Transcript 15.3 Winds - Cobb Learning

15.3 Global Winds and Local
Winds
Why Air Moves
• Wind-movement of air caused by
differences in air pressure
• Greater pressure difference=faster wind
*Air Rises at the Equator and Sinks
at the Poles
• Differences in air pressure are generally
caused by unequal heating of the Earth.
• Equator
– Receives more direct solar energy
– Air is warmer and less dense
– Warm air rises and creates low pressure area
– Warm air flows to poles
*National geographic video clip
• http://video.nationalgeographic.com/video/
player/science/earth-sci/weather-101sci.html?referrer=epals
*Air Rises at the Equator and Sinks
at the Poles, cont’d
• Poles
– Air is cooler and more dense
– Cold air sinks
– Creates high pressure area
– Cold air flows toward equator
*Pressure Belts Are Found Every
30 Degrees
• Pressure belts-bands of high pressure and
low pressure found every 30 latitude.
• Sinking air causes areas of high pressure
because sinking air presses down on the
air beneath it.
The Coriolis Effect
• Apparent curving of
the path of winds and
ocean currents due to
the Earth’s rotation.
• North- winds going
north curve east
• South- winds going
south curve west
Global Winds
• Patterns of air circulation
• Named from direction from which they
blow
• Major global wind systems
– Polar easterlies
– Westerlies
– Trade winds
Global winds
Polar Easterlies
• Poles to 60 latitude in both hemispheres
• Cold, dense air moves from poles to 60
• Can bring cold air to US making snow and
freezing weather
Westerlies
• 30 and 60 latitude in both hemispheres
• Flow from west to east
• Can bring moist air to US making rain and
snow
Trade Winds
• 30 latitude almost to equator in both
hemispheres
• Due to Coriolis-curve to west in N.
Hemisphere and east in S. Hemisphere
• Traders used winds to move from Europe
to Americas.
Doldrums
• Area around equator where there is very
little wind
The Horse Latitudes
• 30 north and south latitude
• Very weak winds
Jet Stream: Atmospheric Conveyor
Belts
• Narrow belts of high speed winds
• Blow in the upper troposphere and lower
stratosphere
• Can affect movement of storms and
airplane flights
Local Winds
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•
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•
Move short distances
Blow from any direction
Caused by differences in temperature
Sea breeze moves from sea to land
Land breeze moves from land to sea
How does wind blow?
• Wind will blow from high to low!!!
Wrapping it up
• What role does the Sun play?
– Sun heats the land and water, changing
temperatures
– Different heating causes density differences,
causing wind!
– UNEQUAL HEATING CAUSES THE WIND!
*Temperature of Coast vs.
Inland
• Avg temperature Atlanta: low-23 to 51: 28
degree difference for January
• Avg temp. for Savannah: low-38 to 60: 22
degree difference
• Avg for July: Atlanta-88
•
Savannah- 92
• Why is Savannah warmer?
– Gulf Stream runs by it and there is a constant
breeze blowing near the ocean
– Lower temp range on coast
Temperature of Coast vs. Inland
• Coastal areas don’t get as warm or as cold
as inland areas because it has the ocean
to moderate their temperatures.