Improved Absorbing Aerosol Index Results for EMI on Board Atmospheric Environment Monitoring Satellite

Following the success of the environmental trace gases monitoring instrument (EMI) on board the GaoFen5 satellite, algorithms have been applied to the EMI onboard the atmospheric environment monitoring satellite (DQ-1) to provide global absorbing aerosol index (AAI) products. Despite improvements to the accuracy of satellite-derived AAI products, the presence of viewing geometries and radiometric calibration problems substantially degrade EMI AAI product quality. To overcome these constraints, we propose a reflectance correction method based on a large-scale statistical method. Appropriate correction coefficients were determined for each ground pixel in the EMI reflectances for the ultraviolet visible through a comparison with reflectances calculated using the radiative transfer model, and correction coefficients were applied to AAI results to remove the structural features induced by viewing geometries and radiometric calibration problems. Reflectance calibration was performed using extensive real-time data from global regions collected between June 2022 and January 2023. The corrected reflectances were then used to derive the AAI and analyze seasonal variations. Based on a comprehensive validation of the TROPOMI products, the proposed method significantly improved the capability of EMI in identifying aerosol plumes and provided a more homogeneous AAI distribution. The correction method is satisfying for eliminating the asymmetry in AAI values. The comparison of the EMI with TROPOMI shows a high correlation of 0.91 and a root mean square of 0.296.