What phenomenon occurs when warm air flows over a cold surface?

When warm air flows over a cold surface, advection fog can occur. This phenomenon happens when warm, moist air moves horizontally (or advects) over a cooler surface, causing the temperature of the air just above the surface to drop to its dew point. As the air cools, it becomes saturated, resulting in fog formation.

In contrast, other types of fog listed in the options are formed through different processes. For example, radiation fog occurs when the ground loses heat during the night through radiation, causing moisture near the ground to condense when the temperature drops. Ground fog is a type of radiation fog that forms closer to the surface. While convection refers to the movement that involves warm air rising and cool air sinking, it is not directly related to the process described in the question, which specifically focuses on the interaction between warm air and a cold surface rather than vertical movement of air.