Bottom Reflectance Discrimination Using Water Leaving Radiance from Coastal Zone Color Scanner.

摘要

A method of discriminating radiance due to bright bottom reflectance from water volume reflectance has been developed for evaluating Coastal Zone Color Scanner (CZCS) products of chlorophyll concentrations and diffuse attenuation coefficients. A simple three-band threshold algorithm is applied to CZCS water leaving radiance at 443,520, and 550 nanometers. Thirty CZCS images were processed to characterize normalized water leaving radiances in three-channels. Statistics were obtained from reflectance signatures in areas of known bottom reflectance and areas of high volume scattering (significant sediment concentrations and low chlorophyll concentrations). High bottom reflectance areas located in clear shallow waters (optically shallow) of Bahamian and Florida Keys were found to have higher water leaving radiance in all three channels than areas of exclusively high volume scattering (optically deep), e.g. Mississippi Delta, Chesapeake Bay, and Sargasso Sea. Radiances exceeding thresholds in any of the three spectral channels are assumed to be corrupted by bottom reflectance and derived bio-optical products are assumed to be invalid. Comparisons of bottom corrupted pixels are in close agreement with charted bathymetry and in-situ ship radiance data.