Atmosphere is a layer of gases surrounding the Earth and comprises 4 layers. Together with the Earth it makes a unique system that undergoes the laws of cosmic and planetar dynamics. The gas layer of the Earth and the Earth itself belong to the solar system and go around the Sun.
The gases in the atmosphere are a mechanical mixture, not chemical compound. There are numerous processes in the atmosphere that are crucial for overall life on Earth.
Atmosphere is clearly defined only in its lower part. Its lower border is the Earth’s surface, land and water. But, the upper border is not clear because it passes into very diluted interplanetary space with increasing altitude.
The atmosphere is composed of:
Nitrogen, an inert gas. It has a great importance for life on Earth. Under the influence of electric discharge nitrogen binds to oxygen and hydrogen. Oxygen is a very active gas that enables breathing and protects the Earth from solar radiation. Oxygen is formed by photosynthesis of the plants and is constantly renewed. Carbon dioxide has multiple importance for the Earth. Although in small percentage, it protects the Earth from solar infrared radiation. Ozone is present in low concentrations in the atmosphere and is formed by atmospheric discharge. Argon is not of particular importance for the processes in the atmosphere.
Besides the air, the atmosphere is composed of the following:
Suspended particles or aerosols that play important role in the events in the atmosphere and that serve as condensation nuclei around which water vapour passes into liquid or solid state. Water vapour comes to the atmosphere by water evaporation from Earth. Its amount is very changeable. It is mostly present in lower layer of the air.
Atmosphere is not unique or homogenous. According to the termical regime, gas composition and some electric properties, it is divided into 5 spheres:
troposphere – from 0 to 11 km is the lowest layer of the atmosphere with the highest density. Almost all water vapour is in the troposphere. All the processes that directly influence the weather and climate on the Earth are performed in this sphere. stratosphere – 11 – 40 km, extends above troposphere till the hight of 40 km. Here, there are no vertical motions of the air, only horizontal. Mesosphere – 40 – 80 km. Temperature decreases with height in the mesosphere. It is consisted of great amounts of ozone. Because of this, it acts as a protective layer from UV radiation. Thermosphere – 80 – 800 km. It is the highest layer of the atmosphere. Temperature increases with the height very fast in thermosphere. They can reach 2000 C during the day, and at night they decrease to 1000 C. This is the consequence of solar radiation and the lack of gases that would prevent such a great heating and cooling of the atmosphere. exosphere – above 800 km. It is the outmost layer where the atmosphere is completely lost. From this layer gas molecules freely move to interplanetary space.