PDAF_assim_offline_3dvar

This page documents the routine PDAF_assim_offline_3dvar of PDAF. The routine was introduced by PDAF V3.0.

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

The interface for using the parameterized 3D-Var is:

  SUBROUTINE PDAF_assim_offline_3dvar(U_init_dim_obs, U_obs_op, U_init_obs, U_prodRinvA, &
                                 U_cvt, U_cvt_adj, U_obs_op_lin, U_obs_op_adj, &
                                 U_prepoststep, outflag)

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_prodRinvA: The name of the user-supplied routine that computes the product of the inverse of the observation error covariance matrix with some matrix provided to the routine by PDAF. This operation occurs during the analysis step of the ETKF.
• U_cvt: The name of the user-supplied routine that applies the control-vector transformation (square-root of the B-matrix) on some control vector to obtain a state vector.
• U_cvt_adj: The name of the user-supplied routine that applies the adjoint control-vector transformation (with square-root of the B-matrix) on some state vector to obtain the control vector.
• U_obs_op_lin: The name of the user-supplied routine that acts as the linearized observation operator on some state vector
• U_obs_op_adj: The name of the user-supplied routine that acts as the adjoint observation operator on some state vector
• U_prepoststep: The name of the pre/poststep routine as in PDAF_get_state
• status: 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 implementing the analysis step of 3D-Var.

It is recommended that the value of status_pdaf is checked in the program after PDAF_put_state_3dvar is executed. Only if its value is 0 the initialization was successful.