Global Atmospheric Circulation

• Global Atmospheric Circulation


  Worldwide system of winds moving heat from the equator to the poles to reach a balance in temperature
• Wind formation


  1. Air always moves from high pressure to lower pressure, generating wind

  2. Winds are large scale movements of air due to differences in air pressure

  3. Irregular heating of Earth's surface creates various pressure cells, each generating different weather patterns

  4. Movement of air within each cell is roughly circular and moves surplus heat from equatorial regions to other parts the Earth
• Three-cell model


  • Shows global circulation: the Hadley, Ferrel and Polar cells
• Atmospheric cells


  • Hadley cell
  • Ferrel cell
  • Polar cell
• Hadley cell


  • Largest cell, extends from equator to 30-40 degrees north and south
  • Trade winds blow from tropical regions to equator, hot air rises and forms thunderstorms
  • Air flows towards higher latitudes, becomes cooler and sinks over subtropical regions, bringing dry, cloudless air
• Ferrel cell

  • Middle cell, occurs from edge of Hadley cell to 60-70 degrees north and south
  • Moves in opposite direction from Hadley and Polar cells
  • Air joins sinking air of Hadley cell and travels to mid-latitudes where it rises along border with cold air of Polar cell, causing frequent unsettled weather
• Polar cell


  • Smallest and weakest cell, extends from edge of Ferrel cell to poles
  • Cold air sinks creating high pressure over highest latitudes, flows out towards lower latitudes at surface where it is slightly warmed and rises to return to poles
• Coriolis effect


  Appearance that global winds and ocean currents curve as they move, due to Earth's rotation on its axis
• Global wind belts


  • Trade winds
  • Westerlies
  • Easterlies
• Global atmospheric circulation


  Affects the Earth's climate, causing some areas to have certain types of weather more frequently than other areas
• The UK has a lot of low-pressure weather systems that are blown in from the Atlantic Ocean on south-westerly winds, bringing wet and windy weather