Estimation Of Surface NO₂ Concentration Based On Remote Sensing And Atmospheric Transport Model

NO₂?Nitrogen Dioxide?is one of the crucial trace gases in atmosphere,which has strong affect on the atmospheric environment,human lives and ecological environment.The temporal and spatial distribution of surface NO₂ is important to study the atmospheric environment in China,and it is also guideline and reference to recognize the role of trace gases in air chemical reaction and control of air quality in China.This study aims to simulate surface NO₂ concentrations in China using remote sensing data and the simulated data by MOZART.Gaussian formula was used to simulate the vertical profile of atmospheric NO₂ according to three dimension NO₂ output by MOZART.With the simulated Gaussian formulas and NO₂ tropospheric column densities retrieved by OMI,NO₂ vertical profile and surface NO₂ illustrated by remote sensed data was calculated.The vertical profiles fitted by Gaussian formula was well simulated as almost all of the determination coefficient R²>0.95,accounting for 99.99%,with the root mean square error?RMSE?of 4.88×10⁷molec./cm³.The best fitting results occurred in winter,while worst in spring,and good fitting results were in most area of China.Verification on estimated surface NO₂ with the ground-based observations showed that the surface NO₂ simulatd could reflect the atmospheric NO₂ concentrations in low atmospheric boundary layer than the remote sensing NO₂ observed by OMI,and the simulation results in the south is lower than observed.According to the analysis on city scale and regional scale,result from this study is more sensitive to surface NO₂ on spatial heterogeneity than on temporal heterogeneity.And then,vertical profiles of NO₂ combined with air mass vectors by the forward trajectory and cross-section drawn were analyzed and discussed in the eight physicogeographical regions in China.Finally,temporal and spatial distribution of surface NO₂ was calculated,analyzed and discussed.Main conclusions are listed below:The average vertical profiles in the eight physicogeographical regions is different.Below the height of 2km,vertical profiles illustrated by remote sensing data are higher in Huabei and Huazhong regions than that in others,in 2007.Above height of 2km,the shape of NO₂ vertical profile are various and change of NO₂ concentration are different from low layers,vertical and horizontal convection current,atmospheric transportation and lightning make influences on distribution of NO₂ above this height.Comprehensive analysis with air mass vectors by the forward trajectory,in Jingjinji region,NO₂ is mainly exist under 1km in the atmosphere,and effect NO₂ concentrations on height of 1km in south of Hebei and north of Henan,west of Shandong and on height of 600m to 1km in China yellow sea and East China sea.In the north of Xinjiang,vertical and horizontal transportation is un-obvious,high NO₂ concentration mainly exist under 200m.NO₂ coming from Yangtz River Delta effect the NO₂ concentration above southeastern coastal areas,Anhui,north of Jiangsu and Shandong,and transport vertically high,higher NO₂ concentration than around on height of 600m to 1000m.From NO₂ vertical cross-section at latitude 37°N,the high NO₂ concentration area is mainly located between 110°E to 124°E in China,and this range changes influenced by seasonal NO₂ fluctuation in Jingjinji region.Concentration gradient is high from ground to high air place in winter in Jingjinji region,and the nearer to the high concentrations the faster changing of NO₂ content in both vertical and horizontal direction.The contour line of value 10×10¹⁰molec./cm³ reach up to 1km in autumn and winter,while to 500m in other season.According to temporal and spatial analysis of reversed surface NO₂,for the whole nation,the surface NO₂ concentration is higher in east than west,north than south,and NO₂ concentrations are high in the north of Xinjiang.Area with high NO₂ concentration is expanding,indicating more territory with surface NO₂ increasing in China.Surface NO₂ concentration increased in annual rate of 0.046×10¹⁰molec./cm³ in the whole nation,and showed seasonal fluctuation in different regions,high in winter and low in summer.Based on regional statistics,the surface NO₂ concentration increased by different rates in all regions,except Huanan region.According to regions' average surface NO₂ concentration from 2007 to 2014,the order is followed as Huabei>Huazhong>Huanan>Dongbei>Neimeng>Xibei>Xinan>Qingzang.Among them,Huabei has the most serious NO₂ polluted area.Huabei has the highest changes of surface NO₂ every year,and has positive effect on changes of whole nation's surface NO₂ concentration.This study showed that the method proposed in this study could gain high spatial resolution of NO₂ profiles,based on the remote sensing and atmospheric transport model data.And NO₂ content in different regions are effected by NO₂ from local and neighborhood.