Which fog forms when cold air moves over warm water?

The phenomenon you are describing is known as steam fog, which occurs when cold air moves over warmer water. This situation leads to the evaporation of water into the colder air above, causing condensation to form as the warm, moist air rises and cools. As the water vapor condenses, it appears as visible fog, resembling steam rising from the water surface, hence the name steam fog.

Understanding the formation process helps differentiate it from other types of fog. For instance, advection fog typically occurs when warm, moist air moves horizontally over cooler surfaces (not specifically dealing with warm water), resulting in cooling and consequent condensation. Ice fog, on the other hand, forms in very cold conditions when the air is saturated with water vapor that sublimates into tiny ice crystals. Lastly, radiation fog develops under clear skies during the night when the ground cools rapidly, cooling the air close to the surface and allowing moisture to condense into fog, which is unrelated to warm water dynamics.

Recognizing the conditions that lead to steam fog clarifies its unique formation mechanism, establishing it as the correct answer in this context.