Validating MERIS and MODIS TSM and Chl-a Results (2003-2011) from the WISP and HYDROPT Algorithms
Peters, Steef1; hommersom, annelies2; Poser, Kathrin2; de Reus, Nils2; Laanen, Marnix2; van der Woerd, Hans3; Eleveld, Marieke3

During the lifetime of MERIS a strong record of coastal waters observations was build up. This data (Chl-a and TSM based on the HYDROPT algorithm)was used intensively for National monitoring applications in the Netherlands. Currently MODIS-AQUA is being investigated since data is needed to fill the gap between MERIS and OLCI. Using the innovative WISP algorithm and an in depth study of MODIS response and sensitivity to coastal water colour, we have come to very good Chl-a and TSM retrievals, even at monitoring locations close to the coast (2-5 km) with high turbidity. Although MODIS results exhibit a somewhat larger variability because of striping, the seasonality and ranges of TSM and Chl-a are very well represented in the time series. Validation with over 2000 in-situ measurements of TSM and Chl-a show that both instruments approximately provide similar accuracy when looking at annual mean values at the monitoring stations (although derived from very different algorithms). Single values obtained from MODIS show some more scattering because of striping. Based on the results of this study we define criteria for using S3 OLCI data.