PDAF_init_forecast

This page documents the routine PDAF_init_forecast of PDAF. The routine was introduced with PDAF V3.0 as a replacement of PDAF_get_state. The new name PDAF_init_forecast is intended to make the purpose of the routine clearer.

The routine PDAF_init_forecast has to be called once at the end of the initialization of PDAF. Usually, the call will be part of the routine init_pdaf that was discussed on the page on initializing PDAF.

The routine PDAF_init_forecast has the purpose to initialize the model fields to be propagated from the array holding the ensemble states. In addition, the routine provides the information on how many time steps have to be performed in the upcoming forecast phase. The routine can also initialize the information, whether further model integrations have to be computed. For the fully-parallel implementation variant, the number of time steps is used inside PDAF, while the flag on further model integrations is not used.

The interface of PDAF_init_forecast is the following:

  SUBROUTINE PDAF_init_forecast(nsteps, timenow, doexit, U_next_observation, U_distribute_state, &
                            U_prepoststep, status)

with the following arguments:

• nsteps: An integer specifying upon exit the number of time steps to be performed
• timenow: A real specifying upon exit the current model time. (This value is usually not used in the fully-parallel implemenation variant)
• doexit: An integer variable defining whether the assimilation process is completed. For compatibility 1 should be used for exit, 0 for continuing. (This value is not used in the fully-parallel implemenation variant)
• U_next_observation: The name of a user supplied routine that initializes the variables nsteps, timenow, and doexit
• U_distribute_state: The name of a user supplied routine that initializes the model fields from the array holding the ensemble of model state vectors
• U_prepoststep: The name of a user supplied routine that is called before and after the analysis step. Here the user has the possibility to access the state ensemble and can e.g. compute estimated variances or can write the ensemble states the state estimate into files.
• status: The integer status flag. It is zero, if the routine is exited without errors.

The specifications of the user-supplied routines (U_next_observation, U_distribute_state, U_prepoststep) are documented on the page on inserting the analysis step.