1. Structure, Layers, and the Greenhouse Effect
Earth’s Atmosphere
Structure, Layers, and the Greenhouse Effect

2. Elevation Density and Pressure
The Atmosphere extends to hundreds of km above the Earth
The Weight of the upper layers pushes down generating pressure concentrating the air in the lowest layer.
Thus Elevation is inversely related to both pressure and density.

4. The Troposphere or “Weather Sphere”
From 0 – 18 km, the lowest layer
Most dense, containing 70 – 80 % of the air
Most weather and clouds occur here
Elevation and Temperature are inversely related

5. The Stratosphere or “Blanket-sphere”
18 – 50 km elevation
Little weather occurs here, flat stratus clouds in the lower levels & High winds (Jet streams)
Elevation and temperature are directly related
Near the top is a thin layer of Ozone (O3) that blocks UV light.

6. Mesosphere “Middle-sphere”
50 – 90 km
Very low density
Elevation and temperature are inversely related

7. Ionosphere 90 – 400 km So little density its almost “space”
Made of Ionized Gas
Temperature and Elevation are directly related
Aurora Borealis occurs here

8. The Greenhouse Effect
The Atmosphere lets visible light pass through but absorbs most infrared light
Light reaches Earth’s surface which is warmed and radiates Infrared light which is absorbed
Thus trapped by the atmosphere, and…
The average temperature rises.
Temperatures are more moderate
Some gasses called “green house gasses” (such as CO2) absorb better than others.
If they increase so will the average temperature