2. Air Pressure 2 nd Factor that Affects Weather

3. What is Air Pressure? The weight of the air pushing down on us and everything else around us. Happens because of the gravitational pull.

4. Air Pressure Air pushes on you with a force of 14.7 pounds per square inch. The force on 1,000 square centimeters (a little larger than a square foot) is about a ton! Why doesn't all that pressure squash me? Remember that you have air inside your body too, that air balances out the pressure outside so you stay nice and firm and not squishy.

5. HIGH & LOW PRESSURE SYSTEMS HIGH PRESSURE Cold Dry Sinking air Clockwise rotation LOW PRESSURE Warm Moist Rising air Counterclockwise rotation

6. Factors That Affect Air Pressure ELEVATION Higher elevation = lower pressure Lower elevation = higher pressure The column of air over low elevations is longer, so the pressure is higher The column of air over high elevations is shorter, so the pressure is lower

7. Factors That Affect Air Pressure TEMPERATURE Warm, moist air = lower pressure (lighter) Cold, dry air = higher pressure (heavier) Molecules spread out; Fewer molecules in a certain space Molecules crowd together; More molecules in a certain space

8. How does air pressure relate to weather? Helps to determine if there will be rain or sunny skies; cold or hot air; etc…

9. Low Pressure systems Warm Humid Rainy Cloudy weather Thunderstorms Severe weather The warm air rises, condenses, forms clouds and rains!

10. Low Pressure Weather Results

11. High Pressure systems Sunny skies Cooler temperature Dry air Beautiful weather

12. High Pressure Weather Results

13. Your Turn!!! Now YOU are going to demonstrate air pressure by doing a Metal Can Experiment!!