The polarization properties of reflectance from coastal waters and the ocean-atmosphere system

The polarization characteristics of the water leaving radiance can provide information on bio-optical properties and composition of coastal water and can be used as well as a tool for the separation of chlorophyll fluorescence from elastic reflectance spectra. We report the results of simulations using a coupled ocean-atmosphere vector radiative transfer code (NASA GISS) to obtain the polarized reflectance for various water compositions typical for coastal zones, as function of wavelength and sun/sensor geometry. Results show that even for sensor orientations outside of the principal scattering plane, the polarization can nearly approach the maximum values observable in the principal scattering plane thereby minimizing undesirable sun glint effects. Simulations are complemented by laboratory and field measurements in Chesapeake Bay and near Sapelo Island, GA. We also report the results of the fluorescence retrieval from reflectance spectra using polarization discrimination as well as fluorescence line height (FLH) algorithms. Performance of these algorithms is analyzed in conjunction with the relationship between fluorescence magnitude and chlorophyll concentrations in the conditions typical for coastal waters.