Documentation for the 1996 U.S. Navy's Generalized Digital Environmental Model (GDEM) product database (NCEI Accession 9600094)

This archival package contains a document describing the US Navy Generalized Digital Environmental Model (GDEM). It does not include the profile data.

The GDEM is a four-dimensional (4-D) steady-state digital model of ocean temperature and salinity. The model consists of gridded sets of coefficients with a grid spacing of 30 arcminutes (') in space and 3, 6, or 12 months in time with the exception of the coefficient describing sea-surface temperature, which is gridded at a 1-month interval. Utilizing these coefficient sets with the appropriate one-dimensional linear or cubic spline interpolation in time, vertical profiles of historical temperature and salinity extending from the surface to the bottom may be computed for a desired time for all locations where the water depth is at least 100 m.

The VGDEM is a 4-D model of ocean temperature variability. A number of accumulations and parameters exists for each grid cell such that statistics on the observations can be derived; statistics based on comparing the observations with GDEM can be computed; and statistics computed for the mixed-layer depth and the in-layer and below-layer gradients. The percent of the observations suggesting half-channel is also available. Variability models will be constructed only in the ocean basins where data density permits. Therefore, models for the South Atlantic, South Pacific, and Arctic Oceans will not be developed at this time.

The original source of data for the construction of these climatological models is the Master Oceanographic Observation Data Set (MOODS), which contains over 4.5-million profiles of temperature/salinity dating back to 1920. This data base is maintained by NAVOCEANO and is continually updated.