Sensitivity of aerosol models in satellite-based AOD retrieval: a quantitative analysis using Oceansat-3/OCM-3 multi-spectral measurements

This study examines the sensitivity of aerosol models in satellite-based measurements of aerosol optical depth (AOD), by comparing the retrievals using look-up-tables (LUTs) generated with two region/season-specific (RM) and three representative (GM) marine aerosol models. The RMs are developed based on ship-borne measurements over the Arabian Sea (AS) and the Bay of Bengal (BoB) in winter. AOD retrievals from Ocean Colour Monitor-3 (OCM-3), onboard Oceansat-3, are carried out using an in-house developed inversion algorithm. Compared to the retrievals using LUTs based on RMs, those with GMs show a negative bias of 15–22%. While the difference in single scattering albedo (SSA) accounts for 90% of this bias, that in angular scattering phase function contributes only 10%. Here, SSA values of GMs are 0.975, 0.997 and 0.998, whereas those of RMs are 0.87 and 0.88. Mean absolute difference, RMSE, linear regression slope (m) and correlation coefficient between the retrievals using RMs and GMs are 0.05 ± 0.04 (0.06 ± 0.04), 0.07 (0.06), 0.8 (0.7), and 0.99 (0.95), respectively, over AS (BoB). OCM-3 and MODIS AODs show good agreement; but the m value deviates from unity, potentially due to the higher SSA values of MODIS aerosol models. These results underscore the criticality of aerosol models in satellite-based retrievals of aerosol properties.