WRF Basics

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WRF Basics Weather Research and Forecasting
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• What is it?
• State of the art numerical weather forecasting
  model
• Useful from many km scale down to 100s of m
• Geographical dataset accounts for orography,
• land use, vegetation type, albedo, etc.
• Full range of sophisticated boundary layer
  schemes,
• microphysical schemes, Cumulus schemes,
  turbulence,
• soil moisture, ... etc
• International user base well supported
• Run from linux/unix using paralell processors
• Free!!

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WRFV3 flow chart
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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

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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

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Determining your domain
WRF Domain Wizard
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Outer domain 9km resolution 100x126
gridpoints Intermediate domain 3km
resolution 55x76 gridpoints Inner domain 1km
resolution 31x40 gridpoints
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WRF code

• 160,000 lines of code (Fortran90/C/Perl)
• But, you dont need to edit any of it!
• To run WRF you only need to edit two
• ascii files

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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

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Acquire some met data (forecast files)
GFS 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
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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

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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
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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)
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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 files
Interpolates the met. data onto your grid
(defined above)
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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
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For the Arran fieldcourse WRF runs
Operation Operator effort Computer effort
Download forecast files 5 mins 30 mins
Edit namelist files 2 mins
Run WPS and WRF 5 mins 6 hours
geogrid.exe ungrib.exe metgrid.exe qsub
real_exe.sh qsub wrf_exe.sh
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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

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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
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23/02/08 12Z T60
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23/02/08 12Z T60
Cloud water mixing ratio 0.1g / Kg
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WRF GNR 1km results
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23/02/08 12Z (T60)
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Estimated that a third of the worlds population
receive their weather forecast via WRF. Adopted
by China, India, Korea, etc etc.