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A convection cell in a planetary atmosphere.  These cells circle the planet; the Sun's heating at the Equator causes air to rise there and descend at higher latitudes in both the Northern and Southern hemispheres.

On a planet with little or no rotation, such as Venus, air circulates all the way to both poles before it descends.  On a rotating planet, such as the Earth,  the Coriolis Effect causes the air to shear off eastward or westward and descend at a lower latitude.  In turn, this descending air causes more cells to form at higher latitudes.

On rapidly rotating planets such as Jupiter or Saturn,  the Coriolis Effect causes many, may cells to form, resulting in the banded appearance of those planets.
 
 

       Earth      Polar Cell   _____   _____
                          _-_ (_____) (____ `-.         Venus
           Ferrell Cell  /  _)    ___-___  `-> `<-.
                        v  /   _--       --_  `-.  \  One big
    Horse Latitudes    _\_/  _-             -_   \  \    Hadley Cell
                      / \   /  - - - -        \   \ |
         Hadley Cell  ^ v  /                   \  v ^
                      | | |                     | | |
                      \_/ | _ _ _ _ _ _ _ _ _ _ | \_/
                      / \ |                     | / \
                      | | |                     | | |
                      v ^  \                   /  ^ v
                      \_/_  \_               _/  /  |
                        / \   -_           _-   /   /
                        ^  \_   --___ ___--  .-'   /
                         \_ _) _____ - ___.-> _.<-'
                           -  (_____) (______'
 
 
In the troposphere of the Earth, there are three groups of cells: One pair between the Equator and about 30 degrees in each hemisphere, one pair between about 30 degrees and 60 degrees, and one pair between 60 degrees and the poles.  Only the equatorial cells are called "Hadley Cells"; the midlatitude cells are called "Ferrell cells".   The areas around 30 degrees in each hemisphere are known as the horse latitudes.   Obviously, these circulation patterns set the conditions that characterize all the Earth's major climactic zones.  At the interstices between the cells, strong westerly wind bands known as jet streams develop.

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