Which type of fog forms when air near the ground cools rapidly on a clear night?

Which type of fog forms when air near the ground cools rapidly on a clear night?

• A. Advection fog
• B. Radiation fog
• C. Upslope fog
• D. Sea fog

Answer: (B)

Radiation fog forms when the ground loses heat to the sky on a clear night, cooling the air right at the surface. If that near-surface air cools to the dew point, water vapor condenses into tiny droplets and a fog blanket settles over the ground. This type is typical after sunset or overnight when skies are clear and winds are light, letting radiational cooling do the work. The other fogs come from different processes: advection fog needs moist air moving horizontally over a cooler surface, upslope fog forms as air rises and cools on a slope, and sea fog develops over water from temperature contrasts between air and sea.

Radiation fog forms when the ground loses heat to the sky on a clear night, cooling the air right at the surface. If that near-surface air cools to the dew point, water vapor condenses into tiny droplets and a fog blanket settles over the ground. This type is typical after sunset or overnight when skies are clear and winds are light, letting radiational cooling do the work. The other fogs come from different processes: advection fog needs moist air moving horizontally over a cooler surface, upslope fog forms as air rises and cools on a slope, and sea fog develops over water from temperature contrasts between air and sea.