Wind as a natural phenomenon has been known to everyone since early childhood. It pleases with a fresh breeze on a hot day, drives ships across the sea, and can even bend trees and break roofs on houses. The main characteristics that determine the wind are its speed and direction.

From a scientific point of view, wind is called movement air masses in the horizontal plane. This movement occurs because there is a difference atmospheric pressure and heat between two points. Air moves from areas high pressure to areas where the pressure level is lower. As a result, wind arises.

Wind characteristics

In order to characterize the wind, two main parameters are used: direction and speed (force). The direction is determined by the side of the horizon from which it blows. It can be indicated in points, in accordance with the 16-point scale. According to it, the wind can be north, southeast, north-northwest, and so on. can also be measured in degrees, relative to the meridian line. On this scale, north is defined as 0 or 360 degrees, east as 90 degrees, west as 270 degrees, and south as 180 degrees. In turn, they are measured in meters per second or in knots. A knot is approximately 0.5 kilometers per hour. Wind strength is also measured in points, according to the Beaufort scale.

According to which the wind force is determined

This scale was introduced in 1805. And in 1963, the World Meteorological Association adopted a gradation that is still in effect today. Within its framework, 0 points corresponds to calm, in which the smoke will rise vertically and the leaves on the trees will remain motionless. A wind force of 4 corresponds to a moderate wind, in which small waves form on the surface of the water and thin branches and leaves on trees can sway. 9 points correspond to a storm wind, in which even big trees, tiles are torn off roofs, high waves rise on the sea. And the maximum wind force in accordance with this scale, namely 12 points, occurs in a hurricane. This is a natural phenomenon in which the wind causes serious damage; even permanent buildings can collapse.

Harnessing the power of the wind

Wind power is widely used in the energy sector as one of the renewable natural sources. Since time immemorial, humanity has been using this resource. Suffice it to recall sailing ships. Windmills, with the help of which wind is converted for further use, are widely used in those places characterized by constant strong winds. Among the various areas of application of such a phenomenon as wind power, it is also worth mentioning the wind tunnel.

Wind - a natural phenomenon, which can bring pleasure or destruction, as well as be useful to humanity. And its specific action depends on how great the strength (or speed) of the wind turns out to be.

The main quantity characterizing the strength of the wind is its speed. The magnitude of the wind speed is determined by the distance in meters it travels during 1 second. For example, if in 20 sec. the wind traveled a distance of 160 m, then its speed v for a given period of time was equal to:

Wind speed is highly variable: it changes not only over a long period of time, but also over short periods of time (within an hour, a minute and even a second) by large amount. In fig. Figure 1 shows a curve showing the change in wind speed over 6 minutes. From this curve we can conclude that the wind moves at a pulsating speed.

Fig. 1. Characteristics of wind speed.

Wind speeds observed over short periods of time from a few seconds to 5 minutes are called instantaneous or real. Wind speeds obtained as arithmetic averages from instantaneous speeds are called average wind speeds. If you add up the measured wind speeds during the day and divide by the number of measurements, you get the average daily wind speed. If we add up the average daily wind speeds for the entire month and divide this sum by the number of days of the month, we get the average monthly wind speed. Adding up the average monthly speeds and dividing the sum by twelve months, we get the average annual wind speed. An interesting student project. Famous people of Russia. A very large database of surnames and everything is free.
Wind speeds are measured using instruments called anemometers. The simplest anemometer, which allows one to determine instantaneous wind speeds and is called the simplest weather vane anemometer, is shown in Fig. 2.

Fig. 2. The simplest weather vane anemometer.

It consists of a metal board swinging about a horizontal axis a, mounted on a vertical stand b. On the side of the board, on the same axis a, sector b is fixed, with eight pins. A weather vane d is attached to the stand b below the sector, which always positions the board with its plane facing the wind. When the latter operates, the board deflects and passes past the pins, each of which indicates a certain wind speed. The post b with the weather vane d rotates around the bushing d, in which 4 long rods are fixed in the horizontal plane, indicating the main cardinal directions: north, south, east and west, and between them 4 short ones, pointing to the northeast, northwest, south -east and southwest. Thus, using a weather vane anemometer, you can simultaneously determine both the speed and direction of the wind.
The values ​​of wind speeds corresponding to each pin of sector b are given in Table. 1.

It is convenient to determine average wind speeds over short and long periods of time using an anemometer from the Metrpribor plant (Fig. 3). It consists of a crosspiece with hemispheres placed on an axle, which meshes with a gear train placed in a dial box.

Fig. 3. Anemometer from the Metrpribor plant.

The gear axes are displayed on the dial and have arrows at their ends that show on the scale the path traveled by the wind in a given period of time. Dividing the number shown by the hands on the dial by the number of seconds during which the anemometer rotated, we obtain the wind speed per second for the observed period. For example, before the start of observation, the arrows on the dial showed 7170 m, but after 2 minutes, equal to 120 seconds, the arrows showed 7650 m. Therefore, average speed wind over a period of time of 2 minutes. was equal to:

If the above instruments are not available, then the wind speed can be determined approximately by external signs observed in nature (see Table 2).

Each natural phenomenon, which has different degrees of severity, is usually assessed in accordance with certain criteria. Especially if information about it must be transmitted quickly and accurately. For wind strength, the Beaufort scale has become a common international reference point.

Developed by the British rear admiral, a native of Ireland, Francis Beaufort (accent on the second syllable) in 1806, the system, improved in 1926 by adding information about the equivalence of wind strength in points to its specific speed, allows you to fully and accurately characterize this atmospheric process, while remaining relevant and to this day.

What is wind?

Wind is the movement of air masses parallel to the surface of the planet (horizontally above it). This mechanism is caused by pressure differences. The direction of movement always comes from a higher area.

To describe the wind it is customary to use the following characteristics:

• speed (measured in meters per second, kilometers per hour, knots and points);
• wind force (in points and m.s. - meters per second, the ratio is approximately 1:2);
• direction (according to the cardinal points).

The first two parameters are closely related. They can be mutually designated by each other's units of measurement.

The direction of the wind is determined by the side of the world from which the movement began (from the north - north wind, etc.). The speed is determined by the pressure gradient.

Pressure gradient (otherwise known as barometric gradient) is the change in atmospheric pressure per unit distance normal to a surface of equal pressure (isobaric surface) in the direction of decreasing pressure. In meteorology, they usually use the horizontal barometric gradient, that is, its horizontal component (Great Soviet Encyclopedia).

Wind speed and strength cannot be separated. A large difference in indicators between atmospheric pressure zones gives rise to strong and rapid movement of air masses above the earth's surface.

Features of wind measurement

In order to correctly correlate weather service data with your actual position or make a correct measurement, you need to know what standard conditions professionals use.

• Wind force and speed are measured at a ten-meter height on an open, flat surface.
• The name of the direction of the wind is given by the cardinal direction from which it blows.

Water transport managers, as well as those who like to spend time in nature, often purchase anemometers that determine speed, which is easily correlated with wind force in points. There are waterproof models. For convenience, devices of various compactness are produced.

In the Beaufort system, a description of the height of waves correlated with a certain wind force in points is given for an open maritime space. It will be significantly less in shallow waters and coastal areas.

From personal to global use

Sir Francis Beaufort not only had a high military rank in the navy, but was also a successful practical scientist who held important positions, a hydrographer and cartographer who brought great benefit to the country and the world. One of the seas in the Arctic Ocean, washing Canada and Alaska, bears his name. An Antarctic island is named after Beaufort.

A convenient system for assessing wind strength in points, accessible to all precise definition manifestation of the phenomenon “by eye”, Francis Beaufort created for his own use in 1805. The scale ranged from 0 to 12 points.

In 1838 the system visual assessment weather and wind force in points began to be officially used by the British fleet. In 1874 it was adopted by the international synoptic community.

In the 20th century, several more improvements were made to the Beaufort scale - the ratio of points and verbal description of the manifestation of the elements with wind speed (1926), and five more divisions were added - points for grading the strength of hurricanes (USA, 1955).

Criteria for estimating wind force in Beaufort points

IN modern form The Beaufort scale has several characteristics that make it possible to most accurately correlate a specific atmospheric phenomenon with his indicators in points.

• Firstly, this is verbal information. Verbal description of the weather.
• Average speed in meters per second, kilometers per hour and knots.
• The impact of moving air masses on characteristic objects on land and sea is determined by typical manifestations.

Harmless wind

Safe wind is determined in the range from 0 to 4 points.

	Name	Wind speed (m/s)	Wind speed (km/h)		Description	Characteristic
	Calm, complete calm (Calm)		less than 1 km/h		The movement of smoke is vertically upward, the leaves of the trees do not move	The surface of the sea is motionless, smooth
	Quiet Wind (Light Air)				The smoke has a slight angle of inclination, the weather vane is motionless	Light ripples without foam. Waves no higher than 10 centimeters
	Light Breeze				You can feel the wind blowing on your face, there is movement and rustling of leaves, slight movement of the weather vane	Short, low waves (up to 30 centimeters) with a glass-like comb
	Weak (Gentle Breeze)				Continuous movement of foliage and thin branches on the trees, swaying flags	The waves remain short but are more noticeable. The ridges begin to tip over and turn into foam. Rare small “lambs” appear. The height of the waves reaches 90 centimeters, but on average does not exceed 60
	Moderate Breeze				Dust and small debris begin to rise from the ground	The waves become longer and rise up to one and a half meters. "Lambs" appear often

A wind of 5 points, characterized as “fresh”, or fresh breeze, can be called borderline. Its speed ranges from 8 to 10.7 meters per second (29-38 km/h, or 17 to 21 knots). Thin trees sway along with their trunks. Waves rise up to 2.5 (on average two) meters. Sometimes splashes appear.

The wind that brings trouble

With a wind force of 6, strong phenomena begin that can cause damage to health and property.

Points	Name	Wind speed (m/s)	Wind speed (km/h)	Wind speed (sea speed)	Description	Characteristic
	Strong Breeze				Thick tree branches sway strongly, the hum of telegraph wires can be heard	Large waves form, foam crests acquire significant volume, and splashes are likely. The average wave height is about three meters, the maximum reaches four
	Strong (Moderate gale)				The trees are completely swaying	Active movement of waves up to 5.5 meters high, overlapping each other, scattering of foam along the line of wind movement
	Very strong (Gale)				Tree branches break due to the pressure of the wind, making it difficult to walk against the direction of the wind	Waves of considerable length and height: average - about 5.5 meters, maximum - 7.5 m. Moderately high long waves. Sprays fly up. The foam falls in stripes, the vector coincides with the direction of the wind
	Storm (Strong gale)				The wind damages buildings and begins to destroy roof tiles	Waves up to ten meters with an average height of up to seven. The foam stripes become wider. Overturning ridges scatter in spray. Visibility is reduced

Dangerous wind force

Winds with a force of ten to twelve are dangerous and are characterized as a strong and violent storm, as well as a hurricane.

The wind uproots trees, damages buildings, destroys vegetation, and destroys buildings. The waves emit deafening noise from 9 meters and above, and are long. At sea, they reach dangerous heights even for large ships - from nine meters and above. Foam covers the water surface, visibility is zero or close to this.

The speed of movement of air masses ranges from 24.5 meters per second (89 km/h) and reaches from 118 kilometers per hour with a wind force of 12 points. Severe storms and hurricanes (winds equal to 11 and 12 points) occur very rarely.

Additional five points to the classic Beaufort scale

Since hurricanes are also not identical in intensity and degree of damage, in 1955 the United States Weather Bureau adopted an addition to the standard Beaufort classification in the form of five scale units. Wind strength from 13 to 17 points inclusive - these are clarifying characteristics for destructive hurricane winds and accompanying phenomena environment.

How to protect yourself when disaster strikes?

If a storm warning from the Ministry of Emergency Situations occurs at open area, it is better to follow the advice and reduce the risk of accidents.

First of all, you should pay attention to warnings every time - there is no guarantee that atmospheric front will come to the area where you are, but you also cannot be sure that he is in Once again will bypass her. All items should be removed or securely secured to protect pets.

If a strong wind hits a fragile structure - a garden house or other light structures - it is better to close the windows on the side of the air movement and, if necessary, strengthen them with shutters or boards. From the leeward side, on the contrary, open it slightly and fix it in this position. This will eliminate the danger of an explosive effect from the pressure difference.

It is important to remember that any strong wind can bring with it unwanted precipitation - in winter there are blizzards and blizzards, in summer dust and sand storms are possible. It should also be taken into account that strong winds can occur even in absolutely clear weather.

Wind is a horizontal flow of air that differs in a number of specific characteristics: strength, direction and speed. It was to determine the speed of the winds that the Irish admiral back in early XIX century developed a special table. The so-called Beaufort scale is still used today. What is the scale? How to use it correctly? And what does the Beaufort scale not allow you to determine?

What is wind?

The scientific definition of this concept is as follows: wind is an air flow that moves in parallel earth's surface from an area of ​​high to an area of ​​low atmospheric pressure. This phenomenon is characteristic not only of our planet. So, the strongest in solar system winds blow on Neptune and Saturn. And the earthly winds, in comparison with them, may seem like a light and very pleasant breeze.

The wind has always played an important role in human life. He inspired ancient writers to create mythical stories, legends and fairy tales. It was thanks to the wind that a person had the opportunity to overcome significant distances by sea (with the help of sailboats) and by air (by means of balloons). The wind is also involved in the “construction” of many earthly landscapes. Thus, it transports millions of grains of sand from place to place, thereby forming unique aeolian landforms: dunes, dunes and sand ridges.

At the same time, winds can not only create, but also destroy. Their gradient fluctuations can provoke a loss of control over the aircraft. Strong winds significantly expand the scale of forest fires, and on large bodies of water it creates huge waves that destroy houses and take lives. This is why it is so important to study and measure wind.

Basic wind parameters

It is customary to distinguish four main parameters of wind: strength, speed, direction and duration. All of them are measured by special devices. The strength and speed of the wind are determined using a so-called anemometer, and the direction - using a weather vane.

Based on the duration parameter, meteorologists distinguish squalls, breezes, storms, hurricanes, typhoons and other types of winds. The direction of the wind is determined by the side of the horizon from which it blows. For convenience, they are abbreviated with the following Latin letters:

• N (northern).
• S (south).
• W (western).
• E (east).
• C (calm).

Finally, wind speed is measured at a height of 10 meters using anemometers or special radars. Moreover, the duration of such measurements is different countries the world is not the same. For example, at American meteorological stations the average speed of air flows is taken into account in 1 minute, in India - in 3 minutes, and in many European countries- in 10 minutes. The classic tool for presenting data on wind speed and strength is the so-called Beaufort scale. How and when did it appear?

Who is Francis Beaufort?

Francis Beaufort (1774-1857) - Irish sailor, naval admiral and cartographer. He was born in the small town of An Uavy in Ireland. After graduating from school, the 12-year-old boy continued his studies under the leadership of the famous Professor Usher. During this period, he first showed extraordinary ability to study “marine sciences”. IN adolescence he entered the service of the East India Company and took an active part in surveying the Java Sea.

It should be noted that Francis Beaufort grew up to be a rather brave and courageous guy. Thus, during the shipwreck in 1789, the young man showed great dedication. Having lost all his food and personal belongings, he managed to save the team's valuable tools. In 1794, Beaufort took part in a naval battle against the French and heroically towed a ship that was hit by enemy fire.

Development of the wind scale

Francis Beaufort was extremely hardworking. Every day he woke up at five o'clock in the morning and immediately got to work. Beaufort was a significant authority among military men and sailors. However, he gained worldwide fame thanks to his unique development. While still a midshipman, the inquisitive young man kept a daily diary of weather observations. Later, all these observations helped him create a special wind scale. In 1838 it was officially approved by the British Admiralty.

One of the seas, an island in Antarctica, a river and a cape in northern Canada are named after the famous scientist and cartographer. Francis Beaufort also became famous for creating a polyalphabetic military cipher, which also received his name.

Beaufort scale and its features

The scale represents the earliest classification of winds according to their strength and speed. It was developed based on meteorological observations in conditions open sea. Initially, the classical Beaufort wind scale is twelve-point. Only in the middle of the twentieth century was it expanded to 17 levels so that hurricane-force winds could be distinguished.

Wind strength on the Beaufort scale is determined by two criteria:

1. According to its effect on various ground objects and objects.
2. According to the degree of excitement of the open sea.

It is important to note that the Beaufort scale does not allow you to determine the duration and direction of air flows. It contains a detailed classification of winds according to their strength and speed.

Beaufort scale: table for sushi

Below is a table with detailed description the effects of wind on ground objects and objects. The scale, developed by the Irish scientist F. Beaufort, consists of twelve levels (points).

Beaufort scale for sushi

Wind power (in points)	Wind speed	The effect of wind on objects
0	0-0,2	Complete calm. Smoke rises vertically
1	0,3-1,5	The smoke deviates slightly to the side, but the weather vanes remain motionless
2	1,6-3,3	The leaves on the trees begin to rustle, the wind is felt on the skin of the face
3	3,4-5,4	Flags flutter, leaves and small branches sway on the trees
4	5,5-7,9	The wind lifts dust and small debris from the ground
5	8,0-10,7	You can “feel” the wind with your hands. Thin trunks of small trees sway.
6	10,8-13,8	Large branches sway, wires hum
7	13,9-17,1	Tree trunks sway
8	17,2-20,7	Tree branches break. It becomes very difficult to go against the wind
9	20,8-24,4	Wind destroys awnings and roofs of buildings
10	24,5-28,4	Significant damage, wind can tear trees out of the ground
11	28,5-32,6	Large destruction over large areas
12	more than 32.6	Huge damage to houses and buildings. The wind destroys vegetation

Beaufort Table of Sea State

In oceanography there is such a thing as the state of the sea. It includes the height, frequency and strength of sea waves. Below is the Beaufort scale (table), which will help determine the strength and speed of the wind based on these signs.

F. Beaufort scale for the open ocean

Wind power (in points)	Wind speed	Effect of wind on the sea
0	0-1	The surface of the water mirror is perfectly flat and smooth
1	1-3	Small disturbances and ripples appear on the surface of the water
2	4-6	Short waves up to 30 cm in height appear
3	7-10	The waves are short, but clearly defined, with foam and “waddles”
4	11-16	Elongated waves up to 1.5 m in height appear
5	17-21	The waves are long with widespread “lambs”
6	22-27	Large waves with splashes and foamy crests form
7	28-33	Large waves up to 5 m high, foam falls in stripes
8	34-40	High and long waves with powerful spray (up to 7.5 m)
9	41-47	High (up to ten meters) waves are formed, the crests of which overturn and scatter with splashes
10	48-55	Very high waves that capsize with a strong roar. The entire surface of the sea is covered with white foam
11	56-63	The entire water surface is covered with long whitish flakes of foam. Visibility is significantly limited
12	over 64	Hurricane. Visibility of objects is very poor. The air is oversaturated with spray and foam

Thus, thanks to the Beaufort scale, people can observe the wind and estimate its strength. This makes it possible to make the maximum accurate forecasts weather.

The movement of air above the Earth's surface in a horizontal direction is called by the wind. The wind always blows from an area of ​​high pressure to an area of ​​low pressure.

Wind characterized by speed, force and direction.

Wind speed and strength

Wind speed measured in meters per second or points (one point is approximately equal to 2 m/s). The speed depends on the pressure gradient: the greater the pressure gradient, the higher the wind speed.

The strength of the wind depends on the speed (Table 1). The greater the difference between neighboring areas of the earth's surface, the stronger the wind.

Table 1. Wind strength at the earth's surface according to the Beaufort scale (at a standard height of 10 m above an open, flat surface)

Beaufort points	Verbal definition of wind force	Wind speed, m/s	Wind action
			Calm. Smoke rises vertically	Mirror smooth sea
			The direction of the wind is noticeable from the direction of the smoke, but not from the weather vane	Ripples, no foam on the ridges
			The movement of the wind is felt on the face, the leaves rustle, the weather vane moves	Short waves, crests do not capsize and appear glassy

			The leaves and thin branches of the trees sway all the time, the wind flutters the upper flags	Short, well defined waves. The ridges, overturning, form a glassy foam, occasionally small white lambs are formed
	Moderate		The wind raises dust and pieces of paper and moves thin tree branches.	The waves are elongated, white caps are visible in many places
			Thin tree trunks sway, waves with crests appear on the water	Well developed in length, but not very large waves, white caps are visible everywhere (in some cases splashes are formed)
			Thick tree branches sway, telegraph wires hum	Large waves begin to form. White foamy ridges occupy significant areas (splashes are likely)
			The tree trunks are swaying, it’s difficult to walk against the wind	The waves pile up, the crests break off, the foam lies in stripes in the wind
	Very strong		The wind breaks tree branches, it is very difficult to walk against the wind	Moderately high long waves. Spray begins to fly up along the edges of the ridges. Strips of foam lie in rows in the direction of the wind
			Minor damage; the wind tears off smoke hoods and tiles	High waves. The foam falls in wide dense stripes in the wind. The crests of the waves begin to capsize and crumble into spray, which impairs visibility

	Heavy storm		Significant destruction of buildings, trees are uprooted. Rarely happens on land	Very high waves with long, downward-curving crests. The resulting foam is blown away by the wind in large flakes in the form of thick white stripes. The surface of the sea is white with foam. The strong roar of the waves is like blows. Visibility is poor
	Fierce Storm		Large destruction over a large area. Very rarely observed on land	Exceptionally high waves. Small and medium-sized vessels are sometimes hidden from view. The sea is all covered with long white flakes of foam, located downwind. The edges of the waves are blown into foam everywhere. Visibility is poor
		32.7 or more		The air is filled with foam and spray. The sea is all covered with stripes of foam. Very poor visibility

Beaufort scale— a conventional scale for visually assessing the strength (speed) of the wind in points based on its effect on ground objects or on sea waves. It was developed by the English admiral F. Beaufort in 1806 and at first was used only by him. In 1874, the Standing Committee of the First Meteorological Congress adopted the Beaufort scale for use in International Synoptic Practice. In subsequent years, the scale was changed and refined. The Beaufort scale is widely used in maritime navigation.

Direction of the wind

Direction of the wind is determined by the side of the horizon from which it blows, for example, the wind blowing from the south is south. The direction of the wind depends on the pressure distribution and the deflecting effect of the Earth's rotation.

On climate map the prevailing winds are shown by arrows (Fig. 1). The winds observed at the earth's surface are very diverse.

You already know that the surface of land and water heats up differently. On a summer day, the land surface heats up more. When heated, the air over land expands and becomes lighter. At this time, the air above the reservoir is colder and, therefore, heavier. If the body of water is relatively large, on a quiet hot summer day on the shore you can feel a light breeze blowing from the water, above which it is higher than above the land. Such a light breeze is called a daytime breeze breeze(from the French brise - light wind) (Fig. 2, a). The night breeze (Fig. 2, b), on the contrary, blows from land, since the water cools much more slowly and the air above it is warmer. Breezes can also occur at the edge of the forest. The breeze diagram is shown in Fig. 3.

Rice. 1. Distribution diagram of the prevailing winds on the globe

Local winds can occur not only on the coast, but also in the mountains.

Föhn- a warm and dry wind blowing from the mountains to the valley.

Bora- a gusty, cold and strong wind that appears when cold air passes over low ridges to the warm sea.

Monsoon

If the breeze changes direction twice a day - day and night, then seasonal winds - monsoons- change their direction twice a year (Fig. 4). In summer, the land quickly warms up, and the air pressure above its surface increases. At this time, cooler air begins to move inland. In winter, the opposite is true, so the monsoon blows from land to sea. With the change from the winter monsoon to the summer monsoon, there is a change from dry, partly cloudy weather to rainy.

The effect of monsoons is strongly manifested in the eastern parts of the continents, where they are adjacent to vast expanses of oceans, so such winds often bring heavy precipitation to the continents.

The unequal nature of atmospheric circulation in different regions of the globe determines differences in the causes and nature of monsoons. As a result, a distinction is made between extratropical and tropical monsoons.

Rice. 2. Breeze: a - daytime; b - night

Rice. 3. Breeze pattern: a - during the day; b - at night

Rice. 4. Monsoons: a - in summer; b - in winter

Extratropical monsoons - monsoons of temperate and polar latitudes. They are formed as a result of seasonal pressure fluctuations over the sea and land. The most typical zone of their distribution is Far East, Northeast China, Korea, and to a lesser extent Japan and the northeast coast of Eurasia.

Tropical monsoons - monsoons of tropical latitudes. They are caused by seasonal differences in heating and cooling of the Northern and Southern hemispheres. As a result, pressure zones shift seasonally relative to the equator to the hemisphere in which given time summer. Tropical monsoons are most typical and persistent in the northern part of the basin Indian Ocean. This is greatly facilitated by the seasonal change in atmospheric pressure over the Asian continent. The fundamental features of the climate of this region are associated with the South Asian monsoons.

The formation of tropical monsoons in other areas of the globe occurs less characteristically, when one of them is more clearly expressed - the winter or summer monsoon. Such monsoons are observed in Tropical Africa, in northern Australia and in the equatorial regions of South America.

Constant winds of the Earth - trade winds And westerly winds- depend on the position of the atmospheric pressure belts. Since in equatorial belt Low pressure prevails, and near 30° N. w. and Yu. w. - high, at the surface of the Earth throughout the year the winds blow from the thirties latitudes to the equator. These are trade winds. Under the influence of the Earth's rotation around its axis, trade winds deviate to the west in the Northern Hemisphere and blow from northeast to southwest, and in the Southern Hemisphere they are directed from southeast to northwest.

From high pressure belts (25-30° N and S latitude), winds blow not only towards the equator, but also towards the poles, since at 65° N. w. and Yu. w. low pressure prevails. However, due to the rotation of the Earth, they gradually deviate to the east and create air currents moving from west to east. Therefore, in temperate latitudes, westerly winds predominate.