ON SHORT- AND LONG-TERM VARIATIONS IN QUASI-BAROTROPIC FLOW

A. WIIN-NIELSEN Joint Numerical Weather Prediction Unit, Air Weather Service Suitland, Md.

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Abstract

A comparison is made between the stability properties of the non-divergent and divergent one-parameter models. It is show that the introduction of divergence in the one-parameter model reduces the rate of growth of unstable disturbances arid confines the instability to a more narrow band of wavelengths.

Changes in zonal momentum, momentum transports, and energy conversions between mean flow kinetic energy and eddy kinetic energy are investigated in the linear case, as well as by extended integrations of the spectral form of the prognostic equations allowing only a few wave numbers.

Long-term variations in barotropic flow, where the flow is initially stable, are investigated using the spectral formulation, but allowing only as many wave numbers as are needed to investigate variations in the profile of the zonal wind.

*Present affiliation: National Center for Atmospheric research, Boulder, Colo.

Abstract

A comparison is made between the stability properties of the non-divergent and divergent one-parameter models. It is show that the introduction of divergence in the one-parameter model reduces the rate of growth of unstable disturbances arid confines the instability to a more narrow band of wavelengths.

Changes in zonal momentum, momentum transports, and energy conversions between mean flow kinetic energy and eddy kinetic energy are investigated in the linear case, as well as by extended integrations of the spectral form of the prognostic equations allowing only a few wave numbers.

Long-term variations in barotropic flow, where the flow is initially stable, are investigated using the spectral formulation, but allowing only as many wave numbers as are needed to investigate variations in the profile of the zonal wind.

*Present affiliation: National Center for Atmospheric research, Boulder, Colo.

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