PDAF3_assimilate_enkf_nondiagR

This page documents the routine PDAF3_assimilate_enkf_nondiagR of PDAF. 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 the EnKF and LEnKF for the case of a non-diagonal observation error covariance matrix.

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

The general aspects of the filter specific routines PDAF3_put_state_* 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 for the offline mode of PDAF. It can also be used in the 'flexible' parallelization implementation variant of the data assimilation system, but starting with PDAF-3 we recommend to use PDAF3_assimilate_local, which is also used with the 'fully-parallel' implementation variant.

The interface is:

  SUBROUTINE PDAF3_assimilate_enkf_nondiagR(U_collect_state, U_distribute_state, &
                                 U_init_dim_obs_pdafomi, U_obs_op_pdafomi, &
                                 U_add_obs_err_pdafomi, U_init_obscovar_pdafomi, &
                                 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 as well as 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. This is the inverse operation to U_collect_state.
• 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_add_obs_err_pdafomi:
  The name of the user-supplied routine that adds the observation error covariance matrix to the ensemble covariance matrix projected onto the observation space.
• U_init_obscovar_pdafomi:
  The name of the user-supplied routine that initializes the observation error covariance matrix.
• U_prepoststep:
  The name of the user-supplied pre/poststep routine as in PDAF_get_state
• U_next_observation:
  The name of a 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 difference to the routine PDAF3_assimilate_global used for diagonal R-matrices is only in the additional arguments U_add_obs_err_pdafomi and U_init_obscovar_pdafomi.
• To use the localization in the LEnKF, one needs to call PDAFomi_set_localize_covar in the observation modules to initialize the localization information.
• The global filters ESTKF, ETKF, and SEIK use the separate routine PDAF3_assimilate_global_nondiagR.
• The global filters NETF and PF use the separate routine PDAF3_assimilate_nonlin_nondiagR.
• It is recommended that the value of status_pdaf is checked in the program after this 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 global filters.