The Structure of the Atmosphere
Atmosphere Layers
The atmosphere is basically constructed of five layers
- Troposphere – 0–10 km (0–6 mi)
- Stratosphere – ~10–50 km (6–30 mi)
- Mesosphere – ~50–80 km (30–50 mi)
- Thermosphere – ~80–500 km (50–300 mi)
- Exosphere – ~500 km+ (300 mi+)
- Troposphere – Extends from Earth’s surface to about 8–15 km (5–9 mi). Contains most of our weather, clouds, and the bulk of atmospheric mass. Temperature decreases with altitude.
- Stratosphere – About 15–50 km (9–31 mi) above the surface. Home to the ozone layer, which absorbs harmful UV radiation. Temperature increases with altitude due to ozone absorption of sunlight.
- Mesosphere – About 50–80 km (31–50 mi) high. Coldest layer of the atmosphere; meteors burn up here. Temperature decreases with altitude.
- Thermosphere – About 80–500 km (50–300 mi) high. Very thin air; absorbs high-energy solar radiation, causing temperatures to rise sharply. Contains auroras and orbits for the ISS.
- Exosphere – Above ~500 km (300 mi). Outer limit of the atmosphere where it gradually transitions into space. Contains sparse particles of hydrogen and helium.
What Makes Up the Atmosphere
The following elements make up the atmosphere and their percentages.
Nitrogen - Approx 78%
Oxygen - Approx 21%
Argon - Approx 1%
The following are trace gases in the atmosphere
Carbon Dioxide CO^2
Methane CH^4
Ozone O^3
Water Vapor H2O
GreenHouse Gases
- Water vapor (H₂O) – Most abundant GHG; naturally present, varies with temperature; major contributor to the greenhouse effect.
- Carbon dioxide (CO₂) – Produced naturally (volcanoes, respiration, decay) and by humans (burning fossil fuels, deforestation); long atmospheric lifetime.
- Methane (CH₄) – Emitted from wetlands, livestock digestion, landfills, and fossil fuel extraction; much more effective than CO₂ at trapping heat, but shorter-lived.
- Nitrous oxide (N₂O) – Released from agricultural soils, fertilizers, combustion, and some industrial processes; very potent and long-lived.
- Ozone (O₃) – In the lower atmosphere (troposphere), acts as a GHG; formed by chemical reactions involving pollutants; also exists naturally in the stratosphere (where it protects us from UV).
- Fluorinated gases – Human-made industrial chemicals (HFCs, PFCs, SF₆, NF₃); extremely potent GHGs with long lifetimes, but present in small concentrations.