A Controllable Automated Environmental Data Acquisition and Monitoring System

Dimmler, D. G.; Greenlaw, N.; Rankowitz, S.

doi:10.1109/tns.1976.4328338

Cited by 5 publications

(2 citation statements)

References 2 publications

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“…Extensive calibration data with steady and variable velocities have suggested that errors due to such disturbances were acceptably low with the meters we used. The mooring was of the 'Shelton buoy" type (for details, see again Dimmler et al [1976]), consisting mainly of a plastic tube articulated by universal joints so as not to be subject to rotation (an articulated spar buoy, in effect). The two axes of the moored em current meters thus did not rotate during the experiment, a feature thought to be important in minimizing errors.…”

Section: Current Measurementsmentioning

confidence: 99%

Nearshore currents off Long Island

Scott¹,

Csanady²

1976

J. Geophys. Res.

136

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Some new and interesting current meter observations have recently been reported by Scott and Csanady [1976]. One of their results is the finding of a linear relationship between longshore wind stress and currents observed 2 m above the bottom. Using a frictional model, they are able to draw inferences about the longshore slope of sea level in the absence of wind. The purpose of the present note is to expand on their interpretation of the longshore slope and to offer some cautionary remarks concerning the comparison with geodetic leveling.The model of Scott and Csanady (their equation (3a)) becomes rwx/p = rt2b + gh ( O •'/ O x )where the x direction is along the coast, rw is the wind stress, and r is a resistance coefficient; the other symbols have traditional meanings. By careful analysis and prudent averaging they arrive at their Figure 8, which allows them to determine a value of 0.158 cm/s for r and an intercept of 0.46 cm"/s" for the wind stress (divided by p) when the longshore current goes to zero, 2 m above the bottom. From the intercept, Scott and Csanady calculate a longshore slope of the sea surface of 1.4 X 10-*, or about 7 cm in 500 km. They conclude that sea level falls about 7 cm from Boston, Massachusetts, to Atlantic City, New Jersey. Such slopes of sea level, on the coastal side, are found with every known current; they are consistent with the observed density distributions and are dynamically in balance with the slope of the sea surface across the coastal flows as the currents change latitude. These effects have been discussed elsewhere [Sturges, 1974].The density distribution off the northeastern coast of the United States suggests that sea level slopes down from north to south about 10 cm along the 2000-m isobath, relative to the 2000-dbar surface, from Cape Cod to the Chesapeake Bay. The data of Scott and Csanady gave much the same longshore slope close to shore, suggesting that the longshore gradient changes little with distance from the shore, at least out to the 2000-m isobath. One interesting and perhaps surprising aspect of this resultis to see how the longshore sea level slope changes with season. Figure ! shows the annual trend of sea level at Boston and Atlantic City. The means between the two curves have been offset by 7 cm in the sense suggested by Scott and Csanady, which is in reasonable agreement with the value obtained from the large-scale density field just offshore discussed above [see Sturges, 1974, Figure 1]. It appears that the longshore slope is a minimum in the fall of the year when the longshore wind stress is also a minimum. The yearly average winds are out of the west southwest; the longshore stress is approximately 0.5 dyn cm" [Hellerman, 1967]. In the summer they are lighter and Copyright ¸ 1977 by the American Geophysical Union. Paper number 6C0919. more variable; in September they are weak and shift around from SSW to the north or northeast [Marine Climatic Atlas, 1956]. Whether this change in longshore slope is associated with a change in the mean flow field is a...

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Section: Current Measurementsmentioning

confidence: 99%

Nearshore currents off Long Island

Scott¹,

Csanady²

1976

J. Geophys. Res.

136

View full text Add to dashboard Cite

show abstract

“…A description of the development of this telemetered, moored instrument array is given by Dimmler, et al · (1975). Wave heights and wave periods were observed with a ''waverider" which is essentially a buoy t~at fo~lows the movements of the water surface and measures waves by measuring the vertical acceleration of the buoy.…”

Section: Measurementsmentioning

confidence: 99%