Barometric pressure is the pressure of the atmosphere. This name is due to the fact that the device for measuring pressure is a barometer. However, barometric pressure is an outdated term. In modern meteorology, it is called atmospheric pressure. At sea level, its average value is 760 mmHg, which is equivalent to a weight of 1 kg, acting per 1 square centimeter.
Atmospheric and underwater pressure fluctuations
When immersed in the water column, a rapid increase in pressure is observed - by 1 atmosphere for every 10 meters of depth growth. This forces deep-sea organisms to adapt to this effect. Under normal pressure, they cannot exist and die.
The increase in pressure under water is one of the main problems of deep diving. A sharp rise to the surface is especially unfavorable, which can lead to dangerous decompression.
Staying at high altitudes also poses a potential threat to health, since the human body is little adapted to such low values. Due to a decrease in the partial pressure of oxygen, oxygen deficiency in the body may occur - hypoxia. At an altitude of 8 km, atmospheric pressure is several times lower than at sea level, and is 270 mm. Hg. Art.
The Earthβs surface can also have significant differences in atmospheric pressure, but very rarely. The maximum range of oscillation is from 640 to 816 mm RT. Art. However, under certain conditions (tornadoes, tornadoes), pressure can drop even lower.
Meteorological processes affect the value of atmospheric pressure, but most often its differences are small. Therefore, their effect on the human body is less pronounced.
Barometric Pressure Units
The recognized unit of atmospheric pressure is Pascal. But in Russia, another gradation is popular - a millimeter of mercury. Other units are less commonly used. The barometric pressure sensor is a barometer.
The effect of pressure and altitude on the gas composition of air
The effect of barometric pressure is not limited to the effect on human well-being. With a decrease in atmospheric pressure at altitudes, the gas composition of the atmosphere also changes. First of all, the percentage of water vapor is reduced, which is associated with its freezing and condensation. Any gases that are heavier than air (such as carbon dioxide) climb faster than lighter ones (such as methane). This can affect the nature of the greenhouse effect of the atmosphere at different heights, which decreases rapidly with height, due to a decrease in water vapor content. Since methane penetrates to a higher degree in the higher atmosphere, the nature of the greenhouse effect it causes and the impact on the climate will not be exactly the same as for carbon dioxide.
Natural fluctuations in atmospheric pressure
Natural fluctuations in barometric air pressure are associated with uneven heating of various parts of the globe, with the interaction of land and ocean, and with the rotation of the Earth. Air over warmer areas becomes more mobile, and therefore expands and spreads to the sides, which leads to a decrease in atmospheric pressure. And, on the contrary, over less warmed places the air is less mobile, and therefore is more inclined to contract and condense. In accordance with the formula: P = Οgh, where Ο is the density, g is the acceleration, and h is the height above sea level, denser air at the same height creates a higher pressure, which is recorded by barometers.
During a thunderstorm and immediately in front of it, atmospheric pressure usually decreases, which can cause a change in well-being in weather-sensitive people. Also, a decrease in pressure can be observed immediately before the arrival of a cold atmospheric front.
Cyclones and anticyclones
Large-scale atmospheric circulation and uneven heating of the earth's surface lead to the appearance of cyclones and anticyclones. Cyclones are large areas with low atmospheric pressure, and anticyclones, on the contrary, with high.
Cyclones are usually more mobile and dynamic than anticyclones. The air in the cyclone rises from the lower part of the atmosphere to higher ones, and since it is warm and humid, dense clouds often form and rainfall.
In anticyclones, the opposite is true: air, on the contrary, falls, is pressed to the earth's surface. This air comes from higher layers of the atmosphere, where the water vapor content is relatively low. For this and other reasons, the chances of the formation of rain clouds in the anticyclone are small, and the relative and absolute humidity is much lower than in the cyclone.
Thus, barometric pressure is one of the main characteristics of the atmosphere. The weather, climate and our well-being depend on it. Barometric pressure is the same as atmospheric pressure. However, now this term is rarely used.