prepoststep_pdaf

The page document the user-supplied call-back routine prepoststep_pdaf.

The routine prepoststep_pdaf (called U_prepoststep in the PDAF core routines) is a call-back routine that has to be provided by the user. prepoststep_pdaf is called by PDAF_get_state, PDAF_put_state_X, and PDAF_assimilate_X with 'X' being the name of a filter method. The routine is called at the initial time and after a forecast (directly before computing the filter analysis step) and after the analysis step. The purpose of the routine is to give the user access to the forecast and the analysis ensembles. Typically operations that are performed in prepoststep_pdaf are to compute the estimated RMS errors form the ensemble and to write e.g. the state estimate (i.e. the ensemble mean state). In case of the offline mode, one will also write the model restart files in prepoststep_pdaf.

The interface is the following:

SUBROUTINE prepoststep_pdaf(step, dim_p, dim_ens, dim_ens_p, dim_obs_p, &
                       state_p, Uinv, ens_p, flag)

with

INTEGER, INTENT(in)

step ! Current time step ! (When the routine is called before the analysis -step is provided.)

INTEGER, INTENT(in)

dim_p ! PE-local state dimension

INTEGER, INTENT(in)

dim_ens ! Size of state ensemble

INTEGER, INTENT(in)

dim_ens_p ! PE-local size of ensemble

INTEGER, INTENT(in)

dim_obs_p ! PE-local dimension of observation vector

REAL, INTENT(inout)

state_p(dim_p) ! PE-local forecast/analysis state ! The array 'state_p' is not generally not initialized in the case of SEIK/EnKF/ETKF. ! It can be used freely in this routine.

REAL, INTENT(inout)

Uinv(dim_ens-1, dim_ens-1) ! Inverse of matrix U

REAL, INTENT(inout)

ens_p(dim_p, dim_ens) ! PE-local state ensemble

INTEGER, INTENT(in)

flag ! PDAF status flag

The routine U_prepoststep is called once at the beginning of the assimilation process. In addition, it is called during the assimilation cycles before the analysis step and after the ensemble transformation. The routine is called by all filter processes (that is filterpe=1).

The routine provides for the user the full access to the ensemble of model states. Thus, user-controlled pre- and post-step operations can be performed. For example the forecast and the analysis states and ensemble covariance matrix can be analyzed, e.g. by computing the estimated variances. If the smoother is used, also the smoothed ensembles can be analyzed. In addition, the estimates can be written to disk.

Hint:

• If a user considers to perform adjustments to the estimates (e.g. for balances), this routine is the right place for it.
• Only for the SEEK filter the state vector (state_p) is initialized. For all other filters, the array is allocated, but it can be used freely during the execution of U_prepoststep.
• The interface through which U_prepoststep is called does not include the array of smoothed ensembles. In order to access the smoother ensemble array one has to set a pointer to it using a call to the routine PDAF_get_smootherens (see page on auxiliary routines)