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<p> Ocean tides worldwide have exhibited secular changes in the past century, simultaneous with a global secular rise in mean sea level (MSL). The combination of these two factors contributes to higher water levels, and may increase threats to coastal regions and populations over the next century. Equally as important as these long-term changes are the short-term fluctuations in sea levels and tidal properties. These fluctuations may interact to yield locally extreme water level events, especially when combined with storm surge. This study, presented in three parts, examines the relationships between tidal anomalies and MSL anomalies on yearly and monthly timescales, with a goal of diagnosing dynamical factors that may influence the long-term evolution of tides in the Pacific Ocean. Correlations between yearly averaged properties are denoted tidal anomaly trends (TATs), and will be used to explore interannual behavior. Correlations of monthly averaged properties are denoted seasonal tidal anomaly trends (STATs), and are used to examine seasonal behavior. Four tidal constituents are analyzed: the two largest semidiurnal (twice daily) constituents, M2 and S2, and the two largest diurnal (once daily) constituents, K1 and O1. </p><p> Part I surveys TATs and STATs at 153 Pacific Ocean tide gauges, and discusses regional patterns within the entire Pacific Ocean. TATs with statistically significant relations between MSL and amplitudes (A-TATs) are seen at 89% of all gauges; 92 gauges for M2, 66 for S2, 82 for K1, and 59 for O1. TATs with statistically significant relations between tidal phase (the relative timing of high water of the tide) and MSL (P-TATs) are observed at 55 gauges for M2, 47 for S2, 42 for K1, and 61 for O1. Significant seasonal variations (STATs) are observed at about a third of all gauges, with the largest concentration in Southeast Asia. The effect of combined A-TATs was also considered. At selected stations, observed tidal sensitivity with MSL was extrapolated forward in time to the predicted sea level in 2100. Results suggest that stations with large positive combined A-TATs produce total water levels that are greater than those predicted by an increase in MSL alone, increasing the chances of high-water events. </p><p> Part II examines the mechanisms behind the yearly (TAT) variability in the Western Tropical Pacific Ocean. Significant amplitude TATs are found at more than half of 26 gauges for each of the two strongest tidal constituents, K1 (diurnal) and M2 (semidiurnal). For the lesser constituents analyzed (O1 and S2), significant trends are observed at ten gauges. </p><p> Part III analyzes the seasonal behavior of tides (STATs) at twenty tide gauges in the Southeast Asian waters, which exhibit variation by 10 &ndash; 30% of mean tidal amplitudes. A barotropic ocean tide model that considers the seasonal effects of MSL, stratification, and geostrophic and Ekman velocity is used to explain the observed seasonal variability in tides due to variations in monsoon-influenced climate forcing, with successful results at about half of all gauges. The observed changes in tides are best explained by the influence of non-tidal velocities (geostrophic and Ekman), though the effect of changing stratification is also an important secondary causative mechanism. </p><p> From the results of these surveys and investigations, it is concluded that short-term fluctuations in MSL and tidal properties at multiple time scales may be as important in determining the state of future water levels as the long-term trends. Global explanations for the observed tidal behavior have not been found in this study; however, significant regional explanations are found at the yearly time scale in the Solomon Sea, and at the seasonal time scale in Southeast Asia. It is likely that tidal sensitivity to annual and seasonal variations in MSL at other locations also are driven by locally specific processes, rather than factors with basin-wide coherence. (Abstract shortened by ProQuest.)</p>

<p> Oceanic motion outside thin boundary layers is primarily a mixture of quasi-geostrophic flow and internal waves with either near-inertial frequencies or the frequency of the semidiurnal lunar tide. This dissertation seeks a deeper understanding of waves and flow through reduced models that isolate their nonlinear and coupled evolution from the Boussinesq equations. Three physical-space models are developed: an equation that describes quasi-geostrophic evolution in an arbitrary and prescribed field of hydrostatic internal waves; a three-component model that couples quasi-geostrophic flow to both near-inertial waves and the near-inertial second harmonic; and a model for the slow evolution of hydrostatic internal tides in quasi-geostrophic flow of near-arbitrary scale. This slow internal tide equation opens the path to a coupled model for the energetic interaction of quasi-geostrophic flow and oceanic internal tides. </p><p> Four results emerge. First, the wave-averaged quasi-geostrophic equation reveals that finite-amplitude waves give rise to a mean flow that advects quasi-geostrophic potential vorticity. Second is the definition of a new material invariant: Available Potential Vorticity, or APV. APV isolates the part of Ertel potential vorticity available for balanced-flow evolution in Eulerian frames and proves necessary in the separating waves and quasi-geostrophic flow. The third result, hashed out for near-inertial waves and quasi-geostrophic flow, is that wave-flow interaction leads to energy exchange even under conditions of weak nonlinearity. For storm-forced oceanic near-inertial waves the interaction often energizes waves at the expense of flow. We call this extraction of balanced quasi-geostrophic energy 'stimulated generation' since it requires externally-forced rather than spontaneously-generated waves. The fourth result is that quasi-geostrophic flow can encourage or 'catalyze' a nonlinear interaction between a near-inertial wave field and its second harmonic that transfers energy to the small near-inertial vertical scales of wave breaking and mixing. </p>

<p> Passive longwave infrared radiometric satellite-based retrievals of sea surface temperature (SST) at instrument nadir are investigated for cold bias caused by unscreened optically-thin cirrus (OTC) clouds (cloud optical depth &le; 0.3; COD). Level 2 split-window SST retrievals over tropical oceans (30&deg; S - 30&deg; N) from Moderate Resolution Imaging Spectroradiometer (MODIS) radiances collected aboard the NASA Aqua satellite (Aqua-MODIS) are collocated with cloud profiles from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument, mounted on the independent NASA CALIPSO satellite. OTC are present in approximately 25% of tropical quality-assured (QA) Aqua-MODIS Level-2 data, representing over 99% of all contaminating cirrus found. This results in cold-biased SST retrievals using either split- (MODIS, AVHRR and VIIRS) or triple-window (AVHRR and VIIRS only) retrieval methods. SST retrievals are modeled based on operational algorithms using radiative transfer model simulations conducted with a hypothetical 1.5 km thick OTC cloud placed incrementally from 10.0 - 18.0 km above mean sea level for cloud optical depths (COD) between 0.0 - 0.3. Corresponding cold bias estimates for each sensor are estimated using relative Aqua-MODIS cloud contamination frequencies as a function of cloud top height and COD (assuming them consistent across each platform) integrated within each corresponding modeled cold bias matrix. Split-window relative OTC cold biases, for any single observation, range from 0.40&deg; - 0.49&deg; C for the three sensors, with an absolute (bulk mean) bias between 0.10&deg; - 0.13&deg; C. Triple-window retrievals are more resilient, ranging from 0.03&deg; - 0.04&deg; C relative and 0.11&deg; - 0.16&deg; C absolute. Cold biases are constant across the Pacific and Indian Ocean domains. Absolute bias is smaller over the Atlantic, but relative bias is larger due to different cloud properties indicating that this issue persists globally.</p>

A spectral Chebyshev-collocation method is devised for the 1-1/2 layer non-linear reduced-gravity equations. Following a general description of spectral methods with their application to meteorological and oceanographic problems the implementation of the numerical technique is described. A bicharacteristic scheme is applied to solve the equations at the boundaries incorporating the boundary conditions. This treatment enables stable time integrations (spectral methods in general are very sensitive to boundary errors). A simple transfinite grid generation method is used to construct grids over irregular (non-rectangular) simply-connected domains. / The model is used in a study of the dynamics of Yanai (or mixed Rossby-gravity) wave packets. These are of interest because of the observations of equatorial instability waves (which have the characteristics of Yanai waves) and their role in the momentum and heat budgets in the tropics. A series of experiments is performed to investigate the generation of the waves by simple cross-equatorial wind stress forcings in various configurations and the influence of a western boundary on them. They may be generated in the interior ocean as well as from a western boundary. The observations from all the oceans indicate that the waves have a preferential period and wavelength of around 26 days and 1000 km respectively. This is seen in the model results too and a plausible explanation is provided as being due to the dispersive properties of Yanai waves. / Source: Dissertation Abstracts International, Volume: 53-10, Section: B, page: 5132. / Major Professor: James J. O'Brien. / Thesis (Ph.D.)--The Florida State University, 1992.

Submarine groundwater discharge and recirculated seawater may provide important chemical constituents to the ocean, but the dispersed nature of this process makes locating and quantifying its input difficult. Two approaches were taken to evaluate subsurface fluid discharge into an area of the northeastern Gulf of Mexico: (1) direct measurements of seepage; and (2) use of naturally-occurring $\sp{222}$Rn as a tracer of this flow. / The response of seepage meters to water motion effects was evaluated in the nearshore study area through time-series experiments using empty and 1000-mL prefilled collection bags. It was confirmed that prefilling the plastic bags effectively alleviated an anomalous, short-term influx. Control experiments demonstrated that water motion did not cause artifacts in seepage measurements. Temporal and spatial variations in seepage fluxes were found along an 7-km stretch of coastline in this study area. Tidal cycle influences on seepage rates were negligible, but long-term temporal variations in seepage proved substantial. / Concentrations of $\sp{222}$Rn in groundwater are 3 to 4 orders of magnitude higher than seawater. Integrated concentrations in the nearshore waters overlying a seepage meter transect showed a significant positive relationship to direct seepage measurements. These waters receive only a small contribution of $\sp{222}$Rn by diffusion based on flux measurements. Radon inventories in these shallow waters are consistent with the input of radon-bearing groundwaters and suggest that $\sp{222}$Rn is an excellent tracer of this process. / Factors influencing the concentration of radon in the inner continental shelf waters (i.e., production-decay, horizontal transport, and benthic advection and diffusion) were evaluated using a linked benthic exchange-horizontal transport model. Simulations of $\sp{222}$Rn activities in a water mass moving across the seafloor demonstrate that inventories are relatively insensitive to horizontal flow, at least when a strong pycnocline is present and net current velocities are slow. The regional subsurface fluid flow into the 620-km$\sp2$ study area is estimated to be 180 to 710 $\rm m\sp3\cdot sec\sp{-1}$, equivalent to at least 50 first magnitude springs. / Source: Dissertation Abstracts International, Volume: 57-04, Section: B, page: 2444. / Major Professor: William C. Burnett. / Thesis (Ph.D.)--The Florida State University, 1996.

The small-scale spatial variations of the Bottom Boundary Layer (BBL) associated with anomalous bottom layers in the form of cold eddies or cold filaments are studied here. / Statistics of long term records from the HEBBLE area ($\sp\sim$40$\sp\circ$N, 62$\sp\circ$W), where the deep jet known as the Cold Filament (CF) is found, indicate a permanent benthic front, a few Rossby radii of deformation wide, with which are associated significant horizontal gradients of temperature and velocity. / Empirical formulas are found for the parameterization of the eddy diffusivity, which fit the calculations of the level 2.5 scheme of Mellor and Yamada (1974, 1982). When they are used in a K-model (i.e., a model in which the eddy viscosity is calculated directly from the stratification and the velocity field), about 20% of the computational time can be saved compared to a second order turbulence closure model. / A two dimensional (x-z) primitive equation model is used to study the interaction between the BBL and the CF under constant forcing conditions. The results of the numerical simulations are compared favorably to observations of temperature and velocity profiles. The major effect of the interaction process results from the cross isotherm flow associated with the Ekman veering in the BBL. In the left edge (looking down-stream) of the CF the intrusion of cold core water under warm interior water forms a very thin and stable BBL, while in the right edge the Ekman transport forms an unstable, thermally convective, region with large turbulence. The velocity profiles as well as the Ekman spirals in the vicinity of the CF show significant modification from the ones obtained by classical Ekman dynamics, mainly due to thermal wind effects associated with the CF. / Source: Dissertation Abstracts International, Volume: 50-03, Section: B, page: 0890. / Major Professor: Georges L. Weatherly. / Thesis (Ph.D.)--The Florida State University, 1989.

An objective technique which produces regularly spaced fields of winds, temperatures, humidity, wind stress and sensible and latent heat fluxes is developed. It combines in-situ Volunteer Observing Ship (VOS) data and remotely sensed data from SEASAT during the analysis period, July 7-October 10, 1978 for the north Atlantic. The objective technique is a variational method which reduces a set of several constraints expressing closeness to input data, climatology and kinematics. Analysis results are presented for monthly and 5-day periods during the analysis period. / Seasonal (3 month) means of temperature, humidity, and flux determined by the monthly and 5-day results are comparable. However, 5-day wind results had much smaller errors than the monthly mean winds averaged over the 3-month period. / Variability of the 5-day results indicates high variability of temperatures, humidity, and heat fluxes in the vicinity of the Gulf Stream. Sea surface temperature (SST) variability is high in the eastern Atlantic and is coupled to wind driven ocean variability in the region. / Heat fluxes are coupled to and determined by various parameters. The variations for both sensible and latent heat fluxes in the extra-tropics are determined by the position and strength of the circulation of the semi-permanent high pressure system. Some evidence is also found to indicate dependence of SST on latent heat. In the tropics, the heat fluxes are determined by a combination of factors, including zonal wind and SST. / Estimates of errors due to insufficient sampling and random data are presented for the monthly results. The sampling and random errors in wind stress are in the range of 10%-20% of the mean values. For the sensible and latent heat fluxes, the sampling errors are about half of those attributable to random errors. Because of the difference operator used in diagnosing heat fluxes, these fluxes are found to be more sensitive to the accuracies of temperatures and humidity than accuracies of winds. / Source: Dissertation Abstracts International, Volume: 53-03, Section: B, page: 1417. / Major Professor: James J. O'Brien. / Thesis (Ph.D.)--The Florida State University, 1992.

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