Which type of fog is formed when cooling occurs near the ground in lower-lying areas?

Which type of fog is formed when cooling occurs near the ground in lower-lying areas?

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

Answer: (A)

Radiation fog forms when the ground loses heat by radiation on clear, calm nights, cooling the air just above the surface to its dew point. In lower-lying areas, cold air tends to settle into valleys and pockets near the ground, so the shallow layer near the surface becomes saturated and fog develops there. Warm, moist air near the surface is allowed to cool efficiently because there’s little wind to mix it, and high humidity helps reach the dew point. This type of fog usually forms overnight and dissipates after sunrise as the ground warms. Other fog types involve different cooling or moisture processes. Advection fog results from moist air moving horizontally over a cooler surface, often along coasts or over snow, rather than from ground cooling. Ice fog occurs in extremely cold conditions when water vapor turns directly into ice crystals, not simply by surface cooling to dew point. Frontal fog forms when fog develops in association with precipitation released from a warm front.

Radiation fog forms when the ground loses heat by radiation on clear, calm nights, cooling the air just above the surface to its dew point. In lower-lying areas, cold air tends to settle into valleys and pockets near the ground, so the shallow layer near the surface becomes saturated and fog develops there. Warm, moist air near the surface is allowed to cool efficiently because there’s little wind to mix it, and high humidity helps reach the dew point. This type of fog usually forms overnight and dissipates after sunrise as the ground warms.

Other fog types involve different cooling or moisture processes. Advection fog results from moist air moving horizontally over a cooler surface, often along coasts or over snow, rather than from ground cooling. Ice fog occurs in extremely cold conditions when water vapor turns directly into ice crystals, not simply by surface cooling to dew point. Frontal fog forms when fog develops in association with precipitation released from a warm front.