Tesis: "Ocean field"

1

Melo, Jose Luis Branco Seabra de. "Nonlinear parametric wave model compared with field data". Monterey, Calif. : Naval Postgraduate School, 1985. http://catalog.hathitrust.org/api/volumes/oclc/57738811.html.

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2

Brown, Jennifer. "Field measurements and modeling of surfzone currents on inhomogeneous beaches". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 117 p, 2009. http://proquest.umi.com/pqdweb?did=1885467621&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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3

Lilly, Jonathan M. "Observations of the Labrador Sea eddy field /". Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/11041.

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4

Colbert, David B. "Field evaluation of ocean wave measurements with GPS buoys". Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5117.

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Approved for public release; distribution is unlimited
An intercomparison of Datawell accelerometer buoys, Datawell GPS buoys, and prototype GPS buoys was conducted to determine the viability of using off-the-shelf GPS receivers to measure ocean surface waves. In the experiment, conducted off the coast of California near Bodega Bay, clusters off Datawell and prototype GPS buoys were deployed to collect ocean surface wave measurements. The first phase of the research was an intercomparison of wave measurements from a Datawell accelerometer sensor, the Magellan MMCX GPS receiver and the GlobalSat MR-350 GPS receiver. The Datawell accelerometer and the Magellan MMCX receiver measurements of both vertical and horizontal wave orbital excursions are in good agreement. The GlobalSat MR-350 receiver also accurately resolved horizontal wave orbital displacements but failed to reproduce the vertical wave excursion measurement by the accelerometer sensors. The second phase of the project was an independent intercomparison between the Datawell MK-II accelerometer buoys, Datawell Waverider GPS buoys, and the prototype GPS buoys built by the NPS team using the Magellan MMCX receiver. The intercomparison showed good agreement between the off-the-shelf GPS buoys, the newer Datawell GPS buoys as well as the traditional Datawell accelerometer buoys in the energetic part of the wave spectrum.

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5

Strohm, Frederic M. "Simulation of ocean acoustic tomography using matched field processing". Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/26243.

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6

Brown, Jeffrey W. "Lagrangian field observations of rip currents". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 133 p, 2008. http://proquest.umi.com/pqdweb?did=1633772921&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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7

Henry, Legena Albertha. "A study of ocean wave statistical properties using nonlinear, directional, phase-resolved ocean wave-field simulations". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1912/3230.

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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), February 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 327-334).
In the present work, we study the statistics of wavefields obtained from non-linear phase-resolved simulations. The numerical model used to generate the waves models wave-wave interactions based on the fully non-linear Zakharov equations. We vary the simulated wavefield's input spectral properties: directional spreading function, Phillips parameter and peak shape parameter. We then investigate the relationships between a wavefield's input spectral properties and its output physical properties via statistical analysis. We investigate surface elevation distribution, wave definition methods in a nonlinear wavefield with a two-dimensional wavenumber, defined waves' distributions, and the occurrence and spacing of large wave events.
by Legena Albertha Henry.
S.M.

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8

Deffenbaugh, Max. "A matched field processing approach to long range acoustic navigation". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/34053.

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9

Stephens, Britton Bruce. "Field-based atmospheric oxygen measurements and the ocean carbon cycle /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1999. http://wwwlib.umi.com/cr/ucsd/fullcit?p3035435.

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10

Grant, Justin Alexander. "Far-field noise from a rotor in a wind tunnel". Thesis, Florida Atlantic University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10154927.

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This project is intended to demonstrate the current state of knowledge in the prediction of the tonal and broadband noise radiation from a Sevik rotor. The rotor measurements were made at the Virginia Tech Stability Wind Tunnel. Details of the rotor noise and flow measurements were presented by Wisda et al(2014) and Murray et al(2015) respectively. This study presents predictions based on an approach detailed by Glegg et al(2015) for the broadband noise generated by a rotor in an inhomogeneous flow, and compares them to measured noise radiated from the rotor at prescribed observer locations. Discrepancies between the measurements and predictions led to comprehensive study of the flow in the wind tunnel and the discovery of a vortex upstream of the rotor at low advance ratios. The study presents results of RANS simulations. The static pressure and velocity profile in the domain near the rotor’s tip gap region were compared to measurements obtained from a pressure port array and a PIV visualization of the rotor in the wind tunnel

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11

Wu, Guangyu 1972. "Direct simulation and deterministic prediction of large-scale nonlinear ocean wave-field". Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/33450.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004.
Includes bibliographical references (p. 251-258).
Despite its coarse approximation of physics, the phase-averaged wave spectrum model has been the only type of tool available for ocean wave prediction in the past 60 years. With the rapid advances in sensing technology, phase-resolved nonlinear wave modeling, and high performance computing capability in recent years, the time has come to start developing a new generation tool for ocean wave prediction using direct phase-resolved simulations. The key issues in developing such a tool are: (i) proper specification of initial/boundary conditions of the nonlinear ocean wave-field; (ii) development of efficient algorithm for simulation of large-scale wave-field evolution on high performance computing platforms; (iii) modeling of nonlinear physics in ocean wave evolution such as wave-wave, wave-current, wave-bottom and wave-wind interactions. The objective of this thesis is to address (i), (ii) and part of (iii). For (i), a multi-level iterative wave reconstruction tool is developed to deter- ministically reconstruct a nonlinear ocean wave-field based on single or multiple wave probe records, using both analytic low-order Stokes solutions and High-Order-Spectral (HOS) nonlinear wave model.
(cont.) With the reconstructed wave-field as the initial conditions, the ocean wave-field can then be simulated and forecasted into the future deterministically with the physics-based phase-resolved wave model. A theoretical framework is developed to provide the validity of the reconstructed wave-field and the predictability of future evolution of the reconstructed wave-field for given wave conditions. The effects of moving probe, ambient current and finite water depth on the predictable region are studied respectively. To demonstrate its efficacy and useful- ness, the wave reconstruction tool is applied to reconstruct the full kinematics of steep two- and three-dimensional irregular waves using both wave-basin measurements and synthetic data. Excellent agreements between the reconstructed nonlinear wave-field and the original specified wave data are obtained. In particular, it is shown that the inclusion of high-order effects in wave reconstruction is of significance, especially for the prediction of the wave kinematics such as velocity and acceleration. For (ii), a highly scalable HOS wave model is developed and applied to study both two- and three-dimensional ocean wave-field evolution for a realistic space and time scale.
(cont.) Effective filtering tools are developed to model the wave breaking process in wave evolution. For (iii), the HOS wave model is enhanced to account for not only nonlinear wave-wave interactions, but also nonlinear wave interaction with variable ambient current. With this tool, the effects of variable ambient current on nonlinear wave-field evolution are investigated. As a final illustration, this tool is applied in practical ship motion control. Based on the deterministically forecasted wave-field provided by this tool, an optimal path is obtained to reduce the RMS heave motion of ship in point-to-point transit.
by Guangyu Wu.
Ph.D.

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12

Dostal, Jan [Verfasser]. "Modelling of the Magnetic Field Induced by Ocean Circulation / Jan Dostal". Berlin : Freie Universität Berlin, 2015. http://d-nb.info/1069532568/34.

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13

Wu, Cheng Y. (Cheng Yi) 1938. "Wave-wave interactions and the infrasonic pressure field in the ocean". Thesis, University of Auckland, 1988. http://hdl.handle.net/2292/2469.

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Building on Kibblewhite's long term investigations of the nonlinear wave-wave interactions and the infrasonic ocean noise and the microseisms these induce, this thesis further explores the physical nature of these processes. The classical description of this interaction, which takes into account only the homogeneous component of the induced field, has been extended to include the inhomogeneous component. A complete expression for the wave induced noise spectrum is established following a geometrical analysis of the dispersion relations among interacting waves. The relative importance of these two components and their directivity properties are also calculated and discussed. It is shown that while at observation points deeper than 500 meters the effects of the inhomogeneous component can be regarded as negligible, it can cause an increase of noise level of up to 40 dB in the region near the surface of the sea. Furthermore, in contrast to the nearly omni-directional distribution of the homogeneous component of the induced acoustic field, there is a tendency for the energy associated with the inhomogeneous component to focus in the wind direction. Based upon a multilayer analysis of a visco-elastic geoacoustic model, Green's functions and the spectral transfer functions relating the surface source pressure field to the underwater noise and microseism fields are derived for both near and far field cases. A 3-dimensional presentation defined on the dispersion plane (frequency and horizontal wave number) is introduced to describe the sea bottom reflection-loss and, Green's functions, and is extended to include the inhomogeneous region for the first time. The characteristics of this 3-D presentation are explained in terms of the geoacoustic parameters. The influence of the interaction of multiple seas (and swell) on the induced acoustic field are also discussed in this thesis. All these effects are considered in the calculation of the synthetic spectra of both the noise and microseism field. When compared with measured data excellent agreement is found between the theoretical and experimental results, which provides further confirmation that the nonlinear interaction is the most important source of the infrasonic ocean noise, as well as confirming the basic validity of the procedure introduced by Kibblewhite and Ewans to derive the ocean noise spectra from microseism records.

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14

Daly, Pter M. (Peter Michael). "Cramér-Rao bounds for matched field tomography and ocean acoustic tomography". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43920.

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15

Trainor, Lincoln Thomas. "Field observations and SWAN model predictions of wave evolution in a muddy coastal environment". Thesis, Monterey, Calif. : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Jun/09Jun%5FTrainor.pdf.

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Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, June 2009.
Thesis Advisor(s): Herbers, Thomas H. C. ; Janssen, Tim T. "June 2009." Description based on title screen as viewed on July 14, 2009. Author(s) subject terms: ocean waves, continental shelf, mud, littoral, SWAN. Includes bibliographical references (p. 69-71). Also available in print.

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16

Harker, Genevra E. L. "A comparison between optical properties measured in the field and the laboratory, and the development of an optical model". Thesis, Bangor University, 1997. https://research.bangor.ac.uk/portal/en/theses/a-comparison-between-optical-properties-measured-in-the-field-and-the-laboratory-and-the-development-of-an-optical-model(73ac3679-0a9e-4fed-af24-560041daca25).html.

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17

Link, Shmuel G. "Field measurements of a swell band, shore normal, flux divergence reversal". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/67625.

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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), June 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 55-56).
Throughout this thesis we will discuss the theoretical background and empirical observation of a swell band shore normal flux divergence reversal. Specifically, we will demonstrate the existence and persistence of the energy flux divergence reversal in the nearshore region of Atchafalaya Bay, Gulf of Mexico, across storms during the March through April 2010 deployment. We will show that the swell band offshore component of energy flux is rather insignificant during the periods of interest, and as such we will neglect it during the ensuing analysis. The data presented will verify that the greatest flux divergence reversal is seen with winds from the East to Southeast, which is consistent with theories which suggest shoreward energy flux as well as estuarine sediment transport and resuspension prior to passage of a cold front. Employing the results of theoretical calculations and numerical modeling we will confirm that a plausible explanation for this phenomena can be found in situations where temporally varying wind input may locally balance or overpower bottom induced dissipation, which may also contravene the hypothesis that dissipation need increase shoreward due to nonlinear wave-wave interactions and maturation of the spectrum. Lastly, we will verify that the data presented is consistent with other measures collected during the same deployment in the Atchafalaya Bay during March - April 2010.
by Shmuel G. Link.
S.M.

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18

Joyce, Michael D. "Quadruplet expansion of the acoustic pressure field in a wedge shaped ocean". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from the National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA275121.

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19

Baker, Joshua L. "Mooring Analysis of the Ocean Sentinel through Field Observation and Numerical Simulation". Thesis, Oregon State University, 2013. http://hdl.handle.net/10945/43474.

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CIVINS
Mooring systems are used to secure offshore structures to the ocean floor. They can provide general station-keeping, where a ship, buoy, or platform is kept in a general location. They can also provide more finite positioning, where heading, draught, elevation, and GPS coordinates are tightly controlled. The behavior of a mooring system depends greatly on its configuration and components, which is discussed in more detail in this section. There are two major organizations that produce mooring system specifications: Det Norske Veritas (DNV) and the American Petroleum Institute. DNV specifications are available for free online, and several of them were reviewed during this study (DNV 2005, DNV 2008, and DNV 2010). Additionally, two reports prepared specifically for the Oregon Coast by Sound and Sea Technology Engineering Solutions (SST) were important sources for this study (SST 2009 and SST 2012).

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20

Hobe, Marc von. "The behaviour of carbonyl sulphide in the ocean : field and modelling studies". Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323224.

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21

Ainslie, Michael Anthony. "The sound pressure field in the ocean due to bottom interacting paths". Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314950.

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22

Friman, Sonja. "Field Test of a Brillouin LIDAR for Temperature Profiles of the Ocean". Thesis, KTH, Tillämpad fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-185795.

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23

McAllister, Mark Laing. "Analysis of laboratory and field measurements of directionally spread nonlinear ocean waves". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28762.

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Surface gravity waves exist in the oceans as multi-directional nonlinear phenomena. Understanding how these two properties interact is intrinsically important in itself. Furthermore, an understanding of this relationship may be used to gain insight into other oceanic phenomena. This thesis first describes an experimental investigation into the relationship between directionality and non-linearity (Part I). This relationship was then used as a tool to estimate the directional spreading of field data (Part II). Experiments have been conducted in which directionally spread focused wave groups were created in a wave tank. The relationship between the degree of directional spreading and the second-order bound harmonics of the wave groups was examined, in particular the formation of a `set-up'. These measurements were then compared to predictions from second-order theories, finding good agreement. The two-dimensional structure of the bound waves was explored giving new insight into the underlying physics. Experiments were then carried out for directionally spread crossing wave groups. It is believed that the crossing of two sufficiently separated wave groups may be the cause of an anomalous set-up in the second-order bound waves observed for some extreme and potentially freak waves. This set-up is reproduced experimentally. Again, the results of these test agreed very well when compared to second-order theory. The insight gained from the foregoing experiments was then utilised in the analysis of field data. A method, which requires only a single measurement to estimate the observed degree of directional spreading, was applied to a large dataset of field measurements from the North Alwyn platform in the North Sea. This method was then compared to conventional approaches, which require multiple concurrent measurements. The method that requires only a single measurement was shown to be effective, and presents a promising approach to gaining additional insight about the directional spreading of point observations.

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24

Woodward, E. C. (Ernst Carl) 1968. "Acoustic characterization of a stationary field synchronous motor". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/91348.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.
by E.C. Woodward, Jr.
S.M.

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25

Van, der Westhuysen A. J. "The application of the numerical wind wave model SWAN to a selected field case on the South African coast". Thesis, Link to the online version, 2002. http://hdl.handle.net/10019.1/3632.

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26

Tarrell, Alvin E. (Alvin Edward) 1962. "A field investigation of diffusion within a submerged plant canopy". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10218.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1997, and Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1997.
Includes bibliographical references (leaves 66-69).
by Alvin E. Tarrell.
M.Eng.
M.S.

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27

Prabhakar, Gouri. "Characteristics of Regional Aerosols: Southern Arizona and Eastern Pacific Ocean". Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/332834.

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Atmospheric aerosols impact the quality of our life in many direct and indirect ways. Inhalation of aerosols can have harmful effects on human health. Aerosols also have climatic impacts by absorbing or scattering solar radiation, or more indirectly through their interactions with clouds. Despite a better understanding of several relevant aerosol properties and processes in the past years, they remain the largest uncertainty in the estimate of global radiative forcing. The uncertainties arise because although aerosols are ubiquitous in the Earth's atmosphere they are highly variable in space, time and their physicochemical properties. This makes in-situ measurements of aerosols vital in our effort towards reducing uncertainties in the estimate of global radiative forcing due to aerosols. This study is an effort to characterize atmospheric aerosols at a regional scale, in southern Arizona and eastern Pacific Ocean, based on ground and airborne observations of aerosols. Metals and metalloids in particles with aerodynamic diameter (Dp) smaller than 2.5μm are found to be ubiquitous in southern Arizona. The major sources of the elements considered in the study are identified to be crustal dust, smelting/mining activities and fuel combustion. The spatial and temporal variability in the mass concentrations of these elements depend both on the source strength and meteorological conditions. Aircraft measurements of aerosol and cloud properties collected during various field campaigns over the eastern Pacific Ocean are used to study the sources of nitrate in stratocumulus cloud water and the relevant processes. The major sources of nitrate in cloud water in the region are emissions from ships and wildfires. Different pathways for nitrate to enter cloud water and the role of meteorology in these processes are examined. Observations of microphysical properties of ambient aerosols in ship plumes are examined. The study shows that there is an enhancement in the number concentration of giant cloud condensation nuclei (Dp>2 μm) in ship plumes relative to the unperturbed background regions over the ocean.

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28

Wist, Hanne Therese. "Statistical properties of successive ocean wave parameters". Doctoral thesis, Norwegian University of Science and Technology, Norwegian University of Science and Technology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16.

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For random waves the free surface elevation can be described by a number of individual wave parameters. The main objective of this work has been to study the statistical properties of individual parameters in successive waves; the wave crest height, the wave height and the wave period.

In severe sea states the wave crest heights exhibit a nonlinear behavior, which must be reflected in the models. An existing marginal distribution that uses second order Stokes-type nonlinearity is transformed to a two-dimensional distribution by use of the two–dimensional Rayleigh distribution. This model only includes sum frequency effects. A two-dimensional distribution is also established by transforming a second order model including both sum and different frequency effects. Both models are based on the narrow-band assumption, and the effect of finite water depth is included. A parametric wave crest height distribution proposed by Forristall (2000) has been extended to two dimensions by transformation of the two-dimensional Weibull distribution.

Two successive wave heights are modeled by a Gaussian copula, which is referred to as the Nataf model. Results with two initial distributions for the transformation are presented, the Næss (1985) model and a two-parameter Weibull distribution, where the latter is in best agreement with data. The results are compared with existing models. The Nataf model has also been used for modeling three successive wave heights. Results show that the Nataf transformation of three successive wave heights can be approximated by a first order autoregression model. This means that the distribution of the wave height given the previous wave height is independent of the wave heights prior to the previous wave height. The simulation of successive wave heights can be done directly without simulating the time series of the complete surface elevation.

Successive wave periods are modeled with the Nataf transformation by using a two-parameter Weibull distribution and a generalized Gamma distribution as the initial distribution, where the latter is in best agreement with data. Results for the marginal and two-dimensional distributions are compared with existing models. In practical applications, it is often of interest to consider successive wave periods with corresponding wave heights exceeding a certain threshold. Results show that the distribution for successive wave periods when the corresponding wave heights exceed the root-mean-square value of the wave heights can be approximated by a multivariate Gaussian distribution. When comparing the results with data, a long time series is needed in order to obtain enough data cases. Results for three successive wave periods are also presented.

The models are compared with field data from the Draupner field and the Japan Sea, and with laboratory data from experiments at HR Wallingford. In addition, data from numerical simulations based on second order wave theory, including both sum and frequency effects, are included.

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29

Zhang, Xue-Yong. "Ocean outfall modeling--interfacing near and far field models with particle tracking method". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11205.

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30

Trimble, Jenifer. "Influencing students to become stewards of the Earth's ocean". Master's thesis, University of Central Florida, 2012. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5539.

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The purpose of this action research study was to document 8th grade students' experiences at a residential marine learning facility as they discovered the interconnections between life on Earth and its dependency on ocean health. My goal was for students to take their new knowledge and share it with others in a quest to become educated and caring stewards of the Earth's ocean. Students in this study participated in open peer and instructor discussions, performed full and guided inquiry activities, and snorkeled among the shallow water habitats that transition from mangroves toward coral reefs to discover the interconnections among shallow water marine habitats and the critical necessity of biological diversity among habitats. The processes used to collect data for this action research study were a pre/post knowledge assessment about coral reefs, videotaped conversations among peers and instructors, photographs documenting student engagement in activities, and interviews conducted at the conclusion of the trip. The themes that emerged included a mindset of ocean stewardship, deep engagement in inquiry-driven activities while interacting among peers, the ability to clearly articulate the effects of human impact on biological diversity and the need to maintain sustainable shallow water ecosystems that are biologically diverse. Although this study was only conducted over a three day weekend, the emergent themes highlight the value of providing students with opportunities to interact with nature. Experiential learning not only contributes to the various ways of knowing but such experiences help students develop a stronger sense of self perception and values as they begin formulating their sense of relationship to and responsibilities toward their own communities and the larger, natural world.
M.Ed.
Masters
Teaching, Learning and Leadership
Education and Human Performance
K-8 Math and Science

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31

Xu, Wen 1967. "Performance bounds on matched-field methods for source localization and estimation of ocean environmental parameters". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/91333.

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Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering and the Woods Hole Oceanographic Institution), 2001.
Includes bibliographical references (leaves 207-215).
Matched-field methods concern estimation of source location and/or ocean environmental parameters by exploiting full wave modeling of acoustic waveguide propagation. Typical estimation performance demonstrates two fundamental limitations. first, sidelobe ambiguities dominate the estimation at low signal-to-noise ratio (SNR), leading to a threshold performance behavior. Second, most matched-field algorithms show a strong sensitivity to environmental/system mismatch, introducing some biased estimates at high SNR. In this thesis, a quantitative approach for ambiguity analysis is developed so that different mainlobe and sidelobe error contributions can be compared at different SNR levels. Two large-error performance bounds, the Weiss-Weinstein bound (WWB) and Ziv-Zakai bound (ZZB), are derived for the attainable accuracy of matched-field methods. To include mismatch effects, a modified version of the ZZB is proposed. Performance analyses are implemented for source localization under a typical shallow water environment chosen from the Shallow Water Evaluation Cell Experiments (SWellEX). The performance predictions describe the simulations of the maximum likelihood estimator (MLE) well, including the mean square error in all SNR regions as well as the bias at high SNR. The threshold SNR and bias predictions are also verified by the SWellEX experimental data processing. These developments provide tools to better understand some fundamental behaviors in matched-field performance and provide benchmarks to which various ad hoc algorithms can be compared.
by Wen Xu.
Ph.D.

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32

Kim, Won-Gyu 1962. "A Study of Nonlinear Dynamics in an Internal Water Wave Field in a Deep Ocean". Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc278092/.

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The Hamiltonian of a stably stratified incompressible fluid in an internal water wave in a deep ocean is constructed. Studying the ocean internal wave field with its full dynamics is formidable (or unsolvable) so we consider a test-wave Hamiltonian to study the dynamical and statistical properties of the internal water wave field in a deep ocean. Chaos is present in the internal test-wave dynamics using actual coupling coefficients. Moreover, there exists a certain separatrix net that fills the phase space and is covered by a thin stochastic layer for a two-triad pure resonant interaction. The stochastic web implies the existence of diffusion of the Arnold type for the minimum dimension of a non-integrable autonomous system. For non-resonant case, stochastic layer is formed where the separatrix from KAM theory is disrupted. However, the stochasticity does not increase monotonically with increasing energy. Also, the problem of relaxation process is studied via microscopic Hamiltonian model of the test-wave interacting nonlinearly with ambient waves. Using the Mori projection technique, the projected trajectory of the test-wave is transformed to a form which corresponds to a generalized Langevin equation. The mean action of the test-wave grows ballistically for a short time regime, and quenches back to the normal diffusion for a intermediate time regime and regresses linearly to a state of statistical equilibrium. Applying the Nakajima-Zwanzig technique on the test-wave system, we get the generalized master equation on the test-wave system which is non-Markovian in nature. From our numerical study, the distribution of the test-wave has non-Gaussian statistics.

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33

Crawford, James H. "An analysis of the photochemical environment over the Western, North Pacific based on airborne field observations". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/25867.

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34

Murphy, Paulette P. "The carbonate system in seawater : laboratory and field studies /". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/8509.

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35

Tiessen, Meinard. "Predicting the development of crescentic bed patterns : a comparison of linear stability model results with field observations". Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11028/.

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Large scale patterns in the seabed often occur in the nearshore zone of sandy beaches. A widely occurring bed pattern is the crescentic bar. These bed patterns develop under moderate wave conditions, and form a lunate shaped alongshore pattern in front of a coast. Over recent years, knowledge concerning the development, occurrence, and characteristics of these bed patterns has been significantly expanded through field studies and modelling attempts. An example of such a model is the linear stability analysis, which describes the initial development of crescentic bed patterns along an undisturbed beach. To date, comparisons between field measurements and modelling results have been general in nature. The purpose of this research is to investigate whether a linear stability analysis, which is useful for understanding the physics of emerging bed-forms, can be used to make quantitative predictions in the field. To this end a morphodynamical linear stability model (Morfo60, [Calvete et al., 2005]) is used to describe the development of crescentic bed patterns at the coast at the USACE Field Research Facility in Duck, North Carolina, USA. Wave, tide and bathymetry data recorded at Duck over a two month period in 1998 are used to model the development of these morphodynamical patterns. The model predictions are compared with field observations made at Duck, over the same two month period, reported by van Enckevort et al. [2004]. A direct comparison shows that predicted length scales of crescentic bed patterns are similar to those observed. However, the model predictions show more fluctuations than are observed in the field. This is because the model describes the development of crescentic bed patterns starting from an alongshore constant bed, whereas in reality bed patterns already exist in most situations. An algorithm is developed to overcome these fluctuations and identifies the more physically significant model predictions based on large growth rates and consistency in length scales. The moments at which physically significant model predictions occur correspond better with field observations than the original model predictions. The effects of pre-existing bed-forms on the development of crescentic bed patterns are investigated using a non-linear model (Morfo55, [Garnier, 2006]). Results show that pre-existing bed patterns can have significant effects, however, the finally dominant length scale, the linear growth and decay rates, and the migration rate can be accurately described by a linear stability model. Pre-existing length scales that exhibit significant linear growth will remain and undergo further development, whereas length scales that are outside the linear growth rate curve decay and give rise to a bed pattern with a bigger linear growth rate. The conclusions drawn from the research concerning pre-existing bed patterns are applied to improve predictions linear stability model. This results in considerable improvements in the comparison of model predictions with field observations, for certain periods of time.

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36

Bowles, Julie Ann. "Paleointensity of Earth's magnetic field, with applications to the study of mid-ocean ridge accretionary processes". Diss., Connected to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3179291.

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Thesis (Ph. D.)--University of California, San Diego, 2005.
Title from first page of PDF file (viewed March 1, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

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37

Hopkins, Julia A. "Field observations and numerical model simulations of a migrating inlet system". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113475.

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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution), 2017
Cataloged from PDF version of thesis.
Includes bibliographical references.
Waves, currents, and bathymetric change observed along 11 km of the southern shoreline of Martha's Vineyard include storm events, strong tidal flows (> 2 m/s), and an inlet migrating 2.5 km in ~7 years. A field-verified Delft3D numerical model developed for this system is used to examine the hydrodynamics in the nearshore and their effect on the migrating inlet. An initial numerical experiment showed that the observed 700 tidal modulation of wave direction in the nearshore was owing to interactions with tidal currents, and not to depth-induced refraction as waves propagated over complex shallow bathymetry. A second set of simulations focused on the separation of tidal currents from the southeast corner of Martha's Vineyard, showing the positive correlation between flow separation and sediment transport around a curved shoreline. Observations of waves, currents, and bathymetric change during hurricanes were reproduced in a third numerical experiment examining the competition between storm waves, which enhance inlet migration, and strong tidal currents, which scour the inlet and reduce migration rates. The combined field observations and simulations examined here demonstrate the importance of wave and tidal current forcings on morphological evolution at timescales of days to months.
by Julia A. Hopkins.
Ph. D.
Ph.D. Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution)

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38

Sun, Sihao. "Maritime Mesh Network Simulation". Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/84871.

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Maritime network plays an important role in civilian and academic applications. However, traditional maritime communication technologies cannot provide broadband services that can satisfy users' need. In this thesis, we proposed a buoy-based maritime mesh network and analyzed the maritime communication characteristics. Then we proposed a link-state-aware routing protocol to address link blockage problem when routing packets and built a simulator to evaluate the network performance. There are several parts of my work. Firstly, we simulated ocean water field. Jerry Tessendorf proposed a method to create ocean surface based on Phillips spectrum which is a wind-driven, semi-empirical oceanography model. We implemented this algorithm in MATLAB and adjusted a key parameter in this algorithm. Secondly, we proposed a link-state-aware routing protocol. Link stability is related to sea state and instant nodes elevation. In link-state-aware routing protocol, the transmitter will send predicted elevation information to receiver, and receiver will decide if the link is stable in next several seconds based on sea states and node elevation information. Finally, we simulated this mesh network in network simulator 3 (NS3). This simulator will enable users to assess the network performance in various sea states. We also need to build a new mobility model, a new propagation model and implement a collision-free access method (spatial TDMA) model in simulation.
Master of Science

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39

Wichers, Sacha. "Verification of numerical models for hydrothermal plume water through field measurements at TAG". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/39173.

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Thesis (S.M.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering; and the Woods Hole Oceanographic Institution), 2005.
Includes bibliographical references (p. 63-65).
Hydrothermal vents discharge superheated, mineral rich water into our oceans, thereby providing a habitat for exotic chemosynthetic biological communities. Hydrothermal fluids are convected upwards until they cool and reach density equilibrium, at which point they advect laterally with the current. The neutrally buoyant plume layer can have length scales on the order of several kilometers, and it therefore provides the best means to detect the presence of vent fields on the seafloor, which typically have length scales on the order of a few meters. This thesis uses field measurements of the velocity, temperature and particulate anomalies associated with the TAG hydrothermal plume to demonstrate that tidal currents exert a strong impact on the plume shape, and to provide new constraints on the thermal power of the TAG hydrothermal system. The results show that the power output of the TAG system is on the order of 6000 MW, which is up to two orders of magnitude greater than previous estimates, and that there is considerably more entrainment than had previously been assumed.
by Sacha Wichers.
S.M.

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40

Scott, Robert Samuel. "The influence of tidal, despinning and magma ocean cooling stresses on the moon's early global stress field". Thesis, Lancaster University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440392.

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41

Rodríguez, Buño Mariana. "Near and far field models of external fluid mechanics of Ocean Thermal Energy Conversion (OTEC) power plants". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79495.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 126-130).
The world is facing the challenge of finding new renewable sources of energy - first, in response to fossil fuel reserve depletion, and second, to reduce greenhouse gas emissions. Ocean Thermal Energy Conversion (OTEC) can provide renewable energy by making use of the temperature difference between the surface ocean and deep ocean water in a Rankine cycle. An OTEC plant pumps huge volumes of water from the surface and nearly 1 km depth, and releases it at an intermediate depth. The effects of this enormous flux are crucial to understand since disruption of the ambient temperature stratification can affect the efficiency of the plant itself and of adjacent plants. This thesis aims to study the external fluid mechanics of offshore OTEC power plants, to assess their environmental impact and to help analyze whether OTEC plants can provide a sustainable source of energy. Although there has been interest in OTEC for several decades, so far primarily physical and analytical models have been developed. In this study numerical models are developed to model OTEC operating plants: integral models for the near and intermediate field and a large-scale ocean general circulation model. Two strategies in modeling OTEC plant discharge are used to analyze plume dynamics: the "Brute Force" approach, in which a circulation model, MITgcm, computes the near, intermediate and far field mixing; and the "Distributed Sources and Sinks" approach, in which the near and intermediate field are represented in the circulation model by sources and sinks of mass computed by integral models. This study concludes that the Brute Force modeling strategy is highly computationally demanding and sometimes inaccurate. Such simulations are very sensitive to model resolution and may require the use of unrealistic model parameters. The Distributed Sources and Sinks approach was found to be capable of modeling the plume dynamics accurately. This method can be applied to the study of adjacent OTEC power plant interaction, redistribution of nutrients, and propagation of contaminants.
by Mariana Rodríguez Buño.
S.M.

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42

De, Figueiredo Mark A. (Mark Anthony) 1978. "The Hawaii carbon dioxide ocean sequestration field experiment : a case study in public perceptions and institutional effectiveness". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/16929.

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Thesis (S.M.)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.
Includes bibliographical references.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
In December 1997, an international project agreement was signed in Kyoto for a collaborative study of the direct injection of carbon dioxide into the deep ocean. After a detailed international site selection process, the Natural Energy Laboratory of Hawaii Authority (NELHA), a quasi-governmental organization, was chosen as the host for the project in March 1998. In addition to fulfilling the necessary technical criteria, NELHA maintained an ocean research corridor, and it was impressed upon the project team that this could facilitate the permitting process. International steering and technical committees served as advisors to the Hawaii-based project general contractor, Pacific International Center for High Technology Research. The committees also planned a multi-year public outreach program to engage residents of Hawaii about the carbon sequestration project. Before the outreach program began, a reporter wrote about the planned carbon sequestration experiment in a March 18, 1999 front-page article in the local newspaper, West Hawaii Today. As a result, some members of the community started organizing an opposition to the project, culminating in the creation of the "Coalition Against CO2 Dumping." Concerns raised by the opposition included the environmental impacts on the ocean ecology, Not-In-My-Backyard feelings, anti-fossil fuel sentiment, and issues regarding native Hawaiian sovereignty. The project team reacted by implementing a dual public relations and outreach strategy, creating a website, responding to hundreds of emails and letters, and holding public meetings. A major fallout from the opposition was that permitting became much more difficult, involving multiple agencies on the state and federal level. In addition, the controversy affected the project's relationship to its NELHA host and caught the attention of the Hawaii state legislature. After the project team conducted an Environmental Assessment, US Department of Energy issued a Finding of No Significant Impact (FONSI), an important milestone in the permitting process. This thesis summarizes the events from project start through the issuing of the FONSI, discusses the lessons learned from the experience, and provides recommendations for institutions dealing with public perception issues in future projects.
by Mark Anthony de Figueiredo.
S.M.

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43

Moore, Tommy S. "Time-series electrochemical studies in the lower Delaware Bay and at the 9 degrees 50' north East Pacific Rise hydrothermal vent field". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 137 p, 2009. http://proquest.umi.com/pqdweb?did=1654491241&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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44

Xu, Zao Mech E. Massachusetts Institute of Technology. "A DNS capability for obtaining underwater light field and retrieving upper ocean conditions via in-water light measurements". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67775.

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Thesis (Mech. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 189-192).
Predicting the ocean surface conditions (surface elevation, temperature, wind speed, etc.) becomes more and more important for both real life and military applications. This thesis presents a direct numerical simulation (DNS) capability of solving complicated natural light field patterns in the ocean-atmosphere system. The DNS is applied by means of Monte Carlo method to solve radiative transfer for both unpolarized and polarized natural light radiation, especially strongly affected with dynamic air-sea boundary conditions and inhomogeneous ocean turbulence. In the thesis, radiative transfer theory and Monte Carlo method are introduced. The realization and rigorous code validation are given. In order to apply this software to engineering, applications of radiative transfer theory in ocean-atmosphere system is briefly introduced. To achieve most of the engineering of retrieving ocean surface properties, systematical investigations of how dynamic air-sea boundaries affect the underwater radiance and polarization are taken and discussed. To predict the upper-level ocean conditions based on radiometric underwater measurements, a scheme of inversion algorithm of reconstructing inherent optical properties based on a underwater radiance and irradiance radiometric measurements are described. The key step of the inversion is an analytical solution of Green's function of RTE under the approximation of single scattering. The preliminary trial of the inversion are being taken.
by Zao Xu.
Mech.E.

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45

Kim, Katherine Haekyung. "Source detection and localization performance of matched field processors in a real and uncertain, shallow water, ocean environment /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3055787.

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46

Richmond, Matthew D. "The biodiversity and biogeography of shallow-water flora and fauna of the Western Indian ocean : with special reference to the Polychaeta, Mollusca and Echinodermata". Thesis, Bangor University, 1998. https://research.bangor.ac.uk/portal/en/theses/the-biodiversity-and-biogeography-of-shallowwater-flora-and-fauna-of-the-western-indian-ocean(5b477d4e-2ed5-4549-bfb5-aaafc6df96f0).html.

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The biodiversity and biogeography of the western Indian Ocean shallow-water marine flora and fauna was examined with special emphasis on Polychaeta, Mollusca (excluding Opisthobranchia) and Echinodermata. A collection of predominantly eulittoral polychaetes from Zanzibar and Mafia (Tanzania) revealed a minimum of91 species, of which 29 % are reported to occur across the Indian Ocean to the West Pacific, and 21 % are regarded as 'cosmopolitan'. Taxonomic problems associated with this taxon are discussed. Over 3,200 species of shelled Mollusca have been reported from the region, though the overall diversity of the groups are likely to be less due to the presence of many synonyms within the taxa which remain to be resolved. Of those families which have been taxonomically reviewed, it appears that the western Indian Ocean supports up to 15-20 % endemism, with noticeable differences in species diversity between the mainland of Africa and the western Indian Ocean islands, especially among bivalves. A total of 419 species of echinoderms are now known from this region, with 107 species (25 %) endemic. About 84 % of the nonendemic species are reported from several localities across the Indian Ocean to the West Pacific. Differences in the diversity of this group between mainland Africa-Madagascar and the western Indian Ocean islands are shown and possible reasons discussed. Origins of the marine macro-invertebrate taxa in the western Indian Ocean include the maintenance of ancient Tethyan Sea fauna and larval (or adult) dispersal across the northern Indian Ocean. The possibility of species diversity being a function of coastline length was briefly investigated. The preparation of A Guide to the Seashores of Eastern Africa and the Western Indian Ocean Islands, describing over 1,600 species, forms part of the work of this thesis and provides a baseline of taxonomic information for macrofauna and flora. From the latter, together with predictions provided by specialists, an estimate of about 10,000 species of shallow-water marine macrofauna and flora are found in this region. It is acknowledged that taxonomic problems affect many invertebrate taxa which require additional attention before estimates can be defined more precisely. Continued taxonomic research and dissemination of biodiversity findings are considered priorities to help stem the degradation and misuse of marine resources of this region resulting from human exploitation which is expected to increase considerably over the coming decades.

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47

Sin, Yongsik. "Ecosystem analysis of water column processes in the York River estuary, Virginia: Historical records, field studies and modeling analysis". W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539616855.

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Analyses of EPA long-term datasets (1985--1994) combined with field studies and ecosystem model development were used to investigate phytoplankton and nutrient dynamics in the York River estuary. Analysis of the EPA dataset showed that algal blooms occurred during winter-spring followed by smaller summer blooms. Peak phytoplankton biomass during the winter-spring blooms occurred in the mid reach of the mesohaline zone whereas during the summer bloom it occurred in the tidal fresh-mesolialine transition zone. River discharge appears to be the major factor controlling the location and timing of the winter-spring blooms and the relative degree of potential nitrogen (N) and phosphorus (P) limitation. Phytoplankton biomass in tidal fresh water regions was limited by high flushing rates. Water residence time was less than cell doubling rate during seasons of high river flow. Positive correlations between PAR at 1m depth and chlorophyll a suggested light limitation of phytoplankton in the tidal fresh-mesohaline transition zone. A significant relationship between the delta of salinity between surface and bottom water and chlorophyll a distribution suggested the importance of tidal mixing for phytoplankton dynamics in the mesohaline zone. Accumulation of phytoplankton biomass in the mesohaline zone was generally controlled by N with the nutrient supply provided by benthic or bottom water remineralization. In general, phytoplankton dynamics appear controlled to a large extent by resource limitation (bottom-up control) rather than zooplankton grazing (top-down control). The dynamics of phytoplankton size structure were investigated in the freshwater, transitional and estuarine reaches of the York River over an annual cycle. The contribution of large cells (micro-plankton, >20 mum) to total biomass increased downstream during winter whereas that of small cells (nano-, 3--20 mum) pico-plankton, <3 mum) increased downstream during summer. I conclude from these studies that spatial and seasonal variations in size structure of phytoplankton observed on the estuarine scale are determined both by the different preferences of micro-, nano-, and picoplankton for nutrients and by their different light requirements. Analyses of phytoplankton size structure are, thus, necessary to better understand phytoplankton dynamics and to better manage water quality in estuarine systems. An ecosystem model was developed to integrate these data and to investigate mechanisms controlling the size-structured phytoplankton dynamics in the mesohaline zone of the York River estuary. The model developed in Fortran90 included 12 state variables describing the distribution of carbon and nutrients (nitrogen, phosphorus) in the surface mixed layer. Forcing functions included incident radiation, temperature, wind stress, mean flow and tide including advective transport and turbulent mixing. Model results supported the general view that phytoplankton dynamics are controlled by abiotic mechanisms (i.e. bottom-up control) rather than biotic, trophic interactions in the York River estuary. Model sensitivity tests showed that small cells (pico-, nano-sized) are more likely regulated by temperature and light whereas large cells (micro-sized) are regulated by physical processes such as advection, and tidal mixing. Microphytoplankton blooms during winter- pring resulted from a combination of longitudinal advection and vertical diffusion of phytoplankton cells rather than in-situ production.

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48

Shon, Zang-Ho. "Photochemical assessment of oceanic emissions of DMS and its oxidation to SO₂ based on airborne field observations". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/25998.

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49

Gorman, Geoffrey Allen. "Field deployable dynamic lighting system for turbid water imaging". Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68945.

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Thesis (S.M.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), September 2011.
"September 2011." "©2011"--P. 2. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 97-101).
The ocean depths provide an ever changing and complex imaging environment. As scientists and researches strive to document and study more remote and optically challenging areas, specifically scatter-limited environments. There is a requirement for new illumination systems that improve both image quality and increase imaging distance. One of the most constraining optical properties to underwater image quality are scattering caused by ocean chemistry and entrained organic material. By reducing the size of the scatter interaction volume, one can immediately improve both the focus (forward scatter limited) and contrast (backscatter limited) of underwater images. This thesis describes a relatively simple, cost-effective and field-deployable low-power dynamic lighting system that minimizes the scatter interaction volume with both subjective and quantifiable improvements in imaging performance.
by Geoffrey Allen Gorman.
S.M.

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50

Panzetta, Francesca. "Determination of the ocean tide model from LEO satellite orbital perturbation analysis". Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3423424.

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The present study concerns the determination of ocean tide model parameters from GOCE orbital perturbation analysis. The GOCE satellite was launched by the European Space Agency in 2009 and is flying on a Sun-synchronous near circular orbit, at the very low altitude of about 250 km which makes it very sensitive to tidally induced orbit perturbations. The strategy adopted for analyzing GOCE GPS tracking data is the direct fully-dynamic approach, consisting in the GOCE precise orbit determination (POD) and accumulation of the normal equations for each orbital arc, followed by a multiarc solution for the estimation of the global ocean tide parameters. The GOCE GPS observations are processed using the NAPEOS S/W system (ESA/ESOC), specific for satellite orbit determination and prediction, upgraded to inclusion of the partial derivatives with respect to the ocean tide parameters and the ocean tide model inversion capability. A sensitivity study of the ocean tide perturbations on GOCE orbit was carried out using as a reference the FES2004 model, in order to define the set of tidal harmonic parameters affecting GOCE orbit. In particular, the secular rates of the GOCE angular elements are estimated through a linear least-square fit. From GOCE mean orbital characteristics, the spectral analysis of ocean tide perturbations in the radial, transverse and normal direction is performed using Kaula's linear satellite theory. Then, the perturbation statistics by coefficient is computed, obtaining a maximum RMS of about 1.323 m for the radial component, 363.136 m for the transverse component and 76.241 m for the normal component. The temporal aliasing problem is also accounted for the recovery of tidal parameters with GOCE and the principal alias periods are calculated for each tidal perturbation frequency, considering the length of the available GOCE data record. To fix a limit for the number of parameters to be estimated, three different cutoffs are applied to the RMS perturbation coefficients, respectively equal to 5 mm for the radial component, 2 cm for the transverse component and 1 cm for the normal component, both in the prograde and retrograde case. The total parameters to be estimated result to be 490. GOCE data are processed to perform the fully-dynamic POD over daily orbital arcs from the 1st November 2009 until the 31st May 2011, but only arcs with a post-fit RMS of the GPS phase observations residuals lower than 8 mm are considered for the multiarc processing, for a total of 431 days. The obtained preliminary results show the relative error of the estimated parameters with respect to the corresponding FES2004 parameters lower than 1 for about the 16\% of the total, meaning that they are of the order of magnitude of the FES2004 parameters. GOCE orbital data were reprocessed along the same period of the previous run, initializing the ocean tide model with the estimated parameters, if present, and maintaining otherwise the FES2004 parameters. The post-fit RMS of the GPS phase residuals obtained with the new ocean tide model has a mean value of 6.5 mm, and it is noteworthy that the difference between the post-fit RMS obtained with the FES2004 model and that resulting from the new ocean tide model indicates a mean improvement of about 0.6 mm in for the 96\% of the analyzed arcs and greater than 1 mm for the 16\%, few days reach a difference of 2 mm. Finally, the orbits obtained with the estimated parameters are compared with the orbits obtained employing the FES2004 model and the official GOCE Reduced-Dynamic PSO. The 3D RMS of the difference between the orbits computed using FES2004 and those recomputed with the new parameters shows a mean value of 2.5 cm, while the 3D RMS of the difference with respect to the official R/D PSO has a mean value of 4.9 cm. Moreover, the difference between the 3D RMS of the orbit residuals between the R/D PSO and the GOCE POD with FES2004 and the RMS of the difference between the GOCE R/D PSO and the GOCE POD with the new parameters results to have a mean improvement of 0.9 cm. Further POD-Multiarc runs are certainly necessary, together with the refinement of the list of parameters to be estimated, removing excessively ill-estimated ocean tide parameters and introducing new parameters where appropriate. Indeed, the model parameter tuning and investigation is essential to adjust the best combination of parameters to be estimated. Moreover, an extension of the data set to much longer time-period should allow a substantial improvement of the obtained results. The task has proven very intensive and challenging, but the partial results obtained are encouraging and a motivation for future analysis.
Il presente lavoro di ricerca riguarda la determinazione dei parametri del modello di marea oceanica dall'analisi delle perturbazioni orbitali di GOCE. Il satellite GOCE è stato lanciato dall'Agenzia Spaziale Europea nel 2009 e volando a quota estremamente bassa, pari a circa 250 km, è molto sensibile alle perturbazioni orbitali indotte dalle maree. La strategia adottata per l'analisi dei dati GPS GOCE è l'approccio numerico diretto caratterizzato da un modello di forza completo, per questo detto completamente dinamico, che consiste nella determinazione orbitale precisa (POD) di GOCE con accumulo delle equazioni normali per ogni arco orbitale, seguiti da una soluzione multiarco per la stima dei parametri globali di marea oceanica. Le osservazioni GPS di GOCE vengono elaborate utilizzando il S/W NAPEOS (ESA/ESOC), specifico per la determinazione orbitale di satelliti e aggiornato per includere le derivate parziali rispetto ai parametri di marea e la struttura che permetta l'inversione del modello di marea. Uno studio di sensibilità delle perturbazioni mareali sull'orbita di GOCE è stato eseguito utilizzando come modello di riferimento il FES2004, al fine di definire la griglia di parametri di marea che influenzano maggiormente l'orbita di GOCE. In particolare, è stata seguita la seguente procedura. Prima di tutto, le variazioni secolari degli elementi angolari di GOCE (argomento di perigeo, longitudine del nodo ascendente, anomalia media) sono state stimate con un fit lineare ai minimi quadrati. Dalle caratteristiche orbitali medie di GOCE, è stata eseguita l'analisi spettrale delle perturbazioni di marea oceanica in direzione radiale, trasversale e normale, utilizzando la teoria lineare di Kaula. In seguito, è stata effettuata la statistica delle perturbazioni per coefficiente, ottenendo un RMS massimo di circa 1.323 m per la componente radiale, 363.136 m per la componente trasversale e 76.241 m per la componente normale. E' stato affrontato anche il problema di aliasing temporale di cui soffrono i parametri di marea che devono essere stimati con GOCE e per ogni frequenza di perturbazione mareale sono stati calcolati i periodi principali di aliasing; si è considerata infine la lunghezza del set di dati GOCE disponibili. E' stato inoltre necessario fissare un limite per il numero di parametri da stimare, tre soglie diverse sono state applicate all'RMS delle perturbazioni per coefficiente, rispettivamente pari a 5 mm per la componente radiale, 2 cm per la componente trasversale e 1 cm per la componente normale, sia nel caso progrado che retrogrado. In tal modo, i parametri totali da stimare risultano essere 490. I dati orbitali di GOCE sono stati analizzati per la stima della POD su archi orbitali giornalieri, coprendo un periodo che va dal 1 novembre 2009 al 31 maggio 2011, ma sono stati considerati per il multiarc solo i giorni con un post-fit RMS dei residui delle osservazioni di fase GPS inferiore a 8 mm, per un totale di 431 giorni. I risultati ottenuti sono preliminari e mostrano un errore relativo dei parametri stimati rispetto ai corrispondenti parametri del FES2004 inferiore a 1 per circa il 16% del totale, il che significa che sono dell'ordine di grandezza dei parametri del FES2004. I dati orbitali di GOCE sono stati poi rielaborati lungo lo stesso periodo di analisi, inizializzando il modello di marea oceanica con i nuovi parametri stimati, dove possibile, mantenendo altrimenti i parametri del FES2004. Il post-fit RMS dei residui di fase GPS ottenuti con il nuovo modello di marea ha un valore medio di 6.5 mm, ed è da notare che la differenza tra i post-fit RMS ottenuti con il FES2004 e quelli risultanti dal nuovo modello indicano un miglioramento medio di circa 0.6 mm per il 96% degli archi analizzati e maggiore di 1 mm per il 16%, mentre pochi giorni raggiungono una differenza di 2 mm. Infine, le orbite di GOCE ottenute con i parametri stimati vengono confrontate con le orbite ottenute usando il FES2004 e con le PSO ufficiali a dinamica ridotta. L'RMS 3D della differenza tra le orbite calcolate utilizzando il FES2004 e quelle calcolate con i nuovi parametri mostra un valore medio di 2.5 cm, mentre l'RMS 3D della differenza rispetto alle PSO a dinamica ridotta ha un valore medio di 4.9 cm. Inoltre, la differenza tra l'RMS 3D dei residui orbitali tra le PSO e la POD eseguita con il FES2004 e l'RMS 3D della differenza tra le PSO e la POD di GOCE eseguita con l'aggiunta dei parametri stimati mostra miglioramento medio di 0.9 cm. Ulteriori run di POD e multiarc sono certamente necessari, insieme alla rifinitura della lista dei parametri da stimare, rimuovendo quelli eccessivamente fuori dalla soluzione del FES2004 ed eventualmente introducendone opportunamente di nuovi. Infatti, è essenziale fare ulteriori e approfondite indagini per individuare la migliore combinazione di parametri di marea da stimare. Inoltre, l'estensione dei dati GOCE a un periodo di tempo più lungo dovrebbe consentire un sostanziale miglioramento dei risultati ottenuti. Il compito del presente lavoro di ricerca si è dimostrato molto intenso e impegnativo, ma i risultati parziali ottenuti sono incoraggianti e rappresentano una motivazione per le analisi future.

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