Notes: Air Pressure and Wind

Air pressure is the ___weight______ of the
atmosphere pushing down on earth’s
______surface__________

Air pressure depends on the weight of the air above
o
If you climb a mountain, your altitude has
_______increased_______________
o
If you climb a mountain, the amount of air above you has
________decreased______________
o
As you climb a mountain the air pressure
_________decreases______ because there is
_______less_______ air above you.

How is Air Pressure Measured?
o
Barometer – a tool that measures
____air pressure__
o
Measured in millibars (mb) or millimeters of
mercury (mmHg)
Why Does Air Pressure Change?

If the air is warm what will happen to the air pressure?
o
Warm air is ____less_________ dense so it ____rises________ causing
the air pressure to ______decrease___________ or be lower
o
Cold air is ____more______ dense so it ______sinks________ causing the air pressure to
______increase_______ or be higher

How does Humidity affect air pressure?
o
The ___more______ water in the air, the _____less________ it weighs
o
Humid air has _____more________ water in it

The air mass will weigh _____less_____ so the air pressure will
______decrease________ or be lower
o
Dry air has _____less_________ water in it

The air mass will weigh ______more______ so the air pressure will
______increase________ or be higher
Air Pressure and Weather
Comparing and Contrasting High and Low Pressure


LOW PRESSURE
o
Warm, moist air is ___rising_____
o
Clouds and precipitation are ___likely_______
o
Air moves __in______ and ___up_____, counter-clockwise
L
HIGH PRESSURE
o
Cold, dry air is _____sinking________
o
Clear skies with no precipitation are __likely______
o
Air moves ___down_____ and ___out_____, clockwise
H
H
Montana
L

What type of weather would you expect in Montana?
Clear, no precipitation

What type of weather would you expect in Virginia?
Clouds, precipitation
Virginia