ATTENUATION OF VISIBLE-LIGHT BY PHYTOPLANKTON IN A VERTICALLY STRUCTURED OCEAN - SOLUTIONS AND APPLICATIONS

To find the solution to problems in applied marine optics, we do not a lways need to compute the submarine irradiance at all depths; in many cases, it is sufficient to know the average attenuation of light for f inite layers of arbitrary thickness. If multiple scattering can be neg lected, the average attenuation of light in a finite layer of the wate r column depends only on the vertical distribution of the attenuating substances; in open-ocean waters, the most important of these is phyto plankton. It is shown how the average attenuation of monochromatic lig ht in an arbitrary layer can be determined when the vertical pigment p rofile takes one of two standardized forms: a shifted Gaussian or a tr iangle. The choice of efficient algorithms to compute the attenuation in a layer using these models is discussed. The extension to polychrom atic light involves the selection of a function to represent the spect ral distribution of the specific absorption coefficient for phytoplank ton, as determined by observation. Chebyshev polynomial representation is shown to be convenient for applications which require the calculat ion of a weighted wavelength integral. An efficient procedure for the evaluation of these integrals, Gauss-Chebyshev quadrature, is presente d and evaluated. The extension to the computation of bulk properties f or discrete layers is straightforward.