Transcript ch 15 sec 3

Global Winds and Local Winds
Wind- movement of air caused by differences in air
pressure
Air rises at the equator and sinks at the poles
The equator receives more direct sunlight creating
less dense, warm, rising air toward the poles
leaving an area of low pressure.
At the poles, air is colder so it sinks toward the
equator leaving an area of high pressure.
Why does sinking air cause
areas of high pressure?
Sinking air causes areas of high
pressure because sinking air
presses down on the air beneath it.
Pressure Belts are found every 30
degrees
Pressure belts- bands of high pressure and
low pressure found every 30° latitude
The uneven heating of the Earth produces
pressure belts. These belts occur at about
every 30° of latitude.
Coriolis effect- curving of the path of
winds and ocean currents due to
Earth’s rotation
Global Winds
- Produced from the combination
of convection cells found at
every 30° latitude and the
Coriolis effect.
Global winds
- Polar easterlies
- Westerlies
- Trade winds
- Doldrums
- Horse latitudes
Polar easterlies
 Cold, sinking air that blow from east to west
from the poles to 60° latitude
- Can carry cold arctic air over the United
States producing snow and freezing weather
Westerlies
 Winds that blow from west to
east toward the poles
Trade winds
 Early traders used the trade winds to sail
from Europe to the Americas
 Winds that blow toward the equator
Doldrums
 Means “dull” or “sluggish”
- Area near the equator where trade winds
meet from the Northern and Southern
hemispheres
Jet streams
Narrow belts of high-speed winds that blow in
the upper troposphere
Local winds
Sea breeze
Land breeze
Mountain breeze
Valley breeze
Sea and Land Breezes
Mountain Breezes and Valley
Breezes
During the day, the sun warms the air along
the mountain slopes. This warm air rises up
the mountain slopes, creating a valley
breeze
At night time, the air along the mountain
slopes cools. This cool air moves down the
slopes into the valley, producing a mountain
breeze.
Why does the wind tend to blow
down from mountains at night?
At night, the air along the
mountain slopes cools. This
cool air moves down the slopes
into the valley and produces a
mountain breeze.