What type of fog is formed when warm air moves over a cold surface?

Advection fog occurs when warm, moist air moves horizontally over a cooler surface. The temperature of the warm air decreases due to contact with the cold surface, leading to condensation of water vapor and the formation of fog. This type of fog is commonly seen in coastal areas where warm air from the ocean moves over colder land or water, cooling the air sufficiently to produce fog.

The process highlights the importance of temperature gradients in the atmosphere. When the warm air loses heat to the colder surface—whether it’s land or water—the air's capacity to hold moisture decreases, resulting in fog. This phenomenon can happen fairly quickly, especially when there is a significant difference between the temperature of the air and the surface beneath it.

In contrast, other types of fog such as radiation fog occurs due to the cooling of the ground overnight, leading to condensation near the surface. Upslope fog is associated with air rising along a slope and cooling adiabatically, while ground fog typically forms in low-lying areas under specific temperature and humidity conditions. Each of these processes relies on different mechanisms of cooling and moisture condensation, making advection fog distinct in its formation process.