Weather Research and Forecasting Model (WRF)#

The aim of this notebook is to run WRF regional initialized simulations of two events that have specific boundary layer structures of interest

With these exercises we hope for you to achieve#

  • An understanding of the workflow for a weather forecast model

  • The ability to perform basic sensitivity experiments

  • An understanding of how boundary layer evolution maybe impact forecast evolution

  • A baseline diagnosis of multiple WRF experiments

Note

To the greatest extent possible we will follow the Weather Research and Forecasting Model (WRF) users’ guide for setting up, submitting, running and processing output from simulations.

Description of Model Cases and Configurations#

While WRF is able to simulation weatehr events in a regional domain over much of the globe, we will limit our experiments, at least initially to 2 case studiesthat will hopefully illusttae teh role of boundary layer processes in the evolution of these events

Test Run of WRF Cases#

Please follow as closely as possible the test cases of the WRF users’ guide, the online tutorial and the accompanying tutorial guide as closely as possible. Additionaly, there are number of great pre-recorded lectures from the WRF in-person tutorial here. If you are unfamliar with WRF, of particular interest will be the Introduction to WRF, Running the WPS system, Running WRF and importantly to Boundary Layer Physics and Surface Process avalailable.

If you are not currently on Cheyenne then login. The model will not compile and run properly on Casper

ssh -XY $USER@cheyenne.ucar.edu

Below is a condensed summary of the key steps. If you haven’t already create a ASP2023 work directory

mkdir /glade/work/$USER/ASP2023

  1. Download the WRF model code and the WRF Pre-Processing System (WPS) code 

cd /glade/work/$USER/ASP2023
git clone https://github.com/wrf-model/WRF
git clone https://github.com/wrf-model/WPS

We will return to the WPS code later.

  1. Change to (checkout) the current version (4.5) release branch

cd WRF
git checkout release-v4.5.1

This now stages the code we need to use

  1. Configure WRF

./configure

You will be presented with options, so make the following choices.

  • Choose option 13 for serial generic intel

  • Then, choose option 1 basic nesting This then generates the configure.wrf file if succesfull with the following end message

*****************************************************************************
This build of WRF will use NETCDF4 with HDF5 compression
*****************************************************************************

  1. Compile WRF

Compile WRF where the build type is em_real to denote a real case study (as opposed to seomthing like idealised)

Note

Below commands starting with qcmd push the work to a separate compute node to avoid congestion on the login nodes. These are interactive sesssions so you wll have to stay logged on to cheyenne for the executable to complete

Need to do a small code grab first and then compile

cd phys && make submodules && cd ..
qcmd -q S2036390 -- ./compile -j 8 em_real >& log.compile

Warning

Remove the -q S2036390 is submitting outside the hours of 1:30pm to midnight. Which is the period of our special reservation

Leave this running in your window until complete

Warning

This compile can take up to 30 minutes so feel free to move onto some of the other project tasks in the mean time. Maybe start thinking about WRF sensitivity experiments or starting with the CLASS set-up if you haven’t already.

  1. Check build When complete do a build check by viewing the end of the compile log file log.compile

tail log.compile

If the code compiled correctly near the end you should see

--->                  Executables successfully built                  <---

Note

If you need to recompile the whole set of executables for WPS and WRF run the local /clean command

  1. Code and executable check Once the compilation completes, to check whether it was successful, you need to look for executable in the WRF/main directory:

ls -l main/*.exe

  1. WPS code configure - find a more detailed description here Go to the WPS code based and select the right code branch

cd ../WPS
git checkout release-v4.5

  1. Configure WPS As for WRF, configure WPS to be ready for compilation

./configure

You will be presented with compile/platform options, so make the following choices.

  • Choose 17 for serial compile on intel You should see a configure.wps file when this completes

  1. Compile WPS

./compile >& compile.log

This should take much less take than WRF (a few minutes)

If your compilation was successful, you should see these executables created in (make sure they are not of size zero)

geogrid.exe, ungrib.exe, metgrid.exe

Note

If they are zero size type the following to see if there were errors output (i.e. does the word ‘error’ occur)

grep -i error compile.log

This should have completed your setup. To summarize, this is the prestaging of code required for running WRF. It should not need to be repeated from now on, unless code is changed:

Summary WRF/WPS Workflow

WPS
geogrid.exe - creates terrestrial data (static).
ungrib.exe - unpacks GRIB meteorological data and packs it into an intermediate file format.
metgrid.exe - interpolates the meteorological data horizontally onto your model domain (WRF input)
WRF
real.exe - vertically interpolates the data onto the model coordinates.
wrf.exe - generates the model forecast.

Now move on to running the WRF control simulation which specifies the domain