What effect does surface friction have on wind?

• A. It slows wind speed and reduces the Coriolis deflection of air across isobars.
• B. It accelerates wind near the surface and increases Coriolis deflection.
• C. It has no effect on wind speed or direction.
• D. It causes wind to circulate around high-pressure centers.

Answer: (A)

Surface friction slows winds in the lowest layer of the atmosphere. Because the Coriolis effect grows with wind speed, weaker surface winds feel less deflection, so the balance between forces shifts and the wind crosses the isobars toward lower pressure rather than staying parallel to them. In contrast, aloft, where friction is negligible, winds tend to align with isobars (geostrophic balance). So the main idea is that friction reduces wind speed and reduces Coriolis deflection, causing cross-isobaric flow toward lower pressure.