General Circulation of the Atmosphere

1
General Circulation of the Atmosphere

• General Circulation
• Three-Cell Model of General Circulation
• Tropical Circulation
• Extra-tropical Circulation
• Global Pressure Patterns
• Chapters 7.0 7.3 8.1

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General Circulation
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• The primary circulation features are the features
  which cover large areas of the globe, and exist
  at all times

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General Circulation
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• A three-cell circulation model was proposed early
  in the twentieth century to describe the task of
  maintaining the Earths heat balance

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General Circulation
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Figure 7.3
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General Circulation
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• Three-Cell Model of General Circulation
• Hadley Cell (thermally direct)
• Polar Cell (thermally direct)
• Ferrel Cell (thermally indirect)
• An over-simplification of reality, and partially
  incorrect

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General Circulation
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Figure 7.3
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General Circulation
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Relates to Figure 7.3
Strahler and Strahler Introducing Physical
Geography
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General Circulation
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• While the three-cell model is an
  over-simplification of reality, it does serve as
  a basis to examine the general circulation
• Tropical Circulation
• (Hadley Cell)
• Extra-tropical Circulation
• Mid-Latitudes (Ferrel Cell)
• Polar Circulation (Polar Cell)

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Tropical Circulation
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• Hadley Cell
• Intertropical Convergence Zone (ITCZ)
• Subtropical Highs
• Trade Winds
• Described in Section 8.1 of the Book

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The Hadley Cell
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Figure 8.1
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The Hadley Cell
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The Hadley CellAverage Position of the ITCZ
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The Hadley CellSubtropical High Pressure
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The Hadley CellThe Surface Trade Winds
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The Hadley CellSeasonal Migration of the ITCZ
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The Extra-Tropical Circulation
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• Mid-latitude surface westerlies
• Polar surface easterlies
• The polar front
• Interaction between the surface westerlies and
  surface easterlies (warm and cold air)
• Upper-air westerlies

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The Extra-Tropical Circulation
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Relates to Figure 7.3
Strahler and Strahler Introducing Physical
Geography
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The Extra-Tropical Circulation
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Low Pressure
High Pressure
High Pressure
Low Pressure
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The Extra-Tropical CirculationThe Surface
Westerlies
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Upper-Air Westerlies
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Global Surface Pressure Patterns
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• North-South Cross Section
• January
• July

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North-South Cross Section
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Low Pressure
High Pressure
High Pressure
Low Pressure
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January Surface Pressure
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July Surface Pressure
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Summary
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Summary
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Relates to Figure 7.3
Strahler and Strahler Introducing Physical
Geography
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Summary Precipitation
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