Characteristics of ice in the St. Lawrence River

2003 ◽  
Vol 30 (4) ◽  
pp. 766-774 ◽  
Author(s):  
Brian Morse ◽  
Masoud Hessami ◽  
Céline Bourel
Keyword(s):  
Fuzzy Logic ◽  
Wind Velocity ◽  
Air Temperature ◽  
Acoustic Doppler Current Profiler ◽  
Navigation Channel ◽  
Current Profiler ◽  
Adcp Data ◽  
St Lawrence River ◽  
Good Agreement

The main objective of this paper is to describe the characteristics of brash ice in the St. Lawrence River downstream of Montréal over a period of three winters. We used two instruments deployed in the St. Lawrence River navigation channel through Lake St. Pierre to measure ice parameters: an acoustic Doppler current profiler (ADCP) and an ice-profiling sonar (IPS). This paper discusses the capacities of these instruments to quantify ice characteristics and to predict the risk of ice congestion. It was found that wind velocity and air temperature play major roles in the variation in ice parameters and, consequently, in the occurrence of ice congestion in the navigation channel through Lake St. Pierre. Comparison of the IPS and ADCP data showed good agreement and demonstrated that these two instruments can be very effective for certain ice applications.Key words: ice characteristics, ice congestion, ADCP, IPS, fuzzy logic.

Assimilation of Ship-Mounted ADCP Data for Barotropic Tides: Application to the Ross Sea

2005 ◽  
Vol 22 (6) ◽  
pp. 721-734 ◽  
Author(s):  
S. Y. Erofeeva ◽  
Laurie Padman ◽  
Gary Egbert
Keyword(s):  
Numerical Solutions ◽  
Ross Sea ◽  
Acoustic Doppler Current Profiler ◽  
Tidal Currents ◽  
Open Boundary ◽  
Open Boundary Conditions ◽  
Current Profiler ◽  
Inverse Solutions ◽  
Adcp Data ◽  
Mean Circulation

Abstract The application of a generalized inverse approach for assimilating vessel-mounted acoustic Doppler current profiler (VM-ADCP) data into numerical solutions of barotropic tides is described. The derived estimates of tidal currents can be used to detide the VM-ADCP data and expose underlying mean circulation. The methodology is illustrated with data assimilation models of tidal currents in the Ross Sea. The prior solution, obtained by solving the nonlinear shallow-water equations by time stepping with a linear bottom friction parameterization and elevation of open boundary conditions obtained from a circum-Antarctic tide model, provides reasonably good fit to most available moored current meter data. Two inverse solutions were obtained: one assimilating moored current meter records and the other assimilating three cruises of VM-ADCP data. Fitting either the mooring time series or the VM-ADCP records leads to only small changes relative to the prior solution currents, except over the shelf break where short length scale, energetic diurnal topographic vorticity waves are present. It is shown that the dynamics embedded in the representer functions provides reasonable tidal corrections even with no prior information about forcing at open boundaries.

scholarly journals A NEW STRATEGIC WAVE MEASUREMENT STATION OFF NAPLES PORT MAIN BREAKWATER

2017 ◽  
pp. 36 ◽  
Author(s):  
Luca Centurioni ◽  
Lance Braasch ◽  
Enrico Di Lauro ◽  
Pasquale Contestabile ◽  
Francesco De Leo ◽  
...  
Keyword(s):  
Wave Energy ◽  
Low Cost ◽  
Acoustic Doppler Current Profiler ◽  
Wave Spectra ◽  
Sea State ◽  
Gulf Of Naples ◽  
Current Profiler ◽  
Directional Wave ◽  
Low Costs ◽  
Good Agreement

The accuracy of directional wave spectra sensors is crucial for obtaining accurate forecasts of ocean and coastal wave conditions for scientific and engineering applications. In this paper, a newly designed, low-cost GPS-based wave buoy, called the Directional Wave Spectra Drifter (DWSD), is presented. A field test campaign was conducted at the Gulf of Naples, Italy with the goal of comparing the directional wave properties obtained with the DWSD and with a nearly co-located bottom-mounted Acoustic Doppler Current Profiler (ADCP) from Teledyne RD-Instruments. The comparison shows a very good agreement between the two methodologies. The reliability of this innovative instrument and its low costs allow a large variety of applications, including the implementation of a global, satellite-linked, real-time open-ocean network of drifting directional wave spectra sensors and monitoring the sea-state in harbors to aid ship transit and for planning coastal and offshore constructions. The DWSD is currently in use to better constrain the wave energy climatology with the goal of optimizing the design of a full-scale prototype Wave Energy Converter (WEC) in the port of Naples, Italy.

scholarly journals Observing Directional Properties of Ocean Swell with an Acoustic Doppler Current Profiler (ADCP)

2010 ◽  
Vol 27 (1) ◽  
pp. 210-225 ◽  
Author(s):  
T. H. C. Herbers ◽  
S. J. Lentz
Keyword(s):  
Continental Shelf ◽  
Acoustic Doppler Current Profiler ◽  
Parametric Estimation ◽  
Monitoring Applications ◽  
Current Profiler ◽  
Adcp Measurements ◽  
Directional Wave ◽  
Acoustic Doppler Current Profilers ◽  
Good Agreement

Abstract Acoustic Doppler current profilers (ADCPs) are widely used for routine measurements of ocean currents and waves in coastal environments. These instruments have the basic capability to measure surface wave frequency–directional spectra, but the quality of the estimates is not well understood because of the relatively high noise levels in the velocity measurements. In this study, wave data are evaluated from two 600-kHz ADCP instruments deployed at 20- and 45-m depths on the Southern California continental shelf. A simple parametric estimation technique is presented that provides robust estimates of the gross directional wave properties, even when the data quality is marginal, as was often the case in this benign wave environment. Good agreement of mean direction and (to a lesser degree) directional spreading estimates with measurements from a nearby surface-following buoy confirms that reliable wave information can generally be extracted from ADCP measurements on the continental shelf, supporting the instrument’s suitability for routine wave-monitoring applications.

Observations of Nepheloid Layers in the Yangtze Estuary, China, Through Phase-Corrupted Acoustic Doppler Current Profiler Speeds

2012 ◽  
Vol 46 (4) ◽  
pp. 60-70 ◽  
Author(s):  
Zhenyi Cao ◽  
Xiao Hua Wang ◽  
Weibing Guan ◽  
Les J. Hamilton ◽  
Qi Chen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Acoustic Doppler Current Profiler ◽  
Yangtze Estuary ◽  
Fluid Mud ◽  
Nepheloid Layer ◽  
The Yangtze Estuary ◽  
Mean Velocity ◽  
The North ◽  
Navigation Channel ◽  
Current Profiler

AbstractA bottom quadrapod was deployed from March 29 to April 5, 2009 to measure bottom boundary layer (BBL) flows and nepheloid layer properties in the Deepwater Navigation Channel in the North Passage of Shanghai Port in the Yangtze estuary. Using a downward-looking acoustic Doppler current profiler (ADCP) and acoustic Doppler velocimeter, detailed measurements of mean velocity and turbulence distribution within 1 m above the seabed were obtained. It appears that corrupted speeds measured for the deeper bins are caused by formation of the nepheloid layer at the seabed, implying that the ADCP is not a suitable instrument to measure current velocities in the bins nearest the seafloor. A statistical clustering method was used to characterize the current profiles in the BBL. The majority of current profiles within the BBL had a simple shape with current speed monotonically decreasing with depth, reflecting a logarithmic boundary layer. Phase-corrupted ADCP speeds measured for bins close to the bottom are shown to be useful as proxies to indicate the presence of primary and secondary lutoclines/nepheloid layers. A lutocline is a sediment-induced density gradient or pycnocline. The primary lutocline is closest to the bottom, and below it is the nepheloid layer, which is commonly composed of fluid mud. The proxies indicated that a nepheloid layer formed in the neap tide when the current velocity 1 m above the seabed dropped below a threshold of 0.65 m/s. The lutocline height was indicated to be about 0.2 m above the seabed. A secondary lutocline in the water column was also observed in the second half of the record, when the lowest maximum currents occurred.

scholarly journals Acoustic Doppler current profiler observations of herring movement

2003 ◽  
Vol 60 (4) ◽  
pp. 846-859 ◽  
Author(s):  
Len Zedel ◽  
Tor Knutsen ◽  
Ranjan Patro
Keyword(s):  
Swimming Speed ◽  
Acoustic Doppler Current Profiler ◽  
Clupea Harengus ◽  
Night Time ◽  
Individual Fish ◽  
Current Profiler ◽  
Adcp Data ◽  
Increased Activity

Abstract Observations were made of over-wintering (December 1997) and migrating (January 1998) Norwegian, spring-spawning herring (Clupea harengus) using a moored 307 kHz acoustic Doppler current profiler (ADCP). The location of herring in ADCP data is identified by regions of volume-backscatter strength greater than −60 dB re 1 m−1. The presence of herring was verified using net trawls and 38 kHz, EK500 data. While the ADCP cannot make speed measurements of individual fish, the system does provide a measure of the swimming speed and direction of large herring schools. Herring were observed to move both horizontally and vertically: horizontal speeds were from 0 to 50 cm s−1. Higher speeds were observed during daylight hours for both deployments with somewhat increased activity at both dawn and dusk. At night-time, over-wintering herring demonstrated no well-defined velocity.

scholarly journals Interoperability of SeaSondes and Wellen Radars in Mapping Radial Surface Currents

2013 ◽  
Vol 30 (11) ◽  
pp. 2662-2675 ◽  
Author(s):  
J. Martinez-Pedraja ◽  
L. K. Shay ◽  
B. K. Haus ◽  
C. Whelan
Keyword(s):  
Acoustic Doppler Current Profiler ◽  
Hf Radar ◽  
Small Scale ◽  
Surface Currents ◽  
Florida Current ◽  
Current Profiler ◽  
Florida Straits ◽  
Subsurface Current ◽  
Geometric Dilution Of Precision ◽  
Good Agreement

Abstract A dual-station high-frequency (HF) Wellen Radar (WERA) transmitting at 16 MHz has observed near-real-time surface currents over an approximate range of 100 km across the Florida Straits since July 2004. During a 10-day period in April 2005 (15–25 April), a pair of 12.6-MHz SeaSondes (SS) were deployed south of the WERAs sites by NOAA's Center for Operational Oceanographic Products and Services (CO-OPS). The resulting SS grid overlapped the southern portion of the WERA domain. During the same period of time, a bottom-mounted acoustic Doppler current profiler (ADCP) acquired subsurface current measurements within these HF radar grids starting at 14 m below the surface in water of 86-m depth. The interoperability of beam-forming (WERA) and direction-finding (SS) HF radar technologies was examined. Comparisons of radial and vector currents for an 8-day concurrent time series suggested good agreement in current direction over both domains, where the surface currents' magnitudes were a maximum of 1.2 m s−1. In the core of the radar domains consisting of 108 cells, hourly vector currents were obtained by combining WERA and SS radials. Generally, this can be done in a relatively straightforward manner, considering the geometric dilution of precision (GDOP). A second key issue is downscaling the SS measurements from a 3-km grid to a 1.1-km grid to match the WERA output. This enhanced grid spacing is important along the western flank of the Florida Current, where energetic, small-scale surface features have been observed.

The Leeuwin Current near Rottnest Island, Western Australia

1996 ◽  
Vol 47 (3) ◽  
pp. 483 ◽  
Author(s):  
G Cresswell
Keyword(s):  
Satellite Image ◽  
Acoustic Doppler Current Profiler ◽  
Maximum Speed ◽  
Temperature Structure ◽  
Near Surface ◽  
Fish Schools ◽  
Leeuwin Current ◽  
Low Salinity ◽  
Current Profiler ◽  
Good Agreement

Ship data and a satellite image in June 1987 showed the Leeuwin Current as a warm, low-salinity tropical stream travelling southward inshore of the 180-m isobath with near-surface speeds up to 0.9 m s-1. Farther offshore, where the waters became progressively more subtropical, the southward currents were also quite strong--0.75 m s-1 above the continental slope and over 0.4 m s-1 out to 70 km beyond the shelf edge. Beyond this, a doming of 150 m in the temperature structure at several hundred metres depth drove a cyclonic eddy that had its maximum speed of ~0.5 m s-1 in a ring at 200-400 m depth. The presence of the eddy was confirmed by the path of a drifter. Geostrophic currents and currents measured directly with an Acoustic Doppler Current Profiler showed good agreement. The warm 'shoulder' of the Leeuwin Current between the 105-m and 135-m isobaths was a biological oasis characterized by, inter alia, several fish schools at least 10 km long and 1 km wide and with vertical extents from 20 m to more than 100 m depth.

scholarly journals Thermal structure and circulation in Lake Chapala, Mexico

2016 ◽  
Vol 75 (s1) ◽  
Author(s):  
David Avalos-Cueva ◽  
Anatoliy Filonov ◽  
Iryna Tereshchenko ◽  
César O. Monzón ◽  
Federico Á. Velázquez-Muñoz
Keyword(s):  
Thermal Structure ◽  
Acoustic Doppler Current Profiler ◽  
Dry Season ◽  
Spatial Average ◽  
Average Temperature ◽  
Lake Chapala ◽  
Anticyclonic Gyre ◽  
Current Profiler ◽  
Adcp Measurements ◽  
Good Agreement

<p>This study analyzed and discussed the instrumental measurements of temperature and currents made on January 10, 2007, in Lake Chapala. We received new data on the formation of the thermocline. It is shown that the thermocline of the lake is formed only in the daytime and in a top-heated 0.5-1.0 m layer. The vertical temperature gradient reaches 2.5°C in the first meter, and the spatial average temperature across the lake showed that the northern end of the lake is, on average, 1°C warmer than the southern end. We numerically modelled the currents in the lake for the dry season using the HAMSOM 2D hydrodynamic model. The simulation results are in good agreement with the acoustic Doppler current profiler ADCP measurements. In the dry season, two gyres were found: a cyclonic gyre in the eastern part and an anticyclonic gyre in the western part.</p>

Thermal Performance of Spray Cooling Ponds at Zero Wind Velocity

1987 ◽  
Vol 109 (1) ◽  
pp. 212-217
Author(s):  
N. Moussiopoulos ◽  
G. Ernst
Keyword(s):  
Water Vapor ◽  
Numerical Solution ◽  
Wind Velocity ◽  
Air Temperature ◽  
Thermal Performance ◽  
Present Model ◽  
Spray Cooling ◽  
Vapor Transfer ◽  
Water Vapor Transfer ◽  
Good Agreement

The present model allows predictions of the thermal performance of spray cooling ponds in the case of zero wind velocity. Droplet cooling is described by modeling of the heat and water vapor transfer to the air. Temperature and humidity of air are obtained by the numerical solution of transport differential equations. Detailed results are presented and discussed. Predictions are in good agreement with the observed thermal performance of spray cooling ponds. Results are utilized for a check of assumptions made by NTU models.

scholarly journals Detiding ADCP Data in a Highly Variable Shelf Sea: The Celtic Sea

2005 ◽  
Vol 22 (1) ◽  
pp. 84-97 ◽  
Author(s):  
L. Carrillo ◽  
A. J. Souza ◽  
A. E. Hill ◽  
J. Brown ◽  
L. Fernand ◽  
...  
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Three Dimensional ◽  
Acoustic Doppler Current Profiler ◽  
Tidal Currents ◽  
Shelf Area ◽  
Residual Currents ◽  
Current Profiler ◽  
Adcp Data ◽  
Celtic Sea

Abstract This paper presents a comparison of two conventional detiding techniques carried out for ship-mounted acoustic Doppler current profiler (ADCP) data collected in the European shelf area of the Celtic Sea during the summer of 1998. One technique consisted of extracting the vertically averaged tidal currents obtained from a barotropic three-dimensional numerical tidal model. The second technique consisted of fitting the spatiotemporal ADCP data using least squares and polynomial spatial functions. In the least squares technique, the incorporation of zero velocity normal to the coast appears to improve the estimation of the tidal currents near the coast. Quantitative comparisons of the results from both techniques with historical current meter observations are shown. However, both methods showed limitations in accurately representing the tidal currents in the study area. Consequently, an alternative detiding technique is proposed. This technique consists of blending the tidal currents derived from the numerical model with those fitted to the ADCP data from the least squares method. Improved results were obtained using the blending technique. ADCP-derived residual currents were comparable with contemporaneous flows measured using drifting buoys and also with estimates obtained by geostrophic calculations.

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