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WRF Digital Filter Initialization 在中央氣象局的應用

WRF Digital Filter Initialization 在中央氣象局的應用. 柳再明. Digital Filter Initialization. Lynch, P. and X.-Y. Huang, 1992 : Initialization of the HIRLAM Model Using a Digital Filter., Mon. Wea. Rev.

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WRF Digital Filter Initialization 在中央氣象局的應用

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  1. WRF Digital Filter Initialization 在中央氣象局的應用 柳再明

  2. Digital Filter Initialization • Lynch, P. and X.-Y. Huang, 1992 : Initialization of the HIRLAM Model Using a Digital Filter., Mon. Wea. Rev. • Huang, X.-Y. and P. Lynch, 1993 : Diabatic Digital-Filtering Initialization : Application to the HIRLAM Model., Mon. Wea. Rev. • Lynch, P. and X.-Y. Huang, 1994 : Diabatic Initialization using recursive filters., Tellus.

  3. DFI: Digital Filter Initialization (By Hans Huang)

  4. Implemented options of DFI Filtering DFL: (Lynch and Huang, 1992) Forecast Backward integration DDFI: (Huang and Lynch, 1993) Filtering Forecast Backward integration TDFI: (Lynch and Huang, 1994) Filtering Forecast (By Hans Huang)

  5. Digital Filter Initialization • DFI (Lynch and Huang, 1992) • DDFI (Huang and Lynch, 1993) • … Schemes based on DFI (By Hans Huang)

  6. Terrain pressure(hpa) (117,56), 12h fst 940hpa DDFI OBJ 930hpa 12h

  7. 500hpa omega(hpa/h)(117,56), 12h fst 20 DDFI 0 OBJ -20 12h

  8. Initial field (0.526hpa) DDFI Analysis

  9. 24h forecast( -0.216) DDFI NO_dfi

  10. 48h forecast(0.118) DDFI NO_dfi

  11. Terrain pressure(hpa) (117,56), 12h fst OBJ DDFI_3h DDFI_2h DDFI_1h 12h

  12. Wrf 3.0 • Initialization/Nesting/Restart/Lateral boundary/IO • - More options in program real to control near-surface interpolation.Option for not using surface data is added.- Improved T and RH at nest boundaries - Exponential lateral boundary namelist switch (spec_exp)- Doubly periodic boundary support from RSL_LITE - Automatic-vortex tracking level becomes runtime option (track_level).- Digital filter initialization (thanks to the contributions from GSD/NOAA, and Min Chen of BMB, China)- Variable time stepping: allows time step to increase and decrease according to model stability criterion during a model integration (contributed by Hutchinson of WSI)- Time series outputting capability (checks for the presence of time series station file: tslist. See run/README.tslist for details) - wrflowinp input stream is changed from auxiliary stream 5 to 4 - Three new idealized test cases: • * em_heldsuarez: idealized global case* em_les: large eddy simulation case (contributed by Moeng, NCAR)* em_seabreeze2d_x: an example to illustrate how to set up idealized case to utilize full physics, especially land surface physics (contribued by Joe Galewsky of University of NM)

  13. Digital Filter Initialization • DFI is a way to remove initial model noise as measured by the surface pressure tendency. • It runs a digital filter during a model integration, backward and forward, and then start the forecast, this can all be done in one job run. • In V3, DFI can only be used in a single domain run. • No special requirement for data preparation. • &dfi_control. In namelist.input

  14. Wrf 3.0 namelist • &dfi_control digital filter option control (does not yet support nesting) • dfi_opt 3 which DFI option to use 0: no digital filter initialization 1: digital filter launch (DFL) 2: diabatic DFI (DDFI) 3: twice DFI (TDFI)(recommended) • dfi_nfilter 7 digital filter type: 0 – uniform; 1- Lanczos; 2 – Hamming; 3 – Blackman; 4 – Kaiser; 5 – Potter; 6 – Dolph window; 7 – Dolph (recommended); 8 – recursive high-order • dfi_write_filtered_input .true. whether to write wrfinput file with filtered model state before beginning forecast • dfi_write_dfi_history .false. whether to write wrfout files during filtering integration • dfi_cutoff_seconds 3600 cutoff period, in seconds, for the filter. Should not be longer than the filter window • dfi_time_dim 1000 maximum number of time steps for filtering period, this value can be larger than necessary

  15. WRF 3.0(tdfi_3,2,1h, obj)(116,56) TDFI_1h OBJ TDFI_3h TDFI_2h 12h

  16. WRF 3.0(tdfi,ddfi,dfi_3h, obj)(116,56) DFI_3h OBJ TDFI_3h DDFI_3h 12h

  17. WRF 3.0(tdfi,ddfi,dfi_3h, obj)(116,56),72h 72h

  18. WRF 3.0(tdfi_3h_10800, 7200, 3600s)(116,56) 3600 OBJ 7200 10800 12h

  19. Testing of 8 filteres on TDFI_3h : uniform; Lanczos; Hamming; Blackman; Kaiser; Potter; Dolph window; Dolph (recommended); recursive high-order Blackman OBJ Dolph 12h

  20. 結論 • Digital Filter Initialization(DFI)以數值濾波為理論基礎, 並藉助動力初始化的過程, 來完成對於高頻雜波的抑制。此外DFI對分析場的改變幾可忽略，且DFI的使用不影響預報的結果。 • TDFI, DDFI兩者較適用, 不要使用DFI • 2h或3h是較有效的back-forward period • Filters:Dolph較好, 不要用Blackman • DFI需額外約5%的CPU時間

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