Key Concepts of Global Circulation and Atmospheric Cells

Uneven Heating of the Earth

• The equator receives more heat from the Sun than the poles.
• Purpose of Global Circulation: Redistribute heat across the planet.

Circulatory Cell Model

• Simple Model: If Earth didn't rotate and was a single landmass with no oceans, there would be one circulatory cell per hemisphere:
  • Hot air rises at the equator, flows towards the poles, cools, sinks, and returns to the equator.
• Complex Reality: Unequal land/ocean distribution and Earth's rotation lead to a 3-cell pattern in each hemisphere.

Three-Cell Model in Each Hemisphere

• Hadley Cells:

  • Largest cells located at the equator.
  • Warm, less dense air rises, reaching about 18 kilometers.
  • Air spreads out under the tropopause (the atmospheric lid).
  • Cools, sinks, and returns to the equator.

• Polar Cells:

  • Smallest cells, located in polar regions.
  • Cold, dense air descends, flows to 60-70 degrees latitude.
  • Air warms, rises, and returns to poles at higher levels.

• Ferrel Cells:

  • Situated between Hadley and Polar cells.
  • Not driven by temperature; flow opposite to Hadley and Polar cells.
  • Function like a gear in the circulation system.

Impact on Climate and Pressure Systems

• Heat and Pressure: Circulating cells transport heat, creating semi-permanent high/low pressure areas.
• Low Pressure: Areas where air rises:
  • Associated with high rainfall, e.g., rainforests near the equator, UK's climate.
• High Pressure: Areas where air descends:
  • Lead to clear skies, low rainfall, e.g., deserts.
  • Note: Antarctica is a cold desert with less precipitation than Sahara.

Additional Resources

• A video on atmospheric pressure explains further how pressure influences weather.
• Upcoming video will explore how Earth's rotation creates jet streams and prevailing winds.