The Geographical Locations of Southern Hemisphere Storm Tracks: Linear Theory

J. S. Frederiksen CSIRO, Division of Atmospheric Research, Aspendale, Victoria, Australia

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Abstract

The instability properties of a three-dimensional climatological January Southern Hemisphere flow field are examined using a five-level spherical quasi-geostrophic spectral model. The growth rates, phase frequencies, disturbance streamfunctions and eddy momentum and heat fluxes are studied for the eight fastest growing modes, all of which we monopole cyclogenesis modes. There is reasonable agreement between instability theory and observations as far as the geographical locations of the storm tracks and eddy fluxes are concerned. The principal storm track is located in the eastern part of the hemisphere slightly downstream and poleward of the jet stream maxima. The usual vertical structure problem of instability theory occurs with the theoretical disturbance streamfunctions and eddy fluxes being relatively too large at the surface compared with values at the tropopause.

Abstract

The instability properties of a three-dimensional climatological January Southern Hemisphere flow field are examined using a five-level spherical quasi-geostrophic spectral model. The growth rates, phase frequencies, disturbance streamfunctions and eddy momentum and heat fluxes are studied for the eight fastest growing modes, all of which we monopole cyclogenesis modes. There is reasonable agreement between instability theory and observations as far as the geographical locations of the storm tracks and eddy fluxes are concerned. The principal storm track is located in the eastern part of the hemisphere slightly downstream and poleward of the jet stream maxima. The usual vertical structure problem of instability theory occurs with the theoretical disturbance streamfunctions and eddy fluxes being relatively too large at the surface compared with values at the tropopause.

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