The large scale differential heating of the IOM produces prevailing winds which travel over great distances. Because of the great distances involved these winds are influenced by the Coriolis effect and veer to the right in the northern hemisphere and to the left in the southern hemisphere.
Coriolis is an apparrent force resulting from the Earth's rotation. Just as the outside of a record moves faster than the inside, the speed of the surface of the Earth closer to the equator moves faster than it does away from the equator. Therefore when a parcel of air or water moves over a great distance its movement must compensate for the change in speed of the earth's surface underneath it. In the northern hemisphere this results in a change of direction to the right of the motion of the parcel. In the southern hemisphere this is reversed.
