Strong wind causing big waves on the sea. Why waves on the sea? Signs of a tsunami
How are waves formed? Surf reports and wave forecasts are based on scientific research and weather modeling. In order to know what waves will form in the near future, it is important to understand how they are formed.
The main reason for the formation of waves is the 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. Wind action is the first stage of wave formation.
Winds blowing in a given area from the shore can also cause waves, but they can also lead to a deterioration in the quality of breaking waves.
It has been established that winds blowing from the sea usually lead to the formation of unstable and uneven waves, since they affect the direction of the wave. The winds blowing off the coast serve in a sense as a sort of balancing force. The wave travels many kilometers from the depths of the ocean to the shore, and the wind from the land has a “braking” effect on the face of the wave, allowing it not to break for longer.
Low pressure areas = good waves for surfing
Theoretically, areas of low pressure contribute to the formation of good, powerful waves. In the depths of such areas, the wind speed is higher, and gusts of wind form more waves. The friction created by these winds helps to form powerful waves that travel thousands of kilometers until they hit the final obstacles, that is, the coastal areas where people live.
If the winds generated in areas of low pressure continue to blow on the surface of the ocean for a long time, then the waves become more intense, as energy accumulates in all the waves that are formed. In addition, if winds from low pressure areas affect a very large area of the ocean, then all the resulting waves concentrate even more energy and power in themselves, which leads to the formation of even larger waves.
From waves in the ocean to waves for surfing: the seabed and other obstacles
We have already analyzed how waves are formed in the sea and the waves generated by it, but after the “birth”, such waves still have to travel a huge distance to the coast. Waves originating in the ocean have a long way to go before they reach land.
During their journey, even before surfers 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 on which the surfers ride.
Moving through the ocean, the waves are exposed to the roughness of the seabed. When giant moving masses of water overcome elevations on the sea floor, the total amount of energy concentrated in the waves changes.
For example, continental shelves at a distance from the coast resist moving waves due to the force of friction, and by the time the waves reach coastal waters, where the depth is shallow, they already lose their energy, strength and power.
When waves move through deep waters without encountering obstacles in their path, they tend to hit the coastline with great force. The depths of the ocean floor and their changes over time are studied as part of bathymetric studies.
Using the depth map, it is easy to find the deepest and shallowest areas of the oceans of our planet. The study of the topography of the seabed is of great importance in preventing the wrecks of ships and cruise liners.
In addition, by studying the structure of the bottom, you can get valuable information for predicting surf at a particular surf spot. When the 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. That is why the quality of the waves changes over time for better or worse. The sandy undulations on the ocean floor allow for the formation of well-defined, concentrated wave crests from which surfers can begin their slide.
When a wave hits a new sandbank, a wave usually 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 ships, or simply natural or artificial reefs.
Waves are generated by the wind and, as they move, are affected by the topography of the seabed, precipitation, tides, rip currents along the coasts, local winds and uneven bottoms. All these weather and geological factors contribute to the formation of waves suitable for surfing, kitesurfing, windsurfing and boogie surfing.
Wave Forecasting: Theoretical Foundations
- Waves with a long period tend to be larger and more powerful.
- Waves with a short period tend to be smaller and weaker.
- The period of a wave is the time between the formation of two distinct crests.
- The frequency of waves is the number of waves passing through a certain point in a certain time.
- Big waves move fast.
- Small waves move slowly.
- In areas of low pressure, intense waves form.
- The areas of low pressure are characterized by rainy weather and cloudiness.
- For areas high pressure characterized by warm weather and clear skies.
- Larger waves form in deep coastal areas.
- Tsunamis are not suitable for surfing.
Man perceives many natural phenomena as self-evident. We are accustomed to summer, autumn, winter, rain, snow, waves and do not think about the reasons. And yet, why do waves form in the sea? Why do ripples appear on the surface of the water even in complete calm?
Origin
There are several theories explaining the origin of sea and ocean waves. They are formed due to:
- changes in atmospheric pressure;
- ebbs and flows;
- underwater earthquakes and volcanic eruptions;
- ship movements;
- strong wind.
To understand the mechanism of formation, one must remember that water is agitated and oscillates involuntarily - as a result of physical impact. A pebble, a boat, a hand touching it set the liquid mass in motion, creating vibrations of different strengths.
Characteristics
Waves are also the movement of water on the surface of a reservoir. They are the result of the adhesion of air particles and liquid. At first, water-air symbiosis causes ripples on the surface of the water, and then causes the water column to move.
Size, length and strength vary, depending on the strength of the wind. During a storm, powerful pillars rise to 8 meters and stretch in length for almost a quarter of a kilometer.
Sometimes the force is so destructive that it falls on the coastal strip, uproots umbrellas, showers and other beach buildings, demolishes everything in its path. And this despite the fact that fluctuations are formed several thousand kilometers from the coast.
All waves can be divided into 2 categories:
- wind;
- standing.
wind
Windmills, as the name implies, are formed under the influence of wind. Its gusts rush at a tangent, forcing the water and forcing it to move. The wind pushes the liquid mass forward in front of it, but gravity slows down the process, pushing it back. Movements on the surface, resulting from the influence of two forces, resemble ups and downs. Their peaks are called crests, and their bases are called soles.
Having found out why waves form on the sea, the question remains open as to why they make oscillatory movements up and down? The explanation is simple - the inconstancy of the wind. He then quickly and impetuously swoops, then subsides. The height of the crest, the frequency of oscillations directly depend on its strength and power. If the speed of movement and the strength of the air currents exceed the norm, a storm rises. Another reason is renewable energy.
Renewable energy
Sometimes the sea is completely calm, and the waves are formed. Why? Oceanographers and geographers attribute this phenomenon to renewable energy. Water fluctuations are its source and ways to keep the potential for a long time.
In real life, it looks like this. The wind creates a certain amount of vibration in the pond. The energy of these oscillations will last for several hours. During this time, liquid formations cover a distance of tens of kilometers and "moor" in areas where it is sunny, there is no wind, and the reservoir is calm.
standing
Standing or solitary waves occur due to shocks on the ocean floor, characteristic of earthquakes, volcanic eruptions, and also due to a sharp change in atmospheric pressure.
This phenomenon is called seiches, which is translated from French as "to sway." Seiches are typical for bays, gulfs and some seas; they pose a danger to beaches, structures in the coastal strip, ships moored at the pier and people on board.
constructive and destructive
Formations that overcome long distances and do not change shape and do not lose energy, hit the coast and break. At the same time, each run-up has a different effect on the coastal strip. If it washes the shore, it is classified as constructive.
The destructive surge of water falls with its power on the coast, destroying it, gradually washing away sand and pebbles from the beach strip. In this case, the natural phenomenon is classified as destructive.
Destruction is of different destructive power. Sometimes it is so powerful that it brings down slopes, splits cliffs, separates rocks. Over time, even the hardest rocks are destroyed. America's largest lighthouse was built at Cape Hatteras in 1870. Since then, the sea has moved almost 430 meters inland, washing away the coastline and beaches. This is just one of dozens of facts.
Tsunamis are a type of destructive water formations characterized by great destructive power. The speed of their movement reaches 1000 km / h. This is higher than that of a jet aircraft. At depth, the height of the tsunami crest is small, but near the coast they slow down, but increase the height to 20 meters.
In 80% of cases, tsunamis are the result of underwater earthquakes, in the remaining 20% - volcanic eruptions and landslides. As a result of earthquakes, the bottom shifts vertically: one part of it sinks, and the other part rises in parallel. Fluctuations of different strength are formed on the surface of the reservoir.
Anomalous Assassins
They are also known as wanderers, monsters, anomalous, and more characteristic of the oceans.
Even 30-40 years ago, sailors' stories about anomalous water fluctuations were considered fiction, because eyewitness accounts did not fit into the existing scientific theories and calculations. A height of 21 meters was considered the limit for oceanic and sea vibrations.
Initially, the wave appears due to the wind. A storm formed in the open ocean, far from the coast, will create winds that will begin to affect the surface of the water, in connection with this, a swell begins to occur. Wind, its direction, as well as speed, all these data can be seen on weather forecast maps. The wind begins to inflate the water, and "Small" (capillary) waves will begin to appear, initially they begin to move in the direction in which the wind blows.
The wind blows on a flat water surface, the longer and stronger the wind starts to blow, the greater the impact on the water surface. Over time, the waves merge and the size of the wave begins to increase. The constant wind begins to form a large swell. The wind has a much greater effect on the already created waves, although not large - much more than on the calm expanse of water.
The size of the waves directly depends on the speed of the blowing wind that forms them. A wind blowing at a constant speed can generate a wave of comparable size. And as soon as the wave acquires the size that the wind put into it, it becomes a fully formed wave that goes towards the coast.
Waves have different speeds and periods. Waves with a long period move fast enough and cover greater distances than their counterparts with a lower speed. As you move away from the source of the wind, the waves combine to form a swell that goes towards the coast. Waves that are no longer affected by the wind are called "Bottom Waves". These are the waves that all surfers hunt for.
What affects the size of a swell? There are three factors that affect the size of waves in the open ocean:
Wind speed - The higher the speed, the larger the wave will eventually be.
Wind duration - the longer the wind blows, similarly to the previous factor, the wave will be larger.
Fetch (wind coverage area) - The larger the coverage area, the larger the wave.
When the effect of the wind on the waves stops, they begin to lose their energy. They will continue to move until such time as they hit the ledges of the bottom of some large oceanic island and the surfer catches one of these waves in case of good luck.
There are factors that affect the size of the waves in a particular location. Among them:
The direction of the swell is what will allow the waves to come to the place we need.
Ocean floor - A swell moving from the open ocean bumps into an underwater ridge of rocks, or a reef - forms large waves with which they can twist into a pipe. Or a shallow ledge of the bottom - on the contrary, it will slow down the waves and they will spend part of their energy.
The tidal cycle - many surf spots are directly dependent on this phenomenon.
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 the wind is blowing.
The stronger and longer the wind blows, the greater its effect on the surface of the water. Over time, the waves begin to increase in size.
The wind has a greater effect on small waves than on a calm surface of the water.
The size of a wave depends on the speed of the wind that forms it. Wind blowing at some constant speed will be able to generate a wave of comparable size. And once a wave reaches the size that the wind can put into it, it becomes "fully formed."
The generated waves have different wave speeds and periods. (More details in the article) Waves with a long period move faster and cover greater distances than their slower counterparts. As they move away from the wind source (propagation), the waves form lines of swells, which inevitably roll onto the shore. Most likely, you are familiar with the concept of a set of waves!
Waves that are no longer affected by the wind are called ground waves (ground swell)? This is exactly what surfers are looking for!
What affects the size of a swell?
There are three main factors that affect the size of waves on the high seas.
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 influence of the wind on them stops, the waves begin to lose their energy. They will move until the moment when 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 affect 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- Swell, moving from the depths of the ocean to the 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 are completely dependent on it.
Find out how the best waves come about.
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 on the sea and in the oceans.
And today we just want to pay attention to the last question, the question of why waves form on the sea.
Why do waves form in the sea
There are theories that waves in the seas and oceans arise due to pressure drops. However, these are often just the assumptions of people who quickly try to find an explanation for such a natural phenomenon. In reality, things are somewhat different.
Remember what makes the water "worry". This is a physical effect. Throwing something into the water, running a hand over it, hitting the water sharply, vibrations of different sizes and frequencies will certainly begin to go through it. Based on this, it can be understood 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? Another natural phenomenon is to blame - the 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 action that pumps water and makes it move in waves.
Someone, of course, will ask another question about why the waves on the sea and in the ocean move with oscillatory movements. However, the answer to this question is even simpler than the very nature of waves. The fact is that the wind has a non-permanent physical effect on the surface of the water, because it is directed towards it by gusts of different strength and power. This affects the fact that 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 on the 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 the wind is completely absent.
And here the answer to the question will be the fact that water waves are an ideal source of renewable energy. The fact is that waves are able to store their potential for a very long time. That is, the wind that brought 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 has not exhausted itself even after tens of kilometers from the point of origin of the wave.
That's all the answers to questions about why there are waves on the sea.
