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DART interface module for the Lorenz-05 models II and III. 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 reference for these models is Lorenz, E.N., 2005: Designing chaotic models. J. Atmos. Sci., 62, 1574-1587.

Model II is a single-scale model, similar to Lorenz 96, but with spatial continuity in the waves. Model III is a two-scale model. It is fudamentally different from the Lorenz 96 two-scale model because of the spatial continuity and the fact that both scales are projected onto a single variable of integration. The scale separation is achived by a spatial filter and is therefore not perfect (i.e. there is leakage). The slow scale in model III is model II, and thus model II is a deficient form of model III. The basic equations are documented in Lorenz (2005) and also in the model_mod.f90 code. The user is free to choose model II or III with a Namelist variable.

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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 model_size = 960, forcing = 15.00, delta_t = 0.001, space_time_scale = 10.00, coupling = 3.00, K = 32, smooth_steps = 12, time_step_days = 0, time_step_seconds = 3600, model_number = 3 /

Contents | Type | Description |
---|---|---|

model_size | integer | Number of variables in model |

forcing | real(r8) | Forcing, F, for model |

delta_t | real(r8) | Non-dimensional timestep |

space_time_scale | real(r8) | Determines temporal and spatial relationship between fast and slow variables (model III) |

coupling | real(r8) | Linear coupling between fast and slow variables (model III) |

K | integer | Determines the wavenumber of the slow variables (K=1, smooth_steps=0 reduces model II to Lorenz 96) |

smooth_steps | integer | Determines filter length to separate fast and slow scales |

time_step_days | integer | Arbitrary real time step days |

time_step_seconds | integer | Arbitrary real time step seconds (could choose this for proper scaling) |

model_number | integer | 2 = single-scale, 3 = 2-scale. (This follows the notation in the paper.) |

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types_mod time_manager_mod oned/location_mod utilities_mod

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Optional namelist interface
*&model_nml*
may be read from file *input.nml*.

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. Settable by namelist, the default is 960.

model_size |
The length of the model state vector. |

real(r8), dimension(:), intent(inout) ::xtype(time_type), intent(in) ::time

Advances a model for a single time step using a four-step Runga-Kutta. The time argument is passed in but not used by this model.

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 (at present, a variety of simple location models for support of gridpoint models are provided) while the type of the variable (for instance temperature, or u wind component) is returned by var_type. In this model there are no types so it always returns 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 of variable itype interpolated to a given location.

x |
A model state vector. |

location |
Location to which to interpolate. |

itype |
Integer indexing which type of state variable is to be interpolated. Is ignored for this model since there is only a single type of variable. |

obs_val |
The interpolated value from the model. |

istatus |
Quality control information about the observation of the model state. 0 == successful. |

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. |

Reads the namelist, allocates space for the state vector, initializes the locations, generates some initial parameters.

A stub routine in this model.

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

Sets the entire state variable to the value of the forcing and then slightly perturbs the first element.

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. |

integer ::ierrinteger, intent(in) ::ncFileIDreal(r8), dimension(:), intent(out) ::statevecinteger, intent(in) ::copyindexinteger, intent(in) ::timeindex

A general interface routine to read the state vector at a particular time for a particular ensemble member.

ierr |
Returned error code. 0 == normal termination. |

ncFileID |
Integer file descriptor connected to NetCDF file. |

statevec |
State vector. |

copyindex |
Integer index to designate copy to be read. |

timeindex |
Integer index of desired time to be read. |

This interface is essentially untested in the Lorenz 04/05 model. It began life as a stub, but there is so little to it ... TJH 05 Aug 2005.

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 is used to generate initial ensemble conditions perturbed around some control trajectory state when one is preparing to spin-up 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. This model returns .false. for interf_provided and uses the default DART perturbation routine.

state |
State vector to be perturbed |

pert_state |
Perturbed state vector is returned |

interf_provided |
Returns false to have DART perturb state |

The Lorenz 04/05 model relies implicitly on the default DART perturbation
mechanism, i.e. this routine always returns *.false.*.

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 |

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 |

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- Lorenz, E.N., 2005: Designing chaotic models. J. Atmos. Sci., 62, 1574-1587.

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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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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: | DART core group |

Revision: | $Revision: 6382 $ |

Source: | $URL: https://svn-dares-dart.cgd.ucar.edu/DART/releases/Lanai/models/lorenz_04/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" |