Global Atmosphere Circulation

• Definition of Global Atmosphere Circulation

  • Global atmospheric circulation is a worldwide system of winds. This transports heat from tropical to polar latitudes.
  • In each hemisphere, air circulates in cells.
• When hot air rises, driven by the equator?

  • Low pressure
  • Draws moisture from the ground
  • Creating clouds, rain and storms
• When cool air sinks?

  • High pressure
  • Brings fine weather
• How is wind caused?

  • Air moves from high atmospheric pressure to low atmospheric pressure

  
• Three cells in each hemisphere?

  1. Hadley Cell
  2. Ferrel Cell
  3. Polar cell
• Describe function of Hadley Cell : Low pressure belt

  1. Heat of the sun concentrated at the equator causes air to rise.
  2. Forms a low pressure belt.
  3. Huge rain clouds formed.
  4. Ecosystems like tropical rainforests form here.
• Describe function of Hadley cell : High pressure belt

  1. Cool air sinks, towards the earth at 30 degrees.
  2. This creates a high pressure belt.
  3. This causes low rainfall so deserts form here.
• What are Trade Winds?

  • Surface winds blowing towards the equator
• Function of polar cell

  1. At the poles, air sinks due to low temperature.
  2. This air will then move towards the equator at a low level.
  3.  Approx. 60 degrees, this air will meet warmer air, and move towards the poles.
  4. The air will rise upward until it reaches the top of the atmosphere. The air moves in two directions.
  5. Some air goes back to the poles as surface winds are forming the polar cell.
• Function of ferrel cell

  • Some air from the Polar cell moves back to the equator meeting the Hadley cell
  • This forms the middle cell called the Ferrel cell. 
• Global Distribution of Tropical Storms : Typhoons

  • South China Sea and west Pacific Ocean
• Global Distribution of Tropical Storms : Hurricanes

  •  Gulf of Mexico, Caribbean Sea and west coast of Mexico
• Global Distribution of Tropical Storms : Cyclones

  •  Bay of Bengal, Indian Ocean and northern Australia
• Where do Tropical Storms form?

  • They develop over the warm tropical oceans between 5° and 30° north and south of the equator.