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WRF Tutorial. A Hands-on Overview of the WRF Modeling Process Condensed Version for WFO ANC. July 2009. WRF Architecture. A Typical WRF Run on midnight (Overview). Run a script to install template directories in your filesystem Create a model domain

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Wrf tutorial

WRF Tutorial

A Hands-on Overview of the WRF Modeling Process

Condensed Version for WFO ANC

July 2009



A typical wrf run on midnight overview
A Typical WRF Run on midnight (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Install template directories in your filesystem
Install Template Directories in Your Filesystem

  • There is a centralized version of WRF installed on midnight.

  • However, WRF is set up such that you need to be doing your runs in the same directory as the executables.

  • We have set up a system that will create template directories in your own filesystem for WPS and WRF

  • For each domain that you work with, you’ll set up your own WPS/WRF template directories

    • Example – for a 10km domain over Alaska, you might have your work in directories WPS-Alaska10km and WRFRun-Alaska10km



A typical wrf run on midnight overview1
A Typical WRF Run on midnight (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Create a model domain
Create a Model Domain

  • This step sets up the model domain boundaries, resolution, topography, nests and creates the static file (land use, soil type, etc.) needed by a model run

  • We only do this once for a given model domain

  • Procedures

    • Define your domain – lat/lon, size, resolution, projection, etc.

    • Edit a namelist file (specifying domain parameters)

    • Run geogrid.exe to create the domain

    • Verify successful creation



Create the domain
Create the Domain

netCDF file produced by

geogrid.exe


Create the domain then verify
Create the Domain, Then Verify

  • Run geogrid.exe – this program looks at parameters in namelist.wps, then generates the domain in a netCDF file, geo_em.d01.nc

  • This file is viewable with various tools, including ncview


Height from geo em d01 nc
Height from geo_em.d01.nc


Or generate map outline
Or, Generate Map Outline

NOTE – you may need to run

module load ncl-5.1.0

before idt will work




A typical wrf run overview
A Typical WRF Run (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Get input data
Get Input Data

  • Numerous sources of different types

    • Reanalysis for historical runs

      • Global Final Analysis (FNL) – global coverage, 1-degree resolution

      • North American Regional Reanalysis (NARR)

    • Recent model output for real-time runs

      • North American Mesoscale model (NAM)

      • Global Forecast System (GFS)

    • Observations for data assimilation







A typical wrf run overview1
A Typical WRF Run (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Modify namelist wps
Modify namelist.wps



Make links to the input files
Make links to the input files

Contents of /datadir/morton/TutorialData/KatrinaAVN


Run ungrib exe
Run ungrib.exe

Ungribbed files


A typical wrf run overview2
A Typical WRF Run (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Extract and interpolate degribbed data to match model domain
Extract and Interpolate Degribbed Data to Match Model Domain

  • So far, we’ve managed to convert the original input data to an intermediate form

  • Next, we extract data from the intermediate files that correspond to our selected domain. Where necessary, we interpolate so that the resulting files consist of input values matched to our specific grid

  • To do all this, we modify namelist.wps (though it’s typically already set up correctly for this), and then we run metgrid.exe


Run metgrid exe
Run metgrid.exe

netCDF files containing input

data translated and interpolated

for our particular grid


A typical wrf run overview3
A Typical WRF Run (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Extract initial and boundary conditions
Extract Initial and Boundary Conditions

  • The files we created with metgrid.exe represent the input data mapped to our specific domain grid

  • The next step is to extract what we need from this input data for initial and lateral boundary conditions

  • To do this, we

    • Change to our WRFRun directory

    • Edit namelist.input

    • Copy the met_em* files produced with metgrid.exe

    • Run real.exe, and get two files that will contain the boundary conditions for running WRF – wrfbdy_d01 and wrfinput_d01


Get value of num metgrid levels
Get Value of num_metgrid_levels

Use ncdump to query one of the met_em* files





Run real exe or real serial exe
Run real.exe (or real-serial.exe)

From WPS

Lateral BC’s

Initial conditions


Psfc from wrfinput d01 verify with ncview
PSFC from wrfinput_d01(Verify with ncview)


A typical wrf run overview4
A Typical WRF Run (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Run the model
Run the Model

  • Use the same namelist.input from the previous step (real.exe). In most cases you won’t need to modify anything.

  • Run ./wrf.exe (or ./wrf-serial.exe)


A typical wrf run overview5
A Typical WRF Run (Overview)

  • Run a script to install template directories in your filesystem

  • Create a model domain

  • Get input data for initial and lateral boundary conditions

  • Ungrib the input data to an intermediate standard form understood by WRF pre-processing utilities

  • Extract and interpolate the input data to match the model domain

  • Extract initial and lateral boundary conditions from input data and modify vertical coordinate system

  • Run the model

  • Do something with the output


Postprocessing
Postprocessing

  • The default output file is a netCDF file, named something like

    wrfout_d01_2005-08-28_00:00:00

  • Numerous utilities exist for viewing in native netCDF format, or converting to other formats (e.g. GRIB, Vis5D, BUFR)

Start

time


Ncview model output
ncview Model Output

  • Using a quick and dirty netCDF viewer to look at model output


Running wrf exe in parallel
Running wrf.exe in Parallel

wrfrun.pbs



Viewing stdout
Viewing stdout


Viewing stdout1
Viewing stdout


Resources
Resources

  • ARSC-WRF Google Group – http://groups.google.com/group/arsc-wrf

  • WRF Users Page – http://www.mmm.ucar.edu/wrf/users/

  • WRF ARW Users Guide – http://www.mmm.ucar.edu/wrf/users/docs/user_guide_V3/contents.html

  • WRF ARW Online Tutorial – http://www.mmm.ucar.edu/wrf/OnLineTutorial/index.htm


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