Aerosol Optical Properties above Productive Waters of Gorky Reservoir for Atmospheric Correction of Sentinel-3/OLCI Images
Fedorov, S. V., Molkov, A. A., Kalinskaya, D. V.
Atmospheric correction (AC) of productive inland waters is hampered by the difficulty of separating aerosol radiance from water-leaving radiance in the near-infrared, which corrupts both the retrieved aerosol parameters and the remote-sensing reflectance (Rrs). For the Gorky Reservoir, where the team develops regional bio-optical models, this is compounded by the absence of nearby AERONET stations. Standard AC algorithms greatly overestimate aerosol radiance during intense cyanobacteria blooms, whereas fixing the aerosol optical depth (AOD) from a clean-water area gives encouraging results. Regular in-situ AOD and Ångström-exponent measurements with a handheld sun photometer were compared with two Sentinel-3/OLCI Level-2 products (SYN and OL_2_WFR), which overestimated AOD by two to three times. Applying AC with a fixed, measured AOD removed negative Rrs and recovered spectra typical of the reservoir; AOD spectra at low percentiles of the pixel distribution approximate the measured spectrum, giving Rrs errors of 3–35% in the green and red OLCI bands.