Inversion of reflectance spectra of nonchlorophyllous turbid coastal waters

This article deals with the inversion of reflectance spectra measured in th e Rhone River mouth area during a flood event in terms of parameters charac terizing the turbid renter components. The optically active constituents co nsidered are the total suspended matter, mainly composed of sediment, of kn own concentration ranging from 3.7 mg L-1 to 234 mg L-1, and yellow substan ce. A simple reflectance model is presented. Scattering is treated by Mie t heory applied to a collection of particles of real refractive index m(p) an d obeying a Jungle size distribution law. A sensitivity study performed on the model shows that both concentration ann refractive index and both cutof f particle diameters of the Junge size distribution law cannot be accuratel y determined from a given reflectance spectrum. Two model parameters, among a total of six, are estimated from model inversion: m(p) and a parameter c haracterizing the yellow substance absorption spectrum, a(y0)=a(y) (440 nm) . The derived values are realistic as compared to the values that can be fo und in literature. Other combinations of parameters could be determined by inversion but measurement of m(p) and a(y0) from reflectance spectra alread y has interesting applications in a satellite remote sensing perspective. I ncreasing the number of parameters of the model is feasible, but much work is needed to envisage the inverse problem. (C) Elsevier Science Inc.. 1999.