Polarization characteristics of water-leaving radiance: application to separation of fluorescence and scattering components in coastal waters

摘要

Previously, it was shown that it is possible to separate the elastic scattering from the chlorophyll fluorescence signal using a polarization discrimination technique. The separation procedure depends however fundamentally on the degree of polarization of the water leaving radiance. In this paper, we study this dependence by simulating the total and polarized reflectance of waterleaving radiances originating from elastic scattering in case 1 and case 2 waters, by superimposing upon these reflectances the contribution of known fluorescence spectra, and by using our procedure to invert the resulting data back into fluorescence spectra. It is shown that the results of this retrieval compare well with the input values of fluorescence spectra for a wide range of underwater light scattering conditions. We show also that height baseline method, which is frequently used for the retrieval of fluorescence, can lead to significant overestimation of fluorescence for coastal zone conditions. The effects of different depths, surface roughness and bottom albedo are also analyzed. It is shown that in most cases fluorescence can be successfully retrieved with acceptable accuracy.