Which fog forms when near-surface air is moved horizontally over a cooler underlying surface?

Which fog forms when near-surface air is moved horizontally over a cooler underlying surface?

• A. Advection fog
• B. Radiation fog
• C. Ice fog
• D. Frontal fog

Answer: (A)

Advection fog forms when warm, moist air is transported horizontally over a surface that is cooler than the air. As that air moves over the cooler surface, heat is conducted away and the air near the ground is cooled to its dew point, causing water vapor to condense into tiny droplets and create fog at the surface. This commonly happens when moist air moves over cooler land or water. Radiation fog, by contrast, comes from radiative cooling of the ground on calm nights, not from horizontal air movement; ice fog forms at extremely low temperatures through deposition of water vapor into ice crystals; and frontal fog arises from rain evaporating into a cool air mass near a front, not from air moving over a cooler surface.

Advection fog forms when warm, moist air is transported horizontally over a surface that is cooler than the air. As that air moves over the cooler surface, heat is conducted away and the air near the ground is cooled to its dew point, causing water vapor to condense into tiny droplets and create fog at the surface. This commonly happens when moist air moves over cooler land or water. Radiation fog, by contrast, comes from radiative cooling of the ground on calm nights, not from horizontal air movement; ice fog forms at extremely low temperatures through deposition of water vapor into ice crystals; and frontal fog arises from rain evaporating into a cool air mass near a front, not from air moving over a cooler surface.