Mathematics Colloquia and Seminars

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The effects of zonally non-uniform background flow on the three-dimensional propagation of large-scale waves in Earth’s atmosphere are examined using the WKB formalism. Emphasis is placed on the vertical propagation of wave activity. Local vertical propagation is shown to be strongly dependent on the phasing of the wave source relative to the background flow. Specifically, in zonally non-uniform background flow, vertical propagation is confined to local vertical wave guides whose formation is controlled by the orientation of the background wind relative to the wave fronts. Within the waveguide vertical propagation is optimized when the disturbance wind field is parallel to the background potential vorticity gradient. As the wave packets move from the tropospheric source into the stratosphere they expand in zonal scale. The implications of these results to observed phenomena in the atmosphere are discussed.