= PDAF_assim_offline_lenkf = 

This page documents the routine `PDAF_assim_offline_lenkf` of PDAF. The routine is called for the localized EnKF. The routine was introduced with PDAF V3.0.

The routine is used for the offline coupled mode of PDAF, which is described on the page: [wiki:OfflineImplementationGuide Implementation Guide for Offline Coupling].

The interface when using the LEnKF is the following:
{{{
  SUBROUTINE PDAF_assim_offline_lenkf(U_init_dim_obs, U_obs_op, &
                                 U_init_obs, U_prepoststep, U_localize, &
                                 U_add_obs_err, U_init_obscovar, status_pdaf)
}}}
with the following arguments:
 * `U_init_dim_obs`: The name of the user-supplied routine that provides the size of observation vector
 * `U_obs_op`: The name of the user-supplied routine that acts as the observation operator on some state vector
 * `U_init_obs`: The name of the user-supplied routine that initializes the vector of observations
 * `U_prepoststep`: The name of the pre/poststep routine as in `PDAF_get_state`
 * `U_localize`: The name of the routine that applied the covariance localization
 * `U_add_obs_err`: 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`: The name of the user-supplied routine that initializes the observation error covariance matrix.
 * `status_pdaf`: The integer status flag. It is zero, if the routine is exited without errors. 

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

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