Geography: Global Air Circulation

Global Air Circulation
Global air circulation of atmosphere is vertical and horizontal movement of air on a large
scale


Factors that contribute to global air circulation:
• Pressure belts
• Tri-cellular circulation
• Planetary winds
• Geostrophic flow
• Regional and local air movement
• Air masses



Pressure belts
A pressure belt is a large part of Earth where predominantly high/low atmospheric pressure
occurs


• Equatorial LP belt (doldrums) – no winds – sailors would get stuck
• Subtropical HP belt (horse latitudes)
• Sub-polar LP belt
• Polar HP belt


o Equatorial + polar – thermal pressures – pressure due to hot/cold temperatures of air
o Subtropical + sub-polar – dynamic pressures – pressure due to convergence and
rising/subsidence of air