NCEP GODAS¶

NCEP Global Ocean Data Assimilation System (GODAS)

Available

At a glance¶

Note on period: PSL monthly means start in January 1980. When checked on 2026-10-12, pottmp, salt, ucur, sshg and the other fields ran through August 2026, and thflx (total downward heat flux) through June 2026. The NCAR GDEX copy (d277006) ends in October 2024. The CPC home page offers monthly and pentad (5-day) data downloads and pentad maps for the past 3 months.

Overview¶

GODAS is the ocean data assimilation system NCEP has run for climate monitoring and to provide ocean initial conditions for the Climate Forecast System (CFS) — "a real-time ocean analysis and a reanalysis". It uses the GFDL MOM v3 model and assimilates temperature profiles (XBT, TAO moorings, Argo, etc.) and synthetic salinity profiles derived from temperature–salinity relationships with a 3DVAR scheme; altimetry sea level has been assimilated since March 2007 (NCAR Climate Data Guide). Surface momentum, heat and freshwater fluxes come from NCEP–DOE R2, the top-level temperature is relaxed to weekly SST analyses, and surface salinity to annual climatology. Its resolution is coarse, but it has been updated monthly since 1980 and is widely used for CPC's monthly ocean briefings and for heat content and thermocline monitoring of ENSO.

Available variables¶

Main variables from the NOAA PSL netCDF files (OPeNDAP attributes). Names are the variable names inside the files; files are named <variable>.<year>.nc. Units differ from most ocean datasets (temperature in K, salinity in kg/kg, salt flux in g/cm2/s), so check them before use.

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

3-D ocean (40 levels)¶

2-D ocean¶

Surface fluxes¶

The full variable list is in the official documentation.

How to get the data¶

• NOAA PSL — GODAS dataset page — Variable list, plotting and subsetting No login needed
  • No account needed. netCDF4 files, one per variable per year.
• NOAA PSL download server — Direct HTTPS download No login needed
  • Per-variable, per-year files, a ReadMe, and a Derived/ directory with monthly long-term means (1991–2020 and others).
• NOAA PSL THREDDS / OPeNDAP — Remote access via OPeNDAP / NetCDF Subset Service No login needed
• NOAA CPC — GODAS home page — Maps and animations, monthly and pentad download links, monthly ocean briefing No login needed
  • The original CPC GRIB files are pointed to the pub/cfs/godas path on cfs.ncep.noaa.gov. Most of the page has not been changed since 2019 (last modified July 30, 2019).
• NSF NCAR GDEX — NCEP GODAS (d277006) — Web download
  • Monthly means in WMO GRIB1, CC BY 4.0, dataset DOI 10.5065/ZAHZ-3174. As of October 2026 it only runs through October 2024.

Example code¶

The PSL OPeNDAP URLs open directly in xarray. Temperature is in K, and the time value is the 1st of the month.

import xarray as xr

base = "https://psl.noaa.gov/thredds/dodsC/Datasets/godas"
t = xr.open_dataset(f"{base}/pottmp.2025.nc")["pottmp"] - 273.15   # K → °C
# Mean temperature of the upper 300 m in the Niño 3.4 region (5°S–5°N, 170°W–120°W)
box = t.sel(lat=slice(-5, 5), lon=slice(190, 240), level=slice(0, 300))
print(box.mean(["lat", "lon", "level"]).values)

Practical tips¶

• GODAS surface fluxes come from NCEP–DOE R2 (about 2.5°, T62). R2 stopped at 28 February 2026 and there is no official word on how GODAS has been forced since March 2026, so compare recent flux and mixed-layer changes against other ocean reanalyses before interpreting them.
• The NCAR Climate Data Guide rates GODAS salinity as poor (synthetic salinity assimilation and relaxation to climatology) and notes large biases in the velocity fields. Use another reanalysis alongside it for salinity or current studies.
• The last available month can differ between variables in the PSL files (in October 2026, thflx ended in June and the rest in August). Align the time axes when combining variables.
• The domain is 75°S–65°N, so most of the Arctic Ocean is missing. There are no sea-ice variables.
• The PSL file attributes say 'THESE ARE THE BIAS CORRECTED GODAS FILES', but we found no official document explaining what correction this refers to.

Notices and change history¶

References for your paper¶

Dataset citation¶

NCAR GDEX copy (d277006) — DOI 10.5065/ZAHZ-3174

@misc{ncep_godas_gdex,
  author    = {{National Centers for Environmental Prediction/National Weather Service/NOAA/U.S. Department of Commerce}},
  title     = {{NCEP} Global Ocean Data Assimilation System ({GODAS})},
  year      = {2006},
  publisher = {NSF National Center for Atmospheric Research, Geoscience Data Exchange},
  doi       = {10.5065/ZAHZ-3174}
}

Reference papers¶

GODAS description and evaluation (conference paper, no DOI)

@inproceedings{behringer2004godas,
  author    = {Behringer, David W. and Xue, Yan},
  title     = {Evaluation of the global ocean data assimilation system at {NCEP}: The {Pacific} Ocean},
  booktitle = {Eighth Symposium on Integrated Observing and Assimilation Systems for Atmosphere, Oceans, and Land Surface, 84th AMS Annual Meeting},
  address   = {Seattle, WA},
  year      = {2004},
  url       = {https://ams.confex.com/ams/84Annual/webprogram/Paper70720.html}
}

GODAS mixed-layer heat budget (related publication listed by NCAR GDEX) — DOI 10.1175/2010JCLI3373.1

Acknowledgements¶

If you obtained the data from PSL, the usual practice is to include an acknowledgement such as "GODAS data provided by the NOAA PSL, Boulder, Colorado, USA, from their website at https://psl.noaa.gov" and cite Behringer and Xue (2004), which is also the GODAS reference given in the CPC ocean briefings. If you used the NCAR copy, also give the GDEX DOI.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• NOAA PSL GODAS dataset page
• CPC GODAS home page
• CPC GODAS background
• Behringer and Xue (2004) conference paper (PDF)
• NCAR Climate Data Guide — GODAS
• PSL Data Notices