1. An atmosphere in which visibility is reduced because of a cloud of some substance; SYN. fogginess, murk, murkiness.
2. Droplets of water vapor suspended in the air near the ground.
Cloud that collects at the surface of the Earth, composed of water vapor that has condensed on particles of dust in the atmosphere. Cloud and fog are both caused by the air temperature falling below dew point. The thickness of fog depends on the number of water particles it contains. Officially, fog refers to a condition when visibility is reduced to 1 km or less, and mist or haze to that giving a visibility of 1–2 km.
There are two types of fog. An advection fog is formed by the meeting of two currents of air, one cooler than the other, or by warm air flowing over a cold surface. Sea fogs commonly occur where warm and cold currents meet and the air above them mixes. A radiation fog forms on clear, calm nights when the land surface loses heat rapidly (by radiation); the air above is cooled to below its dew point and condensation takes place. A mist is produced by condensed water particles, and a haze by smoke or dust.
In drought areas, for example, Baja California, Canary Islands, Cape Verde islands, Namib Desert, Peru, and Chile, coastal fogs enable plant and animal life to survive without rain and are a potential source of water for human use (by means of water collectors exploiting the effect of condensation).
Industrial areas uncontrolled by pollution laws have a continual haze of smoke over them, and if the temperature falls suddenly, a dense yellow smog forms. At some airports since 1975 it has been possible for certain aircraft to land and take off blind in fog, using radar navigation. + prikaži više

ETYM AS. mist.
(Homonym: missed [from to miss]).
A thin fog with condensation near the ground.
Low cloud caused by the condensation of water vapor in the lower part of the atmosphere. Mist is less thick than fog, visibility being 1–2 km.

Air pollution by a mixture of smoke and fog; SYN. smogginess.
Natural fog containing impurities, mainly nitrogen oxides (NOx) and volatile organic compounds (VOCs) from domestic fires, industrial furnaces, certain power stations, and internal-combustion engines (gasoline or diesel). It can cause substantial illness and loss of life, particularly among chronic bronchitics, and damage to wildlife.
Photochemical smog is mainly prevalent in the summer as it is caused by chemical reaction between strong sunlight and vehicle exhaust fumes. Such smogs create a buildup of ozone and nitrogen oxides which cause adverse symptoms, including coughing and eye irritation, and in extreme cases can kill.
The London smog of 1952 lasted for five days and killed more than 4,000 people from heart and lung diseases. The use of smokeless fuels, the treatment of effluent, and penalties for excessive smoke from poorly maintained and operated vehicles can be effective in reducing smog but it still occurs in many cities throughout the world. + prikaži više