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Development of MERIS Lake Water Algorithms: Validation results from Europe

Antonio Ruiz-Verdú(1), Sampsa Koponen(2), Thomas Heege(3), Roland Doerffer(4), Carsten Brockmann(5), Kari Kallio(6), Timo Pyhälahti(6), Ramón Peña(1), Ángel Polvorinos(7), Jörg Heblinski(3), Pasi Ylöstalo(6), Laura Conde(1), Daniel Odermatt(8), Victor Estellés(9) and Jouni Pulliainen(10)

(1) Centre for Hydrographic Studies - CEDEX, Pº Bajo de la Virgen del Puerto, 3, 28005 Madrid, Spain
(2) Helsinki University of Technology (TKK), Otakaari 5A, 02015 TKK, Finland
(3) EOMAP GmbH & Co.KG, Sonderflughafen Oberpfaffenhofen, Geb. 319, D-82205 Gilching, Germany
(4) GKSS Forschungszentrum Geesthacht, Max-Planck-Str., 21502 Geesthacht, Germany
(5) Brockmann Consult, Max-Planck-Str. 2, 21502 Geesthacht, Germany
(6) Finnish Environment Institute (SYKE), Mechelininkatu 34a, FI - 00251 Helsinki, Finland
(7) University of Sevilla, Profesor García González, s/n, 41012 Sevilla, Spain
(8) University of Zurich - Irchel, Winterthurerstr. 190, CH-8057 Zurich, Switzerland
(9) University of Valencia, Dr. Moliner 50, 46100 Burjassot - Valencia, Spain
(10) Finnish Meteorological Institute (FMI), Erik Palménin aukio, FI-00560 Helsinki, Finland

Abstract

The objective of the ESA project “Development of MERIS Lake Water Algorithms” (Jan. 2007 – June 2008) was to develop and validate a plug-in module for the BEAM toolbox that allows the retrieval of water quality parameters in lake waters from MERIS imagery. For this purpose, new algorithms were developed, based on the optical properties of lakes and characteristics of atmospheric aerosols in different areas of Europe.

In order to validate the processor, field campaigns were carried out in eleven lakes from Finland, Germany and Spain during April – August 2007. The studied lakes cover a wide range of water types and are distributed along a climatic gradient across Europe. In Finland, 12 stations in 4 boreal lakes, characterised by moderate to high CDOM concentrations, were visited during three campaigns. The alpine oligotrophic Lake Constance, in Germany was visited on 2 days with a total of 8 sampling stations. In the six lakes studied in Spain, mostly eutrophic or hypereutrophic with high chlorophyll-a concentration, a total of 13 sampling stations were visited.

The field campaigns included measurements of water leaving radiance reflectances and in some cases total water absorption, scattering and backscattering coefficients. The absorption coefficients of CDOM, phytoplankton and tripton were determined from water samples, as well as the concentration of Chlorophyll-a and total suspended solids. Measurements of the atmospheric aerosol optical thickness, columnar water vapour and ozone content were also taken at the Spanish sampling sites. A set of MERIS images, acquired with cloudless and sunglint free conditions over the study sites, were selected for validation. The effect of adjacency correction was also studied.

The results of the Atmospheric Correction (AC) and the bio-optical models of the processor were validated separately with the field dataset. This presentation shows the main results of the validation exercise and discusses the applicability of the processor in different types of lakes.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry