European Seas, including NE Atlantic, NW Africa, North Sea and Baltic Sea, Mediterranean Sea and Black Sea

Ocean colour and earth-leaving visible waveband spectral radiation

Ocean colour radiometers

The Coastal Zone Color Scanner (CZCS) European Archive was generated by the Ocean Colour European Archive Network (OCEAN) Project, which performed a complete reappraisal of all of the CZCS ocean colour data available for the European Seas, for the period between 1979 and 1985. The OCEAN Project processed about 15,000 CZCS images at level 1 (original top-of-the-atmosphere radiances, archived in standard format), 7.000 images at level 2 (surface reflectances and derived geophysical parameters) and 3.500 images at level 3 (remapped, composited statistical products) of the main European basins. The original data were corrected for atmospheric contamination on the basis of a reflectance-model-based algorithm. A Rayleigh correction was applied consistently for all water pixels, using a multiple scattering approach, and introducing atmospheric pressure and ozone concentration data in the computation. A marine aerosol correction used a pixel by pixel iterative procedure, which allowed successive estimates of both the marine reflectance in the red spectral region (670 nm) and the Angstrom exponent, which links simple wavelength ratios to reflectance ratios. For case 1 waters - the optical properties of which are essentially dominated by planktonic pigments - the inter-relations between marine reflectances and reflectance ratios at various wavelengths were derived from modelled calculations. For identified case 2 waters, - where water constituents other than planktonic pigments (i.e. dissolved organics and suspended sediments) dominate the water optical properties - the evaluation of marine reflectances was approximated by means of interpolated Angstrom exponent values computed over case 1 water pixels and of empirical relationships derived from in situ measurements. The computation of water constituents concentration was performed with algorithms based on blue/green (443/550 nm) reflectance ratios, for lower pigment concentration, or on green/green (520/550 nm) reflectance ratios, for higher pigment concentration. As for the case of atmospheric corrections, the inter-relations between pigment concentration and reflectance ratios were model-derived for case 1 waters, and empirically determined for case 2 waters. Individual images of pigment concentration were remapped on a standard 1 km pixel grid for a number of European basins (NE Atlantic, NW Africa, North Sea & Baltic Sea, Mediterranean Sea, Black Sea), for each available day. The daily images were then averaged on a pixel by pixel basis, to generate monthly, seasonal, and annual composites.

Barale, V., D. Larkin, L. Fusco, J.M. Melinotte, and G. Pittella (1999) 'OCEAN' PROJECT: THE EUROPEAN ARCHIVE OF CZCS HISTORICAL DATA, International Journal of Remote Sensing, vol. 20, no. 7, p. 1201-1218.; Sturm, B., V. Barale, D.J. Larkin, J.H. Andersen, and M. Turner (1999) OCEANcode: THE COMPLETE SET OF ALGORITHMS AND MODELS FOR THE LEVEL-2 PROCESSING OF EUROPEAN CZCS HISTORICAL DATA, International Journal of Remote Sensing, vol. 20, no. 7, p. 1219-1248.

Joint Research Centre
Space Application Institute Marine Environment Via E. Fermi 2749
ISPRA (VA)

I-21027
Italy