How are waves formed? Surf condition reports and wave formation forecasts are compiled based on the results scientific research and weather modeling. In order to find out what waves will form in the near future, it is important to understand how they are formed.

The main cause of wave formation is wind. waves, the best way suitable for surfing, are formed as a result of the interaction of winds above the surface of the ocean, away from the coast. The action of wind is the first stage of wave formation.

Winds blowing offshore in a particular area can also cause waves, but they can also lead to deterioration in the quality of breaking waves.

It has been found that winds blowing from the sea tend to produce unstable and uneven waves as they affect the direction of wave travel. The winds blowing from the coast serve, in a certain sense, as a kind of balancing force. The wave travels many kilometers from the depths of the ocean to the shore, and the wind from land has a “braking” effect on the face of the wave, allowing it to avoid breaking longer.

Low pressure areas = good waves for surfing

Theoretically, areas low pressure contribute to the formation of good, powerful waves. In the depths of such areas, wind speeds are higher and wind gusts form more waves. The friction created by these winds helps create powerful waves that travel thousands of kilometers until they hit their final obstacles, the coastal areas where people live.

If winds generated in areas of low pressure continue to blow on the ocean surface for a long time, the waves become more intense as energy accumulates in all the resulting waves. In addition, if winds from areas of low pressure affect a very large area of ​​​​the ocean, then all the resulting waves concentrate even more energy and power, which leads to the formation of even larger waves.

From ocean waves to surf waves: the seabed and other obstacles

We have already analyzed how disturbances in the sea and the waves generated by them are formed, but after “birth” such waves still have to travel a huge distance to the shore. Waves originating in the ocean have a long journey to travel before they reach land.

During their journey, before surfers even get on them, these waves will have to overcome other obstacles. The height of the emerging wave does not match the height of the waves the surfers are riding.

As waves move through the ocean, they are exposed to irregularities in the seabed. When gigantic moving masses of water overcome rises on the sea floor, total the energy concentrated in the waves changes.

For example, continental shelves far from the coast offer resistance to moving waves due to the force of friction, and by the time the waves reach coastal waters, where the depth is shallow, they have already lost their energy, strength and power.

When waves move through deep-sea waters without encountering obstacles on their way, they usually crash into coastline with great strength. Depths ocean floor and their changes over time are studied through bathymetric studies.

Using the depth map, it is easy to find the deepest and shallowest waters of the oceans of our planet. Studying the topography of the seabed has great importance to prevent shipwrecks and cruise liners.

In addition, studying the structure of the bottom can provide valuable information for predicting the surf at a particular surf spot. When waves reach shallow water, their speed usually decreases. Despite this, the wavelength shortens and the crest increases, resulting in an increase in wave height.

Sandbanks and wave crest increase

Sandbanks, for example, always change the nature of beach breaks. This is why the quality of waves changes over time, for better or worse. Sandy irregularities on the ocean floor allow the formation of distinct, concentrated wave crests from which surfers can begin their slide.

When a wave encounters a new sandbar, it will typically form a new crest, since such an obstacle causes the crest to rise, that is, the formation of a wave suitable for surfing. Other obstacles to waves include groins, sunken vessels, or simply natural or artificial reefs.

Waves are generated by the wind and as they travel are influenced by the topography of the seabed, precipitation, tides, rip currents off the coast, local winds and bottom irregularities. All these weather and geological factors contribute to the formation of waves suitable for surfing, kitesurfing, windsurfing and boogie surfing.

Wave forecasting: theoretical foundations

• Long-period waves tend to be larger and more powerful.
• Waves with short period, as a rule, smaller and weaker.
• The wave period is the time between the formation of two clearly defined crests.
• Wave frequency is the number of waves passing through a certain point in a certain time.
• Big waves move fast.
• Small waves move slowly.
• Intense waves form in areas of low pressure.
• Low pressure areas are characterized by rainy weather and cloudiness.
• For regions high pressure characteristic warm weather and clear skies.
• Larger waves form in deep coastal areas.
• Tsunamis are not suitable for surfing.

Ocean water is in constant movement. Most often, people observe waves on its surface. But in fact, the entire thickness of water moves continuously - from the surface to the deepest layers.

The movement of water is caused different forces: space, atmospheric, intraterrestrial (earthquakes, underwater volcanic eruptions), intraoceanic (differences in temperature, salinity and water density). All movements of water in the ocean are divided into two types - waves and currents.

The highest part of the wave is the crest, the lowest is the bottom. The main characteristics of a wave are its length and height. Determine what wavelength and height are.

Rice. 123. Wave elements

What are waves? The word “sea” most often evokes a picture of waves rolling onto the shore. However, if you go out to sea on a boat and put its bow to the wave, you will notice that the waves only raise and lower the boat, without bringing it closer to the shore. This means that the water on which the boat floats also sways in one place. Consequently, while waves run along the surface of the water, the water itself, or rather its particles, only oscillates up and down (Fig. 123).

Waves are the oscillatory movements of water.

There are deep and surface waves. Deep waves arise at the boundaries of layers of water with different densities. Such waves are a common occurrence at any depth of the oceans, they are unsafe for divers, submarines, large ocean liners with deep draft.

Surface waves are formed under the influence of winds, underwater earthquakes, and tides.

Wind waves. Wind waves arise from the friction of wind on water. When there is a weak wind, small waves - ripples - appear on the surface of the water. In a very strong wind - a storm - their height can reach the height of a five-story building.

Most often, storms occur in the northern parts of the Pacific and Atlantic oceans, as well as around Antarctica south of 40° S. w. These latitudes are called the “roaring forties.” The wave height here is always more than 3 m. Antarctic waters The highest storm wave was also recorded - 30 m.

On approaching the gently sloping shallow shores, the waves touch the bottom and their height increases. In this case, the wave crest tilts forward and capsizes. This is how the surf arises (Fig. 124).

Rice. 124. Surf on the sea coast

The surf washes away beaches and creates shallows of sand, pebbles and other sediment.

When encountering steep, deep shores, the wave hits the high shore with tremendous force. Because of great strength The impact destroys the rocks and the high bank retreats. On such coasts, people build special breakwaters to protect ports and other structures.

The impact of a storm wave on a steep bank can be compared to the force of a car traveling at 80 km/h hitting a concrete wall.

Tsunami. During strong underwater earthquakes, vibrations earth's crust transmitted to water. At the same time, special waves are formed on the surface of the oceans - tsunamis (Fig. 125). IN open ocean the height of such waves is small - 1-2 m with a length of up to 600 km. Therefore, they are safe for ships and even almost invisible. Spreading at a speed of 400-800 km/h, they reach the coast.

Rice. 125. The occurrence of a tsunami

When entering shallow water, due to the proximity of the bottom, the height of the tsunami increases to 10-20 m. In narrow bays and bays - up to 35-50 m, hence their Japanese name “tsunami” - “ a big wave, flooding the bay." Before a tsunami arrives, the sea recedes so far that it becomes invisible. And then giant water shafts collapse on the coast, washing away and destroying everything in their path (Fig. 126).

Rice. 126. Consequences of the tsunami

Tidal waves (tides). Residents sea ​​coasts They know well that the water level in the sea rises and falls 2 times a day. When the water rises - the tide - the water comes onto land. During low tide, the bottom strip becomes dry. The reason for the ebb and flow of the tides is the attraction of ocean waters by the Moon and the Sun.

In the open ocean, a tidal wave is almost invisible. But, running onto the shore, it floods it, i.e. the tide occurs. When water rises in one place on Earth, its level falls in another. The tide is low there.

Rice. 127. a - tides; b - low tides

On the side of the Earth opposite which the Moon is located, the water seems to swell and form a giant, gentle shaft. It follows the Moon around the entire globe.

Rice. 128. The magnitude of tides in the World Ocean

The magnitude of the tides depends on various reasons: on the depth and shape of the seabed, on the height and contours of the coast. The highest tides are recorded off the coast North America in the Bay of Fundy - 18 m. In our country, the highest tide height in the Penzhina Bay of the Sea of ​​Okhotsk is 13 m (Fig. 128). For safe navigation, accurate data on the time of occurrence and height of tides in the seaports of the world is necessary. This is reflected in special tide tables.

Questions and tasks

1. Name the main types of water movements in the ocean.
2. What are the main reasons for the formation of waves?
3. Why do ships try to take shelter in the bay during a storm, and go further out into the open sea during a tsunami?
4. Using Figure 128, determine where the highest tides are in Russia.

There is no sea without waves; its surface always fluctuates. Sometimes these are just light ripples on the water, sometimes rows of ridges with cheerful white caps, sometimes menacing waves carrying clouds of spray. Even the calmest sea “breathes”. Its surface seems completely smooth and shines like a mirror, but the shore is licked by quiet, barely noticeable waves. This is the ocean swell, the harbinger of distant storms. What are the main reasons for the occurrence of this natural phenomenon?

For scientific, and most importantly, for practical purposes, you need to know everything about waves: their height and length, the speed and range of their movement, the power of an individual shaft and the energy of the agitated sea. You need to know the depth at which the wave movement of the water is still felt, and the height of the splashes thrown by the waves.

First wave measurements Mediterranean Sea made in 1725 by the Italian scientist Luigi Marsigli. At the turn of the 18th and 19th centuries, regular observations of sea ​​waves and their measurements were carried out during long voyages across the World Ocean by Russian captains I. Krusenstern, O. Kotzebue and V. Golovin. These navigators and scientists had to be content with limited technical capabilities of that time and develop and apply research methods themselves.

Nowadays, waves are studied using complex and very precise instruments that operate automatically and provide information in the form of columns of ready-made digital data.

The easiest way to measure waves is near the shore in a shallow place. To do this, just stick a foot rod into the bottom. With a chronometer in hand and notebook, it is easy to find out the height of the wave and the time between the approach of two waves. Using several of these measuring sticks, you can also determine the wavelength and thus calculate its speed. On the high seas things become much more complicated. For this purpose, it is necessary to construct a complex structure consisting of a large float, which is sunk to a certain depth and secured on a long cable using a dead anchor. The submerged float serves as a place for attaching the same measuring ruler.

The readings of such an installation are not highly accurate; in addition, it has another significant drawback: the observer must always be close to the footpole, while waves and wind tend to carry his ship to the side. In the days of the sailing fleet, it was practically impossible to keep the ship in one place, and therefore the height of the waves was measured while moving. For this purpose, the mast of one of the two ships participating in the measurements, which followed each other at a short distance, was turned into a measuring ruler. The observer, standing at the stern of the leading ship, watched how the crest covered the mast of the second ship from him, and thus assessed the height of the wave.

At the beginning of the twentieth century, wave heights began to be measured using a very sensitive barometer (altimeter). This device accurately records the rise and fall of the ship in the waves, but, unfortunately, it also senses all sorts of interference, in particular changes in barometric pressure, which quickly occur and are repeated repeatedly in strong winds.

Pressure gauges lying on the bottom react much more accurately to disturbances. As a wave passes, the pressure above the device changes, and the signals are transmitted via wires to land or recorded directly at the bottom by a recorder. True, in this way it is possible to measure wave heights only in shallow water, where the depth is comparable to the height of the waves. At great depths, in accordance with Pascal's law, the pressure equalizes and with increasing depth depends less and less on the height of the waves.

Very accurate and varied wave data is obtained by processing stereoscopic photographs of the ocean surface. To do this, two synchronously operating cameras are placed on different masts of one ship, on the ends of the wings of an aircraft flying low over the sea, or even on two aircraft flying on a parallel course. By photogrammetric processing of images, the relief of the sea is restored at the time of photographing. It looks like a picture of frozen waves. On this paradoxical model of a turbulent but motionless sea, any necessary measurements are made.

The main force causing disturbances is the wind. In calm weather, especially in the mornings, the surface of the sea seems mirror-like. But as soon as even the weakest wind rises, turbulences arise in it due to the friction of the air on the surface of the water. As a result of the formation of vortices over a smooth water surface, the pressure becomes uneven, which leads to its distortion - ripples appear. Behind the tops of the ripples, the process of vortex formation intensifies, and ultimately this leads to the formation of waves propagating in the direction of the wind.

A weak wind disturbs only the thinnest layer of water; the wave process is determined by surface tension. When the wind increases, when the length of the waves reaches approximately 17 millimeters, the resistance of surface tension is overcome and the waves become gravitational. In this case, the wind has to fight against the force of gravity. If the wind turns into a storm, the waves reach gigantic sizes.

Long after the wind subsides, the sea continues to swell, forming swells. Wind waves also turn into swells when they move outside the area where the hurricane is raging. Low and long swell waves are invisible in the open sea. Approaching the shallows, they become higher and shorter, forming a powerful surf near the shore. In a vast area of ​​the ocean, a storm is always raging here and there. The swell waves scatter from it in all directions over a huge distance, and therefore the swell of the ocean never stops.

When air currents flow around a wave surface, infrasounds arise, which Academician V. Shuleikin called “the voice of the sea.” Infrasounds, originating above the waves as a result of the disruption of vortices from the wave crests, propagate in the air at the speed of sound, that is, faster than the waves. Due to its low frequency, the “voice of the sea” is weakly absorbed by the atmosphere and can be detected at a great distance by special instruments. These infrasound signals serve as a warning of an approaching storm.

The height of waves in the open sea can reach significant values, and it depends, as already mentioned, on wind speed. The highest wave that could be measured in Atlantic Ocean, turned out to be equal to 18.3 meters.

In 1956 in the southwestern part Pacific Ocean On the Soviet ship Ob, which makes regular scientific voyages to Antarctica, waves 18 meters high were also recorded. Typhoons of the Pacific Ocean contain enormous waves of thirty meters in height.

To a person standing on the deck of a ship in a stormy sea, the waves seem very steep, hanging like walls. In fact they are flat. Usually the wavelength is 30-40 times greater than its height, only in rare cases the ratio of the wave height to its length is 1:10. Thus, the greatest steepness of waves in the open sea does not exceed 18 degrees.

The length of storm waves does not exceed 250 meters. In accordance with this, their speed of spread reaches 60 kilometers per hour. Swell waves, like longer ones (up to 800 meters or more), roll at a speed of about 100 kilometers per hour, and sometimes even faster.

It must be borne in mind that at this gigantic speed it does not move water mass, which forms a wave, but only its form, more strictly, the energy of the wave. A particle of water in a rough sea makes not translational, but oscillatory movements. Moreover, it oscillates in two directions simultaneously. In the vertical plane, its fluctuations are explained by the difference in levels between the wave crest and its base. They arise under the influence gravitational forces. But since when the ridge is lowered to the level of the sole, the water is pressed to the sides, and when it rises it returns to its original place, the water particle involuntarily performs oscillatory movements also in the horizontal plane. The combination of both movements leads to the fact that water particles actually move in circular orbits, the diameter of which at the surface is equal to the height of the wave. More precisely, they describe spirals, since under the influence of the wind the water also receives forward motion, due to which, as was said, sea currents arise.

Only the speed of movement of particles in orbits significantly exceeds the speed of movement of the centers of these orbits in the direction of the wind.

The oscillatory movements of water particles quickly decrease with depth. When the wave height is 5 meters ( average height waves during a storm), and the length is 100 meters, then at a depth of 1–2 meters the diameter of the wave orbit of water particles is 2.5 meters, and at a depth of 100 meters it is only 2 centimeters.

Short, steep waves disturb deep waters less than long, flat waves. The longer the wave, the deeper its movement is felt. Sometimes fishermen who set their lobster traps in the English Channel at a depth of 50-60 meters found them with half-kilogram stones after a storm. It is clear that these were not jokes of the lobsters: the stones are rolled into the trap by deep waves. In some underwater photographs, sand ripples can be seen on the bottom down to a depth of 180 meters, resulting from oscillatory movements bottom layers of water. This means that even at such a depth, the disturbance of the ocean surface is still felt.

Under the influence of wind, a huge amount of energy accumulates in the surface layers of the sea, which has not yet been utilized.

Storm waves 5 meters high and 100 meters long at each meter of their crest develop a power of over three thousand kilowatts, and the energy of a square kilometer of a raging sea is measured in billions of kilowatts per second. If a way is found to use the energy of the wave movement of the ocean, humanity will forever get rid of the threat of the energy crisis. In the meantime, this formidable force brings people nothing but trouble. It's about not at all about such trifles as seasickness, although many who have experienced it do not share this opinion. Storm waves, even very gentle ones, pose a formidable danger to modern ocean-going ships, the roll of which during rolling reaches such a magnitude that the ship can capsize.

There are countless examples of this. L. Titov in his book “Wind Waves on the Oceans and Seas” provides data on the victims swallowed up by the sea on December 5-8, 1929.

For four days, a 10-12 force storm raged off the coast of Europe. On the very first day, a huge wave capsized the Duncan steamship with a displacement of 2,400 tons off the coast of England. Then a floating dock with a displacement of 11 thousand tons was flooded by waves and sank off the coast of Holland. In the waves of the English Channel, two steamships with a displacement of 5 and 8 thousand tons sank with their entire crew, the English steamer Volumnia with a displacement of 6,600 tons, as well as several dozen other small ships, perished with their entire crew. Even the huge transatlantic liners were badly battered.

In such weather, sometimes even sailors who are accustomed to the hardships of the sea cannot stand it; one can imagine what it is like for ordinary passengers, about whose experiences Rudyard Kipling spoke very well: “If there is green darkness in the glass of the cabin, and the spray flies up to the chimneys, and rises every minute, then bow, then stern, and the servant pouring soup suddenly falls into the cube, if the boy is not dressed in the morning, not washed and his nanny is lying like a sack on the floor, and his mother’s head is cracking from pain, and no one laughs, drinks or eats, - then we understand what the words mean: forty Nord, fifty West!”

Many ocean-going ships are now equipped with stabilizers. If necessary, four wings, similar to fish fins, extend from the underwater part of the hull. Roll meters are installed in several places on the ship, and their readings are sent via wires to a special computing device, which controls the movement of the hydrofoils. As soon as the ship tilts slightly to the side, the wings begin to move. Obeying the signals, each of them rotates at a certain angle, and their joint actions align the position of the body.

The operation of the stabilizers somewhat slows down the speed, but does not allow the ship to fall from side to side, although, unfortunately, they do not prevent pitching.

In the practice of navigation, a fairly simple but very correct technique has been used to calm a raging sea since ancient times. It is known that an oily liquid poured overboard instantly spreads over the surface and smoothes out the waves, and also reduces their height. Animal fat, such as whale blubber, produces the best results. Less viscous vegetable and mineral oils are much weaker.

The mechanism of the effect of oily liquids on waves was unraveled by Academician V. Shuleikin. He found that even a thin layer of oil film absorbs a significant portion of the energy of the vibrational movements of water.

For the same reason, excitement decreases during heavy rain or hail, as well as in the area floating ice. Ice, hail and raindrops delay the orbital movements of water particles and “quench” excitement. Currently, due to the need to take care of the cleanliness of the ocean, pouring oil barrels overboard is no longer practiced.

The waves bring a lot of troubles, sometimes turning into real disasters, to the shore. Even moles, dams and breakwaters do not always protect harbors. They reliably close the entrance to relatively short storm waves, but gentle swells with a height of only 30-40 centimeters penetrate into the harbor unhindered, and then all the water in it begins to move. Vessels at anchor begin to twitch randomly, turn their hulls either across or against the wind, and collide with each other. And those standing at the pier are tearing the mooring lines.

As the wave approaches the shore, it changes its shape and height as it begins to “feel” the bottom. From this moment on, its front slope becomes steeper and steeper, becomes completely vertical, and finally the ridge begins to hang forward and falls onto the shallows in a cascade of spray and foam.

At great depths, significant masses of water are involved in the wave process, even when the wave is not very high. When such a wave enters shallow water, the mass of water decreases, but the energy, if we neglect friction losses, remains the same, while the amplitude of the wave should increase. The water particles that form the wave, when approaching the shore, change the orbit of their movement: from circular it gradually becomes elliptical with a large horizontal axis. At the very bottom, these ellipses become so elongated that water particles begin to move horizontally back and forth, carrying sand and stones with them. Anyone who has swam during the surf knows how painfully these stones hit the legs. If the surf is strong enough, it carries with it boulders that can knock a person off his feet.

Even people on land can get into trouble. In 1938, hurricane waves swept away about 600 people from the coast of England forever. In 1953, 1,500 people died under similar circumstances in Holland.

No less tragic consequences are caused by the so-called single baric waves that arise as a result of a sharp drop atmospheric pressure. Having traveled several hundred, or even thousands of kilometers from the place of origin, such a wave suddenly hits the shore, washing away everything in its path. In 1900, a single wave that struck the coast of the North American state of Texas, in the city of Galveston alone, carried 6 thousand people out to sea. The same wave in 1932 killed 2,500 people—more than half the residents of the small Cuban town of Santa Cruz del Sur. In September 1935, a single pressure wave 9 meters high rolled onto the coast of Florida, taking 400 lives.

It has long been known that man can use even the most formidable forces of nature to his advantage. Yes, residents Hawaiian Islands, having figured out the nature of the rolling waves of the surf, managed to “ride” them. Returning from fishing, they approach the breakers area, deftly place the boat on the crest of a wave, which in a matter of minutes carries them to the shore.

Wave riding is also an ancient national sport of the islanders. A water ski is made from a wide, two-meter long board with rounded edges. The swimmer lies down on it and rows his hands towards the sea. It is very difficult to overcome the surge in this way, but local residents are well aware of the places of the so-called rip currents and skillfully use them.

Rip currents are a by-product of the surf, causing the water level near the shore to rise slightly. The accumulated water tends to go back to the sea, but its outflow is prevented by new incoming waves. This cannot continue indefinitely; sooner or later the surge waters are broken by the surf waves in some places and rush towards them in a fast narrow stream into the open sea.

An inexperienced swimmer, caught in a rip current and seeing that he is being carried away from the shore, tries to swim towards him, but soon gets tired and then easily becomes a victim of the sea. Meanwhile, it is very easy to escape; to do this, it is enough to swim a few meters not to the shore, but along it and get out of the danger zone.

Athletes on boards in rip currents go beyond the breakers in a few minutes and turn back there. Having caught the moment when the crest of a collapsing wave begins to grow, becoming covered with white foam, the brave swimmer rushes towards it and stands on the board in full height. Deftly controlling his sports equipment, he quickly rushes on the crest of a wave, surrounded by streams of bubbling foam. This sport has also taken root in Australia, where swimmers on boards not only have fun - they have saved many people who were attacked by sharks or began to drown.

Introduction

There is no sea without waves; its surface always fluctuates. Sometimes these are just light ripples on the water, sometimes rows of ridges with cheerful white caps, sometimes menacing waves carrying clouds of spray. Even the calmest sea “breathes”. Its surface seems completely smooth and shines like a mirror, but the shore is licked by quiet, barely noticeable waves. This is the ocean swell, the harbinger of distant storms. What are the main reasons for the formation of waves, and how do sea waves affect a person and his activities?

Relevance this issue increases constantly, in proportion to the development of human civilization and the development of sea spaces.

This work is intended to help in resolving issues related to wave processes and to describe in as much detail as possible everything connected with them, their nature and activity.

Types of sea disturbances

Sea disturbances can be divided into several types. These types are distinguished according to the characteristics of each of them.

Wave classification

There are many classifications of waves, differing in their physical nature, according to a specific distribution mechanism, according to the distribution medium, etc.

According to the nature of the wave-forming forces, waves are divided into 2 types: free and forced.

Free waves are not directly influenced by the forces that cause them, but are excited by initial or boundary disturbances. Depending on the nature of the disturbing force, the following subtypes of free waves are distinguished:

wind waves caused by initial disturbance - the action of wind tension;

seismic waves caused by underwater earthquakes and volcanic eruptions (tsunamis);

waves caused by the dynamic instability of large-scale currents.

Forced waves are under the direct influence of the forces that cause them. They are divided into 3 subtypes:

wind waves excited by the action of wind on the water surface;

baric waves excited by an atmospheric pressure gradient (see Anemobaric 1 waves);

tidal waves excited by the tidal forces of the Moon and the Sun.

Depending on the stratification of waters, all waves are divided into 2 types: surface and internal.

Surface waves have a maximum amplitude on the free surface, and their characteristics do not depend on the stratification of water by density. With increasing depth, the amplitude of such waves decreases according to a law close to exponential. Buoyancy forces play a significant role in the formation of internal waves; the characteristics of these waves significantly depend on the stratification and vertical stability of the waters. The amplitude of internal waves is inversely proportional to the vertical gradient of water density.

Anemobaric waves - Forced long gravitational or inertial-gravitational waves arising under the influence of wind and atmospheric pressure. They can be progressive or standing. The periods of anemobaric waves range from several minutes to a day, the height in the open sea does not exceed 1 m. coastal zone long waves of anemobaric origin make a significant contribution to storm surges, sometimes leading to catastrophic floods.

Depending on the degree of participation in the formation of surface and internal waves of gravity and forces caused by the rotation and sphericity of the Earth, classes of waves are distinguished. The division into classes is based on the ratio of the period of waves T to the period of inertial oscillations Тр = р/шsinт, where у is the angular velocity of the Earth's rotation; c -- geogr. latitude of the place. The following classes of waves are distinguished:

gravitational, in the formation of which gravity forces play a dominant role (T<

inertial-gravitational, for the formation of which both gravity and the deflecting force of the Earth's rotation are essential (T<Тp);

inertial, or gyroscopic, in the formation of which the dominant force is the Coriolis force (T = Tp);

planetary (so-called Rossby waves), caused by the combined effect of rotation and sphericity of the Earth (T>>Tr).

The class of inertial waves in internal waves is not distinguished, since they propagate mainly in the horizontal plane and do not depend on the stratification of waters. In the classes of surface and internal gravity waves, types are distinguished: short waves, the length of which is significantly less than the depth of the sea, and long waves or waves of shallow water, the length of which is much greater than the depth of the sea.

In the class of planetary waves, short and long waves are divided depending on the ratio of wavelength to pool length. When this ratio is small, the waves are short, when it is high, the waves are long.

In the classes of inertial-gravity and inertial waves, types are not distinguished.

Finally, according to the nature of their propagation, waves are divided into progressive (progressive or, as they are also called, traveling) and standing. Translational waves (eg wind waves) have a visible movement of shape. Standing people do not have such movement. In real ocean conditions, the observed waves are a complex combination of free and forced, standing and forward wave systems of various origins. The nature of wave processes is especially complicated in coastal areas due to the influence of the topography of the bottom and shores, reflection, diffraction and refraction of sea waves.

Wave is a form of periodic, continuously changing motion in which water particles oscillate around their equilibrium position.

If, for some reason, water particles are removed from the equilibrium position, then under the influence of gravity they will strive to restore the disturbed equilibrium. In this case, each water particle will perform an oscillatory motion relative to the equilibrium position, without moving along with the visible form of wave motion.

Waves can arise under the influence of various reasons (forces). Depending on the origin, i.e., on the causes that caused them, the following types of sea waves are distinguished.

1. Friction waves (or friction waves). These waves primarily include wind waves, which arise when the wind acts on the sea surface. These also include the so-called internal, or deep, waves, which arise at depths when a layer of water of one density moves over a layer of water of another density.

Research has established that if another liquid of a different density moves over a liquid of one density, then waves are formed on the surface separating both liquids. The size of these waves depends on the difference in the speed of movement of liquids in relation to each other and the difference in the density of the two media. This also applies to the case of air movement over water. This is why waves arise both in the depths of the ocean and in the high layers of the atmosphere, if there is a similar movement of two water or air masses of different densities.

1. Baric waves occur when atmospheric pressure fluctuates. Fluctuations in atmospheric pressure cause rises and falls of water masses, in which water particles strive to occupy new equilibrium positions, but, having reached them, perform oscillatory movements by inertia.


2. Tidal waves arise under the influence of the phenomenon of ebb and flow of tides.


3. Seismic waves are formed during earthquakes and volcanic eruptions. If the source of an earthquake is located under water or close to the shore, then the vibrations are transmitted to the water masses, causing seismic waves in them, which are also called tsunamis.


4. Seiches. In seas, lakes, and reservoirs, in addition to vibrations of water particles in the form of translational waves, periodic vibrations of water particles only in the vertical direction are often observed. Such waves are called seiches. During seiches, oscillations occur, similar in nature to oscillations, in a periodically rocked vessel. The simplest type of seiche occurs when the water level rises at one edge of the reservoir and simultaneously falls at the other. In this case, in the middle of the reservoir there is a line along which water particles do not have vertical movements, but move horizontally. This line is called the seiche node. More complex seiches are two-node, three-node, etc.

Seiches can occur as a result of various reasons. A wind blowing over the sea for some time in the same direction produces a surge of water at the leeward coast. With the cessation of wind, seiche-like level fluctuations immediately begin. The same phenomenon can occur under the influence of differences in atmospheric pressure in different places in the water basin. Senche fluctuations in sea level are created by seismic vibrations in very small basins (in a harbor, in a bucket, etc.) Seiches can occur during the passage of ships.