Planetary Scale Barotropic Spectral Model.

The present work employes a highly truncated spectral baratropic model which is used to qualitatively reproduce certain recurrent planetary scale atmospheric flow configurations, in particular, quasistationary states having high and low zonal index. The model includes single spectral component topography and suitably parameterized eddy divergence due to latent heating; both the topography and the eddy divergence possess Zonal Wavenumber 2 and therefore represent important spectral terms for the actual large scale mountains and patterns of tropical heating. Zonally-symmetric momentum forcing and linear clamping are also included in the model. Equilibrium solutions for several different cases of external forcing are presented. Stability properties of the equilibria are also determined and the physical mechanisms generating any unstable behavior are inferred. The sets of solutions derived from the model are checked for consistency with realistic mid-tropospheric flow conditions. External forcing conditions giving rise to multiple equilibrium solutions are determined and the flow profiles of the resulting multiple equilibria are described in detail. The spectral system is also applied to real data in order to, first, determine the degree of validity of the model and, second, to provide some physical interpretation to a case of actual atmospheric flow in the planetary-scale regime.