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DART interface module for the WRF model. This page documents the details of the module compiled into DART that interfaces with the WRF data in the state vector. There is additional overview and tutorial documentation for running a WRF/DART assimilation on this web page:
http://www.image.ucar.edu/wrfdart/tutorial
The WRF model_mod code reads the state data from a filter initial condition/restart file, typically called filter_ics or filter_restart. It also requires a NetCDF file named wrfinput_d01 in the current directory (and d02, etc. for multiple domain cases). This file must be at the same resolution and have the same surface elevation data as the files converted to create the DART initial conditions. No data will be read from this file, but the grid information must match exactly. See the wrf_to_dart documentation for more information on how to generate DART IC/restart files given WRF NetCDF files.
The model interface code supports WRF configurations with multiple domains. Data for all domains is read into the DART state vector. During the computation of the forward operators (getting the estimated observation values from each ensemble member), the search starts in the domain with the highest number, which is generally the finest nest or one of multiple finer nests. The search stops as soon as a domain contains the observation location, working its way from largest number to smallest number domain, ending with domain 1. For example, in a 4 domain case the data in the state vector that came from wrfinput_d04 is searched first, then wrfinput_d03, wrfinput_d02, and finally wrfinput_d01. The forward operator is computed from the first domain grid that contains the lat/lon of the observation. During the assimilation phase, when the state values are adjusted based on the correlations and assimilation increments, all points in all domains that are within the localization radius are adjusted, regardless of domain. The impact of an observation on the state depends only on the distance between the observation and the state vector point, and the regression coefficient based on the correlation between the distributions of the ensemble of state vector points and the ensemble of observation forward operator values.
The fields from WRF that are copied into the DART state vector are controlled by namelist. See below for the documentation on the &model_nml entries. The state vector should include all fields needed to restart a WRF run. There may be additional fields needed depending on the microphysics scheme selected. See the ascii file wrf_state_variables_table in the models/wrf directory for a list of fields that are often included in the DART state.
The 16 public interfaces are standardized for all DART compliant models. These interfaces allow DART to advance the model, get the model state and metadata describing this state, find state variables that are close to a given location, and do spatial interpolation for a variety of variables required in observational operators.
This namelist is read from the file input.nml. Namelists start with an ampersand '&' and terminate with a slash '/'. Character strings that contain a '/' must be enclosed in quotes to prevent them from prematurely terminating the namelist.
&model_nml default_state_variables = .true., wrf_state_variables = 'NULL', wrf_state_bounds = 'NULL', num_domains = 1, output_state_vector = .false., calendar_type = 3, num_moist_vars = 3, surf_obs = .true., soil_data = .true., h_diab = .false., assimilation_period_seconds = 21600, adv_mod_command = './wrf.exe', allow_obs_below_vol = .false., vert_localization_coord = 3, center_search_half_length = 500000., center_spline_grid_scale = 10, circulation_pres_level = 80000.0, circulation_radius = 108000.0, sfc_elev_max_diff = 1.0, polar = .false., periodic_x = .false., periodic_y = .false., scm = .false. / # Notes for model_nml: # (1) vert_localization_coord must be one of: # 1 = model level # 2 = pressure # 3 = height # 4 = scale height # (2) see bottom of this file for explanations of polar, periodic_x, # periodic_y, and scm # (3) calendar = 3 is GREGORIAN, which is what WRF uses. # (4) if 'default_state_variables' is .true. the model_mod.f90 code will # fill the state variable table with the following wrf vars: # U, V, W, PH, T, MU # you must set it to false before you change the value # of 'wrf_state_variables' and have it take effect. # (5) the format for 'wrf_state_variables' is an array of 5 strings: # wrf netcdf variable name, dart KIND_xxx string, type string (must be # unique, will soon be obsolete, we hope), 'UPDATE', and '999' if the # array is part of all domains. otherwise, it is a string with the domain # numbers (e.g. '12' for domains 1 and 2, '13' for domains 1 and 3). # example: # wrf_state_variables='U','KIND_U_WIND_COMPONENT','TYPE_U','UPDATE','999', # 'V','KIND_V_WIND_COMPONENT','TYPE_V','UPDATE','999', # 'W','KIND_VERTICAL_VELOCITY','TYPE_W','UPDATE','999', # 'T','KIND_POTENTIAL_TEMPERATURE','TYPE_T','UPDATE','999', # 'PH','KIND_GEOPOTENTIAL_HEIGHT','TYPE_GZ','UPDATE','999', # 'MU','KIND_PRESSURE','TYPE_MU','UPDATE','999', # 'QVAPOR','KIND_VAPOR_MIXING_RATIO','TYPE_QV','UPDATE','999', # 'QCLOUD','KIND_CLOUD_LIQUID_WATER','TYPE_QC','UPDATE','999', # 'QRAIN','KIND_RAINWATER_MIXING_RATIO','TYPE_QR','UPDATE','999', # 'U10','KIND_U_WIND_COMPONENT','TYPE_U10','UPDATE','999', # 'V10','KIND_V_WIND_COMPONENT','TYPE_V10','UPDATE','999', # 'T2','KIND_TEMPERATURE','TYPE_T2','UPDATE','999', # 'TH2','KIND_POTENTIAL_TEMPERATURE','TYPE_TH2','UPDATE','999', # 'Q2','KIND_SPECIFIC_HUMIDITY','TYPE_Q2','UPDATE','999', # 'PSFC','KIND_PRESSURE','TYPE_PS','UPDATE','999', # (6) the format for 'wrf_state_bounds' is an array of 4 strings: # wrf netcdf variable name, minimum value, maximum value, and either # FAIL or CLAMP. FAIL will halt the program if an out of range value # is detected. CLAMP will set out of range values to the min or max. # The special string 'NULL' will map to plus or minus infinity and will # not change the values. arrays not listed in this table will not # be changed as they are read or written. # # # polar and periodic_x are used in global wrf. if polar is true, the # grid interpolation routines will wrap over the north and south poles. # if periodic_x is true, when the east and west edges of the grid are # reached the interpolation will wrap. note this is a separate issue # from regional models which cross the GMT line; those grids are marked # as having a negative offset and do not need to wrap; this flag controls # what happens when the edges of the grid are reached. # the scm flag is used for the 'single column model' version of WRF. # it needs the periodic_x and periodic_y flags set to true, in which # case the X and Y directions are periodic; no collapsing of the grid # into a single location like the 3dspherical polar flag implies.
Item  Type  Description 

default_state_variables  logical  If .true., the dart state vector contains the fields U, V, W, PH, T, MU, in that order, and only those. Any values listed in the wrf_state_variables namelist item will be ignored. 
wrf_state_variables  character(:, 5)  A 2D array of strings, 5 per wrf array
to be added to the dart state vector. If default_state_variables
is .true., this is ignored. When .false., this list of array
names controls which arrays and the order that they are added
to the state vector. The 5 strings are:

wrf_state_bounds  character(:, 4)  A 2D array of strings, 4 per wrf array. During the copy of data to and
from the wrf netcdf file, variables listed here will have minimum and maximum
values enforced. The 4 strings are:

output_state_vector  logical  Controls the output to netCDF files. If .true., output the raw dart state vector. If .false., output the prognostic flavor (gridded data) for easier plotting (recommended). 
num_domains  integer  Total number of WRF domains, including nested domains. 
calendar_type  integer  Calendar type. Should be 3 (GREGORIAN) for WRF. 
assimilation_period_seconds  integer  The time (in seconds) between assimilations. This is modified if necessary to be an integer multiple of the underlying model timestep. 
periodic_x  logical  If .true., the grid is periodic in longitude, and points above the last grid cell and points below the first grid cell are wrapped. Note this is not the same as a grid which crosses the prime meridian. WRF handles that with an offset in longitude and points beyond the last grid index are outside the domain. 
periodic_y  logical  Used for the Single Column Model to make the grid wrap in Y (see scm below). This is NOT the same as wrapping in latitude (see polar below). 
polar  logical  If .true., points at the poles are wrapped across the grid. It is not clear this is a good idea since the grid is degnerate here. 
scm  logical  If .true. the Single Column Model is assumed. The grid is a single vertical column, and there are 9 cells arranged in a 3x3 grid. See the WRF documentation for more information on this configuration. periodic_x and periodic_y should also be .true. in this case. 
sfc_elev_max_diff  real(r8)  If > 0, the maximum difference, in meters, between an observation marked as a 'surface obs' as the vertical type (with the surface elevation, in meters, as the numerical vertical location), and the surface elevation as defined by the model. Observations further away from the surface than this threshold are rejected and not assimilated. If the value is negative, this test is skipped. 
allow_obs_below_vol  logical  If .false. then if an observation with a vertical coordinate of pressure or height (i.e. not a surface observation) is below the lowest 3d sigma level, it is outside the field volume and the interpolation routine rejects it. If this is set to .true. and the observation is above the surface elevation but below the lowest field volume level, the code will extrapolate downward from data values at levels 1 and 2. 
center_search_half_length  real(r8)  The model_mod now contains two schemes for searching for a vortex center location. If the old scheme is compiled in, then this and the center_spline_grid_scale namelist items are used. (Search code for 'use_old_vortex'.) Half length (in meters) of a square box for searching the vortex center. 
center_spline_grid_scale  integer  The model_mod now contains two schemes for searching for a vortex center location. If the old scheme is compiled in, then this and the center_search_half_length namelist items are used. (Search code for 'use_old_vortex'.) Ratio of refining grid for splineinterpolation in determining the vortex center. 
circulation_pres_level  real(r8)  The model_mod now contains two schemes for searching for a vortex center location. If the new scheme is compiled in, then this and the circulation_radius namelist items are used. (Search code for 'use_old_vortex'.) Pressure, in pascals, of the level at which the circulation is computed when searching for the vortex center. 
circulation_radius  real(r8)  The model_mod now contains two schemes for searching for a vortex center location. If the new scheme is compiled in, then this and the circulation_pres_level namelist items are used. (Search code for 'use_old_vortex'.) Radius, in meters, of the circle over which the circulation calculation is done when searching for the vortex center. 
vert_localization_coord  integer  Vertical coordinate for vertical localization.

surf_obs  logical  DEPRECATED  has no effect on the code and will be removed. 
soil_data  logical  DEPRECATED  has no effect on the code and will be removed. 
h_diab  logical  DEPRECATED  has no effect on the code and will be removed. 
num_moist_vars  integer  DEPRECATED  has no effect on the code and will be removed. 
adv_mod_command  character(len=32)  DEPRECATED  A variable with the same name has moved to the &dart_to_wrf namelist and does the same function from there. This one has no effect on the code and will be removed soon. 
types_mod time_manager_mod threed_sphere/location_mod utilities_mod obs_kind_mod map_utils netcdf typesizes
The last 4 interfaces are only required for loworder models where advancing
the model can be done by a call to a subroutine. The WRF model only advances by
executing the program wrf.exe. Thus the last 4 interfaces only appear as stubs
in the wrf module.
The interface pert_model_state is presently not provided for WRF. The initial
ensemble has to be generated offline. If coherent structures are not required,
the filter can generate an ensemble with uncorrelated random Gaussian noise of
0.002. This is of course not appropriate for a model like WRF which has
variables expressed in a wide range of scales. It is thus recommended to
generate the initial ensemble offline, perhaps with the tools provided in
models/wrf/PERTURB/3DVARCOVAR.
A note about documentation style. Optional arguments are enclosed in brackets [like this].
integer :: get_model_size
Returns the length of the model state vector as an integer. This includes all nested domains.
model_size  The length of the model state vector. 
integer, intent(in) :: index_in type(location_type), intent(out) :: location integer, optional, intent(out) :: var_type_out integer, optional, intent(out) :: id_out
Returns metadata about a given element, indexed by index_in, in the model state vector. The location defines where the state variable is located while the type of the variable (for instance temperature, or u wind component) is returned by var_type. The integer values used to indicate different variable types in var_type are themselves defined as public interfaces to model_mod if required. The last optional argument is the wrf domain identification number  obviously this is unique to the WRF version of this required routine.
index_in  Index of state vector element about which information is requested. 
location  Returns location of indexed state variable. The location should use a location_mod that is appropriate for the model domain. For realistic atmospheric models, for instance, a threedimensional spherical location module that can represent height in a variety of ways is provided. 
var_type_out  Returns the type of the indexed state variable as an optional argument. 
id_out  Returns the wrf domain identification number of the indexed state variable as an optional argument. 
real(r8), dimension(:), intent(in) :: x type(location_type), intent(in) :: location integer, intent(in) :: obs_kind real(r8), intent(out) :: obs_val integer, intent(out) :: istatus
Given model state, returns the value of observation type interpolated to a given location by a method of the model's choosing. All observation kinds defined in obs_kind_mod are supported. In the case where the observational operator is not defined at the given location (e.g. the observation is below the model surface or outside the domain), obs_val is returned as 888888.0 and istatus = 1. Otherwise, istatus = 0. The interpolation is performed in the domain with the highest resolution containing the observation.
x  A model state vector. 
location  Location to which to interpolate. 
obs_kind  Integer indexing which type of observation is to be interpolated. 
obs_val  The interpolated value from the model. 
istatus  Integer flag indicating the result of the interpolation. 
type(time_type) :: get_model_time_step
Returns the model base time step as a time_type. For the model wrf, it returns the time step used for domain 1 (usually the largest time step among all domains because domain 1 is the coarser grid). The time step is read from the wrfinput_d01 file (used to be namelist.input). In the long run, a more general extended interface may be required that specifies the models range of time stepping possibilities.
var  Smallest time step of model. 
Used for runtime initialization of the model. This is the first call made to the model by any DART compliant assimilation routine. It reads the model namelist parameters, set the calendar type (the GREGORIAN calendar is used with the WRF model), and determine the dart vector length. This subroutine requires that wrfinput_d01, wrfinput_d02, ... (one file for each domain) be present in the working directory to retrieve model information (grid dimensions and spacing, time step, pressure at the top of the model, map projection parameters, etc).
integer :: nc_write_model_atts integer, intent(in) :: ncFileID
Function to write model specific attributes to a netCDF file. At present, DART is using the NetCDF format to output diagnostic information. This is not a requirement, and models could choose to provide output in other formats. This function writes the metadata associated with the model to a NetCDF file opened to a file identified by ncFileID.
ncFileID  Integer file descriptor to previouslyopened netCDF file. 
ierr  Returns a 0 for successful completion. 
integer :: nc_write_model_vars integer, intent(in) :: ncFileID real(r8), dimension(:), intent(in) :: statevec integer, intent(in) :: copyindex integer, intent(in) :: timeindex
Writes a copy of the state variables to a netCDF file. Multiple copies of the state for a given time are supported, allowing, for instance, a single file to include multiple ensemble estimates of the state.
ncFileID  file descriptor to previouslyopened netCDF file. 
statevec  A model state vector. 
copyindex  Integer index of copy to be written. 
timeindex  The timestep counter for the given state. 
ierr  Returns 0 for normal completion. 
real(r8), dimension(:), intent(in) :: state real(r8), dimension(:), intent(out) :: pert_state logical, intent(out) :: interf_provided
Given a model state, produces a perturbed model state. This is used to generate initial ensemble conditions perturbed around some control trajectory state when one is preparing to spinup ensembles. A DART compliant model can choose not to provide an implementation of this algorithm and use the default mechanism in DART by simply returning .false. as a returned value for the interf_provided argument. In this case, DART perturbs the state to generate ensemble members by adding a random sample from a N(0.0, 0.002) distribution independently to each state variable. Models should override this if some structure is required for perturbations or if the magnitude of perturbations in DART is too large. It is thus recommended to generate the initial ensemble offline, perhaps with the tools provided in models/wrf/PERTURB/3DVARCOVAR.
state  State vector to be perturbed. 
pert_state  Perturbed state vector is returned. 
interf_provided  Return false to have DART perturb state . 
type(get_close_type), intent(inout) :: gc real(r8), intent(in) :: maxdist
Passthrough to the 3D sphere locations module. See get_close_maxdist_init() for the documentation of this subroutine.
type(get_close_type), intent(inout) :: gc integer, intent(in) :: num type(location_type), intent(in) :: obs(num)
Passthrough to the 3D sphere locations module. See get_close_obs_init() for the documentation of this subroutine.
type(get_close_type), intent(in) :: gc type(location_type), intent(in) :: base_obs_loc integer, intent(in) :: base_obs_kind type(location_type), intent(in) :: obs(:) integer, intent(in) :: obs_kind(:) integer, intent(out) :: num_close integer, intent(out) :: close_ind(:) real(r8), optional, intent(out) :: dist(:)
Calls the 3D sphere locations module to get a list of potentially close state vector points, and again for unassimilated observations. See get_close_obs() for the documentation of the locations module version of this code. Then, if vertical localization is enabled, this code converts all vertical locations to the selected vertical type (&model_nml::vert_localization_coord). It then computes a real 3D distance and returns it to the calling code.
real(r8), dimension(:), intent(in) :: ens_mean
A local copy is kept and used during other computations in the model_mod code.
ens_mean  Ensemble mean state vector 
real(r8), dimension(:), intent(inout) :: x type(time_type), intent(in) :: time
This operation is not defined for the WRF model. If called it will throw a fatal error.
x  State vector of length model_size. 
time  Gives time of the initial model state. 
Called when use of a model is completed to clean up storage, etc. A stub is provided for the WRF model.
type(time_type), intent(in) :: i_time
Not supported for the WRF model.
real(r8), dimension(:), intent(out) :: x
Not supported for the WRF model. Will throw a fatal error if called.
x  Model state vector. 
Routine  Message  Comment 

static_init_model nc_write_model_vars 
num_moist_vars is too large  The maximum number of moist variable in WRFV2.1 is 7 
static_init_model  'Please put wrfinput_d0'//idom//' in the work directory.'  One of the wrfinput_d0# is missing in the work directory 
static_init_model  Map projection no supported  Try PROJ_LATLON(0), PROJ_LC(1), PROJ_PS(2), PROJ_MERC(3) 
static_init_model nc_write_model_atts nc_write_model_vars 
Various NetCDFf90 interface error messages  From one of the NetCDF calls in the named routine 
get_state_meta_data  dart index out of range  Unlikely. Would indicate a serious bug in the code 
model_interpolate get_dist_wrf 
wrong option for which_vert  See which_vert description in location/threed_sphere/location_mod.html 
model_interpolate  'do not recognize obs kind ',obs_kind  See list in 'use obs_kind_mod' statement in model_mod.f90 
get_wrf_index  'Indices ',i,j,k,' exceed grid dimensions: ',#1,#2,#3  One of the grid indices exceeds the corresponding dimension for the var_type input. Unlikely to happen but would indicate a serious bug in the code 
get_dist_wrf  Unable to define vloc  The vertical location is below the model surface or above the model lid 
nc_write_model_atts  Time dimension ID # must match Unlimited Dimension ID #  NetCDF file writing error 
read_dt_from_wrf_nml  Please put namelist.input in the work directory  The file namelist.input is missing in the work directory 
read_dt_from_wrf_nml  'max_dom in namelist.input = ',max_dom'num_domains in input.nml = ',num_domains'Make them consistent.'  The number of WRF domains in namelist.input and in input.nml do not match 
Only the Lambert projection (MAP_PROJ = 1) is working. Other map projections (0=none, 2=polar, 3=Mercator) are likely to break the code.
none at this time
integer :: get_wrf_index integer, intent(in) :: i,j,k,var_type,id
Given grid indices, variable type, and domain identification number, returns the index in the model state vector as an integer.
real(r8) :: get_dist_wrf integer, intent(in) :: i,j,k,var_type,id type(location_type), intent(in) :: o_loc real(r8), dimension(:), intent(in) :: x
Given grid indices, variable type, and domain identification number, computes the distance to the observation at location o_loc.
integer, intent(in) :: i,j,var_type,id real(r8), intent(out) :: long, lat
Given horizontal grid indices, variable type, and domain identification number, returns the longitude and latitude in degrees.
real(r8), intent(in) :: x real(r8), intent(out) :: dx, dxm integer , intent(out) :: j
Given position x, find nearest grid point j (but smaller than or equal to x) and calculate its distance to grid j and j+1.
real(r8), intent(in) :: pres integer intent(in) :: n3 real(r8), dimension(0:n3), intent(in) :: mdl_v real(r8), intent(out) :: zk
Calculate the position zk on half (mass) levels in the profile mdl_v corresponding to pressure location pres.
real(r8), intent(in) :: obs_v integer intent(in) :: n3 real(r8), dimension(0:n3), intent(in) :: mdl_v real(r8), intent(out) :: zk
Calculate the position zk on half (mass) levels in the profile mdl_v corresponding to height location obs_v.
integer intent(in) :: i,j,n,id real(r8), intent(in) :: dx,dy,dxm,dym real(r8), dimension(:), intent(in) :: x real(r8), dimension(0:n), intent(out) :: v_p
Extract the pressure profile at position (i+dx, j+dy) on the nonstaggered vertical grid (half (mass) levels).
real(r8), :: model_pressure integer intent(in) :: i,j,k,id,var_type real(r8), dimension(:), intent(in) :: x
Calculate the pressure at grid point (i,j,k), domain id. The grid is defined according to var_type.
real(r8) :: model_pressure_t integer intent(in) :: i,j,k,id real(r8), dimension(:), intent(in) :: x
Calculate the pressure at grid point (i,j,k), domain id, on mass point (half (mass) levels, Tpoint).
real(r8) :: model_rho_t integer intent(in) :: i,j,k,id real(r8), dimension(:), intent(in) :: x
Calculate the total density at grid point (i,j,k), domain id, on mass point (half (mass) levels, Tpoint).
integer intent(in) :: i,j,n,id real(r8), intent(in) :: dx,dy,dxm,dym real(r8), dimension(:), intent(in) :: x real(r8), dimension(n), intent(out) :: fld
Extract the height profile at position (i+dx, j+dy) on the nonstaggered vertical grid.
real(r8) :: model_height integer intent(in) :: i,j,k,id,var_type real(r8), dimension(:), intent(in) :: x
Calculate the height at grid point (i,j,k), domain id. The grid is defined according to var_type.
Read the wrf model time step from namelist.input for all domains.
DART software  Copyright 2004  2013 UCAR.
This open source software is provided by UCAR, "as is",
without charge, subject to all terms of use at
http://www.image.ucar.edu/DAReS/DART/DART_download
Contact:  Hui Liu, Glen Romine, Chris Synder, David Dowell 
Revision:  $Revision: 7668 $ 
Source:  $URL: https://svndaresdart.cgd.ucar.edu/DART/releases/Lanai/models/wrf/model_mod.html $ 
Change Date:  $Date: 20150305 16:08:55 0700 (Thu, 05 Mar 2015) $ 
Change history:  try "svn log" or "svn diff" 