| 1 | Running grid nudging |
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| 2 | -------------------- |
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| 3 | Grid nudging is available in Version 2.2. |
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| 4 | This nudges the WRF run towards a gridded analysis linearly interpolated in time between |
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| 5 | specified analyses. It only requires multiple time periods of analyses for each domain |
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| 6 | to be nudged, and these are input to real in the same format as the initial conditions. |
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| 7 | To run an fdda job |
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| 8 | |
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| 9 | - run real.exe with grid_fdda = 1 |
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| 10 | This will generate an extra input file with the time-varying analyses called wrffdda_d0<n> |
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| 11 | - note that each domain can have grid_fdda = 1 or 0 when running nesting |
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| 12 | - run wrf.exe with the same grid_fdda setting to use the wrffdda files generated |
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| 13 | Also select wrf run-time options from the list described below to determine which fields to nudge, |
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| 14 | how strongly to nudge, whether to nudge in the boundary layer, or whether to truncate |
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| 15 | nudging below a certain grid level |
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| 16 | - There is a ramping capability for dynamic initialization that turns nudging off over a |
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| 17 | specified period |
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| 18 | |
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| 19 | &fdda |
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| 20 | grid_fdda (max_dom) = 1 ; grid-nudging fdda on (=0 off) for each domain |
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| 21 | gfdda_inname = "wrffdda_d<domain>" ; defined name in real |
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| 22 | gfdda_interval_m (max_dom) = 360 ; time interval (min) between analysis times |
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| 23 | gfdda_end_h (max_dom) = 6 ; time (h) to stop nudging after start of forecast |
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| 24 | io_form_gfdda = 2 ; analysis data io format (2 = netCDF) |
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| 25 | fgdt (max_dom) = 0 ; calculation frequency (minutes) for grid-nudging (0=every step) |
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| 26 | if_no_pbl_nudging_uv (max_dom) = 0 ; 1= no nudging of u and v in the pbl, 0=nudging in the pbl |
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| 27 | if_no_pbl_nudging_t (max_dom) = 0 ; 1= no nudging of temp in the pbl, 0=nudging in the pbl |
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| 28 | if_no_pbl_nudging_q (max_dom) = 0 ; 1= no nudging of qvapor in the pbl, 0=nudging in the pbl |
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| 29 | if_zfac_uv (max_dom) = 0 ; 0= nudge u and v all layers, 1= limit nudging to levels above k_zfac_uv |
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| 30 | k_zfac_uv (max_dom) = 10 ; 10=model level below which nudging is switched off for u and v |
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| 31 | if_zfac_t (max_dom) = 0 ; 0= nudge temp all layers, 1= limit nudging to levels above k_zfac_t |
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| 32 | k_zfac_t (max_dom) = 10 ; 10=model level below which nudging is switched off for temp |
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| 33 | if_zfac_q (max_dom) = 0 ; 0= nudge qvapor all layers, 1= limit nudging to levels above k_zfac_q |
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| 34 | k_zfac_q (max_dom) = 10 ; 10=model level below which nudging is switched off for qvapor |
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| 35 | guv (max_dom) = 0.0003 ; nudging coefficient for u and v (sec-1) |
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| 36 | gt (max_dom) = 0.0003 ; nudging coefficient for temp (sec-1) |
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| 37 | gq (max_dom) = 0.0003 ; nudging coefficient for qvapor (sec-1) |
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| 38 | if_ramping = 0 ; 0= nudging ends as a step function, 1= ramping nudging down at end of period |
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| 39 | dtramp_min = 60.0 ; time (min) for ramping function, 60.0=ramping starts at last analysis time, |
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| 40 | -60.0=ramping ends at last analysis time |
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| 41 | |
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