What is atmospheric air pressure definition. Atmosphere pressure

It is known that Atmosphere pressure during horse racing affects a person’s well-being and health. Every third inhabitant of the Earth is affected by the attraction of air to the surface.

Let's figure out what this concept is and why it negatively affects well-being.

What is atmospheric pressure and how is it measured?

The definition of atmospheric (barometric) pressure is the pressure of air on objects present in it and on the surface. It is measured with barometers or thermohygrometers.

The following units are used:

• bars (1 Ba = 100 thousand Pa);
• Pascals (kPa, hPa, mPa);
• mm mercury(1 mmHg = 133.3 Pa);
• atmosphere (1 at = 98066 Pa);
• kg force per cm 2 (1 kgf/cm 2 = 98066 Pa).

Assuming air temperature remains constant, pressure decreases exponentially as it rises. For altitudes up to approximately 100 km it is calculated by the formula:

p h—pressure at a certain height, Pa;

p 0—surface pressure, Pa;

ρ 0 — density air masses at zero altitude;

h—height, m;

g is a constant equal to 9.80665;

e - base natural logarithm, a constant equal to 2.71828.

This is interesting: the maximum pressure at sea level was recorded on December 31, 1968 at locality Agatha Krasnoyarsk Territory and reached 812 mm. rt. Art. Lowest value took place on September 24, 1958 in the center of the typhoon near the Philippines and did not exceed 654.8 mm. rt. Art.

Normal atmospheric pressure

Normal pressure is 760 mmHg. Art. At the same time, people feel comfortable or feel good.

The pressure is unstable and fluctuates daily. However, the body is able to calmly withstand a wide range of values. So, in Mexico City average value no more than 570 mm Hg. Art. (due to being at a significant altitude).

The changes are not felt by people. Let’s say that at night the mercury rises by 1-2 units. Jumps of 5-10 or more points can cause painful sensations, and sudden strong fluctuations can even lead to death. For example, loss of consciousness occurs when the pressure drops by 30 points, i.e. at an altitude of 1000 meters.

A continent or a specific country can be divided into zones with different rates of indicator. The optimal value is determined by the area of ​​permanent residence. The human body is capable of adapting to unusual natural conditions.

Banal acclimatization at resorts serves as an example of this. Sometimes a person is unable to change his mind. Thus, those living in the mountains experience poor health in lowland areas, no matter how long they live there.

Thus, the value of the standard pressure is clearly established. And comfortable meaning has a wide range. It is individual and determined by the familiar environment. With prolonged acclimatization, the negative effects are minimized.

High and low atmospheric pressure

Low values ​​cause symptoms similar to those associated with climbing uphill. The lack of oxygen causes shortness of breath, the pulse becomes faster, pain occurs in the temples and pressure on the head.

All this poses a threat to those suffering from hypertension and atherosclerosis, as it causes blood thickening, lack of oxygen and an increase in the number of blood cells. The heart and blood vessels function in an enhanced mode, which contributes to an increase in blood pressure, tachycardia and arrhythmia. Very dangerous for elderly people.

Dizziness and migraines are also common, and the risk of attacks is greater in those suffering from allergies and asthma. Less susceptible, healthy and persons young feel the desire to sleep and lack of strength.

In areas of higher values, the weather is calm, there are almost no clouds in the sky, and wind gusts are not strong. The weather is dry and hot.

In zones low pressure a lot of clouds, rainy and windy. Due to such areas, it is cool in the summer with rain, there are a lot of clouds in the sky, and in the winter it snows.

The large difference in the two zones is a factor in causing hurricanes and storms.

Elevated values ​​have a detrimental effect on those suffering from low blood pressure blood, negatively affect digestion, heart and blood vessels.

Atmospheric pressure is normal for humans

People can get used to change. There is no need to be upset if you find out that you live in a region of low pressure. Let’s say that the inhabitants of skyscrapers do not feel a decrease, although a rapid rise of 100 m is very stressful.

In the Central Asian zone, the norm is slightly reduced (715-730 mm Hg). For middle zone RF norm will be 730-770 mmHg. Art.

The body can adapt to different altitudes. According to doctors, if pressure does not have an extremely dangerous effect on people, then this is a variant of the norm. It all depends on adaptation. Doctors often consider values ​​from 750 to 765 mm Hg to be normal. Art.

In Moscow the norm is 747-749 mm Hg. Art.

Since Novosibirsk is located at an altitude of 120-130 m, 750 mm Hg is considered the norm. Art.

In Samara - 752-753, in St. Petersburg - 753-755 mm Hg. Art.

Norm in Nizhny Novgorod in the trans-river zone - 754 mm Hg. Art., in Nagornaya - 747.

It is worth noting: there is no overall best indicator. There are territorial norms. People are able to tolerate jumps in values ​​without pain if it goes away gradually.

How healthier image life and the more often one manages to maintain a daily routine (getting up, sleeping long hours at night, following a regular diet), the less a person is exposed to meteorological dependence.

Average mass of 1 m 3 of air at sea level at temperature environment 4°C is equal to 1 kg 300 g. This confirms the existence of atmospheric pressure. All living things, including a healthy person, do not feel this pressure due to the fact that it is in balance with the internal pressure of organisms.

Atmospheric air pressure is systematically assessed at weather stations. Barometers are used to measure atmospheric pressure. There are mercury and spring (aneroid) barometers. The units are pascals (Pa). The normal value of atmospheric pressure is taken to be atmospheric pressure at a latitude of 45° at a temperature of 4°C at an altitude of 0 m above sea level. Normal pressure is 1013 hPa, or 1 atmosphere, or 760 mmHg. It has been proven that atmospheric pressure decreases with altitude. For every 8 m of height, the pressure decreases by 1 hPa. Taking into account the knowledge of pressure earth's surface and at a certain height, by making a simple equation, you can calculate this height. For example, a pressure difference of 200 Pa means that the pressure measurement was carried out at an altitude of 1600 m.

Definition and indicators

Atmospheric pressure is determined not only by altitude, but also by air density. Warm air less dense and lighter than cold. In a certain area there may be high or low atmospheric pressure due to the dominance of different air masses. Automatic devices (barographs) located at weather stations or observation points evaluate air pressure.

Then the indicators of the measuring instruments are plotted on the map. Points indicating the same pressure are connected to form isobars - lines that show how pressure is distributed over the Earth's surface.

When studying isobars, more definite patterns were revealed. So, atmospheric pressure is not constant. It varies zonally from the equator to the northern and south poles. In tropical, polar latitudes and over the oceans, pressure is usually increased, in equatorial belt reduced, and in areas with temperate climate variable according to the seasons.

IN summer period over land temperate zone There is low blood pressure, and in winter, on the contrary, high blood pressure. This is explained simply. In summer, the air over land is warm and less dense, while in winter it becomes colder and denser.

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For normal atmospheric pressure, it is customary to take the air pressure at sea level at a latitude of 45 degrees at a temperature of 0°C. In these ideal conditions a column of air presses on each area with the same force as a column of mercury 760 mm high. This figure is an indicator of normal atmospheric pressure.

Atmospheric pressure depends on the altitude of the area above sea level. At higher elevations, the indicators may differ from ideal, but they will also be considered the norm.

Atmospheric pressure standards in different regions

As altitude increases, atmospheric pressure decreases. So, at an altitude of five kilometers, pressure indicators will be approximately two times less than below.

Due to the location of Moscow on a hill, the normal pressure level here is considered to be 747-748 mm column. In St. Petersburg, normal pressure is 753-755 mm Hg. This difference is explained by the fact that the city on the Neva is located lower than Moscow. In some areas of St. Petersburg you can find a pressure norm of an ideal 760 mm Hg. For Vladivostok, normal pressure is 761 mmHg. And in the mountains of Tibet – 413 mmHg.

Impact of atmospheric pressure on people

A person gets used to everything. Even if the indicators normal pressure low compared to the ideal 760 mmHg, but are the norm for the area, people will.

A person’s well-being is affected by sharp fluctuations in atmospheric pressure, i.e. decrease or increase in pressure by at least 1 mmHg within three hours

When pressure decreases, a lack of oxygen occurs in a person’s blood, hypoxia of body cells develops, and the heartbeat increases. Headaches appear. There are difficulties from respiratory system. Due to poor blood supply, a person may experience pain in the joints and numbness in the fingers.

Increased pressure leads to an excess of oxygen in the blood and tissues of the body. The tone of blood vessels increases, which leads to their spasms. As a result, the body's blood circulation is disrupted. Visual disturbances may occur in the form of spots before the eyes, dizziness, and nausea. A sharp increase in pressure to large values ​​can lead to rupture of the eardrum.

Sources:

• What atmospheric pressure is considered normal?

It is known that there are people who are particularly sensitive to weather. It's about about those who react to changes in pressure by changing their state of health. It often happens that when you change your place of residence, your health condition worsens - this is how the body reacts to a change in pressure, it may differ from the usual indicators.

Instructions

A person tolerates an increase in atmospheric pressure quite easily; only at exceptionally high levels are disturbances in the functioning of the respiratory system and heart observed. Typically, the response is a slight decrease in the frequency and slowing of breathing. If the pressure is excessive, then dry skin, a feeling of slight numbness, and dry mouth may occur, but all these conditions, as a rule, do not cause excessive discomfort.

If we easily tolerate the increased pressure of the atmosphere around us, then a decrease in pressure is fraught with problems. First, the heartbeat becomes rapid and irregular, which can be very uncomfortable for some people. A drop in pressure leads to a slight oxygen starvation of the body, which is why such problems arise. As soon as the pressure in the atmosphere as a whole decreases, so does the partial oxygen pressure. As a result, a person receives a reduced amount of oxygen, and it is no longer possible to replenish the reserves with normal breathing.

Experts recommend that when atmospheric pressure drops and you are particularly sensitive to changes, you should rest, move less, and give up sports and active work. You should spend more time on fresh air, preferably in nature. Avoid heavy foods, do not eat, do not smoke. Eat food in small portions, but often. You can take sedative teas and light teas (after consulting your doctor first).

A person spends his life, as a rule, at an altitude of the Earth's surface, which is close to sea level. The body in such a situation experiences pressure from the surrounding atmosphere. The normal pressure value is considered to be 760 mmHg, also called “one atmosphere”. The pressure we experience externally is balanced by internal pressure. In this regard, the human body does not feel the heaviness of the atmosphere.

Atmospheric pressure can change throughout the day. Its performance also depends on the season. But, as a rule, such pressure surges occur within no more than twenty to thirty millimeters of mercury.

Such fluctuations are not noticeable to the body of a healthy person. But in people suffering from hypertension, rheumatism and other diseases, these changes can cause disturbances in the functioning of the body and a deterioration in general well-being.

A person can feel low atmospheric pressure when he is on a mountain and takes off on an airplane. The main physiological factor of altitude is reduced atmospheric pressure and, as a result, reduced partial pressure of oxygen.

The body reacts to low atmospheric pressure, first of all, by increasing breathing. Oxygen at altitude is discharged. This causes excitation of the chemoreceptors of the carotid arteries, and it is transmitted to the medulla oblongata to the center, which is responsible for increasing breathing. Thanks to this process, the pulmonary ventilation of a person who experiences low atmospheric pressure increases within the required limits and the body receives a sufficient amount of oxygen.

An important physiological mechanism that is triggered by low atmospheric pressure is considered to be an increase in the activity of the organs responsible for hematopoiesis. This mechanism manifests itself in an increase in the amount of hemoglobin and red blood cells in the blood. In this mode, the body is able to transport more oxygen.

Video on the topic

The weight of air determines atmospheric pressure (1 m 3 of air weighs 1.033 kg). For every meter of the earth's surface, air presses with a force of 10033 kg. This is a column of air from sea level to upper layers atmosphere. For comparison: a column of water of the same diameter would have a height of only 10 m. In other words, the own mass of air creates atmospheric pressure, the value of which per unit area corresponds to the mass of the air column located above it. In this case, a decrease in air in this column leads to a decrease (drop) in pressure, and an increase in air leads to an increase (increase) in pressure. Normal atmospheric pressure is taken to be air pressure at sea level at a latitude of 45° and at a temperature of 0°C. In this case, it presses on every 1 cm 2 of the earth's surface with a force of 1.033 kg, and the mass of this air is balanced by a mercury column 760 mm high. The principle of pressure measurement is based on this dependence. It is measured in millimeters (mm) of mercury (or millibars (mb): 1 mb = 0.75 mmHg) and in hectopascals (hPa), when 1 mm = = 1 hPa.

Atmospheric pressure is measured using barometers. There are two types of barometers: mercury and metal (or aneroid).

A mercury cup consists of a glass tube sealed at the top and immersed with the lower open end into a metal cup containing mercury. A column of mercury in a glass tube balances with its weight the air pressure acting on the mercury in the cup. When the pressure changes, the height of the mercury column also changes. These changes are recorded by the observer on a scale attached next to the glass tube of the barometer.

A metal barometer, or aneroid, consists of a hermetically sealed thin-walled corrugated metal box, inside which the air is rarefied. When the pressure changes, the walls of the box vibrate and are pressed in or out. These vibrations are transmitted by a system of levers to the arrow, which moves along a graduated scale.

Self-recording barometers called barographs are used to record changes in pressure. The operation of the barograph is based on the fact that the vibrations of the walls of the aneroid box are transmitted, which draws a line on the tape of the drum rotating around its axis.

Pressure on the globe can vary widely. Thus, the maximum value is 815.85 mm Hg. (1087 mb) was registered in winter in Turukhansk, the minimum is 641.3 mm Hg. (854 MB) - in “Nancy” over the ocean.

Pressure changes with altitude. It is generally accepted that the average value of atmospheric pressure is pressure above sea level - 1013 mb (760 mm Hg). As altitude increases, the air becomes more rarefied and the pressure decreases. In the lower layer of the troposphere to a height of 10 m it decreases by 1 mm Hg. for every 10 m, or 1 mb (hPa) for every 8 m. At an altitude of 5 km it is already two times less, 15 km - 8 times, 20 km - 18 times.

Atmospheric pressure changes continuously due to the change and movement of air. During the day it increases twice (in the morning and in the evening), and decreases twice (after noon and after midnight). During the year on the continents, the maximum pressure is observed in winter, when the air is supercooled and compacted, and the minimum pressure is observed in summer.

The distribution of atmospheric pressure over the earth's surface has a well-defined zonal character, which is due to uneven heating of the earth's surface, and consequently, changes in pressure. The change in pressure is explained by the movement of air. It is high where there is more air, low where the air leaves. When heated from the surface, the air rushes upward and the pressure on the warm surface decreases. But at altitude, the air cools, becomes denser and begins to fall to neighboring cold areas, where the pressure increases. Thus, heating and cooling of air from the Earth's surface is accompanied by its redistribution and pressure changes.

IN equatorial latitudes air temperatures are constantly high, the air, heating up, rises and moves towards tropical latitudes. Therefore in equatorial zone pressure is constantly low. In tropical latitudes, increased pressure is created as a result of air influx. Above the constantly cold surface of the poles (and) the pressure is increased, it is created by air coming from latitudes. However, in temperate latitudes the outflow of air forms a belt of low pressure. As a result, belts of low (and two moderate) and high (two tropical and two polar) pressures are formed on Earth. Depending on the season, they shift somewhat towards the summer hemisphere (following the Sun).

Polar high pressure areas expand in winter and contract in summer, but persist throughout the year. Low pressure belts persist throughout the year near and in temperate latitudes southern hemisphere. The picture is different in the northern hemisphere. Here in winter, in temperate latitudes over the continents, the pressure increases greatly and the low pressure field seems to be “broken”: it is preserved only over the oceans in the form of closed areas of low pressure - the Icelandic and Aleutian lows. But over the continents, where the pressure has noticeably increased, so-called winter maxima are formed: Asian (Siberian) and North American (Canadian). In summer, in the temperate latitudes of the northern hemisphere, the low pressure field is restored. At the same time, a vast area of ​​low pressure forms over Asia - the Asian Low.

In tropical latitudes - the belt high blood pressure— continents always warm up more than the oceans, and the pressure above them is lower. This causes subtropical maxima over the oceans: North (Azores), North Pacific, South Atlantic, South Pacific and Indian.

In other words, the Earth’s belts of high and low pressure, despite large-scale seasonal changes their indicators are quite stable formations.

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Normal atmospheric pressure is equal to the pressure of a column of mercury 760 mm high on its horizontal base, with a weight per unit volume of mercury of 135951 g/cm3 and normal acceleration of gravity.

Normal atmospheric pressure is equal to the pressure of a column of mercury 760 mm high on its horizontal base with a density of mercury of 13,5951 g/cl 3 and with a normal acceleration of gravity of 980,665 cm/sec.

Normal atmospheric pressure is equal to the pressure of a column of mercury 760 mm high on its horizontal base when the weight of a unit volume of mercury is 135951 g/cm3 and at normal acceleration of gravity.

Normal atmospheric pressure is conventionally assumed to be equal to the average pressure of the air column of the earth's atmosphere.

Normal atmospheric pressure is considered to be an absolute pressure at the surface level of the World Ocean of 101 ZkPa, corresponding to 760 mm Hg. Art. or 1 atm. Within globe There are constant areas of high and low atmospheric pressure, and seasonal and daily fluctuations are observed at the same points. As altitude increases relative to ocean level, pressure decreases, partial pressure of oxygen decreases, and transpiration in plants increases.

Normal atmospheric pressure (physical atmosphere) is taken to be the pressure of the air around us, which averages 760 mmHg. Art. The actual atmospheric pressure can be both higher and lower than the physical atmosphere. Vacuum shows how much less pressure in the vessel is atmospheric.

What is normal atmospheric pressure equal to 760 mmHg? Art., expressed in Pascals.

Under normal atmospheric pressure 101,325 n/m2 7 5% water solution Potassium chloride boils at 101 C.

Under normal atmospheric pressure of 101,325 Pa, an aqueous solution of potassium chloride, the concentration of which is 0,075 (7 5%) mass, fractions of KC1 boils at 101 C.

At normal atmospheric pressure and temperature - 84 C, acetylene turns into a liquid state, and at a temperature of - 85 C it solidifies.

At normal atmospheric pressure, the boiling point of water is approximately 100 C. With increasing pressure, the boiling point increases, as can be seen from the table. This means that a certain boiling point corresponds to a certain pressure. If water is to circulate in the heating system, then the entire system must be kept under more high pressure than the pressure corresponding to the temperature. The content of a certain amount of steam in the water does not interfere with the circulation of water, on the contrary, it increases it. Natural circulation, however, has certain limits. It is known that the maximum pressure during natural circulation is approximately 180 - 200 ata.

At normal atmospheric pressure, arsenic sublimates at 613 C. Refers to solid nitrogen at its melting point.

At normal atmospheric pressure, the boiling point of water is approximately 100 C. With increasing pressure, the boiling point increases, as can be seen from the table. This means that a certain boiling point corresponds to a certain pressure. If water is to circulate in a heating system, the entire system must be at a higher pressure than the pressure corresponding to the temperature. The content of a certain amount of steam in water does not interfere with water circulation, but on the contrary, it increases it. Natural circulation, however, has certain limits. It is known that the maximum pressure during natural circulation is approximately 180 - 200 ata.

At normal atmospheric pressure, a solution of sodium chloride in water boils at a temperature above 100 C.