1. Air Pressure & Layers of the Atmosphere

2. Air Pressure
the force exerted on you by the weight of tiny particles of air
the particles have weight and take up space.

3. Why doesn't all that pressure squash me?
You have air inside your body too
The air inside your body is pushing out as the air outside your body is pushing in.

4. Air Pressure
Earth's atmosphere is pressing against each square inch of you with a force of 1 kilogram per square centimeter (14.7 pounds per square inch) at sea level.
The force on 1,000 square centimeters (a little larger than a square foot) is about a ton!

5. Air Pressure As your altitude increases the air pressure decreases.
As your altitude decreases the air pressure increases.
This is an inverse relationship!

7. Barometers are used to measure air in "inches of mercury“ (in Hg) or in "millibars" (mb).
Air pressure can tell us about what kind of weather to expect as well.
If a high pressure system is on its way, often you can expect cooler temperatures and clear skies.
If a low pressure system is coming, then look for storms and rain.
Pressure & Weather

8. Early Earth Atmosphere
A dense atmosphere emerged from the vapor and gases that were given off as the planet began cooling. These gases consisted of:
Hydrogen (H2)
Water Vapor (H2O)
Methane (CH4)
Carbon Oxides (CO2, CO)
What’s missing?
Oxygen!
Early algae and plants eventually changed the atmosphere by giving off “free” oxygen (O2).

9. Composition of Air Today
Nitrogen (N2) %
Oxygen (O2) %
Argon (Ar) %
Carbon Dioxide (CO2) and other trace elements %

10. Troposphere 90% of content of the atmosphere within 16 km of surface
Most weather occurs here
Temperature goes down with altitude

11. Stratosphere
Contains ozone layer which plays a major role in regulating temperature
Temperature goes up with altitude

12. Ozone Layer Found in the Stratosphere
Ultra-Violet light creates O3 from O2
Prevents a lot of UV radiation from reaching surface
O3 destroyed by manmade gasses (CFCs)

14. Mesosphere
The mesosphere is characterized by temperatures that quickly decrease as height increases.
With increasing distance from Earth's surface the chemical composition of air becomes strongly dependent on altitude and the atmosphere becomes enriched with lighter gases.

15. Thermosphere
In the thermosphere, temperature increases with altitude because molecular oxygen absorbs the intense solar radiation.
Auroras are found in this layer

16. Exosphere/ Ionosphere
The outermost layer of the Earth's atmosphere.
The exosphere is a transitional zone between Earth's atmosphere and interplanetary space.

17. Lab: Air Pressure