"CHARTS" directory contains charts of time series of monthly and annual mean snow extent over 
North America, Eurasia and Northern Hemisphere estimated from the following four datasets:

1. GMASI V3 reprocessed daily maps at 4 km resolution, 1988-current
2. NOAA CDR/Rutgers maps at 200 km resolution 1972-current 
	data obtained from https://climate.rutgers.edu/snowcover/table_area.php?ui_set=1&ui_sort=0
3. NOAA IMS daily maps at 24 km resolution, 1999-current
4. NOAA IMS daily maps at 4 km resolution, 2005-current  

!!! Yearly mean snow extent values are calculated for calendar years (Jan-Dec), not "hydrological" years (Jul-Jun)

Charts are updated occasionally, once or twice per year. Please let me know if you need an updated chart sooner.