Remote sensing for eutrophication monitoring
Knowledge of phytoplankton distribution and dynamics in North Sea coastal waters is vital to ensure a scientific basis for coherent management of human activities which impact the coastal environment. Conventional water sampling programs can support only sparse spatial and temporal coverage, and subsequently cannot identify the causes of specific events or cover the strong variability characterising coastal waters. The REVAMP project's ultimate aim was to develop an improved product from MERIS observations, namely an atlas containing maps of validated chlorophyll concentrations for the North Sea. The new generation satellite sensor MERIS, designed for monitoring marine water quality through high spectral and spatial resolution observations of water colour, could potentially revolutionise the monitoring of algal biomass. Before this can be achieved MERIS algorithms require rigorous development, testing and validation. For this purpose, a dedicated software environment has been developed for validating the suitability of bio-optical models and inversion algorithms for retrieving regional chlorophyll concentrations from MERIS observations. The REVAMP MERIS processor exploits the Basic Envisat MERIS and AATRS (Advanced Along-Track Scanning Radiometer) toolbox, which is freely available from ESA. Implemented in the Java programming language, it allows the development of specific algorithms for processing the MERIS images without requiring knowledge of file formats. The REVAMP MERIS processor supports requests in the form of XML files or posed through an interactive interface that may include simple processing calls for one REVAMP product. Large batch processing jobs are also supported, which is an important feature for the production of a yearly atlas of chlorophyll concentration maps and indices to underlying processes such as a eutrophication index. Importantly, requirements for image suitability and indicators for chrolophyll-product quality have been designed and incorporated into the operational version of the processor. The latter is expected to contribute to chlorophyll a mapping within the framework of the future Global Monitoring for Environment and Security (GMES) project.