Air Pressure

Air in the Troposphere Air and density- Air particles have mass. Particles near ground are compressed More particles squished together = more m/v = greater density More dense = more collisions = more pressure

How is AP measured? With a barometer Unit is inches of mercury or millibars

How is AP shown on a weather map? Lines of equal AP are called isobars.

What is the connection btwn AP and altitude? Air closer to surface has higher pressure due to higher density and more collisions Higher up near stratosphere, air is thin so less density and less pressure **** Avg. sea level pressure = 1013 mb On top of Mt. Everest = 300 mb

What is the connection between AP and temperature? Density as temp. b/c warm stuff expands Cold air has high density b/c cold stuff contracts Lower density = lower AP = air rising Warmer air will have lower AP than colder air.

What is the connection btwn AP and humidity? Moist air is less dense b/c H2O is light but takes up lots of space. Lower density = lower AP

If so much air pressing on us, why don’t we collapse? What happens to a balloon that floats up to upper atmosphere? Our bodies reach equilibrium b/c not airtight (holes) It would pop b/c air inside would want to expand due to less pressure on outside of balloon.

How is air pressure related to weather? High AP = happy weather, air is heavy so sinking, so not rising and forming clouds Low AP = lousy weather, air is light and lifting, so it is rising and forming clouds