National Aeronautics and Space Administration

Though the mean winter maximum snow-cover extent (SCE) can cover up to ~50 million km2 over Northern Hemisphere land areas, there is a large amount of variability in the month-to-month and interannual SCE in the Northern Hemisphere where ~98 percent of Earth’s seasonal snow is located. We use the Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) daily cloud-gap filled 375-m resolution Normalized-Difference Snow Index (NDSI) maps derived from the VNP10A1F NASA standard data snow-cover product to develop a time series of SCE in North America. To assess the data-product quality, we compare VIIRS snow-mapping results with a climate data record-quality SCE product generated at the Rutgers University Global Snow Lab from the NOAA/U.S. National Ice Center 24-km Interactive Multisensor Snow and Ice Mapping System (IMS) (the NOAA/Rutgers IMS product). To compare with the NOAA/Rutgers IMS snow maps, we developed monthly VIIRS maps showing percent of days in a month that were snow covered for the first six months of 2019, degrading the resolution of the VIIRS maps to 24 km so that the VIIRS and NOAA/Rutgers IMS maps could be compared directly on the same grid. Results show good correspondence between the VIIRS and NOAA/Rutgers IMS monthly SCE snow-frequency maps for North America, with 88.2 – 99.8 percent agreement for total snow cover. The correspondence between the two independent datasets increases our confidence in satellite-derived SCE from both products.