Distribution of atmospheric pressure on earth. Distribution of atmospheric pressure belts on earth - equatorial latitudes

Since our Earth is spherical, different parts of its surface heat up unevenly. This leads to the formation various areas atmospheric pressure, the distribution of which reveals a strict pattern - latitudinal zoning.

At the equator, the air is heated by the Earth. Being a mixture of gases, when heated it expands, becomes light and rises. Rising air currents form an area at the equator near the earth's surface low pressure. In the upper troposphere, air flows towards the poles. In polar latitudes, poorly heated by the Sun, cold air descends and forms regions at the poles high blood pressure.

Since wind moves from places of high pressure to places of low pressure, air masses from the poles must move back towards the equator. Such simple air circulation could exist on a non-rotating planet. On Earth, atmospheric circulation is much more complex. Due to the rotation of our planet around its own axis, the air coming from the equator gradually deviates to the east in the Northern Hemisphere and does not reach the poles. As it cools, it becomes heavier and sinks approximately at the 30° parallels in both hemispheres. At the same time, an area is formed here high pressure. At 60° latitudes of the Northern and Southern Hemispheres, the air, warming up, rises, forming an area of ​​low pressure near the earth's surface. In the troposphere, this air flows towards the poles and western latitudes, where downward air currents form areas of high pressure near the earth's surface.

Thus, as a result of the uneven heating of the Earth and the influence of the deflecting force of the Earth’s rotation around its own axis, belts of atmospheric pressure are formed on the planet: low - equatorial and moderate latitudes; high - tropical and subpolar latitudes. But it must be remembered that these belts can move. This is, firstly, influenced by differences in the heating of continents and oceans. In temperate latitudes in winter, the air over land is colder than over the ocean (land warms up faster, but also cools down faster), so the pressure over land is higher than over the ocean. In summer, the ocean warms more slowly, and the pressure over land is lower than over the ocean. In tropical latitudes, where the land is warmer than the ocean all year round, such a shift in pressure areas may not be observed. Secondly, the shift in pressure areas is associated with a shift in temperatures in the Northern and Southern Hemispheres. In summer, pressure areas are shifted to the north, in winter - to the south. This is explained by the inclination of the earth's axis to the plane of its orbit.

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Climate zones

On Earth, depending on the prevailing type of climate, the following climate zones are distinguished: two polar (Arctic and Antarctic), two temperate, two tropical, one equatorial and transitional - two subequatorial, two subtropical, two subpolar.

Equatorial belt extends to the basins of the Amazon and Congo rivers, the shores of the Gulf of Guinea, and the Sunda Islands. The sun occupies a high position all year round, due to which the earth's surface heats up greatly. Average annual temperatures in that climatic zone range from 25 to 28 °C. Moreover, this area is characterized by high humidity (70-90%). Annual precipitation is usually more than 2000 mm, and it is evenly distributed throughout the year. Thanks to the constant hot weather and high humidity, the preconditions are created for the development of lush vegetation - the equatorial jungle.

Subequatorial belts cover a vast territory, in particular Central Africa north and east of the Congo River basins, the Brazilian Highlands in South America, the Hindustan and Indochina peninsulas, Northern Australia. Characteristic feature climate of a given zone is the change in types of air masses during the seasons: in summer period the entire territory is covered by equatorial masses, and in winter by tropical ones. Accordingly, two seasons are distinguished: summer wet and winter tropical. Most of the belt's territory is covered by open forests and savannas.

Tropical zone located on both sides of the tropics on sea and land. Tropical air masses prevail here all year round. In the presence of high atmospheric pressure and slight cloudiness, it is characterized by high temperatures. Average monthly temperature the hottest month is more than 30 °C. There is very little precipitation here (less than 200 mm). It is in this belt that the most extensive deserts in the world are located - the Sahara, the desert of the Arabian Peninsula, and Western Australia.

Subtropical zone passes between 25° and 40° north and south latitude. The climate here is characterized by changing types of air masses according to the seasons of the year. Thus, tropical air dominates in summer, and air masses of temperate latitudes dominate in winter. This belt is divided into three more climatic region: western, eastern and central. Summer in the western region is characterized by clear and dry weather, while winter is warm and humid. This is the so-called Mediterranean climate. In the central and eastern regions the climate is slightly different.

Temperate zone extends north and south from the subtropical and reaches the polar circles. IN Southern Hemisphere It is characterized by an oceanic type of climate; in the North it is divided into three climatic regions: western, central and eastern. The western region and the Southern Hemisphere are dominated by humid sea ​​air. Annual amplitudes temperatures are low. The distribution of precipitation throughout the year is uniform. A decrease in temperature in winter is observed due to the movement of Arctic (Antarctic) air masses. The eastern region has a monsoon climate. Continental air masses of temperate latitudes accumulate in the central region and are characterized by sharp temperature changes throughout the year. The transitional subarctic and subantarctic belts extend to the north temperate zones two hemispheres. They are characterized by changes in air masses in accordance with the changing seasons of the year. Summer is short and cold, winter is long, snowy, with frosts and snowstorms.

The Arctic and Antarctic belts lie in the polar regions. The climate here is formed at high atmospheric pressure by cold air masses. Characteristic feature These zones include polar nights and days lasting up to six months. The ice sheet does not melt and covers Antarctica and Greenland.

Related materials:

1. Atmosphere
2. Clouds

5. Air temperature

Equatorial belt - geographical zone Earth, located on both sides of the equator from 5°-8° N. w.

to 4°-11° south sh., between subequatorial belts.

Characteristics of the equatorial belt:

• The predominance of equatorial air masses throughout the year.
• Constantly high temperatures (on the plains 24°-28 °C).
• Weak, unstable winds. Characterized by the presence of a stripe low blood pressure with a constant influx of trade winds into it and a tendency towards general upward air movements and the rapid transformation of tropical air into humid equatorial air ( relative humidity 80-95 %).
• Heavy precipitation throughout the year (1500-3000 mm, in some places up to 10,000 mm).
• Constantly hot and humid equatorial climate, caused by a large influx of solar radiation. Climate seasons not expressed or weakly expressed. Low blood pressure, abundant tropical rains, high temperatures, but without dry periods, create conditions for the growth of humid equatorial forests and the cultivation of valuable tropical crops (sago and coconut palms, bananas, pineapples, cocoa).
• Dense multi-story forests with an exceptional diversity of flora and fauna predominate. Animal world equatorial forests are rich and varied. Many animals live in trees. Various monkeys are numerous. There are a variety of birds, insects, and termites. Terrestrial inhabitants include small ungulates (African deer, etc.).

SECTION 3 GEOGRAPHICAL ENVIRONMENT

Topic 2. Atmosphere

§ 35. Atmospheric pressure. Atmospheric pressure belts on Earth

Remember

Does air have weight?

Air presses on the earth's surface. For a long time, people believed that air was weightless. Only in the 17th century. Italian scientist E. Torricelli proved that air presses on the earth's surface and surrounding objects with a certain force, which he called atmospheric pressure. So, Atmosphere pressure- this is the force with which a column of air placed between the surface of the Earth and the upper boundary of the atmosphere presses on each unit of the earth’s surface. This force is usually measured in millimeters. mercury(mm Hg) using barometers (Fig. 94).

Air presses on the earth's surface different places With different strengths. This is explained by the uneven heating of the Earth's surface, which, in turn, heats the air. Let's assume that some part of the earth's surface has a higher temperature. The surrounding air will also heat up and begin to rise. Rising upward (updraft), the air will press on the surface with less force. Where the air descends (downdraft), it puts more pressure on the ground. Therefore, high pressure zones arise here.

Rice. 94. Aneroid barometer (1), electronic barometer (2)

At sea level, the atmospheric pressure is close to the pressure of a column of mercury 760 mm high. This pressure is taken to be normal atmospheric pressure.

Changes in atmospheric pressure. Atmospheric pressure varies depending on the altitude of the area. Thus, high in the mountains the atmospheric pressure is much lower than at sea level. This is explained by the fact that with height the column and air density decrease, and therefore its pressure decreases.

Atmospheric pressure changes not only with altitude, but also in the horizontal direction due to air movement. The pressure difference causes air to move from an area of ​​high pressure to an area of ​​low pressure. As a result of this movement to certain territories excess air mass is formed, which causes an increase in pressure here.

Facts of our time

Atmospheric pressure and human well-being. When a person rises to a significant altitude, her health deteriorates significantly due to lack of oxygen and low pressure. Already at an altitude of about 5 km it is necessary to use oxygen masks, although there are athletes who climbed Everest (height 8841 m) without oxygen masks. However, this is at the limit of human capabilities.

Planetary "belts" of atmospheric pressure. On Earth, there are several main stripes, elongated along parallels, with a predominance of high or low pressure. they are called atmospheric pressure belts (Fig. 95). In equatorial latitudes, where high temperatures persist throughout the year, heated air constantly rises, leaving behind a belt of low atmospheric pressure. Rising above the equator warm air cools and spreads in all directions. Under the influence of the force of the Earth's rotation, large masses of this air descend in tropical latitudes (near 30° latitude and latitude). As the air descends, it presses on the earth's surface and creates belts of high atmospheric pressure here. In the surface layer of air it moves both north and south, respectively, towards temperate or equatorial latitudes.

Rice. 95. Distribution of atmospheric pressure on Earth

Rice. 96. Isobar map (fragment)

In temperate latitudes, a belt of low atmospheric pressure is formed, which is mainly due to constant air movement. In the polar latitudes, a belt of high pressure is formed, which is explained by the prevalence of low temperatures throughout the year.

Lines with the same atmospheric pressure on a map. Atmospheric pressure distribution on geographical map shown using lines (Fig. 96). Lines connecting points on a map with the same atmospheric pressure are called isobars. (Remember that maps show isotherms.) Using the isobar map, you can determine the features of the spatial distribution of atmospheric pressure on Earth, see areas of high and low pressure that significantly influence the formation of weather in a given area.

Air presses on the surface of the Earth.

The force with which a column of air presses on each unit of the earth's surface is called atmospheric pressure.

On globe There are seven main atmospheric pressure belts: equatorial - low pressure, two tropical - high pressure, two moderate - low pressure, two polar - high pressure.

Questions and tasks for self-test

Draw a diagram of the distribution of atmospheric pressure on the globe and explain it.

What determines the distribution of atmospheric pressure on Earth? Choose the correct answer. Atmospheric pressure is measured using: a) a thermograph; b) thermometer; c) barometer; d) weather vane. What is atmospheric pressure?

Atmospheric pressure is the pressure of the atmosphere on all objects in it and the Earth's surface. Atmospheric pressure is created by the gravitational attraction of air towards the Earth.

In 1643 Evangelista Torricelli showed that air has weight. Together with V. Viviani, Torricelli conducted the first experiment in measuring atmospheric pressure, inventing the Torricelli tube (the first mercury barometer), a glass tube in which there is no air. In such a tube, mercury rises to a height of about 760 mm.

On the earth's surface, atmospheric pressure varies from place to place and over time. Particularly important are the non-periodic changes in atmospheric pressure that determine the weather, associated with the emergence, development and destruction of slowly moving areas of high pressure (anticyclones) and relatively fast moving huge eddies (cyclones), in which low pressure prevails. Fluctuations in atmospheric pressure at sea level were noted within the range of 684 - 809 mm Hg. Art.

Normal atmospheric pressure is a pressure of 760 mmHg. Art. at sea level at 15°C. (International Standard Atmosphere - ISA) (101,325 Pa) .

Atmospheric pressure decreases as altitude increases, since it is created only by the overlying layer of the atmosphere. The dependence of pressure on height is described by the so-called. barometric formula. The height to which one must rise or fall in order for the pressure to change by 1 hPa is called the barometric (barometric) step. At the earth's surface at a pressure of 1000 hPa and a temperature of 0 °C, it is equal to 8 m/hPa. With increasing temperature and increasing altitude above sea level, it increases, i.e. it is directly proportional to temperature and inversely proportional to pressure. The reciprocal of the pressure level is the vertical pressure gradient, i.e., the change in pressure when rising or falling by 100 meters. At a temperature of 0 °C and a pressure of 1000 hPa, it is equal to 12.5 hPa.

On maps, pressure is shown using isobars - lines connecting points with the same surface atmospheric pressure, necessarily reduced to sea level. Atmospheric pressure is measured by a barometer.

In chemistry, the standard atmospheric pressure since 1982, according to IUPAC recommendations, is considered to be a pressure of exactly 100 kPa

Air movement depends on uneven heating of the earth's surface sun rays. Due to the unequal accumulation of air masses and the difference in atmospheric pressure at different points on the earth's surface, ascending and descending air currents arise, which move air masses in both horizontal and vertical directions. Wind speed (horizontal movement of air masses) is measured by the distance traveled by an air mass per unit time and is expressed in meters per second (m/sec).

It is widely used to determine the speed of air movement in points on the twelve-point Beaufort scale.

The speed of air movement varies widely, from tenths of a meter to 30 or more meters per second during storms, blizzards, and hurricanes.

A characteristic feature of air movement is its unevenness, or turbulence, depending on the presence of various obstacles and uneven terrain in the path of air movement, forest areas, settlements etc.

The direction of the wind is determined by the point on the horizon from where the wind blows, and is indicated in rhumbs, letters of the Latin or Russian alphabet according to the names of the countries of the world: north through N, or N, south through S, or S, east through E, or E, and west through W , or W.

In addition to the main points, the wind direction is also indicated by additional or intermediate points: northeast through NE, or NE, southeast through SE, or SE, southwest through SW, or SW, etc.

The direction of the wind changes both during the day and throughout the year. Moreover, at each point there is a known repeatability or frequency of the wind direction along the horizon points.

A graphic representation of the frequency of wind direction at a particular point is called a wind rose. The wind rose is compiled based on determining wind directions over a long period of time (two years), and sometimes based on monthly and seasonal data.

From the center (point) lines (points) are drawn in eight directions and on each of them segments proportional to the frequency of winds are laid.

Calm days are indicated by a circle, the radius of which must correspond to the number of days of calm. The ends of the segments are connected by lines and as a result, a (closed) figure is obtained, which will be the compass rose.

The wind rose gives a visual representation of the predominance of one or another wind direction at a given point for a month, season, or year.

Determining the wind rose or their frequency is of great hygienic importance, especially when planning livestock farms, relative position and the direction of the façade of the premises, the choice of places for camps and camps for animals in order to protect against harmful influence prevailing winds in the area.

Up to 30° northern latitude Northeast winds predominate, from 30 to 60° - southwest and from 60 to 903 - again northeast.

In coastal and mountainous areas local winds are observed: during the day from water to land, at night from land to sea; during the day from the plains to the mountains, at night from the mountains to the plains.

In animal premises, the air is in continuous and uneven movement.

The speed of air movement and its direction are determined by the presence of ventilation structures, the opening of gates and windows, the crackiness of walls and ceilings, the release of heat by animals, etc.

In winter, the speed of air movement in enclosed spaces for animals in the absence of defects in the walls and ceilings at a height of 0.5 m from the floor fluctuates more often in the range of 0.05-0.25 m/sec and rarely reaches a value of 0.3 m/sec . In autumn and spring, air movement in rooms decreases somewhat, and in summer, when open windows and doors reaches 7 m/sec.

The speed of air movement in rooms fluctuates more sharply in the end parts of the building and in the area where animals lie (in barns).

Wind, as a weather factor, has an indirect and direct effect on the animal's body. The movement of air, along with its temperature and humidity, significantly affects the heat exchange of the animal body. The higher the speed of air movement, the faster the change of layers directly adjacent to the skin occurs. If the air temperature is lower than the skin temperature and the buffer air in hairline, then the movement of air breaks the air shell, the cold mass of air comes into contact with the skin and promotes increased heat transfer through convection and evaporation from the surface of the skin.

If the air temperature is higher than the skin temperature, then heat transfer by convection is weakened or stopped; in these cases, if the air humidity is low, the heat transfer by evaporation increases.

Indoor air movement in summer from 0.3 to 1.6 m/sec contributes to the better condition of animals.

Experiments conducted over two summer seasons at the University of California (USA) found that when outside temperature 31-32 in the pen with a fan, where the air speed reached 1.6 m/sec, the weight gain of animals was 1075-1088 g per day per head, and in the pen where the natural air speed was on average 0.2 m/sec , the weight gain was only 585-848 g at equal conditions feeding and watering.

At low temperatures and high humidity, air mobility promotes enhanced heat transfer through convection, heat conduction and heat radiation.

Thus, at high temperatures, moving air (wind) protects animals from overheating, and at low temperatures it increases the possibility of hypothermia.

Moderate winds have a beneficial effect on animals, especially during hot weather.

Cold and damp winds cause severe cooling and even frostbite in animals. Strong winds at high temperature and dry air contribute to the burning of vegetation, saturate the air with dust, cause severe sweating and evaporation in animals, thirst, decreased appetite, constipation, decreased productivity, etc.

Cold and damp winds represent great danger for animals and when keeping them indoors, when doors, windows are opened on both sides or when there are cracks in the walls (drafts).

To protect animals from chilling during the cold season, strong air movement should not be allowed in the premises.

The maximum exchange of air in animal premises, if the air is not preheated, should not exceed 5 times the volume of the internal cubic capacity of the room. It is advisable to maintain the speed of air movement in animal premises in winter within the range from 0.05 to 0.25 m/sec. However, the issue of optimal air movement speeds in animal premises has not been sufficiently developed and requires more in-depth study, taking into account various microclimatic conditions.

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LECTURE 3.

Atmosphere pressure

Physical properties of air

Pressure change with height, Pressure change horizontally. Isobars.

Pressure distribution at the Earth's surface

Wind.

Physical properties of air

Air creates pressure on the surface of the earth and on all objects located near its surface.

Consequently, this air correspondingly exerts a pressure of about 16-18 tons on the entire surface of the human body, which has an area of ​​1.6-1.8 m². Usually we do not feel this, since under the same pressure the gases are dissolved in the fluids and tissues of the body and from the inside balance the external pressure on the surface of the body.

However, when external atmospheric pressure changes due to weather conditions it takes some time to balance it from within, which is necessary for the amount of gases dissolved in the body to increase or decrease. Changing pressure in the accessory cavities of the skull promotes blood circulation in the brain. Changes in pressure difference between external environment and closed body cavities affect the human condition. During this time, a person may feel some discomfort, since when the atmospheric pressure changes by only a few mmHg.

Art. the total pressure on the surface of the body changes by tens of kilograms. These changes are especially clearly felt by people suffering from chronic diseases of the musculoskeletal system, cardiovascular system, etc. A decrease in atmospheric pressure affects the sympathetic nervous system; suppresses mood, reduces performance, increases susceptibility to infectious diseases.

Conversely, its increase excites the nervous system to a greater extent.

Basic physical properties air: density, pressure, temperature.

Density is the ratio of the mass of a substance to its volume. 1 m3 of water at a temperature of 4°C has a mass of 1 ton, and 1 m3 of air at 0°C and normal pressure (760 mm Hg).

Art.) has a mass of 1.293 kg. Therefore, under these conditions, the density of water is 1000 kg/m3, and the density of air is 1.293 kg/m3. Thus, the density of air is approximately 800 times less than the density of water.

The density of the atmosphere decreases rapidly with altitude.

Half of the total mass of the atmosphere is concentrated in a layer up to a height of 5.5 km.

Atmospheric pressure - this is the force with which a column of air, extending from the surface of the earth to the upper boundary of the atmosphere, presses on a unit of the earth’s surface. Atmosphere pressure for a long time expressed in millimeters (mm) of mercury, i.e.

That is, force was measured using a linear measure, which was inconvenient when solving many problems. In practice, 1/1000 of a bar is used as a pressure unit. millibar . At sea level, the height of the mercury column in the tube is usually about 760 mm. The value of 760 mm was first obtained in 1644 by Evangelista Torricelli (1608-1647) and Vincenzo Viviani (1622-1703) - students of the Italian scientist Galileo Galilei.

1 mb (millibar) = 1 GPa (gigapascal) = 0.75 mm Hg.

Art. (rounded 3/4 mm Hg.

Atmosphere pressure. Change and influence on weather

1 mmHg Art. = 1.33 mb = 1.33 GPa (rounded to 4/3 mb).

The pressure level is the vertical distance that must be raised or lowered for the pressure to change by 1 mb.

Temperature . The higher the temperature, the lower the air density. In the case of constant pressure, air density depends on temperature changes. As the flight altitude increases, the pressure decreases and the temperature decreases.

The pressure decreases faster than the temperature. A decrease in temperature somewhat slows down the decrease in density. Air density decreases with altitude more slowly than pressure.

Pressure distribution at the Earth's surface

Pressure around the globe can vary widely.

Thus, the maximum atmospheric pressure is 815.85 mm Hg. Art. (1087 mb) was registered in winter in Turukhansk, the minimum is 641.3 mm Hg. Art. (854 mb) - in Hurricane Nancy over the Pacific Ocean.

Air pressure on our planet can vary widely.

If the air pressure is more than 760 mm Hg. Art., then it is considered increased, less - decreased.

Atmospheric pressure rises twice during the day (morning and evening) and decreases twice (after noon and after midnight). These changes are due to temperature changes and air movement. During the year on the continents, the maximum pressure is observed in winter, when the air is supercooled and compacted, and the minimum in summer.

The distribution of atmospheric pressure over the earth's surface has a pronounced zonal character.

This is due to uneven heating of the earth's surface, and consequently, changes in pressure.

On the globe there are three zones with a predominance of low atmospheric pressure (minimums) and four zones with a predominance of high atmospheric pressure (maxima).

At equatorial latitudes, the Earth's surface warms up greatly.

Heated air expands, becomes lighter and therefore rises. As a result, low atmospheric pressure is established near the earth's surface near the equator.

At the poles, under the influence of low temperatures, the air becomes heavier and sinks.

Therefore, at the poles the atmospheric pressure is increased by 60-65° compared to the latitudes.

In the high layers of the atmosphere, on the contrary, over hot areas the pressure is high (although lower than at the Earth's surface), and over cold areas it is low.

The general pattern of atmospheric pressure distribution is as follows: along the equator there is a belt of low pressure; at 30-40° latitude of both hemispheres - high pressure belts; 60-70° latitude - low pressure zones; in the polar regions there are areas of high pressure.

As a result of the fact that in the temperate latitudes of the Northern Hemisphere in winter the atmospheric pressure over the continents increases greatly, the low pressure belt is interrupted.

It persists only over the oceans in the form of closed areas of low pressure - the Icelandic and Aleutian lows. On the contrary, winter maximums form over the continents: Asian and North American.

General diagram of atmospheric pressure distribution

In summer, in the temperate latitudes of the Northern Hemisphere, the belt of low atmospheric pressure is restored. A huge area of ​​low atmospheric pressure centered in tropical latitudes - the Asian Low - forms over Asia.

In tropical latitudes, the continents are always warmer than the oceans, and the pressure above them is lower.

Thus, there are maxima over the oceans throughout the year: North Atlantic (Azores), North Pacific, South Atlantic, South Pacific and South Indian.

The formation of atmospheric pressure belts near the earth's surface is influenced by the uneven distribution of solar heat and the rotation of the Earth. Depending on the time of year, both hemispheres of the Earth are heated by the Sun differently. This causes some movement of the atmospheric pressure belts: in summer - to the north, in winter - to the south.

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Normal atmospheric pressure for humans

The normal atmospheric pressure for humans is 760 millimeters of mercury.

Atmosphere pressure

If we translate this meaning into something more understandable for common man units of measurement, it turns out that the mass of the air column above each square meter of the earth’s surface is 10,000 kilograms! Impressive, isn't it? The dense air “blanket” enveloping our planet exerts powerful pressure on all objects near us and on ourselves.

How does a person manage to cope with such a huge load?

The fact is that air presses on objects from all sides. The forces are balanced and we do not feel any discomfort. However, this rule only works on the earth's surface. The human body is adapted to exist under such pressure, so as soon as it dives into water or climbs to the top of a mountain, it will feel unwell.

However, sometimes people feel bad even under normal conditions.

Over continents, atmospheric pressure rises during periods of high humidity: spring, autumn and winter, as water droplets contained in the air make it heavier.

In summer, during dry weather, the atmospheric pressure above the surface of the earth in the interior of the continents usually decreases as the air becomes drier. Temperature also affects atmospheric pressure. As you know, warm air is lighter than cool air. Much depends on geographical location and altitude above sea level.

Since people are born and live in the most different corners planets and at very different altitudes, it is impossible to say that there is ideal atmospheric pressure for humans.

Normal atmospheric pressure for humans

The optimal atmospheric pressure for a person is the pressure to which he has adapted well, living in a particular area under certain climatic conditions.

For example, normal atmospheric pressure for a person in Moscow will be 748 millimeters Hg. Art. To the north, for example, in St. Petersburg, this value will be 5 mm Hg higher.

The difference is easily explained: Moscow is located on a hill and, compared to St. Petersburg, is slightly higher above sea level. Tibet will be indicative in this example, where normal pressure air for humans is 413 millimeters Hg. Art., although for tourists from Moscow, for example, living in such conditions will be quite difficult.

That is why it is possible to determine what atmospheric pressure is considered high and what atmospheric pressure is considered low only in relation to a specific person.

Changes in atmospheric pressure affect weather-dependent people, of whom there are about 4 billion today.

Sharp fluctuations cause deterioration in health and the following symptoms:

• irritability, headache and drowsiness;
• increased blood clotting;
• numbness of the limbs, joint pain;
• difficulty breathing and rapid heartbeat;
• increased vascular tone and spasms, circulatory disorders;
• visual impairment;
• nausea and dizziness;
• excess oxygen in tissues and blood;
• rupture of the eardrum;
• problems with the gastrointestinal tract.

As a rule, fluctuations in atmospheric pressure are accompanied by changes in weather conditions, which is why weather-dependent people feel unwell before precipitation, storms, and thunderstorms.

That is why the importance of atmospheric pressure for humans is very significant.

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How pressure affects people

Atmospheric pressure over 760 millimeters Hg. Art. considered elevated. Many people feel uneasy with such changes. It is especially noticeable in people with various neuropsychiatric diseases.

In some European countries police officers closely monitor fluctuations in atmospheric pressure, since on such days and hours the number of crimes committed begins to increase.

There's more going on during this time. car accidents, since the reaction speed of drivers decreases. Concentration deteriorates, resulting in increased risk various kinds industrial emergencies and industrial accidents related to human factor. Most often on such days people suffer from insomnia.

Hypotensive people feel bad: blood pressure drops, breathing becomes deep, pulse quickens.

Problems with the gastrointestinal tract begin as peristalsis decreases.

Low atmospheric pressure and well-being

Atmospheric pressure below 760 mmHg is considered low.

Art. A sharp decrease in pressure is dangerous for hypertensive patients and people suffering from atherosclerosis, since at such moments oxygen starvation begins, the number of blood cells increases and the blood thickens. The cardiovascular system begins to work under conditions of increased stress, which leads to an increase in blood pressure, arrhythmia, and an increase in heart rate.

Elderly people suffer from this. On such days, the number of strokes and heart attacks increases.

Headaches and migraines occur, which often cannot be relieved with pills. With a sharp decrease in atmospheric pressure, the risk of asthma attacks in asthmatics and allergy sufferers increases.

Less sensitive, young and relatively healthy people feel drowsiness and loss of energy.

Ideal atmospheric pressure for humans and doctors' recommendations

Most often, people suffering from weather dependence are overweight.

Also susceptible to this disease are those who poorly monitor the condition of their body, move little, watch TV for a long time or work at the computer, and have reduced immunity. Even minor deviations may be noticeable to them. At the same time, normal weather pressure for a person cannot be maintained even during the day, since it decreases in the morning and evening.

To get rid of weather dependence, first of all, you need to eat right. Vitamin B6, potassium and magnesium will help cope with reactions to weather changes, strengthen the cardiovascular system, support the nervous system and reduce sensitivity during overload. It is also recommended to reduce the load on the body and switch to a diet with a reduced meat content.

It is necessary to monitor your diet, avoid eating fatty, fried, sweet, and salty foods. It won’t hurt to give up spices for a while either. It is known, for example, that hot red pepper can increase blood pressure. Nicotine and alcohol increase weather dependence.

In moments of changing weather and changes in atmospheric pressure, it is worth giving up excess physical activity: cycling, jogging, excessive work summer cottage etc.

Help in the fight against weather dependence:

• physiotherapy. For example, hardening procedures can be carried out even at home. Contrast showers, cold water rubdowns, swimming in the pool, mud treatments and therapeutic baths will strengthen blood vessels and the nervous system.

  Massage and acupuncture will undoubtedly help you relax;

• regular classes various types gymnastics: yoga, qigong, tai chi, etc.
• walks every day in the fresh air, going out into nature and relaxing;
• correct daily routine, sleep and wakefulness, work and rest;
• caring attitude towards your mental health And nervous system, creating a favorable atmosphere around.

To maintain health, there are natural preparations: ginseng, extract from deer antlers, eleutherococcus, honey and bee products.

However, before taking natural supplements, you should definitely consult your doctor.

Those suffering from weather dependence should listen more to their body and try to take care of their health, and then any barometer readings will mean good atmospheric pressure for a person.

§ 31. Atmospheric pressure (textbook)

§ 31. Atmospheric pressure

Remember from your natural history course what is called atmospheric pressure.

The concept of atmospheric pressure. Air is invisible and light.

However, like any substance, it has mass and weight. Therefore, it exerts pressure on the earth’s surface and on all the bodies on it. This pressure is determined by the weight of a column of air as high as the entire atmosphere - from the earth’s surface to its very upper boundary. It has been established that such a column of air presses on every 1 cm2 of the surface with a force of 1 kg 33 g (correspondingly, per 1 m2 - More than 10 tons!) So, Atmosphere pressure- This is the force with which the air presses on the earth’s surface and on all objects on it.

The surface of the human body is on average 1.5 m2. According to the air, a weight of 15 tons is pressed on it.

Such pressure can crush all living things. Why don't we feel it? This is due to the fact that there is also pressure inside the human body - internal, and it is equal to atmospheric pressure. If this balance is disturbed, the person feels unwell.

Measuring atmospheric pressure. Atmospheric pressure is measured using a special device - a barometer. Translated from Greek, this word means “gravity meter”.

Weather stations use mercury barometer.

Its main part is a glass tube 1 m long, sealed at one end. It's filled with mercury - heavy liquid metal. The open end of the tube is immersed in a wide bowl, also filled with mercury. When turned over, the mercury flowed out of the tube only to a certain level and stopped. Why did it stop and not all pour out? Because the air puts pressure on the mercury in the bowl and does not release all of it from the tube. If the atmospheric pressure decreases, the mercury in the tube drops and vice versa.

Based on the height of the mercury column in the tube on which the scale is applied, the value of atmospheric pressure in millimeters is determined.

At parallel 450 at sea level, at an air temperature of 0 0C, under air pressure, a column of mercury rises in the tube to a height of 760 mm.

This air pressure is considered normal atmospheric pressure. If the mercury column in the tube rises above 760 mm, then the pressure elevated, Below - reduced Therefore, the pressure of the air column of the entire atmosphere is balanced by the weight of a mercury column with a height of 760 mm.

On hikes and expeditions they use a more convenient device - aneroid barometer"Aneroid" translated from Greek means "without ridinium": it does not contain mercury.

Its main part is a metal elastic box from which air is pumped. This makes it very sensitive to changes in pressure from the outside. At elevated pressures it contracts, at lower pressures it expands. These vibrations are transmitted through a special mechanism to a arrow, which indicates on the scale the amount of atmospheric pressure in millimeters of mercury.

Dependence of pressure on terrain altitude and air temperature. Atmospheric pressure depends on the altitude of the area.

The higher the sea level, the lower the air pressure. It decreases because as it rises, the height of the column of air that presses on the earth’s surface decreases. In addition, with height, pressure also drops because the density of the air itself decreases. At an altitude of 5 km, atmospheric pressure is reduced by half compared to normal pressure at sea level.

In the troposphere, with rise for every 100 m, the pressure decreases by approximately 10 mm Hg. Art.

Knowing how pressure changes, you can calculate both the absolute and relative height of a place. There is also a special barometer - altimeter, In which, along with the atmospheric pressure scale, there is also an altitude scale.

So, each area will have its own normal pressure: at sea level - 760 mm Hg, in the mountains, depending on the height - lower. For example, for Kyiv, which lies at altitudes of 140-200 m above sea level, the average pressure will be 746 mm Hg. Art.

Atmospheric pressure also depends on air temperature. When heated, the volume of air increases, it becomes less dense and light. For this, atmospheric pressure also decreases.

When cooling, the opposite phenomena occur. Consequently, as the air temperature changes, the pressure continuously changes. During the day, it increases twice (morning and evening) and decreases twice (after noon and after midnight).

In winter, when the air is cold and heavy, the pressure is higher than in summer, when it is warmer and lighter. So, changes in pressure can predict weather changes.

A decrease in pressure indicates precipitation, an increase indicates dry weather. Changes in atmospheric pressure affect people's well-being.

Distribution of atmospheric pressure on Earth. Atmospheric pressure, like air temperature, is distributed on Earth in stripes: there are belts of low and high pressure.

Their formation is associated with heating and air movement.

Above the equator, the air warms up well. Because of this, it expands, becomes less dense, and therefore lighter.

Lighter than air rises - happens upward movement air. Therefore, there at the surface of the Earth the course of the year is established low waist pressure.

What is the relationship between atmospheric and blood pressure?

Above the poles, where temperatures are low throughout the year, the air cools and becomes denser and heavier. That's why it goes down - happens downward movement air - and the pressure increases. Therefore, the poles were formed high pressure belts. The air rising above the equator spreads towards the poles. But, before reaching them, at altitude it cools, becomes heavier and descends at parallels 30-350 in both hemispheres.

As a result, there are formed high pressure belts. In temperate latitudes, at parallels 60-650 of both hemispheres, low pressure belts.

Thus, there is a close dependence of atmospheric pressure on the distribution of heat and air temperatures on Earth, when ascending and descending air movements cause uneven heating of the earth's surface.

Questions and tasks

Determine how much the air in the classroom weighs if its length is 8 m, width is 6 m, and height is 3 m.

2. Why does atmospheric pressure decrease with altitude?

3. Why does the pressure change in the same place? How does a change in air temperature affect this?

4. Determine approximately the relative height of the mountain peak if the barometer shows 720 mm at the base of the mountain, and 420 mm at the top.

How is atmospheric pressure distributed on Earth?

6. Remember what absolute altitude your area. Calculate what atmospheric pressure can be considered normal for your area.

Measuring atmospheric pressure. Torricelli's experience - Kasyanov, Dmitrieva, 7th grade.

1.Why can’t you calculate atmospheric pressure using the formula p = gρh?
Because

it is necessary to know the height of the atmosphere and air density.

2. What contributions did Evangelista Torricelli (1608–1647) make to science?
Allowed to measure atmospheric pressure.

3. Why is the pressure of mercury in the tube at level aa1 equal to atmospheric pressure?

The pressure in the tube at level aa1 is created by the weight of the mercury column in the tube, since there is no air above the mercury in the upper part of the tube.

It follows that atmospheric pressure is equal to the pressure of the mercury column in the tube.

4. What is the relationship between 1 mm. rt. Art. and pascal (Pa)?
1 mm. rt. Art. = 133.3 (Pa)
1 Pa = 0.0075 mm. rt.

5. Atmospheric pressure is 750 mm. rt. Art. What does it mean?
99975 Pa

6. What is the reason for the change in atmospheric pressure?
With the weather changing

What does atmospheric pressure depend on?

A device for measuring atmospheric pressure is a mercury barometer (from the Greek baros - heaviness, metreo - I measure).

8. The weather report announced that the pressure p = 750 mm. rt. Art. Express this pressure in hectopascals (hPa).

9. Why does an aluminum canister become deformed after air is pumped out of it?

External pressure is greater than internal.

What forces prevent the Magdeburg hemispheres from breaking apart?

There is a vacuum inside, so they have enormous power atmospheric pressure acts - it prevents them from breaking.

11. Why do passengers often get blocked ears when taking off and landing planes?
As you rise, atmospheric pressure increases, to which a person is not accustomed.

12. What is the study of atmospheric pressure related to?
Due to consumer needs, pumps were invented with the help of which they wanted to raise water to greater height, but atmospheric pressure was not studied, they did not know about its existence.

What role did Galileo play in the study of atmospheric pressure?
They turned to Galileo for advice. Galileo examined the pumps and found that they were working. Having taken up this issue, he pointed out that the pumps could not raise water higher than 18 Italian cubits (≈10 m).

14. What conclusion did Torricelli draw by continuing Galileo’s research?
The real reason for the rise of mercury in the tube is air pressure, and not “fear of emptiness.”

This pressure produces air with its weight. (And that air has weight was already proven by Galileo.)

15. What is the essence of Pascal’s experiment, which he called the proof of emptiness in emptiness?
The French scientist Pascal learned about Torrichell's experiments. He repeated Torricelli's experiment with mercury and water. However, Pascal believed that in order to definitively prove the existence of atmospheric pressure, it was necessary to perform Torricelli’s experiment once at the foot of a mountain, and another time at its top, and in both cases measure the height of the mercury column in the tube.

If at the top of the mountain the column of mercury turned out to be lower than at its foot, then it would be necessary to conclude that the mercury in the tube is really supported by atmospheric pressure.

Air pressure- the force with which air presses on the earth's surface. It is measured in millimeters of mercury, millibars. On average, it is 1.033 g per 1 cm2.

The reason that causes wind formation is the difference in atmospheric pressure. The wind blows from an area of ​​higher atmospheric pressure to an area of ​​lower. How more difference in atmospheric pressure, the stronger wind. The distribution of atmospheric pressure on Earth determines the direction of the winds prevailing in the troposphere at different latitudes.

They are formed when water vapor condenses in rising air due to its cooling.
. Liquid or solid water that falls on the earth's surface is called precipitation.

Based on their origin, there are two types of sediment:

falling from clouds (rain, snow, graupel, hail);
formed at the surface of the Earth (dew, frost).
Precipitation is measured by the layer of water (in mm) that forms if the fallen water does not drain and evaporate. On average, 1130 mm falls on the Earth per year. precipitation.

Precipitation distribution. Precipitation distributed very unevenly over the earth's surface. Some areas suffer from excess moisture, others from its lack. Territories located along the northern and southern tropics, where air quality is high and the need for precipitation is especially great, receive especially little precipitation.

The main reason for this unevenness is the placement of atmospheric pressure belts. Thus, in the region of the equator in a low-pressure zone, constantly heated air contains a lot of moisture, it rises, cools and becomes saturated. Therefore, in the equator region there are many clouds and heavy rainfall. There is also a lot of precipitation in other areas of the earth's surface where pressure is low.

In high pressure zones, downward air currents predominate. Cold air, as it descends, contains little moisture. When lowered, it contracts and heats up, due to which it moves away from the saturation point and becomes drier. Therefore, areas of high pressure over the tropics and near the poles receive little precipitation.

It is still impossible to judge the moisture supply of a territory by the amount of precipitation. Possible evaporation - volatility - must be taken into account. It depends on the amount of solar heat: the more heat there is, the more moisture, if any, can evaporate. Volatility can be high, but evaporation can be small. For example, evaporation (how much moisture can evaporate at a given temperature) is 4500 mm/year, and evaporation (how much moisture actually evaporates) is only 100 mm/year. The moisture content of the area is judged by the ratio of evaporation and evaporation. To determine moisture, the moisture coefficient is used. Humidity coefficient is the ratio of annual precipitation to evaporation over the same period of time. It is expressed as a fraction as a percentage. If the coefficient is 1, the moisture is sufficient; if it is less than 1, the moisture is insufficient; and if it is greater than 1, the moisture is excessive. Based on the degree of moisture, wet (humid) and dry (arid) areas are distinguished.

Purpose: to study the causes of the formation of atmospheric pressure; find out the dependence of precipitation on atmospheric pressure; develop the ability to establish cause-and-effect relationships between weather elements; upbringing ecological culture and respect for nature.

Equipment: computer with a projector for showing the presentation, visual aids on disk, Internet resources, climate map of the world, atlas maps.

Lesson type: combined

Lesson plan:

1. Organizing time
2. Updating knowledge
3. Learning new material
4. Consolidation
5. Lesson summary

During the classes

I. Organizational moment.

II. Updating knowledge

What is the structure of the atmosphere? What function does it serve? The reason for the formation of the atmosphere. (Children's answers)

Why give away earth's surface Doesn't heat escape into space? (Children's answers)

What is the “ozone hole”, “greenhouse effect”, “global warming”? How has human activity influenced the development of these processes? (children's answers)

III. Learning new material.

Introductory conversation.

Do you often listen to weather reports on TV or radio? What weather elements are often mentioned? (pressure, precipitation, temperature, wind speed, etc.)

Do you notice at what pressure the weather is usually cloudy and raining, and at what pressure the weather is clear and dry? (VD - clear weather; ND - cloudy, rainy)

Problem. What needs to be studied in order to explain the uneven rainfall on the planet? (to explain the uneven precipitation on the planet, you need to know how atmospheric pressure is distributed on it).

So, the topic of the lesson is “Distribution of areas of atmospheric pressure and precipitation near the Earth’s surface”

What questions do we have to answer today:

1. Does air have weight?
2. What devices and in what units is pressure measured?
3. How does atmospheric pressure change with altitude?
4. How are areas of atmospheric pressure distributed across the latitudes of the Earth?
5. How does precipitation depend on atmospheric pressure?

1. The Earth's atmosphere is about 1 thousand kilometers thick, and a column of air weighing 15 tons presses on each of us. Why don't we feel this pressure? (the pressure inside a person is equal to atmospheric pressure, internal and external pressure are balanced).

2. To determine atmospheric pressure, special instruments are used - barometers. The invention of the barometer belongs to the Italian mathematician and physicist Evangelista Torricelli.

3. Let's consider the principle of operation of a mercury barometer and aneroid barometer. Consider the drawing of a mercury barometer. What elements does it consist of?

A mercury barometer is a liquid barometer in which atmospheric pressure is measured by the height of the mercury column in a tube sealed at the top and lowered with the open end into a vessel containing mercury. a Mercury barometers are the most accurate instruments; meteorological stations are equipped with them; the operation of other types of barometers is checked using them.

Mechanical barometers are usually used in everyday life ( Aneroid) <рисунок 1>. There is no liquid in an aneroid (Greek “aneroid” - “anhydrous”). It shows the atmospheric pressure acting on a corrugated thin-walled metal box in which a vacuum is created. When atmospheric pressure decreases, the box expands slightly, and when it increases, it contracts and acts on the spring attached to it. These changes are transmitted to a pointer, which moves along a circular scale divided into millimeters or millibars.

Atmospheric pressure is measured in millimeters of mercury (mmHg) or millibars (MB).

Normal atmospheric pressure is conventionally taken to be 760 mmHg, which is close to the average atmospheric pressure at sea level. Air pressure is more than 760 mm Hg. is considered increased, less is considered decreased.

Class assignment. How will atmospheric pressure change as you rise into the mountains? (pressure decreases with height by an average of 1 mm for every 10.5 m of rise). Define:

• average atmospheric pressure on the shore of Lake Baikal, if its height above sea level is approximately 500m. (710 mmHg)
• average atmospheric pressure for the city of Moscow, if it lies at an altitude of 120m above sea level. (748 mmHg)

4. How does the distribution of atmospheric pressure areas by latitude occur? It depends on the temperature.

What happens to air when heated? (Expands and becomes light)

Where will the heated air tend to? (up)

This process is called upward movement of air.

Using an analogy, explain how downward movement of air occurs.

If atmospheric pressure depends on temperature, explain from the drawing on the board how areas of atmospheric pressure are distributed on the globe<рисунок 2>. Draw in a notebook and distribute the areas of pressure.

On a global scale on the globe, how many pressure belts can be identified? (three with a predominance of low pressure and four with a predominance of high pressure)

How does atmospheric pressure change in the temperate latitudes of the Northern Hemisphere in winter and summer? (In winter – it increases over the continents (winter highs), the low pressure area remains only over the oceans (Icelandic and Aleutian lows))

5.

During VD – clear weather; ND – cloudy, rainy. Using this relationship, mark wet and dry latitudes in your drawings.

Consolidation.

Fill the gaps:

1. 25°-30° N and _____ and at the poles ______ air currents –> ______ –> _______.
2. At ______ and 65° N latitude. and S. _______ air currents –>_______ –> _______.

1. Determine in which pressure zone are located: Oslo, North Pole, Ulan-Ude, Beijing.

Lesson summary.

What reasons underlie the formation of different atmospheric pressures? (distribution of solar heat and rotation of the Earth).

How are atmospheric pressure and precipitation related?