Comparison of the ocean inherent optical properties obtained from measurements and inverse modeling

Abstract

A model developed recently by Loisel and Stramski [Appl. Opt. 39, 3001–3011 (2000)] for estimating the spectral absorption a(λ), scattering b(λ), and backscattering b _b(λ) coefficients in the upper ocean from the irradiance reflectance just beneath the sea surface R(λ, z = 0^-) and the diffuse attenuation of downwelling irradiance within the surface layer 〈K _d(λ)〉₁ is compared with measurements. Field data for this comparison were collected in different areas including off-shore and near-shore waters off southern California and around Europe. The a(λ) and b _b(λ) values predicted by the model in the blue-green spectral region show generally good agreement with measurements that covered a broad range of conditions from clear oligotrophic waters to turbid coastal waters affected by river discharge. The agreement is still good if the model estimates of a(λ) and b _b(λ) are based on R(λ, z = 0^-) used as the only input to the model available from measurements [as opposed to both R(λ, z = 0^-) and 〈K _d(λ)〉₁ being measured]. This particular mode of operation of the model is relevant to ocean-color remote-sensing applications. In contrast to a(λ) and b _b(λ) the comparison between the modeled and the measured b(λ) shows large discrepancies. These discrepancies are most likely attributable to significant variations in the scattering phase function of suspended particulate matter, which were not included in the development of the model.