= PDAF_assim_offline_ensrf = 

This page documents the routine `PDAF_assim_offline_ensrf` of PDAF. The routine is used to execute the ENSRF/EAKF filters, which were added to PDAF with version 3.0. 

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 for using the ENSRF/EAKF is the following:
{{{
SUBROUTINE PDAF_assim_offline_ensrf(U_init_dim_obs, U_obs_op,  U_init_obs, U_init_obsvars, &
     U_localize_covar_serial, &
     U_prepoststep, outflag)
}}}
with the following arguments:
 * `U_init_dim_obs`: [[BR]]The name of the user-supplied routine that provides the size of observation vector
 * `U_obs_op`: [[BR]]The name of the user-supplied routine that acts as the observation operator on some state vector
 * `U_init_obs`: [[BR]]The name of the user-supplied routine that initializes the vector of observations
 * `U_init_obsvars`: [[BR]]The name of the user-supplied routine that initializes the vector of observation error variances.
 * `U_localize_covar_serial`: [[BR]]The name of the user-suppplied routine that applies the covariance localization for a single observation
 * `U_prepoststep`: [[BR]]The name of the user-supplied pre/poststep routine as in `PDAF_get_state`
 * `status_pdaf`: [[BR]]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 [wiki:ImplementAnalysisENSRF_EAKF implementing the analysis step of the ENSRF/EAKF]. Here also the possible choices of `subtype` are explained. These select the particular filter variant.

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.