Characterization of radiance from the ocean surface by hyperspectral imaging.

A novel snapshot hyperspectral imager is introduced for ocean color (OC) applications and its capabilities are demonstrated. The instrument provides hyperspectral radiance images with a wide field-of-view (FOV) and short exposure time, which is valuable for the direct characterization of the wind-roughened surface in various illumination conditions and wind speeds. Uncertainties in the total(L), sky (L) and derived water-leaving (L)radiances at viewing angles of 20-60° are determined as a function of wind speed together with associated correlation coefficients and variances of the sea surface reflectance coefficient ρ. Estimated L uncertainties can partially explain the inaccuracy of satellite retrievals in the blue bands in the coastal waters. It is shown that in above-water measurements in no-glint conditions with viewing and azimuth angles of 40° and 90°, respectively, for both L(λ) and L(λ) the impact of FOV is minimal at least up to measured W = 5.7 m/s for full-angle FOV of 4° and larger. Implications of uncertainties for the derivation of water leaving radiance in above-water ship-borne and AERONET-OC measurements are discussed.