Evaluation of CALIOP derived backscattering coefficient (<i>b</i>_bp(532)) product over contrasted oceanic waters

CALIOP satellite sensor offers advantages over passive sensors, particularly during nighttime and in polar-subpolar regions. Though originally designed for atmospheric studies, it was adapted to retrieve the backscattering coefficient at 532 nm, b_bp(532) in the ocean. Scarce matchups and the lack of standardized protocol hindered previous validation efforts. An evaluation using a standardized protocol and diverse in-situ datasets from contrasted oceanic waters was carried out for the period 2008-2021, with the 2018-2021 period being evaluated for the first time. A strong correlation was observed with R² up to 0.94 (RMS: 0.001-0.01 m^-1, MRE: 42.7%-63%, bias: 36.88%-13.09%). A comparison with MODIS-Aqua b_bp(532) product was performed showing comparable estimates of b_bp(532). BGC-Argo data from 2018-2021 were also used to evaluate CALIOP b_bp(532), revealing a lower correlation compared to 2008-2021 period, probably due to a decrease in CALIOP lidar power.