[The influence of nonuniform vertical profiles of chlorophyll concentration on apparent optical properties]

Previous researches on ocean optics and ocean color were based on the assumption that inherent optical properties and optically significant constituents of seawater are homogeneous in the vertical direction. However, oceanographic observations show that the assumption is not always exact and the vertical inhomogeneity of them exists in the upper ocean. The purpose of the present research is to study the effect of nonuniform vertical profiles of chlorophyll concentration on apparent optical properties with radiative transfer model Hydrolight. The vertical profiles of chlorophyll concentration were approximated according to a Gaussian function (Lewis et al, 1983). The apparent optical properties of seawater with nonuniform chlorophyll concentration profiles were simulated with Hydrolight radiative transfer model and case-1 bio-optical model, and then compared with those for homogenous ocean whose chlorophyll concentration was identical to the background chlorophyll concentration of inhomogenous cases. The results reveal that the subsurface maximal chlorophyll concentration increases the remote sensing reflectance at the blue wavelength and decreases it at the green wavelength, nonuniform vertical profiles of chlorophyll concentration change the diffuse attenuation coefficient profiles and the angular structure of the light field in the seawater, and the diffuse attenuation coefficients maximum and average cosines minimum appear at the depth of the maximal chlorophyll concentration.