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The general circulation of the atmosphere
By S. Tibaldi* and R
Mureau
* Current address: University of Bologna,
Department of Physics, Via Imerio 46, 40126 Bologna, Italy
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5 The existence of circulation regimes
Already very simple annulus experiments show that ultimately turbulent systems with very many degrees of freedom can exhibit different `regimes' of motion that can coexist in the presence of the same external forcing parameters. During the last few years, convincing evidence has been found that some atmospheric observables, notably connected with planetary-scale wave activity during winter, have non Gaussian distributions, see Fig. 10 . The earth's atmosphere can (and does) therefore span the phase space of its possible realisations in a non-simple way.
The existence of such weather regimes has important implications on several aspects of atmospheric science, from climatology (and the very definitions of climate and of general circulation) to weather forecasting and general circulation modelling. We will see in a later lecture how the occurrence of a well known synoptically defined weather regime, that is blocking, affects the skill of the ECMWF operational model.
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07.06.2002 |
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