SeaWiFS data interpretation in relationship with in-situ measurements in a coastal area

The SeaWiFS instrument launched onboard the ORBIMAGE 2 spacecraft, consists of an optical scanner with eight channels which are used to interpret ocean colour, and has been operational since September 97. SeaWiFS data were received by the Dundee Satellite Receiving Station and processed by the Plymouth Marine Laboratory with a slight time-lag (24 h). Just before and during the BIOMET-2 survey (PNOC project), the location of the hydrologic stations was chosen from the Ifremer numerical model and SeaWiFS imagery on 10, 12, 14 Jan. 98 received onboard the “Thalassa” oceanographic ship. Images of chlorophyll a concentrations and normalised water-leaving radiances at 555 nm highlight display the Gironde estuary´s turbid plume moving northwards under the effect of the Coriolis deviation and the southerly winds. In-situ measurements of reflectance (corresponding to the SeaWiFS bands), salinity, seston and chlorophyll a were analysed to get a better knowledge of the dynamics of the turbid plume during this period. Initial results show different relationships between suspended matter concentrations and in-situ reflectances. Comparisons between chlorophyll a, total suspended matter concentrations and SeaWiFS data are being analysed in an attempt to test and improve algorithms