Global and Local Winds

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Global and Local Winds
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Air Movement

• Wind is the horizontal movement of air from high
  pressure to low pressure. It is caused by
  differences in air pressure
• The greater the difference, the faster the wind
  moves

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Air Pressure

• Differences in air pressure are caused by the
  uneven heating of Earth
• Cool, denser air with a higher pressure flows
  underneath the warm, less dense air. This forces
  the warm air to rise.

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1. Wind Vane- measures wind direction.- tells you
   where the wind is coming from. Ex a north wind
   comes FROM the north.
2. Barometer- measures air pressure
3. Anemometer- measures wind speed.
4. Wind chill factor- the increased cooling a wind
   causes.

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Wind Chill

• Why does a cool breeze feel refreshing in the
  summer, but cold in the winter?
• Wind blowing over your skin removes body heat.
  The stronger the wind, the colder you feel.

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Local Winds

• Generally move short distances and can blow in
  any direction
• Caused by geographic features that produce
  temperature differences
• Caused by the unequal heating of Earths surface
  within a small area.

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• It takes more energy to warm up and cool down a
  body of water than it does to warm up land.
• Wherever the cool air is located, that is the
  type of breeze. Ex sea breeze- cool air is over
  the sea.

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Sea Breezes

• High pressure is created over the ocean (cooler
  air) during the day and low pressure (warmer air)
  over land due to uneven heating
• Air moves from the ocean to the land creating a
  sea breeze

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A. Sea Breeze

1. Happens during the day.
2. Land warms up faster than the water.
3. Air over the land becomes warmer than air over
   the water.
4. The warm air expands and rises, creating a
   low-pressure area.
5. Cool air blows inland from over the water and
   moves underneath the warm air, causing a sea
   breeze.
6. Sea Breezes blow FROM THE SEA.

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Sea Breeze
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Land Breezes

• Low pressure occurs over the ocean during the
  night and high pressure over land due to the
  uneven heating of earth
• This causes wind to move from the land to the
  ocean creating a land breeze

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B. Land Breeze

• 1.Happens at night.
• Land cools more quickly than water.
• Air over the land becomes cooler than air over
  the water.
• Warmer air over the water expands and rises.
• Cooler air from land moves beneath it.
• Land Breezes blow FROM THE LAND.

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Land Breeze
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Sea and Land Breeze animation

• http//www.classzone.com/books/earth_science/terc/
  content/visualizations/es1903/es1903page01.cfm

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Question 1

• What causes winds?

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Answer

• Winds are caused by the uneven heating of Earths
  surface, which causes pressure differences

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Teach Time

• Teach your neighbor about land and sea breezes.

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Pressure Belts

• Uneven heating produces pressure belts which
  occur every 30 latitude

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Pressure Belts

• As warm air rises at the equator and moves toward
  the poles, it cools
• As it cools, some of the air sinks around 30
  north and south of the equator

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Pressure Belts

• At the poles, cold air sinks and moves towards
  the equator
• Around 60 north and south, the air begins to
  heat up and rise

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A. Coriolis Effect

• As the winds blow, Earth rotates from West to
  East underneath them, making it seem as if winds
  are curving.
• Global winds in N. Hemisphere turn toward right.
• S. Hemisphere, winds curve toward left.

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Global Winds

• The combination of pressure belts and the
  Coriolis Effect cause global winds
• These are polar easterlies, westerlies, and trade
  winds

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Global Winds

1. Winds that blow steadily from specific directions
   over long distances.
2. Created by the unequal heating of Earths
   surface.
3. Near the equator, suns rays strike earth
   directly. Near the poles, suns rays do not
   strike Earths surface directly.
4. The suns energy is spread out over a larger
   area, so it heats the surface less. Therefore,
   temps. Near the poles are lower than near the
   equator.

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• 5. Temp. differences btwn equator and poles
  create giant convection currents, movements of
  air between the equator and poles.
• 6. Warm air rises at the equator and cold air
  sinks at the poles.
• 7. Air pressure tends to be lower near the
  equator and greater near the poles.
• Winds at the surface blow from poles toward
  equator. High in the atmosphere, air flows away
  from the equator toward the poles.
• They curve because of Earths rotation.

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Polar Easterlies

• Wind belts that extend from the poles to 60
  latitude
• Formed from cold sinking air moving from the
  poles creating cold temperatures

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E. Polar Easterlies

1. Cold air near poles sinks and flow back toward
   lower latitudes (away from the poles).
2. Mixing of warm and cold air along the polar front
   has major effect on weather in US.

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Westerlies

• Wind belts found between 30 and 60 latitude
• Flow towards the poles from west to east carrying
  moist air over the Unites States

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D. Prevailing Westerlies

1. mid-latitudes, btwn 30 and 60 North and South,
   winds blow toward poles are turned toward the
   east by Coriolis effect.
2. Winds blow west to east.
3. PLAY IMPORTANT ROLE IN WEATHER IN USA.

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Trade Winds

• Winds that blow from 30 almost to the equator
• Called the trade winds because of their use by
  early sailors

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C. Trade Winds

1. Cold air over horse latitudes causes high
   pressure when it sinks.
2. High pressure causes surface winds to blow toward
   equator and away from it.
3. Winds that blow toward equator are turned west by
   Coriolis effect.
4. Winds are high and they help ships get across the
   ocean.
5. In the Northern Hemisphere, they move from the
   NE. In the Southern Hemisphere, they move from
   the SE.

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Doldrums

• Located along the equator where no winds blow
  because the warm rising air creates and area of
  low pressure

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A. Doldrums

1. Near equator, sun heats surface strongly. Warm
   air rises, creating low pressure.
2. Cool air moves into area, but is warmed rapidly
   and rises before it moves very far.
3. Little or no wind there (very calm)

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B. Horse Latitudes

• Warm air rises at equator and flows both north
  and south.
• At 30 degrees north and south, air stops moving
  toward poles and sinks.
• Calm air is here.

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Horse Latitudes

• Occur at about 30 north and south of the equator
  where the winds are very weak
• Most deserts on the Earth are located here
  because of the dry air

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Jet Stream

• The jet streams are narrow belts of high speed
  winds that blow in the upper troposphere and
  lower stratosphere
• Separates warm air from cold air

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F. Jet Streams

1. Bands of high-speed winds about 10km above
   Earths surface.
2. They are hundreds of km wide but only a few km
   deep.
3. Jet streams blow from west to east at speeds of
   200-400km/hr.

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Question 2

• What are the three types of global winds?

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Answer

• Polar Easterlies
• Westerlies
• Trade Winds

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Question 3

• What is the difference between a land breeze and
  a sea breeze?

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Answer

• Sea breezes occur during the day when the land is
  warmer than water and a land breeze occurs at
  night when the water is warmer than land

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Bill Nye

• http//www.youtube.com/watch?vJfeaCU2y6t4 Wind
• http//www.youtube.com/watch?vdz4fgG9ZCIc -
  Atmosphere

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Mr. Parr Winds Blow

• http//www.youtube.com/watch?vg4O9z_R5ZSc