NSIDC/NOAA Snow Extent
half-monthly Northern Hemisphere Snow Extent Maps beginning in February 1997

Data used
National Ice Center. 2008, updated daily. IMS Daily Northern Hemisphere Snow and Ice Analysis at 1 km, 4 km, and 24 km Resolutions, Version 1.1-1.3. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: https://doi.org/10.7265/N52R3PMC.