Thesis (M.S.)--Naval Postgraduate School, 1997. / "January 1997." "Prepared for: Oceanographer of the Navy, OPNAV 096, Washington, DC 20392-5421." "NPS-OC-97-002." Includes bibliographical references (p. 152).

Thesis (Ph. D.)--Massachusetts Institute of Technology, 1988. / "June 1988." Funding provided by the National Science Foundation under grant Numbers OCE 82-13967, and OCE 85-15642, and by the WHO/MIT Joint Program Ventures Fund. Includes bibliographical references (p. 142-146).

Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 43-45). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.

The oceanic surface boundary layer is of great importance and interest as its dynamics provides for the exchange of energy, momentum, heat and matter between the atmosphere and the ocean. It is crucial to have a thorough understanding of physical processes that might have a significant influence on its properties and variability. In this study I consider several different facets of mixed layer/boundary layer dynamics. One aspects concerns the consequences of the nonlinearity of the equation of state in mixed layer models. The nonlinearity of the equation of state gives rise to a term in the averaged surface buoyancy flux which can be comparable in magnitude to other terms. Its magnitude is shown to be proportional to the area enclosed by the seasonal cycle of sea-surface temperature T₅ versus the oceanic heat content H. The term always represents a buoyancy input into the ocean and is compensated exactly by the buoyancy loss via cabbeling (densification on mixing) whenever the mixed layer entrains water with different properties from below. Another problem of interest is the role of the coherent wind-induced vortices, commonly known as Langmuir circulation, in generating the surface mixed layer. A simple parameterization of the mixing due to Langmuir circulation is examined in the light of an oceanic dataset. Some evidence for the validity of the parameterization is found, thus drawing attention to Langmuir's assertion that Langmuir circulation is one of the key physical processes in the oceanic boundary layer. The third aspect of surface boundary layer dynamics explored is the mean effect on mixed layer entrainment of periodic vertical movement of isopycnals in the thermocline due to non-breaking internal waves (referred to as heaving). Seasonal model runs incorporating idealized heaving show that heaving can produce significant seasonal differences in sea-surface temperature compared to a reference case without heaving. It is inferred that by periodically stretching and compressing the mixed layer, heaving causes instabilities that result in additional entrainment of colder water from below. A heaving number RH is proposed, and two parameterizations of heaving for use in mixed layer models are suggested. / Graduate

Satellite-sensed Advanced Very High Resolution Radiometer (AVHRR) Sea Surface Temperature (SST) data over eight summers (1984-1991) were used to analyze the summer SST patterns of variability off the west coast of Vancouver Island. Empirical Orthogonal Function (EOF) analysis of the spatial variance for 133 nearly cloud-free summer images was performed. The first EOF mode, which resembled the mean of all images, showed a strong cool water band located at the northwest corner of Vancouver Island, a cool tongue extending seaward from the Strait of Juan de Fuca and a warm patch off Barkley Sound. The second mode revealed topographically controlled upwelling -- coolwater over the shelf region with its seaward boundary roughly following the 200-m depth contour, plus a cold eddy located just north of the Juan de Fuca Canyon. The third mode displayed cool water extending southwestward off Brooks Peninsula, while the fourth mode showed a cool water plume extending off Cape Scott at the northern tip of Vancouver Island. These 4 modes accounted for respectively, 33, 12, 10 and 5% of the SST variance. With the first 4 modes accounting for 60% of the total variance, the EOF method is highly effective in condensing the huge amount of satellite data. The temporal amplitude of the EOF modes revealed how the SST features changed as summer progressed. From these images, we also constructed an overall seasonal coolness index, which revealed the summers of 1986 and 1991 to have the coolest coastal water, with both summers immediately preceding an El Nino. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Distributions of salinity, temperature, and oxygen of Bute Inlet based on eleven oceanographic surveys between the period August 1950 to August 1952 have been examined. The shallow salinity structures of the various seasons can be classified under two main groups, those occurring at periods of small river runoff and the others occurring at periods of large river runoff. In general, the surface salinity increases to seaward and with depth during all seasons. The surface water along the western shore is almost always observed to be less saline than along the eastern shore. The salinity of the deep water is 30.6 % during both periods. The seasonal fluctuation of salinities at the surface is well-marked but below a depth of 60 feet no normal cycle exists. The temperature distributions of both seasons can also be grouped under two main seasons, namely, Winter and Summer. During both seasons the surface temperature generally increases to seaward. The temperature gradients in the upper layers during the Winter and Summer are positive (increasing vertically downward) and negative (decreasing vertically downward) respectively. From the Spring Transitional to the late Autumn, a well-defined temperature minimum, which becomes indistinguishable at the mouth, is evident in the intermediate depths. The water in the greater depths has a temperature of 8°C and remains almost unchanged throughout the seasons. The seasonal temperature variation of the surface and sub-surface water down to a depth of 150 feet is in phase with the air temperature cycle but below this it is less noticeable. Insolation and cold runoff water from the rivers are predominant factors in determining the fluctuation in the temperature. The concentration of dissolved oxygen is usually high in the surface layer. The water at the greater depth is not stagnant as evidenced by the oxygen concentration. The characteristic water types of this inlet are: the Deep Water, Runoff Water, Intermediate Water and Winter Surface Water. The three distinct layers in the oceanographic structures are: the upper brackish layer, mixed layer, and lower layer. The main circulation of this inlet is estuarine. Eddy coefficient of diffusivity of values 0.65 and 0.58 g./cm./ sec., have been determined for the water above and below the layer of minimum temperature respectively. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Satellite technology represents the only technique for measuring sea surface temperatures (SSTs) on a global scale. SSTs are important as boundary conditions for climate and atmospheric boundary layer models which attempt to describe phenomena of all scales, ranging from local forecasts to predictions of global warming. Historical use of infrared satellite measurements for SST determination has been based on a theory which assumes that the atmosphere is 'thin', i.e., that atmospheric absorption of infrared radiation emitted from the sea surface has very little effect on the radiant intensity that is measured by satellites. However, a variety of independent radiative transfer models point to the possibility that the so-called 'thin approximation' is violated for humid atmospheres such as those found in the tropics, leading to errors in the retrieved SST that would be unacceptable to those who make use of such products. Furthermore, such tropical regions represent a significant portion of the globe, where coupled ocean-atmosphere disturbances can have global effects (e.g., the tropical Pacific El Nino-Southern Oscillation events). This study evaluates the thin approximation empirically, by combining radiative transfer theory and satellite data from the Eastern Atlantic ocean region studied during the Atlantic Statocumulus Transition Experiment (ASTEX). Six months of satellite data from May, June, and July of 1983 and 1984 are analyzed. To the degree that the data may be considered representative of globally valid relationships between measured variables, it is shown that the thin approximation is not appropriate for the tropics. This suggests that new methods are necessary for retrieving SSTs from the more humid regions of the globe. / Graduation date: 1993

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: George W. Luther, III., College of Marine & Earth Studies. Includes bibliographical references.

The West African Monsoon (WAM) is a significant component of the global monsoon system and plays a key role in the annual cycle of precipitation in the Sahel region of Africa (10°N to 20°N) during the summer months (July to September). Rainfall in the Sahel varies on timescales ranging from seasons to millennia as a result of changes in the WAM. In the last century, the Sahel experienced a relatively wet period (prior to the 1960s) followed by a period of severe drought (1970s-1980s) with higher-frequency variability superimposed on this low-frequency background signal. Understanding precipitation variability like that which occurred over the 20th Century and its impact on Sahel precipitation is critically important for skillful hydroclimate predictions and disaster preparedness in the region. Previous work has shown that the WAM responds to both internal atmospheric variability and external oceanic forcing. A large fraction of 20th Century Sahel rainfall variability has been linked to nearby and remote oceanic forcing from the Atlantic, Pacific, and Indian Oceans, suggesting that the ocean is the primary driver of variability. However, the mechanisms underlying the influence of sea surface temperature (SST) forcing to land based precipitation and the relative importance of the roles of different basins are not as well understood. To this end, the work completed in this thesis examines the physical mechanisms linking oceanic forcing to recent precipitation variability in the Sahel and identifies them alongside large-scale environmental conditions. A series of moisture budget decomposition studies are performed for the Sahel in order to understand the processes that govern regional hydroclimate variability on decadal and interannual time scales. The results show that the oceanic forcing of atmospheric mass convergence and divergence explains the moisture balance patterns in the region to first order on the timescales considered. On decadal timescales, forcing by the Indian and Atlantic Oceans correlate strongly with precipitation variability. The combination of a warm Indian Ocean and negative gradient across the Atlantic forces anomalous circulation patterns that result in net moisture divergence by the mean and transient flow. Together with negative moisture advection, these processes result in a strong drying of the Sahel during the later part of the 20th Century. Diagnosis of moisture budget and circulation components within the main rainbelt and along the monsoon margins show that changes to the mass convergence are related to the magnitude of precipitation that falls in the region, while the advection of dry air is associated with the maximum latitudinal extent of precipitation. On interannual timescales, results show that warm conditions in the Eastern Tropical Pacific remotely force anomalously dry conditions primarily through affecting the low-troposphere mass divergence field. This behavior is related to increased subsidence over the tropical Atlantic and into the Sahel and an anomalous westward flow of moisture from the continent, both resulting in a coherent drying pattern. The interannual signal is then further explored, particularly in light of the expected link between the El Niño Southern Oscillation and dry conditions in the Sahel, notably unseen during the historic El Niño event of 2015. Motivated by this, recent El Niño years and their precipitation signature in the Sahel along with the associated large-scale environmental conditions are examined. Two different outcomes for Sahel summer season are defined; an anomalously wet or an anomalously dry season coincident with El Niño conditions. The different precipitation patterns are distinguished by increased moisture supply for the wet years, which can be driven by both regional oceanic conditions that favor increased moisture convergence over the continent as well as weaker El Niño forcing. Finally, a series of new idealized SST-forced experiments that explore the causal link between oceanic forcing and the response of convection in the region on daily time resolution are discussed and preliminary results shown. These experiments aim to understand how convection in the Sahel responds to SST forcing using transient model simulations that track the evolving response of the WAM through time, day-by-day, under different oceanic conditions. Preliminary results show the stark differences in seasonal precipitation that occur when anomalies of opposite sign are applied in parts of the Atlantic and Pacific basin. There is also a suggestion of a difference in the timing of the rainy season when the model is run with different SST configurations.