PDAF_iau_init

This page documents the routine PDAF_iau_init of PDAF, which was introduced with PDAF V3.0.

This routine initializes parameters for incremental analysis updating, IAU. It further allocates the array in which the ensemble increments are stored. This array exists on all processes that are part of model tasks.

The routine is usually called in init_pdaf after the initialization of PDAF in PDAF_init. it is important that the routine is called by all model processes because all these processes need the information on the IAU configuration and need to allocate the increment array.

The interface is:

  SUBROUTINE PDAF_iau_init(type_iau, nsteps_iau, flag)

    INTEGER, INTENT(in) :: type_iau     ! Type of IAU
                                        !   (0) no IAU
                                        !   (1) constant increment weight 1/nsteps_iau
                                        !   (2) Linear IAU weight with maximum in middle of IAU period
                                        !   (3) Zero weights for null mode (can be used to apply IAU on user side)
    INTEGER, INTENT(in) :: nsteps_iau   ! Number of time steps in IAU
    INTEGER, INTENT(out) :: flag        ! Status flag

Hints:

• type_iau=2 is linearly increasing and decreasing similar to what is used in the ocean model NEMO. This type is usually used if the IAU is applied in re-running over the previous observation period.
• type_iau=3 stores the increment information, but does not apply the increment. This permits to apply the increment in user-provided code. For this, the routine PDAF_iau_set_pointer can be used to assess the increment array within PDAF.