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We compare, for the overlapping time frame 1962-2000, the estimate of thenorthern hemisphere (NH) mid-latitude winter atmospheric variability within theXX century simulations of 17 global climate models (GCMs) included in theIPCC-4AR with the NCEP and ECMWF reanalyses. We compute the Hayashi spectra ofthe 500hPa geopotential height fields and introduce an integral measure of thevariability observed in the NH on different spectral sub-domains. Only twohigh-resolution GCMs have a good agreement with reanalyses. Large biases, inmost cases larger than 20%, are found between the wave climatologies of mostGCMs and the reanalyses, with a relative span of around 50%. The travellingbaroclinic waves are usually overestimated, while the planetary waves areusually underestimated, in agreement with previous studies performed on globalweather forecasting models. When comparing the results of various versions ofsimilar GCMs, it is clear that in some cases the vertical resolution of theatmosphere and, somewhat unexpectedly, of the adopted ocean model seem to becritical in determining the agreement with the reanalyses. The GCMs ensemble isbiased with respect to the reanalyses but is comparable to the best 5 GCMs.This study suggests serious caveats with respect to the ability of most of thepresently available GCMs in representing the statistics of the global scaleatmospheric dynamics of the present climate and, a fortiori, in the perspectiveof modelling climate change.Comment: 39 pages, 8 figures, 2 table

Intercomparison of the northern hemisphere winter mid-latitude atmospheric variability of the IPCC models