U_localize_covar_serial

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

The routine U_localize_covar_serial is a call-back routine that has to be provided by the user. The typical name in the user code is localize_covar_pdaf, but the user can choose the name of the routine. 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 the following:

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

with arguments:

  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}}}

Hints:
 * To compute the localization one can use the routine `PDAF_local_weight` after computing the distance between two elements in the vector '''Hi P''' or '''Hi PH^T'''.