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

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

3. 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

4. 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

5. &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.

6. &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.

7. &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: Pa)

8. &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

9. 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).

10. 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)

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

12. 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)

13. 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

14. &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) 
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)

15. &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.

16. 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

17. 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; K/km; 3 - adiabatic

18. 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

19. 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

20. 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

21. 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.

22. Digital filter initialization (2)

23. 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

24. 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’

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

26. Thanks for attending….