Propagation properties of inertia–gravity waves through a barotropic shear layer and application to the Antarctic polar vortex

• Main Authors: M. C. Öllers, L. P. J. Kamp, F. Lott, P. F. J. Van Velthoven, H. M. Kelder, F. W. Sluijter
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2002
• Subjects: Antarctic; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.572.525; http://www.lmd.jussieu.fr/~flott/articles/QJ_03.pdf

The propagation of inertia–gravity waves (IGWs) through a dynamical transport barrier, such as the Antarctic polar vortex edge is investigated using a linear wave model. The model is based on the linearized, inviscid hydrostatic equations on an f-plane. Typical values for the parameters that are appropriate to the Antarctic polar vortex are given. The background ow U is assumed to be barotropic and its horizontal shear is represented by a hyperbolic tangent background wind pro le. The wave equation that describes the latitudinal structure of a monochromatic disturbance contains two singularities. The rst corresponds to the occurrence of a critical level where the intrinsic wave frequency Ä D! ¡ kU becomes zero.! is the absolute wave frequency and k its longitudinal wave number in the direction of U. The second is an apparent singularity and does not give rise to singular wave behaviour. It becomes zero whenever the square of the intrinsic wave frequency Ä2 D f.f ¡ Uy /, f being the Coriolis frequency and Uy the horizontal shear of the ow. The wave equation is solved numerically for different values of the angles of incidence of the wave upon the background ow, of the wave frequency, of the horizontal wave number and of the Rossby number. Re ection (jRj) and transmission (jT j) coef cients are determined as a function of these parameters. The results depend on whether the ow is inertially stable or not. They also depend on the presence and location of the turning levels, where the wave becomes evanescent, with respect to the location of the Ä-critical levels. For inertially stable ows, the wave totally re ects at the turning