Assessment of MERIS ocean color data products for European seas

The accuracy of marine data products from the Medium Resolution Imaging Spectrometer (MERIS) operated onboard the Envisat platform, is investigated with the aid of in situ geographically distributed measurements from different European seas. The assessment focusses on standard products from the 2012 data update commonly identified as 3rd Reprocessing. Results indicate atmospherically corrected data affected by a negative bias of several tens percent at the 413 nm center-wavelength, significantly decreasing to a few percent at 560 nm and increasing again at 665 nm. Such an underestimate at the blue center-wavelengths leads to an average overestimate of the algal-1 MERIS pigment index largely exceeding 100% for the considered European seas. A comparable overestimate is also observed for the algal-2 pigment index independently determined from top-of-atmosphere radiance through the application of neural networks.