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WRF namelist.input

Dr Meral DemirtaşDr Meral DemirtaşTurkish State Meteorological ServiceTurkish State Meteorological Service

Weather Forecasting DepartmentWeather Forecasting Department

WMO, Training Course, WMO, Training Course, 2626--3030 SeptemberSeptember 201 20111Alanya, TurkeyAlanya, Turkey

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Outline

• Why do we need a namelist?• Sections of namelist.input:

• time_control• domains• physics• dynamics

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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.namelisttest/em_real/examples.namelist

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• 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

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&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 options1. 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.

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&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.

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• 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)

&domains

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&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

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• 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 3. CAM scheme 4. rrtmg scheme99. GFDL Scheme (Lacis and Hansen).

Radiation related flags

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• 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 prediction1. Thermal Diffusion scheme2. Unified NOAH Land-Surface Model3. RUC Land-Surface Model 7. Pleim-Xiu scheme (ARW only)

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• sf_urban_physics

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

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• num_soil_layers: number of soil layers in land surface model

2. Pleim-Xu land-surface model4. Noah land-surface model5. Thermal diffusion scheme6. RUC Land Surface Model

• bl_pbl_physics: planetary boundary layer 0. no boundary-layer1. 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)

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• cu_physics: cumulus parameterization

0. No cumulus parameterization. 1. Kain-Fritsch scheme2. Betts-Miller-Janjic scheme 3. Grell-Devenyi ensemble scheme4. 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

Flags related with cloud parameterization

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&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)

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&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.

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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

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Vertical interpolation options (1)

Program real for ARW only, optional, &domains:

use_surface: whether to use surface observationsuse_levels_below_ground: whether to use data below the

groundlowest_lev_from_sfc: logical, whether surface data is used

to fill the lowest model level valuesforce_sfc_in_vinterp: number of levels to use surface

data, default is 1extrap_type: how to do extrapolation: 1 - use 2 lowest levels;

2 - constantt_extrap_type: extrapolation option for temperature: 1 -

isothermal; 2 - 6.5 K/km; 3 - adiabatic

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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

model surfaces

constant pressure surfaces

ground

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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 updatetmn_update: deep soil temp update, used with lagdayLagday: averaging timebucket_mm: bucket reset value for rainfallbucket_j: bucket reset value for radiation fluxesspec_exp: exponential multiplier for boundary zone ramping

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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

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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.

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Digital filter initialization (2)

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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

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Global applicationsSetup 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’

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

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Thanks for attending….