| With the acceleration of China's urbanization process,and the rapid,diversified development of the social economy,air pollution has shown a characteristic of complexxity and regionality.Regional air pollution formation is closely related to the three-dimensional distribution,accumulation and regional transport of the tropospheric pollutants.Therefore,it is of great significance to obtain the long-term three-dimensional monitoring data,and analyze the spatial-temporal variation of atmospheric pollutants for understanding the air pollution situation in China.Ground-based Multi Axis Differential Optical Absorption Spectroscopy(MAX-DO AS)technique is a state of the art remote sensing technique for deriving vertical profiles of trace gases and aerosols.The evaluation of profile inversions from MAX-DOAS under heavy aerosol pollution scenarios has not been systematically performed.Aiming at the accurate analysis of the spatio-temporal distribution under heavy aerosol pollution scenarios in China and the requirements of long-term observation for atmospheric pollutants,this study carried out the accurate inversion research by MAX-DOAS technology based on the ground-based passive DOAS network established by our research group.A high-precision inversion method of MAX-DOAS was established by studying the effects of heavy aerosol pollution on retrieving the aerosol and trace gas vertical column density and vertical distribution.By correcting the model input parameters and a priori profile information,the accuracy of the atmospheric pollutants(aerosol and trace gas)inversion during heavy aerosol pollution in autumn and winter was improved.The tropospheric column density of atmospheric trace pollution gases(such as SO2,NO2,HCHO)and aerosol,as well as their vertical distribution,had been observed for a long time by using the MAX-DOAS network in the Yangtze River Delta(YRD)area of eastern China,and the pollution transport and its influence on local air quality was studied during the important period of pollution process.Aiming at the needs of accurate inversion of aerosol and gaseous pollutant in heavy haze,the accurate inversion method of aerosol and pollutant gas suitable for China's atmospheric characteristics was studied based on the atmospheric radiation transfer model.By inputting and optimizing different aerosols types and atmospheric parameters,the effects of heavy aerosol on retrieving trace gas profile based on the PriAM and MAPA inversion algorithms were used to evaluated.PriAM and MAPA belong to the optimal estimation method and the look up table approach,respectively The effects of aerosol optical depths(AOD)ranged from 0.1 to 5.0 on retrieving three typical vertical profiles were analyzed,which were exponential,Gaussian and Boltzmann shapes.These two algor:ithms correctly retrieved the three profile shapes.PriAM was more suitable for Exponential profiles.For the Boltzmann profile,MAPA showed good results.The retrieved scale height of the Gaussian profile was underestimated by PriAM,but MAPA underestimated the value at the peak of the retrieved Gaussian profile.The effect on the inversion gas profile was less significant than aerosol profile inversion with AOD increasing.By optimizing the parameters and algorithms,the correlation coefficient between the inversion profile and the"real"profile was increased from 0.41 to 0.97 when AOD was 5.0.And the accuracy of the instrument performance and the inversion algorithm was verified by participating in international instrument comparison campaign.Based on the above research,long-term observation of trace gas temporal-spatial distribution from 2014 to 2018 were carried out by using the MAX-DO AS network in the Yangtze River Delta(Hefei,Nanjing,and Shanghai).Average diurnal variations of tropospheric NO2 and SO2 in different seasons over the three stations yielded minimum values at noon or in the early afternoon,whereas tropospheric HCHO reached the maximum during midday hours.Regional distribution results showed that overall trace gases concentration in Shanghai was the highest,and in Hefei was the lowest.Under static weather,the spatial distribution characteristics of trace gases and aerosols in the Yangtze River Delta indicated that the pollution was mainly concentrated below 1.5 km.According to analysis of regional transports of pollutants,pollution process in YRD area raised from west to east under the northwest wind.There were transport processes over Hefei and Nanjing,while Shanghai was dominated by ground accumulation.The pollution quickly dissipated under the influence of the southeast wind.And the pollution transport characteristics during the important periods Asia-Pacific Economic Cooperation(APEC)summit were studied.The pollution transport of HCHO during the APEC periods was measured using a MAX-DOAS instrument at the University of Chinese Academy of Science(UCAS)in Huairou District,Beijing.The secondary sources of HCHO through photochemical reactions of volatile organic compounds(VOCs)dominated the HCHO value in the area around UCAS,which was also considerably affected by the transport of pollutants(VOCs)from polluted areas in the south.We also compared the MAX-DOAS results with the Copernicus Atmosphere Monitoring Service(CAMS)model.The HCHO VCDs of the CAMS model and MAX-DOAS were generally consistent with a correlation coefficient R2 greater than 0.68.But the low values were systematically underestimated by the CAMS model.This finding may indicate that the CAMS model can adequately simulate the effects of the transport and the secondary sources of HCHO,but underestimates the local primary sources.Through the research of this thesis,the accuracy of retrieval polluted gases in the complex atmosphere by MAX-DOAS technology is improved.It is quite important for exploring the spatial-temporal distribution,the pollution evolution and transport of tropospheric trace gas based on the MAX-DOAS monitoring network in eastern China,and it also provides reliable data support for the verification of satellite observation and model simulation. |
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