What is a key characteristic of advection fog compared to radiation fog?

Advection fog is characterized by its formation due to the horizontal movement of warm, moist air over a cooler surface, which can occur irrespective of the time of day and in the presence of wind and clouds. This process allows the moisture in the warm air to condense into fog as it interacts with the cooler surface underneath.

In contrast to advection fog, radiation fog typically forms under calm, clear night conditions when the ground cools rapidly, leading to the condensation of moisture in the air close to the ground. Therefore, the requirement of calm conditions is not applicable to advection fog. Additionally, the idea that advection fog occurs only at night is inaccurate, as it can develop at any time when the right temperature and moisture conditions exist.

Lastly, while fog can occur in mountainous areas, it is not exclusive to such regions, making the notion that advection fog forms only in mountainous areas incorrect. The versatility of advection fog in terms of wind and cloud cover greatly differentiates it from radiation fog, solidifying that option as the correct characteristic.