NOAA NESDIS provides a weekly analysis of Northern Hemisphere snow cover from
optical satellite data; the analyses are done by hand. Robinson (pers. comm.)
of Rutgers University provided these data after regridding them to 1 deg. x 1
deg. The U.S. Air Force assembles a monthly snow depth map based on a variety
of sources including satellite data and in situ measurements carried out at
reporting airfields. The NOAA National Meteorological Center (NMC) provided
analyses of sea ice cover and sea surface temperature at monthly time
resolution at the required 1 deg. x 1 deg. resolution. The land/sea mask was
then applied at GSFC. Last, a fine resolution map of the land-ocean boundary
was provided by the National Center for Atmospheric Research (NCAR) based on
data collated by the U.S. Navy.
Global monthly fields of sea surface temperature (SST) and sea ice concentration were also included in the data set in response to requests from GCM modelers who wished to have a complete set of surface boundary conditions on the CD.