scholarly journals Resolving velocity ambiguity of two coded pulse in broad-band acoustic Doppler current profiler

2019 ◽  
Vol 283 ◽  
pp. 07013
Author(s):  
Weixuan Zhang ◽  
Changhong Wang ◽  
Kai Deng
Keyword(s):  
Measurement Accuracy ◽  
Time Lag ◽  
Broad Band ◽  
Acoustic Doppler Current Profiler ◽  
Short Sequence ◽  
Measurable Velocity ◽  
Numerous Experimental Data ◽  
Current Profiler ◽  
Long Time ◽  
Short Time

Broad-band Acoustic Doppler Current Profiler (BBADCP) adopts short-sequence coded pulse to measure high velocity. Short-sequence coded pulse has large measurable velocity, so it is not easy to have velocity ambiguity. But short coded pulse deteriorates the accuracy of the velocity. To obtain more accurate velocity, we adopt two coded pulse with a time lag. This paper analyzes the ambiguity velocity and velocity standard deviation of two coded pulse and single coded pulse, and gives a solution to resolve velocity ambiguity: single coded pulse which has a large ambiguity velocity due to the short time lag is used to establish a coarse estimate of the velocity, two coded pulsewhich has a long time lag is used to have a high accuracy velocity, then we combine the two velocities in a way to provide an accurate velocity. It has been demonstrated that the two coded pulse can reduce variance of velocity through analyzing numerous experimental data of pool. Meanwhile, the efficiency of method to solve ambiguity has been proved in accordance with multiple sets of data. Compared with the traditional methods, this method has good anti-noise performance and high single measurement accuracy.

scholarly journals Temporal variations of zooplankton biomass in the Ligurian Sea inferred from long time series of ADCP data

Ocean Science ◽  
2014 ◽  
Vol 10 (1) ◽  
pp. 93-105 ◽  
Author(s):  
R. Bozzano ◽  
E. Fanelli ◽  
S. Pensieri ◽  
P. Picco ◽  
M. E. Schiano
Keyword(s):  
Time Series ◽  
Acoustic Doppler Current Profiler ◽  
Temporal Variations ◽  
Zooplankton Biomass ◽  
Mesopelagic Fish ◽  
Ligurian Sea ◽  
Time Frequency ◽  
Backscattering Strength ◽  
Current Profiler ◽  
Long Time

Abstract. Three years of 300 kHz acoustic doppler current profiler data collected in the central Ligurian Sea are analysed to investigate the variability of the zooplankton biomass and the diel vertical migration in the upper thermocline. After a pre-processing phase aimed at avoiding the slant range attenuation, hourly volume backscattering strength time series are obtained. Despite the lack of concurrent net samples collection, different migration patterns are identified and their temporal variability examined by means of time–frequency analysis. The effect of changes in the environmental condition is also investigated. The highest zooplankton biomasses are observed in April–May just after the peak of surface primary production in March–April. The main migration pattern found here points to a "nocturnal" migration, with zooplankton organisms occurring deeper in the water column during the day and shallower at night. Also, twilight migration is highlighted during this study. The largest migrations are recorded in November–December, corresponding to lowest backscattering strength values and they are likely attributable to larger and more active organisms (i.e. euphausiids and mesopelagic fish). The results suggest further applications of the available historical acoustic doppler current profiler time series.

scholarly journals The relationship between meteorological variables and sporadic cases of Legionnaires' disease in residents of England and Wales

2014 ◽  
Vol 142 (11) ◽  
pp. 2352-2359 ◽  
Author(s):  
K. D. HALSBY ◽  
C. A. JOSEPH ◽  
J. V. LEE ◽  
P. WILKINSON
Keyword(s):  
Conditional Logistic Regression ◽  
Time Lag ◽  
Time Lags ◽  
England And Wales ◽  
Long Time ◽  
Sporadic Cases ◽  
Risk Of Disease ◽  
Legionnaires Disease ◽  
Short Time ◽  
The Relationship

SUMMARYWe studied the timing of occurrence of 1676 sporadic, community-acquired cases of Legionnaires' disease in England and Wales between 1993 and 2008, in relation to temperature, relative humidity, rainfall, windspeed and ultraviolet light using a fixed-stratum case-crossover approach. The analysis was conducted using conditional logistic regression, with consideration of appropriate lag periods. There was evidence of an association between the risk of Legionnaires' disease and temperature with an apparently long time lag of 1–9 weeks [odds of disease at 95thvs. 75th centiles: 3·91, 95% confidence interval (CI) 2·06–7·40], and with rainfall at short time lags (of 2–10 days) (odds of disease at 75thvs.50th centiles: 1·78, 95% CI 1·50–2·13). There was some evidence that the risk of disease in relation to high temperatures was greater at high relative humidities. A higher risk of Legionnaires' disease may be indicated by preceding periods of warmer wetter weather.

Comparative Evaluation of Volumetric Current Measurements in a Tidally Dominated Coastal Setting: A Virtual Field Experiment

2020 ◽  
Vol 37 (4) ◽  
pp. 533-552
Author(s):  
Trevor Harrison ◽  
Kristen M. Thyng ◽  
Brian Polagye
Keyword(s):  
High Resolution ◽  
Puget Sound ◽  
Acoustic Doppler Current Profiler ◽  
Hydrodynamic Simulation ◽  
X Band ◽  
Virtual Field ◽  
Current Profiler ◽  
Short Time ◽  
Scalar Properties

AbstractHigh-resolution, four-dimensional mapping of currents in tidally dominated coastal settings can be conducted with a range of instrumentation. Here, we assess four approaches to data collection: an X-band radar, a stationary (bottom mounted) acoustic Doppler current profiler (ADCP), a mobile (vessel based) ADCP, and a swarm of Lagrangian floats. Using the output from a hydrodynamic simulation, a virtual field campaign was performed at 24 locations in Admiralty Inlet, Puget Sound, Washington, during spring and neap tidal exchanges. A reconstruction of the volumetric currents was generated for each platform every 15 min and evaluated against the true currents to assess accuracy over a horizontal extent of 400 m × 500 m at 5 m resolution and vertically through the entire water column (20–80 m) at 2 m resolution. Results demonstrate that, for this survey extent and resolution, a vessel-based ADCP survey is most accurate, followed closely by the float swarm. The overall performance hierarchy persists over most locations and times. Thus, if mapping currents at high resolution (<10 m) and short time scales (<1 day) is the primary scientific objective, vessel-based ADCP surveys are likely the best option. For longer-duration surveys, a combined deployment with a stationary ADCP and X-band radar system is the best choice. Last, if in situ measurements of scalar properties (e.g., salinity, temperature, dissolved oxygen) are also desired, float swarms can simultaneously sample these while surveying currents with accuracy comparable to mobile ADCPs.

Performance of a broad-band acoustic Doppler current profiler

1991 ◽  
Vol 16 (4) ◽  
pp. 402-407 ◽  
Author(s):  
B.H. Brumley ◽  
R.G. Cabrera ◽  
K.L. Deines ◽  
E.A. Terray
Keyword(s):  
Broad Band ◽  
Acoustic Doppler Current Profiler ◽  
Current Profiler

scholarly journals Measuring Turbulent Dissipation Using a Tethered ADCP

2014 ◽  
Vol 31 (8) ◽  
pp. 1826-1837 ◽  
Author(s):  
N. S. Lucas ◽  
J. H. Simpson ◽  
T. P. Rippeth ◽  
C. P. Old
Keyword(s):  
Structure Function ◽  
Dissipation Rate ◽  
Acoustic Doppler Current Profiler ◽  
Beam Direction ◽  
Turbulent Dissipation ◽  
Vertical Range ◽  
Current Profiler ◽  
Long Time ◽  
Flow Components ◽  
Free Falling

Abstract The structure function method for estimating the dissipation rate of turbulent kinetic energy, previously validated for measurements from seabed fixed mounts, is applied to data from 1.2-MHz acoustic Doppler current profiler (ADCP) instruments operating in pulse–pulse coherent mode and mounted in midwater below a tethered buoy. Movements of the buoy introduce additional relative velocity components, but it is hypothesized that these flow components should not seriously interfere with the turbulence information because (i) horizontal or vertical translation induces the same flow component in all cells of an ADCP beam and (ii) any rotation of the instrument about its center induces flow components that are normal to the beam direction, and thus neither affect the structure function. This hypothesis is tested by comparing a series of dissipation measurements from a moored ADCP with those from a free-falling Vertical Microstructure Profiler (VMP) shear probe deployed from a nearby research vessel. The results indicate generally good conformity in both mean and variability over almost two decades of dissipation rates. The noise level of the structure function estimates with the pulse–pulse coherent ADCP is close to that of the VMP at ~3 × 10−10 W kg−1. This approach offers the prospect of long time series measurements of dissipation rate from moorings, albeit with restricted vertical range of a few meters.

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