FAA Ground School Practice Test

What types of fog depend upon wind in order to exist?

1. Radiation fog only

2. Advection fog and steam fog

3. Advection fog and upslope fog

4. Upslope fog only

The correct answer is: Advection fog and upslope fog

Advection fog and upslope fog are both dependent on wind for their formation, which makes this answer accurate. Advection fog occurs when moist air moves over a colder surface, often as a result of winds bringing warm, moist air over cooler waters or land. When the air cools to its dew point, condensation occurs, resulting in fog. Thus, for advection fog to form, a notable wind flow is necessary to transport the moist air over the colder surface. Upslope fog forms when moist air is driven up a slope or mountain by wind. As the air rises, it cools adiabatically, reaching its dew point and condensing into fog. Again, wind plays a crucial role, as it is the force that moves the air up the terrain. While radiation fog requires calm conditions mostly at night when the ground loses heat through radiation and cools the air directly above it, it does not rely on wind for its formation. Therefore, it does not fit the criteria of the question. Steam fog requires a different set of conditions where warm water evaporates into cool air, but it also does not directly depend on wind. In summary, both advection and upslope fog depend on wind to exist, which justifies the selection of