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Running WRF on HECToR

Running WRF on HECToR. Ralph Burton, NCAS (Leeds) Alan Gadian, NCAS (Leeds). With thanks to Paul Connolly, Hector support team. WRFV2 flow chart. WRF: Overview. Stages in running WRF. Decide upon which domain you wish to use* Acquire some met. data for the dates you are interested in

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Running WRF on HECToR

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  1. Running WRF on HECToR Ralph Burton, NCAS (Leeds) Alan Gadian, NCAS (Leeds) With thanks to Paul Connolly, Hector support team This is the footer

  2. WRFV2 flow chart

  3. WRF: Overview Stages in running WRF 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 * only need to do this once

  4. Stages in running WRF 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 * only need to do this once

  5. Determining your domain Where do I want my grid? What resolution do I need? How many nests do I want? Either compute manually and enter your values into the WRF input files (see later) [ harder ] or Use the WRFDomainWizard [ easier ]

  6. Determining your domain: WRF domain wizard

  7. Stages in running WRF 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 * only need to do this once

  8. Acquire some met data (forecast files) GRIB data is online Usually the 06Z forecast cycle data is available in the UK mid-afternoon Online: April 21st 2007 – present Offline: Feb 15th 2005 – April 20th 2007

  9. 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

  10. Stages in running WRF 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 * only need to do this once

  11. WPS: Pre-processing Edit the “namelist.wps” file This file contains information about: Start and end times Grid definition Location of the ancillary files (land use, orography, etc

  12. WPS: Pre-processing WRF Pre-processing system (WPS) Computes the grid formulation for your run geogrid.exe ungrib.exe metgrid.exe Extracts the met. data from your input (GRIB) files Interpolates the met. data onto your grid (defined above)

  13. Stages in running WRF 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 * only need to do this once

  14. Running WRF Edit the “namelist.input” file Start and end times

  15. Running WRF Edit the “namelist.input” file Time step and grid definition

  16. Running WRF Edit the “namelist.input” file Microphysics; surface layer; boundary layer

  17. Running WRF Edit the “namelist.input” file Dynamics options

  18. Running WRF For each WRF run, two separate executables need to be run. real.exe wrf.exe these are already compiled; independent of choice of grid, number of processors requested, microphysics schemes, 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

  19. Running WRF Standard scripts exist for submitting real.exe and wrf.exe e.g. wrf_exe.sh This will request 512 dual-core preocessors; 12 hours wallclock time no need to alter anything below here

  20. 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 files every hour, including 2 restart files takes ~10 hours using 512 dual core processors.

  21. Stages in running WRF 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 * only need to do this once

  22. 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 Viewer RIP and RIP4 GrADS Vis5D Matlab wrfpost ... generic netCDF viewers

  23. Summary In short, this is all you need to do: geogrid.exe ungrib.exe metgrid.exe qsub real_exe.sh qsub wrf_exe.sh

  24. Further info WRF on Hector: full details and examples of UK forecast runs http://ncasweb.leeds.ac.uk/weather WRF on Hector: UK forecast runs

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