Some Dynamical Properties of Non-Linear Baroclinic Waves in a Quasi-Geostrophic Model

[摘要] The two-layer quasi-geostrophic spectral model with friction and diabatic heating, which was used by Lorenz (1963) for the study of the mechanics of vacillation, is extended to a less severe truncated model with m lateral modes on a β-plane, in order to investigate the dynamical properties of non-linear baroclinic waves in a rotating fluid with differential heating.Two experiments are performed by using this extended model: One is 4-mode experiment aiming to depict the barotropic process more sufficiently than Lorenz's model through higher modes, and the other is β-plane experiment to clarify the effect of sphericity on finite amplitude baroclinic waves.In the 4-mode experiment the flow regimes qualitatively similar to the result of laboratory experiments are obtained with the aid of analytical and numerical procedures. Zonal mean flow, eddy fluxes and energy budget are also calculated to elucidate the feature of vacillation. It is found that vacillations are primarily caused by the alternating dominance of baroclinic and barotropic processes.Results of the β-plane experiment indicate that the regimes of flow do not change so drastically by the β-effect but the cycle of vacillation is elongated due to the change of the phase velocity of disturbances.

[学科分类] 大气科学