Dynamics of fine‐scale variables versus averaged observables in a T21L3 quasi‐geostrophic model

The dynamics of space‐ and time‐averaged observables of a 3‐level quasi‐geostrophic model is investigated and compared with that of the fine‐scale variables, with emphasis on the role of the initial error field on predictability. The invariance of the largest Lyapunov exponent against averaging of up to 10 days is established. Some improvements of predictability of the averaged variables turn out to be possible, at least for certain classes of initial perturbations. Finally, a map of error distribution in space and a classification of weather regimes are derived on the basis of the average properties of the Lyapunov vectors.