Increase In Current Speed Research Articles

Experimental Study for Wave Overtopping Volume Estimation of Rubble-Mound Structure Using Pressure-Current Speed Relationship

In this study, a new method for wave overtopping measurement was proposed. The proposed method utilize the pressure-current speed relationship and the wave overtopping height. The relationship between pressure and current speed was studied using a flow channel, and the validity of the method for measuring wave overtopping was examined using a two-dimensional wave flume. After installing a pressure gauge in the current channel, the change in pressure according to the increase in current speed was measured, and the relationship between pressure and current speed was derived. The proposed method showed high accuracy when the incident angle was normal condition, and it was confirmed that the accuracy decreased somewhat as the incident angle increased. The reason that the accuracy is somewhat lower under oblique incidence conditions is because the sensitivity to pressure and current speed is high. In addition, when the amount of wave overtopping was large, the relative error increased, but the correlation coefficient between the measured and the estimated overtopping volume was relatively high. It was confirmed that the proposed method was possible as a method for wave overtopping measurement in the field.

Numerical modeling on wave–current flows and bed shear stresses over an algal reef

AbstractCurrents in coastal zones under multiple mechanisms in terms of tides, waves, wind, and high roughness are difficult to model; bed shear stresses under wave–current flows are particularly challenging yet not being well studied. Few studies reported the modeling and validation of the bed shear stress in reef environments. In this paper, we present the first direct assessment of numerical modeling on depth-averaged currents and bed shear stresses over an algal reef using a coupled wave–current model (Delft-3D). The modeled results were validated and compared to the field observed data. The model considers hydrodynamic forcing in terms of tides, waves, wind stresses, and bed friction. Results show that the model generally reproduces the depth-averaged currents and bed shear stresses when considering all the mechanisms. Two numerical cases with and without wind forcing were tested to examine the effects of the winds. We found that the tide is mostly the primary factor driving the current, even in shallow waters within a depth of 3 m; however, the currents are also significantly affected by wind speeds and wind directions during high-wind events. When the wind direction is in the same direction as the tidal current, the current speed increases, suggesting the importance of the wind stress on the coastal currents. In addition, two models were chosen to study the nonlinear enhancement of bed shear stress by waves. We found a significant difference between the two models in predicting the bed shear stresses compared to the observed data. Nonlinear contribution from wave enhances the magnitude of bed shear stresses, which reduces the model error. The results highlight the nonlinear interaction between waves and currents is meaningful in predicting the bed shear stresses during high-wave-orbital motions; improvement of the present wave-current nonlinear interaction model for predicting the bed shear stresses may be needed.

Performance analysis of a battery thermal management system combining thermoelectric, composite phase change material, and liquid cooling under extreme operating conditions

To maintain optimal operating temperatures for lithium-ion batteries under extreme operating conditions, a battery thermal management system (BTMS) integrating the thermoelectric cooler (TEC), liquid cooling, and composite phase change material (CPCM) is developed. Moreover, a transient numerical model has been established, considering thermal, electrical, and fluid multiphysics fields, to precise evaluation the system's performance. The outcomes indicate a decrease in both the maximum battery temperature and CPCM liquid fraction as the expanded graphite (EG) mass fraction, TEC cooling input current, and coolant flow speed increase. Furthermore, the temperature difference among batteries exhibits a decrease as the EG mass fraction increases, but experiences an elevation with an increase in both current and coolant flow speed. The BTMS features the lowest power consumption and optimal cooling performance at the EG mass fraction of 12 %, the TEC cooling input current of 3 A, and the coolant flow speed of 0.05 m/s. In preheating situations, the battery pack can achieve a temperature of 293.15 K starting from 263.15 K with the assistance of TEC preheating input currents of 4 A and 5 A, taking 5600 s and 2240 s, respectively, to complete the entire preheating procedure. This study will offer new insights into the advancement of the BTMS, allowing for the control of battery temperatures in high-temperature and high-discharge rate conditions, coupled with preheating at low-temperature.

A theoretical model for wave attenuation by vegetation considering current effects

A new theoretical model is derived to predict wave attenuation in an emerged vegetation domain under current influences by considering the current effects on changing both wave group velocity and energy dissipation rate. Considering the current effect on changing wave group velocity, the theory predicts an asymmetric behavior of wave decay in following and opposing currents, different from the earlier theory that predicts a symmetry decay behavior by ignoring the current effect on wave group velocity. The new theory dictates that as the current speed increases, the rate of wave decay changes from the traditionally reciprocal law to the exponential law, where the mixed exponential and reciprocal decay law exists under intermediate current conditions. Furthermore, the present theory can be reduced to an explicit expression of the drag coefficient for weak and strong current conditions. In addition, the theory shows that the decay rate depends on both incident wave amplitude and current velocity when the current velocity is relatively small to wave orbital velocity, whereas it is independent of incident wave amplitude when the current is strong. All of these wave decaying characteristics predicted by the theory have been confirmed by the available experimental data and the numerical results from a 2D RANS model (NEWFLUME).

Improving Water Quality in a Sea Bay by Connecting Rivers on Both Sides of a Harbor

Improving water quality is imperative for many sea bays, including Laizhou Bay, China, to achieve sustainable marine development. In 2010, two 17.3 km long sand-retaining embankments were built in southwestern Laizhou Bay, which weakened the nearshore hydrodynamics and seriously impacted the water quality. To mitigate this issue, this study proposes connecting the two rivers on both sides of the embankments to improve the hydrodynamics and thus water exchange in the sea bay. The effectiveness was examined with a numerical model using Mike 21, which was validated for both tidal current velocity and direction at six monitoring locations in the sea bay. The results show that over 53% of the core research area displays an increase (0.0–0.4 m/s) in tidal current speed after the connection, primarily in and around the Haihengwei Fishing Port. Meanwhile, the Eulerian residual currents in the Haihengwei Fishing Port, Mi River estuary and Bailang River estuary become substantially larger (with a maximum increase of 0.16 m/s). In addition, the net transport distance of particles released near the connection increases by up to 39.89 km in one month. Overall, this case study demonstrates that connecting rivers next to a harbor can effectively improve hydrodynamics and thus improve water quality in the bay.

Numerical Study of Ducted Turbines in Shallow Water Environment

The development of tidal turbines, particularly for shallow water applications, is still in its early stages. Vertical axis tidal turbines (VATT) are often preferred for shallow water due to the bidirectional nature of tidal currents. Implementing a channelling system around a tidal turbine can significantly stabilise the flow field, increase the current velocity, and enhance the energy efficiency of the turbine. However, there has been limited exploration of using channelling techniques to improve the performance of VATTs in turbid areas. This study employs a numerical analysis using computational fluid dynamics (CFD) to investigate VATTs. The VATT model is represented by a cylindrical object with a diameter and height of 5 meters. The simulation focuses on the wake characteristics and the design of turbine arrays. The Reynolds-Averaged Navier-Stokes (RANS) equations are utilised as flow viscous solvers in ANSYS Fluent, and the effectiveness of the ducts in energy conversion is calculated using the realizable two-layer turbulence model. The primary objective of this study is to examine the impact of converging devices on tidal turbine performance and propose an optimal design for shallow water applications. The proposed ducted design shows an increase in current speed passing through the device by 11.1%. Although the wake generated by the multi-row staggered array layout disperses the flow to the side of the domain, the model demonstrates a 0.9% improvement in velocity magnitude. Conversely, the results for the single-row inline layout indicate the most favorable arrangement for shallow water applications, with a 19.4% increase in velocity magnitude and a shorter wake generation.

Underwater noise from submarine turbidity currents

Submarine landslides and associated turbidity currents can be orders of magnitude larger than their terrestrial equivalents. Their prevalence globally is hugely underrepresented by in situ observations. In addition to their importance in mass transport and morphologic change they can pose significant threat to coastal communities and subsea infrastructure. This presentation focusses on noise measurements from turbidity currents flowing down the face of a fjord delta and how they can inform the use of passive acoustics as a tool for future observations of these under sampled phenomena. Noise was measured underwater at frequencies from 1 to 1200 kHz. The noise spectra are consistent with sound generation by collisions among sand-sized particles within the turbidity current, also known as acoustic sediment-generated noise or SGN. The spectra from the leading head of the current extend to higher frequencies than those from the trailing body, indicating that collisions were between finer-grained particles in the head and coarser-grained particles in the body. Noise intensity increased 100-fold for a two-fold increase in current head speed, consistent with the expected collision rate for granular materials in the high-flow gas-like phase and highly turbulent particle-laden flows.

Study on the process optimization and wear resistance of electron beam cladding AlCoCrFeNi coating on 253MA austenitic stainless steel surface

This study employs a continuous scanning electron beam to deposit AlCoCrFeNi composite cladding on the surface of 253MA austenitic stainless steel to enhance its surface properties. The characteristics were examined through a scanning electron microscope (SEM), backscattered electron diffraction (EBSD), and white light interferometric three-dimensional surface profile instrument. This study investigated the effect of electron beam process parameters on the surface organization and mechanical properties of 253MA steel. The sample surface was divided into four zones: overlay, bonding, thermal influence, and substrate, according to the results. Coarse columnar and island-shaped crystals composed the overlay zone, while equiaxed austenite grains primarily constituted the substrate. With the increase of the beam current, the microstructure's grain size decreased, the substructures increased, and the BCC phase transformed into the FCC phase. The grain size slightly decreased, substructures changed marginally, and the BCC phase increased as the scanning speed increased. Additionally, the microhardness and mechanical properties of the overlay layer increased significantly, and wear volume and wear rate decreased progressively with the increase in beam current and scanning speed. At a beam current of 18 mA and a scanning speed of 200 mm/min, the surface hardness of 253MA steel reached the maximum value of 520 HV. When the beam current was 24 mA, and the scanning speed was 200 mm/min, the wear volume and wear rate of the overlay sample were minimal, accounting for 37.4% of the original sample's, and its wear resistance was 2.67 times more than that of the substrate.

Wave resonances and hydroelastic wave motion

Three different types of resonances, i.e. blocking, trapping and Bragg resonance, associated with flexural gravity wave motion in the presence of current and permeable bottom are discussed. Also, using the different modes of wave propagation, the interconnection among all these resonances is analysed. An uneven pattern in the plate deflection is seen inside the blocking resonance zone. The uniform convergence of the infinite series associated with the trapped mode is proved. We have found that the trapped mode does not exist if the magnitude of the opposing current is higher or whenever we move the cylinder away from the platecovered surface. It is also observed that two propagating modes within the blocking frequencies create the environment for the occurrence of trapped waves. At the same time, all three modes have a remarkable contribution to Bragg resonance. The Bragg reflection increases in the blocking zone and decreases outside of it. We have seen that the amplitude of the Bragg reflection increases with the increase in current speed and porosity parameter. Also, the discontinuities in Bragg reflection coefficients are seen at blocking frequencies. The model is also carefully validated numerically for trapped and Bragg resonances against the results available in the existing literature.

Use of drifting buoys for wave observation: Effect of current on wave data

Drifting buoys can measure wave data even in areas far from land and with strong currents, such as the western boundary current. We evaluated the dependence of the difference between ERA5 wave data and buoy data on the Lagrangian surface current speeds derived from the drifting buoy positions. The ERA5 wave data does not consider the effects of ocean currents. The difference between the ERA5 wave heights and the buoy wave heights increases as the surface current speed increases. The ERA5 wave height is notably underestimated in the case of the opposing current to the mean wave direction, and the wave height is overestimated in the case of the following current to the mean wave direction. The magnitude of them is up to 20%. The wave periods from ERA5 data and the drifting buoy also have differences in the case of opposing and following currents, mainly due to the Doppler shift. Marked over- and underestimation of the ERA5 wave heights can be observed at higher surface current speeds in the Kuroshio extension area, where currents are influenced by mesoscale eddies. Overestimation and underestimation of the ERA5 wave heights are also frequent in the Kuroshio area.

Study on dynamic characteristics of drill string in deep-water riserless drilling

The cost and security of ocean drilling are directly related to the efficient exploration and development of ocean resources. The riserless drilling system is usually adopted in the ocean drilling. With the consideration of marine environment load, a dynamic analysis model of drill string in deep-water riserless drilling is established. This model aims to analyze the dynamic characteristics of drill string in the water and down hole during the process of deep-water riserless drilling. The research results are as follows. For the drill string in water, its displacement increase with the increase of ocean current velocity, water depth, rotation speed, and WOB. But the rotation speed and WOB have less influence. The drill string in down hole shows the same pattern. However, the drill string in down hole is only affected near the mud line and the bit, and the rest of the drill string is almost unaffected. In deep-water riserless drilling, stress on the drill string at the wellhead, near the mudline, and at the bottom hole assembly (BHA) is complex. The safety of drill string at these locations should be given great attention.

Characteristics of surface currents in Manado Bay, North Sulawesi, Indonesia

Manado Bay is a complex waterway located in Manado City, North Sulawesi, Indonesia. It is an entry point for the Indonesia Trough-Flow, and its circulation is affected by the seasonal winds. Manado City has no debris net on its river estuaries. Therefore, marine debris can easily be carried away by the ocean currents and accumulate in the tourism areas located along the coast of Manado Bay. Consequently, it is important to study the sea surface current circulation in Manado Bay to deal with marine debris accumulation. In the present study, we utilized the DELFT3D software to simulate the hydrodynamic circulation in Manado Bay from 2016-2017. We conducted a 2-dimension (2D) horizontal hydrodynamic simulation using tidal and wind forcing from European Centre for Medium-Range Weather (ECMWF). The simulation results indicate that the change in bathymetry and wind affect the sea surface currents. During the summer monsoon (June-August), the sea surface current flows from the northeast to the southwest with an average speed of 1.1 cm s-1. On the contrary, during the transitional monsoon 1 (September-November), the sea surface current flows from the southeast to the northwest with an average speed of 1.3 cm s-1. Meanwhile, in the winter monsoon (December-February), the sea surface current originated from the southwest flows to the east with an average velocity of 1.9 cm s-1. Then, it moves from west to east during transitional monsoon 2 (March-May) with an average speed of 1.5 cm s-1. The current speed increases whenthe water enters the strait between the Bunaken Islands due to refraction, diffraction, and shallowing effect. As current flows toward the shallower area, the current speed increases, compensating the water column reduction.

Trajectory tracking and hydrodynamics of a tethered underwater vehicle based on hybrid grid

A coupling hydrodynamic model including a tethered underwater vehicle integrated with three 19 A + Ka 4–70 ducted propellers and PID control algorithm is proposed. The paper focused on the trajectory tracking and hydrodynamic performance of a tethered underwater vehicle under the influence of sea current. The proposed model is solved by Star-ccm+, a commercial software based on the finite volume method, and hybrid grids, including sliding mesh and overset grid, are utilized. The Navier-Stokes equation governs the flow field around a tethered underwater vehicle, and determination of the cable is based on the catenary equation. The six-degrees-of-freedom for a tethered underwater vehicle's motion is also analyzed. The numerical result indicates that the horizontal trajectory of a tethered underwater vehicle is greatly influenced by sea current without adjusting by the control algorithm, while the vertical trajectory controlled by the PID algorithm is influenced little by sea current. The control effect of the ducted propeller decreases as the sea current speed increases. The coupling approach of the hydrodynamic model and PID control scheme is feasible, and provides a new way to analyze the underwater vehicle trajectory.

Projected Changes of Water Currents and Circulation in Lake Michigan Under Representative Concentration Pathways Scenarios

AbstractThe Great Lakes’ atmosphere predominantly signposts signatures of climate change in terms of an elongated summer, depletion of ice‐cover, and up‐surging lake surface temperature and air temperature, which demands an in‐depth comprehension of future lake circulation dynamics. After satisfactory validations for the lake meteorology and hydrodynamics during 2010–2019, historical and future predictions based on a downscaled climate model for the Great Lakes region under Representative Concentration Pathways (RCP) 4.5 and 8.5 scenarios are used to drive the Finite‐Volume Community Ocean Model applied to Lake Michigan during the ice‐free months of 2010–2069. Substantial rises in lake surface current speed during May–June and September–October are connected to the rising wind speed and air temperature in the lake domain. Under the RCP 4.5 scenario, the study expects a 6.5% per decade relative increase in surface current speed, with a rise of 1.3% in the coastal circulation (within 50‐m depth from the coast) until 2050. Surface circulation strength can reach the highest rise (13%) during 2030–2039 and a slight drop (−1%) during 2050–2069. During May–December, only a 0.3% variation is predicted in current magnitudes under RCP 4.5 and 8.5 scenarios. The projections anticipate the occurrence of a stronger, wider, and northward shifting lake gyre with changing lake meteorology. Further analysis indicates that the reduced thermal gradient over the lake surface tends to resist sharp modulations in winds and lake dynamics in the successive decades.

Experimental study on the tension of cables and motion of tunnel element for an immersed tunnel element under wind, current and wave

The tension of cables and motion response significantly affect safety of an immersed tunnel element in the immersion process. To investigate those, a hydrodynamic scale-model test was carried out and the model experiments was conducted under wind, current and wave loads simultaneously. The immersion standby (the process that the position of the immersed tunnel element should be located before the immersion process) and immersion process conditions have been conducted and illustrated. At the immersion standby conditions, the maximum force of the cables and motion is much larger at the side of incoming wind, wave and current, the maximum force of Element-6 (6 cables directly tie on the element) is larger than for Pontoon-8 (8 cables tie on pontoon of the element), and the flexible connection can reduce the maximum force of the mooring cables and motion of element (i.e. sway is expecting to decrease approximate 40%). The maximum force of the mooring cables increases with the increase of current speed, wave height, and water depth. The motion of immersed tunnel element increases with increase of wave height and water depth, and the current speed had little effect on it. At the immersion process condition, the maximum force of the cables decrease with the increase of immersion depth, and dramatically increase with the increase of wave height (i.e. the tension of cable F4 of pontoons at wave height of 1.5 m (83.3t) is approximately four times that at wave height of 0.8 m). The current speed has no much effect on the maximum force of the cables. The weight has little effect on the maximum force of the mooring cables, and the maximum force of hoisting cables increase with the increase of weight. The maximum value of six-freedom motion amplitude of the immersed tunnel element decreases with the increase of immersion depth, increase with the increase of current speed and wave height (i.e. the roll motion at wave height of 1.5 m is two times that at wave height of 0.8 m). The weight has little effect on the maximum motion amplitude of the immersed tunnel element. The results are significant for the immersion safety of element in engineering practical construction process.

Effect of eco-physiological factors on biometric traits of green mussel Perna viridis cultured in the south-east coast of the Bay of Bengal, Bangladesh

Information on allometry, condition indices (CIs), and biometric traits (BTs) of marine bivalves are necessary for determining the growth pattern and the size at which harvest can be intensified to maximize production in aquaculture. These parameters of marine bivalves are largely regulated by the complex interactive effects of various ecological and physiological factors. Therefore, the present study aimed to apply an integrated multivariate approach to explore a comprehensive knowledge about how allometry, condition indices (CIs) and BTs are interlinked with various eco-physiological factors of cultured green mussel (Perna viridis), with a particular focus on the effect of seasonality. Six selected length-weight dimensions (shell length, shell width and shell height against total weight and soft tissue weight) were proved to be positively correlated with negative allometric relation (slope<3) by regression analysis in male, female and sexually undifferentiated individuals. Linear discriminant function analysis (LDFA) displayed that CIs and BTs of green mussel were not differentiated by the sex, rather evidenced a pronounced discrimination by the seasonality and reproductive cycle. The correlation analysis demonstrated that different CIs and BTs were significantly correlated with different ecological factors, ingested plankton and gonadosomatic index (GSI) of the green mussel. Taken together all datasets, the principal component analysis (PCA) showed that seasonality and reproductive cycle explained>60 % of the variability. In both cases, PCA analysis further revealed that CIs and BTs increased with the increase of salinity, dissolved oxygen, food availability, plankton ingestion and GSI value, while they decreased with the increase of temperature, current speed and turbidity. Thus, our results clearly demonstrated that CIs and BTs of the green mussel were influenced by seasonality, ecological factors, plankton ingestion and reproductive cycle of the species. The findings of the present study represent a step toward a better comprehension of the CIs and BTs of P. viridis in relation to different eco-physiological factors and would be helpful to determine the ideal period for commercial exploitation, biodiversity conservation and future potential aquaculture of this commercially important species to a greater extent.

ANALYSIS OF SHORELINE DYNAMICS FOR COASTAL MANAGEMENT PRACTICE IN PARIAMAN, WEST SUMATERA

Coastal dynamics have a significant effect on the use of coastal resources where more than 60 percent of cities in the world develop in this region and use it for urban infrastructure, settlements, and economic development. shoreline change is one of many indicators of coastal dynamics which is the result of interaction between biotic, abiotic and human activities which further influences policy and management practices for coastal areas. This paper presents the results of study on shoreline dynamics in Pariaman, West Sumatra using vector analysis in DSAS 4.3 between 1988-2003 and 2003-2018. The shoreline is interpreted from three Landsat images, namely Landsat 5 TM 1988, Landsat 7 ETM + 2003 and Landsat 8 OLI / TIRS 2018 that have been corrected (radiometric and geometric). The shorelines derived from Landsat combined with shoreline from topographic map by Badan Informasi Geospasial (BIG) as baseline for net shoreline movement (NSM) and end point rate (EPR) analysis. Then, The data of shoreline changes is used as a basis for qualitative analysis of local government policies on coastal management. The results show that shoreline changes occur dynamically wherein 1988-2003 abrasion occurred with an average rate of 2.88 m/yr and accretion of 1.64 m/yr while in the 2003-2018 an abrasion rate of 2.76 m/yr occurred and accretion rate 1.12 m/yr. This condition occurs along with the increase of longshore current speed. Some of the locations also have faster abrasion and accretion rates due to structural built.

Rip Current Hazard Analysis

Zhang, K.; Zhang, M.C.; Leatherman, S.B., and Leatherman, S.P., 2020. Rip current hazard analysis. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 969–973. Coconut Creek (Florida), ISSN 0749-0208.The effect of rip currents on swimmers was analyzed based on the drag force acting on swimmers and the power they need to generate to overcome the drag force. The drag force and power increase quadratically and cubically, respectively, with increase of rip current and swimming speeds. An additional 50% increase in rip current speed above swimmer's speed results in a 125% increase in drag force, requiring a 238% increase in power by the swimmer to overcome the additional drag. Hence, even rip currents of low velocity can be dangerous and swimming against the current should be avoided.

Storm-driven across-shelf oceanic flows into coastal waters

Abstract. The North Atlantic Ocean and northwest European shelf experience intense low-pressure systems during the winter months. The effect of strong winds on shelf circulation and water properties is poorly understood as observations during these episodes are rare, and key flow pathways have been poorly resolved by models up to now. We compare the behaviour of a cross-shelf current in a quiescent period in late summer, with the same current sampled during a stormy period in midwinter, using drogued drifters. Concurrently, high-resolution time series of current speed and salinity from a coastal mooring are analysed. A Lagrangian analysis of modelled particle tracks is used to supplement the observations. Current speeds at 70 m during the summer transit are 10–20 cm s−1, whereas on-shelf flow reaches 60 cm s−1 during the winter storm. The onset of high across-shelf flow is identified in the coastal mooring time series, both as an increase in coastal current speed and as an abrupt increase in salinity from 34.50 to 34.85, which lags the current by 8 d. We interpret this as the wind-driven advection of outer-shelf (near-oceanic) water towards the coastline, which represents a significant change from the coastal water pathways which typically feed the inner shelf. The modelled particle analysis supports this interpretation: particles which terminate in coastal waters are recruited locally during the late summer, but recruitment switches to the outer shelf during the winter storm. We estimate that during intense storm periods, on-shelf transport may be up to 0.48 Sv, but this is near the upper limit of transport based on the multi-year time series of coastal current and salinity. The likelihood of storms capable of producing these effects is much higher during positive North Atlantic Oscillation (NAO) winters.

Diel vertical migration of zooplankton and micronekton on the northern slope of the South China Sea observed by a moored ADCP

Acoustic Doppler current profiler (ADCP) echoes can be transformed into mean volume backscattering strength (MVBS), which is positively proportional to the biomass of zooplankton and micronekton. A mooring with an upward-looking 75-kHz ADCP was deployed on the northern slope of the South China Sea to monitor diel vertical migration (DVM) and vertical distributions of zooplankton and micronekton under general conditions and extreme conditions such as typhoons. DVM occurs throughout the year, with the maximum migrating speed reaching 9.0 cm s−1. It had some cyclic variation, which was in response to marine environment and astronomical influence. Light initiates the ascents and descents of the migrators, and migration intensity may be proportional to the solar altitude. Neap-spring tidal cycle and full moon phase influences are prominent, and the peak at 112 d may be driven by variation of currents. In addition, 270 m is the demarcation between upward and downward migrations; some organisms living below this layer, especially zooplankton and micronekton, migrate to the surface to obtain nutrients and energy; other marine mesopelagic organisms also survive in this manner. Super and severe typhoons reduced vertical migration, having less influence on the deep scattering layer. As Super Typhoon Rammasun passed by the mooring station, current speed increases and temperature decreases were synchronous with changes in the deep scattering layer; the migrators swam downward to evade the influence of a higher-speed current rather than swam upward to compensate for the decrease of temperature.