PDAF3_assimilate_local

This page documents the routine PDAF3_assimilate_local. The routine is part of the advanced PDAF3 interface that was introduced with PDAF V3.0.

The routine is used to execute the analysis step of all local ensemble filters including the nonlinear filter LNETF, the hybrid filter LKNETF, and the ENSRF/EAKF (but except the LEnKF). The routine uses the functionalities provided by PDAF-OMIto yield a small number of arguments. For backward-compatibility, the routine does not use PDAFlocal, but lets the user provide the routines for filling the local state vector and to fill the global analysis state vectors with the local analysis states.

The routine is typically called in assimilate_pdaf or directly in the model code.

The general aspects of the filter specific routines PDAF3_assimilate_* are described on the page Modification of the model code for the ensemble integration and its sub-page on inserting the analysis step. The routine is used in both the fully-parallel and the flexible parallelization variant of the data assimilation system.

The interface for the routine PDAF3_assimilate_local contains names for routines that operate on the local analysis domains (marked by the suffix _l).

The interface is:

  SUBROUTINE PDAF3_assimilate_local(U_collect_state, U_distribute_state, &
             U_init_dim_obs_pdafomi, U_obs_op_pdafomi, &
             U_init_n_domains, U_init_dim_l, U_init_dim_obs_l_pdafomi, &
             U_g2l_state, U_l2g_state, &
             U_prepoststep, U_next_observation, status)

with the following arguments:

• U_collect_state:
  The name of the user-supplied routine that initializes a state vector from the array holding the ensemble of model states from the model fields. This is basically the inverse operation to U_distribute_state used in PDAF_get_state and also here.
• U_distribute_state:
  The name of a user supplied routine that initializes the model fields from the array holding the ensemble of model state vectors.
• U_init_dim_obs_pdafomi:
  The name of the user-supplied routine that initializes the observation information and provides the size of observation vector. This routine is part of an OMI observation module.
• U_obs_op_pdafomi:
  The name of the user-supplied routine that acts as the observation operator on some state vector. This routine is part of an OMI observation module.
• U_init_n_domains:
  The name of the routine that provides the number of local analysis domains
• U_init_dim_l:
  The name of the user-supplied routine that provides the state dimension for a local analysis domain
• U_init_dim_obs_l_pdafomi:
  The name of the user-supplied routine that initializes the size of the observation vector for a local analysis domain. This routine is part of an OMI observation module.
• U_g2l_state: The name of the routine that initializes a local state vector from the global state vector
• U_l2g_state: The name of the routine that initializes the corresponding part of the global state vector from the provided local state vector
• U_prepoststep:
  The name of the user-supplied pre/poststep routine as in PDAF_get_state
• U_next_observation:
  The name of the user-supplied routine that initializes the variables nsteps, timenow, and doexit. The same routine is also used in PDAF_get_state.
• status:
  The integer status flag. It is zero, if the routine is exited without errors.

Notes:

• The routine is identical to the routine PDAFomi_assimilate of PDAF 2.3, except that the argument U_prepostep is at a different place here.
• The order of the routine names does not show the order in which these routines are executed. See the section on the order of the execution on the page on implementing the analysis step of the local filter algorithms.
• To use the localization in the ENSRF/EAKF, one needs to call PDAFomi_set_localize_covar in the observation modules to initialize the localization information.
• It is recommended to check the value of status_pdaf in the program after the routine is executed. Only if its value is 0 the initialization was successful.

The user-supplied call-back routines are described on the page on implementing the analysis step of the local filters.