SeaWiFS-derived products in the Baltic Sea: performance analysis of a simple atmospheric correction algorithm

• Main Authors: Barbara Bulgarelli, Frédéric Mélin, Giuseppe Zibordi
• Format: Article
• Language: English
• Published: Elsevier 2003-12-01
• Series: Oceanologia
• Subjects: Baltic Sea; Remote sensing; SeaWiFS; Atmospheric correction; Ocean colour; Radiative transfer
• Online Access: http://www.iopan.gda.pl/oceanologia/45_4.html#A8

The accuracy analysis of an approximate atmospheric correction algorithm for the processing of SeaWiFS data has been investigated for the Baltic Sea. The analysis made use of theoretical radiances produced with the FEM radiative transfer code for representative atmosphere-water test cases. The study showed uncertainties in the determination of the aerosol optical thickness at 865 nm and of the Ångström exponent lower than ± 5% and ± 10%, respectively. These results were confirmed by the analysis of 59 match-ups between satellite-derived and <i>in situ</i> measurements for a site located in the central Baltic. Because of the relatively high yellow substance absorption, often combined with the slanted solar illumination, the retrieval of the water-leaving radiance in the blue part of the spectrum appeared to be highly degraded, to the extent that almost no correlation was found between retrieved and simulated values. Better results were obtained at the other wavelengths. The accuracy in the estimation of the remote sensing reflectance ratio <i>R</i>₃₅ decreased with diminishing chlorophyll <i>a</i> concentration and increasing yellow substance absorption, ranging between ± 7% and ± 47%. The propagation of <i>R</i>₃₅ uncertainties on chlorophyll <i>a</i> estimation was quantified. Keeping the same atmosphere-water conditions, the atmospheric correction scheme appeared sensitive to seasonal changes in the Sun zenith.