Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science. / Bibliography: leaves 159-163. / by Brian Bennett Reinhold. / Ph.D.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 209-215). / Observations from a three-year field program on the inner shelf south of Martha's Vineyard, MA and a numerical model are used to describe the effect of stratification on inner shelf circulation, transport, and sediment resuspension height. Thermal stratification above the bottom mixed layer is shown to cap the height to which sediment is resuspended. Stratification increases the transport driven by cross-shelf wind stresses, and this effect is larger in the response to offshore winds than onshore winds. However, a one-dimensional view of the dynamics is not sufficient to explain the relationship between circulation and stratification. An idealized, cross-shelf transect in a numerical model (ROMS) is used to isolate the effects of stratification, wind stress magnitude, surface heat flux, cross-shelf density gradient, and wind direction on the inner shelf response to the cross-shelf component of the wind stress. In well mixed and weakly stratified conditions, the cross-shelf density gradient can be used to predict the transport efficiency of the cross-shelf wind stress. In stratified conditions, the presence of an along-shelf wind stress component makes the inner shelf response to cross-shelf wind stress strongly asymmetric. / by Rachel Mandy Horwitz. / Ph.D.

Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2006. / Includes bibliographical references (p. 69-74). / Interactions between physical and biological processes in the Southern Ocean have significant impacts on local ecosystems as well as on global climate. In this thesis, I present evidence that the Southern Ocean circulation affects the variability of zooplankton and sea surface temperature, both of which are involved in air-sea exchanges of carbon dioxide. First, I examine the formation of spatial patterns in the distribution of Antarctic krill (Euphausia superba) resulting from social behavior. Turbulence of the flow is found to provide favorable conditions for the evolution social behavior in an idealized biological-physical model. Second, I analyze observations of sea surface temperature variability in the region of the Antarctic circumpolar current. Results suggest that propagating anomalies can be explained as a linear response to local atmospheric forcing by the Southern Annular Mode and remote forcing by El-Nifio southern oscillation, in the presence of advection by a mean flow. / by Ariane Verdy. / S.M.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 152-159. / by Long Sang Chiu. / Sc.D.

Thesis: Ph. D., Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2014. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 175-180). / This thesis explores the buoyancy-driven circulation in the Red Sea, using a combination of observations, as well as numerical modeling and analytical method. The first part of the thesis investigates the formation mechanism and spreading of Red Sea Overflow Water (RSOW) in the Red Sea. The preconditions required for open-ocean convection, which is suggested to be the formation mechanism of RSOW, are examined. The RSOW is identified and tracked as a layer with minimum potential vorticity and maximum chlorofluorocarbon-12. The pathway of the RSOW is also explored using numerical simulation. If diffusivity is not considered, the production rate of the RSOW is estimated to be 0.63 Sv using Walin's method. By comparing this 0.63 Sv to the actual RSOW transport at the Strait of Bab el Mandeb, it is implied that the vertical diffusivity is about 3.4 x10-5 m 2 s-1. The second part of the thesis studies buoyancy-forced circulation in an idealized Red Sea. Buoyancy-loss driven circulation in marginal seas is usually dominated by cyclonic boundary currents on f-plane, as suggested by previous observations and numerical modeling. This thesis suggests that by including [beta]-effect and buoyancy loss that increases linearly with latitude, the resultant mean Red Sea circulation consists of an anticyclonic gyre in the south and a cyclonic gyre in the north. In mid-basin, the northward surface flow crosses from the western boundary to the eastern boundary. The observational support is also reviewed. The mechanism that controls the crossover of boundary currents is further explored using an ad hoc analytical model based on PV dynamics. This ad hoc analytical model successfully predicts the crossover latitude of boundary currents. It suggests that the competition between advection of planetary vorticity and buoyancy-loss related term determines the crossover latitude. The third part of the thesis investigates three mechanisms that might account for eddy generation in the Red Sea, by conducting a series of numerical experiments. The three mechanisms are: i) baroclinic instability; ii) meridional structure of surface buoyancy losses; iii) cross-basin wind fields. / by Ping Zhai. / Ph. D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science / Bibliography: leaves 194-201. / by Amram Golombek. / Ph.D.

[Truncated abstract] The lake boundaries are an important source of sediment, nutrients and chemicals. For life inside the lake, the exchange between the lake boundaries (littoral) and lake interior (pelagic) is of central importance to Limnology as the net flux of nutrients into the water column is both the driving force and limiting factor for most algae blooms found during the stratification period. Consequently, the understanding of the relevant processes defining such an exchange is a further step toward a sound basis for future decisions by lake managers in order to ensure high water quality. The objective of this research was to investigate the physical processes responsible for the exchange of water and particles between the lake boundaries and the lake interior. An integrated approach using field experiments and 3D modelling as applied to Lake Kinneret (Israel) is presented. The field data revealed large-scale metalimnion oscillations with amplitudes up to 10 m in response to westerly diurnal winds, the existence of a well-defined suspended particle intrusion into the metalimnion of the lake, characterized by high concentrations of organic matter, and a well-mixed benthic boundary layer (BBL). The changes in the thermal structure explained the observed vertical and horizontal movements of the suspended particle intrusion. The horizontal advective transport via the metalimnion, associated with the velocities induced by the basin-scale mode-two Poincare wave, controlled the exchange between the lake boundaries and lake interior on daily time scales. The observed BBL over the lake slope varied markedly with time and space. Detailed comparison of simulation results with field data revealed that the model captured the lake hydrodynamics for time scales from hours to days. The model could then be used to extract the residual motions in the various regions of the lake. The residual motions below the surface layer were predominantly forced by the basin-scale internal wave motions, but the residual motion in the surface layer was found to be very sensitive to the curl of the wind field. The residual circulation was responsible for redistributing mass throughout the lake basin on time scales from days to weeks. A clear connection of dynamics of the BBL with the large-scale features of the flow was addressed. The time history of the mixing in the BBL and the resulting cross-shore flux was shown to vary with the phase of the basin-scale internal waves.

Au sortir de l'époque maoïste, le Parti communiste chinois a cherché à s’appuyer sur une bureaucratie plus compétente pour réussir le développement économique dans un contexte de stabilité politique. Les réformes ont concerné le recrutement, la gestion et l'organisation d’encadrement des fonctionnaires, mais aussi leur formation, dans l’objectif de renforcer leurs compétences. L'introduction en 1999 du Master in Public Administration (MPA) en milieu universitaire valorise la scientificité du savoir administratif, sans abandonner les dispositifs et les critères de sélection préexistants. À la lumière d’une mise en perspective historique, de l’analyse de la circulation transnationale de modèle éducatif et de l’étude de la modernisation de la bureaucratie, le MPA se révèle être l’instrument d’une double transformation, celle de l’enseignement supérieur et celle de l’administration chinoise contemporaine. Le MPA accompagne et rend possible la modernisation du pays, en permettant à l’enseignement supérieur d’introduire de nouvelles pratiques, à l'État-Parti de réformer l’administration sans rupture et aux agents du secteur public d’acquérir des ressources valorisables, quel que soit le scénario de transformation. / Changing nothing to change everything: innovation and continuity in the reforms of Chinese administrative training — At the end of the Maoist era, the Communist Party of China (CPC) attempted to create a more highly‑skilled bureaucracy to achieve economic development in a stable political context. Reforms concerned not just recruitment, management and civil service organization, but also the training of officials in order to improve their skills. The introduction of the Master of Public Administration (MPA) in 1999 enhanced the scientific character of administrative knowledge while pre‑existing selective mechanisms were retained. The MPA supports the country’s modernization by enabling the State‑Party to undertake continuous reform of public administration. It allows as well the emergence of a new ethos and a community of vision among the new generation of civil servants, whose competences are adjustable to several possible political scenarios.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2013. / "February 2013." Cataloged from PDF version of thesis. / Includes bibliographical references (p. 175-184). / Efforts to monitor the ocean for signs of climate change are hampered by ever-present noise, in the form of stochastic ocean variability, and detailed knowledge of the character of this noise is necessary for estimating the significance of apparent trends. Typically, uncertainty estimates are made by a variety of ad hoc methods, often based on numerical model results or the variability of the data set being analyzed. We provide a systematic approach based on the four-dimensional frequency-wavenumber spectrum of low-frequency ocean variability. This thesis presents an empirical model of the spectrum of ocean variability for periods between about 20 days and 15 years and wavelengths of about 200-10,000 km, and describes applications to ocean circulation trend detection, observing system design, and satellite data processing. The horizontal wavenumber-frequency part of the model spectrum is based on satellite altimetry, current meter data, moored temperature records, and shipboard ADCP data. The spectrum is dominated by motions along a "nondispersive line". The observations considered are consistent with a universal [omega] -² power law at the high end of the frequency range, but inconsistent with a universal wavenumber power law. The model spectrum is globally varying and accounts for changes in dominant phase speed, period, and wavelength with location. The vertical structure of the model spectrum is based on numerical model results, current meter data, and theoretical considerations. We find that the vertical structure of kinetic energy is surface intensified relative to the simplest theoretical predictions. We present a theory for the interaction of linear Rossby waves with rough topography; rough topography can explain both the observed phase speeds and vertical structure of variability. The improved description of low-frequency ocean variability presented here will serve as a useful tool for future oceanographic studies. / by Cimarron James Lemuel Wortham, IV. / Ph.D.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 187-195). / Large-scale thermal forcing and freshwater fluxes play an essential role in setting temperature and salinity in the ocean. A number of recent estimates of the global oceanic freshwater balance as well as the global oceanic surface net heat flux are used to investigate the effects of heat- and freshwater forcing at the ocean surface. Such forcing induces changes in both density and density-compensated temperature and salinity changes ('spice'). The ratio of the relative contributions of haline and thermal forcing in the mixed layer is maintained by large-scale surface fluxes, leading to important consequences for mixing in the ocean interior. In a stratified ocean, mixing processes can be either along lines of constant density (isopycnal) or across those lines (diapycnal). The contribution of these processes to the total mixing rate in the ocean can be estimated from the large-scale forcing by evaluating the production of thermal variance, salinity variance and temperature-salinity covariance. Here, I use new estimates of surface fluxes to evaluate these terms and combine them to generate estimates of the production of density and spice variance under the assumption of a linear equation of state. As a consequence, it is possible to estimate the relative importance of isopycnal and diapycnal mixing in the ocean. While isopycnal and diapycnal processes occur on very different length scales, I find that the surface-driven production of density and spice variance requires an approximate equipartition between isopycnal and diapycnal mixing in the ocean interior. In addition, consideration of the full nonlinear equation of state reveals that surface fluxes require an apparent buoyancy gain (expansion) of the ocean, which allows an estimate of the amount of contraction on mixing due to cabbeling in the ocean interior. / by Julian J. Schanze. / Ph.D.