FAA Commercial Pilot Airplane (CAX)WeatherMedium
A pilot notices the formation of fog over an area where warm, moist air is moving horizontally over a cold surface. What type of fog is most likely forming?
- AAdvection fog.
- BSteam fog.
- CUpslope fog.
- DRadiation fog.
Show answer & explanationAnswer & explanation
Correct answer: A. Advection fog.
Advection fog forms when warm, moist air moves horizontally over a cooler surface. As the warm, moist air passes over the cold ground or water, it cools to its dew point, leading to condensation and the formation of fog. This is common along coastlines or over large bodies of water.
Why the other options are wrong
- B. Incorrect; steam fog forms when cold, dry air moves over warm water, causing evaporation and subsequent condensation.
- C. Incorrect; upslope fog forms when moist, stable air is forced up a topographic slope, cooling adiabatically.
- D. Incorrect; radiation fog forms on clear, calm nights when the ground cools rapidly by radiation.
Advection Fog
Fog that forms when warm, moist air moves horizontally over a cooler surface, causing the air to cool to its dew point.
- Common along coastlines and over oceans.
- Can be quite dense and widespread.
- Often forms with light to moderate winds, unlike radiation fog which requires calm conditions.
Memory trick: Advection's Air: Moves Warm over Cold.