What is wind from a physics point of view? Why does the wind blow? Local effects of air mass formation

What is wind? It's complicated atmospheric phenomenon, which occurs under certain conditions. Why is this atmospheric phenomenon? Because the area where this phenomenon occurs is the lowest atmospheric layer - the troposphere (8-12 km altitude above the earth's surface).

The concept of wind and its features

Wind is the movement of air, and not just movement, but its movement in a horizontal direction above the earth's surface. When the pressure is in different glasses globe differently, air masses tend to be distributed over the earth's surface more evenly and fill the space where the atmosphere is not so dense.

Atmospheric pressure itself is the pressure of air on the earth's surface through gravity air masses to Earth. In this case it applies gravitational force, which holds air near the surface of the Earth, and allows people and objects to come into close contact with the earth, and not fly into space.

Based on the above, we can conclude: the wind moves not only horizontally above the Earth’s surface, but also from an area of ​​high atmospheric pressure to the low area.

The air is heated extremely unevenly, which is partly due to the constant presence of winds on the planet.

Air masses warm up most strongly at the Equator, the central latitude of the Earth. From there the winds are distributed throughout earth's surface.

Wind strength and speed

The wind cannot be seen, but it can be felt, for example, its strength or the speed with which the wind blows a hat off one’s head or ruffles leaves on the trees. It’s not for nothing that the verbal expression “knocked down by the wind” is sometimes used, meaning that the wind was very strong.

Wind speed is expressed in terms of “meter per second”, “kilometer per hour”, and its speed can also be expressed on a point scale.

There is a so-called Beaufort scale- a scale with twelve dimensions developed by the World Meteorological Organization to measure wind speed by the waves it creates in open water spaces (most often at sea) and the force of its impact on ground objects.

When the Beaufort scale index is “0”, the wind speed reaches about 0-0.2 m/s and is characterized by calm. The leaves of the trees do not move.

With a Beaufort scale of 4, the wind is considered moderate at a speed of 5.5-7.5 m/s. On the ground, the force of such a wind is visible as follows: a strong air flow lifts dust and debris and rolls it along the road, and also sets tree branches in motion.

A storm with wind speed on the Beaufort scale occurs at number “9”: trees on the ground begin to be uprooted and roof coverings of houses begin to collapse.

Varieties of wind

There are several types of winds as currents of air masses over gigantic areas: monsoons, trade winds, foehn, breeze, bora.

Monsoon is a wind with clearly defined periods of activity. Air masses under this name blow from land to sea in winter, and from sea to land in summer. The wind is rich in moisture. Its localization is mainly in Asia.

Passat- a type of wind that blows between the tropics. The time of his observation is all year round. On a 12-point scale, this wind blows with a force of 3-4 points.

Breeze– a warm wind with less localization than, for example, a monsoon or trade wind. The breeze mainly blows at night from the shore to the sea, and during the day from the sea to the shore. The direction can change several times a day.

Irina Tulenkova
Cognitive experimentation lesson “Why does the wind blow?” (senior group)

Municipal state preschool educational institution

Kindergarten "Fairy tale".

Cognitive experimentation.

Subject: « Why does the wind blow?»

Tulenkova Irina Yurievna

Educator II

qualifying

MKDOU d/s "Fairy tale"

Tyumen region,

Kondinsky district,

With. Leushi, st.

Volgogradskaya. 56,

tel. (34677) 37-134

With. Leushi 2011

Target: Introduce children with the cause of wind - the movement of air masses.

Tasks:

1. Clarify children’s ideas about properties air: hot rises up - light; the cold one goes down - it is heavy.

2. Strengthen children's knowledge about air.

3. Develop skills in conducting experiments.

4. Improve breathing technique skills.

5. Instill in children the initial elements of environmental culture.

6. Introduce children with such a natural phenomenon as wind, its role in the life of nature and man.

7. Foster a culture of communication, activate speech activity. Methodological techniques We: Experiments conducted by the teacher together with the children; artistic word (riddles, poems about the wind); breathing exercises; physical training; game; surprise moment; result; analysis.

Educator: Guys, let's close our eyes and listen, what do you hear? Children: (children's answers).

And I hear the rustling of leaves and imagine how in our the breeze flies through the group, fresh, light. Do you hear?

Or maybe you and I will turn into trees and imagine that breeze sways our branches.

Fizminutka: « The wind blows in our faces» .

Educator: Guys, while we were listening breeze, he visited us group and brought us a balloon. Let's see what it says there. (The teacher reads the note attached to the ball). There is a riddle here, pay attention to it listen:

We need him to breathe, to inflate the balloon. He is next to us every hour, but he is invisible to us.

What is this? (air)

That's right, it's air. And today we will talk about air, we will conduct experiments like real scientists. And for this we have an air transformation laboratory.

(we go into the laboratory)

Educator: Guys, who saw the air? Maybe he doesn’t exist at all? (children's answers) Let's check this with you now.

with BAGS Teacher: What do we have in our bags?

Children: Air.

Educator: What is he like? Do we see him? Why don't we see him?? Why they call him invisible?

Children: The air is transparent, which means everything can be seen through it.

Educator: Guys, look what I have?

Children: Cup.

Educator: What is it made of?

Children: Made of glass.

Educator: So the glass is glass. Look through it, you see

anything.

Children: Yes!

Educator: So what glass?

Children: Transparent.

Educator: Do you think this glass is empty? Is there anything in it?

(children's answers)

Educator: We'll check now.

WITH GLASS

Educator: There are bowls of water and glasses on the table. You need to turn the glass upside down and slowly release it into the bowl. You need to hold the glass very level. What happened? Does water get into the glass? Why not. (children's answers) Educator: We learned that there is air in the glass and releases water into it. Now let's tilt the glass a little, what appears in the water?

Children: (bubbles)

Educator: That's right, air comes out of the glass, and water takes its place. How else can you see the air?

(children's answers)

Educator: Let's take a straw, put it in the water and blow. What comes out of the water with bubbles?

Children: Air.

Educator: Right. You and I exhaled air, because all people breathe air. When we simply inhale and exhale air, do we see it? Children: No!

Educator: (takes a napkin). Can you see it with a napkin?

Children: Yes!

Educator: And you can also see how we breathe in winter - what comes out of our mouths? Children: Steam.

Educator: Let us show you how our noses breathe.

Breathing exercises:

1. "Breath" Breathe through one nostril and peace will come to you.

I. p. - standing, the torso is straightened, but not tense; close the right nostril index finger right hand, take a long, long breath with your left nostril; as soon as the inhalation is completed, take a long breath through your nose (4 times,

The same exercise with the left nostril.

2. "Breath". Quiet. We will breathe quietly, we will hear our hearts.

I. p. - o. With. - inhale slowly through the nose, hold your breath for 4 seconds, exhale smoothly through the mouth (2 times).

3. « Balloons» . Now let’s check whether there is a lot of air in our chest. Let's blow up the balloons (children inflate balloons and hold them). Now let's let go a little, how do you feel?

Children: Wind.

Educator: That's right, that's wind. Guys, do you know what it is? wind?

(children's answers)

Educator: Wind- this is the movement of air, it is around us, we do not see it, but it is necessary for all living beings. The wind has power. He can move ships, inflate sails, rotate mills, bend trees. Is it possible the wind can harm a person?

(children's answers)

Educator: Right, the wind varies: a hurricane, tornado, dry wind can harm people, but a light one is calm breeze, brings coolness. yj Over the seas the wind is rushing,

Sails fly like birds.

And salty, like a whim. It is called - (breeze).

The wind is strong and mighty,

He gathered clouds over the house,

The rain beats like a drum

Conductor -

(hurricane).

If the wind blows hotly,

He's called -

(dry wind)

It drives away sand and dust

Feather grass bends to the ground in the steppe.

This wind, everyone needs to know

It's called - (tornado) He captured everyone in a whirlwind, Spun from all sides.

Ellie disappeared into a fairy tale

And suddenly he fell silent.

Educator: Do you want to become the wind for a few minutes?

WITH BOARDS.

Educator: Our bowls turn into the sea. And you will be the winds. Let's blow on the water. What happens?

Children: Waves.

Educator: The stronger the wind is blowing, those more waves (but in everything you need to know when to stop). Now let go sailing ships ki, if you blow on it, what will happen?

Children: The ship is sailing.

Educator: Likewise, large sailing ships move thanks to the wind. What happens to the boat if there is no wind? What if the wind is very strong?

Children: Starts wind and the ship may be wrecked.

Educator: Now let’s take a fan and wave it over the water. Why did the waves appear?? The fan moves and pushes the air. The air also begins to move. Means wind- this is the movement of air. Why does air move? Let's do another experiment.

WITH A CANDLE.

Educator: Let's clamp the candle and place it on a stand on the table. Let's place it in a lamp glass, under which we put some blocks. Hold your hand over the lamp glass. How does this make you feel?

Children: Air is coming out of the lamp glass.

Educator: Now let’s hold a piece of paper cut into thin strips under the lamp glass. What will happen?

Children: The stripes are deviated upward.

Educator: This means that the air is heated and the heated air rises. Guys, what do you think, if we open the door slightly, will it fly towards us? breeze?

(children's answers)

Educator: Let's check.

WITH A CANDLE.

Educator: We bring a lit candle to the slightly open door. If you hold a candle over the top edge of the door, the flame of the candle will deviate towards the street.

If the candle is placed on the floor, the flame will deviate to the side groups. This means that warm air is light, it flows out of our groups on the street, and its place is taken by a cold one.

So it is on the street. Our Earth is heating unevenly. Where it heats up more, streams of warm air are formed, which rush upward, and in their place streams of cold air rush. That's how it works wind. Or maybe it will happen that all the air in the yard will heat up and fly away, and we will have nothing to breathe?

(children's answers)

Leading: That's right, this won't happen, if the sun is warming us, then at the same time there is somewhere cold weather. And the air there is colder, which means it’s heavier. Therefore, cold air rushes to where it is warmer, and warm air has already made room by rising upward. So it turns out wind

(show diagram.)

It's clear now who's pushing wind who makes the air fly from place to place? Didn't you guess? Then I’ll give you a hint - it’s the sun. It doesn't warm the earth (evenly) the same, always somewhere colder. And if there were the same temperature on Earth, then there would be no breeze. The clouds would stop. If there was no rain, there would be a drought. Smoke from cars and factories would hang over the cities. So bad weather, it's not that bad. After all, at this time, the sun is shining happily for other children far from us.

Educator: How can we determine if on the street wind?

Children: By trees, using a ribbon, a weather vane on a house, a turntable. Educator: Well done guys, we learned a lot of interesting things, let's remember what we have today met?

Which experience did you like best?

What can you praise yourself for?

Educator: To consolidate our knowledge, I give you a pinwheel and, going out into the street, you and I will determine whether there is the wind outside and how it blows.

General atmospheric circulation- a system of air currents on the globe that promotes the transfer of heat and moisture from one area to another. Air moves from areas high pressure in the area of ​​low . High and low pressure are formed as a result of uneven heating of the earth's surface. Under the influence of the Earth's rotation, air flows are deflected to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

IN equatorial in latitudes, due to high temperatures, there is a constantly existing belt low pressure with weak winds. The heated air rises and spreads at altitude to the north and south. At high temperatures And upward movement air, with high humidity, large clouds form. Falls out here large number precipitation.

Approximately between 25 and 30° N. and Yu. w. air descends to the surface of the Earth, where, as a result, belts are formed high pressure. Near the Earth, this air is directed towards the equator (where there is low pressure), deviating to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This is how they are formed trade winds. In the central part of the high pressure belts there is a calm zone: the winds are weak. Thanks to downward air currents, the air dries out and warms up. The hot and dry regions of the Earth are located in these belts.

IN moderate latitudes with centers around 60° N. and Yu. w. pressure low. The air rises and then rushes to the polar regions. IN temperate latitudes Western air transport predominates (the deflecting force of the Earth's rotation acts).

Polar latitudes are different low temperatures air and high pressure. The air coming from the temperate latitudes descends to the Earth and is again directed to the temperate latitudes with northeastern (in the Northern Hemisphere) and southeastern (in the Southern Hemisphere) winds. There is little precipitation.

Winds

Wind- horizontal movement of air relative to the earth's surface. It arises as a result of uneven distribution of atmospheric pressure and its movement is directed from areas with higher pressure to areas where the pressure is lower. The reason for the occurrence of wind is the difference in pressure between territories, and the reason for the difference is heterogeneity in heating. The direction of the wind is determined by the part of the horizon from which it blows ( north wind blows from north to south). The direction of the winds is affected by the deflecting force of the Earth's rotation.

The winds vary origin, character, meaning . The general circulation of winds, caused by the difference in atmospheric pressure, includes: monsoons, zonal transports, cyclones, anticyclones. Local atmospheric circulation is expressed in breezes.

Types of winds.

TO local winds include breezes, mountain-valley, fen, bora, sirocco, samum, etc. IN equatorial belt Low pressure prevails, in the subtropical - high pressure, so the winds blow towards the equator. Under the influence of the Coriolis force, they are deflected to the right in the northern hemisphere and have a north- east direction, in the south - to the left and become southeast.

Föhn- warm, dry and gusty wind from the mountains. It blows when there is lower pressure on one side of the ridge than on the other. Bora- a strong, cold, gusty wind, formed when cold air passes over low ridges to the warm sea.

Trade winds– constant winds in the tropical regions of the North and Southern hemispheres, blowing from high pressure belts (25-35° N and S) to the equator (into the belt low blood pressure). Under the influence of the Earth's rotation around its axis, the trade winds deviate from their original direction. In the Northern Hemisphere they blow from northeast to southwest, in the Southern Hemisphere they blow from southeast to northwest. Trade winds are characterized by great stability of direction and speed.

In temperate latitudes of both hemispheres, westerly transports dominate ( westerly winds). Temperate westerlies are the predominant winds blowing in temperate zone approximately between 35 and 65 degrees north and south latitude. These winds blow predominantly from west to east, more precisely from the southwest in the Northern Hemisphere and from the northwest in the Southern Hemisphere.

During the day, the land heats up faster than the sea, and the air above it is warmer than above the water. An area of ​​low pressure forms above the land, and high pressure above the water, and the wind blows from the sea to the land. This afternoon breeze. At night, the land cools faster than the sea, over which an area of ​​low pressure forms, and the wind blows in reverse side - night breeze.

The formation mechanism is similar monsoon- seasonal winds that change their direction twice a year: in summer they blow on land, in winter - on the sea. In winter, the air over land is colder, over the ocean it is warmer. Consequently, the pressure is higher over the continent, lower over the ocean. Therefore, in winter, air moves from the mainland (an area of ​​higher pressure) to the ocean (over which the pressure is lower). In the warm season, it’s the other way around: the monsoons blow from the ocean to the mainland. Therefore, in monsoon areas, precipitation usually occurs in summer. Due to the rotation of the Earth around its axis, the monsoons deviate to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere from their original direction.

Special wind systems.

As a result of the uneven heating of the earth's surface and the deflecting force of the earth's rotation, huge (up to several thousand kilometers in diameter) atmospheric vortices are formed: cyclones and anticyclones. Cyclone- atmospheric vortex with low blood pressure in the center. Anticyclone- atmospheric vortex with high blood pressure in the center.

Cyclone – an ascending vortex in the atmosphere with a closed region of low pressure, in which winds blow from the periphery to the center (counterclockwise in the Northern Hemisphere, clockwise in the Southern Hemisphere). Average speed the cyclone moves 35-50 km/h, and sometimes up to 100 km/h. In a cyclone, air rises, which affects the weather. With the emergence of a cyclone, the weather changes quite dramatically: winds become stronger, water vapor quickly condenses, generating heavy cloudiness, and precipitation falls.

Anticyclone - a downward atmospheric vortex with a closed area of ​​​​high pressure, in which winds blow from the center to the periphery (in the Northern Hemisphere - clockwise, in the Southern - counterclockwise). The speed of anticyclones is 30-40 km/h, but they can linger in one place for a long time, especially on continents. In an anticyclone, the air sinks down, becoming drier as it warms up, since the vapors contained in it move away from saturation. This, as a rule, excludes the formation of clouds in the central part of the anticyclone. Therefore, during an anticyclone the weather is clear, sunny, without precipitation. In winter it is frosty, in summer it is hot.

Wind speed scale (Beaufort scale)

Points Beaufort	Wind speed, m/s	Characteristic wind	Apparent wind action
0	0-0,2	Calm	The smoke rises vertically, the leaves on the trees are motionless
1	0,3-1,5	Quiet wind	Light air movement, smoke deviates slightly
2	1,6-3,3	light wind	You can feel the movement of air on your face, the leaves rustle
3	3,4-5,4	Light wind	Leaves and thin branches on the trees sway
4	5,5-7,9	Moderate wind	Tree tops bend, small branches move, dust rises
5	8-10,7	fresh wind	Branches and thin tree trunks sway
6	10,8-13,8	Strong wind	Thick branches sway, telephone wires hum
7	13,9-17,1	strong wind	Tree trunks sway, large branches bend, it becomes difficult to walk against the wind
8	17,2-20,7	Very strong wind	Large trees sway, small branches break, it is very difficult to walk
9	20,8-24,4	Storm	Minor damage to buildings, thick tree branches breaking
10	24,5-28,4	Severe storm	Trees break or are uprooted, major damage to buildings
11	28,5-32,6	Fierce Storm	Great destruction
12	32,7-36,9	Hurricane	Devastating destruction

Lesson summary " Wind. Wind systems". Next topic:

The relationship between man and the wind has always been extremely closely related to each other. It is from this natural phenomenon that prehistoric times(as, indeed, now) a person’s life often directly depended. With its help, humanity was able to develop crafts and make their lives much easier, which can be observed even in such a banal example as a windmill. It is not surprising that for as long as humanity has existed, so many people have asked and are still asking themselves and each other the question, why does the wind blow?

This riddle still remains extremely difficult to understand not only for a child, but also for an adult. Scientists who study inanimate nature still argue about why the wind blows, where the wind blows from, and where the wind blows.

Scientific and technical encyclopedic dictionary defines wind as a flow of air masses (a mixture of gases, particles of which fly freely in space), which quickly moves parallel to the surface of the Earth. Another interpretation of wind says that wind is a natural phenomenon that causes air masses to move due to certain changes that occur in the environment.

Wind arises due to uneven distribution of pressure in the atmosphere. As soon as it appears, it immediately begins to move from the high pressure zone to the low pressure zone. To put it more simply, why the wind blows, we can safely say that if it weren’t for the Sun, the land and the oceans of our planet, then after a fairly short time the air would have the same temperature and humidity everywhere, which is why the wind would not blow I would never.

How do air masses move?

Throughout the day, the surface of our planet heats up unevenly. This applies not only to objects that are located at a distance from each other, but also to those that are located very close. For example, over the same period of time things are more dark color heat up (absorb heat) much more than light ones. The same can be said when comparing water with land (the latter reflects less sunlight).

In turn, heated objects transfer heat unevenly to the air that surrounds them. For example, since the earth heats up much more than the water, during the day air from the earth rises upward, and colder air from the sea comes in its place. At night, the reverse process occurs - while the earth has cooled, the waters of the sea remain warm. Accordingly, the warm air above the sea goes up, and the air from the land goes in its place.

Warmer air rises where it collides with colder air. This happens because heated air becomes light and rushes upward, while cold air, on the contrary, becomes heavier and rushes down. How big difference have temperatures of cold and warm flow, the stronger the wind usually blew. Thus, not only a light breeze arises, but also small whirlwinds, hurricanes and even tornadoes.

The air itself tends to be the same everywhere. When some heterogeneity forms (in one place it is warmer, in another it is colder, in a third there are more gas particles, in a fourth there are fewer), it moves horizontally, trying to eliminate the “inequality”.

A similar process occurs throughout the globe. Most warm place on our planet this is the equator. It is here that the heated warm air constantly goes up, and from there it goes either to the North, or South poles. After this, at certain latitudes it descends again to the ground and begins to move. Where exactly the wind blows depends on the circumstances. Maybe further to the poles, or maybe back to the equator.

Earth Rotation

The flow of air masses is affected by the rotation of our planet. It is because of it that all the winds that blow in the Northern Hemisphere shift to the right, and in the Southern Hemisphere - to the left.

Atmospheric pressure

Our body, without even knowing it, constantly feels air pressure - despite the fact that it seems absolutely weightless to us. According to the latest scientific data, the entire atmosphere of our Earth (in other words, the layer of gases), consisting mainly of nitrogen and oxygen, weighs five quadrillion tons.

Atmospheric pressure is different in different places on Earth. Gas molecules strive to compensate for this, and constantly move at great speed in different directions(due to the gravity of the Earth, these particles are completely attached to it, and cannot fly into space in any way).

This is how it turns out that wind is the movement of a huge number of molecules of atmospheric gases in one direction. Air masses usually flow from an area of ​​high pressure (when the air is cold - an anticyclone) to an area of ​​low pressure (when it is warm - a cyclone), thereby filling the voids of rarefied air.

Wind classification

Strong winds that have an average duration (one minute) are squalls. There are these types of winds:

• Breeze is a warm wind near the sea, where you can see a light wind blowing on the coast. The wind direction changes twice during the day. The daytime (or sea) wind often blew from the sea to the shore, and the nighttime (or coastal) wind - vice versa. The breeze speed is usually from 1 to 5 m/s;
• A storm is an extremely strong wind, the speed of which ranges from 16 to 20 m/s.
• Storm – occurs during a cyclone, speed – from 15 to 32 m/s;
• A hurricane is a very strong storm, which was caused by air masses moving in different directions at enormous speed, the speed of which is from 32 m/s;
• Typhoon is a huge hurricane destructive force, which blew and blows mainly near east coast Asia, on Far East, as well as the western Pacific Ocean.

Gusts of wind are short-term (several seconds) and strong (several hours and even months) movements of air masses. For example, for tropical climate The following types of winds are distinguished:

• Monsoons are winds, characteristic mainly of tropical regions, that blow for several months, sometimes changing the direction of the wind. In summer - from the ocean to land, in winter - vice versa. At the same time, the summer monsoons are characterized by high humidity.
• Trade winds - such a wind usually blows and blows in tropical latitudes throughout the whole year, in the Northern Hemisphere - from the northeast direction, in the Southern Hemisphere - from the southeast. They are separated from each other by a windless strip.

Due to the constant change in pressure, the direction of the wind is constantly changing. But in any case, the wind always moves from an area of ​​high pressure to an area of ​​low pressure.

For thousands of years, people have been observing the winds, drawing certain conclusions, putting forward hypotheses, and drawing up graphs in order to make the best use of this in their activities. amazing phenomenon inanimate nature. Thus, the so-called Wind Rose appeared - a drawing, or more precisely, a diagram that depicts exactly how the wind blows in a particular area.

The Wind Rose is composed in this way: eight straight lines are drawn from the center at a distance of 45° from each other, on which marks are applied with a length proportional to either the frequency of the winds or their speeds. After this, the ends of the marks are connected and two polygonal figures are obtained - the Wind Recurrence Rose and the Wind Speed ​​Rose.

The wind rose makes it possible to determine the direction, strength, and duration of the prevailing wind, as well as the frequency of air currents. The compass rose is drawn both to determine the average values ​​and to determine the maximum values. You can create complex drawing, on which diagrams will be plotted, consisting of several parameters at once, which will also show where the wind is blowing.

The drawings are extremely necessary for a person– during construction, to solve various economic problems (for example, in lately thanks to the wind, it became possible to obtain electricity), etc. After all, the wind may well be both a friend and an enemy - if you do not pay attention to it and do not take into account its influence on environment, he is quite capable of causing irreparable damage by destroying a man-made creation. Although the wind is a phenomenon uncontrollable by man, since it has blown and will blow wherever he wants, but now humanity can predict its approximate direction and strength, which can save many lives.

Moving in a certain direction. On other planets it represents a mass of gases characteristic of their surface. On Earth, wind moves predominantly horizontally. Classification, as a rule, is carried out in accordance with the speed, scale, types of forces that cause them, and places of distribution. Various flows are influenced by natural phenomena and the weather. Wind facilitates the transfer of dust, plant seeds, and facilitates the movement of flying animals. But how does directed air flow occur? Where does the wind blow from? What determines its duration and strength? And anyway, why do the winds blow? This and much more is discussed further in the article.

Classification

First of all, winds are characterized by strength, direction and duration. Gusts are considered to be strong and short-term movements (up to several seconds) of air currents. If a strong wind blows average duration(about a minute), 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, depending on the temperature difference on the relief surface during the day, can last up to several hours. Local and general circulation The atmosphere is made up of trade winds and monsoons. Both of these types fall into the category of "global" winds. Monsoons are caused by seasonal changes in temperature and last up to several months. Trade winds are constantly moving winds. They are caused by temperature differences at different latitudes.

How to explain to a child why the wind blows?

For children in early age this phenomenon is of particular interest. The child does not understand where the air flow is formed, which is why it is present in one place and not in another. It is enough to simply explain to your child that in winter, for example, a cold wind blows due to low temperatures. How does this process happen? It is known that the air flow is a mass of atmospheric gas molecules moving together in one direction. A small-volume air flow can whistle and rip off the hats of 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 enclosed spaces, air practically does not move. And you can even forget about its existence. But if you put your hand out of the window of a moving car, for example, 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 look at this process in more detail.

Atmospheric pressure difference

So why does the wind blow? For children, it is better to use a dam as an example. On one side the height of the water column is, for example, three meters, and on the other - six meters. When the floodgates open, water will flow into the area where there is less water. Roughly the same thing happens with air flows. IN different parts The atmosphere pressure is different. This is due to the difference in temperature. In warm air, molecules move faster. Particles tend to fly apart from each other different sides. Due to this, warm air is more discharged and weighs less. As a result, the pressure that is created in it decreases. If the temperature is lowered, the molecules form closer clusters. Air, accordingly, weighs more. This increases the pressure. Similar to water, air has the ability to flow from one zone to another. Thus, the flow moves from an area with high pressure to an area with low pressure. That's why the winds blow.

Movement of streams near bodies of water

Why does the wind blow from the sea? Let's look at an example. On a sunny day, the rays warm both the shore and the pond. 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 is heating up much faster. And the air above it is more rarefied, and the pressure, accordingly, is lower. Atmospheric currents rush from the reservoir to the shore - to a freer area. There they, heating up, rise upward, 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.

Meaning of winds

Having figured out why the winds blow, we should talk about the impact they have on life on Earth. The wind has great value for human civilization. Vortex flows inspired people to create mythological works, expanded the trade and cultural range, and influenced historical phenomena. Winds also acted as energy suppliers for various mechanisms and units. Due to the movement of air currents, they were able to overcome significant distances across oceans and seas, and balloons- across the sky. For modern aircraft the winds are great practical significance- they allow you to save fuel and increase But it should be said that air currents can also cause harm to humans. For example, due to gradient wind fluctuations, control over the control of the aircraft may 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 growth of fires. In general, phenomena associated with the formation of air flows in various ways impact on living nature.

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 predominate, and in temperate latitudes, westerly winds predominate. At the same time, in the tropics, air flows again take an eastern direction. At the boundaries between these zones - the subtropical ridge and the polar front - there are so-called calm areas. There are practically no prevailing winds in these areas. Here the air movement is mainly vertical. This explains the appearance of zones of high humidity (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 occur on a significant scale. So, for example, trade winds moving over Atlantic Ocean, carry dust from African desert areas to the West Indies and some areas of North America.

Local effects of air mass formation

When figuring out why the winds blow, we should also talk 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 distant areas. It can be caused by different light absorption coefficients or different heat capacities surfaces. The latter effect is strongest between and land. The result is a breeze. Another local factor of importance is the presence of mountain systems.

Mountain influence

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

An increase in friction near the valley surface leads to a deflection of the parallel-directed air flow to the height of nearby mountains. This contributes to the formation of a high-altitude jet current. The speed of this flow can exceed the strength of the surrounding wind by up to 45%. As mentioned above, mountains can act as an obstacle. When going around the circuit, the flow changes its direction and strength. Changes in mountain ranges have significant influence to the movement of the wind. For example, if in a mountain range that is traversed atmospheric mass, there is a pass, 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 changes in height cause fluctuations. Due to a significant gradient in air speed, the flow becomes turbulent and continues to remain so even behind a mountain on a plain at a certain distance. Such effects are present in some cases special meaning. For example, they are important for aircraft taking off and landing at mountain airfields.