Global Circulation and Atmospheric Cells

Unequal Heating of the Earth

• The equator receives more solar heat than the poles.
• Global circulation redistributes this heat.

Single Circulatory Cell Model

• If the Earth didn't rotate and had no oceans, it would have a single circulatory cell in each hemisphere:
  • Hot air rises at the equator.
  • Flows toward the poles, cools, sinks, and returns to the equator.

Real-World Complex Circulation

• Earth's rotation and uneven land/ocean distribution create a 3-cell circulation pattern in each hemisphere:
  • Hadley Cells
    • Located at the equator.
    • Warm air rises, reaches 18 km height, spreads under the tropopause.
    • Cools, sinks, returns to the equator.
  • Polar Cells
    • Smallest cells.
    • Cold, dense air descends, flows to 60-70 degrees latitude.
    • Warms, rises, returns to poles.
  • Ferrel Cells
    • Located between Hadley and Polar cells.
    • Not driven by temperature.
    • Flow opposite to Hadley and Polar cells, acting like a gear.

Impact on Climate

• Circulation cells transport heat and create semi-permanent high and low-pressure areas:
  • Rising air = low pressure = more rainfall.
    • Rainforests near the equator.
    • UK's wet climate.
  • Descending air = high pressure = clear skies, low rainfall.
    • Desert regions.
    • Antarctica is a cold desert with less precipitation than Sahara.

Further Exploration

• Atmospheric Pressure: See video on how pressure influences weather.
• Jet Streams and Prevailing Winds: Upcoming video on Earth's rotation effects.