PDAFomi_diag_stats

This page documents the routine PDAFomi_diag_stats of PDAF, which was introduced with PDAF V3.0. This is part of the PDAF-OMI observation diagnostics module.

The routine returns a pointer to an array of a selection of 6 statistics comparing the observations and the observed ensemble mean for each observation type.

Usually all PDAFomi_diag routines are called in prepoststep_pdaf where the observation information can be retrieved and analyzed. These statistics can, for exmaple, be used to plot a Taylor diagram.

The interface is the following:

  SUBROUTINE PDAFomi_diag_stats(nobs, obsstats_ptr, verbose)

with the following arguments:

    INTEGER, INTENT(inout) :: nobs                     ! Number of observation types
    REAL, POINTER, INTENT(inout) :: obsstats_ptr(:,:)  ! Array of observation statistics; content:
                                                       ! (1,:) correlations between observation and observed ensemble mean
                                                       ! (2,:) centered RMSD between observation and observed ensemble mean
                                                       ! (3,:) mean bias for observation minus observed ensemble mean
                                                       ! (4,:) mean absolute difference between observation and observed ensemble mean
                                                       ! (5,:) variance of observations
                                                       ! (6,:) variance of observed ensemble mean
    INTEGER, INTENT(in) :: verbose                     ! Verbosity flag

Note:

• The computed statistics are for the global model domain. Thus, in case of a parallelized model, all process sub-domains are taken into account and calling PDAFomi_diag_stats will return the same value for all processes.
• In Fortran user code the pointer should be declared in the form
  REAL, POINTER :: obsstats_ptr(:)
  It does not need to be allocated.. The target array has the size (6, nobs).
• If the observation diagnostics have not be activated by using PDAFomi_set_obs_diag the pointer array will not be set and nobs=0 is. One can check this value before assessing the pointer array
• The routine returns the centered RMSD as displayed in Taylor diagrams. The non-centered RMSD can be computed using PDAFomi_diag_obs_rmsd.