Which fog forms due to adiabatic cooling of upward-moving air along terrain?

Which fog forms due to adiabatic cooling of upward-moving air along terrain?

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

Answer: (B)

Fog forms when air cools to its dew point enough for water vapor to condense into tiny droplets. When moist air is pushed up a slope, it rises and expands, cooling adiabatically. That cooling continues until the air reaches its dew point, causing condensation to occur right along the hillside. Because the fog is produced by lifting and adiabatic cooling as air travels up terrain, this is the form that fits the scenario best. Other fog types happen through different processes—radiative cooling near the ground on calm nights, horizontal movement of moist air over a cooler surface, or marine air interacting with sea temperatures—so they don’t rely on lifting up terrain.

Fog forms when air cools to its dew point enough for water vapor to condense into tiny droplets. When moist air is pushed up a slope, it rises and expands, cooling adiabatically. That cooling continues until the air reaches its dew point, causing condensation to occur right along the hillside. Because the fog is produced by lifting and adiabatic cooling as air travels up terrain, this is the form that fits the scenario best. Other fog types happen through different processes—radiative cooling near the ground on calm nights, horizontal movement of moist air over a cooler surface, or marine air interacting with sea temperatures—so they don’t rely on lifting up terrain.