FAA Sport Pilot Airplane (SPA)WeatherMedium
A pilot at a coastal airport is told during a briefing that fog is expected to form as warm, moist air moves horizontally over the cool coastal waters. What type of fog is being described?
- AAdvection fog
- BRadiation fog
- CUpslope fog
- DIce fog
Show answer & explanationAnswer & explanation
Correct answer: A. Advection fog
Advection fog forms when warm, moist air moves horizontally over a colder surface, cooling the air to its dew point. It is common along coastlines and is often accompanied by wind, unlike radiation fog which requires calm conditions.
Why the other options are wrong
- B. Radiation fog forms from nighttime surface cooling under calm, clear skies, not horizontal air movement.
- C. Upslope fog forms when moist air is forced to rise along sloping terrain.
- D. Ice fog forms in very cold temperatures when water vapor sublimates directly into ice crystals.
Advection Fog
Fog that forms when warm, moist air moves horizontally over a colder surface, cooling the air below its dew point.
- Common along coastlines and over cold ocean currents
- Can occur with wind, unlike radiation fog
- Often extends over large areas and can be persistent
- Requires horizontal air movement (advection) to transport the moist air
Memory trick: Advection = Air on the Move over a cold sea.