iCOR Atmospheric Correction on Sentinel-3/OLCI over Land: Intercomparison with AERONET, RadCalNet, and SYN Level-2

To validate the iCOR atmospheric correction algorithm applied to Sentinel-3 Ocean and Land Color Instrument (OLCI), Top-of-Atmosphere (TOA) observations over land, globally retrieved Aerosol Optical Thickness (AOT), Top-of-Canopy (TOC) reflectance, Vegetation Indices (VIs) were intercompared with (i) AERONET AOT AERONET-based TOC reflectance simulations, (ii) RadCalNet surface observations, (iii) SYN Level 2 (L2) AOT, VIs. The results reveal that, overall, iCOR’s statistical temporal consistency is high. retrievals overestimate relative AERONET, but less than L2. L2 reflectances exhibit a negative bias of ~−0.01 −0.02, respectively, in Blue bands compared simulations. This diminishes for RED NIR, except +0.02 NIR. intercomparison shows differences < ±6%, Oa02 (Blue) Oa21 (NIR), which likely related reported OLCI “excess brightness”. between showed R2 = 0.80–0.93 0.92–0.96 VIs, respectively. higher smoothness does not propagate into significantly Altogether, we conclude that well suitable retrieve statistically temporally consistent VIs land surfaces from Sentinel-3/OLCI observations.