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Journal Article: ID no. (ISBN etc.):  0043-1397 BibTeX citation key:  Onibon2004a
Onibon, H., Lebel, T. & Afouda, A. (2004) Gibbs sampling for conditional spatial disaggregation of rain fields. IN Water Resources Research, 40. W08401.
Added by: Thierry Lebel 2008-12-17 15:47:30    Last Edited by: Fanny Lefebvre 2011-01-12 17:11:36
Categories: General
Keywords: Downscaling, Hydrology, Precipitation
Creators: Afouda, Lebel, Onibon
Collection: Water Resources Research
Bibliographies: Prior150410

Peer reviewed
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Gibbs sampling is used to simulate Sahelian rainfields conditional to an areal estimate provided either as the output of an atmospheric model or by a satellite rainfall algorithm. Whereas various methods are widely used to generate simulated rainfields conditioned on point observations there are much less simulation algorithms able to produce a spatially disaggregated rain field of known averaged value. The theoretical and practical aspects of Gibbs sampling for the purpose of conditional rainfield simulation are explored in the first part of the paper. It is proposed to used a so-called acceptation-rejection algorithm to ensure convergence of the conditional simulation. On a Sahelian case study, it is then showed that Gibbs sampling performs similarly to the well known turning band method in an unconditional mode. A preliminary validation of the method in conditional mode is presented. Several rainfields are simulated conditionally on an observed rainfield, whose only the spatial average over a 100*100 kmĀ² area is supposed to be known. These conditional simulations are compared to the observed rainfield and to other rainfields of similar magnitude. For a given class of events, the conditional rainfields have a distribution of point values similar to the distribution of observed point values. At the same time the model is producing a wide range of spatial patterns corresponding to a single area average, giving an idea on the variety of possible fields of equal areal value.
Added by: Thierry Lebel    Last Edited by: Fanny Lefebvre