MODULE model_mod (Ikeda)

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$Id: model_mod.html 11626 2017-05-11 17:27:50Z $



DART interface module for the Ikeda 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.

The Ikeda model is a 2D chaotic map useful for visualization data assimilation updating directly in state space. There are three parameters: a, b, and mu. The state is 2D, x = [X Y]. The equations are:

X(i+1) = 1 + mu * ( X(i) * cos( t ) - Y(i) * sin( t ) )
Y(i+1) =     mu * ( X(i) * sin( t ) + Y(i) * cos( t ) ),


t = a - b / ( X(i)**2 + Y(i)**2 + 1 )

Note the system is time-discrete already, meaning there is no delta_t. The system stems from nonlinear optics (Ikeda 1979, Optics Communications). Interface written by Greg Lawson, CalTech. Thanks Greg!

"The initial conditions were generated by observing state variable 1 with an enormous (~1,000,000.0) observation error variance. The observation was defined to be taken at day=0, seconds = 0. create_fixed_network_sequence was run to create a sequence with 3000 hourly observations starting at day=0, seconds =0. The initial conditions for filter can accomodate 100 ensemble members."



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.

   a  = 0.40,
   b  = 6.00,
   mu = 0.83,
   time_step_days      = 0,
   time_step_seconds   = 3600,
   output_state_vector = .true.  

Item Type Description
a real(r8) Model parameter.
b real(r8) Model parameter.
mu real(r8) Model parameter.
time_step_days integer Model advance time in days.
time_step_seconds integer Model advance time in seconds.
output_state_vector logical If true, output the state vector data to the diagnostic files as a single 1D array. If false, break up output data into logical model variables.





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 length of the model state vector as an integer. This is fixed at 2 for this model.

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    Unused in this model.

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 the location of the given index, and a dummy integer as the var_type.

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 three-dimensional spherical location module that can represent height in a variety of ways is provided.
var_type Returns the type of the indexed state variable as an optional argument.

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

A NULL INTERFACE in this model. Always returns istatus = 0.

x A model state vector.
location    Location to which to interpolate.
itype Integer indexing which type of state variable is to be interpolated. Can be ignored for low order models with a single type of variable.
obs_val The interpolated value from the model.
istatus Quality control information about the observation of the model state.

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

Returns the models base time step, or forecast length, as a time_type. This is settable in the namelist.

var    Smallest time step of model.

call static_init_model()

Reads the namelist, defines the 2 initial locations of the state variables, and sets the timestep.

call end_model()

A NULL INTERFACE in this model.

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

Returns a time of 0.

time    Initial model time.

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

Sets 2 initial locations close to the attractor.

x    Initial conditions for state vector.

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

Uses the default template code.

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

Uses the default template code.

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, produces a perturbed model state. This particular model does not implement an interface for this and so returns .false. for interf_provided.

state State vector to be perturbed.
pert_state Perturbed state vector: NOT returned.
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

Pass-through to the 1-D locations module. See get_close_maxdist_init() for the documentation of this subroutine.

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 1-D 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(:)

Pass-through to the 1-D 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

A NULL INTERFACE in this model.

ens_mean    State vector containing the ensemble mean.



filename purpose
input.nml to read the model_mod namelist the time-history of the model state before assimilation  the time-history of the model state after assimilation
dart_log.out [default name] the run-time diagnostic output
dart_log.nml [default name] the record of all the namelists actually USED - contains the default values



Ikeda 1979, Optics Communications



Routine Message Comment
Various netCDF-f90 interface error messages From one of the netCDF calls in the named routine


none at this time



none at this time





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Contact: DART core group
Revision: $Revision: 11626 $
Source: $URL: $
Change Date: $Date: 2017-05-11 11:27:50 -0600 (Thu, 11 May 2017) $
Change history:  try "svn log" or "svn diff"