The Influence of the Earth's Rotation Rate on the General Circulation of the Atmosphere

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  • 1 Australian Numerical Meteorology Research Centre, P.O. Box 5089AA, Melbourne, Australia, 3001
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Abstract

A general circulation model has been used to investigate the climatic and dynamical consequences of increasing and decreasing the rotation rate of the earth by a factor of 5. The model was hemispheric, devoid of topographical features, non-diurnal, and set up for annual mean conditions based on fixed, specified cloud, ozone, water vapor and surface albedo.

The high rotation rate model tended toward a multicellular mean meridional streamfunction with a weak tropospheric jet at very low latitudes, while the slow rotation rate model had a two-cell structure with an intense tropospheric jet at middle latitudes. These differences were interpreted in terms of the requirements for conservation of absolute angular momentum, and they indicate that such conservation was the single most important constraint in determining the dynamical structure of the model atmospheres. The latitudinal extent of the Hadley cell and the associated region of high surface pressure, the location and intensity of the tropospheric jet, and the conservation requirements were found to be mutually and dynamically related for both the fast and slow rotation rates as well as the control experiment.

The slow rotation rate model had quasi-axisymmetric synoptic distributions, a small tropospheric latitudinal temperature gradient, a sufficiently warm polar region to question the existence of permanent ice cover, and an enlarged and zone in the subtropics.

The fast rotation rate model exhibited irregular small-scale synoptic features, a marked tropospheric latitudinal temperature gradient, a very narrow arid zone in the tropics, and a very dry and cold high-latitude region.

Energy comparisons showed that the high rotation rate model had almost twice as much total energy as the control and slow rotation rate models combined, with most of this energy in the form of zonal available potential energy. In all three models the baroclinic cycle prevailed in the atmosphere, but the overall “efficiency” of the atmosphere declined with increasing rotation rate.

Abstract

A general circulation model has been used to investigate the climatic and dynamical consequences of increasing and decreasing the rotation rate of the earth by a factor of 5. The model was hemispheric, devoid of topographical features, non-diurnal, and set up for annual mean conditions based on fixed, specified cloud, ozone, water vapor and surface albedo.

The high rotation rate model tended toward a multicellular mean meridional streamfunction with a weak tropospheric jet at very low latitudes, while the slow rotation rate model had a two-cell structure with an intense tropospheric jet at middle latitudes. These differences were interpreted in terms of the requirements for conservation of absolute angular momentum, and they indicate that such conservation was the single most important constraint in determining the dynamical structure of the model atmospheres. The latitudinal extent of the Hadley cell and the associated region of high surface pressure, the location and intensity of the tropospheric jet, and the conservation requirements were found to be mutually and dynamically related for both the fast and slow rotation rates as well as the control experiment.

The slow rotation rate model had quasi-axisymmetric synoptic distributions, a small tropospheric latitudinal temperature gradient, a sufficiently warm polar region to question the existence of permanent ice cover, and an enlarged and zone in the subtropics.

The fast rotation rate model exhibited irregular small-scale synoptic features, a marked tropospheric latitudinal temperature gradient, a very narrow arid zone in the tropics, and a very dry and cold high-latitude region.

Energy comparisons showed that the high rotation rate model had almost twice as much total energy as the control and slow rotation rate models combined, with most of this energy in the form of zonal available potential energy. In all three models the baroclinic cycle prevailed in the atmosphere, but the overall “efficiency” of the atmosphere declined with increasing rotation rate.

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