The Madden-Julian oscillation (MJO) and the quasi-biennial oscillation (QBO) are two key modes of variability in the tropical atmosphere. The MJO, characterized by propagating, planetary-scale signals in convection and winds, is the main source of subseasonal variability and predictability in the tropics. The QBO is a ~28-month cycle in which the tropical stratospheric zonal winds alternate between easterly and westerly regimes. Via thermal wind balance these winds induce temperature anomalies, and both wind and temperature signals reach the tropopause. Recent observational results show a remarkably strong link between the MJO and the QBO during boreal winter: the MJO is stronger and more predictable when QBO winds in the lower stratosphere are easterly than when winds are westerly. Despite its important implications for MJO theory and prediction, the physical processes driving the MJO-QBO interaction are not well-understood. In this thesis, we use a hierarchy of models – including a cloud-resolving model, a forecast model, and a global climate model – to examine whether models can reproduce the MJO-QBO link, and better understand the possible mechanisms driving the connection. Based in part on our modeling findings, we further explore observed QBO temperature signals thought to be important for the MJO-QBO link. After providing necessary background and context in the first two chapters, the third chapter looks at the MJO-QBO link in a small-domain, cloud-resolving model. The model successfully simulates convection associated with two MJO events that occurred during the DYNAMO field campaign. To examine the effect of QBO, we add various QBO temperature and wind anomalies into the model. We find that QBO temperature anomalies alone, without wind anomalies, qualitatively affect the model MJO similarly to the observed MJO-QBO connection. QBO wind anomalies have no clear effect on the modeled MJO. We note however that the MJO response is quite sensitive to the vertical structure of the QBO temperature anomalies, and for realistic temperature signals the model response is very small. In the fourth chapter, we look at the MJO-QBO link in a state-of-the-art global forecast model with a good representation of the MJO. We conduct 84 hind-cast experiments initialized on dates across winters from 1989-2017. For each of these dates, we artificially impose an easterly and a westerly QBO in the stratospheric initial conditions, and examine the resulting changes to the simulated MJO under different stratospheric states. We find that the effect of the QBO on the model MJO is of the same sign as observations, but is much smaller. A large sample size is required to capture any QBO signal, and tropospheric initial conditions seem more important than the stratosphere in determining the behavior of the simulated MJO. Despite the weak signal, we find that simulations with stronger QBO temperature anomalies have a stronger MJO response. In the fifth chapter, we conduct experiments in recent versions of a NASA general circulation model. We find that a version with a high vertical resolution generates a reasonable QBO and MJO, but has no MJO-QBO link. However, this model has weaker-than-observed QBO temperature anomalies, which may explain the lack of an MJO impact. To explore this potential bias, we impose the QBO by nudging the model stratospheric winds towards reanalysis, leading to more realistic simulation of QBO temperature anomalies. Despite this, the model still fails to show a strong MJO-QBO link across several ensemble experiments and sensitivity tests. We conclude with discussion of possible reasons why the model fails to capture the MJO-QBO connection. The sixth chapter examines QBO temperature signals in a range of observational and reanalysis datasets. In particular, we are motivated by two elements of the MJO-QBO relationship which are especially puzzling: the seasonality (i.e. that the MJO-QBO link is only significant in boreal winter) and long-term trend (i.e. that the MJO-QBO link seems to have only emerged since the 1980s). By examining QBO temperature signals around the tropopause, we highlight changes to the strength and structure of QBO temperature anomalies both in boreal winter and in recent decades. Whether these changes are linked to the MJO-QBO relationship, and what more generally might explain them, is not presently clear. Overall, we demonstrate that capturing the MJO-QBO relationship in a variety of models is a difficult task. The majority of evidence indicates that QBO-induced temperature anomalies are a plausible pathway through which the QBO might modulate the MJO, but the theoretical description of precisely how these temperature anomalies may impact convection is lacking and likely more nuanced than the literature to date suggests. Most models show only a weak modulation of the MJO associated with changes in upper-tropospheric temperatures, and even when those temperature signals are artificially enhanced, comprehensive GCMs still fail to show a significant MJO-QBO connection. Our observational study indicates that temperature anomalies associated with the QBO show striking modulations on various timescales of relevance to the MJO-QBO link, but do not conclusively demonstrate a clear connection to the MJO. This difficulty simulating a strong MJO-QBO connection suggests that models may lack a key process in driving the MJO and coupling the tropical stratosphere and troposphere. It is further possible that the observed link may be in some regards different than is currently theorized -- for example statistically not robust, due to non-stratospheric processes, or driven by some mechanism that has not been suitably explored.

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Tidal variations of gravity were measured at fourteen sites in southeastern North America for periods of between 40 and 199 days. These measurements were used to obtain tidal gravity anomalies that indicate the geologic effect of the earth on tidal gravity. The tidal gravity anomaly is a vector quantity representing the difference between measured tidal gravity and the theoretical tidal gravity on a spherically symmetrical earth model subject to ocean tidal loading. The real part of the anomaly vectors include 8 values in the range of ±0.5 microgals, 4 values in the range of 0.5 to 1.5 microgals, 1 value of 1.5 to 2.5 microgals, and 1 other value in the range of -0.5 to -1.5 microgals, This grouping is consistent with a worldwide distribution of values from regions where the asthenosphere is at intermediate depth, the stress conditions are not excessive, and geothermal heat flow is approximately 60 mW/m². / Master of Science

Previous studies have identified longitudinal structures associated with non-migrating tides in observations of the upper neutral atmosphere of Mars. MAVEN’s Imaging Ultraviolet Spectrometer (IUVS) observations of the upper atmosphere reveal variations in density with longitude at altitudes of 130 – 200 km, and can be used to identify non-migrating tides. These observations cover higher latitudes and allow for studying the local time variations of tides. The analysis presented here shows that the longitudinal structure attributed to non-migrating tides is dominated by wavenumber 2 and wavenumber 3 harmonics during the periods studied. Comparison with the Neutral Ion and Gas Mass spectrometer (NGIMS) shows a good agreement in wave amplitudes observed for the first two cases studied. The temperatures and 𝑂/𝐶𝑂# ratios from the IUVS L2 data files revealed an anti-correlation with the densities which confirms the theoretical interpretation from the linear wave theory. / Master of Science / There are waves internal to all fluids in our surroundings and daily lives, such as sound waves. Waves in the atmosphere are also fluid in nature. In planetary atmospheres, the scale sizes of some of these waves become comparable to the size of the planet itself. The waves interact with the structure of the surface of Mars to form a certain type of wave called “Non-migrating tides”. These waves have been observed in multiple previous studies in the upper atmosphere of Mars (~130 km and above). These waves cause the atomic and molecular content of the upper atmosphere to be displaced in a particular manner to form a unique structure. The structures formed are observed on a scale that covers the entire planet. It is by studying these structures in the upper atmosphere that it is possible to characterize the waves that control them and thereby understand their nature and impact. Understanding how these waves vary helps spacecraft to gain better control over mechanisms required to swing them into the desired orbit (location). This study uses the observations from an instrument aboard the MAVEN mission and compares it to the observations from another instrument aboard the same mission. The results of this study demonstrate that these “Non-migrating” tides play a vital role in controlling the behavior of the upper atmosphere.

"My wound is geography. It is also my anchorage, my port of call." -Pat Conroy "Existential contents have their source in the landscape." -Willy Hellpach The preceding statements each reflect the significance of the landscape to one's existential being. The first embodies the veracity of the latter in its specificity of place, the tidal marshes and sea islands of the Carolinas. How do we come to know a place? What is the significance of one's participatory perception of the qualitative experience of the natural world? How can that awareness of the specificity of the surrounding physical environment be imparted through architecture? / Master of Architecture

Tide-topography coupling is important for understanding surface-tide energy loss, the intermittency of internal tides, and the cascade of internal-tide energy from large to small scales. Although tide-topography coupling has been observed and modeled for 50 years, the identification of surface and internal tides over arbitrary topography has not been standardized. Here, we begin by examining five surface/internal-tide decompositions and find that only one is (i) consistent with the normal-mode description of tides over a flat bottom, (ii) produces a physically meaningful depth-structure of internal-tide energy flux, and (iii) results in an established expression for internal-tide generation. Next, we examine the expression for internal-tide generation and identify how it is influenced by remotely-generated shoaling internal tides. We show that internal-tide generation is subject to both resonance and intermittency, and can not always be predicted from isolated regional models. Lastly, we quantify internal-tide generation and scattering on the Oregon Continental slope. First, we derive a previously unpublished expression for inter-modal energy conversion. Then we evaluate it using observations and numerical simulations. We find that the surface tide generates internal tides, which propagate offshore; while at the same time, low-mode internal tides shoal on the slope, scatter, and drive turbulent mixing. These results suggest that internal tides are unlikely to survive reflection from continental slopes, and that continental margins play an important role in deep-ocean tidal-energy dissipation. / Graduation date: 2011

Ocean tides worldwide have exhibited secular changes in the past century, simultaneous with a global secular rise in mean sea level (MSL). The combination of these two factors contributes to higher water levels, and may increase threats to coastal regions and populations over the next century. Equally as important as these long-term changes are the short-term fluctuations in sea levels and tidal properties. These fluctuations may interact to yield locally extreme water level events, especially when combined with storm surge. This study, presented in three parts, examines the relationships between tidal anomalies and MSL anomalies on yearly and monthly timescales, with a goal of diagnosing dynamical factors that may influence the long-term evolution of tides in the Pacific Ocean. Correlations between yearly averaged properties are denoted tidal anomaly trends (TATs), and will be used to explore interannual behavior. Correlations of monthly averaged properties are denoted seasonal tidal anomaly trends (STATs), and are used to examine seasonal behavior. Four tidal constituents are analyzed: the two largest semidiurnal (twice daily) constituents, M2 and S2, and the two largest diurnal (once daily) constituents, K1 and O1. Part I surveys TATs and STATs at 153 Pacific Ocean tide gauges, and discusses regional patterns within the entire Pacific Ocean. TATs with statistically significant relations between MSL and amplitudes (A-TATs) are seen at 89% of all gauges; 92 gauges for M2, 66 for S2, 82 for K1, and 59 for O1. TATs with statistically significant relations between tidal phase (the relative timing of high water of the tide) and MSL (P-TATs) are observed at 55 gauges for M2, 47 for S2, 42 for K1, and 61 for O1. Significant seasonal variations (STATs) are observed at about a third of all gauges, with the largest concentration in Southeast Asia. The effect of combined A-TATs was also considered. At selected stations, observed tidal sensitivity with MSL was extrapolated forward in time to the predicted sea level in 2100. Results suggest that stations with large positive combined A-TATs produce total water levels that are greater than those predicted by an increase in MSL alone, increasing the chances of high-water events. Conversely, negative correlation between sea level and tidal properties may mitigate somewhat against sea level rise; changes in total water levels in 2100 at stations with a negative combined A-TAT are less than that predicted by MSL rise alone. Climate change scenarios that take into account greater increases in MSL due to increased Antarctic ice melt show larger changes in total water levels over the same time period. Part II examines the mechanisms behind the yearly (TAT) variability in the Western Tropical Pacific Ocean. Significant amplitude TATs are found at more than half of 26 gauges for each of the two strongest tidal constituents, K1 (diurnal) and M2 (semidiurnal). For the lesser constituents analyzed (O1 and S2), significant trends are observed at ten gauges. Frictional mechanisms related to the El Nino Southern Oscillation (ENSO) are found to be important in influencing tides in the Western Pacific, as well as resonant triad interactions, a nonlinear coupling that exchanges energy between the M2, K1, and O1 tides. Both of these factors contribute to the observed tidal variability in the Solomon Sea region. Part III analyzes the seasonal behavior of tides (STATs) at twenty tide gauges in the Southeast Asian waters, which exhibit variation by 10-30% of mean tidal amplitudes. A barotropic ocean tide model that considers the seasonal effects of MSL, stratification, and geostrophic and Ekman velocity is used to explain the observed seasonal variability in tides due to variations in monsoon-influenced climate forcing, with successful results at about half of all gauges. The observed changes in tides are best explained by the influence of non-tidal velocities (geostrophic and Ekman), though the effect of changing stratification is also an important secondary causative mechanism. From the results of these surveys and investigations, it is concluded that short-term fluctuations in MSL and tidal properties at multiple time scales may be as important in determining the state of future water levels as the long-term trends. Global explanations for the observed tidal behavior have not been found in this study; however, significant regional explanations are found at the yearly time scale in the Solomon Sea, and at the seasonal time scale in Southeast Asia. It is likely that tidal sensitivity to annual and seasonal variations in MSL at other locations also are driven by locally specific processes, rather than factors with basin-wide coherence.

Les marées internes sont des processus dynamiques très répandus observés de façon intense près des marges continentales. Leur signature sur la surface libre de la mer est souvent observée sur les images satellites, montrant des systèmes d'ondes complexes au dessus des marges continentales irrégulières tels que la marge Ouest-Ibérique. Leur génération et leur distribution spatiale sont l'objet du présent travail, qui explore les processus physiques derrière la génération et la propagation de ces modes baroclines, au-dessus de canyons sous-marins et de promontoires, représentatifs des structures observées sur le talus Ouest-Ibérique. La solution de marée super inertielle est étudiée par le biais de simulations numériques, utilisant des configurations de topographie, soit réalistes soit idéalisée, en océan homogène ou stratifié (configuration bi couches et stratification continue). Les bassins océaniques sont dotés de talus et plateaux continentaux de faible profondeur qui détournent la propagation des marées océaniques de leur cours naturel. Les ondes de marée côtières sont ensuite réfléchies et/ou piégées sous différents modes possibles, fonction de la latitude, de la fréquence de forçage, du relief topographique et de la stratification de la colonne d'eau. Différents accidents topographiques, tels que les canyons sous-marins, les vallées, les promontoires et les bosses peuvent façonner des marges continentales afin de créer des pentes abruptes tangentielles au talus, qui deviennent effectivement des sites de production des marées internes. L'origine des marées internes se situe dans les forces d'attraction astronomiques, mais la répartition spatiale des solutions le long des marges continentales est distincte à travers le monde. La diversité du relief topographique module de façon spécifique les solutions de courant de marée barotropes, dont l'énergie est ensuite dissipée dans les modes baroclines en de nombreux endroits accidentés et à différents instants par rapport à la phase de marée.A mi-latitude, la force d'inertie terrestre divise le spectre de marée en ondes diurnes sub-inertielles et ondes semi-diurnes super-inertielles, donnant lieu à des ajustements en différents types de modes. La modélisation réaliste de la marée barotrope le long de la marge ouest-Ibérique vérifie cette différence de comportement et devient le point de départ de la présente thèse. Alors que les composantes diurnes génèrent des modes d'ondes continentales piégées le long du littoral, les harmoniques semi-diurnes montrent des structures de courants complexes, corrélées spatialement aux canyons sous-marins locaux et aux promontoires (pour lesquels on modélise une accroissement de l'amplitude du courant de marée associé à une inversion du sens de rotation).Ces distorsions super-inertielles des ondes de marée sont analysées et interprétées en utilisant des configurations de bathymétrie idéalisées. Les configurations canyon sous-marin et promontoires sont considérées comme des anomalies (sinusoïdale de signe opposé) de la largeur du plateau continental, situées au milieu du domaine modélisé. L'onde de marée monocromatic super-inertielle forcée aux limites, tient compte de l'hypothèse d'un plateau uniforme dans la direction tangentielle. Les résultats obtenus révèlent une distorsion importante du flux de marée qui peut être interprétée par la dynamique de la vorticité du fluide dans le cadre du principe de conservation du moment angulaire. / Oceanic internal tides are ubiquitous dynamic features, densely observed near continental margins. Their sea-surface signature is frequently printed in remote sensing images, showing complex wave patterns over irregular shelves such as the West-Iberian margin. Their origin and spatial distribution is the subject of the present work, which explores the physics behind the generation and propagation of these baroclinic modes, over submarine canyon and promontory shelf features. It focuses on the study of the super-inertial tide solution by the use of numerical model simulations of realistic and idealized topography configurations, under homogeneous, two-layers and continuous stratified water columns. The ocean basins are flanked by shallow water continental margins that divert ocean tides from their natural course. Coastal tide waves are then reflected and/or trapped in several possible wave modes, function of the latitude, forcing frequency, topographic relief and water column stratification. Different shelf features, such as submarine canyons, valleys, promontories and bumps can shape continental margins to create abrupt along-shelf slopes that become effective internal tide generation sites.

Ondas internas são movimentos ondulatórios que ocorrem no interior da coluna de água, associadas à estratificação de densidade. Ondas internas cuja frequência de oscilação se assemelha à das marés são chamadas marés internas. Estas ocasionam escoamentos intensos que influenciam a dinâmica de sedimentos, os processos de mistura e a produtividade primária. Em um ambiente energético como a Plataforma Continental Amazônica (PCA), localizada na costa norte brasileira, a estratificação varia consideravelmente, tanto espacial quanto temporalmente, de acordo com o balanço entre as diversas forçantes presentes. Na região da PCA alguns autores sugerem a presença de marés internas, entretanto, estudos específicos acerca do tema não figuram na literatura. Dessa forma, desenvolvemos neste trabalho um estudo da maré interna na região da PCA. Como objetivo, procuramos comprovar a ocorrência de marés internas na PCA, caracterizar seu comportamento e verificar sua intermitência. Para tal foram realizadas análises de dados provenientes do programa AMASSedS (A Multidisciplinary Amazon Shelf Sediment Study). Para caracterizar as marés internas, aplicamos dois métodos distintos para obtenção do campo baroclínico. O primeiro foi fundamentado no estabelecimento de uma corrente barotrópica préviamente obtida atráves de simulações numéricas. O segundo método empregado embasou-se na aplicação das funções empíricas ortogonais para a separação em modos estatísticos. Verificamos que as ondas internas na PCA estão ligadas à vazão do Rio Amazonas e são observadas, principalmente, na frequência semi-diurna. Aparentemente, as marés internas semi-diurnas influenciam não somente a hidrodinâmica da PCA como também são responsáveis por parte da variabilidade da salinidade próximo à superfície. / Internal waves are oscillatory motions that occur within the density stratified ocean. The ones with tidal frequency are then called internal tides or baroclinic tides, and are, on several locations around the planet, responsible for strong fluxes that affect several processes, like sediment transport, mixing processes and primary production. In such a strong environment as the Amazon Continental Shelf (ACS), located at the northern brazilian coast, it\'s stratification changes considerably with time and space, accordingly with the balance between the several forcing variables present. In this region, some authors suggest that internal tides occur, however, none research have been made about it on the ACS. That being said, we propose a study on internal tides on the ACS. As we hypothesize that internal tides occur, we look forward to characterize it\'s behavior and verify it\'s intermittency on the ACS. To do so, the data collected during the AMASSedS project (A Multidisciplinary Amazon Shelf Sediment Study) is going to be analyzed. In order to characterize it, two different method were applied to obtain the baroclinic field. The first method was the definition of a modeled-based barotropic current of the ACS obtained on the literature. The second method was the application of Empirical Orthogonal Functions in order to split the field on statistical modes of variability and analyze them separately. Our results indicate that internal tides on the ACS occur preferentially on the semi-diurnal frequency and it\'s generation is intimately connected to river discharge. Also, the analysis of the salinity anomaly field indicates that internal tides are responsible for part of the variability of the later on the surface on mid-shelf.