Running WRF on HECTo R Ralph Burton NCAS

Running WRF on HECTo. R Ralph Burton, NCAS (Leeds) Alan Gadian, NCAS (Leeds) With thanks to Paul Connolly, Hector support team 1 This is the footer http: //www. ncas. ac. uk

WRFV 2 flow chart http: //www. ncas. ac. uk

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 http: //www. ncas. ac. uk

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 http: //www. ncas. ac. uk

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 WRFDomain. Wizard [ easier ] http: //www. ncas. ac. uk

Determining your domain: WRF domain wizard http: //www. ncas. ac. uk

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 http: //www. ncas. ac. uk

Acquire some met data (forecast files) GRIB data is online Usually the 06 Z forecast cycle data is available in the UK mid-afternoon Online: April 21 st 2007 – present Offline: Feb 15 th 2005 – April 20 th 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 : 0 Z, 6 Z, 12 Z, 18 Z Forecast hours: analysis, T+3, T+6, . . . , T+180 Download speed varies, but each GRIB file (~20 Mb) takes ~ 3 minutes Do this stage some time before you need to do the run http: //www. ncas. ac. uk

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 http: //www. ncas. ac. uk

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 http: //www. ncas. ac. uk

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

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 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 and grid 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 Dynamics options http: //www. ncas. ac. uk

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. 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 This will request 512 dual-core preocessors; 12 hours wallclock time no need to alter anything below here 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 files every hour, including 2 restart files takes ~10 hours using 512 dual core processors. http: //www. ncas. ac. uk

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 http: //www. ncas. ac. uk

Examining the output WRF output files are enormous (WRF UK output data ~60 Gb) One output file per nest; net. CDF format Post processing and looking at the output: IDV – Interactive Data Viewer RIP and RIP 4 Gr. ADS Vis 5 D Matlab wrfpost. . . generic net. CDF viewers http: //www. ncas. ac. uk

Summary In short, this is all you need to do: geogrid. exe ungrib. exe metgrid. exe qsub real_exe. sh qsub wrf_exe. sh Operation Operator effort Hector effort Download GRIB files 5 mins 40 mins Edit namelist files 2 mins Run WPS and 5 mins WRF 10 hours http: //www. ncas. ac. uk

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 http: //www. ncas. ac. uk