On the interactions among flow components in different frequency bands in the Canadian climate centre general circulation model

Abstract

Abstract Spectral energetics analyses in the frequency domain are made of the atmosphere as simulated by the Canadian Climate Centre general circulation model for the summer and winter seasons separately. Five years of model results produce energy cycles in qualitative agreement with the real atmosphere. The high‐frequency eddies in the model are identified as the transient baroclinic waves, which show well defined storm track structures and are largely maintained by the baroclinic conversion from available potential energy (APE) to kinetic energy (KE). The low‐frequency eddies, on the other hand, exhibit their maximum amount of KE in the eastern parts of the Pacific and the Atlantic oceans. They are supported both by a baroclinic conversion and, to a smaller extent, by a non‐linear exchange of KE. The E vector analyses applied to the calculation of the barotropic conversion demonstrate a sharp contrast between the high‐and low‐frequency transients of eddy activity. It is shown that the barotropic conversion of KE from the time‐mean flow to the low‐frequency eddies is a direct consequence of the east‐west elongation of the slow transients. Barotropic conversions typical of stable and unstable time‐mean states are obtained in the summer and winter seasons, respectively. The energetics are compared with the observed and theoretical results where possible.