WRF namelist.input Dr Meral Demirtaş Turkish State Meteorological Service Weather Forecasting Department WMO, Training Course, 26-30 September 2011 Alanya, Turkey

Outline Why do we need a namelist? Sections of namelist.input: time_control domains physics dynamics

Why do we need namelist? The namelist.input file helps users to design their model run. A Fortran namelist contains a list of runtime options for the code to read in during its execution. Use of a namelist allows one to change runtime configuration without the need to recompile the source code. Before running real.exe and wrf.exe, edit namelist.input file for runtime options. The most up-to-dated namelist.input instructions are given in the WRF User’s Guide. Full list of namelists and their default values may be found in Registry files: Registry.EM (ARW), Registry.NMM and registry.io_boilerplate (IO options, shared). Use related documents to guide the modification of the namelist values given in: run/README.namelist test/em_real/examples.namelist

Fortran 90 namelist has very specific format, so edit with care: &namelist-record - start / - end As a general rule: Multiple columns: domain dependent Single column: value valid for all domains

&time_control interval_seconds: Time interval between WPS output times, and LBC update frequency history_interval: Time interval in minutes when a history output is written frame_per_outfile: Number of history times written to one file. restart_interval: Time interval in minutes when a restart file is written. By default, restart file is not written at hour 0. A restart file contains only one time level data, and its valid time is in its file name, io_form_history/restart/input/boundary: IO format options 1. binary; 2. netCDF (recommended option); 4. PHDF5 5. Grib-1; 10. Grib-2 debug_level: 0. for standard runs, no debugging. 1. netCDF error messages about missing fields. 50,100,200,300 values give increasing prints. Large values trace the job's progress through physics and time steps.

&domains time_step: Time step for model integration in seconds. ARW: 6*dx (dx is the grid distance in km) NMM: 2.25*dx time_step_fract_num, time_step_fract_den: Fractional time step specified in separate integers of numerator and denominator. e_we, e_sn, e_vert: Model grid dimensions (staggered) in x, y and z directions. num_metgrid_levels: Number of metgrid data levels. num_metgrid_soil_levels: Number of soil data levels in the input data dx, dy: grid distances: in meters for ARW; in degrees for NMM.

&domains p_top_requested: Pressure value at the model top. Constrained by the available data from WPS. Default is 5000 Pa eta_levels: Specify your own model levels from 1.0 to 0.0. If not specified, program real will calculate a set of levels ptsgm (NMM only): Pressure level (Pa) at which the WRF-NMM hybrid coordinate transitions from sigma to pressure (default: 42000 Pa)

&physics: Physics options mp_physics: microphysics 0. No microphysics 1. Kessler scheme 2. Lin et al. scheme 3. Single-Moment (WSM) 3-class simple ice scheme 4. Single-Moment (WSM) 5-class scheme 5. Ferrier scheme 6. WSM 6-class graupel scheme 7. Goddard GCE scheme (also use gsfcgce_hail and gsfcgce_2ice) 8. Thompson graupel scheme (2-moment scheme in V3.1) 9. Milbrandt-Yau 2-moment scheme 10. Morrison 2-moment scheme  13. Stonybrook University scheme

Radiation related flags ra_lw_physics: longwave radiation 1. RRTM scheme 3. CAM scheme 4. rrtmg scheme 5. New Goddard longwave scheme (Since V3.3) 99. GFDL scheme (Schwarzkopf and Fels ) ra_sw_physics: shortwave radiation 1. Dudhia Scheme 2. Goddard Shortwave scheme 99. GFDL Scheme (Lacis and Hansen).

sf_sfclay_physics: surface layer 0. No surface-layer scheme 1. Monin-Obukhov Similarity scheme 2. Monin-Obukhov-Janjic Similarity Scheme 3. Global Forecasting System (GFS) scheme (NMM only)  4. QNSE  5. MYNN  7. Pleim-Xiu (ARW only), only tested with Pleim-Xiu surface and ACM2 PBL 10. TEMF surface layer sf_surface_physics: land surface 0. No surface temperature prediction 1. Thermal Diffusion scheme 2. Unified NOAH Land-Surface Model 3. RUC Land-Surface Model 7. Pleim-Xiu scheme (ARW only)

sf_urban_physics 1. Urban Canopy Model 2. Building Environment Parameterization 3. Building Energy Model

num_soil_layers: number of soil layers in land surface model 2. Pleim-Xu land-surface model 4. Noah land-surface model 5. Thermal diffusion scheme 6. RUC Land Surface Model bl_pbl_physics: planetary boundary layer 0. no boundary-layer 1. Yonsei University scheme (use with sf_sfclay_physics=1) 2. Mellor-Yamada-Janjic TKE Scheme (use with sf_sfclay_physics=2) 3. NCEP Global Forecast System scheme (use with sf_sfclay_physics=3) 4. QNSE (use with sf_sfclay_physics=4) 5. MYNN 2.5 level TKE (use with sf_sfclay_physics=1,2 and 5) 6. MYNN 3rd level TKE (use with sf_sfclay_physics=5) 7. ACM2 (Pleim) scheme (use with sf_sfclay_physics=1, 7) 8. Bougeault and Lacarrere (BouLac) TKE (use with sf_sfclay_physics=1,2) 9. CAM UW PBL 10. Total Energy - Mass Flux (TEMF) 99. MRF scheme (to be removed)

Flags related with cloud parameterization cu_physics: cumulus parameterization 0. No cumulus parameterization. 1. Kain-Fritsch scheme 2. Betts-Miller-Janjic scheme 3. Grell-Devenyi ensemble scheme 4. Simplified Arakawa-Schubert scheme (NMM only)   5. New Grell 3D scheme (G3)  6. Tiedtke scheme 7. CAM Zhang-McFarlane scheme 14. New Simpified Arakawa-Schubert

&dynamics Diffusion, damping, advection options rk_ord:  time-integration scheme option:  2. Runge-Kutta 2nd order  3. Runge-Kutta 3rd order (recommended) diff_opt:  turbulence and mixing option:  0. no turbulence or explicit spatial numerical filters (km_opt IS IGNORED).  1. evaluates 2nd order diffusion term on coordinate surfaces. uses kvdif for vertical diff unless PBL option is used. may be used with km_opt = 1 and 4. (Note that option 1 is recommended for real-data cases.)  2. evaluates mixing terms in physical space (stress form) (x,y,z). turbulence parameterization is chosen by specifying km_opt. km_opt:  eddy coefficient option  1. constant (use khdif and kvdif)  2. 1.5 order TKE closure (3D)  3. Smagorinsky first order closure (3D) (Note: option 2 and 3 are not recommended for dx > 2 km) 4. horizontal Smagorinsky first order closure (recommended for real-data case)

&bc_control: Boundary control spec_bdy_width: Total number of rows for specified boundary value nudging. & namelist_quilt: Specifies asynchronized I/O for MPI applications. nio_tasks_per_group: Default value is 0, means no quilting; value > 0 quilting I/O nio_groups: Default is 1, do NOT change.

More options More are introduced here: IO options Vertical interpolation options SST update and other options for long simulations Adaptive-time step Digital filter Global runs Moving nest TC options IO quilting

Vertical interpolation options (1) Program real for ARW only, optional, &domains: use_surface: whether to use surface observations use_levels_below_ground: whether to use data below the ground lowest_lev_from_sfc: logical, whether surface data is used to fill the lowest model level values force_sfc_in_vinterp: number of levels to use surface data, default is 1 extrap_type: how to do extrapolation: 1 - use 2 lowest levels; 2 - constant t_extrap_type: extrapolation option for temperature: 1 - isothermal; 2 - 6.5 K/km; 3 - adiabatic

Vertical interpolation options (2) Program real for ARW only, optional: interp_type: in pressure or log pressure lagrange_order: linear or quadratic zap_close_levels: delta p where a non-surface pressure level is removed in vertical interpolation related namelists: examples.namelist constant pressure surfaces model surfaces ground

SST update for long simulations (1) Lower boundary update control: allow SST, seaice monthly vegetation fraction and albedo to be updated during a model run: sst_update: 0 – no SST update 1 – update SST Set before running real, and this will create additional output files: wrflowinp_d01, wrflowinp_d02, .. To use these files in wrf, in &time_control, add auxinput4_inname = “wrflowinp_d<domain>” auxinput4_interval = 360 sst_skin: diurnal water temp update tmn_update: deep soil temp update, used with lagday Lagday: averaging time bucket_mm: bucket reset value for rainfall bucket_j: bucket reset value for radiation fluxes spec_exp: exponential multiplier for boundary zone ramping

Adaptive time steps Adaptive-time-step is a way to maximize the model time step while keeping the model numerically stable New since V3. (Very efficient to use for real-time runs.) Namelist control: &domains use_adaptive_time_step: logical switch step_to_output_time: whether to write at exact history output times target_cfl: maximum cfl allowed (1.2) max_step_increase_pct: percentage of time step increase each time; set to 5, 51, (larger values for nests) starting_time_step: in seconds; e.g. set to 4*dx max_time_step: in seconds; e.g. set to 8*dx min_time_step: in seconds; e.g. set to 4*dx

Digital filter initialization (1) Digital filter initialization is a simple way to remove initial model imbalance: – May be introduced by simple interpolation, different topography, or by objective analysis, or data assimilation – It may generate spurious gravity waves in the early simulation hours, which could cause erroneous precipitation, numerical instability and degrade subsequent data assimilation Using DFI – can construct consistent model fields which do not exist in the initial conditions, e.g. vertical motion, cloud variables – may reduce the spin-up problem in early simulation hours DFI is done after real, or data-assimilation step, just before model integration.

Digital filter initialization (2)

Digital filter initialization (3) DFI is done after real, or data-assimilation step, just before model integration. Namelist control: &dfi dfi_opt: dfi options: 0: no DFI; 1: DFL; 2: DDFI; 3: TDFI (recommended) dfi_nfilter: filter options 0 - 8, recommended: 7 dfi_cutoff_seconds : cutoff period dfi_write_filtered_input : whether to write filtered IC dfi_bckstop_* : stop time for backward integration dfi_fwdstop_* : stop time for forward integration

Global applications Setup is mostly done in WPS: map_proj = ‘lat-lon’ e_we, e_sn: geogrid will compute dx, dy See template ‘namelist.wps.global’ for details. In the model stage: fft_filter_lat: default value is 45 degrees Caution: some options do not work, or have been tested with global domain. Start with template ‘namelist.input.global’

Acknowledgements: Thanks to earlier presentations of NCAR/MMM Division (Wei Wang), for providing excellent starting point for this talk!

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