MODULE model_mod (pe2lyr)

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$Id: model_mod.html 11306 2017-03-14 20:20:57Z $



DART standard interfaces for a two-layer isentropic primitive equation model.

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 model state variables.

This model is a 2-layer, isentropic, primitive equation model on a sphere. TODO: add more detail here, including equations, etc.






use model_mod, only : get_model_size

A note about documentation style. Optional arguments are enclosed in brackets [like this].

model_size = get_model_size( )
integer :: get_model_size

Returns the size of the model as an integer. For this model the default grid size is 96 (lon) by 48 (lat) by 2 levels, and 3 variables (U, V, Z) at each grid location, for a total size of 27,648. There are alternative include files which, if included at compile time instead of the default file, defines a grid at twice and 4 times this resolution. They have corresponding truncation values of T63 and T127 (the default grid uses T31).

model_size The length of the model state vector.

call adv_1step(x, time)
real(r8), dimension(:), intent(inout) :: x
type(time_type),        intent(in)    :: time

Advances the model for a single time step. The time associated with the initial model state is also input although it is not used for the computation.

x State vector of length model_size.
time    Specifies time of the initial model state.

call get_state_meta_data (index_in, location, [, var_type] )
integer,             intent(in)  :: index_in
type(location_type), intent(out) :: location
integer, optional,   intent(out) ::  var_type 

Returns metadata about a given element, indexed by index_in, in the model state vector. The location defines where the state variable is located.

For this model, the default grid is a global lat/lon grid, 96 (lon) by 48 (lat) by 2 levels. The variable types are U, V, and Z:

Grids at twice and 4 times the resolution can be compiled in instead by using one of the alternative header files (see resolt31.h (the default), resolt63.h, and resolt127.h).

index_in    Index of state vector element about which information is requested.
location The location of state variable element.
var_type The type of the state variable element.

call model_interpolate(x, location, itype, obs_val, istatus)
real(r8), dimension(:), intent(in)  :: x
type(location_type),    intent(in)  :: location
integer,                intent(in)  :: itype
real(r8),               intent(out) :: obs_val
integer,                intent(out) :: istatus

Given a state vector, a location, and a model state variable type, interpolates the state variable field to that location and returns the value in obs_val. The istatus variable is always returned as 0 (OK).

x A model state vector.
location    Location to which to interpolate.
itype Type of state field to be interpolated.
obs_val The interpolated value from the model.
istatus Integer value returning 0 for successful, other values can be defined for various failures.

var = get_model_time_step()
type(time_type) :: get_model_time_step

Returns the the time step of the model; the smallest increment in time that the model is capable of advancing the state in a given implementation. For this model the default value is 20 minutes (1200 seconds), but also comes with header files with times steps of 10 and 5 minutes (for higher grid resolution and truncation constants).

var    Smallest time step of model.

call static_init_model()

Used for runtime initialization of a model, for instance calculating storage requirements, initializing model parameters, etc. This is the first call made to a model by any DART compliant assimilation routines.

In this model, it allocates space for the grid, and initializes the grid locations, data values, and various parameters, including spherical harmonic weights.

call end_model()

A stub since the pe2lyr model does no cleanup.

call init_time(time)
type(time_type), intent(out) :: time

Returns the time at which the model will start if no input initial conditions are to be used. This model sets the time to 0.

time    Initial model time.

call init_conditions(x)
real(r8), dimension(:), intent(out) :: x

Returns default initial conditions for model; generally used for spinning up initial model states. This model sets the default state vector based on the initialized fields in the model. (TODO: which are what?)

x    Initial conditions for state vector.

ierr = nc_write_model_atts(ncFileID)
integer             :: nc_write_model_atts
integer, intent(in) :: ncFileID

This routine writes the model-specific attributes to a netCDF file. This includes coordinate variables and any metadata, but NOT the model state vector. This model writes out the data as U, V, and Z arrays on a lat/lon/height grid, so the attributes are organized in the same way.

ncFileID    Integer file descriptor to previously-opened netCDF file.
ierr Returns a 0 for successful completion.

ierr = nc_write_model_vars(ncFileID, statevec, copyindex, timeindex)
integer                            :: nc_write_model_vars
integer,                intent(in) :: ncFileID
real(r8), dimension(:), intent(in) :: statevec
integer,                intent(in) :: copyindex
integer,                intent(in) :: timeindex

This routine writes the model-specific state vector (data) to a netCDF file. This model writes out the data as U, V, and Z arrays on a lat/lon/height grid.

ncFileID file descriptor to previously-opened 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.

call pert_model_state(state, pert_state, interf_provided)
real(r8), dimension(:), intent(in)  :: state
real(r8), dimension(:), intent(out) :: pert_state
logical,                intent(out) :: interf_provided

Given a model state vector, perturbs this vector. Used to generate initial conditions for spinning up ensembles. This model has no code to generate these values, so it returns interf_provided as .false. and the default algorithms in filter are then used by the calling code.

state State vector to be perturbed.
pert_state Perturbed state vector
interf_provided    Returned false; interface is not implemented.

call get_close_maxdist_init(gc, maxdist)
type(get_close_type), intent(inout) :: gc
real(r8),             intent(in)    :: maxdist

In distance computations any two locations closer than the given maxdist will be considered close by the get_close_obs() routine. Pass-through to the 3-D sphere locations module. See get_close_maxdist_init() for the documentation of this subroutine.

gc   The get_close_type which stores precomputed information about the locations to speed up searching
maxdist   Anything closer than this will be considered close.

call get_close_obs_init(gc, num, obs)
type(get_close_type), intent(inout) :: gc
integer,              intent(in)    :: num
type(location_type),  intent(in)    :: obs(num)

Pass-through to the 3-D sphere locations module. See get_close_obs_init() for the documentation of this subroutine.

call get_close_obs(gc, base_obs_loc, base_obs_kind, obs, obs_kind, num_close, close_ind [, dist])
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(:)

Given a location and kind, compute the distances to all other locations in the obs list. The return values are the number of items which are within maxdist of the base, the index numbers in the original obs list, and optionally the distances. The gc contains precomputed information to speed the computations.

Pass-through to the 3-D sphere locations module. See get_close_obs() for the documentation of this subroutine.

call ens_mean_for_model(ens_mean)
real(r8), dimension(:), intent(in) :: ens_mean

Stub only. Not needed by this model.

ens_mean    State vector containing the ensemble mean.


This model currently has no values settable by namelist.





Zou, X., Barcilon, A., Navon, I.M., Whitaker, J., Cacuci, D.G.. 1993: An Adjoint Sensitivity Study of Blocking in a Two-Layer Isentropic Model. Monthly Weather Review: Vol. 121, No. 10, pp. 2833-2857.





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Change Date: $Date: 2017-03-14 14:20:57 -0600 (Tue, 14 Mar 2017) $
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