Validation of MERIS Level‐2 products in the Baltic Sea, the Namibian coastal area and the Atlantic Ocean

Measurements of water‐leaving reflectance and optically active water constituents in the Baltic Sea, the Namibian coastal area and the Atlantic Ocean were performed to validate MERIS Level‐2 products. Two different validation methods were applied with the recommended match‐up analysis based on comparison of in situ measurements with MERIS Level‐2 products of simultaneous Envisat overpasses and the second analysis on comparison of natural variation ranges with derived MERIS product ranges. The MERIS water‐leaving reflectances correlate to in situ shapes and magnitudes in all investigated areas. The comparison shows mean deviations of MERIS reflectances between 23% and 26% for the current official instrument processing facility (IPF 4.07) but only 20% for the prototype version 7.0 up to now only available to the validation team. The comparison of water constituents shows the underestimation of MERIS ALGAL_2 index, YSBPA and TSM in turbid waters of the Baltic Sea of the current instrument processing facility (IPF 4.07). The mean MERIS ALGAL_1 index is close to in situ values but the mean MERIS ALGAL_2 index, the MERIS YSBPA and MERIS TSM products are still too low in Namibian coastal areas for the prototype version 7.0. The investigations demonstrate the quality improvement of all MERIS Level‐2 products from the current official instrument processing facility to the prototype version 7.0.