Release date: March 11, 2020
The Unified Forecast System (UFS) is a community-based, coupled, comprehensive Earth modeling system. The UFS numerical applications span local to global domains and predictive time scales from sub-hourly analyses to seasonal predictions. UFS is designed to support an active research program and to be the source system for NOAA’s operational numerical weather prediction forecasts. The emerging Earth Prediction Innovation Center (EPIC) will help make the UFS community system one that more participants can help build.
UFS can be configured into multiple applications. The first of these to be released to the community is the UFS Medium-Range (MR) Weather Application, which targets predictions of global atmospheric behavior out to about two weeks.
The MR Weather Application 1.0 includes a prognostic atmospheric model, pre- and post-processing, and a community workflow. This first release does not include data assimilation (DA) or a verification package (e.g. METplus) as part of the workflow, and is not coupled to ocean, ice, or wave models.
The release is available through GitHub. To access the code and documentation, see:
The MR Weather Application is designed to be a code that the research community can run and improve. It is portable to a set of commonly used platforms. Specific configurations of the release (e.g. specific model resolutions and physics options) are documented and supported. The documentation includes a description of how to get code changes back into the application.
The prognostic model in the UFS MR Weather Application is the UFS global atmosphere with the Finite-Volume Cubed-Sphere (FV3) dynamical core. The dynamical core is the computational part of a model that solves the equations of fluid motion. The version of the atmospheric model in this release is an updated version of the atmospheric model that is being used in the operational Global Forecast System v15 (GFSv15). [When we refer to GFS we mean the end-to-end global operational system that includes the model, DA, post processing, products and verifications.]
Supported model resolutions in this release are C96 (~100km), C192 (~50km), C384 (~25km), and C768 (~13km), all with 64 vertical levels. The Geophysical Fluid Dynamics Laboratory website provides more information about FV3 grids here: https://www.gfdl.noaa.gov/fv3/fv3-grids/
Interoperable atmospheric physics, along with the Noah land surface model, are supported through the use of the Common Community Physics Package (CCPP). Atmospheric physics are a set of numerical methods describing small-scale processes such as clouds, turbulence, radiation, and their interactions. There are four physics options supported for the release. Two of them are updated versions of the physics suite used in the operational GFS v15 (with different levels of complexity in evolving sea surface temperatures), and the other two are experimental suites that include the developments as of October 2019 for the next version of GFS, GFS v16 (also with different levels of complexity in evolving sea surface temperatures). The use of stochastic processes to represent model uncertainty is an option in this release, although the option is off by default in both of the supported physics suites.
Workflow and Build System
The MR Weather Application has a user-friendly workflow and a portable build system.
The workflow leverages the Common Infrastructure for Modeling the Earth (CIME) Case Control System (CCS). This established community workflow is familiar to many through its use in the Community Earth System Model (CESM) and the Energy Exascale Earth System Model (E3SM). CIME generates a default namelist for the atmospheric model and provides a way to change namelist options, such as history file frequency. It also allows for configuration of other elements of the workflow; for example, whether to run some or all of the pre-processing, forecast model, and post-processing steps.
The CIME-CCS builds the forecast model and the workflow itself. A separate set of scripts, available through the NCEPLIBS repository, builds the prerequisite libraries for the application, along with pre- and post-processing software. There is a small set of system libraries that are assumed to be present on the target computer: the CMake build software, compiler, and MPI library.
This release can be run with Linux and Mac operating systems with Intel and GNU compilers. It has been tested in a variety of platforms widely used by researchers, such as the NOAA research Hera system, the National Center for Atmospheric Research (NCAR) Cheyenne system, the National Science Foundation Stampede2 system, and Mac laptops.
Input Files and Pre-Processing
The MR Weather Application can easily be initialized from a range of GFS analyses.
It is possible to initialize the model from GFS analysis files in Gridded Binary v2 (GRIB2) and NEMSIO format for past dates, starting January 1, 2018. Dates before that may work, but are not guaranteed. The release includes pre-processing software, called chgres_cube, that converts GFS analyses to the format needed as inputs to the model.
Initial conditions in 0.5-degree spacing and GRIB2 format may be automatically downloaded by the CIME workflow from the NOMADS data server if available for the requested date and time; otherwise the user will need to perform the download themselves. The CIME workflow will retrieve fixed files, which are input files that change infrequently, for target resolutions.
Post-Processing and Visualization
Output is provided in two formats. The forecast model output is in NetCDF format on a Gaussian grid in the horizontal and model levels in the vertical. The Unified Post Processor (UPP) is included in the workflow as a way to convert the native NetCDF output from the model output to the GRIB2 format on standard isobaric coordinates in the vertical. The UPP can also be used to compute a variety of useful diagnostic fields.
These output formats can be used with visualization, plotting and verification packages, or for further downstream post-processing, e.g. statistical post-processing techniques.
Verification and Examples
A comprehensive example is provided, including output data sets. It will be possible to do a visual check to verify that the application is set up correctly and producing correct results.
User Support and Documentation
A forum-based online support system (forums.ufscommunity.org) with topical sections provides a centralized location for UFS users and developers to post questions and exchange information.
There is no data assimilation capability.
A verification package is not included in the workflow.
The atmospheric model is not coupled to ocean, wave, or ice models.
A limited set of developmental physics suites is supported.
Future releases will address these limitations and add other improvements.