Current Speed Measurements Research Articles

Condition of Coral Reefs and Abundance of Coral Fishes of the Chaetodontidae Family in the Waters of Sironjong Gadang Island, Pesisir Selatan District, West Sumatra Province

Sironjong Gadang Island is one of the islands in the Mandeh Tourism area in Pesisir Selatan Regency, West Sumatra, Indonesia. One of the ecosystems affected by tourism activities is coral reefs. Monitoring the coral reefs' condition and the abundance of coral fish in the Chaetdontidae family is carried out to find out this. This research uses survey research methods. The temperature measurement results obtained an average of 30.2oC, current speed measurements received an average of 0.12 m/s, salinity measurements obtained an average of 30 ppt, and brightness measurements show that the brightness of these waters is 9 m. Tide measurements in the waters of Sironjong Gadang Island, carried out on March 7–8, 2023, are double daily tides (semi diurnal tide). Then, the results from the coral reef cover of Sironjong Gadang Island waters obtained a percentage ranging from 2.34 - 12.83%, with an average rate of live coral reef cover of 5.96%, which is included in the poor category. Furthermore, the results at each research station in the waters of Sironjong Gadang Island showed that 54 coralfish individuals were found, with the number of coralfish at each depth ranging from 4 - 10 individuals. The most common types of coral fish are species. Acuminate had 18 individuals; the fewest types of coral fish found were Chaetodon trifasciatus and C. tristichous, each numbering two individuals. There is a solid relationship between live coral reef cover and the abundance of coral fish in the Chaetodontidae family, where live coral reef cover influences the plenty of coral fish by 61.11%, which means that the higher the percentage of live coral cover, the higher the value of coral fish abundance.

PHYSICAL WATER QUALITY PARAMETERS IN BOYO RIVER ONOWAEMBO VILLAGE, GUNUNGSITOLI SUBDISTRICT, GUNUNGSITOLI CITY

Water is a natural resource needed for many people’s livelihood. Clean water quality would affect the health of the environment and all activities beyond. This research was conducted on October 28th 2022 in Boyo River. The purpose of this study was to figure out the measurement of physical quality parameters and to determine the condition of Boyo River. Observations of physical water quality parameters were carried out at 3 location points through observation method. Data from measurements of current speed, depth, sunlight penetration, bottom substrate, river width, water color and odor were analyzed descriptively. The research result showed that the Boyo River in Onowaembo Village had not been polluted in accordance with PP No. 82 of 2001.

Multi resolution appraisal of Cork Harbour estuary: An object based image analysis approach

Lithic sedimentary benthic habitats are often organised by the overlying hydrodynamic regime, generating seabed sedimentary bedforms (SSBs) whose morphology and sediment composition are controlled by the current flow properties including speed, direction, and duration. Furthermore, SSBs can manifest at a variety of spatial scales reflecting different aspects of the hydrodynamic regime that operate at distinct intensities and temporal scales. Acoustic seabed mapping of SSBs permits the quantification of the complex seafloor hydrodynamics without in situ measurements. As such, seabed mapping efforts must determine the minimum spatial resolution required to effectively capture the complete seabed hydrodynamic picture. Here, we provide a semi-automated, object-based image analysis (OBIA) of SSBs occurring over 0.5, 1.0, 1.5, 2.0, and 2.5 m spatial resolutions of multibeam echosounder (MBES) data acquired in Cork Harbour, Ireland, to ascertain the optimum resolution at which to derive current velocity attributes. Estimations of seabed sediment grain size were completed through the angular range analysis (ARA) of co-located 400 kHz multibeam backscatter data. Results show that current flow estimations derived at 0.5, 1.0 and 1.5 m resolutions of MBES bathymetry agree with previous in situ current speed measurements. Moreover, sediment grain size estimations produced during the ARA of the 400 kHz backscatter data displayed a clear pattern of sediment resuspension at each section of the harbour, and this was effectively depicted at 0.5, 1.0, and 1.5 m resolution of MBES bathymetry data. However, current flow estimates derived from 2.0 and 2.5 m resolution failed to portray the short-term current variation induced by the ebb phase of the tide. Therefore, it is recommended that MBES data with a pixel size of >50 % of the wavelength of the SSB observed is insufficient for inclusion in an OBIA workflow.

Dual wavelength laser Doppler anemometer for simultaneous velocity and particulate size distribution measurements in submarine environments.

An in-situ laser Doppler current probe (LDCP) for the simultaneous measurements of the micro-scale subsurface current speed and the characterizations of micron particles is dedicated in this paper. The LDCP performs as an extension sensor for the state-of-the-art laser Doppler anemometry (LDA). The all-fiber LDCP utilized a compact dual wavelength (491 nm and 532 nm) diode pumped solid state laser as the light source to achieve the simultaneous measurements of the two components of the current speed. Besides its ability for the measurements of the current speed, the LDCP is also capable of obtaining the equivalent spherical size distribution of the suspended particles within small size range. The micro-scale measurement volume formed by two intersecting coherent laser beams makes it possible to accurately estimate the size distribution of the micron suspended particles with high temporal and spatial resolution. With its deployment during the field campaign at Yellow Sea, the LDCP has been experimentally demonstrated as an effective instrument to capture the micro-scale subsurface ocean current speed. The algorithm for retrieving the size distribution of the small suspended particles (2∼7.5µm) has been developed and validated. The combined LDCP system could be applied to the continuous long-term observations of plankton community structure, ocean water optical parameter over a wide range, and useful to elucidate the processes and interactions of the carbon cycles in the upper ocean.

A Platform Errors Estimation Method Based on Radar Echo for Spaceborne Doppler Scatterometer

The Doppler scatterometer is a type of rotating radar platform used for the estimation and monitoring of ocean current to achieve fast mapping of global vector current with a monostatic system. Accurate measurement of the ocean surface current imposes strong requirements on the accuracy of the platform errors. If the ocean surface current speed measurement accuracy can be less than 5 cm/s, the slant range error should be smaller than 20 m and the attitude measurement error should reach 1×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> °. No available attitude determination technique is capable of this level of accuracy. In this study, we propose a method of platform errors estimation based on echo signals. A model describing the relation of the Doppler centroid to platform errors is established. Then, a Doppler centroid frequency estimation method based on deramping is proposed to improve the estimation accuracy, which showed a 26.15% improvement compared with the classical average cross-correlation coefficient (ACCC) method. Finally, using the weighted least square technique, the platform errors estimation method based on Doppler centroid estimation of echo signals from the stationary land area is constructed. Simulation experiments were performed to analyze the accuracy, feasibility, and robustness of the proposed method. Through simulation of one circle echo data, the root-mean-square errors of slant range error, roll, pitch, and yaw were shown to reach 1.12×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> m, 1.69×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> °, 2.44×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> °, and 8.52×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> °, respectively. These findings represent a much smaller error level than the requirement for the slant range error and attitude angles.

The impact of ocean data assimilation on the simulation of mesoscale eddies at São Paulo plateau (Brazil) using the regional ocean modeling system

This work presents simulations of ocean circulation in the southwestern South Atlantic Ocean with emphasis on the São Paulo Plateau region, a unique physiographic feature at the foot of the continental slope offshore southeast Brazil, where the flow is dominated by ocean eddies and dipoles. Surface dynamics south of 23°S presents a heterogeneous circulation pattern intimately related to the presence of mesoscale features, such as meanders of the Brazil Current along the continental slope, and eddies that interacts with deep ocean features. The reproduction of these eddies at the correct time and spatial structure are quite challenging in the context of a non-assimilative model, considering the limitations imposed by the model’s numerical schemes, physical parameterizations, boundary conditions and surface forcing. In this sense, the Regional Ocean Modeling System (ROMS) 4-dimensional Variational Data Assimilation (4D-Var) module was used to increase model skill and minimize deviations from oceanic observations. Weekly observations of Sea Surface Height (SSH), daily Sea Surface Temperature (SST) fields and in situ vertical profiles of temperature and salinity from multiple sources were used in consecutive assimilation cycles to produce an accurate representation of ocean features and their variability. Both the assimilative and free run were evaluated against observations, including in situ current measurements. Results showed significant improvements of the assimilation procedure on both assimilated and non-assimilated variables, with RMSE reductions of 27% and 47% for SST and SSH, respectively, and 51% for current speed measurements during a dipole event in the São Paulo Plateau. The assimilative run was able to reproduce a remarkable event of mesoscale eddies interaction (dipole) and consequent current intensification, leading to important improvements on model skill. The correct use of observational information of open ocean surface features through data assimilation is a key factor for a proper simulation of such eddy dipole events.

A new stochastic ocean physics package and its application to hybrid‐covariance data assimilation

AbstractGenerating optimal perturbations is a key requirement of several data assimilation schemes. Here, we present a newly developed stochastic physics package for ocean models, implemented in the NEMO ocean general circulation model. The package includes three schemes applied simultaneously: stochastically perturbed parametrization tendencies (SPPT), stochastically perturbed parameters (SPP) and stochastic kinetic energy backscatter (SKEB) schemes. The three schemes allow for different temporal and spatial perturbation scales. Within a limited‐area ocean model configuration, ensemble free‐running simulations were performed to assess the impact and reliability of the schemes. They prove complementary in increasing the ensemble spread at different scales and for different diagnostics. The ensemble spread appears reliable; for instance, it proves consistent with the root‐mean‐square differences with respect to higher‐resolution (sub‐mesoscale) simulations that here represent the “truth” (in the sense that it includes “unresolved physics”). Interestingly, both the SPPT and the SKEB schemes lead to an increase of eddy kinetic energy at small spatial scales (2–10 km), and contribute to modify the ensemble mean state, mitigating warm biases near the thermocline due to the enhancement of the upper ocean vertical mixing. As an application of the stochastic packages, the ensemble anomaly covariances coming from the ensemble free‐running simulations are used to feed large‐scale anisotropic covariances that complement smaller‐scale ones in a hybrid‐covariance regional analysis and forecast system in the Mediterranean Sea. Ensemble‐derived covariances are formulated as slowly varying three‐dimensional low‐resolution empirical orthogonal functions (EOFs). The improvements due to the addition of such covariances to the stationary ones are found significant in real‐data experiments, within verification skill scores against glider profile data, remotely sensed observations and current speed measurements from drifters, radar and moorings.

Design and implementation of a speed test system for campus network based on IPv6

In order to realize the end-to-end network speed measurement in the campus network and solve the problem that the current speed measurement system is not well adapted for IPv6 campus network, we adopt the C/S mode to build a software for the client/server ends distributed in the selective target area. For end-to-end testing, the software provides various methods of network speed measurement including FTP download, and provides current network speed measurement data. We also design network quality classification standards, and evaluate current network conditions according to them. At the same time, our software can do the speed measurement for localized download service of high-quality resources.

Maximum Power-Point Tracking Control Using Perturb and Observe Algorithm for Tidal Current Generation System

Because wind turbines and tidal current generation rely on irregular wind or tidal speed, maximum power-point tracking (MPPT) control is required in order to generate maximum turbine power. The most common turbine generation is obtained by employing the MPPT scheme using the tip speed ratio (TSR). However, this scheme has a disadvantage in that it relies on the characteristics of tidal current turbines, and it requires expensive tidal current speed-measurement equipment. The tidal current speed measurement is also affected by the installed location and distance to the equipment. To avoid these disadvantages, this paper proposes the maximum power control scheme using perturb and observe (P&O) for tidal current generation systems. The proposed P&O MPPT scheme can generate maximum power regardless of the characteristics of the turbine and the information about the tidal current speed. The reliability and suitability of the proposed scheme are proven using simulation and experiment results at the tidal current generation laboratory in Jin-do, South Korea.

In-Situ Current Speed Measurement and Sediment Characteristics at UPNM Lake

In-Situ Current Speed Measurement and Sediment Characteristics at UPNM Lake

Marine Current Technology Design to Support the Poteran Island Economy Based on Fisheries

Poteran is a small island as part of Sumenep Madura Indonesia where it has the natural resorces to be developed into a sustainable small island. Increasing the local economy based on fisheries sector has a high potential to be developed. In small fisheries industry, the electrical energy is necessary needed, so that the marine power plant technology is relevant to be employed in this island. This paper describe the concept design of current power technology which is suitable to be implemented in the island consider to the enviromental sea condition. Potential current energy captured is identified based on the measurement of current speed for the short period of time at the coastal area of island. Futhermore, the turbine design of current power technology is introduced as well as the design of floating platform.

Design of a Centrifugal Force-Based Speed Sensor for Downhole Turbodrills

Turbodrill is an important type of drilling tool. Rotating speed is a key parameter to measure and control the efficiency of a turbodrill. Therefore, it is necessary to measure the rotating speed when a turbodrill is working under a well. However, current speed measurement devices and sensors cannot meet the requirements of the on-site downhole conditions due to many factors, including inadequate sealing, signal interference, difficult installation, and theoretical limitations. To break the aforementioned bottleneck, a new speed sensor used for turbodrills is designed based on the centrifugal force theory. In more detail, the measurement of the speed is performed based on a functional relation between the rotating speed and the centrifugal force of the turbodrill. Besides, the sensor was tested both in-lab and on-site. The test results illustrate that the measurement error is within ±4%, which meets the practical on-site conditions.

Tidal energy site resource assessment in the East River tidal strait, near Roosevelt Island, New York, New York

This study demonstrates a site resource assessment to examine the temporal variation of the current speeds, current directions, turbulence intensities, and power densities for a tidal energy site in the East River tidal strait. These variables were derived from two months of acoustic Doppler velocimeter (ADV) measurements at the design hub height of the Verdant Power Gen5 hydrokinetic turbine. The study site is a tidal strait that exhibits semi-diurnal tidal current characteristics, with a mean horizontal current speed of 1.4 m s−1, and a turbulence intensity of 15% at a reference mean current of 2 m s−1. Flood and ebb flow directions are nearly bi-directional, with a higher current speed during flood tide, which skews the power production towards the flood tide period. The tidal hydrodynamics at the site are highly regular, as indicated by the tidal current time series that resembles a sinusoidal function. This study also shows that the theoretical force and the power densities derived from the current measurements can be significantly influenced by the length of the time window used for averaging the current speed data. Furthermore, the theoretical power density at the site, derived from the current speed measurements, is one order of magnitude greater than that reported in the U.S. national resource assessment. This discrepancy highlights the importance of conducting site resource assessments based on measurements at the tidal energy converter device scale.

Interactions between the Agulhas Current and the eastern margin of the Agulhas Bank

Interactions between the Agulhas Current and the ecologically important region of the Agulhas Bank are studied through the analysis of high resolution along-track altimetry, merged mapped altimetry and in situ measurements of current speed and direction undertaken from a moored Accoustic Doppler Current Profiler (ADCP). Comparisons between current observations collected from the ADCP and the satellite altimeters are made to evaluate the validity of the analysis conducted on the altimetry. Both altimetry and in situ observations show that Natal Pulses are a major driver of variability along the eastern margin of the Agulhas Bank. On average, it is estimated that the circulation along the eastern margin of the Agulhas Bank is influenced by Natal Pulses for 110 days per year. In the outer shelf region, the offshore displacement of the Agulhas Current׳s front associated with the passage of the Natal Pulse meander drives a strong cyclonic circulation. Closer to the shore, the impact of a Natal Pulse is felt primarily through the intrusion of the Natal Pulse׳s leading edge onto the shelf. While Natal Pulses are responsible for the largest temperature and current velocity anomalies recorded in the in situ dataset, most of the intra-annual variability observed along the continental slope of the Agulhas Bank and east of 20°E, occurs over shorter time-scales and is currently not adequately observed using altimetry.

Suspended particulate matter depletion and flow modification inside mussel (Mytilus galloprovincialis) culture rafts in the Ría de Betanzos, Spain

The limited availability of empirically derived parameters describing the body drag and trophic resource depletion properties of mussel aquaculture farms has contributed to uncertainty in model predictions of farm carrying capacity. Time-series of flow reduction and total and size-specific suspended particle depletion were obtained for two mussel (Mytilus galloprovincialis) rafts in the Ría de Betanzos based on in situ measurements of current speed, chlorophyll a fluorescence, optical scattering and laser diffraction in water entering and exiting the rafts. Flow reduction across each raft averaged 53% and 62% during the study period and temporal and spatial variability in flow reduction can be explained by a relationship with the approach current speed. The bulk drag coefficient of the mussel rafts was estimated from these measurements as Cd=0.65. This value is lower than previous predictions for individual mussel ropes and appears to result from cumulative wake interactions between the structures and specific roughness elements of natural mussel ropes. The level of phytoplankton and total suspended particulate matter (TPM) depletion was similar at both rafts and averaged 40% and 17%, respectively. Food depletion was highest for particles in the 4 to 45μm size range, which included much of the available phytoplankton. TPM was dominated by larger particles that were less effectively retained within the raft than the available phytoplankton. A raft-scale food depletion model was developed that provided average values over the total study period that were within 5 and 11% of the observed phytoplankton depletion for the two rafts. Novel components of the model include the improved parameterization of raft form drag and inclusion of a function that accounts for the effect of raft-induced flow reduction on food acquisition by the cultured mussels.

An artificial pool experiment in Antarctic sea ice: effects of sea ice melting on physical and biogeochemical components of pool water

AbstractWe performed an artificial pool experiment in the Antarctic multi-year land-fast ice to examine and simulate the effect of sea ice melting on physical and biogeochemical components of the sea ice field. The input of snow and ice meltwater resulted in warmer, low salinity water at the surface of the pool and probably stratification of the less dense water. Current speed measurements also pointed to water stratification within the pool. Rapid phytoplankton growth in the pool resulted in drastic decreases in concentrations of dissolved inorganic carbon and nutrients (NO3- and Si(OH)4) in the surface waters of the pool, particularly depleted for NO3-. There was high correlation between variations of dissolved inorganic carbon and nutrient concentrations, but the apparent uptake ratios of these components deviated from that generally applied to marine phytoplankton. The sequence of changes in the physical and biogeochemical components of the pool water suggests that the onset of rapid phytoplankton growth was closely related to the water stratification, which provided stable conditions for phytoplankton bloom even though the supply of nutrients from under-ice water would have declined.

Tsunami observations by coastal ocean radar

When tsunami waves propagate across the open ocean, they are steered by the Coriolis effect and refraction due to gentle gradients in the bathymetry on scales longer than the wavelength. When the wave encounters steep gradients at the edges of continental shelves and at the coast, the wave becomes nonlinear and conservation of momentum produces squirts of surface current at the head of submerged canyons and in coastal bays. High frequency (HF) coastal ocean radar is well conditioned to observe the surface current bursts at the edge of the continental shelf and give a warning of 40 minutes to 2 hours when the shelf is 50 to 200 km wide. The period of tsunami waves is invariant over changes in bathymetry and is in the range 2 to 30 minutes. Wavelengths for tsunamis (in 500 to 3000 m depth) are in the range 8.5 to over 200 km, and on a shelf where the depth is about 50 m (as in the Great Barrier Reef (GBR)) the wavelengths are in the range 2.5 to 30 km. In the use of HF radar technology, there is a trade‐off between the precision of surface current speed measurements and time resolution. It is shown that the phased array HF ocean surface radar being deployed in the GBR and operating in a routine way for mapping surface currents, can resolve surface current squirts from tsunamis in the wave period range 20 to 30 minutes and in the wavelength range greater than about 6 km. An advantage in signal‐to‐noise ratio can be obtained from the prior knowledge of the spatial pattern of the squirts at the edge of the continental shelf, and it is estimated that, with this analysis, the time resolution of the GBR radar may be reduced to about 2.5 minutes, which corresponds to a capability to detect tsunamis at the shelf edge in the period range 5 to 30 minutes. It is estimated that the lower limit of squirt velocity detection at the shelf edge would correspond to a tsunami with water elevation of about 2.5 cm in the open ocean. This means that the GBR HF radar is well conditioned for use as a monitor of small, as well as larger, tsunamis and has the potential to contribute to the understanding of tsunami genesis research.

Oceanography and submarine sediment distribution in the Marmaris – Ka region of southwest Turkey

We present new oceanographic and modern sediment distribution data for transects along Marmaris-Fethiye- Kalkan-Ka-Finike and Antalya Bays (southwestern Turkey). Water temperature, salinity and dissolved oxygen content were measured and mapped for this region. Furthermore, we made short-term current speed measurements at the surface, 20m depth and the sea floor and use this data to interpret sediment movement. Orange peel and other types of grabs were used for surface sediment sampling. Samples were processed with Standard Methods of grain size analysis. Our regional maps of sediment distribution reflect grain size on a 1:100.000 scale. We used correlations between all our grain size data in our maps. Sediment distribution in this region is affected by current systems, bathymetry and both submarine, and terrestrial topographic features of the region. Finer materials do not accumulate in regions with high wave and current energy. Thus we find mostly thin accumulations of coarse material in our study region. Either sediment does not accumulate at all along continental slopes exceeding 10 degrees or very little sediment accumulates there. Sediments in our study area consist of five types of basic sedimentary material: rock, gravel, sand, silt, clay and mud. Gravelly materials are gravel, sandy gravel and muddy sandy gravel. Sandy materials are sand, gravelly sand, gravelly muddy sand, muddy sand, silty sand and clayey sand. Silty material is composed of silt and sandy silt. Muddy materials consist of mud, gravelly mud and gravelly sandy mud. Deep parts of the area contain as well as mud which is high ratio clay. Generally, grain size distribution in this region is transitional from coarse to fine and trends parallel to the coastline. Generally, gravel and sandy gravel material are found in shallow areas and reach thickness of up to 5 meters. Blocks of limestone occur on the seafloor along coasts with steep seaward slopes. Gravel size materials are uncommon. Sandy materials accumulate at approximately 20-50-100-200 meters water depth. Silty materials are deposited at 200-500-750, 500-1200 meters depth at the sea floor. Muddy materials, however, are not found until 1200-2500 meters water depth and clayey materials spread further out to below 2500 meters depth.

A floating device for stationary hydroacoustic sampling in shallow waters

Abstract A floating device was designed for use in stationary hydroacoustic studies of fish movements and current–speed measurements (Acoustic Doppler Current Profiler, ADCP) in the shallow inter- and subtidal zone of mangrove waters (3–10 m depth). The floating device was a stable platform for the hydroacoustic equipment. It features adjustable depth of the transducer below the water surface and adjustable beam direction (horizontal, vertical) of the echosounder. The design is simple, robust, and rapidly bolted together. The results of the ADCP measurements in the mangrove channel at the end of the wet season were unusable even at weak neap tides because bedload transport of fine muddy substrate led to missing bottom echoes that are required for the current–velocity calculation.

Hydrography of four Mediterranean marine cage sites

Measurements of current speed and direction were made at three marine cage farms in Greece and one in Mediterranean Spain. At two sites where contemporaneous wind measurements were made, current velocity was correlated with wind velocity. It appears that for each of the sites in Greece, at the time of measurement, the wind was the most important driver of water movements. However, at the Spanish site, current speeds were around 10% of the wind speed in the residual flow direction, indicating that the wind was not the only driver of water movements. Mean current speed ranged from 1.2 to 9.1 cm/s, therefore being within the typical range of mean current speeds experienced at tidal North Atlantic fish culture sites. Mediterranean sites differ from Atlantic sites in terms of temperature and salinity but may possess broadly similar surface flow regimens despite lacking macro-tidal forcing.