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Previous work by Oberg and Mueller of the U.S. Geological Survey in 2007 concluded that exposure time (total time spent sampling the flow) is a critical factor in reducing measurement uncertainty. In a subsequent paper, Oberg and Mueller validated these conclusions using one set of data to show that the effect of exposure time on the uncertainty of the measured discharge is independent of stream width,...
The Iroise Sea is located at the western end of Brittany (France), along the route of low-pressure atmospheric systems. The area is shallow (mean depth 110 m) and exhibits strong tidal currents (up to 8 knots in springtime). In summer, tidal fronts are generated in transition zones between the coastal area, where strong tidal currents efficiently mix the whole water column, and the offshore ocean,...
The combination of attenuation measurement with acoustic travel-time current measurement along a common path has produced a new acoustic sensor of suspended particles, the acoustic transmissometer (AT). The AT has been deployed in the OASIS experiment, a particle-measuring experiment to determine suspended particle properties resulting from turbulence and current near the seabed. Acoustic transmission...
The excellent space-time resolution of pure coherent Doppler system has led many scientists to select this processing technique to solve his or her measurement problem. There is nothing in the acoustic Doppler world that can beat the information content of a pure coherent system. The high vertical and temporal resolution give an instantaneous picture of the flow field with photographic clarity; slow...
Two-dimensional river flow patterns have been measured using a pair of RiverSondes in two experiments in the Sacramento-San Joaquin River Delta system of central California during April and October 2007. An experiment was conducted at Walnut Grove, California in order to explore the use of dual RiverSondes to measure flow patterns at a location which is important in the study of juvenile fish migration...
Over 2200 satellite-tracked drifters have been air deployed from fixed wing aircraft into the Gulf of Mexico over the past 25 years as part of a Loop Current monitoring program. The drifters are cylinder shaped and are approximately 96 cm tall and 12 cm in diameter. They each have a 45 m tether attached to a 1.2 m diameter drogue/chute. While the drifter design allows for cost-effective monitoring...
For several years, the Applied Physics Laboratory of the University of Washington has been working with the US Geological Survey to monitor surface currents in various rivers in western Washington State using coherent, continuous-wave (CW) and pulsed microwave systems. The results have demonstrated the feasibility of monitoring horizontal profiles of surface current velocity for use in making non-contact...
The dynamics (currents, pressures/elevations, waves and density field) of Liverpool Bay, Irish Sea, have been measured and modelled continuously since August 2002 in an integrated programme. The Bay has strong tidal mixing, receives fresh water from several estuaries and stratifies intermittently. The measurements include 600 kHz ADCPs sampling the water column in 1 m bins at two sites in water 25...
Recent studies of the Chicago River have determined that gravity currents are responsible for persistent bidirectional flows that have been observed in the river. A gravity current is the flow of one fluid within another caused by a density difference between the fluids. These studies demonstrated how acoustic Doppler current profilers (ADCPs) can be used to detect and characterize gravity currents...
An intercomparison study in June-November 2006 assessed the performance of the Teledyne RDI 75 kHz Long Ranger ADCP (LR-75) in deep, low-scattering waters of the Gulf of Mexico. Two LR-75s and a 300 kHz Workhorse Sentinel ADCP (WHS-300) were deployed by ROV for three 1-month intervals in bottom tripods at 2000 m depth approximately 65 m away from the wellhead of an oil exploration rig. The ADCPs were...
Teledyne RD instruments has recently released a new high frequency acoustic Doppler current profiler (ADCP), the Doppler volume sampler (DVS). The DVS is intended for use in applications where single point current meters are currently used. To evaluate the performance of the DVS, it was deployed on the same taught wire mooring near two current meters. In addition to comparing the results from the...
The introduction of the mineral management services (MMS) notice to Lessees requiring the deployment of current monitoring systems from platforms and mobile offshore drilling units (MODU's) in the gulf of Mexico has raised the awareness of the need for accurate and precise installations of monitoring equipment in order to ensure that the quality and reliability of measured current data are not compromised...
Recently, as part of the CLIMODE (CLIVAR Mode Water Dynamics Experiment) a surface mooring was placed at 38degN, 65degW, a location that was at times in the core of the Gulf Stream. The surface mooring survived the first year at this 5000 m deep site, and the second deployment failed after 2 months. Two Nortek current meters provide some of the first direct near-surface current time series from such...
This paper presents a comparison of microwave radar surface velocity estimates to the estimates derived from video observations in the surf zone. The data presented here were collected during the Nearshore Canyon Experiment (NCEX) in the fall of 2003. The radar estimates are inferred from the Doppler shift of the backscattered radiation while video velocity estimates were produced using particle image...
A field trial was conducted from March 2007 to April 2007 in the Dee estuary comparing AADI RDCP600 measurements with RDI ADCP (1200 KHz) and Triaxys wave buoy measurements. The trial lasted for thirty days. The RDCP600 and RDI ADCP (1200 KHz) were mounted together on the STABLE III frame and deployed at 53 22.151N 3 14.391W. The Triaxys wave buoy was deployed at 53 23.410N 3 14.381W. The depth at...
Coastal surface currents measured remotely by high frequency (HF) radar are compared with those from in situ acoustic Doppler current profilers (ADCP) deployed in both Eulerian and Lagrangian configurations. Two 25 MHz CODAR SeaSondesreg, located at Cape May, NJ and Cape Henlopen, DE, continuously measure surface currents at the Delaware Bay mouth. The radars measure surface current hourly with a...
Ocean currents all over the globe contribute significantly to the state of the world climate. Knowledge of how they vary with time can provide a useful information on future states of the climate system. While satellites provide excellent spatial coverage, they measure only surface currents. To determine mass- and heatfluxes and their change over time accurately requires regular and repeat measurement...
The NOAA IOOS Program has been supporting the development of a national HF radar network data server system with primary nodes at Scripps Institution of Oceanography (SIO), NOAA National Data Buoy Center and Rutgers University. Five regional data portals have been deployed throughout the US. SIO has designed the data management as a scalable, robust solution to the ingest of the increasing number,...
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