Ocean WRIT Web Tools: Reanalysis and Observational Datasets and Variables

Reanalyses and observational datasets available on the page are listed in the tables that follow. For more information and discussion of various atmospheric and oceanic reanalyses, see the "Reanalysis Intercomparison and Observations Wiki" (http://reanalyses.org). This wiki includes references/citations and a detailed reanalyses comparison guide. All depth variables have been interpolated to 1x1 horizontal grids with 18 vertical levels, for ease of comparison. Single level variables are not necessarily interpolated to the same grid, preserving high resolution grids when possible. For those, plot differences are computed by interpolating the lower resolution dataset of the two being compared to the resolution of the higher resolution and subtracting. Anomalies are based on the climatology from each reanalyses dataset separately. Variable units have been changed to be consistent so the datasets can easily be compared. More recent data may be available at the source.


Documentation (source)
Reanalyses Datasets
Dataset Start Date1 End Date1 Climo Available Documentation (source) NCAR Climate Data Guide
NCEP Global Ocean Data Assimilation System (GODAS) Jan 1979 May 2024 1981-2010 PSL Documentation
UMD Simple Ocean Data Assimilation System (SODA V3.4.2: ERA-Interim) Jan 1980 2016 1981-2010 UMD Documentation X
UMD Simple Ocean Data Assimilation System (SODA V3.7.2: JRA-55) Jan 1980 2016 1981-2010 UMD Documentation X
ECMWF Ocean ReAnalysis System 5 (ORAS5) Jan 1980 Dec 2017 1981-2010 ECMWF ORAS5 Documentation
ECMWF Ocean ReAnalysis System 5 (ORA20C) Jan 1979 (Jan 1901 at EC) Dec 2009 1981-2009 ECMWF ORA20C Documentation
CSIRO BRAN2020 Ocean Reanalysis (BRAN) Jan 1993 Dec 2020 1993-2020 BRAN2020 Documentation
NASA (ECCO V4 release 4) Jan 1992 Dec 2017 1992-2010 NASA ECCO Homepage
UK Met Office EN4 V4.2.1 Jan 1980 Mar 2021 1981-2010 UK Met Office EN4 and the NCAR Climate data guide X

Observational Datasets
Dataset Variables Start Date1 End Date1 Climo Available at PSL Documentation NCAR Climate Data Guide
HadISST 1.1 SST,Ice Jan 1870 near present 1981-2010 UK Met Center Doc X
NOAA OI SST SST Jan 1982 near present 1982-2010 PSL Documentation X
GPCP V2.3 Precipitation Jan 1979 near present 1981-2010 PSL Documentation X

1 Start and end dates reflect data on the WRIT pages and may not reflect what is available at the source.


Multiple Depth Variables
Variable Units
Potential temperature K
Zonal current (u) m/s
Meridional current(v) m/s
Salinity kg/kg
Single Level
Variable Also known As Units
SSTSea Surface TemperatureK
Ice Thickness m
Sea surface height Sea Level m
Momentum Flux, u component Wind Stress Forcing, u component N/m**2
Momentum Flux, v component Wind Stress Forcing, v component N/m**2
Total Downward Heat Flux at Surface Net Heating W/m**2
Salt Flux Salinity Flux g/cm2/s
Ocean Mixed Layer Depth m
Ocean Isothermal Layer Depth m
0-300m Heat Content J/m**2
Depth of 20C isotherm m
Bottom Temperature K

Table of Available Variables for the datasets

Potential Temperature X X X X X X X X
Salinity X X X X X X X X
U current X X X X X X X
V current X X X X X X X
Sea Surface Height X X X X X X X
Net Downward Heat Flux X X X X X
Mixed Layer Depth X X X X X
Isothermal Layer Depth X
Surface Salt Flux X X X
U wind Stress X X X X
V wind Stress X X X X X
Bottom Temperature C C C C C X C
Heat Content: 0-300m C X X X C X C
Heat Content: 0-750m C X X C X C
Depth of 20C isotherm C X C C C ?
Ice thickness X X

X:model output. C:calculated from other variables (or top level for SST).



All depth variables have been converted to 1x1 grids and 18 levels. Variables were first linearly interpolated to the new set of levels at each grid point. Then the data was bilinearly interpolated to a 1x1 grid. Values south of the southern extent of the original tart's latitudinal range and north of the original northern extent were set to missing. This made it possible to easily compare depth by latitude and depth by longitude plots.

  • Longitude values for those depth data are 0E,1E,2E...358E,359E.
  • Latitude values for those depth data are 89.5S, 88.5S,...88.5N,89.5N
  • Depth values for those depth data are (in meters)5, 10, 20, 30, 50, 75, 100, 125, 150, 175, 200, 250, 300, 400, 500, 750, 1000, 1500

Single level variables were not interpolated in space so that users will get the highest resolution possible. When maps are compared, the lowest is converted to the highest resolution


Most available data variables are output from the model. The exceptions are:

  • Heat Content:. On the interpolated grids, heat calculate from temperature was interpolated from 300m upward. This will later be done on the original grids.
  • Depth of 20C Isotherm: On the original data grid, each grid point was interpolated to find the depth of the 20C level using NCL subroutine int_2p. Values at the surface or above were set to missing. Some interpolations resulted in missing values if temperature didn't decrease for all levels going down.
  • SST: Some datasets have SST as an output variable. Where it is not, the top most level of temperature was used as SST.
  • Bottom Temperature: THC= is calculated using the original horizontal/vertical resolution potential temperature. The temperature of the lowest depth at each grid point is stored.


To cite dataset if plot or extracted used in any publication, use the reference below. Please read documentation about datasets to see about caveats, analysis methods, and similar information.

  • NCEP GODAS: Huang, Boyin, Yan Xue, Dongxiao Zhang, Arun Kumar, Michael J. McPhaden, 2010: The NCEP GODAS Ocean Analysis of the Tropical Pacific Mixed Layer Heat Budget on Seasonal to Interannual Time Scales. J. Climate, 23, 4901-4925 (DOI: 10.1175/2010JCLI3373.1).
  • ORAS5:Zuo, H., Balmaseda, M. A., Tietsche, S., Mogensen, K., and Mayer, M.: The ECMWF operational ensemble reanalysis–analysis system for ocean and sea ice: a description of the system and assessment, Ocean Sci., 15, 779–808, 2019. https://doi.org/10.5194/os-15-779-2019
  • SODA 3.7.2: A New Ocean Climate Reanalysis James A. Carton; Gennady A. Chepurin; Ligang Chen J. Climate (2018) 31 (17): 6967–6983.doi: 10.1175/JCLI-D-18-0149.1
  • SODA 3.4.2: A New Ocean Climate Reanalysis James A. Carton; Gennady A. Chepurin; Ligang Chen J. Climate (2018) 31 (17): 6967–6983.doi: 10.1175/JCLI-D-18-0149.1
  • EN4: Good, S. A., M. J. Martin and N. A. Rayner, 2013. EN4: quality controlled ocean temperature and salinity profiles and monthly objective analyses with uncertainty estimates, Journal of Geophysical Research: Oceans, 118, 6704-6716, doi:10.1002/2013JC009067.
  • ECCO:
    • ECCO Version 4 Release 4 Dataset ECCO Consortium, Fukumori, I., Wang, O., Fenty, I., Forget, G., Heimbach, P., & Ponte, R. M. July 2020. ECCO Central Estimate (Version 4 Release 4). Retrieved from https://ecco.jpl.nasa.gov/drive/files/Version4/Release4/interp_monthly/
    • ECCO Version 4 Release 4 Synopsis ECCO Consortium, Fukumori, I., Wang, O., Fenty, I., Forget, G., Heimbach, P., & Ponte, R. M. (2020, April 24). Synopsis of the ECCO Central Production Global Ocean and Sea-Ice State Estimate (Version 4 Release 4).
    • ECCO Version 4 Description Forget, G., J.-M. Campin, P. Heimbach, C. N. Hill, R. M. Ponte, and C. Wunsch, 2015: ECCO version 4: An integrated framework for non-linear inverse modeling and global ocean state estimation. Geoscientific Model Development, 8, 3071-3104, doi:10.5194/gmd-8-3071-2015.
  • ORA20C:
    • de Boisseson, E., Balmaseda, M. and M. Mayer (2017). Ocean heat content variability in an ensemble of twentieth century ocean reanalyses. Clinate Dynamics. DOI: 10.1007/s00382-017-3845-0.
    • de Boisseson, E. and M. Balmaseda (2016). An ensemble of 20th century ocean reanalyses for providing ocean initial conditions for CERA-20C coupled streams. ERA report series 24.
  • HadISST1.1: Rayner, N. A.; Parker, D. E.; Horton, E. B.; Folland, C. K.; Alexander, L. V.; Rowell, D. P.; Kent, E. C.; Kaplan, A. (2003) Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century J. Geophys. Res.Vol. 108, No. D14, 4407 10.1029/2002JD002670
  • NOAA OI SST: Reynolds, R.W., N.A. Rayner, T.M. Smith, D.C. Stokes, and W. Wang, 2002: An improved in situ and satellite SST analysis for climate. J. Climate, 15, 1609-1625.
  • GPVP V3.2: Adler, Robert; Wang, Jian-Jian; Sapiano, Matthew; Huffman, George; Chiu, Long; Xie, Ping Ping; Ferraro, Ralph; Schneider, Udo; Becker, Andreas; Bolvin, David; Nelkin, Eric; Gu, Guojun; and NOAA CDR Program (2016). Global Precipitation Climatology Project (GPCP) Climate Data Record (CDR), Version 2.3 (Monthly). National Centers for Environmental Information. doi:10.7289/V56971M6 [access date]

Other Sources of Products

Ocean Reanalysis Comparison References

  • Balmaseda, M. A., and Coauthors, 2015: The Ocean Reanalyses Intercomparison Project (ORA-IP). J. Operational Oceanogr., 8 (S1), S80–S97, https://doi.org/10.1080/1755876X.2015.1022329.
  • Xue, Y., Wen, C., Kumar, A. et al. A real-time ocean reanalyses intercomparison project in the context of tropical pacific observing system and ENSO monitoring. Clim Dyn 49, 3647–3672 (2017). https://doi.org/10.1007/s00382-017-3535-y
WRIT is supported in part by NOAA/ESRL Physical Sciences Laboratory, the NOAA Climate Program Office, and the US Department of Energy's Office of Science (BER). WRIT contributes to the Atmospheric Circulation Reconstructions over the Earth (ACRE) Initiative.