Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science / Bibliography: leaves 40-41. / by Eduardo Pantig Olaguer. / M.S.

The wintertime North-Atlantic exhibits enhanced circulation variability relative to other areas of the globe and is a key determinant of weather and climate in the highly populated regions of Europe and Eastern North America. Previous work has linked extreme stratospheric polar vortex and planetary wave heat flux events with variability of the North-Atlantic circulation. To elucidate the role of the stratosphere in driving variability of the North-Atlantic circulation, the goal of this thesis is to clarify the relationship between extreme planetary wave heat flux and vortex events and understand the dynamical mechanisms driving extreme stratospheric planetary wave heat flux events using an idealized model. The relationship between extreme stratospheric planetary wave heat flux and polar vortex events is clarified by comparing and contrasting their composite lifecycles using reanalysis data. Extreme negative heat flux events, defined as those less than the 5th percentile of the wintertime wave-1 distribution, involve stratospheric EP-flux divergence producing an acceleration of the vortex whereas extreme positive heat flux events, defined as those greater than the 95th percentile, involve stratospheric EP-flux convergence producing a deceleration of the vortex. Similar but smaller magnitude heat flux (22th and 78th percentile) events contribute to the development of longer-timescale vortex events. Negative heat flux events precede strong vortex events, showing that strong vortex events are true dynamical events involving wave-mean flow interaction. Conversely, positive heat flux events precede weak vortex events. The tropospheric jet shifts in the North-Atlantic that occur almost simultaneously with extreme stratospheric heat flux events are shown to be comparable if not larger than those that follow extreme vortex events for several weeks. Next, a dry-dynamical core model is configured to capture the lifecycle of extreme positive and negative heat flux events seen in reanalysis. The events are not captured using the standard model setup with idealized wave-1 topography. A modified control simulation captures the key ingredients of the events: 1) the extremes of the stratospheric eddy heat flux distribution, 2) the cross-spectral correlation and phase between the stratosphere and troposphere, 3) the evolution of the eddy heat flux and EP-flux divergence, 4) the stratospheric evolution of the zonal-mean flow, including the NAM, NAM time-tendency, potential temperature time-tendency and stratospheric wave geometry, and 5) the tropospheric evolution, including the high-latitude wave-1 geopotential height pattern and mid-latitude jet shift. Comparison between the model and reanalysis reveals that higher-order planetary wavenumbers play a role prior to the events. Finally, the dry-dynamical core model is used to examine the large-scale dynamical mechanisms driving extreme stratospheric negative heat flux events and their coupling with the tropospheric circulation. An ensemble spectral nudging methodology is used to isolate the role of: 1) the tropospheric wave-1 precursor, 2) the stratospheric zonal-mean flow and 3) the higher-order wavenumbers. The events are partially reproduced when nudging the wave-1 precursor and the zonal-mean flow whereas they are not reproduced when nudging either separately. In contrast, nudging the wave-1 precursor and the higher-order waves reproduces the events, including the evolution of the zonal-mean flow. Mechanism denial experiments show that the higher-order planetary wavenumbers drive the events by modifying the zonal-mean flow and through wave-wave interaction. Nudging all tropospheric wave precursors confirms they are the source of the stratospheric waves. Nudging all stratospheric waves reproduces the coupling with the tropospheric circulation. Taken together, the experiments show that extreme stratospheric negative heat flux events are consistent with downward wave coupling from the stratosphere to the troposphere.

Regions that have experienced recent successive cold winters such as the Northeast of North America and Siberia have endured critical social and economic impacts from anomalous low temperatures in recent years, despite warming global temperatures. It is well known that the Tropospheric Polar Vortex (TPV), or jet stream, is a primary influence on many mid-latitude winter weather patterns. However, the strong circumpolar westerlies that maximize at around 60° latitude just above the tropopause, known as the Stratospheric Polar Vortex (SPV), can affect tropospheric circulation and thus winter weather in the Northern Hemisphere. Strong upward propagating waves can affect the geographic extent and strength of the SPV resulting in a weakened polar vortex state, which can in turn bring persistent weather events to the mid-latitudes. Here, an index of SPV spatiotemporal variability is presented using observation based analysis of zonal wind and geopotential height to show changes in SPV behavior at a seasonal scale from 1950-2018. Utilizing the CMIP5 suite of global climate models, historical and projected simulations of the SPV's climatological extent and strength are analyzed from 1915 to the end of this century, taking into account models with enhanced stratospheric representation. Simulated results are largely consistent with trends in the observational data, which suggest continued increases in average SPV size throughout this century. If future SPV disturbances increase in frequency, there could be negative impacts in ecosystem and agricultural health, infrastructure damage, and to human safety. A more advanced understanding of SPV trends and anomalous events could improve forecasts of cold air outbreaks (CAOs) and severe or persistent winter weather.

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.

Thesis (Ph. D.)--University of Chicago, Dept. of Geophysical Sciences, August 1999. / Includes bibliographical references. Also available on the Internet.

Thesis (M.Sc.). / Written for the Dept. of Atmospheric and Oceanic Sciences. Title from title page of PDF (viewed 2008/12/10). Includes bibliographical references.

Thesis (Ed.D.)--Teachers College, Columbia University, 1995. / Typescript; issued also on microfilm. Sponsor: Warren E. Yasso. Dissertation Committee: O. Roger Anderson. Includes bibliographical references (leaves 95-109).

Thesis: Ph. D., Joint Program in Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 105-114). / The circulation of air in the stratosphere is important for the distribution of radiatively-important trace gases, such as ozone and water vapor, and other chemical species, including ozone-depleting chlorofluorocarbons. Age of air in the stratosphere is an idealized tracer with unique mathematical properties, which we exploit to derive a theory for the relationship of tracer observations to the stratospheric circulation. We show that the meridional age gradient is a measure of the global diabatic circulation, the total overturning strength through an isentropic surface, and test this time-dependent theory in a simple atmospheric general circulation model. We apply the theory to satellite data of sulfur hexafluoride (SF6 and nitrous oxide to derive the first observationally-based estimates of the global meridional overturning circulation strength at all levels in the stratosphere. These two independent global satellite data products agree to within 5% on the strength of the diabatic circulation in the lower stratosphere. We compare to re-analyses and find broad agreement in the lower stratosphere and disagreement (~ 100%) in the upper stratosphere. To understand the relationship between the diabatic circulation and other metrics of the circulation, we calculate it in a state-of-the-science atmospheric model and in three different reanalysis data products. The variability of the global diabatic circulation is very similar to one typical circulation metric, and it is correlated with total column ozone in the tropics and in Southern hemisphere mid latitudes in both a model and in reanalysis-data comparisons. Furthermore, we develop a metric for the mean adiabatic mixing, showing that it is related to the meridional age difference and the vertical gradient of age. We calculate this metric for a range of simple model runs to determine its utility as a measure of mixing. We find very little mixing of air into the tropics in the mid-stratosphere, and the vertical structure of mixing in the lower stratosphere and upper stratosphere varies among model runs and between hemispheres. A picture of global average stratospheric circulation could thus be obtained using age of air data, given reliable long-term records. / by Marianna Katherine Linz. / Ph. D.

Stationary wave theory elucidates the dynamics of the time mean zonally asymmetric component of the atmospheric circulation and separates it from the dynamics of the zonal mean climatological flow. This thesis focuses on the dynamics of stationary wave nonlinearity and its applications in stationary wave modelling and the stationary wave response to climate change. Stationary wave nonlinearity describes the self-interaction of stationary waves and is important in maintaining the observed zonally asymmetric atmospheric general circulation. Stationary wave nonlinearity is examined in quasi-geostrophic barotropic dynamics in both the presence and absence of transient waves. Stationary wave nonlinearity is shown to account for most of the difference between the linear and full nonlinear stationary waves, particularly if the zonal-mean flow adjustment to the stationary waves is taken into account. Wave activity analysis shows that stationary wave nonlinearity in this setting is associated with Rossby wave critical layer reflection. A time-integration type nonlinear stationary wave modelling technique is tested in this simple barotropic setting and is shown to be able to predict stationary wave nonlinearity and capture the basic features of the full nonlinear stationary wave. A baroclinic nonlinear stationary wave model is then developed using this technique and is applied to the problem of the stationary wave response to climate change. Previous stationary wave modelling has largely focused on the tropospheric circulation, but the stationary wave field extends into the stratosphere and plays an important dynamical role there. This stationary wave model is able to represent the stratospheric stationary wave field and is used to analyze the Northern Hemisphere stationary wave response to climate change simulated by the Canadian Middle Atmosphere Model (CMAM). In the CMAM simulation changes to the zonal mean basic state alone can explain much of the stationary wave response, which is largely controlled by changes of the zonal mean circulation in the Northern Hemisphere subtropical upper troposphere. However, details of the stratospheric wave driving response are also sensitive to other aspects of the zonal-mean response and to the heating response. Many climate change related effects appear to contribute robustly to an increased wave activity flux into the stratosphere.