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, th e eigenfunction of the radiative transfer equation that describes the asymptotic behavior of the angular dependence of the radiation at larg e depths. Calculations were performed for wavelengths ranging from 400 to 700 nm and for chlorophyll concentrations of 0.01-10 mg m-3. The c oefficients monotonically increase with increasing concentration, but not with increasing wavelength. Values at different wavelengths can va ry by as much as a factor of four for concentrations of 1 mg m-3 or gr eater. 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 opt ical properties of water from vector irradiance and scalar irradiance data.