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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.
31

Modeling of forced planetary waves in the Mars atmosphere

Hollingsworth, Jeffery L. 05 June 1992 (has links)
Mariner 9 and Viking spacecraft observations during the 1970's have provided evidence for planetary-scale wave-like disturbances in the Mars atmosphere. It has been suggested that possible sources of the wave activity are dynamical instabilities (e.g., barotropic and/or baroclinic instabilities). An other candidate source is forced, quasi-stationary planetary waves. In connection with Mars' enormous relief, both mechanical forcing and large-scale thermal contrasts due to spatially varying surface thermal-inertia and albedo patterns should provide a strong source for planetary-wave activity. In this thesis, we attempt to model aspects of the observed wave activity, focusing on forced planetary waves in the wintertime atmosphere of Mars. Our approach is to apply two dynamical models: a linear primitive equations model and a quasi-linear 'wave, mean-flow' model. Both models have spherical geometry and represent deviations from zonal symmetry in terms of Fourier modes. The former model permits a separation of responses to different elements that make up the total forcing mechanism, whereas the latter is used principally to investigate the role forced planetary waves may play in the Mars polar warming phenomenon. Basic states representing relatively 'non-dusty' and 'highly dusty' conditions near winter solstice allow wavenumber-1 and -2 disturbances to propagate meridionally and vertically into the winter jet. Higher wavenumbers are strongly vertically trapped. Stationary waves in the northern and southern extratropics differ strongly in amplitude, phase and horizontal wave pattern. The possibility for near-resonant, long-period modes in Mars' winter atmosphere is also examined. For several wave-amplitude measures and dissipation strengths, dusty low-frequency responses are an order of magnitude larger than non-dusty ones. Wave, mean-flow simulations using wavenumber-1 or -2 forcings indicate north polar warmings can occur for the dusty basic states. The sensitivity (magnitude, location, and time scale) of a simulated warming to the wave forcing and the dissipation strength is investigated. / Graduation date: 1993
32

Intraseasonal, large-scale circulations and tropical cylcome activity over the Western North Pacific during Boreal summer /

Delk, Tracey Lee. January 2004 (has links) (PDF)
Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Patrick Harr. Includes bibliographical references (p. 73-75). Also available online.
33

Excitation and dispersion of a Rossby wave train on the polar jet by an extra-tropical transition of a hurricane

Ravia, Roni. January 2006 (has links)
The enhanced potential vorticity gradients along the polar jet serve as a wave guide for trapped Rossby waves. These tropopause level, synoptic scale Rossby waves are of primary importance for weather development at the surface. In particular, extreme weather events have been linked to the existence of overlying upper level meridionally elongated filaments of stratospheric (high potential vorticity) air which form during the breaking of these waves. Motivated by the desire to understand the conditions under which these waves are formed and to improve their predictability, the current thesis discusses one excitation mechanism---the potential vorticity anomaly associated with a hurricane approaching the extra-tropics. / Attention is directed toward the adiabatic interaction of the cyclone with the polar jet before the two features meet. The hurricane's ability to excite Rossby waves is verified from observations of past interactions and theoretical study using a mechanistic model with idealized settings. The nature of the interaction between the cyclone and the polar jet is found to be sensitive to parameters such as the cyclone's radius and PV anomaly. Three different regimes have been identified. It is also concluded that the same parameters have influence on the skill of the Rossby wave prediction. The more intense the cyclone is, the harder it is to accurately predict the response of the polar jet.
34

A study of planetary wave errors in a spectral numerical weather prediction model /

Lambert, Steven J. (Steven John) January 1977 (has links)
No description available.
35

Vertical structure of mesoscale ocean currents in the Indian Ocean observation, numerical modeling and theory /

Chen, Shuiming January 2003 (has links)
Thesis (Ph. D.)--University of Hawaii at Manoa, 2003. / Includes bibliographical references (leaves 206-209).
36

Excitation and dispersion of a Rossby wave train on the polar jet by an extra-tropical transition of a hurricane

Ravia, Roni. January 2006 (has links)
No description available.
37

A study of planetary wave errors in a spectral numerical weather prediction model /

Lambert, Steven J. (Steven John) January 1977 (has links)
No description available.
38

Intraseasonal, large-scale circulations and tropical cyclcone activity over the Western North Pacific during Boreal summer

Delk, Tracey Lee 06 1900 (has links)
Approved for public release; distribution is unlimited. / Large-scale circulations in the 15-25 day period over the western North Pacific during northern summer were determined using the leading modes of a Singular Value Decomposition of 850 hPa winds and outgoing longwave radiation. Composites were constructed to define the wave patterns' structural characteristics. Their evolution is characterized by alternating cyclonic and anticyclonic equatorial anomalies that are linked to anomalous convective activity. Mid-latitude perturbations appear to contribute to the growth of new equatorial disturbances. Variability within the cycle is examined relative to variations in the basic state vertical wind shear and zonal wind convergence or divergence in the region equator-10ðN, 140ðE-160ðE. For the 50 cases in a basic state with easterly vertical wind shear and convergence, westward-moving waves propagate farther northwestward, wavelength contraction is greater, their orientation changes from east-west to southwest-northeast, and waves appear to be coupled with a Southern Hemisphere mid-latitude wave train. For the zonal wind divergence set, wave activity occurs farther eastward, circulations maintain a longer wavelength and more zonal orientation, and linkage with the Southern Hemisphere mid-latitudes is minimal. A statistically-significant relationship exists between the 15-25 day wave phase and tropical cyclone activity. Formation frequency and preferred locations are modulated by the 15-25 day wave. / Lieutenant, United States Navy
39

The vertical structure of the wind-driven circulation /

Young, William Roy. January 1981 (has links)
Thesis (Ph. D.)--Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1981. / Includes bibliographical references (p. 210-215).
40

The vertical structure of the wind-driven circulation /

Young, William Roy. January 1981 (has links)
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1981. / Supervised by Peter B. Rhines. Includes bibliographical references (leaves 210-215).

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