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| Titel |
Disaggregation of spatial rainfall fields for hydrological modelling |
| VerfasserIn |
N. G. Mackay, R. E. Chandler, C. Onof, H. S. Wheater |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 5, no. 2 ; Nr. 5, no. 2, S.165-173 |
| Datensatznummer |
250002405
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| Publikation (Nr.) |
 copernicus.org/hess-5-165-2001.pdf |
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| Zusammenfassung |
| Meteorological models
generate fields of precipitation and other climatological variables as spatial
averages at the scale of the grid used for numerical
solution. The grid-scale can be large, particularly for GCMs, and disaggregation
is required, for example to generate appropriate spatial-temporal
properties of rainfall for coupling with surface-boundary conditions or more
general hydrological applications. A method is presented
here which considers the generation of the wet areas and the simulation of
rainfall intensities separately. For the first task, a nearest-neighbour
Markov scheme, based upon a Bayesian technique used in image processing, is
implemented so as to preserve the structural features of
the observed rainfall. Essentially, the large-scale field and the previously
disaggregated field are used as evidence in an iterative procedure
which aims at selecting a realisation according to the joint posterior
probability distribution. In the second task the morphological characteristics
of the field of rainfall intensities are reproduced through a random sampling of
intensities according to a beta distribution and their
allocation to pixels chosen so that the higher intensities are more likely to be
further from the dry areas. The components of the scheme are
assessed for Arkansas-Red River basin radar rainfall (hourly averages) by
disaggregating from 40 km x 40 km to 8 km x 8 km. The wet/dry
scheme provides a good reproduction both of the number of correctly classified
pixels and the coverage, while the intensitiy scheme generates
fields with an adequate variance within the grid-squares, so that this scheme
provides the hydrologist with a useful tool for the downscaling
of meteorological model outputs.
Keywords: Rainfall, disaggregation, General Circulation Model, Bayesian analysis |
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