Auxiliary Routines

PDAF provide a number of auxiliary routines. They provide access to PDAF-internal data, which is not available through the regular interface of PDAF.

PDAF_interfaces_module.F90

This file contains the module PDAF_interfaces_module. It provides interface definitions for the routines of PDAF. If you like to use explicit Fortran interfaces, or if you have to use then in case of the smoother, you have to include the following line in the header you the calling routine:

  use PDAF_interfaces_module

PDAF-D_get_smootherens.F90

A smoother is available for several filters (ESTKF/LESTKF/ETKF/LETKF/EnKF). This routine is called to set a Fortran pointer to the array in PDAF that stores the ensembles for smoothing. Also, the routine sets the available lag of the smoothing.

CALL PDAF_get_smootherens(sens_pointer, maxlag, status)

The variables in the interface are the following:

• sens_pointer: The pointer to the smoother ensemble. The dimension is sens_pointer(:,:,:). Thus in the program calling PDAF_get_smootherens one has to declare REAL, POINTER :: sens_pointer(:,:,:). On output it points to the smoother ensemble.
• maxlag: Number of lags stored in the smoother ensemble. While in the call to PDAF_init the maximum lag for the smoother is set, not all possible lags are using at the beginning of the assimilations. maxlag shows how many times were already smoothed.
• status: Status flag. 0 for successful exit.

Important:

• Because sens_pointer is a pointer, the call to PDAF_get_smootherens needs an explicit Fortran interface. This is provided by the Fortran module PDAF_interfaces_module. In the header part of the routine that calls PDAF_get_smootherens one has to include use PDAF_interfaces_module!
• Using a pointer combined with an intent, i.e. using a pointer as argument, is a feature of Fortran 2003. Thus, if a too old compiler is used, it will provide an error when the routine is compiled.

Notes:

• PDAF_get_smootherens is typically called in the prepoststep routine after the analysis step. At this time not only the filtered analysis step can be analized, but also all smoothed ensembles.
• The first two indices of sens_pointer are identical to those in the ensemble array ens_p. Thus, the array contains state vectors in its columns. The second index is the ensemble index. The third index is the lag. Thus, if the value of the third index is fixed one can use the array sens_pointer analogous to the ensemble array ens_p.
• For an example using PDAF_get_smootherens see the example implementation testsuite/src/dummymodel_1D/. The routine is called in compute_rms_smoother.F90.

PDAF-D_set_smootherens.F90

A smoother is available for several filters (ESTKF/LESTKF/ETKF/LETKF/EnKF). This routine is called to set a Fortran pointer to the array in PDAF that stores the ensembles for smoothing. In addition, it sets the available lag of the smoothing. This routine is called in the offline mode of PDAF. While in the online mode, the smoother ensemble array is filled automatically by PDAF, one has to fill it manually in the offline mode. PDAF_set_smootherens gives access to the smoother array to fill it.

CALL PDAF_set_smootherens(sens_pointer, maxlag, status)

The arguments are:

• sens_pointer: The pointer to the smoother ensemble. The dimension is sens_pointer(:,:,:). Thus in the program calling PDAF_get_smmotherens one has to declare REAL, POINTER :: sens_pointer(:,:,:). On output it points to the smoother ensemble.
• maxlag: Set the number of lags stored in the smoother ensemble. While in the call to PDAF_init the maximum lag for the smoother is set, not all possible lags are using at the beginning of the assimilations. maxlag says how many times were already smoothed. Both values are usually identical for the offline mode.
• status: Status flag. 0 for successful exit.

Important:

• Because sens_pointer is a pointer, the call to PDAF_set_smootherens needs an explicit Fortran interface. This is provided by the Fortran module PDAF_interfaces_module. In the header part of the routine that calls PDAF_set_smootherens one has to include use PDAF_interfaces_module!
• Using a pointer combined with an intent, i.e. using a pointer as argument, is a feature of Fortran 2003. Thus, if a too old compiler is used, it will provide an error when the routine is compiled.

Notes:

• PDAF_set_smootherens is typically called in the initialization phase of PDAF. It was to be called after the basic initialization of PDAF in PDAF_init. A possible location is to call PDAF_set_smootherens is the ensemble initialization routine U_init_ens.
• The first two indices of sens_pointer are identical to those in the ensemble array ens_p. Thus, the array contains state vectors in its columns. The second index is the ensemble index. The third index is the lag. Thus, if the value of the third index is fixed one can use the array sens_pointer analogous to the ensemble array ens_p.

PDAF-D_get_memberid.F90

This routine can be called from the model during an ensemble integration. It provides access to the number (id) of the ensemble member that is currently integrated.

CALL PDAF_get_memberid(memberid)

The only argument is:

• memberid: In integer providing on output the id the ensemble member

Note:

• Using PDAF_get_memberid is obviously only useful if more than one ensemble member is integrated by a model task. If there are as many model tasks as ensemble members, memberid is always 1. In this case one can use task_id from the module mod_parallel to distinguish the ensemble members.

PDAF-D_get_obsmemberid.F90

This routine can be called from the model during the analysis step. It provides access to the number (id) of the ensemble member for which the user-routine for the observation operator is called.

CALL PDAF_get_obsmemberid(memberid)

The only argument is:

• memberid: In integer providing on output the id the ensemble member

Note:

• The routine an be useful if the observation operator does not actually operate on the state vector that is provided when obs_op_pdaf is called. Their might be cases in which one likes to read model state information from a file (e.g. if the observation operator performs an averaging over time, while the state vector for the analysis step only contains a single time instance).

PDAF-D_incremental.F90

When incremental updating is used, this routine is called during the forecast phase to add a fraction of the analysis increment to an ensemble member.

CALL PDAF_incremental(steps, U_dist_stateinc)

The arguments are:

• steps: The number of time steps over which the increment should be distributed
• U_dist_stateinc: The name of the user supplied call-back function that performs the actual addition of the state vector increment to the individual model fields.

PDAF-D_add_increment.F90

When incremental updating is used, the state increment of the analysis step is not directly added to the forecast state. To add the increment to some state vector PDAF_add_increment is called:

CALL PDAF_add_increment(dim_p, state_p)

The arguments are

• dim_p: An integer giving the state dimension of state_p
• state_p: A real array of size dim_p holding the on input the state vector and on output the state vector plus increment.

Note:

• the routine can be used in the prepoststep routine when the analysis state should be analyzed.

PDAF-D_set_ens_pointer.F90

This routine allows a program to get a Fortran pointer to the internal ensemble array of PDAF.

CALL PDAF_set_ens_pointer(ens_pointer, status)

The arguments are:

• ens_pointer: The pointer to the smoother ensemble. The dimension is ens_pointer(:,:). Thus in the program calling PDAF_set_ens_pointer one has to declare REAL, POINTER :: sens_pointer(:,:). On output it points to the ensemble array.
• status: Status flag. 0 for successful exit.

Important:

• Because ens_pointer is a pointer, the call to PDAF_set_ens_pointer needs an explicit Fortran interface. This is provided by the Fortran module PDAF_interfaces_module. In the header part of the routine that calls PDAF_set_ens_pointer one has to include use PDAF_interfaces_module!
• Using a pointer combined with an intent, i.e. using a pointer as argument, is a feature of Fortran 2003. Thus, if a too old compiler is used, it will provide an error when the routine is compiled.

Notes:

• PDAF_set_ens_pointer is a special routine that is never needed when the standard online or offline modes of the implementation are used. However, the routine allows to build a model that uses each column of the ensemble array to store the model fields. Thus, one can avoid allocating additional memory for the model fields.