What causes advection fog to form?

Advection fog forms when warm, moist air moves over a cooler surface. This process is driven by the air's temperature difference relative to the surface it is moving over. As the warm air comes into contact with the cooler surface, it cools to its dew point, leading to the condensation of water vapor in the air, which results in fog. This phenomenon usually occurs over bodies of water, such as oceans or lakes, where the surface temperature is significantly lower than the temperature of the incoming warm air.

In contrast, cold air moving from the ocean does not directly relate to the mechanisms of advection fog, as it focuses on temperature inversions rather than the warming of air. High humidity levels at altitude might contribute to cloud formation but do not specifically create advection fog by themselves. Rain falling from warm air is more associated with processes leading to precipitation rather than the specific cooling effect needed to form fog. Thus, the dynamics of warm air interacting with cooler surfaces aptly define the formation of advection fog.