Global Atmospheric Circulation

• Global atmospheric circulation


  Is the transfer of heat from the equator to the poles by the movement of air
• How does air move

  Due to differences in air pressure - winds blow from high pressure areas to low pressure areas.
• How is the Global Atmospheric circulation system divided

  It is divided into loops called cells - each cell has warm rising air that creates a low pressure belt and cool sinking air that creates a high pressure belt.
• How many cells does each Hemisphere have

  • Polar
  • Ferrell
  • Hadley
• What causes air to raise at the equator and what does it cause

  Sun warms the earth - causes air to rise - creating a low pressure belt
• When air cools where does it move away from

  As the air rises it cools and moves away from the equator
• What happens 30 degrees North and South of the equator

  cool air sinks - creates a high pressure belt
• What happens at the ground surface

  At the ground surface the cool air moves either back to the equator ( as trade winds) or towards the poles (as westerlies) - these winds curve because of the earth's rotation (called the Coriolis effect)
• What happens 60 degrees North and South of the equator

  The warmers surface winds meet colder air from the poles - warmer air rises creating low pressure
• Some of the air moves back towards the equator and the rest moves towards the poles
• What happens at the poles

  Cool air sinks - creating high pressure - high pressure is then drawn back towards the equator
• How does the Global Atmospheric Circulation affect weather and climate

  • AT the equator the sun is directly overhead - Earth's surface receives a lot of solar radiation, so it's hot. Warm, moist air rises and forms clous so it rains a lot.
  • When air reaches 30 degrees north and south of the eqautor it has relseaed most of its moisture as rain. Dry air means there are few clouds and little rainfall, so deserts are often found at this latitude
  • UK -low pressure at 60 degrees north - warm air rising brings lots of cloud cover and rainfall - low pressure carried by Westerly winds