How waves appear on the sea. Sea waves: nature of occurrence

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.

We have long been accustomed to many phenomena occurring on our planet, without thinking at all about the nature of their occurrence and the mechanics of their action. This is climate change, and the change of seasons, and the change of time of day, and the formation of waves in the sea and oceans.

And today we just want to pay attention last question, the question of why waves form in the sea.

Why do waves appear on the sea?

There are theories that waves in the seas and oceans arise due to pressure changes. However, these are often just assumptions of people who quickly try to find an explanation for such a natural phenomenon. In reality, things are somewhat different.

Remember what makes water “worry”. This is a physical impact. Throwing something into the water, running your hand over it, sharply hitting the water, vibrations of different sizes and frequencies will certainly begin to flow through it. Based on this, we can understand that waves are the result of a physical impact on the surface of the water.

However, why do large waves appear on the sea, coming to the shore from afar? Something else is to blame a natural phenomenon- wind.

The fact is that gusts of wind pass over the water along a tangent line, exerting a physical effect on the sea surface. It is this effect that pumps the water and causes it to move in waves.

Someone, of course, will ask another question about why the waves in the sea and ocean move in oscillatory movements. However, the answer to this question is even simpler than the nature of waves itself. The fact is that the wind has an inconsistent physical effect on the surface of the water, because it is directed towards it in gusts of varying strength and power. This affects what the waves have different size and vibration frequency. Of course, strong waves, a real storm, occur when the wind exceeds the norm.

Why are there waves at sea without wind?

A very reasonable nuance is the question of why there are waves on the sea even if there is absolute calm, if there is no wind at all.

And here the answer to the question is the fact that water waves are an ideal source of renewable energy. The fact is that waves are very capable for a long time store your potential. That is, the wind that set the water into action, creating a certain number of oscillations (waves), may be enough for the wave to continue its oscillation for a very long time, and the wave potential itself does not exhaust itself even after tens of kilometers from the point of origin of the wave.

These are all the answers to the questions about why there are waves on the sea.

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

In theory, areas of low pressure promote the formation of nice, powerful waves. In the depths of such areas, wind speed is 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. The waves that originated in the ocean have to do a long way 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-sea waters without encountering obstacles on their way, they usually crash into coastline With enormous power. 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 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 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 a short period tend to be 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.

Waves are created by the wind. Storms create winds that impact the surface of the water, resulting in ripples, just like the ripples in your cup of coffee after surfing when you blow on it. 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.

As the wind continues to blow and the waves it generates continue to be affected by it, the small waves begin to grow. The wind has a greater effect on them than on a calm water surface.
The size of the wave depends on the speed of the wind that forms it. A wind blowing at a certain constant speed will be able to generate a wave of a certain size. And as soon as the wave reaches its maximum possible sizes given the wind, it becomes "fully formed".

The generated waves have different speeds and wave periods. (See more details in the section on wave terminology)
Long period waves travel faster and travel longer distances than their slower counterparts. As they move away from the source of the wind (propagation), the waves form lines of surf (swells), which inevitably roll onto the shore. You are probably already familiar with the concept of “wave set”!

Waves that are no longer affected by the wind that generated them are called groundwells. This is exactly what surfers are after!

What affects the size of the surf (swell)?

There are three main factors that influence the size of waves on the open sea:
Wind speed - the higher it is, the larger the wave will be.
The duration of the wind is similar to the previous one.
Fetch (fetch, “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 the wave at a particular surf location. Among them:

The direction of the surf (swell) - will it allow the swell to get to the place we need?
Ocean bottom - a swell moving from the depths of the ocean to a reef, forms large waves with barrels inside. A shallow, long ledge extending toward the shore will slow down the waves and they will lose their energy.
Tides - some sports are completely dependent on it.
Find out more in the section on how the best waves appear

Waves are a concept from the “arsenal” of physics. To explain more simply and clearly what this is, we can give an example that would seem far from the topic.

...The coronation of Catherine II took place in Moscow. The newly-crowned empress wanted the solemn moment to be announced with fireworks in St. Petersburg, but how to convey the signal? After all, then there was no Internet, no telephone, or even a telegraph. And yet, a solution was found: from Moscow to St. Petersburg, soldiers were stationed with flags in their hands at a direct line of sight from each other. At the right moment, the first soldier raised the flag, the next, seeing this, did the same, etc. The signal was received in St. Petersburg in less than a quarter of an hour!

What do we see in in this case? Not a single person moved, but a certain state moved, transmitted from person to person. If something similar happens in a certain medium (solid, liquid or gaseous) or in an electromagnetic field, matter does not move, but a certain change moves physical characteristics- this is called a wave (this will be even clearer if we again recall an expression that is far from physics: “A wave of strikes swept across the country” - again, a change in state “rolled”).

A special case of a wave is those oscillatory disturbances that propagate in the water column or along its surface.

Every wave has a top (the very high point its crest), base (the lowest point of the trough), height (exceeding the top), length (the distance between the tops of the crests of two adjacent waves), period (the time interval during which the wave travels a distance equal to its length) and steepness (the ratio of height and wavelength). The speed at which the wave travels in the direction in which it is propagating is also estimated.

The reasons for the formation of waves on the surface of seas and oceans are diverse. Most often you can observe wind waves. Their size and shape are not ordered; a small wave may well be followed by a large one; the crests of the waves do not necessarily move in the direction of the wind. This is due to the fact that the wind that forms the waves has a vortex, turbulent character. The size of wind waves depends not only on the wind speed, but also on its duration.

The wind is not the only reason occurrence of sea waves. There are tidal waves. Contrary to popular belief, they appear not because the Moon “attracts” water, but because the Earth, along with its watery shell, is “stretched” between the point farthest from the Moon and the point closest to it, this occurs due to the difference in gravitational attraction between these two points.

Pressure waves arise due to sudden changes in atmospheric pressure. This happens where there is a cyclone, especially a tropical one. If such waves coincide with high tidal waves, expect trouble! This happens especially often on the coasts of Florida, Japan, China, India, and the Antilles.

Deep waves are especially dangerous for sailors. They occur where there are two layers of water with different properties, and their mixing occurs - for example, near melting ice or in straits.

Tsunami waves are formed by earthquakes on the seabed. The Japanese origin of the name is not accidental - this country especially often suffers from such natural disasters.

When the action of wind, seismic shocks and other forces causing waves ceases, standing waves arise in inland seas and bays by inertia long period- Seiches. Thus, on the Sea of ​​Azov, the period of such waves can reach 23 hours.

Finally, there are ship waves. After all, a ship passing through the sea also causes disturbance in the water of the environment, and hence the formation of waves.