Earth Science
Atmospheric Processes
Circulation in the Atmosphere
Study Tip
Think of the atmosphere as a fluid. Within this fluid would be the convective currents caused by temperature and density differences.
Convection Cells
Within the troposphere are convection cells.
- Air heated in a relatively warm ground region rises, creating a low pressure zone.
- Air from the surrounding area is sucked into the space left by the rising air.
Study Tip
Think of the atmosphere as a fluid. Within this fluid would be the convective currents caused by temperature and density differences.
- Air flows horizontally at top of the troposphere through advection.
- Air cools until it descends.
- Air reaches the ground and creates a region where relatively cool, dense air is sinking (high pressure zone).
- Air flowing from areas of high pressure to low pressure creates winds.
- The greater the pressure difference is between pressure zones, the faster the wind speed is.
Air Pressure Zones
- Warm air can hold more moisture than cool air.
- As the warm air rises, it cools and it cannot hold all the water it contains. Water vapor may condense into clouds or precipitation.
- When cool air descends, it warms up and evaporates water on the ground.
- Air moving between high and low pressure zones creates global wind belts, and smaller pressure systems create localized winds that affect the weather and climate of a local area.
Atmospheric Circulation and Convection
- As more solar energy hits the equator, warmer air starts to form a low pressure zone.
- As less solar energy hits the poles, colder air starts for form a high pressure zone.
- This would a convection cell in each hemisphere, due to the differences in pressure. However, the Earth rotates, and the Coriolis Effect creates three convection cells in each hemisphere, instead of one.
