Validation of MODIS, VEGETATION, and GOES+SSM/I snow cover products over Canada based on surface snow depth observations

The rate and pattern of snow melt control both hydrological and ecological factors. Snow cover maps derived by different satellite sensors can differ considerably from surface observations due to different spatial resolutions and snow cover classification algorithms. This article addresses issues related to the validation of three daily snow cover products over Canada: MODIS and GOES+SSM/I snow maps derived at 500m and 4km resolution, respectively for 2001, and VEGETATION snow maps derived at 1km resolution for 2000. The validation is based on surface snow depth observations from almost two thousand meteorological stations across Canada. The analysis is performed on a daily basis for the period of six months (January-June). A land cover map of Canada at 1km resolution is used to relate the differences within the validation to land cover types. The SPOT product shows an average agreement of 83% ad considerably high percentage of omission error. The MODIS and GOES+SSM/I products have similar percentage average agreements, 93% and 92%, respectively. Generally, less agreement is seen within the evergreen forest cover types, earlier in the snow season and during snow melt. The MODIS product exhibits a high percentage commission error for evergreen forests. The GOES+SSM/I product shows relatively similar ratios of omission and commission errors for all land cover types except deciduous forest.