Where is the Coriolis effect effectively zero, allowing winds to flow directly north-south?

Where is the Coriolis effect effectively zero, allowing winds to flow directly north-south?

• A. Poles
• B. Equator
• C. Mid-latitudes
• D. Tropics

Answer: (B)

The Coriolis effect depends on latitude: the deflection a moving air parcel experiences is proportional to sin(latitude). At the equator, latitude is zero, so the Coriolis parameter is zero and there is no sideways deflection. With no Coriolis turning a north-south flow, the wind can move directly along the pressure gradient, i.e., straight north or south. Away from the equator, the deflection increases, so winds curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Near the poles the deflection is strongest, making straight north-south flow unlikely.

The Coriolis effect depends on latitude: the deflection a moving air parcel experiences is proportional to sin(latitude). At the equator, latitude is zero, so the Coriolis parameter is zero and there is no sideways deflection. With no Coriolis turning a north-south flow, the wind can move directly along the pressure gradient, i.e., straight north or south. Away from the equator, the deflection increases, so winds curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Near the poles the deflection is strongest, making straight north-south flow unlikely.