Transmission of Atmospheric Internal Gravity Waves Into the Stratosphere.
Abstract
Atmospheric internal gravity waves are often produced when air flows over mountainous terrain. Associated with these waves is a transport of horizontal momentum from the surface of the earth to the upper atmosphere. This momentum flux is considered to be a major source of drag in the middle atmosphere. In this thesis we investigate the transmission of mountain induced internal gravity waves through the troposphere and into the stratosphere. To capture the essential dynamical features, we chose an atmospheric structure in which the wind increases linearly with height to the tropopause, above which it remains constant, and the stability is constant in the troposphere and constant, yet larger, in the stratosphere. In this research we use both linear analytic techniques and a nonlinear numerical model. With computeraided analysis we obtained analytic solutions to the problem of this representative tropospherestratosphere model which has remained intractable until now. The nonlinear numerical model developed for this research has the unique feature that it incorporates a conformal terrainfollowing coordinate system, allowing for arbitrary mountain profiles. Results from both the linear analysis and the nonlinear numerical model show that (1) for any except very large Richardson numbers, the lowest mode resonance wave excited by the tropospheric structure is the only one that has appreciable amplitude at tropopause levels, and therefore dominates the tropospherestratosphere solution; (2) the wavelength of the stratospheric wave is close to the tropospheric wavelength that would occur if a rigid lid were placed at the tropopause, (3) the stratospheric stability does not affect the wavelength of either the tropospheric or stratospheric wave, (4) the presence of the stratosphere makes possible a substantial flux of momentum into the middle atmosphere that does not occur if the tropospheric wind shear and stability continue to infinite heights, (5) for mountain forcing with gentle slopes, the halfwidth affects the amplitude but not the wavelength of stratospheric wave, and (6) solutions from the nonlinear model and linear analysis agree reasonally well, leading us to conclude that for our choice of parameters, nonlinear affects do not dominate.
 Publication:

Ph.D. Thesis
 Pub Date:
 1986
 Bibcode:
 1986PhDT.........9K
 Keywords:

 Physics: Atmospheric Science;
 Air Land Interactions;
 Gravitational Waves;
 Internal Waves;
 Momentum Transfer;
 Wave Propagation;
 Wind Profiles;
 Atmospheric Circulation;
 Atmospheric Models;
 Stratosphere;
 Troposphere;
 Wave Drag;
 Geophysics