Mountain Torque and Rossby Wave Radiation

Joseph Egger Meteorologisches Institut, Universität München, Munich, Germany

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Abstract

Planetary-scale orography exerts a substantial pressure drag on the atmosphere. This drag appears to be partially balanced by the convergence of momentum transports by Rossby waves induced by these mountains. Simple models of this process are presented within the framework of inviscid barotropic zonally periodic β-plane flow. Lateral radiation conditions are imposed for steady flow so as to allow for meridional wave radiation. Solutions are presented to the nonlinear vorticity equation and to the linear shallow-water equations. The relation between drag and flow configuration is discussed. An attempt is made to relate the results to the situation in the atmosphere and also in the ocean. In particular, it is demonstrated that coastlines with capes may exert a drag on ocean currents.

Corresponding author address: Prof. J. Egger, Meteorolgisches Institut, Theresienstr, 37, 80333 Munich, Germany.

Email: J.Egger@lrz.uni-muenchen.de

Abstract

Planetary-scale orography exerts a substantial pressure drag on the atmosphere. This drag appears to be partially balanced by the convergence of momentum transports by Rossby waves induced by these mountains. Simple models of this process are presented within the framework of inviscid barotropic zonally periodic β-plane flow. Lateral radiation conditions are imposed for steady flow so as to allow for meridional wave radiation. Solutions are presented to the nonlinear vorticity equation and to the linear shallow-water equations. The relation between drag and flow configuration is discussed. An attempt is made to relate the results to the situation in the atmosphere and also in the ocean. In particular, it is demonstrated that coastlines with capes may exert a drag on ocean currents.

Corresponding author address: Prof. J. Egger, Meteorolgisches Institut, Theresienstr, 37, 80333 Munich, Germany.

Email: J.Egger@lrz.uni-muenchen.de

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