USING MERIS DATA FOR THE RETRIEVAL OF CHLA, CDOM AND TSS VALUES IN THE GULF OF FINLAND AND LAKE LOHJANJARVI

摘要

We present results obtained with data collected during two water quality measurement campaigns: Gulf of Finland (Baltic Sea) on 27 April 2004 and Finnish Lake Lohjanjarvi on 5 August 2004. The concentrations of chlorophylla, total suspended solids and the absorption coefficient of colored dissolved organic matter are retrieved using MERIS and airborne spectrometer data. The retrieval is based on empirical algorithms developed with ground truth data. For the Gulf of Finland case the ground truth data include ten water samples analyzed in a laboratory and 5103 data points measured with a flowthough instrument. For the Lake Lohjanjarvi the number of water samples is 11 and the number of flowthough data points is 27301. The coefficient of determination of the flowthrough data with water sample data is over 95% for all three optically active substances. Hence, the flowthrough data (in total 32404 data points) can be used as accurate ground truth for satellite and airborne observations. In the Gulf of Finland the retrieval accuracy (R{sup}2) of the three parameters is 83.5 95.5% when channel ratio algorithms are used with MERIS and flowthrough data. With airborne data the accuracies are 93.0 - 97.1%. In addition to the water quality analysis, the field campaign data were used to study the usefulness of an atmospheric correction method specifically developed for Case 2 waters. The atmospheric correction method utilizes biooptical reflectance modeling and principal component analysis. Both field campaigns represent high concentrations of optically active substances such as chlorophylla, total suspended sediment and humus.