Changes between Version 1 and Version 2 of PDAF_local_weight


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Timestamp:
Dec 21, 2016, 3:57:16 PM (4 years ago)
Author:
lnerger
Comment:

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  • PDAF_local_weight

    v1 v2  
    44This page documents the routine `PDAF_local_weight` of PDAF.
    55
    6 The routine is used for localization in the analysis step of a filter and computes a weight according to the specified distance and the settings for the localizing function.
     6The routine is used for localization in the analysis step of a filter and computes a weight according to the specified distance and the settings for the localizing function. Typically the routine is called in [wiki:prodRinvA_l_pdaf prodRinvA_l_pdaf] in the filters LESTKF, LETKF, and LSEIK. Also, the routine is typically called for the LEnKF in the routine [localize_l_pdaf localize_l_pdaf].
    77
    88The interface is the following:
     
    1313with the following arguments:
    1414 * `wtype` : `integer, intent(in)`[[BR]] Type of weight function:[[BR]] (0) unit weight (=1 up to radius `cradius`) [[BR]] (1) exponential decrease (1/e at distance=sradius; 0 for distance>cradius)[[BR]] (2) 5th order polynomial with support radius sradius (Gaspari&Cohn 1999; 0 for distance>sradius)
    15  * `rtype` : `integer, intent(in)`[[BR]] Type of regulated weighting:[[BR]] (0) no regulation[[BR]] (1) regulation using mean variances[[BR]] (2) regulation using variance of single observation point
     15 * `rtype` : `integer, intent(in)`[[BR]] Type of regulated weighting:[[BR]] (0) no regulation[[BR]] (1) regulation using mean variances[[BR]]
    1616 * `cradius` : `real, intent(in)`[[BR]] Cut-off radius (weight is always =0 for distance>cradius)
    1717 * `sradius` : `real, intent(in)`[[BR]] Support radius
     
    2424 * `verbose` : `integer, intent(in)`[[BR]] Verbosity flag
    2525
     26Notes:
     27 * 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 [PublicationsandPresentations].
     28 * `PDAF_local_weight` is called with a single distance and return a single weight. In some cases the alternative routine [wiki:PDAF_local_weights] can be used which computes the weights for a vector of distances.
     29 * for `rtype=1` the mean variance is computed as the square-root of the sum of squared entries in the array `A`.
     30 * Array `A` is usually the array `A_l` that is an input argument to the routine [wiki:prodRinvA_l_pdaf prodRinvA_l_pdaf].
    2631
    27 
     32Examples of using `PDAF_local_weight` can be found in the files `prodrinva_l_pdaf.F90` in the tutorial cases. Another example is, e.g. provided in the Lorenz-96 test case (see /testsuite/src/lorenz96/prodrinva_local.F90).