Difference between revisions of "Fog"
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==Origin== | ==Origin== | ||
| − | unknown [[origin]]; the [ | + | unknown [[origin]]; the [https://en.wikipedia.org/wiki/Welsh Welsh] ffwg ‘dry grass’ |
| − | *[ | + | *[https://en.wikipedia.org/wiki/16th_century 1544] |
==Definitions== | ==Definitions== | ||
*1a : vapor condensed to fine particles of [[water]] suspended in the lower [[atmosphere]] that differs from cloud only in being near the ground | *1a : vapor condensed to fine particles of [[water]] suspended in the lower [[atmosphere]] that differs from cloud only in being near the ground | ||
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'''Fog''' is a collection of [[water]] droplets or [[ice]] [[crystals]] suspended in the [[air]] at or near the [[Earth]]'s [[surface]]. While fog is a type of a cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated locally (such as from a nearby [[body]] of [[water]], like a [[lake]] or the [[ocean]], or from nearby moist ground or marshes). | '''Fog''' is a collection of [[water]] droplets or [[ice]] [[crystals]] suspended in the [[air]] at or near the [[Earth]]'s [[surface]]. While fog is a type of a cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated locally (such as from a nearby [[body]] of [[water]], like a [[lake]] or the [[ocean]], or from nearby moist ground or marshes). | ||
| − | Fog is distinguished from [ | + | Fog is distinguished from [https://en.wikipedia.org/wiki/Mist mist] only by its [[density]], as [[expressed]] in the resulting decrease in visibility: Fog reduces visibility to less than 1 km, whereas mist reduces visibility to no less than 1 km but less than 2 km. For aviation purposes in the UK, a visibility of less than 2 km but greater than 999 m is considered to be mist if the [[relative]] humidity is 95% or greater - below 95% haze is reported. |
| − | The foggiest place in the world is the [ | + | The foggiest place in the world is the [https://en.wikipedia.org/wiki/Grand_Banks Grand Banks] off the island of [https://en.wikipedia.org/wiki/Newfoundland_(island) Newfoundland], the meeting place of the cold [https://en.wikipedia.org/wiki/Labrador_Current Labrador Current] from the north and the much warmer [https://en.wikipedia.org/wiki/Gulf_Stream Gulf Stream] from the south. Some of the foggiest land areas in the world include Argentina, Newfoundland, Labrador and [https://en.wikipedia.org/wiki/Point_Reyes Point Reyes, California], each with over 200 foggy days per year. Even in generally warmer southern Europe, thick fog and localized fog is often found in lowlands and valleys, such as the lower part of the [https://en.wikipedia.org/wiki/Po_Valley Po Valley] and the [https://en.wikipedia.org/wiki/Arno Arno] and [https://en.wikipedia.org/wiki/Tiber Tiber] valleys, as well as on the [https://en.wikipedia.org/wiki/Swiss_plateau Swiss plateau], especially in the [https://en.wikipedia.org/wiki/Seeland_(Switzerland) Seeland area], in late [[autumn]] and [[winter]].Other notably foggy areas include coastal Chile (in the south), coastal Namibia, and the [https://en.wikipedia.org/wiki/Severnaya_Zemlya Severnaya Zemlya] islands.[https://en.wikipedia.org/wiki/Fog] |
[[Category: Earth Science]] | [[Category: Earth Science]] | ||
Latest revision as of 00:16, 13 December 2020
Origin
unknown origin; the Welsh ffwg ‘dry grass’
Definitions
- 1a : vapor condensed to fine particles of water suspended in the lower atmosphere that differs from cloud only in being near the ground
- b : a fine spray or a foam for firefighting
- 2: a murky condition of the atmosphere or a substance causing it
- 3a : a state of confusion or bewilderment <spent the morning in a fog>
- b : something that confuses or obscures <hid behind a fog of rhetoric>
- 4: cloudiness or partial opacity in a developed photographic image caused by chemical action or stray radiation
Description
Fog is a collection of water droplets or ice crystals suspended in the air at or near the Earth's surface. While fog is a type of a cloud, the term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated locally (such as from a nearby body of water, like a lake or the ocean, or from nearby moist ground or marshes).
Fog is distinguished from mist only by its density, as expressed in the resulting decrease in visibility: Fog reduces visibility to less than 1 km, whereas mist reduces visibility to no less than 1 km but less than 2 km. For aviation purposes in the UK, a visibility of less than 2 km but greater than 999 m is considered to be mist if the relative humidity is 95% or greater - below 95% haze is reported.
The foggiest place in the world is the Grand Banks off the island of Newfoundland, the meeting place of the cold Labrador Current from the north and the much warmer Gulf Stream from the south. Some of the foggiest land areas in the world include Argentina, Newfoundland, Labrador and Point Reyes, California, each with over 200 foggy days per year. Even in generally warmer southern Europe, thick fog and localized fog is often found in lowlands and valleys, such as the lower part of the Po Valley and the Arno and Tiber valleys, as well as on the Swiss plateau, especially in the Seeland area, in late autumn and winter.Other notably foggy areas include coastal Chile (in the south), coastal Namibia, and the Severnaya Zemlya islands.[1]
