= PDAF3_assim_offline_enkf_nondiagR =

This page documents the routine `PDAF3_assim_offline_enkf_nondiagR` of PDAF. The routine is part of the advanced [wiki:PDAF3_interface PDAF3 interface] that was introduced with PDAF V3.0. 

The routine is used to execute the analysis step of the EnKF and LEnKF of a non-diagonal observation error covariance matrix. 

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 is:
{{{
  SUBROUTINE PDAF3_assim_offline_enkf_nondiagR(U_init_dim_obs_pdafomi, U_obs_op_pdafomi, &
                                 U_add_obs_err_pdafomi, U_init_obscovar_pdafomi, &
                                 U_prepoststep, status)
}}}
with the following arguments:
 * `U_init_dim_obs_pdafomi`: [[BR]]The name of the user-supplied routine that initializes the observation information and provides the size of observation vector. This routine is part of an OMI observation module. 
 * `U_obs_op_pdafomi`: [[BR]]The name of the user-supplied routine that acts as the observation operator on some state vector. This routine is part of an OMI observation module. 
 * `U_add_obs_err_pdafomi`: [[BR]]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`: [[BR]]The name of the user-supplied routine that initializes the observation error covariance matrix. 
 * `U_prepoststep`: [[BR]]The name of the user-supplied pre/poststep routine as in `PDAF_get_state`
 * `status`: [[BR]]The integer status flag. It is zero, if the routine is exited without errors.

Notes:
 * The difference to the routine `PDAF3_assim_offline_global` used for diagdonal R-matrices is only in the additonal arguments `U_add_obs_err_pdafomi` and `U_init_obscovar_pdafomi`.
 * The global filters ESTKF, ETKF, and SEIK use the separate routine [wiki:PDAF3_assim_offline_global_nondiagR].
 * The global filters NETF and PF use the separate routine [wiki:PDAF3_assim_offline_nonlin_nondiagR].
 * 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.

The user-supplied call-back routines are described on the page on [ImplementAnalysisGlobal implementing the analysis step of the global filters].