J. Shevlin
April 11, 2012
Eastern Illinois
University
 What
is wind?
 What causes wind
to form?
At the end of class, you will be able to:
• Relate air pressure and wind direction
• Explain why winds flow in a curved direction
• Discern global winds from local winds
• Describe the three main global wind patterns on
Earth
• Explain two types of local wind patterns
 Wind
 Coriolis
effect
 Jet stream
 Trade
winds
 Westerlies
 Polar easterlies
 Wind
is air in motion.
• Formed by differences in
pressure
 Caused by uneven heating of
the atmosphere
 Law of diffusion: moves from
high to low
 Greater pressure difference =
faster winds
H
L
 Why
doesn’t wind blow directly from the
poles to the equator?
 Why
doesn’t wind blow directly from the
poles to the equator?
 Thought to consider: is the Earth in a fixed position?
 Wind
movement
affected by Earth’s
rotation
• Results in a curved path
of motion
• Depends on
hemisphere you are in
 Northern hemispherewinds curve to the right
 Southern hemispherewinds curve to the left
 The
Coriolis effect is the curving motion of
objects caused by the Earth’s rotation
 Global
winds
• Pattern of circulation across the Earth
• Travel great distances
• Travel in a specific direction
 Local
winds
• Travel short distances
• Can blow from any direction
 Trade
Winds
 Westerlies
 Polar Easterlies
 Doldrums
 Horse Lattitudes
 What
do you think may cause global wind
patterns?
 What
do you think may cause global wind
patterns?
 Thoughts to consider:
 Are regions of high pressure only ever near the poles?
 Are regions of low pressure only ever near the equator?
 High
pressure belts
near 30oN, 30oS
 Low pressure belts
near 60oN, 60oS
 Result in patterns of
rising and sinking
air
• Sounds
familiar…Convection?
 Jet
stream- narrow belt of high speed winds
• Found in upper troposhere, lower stratosphere
• Do not follow regular patterns
 Change positions frequently
• Affect weather movement
 Local
winds are affected by an area’s
geography
• Results in wind blowing from any direction
• Examples:
 Sea breeze
 Land breeze
 Why
does breeze travel one way in the
daytime and in the other direction during
the nighttime?
 Thoughts to consider:
 is ground a good conductor of heat?
 Is water a good conductor of heat?