Non‐linearity in statistical downscaling: does it bring an improvement for daily temperature in Europe?

• Published in: International journal of climatology 2008-04, Vol.28 (4), p.465-477
• Main Authors: Huth, R., Kliegrová, S., Metelka, L.
• Format: Article
• Language: English
• Subjects: classifications; Climatology. Bioclimatology. Climate change; daily temperature; Earth, ocean, space; Europe; Exact sciences and technology; External geophysics; Meteorology; neural networks; non‐linearity; statistical downscaling
• ISSN: 0899-8418; 1097-0088
• DOI: 10.1002/joc.1545

Several linear and non‐linear statistical downscaling methods are compared for winter daily temperature at eight European stations. The linear methods include linear regression of gridpoint values (pointwise regression) and of predictors' principal components (PC regression). The non‐linear methods are represented by artificial neural networks. The non‐linearity is also achieved by a stratification of data by classification of circulation patterns and a linear regression conducted separately within each class. As predictors, gridded 500 hPa heights and 850 hPa temperature are used. The verification is conducted in the cross‐validation framework. The downscaling methods are evaluated according to four criteria: (1) fit to observations (quantified by the correlation coefficient), (2) shape of the statistical distribution, namely its skewness and kurtosis, (3) temporal autocorrelations with 1 day lag, and (4) interstation correlations. Considering all the criteria together, the pointwise linear regression appears to be the best method. It achieves the best fit with the observations and possesses the best temporal structure. The deviations of statistical distributions from normality are only captured by the neural networks, while the classification methods yield the best spatial correlations. Copyright © 2007 Royal Meteorological Society