Strong Currents Research Articles

HYDROKINETIC ENERGY DEVICES: STUDYING DEVICES THAT GENERATE POWER FROM FLOWING WATER WITHOUT DAMS

Hydrokinetic energy devices harness the kinetic energy from flowing water to generate electricity without the need for large dams or reservoirs. This technology represents a significant advancement in renewable energy, offering an environmentally friendly alternative to traditional hydroelectric power. Hydrokinetic devices include various designs such as tidal stream generators, free-flow turbines in rivers and streams, and ocean current turbines. These devices operate by capturing the energy from natural water movements such as tides, river currents, and ocean currents through turbines or other mechanisms that convert kinetic energy into electrical power. The study of hydrokinetic energy devices focuses on their design, development, and deployment in diverse aquatic environments. Key areas of research include optimizing turbine efficiency, improving structural durability, and minimizing environmental impacts. Advances in computational modelling and simulation play a crucial role in this field, allowing researchers to predict device performance under various conditions and to refine designs before physical implementation. Hydrokinetic energy systems offer numerous advantages, including reduced ecological disruption compared to traditional dam-based hydroelectric projects, as they do not require large-scale alterations to watercourses. They also provide a continuous and predictable source of energy, particularly in tidal and ocean current applications, where water movements are regular and reliable. Challenges in the development and deployment of hydrokinetic devices include the harsh underwater environment, which can cause mechanical wear and biofouling, and the need for robust mooring and anchoring systems to withstand strong currents. Additionally, ensuring compatibility with marine ecosystems and minimizing impacts on aquatic life are critical considerations. Overall, hydrokinetic energy devices hold significant promise for expanding the portfolio of renewable energy sources. Continued research and development, supported by advances in materials science, engineering, and environmental science, are essential to overcoming the technical and ecological challenges, making hydrokinetic energy a viable and sustainable option for global energy needs. Keywords: Hydrokinetic Energy, Renewable Energy, Tidal Stream Generators, Free-Flow Turbines.

Cenderawasih Hot Pool: The Frequent High Sea Surface Temperature Phenomena At Cenderawasih Bay, Papua

The term “warm pool” refers to a body of water with the characteristic of SST exceeding 28°C within a particular area and a relatively long period in an annual circle. However, there are regions with an annual mean SST measured above 30°C, and we classified them as hot pools because of the conditions of intense solar radiation and low wind speed. One of the Hot Pool spots was found in Indonesia, in Cenderawasih Bay. The present study examines the existence of the Cenderawasih Hot Pool using long-term observation of satellite SST data. In order to learn more about their mechanisms, we also analyzed surface wind, surface heat flux, and surface current data. The results show that SSTs in Cenderawasih Bay have a 50% chance of exceeding 30°C within the 13 years of study (2013-2015). Heat input comes from strong solar radiation, i.e., 50% of solar radiation is more than 200 W/m2. The location is also dominated by low wind speed, i.e., 80% wind speed of lower than 4 m/s, which caused the low latent loss in Cenderawasih Bay. Cenderawasih Bay is fully separated from surface currents during the dry and wet seasons since the easterly subsurface water flow does not enter the bay. The absence of strong currents prevents the mixing process, maintaining the high temperature in the surface layer. Those processes are discovered and they serve as compelling evidence to support Cenderawasih Bay as one of the Hot Pool areas within the Indonesian seas.

Microplastics in the tropical Northwestern Pacific Ocean and the Indonesian seas

The abundance of microplastics fragments with sizes larger than 0.30–0.35 mm is measured during two research cruises in the tropical Northwestern Pacific Ocean and inside the Indonesian seas. The fragments are confirmed to be primarily nylon, polyester, and polyethylene etc. microplastics in the western Pacific by Fourier transform infrared spectroscopy (FT-IR), whereas dominated by polyethylene in the Indonesian seas based on Raman spectrum analyses. The abundance of the microplastics is found to be very low (<0.018 particles m−3) in the surface waters of the North Equatorial Current and the Kuroshio, suggesting no westward extension of the Great Pacific Garbage Belt and lack of microplastics accumulation due to mass convergence in the western boundary current. The abundances of the microplastics in the Makassar Strait of the Indonesian seas are found to be higher by an order of magnitude than those in the Northwestern Pacific, believed to be due to river run-offs carrying microplastics from nearby lands. The largest microplastics abundance is found in the northeastern Maluku Sea, where concurrent current measurements suggest a branch of the Indonesian Throughflow bringing accumulated microplastics from the eastern Indonesian seas into the convergent area of multiple strong currents. The study underlines the importance of ocean circulation in the microplastics distributions and transportation, and suggests the importance of high-resolution spatial mapping in the budget analysis of global microplastics distribution.

Особенности современного строения подводной аккумулятивной формы банка Еленина

The Elenina Bank is an underwater accumulative form of the eastern part of the Sea of Azov. It was formed 2.5-1.7 thousand years ago during the Phanagorian regression. During the subsequent sea level rise the Elenina Bank was under water. The analysis of the modern structure of the Elenina Bank was carried out using literary sources and remote sensing data. Digital models of the underwater relief for the Elenina Bank were built on the basis of Sentinel-2 satellite images using the method of mutual correlation of the brightness of the spectrum channels and depth. The length of the Elenina Bank is about 40 km, the width is up to 5 km, the minimum depth of the water area is 1.5-2 m. Arc-shaped ridges up to 6 km long were found at the western tip of the bank. Currently, the Elenina Bank is active accumulative form and influences the lithodynamic regime of the adjacent part of the Sea of Azov. The transverse profile of the bank indicates the predominant direction of sediment movement – from S to N. The Elenina Bank accumulates most of the sediments transferred to the S-SE, but there is practically no extension of the edge of the accumulative body to the North due to a sharp drop in depths. The presence of the accumulative body of the Elenina Bank contributes to the formation of strong and stable currents to the North of it.

Long distance dispersal and oceanographic fronts shape the connectivity of the keystone sponge Phakellia ventilabrum in the deep northeast Atlantic

Little is known about dispersal in deep-sea ecosystems, especially for sponges, which are abundant ecosystem engineers. Understanding patterns of gene flow in deep-sea sponges is essential, especially in areas where rising pressure from anthropogenic activities makes difficult to combine management and conservation. Here, we combined population genomics and oceanographic modelling to understand how Northeast Atlantic populations (Cantabrian Sea to Norway) of the deep-sea sponge Phakellia ventilabrum are connected. The analysis comprised ddRADseq derived SNP datasets of 166 individuals collected from 57 sampling stations from 17 different areas, including two Marine Protected Areas, one Special Area of Conservation and other areas with different levels of protection. The 4,017 neutral SNPs used indicated high connectivity and panmixis amongst the majority of areas (Ireland to Norway), spanning ca. 2,500-km at depths of 99–900 m. This was likely due to the presence of strong ocean currents allowing long-distance larval transport, as supported by our migration analysis and by 3D particle tracking modelling. On the contrary, the Cantabrian Sea and Roscoff (France) samples, the southernmost areas in our study, appeared disconnected from the remaining areas, probably due to prevailing current circulation patterns and topographic features, which might be acting as barriers for gene flow. Despite this major genetic break, our results suggest that all protected areas studied are well-connected with each other. Interestingly, analysis of SNPs under selection replicated results obtained for neutral SNPs. The relatively low genetic diversity observed along the study area, though, highlights the potential fragility of this species to changing climates, which might compromise resilience to future threats.

Real-time on-orbit image quality improvement for a wide-field imaging system with detector arrays.

Wide-field imaging systems are faced with the problem of massive image information processing and transmission. Due to the limitation of data bandwidth and other factors, it is difficult for the current technology to process and transmit massive images in real-time. With the requirement for fast response, the demand for real-time on-orbit image processing is increasing. In practice, nonuniformity correction is an important preprocessing step to improve the quality of surveillance images. This paper presents a new real-time on-orbit nonuniform background correction method, which only uses the local pixels of a single row output in real-time, breaking the dependence of the traditional algorithm on the whole image information. Combined with the FPGA pipeline design, when the local pixels of a single row are read out, the processing is completed, and no cache is required at all, which saves the resource overhead in hardware design. It achieves microsecond-level ultra-low latency. The experimental results show that under the influence of strong stray light and strong dark current, our real-time algorithm has a better image quality improvement effect compared with the traditional algorithm. It will greatly help the on-orbit real-time moving target recognition and tracking.

Optimization of a Tidal–Wind–Solar System to Enhance Supply–Demand Balancing and Security: A Case Study of the Goto Islands, Japan

Due to the expected increase in electric power demand in the coming decades and the economic and environmental issues caused by power generation from the combustion of hydrocarbon fuels, the integration of renewable energy into the grids of remote islands has attracted attention. Among all renewable sources, tidal stream energy shows potential to contribute positively in areas with strong tidal currents due to the predictability and semi-diurnal periodicity of the resource, which makes it compatible with short-term energy storage. However, its performance in areas with lower available power density has not yet been addressed. In this paper, energy systems for the Goto Islands, Japan which combine solar, offshore wind, and tidal energy are evaluated based on whole-system performance indicators such as the annual energy shortage and surplus and the battery load factor. Without energy storage, an energy mix of 31% solar, 47% offshore wind, and 22% tidal energy provides the lowest values for annual energy shortage (29.26% of total power demand) and surplus (29.26%). When batteries are incorporated into the system, tidal stream energy is the main contributor to reducing these two parameters, with values up to 23.58% and 19.60%, respectively, for the solar and tidal scenario with 30 MW of installed storage capacity. These results show the advantages of tidal stream energy exploitation in stand-alone energy systems, even with relatively low capacity factors (0.33).

Measuring Detection Efficiency of High-Residency Acoustic Signals for Estimating Probability of Fish–Turbine Encounter in a Fast-Flowing Tidal Passage

Semidiurnal tidal currents can exceed 5 ms−1 in Minas Passage, Bay of Fundy, where a tidal energy demonstration area has been designated to generate electricity using marine hydrokinetic turbines. The risk of harmful fish–turbine interaction cannot be dismissed for either migratory or local fish populations. Individuals belonging to several fish populations were acoustically tagged and monitored by using acoustic receivers moored within the Minas Passage. Detection efficiency ρ is required as the first step to estimate the probability of fish–turbine encounter. Moored Innovasea HR2 receivers and high-residency (HR) tags were used to obtain detection efficiency ρ as a function of range and current speed, for near-seafloor signal paths within the tidal energy development area. Strong tidal currents moved moorings, so HR tag signals and their reflections from the sea surface were used to measure ranges from tags to receivers. HR2 self-signals that reflected off the sea surface showed which moorings were displaced to lower and higher levels on the seafloor. Some of the range testing paths had anomalously low ρ, which might be attributed to variable bathymetry blocking the line-of-sight signal path. Clear and blocked signal paths accord with mooring levels. The application of ρ is demonstrated for the calculation of abundance, effective detection range, and detection-positive intervals. High-residency signals were better detected than pulse position modulation (PPM) signals. Providing that the presently obtained ρ applies to tagged fish that swim higher in the water column, there is a reasonable prospect that probability of fish–turbine encounter can be estimated by monitoring fish that carry HR tags.

El Niño‐Related Stratification Anomalies Over the Continental Slope Off Oregon in Summer 2014 and 2015: The Potential Vorticity Advection Mechanism

AbstractOver the continental slope off Oregon at the US West Coast, at 44.6°N, vertical stratification is found to be anomalously weak in July–August of 2014 and 2015 both in a regional ocean circulation model and conductivity–temperature–depth (CTD) profile observations. To understand the responsible mechanism, we focus on the layer between the isopycnal surfaces σθ = 26.5 and 26.25 kg m−3 that is found between depths 100 and 300 m and represents material properties characteristic of the slope poleward undercurrent and shelf‐slope exchange. This layer thickness, about 50 m on average, can be twice as large during the above‐mentioned periods. In the 2009–2018 model analysis, this anomaly is revealed over the continental slope only in summers 2014 and 2015 and only off the Oregon and Washington coasts (40°–47°N). The stratification anomaly is explained as the effect of advection of the seasonal along‐slope potential vorticity (PV) gradient by an anomalously strong poleward slope current. In the annual cycle, the zone of strong along‐slope PV gradient is found between 40° and 47°N, supported by the local upwelling that results in the injection of the large PV in the bottom boundary layer over the shelf followed by its offshore transport in the slope region. The positive along‐slope current anomaly propagates to Oregon with coastally trapped waves as part of the El Niño oceanic response and can be up to 0.1 m s−1. Advection by this anomalous poleward current results in transporting the seasonal PV gradient earlier in the season than on average.

Modelling the air-sea-land interactions responsible for the direct trigger of turbidity currents by tropical cyclones

Tropical cyclones directly trigger turbidity currents in submarine canyons as a consequence of storm surges, high waves, onshore blowing winds and extreme currents. The resultant supply of sediment at the heads of the canyons plays a crucial role in the genesis of turbidity currents and thus is key in understanding frequency and duration of their flows. Here we present a single numerical framework capable of modelling turbidity currents driven by cyclone-induced winds and waves through resolved, quasi-3D hydrostatic equations. Our simulations predict the occurrence of a canyon-confined turbid underflow induced by a tropical cyclone that caused a seafloor pipeline to shift. Turbidity current occurrence is shown to be related not just to tropical cyclone intensities but also to their tracks with respect to the canyon head. The modelled underflow is well approximated by similarity profiles from laboratory and field observations which demonstrates the reliability of the model in capturing the structure of turbidity currents. The proposed triggering of turbidity currents off the centre of coastal embayments is likely to occur when the abrupt rotation of incoming winds induced by a passing cyclone remains always coastal-bound all across the cyclone’s waxing and waning stages. Our results show that these conditions can give rise to simultaneous, opposite alongshore currents and eventually result in offshore-bound rip currents. Conversely, it is unlikely that turbidity currents will be triggered by cyclone-induced rip currents when the cyclonic rotation results in peak offshore winds (coming from the land), as no fetch is available for generating large breaking waves to induce simultaneous, opposite alongshore currents. Nevertheless, the sole presence of strong alongshore currents deflected at the headlands of a coastal embayment (or delta) is likely to trigger sediment-gravity flows and eventually result in turbidity currents offshore the edge of the embayment without the aid of rip currents.

Laboratory experiments on coastal current separation and vortex formation in front of Cabo Corrientes and Bahía de Banderas, México

A series of rotating tank experiments are carried out to study the behaviour of a coastal current when encountering a cape and an adjacent bay. The experiments are designed to represent some essential dynamics of the interaction of the Mexican Coastal Current with Cabo Corrientes and Bahía de Banderas on the western coast of Mexico. The experiments show that the current surrounds the cape and accumulates negative relative vorticity in front of the downstream bay. For sufficiently strong currents, the flow separates from the coast and the accumulated vorticity develops an anticyclonic eddy that drifts away from the generation region. Afterwards, the current is re-established and the process is repeated. The periodicity is about 16 periods of the rotating system. The current separation and vortex formation depend on the ratio between the inertial length of the current (defined as the characteristic speed over the Coriolis parameter) and the coastal radius of curvature associated with the cape. Another mechanism for vortex formation is verified when the coastal current is switched off. The current separation and eventual vortex shedding are further studied in additional experiments without the cape or the bay, thus increasing the effective coastal radius of curvature. It is verified that the absence of any of these two features inhibits the current separation. The results illustrate the dynamical conditions that may help to explain the emergence of mesoscale oceanic eddies observed on the lee side of Cabo Corrientes, especially during the summer. This assertion is explored by examining historical data from the GLORYS12V1 reanalysis, in which current separation and eddy-shedding events are found and compared with the experimental observations.

Liquid Superspreading on Surface with Microhexagonal Structure Inspired by Rock‐Climbing Fish

The dynamic spreading mechanism of liquid on a specific surface is vital for understanding interface wetting and antifouling. Whereas, how to control the spreading process and accelerate the spreading speed is a major challenge. The rock‐climbing fish is characterized by its alepidote feature that lives in stream habitats dominated by strong currents. The mucus on its body surface plays a vital role in its adherence and maintenance of antifouling and antibacterial properties. However, the rapid, uniform, and efficient spreading mechanism of mucus on the fish body surface remains largely unknown. Herein, it is revealed that the surface of the rock‐climbing fish is overlaid fully by the microhexagonal texture structure. This hexagonal structure shows a superspreading effect on liquid diffusion, resulting from testing with bionic microfabrication inspired by the rock‐climbing fish. It is demonstrated that the microhexagonal‐textured surface can enhance liquid spreading quickly and evenly on the surface by regulating the moving contact line of the liquid. This kind of superspreading mechanism has great potential applications in the antifouling, electroencephalogram electrode interfaces, flexible skin sensors, and interfacial lubrication of underwater surfaces.

Gateway to the arctic: Defining the eastern channel of the Bering Strait

The Bering Strait is the sole gateway and an oceanographic bottleneck for the seasonally warm and comparatively fresh and nutrient-rich Pacific waters to flow into the Arctic, melting ice, lowering salinity, and feeding bird, mammal, and fish populations. The Diomede Islands split this small strait into two main channels, both with northward flow (in the annual mean). The eastern channel, in U.S. waters, also seasonally carries the warmer, fresher Alaskan Coastal Current. Year-round in situ mooring observations (in place since 1990 with annual servicing) show a significant flow increase in the (northward) throughflow, along with seasonal and annual fluctuations. To help with measuring and modelling water flow estimates, we created the first detailed shore-to-shore bathymetric surface of the Bering Strait’s eastern channel, located its narrowest cross-section (1.8 km2) as occurring 5–10 km south of the moorings, and quantified the cross-section across the moorings (2.0 km2), both slightly larger than previously estimated (1.6 km2). Overlaps between older (∼1950) and newer (∼2010) bathymetry data sets identified clear areas of erosion and deposition, with much of the eastern channel having eroded by > 1 m. Since the depth is uniformly ∼ 50 m across much of the eastern channel, the 1 m of erosion that we quantified would only slightly (2 %) increase the sizes of the cross-sections. Much of the seafloor is hard substrate and probably composed of cobbles, but we hypothesize that friction from strong (∼1 + knot) seafloor currents is the most likely explanation for the erosion that we observed. In softer and siltier areas, the bathymetry showed additional evidence of potential current impacts in the form of small seafloor waves (∼0.5 to ∼ 1.0 m tall) and a shore-parallel bar offshore of Cape Prince of Wales Spit. There are large (∼2 m tall) seafloor waves seaward of Cape Prince of Wales Shoal. A previously undescribed (∼1 to 2 km wide, ∼4 m deep) seafloor channel of unknown origin occurred along a linear north/south axis for the full 75 km extent of the bathymetric surface. The southern end of this seafloor channel was near the end of three larger seafloor channels extending westerly out of nearby Norton Sound, suggesting a common origin. These Norton Sound channels may be paleodrainages, as their eastern ends point toward Seward Peninsula inlets with large drainages where paleoglaciers were reported to have existed, but the morphology of these channels is also consistent with tidal channels.

Estimations of Secchi depth from the turbid Eastern China Coastal Seas using MODIS data

ABSTRACT In this study, a neural network-based Secchi depth retrieval model (NNSD) was developed using observations obtained during 2003–2012 in the Bohai, Yellow, and China East Seas (Eastern China Coastal Seas, ECCS). Based on the results of the analyses, the NNSD model produced less than 25% uncertainty in quantifying the Secchi depth in the optically complex ECCS. The slope of the linear relationship between the field-measured and NNSD model-derived Secchi depth varied from 0.98 to 1.08 among the datasets. However, the corresponding determination coefficients were not any lower than 0.91. To determine the effectiveness of the NNSD model in deriving the Secchi depth in the ECCS, the performances of the three existing models were also evaluated, and the results are presented in this study. By comparison, using the NNSD model decreased the uncertainty by 26% when compared with the three existing models in deriving the Secchi depth in the ECCS. Finally, the NNSD model was further applied to the MODIS data over the ECCS to briefly illustrate its applicability to general oceanographic studies. The NNSD model could produce 24.62% MRE and 0.14 RMSE values in deriving the Secchi depth from the ECCS, which was > 26% MRE and > 0.07 RMSE values better than all the BGSD, KDSD and SASD models. In regards to the spatial distribution pattern of the Secchi depth, the eastern and northern sections of the ECCS were much higher than the western and southern areas. Additionally, the temporal distribution mode indicated that the winter season was higher than the summer season. These spatiotemporal characteristics were caused primarily by the regional climate, river discharges, and strong tidal currents and winds, among other factors.

A new approach to mapping littoral cells within a tide-dominated embayment

Western Port is a large tide-dominated embayment located 75 km east of Melbourne, Victoria that is flanked by a rapidly growing population, significant industrial infrastructure, grazing lands and protected RAMSAR habitats. Remarkably little is known about the sediment dynamics of Western Port despite concerning rates of erosion of the swamp and floodplain deposits including cohesive clay cliffs that fringe the sunkland. As in other tide-dominated systems, sediment dynamics in Western Port are complicated by strong tidal currents, multiple sediment sources and complex circulation. We applied the coastal sediment cell framework to Western Port, in conjunction with high resolution satellite derived rates of coastal change to elucidate sediment sharing among the sub-embayment beaches. Using end member modelling of 20 sediment assemblages based on elemental and mineralogical composition we robustly identified seven end members that correspond to different point and diffuse provenances. Hierarchical clustering of the 20 beaches dispersed across the bay yielded nine coastal cells, delimited by headlands, deep water channels, estuaries or disruptive infrastructure. Analysis of shoreline change within the cells suggests most cells are neutrally or positively balanced but a northward movement of sediments is leading to rotation. The deep channels provide a pathway for Bass Strait sediments to bypass the embayment headlands and tidal currents enable cross shore exchange with the channels beyond wave derived closure depth in some locations. Understanding the sediment cell boundaries and direction of sediment transport can assist with the management of erosion hotspots; the novel approach applied here can resolve complex connected coastal systems such as estuaries and embayments.

Characteristics of sedimentary organic carbon burial in the shallow conduit portion of source-to-sink sedimentary systems in marginal seas

Multistep physical and biological processing of organic matter in marginal seas modifies its composition, sedimentary pathway, and burial efficiency. This study examines how organic geochemical signals pertaining to the source and transformation in surface sediments are transported and preserved in the conduit portion of source-to-sink sedimentary systems in marginal seas such as the Taiwan Strait (TS). The aim is to gain more insight in not only the total OC burial in this highly dynamic region, but also to establish a quantitative assessment of the provenance and age of this carbon. Our study revealed that terrestrial plant wax n-alkanols represent a portion of terrestrial organic matter, characterized by refractory property and strong mobility leading to efficient transfer from the river mouth to the shelf. Soil bacteria-derived branched glycerol dialkyl glycerol tetraethers (br-GDGTs) represent the portion of terrestrial OM characterized by labile properties and low transmissibility restricted within the river mouth under normal conditions, except for episodic and pulse delivery situations. Sedimentary OC in the TS is typically characterized by a large amount of ancient OC with intensive oxidation, indicated by extremely old 14C ages (<13000 ± 180 yr) and lower petrogenic OC content in marine sediments than that of rocks sourced from the land. Diverse sourced OC supply and accumulation patterns in shallow marine conduit systems mainly influenced by complex physical processes. Quantitative source apportionment of sedimentary OC using a ternary mixing model based on the bulk δ13C and Δ14C proxies combined with sediment mass accumulation rates revealed 0.01–3.44, 0.002–3.79, and 0–3.38 mg C cm−2 yr−1 of marine, terrestrial biospheric, and petrogenic OC burial loadings in the TS. Marine OC burial could only explain 30% of net air–sea CO2 sequestration in a narrow conduit system such as the TS, which is characterized by high sediment resuspension and strong hydrodynamic processes due to strong tidal currents and wind-driven circulation. Our findings revealed the net C buried in different marginal seas varies as a function of local couplings between physical processes and biogeochemical characteristics.

Neuronal morphology and network properties modulate signal propagation in multi-layer feedforward network

The propagation and detection of weak signals play a vital role in the central nervous system's information processing. In this paper, a biophysical two-compartment model is adopted to investigate how the neuronal morphology and network properties modulate signal propagation in a multi-layer feedforward network (FFN). The numerical simulation results show that neurons with larger dendrites have higher firing rates and better responses to weak signals. Similarly, the output layer of FFN constructed by larger-dendrite neurons also exhibits better responses. A suitable chaotic current is necessary for the propagation of weak signals. Excessively strong or weak chaotic current leads to propagation failure. Sparse connection and weak synaptic strength optimize the responses of the output layer, which is consistent with real biological networks observed in the brain. It is found that weak signal propagation in FFN is highly correlated with the regulation of firing rate. Our results may provide novel insights into the modeling of complex networks and network function implementation.

Purse Seine Vessel Design under 100 GT Based on the Characteristics of South Sulawesi Waters in Indonesia

The waters of the Makassar Strait of South Sulawesi, where various Purse Seine vessels operate, have characteristics of very high biodiversity, the strength of very strong ocean currents, and the temperature and cultural characteristics of Bugisness and Makassar fishermen. It is necessary to design a purse seine ship that perfectly matches the designs of traditional ships operating in South Sulawesi waters so far. This research aims to create a purse seine vessel design under 100GT with International Maritime Organization standards that match the characteristics of the Makassar Strait. The Design Implementation Method is carried out by considering the length, width, height, shape of the ship's body, the volume of loading space, and construction weight by analyzing the main dimension ratio, hydrostatic parameter analysis and purse seine ship stability analysis. The design results were carried out using a length of 24 meters, width of 4.4 meters, and height of 1.9 meters. The shape of the purse seine vessel body is V-bottom shape, and the middle part towards the stern is U-V flat bottom. The tamping capacity of the first, Second and Third loading room size Volume is 29.48, 26.87 and 15.98 tons, respectively, and The Stowage factor fish is 0.5 tons/m. Ship stability or KG value to three conditions, namely the state of the ship heading to the fishing ground has a KG/VCG fluid value of 1.25 m, this value meets the IMO recommended standards, the second condition is the ship conducting fishing operations, the KG/VCG fluid value in the second condition is 1.22, and the third condition is the condition of the ship heading back to the fishing base, the KG/VCG value of 1.25 meters. The VCG/KG value of the three conditions has met the minimum value issued by IMO. The shape of the ship's body at the bow forms a "V-bottom" model, and at midship to stern has two forms of the ship's body, namely, a Round bottom and U-V flat bottom following the characteristics of South Sulawesi Waters.

Timeliness of Correcting Baseline Error in Wide-Swath Altimeter Based on Reference Topography Data

The baseline error is a primary error source of the wide-swath altimeter, directly related to the cross-track distance, and can lead to serious height errors at the swath’s outer edge. Cross-calibration using discrepancies with reference data can effectively estimate and correct the baseline error. However, building a reference surface that accurately describes the sea surface at the observation time is necessary to use this cross-correction method. The dynamic ocean environments where the sea surface structure changes over time are challenging. This paper proposes a method for constructing reference topography data (RTD) based on multi-source data products to correct the baseline error of the wide-swath altimeter. The effectiveness of the proposed method is evaluated using HYCOM ocean model data to assess the timeliness of the baseline error correction. The results demonstrate that using RTD at the observation time of the wide-swath altimeter can significantly correct the baseline error. The RMSE of the corrected sea surface height (SSH) in different regions is typically between 1~2 cm, except in some regions with strong currents where the RMSE is approximately 3~4 cm. However, the time interval between the RTD and the observation time of the wide-swath altimeter can affect the accuracy of the baseline error correction. The timeliness of this correction is influenced by the variability of SSH in different regions. In regions with relatively slow SSH changes near the equator, the effective time based on HYRTD and MORTD can basically reach more than 7 days. In regions where the SSH changes more rapidly, the correction result may no longer be reliable in only 1~3 days.

Mechanism Analysis of the Strong Coastal Current Zone and Abrupt Strong–Current Phenomena in Spring and Summer in the Yangjiang Sea Area of Western Guangdong in the Northwest of the South China Sea

Residual current analysis of multiple stations’ periodic observational data for sea currents, and multiple voyages, multiple seasons from 2018 to 2022, revealed the existence of a strong southwest current zone, 20–30 m underwater and within the coastal current area of Yangjiang, western Guangdong, in the northwest region of the South China Sea. The velocity of the residual currents in the strong–current zone was 38.2–100.3 cm/s. Observational data for wind, sea currents, salinity and tide from multiple coastal stations in the spring (from March 2019 to May 2019) and summer (from June 2019 to August 2019) of 2019 demonstrated the existence of abrupt strong currents in the coastal current sea area of Yangjiang, western Guangdong. Analyses of continuous sequence hydro meteorological data for the Yangjiang area indicated that wind stress was the main factor determining the direction of sea currents; increases in the near-shore water level produce a westward geostrophic current and a wind current in the shallow sea area; their joint effect was the key factor determining the velocity of the coastal current in this sea area. In spring and summer, when Pearl River runoff into the sea reaches a peak, and under the action of the northeast wind, the water level on the west coast of Guangdong rose. This created a barotropic pressure–gradient force from the shore to the outer sea, generating a southwestward geostrophic current in the same direction as the wind-driven current. The joint action of the wind-driven and geostrophic currents then generated a sudden southwestward coastal current.