Layers of the Atmosphere
Exosphere
Above a height of about 500km is the exosphere, a layer where the atmosphere merges into space. Satellites are stationed in this area, 500km to 1000km from Earth.
Mesosphere
Beyond the stratosphere the air is very thin and cold. This area is known as the mesosphere, and is found between 50km and 80km above the Earth's surface.
Composition
More than three quarters of the atmosphere is made up of nitrogen and most of the rest is oxygen. However it is the remaining 1%, a mixture of carbon dioxide, water vapour and ozone, that not only produces important weather features such as cloud and rain, but also has considerable influence on the overall climate of the Earth,through mechanisms such as the greenhouse effect and global warming. (Stay with us and we'll learn more about the changing climate in a later section!)
Stratosphere
The stratosphere is the second layer of air above the Earth's surface and extends to a height of 50km. It is here that we find the ozone layer. The ozone layer absorbs much of the sun's harmful radiation that would otherwise be dangerous to plant and animal life.
Thermosphere
The thermosphere is the fourth layer in the atmosphere, between 80km and 110km above the Earth. Space shuttles fly in this area and it is also where the aurora lights are found. Auroras are wispy curtains of light caused when the sun strikes gases in the atmosphere above the Poles.
Troposphere
The troposphere is the layer closest to the Earth, approximately 11km high. Weather occurs only in the troposphere because it is this layer that contains most of the water vapour. Weather is the way water changes in the air, and so without water there would be no clouds, rain, snow or other weather features.The troposphere is an unstable layer where the air is constantly moving. As a result, aircraft flying through the troposphere may have a very bumpy ride - what we know as turbulence. You may have experienced this when flying before! Because of this turbulence, most jet airlines fly higher above the Earth in the stratosphere. Here the air is more still and clear as they can fly above the clouds.
