Ask A Scientist© Weather Archive

name         Stephanie
status       student
age          15
Question -   What does the spin of the earth have to do with convection 
currents?

Stephanie,

I'm not sure what you mean by convection currents, but the spin of the 
Earth (a rotating system)
causes a weak non-inertial force (i.e. acceleration) that meteorologists 
call the Coriolis Force, after the French mathematician G. G. Coriolis, 
who first described it.  This force is at work in the oceans
and the atmosphere (which are both fluids).  The Coriolis Force causes 
motions to turn to the right
of a straight line if the surface is rotating counterclockwise (the 
Northern Hemisphere) and turn
to the left on a surface that is turning clockwise (the Southern 
Hemisphere).  That is why high (and low) pressure systems turn in opposite 
directions in the two Hemispheres of earth.

This has nothing to do with convection currents, which come in a variety 
of scales, from small convection cells that produce cumulous clouds, to 
the large scale that produces low-pressure areas and 
hurricanes.  Convection in the large weather systems is more a result of 
air wanting to move from high to low pressure.  When this happens, the air 
converges at the center of the low-pressure system and must rise (since it 
can't go into the ground).

David Cook
Meteorologist
Argonne National Laboratory
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