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Running WRF on HECToR

Ralph Burton, NCAS (Leeds)Alan Gadian, NCAS (Leeds)

With thanks to Paul Connolly, Hector support team

http://www.ncas.ac.uk

WRFV2 flow chart

http://www.ncas.ac.uk

WRF: Overview

Decide upon which domain you wish to use*

Acquire some met. data for the dates you are interested in

Run the WPS

Run WRF

Examine the output

Stages in running WRF

* only need to do this once

http://www.ncas.ac.uk

Decide upon which domain you wish to use*

Acquire some met. data for the dates you are interested in

Run the WPS

Run WRF

Examine the output

Stages in running WRF

* only need to do this once

http://www.ncas.ac.uk

Determining your domain

Either compute manually and enter your valuesinto the WRF input files (see later) [ harder ]

or

Use the WRFDomainWizard [ easier ]

Where do I want my grid? What resolution do I need? How many nests do I want?

http://www.ncas.ac.uk

Determining your domain: WRF domain wizard

http://www.ncas.ac.uk

Decide upon which domain you wish to use*

Acquire some met. data for the dates you are interested in

Run the WPS

Run WRF

Examine the output

Stages in running WRF

* only need to do this once

http://www.ncas.ac.uk

Acquire some met data (forecast files)

GRIB data is online

Usually the 06Z forecast cycledata is available in the UK mid-afternoon

Online:April 21st 2007 – present

Offline: Feb 15th 2005 – April 20th 2007

http://www.ncas.ac.uk

Acquire some met data (forecast files)

Download (FTP) the files from the NOMADS web site:

Frequency of GRIB data varies, but for 1-degree GFS forecast we have

4 cycles / day : 0Z, 6Z, 12Z, 18Z

Forecast hours: analysis, T+3, T+6, ..., T+180

Download speed varies, but each GRIB file (~20Mb)takes ~ 3 minutes

Do this stage some time before you need to do the run

http://www.ncas.ac.uk

Decide upon which domain you wish to use*

Acquire some met. data for the dates you are interested in

Run the WPS

Run WRF

Examine the output

Stages in running WRF

* only need to do this once

http://www.ncas.ac.uk

WPS: Pre-processing

Edit the “namelist.wps” file

This file contains informationabout:

Start and end times

Grid definition

Location of the ancillaryfiles (land use, orography, etc

http://www.ncas.ac.uk

WPS: Pre-processing

WRF Pre-processing system (WPS)

geogrid.exe

ungrib.exe

metgrid.exe

Computes the grid formulation for your run

Extracts the met. data from your input (GRIB) files

Interpolates the met. data onto your grid (defined above)

http://www.ncas.ac.uk

Decide upon which domain you wish to use*

Acquire some met. data for the dates you are interested in

Run the WPS

Run WRF

Examine the output

Stages in running WRF

* only need to do this once

http://www.ncas.ac.uk

Running WRF

Edit the “namelist.input” file

Start and end times

http://www.ncas.ac.uk

Running WRF

Edit the “namelist.input” file

Time step andgrid definition

http://www.ncas.ac.uk

Running WRF

Edit the “namelist.input” file

Microphysics; surface layer;boundary layer

http://www.ncas.ac.uk

Running WRF

Edit the “namelist.input” file

Dynamicsoptions

http://www.ncas.ac.uk

Running WRF

real.exe

wrf.exe

For each WRF run, two separate executables need to be run.

these are already compiled; independent of choiceof grid, number of processors requested, microphysicsschemes, timestep, etc etc.

real.exe takes minutes and is run on a few processors. It sets up the input files required by WRF proper.

wrf.exe is the main body of the code

http://www.ncas.ac.uk

Running WRF

Standard scripts exist for submitting real.exe and wrf.exe

e.g. wrf_exe.sh

no need to alteranything belowhere

This will request 512 dual-corepreocessors; 12 hours wallclocktime

http://www.ncas.ac.uk

Running WRF

Submit the jobs to the queue

qsub real_exe.sh

then

qsub wrf_exe.sh

... and that’s it!

A 60 hour, 3 domain (9 - 3 – 1 km) 60 hr forecast for the UK, output filesevery hour, including 2 restart files takes ~10 hours using 512 dual coreprocessors.

http://www.ncas.ac.uk

Decide upon which domain you wish to use*

Acquire some met. data for the dates you are interested in

Run the WPS

Run WRF

Examine the output

Stages in running WRF

* only need to do this once

http://www.ncas.ac.uk

Examining the output

WRF output files are enormous (WRF UK output data ~60Gb)

One output file per nest; netCDF format

Post processing and looking at the output:

IDV – Interactive Data ViewerRIP and RIP4GrADSVis5DMatlabwrfpost

... generic netCDF viewers

http://www.ncas.ac.uk

Summary

In short, this is all you need to do:

geogrid.exeungrib.exemetgrid.exeqsub real_exe.shqsub wrf_exe.sh

Operation Operator effort

Hector effort

Download GRIB files

5 mins 40 mins

Edit namelist files

2 mins

Run WPS and WRF

5 mins 10 hours

http://www.ncas.ac.uk

Further info

WRF on Hector: full details and examples of UK forecast runshttp://ncasweb.leeds.ac.uk/weather

WRF on Hector: UK forecast runs