MAPPING WATER CONSTITUENTS CONCENTRATIONS IN ESTUARIES USING MERIS FULL RESOLUTION SATELLITE DATA

摘要

In coastal waters directly influenced by human activities and climate change, an operational oceanography is necessary to obtain a better understanding of the involved processes and rapidly provide adapted monitoring systems able to produce predictions and forecasts. For this reason, applied research activities are highly supported by the European Community. The goal of ocean colour remote sensing measurements is to quantify and map the optically significant water constituents: phytoplankton (chlorophyll a (Chla)), coloured dissolved organic matter (CDOM) and non-algal suspended particulate matter (SPM). It consists in estimating these water constituents' concentrations from apparent optical properties (AOP) measurements (namely the irradiance reflectance, R, or remote sensing reflectance, Rrs, signals). This can be done if the inherent optical properties (IOP) of these constituents are sufficiently well documented. The information potentially delivered by ocean colour remote sensing is of first importance in highly dynamic coastal waters where terrigeneous substances are transported from the continent to the ocean. The supplied nutrients enhance the primary production whereas SPM and CDOM limit the solar light penetration within the water column. Pollutants due to anthropic activities can also influence and modify the ecosystems in a way that is detectable in the ocean colour signal (e.g. eutrophication). Transport of suspended sediments has a direct influence on the coastline changes (creation of mudbanks), hydrodynamic conditions (e.g. filling of navigation channels and resulting dredging activities) and biogeochemistry of the environment (e.g. creation of maximum turbidity zones/fluid mud layers systems). Ocean colour remote sensing can provide useful information for monitoring coastal waters, using the recently developed satellite and airborne optical sensors. Such sensors are nowadays adapted to the study of coastal waters, as they are improved in terms of spatial, radiometric and spectral resolutions.