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WRF Basics

Weather Research and Forecasting

http://www.ncas.ac.uk

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

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

Stages in running WRF

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

Stages in running WRF

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Determining your domain

WRF “Domain Wizard”

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Outer domain:9km resolution100x126 gridpointsIntermediate domain:3km resolution55x76 gridpointsInner domain:1km resolution31x40 gridpoints

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WRF code

~ 160,000 lines of code (Fortran90/C/Perl)

But, you don’t need to edit any of it!

To run WRF you only need to edit twoascii files

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Decide upon which domain you wish to use*

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

Run the WPS

Run WRF

Stages in running WRF

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Acquire some met data (forecast files)

GFS 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

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Decide upon which domain you wish to use*

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

Run the WPS

Run WRF

Stages in running WRF

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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

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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)

geogrid.exe

ungrib.exe

metgrid.exe

Computes the grid formulation for your run

Extracts the met. data from your input files

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

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Decide upon which domain you wish to use*

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

Run the WPS

Run WRF

Stages in running WRF

wrf.exe

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For the Arran fieldcourse WRF runs:

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

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

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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

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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 ViewerRIP and RIP4GrADSVis5DMatlabwrfpost

... generic netCDF viewers

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23/02/08:

12Z

T+60

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23/02/08:

12Z

T+60

Cloud water mixing ratio = 0.1g / Kg

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WRF GNR: 1km results

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23/02/08:

12Z

(T+60)

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Estimated that a third of the world’s population receive their weather forecast via WRF.

Adopted by China, India, Korea, etc etc.