Inter-comparison of ocean colour data products during algal blooms in the Skagerrak

Several ocean colour (OC) Earth observation (EO) sensors are presently collecting data on an operational basis, including the Envisat MERIS sensor. This study aims at quantifying the differences in performance of the ocean colour EO sensors MERIS, MODIS/Aqua, and SeaWiFS for coastal monitoring and for the particular case of coastal algal bloom situations. The standard chlorophyll a, and radiance and reflectance products from the three sensors have been processed and compared for data acquired during the development of an early-spring algal bloom in 2004 in the eastern North Sea region. The study shows a high level of consistency between the Case 1 water Chl a products for all sensors. We conclude that the use of MERIS Chl a and other relevant products enable continued and possibly improved performance of an existing system for harmful algal bloom (HAB) detection and monitoring which up to December 2004 has been based on SeaWiFS.