STRUCTURES OF ATMOSPHERE

The Structure of the Atmosphere – The Atmosphere can be divided into layers according to major changes in temperature. Due to the force of gravity most of the earth’s gases, in fact 99% can be found in the botom 32km. 

Troposphere is 0 to 12 km  and contains 75% of the gases in the atmosphere. This is the most unstable of layers and where our weather occurs. As height increases, temperature decreases. The temperature drops about 6.5 degrees celsius for every kilometer above the earth’s surface. However, this is an average and significantly varies from place to place..

Tropopause is a thin band located at the top of the troposphere that separates the troposphere from the stratosphere. The temperature remains fairly constant here. It is within the tropopause that we find the jet stream.

Stratosphere is 12 to 50 km. The temperature remains fairly constant (-60 degrees Celsius) in the lower part of stratopshere. This is largely because of ozone.  Ozone absorbs ultraviolet radiation from the sun and this causes a temperature increase in the upper part of the layer.  

Stratopause is again a thin layer of homogenous atmosphere that separates the stratosphere from the mesosphere

Mesosphere is 50 to 80 km. This is the coldest region of the atmosphere as the temperature drops in this layer to about -100 degrees celsius. It is this layer of the atmosphere where meteorites burn up on entry. At the top of the mesosphere is the uniform mesopause.

Thermosphere begins at 80 km and extends to many hundreds of kilometers up. The air is very thin. Meaning “heat sphere”, the temperature is very high in this layer because ultraviolet radiation is absorbed and turned into heat by ozone and other gases elements. Temperatures often reach 2000 degrees celsius or more. This layer can be further subdivided into: 

Ionosphere – This is the lower part of the thermosphere, extending from about 80 to 550 km. Gas particles absorb ultraviolet and X-ray radiation from the sun. The particles of gas become electrically charged (ions). Here, radio waves are bounced off the ions and reflect waves back to earth. This generally helps radio communication.

Exosphere – the upper part of the thermosphere. It extends from about 550 km for thousands of kilometers. The air is very thin here and this is the area where satellites orbit the earth.


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