Directory contains VIIRS-based global daily gridded maps and images of the binary snow cover and snow cover fraction 
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Snow identification and snow fraction retrieval is performed with NOAA Enterprise algorithms. 
Cloud mask is an external (upstream) dataset for the snow products. It is generated by the VIIRS Cloud Team.

Gridded snow maps are generated from corresponding operational VIIRS granule products. 

The grid projection is geographical (latitude-longitude) with 0.01 degree grid cell size both on latitude and longitude, The size of the grid 
is 36000 by 18000, the upper left corner of the upper left grid cell is located at 90N 180W. The map is oriented west to east and north to south.
Maps are available for three satellites, NOAA-20, NOAA-21 and SNPP. 

In the dataset bianary maps are saved in the "maps" directory while map images (.png format) are in the images directory
All daily data files are arranged by the year.

Binary snow cover and snow cover fraction maps are 1-byte binary files. Snow fraction maps have "snfr" in the file name whle binary maps have "snow"
in the file name. All files are compressed with Linux compress command.

Meaning of byte values in the binary snow and snow fraction maps

       0:  Snow-free land surface
     100:  Snow-covered land in the binary snow cover map
   1-100:  Snow fraction in percent in the snow fraction map
     105:  Water or ice
     110:  Clouds over land
over 110:  No retrieval, questionable (unusable) retrieval, undetermnined