Format for 48 km (1/8’th Bedient) binary file containing daily Northern Hemisphere snow-depth and ice coverage produced by the U.S. Air Force


Each data file contains two identical 20-byte header records in the form of a 16-byte character string of the form NHSNOW  ddmmyy  ‘ (where dd is the day of the month, mm is the first two characters in the month name, and yy is the two digit year), followed by an INTEGER*4 value representing the number of hours since December 31, 1967.


The data are presented on a Polar Stereographic 512 x 512 array, laid out such that point (1,1) starts at the lower left corner.  The top of the file is South America, the left side is the Pacific Ocean, the right side is Africa, and the bottom is Indonesia.


Each row (i) of the array is a data record consisting of 512 INTEGER*2 values [representing the 512 columns (j) in the row].  The first data record holds values in row 512.  The second data record holds values in row 511, etc.  The 512’th (and last) data record holds values in row 1. Data values in the files range from 0 to 4090.  A value of 4090 is the sea ice flag.  Otherwise, the value represents inches of snow*10.  (e.g. 250 means 25.0 inches of snow).


Points in the Southern Hemisphere should be skipped.


The 512 x 512 Polar Stereographic grid has a mesh length of 47.625 km at 60 degrees N latitude and is oriented at 80 degrees W longitude.  The coordinates of the North Pole are (257, 256).  Grid point (1,1) is at 20.721 S latitude, 125.112 W longitude.