Cross-calibration Of FY4A AGRI Blue Channel And Its Application In Aerosol Monitoring

In recent years,air pollution has become an important factor affecting resident's health,daily life and sustainable urban development.Accurate inversion of aerosol optical depth by remote sensing and comprehensive monitoring of air pollution dynamics are of great demand value and scientific significance for environmental governance and urban planning.Based on the data of FY4 A AGRI,which is one of domestic geostationary meteorological satellites,the cross-calibration research of blue band was carries out in the Beijing-Tianjin-Hebei region,realizing the inversion of aerosol optical depth of FY4 A AGRI blue band from March to October 2018.The main achievements of research are summarized as follows:(1)Using the MODIS with high radiation accuracy as the reference sensor,based on the Dunhuang radiometric calibration field,the FY4 A AGRI radiometric calibration coefficient is corrected by cross-calibration principle,and the results have a comparative analysis and accuracy verification with the data of Dunhuang and Frome Lake radiometric calibration fields.The cross-calibration results show that the relative error of cross-calibration coefficients in Dunhuang and Frome Lake calibration field,are less than the original calibration error,5.80% and 2.84%,respectively.The factors of the simultaneous interpreting angle and the spectral response of different sensors all affect the accuracy of the cross-calibration.(2)Based on the MODIS surface reflectance data,considering the difference of spectral response function between AGRI and MODIS,the surface reflectance library of FY4 A AGRI blue band required for inversion of dark blue algorithm is obtained.After the corresponding angle correction at the AGRI imaging time,the aerosol optical depth of the AGRI blue band is reversed with the established surface reflectance database and the 6S look-up table combined.(3)FY4A AGRI inversion results are compared with MODIS aerosol products at similar times.The study shows that the overall spatial distribution trend of the two AOD inversion results is consistent and has a good correlation.The results indicatesthat using FY4 A AGRI blue band to retrieve the spatial distribution of aerosols is reasonable,and the AGRI aerosol inversion accuracy is affected by the AGRI blue band radiometric calibration accuracy,angle difference between the two sensors,spatial registration and others.(4)Taking April 27 and October 2,2018 as examples,the inversion results of AOD at 7 times a day are given.The analysis found that aerosol optical depth varies from time to time in one day,and the change of AOD is obvious in short period of time,which indicates that the aerosol optical depth inversion research based on the high spatial-temporal resolution of FY4 A AGRI data has important application value in monitoring the intraday change of aerosol in short time by remote sensing.