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1
Manyilizu, Majuto Clement. "Numerical modelling of the coastal ocean off Tanzania." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/17968.
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Includes bibliographical references (pages 71-89).<br>In this model study of the coastal ocean off Tanzania, the Regional Ocean Modelling System (ROMS) was employed to model the coastal ocean off Tanzania over the domain of 5°N-15°S and 38-55°E. It was integrated for ten years with monthly mean Comprehensive Ocean and Atmosphere Data Sets (COADS) winds and heat fluxes. Initial and lateral boundary conditions were derived from the World Ocean Atlas. The model was used to simulate the annual cycle, and the sea surface temperature (SST) output compared with the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) sea surface temperature (SST) measurements for the same region. Although broadly comparable, the model SST was generally warmer than that of TMI data. The high SSTs in the Tanzanian coastal waters (greater than 28°C) occur from December to May while SSTs of less than 28°C occur during the rest of the year. The East African Coastal Current (EACC) experiences its lowest spatial and temporal average speeds (about 0.4ms- 1) in February and its maximum speed (1.7 ms⁻¹) in July. Speeds of greater than 1 ms⁻¹ occur during both transition seasons north of 6°S. The meridional wind stresses appear to be positively correlated with the EACC(r>0.6) in all locations and they are statistically significant (p<0.05). The annual cycle of the model flow in the southern Tanzanian waters seems to be positively correlated with the flow to the north of Madagascar (r=0.57 and p=O.O5). The flow in these regions changes in phase with each other from October to April and June to July with minimum speeds in November. For the other months, the flow in these regions is out of phase with each other. The model currents off southern Tanzania attain their maximum speeds in August when the South West monsoon is fully developed while the flow north of Madagascar attains its maximum speed in September when the South West monsoon fades. However, the flow in the southern Tanzanian waters is more affected by the reversal of winds over the tropical western Indian Ocean (r=0.69, p=0.01) than that north of Madagascar (r=0.51, p=0.09). This difference results in a larger annual speed range in the flow off southern Tanzania (about 0.4 ms⁻¹ ) than that to the north of Madagascar (about 0.3ms⁻¹). The ROMS model realistically simulates the annual cycle of the sea surface temperature and heat flux, the East African Coastal Current and the annual cycle of the flow entering the coastal ocean off the southern part of Tanzania. However, studies which integrate the large scale domain and regional coupled ocean-atmosphere interactions are needed to better understand of the East African climate and ocean variability. Such model results combined with suitable remote sensing and in situ observations will help improve understanding of the circulation and properties of the coastal ocean off Tanzania.
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Booth, Charles W. Gutsch Barbara J. "Military applications of intranet technology : Fleet Numerical Meteorology and Oceanography Center /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA337406.
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Thesis (M.S. in Information Technology Management) Naval Postgraduate School, Sept. 1997.<br>Thesis advisors, James C. Emery, Frank L. Barrett. Includes bibliographical references (p. 145-146). Also available online.
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Booth, Charles W., and Barbara J. Gutsch. "Military applications of intranet technology: Fleet Numerical Meteorology and Oceanography Center." Thesis, Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/8677.
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Approved for public release; distribution is unlimited<br>Intranets are rapidly becoming a corporate internal information- sharing medium. Intranet technology is the same robust, proven, industry standard technology that is used on the Internet. The technical aspects of implementing the technology are simple. The organization and management aspects are significant and are key to its successful implementation. This internal use of Internet technology is easy, inexpensive, and has produced savings and benefits for corporate organizations. This thesis reviews corporate and government intranets and examines the feasibility of implementing this technology and benefiting from it, in a military organization. Specific applicability of Intranet technology was examined at Fleet Numerical Oceanographic and Meteorology Center, while maintaining the vision of its applicability to other military organizations. Fleet Numerical Oceanographic and Meteorology Center has the requisite technical and organizational infrastructure necessary to successfully implement Intranet technology. The management and technical skill sets necessary to successfully implement this technology at any military command operating a computer network should be available, or easily trained. Fleet Numerical Oceanographic and Meteorology Center and the U.S. Military should establish the organizational plans and infrastructure to implement and exploit this empowering information sharing medium.
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Bruner, Barry L. "A numerical study of baroclinic circulation in Monterey Bay." Thesis, Monterey, Calif. : Naval Postgraduate School, 1988. http://bosun.nps.edu/uhtbin/hyperion-image.exe/88Mar_Bruner.pdf.
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Thesis (M.S. in Meteorology and Oceanography)--Naval Postgraduate School, March 1988.<br>Thesis Advisor(s): Smith, D.C. "March 1988." Includes bibliographical references (p. 37-38). Also available online.
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Timmermans, Ben. "Uncertainty in numerical wind-wave models." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/378996/.
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The modelling of ocean waves is now carried out routinely at meteorological centres around the world. However, little is know about the source of the uncertainty in the predictions of waves produced, and sources can be numerous depending on the specific application. Historically it was felt that the dominant source of uncertainty originated from incomplete knowledge and expression of forcing winds. However more recent studies have focused on the underlying physical processes and their representations, with some authors questioning whether the limitation of the current modelling approach has been reached. Recently, methods for the statistical analysis of complex computer models, including models such as those used for wave prediction, have been developed. In this thesis these methods are applied to perform the first ever uncertainty analysis of a wave model. These new methods are applied to the state of the art wave model Wavewatch IIIr. This thesis principally explores the effect of tuning parameter uncertainty relating to the “Tolman and Chalikov” input and dissipation parameterisation, the discrete interaction approximation scheme for nonlinear wave-wave interactions and uncertainty about wind forcing, on wave simulation output, in a range of idealised cases, and realistically on Lake Michigan. The effectiveness of the statistical methods is first demonstrated in simple cases, before analysis is performed for progressively more complex simulations. In each case, uncertainty measures are computed with respect to simulation output in terms of summary wave statistics, typically including significant wave height and peak period. The analysis reveals nonlinear response and the relative importance of the various input, which in turn shows the active physical processes, and where the greatest sources of uncertainty lie. Both uncertainty about wind forcing and the process of nonlinear wave-wave interactions are found to be dominant in all cases, although energy dissipation is important in growing sea states. Finally, observational wave height data is used to perform a parameter calibration for simulations of stormy conditions on Lake Michigan, leading to improved performance.
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Carson, Nuala. "Numerical modelling of landfast sea ice." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/18773/.
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Landfast sea ice is a recurring seasonal feature along many coastlines in the polar regions. It is characterised by a lack of horizontal motion, for at least 20 days, and its attachment to the coast or seabed. It can form as a result of restrictive geometry, such as channels or embayments, or through the grounding of thick ice ridges which add lateral stability to the ice cover. Due to its stationary and persistent nature, landfast ice fundamentally modifies the exchange of heat and momentum between the atmosphere and ocean, compared with more mobile pack ice. The current generation of sea ice models is not capable of reproducing certain aspects of landfast ice formation and breakup. In this work two landfast ice parameterisations were developed, which describe the formation and breakup of landfast ice through the grounding of thick ice ridges. The parameterisations assume the sub-grid scale distribution of ice draft and ocean depth, the two parameters important in determining the occurrence of grounded ridges. The sub-grid scale distribution of grounded ice is firstly defined by assuming that ice draft and ocean depth are independent. This parameterisation allowed ice of any thickness to occur and ground at any depth. Advancing from this the sub-grid scale distribution of the grounded ice was restricted in an effort to make it more realistic. Based on Arctic ice scour observations ice was prevented from grounding in regions where the draft thickness was much larger than the ocean depth. Both parameterisations were incorporated into a commonly used sea ice model, the Los Alamos Sea Ice Model (CICE), to which a multi-category ocean depth distribution from high resolution global bathymetry data (ETOPO1) was included. The parameterisations were tested in global standalone format (i.e. no active ocean) with realistic atmospheric forcing. Both parameterisations were found to improve the spatial distribution and the seasonal cycle of landfast ice compared to the control (i.e. no landfast ice parameterisation) in the Arctic and Antarctic. However, the grounded ridges produced by the parameterisations were very stable, and tended to become multiyear leading to the production of multiyear landfast ice, which was particularly widespread in the Antarctic. It was found that tides have a significant impact on both grounded and landfast ice. In some polar locations tides were found to increase the occurrence of landfast ice, by increasing the production of thick ridges which were able to ground. Conversely, in some regions, tides were found to decrease the occurrence of landfast ice, as strong tidal and residual currents increased the mobility of the grounded ridges and landfast ice. This thesis finishes by considering whether a sea ice model could be used to further our understanding of the physical landfast ice system. Analytically derived characteristic numbers, which describe the ability of landfast ice to form, were found to fully describe the formation of landfast ice within the sea ice model CICE during idealised 1D scenarios. For these scenarios the key parameters controlling ice motion were found to be the external forcing component, the width of the ice cover, the internal ice strength, and the thickness of the ice. However, an exact characteristic variable able to describe the occurrence of landfast ice in an idealised 2D scenario could not be found analytically, nor could it be inferred numerically, and this remains an area for further research. This thesis examines different methods of modelling landfast sea ice and provides the sea ice modelling community with a means to parametrise landfast ice formation as a result of grounded ridges without having to work at very fine resolution, as this is computationally inefficient.
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Veitch, Jennifer Anne. "Equilibrium dynamics of the Benguela system : a numerical modelling approach." Doctoral thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/12153.
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Includes abstract.<br>Includes bibliographical references (p. 237-255).<br>The Regional Ocean Modelling System (ROMS) is used to systematically investigate equilibrium conditions and seasonal variations of the Benguela system, including both the large-scale flow regime as well as the coastal upswelling regime. A shelf-edge poleward flow exists in the northern Benguela region and is driven primarily by the wind-stress curl via the Sverdup relation. As such, it is strongly seasonal and is most intense during spring and summer when the wind-stress curl is most negative. The poleward flow deepens as it moves southward and between 25-27° much of it veers offshore due to the nature of of the wind-stress curl. In the mean state, the Benguela Current is characterized by two streams: the more inshore stream is topographically controlled and follows the run of the shelf-edge. The offshore stream is driven by nonlinear reactions of passing Aghulas rings and eddies and does not have a striking seasonal signal. The model simulates all seven of the major upswelling cells within its domain.
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MacKinnon, Douglas J. "A communication link software model for Fleet Numerical Meteorology and Oceanography Center." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA384723.
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Thesis (M.S. in Information Technology Management) Naval Postgraduate School, Dec. 2000.<br>Thesis advisor(s): Osmundson, John S. "December 2000." Includes bibliographical references (p. 29). Also available in print.
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Murton, Gary John. "Wave overtopping : a comparison of physical and numerical studies." Thesis, University of Plymouth, 1991. http://hdl.handle.net/10026.1/2361.
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The overtopping of low-crested breakwater is investigated by means of hydraulic and mathematical models. A conventional laboratory wavemaker with a wedge-type paddle is converted into an absorbing wavemaker so that it can be used to investigate accurately wave overtopping of reflective coastal structures. The absorption system is achieved by use of a feedback loop added to the control circuit. The design criteria and implementation of the circuit are presented in detail. Enhanced control software is used to generate different 'random' sea states with the same statistical properties. The absorption system is validated by an extensive series of tests made possible by the development of automated data acquisition and analysis software. Particular attention is given to the derivation of incident and reflected wave spectra. The results show over 90% success in reducing reflected waves. It is also possible to establish stable standing wave patterns over a wide frequency range. The results show significant improvement over similar existing wavemakers and in effect create an open-ended channel in the sense that the test structure hardly influences incident wave conditions. A closely controlled series of overtopping tests was carried out using the absorption system to prevent any re-reflections. Equipment and software were designed to quantify the overtopping rates for the structures used. The design and implementation of all aspects of the tests is fully described. Overtopping tests were carried out on breakwaters with smooth 1: 1 and 1: 2 seaward slopes. The results are tabulated and plotted in a dimensionless form which permits comparison with earlier work carried out at Hydraulics Research Ltd. The range of available data is extended and the new data for fully-developed sea states shown to be compatible with a linear extrapolation of the earlier results. It is believed that the earlier results were obtained using fully developed sea states but this is not known for certain. The importance of rigorously defining and publishing both test conditions and analysis techniques is highlighted. In the numerical study the 1-D mass and continuity equations were solved by a hybrid finite element/finite difference scheme. Whilst a good comparison is achieved between the physical and numerical tests for breakwater slopes of 1: 2 and less, realistic results are not achieved for steeper slopes. The reasons for this are discussed and the results presented. Both sets of model tests add valuable data to an area presently lacking detailed information.
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Shen, Jian. "Boundary Layer Structure in Homogeneous Tidal Flows: A Theoretical and Numerical Study." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539617653.
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Chang, Nicolette. "Numerical ocean model study of the Agulhas Bank and the cool ridge." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/12426.
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Includes bibliographical references (p. [147]-158).<br>Includes abstract.<br>The oceanic structure and circulation of the Agulhas Bank, the very wide continental shelf area off South Africa, has been explored in this thesis. The Agulhas Bank is a complex ocean region influenced by shelf processes as well as a nearby western boundary current, the Agulhas Current on its eastern margin and the Benguela Upwelling system on its western margin. In addition, a cold water feature, known as the cool ridge, has been observed on the Eastern Agulhas Bank. A consistent dynamical description is not available but it is commonly observed as a south-westerly flow of cold water in the upper water column, roughly following the 100m isobath and extending seawards off the coast. The formation of the cool ridge has also been investigated in this thesis by means of a numerical ocean model. Previous studies on the Agulhas Bank have been limited temporally and / or spatially. Thus, the Agulhas Bank as a whole has been inadequately sampled to provide a comprehensive representation. In order to remedy these deficiencies, the Regional Ocean Modeling System (ROMS) was used to study the Agulhas Bank dynamics. A large-scale model of the surrounding oceans, the SAfE (South African Experiment) configuration of the ROMS model, was used to force a one-way embedded finer-resolution model over the Agulhas Bank. This produced, 8 years of model data at an approximate horizontal resolution of 8km and 32 vertical terrain-following levels. Two main experiments were performed to understand the nature of the Agulhas Bank. Firstly, the "Reference Experiment" derived a seasonal ocean climatology of the Agulhas Bank. Secondly, the "No Agulhas Experiment" was carried out in an approach in which the Agulhas Current was removed from the shelf edge. A comparison of these two experiments yielded the influence of the Agulhas Current on the Agulhas Bank. The ROMS model was able to reproduce the main observed seasonal structure and circulation of the Agulhas Bank as well as the cool ridge. The Agulhas Bank showed marked seasonality, with its two-layer structure being significantly influenced by the Agulhas Current. The direct influence of the Agulhas Current on the Bank occurs on the Outer Agulhas Bank by the Agulhas Current itself or an Agulhas Current filament. Ekman veering by the interaction of the Agulhas Current with the bottom topography on the slope of the eastern Agulhas Bank advect cool water vertically onto the Bank. This strengthens the thermocline from below, in contrast to surface warming by solar insolation in summer and the Agulhas Current in winter. Cold waters, upwelled over the shelf edge, indirectly affect the greater Agulhas Bank by their advection by the predominantly westward mean currents. The most significant influence of the cold shelf-upwelled waters are in bringing cold waters to shallower depths over most of the Agulhas Bank. This may influence the waters that upwell at the coast, which on the eastern Agulhas Bank (without the Agulhas Current) are trapped under a thick warm surface layer.
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Veitch, Jennifer Anne. "Numerical model investigation of near-surface circulation features of the Angola Basin." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/6449.
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Includes bibliographical references.<br>The primary objective of this thesis is to identify and investigate the most prominent circulation features of the Angola Basin from the output parameters of the OPAITOTEM Ocean Parallelisel Trois Oceans Tropicaux) tropical circulation model, focusing particularly on the so-called Angola Gyre and the Angola Dome. Analyses of the effect of windstress, windstress curl and Ekman pumping, all computed from ERS satellite-derived wind speeds, were conducted. The OPAITOTEM model does not resolve the 'Angola Gyre', but it does resolve a large-scale (1000-2000km) dome-like feature, which has been defined as the 'Model Dome' within this study. The most conspicuous feature of the Angola Basin discerned in the thermohaline output of the OPAITOTEM model is a ridge-like structure of the thermocline (the Model Dome), which results in a cool feature that 'outcrops' most distinctly at a depth of 45m. At greater depths, a permanent upward doming of the isotherms beneath the Angola Benguela Frontal Zone (ABFZ) is observed. In January, February, September, October and November the 'outcropping' of the thermocline-ridge is deepest and appears as a distinctly isolated cool feature at 4Sm. No clear cydonic circulation is associated with the Model Dome. However, the northern limb is unequivocally coincident with the South Equatorial Undercurrent (SEUC) at 2-5"S and the South Equatorial Countercurrent (SECC) at 10·S. Upon reaching the African coast, the SEUC and SECC bend poleward to form the southward Angola Current, which constitutes the eastern limb of the Model Dome. The southern and eastern limbs of the dome are not as dearly defined and are associated with a weak westward flow regime. The shallow portion of the Model Dome has a distinct semi-annual signal whereby it migrates southward between September-November and again between January-April. This signal is in accordance with the magnitude and southward displacement of the core of the SEUC. The SEUC is most intense in January, February, September and October reaching velocities of about O.14m.s·1 and is weakest in June and July (O.02-O.06m.s-) The deep portion of the Model Dome shows little seasonal variability, other than a slight northward tilt of its vertical axis when the thermocline-ridge is furthest south. Similarly, the SECC, which constitutes the northern limb of the deeper cool feature, is fairly consistent throughout the year, in both position and magnitude (-0.01 m.s-)
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Holland, David M. "Numerical simulation of the Arctic Sea ice and ocean circulation." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41114.
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A numerical model study of the seasonal cycle of sea-ice cover and ocean circulation in the Arctic Ocean is presented. The investigation is carried out in four parts using the coupled sea ice-ocean model of Oberhuber (1993a). The Oberhuber model is the first global ocean general circulation model to use Lagrangian isopycnal coordinates. First, a sensitivity study is given of the sea-ice model, which is both dynamic and thermodynamic. The robustness of the sea-ice component in an uncoupled mode is demonstrated. Secondly, the addition of a snow model to the coupled sea ice-ocean model of Oberhuber (1993a) is described. The inclusion of snow is shown to be important for obtaining a good simulation of ice thickness in both the Arctic and Antarctic. Thirdly, the coupled ice-ocean model is used to investigate the general circulation of the Artic Ocean and its connection with the North Atlantic. The cyclonic motion of the Atlantic layer within the Arctic is correctly simulated. Fourthly, a sensitivity study of the Arctic mixed-layer circulation is presented.
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Brown, James L., and Dan C. Boger. "A cost benefit analysis of two products of the Fleet Numerical Oceanography Center." Thesis, Monterey, California. Naval Postgraduate School, 1993. http://hdl.handle.net/10945/24139.
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Livings, William T. "Fleet Numerical Oceanography Center software development standards: an implementation of DOD-STD-2167A." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25949.
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Sylaios, Georgios. "A numerical investigation into the dynamics of a partially-mixed estuary." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241267.
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Blamey, Ross. "Numerical simulation of a mesoscale convective system over the east coast of South Africa." Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/6463.
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Includes bibliographical references (leaves 189-200).<br>Weather stations across the northern KwaZulu-Natal coastline recorded over 100 mm of rainfall over the 11112 February 2005, with Cape St. Lucia and Richards Bay measuring 111 mm and 96.8 mm, respectively. This heavy rainfall was associated with a mesoscale convective system (MCS) that initiated through small convective storms beginning early in the afternoon on 11 February 2005 and eventually decayed in the early morning hours on the 12th. The high-lying topography of the eastern escarpment and high diurnal surface heating possibly provided the trigger for the event. It was also identified that a combination of synoptic features in and around South Africa contributed to the evolution of the system. This particular MCS is investigated with a non-hydrostatic numerical model (MM5) to help determine which processes were important in its initiation and development, as well as what factors contributed to the associated heavy rainfall. The model is also used to conduct sensitivity tests to determine the role that local features, such as the regional topography and sea surface temperature, played in the evolution of the system. Through the various MM5 simulations, it was evident that the eastern escarpment played a key role in triggering the convective event, while it also had an influence on the low level winds that advected moisture into the region. A sea surface temperature sensitivity simulation highlighted the important role that the Agulhas Current plays in supplying moisture to fuel extreme precipitation events in South Africa. The significance of resolving large-scale features in the mid-latitudes in numerical simulations of weather events in South Africa was identified when excluding these features from the simulation. Through these simulations it was identified that the development of the MCS and the heavy nocturnal precipitation was due to a combination of the continuous moisture supply into the region, a conditionally unstable atmosphere, and uplift due to low level convergence and the local topography.
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Jones, John Eric. "Numerical modelling of tides, surges, residual circulation and salinity in shelf seas." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240598.
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Meyiwa, Sbongile. "Numerical modelling of Tropical Cyclone Dineo and its rainfall impacts over north-eastern South Africa." Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31174.
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Widespread flooding over parts of Mozambique, Zimbabwe, Malawi, Botswana as well as north-eastern South Africa was experienced in February 2017. The flooding was associated with Tropical Cyclone Dineo that was generated in the Mozambique Channel on 12 February 2017 and made landfall over the south-central coast of Mozambique on 15 February. This study investigates the atmospheric circulation and potential mechanisms responsible for the heavy rainfall that occurred during the passage of ex-Tropical Cyclone Dineo inland from the Mozambican coast with focus on the rainfall patterns over north-eastern South Africa. Output from the Weather Research and Forecasting (WRF) model, the Climate Forecast System Reanalyses version 2 (CFSv2) atmospheric reanalysis, satellite derived rainfall and wind data, and station rainfall data are used for this purpose. Tropical Rainfall Measuring Mission (TRMM) rainfall estimates, WRF model rainfall and rainfall station data indicated that many parts of north-eastern South Africa experienced large amounts of rainfall during the final stages of Dineo (16-17 February 2017) while Mozambique experienced heavy rainfall soon after the cyclone made landfall. An inland trough ahead of Dineo led to substantial rainfall at this time over Malawi and Botswana. Furthermore, analysis of the station data revealed that in north-eastern South Africa some stations recorded about 80 % of their total monthly rainfall from this event. The WRF model run indicated low level monsoonal north-easterly moisture fluxes feeding into Dineo in the Mozambique Channel. Subsequent convergence over south-eastern Africa between this flow and the south-easterly cyclonic flux associated with Dineo led to substantial rainfall over Mozambique, Zimbabwe, Botswana and north-eastern South Africa. Although the 2016/17 tropical cyclone season recorded below average numbers of storms, it is suggested that the conditions prior to the storm iv formation were favourable for the track of Tropical Cyclone Dineo and landfall on the southcentral Mozambican coast.
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Viljoen, Anél. "Investigation of the nearshore, episodic poleward current in the southern Benguela : a numerical modelling approach." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/6448.
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Includes bibliographical references.<br>Fisheries are of great economic importance on the South African West Coast (the Southern Benguela). The St Helena Bay region is a key nursery habitat for these fisheries because of its retention, upwelling and stratified water column characteristics. However, these characteristics also result in other outcomes such as hypoxia and harmful algal blooms (HAB's) which impact on the habitat suitability character of the system. A nearshore, episodic poleward current has been observed in this region, and it is believed that this current plays an important role in the incidence of HABs as well as hypoxia events. The drivers and dynamics of this nearshore, episodic poleward current have not been clearly understood, nor thoroughly investigated, due to the complexity of the scales and processes. However, the importance of this current in transporting harmful algae from the north into St Helena Bay and its role in habitat hypoxia has emphasized the need to understand its dynamics.
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Dupont, Frederic. "Comparison of numerical methods for modelling ocean circulation in basins with irregular coasts." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=37886.
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Comprehension of global oceanic currents and, ultimately, of climate variability requires the use of computer modelling. Although much effort has been spent on the accuracy of traditional finite difference (FD) models used in ocean modelling, there are still concerns, especially since these models have a crude representation of the geometry of oceanic basins. Such a crude representation may influence the accuracy of modelling boundary currents, or unrealisticly represent the impinging of eddies or the propagation of Kelvin waves along the coastline. This motivated the use of alternative modelling techniques applied on completely irregular geometries such as finite element (FE) and spectral element (SE) methods. In this thesis, we want to investigate the accuracy and cost-effectiveness of these three numerical methods in irregular domains and to understand to which extent the unstructured grid FE and SE methods constitute an improvement over the more traditional FD methods. To accomplish this, we limit ourselves to modelling the shallow water equations in presence of irregular coastlines with no bottom topography.<br>In the first part of the thesis, we compare the performances of FD methods on Cartesian grids with FE and SE methods in various geometries for linear and non-linear applications. We argue that the SE method is to a certain extent superior to FD methods. In a second part, we study the influence of step-like walls on vorticity budgets for wind-driven shallow water FD models. We show that vorticity budgets can be very sensitive to the FD formulation. This has certain implications for using vorticity budgets as a diagnostic tool in FD models. In the final part, we use a SE shallow water model for investigating the "inertial runaway problem" in irregular domains for the single-gyre Munk problem. Ideally, one would like the statistical equilibrium observed at large Reynolds number to be insensitive to model choices that are not well founded, e.g., the precise value of the viscous coefficient, and choice of dynamic boundary condition. Simple models of geophysical flows are indeed very sensitive to these choices. For example, flows typically converge to unrealisticly strong circulations, particularly under free-slip boundary conditions, even at rather modest Reynolds numbers. This is referred to as the "inertial runaway problem". We show that the addition of irregular coastlines to the canonical problem helps to slow considerably the circulation, but does not prevent runway.
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McNeall, Douglas James. "Dimension reduction in the Bayesian analysis of a numerical climate model." Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/69028/.
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We present a prediction of the strength of the meridional overturning circulation (MOC) in the Atlantic Ocean during the 21st century, and a quantitative estimate of its uncertainty. The MOC has been suggested as a potential source of abrupt climate change, with the ability to alter the climate of the North Atlantic on a short time-scale. The prediction takes the form of a calibrated uncertainty analysis, combining observations of the MOC, an ensemble of runs from a climate model, and expert knowledge, in a Bayesian fashion. Uncertainty in model behaviour due to the model structure and forcing is explored by running an ensemble of the Earth system model of intermediate complexity GENIE-1. Input parameters representing physical constants, simplified processes, and forcings are varied across the ensemble in a designed computer experiment. We develop quantitative and qualitative methods to compare observational data of the MOC with corresponding output from the ensemble, to learn about plausible input configurations of the model. Dimension reduction is used to express patterns of variation in model behaviour across the ensemble in a low-dimensional form. The ensemble is used to train an emulator; a fast statistical approximation to the expensive model, that includes an estimate of uncertainty due to the limited size of the ensemble. By training the emulator using the low-dimensional representations of the output, we are able to predict high-dimensional model output at input configurations not tested in the original ensemble. This allows a more complete expression of the uncertainty in the evolution of the MOC throughout the 21st century.
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Kent, Elizabeth C. "A numerical model study of the stratocumulus-topped marine boundary layer." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/42126/.
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A one-dimensional model with second order turbulence closure has been developed and used to investigate processes in the cloud-topped marine atmospheric boundary layer. Model developments were required to correctly apply surface flux terms near the sea surface, poor representation of which is common to several models from the recent literature. The improved surface forcing is shown to affect the predicted boundary layer structure. Other developments included the implementation of a fully implicit numerical code, which generated less numerical noise than that originally used in the model, and an improved initialisation procedure. The new model code was then shown to quantitatively reproduce processes in the stratocumulustopped boundary layer using measurements of atmospheric turbulence from aircraft from the North Sea and the subtropical North Atlantic and North Pacific. The model is robust to changes in the mixing length coefficients used in the turbulence closure and to perturbations in the initial profiles. The model is used to simulate conditions that occur as winds circulate from the subtropics towards the tradewind regions. The observed transition from a shallow stratocumulus layer to a deeper stratocumulus layer interacting with cumulus clouds beneath is simulated in response to realistic external forcing. The final stages of transition, from cumulus under stratocumulus to shallow cumulus is however not observed in the simulation; possible reasons for this are discussed. The model shows in detail the interaction between the stratocumulus layer and cumulus clouds beneath. The cumulus clouds thicken, moisten and cool the stratocumulus layer and therefore act to maintain the layer, but can also drive entrainment. The peaks in turbulent kinetic energy in the stratocumulus layer which follow cumulus penetrations of the stratocumulus layer can be large enough to directly cause the boundary layer to entrain air from above the boundary layer and grow in height. The entrained air is warmer and drier than the boundary layer air and tends to dissipate the stratocumulus layer. The model is then used to show how the imposed environmental conditions affect processes within the boundary layer. An important model prediction is that cloud top entrainment instability may act to promote mixing between the surface and cloud in deep-decoupled boundary layers. The mixing acts to replenish the cloud liquid water and sustain the cloud. Cloud top entrainment instability has previously been thought to have the capacity to lead to rapid erosion of the cloud, although this has not been observed in practice. This mechanism could help to explain the observed persistence of stratocumulus clouds under these conditions.
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Jin, San. "A Numerical Model Study of Estuarine Residual Circulation and Stratification Variations during Spring-Neap Tidal Cycles." W&M ScholarWorks, 1990. https://scholarworks.wm.edu/etd/1539617619.
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Russell, Sarah L. (Sarah Louise) 1973. "Shelf currents, ice and wind : a numerical modeling study." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/39225.
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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), 2003.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Includes bibliographical references (p. 190-197).<br>In this thesis, the effects of sea ice, downwelling favorable winds and barotropic background currents on shelf fronts are examined using numerical models. The models are configured with the characteristics of the East Greenland Current, north of the Denmark Strait, in mind. While the models are heavily idealized, basic physical parameters match the observed ocean. The first part of the thesis uses a three dimensional, primitive equation model to examine the behavior of a shelf front under steady, along shelf winds and barotropic currents. The wind stress generates shoreward surface Ekman transport and the barotropic current generates an offshore bottom Ekman transport. In both cases, the Ekman transport causes the creation of mixed layers and a relationship describing the mixed layer thickness is derived relating the cross shelf flux of density to the along shelf flux of density. When there is a barotropic inflow, the cross shelf Ekman mass transport is balanced by a return flow of mass in the interior. When there is a wind stress, in the present model configuration, the influence of the offshore boundary obscures the effect of the Ekman layers. The second part of the thesis focuses on the ice-ocean interaction using a simple, two layer, one dimensional toy model. The interaction of sea-ice, geostrophic currents, and wind are examined. In the presence of a current and the absence of wind, the ice is transported downstream with the current. In the presence of wind and the absence of a current, the net ice-ocean transport is perpendicular to the wind, as is expected for Ekman layer theory. The two layer system acts like a poorly resolved Ekman spiral: the ice has down wind and shoreward transport while the ocean has up wind and shoreward transport.<br>by Sarah L. Russell.<br>Ph.D.
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Bergondo, Deanna L. "Examining the processes controlling water column variability in Narragansett Bay : time series data and numerical modeling /." View online ; access limited to URI, 2004. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3135893.
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Wang, Taiping. "Numerical modeling of eutrophication dynamics in the shallow coastal ecosystem: A case study in the Maryland and Virginia coastal bays." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539616899.
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Shallow coastal bays and lagoons (mean depths <2-3 meters) are important buffer zones and links between terrestrial and deep marine ecosystems. They are inherently vulnerable to eutrophication, and are normally dominated by benthic primary producers such as seagrass, benthic micro- and macroalgae. There is an urgent need for quantitative models that are specifically designed for studying eutrophication dynamics in shallow coastal ecosystems. In this study, a hydrodynamic and water quality modeling system consisting of the hydrodynamic model UnTRIM and the water quality model CE-QUAL-ICM was applied to a representative shallow coastal bay ecosystem, the Maryland and Virginia Coastal Bays (MVCBs). A high-resolution unstructured model grid was generated to resolve the complex geometry. to address the important role played by benthic macroalgae, a benthic macroalgal module, which assimilated macroalgal kinetics from literature and recent laboratory studies, was incorporated into the water quality model framework. The module includes two representative macroalgal species, Ulva lactuca and Gracilaria vermiculophylla , common in the MVCBs, and employs the internal nutrient-limited growth kinetics proposed by Droop. The numerical modeling system has been calibrated against a comprehensive field monitoring data collected by the Maryland Department of Natural Resources in the MVCBs. The data include water level, current velocity, salinity, and major water quality variables, such as chlorophyll a, dissolved oxygen, and nutrients. The calibrated hydrodynamic model was used to calculate the physical transport time scales. The model estimated flushing time for the entire system is on the order of 2-3 months, which are much longer than typical time scales required by most biological processes. In addition, the local residence time is found to be extremely variable throughout the system. Depending on locations, the local residence time can vary from 0 to more than 200 days. The calculated transport time scales were further compared with spatial water quality distributions in the system. The comparisons demonstrate that physical circulations could substantially modulate biological processes in the system. By using the Droop equation, the benthic macroalgae's unique property, the so-called luxury uptake, was satisfactorily captured. Furthermore, the characteristic boom-and-bust life cycle of benthic macroalgae was qualitatively simulated using a box model. The expanded water quality model that includes the benthic macroalgal module reproduced both temporal and spatial distributions of observed benthic macroalgae and major water quality variables reasonably well in the MVCBs. The model results indicate that benthic macroalgae are highly important in regulating ecosystem metabolism in areas where they are abundant. Moreover, spring phytoplankton bloom was substantially suppressed when benthic macroalgae were present. The incorporation of a benthic macroalgal module also improved the model's predictive capability in simulating dissolved oxygen in shallow ecosystems affected by benthic macroalgae. In terms of nutrient budget, the model estimated that benthic macroalgae retain approximately 10% of annual nonpoint source nitrogen inputs from the watershed based on the simulation of year 2004. This is lower than that contributed by benthic microalgae reported in other shallow coastal bays such as the Lynnhaven Bay. It is suspected that the restricted distribution of benthic macroalgae in the MVCBs limited their role from the whole bay perspective. With the incorporation of a benthic macroalgae module, the overall water quality model prediction capability is improved.
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Gao, Jie. "A Numerical Modeling Study of Storm Surge and Inundation in the Chesapeake Bay during the November 2009 Mid-Atlantic Nor'easter." W&M ScholarWorks, 2011. https://scholarworks.wm.edu/etd/1539617907.
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Cai, Xun. "Impact of Submerged Aquatic Vegetation on Water Quality in Cache Slough Complex, Sacramento-San Joaquin Delta: a Numerical Modeling Study." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153628.
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Submerged aquatic vegetation (SAV) plays a significant role in many aquatic systems, and impacts both physical and ecological quantities. It can baffle currents, attenuate waves, recycle nitrogen and phosphorus from the sediment bed, perform ecosystem function as a primary producer, and provide critical habitat for many aquatic species. Conversely, the invasive SAV, Egeria densa (Brazilian waterweed), in the San Francisco Bay & Delta has been a nuisance since its introduction into the system in the 1960s. It has displaced most of the native submersed aquatic plant species in the Delta and restructured the ecosystem, thus threatening the survival of several endangered native fishes such as Delta Smelt. Its impacts on the ecological system remain largely unknown and the need for assessment is growing. This multi-interdisciplinary study, incorporating biogeochemistry, hydrodynamics, and numerical computing and field survey data, accomplishes two main goals. The first goal is to develop a new SAV model imbedded into the unstructured-grid SCHISM-ICM framework. in addition to the advantages of directly simulating the SAV impact on hydrodynamics using high-resolution unstructured grids, this new SAV model can also simulate the competition between SAV and phytoplankton for light and nutrient supplies. The second goal is to apply the new model to Cache Slough Complex, Sacramento-San Joaquin Delta, to estimate the impact on the water quality from intervening SAV removal. Removal of SAV is already being studied in Little Hastings Tract and this study can serve to develop hypotheses for monitoring and ultimately guidance for managing SAV removal in the Bay-Delta region. We benchmark the new SAV model with the tests on the SAV biomass, growth and impacts on light supply and nutrient budget in the water column and sediment bed, respectively. Starting from a uniform biomass distribution, we simulate the evolution of biomass over seasonal scales and validate the calculated distribution with the observed distribution. The model is able to successfully simulate the SAV die-off process in areas where it is known to be unable to colonize. By applying the fully coupled SCHISM-ICM-SAV model in the Cache Slough Complex area, the changes of the water quality state variables due to SAV are estimated over spatial and seasonal scales. Generally, SAV increases the accumulation of phytoplankton by locally reducing flushing and thus increasing the residence time, but in the meantime, reduces its local growth rate due to light shading and nutrient competition. A combination of direct impact from SAV and indirect impact through changed phytoplankton results in changes in other water quality variables: dissolved oxygen and nutrients. SAV tends to increase oxygen and organic nutrients while decreasing inorganic nutrients. For this system, the feedback loop from SAV to the hydrodynamics plays the most important role in the water quality variables among all feedback loops.
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Moriarty, Julia Miege. "The Role of Seabed Resuspension on Oxygen and Nutrient Dynamics in Coastal Systems: A Numerical Modeling Study." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639567.
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Seabed resuspension can impact organic matter fate and water column biogeochemistry in coastal environments. Cycles of erosion and deposition can, for example, affect remineralization rates, seabed-water column fluxes of dissolved oxygen and nutrients, and light attenuation. Yet, models that incorporate both sediment transport and biogeochemical processes are rare, and nearly all neglect the effect of resuspension on oxygen and nutrient dynamics. Development of a novel tool, i.e. a coupled hydrodynamic-sediment transport-biogeochemical model, allowed for an investigation of the role of resuspension on oxygen and nitrogen dynamics within three distinct coastal environments. Called HydroBioSed, the coupled model was built within the Regional Ocean Modeling System and accounted for physical processes including the deposition and erosion of inorganic sediment and particulate organic matter from the seabed, as well as the flux of dissolved inorganic chemical species at the seabed-water column interface. The model also considered biogeochemical reactions including the remineralization of organic matter and oxidation of reduced chemical species, in both the seabed and the water column. HydroBioSed was first implemented as a one-dimensional vertical model for the Rhône River subaqueous delta. Results indicated that cycles of erosion and deposition altered rates of diffusion between the seabed and water column. This process increased fluxes of oxygen into the seabed during erosional periods, and the effect remained significant when results were averaged over time scales longer than individual events. The coupled model was next implemented in three-dimensions for the riverine-influenced northern Gulf of Mexico shelf. In this environment, resuspension-induced effects on bottom water biogeochemistry were dominated by increases in remineralization. Specifically, remineralization of resuspended organic matter increased oxygen consumption and ammonium production, especially in shallow areas where bed stresses were typically high. Finally, HydroBioSed was implemented for the Chesapeake Bay estuary and adapted to account for light attenuation by sediment and resuspended particulate organic matter. Here, resuspension-induced turbidity caused a down-stream shift in primary production. This shift, combined with remineralization of resuspended seabed organic matter, caused oxygen concentrations to decrease and ammonium concentrations to increase throughout the estuary. Overall, use of a novel coupled hydrodynamic-sediment transport-biogeochemical model, showed that cycles of erosion and deposition impact water column biogeochemistry, but the specific effects of resuspension varied across the three distinct environments studied.
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Rapolaki, Ramontsheng Sakia. "A numerical simulation of tropical storm Chedza over south-eastern Africa." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/22953.
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Widespread flooding over parts of Malawi, Mozambique, and Madagascar occurred in January 2015. An impact assessment by the World Bank indicated huge damage to property, infrastructure, and agriculture over several regions in south-eastern Africa. The flooding was associated with tropical storm Chedza that developed in the Mozambique Channel on 11 January 2015. This study investigates the atmospheric circulation and potential mechanisms responsible for the heavy rainfall event that occurred between 11 and 17 January over Mozambique and Malawi using the Weather Research and Forecasting (WRF) model, the Global Forecast System (GFS) atmospheric reanalysis, satellite derived rainfall and wind data, and station rainfall data. Tropical Rainfall Measuring Mission (TRMM) rainfall estimates and rainfall station data indicated that southern Malawi and northern Mozambique experienced the majority of rainfall during the early stages of tropical storm Chedza while Madagascar experienced heavy falls when tropical storm Chedza tracked over the island on January 17. Furthermore, analysis of the station data revealed that the heavy rainfall over Mozambique occurred between 11 and 13 January with some stations recording about 80 % of their total January 2015 rainfall as resulting from this event. The WRF model run of the event indicated a low level easterly to southeasterly onshore flow over southern Mozambique that interacted with a northwesterly monsoonal flow to westerly flow along the northern flanks (periphery) of the storm in the northern Mozambique Channel, leading to surface moisture flux convergence in the regions of heavy rainfall. Furthermore, moisture from the southwest Indian Ocean was advected into the region during the heavy rainfall. It is suggested that multiple favourable factors which included strong moisture fluxes from the southwest Indian Ocean and equatorial South Indian Ocean, near surface convergence over the areas of heavy rainfall, and strong uplift acted together to create favourable conditions for the development of tropical storm Chedza and the associated heavy rainfall.
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Braby, Laura. "A study of Mesoscale Eddies, the Agulhas current and the evolution of its meanders using satellite observations and numerical modelling experiments." Doctoral thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31213.
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The Agulhas Current is the strongest western boundary current in the Southern Hemisphere and plays an important role in the exchange of heat and salt between the Indian and South Atlantic Ocean basins, thereby affecting global climate. The variability in the northern Agulhas Current is influenced by both cyclonic and anticyclonic mesoscale eddies, originating from the Mozambique Channel and south of Madagascar (known as source region eddies) and which propagate toward the offshore edge of the Agulhas Current. Using a combination of an eddy-tracking data set with in-situ surface drifter observations and altimetry-derived geostrophic currents, it is shown that source region eddies dissipate upon approaching the Agulhas Current. Their entrainment into the Agulhas Current affects its mean velocity and offshore position through a transfer of momentum, with anti-cyclonic eddies consistently increasing the Agulhas Current’s velocity by 0.16 ± 0.17 m.s -1 . In contrast, entrainment of cyclonic eddies results in a decrease in velocity by 0.13 ± 0.16 m.s-1 and shifting the current up to 144 ± 85 km offshore. These velocity anomalies propagate downstream at rates of 44 km.d-1 (anti-cyclonic eddies) and 23 km.d-1 (cyclonic eddies). Whilst existing numerical models are successfully able to capture many aspects of the Agulhas Current, many models are unable to accurately represent the observed eddy dissipation and interaction processes, affecting our understanding of mesoscale variability within in the current. In this study, we compare two simulation experiments in a regional Hybrid Coordinate Ocean Model (HYCOM), where we change the wind forcing, and using an eddy tracking algorithm assess the local effect of the changed wind stress on source region eddies and their interaction with the northern Agulhas Current. There is an overall reduction in eddy kinetic energy (EKE) of 33% over the Agulhas Current domain. Changes in eddy pathways, properties and energy conversion terms, resulting from the change in forcing from absolute to relative winds (the wind speed relative to the current speed) have resulted in significantly different mesoscale eddies in the regional HYCOM. The effects of the change in wind forcing on the variability within the Agulhas Current were examined and the differences between the two simulations were found to be very small. Finally, the evolution of meanders in the Agulhas Current, including the properties and dissipation of smaller meanders as well as mesoscale Natal Pulses type meanders, were assessed using both HYCOM experiments and compared to satellite observations. The representation of smaller meanders (under 50km in size) improved with the changed in wind forcing. However, larger Agulhas Current meanders (greater than or equal to 50km) which previously occurred too frequently in the regional HYCOM, are now too infrequent in the regional HYCOM, with an average of 1.1 meanders occurring each year. A decrease in the frequency of larger meanders was observed from the location offshore of Port Edward (30.22° E, 31.05° S) to the region of the ACT array (27.48° E, 33.35° S), in the satellite data as well as both model experiments, indicating that some of the meanders have dissipated and that both regional HYCOM models are able to resolve this.
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Henigin, Matthew K. "An Investigation of numerical techniques for the fourier matching method acoustic scattering model." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Sep%5FHenigin.pdf.
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Thesis (M.S. in Meterology and Physical Oceanography)--Naval Postgraduate School, September 2005.<br>Thesis Advisor(s): D. Benjamin Reeder, John A. Colosi. Includes bibliographical references (p. 73-75). Also available online.
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Bergman, Selwyn. "A description of the seasonality and its variability in a numerical ocean model of the Southern Benguela Region." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/6460.
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Bibliography: leaves 98-104.<br>The Southern Benguela has, for various reasons, been a focal point for research particularly in recent years. One of the most notable reasons for this interest can he found in the presence of economically viable fish species and their relationship to the process of upwelling. A numerical model of the entire Southern Benguela Region has previously been set up in order to assist furlher studies in the region. This dissertation presents the use of the model in an investigation on the seasonality and the interannual variability in temperature, salinity and general circulation in the region. Hovmuller Plots of the climatology and the associated anomalies were calculated in order to determine the characteristics of the seasonal cycle. It also became possible to deduce a vertical structure of upwelling.
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Wang, Zhengui. "The Development and Proliferation of Summer Algal Blooms in the Oligo/Poly-Haline Portion of the Chesapeake Bay - Observational and Numerical Modeling Studies." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639690.
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Algal blooms occur annually in many parts of the Chesapeake Bay. The causes of algal blooms are complex and can be different in different regions. In this study, we will conduct data analysis for the observed data and adopt various methods to investigate algal bloom phenomenon in three separate regions in the oligo/poly-haline portion of the Bay. Chapter 1 provides a general introduction of the algal bloom research in the Chesapeake Bay. In Chapter 2, an observational analysis and a numerical study on the algal blooms in Back River were conducted. A hypothesis was made that high pH can trigger sediment phosphorus release, which in turn can enhance chlorophyll-a and further increase pH to form a positive feedback loop. to test this theory, water quality model ICM coupled onto SCHISM was applied in Back River to study the phenomenon. Moreover, a pH model was developed to describe the aquatic chemistry. The model results with and without pH model were compared with Bay Program observations for verifying our hypothesis. It proves the importance of sediment phosphorus release on the algal blooms in Back River. In Chapter 3, a theoretical study combined with data analysis on cyanobacteria blooms dynamics was conducted in the upper tidal James River. The theory integrates the physical transport and biological effects, which leads to a simple governing equation composed of an advection term and a phytoplankton net growth term, in both linear and nonlinear forms. In this study, we derived a general analytic solution to the equation. Then, we applied the theory in the tidal freshwater portion of the James River. The theoretical predictions of chlorophyll concentrations were compared with observational data and verified the validity of the solution. In addition, the factors related to the local chlorophyll maximum in tidal freshwater rivers were discussed. In Chapter 4, an observational analysis and numerical experiments were performed to investigate the algal bloom in the polyhaline of the Chesapeake Bay. This exploratory study is aimed to explain the broad distribution of C. polykrikoides blooms in the lower Bay and the sudden disappearance of the bloom in 2014. A hypothesis is made regarding the origin of C. polykrikoides cysts. In this hypothesis, the cysts are considered to be originated from coastal ocean and their transport is under the influence of wind patterns and gravitational circulation. In this study, the hydrodynamics in the lower Chesapeake Bay was first analyzed. Then, a series of particle tracking experiments were conducted for investigating the physical transport of C. polykrikoides cysts under different environmental conditions. Finally, water quality model ICM was used to simulate the algal blooms caused by C. polykrikoides in the lower Bay by incorporating the biological features of C. polykrikoides. The model can generate reasonable magnitude of the algal blooms in 2012, 2013 and simulate no algal bloom condition in 2014.The result indicates that C. polykrikoides cysts could be originated from the coastal ocean, while temperature and wind patterns play important roles in further controlling the subsequent development of the blooms.
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Tarpley, Danielle. "Temporal Variability In Cohesive Sediment Dynamics In A Partially Mixed Estuary, The York River Estuary, Virginia, Usa: A Numerical Study Developed From Observations." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091925.
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Fine-grained material such as silts and clays are the predominant sediment type in low energy systems such as micro-tidal embayments and estuaries. Due to its cohesive nature, fine sediment typically moves through marine systems as aggregated particles, or flocs, rather than as individual mineral grains. The particle's components, local hydrodynamics, and concentration influence floc size, density, and fall velocity. These, in turn, impact suspended sediment transport, which complicates predictions of the fate of sediment for water quality, contaminant distribution, and dredging purposes in these systems. This dissertation used a state-of-the-art modeling system and observations to examine the variability in sediment distribution due to cohesive processes along a partially mixed estuary and to determine the role of flocculation on sediment transport for a muddy site within the York River estuary, Virginia. The Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system was used to simulate the hydrodynamics and suspended sediment transport in a muddy estuarine system. The model accounted for flocculation dynamics with a population balance model, FLOCMOD, changes in the erosion of sediment from the bed due to compaction or bed consolidation, and sediment-induced density gradients. The sensitivity of the sediment distribution was performed using an idealized two-dimensional (vertical and longitudinal) model that produced key estuarine features such as salinity-driven circulation and an estuarine turbidity maximum (ETM). The reference model included the effects of flocculation, bed consolidation, and sediment-induced density gradients. Results from the reference model were compared to test cases, each of which removed one of these processes. This showed that the effects of flocculation on suspended sediment concentrations (SSC) were most significant in the surface waters and in the ETM; whereas bed consolidation decreased SSC along the full length of the estuary. Another test case demonstrated that calculations of SSC and median floc diameter (D50) were sensitive to the number of sediment classes used to represent the floc population. The capabilities of the idealized two-dimensional estuary were extended and used to examine the contribution of flocculation compared to other sediment transport mechanisms such as advection, diffusion, settling, and erosion. The dominant processes that impacted the sediment mass balance in the idealized estuary were flocculation, vertical diffusion, and erosion. Next, the D50 produced by FLOCMOD in the idealized estuary was compared to a theoretical equilibrium floc size (Deq) estimated based on the ratio of SSC to the square root of the shear rate (G). This analysis also produced an estimate for a timescale for flocculation. In general, D50 reached Deq in the bottom boundary of the estuary when the flocculation timescales were on the order of minutes. However, immediately above the sediment bed, Deq was very similar to D50 when erosion was minimal or when finer flocs were eroded from the bed. However, the computed D50 most often differed widely from Deq, indicating that equilibrium theory was not appropriate for much of the idealized estuary. To facilitate the direct application of the flocculation model to the York River estuary, a one-dimensional (vertical) model was designed using observations of hydrodynamics and floc properties from the Claybank site for the vertical water column structure. The sensitivity of SSC and floc distribution to the parameterization of FLOCMOD was assessed using a model representing a spring-neap tidal cycle. The SSC was more sensitive to parameterization in the bottom boundary layer, D50 was less sensitive than SSC, and the grain size distribution width (spread) was more sensitive to the fractal dimension. Model results were then compared to observations to choose parameters to represent the floc population in the York River estuary. Parameterization was challenging, but the preferred representation for the York floc population had a low relative error for SSC and acceptable error for the distribution mode and spread. For the spring-neap tidal cycle in general, vertical diffusion, settling, and erosion accounted for more sediment mass transport than flocculation, but flocculation played an important role in the vertical distribution of sediment via changes in floc size.
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Marin-Moreno, Hector. "Numerical modelling of overpressure generation in deep basins and response of Arctic gas hydrate to ocean warming." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/364170/.
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This thesis is split into the two scientific topics studied; overpressure development in deep basins and present-day and future gas hydrate dissociation in the Arctic. Locating and quantifying overpressure is essential to understand basin evolution and hydrocarbon migration in deep basins and thickly sedimented continental margins. The first part of this thesis develops two new methods, including an inverse model, to impose seismic and geological constraints on models of overpressure generated by the disequilibrium compaction and aquathermal expansion mechanisms. The results provide greater understanding of a low velocity zone (LVZ), inferred from wide-angle seismic data, in the centre of the Eastern Black Sea Basin (EBSB). The application of both methods in the study area indicate that the LVZ located within the Maikop formation, at ~3500-6500 m depth below the seabed (mbsf), is linked to overpressure generated, mainly, by disequilibrium compaction.
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Weaver, Andrew John. "Numerical and analytical modelling of oceanic/atmospheric processes." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27560.
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Two problems in oceanic/atmospheric modelling are examined in this thesis. In the first problem the release of fresh water from a midlatitude estuary to the continental shelf is modelled numerically as a Rossby adjustment problem using a primitive equation model. As the initial salinity front is relaxed, a first baroclinic mode Kelvin wave propagates into the estuary, while along the continental shelf, the disturbance travels in the direction of coastally trapped waves but with a relatively slow propagation speed. When a submarine canyon extends offshore from the estuary, the joint effect of baroclinicity and bottom relief provides forcing for barotropic flow. The disturbance now propagates along the shelf at the first coastally trapped wave mode phase speed, and the shelf circulation is significantly more energetic and barotropic than in the case without the canyon. For both the experiments with and without a canyon an anticyclonic circulation is formed off the mouth of the estuary, generated by the surface outflow and deeper inflow over changing bottom topography. As the deeper inflow encounters shallower depth, the column of fluid is vertically compressed, thereby spinning up anticyclonically due to the conservation of potential vorticity. This feature is in qualitative agreement with the Tully eddy observed off Juan de Fuca Strait. A study of the reverse estuary (where the estuarine water is denser than the oceanic water) shows that this configuration has more potential energy available for conversion to kinetic energy than the normal estuary. Bass Strait may be considered as a possible reverse estuary source for the generation of coastally trapped waves. Model solutions are compared with field observations in the Bass Strait region and with the results of the Australian Coastal Experiment. The effects of a wider shelf and a wider estuary are examined by two more experiments. For the wider shelf, the resulting baroclinic flow is similar to that of the other runs, although the barotropic flow is weaker. The wide estuary model proves to be the most dynamic of all, with the intensified anticyclonic circulation now extending well into the estuary.
In the second problem the effect of the horizontal structure of midlatitude oceanic heating on the stationary atmospheric response is examined by means of a continuously stratified model and a simple two level model, both in the quasigeostrophic β-plane approximation.
Solutions are obtained for three non-periodic zonal heating structures (line source, segmented cosine, and segmented sine). Little difference is observed between the solutions for these two different models (continuously stratified and two level). There are two cases which emerge in obtaining analytic solutions. In case 1, for large meridional wavenumbers, there exists a large local response and a constant downstream response. In case 2, for small meridional wavenumbers, the far field response is now sinusoidal. A critical wavenumber separating these two cases is obtained. The effect of oceanic heating on the atmosphere over the Kuroshio region is examined in an attempt to explain the large correlations observed between winter Kuroshio oceanic heat flux anomalies, and the winter atmospheric surface pressure and 500 & 700 mb geopotential heights, both upstream and downstream of the heating region. In both models, the response is consistent with the observed
correlations. When western North Pacific heating and eastern North Pacific cooling are introduced into the models, a large low pressure response is observed over the central North Pacific. This feature is in excellent agreement with the observed correlations. A time dependent, periodic, two level model (with and without surface friction) is also introduced
in order to study the transient atmospheric response to oceanic heating. The height at which the thermodynamic equation is applied is found to be crucial in determining the response of this model. When the heating is entered into the model near to the surface, unstable modes are prevalent sooner than they would be when the heat forcing is applied at a higher level. As in the steady state models, two cases dependent on the meridional wavenumber ɭ emerge in the analysis. For small scale meridional heating structures (large ɭ), the response consists of an upper level high and a lower level low which propagate eastward with time. For large scale meridional heating structures (small ɭ) the response essentially consists of a wavenumber 3-4 perturbation superimposed on the solution for large ɭ.<br>Science, Faculty of<br>Mathematics, Department of<br>Graduate
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Moalusi, Tumelo Comfort. "Investigation of Wind Variability in the South Atlantic Sector of the Southern Ocean and the Influence on the Upper Ocean in a Numerical Ocean Model." Master's thesis, Faculty of Science, 2019. https://hdl.handle.net/11427/31821.
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Several papers have linked climate variability in the Southern Ocean (SO) with the Southern Annular Mode (SAM), which has seen an increase in the positive phase since the mid-1960s, due to the Antarctic ozone depletion and emissions of greenhouse gases. The SAM is recognized as the main mode of atmospheric variability in the SO. The SAM index allows an understanding of the latitudinal movement (south-north) of the westerly wind belt circling Antarctica and has significant impacts on Antarctic surface temperatures, ocean circulation, and many other aspects of Southern Hemisphere climate and thus the global ocean. During negative phases of the SAM Index, westerlies intensify and move north, bringing about more (or stronger) storms, and low pressure systems over southern Australia. The changes associated with SAM forcing may have impacts on carbon uptake and storage in the SO directly through upwelling and outgassing, and indirectly, by influencing nutrient cycles and phytoplankton activity. Understanding the variability of the wind field in the SO and how it affects ocean circulation, climatic and oceanic variables is important. Thus, this thesis presents the relationship of the SAM index and the upper ocean, specifically analysing sea surface salinity (SSS), sea surface temperature (SST) and the mixed layer depth (MLD), in the Southern Atlantic sector of the SO as presented in numerical ocean models. Two resolutions of NEMO ocean model are compared: a) eddy-permitting (SATLANTIC05), b) eddy-resolving (SATLANTIC12) models, with horizontal resolutions of ½ and 1/12 °, respectively. In situ data from 2013 World Ocean Atlas is used as a benchmark for the analysis. Our model‐based analysis confirms previous studies done on the influence of the SAM on the SO, that a strong relationship exists. The SAM index is positively correlated with wind speed in the Antarctic Zone (AZ) and negatively correlated in the Subantarctic Zone (SAZ). The impacts of this is clear in the upper ocean. These correlations between SAM index and the selected variables at these selected locations confirms that the SAM index corresponds with cool surface temperatures at higher latitudes and a weak cooling at midlatitudes during positive phase, which differs regionally.
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Tsandev, Iana. "Numerical study of the factors affecting the cycling of iron, sulfur and phosphorus in lake sediments." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27061.
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In recent years, reaction transport models have gained importance in the study of diagenesis, which describes the chemical, biological and physical processes that take place in sediments. This project reports on factors influencing chemical profiles in lake sediments through an exploration of a generic reaction transport model which includes representations of the major reactions involved in the cycling of iron, sulfur and phosphorus. We have performed a global sensitivity analysis examining the steady state effects of physical, kinetic and thermodynamic factors on the magnitude, shape and burial concentrations of chemical profiles of iron, sulfur and phosphorus-bearing species. The environmental conditions were varied within a broad range typical of lake sediments. The exploration demonstrates the importance of the nature of boundary conditions (i.e. characteristics of the water column) and their coupling to the water column dynamics. The study additionally points to some chemical mechanisms such as precipitation of vivianite and scavenging of vivianite by sulfide having a dominant influence on the depth profiles of chemical species. Investigation also shows the importance of physical transport processes such as bioturbation near the sediment water interface and sedimentation velocity. Additionally, the distribution of reaction rates with depth and their role in shaping the profiles of chemical concentrations under typical environmental conditions were investigated.
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Young, Aaron C. "Two dimensional acoustic propagation through oceanic internal solitary waves weak scattering theory and numerical simulation." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FYoung.pdf.
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Cho, Kyoung-Ho. "A numerical modeling study on barotropic and baroclinic responses of the Chesapeake Bay to hurricane events." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539616608.
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The barotropic and baroclinic responses of the Chesapeake Bay to forcings from two hurricanes were investigated by using unstructured-grid three-dimensional hydrodynamic models. The model domain includes Chesapeake Bay proper, the tributaries, and its extended continental shelf in the mid-Atlantic Bight. Two hurricanes were studied: Hurricane Floyd of September, 1999 and Hurricane Isabel of September, 2003, both of which made landfall within 100 km of the Chesapeake Bay mouth. Hurricane Floyd in 1999 passed through the entrance of the Bay from southwest to northeast along the coastlines of Virginia as a Category 1 storm, whereas Hurricane Isabel in 2003 made landfall on the east coast of North Carolina and moved inland toward the northwest as a Category 2 storm. For the barotropic simulation of the Bay responding to the hurricanes, the model results were compared with Bay-wide water level observations and the model showed reasonable prediction skill. It was found that the storm surge has two phases: a primary surge induced by the remote winds and a secondary surge induced by the local winds. For both hurricanes, the primary surge induced by remote winds propagated into the Bay initially, but the subsequent phase, influenced by the local wind, was notably different. Hurricane Floyd was followed by northerly (down-Bay) winds, that reduced the primary surge effect and caused a localized set-down; Hurricane Isabel was followed by southerly (up-Bay) winds, which superimposed on the primary surge effect and caused a localized set-up. The volume and salt fluxes were estimated at selected cross-sectional transects throughout the Bay, and it was found consistently for each transect that the net influx dominated during Hurricane Isabel while the net outflux dominated during Hurricane Floyd. For the Bay's tributaries, the large inland river discharge at the headwater can couple with the storm surge event to increase sea surface elevation on the second phase of sea surface elevation rise, which has a significant impact on inundation in the local low-lying areas. For the baroclinic response of the Bay to the hurricanes, the model results agreed reasonably well with additional observed data: sea surface elevation, velocity, and salinity profiles. From the perspective of salt flux, oceanic saltwater influx was evidently pushed into the Bay from the continental shelf at the initial phase of Hurricanes Floyd and Isabel associated with storm surge and salt intrusion. In the second phase, follow up with, down-bay local winds of eastern-type storms tend to enhance the stratification whereas up-Bay local winds of western-type storms tend to reduce the stratification. The hurricane surface wind stress is the primary agent for destratifying water column by transferring generated turbulent kinetic energy to the lower layer. The wind-induced straining during Hurricane Floyd was verified using non-dimensional parameters that incorporated the wind direction and the horizontal salinity gradient. Direct precipitation of hurricane rainfall acted more like a point source onto the Bay surface water, which created a layer of low surface salinity on the sea surface. It has an implication dynamically on generating a sea surface horizontal pressure gradient and re-distributing salinity field after the storm. Extra efforts have been made to conduct idealized experiments for comparing long-term recovery of the Bay to the disturbance created by the two hurricanes. Realistic hurricane wind forcing was applied in a 4-day window with the same initial condition applied in the beginning, and the quasi-steady state condition achieved in the end. Through this exercise, it was found that it took Bay 5-7 days to return to normal condition from the sea surface elevation disturbances for both Hurricanes Floyd and Isabel. For the salinity fields, it took within a range of 20-30 days to recover to the pre-storm condition for the middle and southern portions of the Bay. For the northern portion of the Bay, however, due to the landward barotropic pressure gradient generated a strong salinity rebound and the associated oscillation subsequently after Hurricane Floyd passed, it required twice as long to recover. Sensitivity testing of the effect of river discharge (immediately after the storm) on the recovery time has also been performed. Lastly, the influences of continental shelf dynamics on the Bay's response to the hurricane were examined. It was found that the along shelf wind contributed to the inflow and ouflow at the Bay mouth in the form of Ekman transport, which complemented the contribution generated by the Bay's local wind. The onshore and offshore shelf wind also played a significant role. Because the cyclonic pattern of the hurricane wind field, when the hurricane made the landfall in the US East coast, an along-the-shelf pressure gradient from the north to the south was generated. This pressure gradient, coupled with the Coriolis and friction forces, can generate a quasi-geostrophic balance flow serving to prevent or enhance the inflow across the Bay mouth. The effect is particularly noticeable in the relaxation period during the hurricane passage.
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Roe, Stephen Michael. "Numerical and experimental analysis of initial water impact of an air-dropped REMUS AUV." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/39171.
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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 2005.<br>Includes bibliographical references (leaves 78-79).<br>The initial water impact of a free-falling object is primarily related to the fluid forces on the wetted surface of the object. The shape-dependent added-mass coefficients express the fluid forces integrated over the body, and thus physically represent the additional inertia of water accelerated with the body. The field of hydrodynamic impact has been primarily concerned with estimating the added-mass coefficients of various types of bodies for different water impact types, such as seaplane landings, torpedo drops, and ship slamming. In this study, a numerical model has been constructed to estimate the hydrodynamic impact loads of a REMUS dropped in free-fall from a helicopter in a low hover. Developed by von Alt and associates at Woods Hole Oceanographic Institution, the REMUS (Remote Environmental Monitoring UnitS) is a small, man-portable, torpedo shaped Autonomous Underwater Vehicle (AUV) that is normally operated from small boats for a variety of scientific, industrial, and military applications. Finite-element method software and computer aided drafting tools were used to create a simplified model of REMUS without fins, propeller, or transducers.<br>(cont.) This axisymmetric REMUS model was cut by a flat free surface at various pitch angles and submergence values, and a panel mesh of the wetted surface of the vehicle was created using an automatic mesh generator. Surface boundary conditions are enforced for the free surface by reflecting the body panels using the method of images. Each panel mesh was evaluated for its added- mass characteristics using a source collocation panel method developed by Dr. Yonghwan Kim, formerly of the Vortical Flow Research Laboratory (VFRL) at the Massachusetts Institute of Technology. Experimental impact tests were conducted with a specially-instrumented test vehicle to verify the initial impact accelerations.<br>by Stephen Michael Roe.<br>S.M.
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Sugimura, Peter Joseph. "Arctic Ocean circulation in an idealized numerical model." Thesis, Online version of original thesis, 2008. http://hdl.handle.net/1912/2501.
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Botella, Juan 1967. "Mesoscale variability and mean flow interaction near the Gulf Stream as seen by satellite altimetry and numerical modelling." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/39410.
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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), 2001.<br>Includes bibliographical references (p. 115-120).<br>The interaction between the eddy field and the mean flow near the Gulf Stream is studied here using satellite altimeter measurements and an eddy resolving numerical model. The eddy vorticity flux in the quasigeostrophic framework is obtained from the stream function standard deviation and spatial correlation function assuming the correlation function is homogeneous. An analytical expression is found for the stream function correlation using the altimetric and numerical data. Cases when the correlation function is anisotropic are compared to the isotropic case previously studied by Hogg (1993), who found that the eddy vorticity flux drives two counter rotating gyres on either side of the stream. The anisotropy can be important in the eddy vorticity flux, even when its departure from the isotropic case is small. Meridional or zonal anisotropies can drive recirculation gyres similar in strength and position to the ones driven by the isotropic case. The results when including anisotropy in the diagonal direction suggest that the homogenoeus assumption may not be valid.<br>by Juan Botella.<br>S.M.
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Hemer, Mark A. "The oceanographic influence of sedimentation on the continental shelf : a numerical comparison between tropical and Antarctic environments /." Connect to this title online, 2003. http://adt.lib.utas.edu.au/public/adt-TU20051223.102442.
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Wang, Jia 1957. "Interannual variability of sea-ice cover in Hudson Bay, Baffin Bay and the Labrador Sea, and numerical simulation of ocean circulation and sea-ice cover in Hudson Bay." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39802.
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In part 1, the spatial and temporal relationships between subarctic Canadian sea-ice cover and atmospheric forcing are investigated by analyzing sea-ice concentration, sea-level pressure, and surface air temperature, as well as ice thickness, runoff, and sea surface temperature, from 1953-1988. The sea-ice anomalies in Hudson Bay, Baffin Bay and the Labrador Sea are found to be related to the North Atlantic Oscillation (NAO) and the Southern Oscillation (SO). From the application of a spatial Student's t-test and a Monte Carlo simulation, we found that sea ice responds significantly to the SO event only in summer, and to the NAO event only in winter.<br>A spectral analysis shows that sea-ice cover in Baffin Bay and the Labrador Sea responds to the SO and SAT fluctuations at about 1.7 year, 3-5 year and about 8-10 year periods. In addition, a sea-ice signature associated with the so-called "climate jump" during the early 1960s was found. The ice thickness and ice-melt date data are also used to verify the above findings.<br>In part 2, the three-dimensional ocean general circulation model of Blumberg and Mellor (1983, 87) was used to simulate the winter and summer ocean circulation in Hudson Bay under specified atmospheric forcing and runoff. This model uses vertical sigma coordinates and horizontal orthogonal curvilinear coordinates. The vertical viscosity and diffusivity are computed using the Mellor-Yamada (1982) second-order (2.5) turbulence closure, while the values for similar horizontal parameters are calculated using the Smagorinsky (1963) parameterization. The new version of this model uses the semi-implicit scheme for the shallow water equations (Casulli, 1990). A consistent, modified radiation boundary condition has been developed for the surface elevation and the normal barotropic velocity for the universal multi-level, baroclinic model with strong vertical stratification. The surface cyclonic circulation in summer and winter, due in part to the boundary inflow from Roes Welcome Sound to the northwest of the domain, has been well simulated.<br>In part 3, a dynamic thermodynamic model of sea ice with viscous-plastic rheology (Hibler, 1979; 1980) is used to simulate the seasonal cycle of sea-ice motion, thickness, compactness, and growth rate in Hudson Bay under monthly climatological atmospheric forcing. The simulated results for ice cover in other seasons also compare favourably with the observed climatology and with measurements from satellites. In particular, the model gives complete sea-ice cover in winter and ice-free conditions in late summer. (Abstract shortened by UMI.)
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Strauhs, Hilbert. "A numerical modeling study for the Japan/East Sea (JES) seasonal circulation and thermohaline structure." Thesis, access online version, 1999. http://handle.dtic.mil/100.2/ADA374405.
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Thesis (M.S.)--Naval Postgraduate School, 1999.<br>"September, 1999." Includes abstract. DTIC report no.: ADA374405. Includes bibliographical references (p. 75-79). Full text available online from DTIC.
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Mark, Hannah F. "Seismic and numerical constraints on the formation and evolution of ocean lithosphere." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/127722.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2019<br>Cataloged from PDF of thesis.<br>Includes bibliographical references (pages 151-174).<br>This thesis explicates aspects of the basic structure of oceanic lithosphere that are shaped by the processes that form the lithosphere. The strength of lithospheric plates relative to the underlying mantle enables the surface plate motions and plate boundary processes that characterize plate tectonics on Earth. Surprisingly, we have a relatively poor understanding of the physical mechanisms that make the lithosphere strong relative to the asthenosphere, and we lack a reference model for ordinary lithospheric structure that can serve as a baseline for comparing geophysical observations across locations. Chapters 2 and 3 of this thesis investigate the seismic structure of a portion of the Pacific plate where the simple tectonic history of the plate suggests that its structure can be used as a reference model for oceanic lithosphere. We present measurements of shallow azimuthal seismic anisotropy, and of a seismic discontinuity in the upper mantle, that reflect the effects of shear deformation and melting processes involved in the formation of the lithosphere at mid-ocean ridges. Chapter 4 uses numerical models to explore factors controlling fault slip behavior on normal faults that accommodate tectonic extension during plate formation.<br>by Hannah F. Mark.<br>Ph. D.<br>Ph.D. Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution)
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Hufford, Gwyneth Ellin. "Parameterization of convection in a rotating stratified ocean : comparison of numerical and laboratory experiments with theory." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/59632.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, and Woods Hole Oceanographic Institution, 1995.<br>Includes bibliographical references (leaves 70-73).<br>by Gwyneth Ellin Hufford.<br>M.S.