<span style="color: red; font-weight: bold;">NOTE: This data set has been replaced by the <a href="http://nsidc.org/data/g02176.html">Sea Ice Charts of the 
Russian Arctic in Gridded Format, 1933-2006</a> data set.</span>

These gridded ice charts represent a reformatting of information
contained in another data set, the Russian Arctic and Antarctic
Research Institute's (AARI) 10 Day Digital Arctic Sea Ice Charts. AARI
digitized Arctic sea ice concentration and stage of development charts
as part of an international data exchange program. The AARI source
charts, similar to operational charts distributed by the National Ice
Center describing ice type and constitution, were developed from
aircraft and satellite observations for shipping purposes, and provide
extremely detailed information.  Such data are particularly valued in
process studies tracking the growth and recession of polynyas, or for
looking at the preponderance of ice at certain stages of development
in a particular area. NSIDC does not maintain the operational charts,
but archives the AARI digitized version. However, the Arctic and Antarctic Research Institute (AARI) 10 
Day Digital Arctic Sea Ice
Charts were encoded in SIGRID (Sea Ice Grid) format, which assigns
numerical values to ice parameters and records them at specific
lat/lon grid points. But due to the difficulties of visualizing, extracting and working with data in SIGRID, 
NSIDC is now providing
AARI data in NSIDC's Equal Area SSM/I Earth Grid.

The EASE-Grid format makes it especially easy to compare observed ice
concentrations or ice types with the same parameters derived from
satellite data (such as ice concentrations from passive microwave
sensors).

AARI sea ice data in the EASE-Grid projection are gridded at a 12.5 km
resolution, for both Western (24W to 110E) and Eastern (105E to 130W)
sectors . Data extend from 1953 through 1990, and are available via
ftp in compressed tar format. Postscript (.ps) files depicting
coverage per year are also provided with the data.