Atmospheric circulation cells - the three cell model
Hadley cells, 0-30° latitude
- Solar heating at the equator warms the air above.
- The air rises and expands creating low pressure.
- The air travels to around 30°, cooling as it moves.
- At around 30° the cooled air sinks back to Earth to create an area of high pressure.
- Air moves from this high-pressure area to the equatorial low-pressure area.
- This is a A circulation cell (such as the Hadley or Polar cell) where warmer air rises up and colder air sinks. cell.
Polar cells, 60-90° latitude
- The air above the poles is cold.
- The cold air sinks creating high pressure.
- The air moves towards the equatorial low-pressure zone, and warms up when it meets the land or ocean.
- At around 60° this warmed air rises.
- This is another thermally direct cell.
Ferrel cells, 60-30° latitude
- The Ferrel cells are found between the Hadley and Polar cells.
- Cold air sinks near 30° and rises near 60°. The air at the Earth's surface flows northwards and is affected by the Apparent force, due to the spinning of the Earth, which deflects movement of particles and wind..
- The Ferrel cell is A circulation cell (such as the Ferrel cell) where colder air rises up and warmer air sinks..
Global circulation cells
Jet streams
These are very strong and fast-moving meandering wind bands. They are found at high altitudes, just below the The lowest layer in the atmosphere where all of Earth's weather occurs., where the circulation cells meet. Jet streams are caused by pressure differences in the upper atmosphere and they move the weather systems around the planet.