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

Abstract

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.

Acknowledgments

This work was performed through the project Integrating Modelling and Remote Sensing for Algae Bloom Monitoring in the Norwegian Waters (MORAN, #146155/S40) funded by the Research Council of Norway, the project Harmful Algal Bloom Initiation and Prediction in Large European Ecosystems (EVK3‐CT‐2001‐00063 HABILE) funded by EC, and the project Data Integration System for Marine Pollution and Water Quality (DISMAR) (IST‐2001‐37657). The MERIS data have been provided through the ESA Envisat AO project number 813. The authors want to thank Kai Sørensen at Norwegian Institute for Water Research (NIVA) in Oslo, Norway, for his helpful input and comments. He kindly made available shipborne in situ Chl a measurements that were collected within the projects FerryBox (EVK2‐CT‐2002‐00144) (http://www.ferrybox.no) and DISMAR.