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NCEP Global Ocean Data Assimilation System (GODAS)

Brief Description: High Resolution Multi-level ocean analysis from NCEP More Details... Temporal Coverage: Monthly values for 1980/01 - 2022/04 . Spatial Coverage: 0.333 degree latitude x 1.0 degree longitude global grid (418x360). 74.5S - 64.5N, 0.5E - 359.5E. 74.0S - 65.0N, 1.0E - 360.0E.

Levels:

• 5, 15, 25, 35, 45, 55, 65, 75, 85, 95, 105, 115, 125, 135, 145, 155, 165, 175, 185, 195, 205, 215, 225, 238, 262, 303, 366, 459, 584, 747, 949, 1193, 1479, 1807, 2174, 2579, 3016, 3483, 3972, 4478 m depth.
• 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 231, 250, 282, 334, 412, 521, 665, 848, 1071, 1336, 1643, 1990, 2376, 2797, 3249, 3727, 4225, 4736 m depth (for geometric vertical velocity only).
• Sea Surface

Update Schedule:

• Static

Download/Plot Data: (FTP Access)

Variable	Statistic	Level	Download File	Create Plot/Subset
Total downward heat flux at surface	Monthly Mean	Surface	List of thflx.*.nc files
Salt Flux	Monthly Mean	Surface	List of sltfl.*.nc files
Sea Surface Height Relative to Geoid	Monthly Mean	Surface	List of sshg.*.nc files
Geometric Depth Below Sea Surface	Monthly Mean	Isothermal Layer	List of dbss_obil.*.nc files
Geometric Depth Below Sea Surface	Monthly Mean	Mixing Layer	List of dbss_obml.*.nc files
Momentum flux, u component	Monthly Mean	Surface	List of uflx.*.nc files
Momentum flux, v component	Monthly Mean	Surface	List of vflx.*.nc files
Salinity	Monthly Mean	Multiple	List of salt.*.nc files
u-component of current	Monthly Mean	Multiple	List of ucur.*.nc files
v-component of current	Monthly Mean	Multiple	List of vcur.*.nc files
Geometric vertical velocity (dz/dt)	Monthly Mean	Multiple	List of dzdt.*.nc files
Potential temperature	Monthly Mean	Multiple	List of pottmp.*.nc files

Usage Restrictions:

• None

Detailed Description:

• A detailed description can be found here (pdf) from CPC. GODAS is a real-time ocean analysis and a reanalysis. It is used for monitoring, retrospective analysis as well as for providing oceanic initial conditions for the CFS. Both temperature and synthetic salinity profiles are assimilated in a 3DVAR scheme designed by Derber and Rosati (1989). 40 vertical levels are in the model together with 1x1 data values (enhanced in resolution to 1/3x1/3 degrees latitude within 10 degrees of the equator). The data is provided at 1/3x1/3 degrees for all latitudes. The GODAS is forced by the momentum flux, heat flux and fresh water flux from the NCEP atmospheric Reanalysis 2. It appears to reproduce observations quite well (see the references).
  In the GODAS/MOM3 archive distribution there are two fields having to do with vertical mixing, a "mixed layer depth", dbss_obml, and a "boundary layer depth", hblt. Both parameters are products of the KPP mixing scheme. The mixed layer depth is the depth where the buoyancy difference with respect to the surface level is equal to 0.03 (cm/s2). The boundary layer depth is the depth where the bulk richardson number is equal to the critical value of 0.3. In the GRIB distribution the boundary layer depth is mislabeled as an isothermal layer, which is, unfortunately, confusing.

Caveats:

• None

Related File Naming & Structure Information:

File Names:

• var.yyyy.nc   (In directory: /Datasets/godas)

OpenDap File Names:

• /thredds/dodsC/Datasets/godas/var.yyyy.nc   

Dataset Format and Size:

• PSL standard NetCDF 3.6 Mbyte file for each yearly single layer monthly mean file (packed).
• PSL standard NetCDF ~144 Mbyte file for each yearly multi-level monthly mean file (packed).

Missing Data:

• Missing data is flagged with a value of 32767s.

Citation:

• Behringer, D.W., and Y. Xue, 2004: Evaluation of the global ocean data assimilation system at NCEP: The Pacific Ocean. Eighth Symposium on Integrated Observing and Assimilation Systems for Atmosphere, Oceans, and Land Surface, AMS 84th Annual Meeting, Washington State Convention and Trade Center, Seattle, Washington, 11-15.
• Please note: If you acquire GODAS data products from PSL, we ask that you acknowledge us in your use of the data. This may be done by including text such as GODAS data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at / in any documents or publications using these data. We would also appreciate receiving a copy of the relevant publications. This will help PSL to justify keeping the GODAS data set freely available online in the future. Thank you!

References:

• Behringer, D.W., M. Ji, and A. Leetmaa, 1998: An improved coupled model for ENSO prediction and implications for ocean initialization. Part I: The ocean data assimilation system. Mon. Wea. Rev., 126, 1013-1021.
• Behringer, D.W., and Y. Xue, 2004: Evaluation of the global ocean data assimilation system at NCEP: The Pacific Ocean. Eighth Symposium on Integrated Observing and Assimilation Systems for Atmosphere, Oceans, and Land Surface, AMS 84th Annual Meeting, Washington State Convention and Trade Center, Seattle, Washington, 11-15. Derber, J.C., and A. Rosati, 1989: A global oceanic data assimilation system. J. Phys. Oceanogr., 19, 1333-1347.
• Ji, M., A. Leetmaa, and J. Derber, 1995: An ocean analysis system for seasonal to interannual climate studies. Mon. Wea. Rev., 123, 460-481.
• S. Saha, S. Nadiga, C. Thiaw, J. Wang, W. Wang, Q. Zhang, H. M. van den Dool, H.-L. Pan, S. Moorthi, D. Behringer, D. Stokes, M. Pe–a, S. Lord, G. White, W. Ebisuzaki, P. Peng, P. Xie , 2006 : The NCEP Climate Forecast System. Accepted J. Climate.

Original Source:

• NOAA Climate Prediction Center from http://www.cpc.ncep.noaa.gov/products/GODAS/.

Contact:

• Physical Sciences Laboratory: Data Management
  NOAA/ESRL/PSL
  325 Broadway
  Boulder, CO 80305-3328
  psl.data@noaa.gov