30 April 2004 The ocnYYMMDD.nc files are weekly average files of the state variables from the operational NCEP Global Ocean Data Assimilation System (GODAS). Briefly, the system consists of the GFDL MOM3 configured with KPP mixing, G-M isopycnal tracer mixing, non-linear viscosity and explicit sea surface height. The resolution is 1x1 degrees with enhanced meridional resolution (1/3 degree) in the tropics. There are 40 vertical levels with 20 in the top 200 meters. The assimilation is done with a 3D variational scheme. Although the system is capable of assimilating temperature, SSH and salinity, this particular prototype run assimilates only temperature (XBTs, TAO) and synthetic salinity profiles based on the temperature profiles and the local climatological TS-relationship. The forcing fields are weekly averages from the NCEP MRF. Although the forcing fields include heat flux and E-P, the model is also relaxed to the weekly NCEP SST analysis and the Levitus climatological SSS. The files are saved in the netCDF format and are thus self-describing. Software for reading/writing netCDF is supported by UCAR (go to their site at www.unidata.ucar.edu/Software.html) The files are compressed with the UNIX utility "compress" which results in a 20% savings in size. A sample program that will read these files is called rdOcn.f. It should be compiled and linked with the UCAR netCDF library after making an appropriate change of the path in the 'include' statement. These preliminary files are for inspection only, results or conclusions drawn from them should not be disseminated. A new analysis file will routinely appear each week representing the week three weeks prior to the current date. The files on the server will rotate, only the most recent N weeks will be present. Also changes to the analysis system will occur over the next several weeks. The changes will be described in the ChangeLog file. The changes will be made without advance warning. David Behringer NCEP/EMC David.Behringer@noaa.gov POC: Hyun-Chul.Lee@noaa.gov