Though the least squares technique has many advantages, its possible limitations as applied in the atmospheric sciences have not yet been fully explored in the literature. The assumption that the atmosphere responds either in phase or out of phase to the solar input is ubiquitous. However, our analysis found this assumption to be incorrect. If not properly addressed, the possible consequences are bias in the linear trend coefficient and attenuation of the solar response coefficient. Using USU Rayleigh lidar temperature data, we found a significant phase offset to the solar input in the temperatures that varies ±5 years depending on altitude. In addition to introducing a phase offset into the linear regression model, we argue that separating what we identify as the solar-noise is to be preferred because (1) the solar-noise can contain important physical information, (2) its omission could lead to spurious conclusions about the significance of the solar-proxy coefficient, and (3) its omission could also bias the solar proxy coefficient. We also argue that the Mt. Pinatubo eruption caused a positive temperature perturbation in our early mesopause temperatures, exerting leverage on the linear trend coefficient. In the upper mesosphere, we found a linear cooling trend of greater than -1.5 K/year, which is possibly exaggerated because of leverage from the earlier temperatures and/or collinearity. In the middle mesosphere we found a cooling trend of -1 K/year to near zero. We use the autocorrelation coefficient of the model residuals as a physical parameter. The autocorrelation can provide information about how strongly current temperatures are affected by prior temperatures or how quickly a physical process is occurring. The amplitudes and phases of the annual oscillation in our data compare favorably with those from the OHP and CEL French lidars, as well has the HALOE satellite instrument measurements. The semiannual climatology from the USU temperatures is similar to that from the HALOE temperatures. We also found that our semiannual and annual amplitudes and phases compare favorably with those from the HALOE, OHP, and CPC data.

Look up! Travelling over your head in the air are waves. They are present all the time in the atmosphere all over the Earth. Now imagine throwing a small rock in a pond and watching the ripples spread out around it. The same thing happens in the atmosphere except the rock is a thunderstorm, the wind blowing over a mountain, or another disturbance. As the wave (known as a gravity wave) travels upwards the thinning air allows the wave to grow larger and larger. Eventually the gravity wave gets too large – and like waves on the beach – it crashes causing whitewater or turbulence. If you are in the shallow water when the ocean wave crashes or breaks, you would feel the energy and momentum from the wave as it pushes or even knocks you over. In the atmosphere, when waves break they transfer their energy and momentum to the background wind changing its speed and even direction. This affects the circulation of the atmosphere. These atmospheric waves are not generally visible to the naked eye but by using special instruments we can observe their effects on the wind, temperature, density, and pressure of the atmosphere. This dissertation discusses the use of a specialized camera to study gravity waves as they travel through layers of the atmosphere 50 miles above the Andes Mountains and change the temperature. First, we introduce the layers of the atmosphere, the techniques used for observing these waves, and the mathematical theory and properties of these gravity waves. We then discuss the camera, its properties, and its unique feature of acquiring temperatures in the middle layer of the atmosphere. We introduce the observatory high in the Andes Mountains and why it was selected. We will look at the nightly fluctuations (or willy-nillyness) and long-term trends from August 2009 until December 2017. We compare measurements from the camera with similar measurements obtained from a satellite taken at the same altitude and measurements from the same camera when it was used at a different location, over Hawaii. Next, we measure the amount of change in the temperature and compare it to a nearby location on the other side of the Andes Mountains. Finally, we look for a specific type of gravity wave caused by wind blowing over the mountains called a mountain wave and perform statistics of those observed events over a period of six years. By understanding the changes in atmospheric properties caused by gravity waves we can learn more about their possible sources. By knowing their sources, we can better understand how much energy is being transported in the atmosphere, which in turn helps with better weather and climate models. Even now –all of this is going on over your head!

The global analysis fields of the Met Office stratospheric assimilated data set have been investigated. Systematic biases for select years were identified through val- idation with independent satellite observations. Particular attention was given to analyses from January 2005 to October 2009 produced from a 50 level (L50) configuration of the UM with model lid at ∼0.1 hPa, and the impact on analyses fields from November 2009 to September 2010 when the middle atmospheric configuration of the UM was extended to ∼0.01 hPa using 70 levels (L70). Validation results from both the L50 and L70 analyses show that largest tem- perature biases occur at polar latitudes approaching the model lid in the meso- sphere, exhibiting a clear seasonal cycle. Here cold biases in the winter season of the L50 analyses and warm biases in the summer season of the L70 analyses would strongly suggest that the mean meridional circulation in the mesosphere is underestimated, and that small scale gravity wave forcing supplied by the op- erational Ultra Simple Spectral Parameterisation (USSP) scheme is insufficient. Based on the above validation results numerous experiments were conducted to investigate the temperature response in the mesosphere to increased gravity wave forcing. Such experiments concentrated on tuning the energy scale factor (β) in the USSP scheme and the application of a momentum conserving ”opaque” lid. Furthermore, the impact of developing the USSP scheme to include direct heating from gravity wave induced turbulent dissipation was also investigated. Maximum temperature responses in the summer polar upper mesosphere of ∼22 K were found when increasing the standard value of β=0.1 to β=0.14 combined with the application of an opaque lid. Magnitudes of direct heating rates due to gravity wave turbulent dissipation diagnosed via the USSP scheme were found to be consistent with previous estimates. However applying such heating would most likely have a negative impact on the L70 analyses, which already display warm biases in the upper mesosphere, strongly suggesting that additional phys- ical processes such as eddy diffusion must also be accounted for when applying direct heating from gravity wave breaking.

Am Geophysikalischen Observatorium Collm, das 1932 als experimentelle Basis des Geophysikalischen Institutes der Universität Leipzig für meteorologische, seismologische und geomagnetische Messungen von Professor LUDWIG WEICKMANN errichtet worden war, wurde 1956 in Vorbereitung des Internationalen Geophysikalischen Jahres (International Geophysical Year [IGY]) mit hochattnosphärischen Messungen begonnen. Seit 1959 liegt der Schwerpunkt auf Windmessungen im Höhenbereich der oberen Mesosphäre / unteren Thermosphäre (80 - 110 km). Die Meß- und Auswertemethode wurde in den vergangenen Jahrzehnten aus sehr bescheidenen Anfängen heraus theoretisch und experimentell so entwickelt, daß derzeit eine vollautomatische komplexe Apparatur zur quasi-kontinuierlichen Windmessung in drei Referenzpunkten über Mitteleuropa (gegenseitige Entfernung 200 km) zur Verfügung steht, die die Momentanwerte des Windes nach Richtung und Geschwindigkeit mißt, die zugehörige Höhe feststellt, Mittelwerte bildet, Grund- und Gezeitenwind voneinander trennt und Höhen-Wind-Profile über vorgebbare Zeitabschnitte rechnet, aus denen letztendlich Höhen-Zeit-Schnitte der Windfeldparameter konstruiert werden können. Die vorliegende Arbeit skizziert die einzelnen Etappen dieser Entwicklung, berichtet von Problemen und ihrer Lösung und gibt Beispiele von Windfeldanalysen aus dem Jahre 1992. / The Collm Geophysical Observatory was founded by Professor L. WEICKMANN in 1932 as an experimental base of Leipzig University's Geophysical Institute for meteorological, seismological and geomagnetic observations. In 1956 as a preparation for the Internal Geophysical Year (IGY) we began with high-atmosphere measurements, and since 1959 wind measurements in the height range of the upper mesosphere / lower thennosphere (80 - 110 km) have been emphasized. During the past decades the method of measuring and analysing was developped theoretically and experimentally from primitive Starts so far, that at present a fully automatic and complex equipment with quasi-continuous measurements of the wind at three reference points within Central Europe (mutual distance 200 km) is available. These devices measure the instantaneous data of the wind according to direction and velocity, ascertain the corresponding height, calculate averages, separate the tidal wind components from the prevailing wind, and compute height wind-profiles for adjustable periods of time, from which height-time cross section of the wind field parameters can be finally constructed. The following paper outlines the particular stages of this development, informs about problems and their solution, and offers examples of wind field analyses for 1992.

Gravity waves play a fundamental role in driving the large-scale circulation of the atmosphere. They are influenced both by the variation in their sources and the filtering effects of the winds they encounter as they ascend through the atmosphere. In this thesis we present new evidence that gravity waves play a key role in coupling the troposphere, stratosphere and mesosphere. In particular, we examine the connection of gravity waves to two important large-scale oscillations that occur in the atmosphere, namely the Madden-Julian Oscillation (MJO) in the troposphere and the Mesospheric Semi-Annual Oscillation (MSAO). We present the first ever demonstration that the MJO acts to modulate the global field of gravity waves ascending into the tropical stratosphere. We discover a significant correlation with the MJO zonal-wind anomalies and so suggest that the MJO modulates the stratospheric gravity-wave field through a critical-level wave-filtering mechanism. Strong evidence for this mechanism is provided by consideration of the winds encountered by ascending waves. The Ascension Island meteor radar is used for the first time to measure momentum fluxes over the Island. These measurements are then used to investigate the role of gravity-wave in driving a dramatic and anomalous wind event that was observed to occur during the first westward phase of the MSAO in 2002. Gravity waves are shown to play an important role in driving this event, but the observations presented here also suggest that the current theory of the mechanism describing these anomalous mesospheric wind events is not valid. Both of these studies highlight the critical importance of gravity waves to the dynamics of the atmosphere and highlight the need for further work to truly understand these waves, their processes and their variability.

An important property of the Earth's atmosphere is its ability to support wave motions, and indeed, waves exist throughout the Earth's atmosphere at all times and all locations. What is the importance of these waves? Imagine standing on the beach as water waves come crashing into you. In this case, the waves transport energy and momentum to you, knocking you off balance. Similarly, waves in the atmosphere crash, known as breaking, but what do they crash into? They crash into the atmosphere knocking the atmosphere off balance in terms of the winds and temperatures. Although the Earth's atmosphere is full of waves, they cannot be observed directly; however, their effects on the atmosphere can be observed. Waves can be detected in the winds and temperatures, as mentioned above, but also in pressure and density. In this dissertation, three different studies of waves, known as gravity waves, were performed at three different locations. For these studies, we investigate the size of the waves and in which direction they move. Using specialized cameras, gravity waves were observed in the middle atmosphere (50-70 miles up) over Alaska (for three winter times) and Norway (for one winter time). A third study investigated gravity waves at a much higher altitude (70 miles on up) using radar data from Alaska (for three years). These studies have provided important new information on these waves and how they move through the atmosphere. This in turn helps to understand in which direction these waves are crashing into the atmosphere and therefore, which direction the energy and momentum are going. Studies such as these help to better forecast weather and climate.

In-situ composition measurements of the mesosphere/lower thermosphere (MLT) are challenging; this region is only accessible via high-speed sounding rockets, ambient pressures extend into the 10-3 Torr range, and particles of interest range in mass from electrons to meteoric smoke and dust particles. Time-of-flight mass spectrometers (TOF-MS) are capable of making fast, accurate measurements over a wide mass range. However, since they rely on pressure-sensitive microchannel plate (MCP) detectors and high voltages, they have rarely been applied at these altitudes. A new TOF-MS for making in-situ composition measurements in the MLT has been developed at the Space Dynamics Laboratory. This instrument employs modest acceleration potentials and a pressure-tolerant MCP detector. A Bradbury-Nielsen gate is used to produce short, well-defined ion pulses to reduce the temporal and spatial uncertainty of sampled ions. A prototype TOF-MS was constructed and used to demonstrate TOF-MS technology under conditions relevant to in-situ MLT measurements. Operational boundaries and capabilities of this new instrument were identified through laboratory experiments combined with computer modeling. The prototype instrument achieved a maximum resolution of 100 at m/z 40 (Ar), sufficient to resolve major atmospheric species of interest. During experiments at elevated pressures, the MCP detector maintained low background count rates (/second) at pressures as high as 10-3 Torr. A novel getter-based vacuum system was evaluated for use with the new TOF-MS, and a computer model was developed to simulate instrument pressure during a rocket flight. Results from these experiments suggest that when combined with an appropriately sized sampling aperture, this pumping system can extend the measurement range of the instrument to lower altitudes by 10 – 20 km, compared to an unpumped instrument. A computer model was developed to study the effects of critical operating parameters on instrument performance; the most important factor affecting resolution was found to be the initial energy spread of sampled ions. Sensitivity and number density measurement analyses suggest the new instrument will measure major species in the MLT at better than 10% uncertainty. Composition measurements made with the new TOF-MS will contribute to a better understanding of the MLT.

<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>

<p>This thesis concerns the fate of the meteoric smoke in the Middle Atmosphere, and its effect on ice phenomena such as noctilucent clouds (NLC) and polar stratospheric clouds (PSC). </p><p>The potential role of NLC as tracer for mesospheric processes and variability, and as a tool for monitoring this remote and inaccessible region, has generated substantial interest within the scientific community. The nucleation of ice in such a dry environment is not trivial. Supersaturation is considered too low for homogeneous nucleation. Hence, pre-existing condensation nuclei are deemed necessary, with smoke particles having long been considered the most likely candidate. Here we show that the atmospheric circulation transports meteoric smoke particles away from the polar region before they coagulate large enough to efficiently act as ice condensation nuclei. We also show that the charging of meteoric smoke, in combination with deviations from the mean thermal state, may solve this dilemma by significantly altering the ice nucleation properties of smoke. Thus, while it is highly questionable whether neutral smoke can provide sufficient amounts of condensation nuclei for ice formation at the polar summer mesopause, charged meteoric smoke proves to be a promising candidate to explain mesospheric ice phenomena as we observe them.</p><p> We further show that the bulk of the meteoric material is transported to the Arctic winter stratosphere, yielding significantly higher concentrations of meteoric smoke in the region of PSC nucleation than has previously been believed. Our new predictions of meteoric smoke in this region may thus shed new light on open questions relating to PSC nucleation.</p>

<p>Water vapour is the most important greenhouse gas and plays a fundamental role in the climate system and for the chemistry of the Earth's atmosphere. This thesis presents observations of water vapour in the middle atmosphere with a particular focus on the mesosphere. The majority of these observations presented in this thesis have been performed by the Swedish satellite Odin, providing global observations since 2001. Further observations come from the Hygrosonde-2 campaign in December 2001 based on balloon and rocket-borne measurements. A general overview of Odin's water vapour measurements in the middle atmosphere is given. The optimisation of the mesospheric water vapour retrieval is presented in detail.</p><p>The analysis of the observations has focused mainly on different dynamical aspects utilising the characteristic of water vapour as a dynamical tracer in the middle atmosphere. One application is the mesospheric part of the semi-annual oscillation (SAO). The observations reveal that this oscillation is the dominant pattern of variability between 30°S and 10°N in the mesosphere up to an altitude of 80 km. Above 90 km the SAO is dominating at all latitudes in the tropics and subtropics. It is shown that the SAO exhibits a distinct phase change between 75 km and 80 km in the tropical region.</p><p>This thesis also presents the first satellite observations of water vapour in the altitude range between 90 km and 110 km, extending the observational database up into the lower thermosphere. In the polar regions water vapour exhibits the annual maximum during winter time above 95 km, mainly caused by upwelling during this season. This behaviour is different from that observed in the subjacent part of the mesosphere where the annual maximum occurs during summer time.</p><p>The Hygrosonde-2 campaign provided a high resolution measurement of water vapour in the vicinity of the polar vortex edge. This edge prevents horizontal transport causing different water vapour characteristics inside and outside the polar vortex. The observations show that this separating behaviour extends high up into the mesosphere. Small scale transitions in the Hygrosonde-2 profile between conditions inside and outside the vortex coincided with wind shears caused by gravity waves.</p>