= PDAF3_put_state_lenkf =

This page documents the routine `PDAF3_put_state_lenkf` of PDAF. The routine is part of the advanced PDAF3 interface that was introduced with PDAF V3.0. 

|| **Note:** This routine exists for backward-compatibility for the LEnKF with PDAF V2.3, in particular for existing implementations using `localize_covar_pdafomi`. We recommend to use the new PDAF3 interface using [wiki:PDAF3_put_state_global] that avoids the need to implement the additional call-back routine `localize_covar_pdafomi`. ||

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 [ModifyModelforEnsembleIntegration Modification of the model code for the ensemble integration] and its sub-page on [InsertAnalysisStep 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 [wiki:PDAF3_assimimilate_global] for the 'flexible' parallelization variant, which is also used with the 'fully-parallel' implementation variant.


Here, we list the full interface of the routine. 

The interface is:
{{{
  SUBROUTINE PDAF3_put_state_lenkf(U_collect_state, &
                                 U_init_dim_obs_pdafomi, U_obs_op_pdafomi, &
                                 U_prepoststep, U_localize_covar_pdafomi, &
                                 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_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_localize_covar_pdafomi`: The name of the user-supplied routine that Applies covariance localization to the matrices HP and HPH^T^
 * `U_prepoststep`: The name of the user-supplied pre/poststep routine as in `PDAF_get_state` (Note that the place of `U_prepoststep` has changed compared to the previous routine `PDAFomi_assimilate_lenkf`)
 * `status`: The integer status flag. It is zero, if the 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_put_state_lenkf. 

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

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