MODELING SYSTEM OVERVIEW

The description below pertains to WRF ARW solver.

The equation set for ARW is fully compressible, Eulerian and nonhydrostatic with a run-time hydrostatic option. It is conservative for scalar variables. The model uses terrain-following, hydrostatic-pressure vertical coordinate with the top of the model being a constant pressure surface. The horizontal grid is the Arakawa-C grid. The time integration scheme in the model uses the third-order Runge-Kutta scheme, and the spatial discretization employs 2nd to 6th order schemes. The model supports both idealized and real-data applications with various lateral boundary condition options. The model also supports one-way, two-way and moving nest options. It runs on single-processor, shared- and distributed-memory computers.

The flowchart below illustrates the component programs of the WRF Modeling System. The WRF model can be run with either idealized initialization or real-data initialization. In the current release (release 3.0, April 2008), the WRF model supports the Eulerian mass solver, referred to as the advanced research WRF (ARW) dynamical solver. The purpose of the ideal.F (pink) and real_em.F (blue) programs is to generate input and (if necessary) boundary files for the WRF model. This involves a hydrostatic balance adjustment in addition to setting up the initial 3d and 2d fields of the WRF variables. The WRF model supports full physics, two-way, one-way and two-way moving nests, analysis and observation nudging.

The function of the WRF Preprocessing System (WPS) is to define WRF grid, generate map, elevation and land information for WRF, take real-data analyses/forecasts from another model, and interpolate the data to the WRF grid. The time-dependent (analysis) fields consist of 3d wind, potential temperature, and water vapor, and a number of 2d fields.

WRF-Var (which supports 3D-VAR capability in the current release) can be used to assimilate observations into model initial conditions.

The standard output from WPS, real, and WRF model is in netCDF format (one of WRF I/O format) can be displayed by one or more graphic tools: NCAR Graphics NCL, GrADS, or RIP4. Converters to vis5d, GrADS, and RIP4 data formats are available as are sample NCL scripts that can take netCDF files as input.