Thesis (Ph. D.)--University of Hawaii, 1998. / Includes bibliographical references (leaves 124-132).

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Approved for public release; distribution is unlimited / High Frequency (HF) radar backscatter instruments are under development and testing in the marine science and defense science communities for their abilities to remotely sense surface parameters in the coastal ocean over large areas. In the Navy context, the systems provide real-time mapping of ocean surface currents and waves critical to characterization and forecasting of the battlespace environment. In this study, HF radar, aircraft and satellite information were used to investigate and describe surface current in Monterey Bay, California, for a period of ten months, from June 01st, 2003 to March 31st, 2004. A network of five CODAR-type HF radar instruments measured hourly surface currents over the bay. The measurements were averaged over one-hour intervals and total surface velocities were mapped on a grid in the Monterey Bay. From the M1 Buoy located in the middle of the bay, an uninterrupted time series of wind intensity and direction was obtained for the whole period. Major upwelling events were observed during the period of June 14 to June 27, July 4 to July 19, August 8 to August 18 and other upwelling events were observed until late October. These periods of upwelling favorable winds are common during summer with durations of 10 to 20 days. Often they are interrupted by periods of relaxation state of just a few days as the winds veer to the northwest or northeast. Cyclonic circulation cells are developed on shore during upwelling conditions and an anticyclonic circulation in the middle of the bay is observed when the wind shifts to the southwest producing a strong flow out of the bay close to the coastline off Point Piǫs. Downwelling conditions are much common less than upwelling, with occurrences during winter and early fall storms with events lasting between two to five days. When the wind blows to the northeast with an intensity of 4 m/s or more for more than 12 hours, a well developed anticyclonic gyre forms in the middle of the bay. This is associated with a strong current, 35 to 40 cm/s, which flushes out in the southern part of the bay close to the coast off Point Piǫs. This flow reverses when the winds veer to the southwest and enter into the Bay with less intensity. / First Lieutenant, Chilean Navy

Approved for public release; distribution is unlimited / The use of the HF radar to measure and map surface currents has proliferated along the coastlines of many countries for purposes of Search and Rescue, Oil Spill Management, Oceanographic and Fishery Science studies. In the US Navy, these surface current maps are being evaluated for operational use in real-time data assimilating coastal circulation models, and direct monitoring tools in environmentally sensitive operating areas. The SeaSonde HF radar, a DF system, was considered in this study. It uses the MUSIC algorithm to recover bearings from the Doppler backscatter spectrum of the sea surface. By varying the radial and antenna patterns, the simulated backscatter spectra were passed through the SeaSonde software suite for radial pattern recovery. This unprecedented approach directly evaluated SeaSondeâ s MUSIC, and the associated uncertainties were examined against the simulated inputs of (1) fixed amplitude and phase deviations from the ideal antenna pattern, (2) measured antenna patterns and (3) decreasing SNR. It was found that using the measured antenna pattern to recover radials yielded least uncertainty, but a definitive prediction of MUSICâ s radial-recovery capability in relation to the patternâ s complex amplitude and phase structure remained illusive. The results highlighted the need to calibrate the militaryâ s DF-systems for accurate azimuth recovery. / Outstanding Thesis

The interaction between rip channels and cuspate shoreline was examined by analyzing data obtained by the Naval Postgraduate School Imaging System (NAPSIS) during the winter of 2004-2005 in Southern Monterey Bay. Video imaging data was used to determine rip channel locations. The rip fields had constantly changing shapes and sizes, and the beach underwent a transformation from a Transverse-barred-beach (TBB) to a Longshore-bar-trough (LBT) state. Mean rip spacing was determined to be 173 and 258m respectively for the two different beach states (TBB and LBT). Directional wave spectra measured at the offshore NOAA buoy in deep water were refracted to the 10m depth contour at the actual study site. Estimated alongshore sediment transport, Qs, was calculated using the refracted wave data. The hypothesis that rip channel migration is due to alongshore sediment transport is qualitatively confirmed. Little or no migration occurred when Qs values were close to zero. Migration rates were calculated over a three week period during a time of high rip mobility with an average migration rate of 3.2m per day. The rip channel orientations were constantly changing. Three distinct rip channel shapes were common: straight, slanted, or C shaped. The rip channels tended to slant in the opposite direction of the estimated sediment transport, since the rip channels migrated more rapidly at their base (nearest to shore) and more slowly offshore. The hypothesis that the mega-cusps on the beach are erosional features of rip currents was tested by crosscorrelating the 2m beach contour obtained using GPS beach surveys with an alongshore video pixel intensity line. During a time of steady rip channel migration, it was found on average that the cusps lagged the rip channels by 50m with a maximum correlation near one. Assuming the system is in steady state, a response time of 14.7 days was obtained by dividing the lag distance by the average migration rate.

TRACT (maximum 200 words) The Northern Oscillation Index (NOI), an atmospheric climate index relating climate variations in the tropical Pacific and Northeast Pacific was used to selectively average output from the Parallel Ocean Climate Model (POCM 4C) for 1979-1998. Composites, or smart climatologies, were made representing El Nino (EN) and La Nina (LN) conditions, as well as a long term mean (LTM) average or traditional climatology, for November to March. Conditions in the California Current System (CCS) in the smart climatologies were consistent with large scale features noted in previously published studies of EN and LN. Overall, the patterns of anomalies (POCM 4C Smart Climatology minus POCM 4C Traditional Climatology) in salinity, temperature, and currents were opposite in sign and magnitude between the EN and LN composites. This was expected for opposite phases of the same climate variation, and many of the model's EN/LN differences were found to be statistically significant. Therefore, POCM 4C smart climatologies provide better estimates of ocean state and circulation patterns than traditional climatology. Such smart climatologies offer improved environmental information to Naval operational and strategic planners. They are also useful for studying climate variations, and in improving boundary and initial conditions for ocean and atmosphere models.

Accurate prediction of nearshore waves and currents is of critical importance in littoral naval operations. This study examines the effects of complex bathymetry on nearshore currents. Data collected by an array of 12 pressure and velocity sensors in the Nearshore Canyon Experiment (NCEX), conducted near La Jolla, California in 2003, were analyzed to investigate the variability of nearshore currents near a submarine canyon. Time series of pressure, 3-component velocity, and wave heights along the 10 meter depth contour were analyzed to determine the relative importance of tides, waves, and winds in the forcing of nearshore currents outside the surf zone. Additionally, the spatial variability of the observed currents was investigated in relation to the nearby canyon head. Case studies are examined to determine how different wave and tide conditions affect the currents near the canyon. In low-moderate wave conditions, tides dominate longshore currents, whereas cross-shore currents show the passage of irregular bore-like features. The currents are coherent away from the submarine canyon and decay towards the canyon head. Strong longshore currents were observed near the canyon head during a large wave event that were likely driven by an alongshore pressure gradient associated with wave set-up variations.

Approved for public release; distribution unlimited / In conjunction with the Huntington Beach Phase III Investigation, the diurnal variability in the wind and ocean currents from July 1 - October 12, 2001 over the San Pedro Shelf is investigated. Results suggest that the diurnal currents are driven by the diurnal winds but that the strength of the ocean response is modulated by the low frequency flow regime. The spectral peak of the near-surface currents is at the diurnal frequency, which is below the inertial frequency (1.107 cpd). The diurnal currents are surface-intensified, decaying with depth to a minimum at 10-13 m and increasing slightly in strength below that. The near-surface diurnal currents are in phase across the shelf, and are close to in phase with the winds over the shelf. The amplitude modulation of the diurnal energy of the ocean currents is correlated with the direction of the low frequency flow along the shelf;the energy is enhanced when the flow is equatorward, and weak when the flow is poleward. The amplitudes of the diurnal near-surface currents are also correlated with the diurnal winds. However, the low frequency currents and winds are not well correlated. / Lieutenant, United States Navy

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2017. / The purpose of the present study was to apply data collected monthly over a 6-year period along the almost 200 km long St. Helena Bay Monitoring Line in the Southern Benguela upwelling system to investigate co-variation between an upwelling index calculated from nearby wind records and physical and chemical properties along the transect. The extent to which the well-documented seasonal upwelling cycles is manifested at the surface along an inshore-offshore variation was investigated in the context of implications for the validity of remote sensing as a monitoring tool in this ocean area and to improve understanding of the physical drivers of biological processes in St. Helena Bay. This study shows that surface temperature and nutrient concentrations exhibit very poor seasonality and weak correlation with the upwelling index. This is, despite clear evidence for spatial inshore-offshore gradients in temperature, nutrients, and chlorophyll-a, consistent with an upwelling regime. The upper ocean temperature gradient shows a much better correspondence to the upwelling index but at the same time demonstrates that surface heating, and not vertical mixing related to upwelling, controls the upper ocean temperature gradient. In this study linear lagged correlations were also examined and discussed to gain insight into the effect upwelling has on the surface waters in St. Helena Bay with the view of determining the following: (1) Does upwelling lead to an increase or decrease of the water properties? (2) What is the characteristic lag between an upwelling event and its effect on these water properties? (3) Is the effect and/or lag different for the different seasons? and (4) Is the effect and/or lag different for stations inside the bay and those outside the bay?. A combination of surface turbulent cooling through upwelling occurred after a lag of 8 to 10 days in winter and early summer, but less than half in late summer, similar to results obtained with salinity. However, the rest of the salinity results fit in poorly with the temperature results. The only significant correlation obtained with the inshore stations during late summer is the inexplicable positive correlation at a lag of 7 days. For all three seasons virtually none of the oxygen results fit the expected pattern. All three nutrients showed a more positive correlation coefficient and significance than the negative ones. Significant negative correlations occurred mainly during late summer at lags of 7 to 9 days caused by planktonic depletion of nutrients. Also, in this season, significant positive correlations between south-north wind and nutrients only occurred at short lags. This observation supports the earlier temperature-based conclusion that the influence of upwelling develops most rapidly at this time of the year. A rapid increase in chlorophyll-a levels followed by nutrient enrichment of the surface layers are evident. iii The results suggest that remote sensing techniques would be inadequate tools to monitor upwelling events in the Southern Benguela. Secondly, the incidence of phytoplankton blooms is more likely triggered by stratified conditions associated with surface heating than relaxation of upwelling winds. Finally, these results also emphasise the importance of validating lagged outputs against real-time measurements in supporting a simpler hydrological model in narrowing down these significant uncertainties.

Graduation date: 1966