Validation Test Report for GDEM4

Since the 1970s, the U.S. Navy has maintained a state-of-the-art gridded global monthly full-depth climatology of temperature and salinity and their standard deviations called the Generalized Digital Environmental Model (GDEM). The present document describes the development and evaluation of GDEM4, the newest version of GDEM. As part of the evaluation of GDEM4, comparisons are made in this report to GDEM3 and to four other ocean climatologies: the NODC World Ocean Atlas (WOA2005), the NODC 1/4 degree resolution climatology, the WOCE Global Hydrographic Climatology (WGHC), and the NRLMODAS 2D (MODAS2D) surface temperature climatology. GDEM4 combines the methodology originally developed for GDEM3 with an expanded observation data set. In the evaluations performed, the GDEM4 climatology has been shown to be a significant improvement over GDEM3 and to compare favorably and in many ways improve on fields from the other climatologies used in the evaluations.
The original document contains color images.