Assessment of Water-Leaving Reflectances of Oceanic and Coastal Waters Using MERIS Satellite Products off the Southwest Coast of Portugal

Water-leaving reflectances (pw) were estimated from downwelling and upwelling spectral irradiances, and compared with MERIS pw for a period between September and November 2008. The results of the "match-up" analysis showed that there was reasonable agreement between the data sets over the period of study at the offshore site where the land adjacency affect on the satellite data was reduced. The greatest deviation of in situ data from satellite values was at the inshore site and at the lower wavelengths of the visible spectrum, where the pws for the blue band were most affected by atmospheric corrections. This study suggests that calibration algorithms of MERIS products with in situ data from the south west coast of Portugal could be improved by using, for example, ICOL (Improved Contrast between Ocean and Land) processing.