Wave is a natural phenomenon that largely determines the comfort of being on the high seas. Small waves may not even be noticed. But the big ones are capable of causing significant damage to a sea vessel and harming its passengers. This article will focus on wind waves. What are they, how are they formed, and what characteristics do they have? Let's answer all these questions together!
Wind waves - what is it?
No body of water can remain calm and still. After all, even the wind, which is insignificant in strength, will certainly be reflected on its surface. A wind wave is formed as a result of the direct impact of wind on the water surface of a sea or lake. To better understand the mechanism of its formation, you can watch a wheat field in windy weather.
So how do wind waves form? With a light wind, light ripples appear on a calm surface of the water. As its speed increases, small rhythmic waves appear. Gradually, their length and height increase. With furtheras the wind intensifies, “lambs” of white foam begin to form on their crests. The speed of wind waves can vary widely (from 10 to 90 km/h). After the wind stops at sea, you can see long, low and gentle waves, called swell.
It is important to note that water is a much denser substance than air. As a result, the surface of the reservoir "lags" a little after the impact of the wind, and the ripples turn into waves only after a while.
Wind waves should be distinguished from tsunamis and tides. The former arise as a result of increased seismic activity of the earth's crust, and the latter as a result of the impact of our planet's satellite, the Moon.
Sea wave structure
A wind wave consists of several elements (see diagram below):
- The crest is the highest point of the wave.
- The bottom is the lowest point of the wave.
- Slopes - leeward and windward.
The leeward (front) slope of a wave is always steeper than the windward one. Here, by the way, there is a direct analogy with sand dunes, which are also formed under the influence of the wind. Approaching the shore, the sole of the wave slows down on the bottom of the reservoir, and its crest overturns, breaking into many sprays. This process is accompanied by active destruction of rocks. If the wave hits a coastal rock, then the water is thrown up in the form of a powerful foamy column, the height of which can reach several tens of meters.
Characteristics of wind waves
In oceanography, there are four main characteristics of the sea wave. This is:
- Height is the vertical distance between the sole and the ridge.
- Length - the distance between two crests of adjacent waves.
- Speed - the distance that the wave crest travels per unit of time (usually measured in meters per second).
- Steepness is the ratio of wave height to half of its length.
The length of wind waves varies widely from 0.5 to 250 meters, the height can reach 20-25 meters. The most powerful waves are observed in the Southern Hemisphere, in the open ocean. Here the speed of their movement often reaches 15-20 m/s. The smallest waves are typical for inland seas that go deep into the continent (for example, for the Black or Azov Seas).
Sea waves: scale
The state of the sea is a term used in oceanographic science to determine the state of the open surface of large bodies of water (lakes, seas, oceans). It is characterized, first of all, by the height of the waves and their strength. To assess the degree of sea roughness, a 9-point scale developed by the World Meteorological Organization is used.
| Score | Name | Wave height (m) | External signs |
| 0 | Perfectly calm sea | 0 | The surface of the sea is smooth |
| 1 | Calm Sea | 0-0, 1 | Ripples and slight waves |
| 2 | Low excitement | 0, 1-0, 5 | The crests of the waves begin to tip over, but there is no foam yet |
| 3 | Slight excitement | 0, 5-1, 25 | Sometimes "lambs" appear on the crests of the waves |
| 4 | Moderate excitement | 1, 25-2, 5 | "Lambs" are present in large quantities |
| 5 | Rough Sea | 2, 5-4 | Large ridges appear |
| 6 | Major commotion | 4-6 | The ridges form large storm surges |
| 7 | Heavy excitement | 6-9 | Foam stretches into strips and partially covers the slopes of the waves |
| 8 | Very strong excitement | 9-14 | Foam completely covers the slopes of the waves |
| 9 | Exceptional excitement | Over 14 | The entire surface of the waves is covered with a thick layer of foam. The air is saturated with water dust. Visibility drops sharply. |
Sea waves as a source of energy
Usethe natural energy of the ocean waves is one of the promising areas of alternative electric power industry. Scientists have calculated that the total power of all wind waves on the planet is 1020 J/hour. This is a colossal figure, but the trouble is that obtaining and using this energy is very difficult.
Today, such countries as Great Britain, Ireland, Norway and India are seriously engaged in the development of wave energy. The operation of the wave power plant is based on the conversion of the mechanical energy of the sea wave into electrical energy by means of working mechanisms consisting of special floats, blades and pendulums.
The first such power plant was launched in Norway in 1985. Its power is 850 kW. Today, a number of countries use wave energy to power autonomous buoys, lightships, mariculture farms and even small drilling platforms.
