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Speed, strength and direction of the wind. Where the strongest winds on earth blow

“Wind, wind in all God's world,” wrote A. Blok. It is difficult to argue with the poet: it is difficult to find a place on our planet where there has never been a wind. And this is not surprising, because the air, surrounding the earth, is in in constant motion. Why it happens?

Imagine that the air on Earth is heated uniformly. Then there would be no wind in its usual form: the air would move only vertically - it would rise, heating up, and descend, cooling down. But since the atmosphere heats up unevenly, heavier cold air is constantly moving to replace the rising warm air. The air heats up most strongly over the equator, weaker over the poles. Therefore, there are constant winds blowing in the direction from the poles to the equator (of course, not quite rectilinearly, because the rotation of the Earth also affects their direction): in the northern hemisphere - from the northeast, in the southern hemisphere - from the southeast. Over the continents, their direction changes somewhat, but over the oceans nothing interferes with them, and it was these winds that were the main "assistants" of sailors in times sailing ships. That is why they were called "favorable to movement" - in Spanish, viento de pasada, or trade winds.

Over the very region of the equator, between the thirtieth degrees of northern and southern latitude, the trade winds have no power. Here, as a rule, there is a calm - a real "curse" for sailing ships. In the old days, ships, having got here, risked being “stuck” for a long time - water supplies dried up, and in order to save it, sailors had to throw horses on board ships overboard. It was rumored that in these parts at night you can see the ghosts of unfortunate animals ... and therefore these latitudes were called "horse".

The difference in air temperature exists not only between the equator and the poles, but also between the ocean and land. It generates monsoons - seasonal winds in Africa and Asia. In summer they blow from the ocean to the mainland and bring rain, but in winter their direction changes: they blow from the mainland to the ocean.

The direction of constant winds can change not only across the continents depending on the seasons, but also locally - depending on the time of day (after all, air and water temperatures also change during the day). Such a wind blowing on the coast or on the shore big lake called a breeze. During the day, the Sun heats the land faster than water, and blows from the sea to land sea ​​breeze(It is also called the daytime breeze). At night, everything happens exactly the opposite: the land cools faster than the sea - and now the wind blows from the coast to the sea, this is called the coastal (or night) breeze. The speed of such a wind is small, no more than five meters per second, but it can be felt even several tens of kilometers from the coast.

In some cases, the wind is generated by land relief features. So, in areas where low mountains are located near the coast, the flow of cold air, having overcome the obstacle in the form of mountains, can fall on the coast with great force, causing a temperature drop of up to forty degrees. This wind is called bora. He “lives” from one day to a week, but manages to make trouble (for example, in 2002, several dozen people died in Novorossiysk because of such a wind).

There are also winds of "local significance", which may even have proper names Yes, on mediterranean coast France spring blows cold wind from mountain range Cevennes - they call it mistral. He is able to uproot trees, and those that survived grow leaning towards the south. Mistral causes so many problems (especially - agriculture) that A. Dumas called it the scourge of Provence along with the Durance River, infamous for its floods, and ... parliament.

There is also a local wind on Baikal, which comes from the movement of cold air from the Daurian steppes. It is especially strong in autumn, but even then its speed does not exceed 20 m/s. This is about him sung in the old song of exile and penal servitude: "Hey, Barguzin, stir the shaft, thunder is heard."

In the Russian North, the wind blowing from White Sea, called siverko. Pomors have long believed that the siverko invigorates at work and amuses in moments of rest ... However, one can talk endlessly about local winds ... after all, the wind, as you know, is "in all God's world."

Atmospheric pressure and its measurements

The air surrounding the Earth has mass, and therefore presses on the earth's surface. 1 liter of air at sea level weighs about 1.3 g. Therefore, for every square centimeter earth's surface the atmosphere presses with a force of 1.33 kg. This average air pressure at sea level, corresponding to the mass of a mercury column 760 mm high with a cross section of 1 cm2, is taken as normal. Air pressure is also measured in millibars: 1 mm of pressure is 1.33 mbar. So, to convert millimeters to millibars, you need to multiply millimeters of pressure by 1.33.

The pressure value varies with air temperature and altitude. Since air expands when heated and contracts when cooled, warm air is lighter (causes less pressure) than cold air. As air rises upward, the pressure decreases mainly because the height of its column is less per unit area. Therefore, in high mountains pressure is much less than at sea level. The vertical segment through which the atmospheric pressure decreases by one is called the baric degree. In the lower layers of the atmosphere near the surface, the pressure decreases by about 10 mm for every 100 m of elevation.

A mercury barometer is used to measure pressure, and in field conditions- metal aneroid barometer. The latter is a metal box from which air is pumped out. With an increase atmospheric pressure the bottom of the box contracts, and when it decreases, it unbends. These changes are transmitted to the arrow, which moves along the dial.

Winds and their origin

Zonality also appears in the distribution of pressure on the earth's surface. The general planetary pressure distribution scheme is as follows: a belt extends along the equator reduced pressure; to the north and south of it at the C-40 latitudes - belts high blood pressure, further on 60-70 ° with. and yu. sh. - Belts of low pressure, in the polar regions - areas of high pressure. Real distribution pattern

pressure is much more complicated, which is reflected in the maps of July and January isobars).

The uneven distribution of pressure on the globe causes the movement of air from an area of ​​high pressure to an area of ​​low pressure. This movement of air in a horizontal direction is called wind. How more difference pressure, the stronger the wind blows. The strength of the wind is estimated from 0 to 12 points.

The direction of the wind is determined by the side of the horizon from which it blows. The wind changes with changes in pressure. The rotation of the Earth around its axis also has a significant influence on its direction.

General circulation of the atmosphere. Trade winds and other constant winds

The winds observed above the earth's surface are divided into three groups: local winds caused by local conditions (temperature, relief features) winds of cyclones and anticyclones; winds, is part of the general circulation of the atmosphere. The general circulation of the atmosphere is formed by the largest air currents planetary scale, covering the entire troposphere and lower stratosphere (up to about 20 km) and are characterized by relative stability. In the troposphere, these include the trade winds, westerly winds temperate latitudes and east winds polar regions, monsoons. The cause of these planetary air movements is pressure difference.

A belt of low pressure forms above the equator due to the fact that here the air is warm during the year and it mainly rises (upward air movement dominates). In the upper troposphere, it cools and spreads towards high latitudes. The Coriolis force, deflecting air currents coming in the upper troposphere from the equator, provides them with a westerly direction at 30 latitudes, forcing them to move only along the parallels. Therefore, this cooled air is subjected here to a downward movement, causing high pressure (although the air temperature near the surface is even higher than at the equator). These subtropical belts high pressure serve as the main “vitrorozdilams” on Earth. From them, the volumes of air in the lower layer of the troposphere are directed both towards the equator and towards temperate latitudes.

Winds, characterized by stability of direction and speed, throughout the year blow from high pressure belts (25-35 ° N and S) to the equator are called trade winds. Due to the rotation of the Earth around its axis, they deviate from the previous direction, in the Northern Hemisphere they blow from the northeast to the southwest, and in the Southern - from the southeast to the northwest.

Winds blowing away subtropical belts high pressure towards the poles, deviating to the right or left depending on the hemisphere, change their direction to the west. Therefore, in temperate latitudes, westerly winds predominate, although they have not become as strong as the trade winds.

Constant winds also blow from the high pressure regions of the polar latitudes towards the temperate latitudes with relatively low pressure. Experiencing the action of the force of rotation, in the Northern Hemisphere they are northeast, and in the South - southeast.

In temperate latitudes, where warm air masses from the tropics and cold air masses from the polar regions meet, frontal cyclones and anticyclones constantly arise, in which air is transported from west to east.

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

Wind characterized by speed, strength 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 baric gradient: the greater the baric gradient, the higher the wind speed.

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

Table 1. Wind strength near the earth's surface on the Beaufort scale (on standard height 10m above open flat ground)

Beaufort points

Verbal definition of wind strength

Wind speed, m/s

wind action

Calm. Smoke rises vertically

Mirror-smooth sea

The direction of the wind is noticeable but the smoke is carried, but not by 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 is set in motion

Short waves, crests do not tip over and appear glassy

Leaves and thin branches of trees are constantly swaying, the wind is waving the top flags

Short, well defined waves. Combs, tipping over, form a vitreous foam, occasionally small white lambs are formed

Moderate

The wind raises dust and pieces of paper, sets in motion the thin branches of trees.

The waves are elongated, white lambs 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 lambs are visible everywhere (splashes form in some cases)

Thick tree branches sway, telegraph wires hum

Large waves begin to form. White foamy ridges take up significant space (probable splashing)

Tree trunks sway, it's hard to go against the wind

Waves pile up, crests break, foam falls in stripes in the wind

Very strong

The wind breaks the branches of trees, it is very difficult to go against the wind

Moderately high long waves. On the edges of the ridges, spray begins to take off. Stripes of foam lie in rows in the direction of the wind

Minor damage; the wind rips off the smoke caps and roof tiles

high waves. Foam in wide dense stripes lays down in the wind. The crests of the waves begin to capsize and crumble into spray that impair visibility.

Heavy storm

Significant destruction of buildings, trees uprooted. Rarely on land

Very high waves with long downward curved crests. The resulting foam is blown 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

Violent storm

Large destruction over a large area. Very rare on land

Exceptionally high waves. Small to medium sized boats are sometimes out of sight. The sea is all covered with long white flakes of foam, spreading downwind. The edges of the waves are everywhere blown into foam. Visibility is poor

32.7 and more

The air is filled with foam and spray. The sea is all covered with strips of foam. Very poor visibility

Beaufort scale- a conditional scale for visual assessment of the strength (speed) of the wind in points according to its effect on ground objects or on waves at sea. 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 has changed and refined. The Beaufort scale is widely used in marine 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 on the deflecting effect of the Earth's rotation.

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

You already know that the surface of land and water heats up in different ways. On a summer day, the land surface heats up more. From heating, the air above the land expands and becomes lighter. Over the pond at this time the air is colder and therefore heavier. If the reservoir 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 land. Such a light breeze is called daytime. breeze(from the French brise - light wind) (Fig. 2, a). The night breeze (Fig. 2, b), on the contrary, blows from the 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 scheme of breezes is shown in fig. 3.

Rice. 1. Scheme of distribution of 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- gusty, cold and strong wind that appears when cold air rolls 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 warms up quickly, and the air pressure over its surface hits. At this time, cooler air begins to move to land. In winter, the opposite is true, so the monsoon blows from land to sea. With the change of the winter monsoon to the summer monsoon, dry, slightly cloudy weather changes to rainy.

The action 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 rainfall to the continents.

The uneven nature of the circulation of the atmosphere in different areas the globe determines the differences in the causes and nature of the monsoons. As a result, extratropical and tropical monsoons are distinguished.

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

Rice. Fig. 3. Scheme of breezes: a - in the afternoon; 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 fluctuations in pressure over the sea and land. The most typical zone of their distribution is the Far East, Northeast China, Korea, and to a lesser extent Japan and the northeastern coast of Eurasia.

tropical monsoons - monsoons of tropical latitudes. They are due to seasonal differences in the 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 largely facilitated by the seasonal change in the atmospheric pressure regime 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 regions of the globe is less characteristic when one of them, the winter or summer monsoon, is more clearly expressed. Such monsoons are observed in Tropical Africa, in northern Australia and in the equatorial regions of South America.

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

From the high pressure belts (25-30°N and S), the winds blow not only towards the equator, but also towards the poles, since at 65°N. sh. and yu. sh. 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, westerly winds prevail in temperate latitudes.

The wind is one of the most unique natural phenomena. We cannot see it, touch it, but we are able to observe the results of its manifestation, for example, how it slowly or quickly drives clouds and clouds across the sky, with its power tilts trees to the ground or slightly ruffles foliage.

Wind concept

What is wind? The definition from the point of view of meteorology is as follows: this is the horizontal movement of layers of air from a zone with high atmospheric pressure to a zone of low pressure, accompanied by a certain speed. This movement occurs because during the day the sun penetrates the Earth's air layer. Some rays, reaching the surface, heat the oceans, seas, rivers, mountains, soil, rocks and stones, which give off heat to the air, thereby heating it as well. For the same amount of time, dark objects absorb more heat and warm up more.

But what does it matter how heat is given off and how quickly? And how does this help us figure out what wind is? The definition is as follows: land heats up more rapidly than water, which means that the air accumulated above it receives heat from it and rises, therefore, the atmospheric pressure over this area drops. With water, everything is exactly the opposite: above it, the air masses are colder and the pressure is higher. As a result, cold air is displaced from the area of ​​high pressure to the area of ​​low pressure, forming a wind. The greater the difference between these pressures, the stronger it is.

Types of winds

Having dealt with what wind is, you need to find out how many of its types exist and how they differ from each other. There are three main groups of winds:

  • local;
  • permanent;
  • regional.

Local winds correspond to their name and blow only in certain areas of our planet. Their appearance is associated with the specifics of local reliefs and temperature changes in relatively short periods of time. These winds are characterized by short duration and diurnal periodicity.

What is a wind of local origin is now clear, but it is also divided into its subspecies:

  • A breeze is a light wind that changes direction twice a day. During the day it blows from the sea to the land, and vice versa at night.
  • Bora is a high-velocity cold air current that blows from the tops of mountains to valleys or coasts. He is fickle.
  • Föhn is a warm and light spring wind.
  • Dry wind - dry wind prevailing in the steppe regions in warm period time under anticyclone conditions. He foretells drought.
  • Sirocco - rapid southern, southwestern air currents that form in the Sahara.
  • What is the khamsin wind? These are dusty, dry and hot air masses that prevail in northeast Africa and the east of the Mediterranean.

TO constant winds include those that depend on the total air circulation. They are stable, uniform, constant and strong. They belong to:

  • trade winds - winds from the east, are distinguished by constancy, not changing direction and strength of 3-4 points;
  • antitrade winds - winds from the west, carrying huge air masses.

The regional wind appears as a result of pressure drops, a bit like the local one, but more stable and powerful. bright representative This species is considered the monsoon, which originates in the tropics, at the turn of the ocean. It blows periodically, but in large streams, changing its direction a couple of times a year: in the summer season - from water to land, in winter - vice versa. The monsoon brings a lot of moisture in the form of rain.

Strong wind is...

What is a strong wind and how does it differ from other streams? Its most important feature is high speed, which ranges from 14-32 m/s. It produces devastating actions or brings damage, destruction. In addition to speed, temperature, direction, location and duration also matter.

Types of strong winds

  • A typhoon (hurricane) is accompanied by intense precipitation and a drop in temperature, great strength, speed (177 km / h or more), blows at a distance of 20-200 m for several days.
  • What is a wind called a squall? This is a sharp, sudden flow at a speed of 72-108 km / h, which is formed during the hot period as a result of the powerful penetration of cold air into warm zones. It blows for a couple of seconds or tens of minutes, changing direction, and brings a decrease in temperature.
  • Storm: its speed is 103-120 km/h. It is characterized by high duration, strength. He is the source of strong sea vibrations and destruction on land.

  • Tornado (tornado) is an air whirlwind, visually similar to a dark column along which a curved axis passes. At the bottom and top of the column there are expansions similar to a funnel. The air in the vortex rotates counterclockwise at a speed of 300 km / h and draws all nearby objects, objects into its funnel. The pressure inside the tornado is reduced. The column reaches a height of 1500 m, and its diameter is from a dozen (above water) to hundreds of meters (above land). A tornado can travel from a couple of hundred meters to tens of kilometers at a speed of 60 km/h.
  • Storm - air mass, the speed of which is in the range of 62-100 km / h. Storms abundantly cover the area with sand, dust, snow, earth, causing harm to people and the economy.

Description of wind force

Answering the question of what wind force is, it would be appropriate to note that here the concept of force is interconnected with speed: the higher it is, the stronger the wind. This indicator is measured on a 13-point Beaufort scale. Zero value characterizes calm, 3 points - light, weak wind, 7 - powerful, 9 - the appearance of a storm, more than nine - merciless storms, hurricanes. Strong winds often blow over the sea, ocean, because nothing interferes with them here, unlike rocky mountains, hills, forests.

Definition of the solar wind

What is solar wind? This is an amazing phenomenon. Ionized plasma particles flow out of the solar corona (outer layer) into space with a speed range of 300-1200 km/s, which depends on the activity of the Sun.

There are slow (400 km/s), fast (700 km/s), high-speed (up to 1200 km/s) solar winds. They form an area with space around the central celestial body, which protects solar system from interstellar gas. In addition, thanks to them, such phenomena as the radiation belt and the aurora borealis occur on our planet. That's what the solar wind is.

From the area where the pressure is increased, the air moves, "flows" to where it is lower. The movement of air is called wind. To observe the wind - its speed, direction and strength - use a weather vane and an anemometer. Based on the results of observations of the direction of the wind, wind rose(Fig. 37) for a month, season or year. Wind rose analysis allows you to establish the prevailing wind directions for a given area.

Rice. 37. Rose of Wind

Wind speed measured in meters per second. At calm wind speed does not exceed 0 m/s. Wind with a speed of more than 29 m/s is called hurricane. Most strong hurricanes noted in Antarctica, where wind speeds reached 100 m/s.

the strength of the wind measured in points, it depends on its speed and air density. Calm is 0 on the Beaufort scale and hurricane maximum amount points - 12.

Knowing general patterns distribution of atmospheric pressure, it is possible to establish the direction of the main air flows in the lower layers of the Earth's atmosphere (Fig. 38).

Rice. 38. Scheme of the general circulation of the atmosphere

1. From tropical and subtropical areas of high pressure, the main air flow rushes to the equator, to the area constantly low pressure. Under the influence of the deflecting force of the Earth's rotation, these flows deviate to the right in the Northern Hemisphere and to the left in the Southern. These constantly blowing winds are called trade winds.

2. Part of the tropical air moves to temperate latitudes. This movement is especially active in summer, when lower pressure prevails there. These air currents in the Northern Hemisphere also deviate to the right and first take a southwestern and then a western direction, and in the Southern - a northwestern direction, turning into a western one. Thus, in the temperate latitudes of both hemispheres, western air transport.

3. From the polar regions of high pressure, air moves to temperate latitudes, taking a northeasterly direction in the Northern and southeasterly in the Southern Hemispheres.

The trade winds, westerly winds of temperate latitudes and winds from the polar regions are called planetary and distributed regionally.

4. This distribution is disrupted on the eastern coasts of the continents. northern hemisphere in temperate latitudes. As a result of seasonal changes in pressure over land and the adjacent water surface of the ocean, winds blow here from land to sea in winter, and from sea to land in summer. These winds, which change their direction with the seasons, are called monsoons. Under the influence of the deflecting influence of the rotating Earth, the summer monsoons take a southeasterly direction, and the winter monsoons take a northwesterly direction. Monsoon winds especially characteristic of Far East And East China, to a lesser extent they appear on east coast North America.

5. In addition to planetary winds and monsoons, there are local, so called local winds. They arise due to the features of the relief, uneven heating of the underlying surface.

breezes- coastal winds observed in clear weather on the shores of water bodies: oceans, seas, large lakes, reservoirs and even rivers. During the day they blow from the water surface (sea breeze), at night - from land (coastal breeze). During the day, the land heats up more than the sea. The air above the land rises, the currents of air from the sea rush to its place, forming a daytime breeze. In tropical latitudes, daytime breezes are quite strong winds bringing moisture and coolness from the sea.

At night, the surface of the water is heated more than the land. The air rises, and in its place air rushes from the land. A night breeze forms. In terms of strength, it is usually inferior to daytime.

In the mountains there are hair dryers- warm and dry winds blowing on the slopes.

If low mountains rise like a dam in the path of moving cold air, boron. Cold air, having overcome a low barrier, falls down with great force, and in this case, a sharp drop in temperature occurs. Bora is known for different names: on Baikal it is sarma, in North America- chinook, in France - mistral, etc. In Russia, boron reaches its special strength in Novorossiysk.

dry winds are dry and sultry winds. They are typical for arid regions of the globe. IN Central Asia dry wind is called simum, in Algeria - sirocco, in Egypt - hatsin, etc. The speed of the dry wind reaches 20 m / s, and the air temperature is 40 ° C. Relative Humidity during dry winds, it drops sharply and drops to 10%. Plants, evaporating moisture, dry up on the vine. In deserts, dry winds are often accompanied by dust storms.

The direction and strength of the wind must be taken into account during construction settlements, industrial enterprises, dwellings. Wind is one of the most important sources of alternative energy, it is used to generate electricity, as well as to operate mills, water pumps, etc.

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§ 35. Atmospheric pressure§ 37. Weather and its forecasting