Multiple non-linear interaction of Rossby waves via zonal flow

The non-linear interaction between large-scale Rossby waves is considered making use of a spectral model of a barotropic atmosphere in spherical geometry. It is found that, if an arbitrary number of zonal components is taken into account it is possible to predict the non-linear energy and enstrophy flux between Rossby waves whose interaction cannot be predicted by single triadic resonance. It is shown, referring to the results of a paper by Baines, that such kind of, zonally mediated, non-linear energy flux is capable of explaining some relevant features of numerical integrations of truncated models with a large number of components and, could, as a consequence be responsible of some features of the large-scale circulation.