WRF Basics Weather Research and Forecasting 1 This
WRF Basics Weather Research and Forecasting 1 This is the footer http: //www. ncas. ac. uk
What is it? Ø State of the art numerical weather forecasting model Ø Useful from many km scale down to 100 s of m Ø Geographical dataset accounts for orography, land use, vegetation type, albedo, etc. Ø Full range of sophisticated boundary layer schemes, microphysical schemes, Cumulus schemes, turbulence, soil moisture, . . . etc Ø International user base; well supported Ø Run from linux/unix using paralell processors Ø Free!! http: //www. ncas. ac. uk
WRFV 3 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 WRF Preprocessing System Run WRF 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 http: //www. ncas. ac. uk
Determining your domain WRF “Domain Wizard” http: //www. ncas. ac. uk
Outer domain: 9 km resolution 100 x 126 gridpoints Intermediate domain: 3 km resolution 55 x 76 gridpoints Inner domain: 1 km resolution 31 x 40 gridpoints http: //www. ncas. ac. uk
http: //www. ncas. ac. uk
http: //www. ncas. ac. uk
http: //www. ncas. ac. uk
WRF code Ø ~ 160, 000 lines of code (Fortran 90/C/Perl) Ø But, you don’t need to edit any of it! To run WRF you only need to edit two ascii files Ø 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 http: //www. ncas. ac. uk
Acquire some met data (forecast files) GFS 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
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 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) 1) Design the grid formulation for your run 2) Extract the met. data from your input files 3) Interpolate the met. data onto your grid (defined above) http: //www. ncas. ac. uk
WRF Pre-processing system (WPS) Computes the grid formulation for your run geogrid. exe ungrib. exe Extracts the met. data from your input 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 wrf. exe http: //www. ncas. ac. uk
For the Arran fieldcourse WRF runs: geogrid. exe ungrib. exe metgrid. exe qsub real_exe. sh qsub wrf_exe. sh Operation Operator effort Computer effort Download forecast files 5 mins 30 mins Edit namelist files 2 mins Run WPS and 5 mins WRF 6 hours 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 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
23/02/08: 12 Z T+60 http: //www. ncas. ac. uk
23/02/08: 12 Z T+60 Cloud water mixing ratio = 0. 1 g / Kg http: //www. ncas. ac. uk
WRF GNR: 1 km results http: //www. ncas. ac. uk
23/02/08: 12 Z (T+60) http: //www. ncas. ac. uk
Estimated that a third of the world’s population receive their weather forecast via WRF. Adopted by China, India, Korea, etc. http: //www. ncas. ac. uk
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