UFS Short-Range Weather Application Version 1.0 Release Description

Release date: 4 March 2021

The Unified Forecast System (UFS) is a community-based, coupled, comprehensive Earth modeling system. The UFS applications span local to global domains and predictive time scales from sub-hourly analyses to seasonal predictions. The UFS is designed to support an active research program and to be the source system for NOAA’s operational earth system prediction forecasts. The emerging Earth Prediction Innovation Center (EPIC) will help make the UFS a system that more community participants can help build.

The UFS can be configured for multiple applications. The release described here is the UFS Short-Range Weather (SRW) Application, which targets predictions of atmospheric behavior on a limited spatial domain and on time scales from less than an hour out to several days.

The SRW Application 1.0 includes a prognostic atmospheric model, pre- and post-processing, and a community workflow for running the system end-to-end. This first release does not include data assimilation (DA) or a verification package (e.g. METplus) as part of the workflow, and includes only atmosphere and land models.

The release is available through our GitHub repository.

The SRW Application is designed to be code that the research community can run, use for research, and commit any resulting innovation back to the relevant repositories. It is portable to a set of commonly used platforms. Specific configurations of the release (e.g. model resolutions, domain location, and physics options) are documented and supported. The documentation also includes a description of how to contribute code changes back into the application.

Forecast Model

The prognostic model in the UFS SRW Application is the Finite-Volume Cubed-Sphere (FV3) dynamical core configured with a Limited Area Model (LAM) capability. The dynamical core is the computational part of a model that solves the equations of fluid motion.

Supported model resolutions in this release include a 3-km, 13-km, and 25-km predefined Contiguous U.S (CONUS) domain, all with 64 vertical levels. Preliminary tools for users to define their own domain are also included in the release with full, formal support of these tools provided in future releases. The Extended Schmidt Gnomonic (ESG) grid is used with the FV3-LAM, which features relatively uniform grid cells across the entirety of the domain.

Interoperable atmospheric physics, along with the Noah Multi-parameterization (Noah MP) Land Surface Model options, 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 two physics options supported for the release. The first is an experimental physics suite being tested for use in the future operational implementation of the Rapid Refresh Forecast System (RRFS) planned for 2023, and the second is an updated version of the physics suite used in the operational Global Forecast System (GFS), v15.

Workflow and Build System

The SRW Application has a portable build system and a user-friendly, modular, and expandable workflow framework.

An umbrella CMake-based build system is responsible for building all of the components necessary for running the end-to-end regional workflow, including prerequisite libraries for the application, along with model and pre- and post-processing software. There is a small set of system libraries and utilities that are assumed to be present on the target computer: the CMake build software, a FORTRAN, c, and c++ compiler, and MPI library.

Once built, an experiment generator can be used to create a Rocoto-based workflow file that will call each task in the system, or the individual components can be run in a stand-alone, command line fashion if a batch system is not present on the available platform. The generated namelist for the atmospheric model can be modified in order to vary settings such as resolution or history file output 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.

This release can be run with Linux and macOS operating systems with Intel and GNU compilers. It has been tested on a variety of platforms widely used by researchers, such as the NOAA research systems Hera, Orion and Jet, NOAA’s Weather and Climate Operational Supercomputing System (WCOSS), the National Center for Atmospheric Research (NCAR) Cheyenne system, the National Science Foundation Stampede2 system, and generic Linux and macOS systems. Depending on the platform, the testing ranges from preconfigured, to configurable, limited test, and build-only platforms.

Input Files and Pre-Processing

The SRW Application can be initialized from a range of operational model data. It is possible to initialize the model from GFS, NAM, RAP, and HRRR model data files in Gridded Binary v2 (GRIB2) format for past dates. The release includes pre-processing software, called chgres cube, that converts model data to the format needed as inputs to the FV3-LAM.

Please note, for GFS data, dates prior to 1 January 2018 may work but are not guaranteed.

Post-Processing and Visualization

Output is provided in two formats. The forecast model output is in NetCDF format on a Gnomonic 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 to 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.

Validation and Examples

A comprehensive example is provided, including output data sets, through the Graduate Student Test (GST). It is 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 with topical sections provides a centralized location for UFS users and developers to post questions and exchange information. Formal, written documentation is also provided.

Future work and releases will include:

  • A more extensive set of supported developmental physics suites.
  • A larger number of predefined domains/resolutions and a fully supported capability to create a user-defined domain.
  • Inclusion of data assimilation capability.
  • A verification package integrated into the workflow.
  • Stochastic perturbations techniques.

In addition to the above list, other improvements will be addressed in future releases.