cold air pool
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GC: n

S: SPRING – https://bit.ly/32z9bg8 (last access: 19 October 2019); GEOSCI – https://bit.ly/31ucsf0 (last access: 19 October 2019).

N: 1. – cold (adj): Old English cald (Anglian), ceald (West Saxon) “producing strongly the sensation which results when the temperature of the skin is lowered,” also “having a low temperature,” from Proto-Germanic *kaldjon (source also of Old Frisian and Old Saxon kald, Old High German and German kalt, Old Norse kaldr, Gothic kalds “cold”), from PIE root *gel- “cold; to freeze” (source also of Latin gelare “to freeze,” gelu “frost,” glacies “ice”).
Japanese has two words for “cold:” samui for coldness in the atmosphere or environment; tsumetai for things which are cold to touch, and also in the figurative sense, with reference to personalities, behaviors, etc.
– air (n): c. 1300, “invisible gases that surround the earth,” from Old French air “atmosphere, breeze, weather” (12c.), from Latin aer “air, lower atmosphere, sky,” from Greek aēr (genitive aeros) “mist, haze, clouds,” later “atmosphere” (perhaps related to aenai “to blow, breathe”), which is of unknown origin. It is possibly from a PIE *awer- and thus related to aeirein “to raise” and arteria “windpipe, artery” (see aorta) on notion of “lifting, suspended, that which rises,” but this has phonetic difficulties.
– pool (n): “small body of water,” Old English pol “small body of water; deep, still place in a river,” from Proto-West Germanic *pol- (source also of Old Frisian and Middle Low German pol, Dutch poel, Old High German pfuol, German Pfuhl “pool, puddle”), which is of uncertain origin, perhaps a substratum word. As a short form of swimming pool it is recorded from 1901. Pool party is from 1965.
2. A cold air pool is a low pressure system, that only exists in the upper troposhere. The two figures above are an example and show, that the low pressure system is only evident in the 500 hPa weather chart (right figure) and not in the surface weather chart (left figure). Cold air pools are a challange for the weather forecast, because the numerical weather prediction models cannot predict the exact direction of movement. As the cold air pool only exists in the free atmosphere, it is uncoupled from influences from the ground as friction. The cold air pool is often related to bad weather. On its front the weather phenomena are comparable to a cold front. The back side is similar to a warm front. Since the air aloft in a cold air pool is quite cold, its air mass is unstable. This often leads to shower and thunderstorms. As the low pressure of a cold air pool only exists aloft, the barometer often indicates nice weather.
3. A pool of cold air can also become ‘detached’ at lower latitudes, i.e. away from the mid-latitude westerly zone, and drift slowly over relatively warmer seas, (e.g. the Mediterranean), and lead to intense convective development, often taking on marked cyclonic characteristics through the troposphere, and giving rise to locally severe conditions due to heavy rainfall, severe thunderstorms and squally winds. Remnants of these types of cold pool will sometimes drift polewards in summer and bring outbreaks of severe convective activity to mid-latitude regions, as these features will destabilise hot/humid air masses.
4. cold-air drop: Vast volume of cold air separated from the mass of cold air at higher latitudes during the formation of a cut-off low.
5. The cold drop (Spanish: gota fría, Catalan: gota freda) is an archaic meteorological term used popularly in Spain which has commonly come to refer to any high impact rainfall events occurring in the autumn along the Spanish Mediterranean coast.

S: 1. OED – https://bit.ly/2pzeEVo (last access: 19 October 2019). 2. WL – https://bit.ly/2P0djS4 (last access: 19 October 2019). 3. TERMIUM PLUS – https://bit.ly/35Mb4bb (last access: 19 October 2019). 4. METEOTERM – International Meteorological Vocabulary, WMO – No. 182 (last access: 19 October 2019); GDT – https://bit.ly/2nXvgFT(last access: 19 October 2019). 5. Wikipedia – https://bit.ly/35Myq0k (last access: 19 October 2019).

SYN: 1. cold pool, cold-air drop. 2. cold air pool. (depending on context)

S: 1. TERMIUM PLUS – https://bit.ly/35Mb4bb (last access: 19 October 2019); GDT – https://bit.ly/2nXvgFT(last access: 19 October 2019). 2. GDT – https://bit.ly/2BsCntg (last access: 20 October 2019).

CR: cut-off low, low-pressure area.