CHLOROPHYLL CONCENTRATION EFFECTS ON ASYMPTOTIC OPTICAL ATTENUATION

The concentration of chlorophyll in seawater has a significant effect on the asymptotic exponential decay coefficient and, in some cases, the eigenfunction of the radiative transfer equation that describes the asymptotic behavior of the angular dependence of the radiation at large depths. Calculations were performed for wavelengths ranging from 400 to 700 nm and for chlorophyll concentrations of 0.01-10 mg m-3. The coefficients monotonically increase with increasing concentration, but not with increasing wavelength. Values at different wavelengths can vary by as much as a factor of four for concentrations of 1 mg m-3 or greater. The eigenvalues calculated with the Henyey-Greenstein model for scattering anisotropy are in close agreement with those obtained with the delta-Eddington model. Suggestions from this investigation may be helpful when using ''asymptotic closure'' theories for estimating optical properties of water from vector irradiance and scalar irradiance data.