What do these words mean?

You do not need to memorize these terms. Use this page when a word in another guide is unfamiliar.

Terms are grouped by meaning and workflow, rather than alphabetically, so related ideas stay together. External links point to official documentation, standards bodies, or established research-computing documentation and open in a new tab. Terms that are specific to wrfkit link to this site's own documentation.

Weather modeling & WRF

These terms appear together in the WPS → WRF workflow. If you want to see the whole sequence first, use the first-run tutorial.

Core model and preprocessing

Term	Plain-language meaning
WRF	The Weather Research and Forecasting model. It numerically simulates how the atmosphere changes over time.
WPS	The WRF Preprocessing System. It prepares geographical and meteorological input for real-data WRF simulations.

WPS preprocessing programs

Term	Plain-language meaning
geogrid	Defines the model domain and interpolates static geographical data such as terrain and land use onto the model grid.
ungrib	Extracts meteorological fields from GRIB weather-data files and converts them into WPS intermediate files.
metgrid	Interpolates the meteorological fields prepared by ungrib onto the domains defined by geogrid.

WRF initialization and output

Term	Plain-language meaning
real	WRF's real-data initialization program. It turns met_em.* files into the initial and lateral-boundary files needed by WRF.
wrfout	The standard WRF history/output files containing simulated atmospheric fields.

Scientific configuration and input data

Term	Plain-language meaning
namelist	WRF/WPS's native text configuration format. The main files are namelist.wps and namelist.input.
domain	The geographic area and numerical grid that the model simulates.
forcing / meteorological input	In wrfkit, forcing means external analysis or forecast data, such as GFS, that WPS and real process to create initial and lateral boundary conditions. WRF documentation more often describes this as meteorological input or external analysis/forecast data.
GFS	NOAA/NCEP's Global Forecast System. wrfkit currently uses GFS data for its bundled real-data validation workflow.
geography / static data	Time-invariant terrestrial data such as terrain height, land use, soil categories, and related fields used by geogrid.
spin-up	An early part of a simulation during which model fields adjust away from their initial state before the period used for analysis.
WRF physics	Parameterizations that represent atmospheric processes such as clouds, radiation, surface exchange, and the planetary boundary layer.
GRIB	A standardized binary code used to exchange and store gridded meteorological information. WPS ungrib reads GRIB input.
NetCDF	A set of software libraries and machine-independent, self-describing data formats widely used for array-oriented scientific data. WRF commonly reads and writes NetCDF files.

Computing & HPC

Software environment

Term	Plain-language meaning
Nix	A package manager that lets wrfkit construct controlled software environments containing pinned compilers, MPI, NetCDF, and other dependencies.
rootless Nix	The no-administrator-privilege Nix setup used by wrfkit on systems such as shared HPC clusters.

Parallel computing

Term	Plain-language meaning
MPI	Message Passing Interface, a standard for communication among multiple processes in a parallel program.
MPI rank	One participating MPI process, identified by a rank number within an MPI communicator. A 16-rank WRF run has 16 cooperating MPI processes.

HPC clusters

Term	Plain-language meaning
HPC	High-performance computing: using powerful computing resources, often many CPUs or nodes working together, to run calculations that would be too large or slow for an ordinary computer.
cluster	A group of networked computers operated together as a shared computing system. HPC clusters commonly include login or service nodes plus many compute nodes.
node	One computer in a cluster. A node may serve a specialized role, such as providing user access or running computational workloads.
login node	A shared access point used on many HPC clusters for SSH, file management, job preparation, and job submission. Heavy computation normally runs on compute nodes. Login nodes are a common cluster design, not a requirement imposed by Slurm itself.
compute node	A cluster server intended to perform the actual computational workload. Scheduler-managed jobs are assigned resources on one or more compute nodes.

Slurm scheduling

Term	Plain-language meaning
Slurm	A workload manager used on many HPC clusters. It manages resources, queues jobs, and launches work on allocated nodes.
partition	A logical group of Slurm nodes that acts like a job queue with its own limits and policies.
job	A user's request for resources and work to run under Slurm for a specified period of time.
allocation	The compute resources Slurm reserves for a job, such as nodes, CPUs, memory, and time.
job step	A set of tasks launched inside an existing Slurm job allocation. wrfkit's single-node bridge creates a child job step before starting MPI ranks.
sbatch	The Slurm command that submits a batch script to the scheduler.
srun	The Slurm command used to launch tasks or job steps. wrfkit uses a child srun step internally for its validated single-node Slurm path.
interactive job / allocation	Reserved compute resources used interactively from a shell rather than through a fully unattended batch script. Sapelo2 provides its own interact convenience command for this workflow.

wrfkit workflow & files

Term	Plain-language meaning
wrfkit	This project: a reproducible environment and workflow layer around WRF/WPS that manages software setup, case workspaces, execution, and provenance without hiding the scientific namelists.
wrfctl	The main wrfkit command-line wrapper. It enters the managed environment and runs fetch, build, preparation, and execution tasks.
bootstrap	The wrfkit setup step that makes a working Nix environment available when the machine does not already provide one.
case	One experiment's tracked scientific configuration, such as cases/athens-minimal.
workspace	The generated working directory for a case, under .wrfkit/work/<case>, where WPS/WRF intermediate files and model products live.
RSL logs	WRF's per-rank runtime logs, normally named rsl.out.* and rsl.error.*; wrfkit also archives them per run for provenance.

A simple analogy

If these terms still feel abstract

Think of a WRF experiment like cooking from a scientific recipe.

wrfkit / WRF term	Analogy
namelist	recipe
WPS	preparing ingredients
real	setting up the kitchen for this run
WRF	cooking
wrfout	finished result
Slurm	assigning you a kitchen
MPI ranks	cooks working together
Nix	making sure everyone has the same tools
wrfkit	organizer connecting everything

Every term on the left is defined above. The analogy is intentionally simplified; use the glossary definitions for the precise meaning.