CONCENTRATIONS OF CHLOROPHYLL, SUSPENDED MATTER, AND GELBSTOFF IN CASE-II WATERS DERIVED FROM SATELLITE COASTAL ZONE COLOR SCANNER DATA WITH INVERSE MODELING METHODS

Color ratio techniques used to derive chlorophyll concentrations from radiance data of the coastal zone color scanner (CZCS) fail in areas w ith high concentrations of suspended matter and gelbstoff (optically d efined as case II water). In order to take into account all water cons tituents which modify the backscattered radiation field as well as the aerosol path radiance, an inverse modeling technique based on a two-f low radiative transfer approximation and a simplex optimization proced ure has been developed. It uses simultaneously the radiances of the fi rst four CZCS spectral channels and minimizes the chi2 difference betw een the modeled and CZCS-derived ''Rayleigh-corrected radiances.'' The two-flow model is calibrated with a set of radiance data which was si mulated with a matrix-operator radiative transfer model. In a first te st, the inverse modeling procedure has been used to produce maps of th e quantitative distributions of phytoplankton chlorophyll, suspended m atter (dry weight), and gelbstoff; aerosol path radiance; and signal d epth of the North Sea. By including the aerosol path radiance as a var iable, the procedure implies the atmospheric correction. A map of the residual chi2 values indicates the success of the retrieval for each o f the pixels.