Term Definition
Authoritative repository A repository defined by the presence of a governance group and well-defined processes to manage development and periodic releases of reference versions. It exists as a definitive source for a given software development project and must contain a regression suite and documentation.
CCPP (Common Community Physics Package) Model agnostic, vetted, collection of codes containing atmospheric physical parameterizations for use in numerical weather prediction. Common categories of parameterizations include radiation, surface layer, planetary boundary layer and vertical mixing, deep and shallow cumulus, and microphysics. The parameterizations can be grouped in physics suites which are sets of parameterizations known to work well together. See the CCPP home page.
CESM (Community Earth System Model) A community climate model centered at the National Center for Atmospheric Research. See the  CESM home page.
CIME (Common Infrastructure for Modeling Earth) The Common Infrastructure for Modeling Earth (CIME) contains a set of community-based infrastructure utilities including a Case Control System (CCS) along with other software tools. The CIME CCS provides a user-friendly, reproducible workflow for configuring, compiling and executing Earth system models. It consists of an extensible set of object-oriented python scripts and is well documented. The CIME CCS also provides a user-friendly porting capability for CCS-compliant modeling systems, and it is accompanied by comprehensive system and unit testing functionality. The CIME CCS is used in CESM and the first release of UFS, the Medium-Range Weather Application. See the CIME documentation.
Code Manager Person responsible for managing processes and policies related to code in a component repository, including code updates, tagging and releases, and documentation policies.
Component A “composable” software element that has a clear function and interface. In Earth system models, these are often a portion of the Earth System (e.g. atmosphere, ocean, or land surface).
Component repository A repository that contains, at a minimum, source code for a component.
Composable With respect to components, capable of being composed; capable of being assembled into a multi-component system.
Compset (Component set) A component set or compset is a label that describes a coupled model configuration. Originated by the CESM project, it includes a list of the components in the configuration and other information.
CONFIG An input set that fully represents an execution of an experiment. It includes the various coupled components defined in compsets and their parameterisations. This representation for running an experiment can also be used by the Front End to deliver a Job Spec for a particular experiment to run within the Workflow Environment.
Connector Connector is a term for a NUOPC Layer software component that performs one-way data communications and simple transformations, including redistribution and grid remapping.
CROW The Community, Research, and Operational Workflows framework is a toolset for the new unified workflow system designed to consolidate the current multitude of different workflow systems being used at NCEP.
Cylc Cylc is a general purpose workflow engine that orchestrates cycling workflows very efficiently. It was designed for production weather, climate, and environmental forecasting systems but is not specialized for those domains. It is widely used, and is the workflow engine included in CIME. See the Cylc home page.
DA (Data Assimilation) The combining of diverse data, possibly sampled at different times and intervals and different locations, into a unified and consistent description of a physical system, such as the state of the atmosphere or the Earth system.
DA solver Iterative mathematical solver to compute the solution of a large-size data assimilation problem. Variational solvers use computationally efficient minimizers, while ensemble filters reduce the dimensionality of the problem through spatial localization. The output of the DA solver is an analysis increment to the model background.
ecFlow One of the specific Workflow Management System packages used to implement the Workflow Environment. See link for more information.
EnKF The Ensemble Kalman Filter utilizes an ensemble of forecasts to provide estimates of the background error distribution.
Ensemble A collection of forecasts that are reasonably viewed as parts of a whole, e.g., by virtue of being equally probable by construction.
ESMF (Earth System Modeling Framework) ESMF is a community-developed software infrastructure for building and coupling models. See the
ESMF home page.
External component A component with a development team and authoritative code repository that is not at NCEP/EMC.
Forward operator Set of operators to simulate observations from the model fields. The forward operator may contain interpolation, radiative transfer modeling, and various other calculations. Quality control procedures involving observations and model simulated values (e.g. bias correction, cloud detection) are also involved.
Front end User script that instantiates a workflow instance for execution of a specific experiment for a particular Workflow Management System (ie. Rocoto, ecFlow) for a given set of configuration inputs.
FV3 (Finite Volume 3) dynamical core FV3 is a scalable and flexible dynamical core, the part of an atmospheric model that solves the governing equations of fluid motion. It is the dynamical core used in the UFS atmospheric model.
Gatekeeper Person responsible for managing releases in operational and implementation branches within a UFS application umbrella repository. This person is also responsible for enforcing documentation policies and tagging the updates to the trunk of the umbrella repository during a development cycle (e.g. new microphysics).
Hierarchical Test Framework (HTF) Software that supports testing of a full forecasting system like UFS from simple through complex configurations.
Initializations In data assimilation, application of the analysis increment to the model background in order to produce the best initial conditions for a model forecast. This stage may involve spatial interpolation from low-resolution to high-resolution grids, 3D or 4D Incremental Analysis Update (IAU), and other techniques aiming at preserving the model internal balance.
Job specs The instance of a workflow with the prescribed steps to be executed and resources to be used for a given high performance computing batch system.
Mediator A Mediator, sometimes called a coupler, is a software component that includes code for representing component interactions. Typical operations include merging data fields, ensuring consistent treatment of coastlines, computing fluxes, and temporal averaging.
Model background Model fields, usually originating from a short-term forecast, providing the best estimate of the state of the Earth system component prior to assimilating the observations.
Model component A forecast component that represents a physical domain or process, for example sea ice.
Modeling application A NEMS modeling application is software that is designed for a particular forecasting purpose. It is comprised of a set of model components and NEMS coupling infrastructure, and is associated with a range of valid configurations.
Model solver Dycore-specific part of the atmospheric model code that calls the dynamics and the physics driver to advance a given domain by a time step.
NCEP/EMC National Centers for Environmental Prediction/Environmental Modeling Center. The part of the National Weather Service that leads its modeling efforts.
NCEP Production Suite All codes that run in operations.
NEMS (NOAA Environmental Modeling System) Software infrastructure that supports NCEP/EMC forecast products. The coupling software is based on ESMF and the NUOPC layer.
NEMS.x A NEMS executable.
NEMSIO A package developed at EMC to support the input/output for NEMS projects. It was designed to read and write data sets for all the NEMS atmosphere models, and supports serial and parallel I/O. The current version handles binary and GRIB1 data. There are questions about whether to add more data formats such as GRIB2 or NETCDF, or to discontinue use and move to a more widely used I/O format. See the NEMSIO User Guide for more information.
NUOPC Layer The National Unified Operational Prediction Capability (NUOPC) Layer is an addition to ESMF that increases the interoperability and usability of coupled modeling systems by adding rules for how ESMF components behave. It adds to ESMF pre-fabricated modeling system components including Models for wrapping components, Drivers for sequencing them, Connectors for simple data transfers, and Mediators for more complex coupling operations such as merging fields and computing fluxes. These basic elements can be arranged in multiple ways and specialized.
NUOPC Layer cap A cap is the wrapper that is written to adapt a native component interface to the NUOPC Layer interface. It includes a mapping of native data structures to ESMF data structures.
NWS (U.S. National Weather Service) The NWS is an agency of the United States government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the purposes of protection, safety, and general information. It is a part of the National Oceanic and Atmospheric Administration (NOAA) branch of the Department of Commerce.
Operational functioning routinely with a fixed schedule and a well-defined set of deliverables, products or services .
Physics driver Software used to communicate variables between an atmospheric model solver and physical parameterizations. The physics driver can be used to call a variety of physical suites, as long as all necessary variables are supplied by the solver. A physics driver is termed Interoperable when it is agnostic of the other aspects of the model and can therefore be used with a variety of dynamic cores and physics suites.
Physical parameterization Code that represents one or more physical processes that force or close model dynamics. It is defined by the code implementation of the mathematical functions comprising the scheme, and not by a particular set of parameters or coefficients that could be set externally.
Physics suite A set of non-redundant atmospheric physical parameterizations that have been designed or modified to work together to meet the forcing and closure requirements of a dynamical core used for a weather or climate prediction application. A set of physical parameterizations chosen to be identified as a suite results from the needs and judgment of a particular user, developer, or group of either. In some cases, a suite may be identified as a benchmark or reference set of physical parameterizations, against which variations can be tested. Since a suite can be configured in different ways for different applications by modifying its tunable parameters, an accompanying set of tunable parameters should be specified when defining a reference implementation or configuration of a physics suite.
Post-processor Software that enhances the value of the raw forecasts produced by the modeling application to make them more useful and usable. At NCEP, the UPP (Unified Post Processor) software is used to convert data from spectral to gridded format, de-stagger grids, interpolate data vertically (e.g., to isobaric levels) and horizontally (to various predefined grids), and to compute derived variables. Some types of post-processors, such as statistical post-processors, use historical information of previous runs and observations to de-bias and calibrate its output.
Prediction Package A Prediction Package consists of a sequence of jobs that together form an end-to-end forecast. rediction Packages are one of the layers described in the Unified Modeling System Architecture Overview.
Repository A specific location referenced via URL or other identifier that acts as an archive with tracking capability managed through some version control system (e.g. SVN or git). A software development repository may contain source code, an integrated regression test suite/system, documentation, etc.
Rocoto One of the specific Workflow Management System packages used to implement the Workflow Environment. See link for more information.
Scheduler An HPC application service that allocates resources and manages execution of individual batch jobs in a scheduled and prioritized fashion.
Software infrastructure Software infrastructure is a set of technical building blocks. The software infrastructure should be distinguished from the system architecture – the latter defines what is built; the former is a set of tools for building it.
Stakeholders The collection of interested individuals and institutions that have an interest in the outcome; for coupled prediction, stakeholders include either those who have the wherewithal to contribute to system advancement, have a mandate to produce forecasts in an operational manner or have requirements for the forecasts or forecast system.
System architecture The fundamental organization of a system, embodied in its components, their relationships to each other and the environment, and the principles governing its design and evolution.
UFS (Unified Forecast System) The Unified Forecast System (UFS) is a community-based, coupled comprehensive Earth system modeling system. The UFS numerical applications span local to global domains and predictive time scales from sub-hourly analyses to seasonal predictions. It is designed to support the Weather Enterprise and to be the source system for NOAA’s operational numerical weather prediction applications.
UFS App or Application UFS configurations that support specific predictive targets (e.g. Medium-Range Weather, Subseasonal-to-Seasonal, Space Weather) are called applications. Each application combines a numerical model, data assimilation, post-processing, workflow, and other elements. Application outputs are fields of model parameters with a given spatial and temporal resolution, cadence (how often the model is run), and accuracy.
UFS Chemistry Transport App Global model for prediction of air quality and related phenomena.
UFS Regional App Limited-area model based on the FV3 dynamical core, combined with suitable physical parameterizations, for undertaking detailed studies of a particular region or phenomena.
UFS-SC (UFS Steering Committee) The primary governance body of the UFS.
UFS Seasonal Prediction App Global coupled model, specific to the seasonal timeframes, composed of FV3 dynamical core, with appropriate physical parameterizations, coupled to MOM6, CICE5, and WaveWatch III.
UFS system architecture A layered structure that is expected to encompass

  1. a workflow environment that includes a user interface and database of previous runs and verifying analyses,
  2. a prediction suite with a sequence of pre-processing, data assimilation, forecast, and post-processing components,
  3. a model application layer with a coupling framework, a prescribed interface between atmospheric physics and dynamics, model components, and scripting, and
  4. a layer of utilities and numerical libraries.
UFS Working Group A group charged with advancing a particular topic area within the UFS.
Umbrella code One or more configuration files that define a composite application through externals.
Umbrella repository A repository that contains references to external repositories, but no source code.
Verification The process of comparing forecasts to relevant observations and analyses to measure the forecast goodness.
Workflow component One of the major executables used in a Prediction Package, for example, pre-processor, data assimilation, modeling application, post-processor.
Workflow Environment The architectural layer where the Workflow Management System (i.e. Rocoto, EcFlow) and its supported elements, such as the Front End, reside. The Workflow Environment instantiates a specific experiment including its orchestration logic for ordering and scheduling of jobs within the Prediction Package. Described in the Unified Modeling System Architecture Overview.
Workflow Management System (WMS) A piece of software that provides an infrastructure to set up, execute, and monitor scientific workflows. Scientific workflow tasks are usually triggered by the availability of some kind of input data, and a task’s result is usually some kind of data that is fed as input to another task in the workflow. There are two WMSs in use at NOAA, EcFlow and Rocoto.