南京城市下垫面变化对夏季臭氧浓度的影响研究

利用南京基准地面气象站1951~2010年的气象数据分析南京气象要素的长期变化,利用2007年南京草场门大气污染物监测数据探讨O3同气象要素之间关系并分析气象要素改变对污染的可能影响,结合WRF-CALGRID模式基于2008年7月的情景模拟研究1990年代以后南京城市下垫面变化对气象要素变化的贡献,并分析其对O3浓度的影响.结果显示,南京气温呈现增长趋势,平均风速、大气湿度、日照时数呈现降低趋势.气温与O3浓度呈一定的正相关关系、较小的风速和相对湿度有利于O3的生成.城市下垫面的增加使得南京城区气温增高超过1℃、风速减小0.4m/s、湿度下降0.5g/kg、混合层高度增加100m.气象要素的改变使地面NOx浓度减小,最大减小量超过6×10-9.对O3浓度的影响有增有减,南京市北部、西部增加,增加量超过2×10-9,主要受温度增加、风速减小以及NO的垂直输送影响;主城区的南部、东部O3浓度减小,减少量1×10-9~3×10-9,主要受混合层高度增加的影响.

Study on the effects of urban expansion on region climate and ozone pollution over Nanjing in summer

Based on the meteorological observation data from 1951 to 2010 at the station 58238, as well as air pollutant monitoring data in 2007 from Caochangmen air quality monitoring stations, the variation trend of the meteorological factors in Nanjing and the relationship between air pollution and meteorology were analyzed. With the aid of WRF-CALGRID, impacts of urbanization on local meteorological fields and ozone concentration over Nanjing were discussed. The results show that the elevated air temperature, the decreased wind speed and the reduced air humidity in Nanjing can be attributed to urban sprawl. And in consideration of the effects of meteorological factors, such as air temperature and wind, on the concentration of ozone, urbanization in Nanjing may evidently impact ozone formation and distribution. The simulated results illustrated that changes of land-use in Nanjing cause an increase in air temperature over 1℃, a decrease in wind speed with 0.4m/s, a decrease in air humidity with 0.5g/kg, and an increase in mixing layer height with 100m. Urbanization reduces near surface NOx concentration due to the increase of PBLH, with the maximum decrease over 6×10-9. In the north and west of Nanjing, urbanization increases the concentration of O3 with the value over 2×10-9, which can be related to the increase of air temperature, the decrease of wind speed and the change of NO. In the south and east of Nanjing, O3 can be lowered about 1×10-9~3×10-9 due to the increase of the height of mixing layer.