We base our algorithm implementation and validation on a number of selected test sites.

Not many MERIS match-ups can be found for extreme Case 2 waters. We will make use of in-situ data available at team members and Scientific Support Team. It is important to validate the algorithms on in-situ match-ups, but not sufficient due to their small number.

This is particularly the case for marine radiometry data. In order to validate the atmospheric correction we propose therefore to perform tests on the decoupling of the atmospheric signal and the marine reflectance. The correlation coefficient will be calculated for band combinations at top-of-atmosphere, and between the atmospheric path radiance / aerosol optical thickness and the water leaving reflectance. The correlation coefficient of the latter should be zero, or at least significantly lower than the TOA correlation coefficient. A low TOA correlation coefficient will be used to screen out unusable cases.

For the in-water part the availability of in-situ measurements and match-ups is better but still low. Here we will use all in-situ data (also non-match-ups, which increases the number substantially) in order to establish value ranges for the expected concentrations. We will then process all available MERIS data and compare statistically with these expected ranges. Time series of concentrations at selected points or of mean values of water bodies will also be used to check the plausibility of the generated results. Finally we will inspect visually the data.