fog
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GC: n

S: NatGeo – https://bit.ly/2Gfqt87 (last access: 10 April 2019); Met Office – https://bit.ly/2D5wYJy (last access: 10 April 2019).

N: 1. “thick, obscuring mist,” 1540s, a back-formation from foggy (which appeared about the same time) or from a Scandinavian source akin to Danish fog “spray, shower, snowdrift,” Old Norse fjuk “drifting snow storm.” Compare also Old English fuht, Dutch vocht, German Feucht “damp, moist.” Figurative phrase in a fog “at a loss what to do” first recorded c. 1600. Fog-lights is from 1962.
2. Suspension of very small, usually microscopic water droplets in the air, generally reducing the horizontal visibility at the Earth’s surface to less than 1 km.
3. Water droplets suspended in the atmosphere in the vicinity the earth’s surface that affect visibility. According to international definition, fog reduces visibility below 1 km (0.62 miles).
4. Fog differs from cloud only in that the base of fog is at the earth’s surface while clouds are above the surface. When composed of ice crystals, it is termed ice fog. Visibility reduction in fog depends on concentration of cloud condensation nuclei and the resulting distribution of droplet sizes. Patchy fog may also occur, particularly where air of different temperature and moisture content is interacting, which sometimes make these definitions difficult to apply in practice.
5. Fogs of all types originate when the temperature and dewpoint of the air become identical (or nearly so). This may occur through cooling of the air to a little beyond its dewpoint (producing advection fog, radiation fog or upslope fog), or by adding moisture and thereby elevating the dewpoint (producing steam fog or frontal fog). Fog seldom forms when the dewpoint spread is greater than 4°F. According to U.S. weather observing practice, fog that hides less than 0.6 of the sky is called ground fog. If fog is so shallow that it is not an obstruction to vision at a height of 6 ft above the surface, it is called simply shallow fog. In aviation weather observations fog is encoded F, and ground fog GF.
6. Fog is easily distinguished from haze by its higher relative humidity (near 100%, having physiologically appreciable dampness) and gray color. Haze does not contain activated droplets larger than the critical size according to Köhler theory.
7. Mist may be considered an intermediate between fog and haze; its particles are smaller (a few μm maximum) in size, it has lower relative humidity than fog, and does not obstruct visibility to the same extent. There is no distinct line, however, between any of these categories. Near industrial areas, fog is often mixed with smoke, and this combination has been known as smog. However, fog droplets are usually absent in photochemical smog, which only contains unactivated haze droplets.
8. Collocations:

  • Adj. dense, heavy, thick; freezing; patchy; swirling.
  • Quant. bank, blanket, patch The town was shrouded in a thick blanket of fog.
  • Verb + fog: be shrouded in.
  • Fog + verb cover sth, lie, shroud sth; close in, come down, descend, roll in; clear, disperse, lift; drift, swirl fog; obscure sth.
  • Fog + noun: patches.
  • Prep. in/into (a/the) fog; through (a/the) fog.

9. Cultural Interrelation: We can mention the movie The Fog (1980) directed by John Carpenter.

S: 1. OED – https://bit.ly/2X5jiGl (last access: 10 April 2019). 2. METEOTERM –
International Meteorological Vocabulary, WMO – No. 182 (last access: 8 April 2019). 3 to 7. AMS GLOS – https://bit.ly/2Ut2UST (last access: 10 April 2019). 8. OCD – https://bit.ly/2IaOdxq (last access: 10 April 2019). 9. IMDB – https://imdb.to/2CDXtGO (last access: 10 April 2019).

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CR: freezing fog, haze, mist, smog.