1. WRF demo/tutorial 12-13-2004 Robert Fovell rfovell@ucla.edu

2. 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)

3. 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

4. Further advantages Allows real data and idealized simulations in same framework Plug-in architecture (different groups will supply WRF “cores”) What I’m calling WRF is really the “Advanced Research WRF” (ARW) core

5. 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]

6. Overview WRF Standard Initialization (WRFSI) –Set up domain –Prepare data for model run –MM5 equiv: terrain, pregrid, regridder WRF model –Initialize model (MM5’s interpf) –Run model WRF post-processing WRF 3DVAR (not covered today)

7. Web stuff… http://www.mmm.ucar.edu/wrf/users/user_main.html (WRF model users’ site)http://www.mmm.ucar.edu/wrf/users/user_main.html http://www.mmm.ucar.edu/wrf/users/wrfv2/wrf-namelist.html (WRF namelist.input page)http://www.mmm.ucar.edu/wrf/users/wrfv2/wrf-namelist.html http://www.mmm.ucar.edu/wrf/users/docs/user_guide/contents.h tml (WRF users guide)http://www.mmm.ucar.edu/wrf/users/docs/user_guide/contents.h tml http://www.mmm.ucar.edu/wrf/users/tutorial/tutorial-2004.htm (Slides from 2004 WRF tutorial at NCAR)http://www.mmm.ucar.edu/wrf/users/tutorial/tutorial-2004.htm http://www.atmos.ucla.edu/~fovell/WRF/WRF_ports.html (Darwin/Mac OS X port)http://www.atmos.ucla.edu/~fovell/WRF/WRF_ports.html http://www.wrf-model.org/si/ (WRFSI home page)http://www.wrf-model.org/si/ http://www.mmm.ucar.edu/wrf/WG4/tutorial/wrf3dvar_download _data.htm (WRF 3DVAR tutorial)http://www.mmm.ucar.edu/wrf/WG4/tutorial/wrf3dvar_download _data.htm

8. WRF for real data run Example: 24-26 October 2003 (Simi fire)

9. 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

10. WRFSI …/WRFV2/wrfsi/wrf_tools

21. Domain 1 terrain

28. 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

29. WRF model …/WRFV2/

30. 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

31. 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

32. Configuring./configure presents option list Example: chose option 3, MPI

33. Compiling./compile presents options Example: chose compile em_real –Eulerian mass-coordinate real-data model

34. 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

35. Editing namelist.input Web resource –http://www.mmm.ucar.edu/wrf/users/wrfv2/ wrf-namelist.html Namelist sections [partial list] –&time_control –&domains –&physics –&dynamics

36. Setup for single domain run Columns provided for 3 domains (parent & 2 nests) but if max_dom =1 extra columns ignored

37. Setup for single domain run time_step ~ 6*DX (3*DX for MM5)… unless convective; Change max_dom when ready to activate nest

38. 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

39. Setup for single domain run s_we = start index for west-east direction, always 1. e_we = end index west-east, that’s your dimension

40. Setup for single domain run Make sure dx, dy set correctly -- the model does NOT check GUI-created inputs!

41. Setup for single domain run Columns provided for 3 domains (parent & 2 nests) but if max_dom =1 extra columns ignored

42. Setup for single domain run Here, subgrid mixing and computational diffusion is deactivated; model’s odd order advection is diffusive

43. 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

44. Files created by WRF run Named like: wrfout_d01_2003-10-24_12:00:00 [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

45. WRF postprocessing RIP (just like MM5) WRF2GrADS converter WRF2VIS5D converter Software that can handle NetCDF

46. 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*

47. Animation using RIP Part of Domain 1 shown for 24Oct2003 case Color: 2 m temperature; topo contours; 10 m wind vectors

48. 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

49. 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…

50. 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, it’s wrf_real_input_em.d02.2003-10-24_12:00:00 being renamed as wrf_real_input_em.d01.2003-10-24_12:00:00 Then…

51. Fooling real.exe - 2 domain example (cont.) This creates a wrfinput_d01 file (since real.exe thinks it’s domain #1) Rename that file as wrfinput_d02 (since it’s really for domain #2) Restore original domain #1 IC file –Here, it’s wrf_real_input_em.d01.2003-10-24_12:00:00 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

52. 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

53. 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

54. Nesting initialization, step by step (cont.) Temporary namelist.input’s &time_control

55. Nesting initialization, step by step (cont.) Temporary namelist.input’s &domains Run real.exe Rename wrfinput_d01 as wrfinput_d02

56. Nesting initialization, step by step (cont.) Clean up: –Move namelist.input.real to namelist.input –Move wrf_real_input_em.d01.2003-10-24_12:00:00.real back to wrf_real_input_em.d01.2003-10-24_12:00:00 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!

57. Animation of nest Domain 2 shown for 24Oct2003 case Color: 2 m temperature; topo contours; 10 m wind vectors

58. 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

59. WRF performance on my machines

60. 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 –Don’t use -xW [vectorization] flag w/o checking (my results so far always wrong) On Macs, IBM xlf is a great compiler –But use -qfloat=nomaf flag for accuracy –My tests: virtually identical results between optimized and non-optimized when nomaf used

61. 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

62. Ideal run output using WRF2GrADS

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