PDAFomi_assimilate_lenkf_nondiagR

This page documents the routine PDAF_assimilate_lenkf of PDAF. The routine is used to execute the analysis step of the localized EnKF (LEnKF) 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_lenkf_nondiagR? is used.

Here, we list the full interface of the routine.

The interface when using the LEnKF is the following:

  SUBROUTINE PDAFomi_assimilate_lenkf_nondiagR(U_collect_state, U_distribute_state, &
                                 U_init_dim_obs_pdafomi, U_obs_op_pdafomi, &
                                 U_prepoststep, U_localize_covar_pdafomi, &
                                 U_add_obs_err_pdafomi, U_init_obscovar_pdafomi, &
                                 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_prepoststep: The name of the pre/poststep routine as in PDAF_get_state
• U_localize_covar_pdafomi: Apply covariance localization to the matrices HP and HPH^T
• 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_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 this routine is exited without errors.

For the EnKF, the user-supplied routines are essentially executed in the order they are listed in the interface to PDAFomi_assimilate_lenkf_nondiagR.

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

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.

PDAF also has a Simplified Interface providing the routine PDAFomi_assimilate_lenkf_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_lenkf_nondiagR_si. More information on the pre-defined names is provided in the page on implementing the analysis step of the local filters.