Coupled Model Prototype5 (s2sp5)

The UFS S2Sp5 is the latest experimental version of the UFS coupled model (frozen as of September 8, 2020 and available on GitHub). This experimental version represents a significant intermediate stage in the ongoing development of the next release of the UFS  seasonal to sub-seasonal (s2s) application. More details of the model components and configuration are provided below. 

Model and data details

The UFS S2Sp5 is a coupled atmosphere-ocean-sea ice model with FV3 dynamical core for the atmosphere. All components are coupled using the NOAA Environmental Modeling System (NEMS) infrastructure. The UFS S2Sp5 coupled system is being developed based on the uncoupled model (Global Forecast System (GFS)) that is being used operationally for the medium range weather application. More details of the current operational GFS version can be found in the EMC Model Evaluation Group’s briefings

Atmosphere GFDL's Finite Volume Cubed-Sphere dynamical core (FV3) horizontal resolution c384 (~25km), 64 vertical levels
Ocean  GFDL MOM6, Hybrid-coordinates with tripolar grid, 0.25 degree global resolution. 75 hybrid levels, OM4 Set up [Adcroft, 2019]
Sea Ice  Los Alamos Sea Ice Model, version 6 (CICE6). Same grid as the ocean model. 5 thickness categories
No Mushy thermodynamics
Physics  GFSv15 Physics that includes Scale-aware Simplified Arakawa-Schubert Scheme for convection (Han and Pan 2011), Hybrid Eddy-Diffusivity Mass-Flux (EDMF) Boundary Layer Parameterization (Han et al., 2016), Rapid Radiative Transfer Model for GCMs (RRTMG) with Monte-Carlo Independent Column Approximation (McICA) for radiation scheme, GFDL microphysics with 5  prognostics cloud species.
Waves WAVEWATCH III wave model at 0.5 degree regular grid. Provides feedback to the atmosphere and ocean. ST4 Physics [Ardhuin, 2010].


Reforecast period Forecast lead Frequency of initialization Initial conditions (data)


April 2011 to March 2018 (7 years) 6 hourly output, out to 35 days 1st and 15th of each month, 168 forecasts in total. Atm: CFSR
Ocn: 3Dvar CPC
Sea ice: CPC Ice analysis
Waves: generated with CFS forcings
Control run only


Data format, variables

Component Tar file Contents* Output Interval Grid Resolution File Format
Atmosphere gfs_prgb2_0p25.tar Atmospheric temperature, humidity, zonal, meridional and vertical velocity, vorticity, geopotential height, mixing ratios, at mandatory pressure levels 6-hourly C384 converted to regular
gfs_pgrb2b_0p25.tar Atmospheric temperature, humidity, zonal, meridional and vertical velocity, vorticity, geopotential height, mixing ratios, at additional levels
gfs_flux.tar Radiation, heat and momentum fluxes
Cloud height and cover
Surface and near-surface fields
Liquid and solid precipitation
Soil temperature and moisture
Ocean ocn_2D.tar Sea surface height, salinity, temperature, velocity, fluxes
Mixed layer depth
6-hourly Tripolar, primarily at ¼ degree
netcdf gzipped
ocn_3D.tar 3-D fields of potential temperature, salinity, velocity
ocn_daily.tar SST, fluxes Daily
Sea Ice ice.tar Ice area, thickness, velocity, stress, melt, growth, snow cover, freeze/melt onset
Fluxes, temperatures, precipitation rates
6-hourly Tripolar, primarily at ¼ degree
netcdf gzipped

*List of key variables, Tar files contain a number of other fields. 

In collaboration with the NOAA Big Data Program, the s2sp5 data is now available on the AWS here.

Researchers interested in the s2s prediction and model development are invited to evaluate the UFS S2Sp5 data. Analysis of the data may include, but is not limited to, process-based evaluations, diagnostic measures that reveal coupled feedback processes and s2s forecast skill estimations. Interested researchers may also volunteer to communicate their findings to the UFS-R2O project team, see POC below. Note that this is a voluntary opportunity to collaborate. No funding is associated with this announcement at this time.

Requirements for Data usage

Users of UFS S2Sp5 data are requested to acknowledge the data source and sponsoring agencies that support the the UFS-R2O project. In publications, it is recommended to include a text similar to the one below, in the acknowledgement section.

“The Unified Forecast System (UFS) coupled model experimental version 5 (UFS S2Sp5) data used in this study are produced at the National Weather Service Environmental Modeling Center, NWS/NCEP/Environmental Modeling center (EMC), and made available through the UFS Research to Operations (UFS-R2O) project that is sponsored by the National Weather Service (NWS) Office of Science and Technology Integration (OSTI) Modeling Program Division and the National Oceanic and Atmospheric Administration (NOAA) Oceanic and Atmospheric Research (OAR) Weather Program Office (WPO).”


Users are cautioned the data was made with an intermediate version of the UFS that is still under vigorous development and evaluation, see NWS disclaimer for additional details.


Special thanks to the UFS-R2O Coupled System team at NWS/NCEP/EMC, led by Avichal Mehra and Fanglin Yang, for producing and providing the s2sp5 data along with the information on this page..

For additional information about the s2sp5 data set, please contact Stylianos Flampouris at:
For inquiries on how to engage with the UFS R2O project in general, please contact the project leads at