How are waves formed? Surf reports and wave forecasts are compiled from 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

In theory, areas of low pressure promote the formation of nice, 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. As gigantic moving masses of water overcome high spots on the seafloor, the total amount of 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 waters without encountering obstacles on their way, they usually hit the coastline with enormous force. The depths of the 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 is of great importance for preventing 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 typically forms 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 and cloudy weather.
• Areas of high pressure are characterized by warm weather and clear skies.
• Larger waves form in deep coastal areas.
• Tsunamis are not suitable for surfing.

Let's talk about the Black Sea waves. Frequent recurrence of strong winds, significant sea size, great depths, and slightly rugged coastline contribute to the development of waves. The highest wave heights in the Black Sea are 14 meters. The length of such waves is 200 meters. On the approaches to Sochi, the maximum wave height is 6 meters and the length is 120 meters.
You can evaluate excitement not only by wave elements (height, length, period), but also by degree.

The degree of excitement is assessed using a special scale. So, for example, on this scale, 1 point - wave height does not exceed 25 centimeters, 2 points - wave height 25-75 centimeters, 3 points - 0.75-1.25 meters, 4 points - 1.25-2 meters. The scale has 9 points in total. You can describe the state of the sea surface during wind waves: 1 point - the appearance of ripples during gusts of wind, 2 points - transparent glassy foam appears on the crests of the waves, 3 points - individual white “lambs” appear on the crests of the waves, 4 points - the entire sea is covered with “lambs” " etc.

The wind force scale (where points correspond to meters per second) has 12 points. The strength of a storm is determined by the strength of the wind. Therefore, the expression “storm 10 points” will be correct, but the expression “storm 10 points” will be incorrect. In the Black Sea, the frequency of strong waves is low. During the stormiest year, waves of 6-9 points are not observed for more than 17 days.

A distinctive feature of the Black Sea waves is their “stability”. This is the so-called swell, which has a longer period of oscillation than a wind wave. Swell is waves observed in light or no wind ("dead swell"). However, the origin of these waves is related to wind activity. Waves formed in the storm zone, which is located at this time in the western part of the Black Sea, may arrive on the Caucasian coast of the sea. On the Caucasian coast, the winds can be weak and the waves can be large. This will be the swell. The existence of swell is associated with the concept of the “ninth wave”, which has long existed among our sailors, known to many from Aivazovsky’s painting. It cannot be said that the idea of ​​a ninth wave was completely without any basis. The fact is that swell waves, as a rule, travel in groups, with the largest waves in the center of the group, and smaller waves at the edges. Some wave of a given group may indeed be much larger than the others, but it will be the third, fifth or ninth, and from which wave to start counting is unknown. Thus, one should not think at all that the ninth wave is the most terrible. By the way, among the ancient Greeks, every third shaft was considered the most dangerous, and among the Romans - every tenth.

Sailors tolerate swell easier than Azov or Caspian wind waves - “bumpiness” with a period of 3-5 seconds. However, the swell has the unpleasant feature that it produces a strong surf near the shore. The wave, almost imperceptible in the sea due to its slight steepness, hits the shore with enormous force.

Video of stormy sea on the Black Sea (Anapa)

Swimming in the sea during a storm is very dangerous. It is usually quite difficult to overcome the breakers zone and get into the open sea, where you can float relatively calmly, rising and falling as each wave passes. It is much more difficult for a tired person to get to the shore again through a barrier of collapsing and foaming waves. Every now and then he is carried back to the sea. There were cases when even people who knew how to swim well drowned here. This is why warning signs are posted on city and resort beaches during storms. It is appropriate to recall here that all animals, jellyfish, sea fleas and other organisms leave the dangerous surf zone before a storm, seagulls fly to the shore, but you can see how some people choose the time of the storm in order to demonstrate their “bravery” by swinging on waves.

The force of waves hitting the shores and structures is enormous. Near Sochi it exceeds 100 tons per square meter. Such impacts produce bursts several tens of meters high. The colossal energy of breaking waves is spent on crushing rocks and moving sediment. Without the influence of waves, river runoff would gradually roll down to depth, but the waves return them to the shore and force them to move along it. For example, along the Caucasian coast of the Black Sea there is a constant flow of sediment. From Tuapse to Pitsunda, waves move 30 - 35 thousand cubic meters of sediment per year.

Where there is a beach, the waves lose most of their energy. Where there is none, they destroy bedrock. During the Great Patriotic War, the erosion of the coast south of the port of Sochi reached 4 meters per year. Immediately after the end of the war, shore protection work began in this area, and coastal erosion stopped.

A railway runs along the Caucasian coast of the sea. Sanatoriums, theaters, sea terminals and residential buildings were built in the coastal zone. Therefore, the seashores must be protected from erosion. The best protection in this regard is the beach, where the waves break before reaching the shore. To secure the beaches, groins and underwater breakwaters are built. These structures prevent the movement of pebbles along the shore to other areas and their migration into the depths of the sea. This is how the beach grows.

Are there tsunami waves in the Black Sea caused by earthquakes, like we have in the Far East? There are tsunamis, but they are very weak. They are registered only by instruments and are not even felt by humans.

To what depth do ordinary waves travel? Already at a depth of 10 meters they are smaller than on the surface, and at a depth of 50 meters they are completely invisible. Maybe there is peace in the depths, which nothing disturbs? No, that's not true. There are their own, so-called internal waves. They differ from surface ones in their size (tens of meters in height and kilometers in length), and the reasons for their origin are different. They arise, as a rule, at the interface between two layers with different densities. Although they are not visible on the surface, submarines face great difficulties during such an “underwater storm.”

Wave(Wave, surge, sea) - formed due to the adhesion of particles of liquid and air; sliding along the smooth surface of the water, at first the air creates ripples, and only then, acting on its inclined surfaces, gradually develops agitation of the water mass. Experience has shown that water particles do not have forward motion; moves only vertically. Sea waves are the movement of water on the sea surface that occurs at certain intervals.

The highest point of the wave is called comb or the top of the wave, and the lowest point is sole. Height of a wave is the distance from the crest to its base, and length this is the distance between two ridges or soles. The time between two crests or troughs is called period waves.

Main causes

On average, the height of a wave during a storm in the ocean reaches 7-8 meters, usually it can stretch in length - up to 150 meters and up to 250 meters during a storm.

In most cases, sea waves are formed by the wind. The strength and size of such waves depend on the strength of the wind, as well as its duration and “acceleration” - the length of the path along which the wind acts on the water surface. Sometimes the waves that hit the coast can originate thousands of kilometers from the coast. But there are many other factors in the occurrence of sea waves: these are the tidal forces of the Moon and the Sun, fluctuations in atmospheric pressure, eruptions of underwater volcanoes, underwater earthquakes, and the movement of sea vessels.

Waves observed in other water bodies can be of two types:

1) Wind created by the wind, taking on a steady character after the wind ceases to act and called established waves, or swell; Wind waves are created due to the action of wind (movement of air masses) on the surface of the water, that is, injection. The reason for the oscillatory movements of the waves becomes easy to understand if you notice the effect of the same wind on the surface of a wheat field. The inconstancy of wind flows, which create waves, is clearly visible.

2) Waves of movement, or standing waves, are formed as a result of strong tremors at the bottom during earthquakes or excited, for example, by a sharp change in atmospheric pressure. These waves are also called single waves.

Unlike tides and currents, waves do not move masses of water. The waves move, but the water remains in place. A boat that rocks on the waves does not float away with the wave. She will be able to move slightly along an inclined slope only thanks to the force of earth's gravity. Water particles in a wave move along rings. The further these rings are from the surface, the smaller they become and, finally, disappear completely. Being in a submarine at a depth of 70-80 meters, you will not feel the effect of sea waves even during the most severe storm on the surface.

Types of sea waves

Waves can travel vast distances without changing shape and losing virtually no energy, long after the wind that caused them has died down. Breaking on the shore, sea waves release enormous energy accumulated during the journey. The force of continuously breaking waves changes the shape of the shore in different ways. The spreading and rolling waves wash the shore and are therefore called constructive. Waves crashing onto the shore gradually destroy it and wash away the beaches that protect it. That's why they are called destructive.

Low, wide, rounded waves away from the shore are called swells. Waves cause water particles to describe circles and rings. The size of the rings decreases with depth. As the wave approaches the sloping shore, the water particles in it describe increasingly flattened ovals. Approaching the shore, the sea waves can no longer close their ovals, and the wave breaks. In shallow water, the water particles can no longer close their ovals, and the wave breaks. Headlands are formed from harder rock and erode more slowly than adjacent sections of the coast. Steep, high sea waves undermine the rocky cliffs at the base, creating niches. Cliffs sometimes collapse. The terrace, smoothed by the waves, is all that remains of the rocks destroyed by the sea. Sometimes water rises along vertical cracks in the rock to the top and breaks out to the surface, forming a funnel. The destructive force of the waves widens the cracks in the rock, forming caves. When the waves wear away at the rock on both sides until they meet at a break, arches are formed. When the top of the arch falls into the sea, stone pillars remain. Their foundations are undermined and the pillars collapse, forming boulders. The pebbles and sand on the beach are the result of erosion.

Destructive waves gradually erode the coast and carry away sand and pebbles from sea beaches. Bringing the full weight of their water and washed-away material onto slopes and cliffs, the waves destroy their surface. They squeeze water and air into every crack, every crevice, often with explosive energy, gradually separating and weakening the rocks. The broken rock fragments are used for further destruction. Even the hardest rocks are gradually destroyed, and the land on the shore changes under the influence of waves. Waves can destroy the seashore with amazing speed. In Lincolnshire, England, erosion (destruction) is advancing at a rate of 2 m per year. Since 1870, when the largest lighthouse in the United States was built at Cape Hatteras, the sea has washed away beaches 426 m inland.

Tsunami

Tsunami These are waves of enormous destructive power. They are caused by underwater earthquakes or volcanic eruptions and can cross oceans faster than a jet plane: 1000 km/h. In deep waters, they can be less than one meter, but, approaching the shore, they slow down and grow to 30-50 meters before collapsing, flooding the shore and sweeping away everything in their path. 90% of all recorded tsunamis occurred in the Pacific Ocean.

The most common reasons.

About 80% of tsunami generation cases are underwater earthquakes. During an earthquake under water, a mutual vertical displacement of the bottom occurs: part of the bottom sinks, and part rises. Oscillatory movements occur vertically on the surface of the water, tending to return to the original level - the average sea level - and generate a series of waves. Not every underwater earthquake is accompanied by a tsunami. Tsunamigenic (that is, generating a tsunami wave) is usually an earthquake with a shallow source. The problem of recognizing the tsunamigenicity of an earthquake has not yet been solved, and warning services are guided by the magnitude of the earthquake. The most powerful tsunamis are generated in subduction zones. Also, it is necessary for the underwater shock to resonate with the wave oscillations.

Landslides. Tsunamis of this type occur more frequently than estimated in the 20th century (about 7% of all tsunamis). Often an earthquake causes a landslide and it also generates a wave. On July 9, 1958, an earthquake in Alaska caused a landslide in Lituya Bay. A mass of ice and earth rocks collapsed from a height of 1100 m. A wave was formed that reached a height of more than 524 m on the opposite shore of the bay. Cases of this kind are quite rare and are not considered as a standard. But underwater landslides occur much more often in river deltas, which are no less dangerous. An earthquake can cause a landslide and, for example, in Indonesia, where shelf sedimentation is very large, landslide tsunamis are especially dangerous, as they occur regularly, causing local waves more than 20 meters high.

Volcanic eruptions account for approximately 5% of all tsunami events. Large underwater eruptions have the same effect as earthquakes. In large volcanic explosions, not only are waves generated from the explosion, but water also fills the cavities of the erupted material or even the caldera, resulting in a long wave. A classic example is the tsunami generated after the Krakatoa eruption in 1883. Huge tsunamis from the Krakatoa volcano were observed in harbors around the world and destroyed a total of more than 5,000 ships and killed about 36,000 people.

Signs of a tsunami.

• Sudden fast the withdrawal of water from the shore over a considerable distance and the drying of the bottom. The further the sea recedes, the higher the tsunami waves can be. People who are on the shore and do not know about dangers, may stay out of curiosity or to collect fish and shells. In this case, it is necessary to leave the shore as soon as possible and move as far away from it as possible - this rule should be followed when, for example, in Japan, on the Indian Ocean coast of Indonesia, or Kamchatka. In the case of a teletsunami, the wave usually approaches without the water receding.
• Earthquake. The epicenter of an earthquake is usually in the ocean. On the coast, the earthquake is usually much weaker, and often there is no earthquake at all. In tsunami-prone regions, there is a rule that if an earthquake is felt, it is better to move further from the coast and at the same time climb a hill, thus preparing in advance for the arrival of the wave.
• Unusual drift ice and other floating objects, formation of cracks in fast ice.
• Huge reverse faults at the edges of stationary ice and reefs, the formation of crowds and currents.

rogue waves

rogue waves(Roaming waves, monster waves, freak waves - anomalous waves) - giant waves that arise in the ocean, more than 30 meters high, have behavior unusual for sea waves.

Just 10-15 years ago, scientists considered sailors’ stories about gigantic killer waves that appear out of nowhere and sink ships as just maritime folklore. For a long time wandering waves were considered fiction, since they did not fit into any mathematical model that existed at that time for calculating the occurrence and their behavior, because waves with a height of more than 21 meters cannot exist in the oceans of planet Earth.

One of the first descriptions of a monster wave dates back to 1826. Its height was more than 25 meters and it was noticed in the Atlantic Ocean near the Bay of Biscay. Nobody believed this message. And in 1840, the navigator Dumont d'Urville risked appearing at a meeting of the French Geographical Society and declaring that he had seen a 35-meter wave with his own eyes. Those present laughed at him. But there are stories about huge ghost waves that suddenly appeared in the middle of the ocean even with little storm, and their steepness resembled sheer walls of water, it became more and more.

Historical evidence of rogue waves

So, in 1933, the US Navy ship Ramapo was caught in a storm in the Pacific Ocean. For seven days the ship was tossed about by the waves. And on the morning of February 7, a shaft of incredible height suddenly crept up from behind. First, the ship was thrown into a deep abyss, and then lifted almost vertically onto a mountain of foaming water. The crew, who were lucky enough to survive, recorded a wave height of 34 meters. It moved at a speed of 23 m/sec, or 85 km/h. So far, this is considered the highest rogue wave ever measured.

During World War II, in 1942, the Queen Mary liner carried 16 thousand American military personnel from New York to the UK (by the way, a record for the number of people transported on one ship). Suddenly a 28-meter wave appeared. “The upper deck was at its usual height, and suddenly - suddenly! - it suddenly went down,” recalled Dr. Norval Carter, who was on board the ill-fated ship. The ship tilted at an angle of 53 degrees - if the angle had been even three degrees more, death would have been inevitable. The story of "Queen Mary" formed the basis of the Hollywood film "Poseidon".

However, on January 1, 1995, on the Dropner oil platform in the North Sea off the coast of Norway, a wave with a height of 25.6 meters, called the Dropner wave, was first recorded by instruments. The Maximum Wave project allowed us to take a fresh look at the causes of the death of dry cargo ships that transported containers and other important cargo. Further research recorded over three weeks around the globe more than 10 single giant waves, the height of which exceeded 20 meters. The new project is called Wave Atlas, which provides for the compilation of a worldwide map of observed monster waves and its subsequent processing and addition.

Causes

There are several hypotheses about the causes of extreme waves. Many of them lack common sense. The simplest explanations are based on the analysis of a simple superposition of waves of different lengths. Estimates, however, show that the probability of extreme waves in such a scheme is too small. Another noteworthy hypothesis suggests the possibility of focusing wave energy in some surface current structures. These structures, however, are too specific for an energy focusing mechanism to explain the systematic occurrence of extreme waves. The most reliable explanation for the occurrence of extreme waves should be based on the internal mechanisms of nonlinear surface waves without involving external factors.

Interestingly, such waves can be both crests and troughs, which is confirmed by eyewitnesses. Further research involves the effects of nonlinearity in wind waves, which can lead to the formation of small groups of waves (packets) or individual waves (solitons) that can travel long distances without significantly changing their structure. Similar packages have also been observed many times in practice. The characteristic features of such groups of waves, confirming this theory, are that they move independently of other waves and have a small width (less than 1 km), with heights decreasing sharply at the edges.

However, it has not yet been possible to completely clarify the nature of the anomalous waves.

The surface of the seas and oceans is rarely calm: it is usually covered with waves, and the surf continuously beats against the shores.

An amazing sight: a massive cargo ship, which is played by giant storm waves in the open ocean, appears to be no more than a nutshell. Disaster films are replete with similar images - a wave as high as a ten-story building.

Wave oscillations of the sea surface occur during a storm, when a long gusty wind combined with changes in atmospheric pressure forms a complex chaotic wave field.

Running waves, boiling surf foam

Moving away from the cyclone that caused the storm, you can observe how the wave pattern is transformed, how the waves become more even and orderly rows moving one after another in the same direction. These waves are called swell. The height of such waves (that is, the difference in levels between the highest and lowest points of the wave) and their length (the distance between two adjacent peaks), as well as the speed of their propagation, are quite constant. Two crests can be separated by a distance of up to 300 m, and the height of such waves can reach 25 m. Wave vibrations from such waves propagate to a depth of up to 150 m.

From the area of ​​formation, swell waves travel very far, even in complete calm. For example, cyclones passing off the coast of Newfoundland cause waves that in three days reach the Bay of Biscay off the western coast of France - almost 3000 km from where they formed.

When approaching the shore, as the depth decreases, these waves change their appearance. When wave vibrations reach the bottom, the movement of the waves slows down, they begin to deform, which ends with the collapse of the crests. Surfers look forward to these waves. They are especially spectacular in areas where the seabed drops sharply near the coast, for example in the Gulf of Guinea in western Africa. This place is very popular among surfers all over the world.

Tides: global waves

Tides are a phenomenon of a completely different nature. These are periodic fluctuations in sea level, clearly visible off the coast and repeating approximately every 12.5 hours. They are caused by the gravitational interaction of ocean waters mainly with the Moon. The period of tides is determined by the ratio of the periods of the daily rotation of the Earth around its axis and the rotation of the Moon around the Earth. The Sun also participates in the formation of tides, but to a lesser extent than the Moon. Despite the superiority in mass. The sun is too far from the Earth.

The total magnitude of the tides thus depends on the relative positions of the Earth, Moon and Sun, which changes throughout the month. When they are on the same line (which happens during the full moon and new moon), the tides reach their maximum values. The highest tides are observed in the Bay of Fundy on the coast of Canada: the difference between the maximum and minimum sea level positions here is about 19.6 m.

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The wind itself can be seen on weather forecast maps: these are low pressure zones. The greater their concentration, the stronger the wind will be. Small (capillary) waves initially move in the direction in which the wind is blowing.

The stronger and longer the wind blows, the greater its impact on the surface of the water. Over time, the waves begin to increase in size.

Wind has a greater effect on small waves than on calm water surfaces.

The size of the wave depends on the speed of the wind that forms it. A wind blowing at some constant speed will be able to generate a wave of comparable size. And once the wave reaches the size that the wind can push into it, it becomes “fully formed.”

The generated waves have different speeds and wave periods. (More details in the article) Long-period waves travel faster and travel longer distances than their slower counterparts. As they move away from the wind source (propagation), the waves form swell lines that inevitably roll onto the shore. Most likely, you are familiar with the concept of set waves!

Are waves that are no longer affected by the wind called ground swells? This is exactly what surfers are after!

What affects the size of a swell?

There are three main factors that influence the size of waves on the open sea.
Wind speed– The larger it is, the larger the wave will be.
Wind duration– similar to the previous one.
Fetch(wind coverage area) – again, the larger the coverage area, the larger the wave is formed.

As soon as the wind stops affecting them, the waves begin to lose their energy. They will move until the protrusions of the seabed or other obstacles in their path (a large island, for example) absorb all the energy.

There are several factors that influence the size of a wave at a particular location. Among them:

Swell direction– will it allow the swell to get to the place we need?
ocean floor– A swell moving from the depths of the ocean onto an underwater ridge of rocks forms large waves with barrels inside. A shallow ledge opposite will slow down the waves and cause them to lose energy.
Tidal cycle– some sports completely depend on it.

Find out how the best waves are made.