Seawater optical property estimation from in situ irradiance measurements

A simple algorithm that solves the inverse problem is numerically tested for estimating the ratio of the absorption to the transport coefficients from measurements of the irradiance and scalar irradiance at depths sufficiently beneath the surface of seawater. Results of radiative transfer calculations with a phase function for San Diego harbor seawater were used to test the algorithm and show that the ratio is quite insensitive to the depth of the measurements and to the direction of incident solar radiation unless the absorption is very weak. A second algorithm, based on the assumption that the radiance in the diffusion regime is proportional to a (one-parameter) Henyey-Greenstein shape, is examined for estimating the ratio of the backward scattering to absorption coefficients from only irradiance measurements. The algorithm has the advantage that no scalar irradiance measurements are required, but it provides significantly poorer estimates because the radiance is not sufficiently close to the Henyey-Greenst in shape.