Question

what is the Coriolis effect? how does it affect air in the northern and southern hemisheres?

Answer 1

An effect whereby a mass moving in a rotating system experiences a force (the Coriolis force ) acting perpendicular to the direction of motion and to the axis of rotation. On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather systems.
The Coriolis effect describes the pattern of deflection taken by objects not firmly connected to the ground as they travel long distances around and above the Earth. The Coriolis effect is responsible for many large-scale weather patterns. The key to the Coriolis effect lies in the Earth's rotation.

Answer 2

Because the Earth rotates on its axis, circulating air is deflected toward the right in the Northern Hemisphere and toward the left in the Southern Hemisphere. This deflection is called the Coriolis effect. Click the image for a larger view. Coastal currents are affected by local winds.