First TROPOMI Retrieval of Aerosol Effective Height Using O₄ Absorption Band at 477 nm and Aerosol Classification

Abstract

We retrieved aerosol effective height (AEH) values from TROPOspheric monitoring instrument (TROPOMI) measurements based on the O₄ absorption at 477 nm. As the first step in the AEH retrieval algorithm, TROPOMI carbon monoxide and aerosol index products were used for the first time to determine aerosol type. An online radiative transfer calculation method was introduced to the AEH retrieval process. The AEHs were retrieved over northeast Asia (various aerosol types), South Africa (biomass-burning smoke), and the Sahara Desert (dust). The retrieved AEHs were compared with AEHs derived using aerosol extinction profiles from ground and satellite-based lidar measurements. A preliminary evaluation based on comparison with lidar suggests reasonable performance, but shows that cloud masking is the main source of uncertainty. The errors associated with the online-based AEH retrieval algorithm were calculated using synthetic radiance. The total AEH retrieval errors were 0.91 km (0.4 le AOD < 1) and 0.30 km (2 le AOD < 3), highlighting the increased sensitivity of the AEH retrieval algorithm under high AOD conditions. This study demonstrates that the O₄ absorption band at 477 nm is applicable to aerosol height retrieval from TROPOMI with a high spatial resolution.