= PDAF_iau_add_inc = 

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

This routine is used with the flexible parallelization mode if a routine `PDAF3_put_state_X` (or any other PDAF*_put_state) routine is used. Since `PDAF*_put_state` is only called after a model state is integrated over the full forecast period, this routine cannot apply the increment. Hence, the routine `PDAF_iau_add_inc` has to be called at each model time step in the time stepping loop of the model to apply the increment. This routine adds the increment for the currently integrated ensemble member according to the specified IAU type and number of IAU steps.

The routine has to be inserted in time stepping loop of the model code. It has to be called at each time step.

The interface is the following:
{{{
  SUBROUTINE PDAF_iau_add_inc(U_collect_state, U_distribute_state)

    EXTERNAL :: U_collect_state, &      ! Routine to collect a state vector
         U_distribute_state             ! Routine to distribute a state vector
}}}