Ocean currents (wind, trade wind, katabatic; warm, cold). Current of the Western Winds

WIND CURRENT - an ocean current caused by wind over the water surface, especially in those parts of the World Ocean where the wind regime is quite stable, for example in the mid-latitudes of the southern hemisphere.

Dictionary of winds. - Leningrad: Gidrometeoizdat. L.Z. Shit. 1983.

See what “WIND CURRENT” is in other dictionaries:

wind current- drift current A surface current that occurs as a result of the transfer of energy from the wind to surface ocean waters. Sometimes called Ekman drift or wind drift, the true response of surface waters is short-lived... ... Technical Translator's Guide

wind current- Sea current caused by wind pressure on the surface layer of water. Syn.: wave current... Dictionary of Geography

Windshield- Panoramic windshield of a 1959 Edsel Corsair. Windshield, or windshield, is a transparent shield installed in front of the cabin of a car (or other vehicle) to protect the driver and passengers from the oncoming... ... Wikipedia

wave current- Sea current caused by wind pressure on the surface layer of water. Syn.: wind current... Dictionary of Geography

monsoon current- Surface (to a depth of about 200 m) wind current in oceans and seas with seasonal changes in direction caused by monsoons... Dictionary of Geography

Wind (drift) ocean current south of 65° S. sh., arising under the influence of the prevailing eastern winds. Width of P. a. t. about 250 miles. It covers Antarctica in an almost continuous ring... Dictionary of winds

LAKE- a body of water surrounded by land. Lakes range in size from very large ones, such as the Caspian Sea and the Great Lakes of North America, to tiny bodies of water measuring a few hundred square meters or even smaller. The water in them can be fresh,... ... Collier's Encyclopedia

lake- a natural body of water in a depression on the earth’s surface (lake basin). The lakes are fed by atm. precipitation, surface and underground runoff. According to their water balance, lakes are divided into flowing lakes (those with a river or rivers flowing from them) and drainage lakes (without… Geographical encyclopedia

sea ​​currents- translational movements of the waters of the World Ocean caused by the wind and the difference in their pressures at the same horizons. Currents are the main type of water movement and have a huge impact on the distribution of temperature, salinity and... ... Marine encyclopedic reference book

bottom countercurrent- Current in the lower layers of water, compensating for the surface wind current... Dictionary of Geography

Mariners learned about the presence of ocean currents almost as soon as they began to plow the waters of the World Ocean. True, the public paid attention to them only when, thanks to the movement of ocean waters, many great geographical discoveries were made, for example, Christopher Columbus sailed to America thanks to the North Equatorial Current. After this, not only sailors, but also scientists began to pay close attention to ocean currents and strive to study them as best and deeply as possible.

Already in the second half of the 18th century. The sailors studied the Gulf Stream quite well and successfully applied the acquired knowledge in practice: from America to Great Britain they walked with the current, and in the opposite direction they kept a certain distance. This allowed them to stay two weeks ahead of ships whose captains were not familiar with the area.

Ocean or sea currents are large-scale movements of water masses in the World Ocean at speeds from 1 to 9 km/h. These streams do not move chaotically, but in a certain channel and direction, which is the main reason why they are sometimes called rivers of the oceans: the width of the largest currents can be several hundred kilometers, and the length can reach several thousand.

It has been established that water flows do not move straight, but deviate slightly to the side and are subject to the Coriolis force. In the Northern Hemisphere they almost always move clockwise, in the Southern Hemisphere it’s the other way around.. At the same time, currents located in tropical latitudes (they are called equatorial or trade winds) move mainly from east to west. The strongest currents were recorded along the eastern coasts of the continents.

Water flows do not circulate on their own, but are set in motion by a sufficient number of factors - wind, rotation of the planet around its axis, gravitational fields of the Earth and Moon, bottom topography, outlines of continents and islands, differences in temperature indicators of water, its density, depth in different places in the ocean and even its physical and chemical composition.

Of all kinds water flows The most pronounced are the surface currents of the World Ocean, the depth of which is often several hundred meters. Their occurrence was influenced by trade winds constantly moving in tropical latitudes in a west-east direction. These trade winds form the huge flows of the North and South Equatorial Currents near the equator. A smaller part of these flows returns to the east, forming a countercurrent (when the movement of water occurs in the opposite direction from the movement of air masses). Most of them, when colliding with continents and islands, turn to the north or south.

Warm and cold water currents

It must be taken into account that the concepts of “cold” or “warm” currents are conditional definitions. So, despite the fact that the temperature of the water flows of the Benguela Current, which flows along the Cape of Good Hope, is 20°C, it is considered cold. But the North Cape Current, which is one of the branches of the Gulf Stream, with temperatures from 4 to 6 ° C, is warm.

This happens because cold, warm and neutral currents got their names based on a comparison of the temperature of their water with the temperature of the surrounding ocean:

• If the temperature indicators of the water flow coincide with the temperature of the surrounding waters, such a flow is called neutral;
• If the temperature of the currents is lower than the surrounding water, they are called cold. They usually flow from high latitudes to low latitudes (for example, the Labrador Current), or from areas where, due to large river flows, ocean water has a reduced salinity of surface waters;
• If the temperature of the currents is warmer than the surrounding water, then they are called warm. They move from tropical to subpolar latitudes, for example, the Gulf Stream.

Main water flows

At the moment, scientists have recorded about fifteen major oceanic water flows in the Pacific, fourteen in the Atlantic, seven in the Indian and four in the Arctic Ocean.

It is interesting that all currents of the Arctic Ocean move at the same speed - 50 cm/sec, three of them, namely the West Greenland, West Spitsbergen and Norwegian, are warm, and only the East Greenland is a cold current.

But almost all oceanic currents of the Indian Ocean are warm or neutral, with the Monsoon, Somali, Western Australian and Cape Agulhas current (cold) moving at a speed of 70 cm/sec, the speed of the rest varies from 25 to 75 cm/sec. The water flows of this ocean are interesting because, together with the seasonal monsoon winds, which change their direction twice a year, the oceanic rivers also change their course: in winter they mainly flow to the west, in summer - to the east (a phenomenon characteristic only of the Indian Ocean ).

Since the Atlantic Ocean stretches from north to south, its currents also have a meridional direction. Water flows located in the north move clockwise, in the south - counterclockwise.

A striking example of the flow of the Atlantic Ocean is the Gulf Stream, which, starting in the Caribbean Sea, carries warm waters to the north, breaking up into several side streams along the way. When the waters of the Gulf Stream find themselves in the Barents Sea, they enter the Arctic Ocean, where they cool and turn south in the form of the cold Greenland Current, after which at some stage they deviate to the west and again join the Gulf Stream, forming a vicious circle.

The currents of the Pacific Ocean are mainly latitudinal and form two huge circles: northern and southern. Since the Pacific Ocean is extremely large, it is not surprising that its water flows have a significant impact on much of our planet.

For example, trade wind water currents transport warm waters from the western tropical coasts to the eastern ones, which is why in the tropical zone the western part of the Pacific Ocean is much warmer than the opposite side. But in the temperate latitudes of the Pacific Ocean, on the contrary, the temperature is higher in the east.

Deep Currents

For quite a long time, scientists believed that deep ocean waters were almost motionless. But soon special underwater vehicles discovered both slow and fast-flowing water streams at great depths.

For example, under the Equatorial Current of the Pacific Ocean at a depth of about one hundred meters, scientists have identified the underwater Cromwell Current, moving eastward at a speed of 112 km/day.

Soviet scientists found a similar movement of water flows, but in the Atlantic Ocean: the width of the Lomonosov Current is about 322 km, and the maximum speed of 90 km/day was recorded at a depth of about one hundred meters. After this, another underwater flow was discovered in the Indian Ocean, although its speed turned out to be much lower - about 45 km/day.

The discovery of these currents in the ocean gave rise to new theories and mysteries, the main one of which is the question of why they appeared, how they were formed, and whether the entire area of ​​the ocean is covered by currents or there is a point where the water is still.

The influence of the ocean on the life of the planet

The role of ocean currents in the life of our planet can hardly be overestimated, since the movement of water flows directly affects the planet’s climate, weather, and marine organisms. Many compare the ocean to a huge heat engine driven by solar energy. This machine creates a constant exchange of water between the surface and deep layers of the ocean, providing it with oxygen dissolved in the water and influencing the life of marine inhabitants.

This process can be traced, for example, by considering the Peruvian Current, which is located in the Pacific Ocean. Thanks to the rise of deep waters, which lift phosphorus and nitrogen upward, animal and plant plankton successfully develop on the ocean surface, resulting in the organization of a food chain. Plankton is eaten by small fish, which, in turn, become prey to larger fish, birds, and marine mammals, which, given such food abundance, settle here, making the region one of the most highly productive areas of the World Ocean.

It also happens that a cold current becomes warm: the average ambient temperature rises by several degrees, which causes warm tropical showers to fall on the ground, which, once in the ocean, kill fish accustomed to cold temperatures. The result is disastrous - a huge amount of dead small fish ends up in the ocean, large fish leave, fishing stops, birds leave their nesting places. As a result, the local population is deprived of fish, crops destroyed by heavy rains, and profits from the sale of guano (bird droppings) as fertilizer. It can often take several years to restore the previous ecosystem.

Excitement is the oscillatory movement of water. It is perceived by the observer as the movement of waves on the surface of the water. In fact, the water surface oscillates up and down from the average level of the equilibrium position. The shape of waves during waves is constantly changing due to the movement of particles in closed, almost circular orbits.

Each wave is a smooth combination of elevations and depressions. The main parts of the wave are: crest- the highest part; sole - lowest part; slope - profile between the crest and trough of a wave. The line along the crest of the wave is called wave front(Fig. 1).

Rice. 1. Main parts of the wave

The main characteristics of waves are height - the difference in the levels of the wave crest and wave bottom; length - the shortest distance between adjacent wave crests or troughs; steepness - the angle between the wave slope and the horizontal plane (Fig. 1).

Rice. 1. Main characteristics of the wave

Waves have very high kinetic energy. The higher the wave, the more kinetic energy it contains (proportional to the square of the increase in height).

Under the influence of the Coriolis force, a water swell appears on the right side of the current, away from the mainland, and a depression is created near the land.

By origin waves are divided as follows:

• friction waves;
• pressure waves;
• seismic waves or tsunamis;
• seiches;
• tidal waves.

Friction waves

Friction waves, in turn, can be wind(Fig. 2) or deep. Wind waves arise as a result of wind waves, friction at the boundary of air and water. The height of wind waves does not exceed 4 m, but during strong and prolonged storms it increases to 10-15 m and higher. The highest waves - up to 25 m - are observed in the westerly wind zone of the Southern Hemisphere.

Rice. 2. Wind waves and surf waves

Pyramidal, high and steep wind waves are called crowding. These waves are inherent in the central regions of cyclones. When the wind subsides, the excitement takes on a character swell, i.e., disturbances due to inertia.

The primary form of wind waves is ripple It occurs at a wind speed of less than 1 m/s, and at a speed greater than 1 m/s, first small and then larger waves are formed.

A wave near the coast, mainly in shallow waters, based on forward movements, is called surf(see Fig. 2).

Deep waves arise at the boundary of two layers of water with different properties. They often occur in straits with two levels of current, near river mouths, at the edge of melting ice. These waves mix up the sea water and are very dangerous for sailors.

Pressure wave

Pressure waves arise due to rapid changes in atmospheric pressure in the places of origin of cyclones, especially tropical ones. Usually these waves are single and do not cause much harm. The exception is when they coincide with high tide. The Antilles, the Florida Peninsula, and the coasts of China, India, and Japan are most often exposed to such disasters.

Tsunami

Seismic waves occur under the influence of underwater tremors and coastal earthquakes. These are very long and low waves in the open ocean, but the force of their propagation is quite strong. They move at very high speed. Along the coasts, their length decreases and their height increases sharply (on average from 10 to 50 m). Their appearance entails human casualties. First, the sea water retreats several kilometers from the shore, gaining strength to push, and then the waves splash onto the shore with great speed at intervals of 15-20 minutes (Fig. 3).

Rice. 3. Tsunami transformation

The Japanese named seismic waves tsunami, and this term is used all over the world.

The seismic belt of the Pacific Ocean is the main area for tsunami generation.

Seiches

Seiches are standing waves that occur in bays and inland seas. They occur by inertia after the cessation of external forces - wind, seismic shocks, sudden changes, intense precipitation, etc. In this case, in one place the water rises, and in another it falls.

Tidal wave

Tidal waves- these are movements made under the influence of the tidal forces of the Moon and the Sun. Reverse reaction of sea water to the tide - low tide. The strip that drains during low tide is called drying.

There is a close connection between the height of the tides and the phases of the moon. New and full moons have the highest tides and lowest tides. They are called Syzygy. At this time, the lunar and solar tides, occurring simultaneously, overlap each other. In the intervals between them, on the first and last Thursdays of the Moon phases, the lowest, quadrature tides.

As already mentioned in the second section, in the open ocean the tide height is low - 1.0-2.0 m, but near dissected coasts it increases sharply. The tide reaches its maximum value on the Atlantic coast of North America, in the Bay of Fundy (up to 18 m). In Russia, the maximum tide - 12.9 m - was recorded in Shelikhov Bay (Sea of ​​Okhotsk). In inland seas, the tides are little noticeable, for example, in the Baltic Sea near St. Petersburg the tide is 4.8 cm, but in some rivers the tide can be traced hundreds and even thousands of kilometers from the mouth, for example, in the Amazon - up to 1400 cm.

A steep tidal wave rising up a river is called boron In the Amazon, boron reaches a height of 5 m and is felt at a distance of 1400 km from the mouth of the river.

Even with a calm surface, disturbances occur in the thickness of the ocean waters. These are the so-called internal waves - slow, but very significant in scope, sometimes reaching hundreds of meters. They arise as a result of external influence on a vertically heterogeneous mass of water. In addition, since the temperature, salinity and density of ocean water do not change gradually with depth, but abruptly from one layer to another, specific internal waves arise at the boundary between these layers.

Sea currents

Sea currents- these are horizontal translational movements of water masses in the oceans and seas, characterized by a certain direction and speed. They reach several thousand kilometers in length, tens to hundreds of kilometers in width, and hundreds of meters in depth. In terms of physical and chemical properties, the waters of sea currents are different from those around them.

By duration of existence (sustainability) sea ​​currents are divided as follows:

• permanent, which pass in the same regions of the ocean, have the same general direction, more or less constant speed and stable physical and chemical properties of the transported water masses (North and South trade winds, Gulf Stream, etc.);
• periodic, in which direction, speed, temperature are subject to periodic patterns. They occur at regular intervals in a certain sequence (summer and winter monsoon currents in the northern part of the Indian Ocean, tidal currents);
• temporary, most often caused by winds.

By temperature sign sea ​​currents are:

• warm which have a temperature higher than the surrounding water (for example, the Murmansk Current with a temperature of 2-3 ° C among waters O ° C); they have a direction from the equator to the poles;
• cold, the temperature of which is lower than the surrounding water (for example, the Canary Current with a temperature of 15-16 ° C among waters with a temperature of about 20 ° C); these currents are directed from the poles to the equator;
• neutral, which have a temperature close to environment(for example, equatorial currents).

Based on the depth of their location in the water column, currents are distinguished:

• superficial(up to 200 m depth);
• subsurface, having a direction opposite to the surface;
• deep, the movement of which is very slow - on the order of several centimeters or a few tens of centimeters per second;
• bottom regulating the exchange of water between polar - subpolar and equatorial-tropical latitudes.

By origin The following currents are distinguished:

• friction, which may be drift or wind. Drift ones arise under the influence of constant winds, and wind ones are created by seasonal winds;
• gradient-gravitational, among which are stock, formed as a result of the tilting of the surface caused by excess water due to its influx from the ocean and heavy rainfall, and compensatory, which arise due to the outflow of water, scanty precipitation;
• inert, which are observed after the cessation of the action of the factors that excite them (for example, tidal currents).

The system of ocean currents is determined by the general circulation of the atmosphere.

If we imagine a hypothetical ocean extending continuously from the North Pole to the South Pole, and superimpose on it a generalized scheme of atmospheric winds, then, taking into account the deflecting Coriolis force, we obtain six closed rings -
gyres of sea currents: Northern and Southern equatorial, Northern and Southern subtropical, Subarctic and Subantarctic (Fig. 4).

Rice. 4. Cycles of sea currents

Deviations from the ideal scheme are caused by the presence of continents and the peculiarities of their distribution over the Earth's surface. However, as in the ideal diagram, in reality there is zonal change large - several thousand kilometers long - not completely closed circulation systems: it is equatorial anticyclonic; tropical cyclonic, northern and southern; subtropical anticyclonic, northern and southern; Antarctic circumpolar; high-latitude cyclonic; Arctic anticyclonic system.

In the Northern Hemisphere they move clockwise, in the Southern Hemisphere they move counterclockwise. Directed from west to east equatorial inter-trade wind countercurrents.

In the temperate subpolar latitudes of the Northern Hemisphere there are small current rings around baric minimums. The movement of water in them is directed counterclockwise, and in the Southern Hemisphere - from west to east around Antarctica.

Currents in zonal circulation systems are quite well traced down to a depth of 200 m. With depth, they change direction, weaken and turn into weak vortices. Instead, meridional currents intensify at depth.

The most powerful and deepest surface currents play a critical role in the global circulation of the World Ocean. The most stable surface currents are the North and South Trade Winds of the Pacific and Atlantic Oceans and the South Trade Winds of the Indian Ocean. They have a direction from east to west. Tropical latitudes are characterized by warm waste currents, for example the Gulf Stream, Kuroshio, Brazilian, etc.

Under the influence of constant westerly winds in temperate latitudes there are warm North Atlantic and North-

The Pacific Current in the Northern Hemisphere and the cold (neutral) current of the Western Winds in the Southern Hemisphere. The latter forms a ring in the three oceans around Antarctica. The large gyres in the Northern Hemisphere are closed by cold compensatory currents: along the western coasts in tropical latitudes - the Californian, Canary, and in the Southern - the Peruvian, Bengal, and Western Australian.

The most famous currents are also the warm Norwegian Current in the Arctic, the cold Labrador Current in the Atlantic, the warm Alaskan Current and the cold Kuril-Kamchatka Current in the Pacific Ocean.

The monsoon circulation in the northern Indian Ocean generates seasonal wind currents: winter - from east to west and summer - from west to east.

In the Arctic Ocean, the direction of movement of water and ice occurs from east to west (Transatlantic Current). Its reasons are the abundant river flow of the rivers of Siberia, the rotational cyclonic movement (counterclockwise) over the Barents and Kara seas.

In addition to circulation macrosystems, there are eddies of the open ocean. Their size is 100-150 km, and the speed of movement of water masses around the center is 10-20 cm/s. These mesosystems are called synoptic vortices. It is believed that they contain at least 90% of the kinetic energy of the ocean. Eddies are observed not only in the open ocean, but also in sea currents such as the Gulf Stream. Here they rotate at an even higher speed than in the open ocean, their ring system is better expressed, which is why they are called rings.

For the climate and nature of the Earth, especially coastal areas, the importance of sea currents is great. Warm and cold currents maintain the temperature difference between the western and eastern coasts of the continents, disrupting its zonal distribution. Thus, the ice-free port of Murmansk is located above the Arctic Circle, and on the east coast of North America the Gulf of St. Lawrence (48° N). Warm currents promote precipitation, while cold currents, on the contrary, reduce the possibility of precipitation. Therefore, areas washed by warm currents have a humid climate, while areas washed by cold currents have a dry climate. With the help of sea currents, the migration of plants and animals, the transfer of nutrients and gas exchange are carried out. Currents are also taken into account when sailing.

Wind currents lead to a rush of water from the leeward side of the reservoir and to a surge on the windward side. The resulting horizontal pressure gradient, directed in the direction opposite to the wind, causes one of the types of deep compensation currents. [...]

Wind currents in reservoirs, flowing lakes, bays and estuaries almost always interact with katabatic or seiche currents. At the same time, they change the vertical distribution of the velocity of runoff or seiche currents, and in some cases even create unique water circulation systems in any area or even in the entire reservoir.[...]

Wind current is observed in surface layers with a depth of an average of 0.4 reservoir depths (H); it has the same direction as the wind, and its speed varies from r0 on the surface to zero at a depth of 0.4 N. Below lies a layer of compensatory flow, which has a direction opposite to the wind. . When releasing wastewater near the shore (which usually occurs), the worst conditions are created in the reservoir with wind along the shore, in the direction of the nearest water intake5 This case is considered further.[...]

Currents that arise with the participation of friction forces are wind currents caused by temporary and short-term winds, and drift currents caused by established winds that act for a long time. Wind currents do not create a level inclination, but drift currents lead to a level inclination and the appearance of a pressure gradient, which determine the occurrence of a deep gradient current in coastal areas. [...]

WIND CURRENT - movement of water under the influence of wind.[...]

During intense storms, coinciding with spring tides, maximum rates of sediment transport occur, since the currents are intensified by the storm surge and/or wind currents (Fig. 9.50, B). In proximal zones, erosion produces shallow channels, flat erosion surfaces and residual pebble deposits. In downstream zones, rapid migration of bedforms occurs, including the formation of crescent dunes with distal deposition of thinner storm sand layers. The resulting sedimentary cover has a better chance of being preserved.[...]

In addition to wind currents, two additional phenomena may also play an important role in the hydrodynamic picture of inland water bodies. Under the influence of wind, isobaric surfaces become inclined, which in turn causes a change in the angle of inclination of the thermocline and the surface level. With the cessation of wind, long-period oscillations appear in the reservoir, known as seiches (Fig. 4.17).[...]

Since wind currents depend on the wind regime in one or another area, the above parameters are accepted for the European part. USSR according to meteorological stations and taking into account an increase in wind speed by approximately 20%. All calculations were made for wind currents with an average wind speed of 5.5 m/sec. Thus, formula 10.21 was obtained for a special case with the parameters indicated above.[...]

The speed of wind currents in the upper and lower layers in the Caspian Sea near Baku is determined to be 2.0-2.5% of the wind speed. For other sea coasts this value reaches 3-5%.[...]

Unidirectional wind currents were studied, as noted above, in an installation whose design predetermined the formation of water circulation in a horizontal plane under the influence of wind.[...]

In a unidirectional wind flow, a change in the vertical distribution of OG with a change in the H/k ratio was clearly detected. At H/k 1.0, the values ​​of sn decreased from the surface of the water, where they were greatest, to the horizon (0.2... 0.4)R, and then decreased very smoothly or practically did not change until the bottom (see. Fig. 3.7). The values ​​at H/k 1.0 smoothly decreased from the surface to the horizon (0.5... 0.8)R, and then smoothly increased towards the bottom, so that at the surface and at the bottom they turned out to be close and even equal . A further decrease in N/c to 0.4-0.6 led to a leveling of the distribution of st„ vertically.[...]

Materials from the study of currents under natural conditions and in laboratory installations show that the degree of influence of the wind current on the katabatic current increases, other things being equal, with an increase in wind speed and with a decrease in the speed of the katabatic or seiche current.[...]

Under natural conditions, wind currents are often disturbed by seismic, runoff or residual currents. In this regard, from measurement data it is rarely possible to obtain diagrams with a smooth vertical change in velocity and a stable flow direction over time at different horizons. Only in cases where currents on individual verticals are measured for a long time and these measurements are accompanied by recording of wind, water level and waves, from many diagrams it is possible to select those that meet the conditions of quasi-steady wind currents. Measurements of this kind were carried out by expedition groups of the State Hydrological Institute on the Kairakkum, Kakhovsky and Kremenchug reservoirs and on several small lakes. Several diagrams obtained from these measurements are shown in Fig. 4.16. The largest vertical velocity gradients in most of these diagrams are confined to the surface and bottom layers, and the smallest - to the central part of the flow.[...]

In a multidirectional wind flow, vortex formations with a vertical or inclined axis of rotation arise more often than in a unidirectional wind flow. They are more clearly expressed and more often occur in the area of ​​influence of the compensatory flow. The largest of the vortex formations with a vertical axis of rotation penetrate the entire thickness of the zone of action of the compensation current (Fig. 2.5) and even partially penetrate into the zone of action of the drift current.[...]

For the full development of wind current, in contrast to waves, it is necessary that the entire water mass of the reservoir begins to move in accordance with the supply of wind energy and energy losses: friction in the water column. Therefore, at the same speed, wind and other equal conditions, the duration of development of the wind current will be longer in the reservoir in which the depth is greater, and the time of growth of waves in these reservoirs will be approximately the same. This circumstance can be confirmed with an example. The duration of development of wind currents, for example, in a lake. Baikal (Yasr = 730 m) with a wind speed of 10.5 m/s, according to the calculations mentioned above, is 60-110 hours, and the duration of wave development for the central section, according to the work, is about 18 hours [...]

Although tidal currents are bidirectional, linear or circular, they carry out predominantly unidirectional transport of sediment due to the fact that 1) ebb and flow currents are usually not equal in maximum strength and duration (Fig. 7.39, e); 2) ebb and flow currents can follow mutually exclusive transport routes; 3) the retarding effect associated with the circular tide delays the supply of sediment; 4) a unidirectional tidal current can be enhanced by other currents, for example, a drift wind current. The interaction of these processes is well demonstrated by the example of the most studied seas in the world, namely the seas of North-West Europe, the hydrodynamic regime of which is in partial equilibrium with the shapes of the bottom surface and the directions of sediment transport.[...]

Sarkisyan A. S. Calculation of stationary wind currents in the ocean // Izv. USSR Academy of Sciences.[...]

When studying the vertical structure of wind currents, the greatest attention must be paid to the largest vortex formations, since they have the greatest energy of movement and determine, for example, processes such as vertical mixing of water.[...]

The considered types of vortex structures of wind currents, although they are typical, do not exhaust the entire possible variety of particle motion processes even for the specified wind and wave conditions.[...]

As is known (see § 73), with depth the current speed decreases and its direction changes. At some depth, the current may have a direction opposite to the surface one. A reversal of flow direction is not always the result of the geostrophic effect. In reservoirs of limited size, this is often the result of the formation of a compensatory current. Near the coast, wind currents cause drift or surge phenomena. An additional slope of the water surface appears, directed against the wind. As a result, under the influence of gravity, a deep gradient countercurrent (compensatory current) develops, which helps maintain the balance of water in the lake. In this way a mixed flow is formed.[...]

For quasi-steady unidirectional wind currents, the duration of existence of large vortex formations turned out to be close to the above average values, but this information is roughly approximate, since it was obtained by counting the number of shooting frames with clearly defined ascending and descending trajectories of particles. [...]

Some progress has been made in calculating the flow field from the wind field, surface and deep currents, taking into account changes in the density field. However, insufficient knowledge of real parameters (for example, viscosity coefficient) does not allow the problem of wind currents to be considered solved. Therefore, along with theoretical calculations of the flow field, semi-empirical methods have been widely used until recently to solve applied problems.[...]

In narrow bays, seiche and gradient currents predominate, which arise when there are level differences between the reservoir and the bay and act predominantly along the longitudinal axis of the bay. The role of wind currents in such conditions is insignificant, especially in the presence of high banks.[...]

Quite a lot of information about changes in the surface speed of wind currents in coastal shallow water zones was obtained at the State Hydrological Institute mainly from aerial measurements, and information about changes in the average speed on verticals was obtained from measurements by deep floats from boats. Previous analysis showed that most measurements indicate an insignificant change in the speed of wind currents across the width of the zone. However, with a differentiated examination of previously obtained and new current measurement data, it was possible to identify differences in the trends in speed changes across the width of the coastal shallow water zone at different wind directions relative to the coastline. [...]

It was shown above that at the final stages of development of a wind current unidirectional in depth in the water column, the formation of elliptical vortices occurs, which can cover the entire thickness of the flow, and in the longitudinal direction they are 8-10 times greater than the depth. Along with these largest structural formations, smaller vortices with a horizontal axis are formed in the flow, filling the space inside large vortices and along their contour, as well as vortices different sizes with vertical or inclined axes of rotation. Mostly the same structural features prevail in unidirectional wind currents and at the quasi-steady stage of process development.[...]

In wide open bays that freely communicate with a reservoir, the processes of transport of water masses are usually determined by wind currents. Under the influence of wind, waves and wind currents of the reservoir, very unique water macrocirculation systems are formed in such bays.[...]

Based on the consideration of the proposed methods for establishing criterion relationships, it is clear that physical modeling of wind currents is a very labor-intensive task in relation to both the experimental technique and the recalculation of modeling data to natural conditions. However, previous experiments show that the costs of labor and money are most often paid off by the great value of the resulting materials.[...]

As an example in Fig. 4.3 thick line shows the course of the middle, and the dashed line shows the limiting position of the lower boundary of the drift current in the survey field, the dimensions of which along the axial plane of the flume were approximately equal to the total depth of the flow. Fluctuations in the lower boundary of the drift current increased in cases where the size of the vortex formations increased and when the developing wind current was superimposed on the residual current.[...]

Studies have shown that when wastewater containing contaminants enters and is dispersed using special technical devices or currents, chemical compounds are transformed. Pollutants from the dissolved form pass into the solid phase, accumulating in bottom sediments, or enter those marine organisms that, if not used by humans, are food for fish. In this case, it is necessary to take into account the influence of chemical compounds on seashore, as well as the atmosphere when wind currents carry away foam in the form of aerosols. The last factor has been poorly studied, so it is currently difficult to assess its impact. Gas and dust emissions, like wastewater, go through similar stages, and ultimately, as a result of interaction at the water-air interface, active dissolution of individual compounds occurs.[...]

The validity of this opinion can be seen when considering chronograms (Fig. 3.2) for three different lakes: Ladoga, Bely and Balkhash. On the first two lakes during the recording period, wind currents prevailed in relatively stable directions (Fig. 3.2a, b), and on the third lake, seiche currents prevailed with a period varying from 3 to 12 hours (Fig. 3.2). All chronograms clearly show fluctuations in the speed and direction of the current, despite the fact that the first of these characteristics was averaged over 176 s. The presented chronograms allow us to conclude that instantaneous velocities under natural conditions vary within even wider limits than shown in Fig. 3.2. However, obtaining instantaneous values ​​of the speed and direction of the flow in natural conditions, especially in the zone of wave oscillatory movements, is very difficult.[...]

Of particular interest is the fact that the generalized diagram in Fig. 6.4 differs quite significantly from the diagrams obtained from measurements in the lake. Balkhash in conditions of predominance of seiche currents, but is close to diagrams obtained from measurements under the influence of wind currents in reservoirs with limited depth.[...]

Using this technique, it is easy to verify that the width of the zone covered by a wind current multidirectional in depth is usually 4-6 times greater than the width of the zone covered, for example, near the windward coast by a wind current unidirectional in depth. The cross-sectional area covered by the gradient flow under such conditions turns out to be 2.0-2.5 times larger than the cross-sectional area covered by the drift flow. The reasons for these differences are differences in the degree of turbulization of the current - significantly greater in the zone of action of a current multidirectional in depth than in the zone of action of a unidirectional current.