Thesis (Ph. D.)--University of Wisconsin, 1972. / Bound typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 122-125).

Thesis (Ph. D.)--University of Chicago, Dept. of the Geophysical Sciences, June 2000. / Includes bibliographical references. Also available on the Internet.

The earth's atmosphere is a thin fluid layer covering our planet. As a fluid, it has the important characteristic of supporting wave motions. It is this aspect of the atmosphere which constitutes the subject of this thesis.

It is suggested that the stratosphere may-act as a wave-guide for certain types of acoustic-gravity waves. An isothermal layer model is proposed which introduces gravity terms into the equations governing wave propagation. An expression for the phase change on reflection at a boundary of the layer is derived. Numerical solutions to the equation for wave-guide, modes of propagation are obtained by the use of a digital computer. Results are given in the form of dispersion curves. Cutoff is found to occur at a frequency well above the Brunt resonant frequency for the stratosphere. The model stratosphere proposed in this study does not behave as a lossless wave-guide for gravity coupled acoustic waves. This is shown to be consistent with the results of a more complete study by Press and Harkrider. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

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A linear multiple regression statistical model is applied to estimate the solar induced component of odd nitrogen variability in the stratosphere and lower mesosphere using UARS HALOE data for 1991–2003. Consistent with earlier studies, evidence is obtained for a decadal NOx variation at the highest available latitudes (50° – 70°) that projects positively onto the solar cycle. This variation, which is most statistically significant in the Southern Hemisphere, also correlates positively with the auroral Ap index. It is therefore probably caused by downward transport during the polar night of thermospheric and mesospheric odd nitrogen. In addition, at low latitudes near and above the stratopause, evidence is obtained for an inverse solar cycle NOx variation. It is suggested that this low-latitude response may be caused primarily by increased photolysis of NO under solar maximum conditions. Throughout most of the rest of the stratosphere, no statistically significant response is obtained.

Tropospheric ozone plays an important role in the atmosphere especially towards climate change and air quality. In this study, characteristics of tropospheric ozone over the South African Highveld are investigated using the ozonesonde data collected at Irene weather station (25.9°S, 28.2°E, and 1523 m asl) for the period 1990 to 1993 and 1999 to 2003. It was found that synoptic systems have an effect on the vertical distribution of tropospheric ozone. Ozone stratification appeared during anticyclonic conditions as displayed by a continental high ozone profile. During the ridging high, low ozone concentrations are observed with a strong ozone gradient between 10 and 12 km. Ozone enhancement appeared in the lower altitudes, <4 km, in both the ridging high and the westerly disturbance ozone profiles. Ozone profiles exhibited higher ozone concentrations during the westerly wave conditions. Tropospheric ozone over the South African Highveld region follows a clear annual cycle with lower ozone concentrations observed during autumn and higher ozone concentrations during spring. Summer ozone profiles had high ozone concentrations from the earth’s surface up to 9 km compared to winter ozone profiles. However, winter ozone profiles exhibited higher ozone concentrations than summer ozone profiles and they were characterised by a strong ozone gradient at 12 km. Ozone profiles obtained during the Southern African Fire-Atmosphere Research Initiative conducted in 1992 (SAFARI-92) displayed lower ozone concentrations than ozone profiles from the Southern African Regional Science Initiative conducted during 2000 (SAFARI- 2000). Therefore, it is apparent tropospheric ozone over the South African Highveld has increased over the past decade.