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DART interface module for the Lorenz-63 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 distinctive part of the model interfaces is the namelist.
This is the 3-variable model as described in:
Lorenz, E. N. 1963. Deterministic nonperiodic flow. J. Atmos. Sci. 20, 130-141.
It was developed as a simplified model to study
convection rolls in the atmosphere.
Plotting the location of the X, Y, Z values as they progress
through time traces out the classic 'butterfly' attractor plot
which has become an iconic image of chaotic systems:
The system of equations is:
X' = -sigma*X + sigma*Y Y' = -XZ + rX - Y Z' = XY -bZThe values for the constants are settable by namelist (see below). The default values are:
r = 28.0_r8 sigma = 10.0_r8 b = 8.0_r8 / 3.0_r8 runga-kutta delta t: 0.01 seconds assimilation time step: 60 minutes
This model is an interesting data assimilation test in that different ensemble members may bifurcate over to the other lobe of the attractor on different cycles. Also, as they diverge from each other they do not spread out uniformly in 3D space, but spread along the linear attractor lines.
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 sigma = 10.0, r = 28.0, b = 2.6666666666667, deltat = 0.01, time_step_days = 0, time_step_seconds = 3600 /
|deltat||real(r8)||Non-dimensional timestep. This is mapped to the dimensional timestep specified by time_step_days and time_step_seconds.|
|time_step_days||integer||Number of days for dimensional timestep, mapped to deltat.|
|time_step_seconds||integer||Number of seconds for dimensional timestep, mapped to deltat.|
types_mod time_manager_mod oned/location_mod utilities_mod
|use model_mod, only :||get_model_size|
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. Required.
|model_size||The length of the model state vector.|
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.|
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 lorenz-63, the variable 1 (x) is at 0.0, the variable 2 (y) at 1/3, and the variable 3 (z) at 2/3 on a cyclic [0, 1] domain. The variable type is always returned as 1.
|index_in||Index of state vector element about which information is requested.|
|location||The location of state variable element.|
|var_type||Returns the type (always 1) of the indexed state variable as an optional argument.|
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 model state, returns the value interpolated to a given location in [0, 1] by linear interpolation. Variable locations are at 0, 1/3 and 2/3 in the cyclic [0, 1] domain. So, a value of 1/6 is an average of the x and y variables. The type variable is not used here and istatus is always returned as 0 (successful interpolation).
|x||A model state vector.|
|location||Location to which to interpolate.|
|obs_val||The interpolated value from the model.|
|istatus||Quality control information, always returned 0.|
type(time_type) :: get_model_time_step
Returns the time step (forecast length) of the model; The time step defaults to 1 hour but is settable by namelist.
|var||Smallest time step of model.|
Used for runtime initialization of model; reads namelist, initializes model parameters, etc. This is the first call made to the model by any DART-compliant assimilation routine.
A stub since lorenz-63 requires no clean up.
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 is used to spin-up the model from rest. Sets time to 0 in this model.
|time||Initial model time.|
real(r8), dimension(:), intent(out) :: x
Returns default initial conditions for the model; generally used for spinning up initial model states. Values chosen here are 0.1 for all three state variables.
|x||Initial conditions for state vector.|
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 previously-opened 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 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.|
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.|
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.
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.
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.
real(r8), dimension(:), intent(in) :: ens_mean
A NULL INTERFACE in this model.
|ens_mean||State vector containing the ensemble mean.|
|input.nml||to read the model_mod namelist|
|Prior_Diag.nc||the time-history of the model state before assimilation|
|Posterior_Diag.nc||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|
|Various netCDF-f90 interface error messages||From one of the netCDF calls in the named routine|
none at this time
none at this time
DART software - Copyright 2004 - 2013 UCAR.
This open source software is provided by UCAR, "as is",
|Contact:||DART core group|
|Revision:||$Revision: 6382 $|
|Source:||$URL: https://svn-dares-dart.cgd.ucar.edu/DART/releases/classic/models/lorenz_63/model_mod.html $|
|Change Date:||$Date: 2013-08-07 14:45:16 -0600 (Wed, 07 Aug 2013) $|
|Change history:||try "svn log" or "svn diff"|