The atmosphere of our planet is the air shell of the earth that protects the surface from the lethal effects of the sun's ultraviolet rays on all living things. In addition, the atmosphere prevents the entry of dust and meteorites from outer space.
Atmosphere Structure: Composition
The protective shell consists of a mixture of gases: nitrogen occupies two thirds of its volume, oxygen occupies a fifth, and inert gases (krypton, argon, helium, and others) account for one percent. The volume of nitrogen and oxygen remains almost unchanged, since nitrogen practically does not react with other substances and compounds, and oxygen, despite the expenditure, is constantly replenished by plants.
Up to 100 km altitude, the ratio of these gases in percent practically does not change. This is due to the constant mixing of air masses.
In addition to the described components, the atmosphere includes about 0.030 percent carbon dioxide, which is concentrated closer to the earth's surface. Most of it is in industrial centers, cities, in areas of volcanic activity.
The atmosphere also includes a small amount of dust and water vapor in its structure. The volume of the last component depends on the ambient air temperature: with increasing, a greater amount of steam is formed. The presence of water in the vapor state in the air makes it possible to observe such natural phenomena as the refraction of the sun's rays, rainbow, etc.
Dust in the atmosphere occurs during volcanic eruptions, dust and sand storms, as a result of incomplete combustion of fuel at thermal stations.
The density of the air envelope is not the same everywhere. This indicator is affected by the height of the atmosphere. The densest shell at the surface of the planet, and with height it becomes less common. Already at a distance of 11 km, the atmosphere is 4 times less likely than in the surface layer.
Atmospheric structure: vertical section (stratification)
Depending on the properties of the gas, composition and density, the air envelope is divided into 5 main parts - concentric layers.
The lowest layer is the troposphere, the upper boundary of which is located at a distance of 10 km from the surface of the planet at the equator, at the poles this figure is 18 km. The bottom layer contains almost all water gas and almost 80 percent of the total atmosphere.
In the troposphere, air temperature decreases with altitude: every hundred meters it becomes colder by 0.6 degrees, and minus 45-50 degrees are observed at the upper boundary.
In this shell there is a constant movement of air, which moves, mixes. Only here it rains, thunderstorms, fogs, storms or snowfalls are observed.
The second layer in the atmosphere is the stratosphere, which extends to an altitude of 55 km. This shell has negligible pressure and air density. The sparse masses consist of the same gases as the troposphere, however, there is more ozone here. The maximum concentration of this oxygen isotope is observed at a distance of 20-30 km from the surface. The temperature of the stratosphere rises with height, and at the upper boundary, this indicator is 0 degrees. This is due to the absorption of the short-wave part of the solar energy by ozone, due to which air is heated.
Above the stratosphere is the mesosphere, whose height is 80 km from the surface. Here again, the temperature drops to minus 90 degrees at the upper boundary, the air density is two hundred times lower than in the surface layers of the planet’s atmosphere .
The distance from 80 to 800 kilometers is occupied by the mesosphere - the fourth shell included in the structure of the atmosphere. Here, the gases are in an ionized state, and the temperature at an altitude of 160 km is 200 degrees, and at 650 km it reaches 1,500 C. Electric currents are formed that act on a magnetic field, and auroras occur.
The last outer shell is called the exosphere, which is located above 800 km. Here the particle velocity reaches a critical point at which they can go into space, overcoming Earth's gravity.