In the Northern Hemisphere, a large air mass flows from a high-pressure region toward a low-pressure region. Due to the Coriolis effect, how does it deflect?
AIt deflects to the left, producing clockwise circulation around the low
BIt deflects to the right, producing counterclockwise circulation around the low
DIt does not deflect — the Coriolis effect only affects ocean currents
In the Northern Hemisphere, freely moving objects deflect to the right. Air flowing toward a low-pressure center deflects right, curving around it counterclockwise (cyclonically). This is why Northern Hemisphere hurricanes and low-pressure storms rotate counterclockwise.
Question 2 True / False
The Coriolis effect is responsible for the direction that water drains from a bathtub in the Northern Hemisphere.
TTrue
FFalse
Answer: False
This is one of the most widespread misconceptions about the Coriolis effect. At the scale of a bathtub, the Coriolis force is many orders of magnitude weaker than the residual swirl from filling the tub, shape of the drain, or initial disturbances. The effect only dominates at the planetary scale of weather systems spanning hundreds of kilometers.
Question 3 Short Answer
Why is the Coriolis effect zero at the equator and maximum at the poles?
Think about your answer, then reveal below.
Model answer: The Coriolis effect arises from Earth's rotation. At the poles, the rotation axis is perpendicular to the surface, so horizontal motion is maximally deflected by the spin. At the equator, the rotation axis is parallel to the surface, so horizontal motion has no component deflected by Earth's spin — the Coriolis parameter (f = 2Ω sin φ) equals zero when latitude φ = 0.
The Coriolis parameter f = 2Ω sin(latitude) captures this: sin(0°) = 0 at the equator, sin(90°) = 1 at the poles. This is why tropical weather systems are less organized by rotation and why polar vortices are so tightly constrained.