Validation of Meris Products in the Skagerrak

The objectives of this study were firstly to validate the standard MERIS data products for coastal waters (Case 2) after the improvements done in the 2 processing, and secondly to test the performance of the FUB and Case2R processors. Validation was performed for data between 2002 and 2007. The in situ data were mainly collected by a Ferrybox system onboard MS Color Festival between Norway and Denmark. Water samples were analyzed for concentrations of chlorophyll-a and total suspended matter. The validation is based on the MERIS Level 2 Reduced Resolution data available after the 2 reprocessing of MERIS. In this reprocessing data from Skagerrak was used in the training of the neural network. Based on the data available the MERIS standard Case 2 chlorophyll-a product (algal_2) shows some overestimation compared to the in situ data. Retrieved concentrations of total suspended material (TSM) are close to the in situ values. The FUB (v1.3) and Case2R (v1.4 beta) processors show promising results for the algal_2 and TSM products. The comparison performed here are from open sea areas in the Skagerrak. We see that close to the coast and in the Oslofjord the problems of atmospheric correction and/or adjacency effects are significant. This needs to be addressed and solved before the MERIS data can be used quantitatively in the Norwegian Fjords. The study also demonstrates that Ferrybox turbidity data and water sampled by a Ferrybox system and analysed for Chl-a HPLC or TSM can be used in validation in coastal and Case2 waters. The use of data along a whole transect (as opposed to single sampling positions only) improves the interpretation and understanding of the variation that we observe between satellite and in situ data and is therefore valuable for improving the validation in coastal waters.