Which fog forms when a warm, moist surface evaporates additional water vapor into the air and saturates it?

Which fog forms when a warm, moist surface evaporates additional water vapor into the air and saturates it?

• A. Frontal fog
• B. Evaporation/Steam fog
• C. Radiation fog
• D. Ice fog

Answer: (B)

Evaporation/steam fog forms when a warm, moist surface continually adds water vapor to the air, and that moisture saturates the near-surface air so it condenses into tiny droplets. This happens over a lake or pond on a cool morning: the water stays warm and keeps evaporating, mixing with cooler air above it until the added vapor reaches its dew point and fog appears as if steam is rising from the surface. This differs from radiation fog, which forms from radiational cooling of the ground overnight without extra evaporation; frontal fog, which comes from rain evaporating into cool air near a front; and ice fog, which occurs in extremely cold conditions when water vapor sublimates into ice crystals rather than condensing into droplets.

Evaporation/steam fog forms when a warm, moist surface continually adds water vapor to the air, and that moisture saturates the near-surface air so it condenses into tiny droplets. This happens over a lake or pond on a cool morning: the water stays warm and keeps evaporating, mixing with cooler air above it until the added vapor reaches its dew point and fog appears as if steam is rising from the surface. This differs from radiation fog, which forms from radiational cooling of the ground overnight without extra evaporation; frontal fog, which comes from rain evaporating into cool air near a front; and ice fog, which occurs in extremely cold conditions when water vapor sublimates into ice crystals rather than condensing into droplets.