1. The Structure of the Atmosphere
What are the main gases in our atmosphere?
Nitrogen (78%)
Oxygen (21%)
Argon and all others (ozone, Carbon dioxide water vapor etc.) (~1%)
We divide our atmosphere into 4 layers based on temperature
Troposphere
Stratosphere
Mesosphere
Thermosphere

3. Troposphere Troposphere: Temp. and pressure drop as you go up
layer closest to the Earth's surface
extending up to about km above the Earth's surface.
contains 75% of the atmosphere's mass
Most clouds/weather occur in the troposphere.
Temp. and pressure drop as you go up

4. Stratosphere Above the troposphere
extends from about 15 to 50 km above the Earth's surface
Temp. increases with altitude because of absorption of sunlight by ozone (ozone layer)
Temperature increases with altitude
Stratopause

5. Mesosphere Above the stratosphere
Extending from 50 to 80 km above the Earth's surface
A cold layer where the temp. decreases with increasing altitude
Where meteors burn up

6. Thermosphere Extends from 80 km – 320 km Temp. is hot
However, the thermosphere would actually feel very cold to us because so few molecules will hit our skin and transfer enough energy to cause appreciable heat

7. What does our atmosphere do?
Two main natural processes
Greenhouse effect – keeping the planet warm through absorbing long wave radiation from the planet (water, CO2, CH4)
Ozone shield – blocking unwanted UV radiation
Protects life on earth from cataracts, skin cancer.