Global Wind Patterns

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Global Wind Patterns
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Convection Cells

• The air at the equator is humid and warm it
  starts to rise here
• As it loses its moisture through precipitation
  it starts to travel further north
• It starts to cool and become more dense begins
  to fall to the surface (at 30 latitude)
• This is called the Hadley Cell

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Convection Cells

• Likewise at 60 latitude the cool dense air
  starts to move closer to the equator warms and
  rises at 30 and starts to move north again until
  it hits 60 latitude again
• This cell is called the Ferrel Cell

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Convection Cells

• Above 60 latitude there is yet another cell
  which acts in the same manner
• It cools and sinks down to 60 latitude warms,
  rises and moves above 60 latitude
• This cell is called the Polar cell

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Convection Cells

• There are 3 convection cells above the equator
  and 3 convection cells below the equator
• Because the earth is spinning, when these
  convection cells move north or south, the air is
  deflected at an angle
• This allows air to move over the land

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Coriolis Effect

• This movement (deflection) of the wind at an
  angle, because of the spinning of the earth, is
  called the Coriolis Effect
• The air in the northern hemisphere is deflected
  to the right
• The air in the southern hemisphere is deflected
  to the left

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Prevailing Wind Directions
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Prevailing Wind Directions

• In North America, the Coriolis Effect causes the
  winds to blow from west to east
• Weather systems tend to come from the west and
  move east
• Have you ever notice that we quickly get similar
  weather patterns as ON, PQ shortly after they get
  them?

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Assignment

• Draw a picture of the globe on a piece of white
  paper.
• Add these lines of latitude 0 (equator), 30,
  60 and 90
• Draw in your corresponding convection cells,
  where they start and where they end (see notes)
• Draw arrows to show wind movement. Label these
  cells.

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Assignment

• Go to the computer lab.
• Look up what latitude the doldrums, horse
  latitudes, and trade winds are located.
• How did they get their names?
• Why did sea captains try to avoid them?