A. Busuioc et al., Performance of statistical downscaling models in GCM validation and regional climate change estimates: Application for Swedish precipitation, INT J CLIM, 21(5), 2001, pp. 557-578
This study deals with an analysis of the performance of a general circulati
on model (GCM) (HadCM2) in reproducing the large-scale circulation mechanis
ms controlling Swedish precipitation variability, and in estimating regiona
l climate changes owing to increased CO2 concentration by using canonical c
orrelation analysis (CCA). Seasonal precipitation amounts at 33 stations in
Sweden over the period 1899-1990 are used. The large-scale circulation is
represented by sea level pressure (SLP) over the Atlantic-European region.
The link between seasonal Swedish precipitation and large-scale SLP variabi
lity is strong in all seasons, but especially in winter and autumn. For the
se two seasons, the link is a consequence of the North Atlantic Oscillation
(NAO) pattern. In winter, another important mechanism is related to a cycl
onic/anticyclonic structure centred over southern Scandinavia. In the past
century, this connection has remained almost unchanged in time for all seas
ons except spring. The downscaling model that is built on the basis of this
link is skilful in all seasons, but especially so in winter and autumn. Th
is observed link is only partially reproduced by the HadCM2 model, while la
rge-scale SLP variability is fairly well reproduced in all seasons. A conce
pt about optimum statistical downscaling models for climate change purposes
is proposed. The idea is related to the capability of the statistical down
scaling model to reproduce low frequency variability, rather than having th
e highest skill in terms of explained variance. By using these downscaling
models, it was found that grid point and downscaled climate signals are sim
ilar (increasing precipitation) in summer and autumn, while in winter, the
amplitudes of the two signals are different. In spring, both signals show a
slight increase in the northern and southern parts of Sweden. Copyright (C
) 2001 Royal Meteorological Society.