Multi-site simulation of precipitation by conditional resampling

A single-site, regression-based downscaling method is extended to multi-site synthesis of daily precipitation at stations in Eastern England and the Scottish Borders. Area-averaged precipitation series for each region are downscaled using gridded predictor variables selected from a candidate suite r...

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Bibliographic Details
Published in:Climate research 2003-04, Vol.23 (3), p.183-194
Main Authors: Wilby, R. L., Tomlinson, O. J., Dawson, C. W.
Format: Article
Language:English
Subjects:
Atmospheric circulation
Atmospherics
Climate models
Correlations
Modeling
Precipitation
Simulations
Standard deviation
Stochastic models
Vector autoregression
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Summary:A single-site, regression-based downscaling method is extended to multi-site synthesis of daily precipitation at stations in Eastern England and the Scottish Borders. Area-averaged precipitation series for each region are downscaled using gridded predictor variables selected from a candidate suite representing atmospheric circulation, thickness and moisture content at length scales of 300 km. Three simulation methods are compared: (1) a deterministic model in which daily precipitation occurrence and amounts are conditioned by atmospheric predictor variables (DET); (2) a hybrid model in which the unexplained variance of the deterministic model is represented stochastically (VAR); and (3) an unconditional resampling procedure (RND). Downscaled daily area averages are, in turn, used to resample daily precipitation amounts at multiple sites contributing to the unweighted areal mean. The temporal dependence of precipitation amounts at individual sites was explored using the standard deviation and autocorrelation of daily amounts, andN-day winter maxima. Spatial dependency was examined using inter-site correlations, correlation decay lengths, and Kendall's Ď„bstatistic for joint exceedance ofN-day precipitation totals. TheDETprocedure underestimated the variance of daily amounts andN-day totals and over-estimated observed autocorrelation, leading to generally poor representations of spatial dependency. TheRNDprocedure reproduced the distribution of daily amounts and inter-site correlations, but yielded poor representations ofN-day exceedances for largeN. Overall, theVARprocedure was the most successful downscaling approach. Even so, suggestions are made for refinements toVARin order to better capture seasonal variations in decay distances and pairwise correlations of multi-site precipitation amounts.
ISSN:0936-577X
1616-1572
DOI:10.3354/cr023183