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18 d 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0.3~0.4 km,局地可降低2~3 km;城市面积扩张可导致模拟日平均灰霾小时数增加0.3~0.5 h,最大增加可达5 h,苏州地区灰霾面积增加170 km2.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0.1 km,局地降低0.3~0.6 km.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 U-niversity 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 1 986,1 995 and 2006 are used in the simulations and 18 d in Mid January,April,July and October are chosen to simulate.Another 2 pairs 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 2 decades may result in an increase of the PM2.5 concentration by 3~4 μg·m-3 (25~32 μg·m-3 in local area)and a decrease of visibility by 0.3~0.4 km(2~3 km in local area).Consequently,the average haze hours increase by 0.3~0.5 h(5 h at most),and the haze area increases by 1 70 km2 .The changes of building may result in an increase of PM2.5 concentration by 6~12 μg·m-3 in some area and a decrease of visibility by 0.1 km(0.3~0.6 km 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.