  The information entropy budget and the rate of information transfer between
variables is studied in the context of a nonlinear reduced-order atmospheric
model. The key ingredients of the dynamics are present in this model, namely
the baroclinic and barotropic instabilities, the instability related to the
presence of an orography, the dissipation related to the surface friction, and
the large-scale meridional imbalance of energy. For the parameter chosen, the
solutions of this system display a chaotic dynamics reminiscent of the
large-scale atmospheric dynamics in the extra-tropics. The detailed information
entropy budget analysis of this system reveals that the linear rotation terms
plays a minor role in the generation of uncertainties as compared to the
orography and the surface friction. Additionally, the dominant contribution
comes from the nonlinear advection terms, and their decomposition in synergetic
(co-variability) and single (impact of each single variable on the target one)
components reveals that for some variables the co-variability dominates the
information transfer. The estimation of the rate of information transfer based
on time series is also discussed, and an extension of the Liang's approach to
nonlinear observables, is proposed.
