Current Velocity Vector Research Articles

A combined Gaussian process regression and one-dimensional least squares harmonic method for tidal current prediction

Predictions of tidal currents are required for various activities in the maritime industry, including marine power exploitation, operational forecasting, and coastal engineering. In addition to the conventional least squares harmonic method (LSHM) and numerical simulation, a machine learning algorithm has recently been developed and applied for predicting tidal currents in time series. Gaussian Process Regression (GPR) is one of the most important machine learning algorithms due to its ability to process time-series data. In this paper, we propose a combined one-dimensional LSHM and GPR method for predicting depth-averaged current velocity vectors according to time-series changes of water surface elevation due to tide. LSHM firstly decomposes water surface elevation time series into a number of possible constituents (i.e., amplitudes, phase-lags) according to known tidal frequencies. For each of the contributing constituents, GPR is then applied to produce the corresponding current generator using known tidal current as training data. The training data are generated by numerical simulations representing different coastal settings. The predicted tidal current is calculated according to the previously trained GPR model. As a comparison, we also generated tidal current predictions using a conventional two-dimensional LSHM. It is found that the tidal currents predicted using the sequence of computations proposed in this paper show comparable results with slightly better accuracy than conventional two-dimensional LSHM. The results from this study could provide an alternative method of tidal current prediction, minimising the need for the laborious re-runs of numerical simulations and lengthy current observations, as well as removing the requirement to carry out a two-dimensional analysis of the tidal current using LSHM.

Drag-related wave–current interaction inside a dense submerged aquatic canopy

The seabed in coastal regions is often covered by a dense submerged canopy formed by benthic organisms. The in-canopy flow is of great interest to coastal researchers. In this study, a semi-analytical model is proposed for the in-canopy current profile under the influence of coexisting waves. The current is driven by a mean shear stress at the canopy top and a mean streamwise pressure gradient. Wave–current interaction arises from the mean canopy drag, which is described by the conventional quadratic law. An algebraic eddy viscosity model, which accounts for the turbulence generated by a canopy-scale vortex and stem-scale wake, is proposed. The model is calibrated against unidirectional flume experiments, and is subsequently validated against a wave–current flume experiment. It is found that the mean canopy drag experienced by the current can be significantly amplified by a co-existing wave-driven oscillatory flow. Under the same current driving force, the current in wave–current flow is reduced from that in a pure-current flow. The reduction increases with canopy density and wave strength. For a wave and current at an angle, veering of the current velocity vector is suggested by the model, which makes the mean canopy drag align with the driving force of the current.

Research on wave and tidal current law prediction and coupling mechanism applied to ocean energy utilization

The energy efficiency of integrated wave and current turbine is closely related to the velocity and direction of wave force and tidal current force.To study the blade motion of the wave-tidal current integrated variable-pitch turbine, raise the capacity efficiency of the turbine, take Fishing grounds of Changjiang estuary Port as an example,based on the tidal current and wave features data in recent two years,time series prediction model was established to predict the changes of wave and tidal current in the next 24 hours respectively, and the prediction accuracy is up to 93%. The wave theory applicable to Fishing grounds of Changjiang estuary Port was confirmed as the second-order strokes wave theory, the wave-tidal current coupling equivalent velocity vector was deduced, which is related to the tidal current velocity, flow direction, average wave direction, average wave period and significant wave height. The predicted wave-current coupling velocity vector is obtained after the predicted 24 hours wave-current data was substituted into it, which can provide a method and basis for the design of marine energy turbine’s variable angle law in the future, and can be applied to the development of new energy and the prediction of Marine environment.

A Wall-following Controller Design Method for Underactuated AUVs: An Adaptive Internal Model Approach

Abstract This paper addresses the problem of path-following control of an underactuated autonomous underwater vehicle (AUV) subjected to ocean current disturbances along a given spatial path with a certain speed profile. The control architecture is the classical inner-outer loop structure that includes an observer to estimate the ocean current. For disturbance rejection, we model the ocean current as output of an exosystem and then we design an adaptive internal model to estimate the current vector and deal with uncertainties on the frequencies of the current velocity vector components. To complement this controller, we next consider the wall-following problem using profiling mechanical sonar. In order to construct a desired path, we resort to a cubic B-spline fitting method, the control points of which are obtained by a best B-spline fit to the acquired profiling sonar data. We use the above path following controller to drive the vehicle to follow the constructed path. The results of the proposed controller design for the wall-following problem are demonstrated using numerical simulations. Finally, future direction and extension of the current work toward the automatic inspection of underwater structures will be provided in the last section.

Современные исследования динамики вод в северо-западной части Черного моря по данным LADCP

In this work a result of preliminary analysis of current measurements collected in fourteen large-scale expeditions of the Marine Hydrophysical Institute in 2016–2019 in the north-eastern part of the Black Sea is presented. It is shown that the use of the Lowered Acoustic Doppler Current Profiler (LADCP) significantly increases the information content of the expedition materials, opening up new opportunities in the experimental study of water dynamics. Based on the materials of the expeditions, it was found that the upper layer of shear baroclinic currents in the measurement area is limited by the isopycnic depth with a potential density of ~16.75 kg/m3 (~350 m). At this depth, the variability of the buoyancy frequency with the depth changes from a power-law to an exponential dependence. The same depth limits the penetration of seasonal variations of the average kinetic energy into the water column. The highest values of the average kinetic energy are observed in April-May and November–December, the lowest—in June–August. The ratio of the maximum energy values (summer) to its minimum values (spring, late autumn, winter) was ~3. The Rim Black Sea Current is most pronounced near the Crimean Peninsula in the spring and winter seasons. In summer and autumn, the horizontal distribution of the current velocity in depths of 30–80 m is less structured, which is caused by the seasonal intensification of mesoscale processes. At a number of stations, the current velocity profiles contain fragments with a well-defined harmonic variability of the current velocity components with depth, which can be interpreted as the manifestation of near-inertial internal waves. In most cases, the rotation of the current velocity vector with depth occurs clockwise, which determines the main direction of propagation of the inertial internal waves into the water column. The example of one of the stations shows the significant contribution of such waves to the value of shear. This fact suggests a significant influence of near-inertial internal waves on the processes of vertical turbulent exchange in the water column.

РЕЗУЛЬТАТЫ ГИДРОМЕТЕОРОЛОГИЧЕСКИХ ИЗМЕРЕНИЙ КОМПЛЕКСОМ ПРИБОРОВ БУЯ WAVESCAN НА ЮГО-ЗАПАДНОМ ШЕЛЬФЕ ЗАЛИВА ПЕТРА ВЕЛИКОГО В 2016 г.

For the first time, the long-term measurements of meteorological and oceanographic characteristics were measured using the anchored autonomous complex of the WaveScan buoy on the Southwestern shelf of the Peter the Great Bay (Japan Sea) from 21 April to 23 December 2016. The buoy anchor was set at 50 m depth. During 10 minutes of each hour, meteorological characteristics of the near surface layer of the atmosphere, sea water temperature at the horizon of 1.5 m, and vertical profiles of the current velocity vector from the near-surface layer to the near-bottom one were measured with resolution 4 m. During 20 minutes of each hour, the characteristics of waves on the sea surface were measured. In General, most of the meteorological characteristics measured on the buoy are in good agreement with the data of the NCEP-DOE AMIP-II, ERA-Interim and ERA5 reanalysis. The significant wave height for the whole frequency belt, mean wave period and mean spectral direction from the WaveScan Buoy measurements have the best statistical relationship, confidence level is 99%, with the correspondent significant height of the waves, mean wave period and mean spectral wave direction from reanalysis ERA5. The features of variability of vertical profiles of the current velocity vector on the synoptic and seasonal time scales that depend on wind speed and vertical stratification of density are determined. In the warm season the a significant left turn of the vector of the measured current velocity with depth is observed in the seasonal pycnocline below the surface layer of friction. At wind speed, not exceeding 5 m/s, the angle of the current velocity vector left turn reaches 170° in the bottom layer, where countercurrent is formed. During the passage of the Lionrock tropical cyclone, when and the daily mean wind velocity increase to 9 m/s, the angle of left turn of the current velocity vector in the pycnocline decreases to 20°. In the cold season a classic right turn of the current velocity vector is observed in the upper boundary layer, and the vertically average velocity vector within the 50 m layer, as well as the total drift flow in the Ekman friction layer, deviate 90° to the right from the surface wind velocity vector. The left turn of the current velocity vector at the buoy installation point was not observed in the cold season.

Transboundary River Hydrodynamic Conditions Assessment in Sustainable Development Context. A Case Study of Danube River: Chilia Branch - Bystroe Channel Area

Located in the Danube Delta Biosphere Reserve, the Chilia branch serves as country boundary between Romania and Ukraine. The former state started in 2004 a project intended to increase the navigability capacity of Bystroe Channel, the environmental impact of the works carried out being discordantly considered by the Romanian and Ukrainian authorities. The Inquiry Commission established under the Espoo Convention, of which both countries are part of, delivered its final opinion that the project was likely to have a significant adverse transboundary impact on the hydrodynamic local conditions and habitat loss for fish and birdlife. Statistical analysis was operated on daily and monthly averaged water discharge values and the results were graphically displayed as hydrographs and probability curves and distribution. Addressing the in situ data measurements deficit for the Chilia branch - Bystroe Channel Area, measurement campaigns have been carried out in order to monitor the alterations of the hydrodynamic parameters. Using the specialized Acoustic Doppler Current Profilers technique, there have been recorded water flow parameters (water discharge and water current velocity vectors) and the data used for analysis and 2D and 3D representation of the hydrodynamic conditions.

On Tidal Current Velocity Vector Time Series Prediction: A Comparative Study for a French High Tidal Energy Potential Site

Estimating the energy potential of tidal stream site is a key feature for tidal energy system deployment. This paper aims to compare two methods of prediction of tidal current velocities. The first one is based on the use of a fully three-dimensional (3D) numerical approach. However, while being accurate, the numerical model is highly time-consuming. The second method is based on a linear approximation of the tidal current, which only requires preliminary knowledge of local current velocities time series during two typical tidal cycles. This second method allows a very quick evaluation of the tidal stream resource during a long time period. The proposed comparison is done in three different locations of a high potential tidal energy site in west of France. It is carried out in terms of current velocity and energy harnessing for several turbines technology options (with and without yaw). The achieved results show that the linear approximation gives satisfactory evaluation of the tidal stream potential and can be a very interesting tool for preliminary site evaluation and first technology options selection. However, the fully 3D numerical model can obviously be very useful in more advanced steps of a project.

Разработка методологии и моделей бортовых систем реального времени для определения параметров поверхностного морского течения

The mathematical models of inverse trajectory problems of the form “state – measurement” are presented. The aim and main component of the solutions is to estimate the surface sea current velocity vector after reconstructing the absolute (relatively solid Earth) velocity of the object according to its positioning GLONASS data. These models are associated with the model of estimating problem the derivatives of a continuous time function with respect to its temporally measurable values having the Jordan form of a matrix with a nilpotency index. It coincides with the dimension of the system of linear differential equations of state, which causes discretization of the problem in time without methodological errors and the implementation of computational algorithms for dynamic handling Using the ordinary Least Squares method with a sliding window. The peculiarity of this solution methodology is that it identifies the flow with the portable movement of a controlled marine object, considers it as a navigational factor that changes in time and geographical space and requires on-board operational assessment of the current state. The results of computational experiments are also presented.

On the Contribution of the Eddy Transport to the Annual Mean Heat Budget of the Upper Layer in the North Atlantic

According to Ocean Re-Analysis System 3 (ORA-S3) data, all components of the annual mean heat budget of the upper quasi-homogeneous ocean layer (UQL) in the North Atlantic for the period of 1959–2011 have been calculated and errors of these estimates have been determined. It has been shown that the contribution of the horizontal eddy diffusivity (estimated as a residual term of the UQL heat balance equation) to changes in the UQL annual mean temperature is significantly overestimated. This takes place mainly due to neglecting the covariances of seasonal fluctuations of current velocity vector components and UQL temperature gradients in calculations carried out with the use of annual average values. These covariances play an important role in the annual mean heat budget in some regions of the North Atlantic, especially in tropical latitudes. Changes in the annual average UQL temperature in the central and eastern parts of the North Atlantic are significantly affected by errors related to an inaccuracy of estimates of annual average heat fluxes on the ocean surface. The maximum contribution of the horizontal eddy diffusivity to the interannual variability of the UQL temperature is observed in the northwestern part of the North Atlantic and the region of the Subpolar Gyre.

Estimating Water Current Velocities by Using a Model-Based High-Gain Observer for an Autonomous Underwater Vehicle

For accurate control and navigation of an autonomous underwater vehicle (AUV) it is critical to know the water current velocities around the vehicle body. The AUV-onboard acoustic doppler current profilers are unable to measure the current near to the vehicle due to their blanking distance, so an AUV model-based observer can serve the purpose of estimating the current velocities surrounding the vehicle. In this paper, a high-gain observer based on an AUV dynamics model was used to estimate 3D water current velocities. The water current velocities were determined by calculating the differences between the vehicle velocities over the ground measured by a Doppler velocity log-aided inertial navigation system and the vehicle velocities through the water estimated by the model-based observer. Modeling and field trials of a Gavia AUV were used to demonstrate the approach. Instead of deriving the roll, pitch, and yaw motions, these were directly given as simulation inputs which allowed the AUV dynamics model to be simplified to 3–degrees of freedom. This paper presents a real-time model identification algorithm to identify the nonlinear parameters of the AUV model by utilizing a recursive least squares method. The real-time model identification algorithm allows the AUV model to be continuously updated in response to the operational environment. A high-gain observer was chosen as a nonlinear estimation algorithm to obtain the vehicle velocities through the water, and the Lyapunov stability of the estimation error dynamics was investigated. The observer gain was computed by solving the linear matrix inequality which represented the error dynamics. By utilizing the observer in the AUV dynamic model, the vehicle’s velocity vector through the water was estimated, then the current velocity vector was calculated. In order to investigate the differences between the estimated current velocities and the measured current velocities, the standard deviations between these two were quantified. The results showed that the current estimation found by using the model-based observer was improved compared with the previous water current estimation method, which found the water velocity components in a turbulent water column from the AUV motion response.

Close encounters involving RAVE stars beyond the 47 Tucanae tidal radius

The most accurate 6D phase-space information from the Radial Velocity Experiment (RAVE) was used to integrate the orbits of 105 stars around the galactic globular cluster 47 Tucanae, to look for close encounters between them in the past, with a minimum distance approach less than the cluster tidal radius. The stars are currently over the distance range 3.0 kpc $<$ d $<$ 5.5 kpc. Using the uncertainties in the current position and velocity vector for both, star and cluster, 105 pairs of star-cluster orbits were generated in a Monte Carlo numerical scheme, integrated over 2 Gyr and considering an axisymmetric and non-axisymmetric Milky-Way-like Galactic potential, respectively. In this scheme, we identified 20 potential cluster members that had close encounters with the globular cluster 47 Tucanae, all of which have a relative velocity distribution (V$_{rel}$) less than 200 km s$^{-1}$ at the minimum distance approach. Among these potential members, 9 had close encounters with the cluster with velocities less than the escape velocity of 47 Tucanae, therefore a scenario of tidal stripping seems likely. These stars have been classified with a 93\% confidence level, leading to the identification of extratidal cluster stars. For the other 11 stars, V$_{rel}$ exceeds the escape velocity of the cluster, therefore they were likely ejected or are unassociated interlopers.

Предварительные результаты сравнения измерений вектора скорости течения навигационным радаром X-диапазона и донной станцией ADCP

Предварительные результаты сравнения измерений вектора скорости течения навигационным радаром X-диапазона и донной станцией ADCP

Classification of sound-scattering layers using swimming speed estimated by acoustic Doppler current profiler

There are various techniques for identifying fish species, including the multi-frequency method, in situ target strength characteristics, and digital image processing methods. Acoustic Doppler current profilers (ADCPs) are able to determine multiple current fields simultaneously and have been used to observe the swimming speed and behavior patterns of shoals of pelagic fish under natural conditions. In this study, we evaluated a classification method that can be used to determine the swimming velocity of both the sound-scattering layer and pelagic fish shoals using an ADCP (153.6 kHz) and a scientific echosounder (38, 200 kHz). To calculate the actual swimming speed of the fish shoals, the mean swimming velocity vectors of each stratified bin must be compared with the mean surrounding three-dimensional (3D) current velocity vectors. We found the average 3D swimming velocity of the sound-scattering layer to be characterized by a deviation of >5.3 cm/s from the surrounding current field. The average 3D swimming velocity of Pacific saury Cololabis saira was calculated to be 91.3 cm/s, while that of lanternfish Diaphus theta was 28.1 cm/s. These swimming speeds correspond to 4.19- and 4.26-fold the body length, respectively. Thus, the use of ADCP swimming velocity data can be expected to be a valuable species identification method for various fishes distributed in a given survey area.

Field experiments and new design of a spilled oil tracking autonomous buoy

It is important to forecast the location of oil spills to realize effective and adequate oil spill response operations when huge oil spilsl occur. In order to enhance the accuracy of oil drifting simulations, one needs to obtain the meteorological and oceanographic data around the oil slick. In general, the drifting velocity vector of an oil spill contains a wind velocity vector and a water current velocity vector. SOTAB-II was developed for autonomous tracking of oil slicks drifting on the sea surface. It is equipped with a sail whose size and direction are controllable to drift along with the oil slick autonomously. In addition, SOTAB-II transmits its location and necessary measured data around it to the land base in real-time. The results of field experiments using SOTAB-II with a cylindrical hull brought us the effectiveness of the sail and its control. However, the drifting speed of SOTAB-II was lower than a theoretical speed for the oil slick. In order to overcome this problem, SOTAB-II was redesigned. A yacht shape was adopted to reduce the hydrodynamic drag in the water in the advancing direction. Transverse stability, scales of brake board and sail, maneuverability, and performance of tracking spilled oil on the sea surface were considered in the process of the design.

Detection and tracking of short duration variations of power system disturbances using modified potential function

This study introduces a modified potential function based modeling approach for real-time disturbance tracking. Real-time tracking requires the least complex techniques for processing and classification and still provide accurate results. Time required to detection of the power quality disturbance should be small enough so that the further mitigation action may be taken. The proposed FRTD algorithm is able to detect the disturbances in 3–5 samples. The proposed FRTD algorithm is principally based upon potential function, which has been modified so as to give the one-dimensional position vector corresponding to the voltage sag and swell, with complexity O(1) with no pre-process complexity. The method detects the transient in 3–5 samples at sampling frequency of 12.8kHz. Potential function uses the current nonlinear drift velocity vector along with a prior knowledge of the power system disturbance to compute the unknown parameter in the form of diffusion matrix, Dt. The parameter Dt has been used to detect the events in the signal. Magnitude of Dt play vital role to detect the events. FRTD algorithm has been tested to track and detect the power system disturbances such as voltage sag, swell, and transient. The algorithm has been tested on hardware interfaced with MATLAB. 1000 samples of different types of power system disturbances such as voltage swell, voltage sag, oscillatory-transient and impulsive-transient have been tested. FRTD algorithm is having the efficiency of 99.83%.

Noniterative Instantaneous Impact Point Prediction Algorithm for Launch Operations

T HE instantaneous impact point (IIP) in launch operations is defined as the touchdown point of a rocket with an assumption of an immediate end of the propelled flight [1–3]. The IIP is very important information to judge whether the flight is normal or not, and it should be continuously monitored during the whole flight so that proper actions be taken in an emergency to protect human life and property. Therefore, the real-time prediction and monitoring of the IIP is one of the key safety requirements. The IIP prediction problem seeks for the intersection point between the Earth’s surface and the free-flight trajectory of a rocket subject to gravity and other disturbing forces. The current position and velocity vectors are given as inputs to the problem. A numerical integration of the dynamicmodel including all force elementswith an initial position and velocity could yield a very accurate answer to the problem with relative ease. But when the real-time calculation is considered as a constraint, the numerical integration that requires a lot of computational resources is not a feasible option in the majority of launch operations. There has been some research on developing the IIP prediction algorithm that provides the real-time solution within acceptable accuracy with limited computational resources. To calculate the IIP for shortto midrange rockets, simplified models in the localvertical–local-horizontal frame are frequently used [3–6]. These assume that the trajectory of a rocket is parabolic subject to the constant vertical downward gravitational acceleration and often add correction terms to compensate for the modeling errors. Montenbruck and Markgraf [6] developed a linearized IIP calculation algorithm and implemented it for the launch operation of the Maxus-5 sounding rocket. Their algorithm was based on a simple parabolic flight model, and its prediction accuracy was improved by considering the effects of the Earth curvature, the Coriolis force, and the gravity field variation. The Keplerian algorithm predicts the IIP using the equations describing the motion of a rocket under the inverse-square law of gravity. Regan and Anandakrishnan [4] and Zarchan [7] developed a series of formulations that can be used as the base of theKeplerian IIP prediction, such as the expressions for the flight angle and the flight time. Currently, an iterativeKeplerian algorithm is frequently used to predict the IIP for long-range space vehicles [8,9]. The iterative Keplerian algorithm can calculate the true IIP solution for the Keplerian motion of a rocket using an iterative procedure (e.g., successive substitution) to find parameters such as Kepler’s f and g series expansions, the eccentric anomaly of the impact point, and the surface radius at impact. Considering that the IIP prediction for an actual launch operation should be carried out in real time, the iterative procedure that has the risk of computational overload is not very desirable to be included in the prediction algorithm. Especially when the algorithm is implemented in an onboard computer that has limited computing resources but is responsible for multiple mission-critical tasks such as event sequencing, navigation, and attitude control, the potential damage associated with the risk is significantly increased. This engineering Note presents a Keplerian IIP prediction algorithm that does not require any iterative procedure and is thus remarkably faster than the iterative Keplerian algorithm. First, an exact and closed solution for the Keplerian IIP with the spherical Earth model is developed. Then, a noniterative procedure to compensate for the effect of the oblateness of the Earth is added. Finally, the validity of the proposed algorithm is proved through the performance comparison with the iterative algorithm in terms of computational efficiency and the prediction accuracy.

NEAR-BOTTOM FLOW CHARACTERISTICS OF CURRENTS AT ARBITRARY ANGLE TO 2D RIPPLES

Experimental results for near-bottom current velocity profiles for flows over artificial, definitely 2D ripples made of 1.5 cm high aluminum angle-profile spaced at 10 cm intervals are obtained for the following cases: (i) current alone perpendicular to ripples; (ii) current alone parallel to ripples; (iii) combined orthogonal wave-current flows for current parallel to ripples; and (iv) current alone at an angle of 30° to the ripple axis. The velocity profiles are analyzed by the log-profile method, and show the roughness experienced by the current to increase as the angle between ripple and current direction increases, i.e. demonstrating convincingly the reality of the concept of a direction-dependent roughness for flows over a 2D rippled bottom. Roughness experienced by the velocity component perpendicular to the ripples is, however, found to be independent of the direction of the mainstream flow relative to that of the ripples, and the different roughness experienced by the perpendicular and parallel velocity components gives rise to a turning of the current velocity vector to become increasingly aligned with the ripple crests as the bottom is approached from above. Implications of this feature, in terms of net sediment transport direction in combined wave-current flows in inner-shelf coastal waters, is discussed.

Hydrodynamic Processes and Bedload Transport Associated with Large-Scale Sandwaves in the Taiwan Strait

Hydrodynamic processes and bedload transport over a large-scale sandwave field were analyzed along three transects in Taiwan Strait based on measurements of water depth, current velocities within the water column, and the physical properties of the sediment at the seabed. The sandwaves in consideration have steep crests and flat troughs, with a width of 14.4–20.3 m and a length of 325–820 m. Generally, the mean H/L ratio falls in the range of large-scale sandwaves, but the ratio is larger than the average, deviating from the global trend. The H/d ratio is much higher than the global average. The current-velocity vectors at the sandwave crests, troughs, stoss sides, and lee sides turned in a clockwise manner within a tidal cycle; the current speed above the crest was relatively larger than above the trough. During the flood tide, the current speed reached a maximum in the layer 9–11 m below the water surface. During the measurement period, there was net accumulation of sediment over the study area. The migration of the sandwaves caused by bedload transport varied widely at different transects: for the three transects in consideration, migration in the flood direction occurred at two transects, with different migrating speeds; and ebb-dominated migration occurred at the third transect. The migration rate predicted by the bedload transport calculations, based on tidal current measurements, is lower than long-term observations by remote sensing, which may be due to the fact that this region is frequently influenced by storm events, and the long-term migration patterns are related to the enhanced currents and waves during storms. Further, time-velocity asymmetry of the tidal currents, as observed in the present study, may also favor the enhanced migration rate during storm events.

New data on the sea current system in the Somali region, Indian Ocean

Direct measurements of current velocities conducted during the International World Ocean Circulation Experiment (WOCE) yielded new data on spatiotemporal characteristics of a current system off the Somali coast. It is shown that background circulation within the domain of the western boundary current in the Indian Ocean forms a regional anticyclonic gyre similar in general patterns to its counterparts in the Atlantic and Pacific oceans. However, the Indian Ocean is distinguished from other oceans by superimposition of the alternating monsoon signal with the prevalent annual harmonic on the background dynamic structure. It is established that abnormally high velocities in the central part of the Somali Current (up to 2 m/s) during the southwestern monsoon period is related to superimposition of unidirectional background and summer monsoon components of this powerful western boundary current. The Indian Ocean segment adjacent to the northeastern coast of the African continent is one of the most active regions of the planet with respect to climatic perturbations. The vast region of a cold surface layer in the southern Arabian Sea related to upwelling in the Somali Current system [2] substantially influences atmospheric processes and weather conditions in the spacious maritime region of southwestern Asia. There are also grounds to believe that inversion heat transfer from the atmosphere to the ocean observed during the summer monsoon in the Somali temperature anomaly zone acts as a damper in the generation of mobile cyclonic whirlwinds, preventing them from transforming into catastrophic hurricanes. All these and other climatically important peculiarities in the thermodynamic behavior of the ocean and atmosphere near the African Horn attract the constant attention of experts in meteorology and oceanography to this region [3‐7]. Nevertheless, despite a long history of investigations, many problems related particularly to variability in the Somali segment of the oceanic circulation system remain poorly studied so far. The hypothesis of reverse behavior of the Somali Current is one of the most intriguing scenarios of this variability [4, 8, 9]. It is known that the monsoon type of atmospheric circulation that prevails over the northwestern segment of the Indian Ocean influences the system of sea currents and determines the unique characteristic of the powerful jet stream that flows along the northeastern coast of Africa, i.e., annual periodicity in the alternating direction of the current velocity vector [9]. Most researchers believe that the intense western boundary transfer (the Somali Current) appears in the summer monsoon period (approximately from June to September), when a strong favorable southwestern wind accelerates the northeastern alongshore flow of surface waters up to velocities exceeding 300 cm/s. After the onset of the winter phase of the monsoon (November), the Somali Current presumably disappears [10] and gives way to a flow with the southern velocity component under influence of the northeastern wind. It is unclear, however, whether or not this scenario is real. Published materials [11‐13] provide evidence that a countercurrent (opposite to the Somali Current) appears in the subsurface layer at the end of the summer climatic season. The countercurrent also incorporates the surface layer water at the beginning of the winter monsoon period.