Correction methods for low-altitude remote sensing of ocean colo

The spectral distribution of light emerging from the ocean interior, referred to as ocean color, carries information about water composition, particularly about biologically useful chlorophyll concentrations in the surface layer. When ocean color is measured from a remote platform above the ocean (e.g. from ship, aircraft or satellite) the signal received by the sensor contains contributions from surface reflection and atmospheric scattering in addition to the desired water-leaving radiance. In order to retrieve spectral water-leaving radiance from the total signal, these unwanted contributions have to be quantified and removed from the spectra by a correction algorithm. The accuracy of those algorithms are critical for the reliability of the remotely acquired ocean color data.;The main difficulty in correction of above-surface ocean color measurements for surface glint is to account for the reflection of variable sky with randomly scattered clouds from a rough sea. This work represents an attempt to construct an operational surface glint correction method for low-altitude remote sensing of ocean color that applies for variable sky conditions. The method introduces diffuse sky irradiance as the key variable that is used in the sky-glint correction. The proposed surface-glint correction method was successfully tested on data collected by a ship-mounted radiometer in the equatorial Pacific, where the results derived by correction are compared with direct in-water measurements. The procedures necessary to correct low-flying aircraft data for surface glint and atmospheric effects was assessed on dataset collected in the Bering Sea from altitudes 150--300 m. After atmospheric correction, the sky irradiance estimated from a clear sky model was used in the sky-glint correction. The results demonstrate that the low-altitude remote ocean color data collected under clear or variable sky conditions can be accurately corrected for surface glint using measurements of diffuse sky irradiance.