Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 10 5 2006 10.5194/hess-10-679-2006 http://www.hydrol-earth-syst-sci.net/10/679/2006/ http://www.hydrol-earth-syst-sci.net/10/679/2006/hess-10-679-2006.html http://www.hydrol-earth-syst-sci.net/10/679/2006/hess-10-679-2006.pdf 679 689 2006-09-27 Validation of MODIS snow cover images over Austria J. Parajka parajka@hydro.tuwien.ac.at G. Blöschl Institute for Hydraulic and Water Resources Engineering, Vienna University of Technology, Austria Institute of Hydrology, Slovak Academy of Sciences, Bratislava, Slovakia This study evaluates the Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover product over the territory of Austria. The aims are (a) to analyse the spatial and temporal variability of the MODIS snow product classes, (b) to examine the accuracy of the MODIS snow product against in situ snow depth data, and (c) to identify the main factors that may influence the MODIS classification accuracy. We use daily MODIS grid maps (version 4) and daily snow depth measurements at 754 climate stations in the period from February 2000 to December 2005. The results indicate that, on average, clouds obscured 63% of Austria, which may significantly restrict the applicability of the MODIS snow cover images to hydrological modelling. On cloud-free days, however, the classification accuracy is very good with an average of 95%. There is no consistent relationship between the classification errors and dominant land cover type and local topographical variability but there are clear seasonal patterns to the errors. In December and January the errors are around 15% while in summer they are less than 1%. 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