A model of the quasi-biennial oscillation on an equatorial beta-plane

An equatorial beta-plane model of equatorial wave-mean flow interaction in the lower stratosphere is described. Kelvin and mixed Rossby-gravity waves generated by a specified forcing on the lower boundary radiate upward through the model domain where they are subject to thermal and mechanical dissipation. The wave-mean flow feedback problem is solved on the assumption that changes in the zonal mean state occur slowly enough for the wave field to be steady, locally in time. A quasi-biennial oscillation develops in the model with a period of about 1000 days. A novel feature of this model is the incorporation of latitudinal structure and of thermal and meridional wind components of the oscillation. The influence of the meridional circulation on the structure of the zonal wind oscillation is discussed in some detail.

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