2 - Atmospheric Energy and Matter#
2.1 - What is the Atmosphere?#
The atmosphere extends more than 100 km upward from the Earth’s surface. It is made up of the following layers, in ascending order:
The troposphere is the thinnest layer, and contains clouds, wind, rain, and other aspects of weather. About \(70\%\) of the mass of the atmosphere is concentrated in this layer.
The stratosphere begins at 10 km above sea level, at about the elevation of the Earth’s highest peaks. Some commercial flights will take place low in the stratosphere, since there is less resistance. This layer is stratified, with the lower parts being cooler and the higher parts being warmer.
The mesosphere begins at 50 km above sea level and extends to 80 km above sea level. The upper mesosphere is very cold (\(-121 \degree \text{F}\)), and is considered the coldest place in the Earth system. Radio waves bounce off this layer, allowing their range to be greatly extended.
The thermosphere can be very hot (up to \(1500\degree \text{C}\)). Auroras originate from this layer.
The atmosphere is primarily composed of nitrogen (\(78.1\%\)), oxygen (\(20.9\%\)), and argon (\(0.9\%\)), with trace amounts of water vapor, carbon dioxide, neon, helium, ozone, and other gases.