IWA Publishing

Comparison of statistical methods for downscaling daily precipitation

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There are several statistical downscaling methods available for generating local-scale meteorological variables from large-scale model outputs. There is still no universal single method, or group of methods, that is clearly superior, particularly for downscaling daily precipitation. This paper compares different statistical methods for downscaling daily precipitation from numerical weather prediction model output. Three different methods are considered: (i) hybrids; (ii) neural networks; and (iii) nearest neighbor-based approaches. These methods are implemented in the Saguenay watershed in northeastern Canada. Suites of standard diagnostic measures are computed to evaluate and inter-compare the performances of the downscaling models. Although results of the downscaling experiment show mixed performances, clear patterns emerge with respect to the reproduction of variation in daily precipitation and skill values. Artificial neural network-logistic regression (ANN-Logst), partial least squares (PLS) regression and recurrent multilayer perceptron (RMLP) models yield greater skill values, and conditional resampling method (SDSM) and K-nearest neighbor (KNN)-based models show the potential to capture the variability in daily precipitation.

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