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# 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 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.