Show simple item record Tao, K Barros, AP 2011-06-21T17:27:47Z 2010-03-01
dc.identifier.citation Journal of Atmospheric and Oceanic Technology, 2010, 27 (3), pp. 409 - 427
dc.identifier.issn 0739-0572
dc.description.abstract The objective of spatial downscaling strategies is to increase the information content of coarse datasets at smaller scales. In the case of quantitative precipitation estimation (QPE) for hydrological applications, the goal is to close the scale gap between the spatial resolution of coarse datasets (e.g., gridded satellite precipitation products at resolution L × L) and the high resolution (l × l; L»l) necessary to capture the spatial features that determine spatial variability of water flows and water stores in the landscape. In essence, the downscaling process consists of weaving subgrid-scale heterogeneity over a desired range of wavelengths in the original field. The defining question is, which properties, statistical and otherwise, of the target field (the known observable at the desired spatial resolution) should be matched, with the caveat that downscaling methods be as a general as possible and therefore ideally without case-specific constraints and/or calibration requirements? Here, the attention is focused on two simple fractal downscaling methods using iterated functions systems (IFS) and fractal Brownian surfaces (FBS) that meet this requirement. The two methods were applied to disaggregate spatially 27 summertime convective storms in the central United States during 2007 at three consecutive times (1800, 2100, and 0000 UTC, thus 81 fields overall) from the Tropical Rainfall Measuring Mission (TRMM) version 6 (V6) 3B42 precipitation product (~25-km grid spacing) to the same resolution as the NCEP stage IV products (~4-km grid spacing). Results from bilinear interpolation are used as the control. A fundamental distinction between IFS and FBS is that the latter implies a distribution of downscaled fields and thus an ensemble solution, whereas the former provides a single solution. The downscaling effectiveness is assessed using fractal measures (the spectral exponent β, fractal dimension D, Hurst coefficient H, and roughness amplitude R) and traditional operational scores statistics scores [false alarm rate (FR), probability of detection (PD), threat score (TS), and Heidke skill score (HSS)], as well as bias and the root-mean-square error (RMSE). The results show that both IFS and FBS fractal interpolation perform well with regard to operational skill scores, and they meet the additional requirement of generating structurally consistent fields. Furthermore, confidence intervals can be directly generated from the FBS ensemble. The results were used to diagnose errors relevant for hydrometeorological applications, in particular a spatial displacement with characteristic length of at least 50 km (2500 km2) in the location of peak rainfall intensities for the cases studied. © 2010 American Meteorological Society.
dc.format.extent 409 - 427
dc.language.iso en_US en_US
dc.relation.ispartof Journal of Atmospheric and Oceanic Technology
dc.relation.isversionof 10.1175/2009JTECHA1219.1
dc.title Using fractal downscaling of satellite precipitation products for hydrometeorological applications
dc.title.alternative en_US
dc.type Journal Article
dc.description.version Version of Record en_US 2010-3-0 en_US
duke.description.endpage 427 en_US
duke.description.issue 3 en_US
duke.description.startpage 409 en_US
duke.description.volume 27 en_US
dc.relation.journal Journal of Atmospheric and Oceanic Technology en_US
pubs.issue 3
pubs.organisational-group /Duke
pubs.organisational-group /Duke/Pratt School of Engineering
pubs.organisational-group /Duke/Pratt School of Engineering/Civil and Environmental Engineering
pubs.publication-status Published
pubs.volume 27

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