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Dynamics of Frontal Discontinuities in the Semigeostrophic Theory

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  • 1 Department of Physics, University of Toronto, Toronto, Ontario, Canada
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Abstract

A deformation-forced, semigeostrophic (SG) frontogenesis model is extended in time to include frontal evolution after the initial formation of a discontinuity at the surface. The dynamical fields associated with the frontogenesis (e.g., along front cross front and vertical winds, Richardson number) are calculated and compare favorably to the qualitative features of atmospheric cold fronts. In particular, a strong vertical velocity jet exists at the position of the surface front in agreement with observation studies. Results from primitive equation models which include thermal and momentum diffusion are compared to the results presented here in order to assert the validity of the semigeostrophic approximation and to examine the effect of neglecting friction and mixing processes on our model.

Abstract

A deformation-forced, semigeostrophic (SG) frontogenesis model is extended in time to include frontal evolution after the initial formation of a discontinuity at the surface. The dynamical fields associated with the frontogenesis (e.g., along front cross front and vertical winds, Richardson number) are calculated and compare favorably to the qualitative features of atmospheric cold fronts. In particular, a strong vertical velocity jet exists at the position of the surface front in agreement with observation studies. Results from primitive equation models which include thermal and momentum diffusion are compared to the results presented here in order to assert the validity of the semigeostrophic approximation and to examine the effect of neglecting friction and mixing processes on our model.

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