Fine-scale evolution pattern of ozone pollution in the city cluster of Sichuan Basin from observation and modeling perspectives
Based on air pollutants observation and meteorological data in the Sichuan Basin in August 2019,combined with the ERA5 reanalysis data,the changes of upper and lower level weather situation and ozone(O3)pollution during the episode were examined.In addition,the high-resolution mesoscale weather forecast model WRF and multi-scale air quality model CMAQ were used to explore the formation and transport of O3.The results showed that:①The distribution characteristics of ozone concentration were closely related to the distribution of wind direction and temperature,and the area of high O3 value mainly located in the high temperature area and the downwind of dominant wind direction.In the process of pollution,the South Asia High and the West Pacific Subtropical High steadily controlled the entire Sichuan Basin,where 700hPa and 850hPa were controlled by the high pressure,leading to prevailing downdraft,increase of surface temperature,promotion of the rapid O3 generation,and inhibition of the dilution and diffusion of surface O3 to the upper air.②The concentration and spatial distribution of O3 at 1000m height at night were greatly affected by the distribution of O3_8h at ground level and the transmission of wind field during the day.The low O3 values at night were mainly located at the bottom of the basin.Chengdu and Chongqing urban areas were affected by NO titration and were the two remarkable low-value centers in the night.The high-value O3 centers were blocked by mountains and accumulated in a zonal pattern at the edge of the basin.③The relative contributions of different physical and chemical processes to O3 concentration were quantified by process analysis in WRF-CMAQ model.Vertical transport processes and gas phase chemistry were the main sources of daytime O3,dry sedimentation and horizontal advection were the main sinks of surface O3.④The relative contribution of city-to-city transport to O3 concentration was estimated by ISAM comprehensive source analysis method.Under the influence of northeast wind transport,the contribution of model boundary to northeast Sichuan urban agglomeration was about 58.86％～79.23％.The southeast wind greatly affected the O3 concentration in Chongqing,contributing about 72.50％from model boundary.The main sources of NO2 contribution came from city itself and the surrounding regional transmission.The NOx emission in the northeast Sichuan urban agglomeration was lower than that in other regions of the Sichuan Basin,so the NO2 concentration imported from the model boundary and Chongqing had a greater contribution to the northeast Sichuan.⑤Biological sources,industrial sources and transportation sources contributed significantly to O3 concentration in the Sichuan Basin,while residential energy sources and power plants contributed less.The contribution rate of industrial sector in Chengdu,Deyang,Chongqing,Meishan,Neijiang and Yibin was relatively high.
万方数据
维普
