1. Unit 6: The Atmosphere

2. Atmosphere Composition
Different today than long time ago! How?
2 main gases make up 99% of the atmosphere
Nitrogen—78%
Oxygen 21%
Other gases in atmosphere
Carbon Dioxide—small amount/important
Water Vapor—amount varies also important

3. Atmosphere Structure Pressure decreases as you rise in the atmosphere
Air molecules rapidly thin!

4. Heat Transfer Radiation Conduction Convection
Heat that travels through empty space
Conduction
Heat transferred through contact
Convection
Heat transfer through fluids (air and water
Heat is less dense and rises, cold is more dense and sinks

6. Heat Transfer 50% is absorbed by earth
20% is absorbed by clouds and atmosphere
30% is reflected back to space

7. Atmosphere Structure
4 layers determined by temperature gradients

8. Troposphere Closest layer to the Earth Where all weather occurs
Air close to ground is heated by conduction causing temperature to decrease with altitude

9. Stratosphere
Ozone causes temperature to increase with altitude

10. Temperatures decrease with altitude as you move away from ozone
Meteors burn up from friction with our atmosphere
Mesosphere

11. Thermosphere Outermost layer
Temperatures increase with altitude due to UV radiation from the sun
Auroras found here

12. Ozone Ozone is a molecule consisting of 3 oxygen atoms
Ozone in the stratosphere is necessary for life on Earth
Ozone in the troposphere is a pollutant (smog!)
Ozone

13. Stratospheric Ozone
Ozone can be created or destroyed by the Sun’s UV rays

14. Stratospheric Ozone
CFCs (chlorofluorocarbons) and other ozone depleting compounds breakdown and prevent new ozone from forming

15. Thinning of the ozone layer has caused a “hole” to form
Stratospheric Ozone

16. Stratospheric Ozone Good News! The Montreal Protocol (1987)
An international agreement to reduce ozone depleting compounds like CFCs
The ozone layer should recover by 2050