Once air has been set in motion by the Pressure Gradient Force, it undergoes an apparent deflection from its path, as seen by an observer on the earth. This apparent deflection is called the Coriolis Force and is a result of the earth's rotation.

As air moves from high to low pressure in the northern hemisphere, it is deflected to the right by the coriolis force.

This is process further demonstrated by the animated examples below.

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Moving Air Parcel: The balancing of the pressure gradient and coriolis forces leads to the circulation observed around cyclones.

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Real Life Example: This movie of a ball rolling across the surface of a rotating merry-go-round is a real life demonstration of the coriolis force.