ENVIR SCI 1A03 March 3,
What is the General Circulation of the Atmosphere?
• Climate is largely influenced by this
• The cause of this is Earth’s unequal heating
• Lower pressure at the poles, higher at the equator
• Refers to the average air flow
• Generally, warm air transferred from tropics to the poles and cool air
descends to the equator/tropics and get heated again for circulation
• What is the Once-Cell Model?
o Assumption: Earth is uniformly covered by water, sun is always
directly overhead the equator, earth does not rotate
o Big ball of water, with a giant circulation cell
o High surface pressure at poles, low at equator – as a result, wind
rushing in uniformly from poles to equator
o It is impossible for a Hadley cell to extend from the equator to the
poles because of Coriolis force
• What is the Three-Cell Model?
o Allows earth to spin
o Produces three cells
o Alternating belts of pressure
o Alternating belts of winds
o Implies no land surface
o Hadley cell, ferrel cell, polar cell
o Imbalance of winds – air moving from zones of HP to LP
o No friction at the surface associated to this model
What is the Hadley Cell?
• Associated to ITCZ
• Intertropical convergence zone (ITCZ)
• Convergence because air is rushing to the area and associated to cloud
o All of the air’s latent heat will lose its moisture and descend
• Corresponds to the area from equator to the tropics (30degN/S)
• Depends on position of ITCZ
• Changes of position of ITCZ influ