localize_covar_serial_pdaf

The page documents the user-supplied call-back routine localize_covar_serial_pdaf, which was introduced with PDAF V3.0.

The routine localize_covar_serial_pdaf (U_localize_covar_serial inside PDAF) is a call-back routine that has to be provided by the user.

The routine is used in the ENSRF/EAKF and is called during the analysis step. The purpose of the routine is to apply covariance localization to the vectors Hi P and Hi PH^T for the assimilation of a single observation (determined by the index iobs related to the observation operator Hi). Here Hi PH^T is the vector relating to the observed covariance matrix for the full observation vector. This vector is required for parallelization.

The interface is:

  SUBROUTINE localize_covar_serial_pdaf(iobs, dim_p, dim_obs, HP_p, HXY_p)

  INTEGER, INTENT(in) :: iobs                  ! Index of the assimilated single observation
  INTEGER, INTENT(in) :: dim_p                 ! Process-local state dimension
  INTEGER, INTENT(in) :: dim_obs_f             ! Number of full observations
  REAL, INTENT(inout) :: HP_p(dim_p)           ! Process-local part of matrix HP for observation iobs
  REAL, INTENT(inout) :: HXY_p(dim_obs_F)      ! Process-local part of matrix HX(HX_full) for full observations

Hint:

• To compute the localization one can use the routine PDAF_local_weight after computing the distance between two elements in each of the vectors Hi P and Hi PH^T.