Why does the wind blow? What is wind, how does it arise, description, photo and video. Why does wind arise? The value of the wind in nature Where does the warm wind blow from

This is something mysterious. We never see it, but we always feel it. So why does the wind blow? Find out in the article!

Wind is the movement of air masses. Even though we cannot see air, we know that it is made up of molecules of various kinds of gases, mainly nitrogen and oxygen. Wind is a phenomenon in which many molecules move in the same direction.

Where does it come from? Wind is caused by pressure differences in the Earth's atmosphere: air from an area of ​​high pressure will move towards an area of ​​low pressure. Strong winds occur when air moves between areas with huge differences in pressure levels. Actually, this fact largely explains why the wind blows from the sea to land.

wind formation

Wind is the movement of air near the surface of the earth. It can be a gentle breeze or a violent storm. The strongest winds occur during events called tornadoes, cyclones, and hurricanes. It is caused by changes in air, land and water temperature. As air moves parallel to a warm surface, it heats up and rises, leaving room for cooler masses. The air "flowing" into these empty spaces is the wind. It is named after the direction it comes from, not the direction it blows.

Breezes: coastal and sea

Coastal and sea breezes are wind and weather phenomena that are characteristic of coastal areas. A coastal breeze is a breeze blowing from land to a body of water. The sea breeze is the wind blowing from the water to the land. Why does the wind blow from the sea and vice versa? Coastal and sea breezes arise due to a significant difference in the temperatures of the land and water surfaces. They can extend to depths of up to 160 km, or appear as local phenomena that quickly subside in the first few kilometers along the coastline.

From a scientific point of view...

Land and sea breeze patterns can greatly influence the distribution of fog, causing pollution to accumulate or disperse inland. Ongoing research into the principles of land and sea breeze circulation also includes attempts to model wind patterns as this affects energy needs (eg heating and cooling requirements) in affected areas. Wind also has an impact on weather-dependent operations (for example, with an aircraft).

Since water has a much higher heat capacity than sands or other materials in the earth's crust, with a certain amount of solar radiation (insolation), its temperature will rise more slowly than on land. Regardless of the temperature scale, during the daytime the temperature of the land can fluctuate within tens of degrees, while near the water it changes by less than half a degree. Conversely, high heat capacity prevents rapid changes in liquid temperature at night, and thus, while land temperatures can drop by tens of degrees, water temperatures remain relatively stable. In addition, the lower heat capacity of crustal materials often allows them to cool faster than the sea.

Physics of the sea and land

So why is there a strong wind? The air above the respective land and water surfaces heats up or cools down depending on the conductivity of these surfaces. During the day, the warmer ground temperature results in warmer and therefore less dense and lighter air masses over the coast compared to those adjacent to the surface of the water. As warm air rises (a phenomenon of convection), colder air moves towards voids. This is why the wind blows from the sea, and during the day there is usually a cool sea breeze going from the ocean to the shore.

Depending on the temperature difference and the amount of air lifted, the sea breeze can gust at 17 to 25 km per hour. The greater the temperature difference between land and sea, the stronger the land wind and sea breeze.

Why does the wind blow from the sea

After sunset, the air mass over coastal land quickly loses heat, while over water it is usually not too different from its daytime temperature. When the air mass above the land becomes cooler than the air mass above the water, the land wind begins to blow from the land to the sea.

The excitation of warm, moist air from the ocean often results in the formation of daytime clouds over the coastline. In addition, the movement of air masses and sea breezes are often used by tourists for hang-gliding flights. Despite the fact that land and sea breezes dominate the sea coast, they are also often recorded near large bodies of water. Coastal and sea breezes lead to higher levels of humidity, precipitation and moderate temperatures in coastal areas.

Explanation for children: why the wind blows

Sea breezes are most common on hot summer days due to the unequal heating rates of land and water. During the day, the land surface heats up faster than the sea surface. Therefore, part of the atmosphere above the earth is warmer than above the ocean.

Now remember that warm air is lighter than colder air. As a result, he rises. As a result of this process, cooler air over the ocean takes up space near the earth's surface to replace the rising warm masses.

However, it is worth knowing that wind is formed not only as a result of differences in temperature. The global motions of the atmosphere result from the rotation of the Earth. These winds group the trade winds and monsoons. The trade winds occur near the equator and move either from the north or from the south towards the equator. In the middle latitudes of the Earth, between 35 and 65 degrees, westerly winds prevail. They blow from west to east and also towards the poles. Polar winds blow near the north and south poles. They move from the poles to the east or to the west, respectively.

Our world is full of mysteries and interesting things. To solve them is the task of mankind. Even greater discoveries are ahead of us, but for now we already know exactly the answer to the question of how and why the wind blows, as well as what factors determine its formation. This makes it possible to predict changes in weather conditions.

More than three hundred years ago, Halley, known mainly due to the comet he discovered, proposed to explain the occurrence of wind by the action of the Archimedean force during temperature changes: warm and light air rises, heavy and cold air falls.

An international group of researchers, which included employees of the St. Petersburg Institute of Nuclear Physics, proposed a fundamentally new physical mechanism for the formation of wind in the Earth's atmosphere.

Gas flows occur with pressure drops (gradients). Air pressure decreases with height, forming a vertical pressure gradient, but it does not create wind. The work produced by the movement of air by this pressure gradient is exactly compensated by the work of gravity opposite in sign, and the air is in equilibrium.

As the moist air rises, it cools and the water vapor condenses. Therefore, the pressure of water vapor decreases with height faster than required by the equilibrium condition. In this case, the work done by the pressure gradient over moist air when it rises is several times greater than the work of gravity acting on water vapor. It is this difference that creates the wind in the earth's atmosphere. The non-equilibrium vertical distribution of water vapor can be compared to a compressed spring, which straightens when moist air rises, setting it in motion. Therefore, the condensation power associated with the vertical rise of air, in accordance with the law of conservation of energy, is converted into the power of horizontal winds.

The power of the atmospheric circulation is determined by the local rate of condensation and, consequently, by precipitation. The quantitative estimate of the power of global air circulation, obtained on the basis of the new theory, perfectly coincided with the accumulated observational data (the power of wind circulation can be judged independently from the observed horizontal pressure gradients and wind speeds).

In the area of ​​condensation, a zone of low pressure arises, which draws in air from adjacent areas. On land, such stable zones of low pressure are created by vast forests: moisture is stored in the forest soil, evaporates from the surface of the soil and leaves, and condenses above the forest canopy. This creates a wind that brings moisture from the ocean.

The most important consequence of the new mechanism of wind formation is the rethinking of the role of forests in the transfer of moisture from the ocean to land. This transfer compensates for river runoff back to the ocean. The destruction of forests leads to dehydration and desertification of the land and poses a much greater threat to the climate than modern climatology suggests (see also "Science and Life" No. ).

The new theory caused a heated discussion in the scientific community. The paper, submitted to the journal Atmospheric Chemistry and Physics, has been under peer review for more than two and a half years. As a result, the editorial board of the journal accepted the article for publication, providing it with the editor's commentary. It emphasizes that the publication of "a completely new look at the driving force of atmospheric dynamics" should be seen as "a call for further development" of the provisions presented by the authors.

Moving in a certain direction. On other planets, it is a mass of gases characteristic of their surface. On Earth, the wind moves mostly horizontally. Classification, as a rule, is carried out in accordance with the speed, scale, types of forces, their causes, places of distribution. Under the influence of flows are various natural phenomena and weather. The wind contributes to the transfer of dust, seeds of plants, promotes the movement of flying animals. But how does directional airflow come about? Where does the wind blow from? What determines its duration and strength? And why do the winds blow? About this and much more - later in the article.

Classification

First of all, winds are characterized by strength, direction and duration. Gusts are strong and short-term movements (up to several seconds) of air flows. If a strong wind of medium duration (about a minute) blows, then it is called a squall. Longer air currents are named according to their strength. So, for example, a light wind blowing on the coast is a breeze. There is also a typhoon. The duration of the winds can also be different. Some last a few minutes, for example. The breeze, which depends on the temperature difference on the relief surface during the day, can last up to several hours. The local and general circulation of the atmosphere is made up of trade winds and monsoons. Both of these types are classified as "global" winds. Monsoons are caused by seasonal changes in temperature and last up to several months. The trade winds are constantly moving. They are due to temperature differences at different latitudes.

How to explain to a child why the wind is blowing?

For children at an early age, this phenomenon is of particular interest. The child does not understand where the air flow is formed, which is why it is in one place and not in another. It is enough to simply explain to the baby that in winter, for example, a cold wind blows due to low temperatures. How does this process take place? It is known that the air flow is a mass of atmospheric gas molecules moving together in one direction. A small air flow, blowing, can whistle, tear off hats from passers-by. But if the mass of gas molecules has a large volume and a width of several kilometers, then it can cover a fairly large distance. In closed rooms, air practically does not move. And you can even forget about its existence. But if, for example, you put your hand out of the window of a moving car, you can feel the air flow, its strength and pressure with your skin. Where does the wind blow from? The movement of the flow is due to the difference in pressure in different parts of the atmosphere. Let's consider this process in more detail.

Atmospheric pressure difference

So why does the wind blow? For children, it is better to cite a dam as an example. On the one hand, the height of the water column, for example, is three, and on the other, six meters. When the sluices are opened, the water will flow to the area where it is less. The same thing happens with air currents. Different parts of the atmosphere have different pressures. This is due to the difference in temperature. Molecules move faster in warm air. Particles tend to scatter from each other in different directions. In this regard, warm air is more discharged and weighs less. As a result, the pressure that is created in it decreases. If the temperature is lowered, then the molecules form closer clusters. Air therefore weighs more. As a result, the pressure rises. Like water, air has the ability to flow from one zone to another. So, the flow passes from the area with high pressure to the area with low pressure. That's why the winds blow.

The movement of streams near water bodies

Why does the wind blow from the sea? Consider an example. On a sunny day, the rays warm up both the shore and the reservoir. But the water heats up much more slowly. This is due to the fact that the surface warm layers immediately begin to mix with the deeper and therefore cold layers. But the coast heats up much faster. And the air above it is more discharged, and the pressure, respectively, is lower. Atmospheric flows rush from the reservoir to the shore - to a freer area. There they, heating up, rise up, again freeing up space. Instead, a cool stream appears again. This is how air circulates. On the beach, vacationers can periodically feel a light cool breeze.

The meaning of the winds

Having found out why the winds blow, it should be said about the effect they have on life on Earth. The wind is of great importance for human civilization. The whirling currents inspired people to create mythological works, expanded the trade and cultural range, and influenced historical phenomena. The winds also acted as energy suppliers for various mechanisms and units. Due to the movement of air currents, they were able to overcome considerable distances across the oceans and seas, and balloons across the sky. For modern aircraft, winds are of great practical importance - they allow you to save fuel and increase it. But it should be said that air currents can also harm a person. So, for example, due to gradient wind fluctuations, control over the control of the aircraft can be lost. In small bodies of water, fast air currents and the waves they cause can destroy buildings. In many cases, winds contribute to the expansion of the fire. In general, the phenomena associated with the formation of air currents affect wildlife in various ways.

Global Effects

In many areas of the planet, air masses with a certain direction of movement predominate. In the region of the poles, as a rule, eastern winds prevail, and in temperate latitudes - western winds. At the same time, in the tropics, air currents again take an easterly direction. On the borders between these zones - the subtropical ridge and the polar front - there are so-called calm areas. There are practically no prevailing winds in these zones. Here the movement of air is carried out mainly vertically. This explains the appearance of high humidity zones (near the polar front) and deserts (near the subtropical ridge).

Tropics

In this part of the planet, trade winds blow in a westerly direction, approaching the equator. Due to the constant movement of these air currents, the atmospheric masses on Earth are mixed. This can manifest itself on a significant scale. So, for example, the trade winds moving over the Atlantic Ocean carry dust from the African desert territories to the West Indies and parts of North America.

Local effects of air mass formation

Finding out why the winds blow, it should be said about the influence of the presence of certain geographical objects. One of the local effects of the formation of air masses is the temperature difference between not too remote areas. It can be provoked by different coefficients of light absorption or different heat capacity of the surface. The latter effect is most pronounced between and land. The result is a breeze. Another local factor of importance is the presence of mountain systems.

Mountain influence

These systems can be a kind of barrier to the movement of air flows. In addition, mountains in many cases themselves cause wind formation. The air above the hills warms up more than the atmospheric masses above the lowlands at the same height. This contributes to the formation of low pressure zones over mountain ranges and wind formation. This effect often provokes the appearance of mountain-valley atmospheric moving masses. Such winds predominate in areas with rugged terrain.

An increase in friction near the valley surface leads to a deviation of the parallel directed air flow to the height of the nearby mountains. This contributes to the formation of a jet high-altitude current. The speed of this flow can exceed the strength of the surrounding wind up to 45%. As mentioned above, mountains can act as an obstacle. When bypassing the circuit, the flow changes its direction and strength. Changes in mountain ranges have a significant impact on wind movement. For example, if there is a pass in the mountain range that the atmospheric mass overcomes, then the flow passes it with a noticeable increase in speed. In this case, the Bernoulli effect works. It should be noted that even minor elevation changes cause fluctuations. Due to the significant air velocity gradient, the flow becomes turbulent and continues to remain so even behind the mountain on the plain at a certain distance. Such effects are in some cases of particular importance. For example, they are important for aircraft taking off and landing at mountain airfields.

Like some other planets in the solar system, the Earth is surrounded by a layer of gases. This layer is called the atmosphere. The earth's atmosphere consists mainly of nitrogen and oxygen.

Individual gas molecules are constantly moving at high speed in different directions. All together they are firmly attached to the Earth, by the force of its gravity.

What is wind?

Wind is the joint movement in one direction of large masses of atmospheric gas molecules. A stream of such molecules moving synchronously can whistle, blowing around a tall building, and rip off hats from passers-by, but if the molecules are a whole river, and even several kilometers wide, then such a wind can fly around the entire planet.

In a closed room where the air barely moves, you can even forget about its existence. But if you put your hand outside the window of a moving car, it becomes clear that air exists, and although it is invisible, it exerts a noticeable pressure. Indeed, we constantly experience the pressure of air, which seems ephemeral and weightless. But in fact, the entire atmosphere of the Earth weighs no less than 5 quadrillion tons.

Interesting fact: wind blows because air pressure is different in different parts of the atmosphere.

Winds happen because the atmospheric pressure in different parts of the atmosphere is somewhat different. Why does pressure difference cause wind? Imagine a dam. The height of the water level on one side is 6 meters, on the other - 3. If the dam locks are opened, the water will quickly flow in the direction where the water level is 3 meters, and will continue to flow until the water levels are equal. Something similar happens with air.

Wind is air in motion relative to the earth's surface; and it moves due to fluctuations in atmospheric pressure. Otherwise, there would be no wind. Pressure differences exist over regions where the sun heats the earth's surface unevenly.

Above a warm surface, the air also heats up and increases in volume, respectively, its pressure increases compared to cooler areas.

Air can be thought of as layers between surfaces at constant pressure (right), with the densest layer at the bottom. When the air is unchanged, its layers are even and flat, as in stage 1. But if one of the areas (stage 2, yellow) absorbs a certain amount of heat, then the air expands, its pressure increases, and the layers of air pressure also expand and acquire a bend .

The air then begins to move from the high pressure area to the low pressure area, creating wind high above the ground (stage 3). The greater the amplitude of temperature fluctuations - and, accordingly, pressure - between two areas, the stronger the wind blowing between them.

Uneven heating. The sun heats point B, causing the temperature of the air above it to rise (right). The air increases in volume and rises, and its pressure increases.

Convection causes winds

Air pressure increases with increasing temperature. Therefore, if the mass of warm air borders on the mass of colder air, then the pressure in these two massifs will be different. This difference causes convection currents (stages 1-4) that generate wind between the two zones.

Equilibrium. The temperature at points A and B (left) is the same, as is the pressure above them. Therefore, there is no wind between these points.

Creative force. The difference in air pressure over points A and B creates a gradient force that moves air from areas of high pressure to areas of low pressure. It also carries part of the air above point B to point A, causing the upper atmospheric wind (red arrow) in the same direction.

surface winds. The air trapped at point A causes the pressure to rise, while at point B it falls. This generates a surface wind tending in the opposite direction of the upper atmospheric wind. Downflow at A and upflow at B complete the cycle.

Compiling meteorological maps, scientists rely on imaginary atmospheric surfaces called surfaces of constant pressure (curved planes, top). At every point on this surface, the pressure is constant. When an imaginary plane parallel to the Earth (red contour) intersects with a surface of constant pressure, meteorologists draw a line - an isobar - separating areas with different air pressures. The air mass between the isobars (dark blue segment) is driven by a gradient force (green arrow) into an area of ​​lower pressure.

Circular isobars

In areas with different pressures, the direction of the wind is also determined by the centrifugal force. In the upper atmosphere, the pressure gradient force, rotational force, and centrifugal force are in balance if the winds blow clockwise around a high pressure area (far left, top) and counterclockwise around a low pressure area (left, top). Above the surface, the force of friction turns the wind out-up (far left, bottom) and in-down (left, bottom).