What element is essential in the formation of fog beyond condensation nuclei?

Fog formation primarily requires a significant amount of moisture in the atmosphere, which is critical for condensation to occur. When the air is saturated with moisture, it facilitates the condensation of water vapor into tiny water droplets, creating fog. The presence of condensation nuclei plays a supportive role, but without adequate moisture, fog cannot develop.

High temperatures are unlikely to contribute to fog formation, as warmer air tends to hold more moisture, which often prevents saturation. Low temperatures can contribute to fog, particularly in the formation of certain types like radiational fog, but they do not guarantee the necessary moisture levels. Stable atmospheric pressure is also not a direct factor influencing fog formation; instead, it can affect stability and air movement but is not an essential element. Therefore, the presence of significant moisture is the key factor in fog formation beyond condensation nuclei.