Generation of Gravity Waves by Jet Streams in the Atmosphere

Abstract

The characteristics of internal gravity waves generated by tropospheric jet streams are analyzed and discussed. By solving numerically the equations of motion in the linear, inviscid and Boussinesq limit, it is shown that a modal structure exists. Some of these modes have the ability to propagate vertically away from the jet and are likely to he responsible for some of the observed wave activities in the ionosphere as well as at the ground. For selected values of the minimum Richardson number of the flow, growth rates and horizontal phase velocities are given as functions of the horizontal wavenumber, for jet streams of varying width. Finally, a brief study of the stability of the so-called low-level jet, whose spectrum of generated waves undoubtedly will contribute to the dynamics of the nocturnal boundary layer, is undertaken.