wiki:PDAFomi_assimilate_lenkf

Version 1 (modified by lnerger, 12 months ago) (diff)

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PDAFomi_assimilate_lenkf

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.

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 PDAomi_put_state_lenkf? is used.

Here, we list the full interface of the routine.

The interface when using the LEnKF is the following:

  SUBROUTINE PDAFomi_assimilate_lenkf(U_collect_state, U_distribute_state, &
                                 U_init_dim_obs_pdafomi, U_obs_op_pdafomi, &
                                 U_prepoststep, U_localize_covar_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: Apply covariance localization to the matrices HP and HPHT
  • 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_lenkf 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.

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 PDAFomi_assimilate_lenkf is executed. Only if its value is 0 the initialization was successful.

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