  A quasi-geostrophic intermediate complexity model is considered, providing a
schematic representation of the baroclinic conversion processes which
characterize the physics of the mid-latitudes atmospheric circulation. The
model is relaxed towards a given latitudinal temperature profile, which acts as
baroclinic forcing, controlled by a parameter TE determining the forced
equator-to-pole temperature gradient. As TE increases, a transition takes place
from a stationary regime to a periodic regime, and eventually to an earth-like
chaotic regime where evolution takes place on a strange attractor. The
dependence of the attractor dimension, metric entropy, and bounding box volume
in phase space is studied by varying both TE and model resolution. The
statistical properties of observables having physical relevance, namely the
total energy of the system and the latitudinally averaged zonal wind, are also
examined. It is emphasized that while the attractor's properties are quite
sensitive to model resolution, the global physical observables depend less
critically on it. For more detailed physical observables, such as the
latitudinal profiles of the zonal wind, model resolution again may be critical:
the effectiveness of the zonal wind convergence, acting as barotropic
stabilization of the baroclinic waves, heavily relies on the details of the
latitudinal structure of the fields. The necessity and complementarity of both
the dynamical systems and physical approach is underlined.
