What are the key requirements for fog formation?

The formation of fog is primarily influenced by specific atmospheric conditions, particularly related to temperature and moisture. The correct answer outlines conditions that are conducive to fog development.

Fog typically forms when moisture in the air condenses into tiny water droplets at or near the Earth’s surface. For this condensation to happen efficiently, certain visibility and temperature criteria must be met. The conditions mentioned—specifically, a limitation on visibility (less than 5/8 statute miles) and a specific elevation requirement (50 feet above the surface with greater than 20 feet in depth)—indicate an environment where cold air, often trapped near the ground, interacts with moisture, resulting in fog.

In scenarios of poor visibility and specific surface elevation, especially when combined with higher humidity levels, the air is more likely to cool sufficiently to reach the dew point, leading to condensation and fog formation. Hence, the stipulation about visibility and depth contributes to identifying the right conditions needed for fog to occur, illustrating its link to moisture and temperature gradients in the atmosphere.

Understanding these requirements helps in weather forecasting and predicting scenarios where visibility will be significantly reduced due to fog.