The WRF ARW model is a fully compressible, nonhydrostatic model (with a hydrostatic option). Its vertical coordinate is a terrain-following hydrostatic pressure coordinate. The grid staggering is the Arakawa C-grid. The model uses higher-order numerics. This includes the Runge-Kutta 2nd- and 3rd-order time integration schemes, and 2nd- to 6th-order advection schemes in both horizontal and vertical directions. It uses a time-split small step for acoustic and gravity-wave modes. The dynamics conserves scalar variables.

The WRF ARW model code contains initialization programs (ideal.exe and real.exe), a numerical integration program (wrf.exe), and a program to do one-way nesting (ndown.exe). The WRF ARW model Version 3 supports a variety of capabilities. These include:

- Real-data and idealized simulations
- Various lateral boundary condition options for both real-data and idealized simulations
- Full physics options
- Non-hydrostatic and hydrostatic (runtime option)
- One-way, two-way nesting and a moving nest
- Applications ranging from meters to thousands of kilometers


Software requirements

- Fortran 90 or 95 and C compiler
- perl 5.04 or later
- If MPI and OpenMP compilation is desired, MPI or OpenMP libraries are required
- WRF I/O API supports netCDF, pnetCDF, HDF5, GriB 1 and GriB 2 formats; hence one of these libraries needs to be available on the computer on which you compile and run WRF
- The following UNIX utilities: csh and Bourne shell, make, M4, sed, awk, and the uname command

Program Flow

• If you are only planning on running Idealized Cases, you would need:

WRF ARW Model + PostProcessing

• If you are planning on running Real Cases, you would need:

WPS + WRF ARW Model + PostProcessing

• If you are planning on running Real Cases with Variational Analysis, you would need:

WPS + WRF-Var + WRF ARW Model + PostProcessing

If you plan on using WRFDA, be sure to reference Chapter 6 in the WRF-ARW User's Guide, once you have become familiar with the basic WRF ARW Model.

**View the flowchart to see how the programs interact**



Users' Guide
The OnLine Tutorial is complementary to the Users' Guide. The latest WRF and WPS code are described in this document. The Users' Guide is updated for every Bi-Annual Tutorial, and is, therefore, the most up-to-date guide for running the WRF ARW model. It is highly recommended to download this guide before you start running the model.

WRF ARW Technical Note
This document contains:
- Descriptions of ARW model equations, discretization, initialization, and nesting
- General description of physics options available in the model
- General description of the WRF-Var

Bi-Annual Tutorial Presentations
All the slide shows presented at the last Bi-Annual Tutorial Class

Refer to Chapter 6 in the WRF ARW User's Guide.

**Browse the WRF ARW Users Pages for more information and documentation**

Getting Started