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Evaluation of the Performance of MERIS Spectrometer Data in Snow Cover Monitoring in the Boreal Forest Belt

Miia Eskelinen(1) , Jouni Pulliainen(1) , and Peter Regner(2)

(1) Helsinki University of Technology/TKK, Otakaari 1, 02150 Espoo, Finland
(2) ESA/ESRIN, Via Galileo Galilei, 00044 Frascati, Italy


This paper describes a work plan for the evaluation of the capabilities and the performance of the Medium Resolution Imaging Spectrometer (MERIS) data for monitoring snow covered land surfaces specifically in the boreal forest belt. In the Northern Hemisphere seasonal snow cover is the largest element of the cryosphere and important temporary fresh water storage. The snow extent over the Earth's land surface has a significant influence on the global radiation budget and specifically on the air temperatures and moisture balance. Accordingly, seasonal snow cover is a sensitive climate change indicator. A specific problem to determine snow cover in boreal forests from optical remote sensing data, such as MERIS, is that the coniferous trees affect the local reflectance observations. Reflectance determination is similarly sensitive to snow anisotropic reflectance properties and the effects of variable sun illumination and sensor viewing angles.

MERIS Level 1b data will be corrected for atmospheric effects by using the Simplified Method for Atmospheric Corrections of satellite measurements (SMAC) in the BEAM software and the results will be compared with ground- based and airborne measurements derived from local validation datasets in Finland in the winter seasons 2002 to 2004.

The results of this study will be useful in estimating the temporal and spatial variability in the average ground, snow and dense forest reflectance that are an important error source in the snow cover extent determination. In addition, the effects of the forest transmissivity and instrument viewing geometry have to be considered to achieve accurate reflectance for snow mapping algorithms.


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