What are the conditions for advection fog formation?

What are the conditions for advection fog formation?

• A. Light winds, low humidity, warm surface
• B. Strong winds, high humidity, cold surface
• C. Strong winds, low humidity, warm surface
• D. No wind, very humid air

Answer: (B)

Advection fog forms when a moist air mass is transported horizontally over a surface that is cooler than the air. As that air moves over the cooler surface, it is cooled to its dew point, causing the moisture to condense and create fog. The high humidity provides the necessary moisture, and the cool surface provides the cooling to reach saturation. Winds help bring in and sustain that moist air over the cooler surface, which is why a combination of moist air, a cold surface, and some wind is the typical recipe. If there isn’t enough humidity, there isn’t enough moisture to saturate; if the surface isn’t cold enough relative to the air, cooling to the dew point won’t occur; and if there’s no wind, the fog would be radiation fog instead of advection fog.

Advection fog forms when a moist air mass is transported horizontally over a surface that is cooler than the air. As that air moves over the cooler surface, it is cooled to its dew point, causing the moisture to condense and create fog. The high humidity provides the necessary moisture, and the cool surface provides the cooling to reach saturation. Winds help bring in and sustain that moist air over the cooler surface, which is why a combination of moist air, a cold surface, and some wind is the typical recipe. If there isn’t enough humidity, there isn’t enough moisture to saturate; if the surface isn’t cold enough relative to the air, cooling to the dew point won’t occur; and if there’s no wind, the fog would be radiation fog instead of advection fog.