Air Pressure2nd Factor that Affects Weather

What is Air Pressure?

• The weight of the air pushing down on us and everything else around us.

• Happens because of the gravitational pull.

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.

HIGH & LOW PRESSURE SYSTEMS

HIGH PRESSURE

• Cold• Dry• Sinking air• Clockwise

rotation

LOW PRESSURE

• Warm• Moist• Rising air• Counterclockwi

se rotation

Factors That Affect Air Pressure

ELEVATIONHigher 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

Factors That Affect Air PressureTEMPERATURE

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

How does air pressure relate to weather?

• Helps to determine if there will be rain or sunny skies; cold or hot air; etc…

Low Pressure systems

• Warm • Humid• Rainy• Cloudy weather• Thunderstorms• Severe weather• The warm air rises, condenses, forms clouds

and rains!

Low Pressure Weather Results

High Pressure systems

• Sunny skies• Cooler temperature• Dry air• Beautiful weather

High Pressure Weather Results

Your Turn!!!

• Now YOU are going to demonstrate air pressure by doing a Metal Can Experiment!!