Temperature differences also drive a set
of circulation cells, whose axes of circulation are longitudinally oriented.
Thus, the hurricane season falls during that period when the tropical
meridional circulation cell is unable to facilitate the requisite equator - to - pole transfer of energy.
When waves break strongly in some locations and weakly in others, this can
cause circulation cells which are seen as rip currents: narrow, fast - moving belts of water traveling offshore.
The rising and sinking motions within the
MJO circulation cells produce a pattern of enhanced and suppressed convection.
At the polar surface level, the mass of air is driven toward the 60th parallel, replacing the air that rose there, and the
polar circulation cell is complete.
The easterly Trade Winds and the polar easterlies have nothing over which to prevail, as their
parent circulation cells are strong enough and face few obstacles either in the form of massive terrain features or high pressure zones.
In 1856, William Ferrel proposed the existence of
a circulation cell in the mid-latitudes with air being deflected by the Coriolis force to create the prevailing westerly winds.
The circulation cells are large — about 10,000 kilometers wide along the equator — and occur intraseasonally, roughly every 30 to 70 days.