Introduction

The WRF–ARW model is a fully compressible, nonhydrostatic model (with a hydrostatic option). Beginning in V4.0, its default vertical coordinate is a mass–based hybrid sigma–pressure vertical coordinate (prior to V4.0, the coordinate system was a mass–based 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 intergration schemes, and 2nd– to 6th–order advection schemes in both horizontal and vertical directions. It uses a time–split small step for accoustic and gravity–wave modes. The dynamics conserves scalar variables.

The WRF–ARW model code contains initialization programs (ideal.exe and real.exe), a numerical intergration program (wrf.exe), and a program to do one–way nesting (ndown.exe). The WRF–ARW model supports a variety of applications across scales ranging from meters to thousands of kilometers. 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
• Real–time NWP

Software Requirements

• Fortran 90 or 95, and a C compiler
• perl 5.04 or later
• If an MPI or OpenMP compilation is desired (required for parallel runs), MPI or OpenMP libraries are required
• WRF I/O API supports netCDF, pnetCDF, and PHD5, therefore one of these libraries needs to be available on the computer on which you compile and run WRF
• If you plan to run a real–data case, and you plan to use Grib2 data, you must have Jasper, libPNG, and Zlib installed
• The following Unix commands are mandatory:

  ar             head              sed
  awk          hostname      sleep
  cat            ln                  sort
  cd             ls                  tar
  cp             make            touch
  cut            mkdir            tr
  expr          mv                uname
  file             nm                wc
  grep          printf             which
  gzip           rm
  

****Please see our Compiling Tutorial for instructions on installing required software.****

Program Flow

• If you are only planning to run Idealized cases, you need:

  WRF ARW Model + PostProcessing

• If you are planning to run Real cases, you need:

  WPS + WRF ARW Model + PostProcessing

• If you are planning to run Real Cases with Variational Analysis, you need:

  WPS + WRFDA + WRF ARW Model + Postprocessing

  If you plan to run WRFDA, be sure to reference Chapter 6 in the WRF–ARW Users' Guide, once you have become familiar with the basic WRF–ARW model.
  
  **View the flow chart to see how the programs interact**

Documentation

Users' Guide
The Online Tutorial is complimentary 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 review this guide before you start running the model.

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

Bi-Annual Tutorial Presentations
On this page you can find all the slide show presentations presented at previous Bi-Annual Tutorial Classes (look for the section titled 'WRF Basic Tutorial Presentations').

WRFDA
For more information on WRF Data Assimilation, refer to Chapter 6 of the WRF ARW Users' Guide.

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

Getting Started