Introduction to the Atmosphere
The Atmosphere
The atmosphere is a layer of gases surrounding Earth, held by gravity, essential for sustaining life by regulating temperature, filtering radiation, and enabling chemical reactions. It is the outer limit of the biosphere and its composition and processes support life on Earth. Differential heating of the atmosphere creates the tricellular model of atmospheric circulation that redistributes the heat from the equator to the poles. This circulation disperses the heat across the planet, reducing the heat at the equator and increasing the temperature in higher latitudes.
Composition:
- Nitrogen (N₂): ~78%
- Oxygen (O₂): ~21%
- Argon (Ar): ~0.93%
- Trace Gases: CO₂, CH₄, H₂O vapour, and others.
Atmospheric Layers
- Troposphere:
- 0–12 km; weather occurs here; temperature decreases with height.
- Stratosphere:
- 12–50 km; contains the ozone layer; temperature increases with height due to UV absorption.
- Mesosphere:
- 50–85 km; meteors burn here; temperature decreases with height.
- Thermosphere:
- 85–600 km; auroras occur here; temperature increases due to solar radiation.
- Exosphere:
