Who first measured the atmosphere. Atmosphere pressure. Increased atmospheric pressure

The atmosphere surrounding the globe exerts pressure on the surface of the earth and on all objects above the earth. In a resting atmosphere, the pressure at any point is equal to the weight of the overlying column of air extending to the outer periphery of the atmosphere and having a cross section of 1 cm2.

Atmospheric pressure was first measured by an Italian scientist Evangelista Torricelli in 1644. The device is a U-shaped tube about 1 m long, sealed at one end and filled with mercury. Since there is no air in the upper part of the tube, the mercury pressure in the tube is created only by the weight of the mercury column in the tube. Thus, the atmospheric pressure is equal to the pressure of the mercury column in the tube and the height of this column depends on the atmospheric pressure of the surrounding air: the greater the atmospheric pressure, the higher the mercury column in the tube and, therefore, the height of this column can be used to measure atmospheric pressure.

Normal atmospheric pressure (at sea level) is 760 mmHg (mm Hg) at 0°C. If the pressure of the atmosphere, for example, 780 mm Hg. Art., this means that the air produces the same pressure as a vertical column of mercury with a height of 780 mm.

Watching day after day the height of the mercury column in the tube, Torricelli discovered that this height changes, and changes in atmospheric pressure are somehow connected with changes in the weather. Attaching a vertical scale next to the tube, Torricelli received a simple device for measuring atmospheric pressure - a barometer. Later they began to measure pressure using an aneroid barometer ("liquidless"), which does not use mercury, and the pressure is measured using a metal spring. In practice, before taking readings, it is necessary to lightly tap the glass of the instrument with a finger to overcome friction in the leverage.

Made on the basis of the Torricelli tube station cup barometer, which is the main instrument for measuring atmospheric pressure at meteorological stations at present. It consists of a barometric tube about 8 mm in diameter and about 80 cm long, lowered with its free end into a barometric cup. The entire barometric tube is enclosed in a brass frame, in the upper part of which a vertical cut is made for observing the meniscus of the mercury column.

At the same atmospheric pressure, the height of the mercury column depends on temperature and the acceleration of free fall, which varies somewhat depending on latitude and height above sea level. To eliminate the dependence of the height of the mercury column in the barometer on these parameters, the measured height is brought to a temperature of 0 ° C and the acceleration of free fall at sea level at a latitude of 45 ° and, by introducing an instrumental correction, the pressure at the station is obtained.

In accordance with the international system of units (SI system), the main unit for measuring atmospheric pressure is the hectopascal (hPa), however, in the service of a number of organizations it is allowed to use the old units: millibar (mb) and millimeter of mercury (mm Hg).

1 mb = 1 hPa; 1 mmHg = 1.333224 hPa

The spatial distribution of atmospheric pressure is called baric field. The baric field can be visualized using surfaces, at all points of which the pressure is the same. Such surfaces are called isobaric. To obtain a visual representation of the distribution of pressure on the earth's surface, isobar maps are built at sea level. To do this, atmospheric pressure measured at meteorological stations and reduced to sea level is applied to a geographical map. Then points with the same pressure are connected by smooth curved lines. Areas of closed isobars with increased pressure in the center are called baric maxima or anticyclones, and areas of closed isobars with reduced pressure in the center are called baric minima or cyclones.

Atmospheric pressure at every point on the earth's surface does not remain constant. Sometimes the pressure changes in time very quickly, sometimes it remains almost unchanged for quite a long time. In the diurnal course of pressure, two maxima and two minima are found. The maximums are observed at about 10:00 and 22:00 local time, the minimums are at about 4:00 and 16:00. The annual course of pressure strongly depends on physical and geographical conditions. Over the continents, this move is more noticeable than over the oceans.

This pressure is called atmospheric. How big is it?

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Atmospheric pressure is one of the most important climatic characteristics that affect a person. It contributes to the formation of cyclones and anticyclones, provokes the development of cardiovascular diseases in humans. Evidence that air has weight was obtained as early as the 17th century, since then the process of studying its vibrations has been one of the central ones for weather forecasters.

What is atmosphere

The word "atmosphere" is of Greek origin, literally it translates as "steam" and "ball". This is a gaseous shell around the planet, which rotates with it and forms a single whole cosmic body. It extends from the earth's crust, penetrating into the hydrosphere, and ends with the exosphere, gradually flowing into interplanetary space.

The atmosphere of the planet is its most important element, providing the possibility of life on Earth. It contains the oxygen necessary for a person, weather indicators depend on it. The boundaries of the atmosphere are very arbitrary. It is generally accepted that they begin at a distance of about 1000 kilometers from the earth's surface and then, at a distance of another 300 kilometers, smoothly pass into interplanetary space. According to the theories that NASA adheres to, this gaseous envelope ends at an altitude of about 100 kilometers.

It arose as a result of volcanic eruptions and the evaporation of substances in cosmic bodies that fell on the planet. Today it consists of nitrogen, oxygen, argon and other gases.

History of the discovery of atmospheric pressure

Until the 17th century, mankind did not think about whether air has mass. There was also no concept of what atmospheric pressure was. However, when the Duke of Tuscany decided to equip the famous Florentine gardens with fountains, his project failed miserably. The height of the water column did not exceed 10 meters, which contradicted all ideas about the laws of nature at that time. It is here that the story of the discovery of atmospheric pressure begins.

Galileo's student, the Italian physicist and mathematician Evangelista Torricelli, took up the study of this phenomenon. With the help of experiments on a heavier element, mercury, a few years later he was able to prove the presence of weight in air. He first created a vacuum in a laboratory and developed the first barometer. Torricelli imagined a glass tube filled with mercury, in which, under the influence of pressure, such an amount of substance remained that would equalize the pressure of the atmosphere. For mercury, the column height was 760 mm. For water - 10.3 meters, this is exactly the height to which the fountains in the gardens of Florence rose. It was he who discovered for mankind what atmospheric pressure is and how it affects human life. in the tube was named "Torricellian void" after him.

Why and as a result of which atmospheric pressure is created

One of the key tools of meteorology is the study of the movement and movement of air masses. Thanks to this, you can get an idea of ​​\u200b\u200bthe result of which atmospheric pressure is created. After it was proved that air has weight, it became clear that it, like any other body on the planet, is affected by the force of gravity. This is what causes pressure when the atmosphere is under the influence of gravity. Atmospheric pressure can fluctuate due to differences in air mass in different areas.

Where there is more air, it is higher. In rarefied space, a decrease in atmospheric pressure is observed. The reason for the change lies in its temperature. It is heated not from the rays of the Sun, but from the surface of the Earth. As it heats up, the air becomes lighter and rises, while the cooled air masses sink down, creating a constant, continuous movement. Each of these streams has a different atmospheric pressure, which provokes the appearance of winds on the surface of our planet.

Impact on the weather

Atmospheric pressure is one of the key terms in meteorology. The weather on Earth is formed due to the influence of cyclones and anticyclones, which are formed under the influence of pressure drops in the gaseous envelope of the planet. Anticyclones are characterized by high rates (up to 800 mmHg and above) and low speed, while cyclones are areas with lower rates and high speed. Tornadoes, hurricanes, tornadoes are also formed due to sudden changes in atmospheric pressure - inside the tornado, it drops rapidly, reaching 560 mm of mercury.

The movement of air leads to a change in weather conditions. Winds that arise between areas with different pressure levels overtake cyclones and anticyclones, as a result of which atmospheric pressure is created, which forms certain weather conditions. These movements are rarely systematic and very difficult to predict. In areas where high and low atmospheric pressure collide, climatic conditions change.

Standard indicators

The average under ideal conditions is considered to be 760 mmHg. The pressure level changes with altitude: in lowlands or areas below sea level, the pressure will be higher, at an altitude where the air is rarefied, on the contrary, its indicators decrease by 1 mm of mercury with each kilometer.

Reduced atmospheric pressure

It decreases with increasing altitude due to the distance from the Earth's surface. In the first case, this process is explained by a decrease in the impact of gravitational forces.

Heating up from the Earth, the gases that make up the air expand, their mass becomes lighter, and they rise to higher ones. The movement occurs until the neighboring air masses are less dense, then the air spreads to the sides, and the pressure equalizes.

The tropics are considered traditional areas with lower atmospheric pressure. In the equatorial territories, low pressure is always observed. However, zones with an increased and decreased index are unevenly distributed over the Earth: in the same geographical latitude, there may be areas with different levels.

Increased atmospheric pressure

The highest level on Earth is observed at the South and North Poles. This is because the air above the cold surface becomes cold and dense, its mass increases, therefore, it is more strongly attracted to the surface by gravity. It descends, and the space above it is filled with warmer air masses, as a result of which atmospheric pressure is created with an increased level.

Impact on a person

Normal indicators, characteristic of the area where a person lives, should not have any effect on his well-being. At the same time, atmospheric pressure and life on Earth are inextricably linked. Its change - increase or decrease - can provoke the development of cardiovascular diseases in people with high blood pressure. A person may experience pain in the region of the heart, bouts of unreasonable headache, and reduced performance.

For people suffering from respiratory diseases, anticyclones that bring high blood pressure can become dangerous. The air descends and becomes denser, the concentration of harmful substances increases.

During fluctuations in atmospheric pressure, people's immunity decreases, the level of leukocytes in the blood, so it is not recommended to load the body physically or intellectually on such days.