Guertin, Kateri; Villeneuve, Jean-Pierre; Deschenes, Sylvain et Jacques, Ghislain (1988). The choice of working variables in the geostatistical estimation of the spatial distribution of ion concentration from acid precipitation. Atmospheric Environment (1967) , vol. 22 , nº 12. pp. 2787-2801. DOI: 10.1016/0004-6981(88)90446-5.
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Ordinary kriging presents an optimal tool to estimate the spatial distribution of ion concentration from acid precipitation and produce risk-qualified maps of the phenomenon over the studied area. However, being expressed as a linear combination of data values, the kriging estimator should not be calculated directly from ion concentration values unless their corresponding precipitation volumes are essentially constant over the area. In theory, spatial linear combinations of volume-weighted concentrations should be considered, meaning that concentration estimates should be obtained by dividing kriged depositions by their corresponding kriged precipitation totals. In practice, the choice of appropriate working variables for the estimation of ion concentration will depend on the nature of the studied phenomena and on the objective of the study. In this paper, the effect of this choice on estimation results is illustrated through a comparison of experimental results obtained from the direct kriging of concentration and from the estimation of concentration by quotient. It appears that even with fairly constant precipitation totals with respect to ion concentrations and given a small correlation between both variables, discrepancies between results from the two approaches can be significant, especially at a local scale: the spatial distribution of estimated values varies locally according to each procedure, and the level of uncertainty is systematically better predicted through an estimation by quotient, even though it is based on an approximate formula. In order to avoid misleading results, the direct kriging of ion concentration should be applied only for global estimation purposes after its practical equivalence with the estimation by quotient has been appraised.
| Type de document: | Article |
|---|---|
| Mots-clés libres: | geostatistics; acid precipitation; ion concentration; kriging; additive working variables |
| Centre: | Centre Eau Terre Environnement |
| Date de dépôt: | 17 févr. 2021 16:10 |
| Dernière modification: | 17 févr. 2021 16:10 |
| URI: | https://espace.inrs.ca/id/eprint/11281 |
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