Trowbridge John H.

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Trowbridge
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John H.
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Author: Williams, Albert J. ×

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  • Technical Report
    Fluid mechanical measurements within the boundary layer over the northern California Continental Shelf during STRESS
    (Woods Hole Oceanographic Institution, 1993-09) Fredericks, Janet J. ; Trowbridge, John H. ; Williams, Albert J. ; Lentz, Steven J. ; Butman, Bradford ; Gross, Thomas F.
    In studying the processes controlling particle distrbution of fine sediments over the continental shelf, the height, structure and dynamics of the bottom boundary layer must be better understood. The Sediment Transport Events on Shelves and Slopes (STRESS) program provides a comprehensive set of data over the bottom half of the water column at the 90m and the 130m isobaths along the northern California continental shelf during the winters of 1988-89 and 1990-91. This report presents the STRESS salinity, temperature, velocity, wave characteristics and attenuation data. The report describes the processing, provides plots and tables of the data and corresponding statistics for evaluation of the data, and documents the data fies. The combined set of moored and tripod mounted instrument measurements provides integrated, hourly-averaged profiles of the lower half of the water column at the four sites which can be used for analysis and modeling purposes.
  • Technical Report
    Vorticity measurements within the bottom boundary layer in the Strait of Juan De Fuca
    (Woods Hole Oceanographic Institution, 1998-07) Fredericks, Janet J. ; Trowbridge, John H. ; Williams, Albert J.
    Electromagnetic fluctuations and turbulent vorticity fluctuations were measured over a nine month period in the strong tidal flows of the Strait of Juan De Fuca off the coast of the Olympic Peninsula of Washington. A collaborative experiment was designed to test the hypothesis that electromagnetic fluctuations at the sea floor are forced by turbulent vorticity fluctuations in the bottom boundary layer. This report describes the measurement of turbulent vorticity fluctuations and the associated analysis which focuses on testing existing theoretical predictions for the inertial subrange and on characterizing spectra at frequencies below the inertial subrange.
  • Technical Report
    Stress, salt flux, and dynamics of a partially mixed estuary
    (Woods Hole Oceanographic Institution, 1998-08) Fredericks, Janet J. ; Trowbridge, John H. ; Geyer, W. Rockwell ; Williams, Albert J. ; Bowen, Melissa M. ; Woodruff, Jonathan D.
    A field study was performed in the lower Hudson River, a partially mixed estuary with a relatively simple geometry (Figure 1), between August and October of 1995. The objectives of the study were (1) to quantify and characterize the turbulent transport of momentum and salt, and (2) to relate the turbulent transport processes to the local and estuary-wide dynamics. The measurement program consisted of fixed and shipboard components. At a central site, a moored array of temperature-conductivity sensors and optical backscatter sensors (OBS), a bottom-mounted acoustic Doppler current profiler (ADCP), and a bottom-mounted array of acoustic travel-time current sensors (BASS), temperature-conductivity sensors, and OBS sensors resolved the vertical structure of velocity, salinity and turbidity and the near-bottom turbulence structure. Moored and bottom-mounted velocity, temperature, conductivity and pressure sensors at five secondary sites quantified the spatial and temporal variabilty of velocity, salinity and bottom pressure. Shipboard measurements with an ADCP and a conductivity-temperature-depth (CTD) profiler, accompanied by an OBS sensor, resolved the spatial structure and tidal variability of velocity, salinity and turbidity along several cross-channel and along-channel transects. This report describes the measurements in detail. Section II describes the instrumentation, Section III describes the deployment and sampling schemes, Section IV describes the data processing, and Section V is a summary of plots of selected data. Section VI documents the data files and Sections VII and VII give acknowledgments and references.
  • Technical Report
    Fluid mechanical measurements within the bottom boundary layer during coastal mixing and optics
    (Woods Hole Oceanographic Institution, 2001-08) Fredericks, Janet J. ; Trowbridge, John H. ; Williams, Albert J. ; Voulgaris, George ; Shaw, William J.
    To quantify and understand the role of vertical mixing processes in determining mid-shelf vertical structure of hydrographic and optical properties and particulate matter, the Office of Naval Research (ONR) funded a program called Coastal Mixing and Optics (CMO), which was conducted at a mid-shelf location in the Mid-Atlantic Bight, south of Martha's Vineyard, Massachusetts. As part of the CMO program, a tall tripod, called 'SuperBASS,' was equipped to collect a year-long, near-bottom time-series of velocity, temperature, salinity and pressure. The BASS sensors were modified to measure absolute as well as differential acoustic travel time, to provide sound speed (a surrogate for temperature) and velocity in a single sample volume. Seven BASS velocity and time travel sensors were placed between 0.4 and 7 meters above bottom. Three acoustic Doppler velocity (ADV) meters were mounted near the bottom-most BASS sensors at 0.3 meters above bottom. The sensors were used to obtain high-quality time-series measurements of velocity and temperature throughout a large fraction of the bottom bondary layer on the New England shelf. The measurements provide vertical structure of the Reynolds-averaged velocity and temperature fields, direct covariance estimates of turbulent Reynolds stress and turbulent heat flux, and indirect inertial range estimates of dissipation rate for turbulent kinetic energy and temperature variance. The purpose of this report is to describe the SuperBASS instrumentation and deployments, to provide summaries of the data collected, and to document the processing, preliminary analysis and archival of data collected for this component of the program.
  • Article
    The coupled boundary layers and air-sea transfer experiment in low winds
    (American Meteorological Society, 2007-03) Edson, James B. ; Crawford, Timothy ; Crescenti, Jerry ; Farrar, J. Thomas ; Frew, Nelson M. ; Gerbi, Gregory P. ; Plueddemann, Albert J. ; Trowbridge, John H. ; Weller, Robert A. ; Williams, Albert J.
    The Office of Naval Research's Coupled Boundary Layers and Air–Sea Transfer (CBLAST) program is being conducted to investigate the processes that couple the marine boundary layers and govern the exchange of heat, mass, and momentum across the air–sea interface. CBLAST-LOW was designed to investigate these processes at the low-wind extreme where the processes are often driven or strongly modulated by buoyant forcing. The focus was on conditions ranging from negligible wind stress, where buoyant forcing dominates, up to wind speeds where wave breaking and Langmuir circulations play a significant role in the exchange processes. The field program provided observations from a suite of platforms deployed in the coastal ocean south of Martha's Vineyard. Highlights from the measurement campaigns include direct measurement of the momentum and heat fluxes on both sides of the air–sea interface using a specially constructed Air–Sea Interaction Tower (ASIT), and quantification of regional oceanic variability over scales of O (1–104 mm) using a mesoscale mooring array, aircraft-borne remote sensors, drifters, and ship surveys. To our knowledge, the former represents the first successful attempt to directly and simultaneously measure the heat and momentum exchange on both sides of the air–sea interface. The latter provided a 3D picture of the oceanic boundary layer during the month-long main experiment. These observations have been combined with numerical models and direct numerical and large-eddy simulations to investigate the processes that couple the atmosphere and ocean under these conditions. For example, the oceanic measurements have been used in the Regional Ocean Modeling System (ROMS) to investigate the 3D evolution of regional ocean thermal stratification. The ultimate goal of these investigations is to incorporate improved parameterizations of these processes in coupled models such as the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) to improve marine forecasts of wind, waves, and currents.
  • Article
    Vertical structure of dissipation in the nearshore
    (American Meteorological Society, 2007-07) Feddersen, Falk ; Trowbridge, John H. ; Williams, Albert J.
    The vertical structure of the dissipation of turbulence kinetic energy was observed in the nearshore region (3.2-m mean water depth) with a tripod of three acoustic Doppler current meters off a sandy ocean beach. Surface and bottom boundary layer dissipation scaling concepts overlap in this region. No depth-limited wave breaking occurred at the tripod, but wind-induced whitecapping wave breaking did occur. Dissipation is maximum near the surface and minimum at middepth, with a secondary maximum near the bed. The observed dissipation does not follow a surfzone scaling, nor does it follow a “log layer” surface or bottom boundary layer scaling. At the upper two current meters, dissipation follows a modified deep-water breaking-wave scaling. Vertical shear in the mean currents is negligible and shear production magnitude is much less than dissipation, implying that the vertical diffusion of turbulence is important. The increased near-bed secondary dissipation maximum results from a decrease in the turbulent length scale.