Which fog can form from moist air rising along a mountain slope?

Correct answer: Upslope fog

Direct answer: A, upslope fog. When moist air is forced to move upward along a mountain or hill slope, the air encounters lower pressure and expands. Expansion causes adiabatic cooling, meaning the air cools because of expansion rather than because it directly loses heat to a surface. If it cools to its dew point, relative humidity reaches saturation. Water vapour then condenses on tiny particles in the air and forms suspended droplets, producing fog on or near the slope. A is therefore the only option that names the fog type produced by rising moist air along terrain. B, a sea tide, is the periodic rise and fall of sea level due mainly to gravitational effects and is not fog. C, a dry dust storm contains airborne dust in dry conditions, not condensed water droplets. D, fluvial deposition is the laying down of sediment by running water. Memory cue: air forced uphill, expansion, cooling, saturation, and fog equals upslope fog. The key process is adiabatic cooling.