What factors affect the CTWM climate

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What factors affect the CTWM climate?

• Tuesday 13th September 2005 and Wednesday 14th
  September 2005
• Miss Eagles

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Learning Objectives

• By the end of the lesson I will
• Understand the atmospheric processes responsible
  for CTWM climates

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Lesson Structure

• Atmospheric processes
• Marketplace

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Atmospheric Processes

• Key questions
• What processes are operating in the atmosphere?
• What is the tri-cellular model?
• What are jet streams?
• How do they affect the weather in mid-latitude
  areas?

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The Global Atmospheric System

• The global circulation model is a theory put
  forward to explain the general circulation of the
  atmosphere.
• It explains global wind patterns as a result of
  the differential distribution of solar radiation
  over the Earths surface.

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The Global Atmospheric System

• Global wind patterns and ocean currents transfer
  heat from the tropics to polar latitudes.
• Warm air rises at the equator (creating low
  pressure) and sinks at the poles (creating high
  pressure).
• This theory was first suggested by Hadley
  (1686!), and later refined by Ferrel and then
  Rossby.

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The Coriolis Force

• A force resulting from the rotation of the earth.
  It causes winds to deflect to the right in the
  northern hemisphere and to the left south of the
  equator.

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The Global Atmospheric System

• Although this tri-cellular model forms the basis
  of our understanding of he global circulation it
  does not allow for the influence of
  depressions/anticyclones or high level jet
  streams in the redistribution of energy.
• We will look at these in later lessons.

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Jet Streams

• Pilots of jet air craft were the first to become
  aware of the existence of jet streams (hence
  their name!)
• They are high-altitude winds (about 12,000km)
  which can reach speeds of over 200km/h.

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• They occur when warm tropical air meets cold
  polar air and a significant pressure difference
  is created.
• The Coriolis effect spins the jet stream around
  the globe in loops of fast flowing upper air
  called Rossby waves.

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• The Polar Front Jet Stream lies at about 30-50
  north and south broadly marking the boundary
  between polar air to the north and tropical air
  to the south.
• Air travels through the Rossby waves at varying
  speeds. As it turns away from the pole it slows
  down. As it bends back towards the pole it
  quickens up.

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• When the jet stream slows down, excess air piles
  up and descends to the ground (creating areas of
  high pressure).
• When the jet stream speeds up, air is sucked up
  from the ground level to fill the gap.
• Therefore Rossby waves create alternative areas
  of high and low pressure.

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Impact on the weather of Mid-latitude areas

• These alternating areas of low (depressions) and
  high (anticyclones) pressure are important
  factors in the weather of mid-latitude areas.
• Jet streams also guide depressions.
• Occasionally jet streams move from north to
  south. When it comes from the south it can bring
  powerful depressions and from the north stable
  conditions as it deflects depressions.

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Marketplace

• Stage 1 1 minute Aim and test questions
• Stage 2 15 minutes The poster
• Stage 3 10 minutes Marketplace
• Stage 4 10 minutes Return to homebase
• Stage 5 10 minutes Test
• Stage 6.

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Aim

• To understand the atmospheric processes, which
  affect CTWM climates.

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• Test Questions
• Atmospheric movement and winds
• Coriolis force
• Global circulation and convection cell models
• Mid-latitude movements
• Vorticity
• Jet streams

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Stage 2

• Convert the resource material into a poster,
  using the large paper and pens.
• The poster must be designed for visitors to view
  and understand.
• The poster can have up to 30 words and no more.

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Stage 3

• Your group has only a fraction of the information
  needed for success in the test, so you need to
  learn from each other.
• Who will stay at home and be the stallholder?
• The others will go out into the marketplace to
  gather information.

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Stage 4

• Everyone returns to their home base.
• Those who went into the marketplace to research
  information should now take turns to teach what
  they found out.

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Stage 5

• All notes, posters and original source materials
  should be put out of sight.
• The test will be conducted under examination
  conditions, individually and in silence.

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Stage 6

• In each group, you should put your heads together
  to see if you can come up with a complete and
  accurate set of answers.

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The Test

• What questions did you find difficult?

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Homework

• Due in on Tuesday 20th September 2005
• Add the labels onto the global circulation model.
  
• Use page 209 in the integrated approach to help
  you.
• Take notes on the chapter from the Bill Bryson
  book. Make sure you only produce two sides of
  A4.