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Geller, M. Fritts, David Conrad 2011-07-01T18:34:31Z 2011-07-01T18:34:31Z 10000-01-01 1977 Three models are developed to examine various features of the gravity wave-critical level interaction and some of its possible roles in the dynamics of the atmosphere and the oceans. A linear inviscid steady state model is designed which, though singular at the critical level, illustrates certain important features of the gravity wave-critical level interaction. A linear viscous steady state model is used to examine the effects of dissipation. And a nonlinear viscous time dependent model is developed to evaluate the importance of time dependence and nonlinear effects on the development of the gravity wave-critical level interaction. Results obtained with the three models indicate that a number of effects may be important in correctly modelling the gravity wave-~ritica1 level interaction. Viscosity and heat conduction tend to stabilize the interaction and can, if sufficiently large, prevent the formation of unstable velocity shears. A Viscous Stability Criterion is obtained and its predictions are found to be consistent with observations in a number of laboratory, atmospheric, and oceanic critical level flows. Nonlinear and time dependent effects are found to be important in gravity wave-critical level interactions in which unstable velocity shears are formed. Such an unstable critical level interaction develops long thin nearly horizontal regions of unstable velocity shear which break down through the development and growth of Kelvin-Helmholtz instabilities. This suggests that the gravity wave-critical level interaction may be responsible for some of the thin turbulent layers observed at various levels in the atmosphere and the oceans. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-07-01T18:34:31Z No. of bitstreams: 1 1977_fritts.pdf: 5514384 bytes, checksum: 497133fde71432b855a1ae4fed5876e2 (MD5) Made available in DSpace on 2011-07-01T18:34:31Z (GMT). No. of bitstreams: 1 1977_fritts.pdf: 5514384 bytes, checksum: 497133fde71432b855a1ae4fed5876e2 (MD5) Previous issue date: 1977 Restriction data tranferred 2014-07-01T11:32:35-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-07-01T18:34:31Z Item is restricted indefinitely. Thesis U of I Only 255047 http://hdl.handle.net/2142/25630 en 1977 David Conrad Fritts Gravity Wave critical level ocean dynamics atomosphere dynamics linear inviscid steady state model The gravity wave-critical level interaction Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.