What type of weather phenomenon is formed when air masses collapse near the ground, resulting in low visibility?

Fog is formed when air masses collapse near the ground, leading to a saturation of moisture in the air. This process typically occurs when warm, moist air cools rapidly, often during the night or in the early morning. As the air cools, it can no longer hold the same amount of moisture, causing the water vapor to condense into tiny droplets that hang in the air, resulting in a thick mist. This condensed moisture significantly reduces visibility, making it difficult to see distances.

While clouds, rain, and haze are all related to moisture and temperature interactions in the atmosphere, they do not specifically involve the process of condensation occurring close to the surface in the same way that fog does. Clouds form higher in the atmosphere and require different atmospheric conditions, rain typically results from larger scale weather systems and not from the immediate collapse of air masses, and haze involves dry particles that impact visibility but not through moisture condensation like fog.