Validation of the MERIS products on large European lakes: Peipsi, Vänern and Vättern
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The Medium Resolution Imaging Spectrometer (MERIS/Envisat) was launched in March 2002 for coastal zone monitoring. Preliminary data from MERIS show that its imagery of large lakes is superior to that of other common ocean colour sensors. The main objective of the present study is to evaluate the MERIS data on large European lakes, Vänern and Vättern in Sweden and Peipsi in Estonia/Russia. In these lakes, coloured dissolved organic matter (CDOM) can be a major contributor to the optical properties of the water. Another characteristic of the waters under investigation is the large temporal and spatial variability in the concentrations of chlorophyll (C Chl) and suspended sediments (C TSS). Potentially toxic cyanobacterial blooms occur in Lake Peipsi in late summer. We have compared the MERIS products from the latest reprocessing (finished in March 2006) with available in situ data. There is a reasonably good correlation between the MERIS algal_2 product and the measured C chl over all three lakes, but no correlation was found for other optically active substances. A significant portion of the pixels (up to 90%) are flagged as invalid results after atmospheric correction.
KeywordsRemote sensing MERIS Large lakes Optical properties
We thank ESA/ENVISAT, EO Help Desk and Brockmann Consult for the production and distribution of images. This study is supported by the Estonian Science Foundation Grant’s 6814 and 5738 and the Swedish National Space Board grant 132/03. We thank the Võrtsjärve Limnological Station for water sample analyses.
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