Comparison of MODIS and VIIRS Snow Cover Products for the 2016 Hydrological Year

The VIIRS (Visible Infrared Imaging Radiometer Suite) on board the Suomi-NPP (National Polar-orbiting Partnership) satellite aims to provide long-term continuity of several environmental data series including snow cover initiated with the MODIS (Moderate Resolution Imaging Spectroradiometer) instrument carried aboard Aqua and Terra satellites. There are speculations concerning differences between MODIS and VIIRS snow cover products because of different spatial resolution and spectral coverage. However, the quantitative comparisons between VIIRS and MODIS snow products are currently limited. Consequently, this study intercompares MODIS and VIIRS snow products during the 2016 hydrological year. To accomplish its research objectives, 244 swath snow products from MODIS/Aqua (MYD10L2) and the VIIRS EDR (VSCMO/binary) were intercompared for the 2016 hydrological year from October 1, 2015 to May 31, 2016 using confusion matrices, comparison maps and false color imagery. The current VIIRS snow product is binary, therefore to produce MODIS binary snow maps, the MODIS snow cover fraction threshold value of 30% was determined by examining snow cover area at four different thresholds (20%, 30%, 40% and 50%) and comparing them with the VIIRS binary snow map. Overall VIIRS appears to map more snow and less clouds than MODIS. On average, MODIS snow maps mapped snow but VIIRS in 1% of cloud free pixels, whereas 2% of the time VIIRS mapped snow but MODIS did not. The average agreement between MODIS and VIIRS was approximately 98% indicating good agreement between them. Agreement between MODIS and VIIRS was high during the winter but lower during late fall and spring, mostly over dense forest. Both MODIS and VIIRS often mapped snow/no-snow transition zones as cloud. The visual comparison depicts good qualitative agreement between snow cover area visible in MODIS and VIIRS false color imagery and mapped in their respective snow cover products