The word atmosphere comes from the Greek words atmós for vapor, fog, breath, and sphaira for sphere. Earth’s atmosphere is the gaseous layer above the Earth’s surface that covers our planet.
Some facts about atmosphere
The Earth’s atmosphere protects us from the Sun’s harmful UV and X rays, but allows significant sunlight to pass through the Earth’s surface. In addition, certain gases in the atmosphere (greenhouse gases) ensure that the temperature makes life possible.
Without greenhouse gases, the average temperature would be -18 °C instead of 15 °C (greenhouse effect). Most of the water cycle also happens in the atmosphere: evaporated water condenses, forms clouds, and falls back to Earth as precipitation.
The atmosphere is composed of 78.084% nitrogen, 20.942% oxygen, 0.934% argon and other rare gases. Greenhouse gases represent less than 1%. The carbon dioxide content is only 0.038%. However, along with water vapour, carbon dioxide is the most important greenhouse gas.
Composition of the Atmosphere Floor
Based on the temperature conditions, the Earth’s atmosphere is divided into several layers.
The lowest layer of the Earth’s atmosphere is called the troposphere. It extends from land up to 8 km at the poles and up to 18 km at the equator.
The upper boundary of this layer is called the tropopause. The troposphere is characterized by a steady decrease in temperature with altitude.
This means that it is warm on the ground and the temperature drops to -60 °C during the tropopause. The troposphere comprises 80% of the total mass of the atmosphere and almost all water vapour.
Therefore, almost all weather events, such as cloud formation and precipitation, occur in the troposphere.
The stratosphere is located above the troposphere. It reaches an altitude of about 50 km and is characterized by a particularly high percentage of ozone.
The maximum concentration of ozone is about 30 km above sea level. Ozone absorbs dangerous shortwave solar radiation and is therefore of great importance for life on Earth.
The temperature in the stratosphere remains constant around -60 °C up to an altitude of about 20 km. Above that, it rises to 0°C at the upper boundary of the stratosphere, which is called the stratosphere.
There is hardly any water vapor in the stratosphere. Therefore, there are hardly any weather events here.
The mesosphere is located above the stratosphere. It extends from 50 km to 85 km above sea level. In the mesosphere, the temperature drops to -100 °C. It reaches a minimum altitude of about 80 km. Mesopause is upon him.
The thermal climate varies from 85 to 500 km in altitude. However, there are so few particles in this layer that temperature measurement is no longer possible, only a measurement of radiation energy.
Above the thermosphere is the exosphere. It is the outermost layer of Earth’s atmosphere and it flows smoothly in space. Here the pressure is so low that we can talk of zero.