Retrieval Of Ground-level NO₂ And SO₂ Concentrations From Satellite Observations

In the past decades,air pollution has increasingly significant impact on atmosphere quality and climate change,it has become an urgent problem caused great concern.Nitrogen dioxide?NO₂?and Sulfur dioxide?SO₂?are pollutant trace gases in the atmosphere that play important roles in atmospheric tropospheric chemistry and air pollution.This paper focused on the algorithm for retrieval of tropospheric NO₂ columns by the Ozone Monitoring Instrument?OMI?.In addition,this paper retrieved SO₂ vertical columns using the Band Residual Difference algorithm?BRD?by OMI.The retrieved NO₂,SO₂ columns were compared with OMI level 2 products and the ground-based MAX-DOAS columns.However,public concern and related research based on satellite observations of NO₂,SO₂ columns have been focusing mainly on tropospheric NO₂,SO₂ columns instead of the ground-level NO₂,SO₂ concentrations,but in practice ground-level NO₂,SO₂ concentrations are more closely linked to anthropogenic emissions and human health.So this paper presents one method to derive the ground-level NO₂,SO₂ concentrations using the total column of NO₂,SO₂ observed from OMI and the simulations from the Community Multi-scale Air Quality?CMAQ?.The results were compared with ground-based NO₂,SO₂ measurements from a network of China's National Environmental Monitoring Centre?CNEMC?.The main results are summarized as follows:?1?The algorithm using DOAS method for the retrieval of tropospheric NO₂ columns by OMI is developed,and the retrieved tropospheric NO₂ columns were compared with OMI level 2 NO₂ products and the ground-based MAX-DOAS NO₂ columns.Correlations coefficients were 0.90 and 0.72,respectively.?2?The algorithm using BRD method for the retrieval of SO₂ vertical columns by OMI is developed,and the retrieved SO₂ vertical columns were compared with the ground-based MAX-DOAS SO₂ columns.Correlations coefficients were about 0.55.?3?A means of estimating ground-level NO₂ concentrations based on OMI tropospheric NO₂ columns and the vertical distribution of tropospheric NO₂ profiles simulated using the RAMS-CMAQ model was presented.The different spatial resolution from the OMI level 3 NO₂ product and simulation from the RAMS-CMAQ modeling system has hindered the estimating ground-level NO₂ concentrations,so optimal interpolative assimilation method was used to reconstruct consistent spatial resolution.The retrieved ground-level NO₂ concentrations were compared with ground-based NO₂ measurements from a network of China's National Environmental Monitoring Centre?CNEMC?.Take the ground-level NO₂ concentrations over China in January,2014 as example,the standard deviation between the CMAQ simulated measurements and in-situ measurements by CNEMC was 21.79 ?g/m3,it was improved to 18.90 ?g/m3 between our method and CNEMC data,the variance between our method and that released by CNEMC was 257.19,and the variance between the RAMS-CMAQ and CNEMC data was 353.09.?4?A means of estimating ground-level SO₂ concentrations based on OMI SO₂ columns and the vertical distribution of SO₂ columns profiles simulated using the RAMS-CMAQ model was presented.The retrieved ground-level SO₂ concentrations were compared with ground-based NO₂ measurements from CNEMC.Take the derived ground-level SO₂ concentrations over Beijing in the four seasons,2014 as example,correlations coefficients between our method and CNEMC data was 0.60.At present the research of estimating ground-level NO₂,SO₂ concentrations based on satellite observation is still immature.In view of this research gap,this paper presented one method to derive the ground-level NO₂,SO₂ concentrations using the total column of NO₂,SO₂ observed from the OMI and the simulations from the CMAQ,and the derived results were verified.In the future we will conduct research for the application of the derived ground-level NO₂,SO₂ concentrations in the field of NO₂,SO₂ artificial emission monitoring and atmospheric pollutant emission inventory verification.