Results of Meris Level-2 Validation in Namibian Coastal Area and Atlantic Ocean

In-situ data of optically active water constituents and their inherent optical properties were collected during a four-week field cruise in Namibian coastal waters and Atlantic Ocean to validate MERIS geophysical products. The in-situ data set covered a wide range of different water types from very productive coastal upwelling waters to clear open ocean waters where the water color varied from green-yellow to blue. Very high productive water with HPLC chlorophyll-a concentration up to 18 mg m, yellow substance absorption up to 0.17 m and total suspended matter concentration up to 4.4 g m were determined near the Namibian coast due to upwelling processes caused by south-easterly winds. The measured water-leaving reflectance curves in the open Atlantic Ocean show the typical optical behaviour of blue ocean water. The concentrations of water constituents are very low. The HPLC chlorophyll-a concentration is lower than 0.07 mg m, total suspended matter concentration is lower than 0.8 g m and yellow substance absorption is up to 0.05 m. The best results for water-leaving reflectances were found for the newest processing version MEGS 7.0 where 20% mean deviation was determined. The goal of 5% accuracy in complex waters is up to now not reached but the quality of reflectances was continuously improved from the older to the newer processing version. The comparison of in-situ and MERIS data for MEGS 7.0 processing version shows expected mean MERIS Algal_1 indices but to low mean Algal_2 indices, TSM values and YSBPA values in Namibian coastal waters. The older processing version MEGS 6.2p3 delivers only good results for MERIS YSBPA in the Atlantic Ocean but the mean MERIS Algal_1and Algal_2 indices are to high and the mean MERIS TSM values are to low.