Radiation fog is most likely to occur under what conditions?

Radiation fog typically forms under specific atmospheric conditions, which are indeed supported by all the provided options.

During the evening, as the sun sets, the ground cools rapidly due to the loss of incoming solar radiation. When the air near the surface cools to its dew point and moisture is present in the air, fog can form. High humidity during early evening can elevate the likelihood of this phenomenon, as moisture is essential for fog development.

Cool cloudless nights enhance the cooling process, allowing the ground to lose heat more effectively and thus leading to the conditions necessary for radiation fog formation. The presence of light winds also plays a role; while too strong of winds can mix the air and prevent the air from cooling efficiently, light winds provide enough movement to avoid the build-up of temperature inversions, which can hold moisture in place.

Additionally, favorable topography, such as valleys, can lead to pooling of cold air, reinforcing the cooling effect at the surface. This topographic influence ensures that moisture and cooler temperatures are present, which are key ingredients in radiation fog development.

Thus, all these conditions combined create an environment where radiation fog is not only possible but likely.