The relationship between the outgoing long-wave radiation (OLR) field over the tropical Pacific and wintertime monthly precipitation for the western U. S. is investigated, using the mid-latitude upper-air circulation as an intermediary. Principal components (PC's) of the 500mb monthly averaged height field over the NE Pacific and western North America are compared with those of the monthly tropical Pacific OLR field. It is found that, of the first 6 PC's of the height field, five are correlated significantly with the first 3 OLR field PC's at lags of between two and six months. Canonical correlations between the two sets of PC's are greatest at a lag of four months and are highly significant. When stratified by different levels of the OLR field PC's, the separations between means of the height field PC's are highly significant as well. Differing distributions of the height field PC ensemble are also found to be associated with different OLR field PC levels. The relationship between the 500mb height field and concurrent western district precipitation is examined. Using a hybrid model including both linear statistical and non-linear physical components it is found that considerably more of the variance in the precipitation can be explained by that of the height field alone than when the precipitation is inferred directly from a linear statistical model. A set of reconstructed height field PC's is predicted from OLR values based on the height field/OLR stratification associations compiled for a period separate from that of the forecast. Applied to the precipitation model, this results in predicted western district precipitation which is better correlated with the observations than is the equivalent precipitation forecast from the linear statistical relationship of precipitation to the Southern Oscillation Index. / Graduation date: 1995

Planetary waves are known to play an important role in determining the annual variability in the severity of Antarctic ozone depletion. In this thesis, data obtained from the TOMS experiment on board the Nimbus-7 satellite are used to create global maps of total column ozone for each day from 1979 to 1992. Planetary wave morphology within these distributions is examined using spatial spectral analysis. The wave powers obtained are compared with a measure of the depth and area of the Antarctic ozone hole. A theoretical overview is given of middle atmosphere dynamics and how it influences the global distribution of ozone. Planetary waves play a predominant role in this dynamical distribution as they are responsible for the eddy transport of heat, momentum and long-lived tracers. A discussion of the equations of motion governing planetary wave propagation and their physical interpretation is given. The use of derived meteorological parameters, such as potential vorticity, in the study of planetary waves is developed. The theoretical tools, together with the equations of motion, are used to examine the excitation mechanisms for planetary waves. This theoretical analysis is also used to show that the strength of the westerly jet within the polar vortex determines which planetary wave modes can be expected in the geopotential height fields. In general only wavenumber 1 and 2 propagate during the Southern Hemisphere winter and the strength of these waves strongly modulates the severity of the Antarctic ozone depletion. Furthermore, the timing of the breakdown of the polar vortex is connected with the temporal variation of planetary wave power. A review of the current research in the field of planetary waves and the global distribution of ozone is given. To quantify planetary wave activity, spatial spectral analysis (Fourier Transforms) of midlatitude zonal profiles of total column ozone are used to calculate wave powers in the ozone distribution. Powers at wavenumber 1 to 6 are calculated for each day from 1979 to 1992 for both the Northern and Southern Hemispheres. The powers are seen to decrease with wavenumber throughout the year and the amplitude of wave modes 3 and higher is suppressed during the winter in accordance with the theoretical discussion. Southern Hemisphere wave powers are compared with a daily depleted mass of ozone over the Antarctic from 1979 to 1992. It is found that during years of high (low) planetary wave activity Antarctic ozone depletion is very weak (severe). Finally, the planetary wave morphology observed in the Southern Hemisphere total column ozone distribution is compared with geopotential height waves reported in the literature. Comparison of Northern Hemisphere wave powers and Arctic ozone depletion shows little or no correlation. To examine whether planetary waves may effect the interannual variability in Antarctic vortex temperatures, winter averaged 100 hPa upper air temperatures from SANAE (70°18' S, 2°21' W) are compared with derived planetary wave powers. It is found that during years of high (low) planetary wave activity the SANAE 100 hPa temperatures are above (below) the mean. Analysis of daily total column ozone and upper air temperatures at SANAE, during the winters of 1987 and 1988, shows that wave 1 forcing can significantly influence the day-to-day variation in these quantities. A statistical model of total ozone variation over the entire globe, from 1979 to 1992, has been developed. This model incorporates a long-term linear trend, an annual variation, a quasi-biennial oscillation, a solar cycle variation and a semiannual variation. Since monthly average total column ozone data are used in this model, short term planetary wave influences are masked, and the variations in global ozone are determined primarily by the 5 signals discussed above. However, analysis of the model coefficients indicates that planetary wave activity may significantly contribute to zonal asymmetry in global total ozone trends. Differences between model results and measured data are compared with planetary wave activity. The timing of the breakdown of the Antarctic circumpolar vortex causes large interannual differences in monthly average total column ozone for the months of October and November in the Southern Hemisphere. This analysis is made more specific for South Africa by examining the variation in monthly average total column ozone over the five South African cities of Pretoria, Bloemfontein, Durban, Port Elizabeth and Cape Town for the years 1979 to 1992. A model of surface erythemal irradiance as a function of total column ozone, time of the year and other meteorological parameters is developed. Total ozone data for the 5 cities, used within the context of the statistical model and the DV irradiance model, allows the prediction of future DV levels over South Africa to the year 2000. Planetary wave motion owes its existence to the conservation of potential vor-ticity. However, to make use of this conservation principle as a diagnostic for planetary wave propagation, it is necessary to know the conditions under which it is conserved. A formalism developed by Plumb and Ko (1992) has been used to suggest a technique whereby the 'lifetime' of potential vorticity may be determined. Use was made of data from the NCAR CCM2 model to test this hypothesis. The concentrations of long-lived tracers (CH4 and NzO) extracted from the CCM2 also show the effects of planetary wave breaking on the meridional distribution of these species. This study has important implications for airborne polar chemistry campaigns. / Thesis (Ph.D.)-University of Natal, 1994.

In this thesis, the dynamics and coupling in the middle atmosphere over the Southern Hemisphere are investigated using SuperDARN high frequency (HF) radar wind data, satellites, light detection and ranging (LIDAR), the South African National Antarctic Expedition (SANAE) imaging riometer and models. In particular, the study focuses on the unprecedented 2002 major stratospheric warming and its role in coupling the middle atmosphere. The dynamics of the middle atmosphere is investigated in terms of mean wind, temperature, gravity waves and planetary wave activity. Studying the middle atmospheric thermal structure over Southern Africa is an important activity to improve the understanding of atmospheric dynamics of this region. Observation of a middle atmosphere thermal structure over Durban (29.9 S, 31.0 E, South Africa) using LIDAR data collected from April 1999 to July 2004 (277 nights), including closest overpasses of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) and Halogen Occultation Experiments (HALOE) satellites, and the COSPAR International Reference Atmosphere (CIRA-86) are presented in this thesis. The observations from the LIDAR instrument, satellites and CIRA-86 exhibit the presence of annual oscillation in the stratosphere, whereas in the mesosphere the semi-annual oscillation seems to dominate the annual oscillation at some levels. The stratopause is observed in the height range of 40-55 km for all the instruments, with the stratopause temperatures being 260- 270 K for the LIDAR, 250-260 K for the SABER, and 250-270 K for the HALOE. Data from the LIDAR, satellites and CIRA-86 model indicate almost the same thermal structure of the middle atmosphere over Durban. This indicates a good agreement between LIDAR, satellites and the CIRA-86 model. Mean wind and planetary waves are investigated on a climatological scale in this study. Mean wind observations from the SANAE SuperDARN HF radar are compared with observations from Halley SuperDARN HF radar. There is a good agreement between the observations from the two stations both in the zonal and meridional wind components. Zonal wind is observed to be consistently larger than the meridional wind. The zonal wind is also consistently more eastward at both stations with maxima occurring during the solstice months. High latitude summer zonal mean ow at 94 km is observed to be weaker and more variable compared to the eastward winter mean circulation owing to tropospherically forced planetary waves propagating through the middle atmosphere. The zonal mean wind shows greater seasonal variability than does the meridional mean wind. This seasonal behaviour is reasonably well understood in terms of the upward propagating planetary waves and gravity waves interacting with the mean ow. The Coriolis force also plays an important role in the case of meridional wind component. The climatology of planetary waves both in the zonal and meridional wind components indicates an ampli cation of planetary waves of shorter wavenumbers (s = 3) in the winter months. During summer, long period oscillations (e.g. >10 days) which are dominant in winter disappear, and oscillations with shorter period (e.g. <10 days) become dominant. vi There is a strong planetary wave coupling between the stratosphere and mesosphere-lower thermospheric (MLT) during the year 2002 winter season, whilst the coupling is observed to be relatively weak during the other years. The strong planetary wave coupling in 2002 is understandable because during this year the middle atmosphere winter months were characterised by strong planetary wave activity which led to the rst ever detection of the SSW in the Southern Hemisphere. In the year 2002 winter period the mean circulation in the stratosphere is characterized by a series of planetary wave events that weakened the polar vortex and triggered the sudden stratospheric warming in late September. In particular, in the stratosphere there is a presence of a quasi 10-day eastward propagating planetary wave of wavenumber s=1, while in the MLT a quasi 14-day eastward propagating planetary wave of wavenumber s=1 is observed to be dominant. The Eliassen Palm ux (E-P) ux shows that strong planetary wave activity observed in the middle atmosphere originates from the troposphere. Zonal winds at the MLT show reversal approximately 7 days before the reversal at stratosphere, indicating a downwards propagation of circulation disturbance in the middle atmosphere. Eastward zonal winds dominate the winter MLT, but during the 2002 winter there are many periods of westward winds observed compared to the other years. The SABER vertical temperature pro les indicate cooling of the MLT region during the SSW occurrence. Gravity wave horizontal phase velocities and horizontal wavelengths as seen by the SANAE imaging riometer are observed to reduce dramatically over SANAE during the occurrence of the stratospheric warming. The disturbance of the middle atmosphere during the Southern Hemisphere stratospheric warming in year 2002 winter preconditioned the region for gravity waves to propagate upward to the MLT. The potential energy of these gravity waves is observed to increase with height up until they reach the lower thermosphere. At the MLT they lose their energy, thus depositing their momentum, leading to the MLT cooling and mean wind reversal. Keywords: SSW, Planetary waves, Gravity waves, Stratosphere, MLT, SuperDARN radar, Mean wind, Temperature, Middle atmosphere, SANAE. / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2012.

No description available.

Thesis (Ph. D.)--University of Adelaide, Mawson Institute for Antarctic Research, 1990. / Copies of author's previously published articles inserted. Includes bibliographical references (leaves 219-226).

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [147]-157).

Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1977. / "March 1978." Vita. Includes bibliographical references (p. 167-170).

Thesis (Ph. D.)--University of British Columbia, 1996. / Includes bibliographical references (leaves 260-262).

abstract: The formation and stability of a slowly evolving zonal jet in 2-D flow with beta effect is analyzed using the model developed by Manfroi and Young in which the final governing equation was derived by means of a perturbation analysis of a barotropic vorticity equation with sinusoidal meridional mean flow. However in the original study the term β0, that represents the effect of large-scale Rossby waves, was dropped and was proceeded on a path of finding solutions for a simplified 1-D flow. The idea of this study is to understand the effects of the dropped term on the overall dynamics of the zonal jet evolution. For this purpose the system that is entirely deterministic with no additional forcing is solved by means of a standard finite difference scheme. The Numerical solutions are found for varying β0 and μ values where μ represents the bottom drag. In addition to this the criteria for the formation of zonal jets developed originally for the 1-D system is verified for the 2-D system as well. The study reveals the similarity in some of the results of the 1-D and the 2-D system like the merging of jets in the absence of bottom drag, formation of steady jets in presence of a non-zero bottom drag and the adherence to the boundary criteria for the formation of zonal jets. But when it comes to the formation of steady jets, a finite β0 value is required above which the solution is similar to the 1-D system. Also the jets formed under the presence of non-zero bottom drag seem wavy in nature which is different from the steady horizontal jets produced in the 1-D system. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2017

Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Meteorology. / Vita. / Bibliography: leaves 169-174. / Ph.D.