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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A theoretical study of tides in the upper atmosphere. / Tides in the upper atmosphere.

Nunn, David January 1967 (has links)
No description available.
2

Chandler period atmospheric oscillations at the 700 hectoPascal level over the Northern Hemisphere

Benuzzi, Eugene Joseph. January 1978 (has links)
Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 30-31).
3

Atmospheric and oceanic 40- to 50-day oscillations in the source region of the Somali Current

Mertz, Gordon James January 1985 (has links)
Current and temperature data were acquired in the source region of the Somali Current, jointly by the Universities of Kiel and Miami, as part of the INDEX pilot studies. The data were acquired over a six-month period (January-July, 1976) which spans the springtime Monsoon reversal. The experiment and the data are described in Düing and Schott (1978). This thesis describes the results of the spectrum analysis of fluctuations found in data from the experiment's two southernmost sensor locations. It is found that, once the annual cycle is removed, most of the variance in these current and temperature records resides in subinertial fluctuations. The most prominent spectral feature is a 40- to 50-day peak. This 40- to 50-day period is coincident with that of the global-scale circulation cells found in the tropical atmosphere by Madden and Julian (1971 and 1972). The analysis of wind stress and wind stress curl data for the years 1976 and 1979 presented in this thesis indicate that the 40-to 50-day oscillation was present over the Western Indian Ocean during these years. It is suggested here that wind-forcing excites a long coastally trapped wave. To test this idea, a wind-forced quasi-geostrophic, three-layer model and a reduced-gravity model incorporating lateral mean current shear are applied to the Somali Current regime. Model results suggest that the wind forcing is strong enough to excite the observed current and temperature fluctuations. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
4

A theoretical study of tides in the upper atmosphere.

Nunn, David January 1967 (has links)
No description available.
5

MF radar observations of tides and planetary waves

Kovalam, Sujata. January 2000 (has links) (PDF)
Copies of previously published articles inserted. Bibliography: p. 185-200. Data obtained from six radar stations covering a wide latitude range has been used to determine the global distribution of planetary waves and tides. In the process a number of data analyses techniques were considered for their characterisation.
6

A study of thermospheric dynamics using electron content power spectrum estimations

Low, Nam Chong January 1974 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1974. / Bibliography: leaves 310-320. / xvi, 320 leaves ill
7

MF radar observations of tides and planetary waves / by Sujata Kovalam.

Kovalam, Sujata January 2000 (has links)
Copies of previously published articles inserted. / Bibliography: p. 185-200. / xxv, 200 p. : ill. author's (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Data obtained from six radar stations covering a wide latitude range has been used to determine the global distribution of planetary waves and tides. In the process a number of data analyses techniques were considered for their characterisation. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Math Physics, 2000
8

MF radar observations of tides and planetary waves /

Kovalam, Sujata. January 2000 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, Dept. of Physics and Math Physics, 2000. / Copies of previously published articles inserted. Bibliography: p. 185-200.
9

Possible tidal modulation of the Indian monsoon onset

Campbell, William Henry. January 1900 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 135-139).
10

Vertically Propagating Tides in the Martian Atmosphere

Kumar, Aishwarya 18 September 2023 (has links)
Atmospheric tides significantly influence the dynamics of Mars' upper atmosphere. The impact of tides on the mean state of the present-day Martian atmosphere is especially large at high altitudes. Certain tides can propagate away from the region of generation in the lower atmosphere and reach the upper atmosphere, where they can achieve significant amplitudes. Such vertically propagating tides constitute one of the primary mechanisms by which energy and momentum are transferred between atmospheric layers. Much of the initial evidence of tides reaching the upper atmosphere came from the Mars Global Surveyor mission (MGS). The MGS aerobraking densities revealed large-amplitude large-scale wavenumber-2 signature attributed to a class of tides known as nonmigrating tides. Recent observations from the Mars Atmosphere and Volatile Evolution mission (MAVEN) suggest that tides producing wavenumber-2 and wavenumber-3 structures are strongest in the upper atmosphere in a fixed local time reference frame. However, the energy carried by these tides and the region of deposition has not been well characterized. Moreover, it has been challenging to obtain a global understanding of the behavior of tides due to observations being limited in altitude combined with sparse geographical coverage. Over the recent years, multiple missions have been active simultaneously, presenting an excellent opportunity to understand the nature and behavior of vertically propagating tides from an observational lens. This dissertation aims to infer the vertical propagation characteristics of tides by combining the relative strengths of in situ and remotely sensed data from multiple instruments on different spacecrafts over a broad range of altitudes. Estimates of tidal amplitudes for five cases around the equator are presented. Hemispherical differences in the dominant wavenumber are reported in the middle atmosphere. It is seen that the wavenumber structure in the upper atmosphere reflects that seen in the lower atmosphere about half the time. Of note is that most of the energy carried by the wave is dissipated by ~90 km. This analysis is also extended to high latitudes, where wave signatures are identified in the upper atmosphere using solar occultation observations for the first time. The eastward propagating non-migrating tides are shown to dominate the tidal spectrum. A key finding is that the relative importance of the tides with different periods is more significant at high latitudes, leading to a change in the observed wavenumber structure with local time. Comparison to physics-based models reveal that the model performs generally better at low latitudes than high latitudes. / Doctor of Philosophy / Various waves exist in nature, some visible like ocean tides, others unseen like sound waves, but their effects are undoubtedly perceptible. Often when we think of waves, we envision those that ripple across the ocean, but the atmosphere also hosts a multitude of waves, driving a large part of our weather systems. If you consider the atmosphere a fluid, it carries waves of different sizes. One such category of waves, on a scale comparable to the planet's size, is called atmospheric tides. These atmospheric tides are classified into 'migrating tides' and 'non-migrating tides'. 'Nonmigrating tides' are generated near the surface. Some of these tides can propagate upward, reaching what is referred to as the 'upper atmosphere'. As they ascend, these tides grow in size, similar to how an ocean wave lifts a boat higher as the wave itself grows larger. The tides that reach the upper atmosphere can cause considerable displacement of atoms and molecules. These tides are particularly large on Mars, presenting a challenge for spacecraft that rely on precise knowledge of the total amount of molecules in the upper atmosphere for slowing down the spacecraft. This study aims to understand the nature of these tides as they propagate into the upper atmosphere and how they evolve as they pass through different regions of the Martian atmosphere. To do this, combining observations from multiple spacecraft is necessary, as a single spacecraft's observations are insufficient for probing these tides. One notable finding is that the tides lose most of their energy by the time they reach an altitude of 90 km, but they are still noticeable in the upper atmosphere. Previous work has relied on 'snapshots' in time to identify the strongest wave. This approach may work well near the equator, but this study reveals that closer to the poles, the strongest wave can change due to the presence of tides with different periods (24 hr, 12 hr, and so on).

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