PDAFomi_assimilate_enkf_nondiagR

This page documents the routine PDAFomi_assimilate_enkf_nondiagR of PDAF. The routine is used to execute the analysis step of the EnKF with PDAF-OMI for the case of a non-diagonal observation error covariance matrix. This routine was introduced with PDAF V2.3.

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

The general aspects of the filter specific routines PDAFomi_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 the fully-parallel implementation variant of the data assimilation system. When the 'flexible' implementation variant, the routine PDAFomi_put_state_enkf_nondiagR is used.

Here, we list the full interface of the routine.

The interface is:

  SUBROUTINE PDAFomi_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.
• U_init_dim_obs_pdafomi: The name of the user-supplied routine that initializes the observation information and provides the size of observation vector
• U_obs_op_pdafomi: The name of the user-supplied routine that acts as the observation operator on some state vector
• 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_add_obs_error_pdafomi: The name of the user-supplied routine that computes the product of the inverse of the observation error covariance matrix with some matrix provided to the routine by PDAF.
• U_prepoststep: The name of the 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 PDAFomi_assimilate_enkf_nondiagR is exited without errors.

Notes:

• The difference to the routine PDAFomi_assimilate_global used for diagdonal R-matrices is only in the additonal arguments U_add_obs_err_pdafomi and U_init_obscovar_pdafomi.
• The global filters ESTKF, ETKF, and SEIK use the separate routine PDAFomi_assimilate_global_nondiagR.
• The filters NETF and PF use the separate routine PDAFomi_assimilate_nonlin_nondiagR.

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

It is recommended that the value of status_pdaf is checked in the program after PDAFomi_assimilate_enkf_nondiagR is executed. Only if its value is 0 the initialization was successful.

PDAF also has a Simplified Interface providing the routine PDAFomi_assimilate_enkf_nondiagR_si. In the simplified interface, the name of the user-supplied routines have predefined names and do not appear in the call to PDAFomi_assimilate_enkf_nondiagR_si. More information on the pre-defined names is provided in the page on implementing the analysis step of the global filters.