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Studying the ocean geostrophy from space / Estudio de la geostrofia de los océanos desde el espacioSánchez Reales, José María 03 March 2012 (has links)
No description available.
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Improved modelling of zonal currents and SST in the tropical PacificKeenlyside, Noel S.,1974- January 2001 (has links)
Abstract not available
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A spectral approach to the transient analysis of wave-formed sediment ripples.Davis, Joseph P. January 2005 (has links)
Wave-formed rippled sediment beds are extremely important to the processes that act on or across the sediment-water interface. Ripples increase the exchange of materials between the sediment and the water column, enhance sediment transport rates, and act to increase the dissipation of waves by increasing the hydraulic roughness of the seafloor. Previous research has, however, failed to take into account the substantial spatial and temporal variation rippled beds display when formed under real sea conditions. Based on a set of laboratory experiments a spectral method to predict and model rippled beds has been developed. Through the use of the rippled surface's spectral density function the spatial and temporal variability of the rippled surface can be taken into account with greater efficiency. A prediction method for the equilibrium ripple spectrum was developed based on a nondimensional spectral form, which utilised the peak orbital excursion diameter and the 50th percentile grain size diameter of the sediment bed. The method provided an effective technique to predict ripple parameters with the same degree of accuracy achievable at small scale as more accepted ripple prediction methods. A new method was derived to model the changes a rippled bed undergoes as it actively evolves between two given equilibrium states due to a change in surface wave conditions. The evolution of a rippled bed can be described mathematically in exactly the same way as a rippled bed growing from a flat bed condition. The method allows any bed to be modelled through time if the flow conditions and sediment properties are known. There is little advantage in using the spectral method to predict rippled beds when they are in equilibrium with the flow conditions. The main benefit of the spectral method comes when attempting to model rippled beds evolving under changed flow conditions. In the same way as the parameterisation of surface waves in terms of their spectral density function has increased the ability to model wind generated wave fields, studies of rippled beds would benefit from the increased detail and ease the spectral method brings. / Thesis (Ph.D.)--School of Civil and Environmental Engineering, 2005.
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Low frequency variations in the sea level and currents over the Oregon continental shelfCutchin, David L. 14 July 1971 (has links)
Sea level and current observations made over the Oregon
continental shelf exhibit wavelike characteristics in a frequency band
from approximately 0.15 to 0.45 cpd. In a narrow band around
0.22 cpd the current-sea level relationship is consistent with the
predicted values for the first mode of Robinson's continental shelf
waves. In addition, an interesting relationship exists between the
form of the sea level-current coherency spectra and the arrangement
of the maximum frequencies for the first three shelf wave modes.
The currents were measured in 100 m of water about seven
nautical miles off Depoe Bay, Oregon. Current meters were placed
at 25, 50 and 75 m depth. The duration of the experiment was from
18 April 1968 until 11 September 1968. Due to some instrument failures
a complete current data set for this period was not obtained.
Simultaneous and continuous measurements of surface elevation and
atmospheric pressure were also obtained at Newport, Oregon, a
nearby coastal station.
Shelf wave dispersion curves and eigenfunctions for the Oregon
coastal profile are computed using a new numerical technique. These
are compared with a low frequency (about 0.03 cpd to 0.75 cpd)
spectral analysis of the current, sea level and atmospheric pressure
records.
The relative vertical uniformity of the currents, as a function of
frequency, is examined. The longshore component of the current
appears to be substantially more barotropic than the onshore-offshore
component. / Graduation date: 1972
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Characteristics and distribution of water masses off the Oregon coastRosenberg, Donald H. 03 August 1962 (has links)
Graduation date: 1963
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Circulation inside the Narrows of St. John's Harbor /Guo, Ming, January 2005 (has links)
Thesis (M.Sc.)--Memorial University of Newfoundland, 2005. / Bibliography: leaves 106-114.
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Simulation of coastal processes in a circular wave basinKatzev, David H. 14 January 1992 (has links)
The circular wave basin provides a means of physically modeling the nearshore
without the typical problems associated with end walls. Three different coastal
processes were examined to demonstrate the use of a spiral wavemaker in a circular
wave basin. These were longshore currents, shear waves, and groin circulation. A
beach was designed and constructed to concentrate breaking in a narrow region and
minimize wave reflection. Currents in the longshore direction were generated by both
the motion of the wavemaker and oblique wave approach. Two methods for measuring
nearshore currents were employed. First, a 3-D acoustic current meter was positioned
at various locations in the cross shore and the local radial and tangential velocities
were recorded. Second, a video camera was placed approximately 8 meters above the
wave basin to record the motion of a ball in the nearshore. The video tape was
digitized by an image processor and the motion of the ball was determined.
Measurements of nearshore circulation in the circular wave basin were used to
investigate longshore currents, shear waves, and groin circulation. Average measured
longshore current profiles in the cross shore were compared with numerical model
predictions. An analysis of the existence of shear waves in the circular wave basin
was performed by calculating longshore and cross shore current spectra. Particular
attention was focused on the low frequency end of the spectra where shear waves are
most energetic. Model groins were placed in the circular wave basin and measured
currents were compared to predicted circulation patterns. All three applications
indicated that the circular wave basin is a useful device for simulating coastal processes
in a laboratory environment. / Graduation date: 1992
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Observations of Laboratory Rip CurrentsSapp, Brian Keith 17 January 2006 (has links)
Laboratory experiments of rip current systems are performed in a wave basin with a bar and rip channel geometry at the Ocean Engineering Laboratory at the University of Delaware. The experiments include both in situ water level and velocity measurements and optical visualization of the flow field under a variety of normal-incident wave conditions. Digital video is used to record surface drifters moving through a rip current system. A method is presented that tracks these digitally-recorded drifters into long Lagrangian sequences. The laboratory measurements capture both an Eulerian and Lagrangian description of the rip current system.
Time-averaged rip current properties are calculated and analyzed using both in situ and video measurements. From the video, Lagrangian velocities are computed with forward differencing of the low-pass filtered drifter tracks. Wave properties are also estimated using the orbital drifter motions and linear (Airy) wave theory. The effects of various wave conditions on the time-averaged rip current systems are investigated to show that wave height is a critical parameter. Measurements of circulation cells are obtained by spatially averaging the drifter track velocity measurements into a polar grid ranging from 0.25 m to 3.25 m from the center of the cell. Circulation cell features, such as the center of circulation and cell width, are calculated to characterize their response to various wave conditions.
Spectral analyses are used to characterize the rip current pulsations in the experimental measurements. Three frequencies are found to be energetic in several of the experiments in the low frequency band: the wave group frequency, a lower frequency, and the interaction of the wave group and lower frequencies. Some experiments have significant energy at each of the three peaks, where others have only one or none. The lower frequency motions have also been found in the video measurements and attributed to rip meandering. Possible causes for the low-frequency pulsations, including wave basin seiching, circulation cell instabilities, and wave-current interaction, are discussed.
This thesis adds to previous rip current studies by providing a spatially-large and time-varying perspective of rip current systems as a whole.
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Turbulent diffusion, advection, and water structure in the North Indian OceanBennett, Edward Bertram January 1970 (has links)
Typescript. / Bibliography: leaves 131-133. / xi, 133 l charts, graphs, maps, tables
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A spectral approach to the transient analysis of wave-formed sediment ripples.Davis, Joseph P. January 2005 (has links)
Wave-formed rippled sediment beds are extremely important to the processes that act on or across the sediment-water interface. Ripples increase the exchange of materials between the sediment and the water column, enhance sediment transport rates, and act to increase the dissipation of waves by increasing the hydraulic roughness of the seafloor. Previous research has, however, failed to take into account the substantial spatial and temporal variation rippled beds display when formed under real sea conditions. Based on a set of laboratory experiments a spectral method to predict and model rippled beds has been developed. Through the use of the rippled surface's spectral density function the spatial and temporal variability of the rippled surface can be taken into account with greater efficiency. A prediction method for the equilibrium ripple spectrum was developed based on a nondimensional spectral form, which utilised the peak orbital excursion diameter and the 50th percentile grain size diameter of the sediment bed. The method provided an effective technique to predict ripple parameters with the same degree of accuracy achievable at small scale as more accepted ripple prediction methods. A new method was derived to model the changes a rippled bed undergoes as it actively evolves between two given equilibrium states due to a change in surface wave conditions. The evolution of a rippled bed can be described mathematically in exactly the same way as a rippled bed growing from a flat bed condition. The method allows any bed to be modelled through time if the flow conditions and sediment properties are known. There is little advantage in using the spectral method to predict rippled beds when they are in equilibrium with the flow conditions. The main benefit of the spectral method comes when attempting to model rippled beds evolving under changed flow conditions. In the same way as the parameterisation of surface waves in terms of their spectral density function has increased the ability to model wind generated wave fields, studies of rippled beds would benefit from the increased detail and ease the spectral method brings. / Thesis (Ph.D.)--School of Civil and Environmental Engineering, 2005.
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