In what atmospheric condition would you expect to find radiation fog?

Radiation fog typically forms under specific atmospheric conditions that facilitate cooling and condensation of moisture in the air. Calm, clear, cool nights provide an ideal scenario for this phenomenon.

During these conditions, the ground loses heat rapidly through radiation, causing the air close to the surface to cool down. As the air temperature drops, it can reach the dew point, which results in the moisture in the air condensing into tiny water droplets, forming fog. The lack of wind is crucial here, as it allows the cooled air to remain in place and promote the development of fog rather than dispersing it.

Warm, humid conditions or windy weather would not create the necessary cooling for radiation fog to develop, and abrupt temperature rises would typically lead to the dissipation of fog, rather than its formation. Thus, the conditions described are key elements in the formation of radiation fog, making this the most accurate answer.