A three-dimensional mechanistic model of the middle atmosphere is used to model various classes of equatorial wave motions that are observed in the atmosphere. These waves are thought to be largely responsible for the forcing of the quasi-biennial oscillation (QBO) in the tropical lower stratosphere. By generating a combination of different classes of equatorial waves in the model, an oscillation which has many similarities to the observed QBO is produced in the model. The numerical model used is run in a variety of configurations, including running it at different vertical resolutions and with two different radiation parameterisation schemes. It is found that model used in the project must be modified to allow the accurate modelling of equatorial waves. Several modelling problems are encountered while applying the modifications necessary in the model; the steps necessary to rectify these problems are detailed in this thesis. Equatorial waves are then forced in this modified model under a range of conditions and their interaction with the mean flow is observed. Their dissipation mechanisms and the influence of changes in model conditions on these waves are investigated. The model is found to be generally very successful in modelling these equatorial waves. Modelling of the QBO is one of the principle aims of this project and a QBO is successfully generated in a variety of model configurations. The modelled QBO is found to be sensitive to changes in the temperature structure of the model (brought about by changes in the model's radiation scheme) and several experiments are performed in order to learn what processes affect this sensitivity. A QBO is then generated in series of model runs where the state of the model is varied from very idealised (where temperatures in the model are relaxed towards an isothermal state by the radiation scheme) to a state that is far more realistic (a perpetual January run with realistic boundary information). A fairly realistic QBO is generated throughout many of the experiments. The properties of this QBO are investigated and compared to the observed QBO. The model is then run with planetary waves forced in addition to the QBO. The interaction between the planetary waves and the QBO is investigated. It is found that the planetary waves have little effect on the QBO propagation. The QBO however has a fairly strong modulating effect on the planetary waves in certain regions.

Thesis (Ph. D.)--York University, 2005. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 120-133). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004 & res_dat=xri:pqdiss & rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation & rft_dat=xri:pqdiss:NR11552.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves [71]-74). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves [71]-74). Also available on the Internet.

No description available.

The resonance of stationary waves in a mid-latitude (beta)-plane model is examined. In a series of linear experiments it is found that a large, quasi-resonant response occurs even in the presence of realistic damping. With forcing of reasonable amplitude the resonant growth rates are found to be such that a period of several weeks is required for the resonant mode to achieve large amplitude in the troposphere. When nonlinear effects are included the growing resonant wave is found to cause a stratospheric warming and zonal wind reversal and thus drives the system off resonance. We therefore examine flow configurations for which the nonlinear terms vanish. It is found that these flow configurations can resemble realistic blocking patterns. When diabatically forced, the resonant growth of these patterns does not give rise to any nonlinear interactions, although such interactions do occur if other models, which do not satisfy the non-interaction conditions, are present. We conclude that resonant growth can lead to the establishment of large-amplitude, stationary, long waves even when realistic damping and non-linear effects are operating.

Typescript (photocopy) / 1 v. (various paging) : ill. ; 30 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1982

This thesis is concerned with the dynamics of the middle atmosphere over the southern-most continent on our planet, Antarctica. Building on previous observational and theoretical efforts to understand the dynamics of this region of the atmosphere, the work encompasses instrument improvements as well as data analysis studies of gravity waves in the lower and middle stratosphere, tides in the upper mesosphere and lower thermosphere, and short-period planetary waves in the stratosphere and mesosphere. An upgrade of the Medium-Frequency Spaced Antenna (MFSA) radar at Scott Base, Antarctica, was carried out in 2004/5 in order to ensure continued operation and enhance its capabilities to measure gravity waves. As a result, the quality of the wind measurements was greatly enhanced and the amount of data collected is now greater by a factor of approximately 15 compared with before the upgrade. Analysis of over two decades of wind velocity data from Scott Base yields a reliable climatology of the dynamics of the upper mesosphere and lower thermosphere in this area, namely the tidal oscillations and the background winds. In addition, interannual variability is assessed and periodicities of approximately 11 years and strong positive trends in tidal amplitudes are reported. Mechanisms that could explain the observed behaviour are proposed. The data are then combined with wind measurements from Halley, the longitudinal conjugate site, in order to study the zonal character of the semi-diurnal tide. Zonal wavenumber 1 and 2 waves are both found and mechanisms that could explain the generation of a wavenumber 1 component are suggested. Two further sets of MFSA radar wind measurements are used to investigate the behaviour of planetary waves with periods of between two and four days in the Antarctic middle atmosphere. Satellite temperature measurements further help to create a more complete picture of these waves. Baroclinic and barotropic instabilities, which result from shears of the zonal wind, appear to be responsible for much of the observed wave activity. In addition, a quasi-to day wave event in mid-May 2005 with unusually large amplitudes is examined and suggested to be linked to a solar proton event. Gravity wave activity over Antarctica is studied using temperature profiles obtained through the satellite radio occultation technique. Although the measurements are restricted to below 35 km altitude, high-resolution temperature profiles allow conclusions to be drawn about the seasonal, geographical, and height distribution of gravity wave activity. Mountain waves are found to be important over the Antarctic Peninsula and the Transantarctic mountains where they contribute more than 20% of the observed wave activity in the lower stratosphere. In addition, the analysis indicates the importance of critical-level filtering and Doppler-shifting.

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics, 1982. / Typescript (photocopy).

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics, 2000? / Copies of author's previously published articles inserted. Bibliography: p. 227-245.