Three cell model

• The three cell model is repeated in the southern hemisphere.
• the Hadley and Polar Cells are thermally direct and the Ferrel Cell is thermally indirect
• Hadley cell: Warm air rises at the Equator creating low pressure, the air splits in the atmosphere and moves towards the poles. Air has been cooled and so sinks at the Tropics creating high pressure. The North East Trade winds move air back to the Equator completing the Hadley cell
• Ferrel cell: The Ferrel cell is located between 30 and 60 degrees north. The Ferrel cell transfers air between the Hadley and Polar cells forming the westerlies
• Polar cell: Cold air sinking at the poles creates a high pressure area. The Polar Easterlies transfer cold air from the poles towards the Equator (polar front) here it meets warmer air from the tropics, causing air to rise. Air moves back to the Poles in the upper atmosphere completing the Polar Cell.