WRF demo/tutorial

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WRF demo/tutorial

• 12-13-2004
• Robert Fovell
• rfovell_at_ucla.edu

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Background on WRF model

• Weather Research and Forecasting
• Co-developed by research and operational
  communities
• Replaces MM5 and Eta models
• Current version 2.0.3.1
• Platforms (for model) Linux, IBM/AIX, SGI, Cray,
  Darwin and Sun (hideous)

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WRF advantages

• Better numerics than MM5
• Arakawa C grid, R-K scheme, odd order advection
  w/ implicit diffusion
• Much less diffusive, larger effective resolution,
  permits longer time steps
• Better topography than Eta
• GUI-driven domain configuration, initialization
• Fortran 95 (MM5 was F77)
• NetCDF output

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Further advantages

• Allows real data and idealized simulations in
  same framework
• Plug-in architecture (different groups will
  supply WRF cores)
• What Im calling WRF is really the Advanced
  Research WRF (ARW) core

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WRF disadvantages

• Bleeding edge
• Smaller range of physics choices overall
• No radiation upper bdry condition yet
• Software design cumbersome, obtuse opinion may
  change with experience
• Nesting is very serious pain that will change

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Overview

• WRF Standard Initialization (WRFSI)
• Set up domain
• Prepare data for model run
• MM5 equiv terrain, pregrid, regridder
• WRF model
• Initialize model (MM5s interpf)
• Run model
• WRF post-processing
• WRF 3DVAR (not covered today)

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Web stuff

• http//www.mmm.ucar.edu/wrf/users/user_main.html
  (WRF model users site)
• http//www.mmm.ucar.edu/wrf/users/wrfv2/wrf-nameli
  st.html (WRF namelist.input page)
• http//www.mmm.ucar.edu/wrf/users/docs/user_guide/
  contents.html (WRF users guide)
• http//www.mmm.ucar.edu/wrf/users/tutorial/tutoria
  l-2004.htm (Slides from 2004 WRF tutorial at
  NCAR)
• http//www.atmos.ucla.edu/fovell/WRF/WRF_ports.ht
  ml (Darwin/Mac OS X port)
• http//www.wrf-model.org/si/ (WRFSI home page)
• http//www.mmm.ucar.edu/wrf/WG4/tutorial/wrf3dvar_
  download_data.htm (WRF 3DVAR tutorial)

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WRF for real data run

• Example
• 24-26 October 2003 (Simi fire)

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Directory structure

• /WRFV2/
• Parent directory
• /WRFV2/wrfsi
• WRFSI location
• /WRFV2/wrfsi/domains/SoCal
• Domain setup SoCal location
• /WRFV2/test/em_real
• Where real data run will be made

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WRFSI /WRFV2/wrfsi/wrf_tools
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Domain 1 terrain
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Output from WRFSI

• /WRFV2/wrfsi/domains/SoCal/siprd
• IC, BC files for D1, IC file for D2
• Move or link into /WRFV2/test/em_real

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WRF model /WRFV2/
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Directory structure

• In ../WRFV2
• main/ is where executables live
• arch/ default config stuff
• frame/ model framework stuff
• phys/, dyn_em/ model physics, solver
• external/ mainly I/O, MPI stuff
• test/ test cases live here
• run/ can run model from here, too

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Preparing to run

• Configure
• ./configure
• Select platform, compiler, whether single
  threaded, OpenMP or MPI
• Compile
• ./compile em_real
• Creates real.exe and wrf.exe in ../WRFV2/main
• Creates links to real.exe, wrf.exe in
  ../WRFV2/test/em_real

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Configuring

• ./configure presents option list
• Example chose option 3, MPI

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Compiling

• ./compile presents options
• Example chose compile em_real
• Eulerian mass-coordinate real-data model

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Final initialization step

• Move to .../WRFV2/test/em_real
• Edit namelist.input
• Lots to do here
• Execute ./real.exe
• Creates wrfinput_d01, wrfbdy_d01 files
• Run for each nest separately ouch
• Model executable is wrf.exe

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Editing namelist.input

• Web resource
• http//www.mmm.ucar.edu/wrf/users/wrfv2/wrf-nameli
  st.html
• Namelist sections partial list
• time_control
• domains
• physics
• dynamics

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Setup for single domain run
Columns provided for 3 domains (parent 2
nests) but if max_dom 1 extra columns ignored
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Setup for single domain run
time_step 6DX (3DX for MM5) unless
convective Change max_dom when ready to activate
nest
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Setup for single domain run
Here I have my MOAD dimensions (80x67) and nest
dimensions (61x37) entered. Third column ignored
since I only created 2 domains
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Setup for single domain run
s_we start index for west-east direction,
always 1. e_we end index west-east, thats your
dimension
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Setup for single domain run
Make sure dx, dy set correctly -- the model does
NOT check GUI-created inputs!
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Setup for single domain run
Columns provided for 3 domains (parent 2
nests) but if max_dom 1 extra columns ignored
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Setup for single domain run
Here, subgrid mixing and computational diffusion
is deactivated models odd order advection is
diffusive
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Run real.exe wrf.exe

• ./real.exe
• Look for real_em SUCCESS COMPLETE REAL_EM INIT
  message
• mpirun -np 2 wrf.exe
• MPI version creates rsl.out.000 and
  rsl.error.000 files
• tail -f rsl.out.0000
• Look for wrf SUCCESS COMPLETE WRF

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Files created by WRF run

• Named like
• wrfout_d01_2003-10-24_120000
• d01 domain 1
• file started 12Z 24 October 2003
• Files can be HUGE (NetCDF inefficient)
• - to split output files, namelist entry
• frames_per_outfile in time_control

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WRF postprocessing

• RIP (just like MM5)
• WRF2GrADS converter
• WRF2VIS5D converter
• Software that can handle NetCDF

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RIP

• RIP version 4 required
• Real data runs only
• ripdp_wrf expname all wrfout
• Will unpack every wrfout files in local
  directory and all variables and call extracted
  files expname
• Replace all with basic for less output
• RIP4 unpacker for MM5 is now ripdp_mm5 expname
  MMOUT

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Animation using RIP

• Part of Domain 1 shown for 24Oct2003 case

Color 2 m temperature topo contours 10 m wind
vectors
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Nesting

• Created domains 1, 2 for SoCal in WRFSI
• WRFSI created wrf_real_input_em files for both
  domains
• Need to run real.exe once for each domain
• namelist.input needs to be edited for each
  real.exe run
• Files have to be renamed to fool real.exe
• Web page explanation http//www.mmm.ucar.edu/wrf/
  users/wrfv2/runwrf.html

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MM5 v. WRF on nesting

• MM5
• Need only initialize parent (outer) grid
• MM5 interpolates to nests, using nest terrain
  files created using terrain
• WRF
• If let model interpolate to nests, higher res
  topo files are NOT used, unlike MM5
• So, you need to init each domain separately with
  real.exe, and that takes fooling real.exe

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Fooling real.exe - 2 domain example

• Start with domain 2 first
• Edit namelist.input, putting nest information in
  first column
• Previously, that info was for parent grid
• Rename wrf_real_input_em.d02 IC file as
  wrf_real_input_d01 after saving real d01
  file!!!!
• Here, its wrf_real_input_em.d02.2003-10-24_1200
  00 being renamed as wrf_real_input_em.d01.2003-10-
  24_120000
• Then

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Fooling real.exe - 2 domain example (cont.)

• This creates a wrfinput_d01 file (since real.exe
  thinks its domain 1)
• Rename that file as wrfinput_d02 (since its
  really for domain 2)
• Restore original domain 1 IC file
• Here, its wrf_real_input_em.d01.2003-10-24_1200
  00
• Re-edit namelist.input, making sure domain 1
  info in 1st column, domain 2 in 2nd
• Run real.exe again
• Creates wrfbdy_d01, wrfinput_d01

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Nesting initialization, step by step

• This should be scripted somehow, to avoid
  mistakes
• Create your namelist.input, with parent and nest
  domain info, start and stop times, etc
• Set max_dom 2
• Set input_from_file .true., .true.
• ICs for both domains will be read in from files
• Those filenames will be wrfinput_d01, wrfinput_d02

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Nesting initialization, step by step (cont.)

• Rename original d01 IC file as
• Copy d02 IC file with d01 IC file original name
• Copy namelist.input as namelist.input.real
• Edit namelist.input
• This is your temporary namelist.input file
• Set stop time start time only want IC
• Replace parent domain info in column 1 with nest
  info from column 2

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Nesting initialization, step by step (cont.)

• Temporary namelist.inputs time_control

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Nesting initialization, step by step (cont.)

• Temporary namelist.inputs domains
• Run real.exe
• Rename wrfinput_d01 as wrfinput_d02

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Nesting initialization, step by step (cont.)

• Clean up
• Move namelist.input.real to namelist.input
• Move wrf_real_input_em.d01.2003-10-24_120000.rea
  l back to wrf_real_input_em.d01.2003-10-24_12000
  0
• Run real.exe again, this time creating
  wrfinput_d01 and wrfbdy_d01
• Now you have
• wrfinput files for d01 and d02
• wrfbdy file for d01
• namelist.input file controlling both domains
• Run the model!

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Animation of nest

• Domain 2 shown for 24Oct2003 case

Color 2 m temperature topo contours 10 m wind
vectors
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Restarting WRF

• In namelist.input, set restart_interval to
  desired restart output file interval (minutes)
• To restart a simulation
• Set restart .true.
• Set start_ time to reflect restart time

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WRF performance on my machines
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Compile flag notes

• On PCs, Intel beats PGF handily
• But use -mp flag for accuracy, consistency as
  number of CPUs varied
• This flag does NOT refer to multiprocessing w/
  Intel compiler
• Dont use -xW vectorization flag w/o checking
  (my results so far always wrong)
• On Macs, IBM xlf is a great compiler
• But use -qfloatnomaf flag for accuracy
• My tests virtually identical results between
  optimized and non-optimized when nomaf used

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WRF for idealized cases

• Ready-made examples include 2D squall lines and
  3D supercells
• compile em_squall2d_x for the 2D x-z plane squall
  line example
• In /WRFV2/test/em_squall2d_x, run ideal.exe and
  then wrf.exe
• To change IC for this case, modify
  /WRFV2/dyn_em/module_initialize_squall2d_x.F and
  recompile

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Ideal run output using WRF2GrADS
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