Radiation fog is most likely to occur under which conditions?

Radiation fog forms under specific atmospheric conditions primarily characterized by the cooling of air near the ground. The situation described in the chosen option highlights the presence of a shallow surface layer of relatively moist air situated beneath a dry layer, combined with clear skies and light surface winds.

Clear skies allow for maximum heat loss from the surface at night, as there are no clouds to trap heat. The light winds enable the moist, cooler air to remain in close proximity to the surface without significantly mixing with the warmer, drier air above it. As the temperature of the moist air cools down during the night, it reaches its dew point, resulting in the condensation of water vapor and the formation of fog.

The other options describe different weather phenomena. The first option suggests a scenario where moist air moves over a cold surface, leading to condensation due to cooling but lacks the specifics of the clear skies and light winds, which are essential for radiation fog. The third option refers to upslope lifting rather than the cooling of the air mass in place, which aligns more with upslope fog rather than radiation fog. The fourth option describes warm air over a cold wet surface, which typically leads to different types of fog, such as advection fog, rather than radiation fog.