Cacchione David A.

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Cacchione
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David A.
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  • Thesis
    Experimental study of internal gravity waves over a slope
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1970-09) Cacchione, David A.
    A series of laboratory experiments were conducted in a glass wave tank to investigate the propagation of internal gravity waves up a sloping bottom in a fluid with constant Brunt-Vaisala frequency. Measurements of the wave motion in the fluid interior were primarily taken with electrical conductivity probes; measurements in the boundary layer were made with dye streaks and neutrally buoyant particles. The results indicate that, outside of the breaking zone, the amplitude and horizontal wave number of the high-frequency waves increase lineariy with decreasing depth; this is shown to agree with existing linear, inviscid solutions. A zone of breaking or runup is induced by these high-frequency waves well upslope. Shadowgraph observations show that, if the wave characteristics are coincident, or nearly so, with the bottom slope, the upslope propagation of the low-frequency waves causes a line of regularly spaced vortices to form along the slope. Subsequent mixing in the vortex cells creates thin horizontal laminae that are more homogeneous than the adjacent layers. These laminae slowly penetrate the fluid interior, creating a step-like vertical density structure. Available linear theoretical solutions for the velocity in the viscous boundary layer, determined to be valid for certain experimental conditions, are used to develop a criterion for incipient motion of bottom sediment induced by shoaling internal waves. The maximum sediment sizes that can be placed into motion, according to this criterion, are larger than certain mean sediment sizes on the continental margin off New England. This suggests that internal waves might induce initial sediment movement. Speculation about the geological effects of breaking and vortex instabilities is also given. These processes, not definitely measured in the field as yet, might also be conducive to sediment movement.
  • Technical Report
    Variability of sea-floor roughness within the Coastal Ocean Dynamics Experiment (CODE) region
    (Woods Hole Oceanographic Institution, 1983-06) Cacchione, David A. ; Drake, David E. ; Grant, William D. ; Williams, Albert J. ; Tate, George B.
    This report briefly summarizes the geological and biological data taken oft northern California before and during the Coastal Ocean Dynamics Experiment (CODE) (Allen et al, 1982) by the principal investigators of the bottom stress/bottom boundary layer component of CODE (D. Cacchione, D. Drake, USGS; and W. Grant, A. Williams, WHOI) and other cooperating investigators of the U.S. Geological Survey.
  • Technical Report
    High frequency bottom stress variability and its prediction in the CODE region
    (Woods Hole Oceanographic Institution, 1983-06) Grant, William D. ; Williams, Albert J. ; Glenn, Scott M. ; Cacchione, David A.
    High quality bottom boundary layer measurements obtained in the CODE region off Northern California are described. Bottom tripod velocity measurements and supporting data obtained during typical spring and early summer conditions and during a winter storm are analyzed to obtain both velocity profiles and mean bottom stress and bottom roughness estimates. The spring/summer measurements were taken in June, 1981 during CODE-1 at C3 (90 m) by Grant and Williams, WHOI; the winter storm data was taken in November 1980 prior to CODE-1 at the R2 (80 m) site by Cacchione and Drake, USGS. The mean near-bottom (< 2m) velocity profiles are logarithmic (R2 > 0.993) much of the time for everyday flows; deviations are primarily due to kinematical effects induced by unsteadiness from internal waves. Stress profiles show the logarithmic layer corresponds to a constant stress layer as expected for the inertial region of a boundary layer. Stress estimates made from dissipation and profile techniques agree at the 95 percent confidence level. Typical z0 values estimated from measurements greater than 30 cm above the bottom have magnitudes of approximately 1 cm; an order of magnitude larger than the physical bottom roughness. Corresponding u* values have typical magnitudes of 0.5-1.0 cm/sec; more than twice as large as expected from a usual drag law prediction (corresponding to over a factor of four in mean stress). These values are demonstrated to be consistent with those expected for combined wave and current flows predicted theoretically by Grant and Madsen (1979) and Smith (1977). The u* values estimated from the CODE-1 data and predicted by the Grant and Madsen (1979) model typically agree within 10-15 percent. Similar results are demonstrated for the winter storm conditions during which large sediment transport occurs. (Typical z0 values are 4-6 cm; typical u* values are 3-6 cm/sec). The waves influencing the mid-shelf bottom stress estimates are 14-20 second swell associated with Southern and Western Pacific storms. These waves are present over most of the year. The results clearly demonstrate that waves must be taken into account in predicting bottom stress over the Northern California Shelf.
  • Technical Report
    A preliminary description of the CODE-1 field program
    (Woods Hole Oceanographic Institution, 1982-12) Allen, John S. ; Beardsley, Robert C. ; Brown, Wayne S. ; Cacchione, David A. ; Davis, Russ E. ; Drake, David E. ; Friehe, Carl A. ; Grant, William D. ; Huyer, Adriana ; Irish, James D. ; Janopaul, M. M. ; Williams, Albert J. ; Winant, Clinton D.
    A Coastal Ocean Dynamics Experiment (CODE) has been undertaken to identify and study the important dynamical processes which govern the wind-driven motion of coastal water over the continental shelf. The initial effort in this four-year research program is to obtain high-quality data sets of all the relevant physical variables needed to construct accurate kinematic and dynamic descriptions of the response of shelf water to strong wind forcing in the 2 to 10-day band. A series of two small-scale, densely-instrumented field experiments of four-month duration (CODE-1 and CODE-2) is designed to explore and to determine the kinematics and momentum and heat balances of the local wind-driven flow over a region of the northern California shelf which is characterized by both relatively simple bottom topography and large wind stress events in both winter and summer. A more lightly-instrumented, long-term, large-scale component has been designed to help separate the local wind-driven response in the region of the small-scale experiments from motions generated either offshore by the California Current system or in some distant region along the coast, and also to help determine the seasonal cycles of the atmospheric forcing, water structure, and coastal currents over the northern California shelf. This report presents an overview of the CODE program and a preliminary description of the observational programs conducted during CODE-1. The various logical components of CODE are identified and described, and their relationship to the entire effort is discussed. The report itself represents a minor revision of the original cover proposal submitted to NSF in late 1979 by the principal investigators and is not a comprehensive guide nor does it contain any descriptions of the initial results from CODE-1. Scientific and engineering results will be presented elsewhere in individual technical and scientific reports. CODE has been jointly conceived by the following principal investigators (who collectively make up the CODE group): J. Allen , R. Beardsley, W. Brown, 0. Cacchione, R. Davis, D. Drake , C. Friehe, W. Grant, A. Huyer, J. Irish, M. Janopaul, A. Williams and C. Winant.