No description available.

The thesis describes the properties of surface wind and air temperature time series recorded at three locations on the pack ice of the Beaufort Sea. Time series consisting of sequential one-half hourly means were constructed for a period of approximately a year. A diurnal fluctuation in air temperature is found for the late summer, early fall and spring seasons only. Wind speed does not show a significant diurnal fluctuation for any season. There is very little seasonal variability in the wind speed while significant variation is present in the air temperature. The integrated wind speed spectrum (i. e. variance) is 80% less than the integrated sum of the wind component spectra indicating that for periods longer than a day, directional fluctuations contribute much more to the variance of the wind record than do speed fluctuations. Although the measurements only approach the microscale region, there seems to be no consistent indication of a microscale peak in the variance preserving representation of the wind speed spectrum. Time series of daily mean horizontal divergence and vertical component of vorticity for both the wind field and ice motion are examined. For a period of 355 days there is significant negative correlation (-0.65) between the wind divergence and wind vorticity series and significant positive correlation (0.65) between the wind vorticity and ice vorticity series. / Graduation date: 1979

No description available.

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, December 1990. / Thesis Advisor(s): Bourke, Robert H. ; Morison, James. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Buoys, Sea Ice, Arctic Buoys, Ice Forecast, Arctic, Theses. Author(s) subject terms: PIPS, Sea Ice, Arctic Buoys, Ice Forecast, Arctic. Includes bibliographical references (p. 106-111). Also available in print.

The concept of reciprocal acoustical travel-time measurements as a means of determining path-averaged currents is well established. We have designed an instrument to exploit this principle in studies of the boundary layer just beneath the arctic ice cover. Such measurements are of interest both because of the opportunity provided for comparison with the more commonly acquired point measurements and because of a particular configuration allowing determination of average vorticity, which cannot be achieved with the traditional approach; in addition, their unprecedented sensitivity allows detection of phenomena not observable with traditional sensors. The acoustical instrument was deployed during the spring of 1989 in the sub-ice boundary layer of the Eastern Arctic in order to measure turbulence, path-averaged horizontal current, and relative vorticity. A triangular acoustic array of side 200 m was used to obtain reciprocal transmission measurements at 132 kHz, at 8, 10 and 20 m beneath an ice floe. Pseudo-random coding and real-time signal processing provided precise acoustic travel time and amplitude for each reciprocal path. Mean current along each acoustic path is proportional to travel time difference between reciprocal transmissions. Horizontal velocity normal to the acoustic paths is measured using scintillation drift. The instrument measures horizontal circulation and average vorticity relative to the ice, at length scales characteristic of high frequency internal waves in the region. The rms noise level of the measurements is less than 0.1 mm/s for velocity measurements and 0.01 for vorticity, averaged over one minute. Except near the mechanical resonance frequency of the moorings, the measurement accuracy is limited by multipath interference. Path-averaged horizontal velocity is compared to point measurements and marked differences are observed due to local anomalies of the flow field. The integral measurement of current is particularly sensitive to the passage of internal waves that have wavelengths longer than the horizontal separation of the transducers. A comparison of horizontal velocity at two depths in the boundary layer shows good coherence at internal wave frequencies and some attenuation as the ice is approached. Relative vorticity at internal wave length scales is dominated by horizontal shear caused by flow interaction with ice topography and not by planetary vorticity. Reciprocal acoustical travel time measurements over paths of several hundred meters can be used to probe the statistical behaviour of turbulent velocity fine structure in the ocean. For homogenous isotropic flows, and for long measuring baselines, an analytic expression relating line-averaged and point measurements of velocity is derived. Anisotropic and inhomogeneous flows are also considered. Correction formulas for the spatial and temporal variability of advection velocity along the measuring baseline are obtained. Practical limitations are established, and experimental data from the arctic boundary layer beneath ice is compared with the theory. A new remote sensing technique for measuring turbulent kinetic energy dissipation rate is suggested. / Graduate

Thesis (Ocean E)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 178-180. / Ocean E