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DART interface module for the Lorenz-84 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 model is based on:

Lorenz E. N., 1984:

Irregularity: A fundamental property of the atmosphere.

*Tellus*, **36A**, 98-110.

The system of equations is:

X' = -Y^2 - Z^2 - aX + aF Y' = XY - bXZ - Y + G Z' = bXY + XZ - Z

Where a, b, F, and G are the model parameters.

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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 a = 0.25, b = 4.00, f = 8.00, g = 1.25, deltat = 0.01, time_step_days = 0, time_step_seconds = 3600 /

Item | Type | Description |
---|---|---|

a | real(r8) | Model parameter. |

b | real(r8) | Model parameter. |

f | real(r8) | Model parameter. |

g | real(r8) | Model parameter. |

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. |

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types_mod time_manager_mod oned/location_mod utilities_mod

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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) ::xtype(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_intype(location_type), intent(out) ::locationinteger, 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-84, 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) ::xtype(location_type), intent(in) ::locationinteger, intent(in) ::itypereal(r8), intent(out) ::obs_valinteger, 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. |

itype |
Not used. |

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-84 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 for x and z and 1 for y.

x |
Initial conditions for state vector. |

integer ::nc_write_model_attsinteger, 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_varsinteger, intent(in) ::ncFileIDreal(r8), dimension(:), intent(in) ::statevecinteger, intent(in) ::copyindexinteger, 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) ::statereal(r8), dimension(:), intent(out) ::pert_statelogical, 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) ::gcreal(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) ::gcinteger, intent(in) ::numtype(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) ::gctype(location_type), intent(in) ::base_obs_locinteger, intent(in) ::base_obs_kindtype(location_type), intent(in) ::obs(:)integer, intent(in) ::obs_kind(:)integer, intent(out) ::num_closeinteger, 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. |

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filename | purpose |
---|---|

input.nml | to read the model_mod namelist |

preassim.nc | the time-history of the model state before assimilation |

analysis.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 |

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- Lorenz, E.N., 1984: Irregularity: A fundamental property of the atmosphere. Tellus, 36A, 98-110.

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Routine | Message | Comment |
---|---|---|

nc_write_model_atts nc_write_model_vars |
Various netCDF-f90 interface error messages | From one of the netCDF calls in the named routine |

none at this time

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none at this time

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N/A

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DART software - Copyright 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: | DART core group |

Revision: | $Revision: 11626 $ |

Source: | $URL: https://svn-dares-dart.cgd.ucar.edu/DART/releases/Manhattan/models/lorenz_84/model_mod.html $ |

Change Date: | $Date: 2017-05-11 11:27:50 -0600 (Thu, 11 May 2017) $ |

Change history: | try "svn log" or "svn diff" |