But because the Earth rotates, circulating air is deflected. Instead of circulating in a straight pattern, the air deflects toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere, resulting in curved paths. This deflection is called the Coriolis effect.
The Coriolis effect describes how Earth's rotation steers winds and surface ocean currents. ... The Coriolis effect causes the path of a freely moving object to appear to curve. This is because Earth is rotating beneath the object. So even though the object's path is straight, it appears to curve.
