fogs

Fog is a meteorological phenomenon consisting of a cloud of tiny water droplets suspended near the Earth's surface, reducing visibility to less than 1 kilometer. It forms when moist air near the ground cools to its dew point or when warm, humid air moves over a cooler surface, causing condensation of water vapor. Fog is distinguished from mist by visibility: fog reduces visibility to below 1 kilometer, while mist generally remains above that threshold. The droplets in fog are typically in the 10 to 50 micrometer range.

Common types include radiation fog, which forms on clear, calm nights when the ground loses heat and the adjacent air cools to the dew point; advection fog, created when warm, moist air moves horizontally over a cooler surface; upslope fog, produced as air rises along terrain and cools; steam fog (evaporation fog), which occurs when cold air moves over warmer water or damp ground and condenses water vapor; freezing fog, where droplets freeze on contact with surfaces; and ice fog, which forms in very cold, dry air when water vapor sublimates directly into ice crystals.

Fog reduces transportation safety and can cause flight delays and road closures. It also dampens surfaces, affects outdoor work and agriculture, and contributes to localized icing in freezing conditions. Meteorologists monitor fog with ground-based instruments and visibility observations, dew point measurements, and satellite data to forecast its occurrence and duration.