度降低0.3～0.4km,局地可降低2～3km;城市面积扩张可导致模拟日平均灰霾小时数增加0.3～0.5h,最大增加可达5h,苏州地区灰霾面积增加170km^2.城市建筑高度和密度的增加使城区部分地区PM2.5增加6～12μg·m^-3;平均能见度降低0.1km,局地降低0.3～0.6km.城市化发展对局地污染物浓度影响较大,城市面积对城市灰霾的影响远大于建筑高度和密度的影响.随着城市面积扩张,城市＂混浊岛＂、＂灰霾线＂的高度在升高.

The expansion of urban size and denser buildings may have an impact on urban meteorology and environment,weakening urban＇s diffusion capacity,which may lead to urban haze in China.NJU-CAQPS（NanJing University City Air Quality Prediction System）is used in this research to simulate the impact of urban growth on urban haze in Suzhou area.The land-use data of 1986,1995 and 2006are used in the simulations and 18 d in Mid January,April,July and October are chosen to simulate.Another 2pairs of sensitivity experiments are performed to study the impact of the height and density of buildings on the urban haze.The urban expansionin the last 2decades may result in an increase of the PM2.5concentration by 3～4μg·m^-3（25～32μg·m^-3 in local area）and a decrease of visibility by 0.3～0.4km（2～3km in local area）.Consequently,the average haze hours increase by 0.3～0.5h（5hat most）,and the haze area increases by 170km^2.The changes of building may result in an increase of PM2.5concentration by 6～12μg·m^-3 in some area and a decrease of visibility by 0.1km（0.3～0.6km in local area）.The impact of urbanization onpollutants concentration is more significant in the local area of pollutants source,and the expansion of urban size plays a more important role than the changes of buildings.The urban ＂muddy island＂and ＂haze line＂elevate as the urban size expand.