This thesis provides highlights of the atmospheric research conducted during the program of studies 2003-07. The theme is variability of the winds at mesospheric heights (60-100 km) due to Planetary Waves (PW, 2-30 days) over middle and high latitudes. Considerable energy and momentum are transported by atmospheric waves, and their global characteristics are required to understand many phenomena and explain coupling processes within the atmosphere. The vertical propagation of PW from the upper troposphere to the mesosphere is investigated by applying the Morlet wavelet and wave number analysis to the MetO (United Kingdom Meteorological Office) stratospheric assimilated fields, TOMS total (column) ozone, and Medium Frequency (MFR) and Meteor Wind (MWR) radar measurements. The results show that large-scale eastward propagating PW dominate at tropopause and low stratospheric heights, while westward PW become comparable or even stronger in the upper stratosphere and above during months other than summer. There are also strong seasonal dependences of the PW activity in each of the stratospheric and mesospheric regions, which are attributed, at least partially, to the influence of the background wind on PW propagation. Longitudinal variations in PW activity are explained by longitudinal variations in these winds.<p>During summer (westward zonal winds) PW activity is reduced in the stratosphere and only relatively fast westward propagating PW, such as quasi 2-day wave (Q2DW), are able to reach mesospheric heights from below. The results obtained using 14 years of MFR data at Saskatoon provide a unique climatology (70-100 km) of this wave: in addition to summer activity the Q2DW is also present at low mesospheric heights in winter, especially when the eastward winds are weak; there are significant interannual variations in Q2DW activity in both seasons. Strong latitudinal and longitudinal differences in Q2DW occurrence and amplitude are shown from the comparisons of wind data at several stations.<p>During winter, when zonal winds are eastward, the PW coupling between stratosphere and mesosphere is stronger than during other seasons. Detailed data analysis has been performed for the Arctic winter of 2004/05, for which the stratospheric state is described using conventional zonal mean parameters as well as the newer Q-diagnostic. Spectral analyses for this winter show relatively weak PW activity at stratospheric and mesospheric heights and strong latitudinal and longitudinal differences of mean winds and PW characteristics consistent with the form and location of the polar vortex. <p>In addition to the vertical coupling it has also been shown that weaker horizontal inter-hemispheric coupling occurs during equinoctial months, when eastward winds dominate globally. It is demonstrated that with favorable conditions, planetary waves with 10, 16 and 25 day periods penetrate to the opposite hemisphere.

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Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, Discipline of Physics, 2005. / Includes author's previously published papers. Includes bibliographical references. Also available in a print form.

Thesis (M.Sc.)--York University, 2004. Graduate Programme in Earth and Space Science. / Typescript. Includes bibliographical references (leaves 164-174). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss&rft%5Fval%5Ffmt=info:ofi/fmt:kev:mtx:dissertation&rft%5Fdat=xri:pqdiss:MQ99373

This thesis presents observations of the 2-day planetary wave in the stratosphere, mesosphere and lower thermosphere. These observations were made using two ground-based meteor radars at polar latitudes and the satellite-borne microwave limb sounder (MLS) on the NASA Aura satellite. There have been relatively few observations of the 2-day wave at polar latitudes made using ground-based radars. This is particularly so in the Antarctic. Measurements of summertime and wintertime polar 2-day waves in the mesosphere and lower thermosphere (MLT) region were made using identical meteor radars at the conjugate geographical latitudes of Rothera (68!S, 68!W) in the Antarctic and Esrange (68!N, 21!E) in Arctic Sweden. This allows accurate quantification of the differences in the nature and seasonal variability of the 2day wave between the two polar regions. A clear seasonal variability is evident with the maximum amplitudes occurring during the summer months in both hemispheres. However, significant differences are found in the behaviour of the summertime wave between the two polar regions. In particular, wave activity is shorter lived but of larger amplitude in the Antarctic. These differences are suggested to be partly due to the different background winds of the two polar regions and possible differences in the component zonal wavenumbers in the northern and southern hemispheres. These radar studies have excellent spatial, height and time resolution but cannot resolve the component zonal wavenumbers of the 2-day wave. Therefore, Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) measurements of atmospheric temperature were used to investigate the climatology and interhemispheric differences of the different zonal wavenumbers (westward propagating zonal wavenumbers 2, 3 and 4) that compose the 2-day wave “complex”. This study demonstrates that the wave is dominated by different wavenumbers in the northern and southern hemisphere and that some of the interhemispheric differences observed in ground-based studies can be explained by the seasonal variability of these different zonal wavenumbers. These satellite studies led to participation in a multi-technique international collaboration to study the short-term variability of the summertime 2-day wave. Observations made in the northern hemisphere at mid-latitudes revealed that there are typically three peaks of enhanced 2-day wave amplitude during the summer, probably originating from a combination of baroclinic instability and critical wind speed.

Thesis (Ph. D.)--University of Nevada, Reno, 2008. / "August, 2008." Includes bibliographical references (leaves 109-115). Online version available on the World Wide Web.

L'atmosphère moyenne de la Terre est un laboratoire naturel pour les études de la dynamique géophysique des fluides et de l'optique pour la mesure des gaz. Les recherches dans cette région ont longtemps été limitées par le manque d'observations à long terme susceptibles de couvrir l'ensemble de la région, de la troposphère à la haute mésosphère et à la thermosphère inférieure. Les dernières décennies ont vu la construction de nombreux observatoires au sol et le lancement d'instruments par satellite dans le but de fournir les mesures nécessaires pour comprendre la chimie, la dynamique et les changements climatiques à long terme de l'atmosphère moyenne. La télédétection atmosphérique, tant au sol que dans l’espace, présente des avantages et des inconvénients évidents. Les premiers étant capables de fournir des mesures bien calibrées et à haute résolution sur un seul site et les derniers permettant une couverture globale au prix de la résolution et d'un certain degré de certitude lors de l'étalonnage. Pour ce travail, nous utilisons des mesures de température obtenues à l'aide d'une technique de télédétection au sol basée sur le lidar à diffusion de Rayleigh et nous effectuons des comparaisons systématiques avec les profils de température générés à l'aide de trois instruments de télédétection passif basés sur des satellites: Sondeur Micro-onde sur satellite Aura (MLS). Sondage de l'atmosphère par radiométrie des émissions à large bande (SABER) et surveillance mondiale de l'ozone par occultation d'étoiles (GOMOS).Ce manuscrit a trois résultats principaux: 1a) Résultats de plusieurs améliorations de l’algorithme de la température lidar, qui ont permis de corriger un bias froid sur les températures mésosphériques jusqu’à 20 K à 90 km. 1b) Meilleur accord entre les températures du lidar et les profils de température SABER et MLS entre 70 km et 90 km. 1c) Une validation croisée entre les températures d’un lidar de température de Rayleigh et d’un lidar d’ozone co-localisés, qui donne confiance en la stabilité de la technique du lidar et justifie l’utilisation de la température par lidar comme base de données de référence pour la validation par satellite. 2a) Présentation d’une comparaison décennale entre les températures lidar validées et les températures produites par SABER et MLS. 2b) Nous montrons un biais froid dans les mesures satellitaires par rapport au lidar (-6 K pour SABER et -17 K pour MLS) dans la région de stratopause, un biais chaud (6 K près de 60 km) dans la mésosphère d’été, et un biais structuré verticalement pour MLS (-4 à 4 K) qui couvre la moyenne atmosphère. 2c) Nous réduisons l'ampleur du biais en dècallant verticalement la hauteur de la stratopause satellite et constatons une amélioration de la comparaison de température lidar-satellite qui en résulte. Ce résultat a des implications importantes pour la notification des températures des satellites en fonction de la hauteur géopotentielle. 3a) La comparaison des profils de température lidar avec la nouvelle base de données de température GOMOS montre que les altitudes géométriques des satellites peuvent être mieux estimées par les techniques d'occultaion que par l'inférence des niveaux de pression à partir des données radiométriques 3b) de l'effet des marées sur les comparaisons de température entre lidar et satellite lorsque Le passage supérieur du satellite est décalé dans le temps par rapport à la mesure lidar et peut être de l'ordre de 2 à 4 K en fonction de la phase de l'heure solaire. / The Earth's middle atmosphere is a pristine natural laboratory for the study of geophysical fluid dynamics and optics in neutral gasses. Research in this region has long been limited by a lack of long-term observations which are capable of covering the entire region from the troposphere to the upper mesosphere and lower thermosphere. Past decades have seen the construction of many ground based observatories and launches of satellite based instruments in an effort to provide the measurements needed to understand the chemistry, dynamics, and long-term climactic changes in the middle atmosphere. Both ground-based and space-based atmospheric remote sensing have clear strengths as well as limitations; the former being able to provide high resolution, well calibrated measurements at a single site and the latter allowing for global coverage at the cost of resolution and some degree of certainty in calibration. For this work we are using temperature measurements produced from a Rayleigh-scatter lidar ground-based remote sensing technique and making systematic comparisons to temperature profiles produced from three passive scanning satellite-based remote sensing instruments: Microwave Limb Sounder on the Aura satellite (MLS), Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), and Global Ozone Monitoring by Occultation of Stars (GOMOS).This manuscript has three main results: 1a) Results of several improvements to the lidar temperature algorithm resulting in a cooling of the mesospheric temperatures by up to 20 K at 90 km. 1b) Better agreement between the cooled lidar temperatures and temperature profiles from SABER and MLS between 70 km and 90 km. 1c) A cross-validation between temperatures from a co-located Rayleigh temperature lidar and ozone lidar which provides confidence in the stability of the lidar technique and justification for the use of lidar temperatures as a reference database for satellite validation. 2a) Presentation of a decadal comparison between the validated lidar temperatures and the temperatures produced by SABER and MLS. 2b) We show a cold bias in the satellite measurements with respect to the lidar (-6 K for SABER and -17 K for MLS) in the stratopause region, a warm bias (6 K near 60 km) in the summer mesosphere, and a vertically structured bias for MLS (-4 to 4 K) which spans the middle atmosphere. 2c) We reduce the magnitude of the bias by vertically shifting the height of the satellite stratopause and see an improvement in the resulting lidar-satellite temperature comparison. This result has important implications for the reporting of satellite temperatures as a function of geopotential height. 3a) Comparison of lidar temperature profiles with the newly created GOMOS temperature data base shows that satellite geometric altitudes can be better estimated by occultaion techniques than by inference of pressure levels from radiometric data 3b) The effect of tides on lidar to satellite temperature comparisons when the satellite overpass is temporally offset from the lidar measurement can be on the order of 2 to 4 K depending on the phase of the solar hour.

<p>The Earth's middle atmosphere at about 10-100 km has shown a substantial sensitivity to human activities. First, the ozone layer has been reduced since the the early 1980s due to man-made emissions of halogenated hydrocarbons. Second, the middle atmosphere has been identified as a region showing clear evidence of climate change due to increased emissions of greenhouse gases. While increased CO₂abundances are expected to lead to a warmer climate near the Earth's surface, observations show that the middle atmosphere has been cooling by up to 2-3 degrees per decade over the past few decades. This is partly due to CO₂ increases and partly due to ozone depletion.</p><p>Predicting the future development of the middle atmosphere is problematic because of strong feedbacks between temperature and ozone. Ozone absorbs solar ultraviolet radiation and thus warms middle atmosphere, and also, ozone chemistry is temperature dependent, so that temperature changes are modulated by ozone changes.</p><p>This thesis examines the middle atmospheric response to a doubling of the atmospheric CO₂ content using a coupled chemistry-climate model. The effects can be separated in the intrinsic CO₂-induced radiative response, the radiative feedback through ozone changes and the response due to changes in the climate of the underlying atmosphere and surface. The results show, as expected, a substantial cooling throughout the middle atmosphere, mainly due to the radiative impact of the CO₂ increase. Model simulations with and without coupled chemistry show that the ozone feedback reduces the temperature response by up to 40%. Further analyses show that the ozone changes are caused primarily by the temperature dependency of the reaction O+O₂+M->O₃+M. The impact of changes in the surface climate on the middle atmosphere is generally small. In particular, no noticeable change in upward propagating planetary wave flux from the lower atmosphere is found. The temperature response in the polar regions is non-robust and thus, for the model used here, polar ozone loss does not appear to be sensitive to climate change in the lower atmosphere as has been suggested recently. The large interannual variability in the polar regions suggests that simulations longer than 30 years will be necessary for further analysis of the effects in this region.</p><p>The thesis also addresses the long-standing dilemma that models tend to underestimate the ozone concentration at altitudes 40-75 km, which has important implications for climate change studies in this region. A photochemical box model is used to examine the photochemical aspects of this problem. At 40-55 km, the model reproduces satellite observations to within 10%, thus showing a substantial reduction in the ozone deficit problem. At 60-75 km, however, the model underestimates the observations by up to 35%, suggesting a significant lack of understanding of the chemistry and radiation in this region.</p>

The Earth's middle atmosphere at about 10-100 km has shown a substantial sensitivity to human activities. First, the ozone layer has been reduced since the the early 1980s due to man-made emissions of halogenated hydrocarbons. Second, the middle atmosphere has been identified as a region showing clear evidence of climate change due to increased emissions of greenhouse gases. While increased CO2 abundances are expected to lead to a warmer climate near the Earth's surface, observations show that the middle atmosphere has been cooling by up to 2-3 degrees per decade over the past few decades. This is partly due to CO2 increases and partly due to ozone depletion. Predicting the future development of the middle atmosphere is problematic because of strong feedbacks between temperature and ozone. Ozone absorbs solar ultraviolet radiation and thus warms middle atmosphere, and also, ozone chemistry is temperature dependent, so that temperature changes are modulated by ozone changes. This thesis examines the middle atmospheric response to a doubling of the atmospheric CO2 content using a coupled chemistry-climate model. The effects can be separated in the intrinsic CO2-induced radiative response, the radiative feedback through ozone changes and the response due to changes in the climate of the underlying atmosphere and surface. The results show, as expected, a substantial cooling throughout the middle atmosphere, mainly due to the radiative impact of the CO2 increase. Model simulations with and without coupled chemistry show that the ozone feedback reduces the temperature response by up to 40%. Further analyses show that the ozone changes are caused primarily by the temperature dependency of the reaction O+O2+M-&gt;O3+M. The impact of changes in the surface climate on the middle atmosphere is generally small. In particular, no noticeable change in upward propagating planetary wave flux from the lower atmosphere is found. The temperature response in the polar regions is non-robust and thus, for the model used here, polar ozone loss does not appear to be sensitive to climate change in the lower atmosphere as has been suggested recently. The large interannual variability in the polar regions suggests that simulations longer than 30 years will be necessary for further analysis of the effects in this region. The thesis also addresses the long-standing dilemma that models tend to underestimate the ozone concentration at altitudes 40-75 km, which has important implications for climate change studies in this region. A photochemical box model is used to examine the photochemical aspects of this problem. At 40-55 km, the model reproduces satellite observations to within 10%, thus showing a substantial reduction in the ozone deficit problem. At 60-75 km, however, the model underestimates the observations by up to 35%, suggesting a significant lack of understanding of the chemistry and radiation in this region.