Wind ocean currents. wind currents. Warm and cold water streams

AGAINST THE CURRENT The general theory of relativity was created by A. Einstein on the basis of the minimum number of experimental data on gravitation, selected by him with ingenious intuition. For many decades that have passed since then, all the predictions of this theory that could be

VII. COUNTERCURRENTS

VII. COUNTERCURRENTS 1Given the evidence presented in previous chapters, it is easy to see why Polish historians—who, after all, are closest to the core of the problem—agree that “in early period the main core of the Jewish population came from

4. "Currents"

4. "Trends" Rejecting direct decisions, ignoring the will of the workers, the "S.-D. faction" extends in detail about the usefulness of all "trends of Marxism". All over the world, Marxists start from workers' organizations, in our country they want to start from elusive "trends". In Germany, and throughout the world, the Social-Democrats

wind currents

Wind currents lead to water surge from the leeward side of the reservoir and to its surge at 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 runoff or seiche currents. At the same time, they change the distribution of the speed of runoff or seiche currents along the vertical, and in some cases even create a kind of water circulation system in some area or even in the entire reservoir.[ ...]

wind current seen in surface layers depth, on average, 0.4 of the depth of the reservoir (H); it has the same direction as the wind, and its speed varies from r; 0 at the surface to zero at a depth of 0.4 N. Below lies a layer of compensatory current, which has a direction opposite to the wind. . When wastewater is discharged near the coast (which usually takes place), the worst conditions are created in the reservoir with wind along the coast, in the direction of the nearest water intake5 This case is considered further.[ ...]

The currents arising with the participation of friction forces are wind currents caused by temporary and short-lived winds, and drift currents caused by steady, long-term winds. Wind currents do not create a level slope, while drift currents lead to a level slope and the appearance of a pressure gradient, which determine the occurrence of a deep gradient current in coastal areas.[ ...]

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

During intense storms coinciding with spring tides, sediment transport rates are at their maximum, as currents are intensified by storm surge and/or wind currents (Fig. 9.50, B). In the proximal zones, erosion results in shallow channels, flat erosional surfaces, and residual pebble deposits. In downstream zones, there is a rapid migration of bedforms, including the formation of crescent dunes with distal deposition of thinner storm sand layers. The resulting sedimentary cover is more likely to survive.[ ...]

In addition to wind currents, two more additional phenomena can play an important role in the hydrodynamic pattern of inland water bodies. Under the action of the wind, the isobaric surfaces acquire an inclination, which in turn causes a change in the angle of inclination of the thermocline and the level of the surface. With the cessation of wind in the reservoir, long-term oscillations occur, known as seiches (Fig. 4.17).[ ...]

Since the wind currents depend on the wind regime in that “or other area, the above parameters are taken for the European part. USSR according to the data of meteorological stations and taking into account the increase in wind speed by about 20%. All calculations are made for wind currents at average speed wind 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 was 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, on an installation whose design predetermined the formation of water circulation in a horizontal plane under the action of wind.[ ...]

In a unidirectional wind current, a change in the vertical distribution of OR was clearly observed with a change in the H/c ratio. At H/k 1.0, the values ​​of st decreased from the water surface, where they were greatest, to the horizon (0.2...0.4)H, and then decreased very smoothly or remained practically unchanged right down to the bottom (see Fig. Fig. 3.7). Values ​​at Н/к 1.0 gradually decreased from the surface to the horizon (0.5 ... 0.8)R, and then gradually 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 H / k to 0.4-0.6 led to the alignment of the distribution of st along the vertical.[ ...]

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

Under natural conditions, wind currents are often disturbed by sei-shev, runoff or residual currents. In this regard, according to measurement data, it is rarely possible to obtain diagrams with a smooth change in velocity along the vertical and a direction of flow that is stable in time at different horizons. Only in cases where the currents on individual verticals are measured for a long time and these measurements are accompanied by the registration of wind, water level and waves, it is possible to choose from many diagrams those that meet the conditions of quasi-steady wind currents. Measurements of this kind were carried out by expeditionary groups of the State Geophysical Institute at the Kairakkum, Kakhovka and Kremenchug reservoirs and at several small lakes. Several plots 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 current, vortex formations with a vertical or inclined axis of rotation occur more often than in a unidirectional one. They are more clearly expressed and more often occur in the zone of action of the compensatory flow. The largest of the vortex formations with a vertical axis of rotation penetrate the entire thickness of the compensation flow zone (Fig. 2.5) and even partially penetrate into the drift current zone.[ ...]

For the full development of the wind current, in contrast to the excitement, it is necessary that the entire water mass of the reservoir come into motion in accordance with the input of wind energy and energy losses: friction in the water column. Therefore, with the same speed, wind and other equal conditions, the duration of the development of the wind current will be longer in one of the reservoirs in which there is more depth, and the time of rise of waves in these reservoirs will be approximately the same. This circumstance can be confirmed by an example. The duration of the development of the wind current, for example, in the lake. Baikal (Rav = 730 m) with a wind speed of -10.5 m/s, according to the above calculations, is 60-110 hours, and the duration of the development of waves for the central alignment, according to the work, is about 18 hours[ ...]

Although tidal currents are bidirectional, rectilinear or circular, they carry out predominantly unidirectional sediment transport 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 flow 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-Western Europe, the hydrodynamic regime of which is in partial equilibrium with the forms of the bottom surface and the directions of sediment transport.[ ...]

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

When studying the vertical structure of wind currents, the greatest attention has to be paid to the largest eddy formations, since they have the greatest energy of motion and determine, for example, processes such as vertical mixing of waters.[ ...]

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

As is known (see § 73), with depth, the speed of the current decreases and its direction changes. At some depth, the current may have a direction opposite to the surface. The change in the direction of the current to the opposite is not always the result of the influence of the geostrophic effect. In water bodies limited in size, this is more often the result of the formation of a compensatory current. Near the coast, wind currents cause surge or surge phenomena. There is an additional slope of the water surface, directed against the wind. As a result, under the influence of gravity, a deep gradient countercurrent (compensatory current) develops, which contributes to maintaining the balance of water in the lake. Thus, a mixed flow is formed.[ ...]

For quasi-steady unidirectional wind currents, the duration of the existence of large eddy 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 particle trajectories.[ ...]

Some success has been achieved 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 the real parameters (for example, the 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 in the presence of level differences between the reservoir and the bay and act mainly along the longitudinal axis of the bay. The role of wind currents in such conditions is insignificant, especially in the presence of high shores.[ ...]

Quite a lot of information about the change in the surface speed of wind currents in coastal shallow areas was obtained at the State Geophysical Institute mainly from aerial measurements, and information about the change in the average speed on the verticals - from measurements by deep floats from boats. The analysis performed earlier showed that most of the measurements indicate a slight change in the speed of wind currents along the width of the zone . However, with a differentiated consideration of the previously obtained and new current measurement data, it was possible to identify differences in the trends in velocity changes across the width of the coastal shallow water zone for different wind directions relative to the coast line.[ ...]

It was shown above that at the final stages of the development of a wind current unidirectional in depth in the water column, elliptical eddies are formed, which can cover the entire thickness of the stream, and in the longitudinal direction exceed the depth by 8–10 times. 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 of various sizes with vertical or inclined axes of rotation. Predominantly the same structural features prevail in unidirectional wind currents and at the quasi-steady stage of the development of the process.[ ...]

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

Based on the consideration of the proposed methods for establishing criterion relationships, it can be seen that the physical modeling of wind currents is a very laborious task in terms of both the experimental technique and the recalculation of simulation data to natural conditions. However, experiments performed earlier show that the costs of labor and funds are most often paid off by the great value of the materials obtained.[ ...]

As an example, in fig. 4.3, the bold line shows the course of the median, and the dashed line shows the limit 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 of the lower boundary of the drift current increased in cases of an increase in the size of eddy formations and when the developing wind current was superimposed on the residual current.[ ...]

The conducted studies have shown that when sewage containing pollutants enters and is dispersed with the help of special technical devices or currents, chemical compounds are transformed. Contaminants 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, one should take into account the effect of chemical compounds on the seashore, as well as the atmosphere when foam is carried away by wind currents in the form of aerosols. The latter factor has been poorly studied, so it is difficult to assess its impact at present. Gas and dust emissions, as well as wastewater, go through similar stages, and in the end, as a result of interaction at the water-air interface, individual compounds actively dissolve.[ ...]

The validity of this opinion can be seen when considering the chronograms (Fig. 3.2) for three different lakes: Ladoga, Beloye and Balkhash. On the first two lakes during the recording period, wind currents of relatively stable directions prevailed (Fig. 3.2a, b), and on the third lake - seiche currents with a period varying from 3 to 12 hours (Fig. 3.2). Fluctuations in the speed and direction of the current are clearly expressed on all chronograms, despite the fact that the first of these characteristics was averaged over 176 s. The presented chronograms allow us to conclude that instantaneous speeds under natural conditions vary even more widely than shown in Fig. 3.2. However, obtaining instantaneous values ​​of the velocity and direction of the flow in natural conditions, especially in the zone of wave oscillatory movements, 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 the conditions of seiche currents prevailing, but is close to the plots obtained from measurements under the action 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 with different directions in depth is usually 4–6 times the width of the zone covered, for example, at the windward coast by a wind current unidirectional in depth. The cross-sectional area covered by the gradient current under such conditions is 2.0-2.5 times larger than the cross-sectional area covered by the drift current. The reasons for these differences are the differences in the degree of turbulence of the current, which is significantly greater in the zone of action, which is multidirectional in depth, than in the zone of action of a unidirectional flow.

Navigators learned about the presence of ocean currents almost immediately, as soon as they began to surf the waters of the oceans. 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 that, not only sailors, but also scientists began to pay close attention to ocean currents and strive to explore them as best and as deeply as possible.

Already in the second half of the XVIII century. sailors studied the Gulf Stream quite well and successfully applied their knowledge in practice: from America to Great Britain they went with the flow, and in reverse direction kept a certain distance. This allowed them to be two weeks ahead of ships whose captains were not familiar with the terrain.

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

It has been established that water flows do not move straight, but deviating slightly to the side, they obey the Coriolis force. In the Northern Hemisphere they almost always move clockwise, in the Southern Hemisphere it is vice versa.. 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 they are set in motion by a sufficient number of factors - the wind, the rotation of the planet around its axis, the gravitational fields of the Earth and the Moon, the bottom topography, the outlines of continents and islands, the difference in temperature indicators of water, its density, depth in various places of the ocean and even its physico-chemical composition.

Of all the types of 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 the western eastbound. These trade winds form huge streams 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 air masses side). Most, colliding with the continents and islands, turns to the north or south.

Warm and cold water streams

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

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

• If the temperature indicators of the water flow coincide with the temperature of the waters surrounding it, 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 the large flow of rivers, 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 the tropics to subpolar latitudes, such as the Gulf Stream.

Main water flows

On the this 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 the currents of the Arctic Ocean move at the same speed - 50 cm / s, three of them, namely the West Greenland, West Svalbard and Norwegian, are warm, and only the East Greenland belongs to the cold current.

But almost all the oceanic currents of the Indian Ocean are warm or neutral, while the Monsoon, Somali, West Australian and the Cape of Needles (cold) move at a speed of 70 cm / s, the speed of the rest varies from 25 to 75 cm / s. The water flows of this ocean are interesting because, along with the seasonal monsoon winds, which change their direction twice a year, ocean rivers also change their course: in winter they mainly flow west, in summer - 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 streams located in the north move clockwise, in the south - against it.

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, splitting along the road into several side streams. When the waters of the Gulf Stream end up in the Barents Sea, they enter the Arctic Ocean, where they cool and turn south in the form of a cold Greenland current, after which at some stage they deviate to the west and again adjoin 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 most of our planet.

For example, the trade winds move warm water from the western tropical coasts to the eastern ones, which is why the western part of the Pacific Ocean in the tropical zone 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 the deep ocean waters were almost motionless. But soon, special underwater vehicles discovered both slow and fast-flowing water flows at great depths.

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

A similar movement of water flows, but already in Atlantic Ocean, found by Soviet scientists: the width of the Lomonosov current is about 322 km, and maximum speed at 90 km / day was recorded at a depth of about one hundred meters. After that, another underwater stream was discovered in the Indian Ocean, however, 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 of which is the question of why they appeared, how they formed, and whether the entire ocean area 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 cannot 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 powered by solar energy. This machine creates a continuous water exchange between the surface and deep layers of the ocean, providing it with oxygen dissolved in water and affecting the life of marine life.

This process can be traced, for example, by considering the Peruvian current, which is located in pacific ocean. Thanks to the rise of deep waters, which raise phosphorus and nitrogen, animal and plant plankton successfully develop on the ocean surface, as a result of which the food chain is organized. Plankton is eaten by small fish, which, in turn, becomes a victim of larger fish, birds, marine mammals, which, with 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 temperature environment rises by several degrees, causing warm tropical showers to fall on the ground, which, once in the ocean, kill fish accustomed to cold temperatures. The result is deplorable - a huge amount of dead small fish ends up in the ocean, large fish leave, fishing stops, birds leave their nests. As a result, the local population is deprived of fish, crops that were beaten by downpours, and profits from the sale of guano (bird droppings) as fertilizer. It can often take several years to restore the former ecosystem.

wind currents

currents of surface waters of oceans and seas, resulting from the action of wind on the water surface. Wind flow develops under the combined influence of friction forces, turbulent viscosity, pressure gradient, deflecting forces of the Earth's rotation, and so on. The wind component of these currents, without taking into account the pressure gradient, is called the drift current. Under conditions of winds that are stable in direction, powerful wind currents develop, such as the North and South Trade-wind currents, the course of westerly winds, and others. N. S. Lineikin, American G. Stoml.