PDAFomi_observation_localization_weights

This page documents the routine PDAFomi_observation_localization_weights of PDAF-OMI. It is used with non-diagonal observation error covariance matrices, The routine was introduced with PDAF V2.3.

The routine returns a vector of observation localization weights computed according to the localization specifications in thisobs_l and observation coordinates in thisobs. The routine can be called in prodRinvA_l_pdafomi or likelihood_l_pdafomi in order to obtain the localization weights for observations. For diagonal observation error covariance matrices, the weighting is computed by OMI internally, but for nondiagonal R-matrices, the use had to implement the application of the localization.

The interface is the following:

  SUBROUTINE PDAFomi_observation_localization_weights(thisobs_l, thisobs, ncols, &
             A_l, weight, verbose)

    TYPE(obs_l), INTENT(inout) :: thisobs_l  ! Data type with local observation
    TYPE(obs_f), INTENT(inout) :: thisobs    ! Data type with full observation
    INTEGER, INTENT(in) :: ncols             ! Rank of initial covariance matrix
    REAL, INTENT(in) :: A_l(:, :)            ! Input matrix, size (thisobs_l%dim_obs_l, ncols)
    INTEGER, INTENT(in) :: verbose           ! Verbosity flag
    REAL, INTENT(out) :: weight(thisobs_l%dim_obs_l) ! Localization weights

Notes:

• Array A_l is usually the input argument to the routine prodRinvA_l_pdaf. It is only used when the regulated localization is used.
• The regulated localization computes an alternative localization function based on the ration of state error variances to observation error variances. the regulated localization method is described in the paper Nerger et al. (Quarterly Journal of the Royal Meteorological Society, 138 (2012) 802-812; see publications.