A katabatic wind (named from Ancient Greekκατάβασις (katábasis) 'descent') is a drainage wind, a wind that carries high-density air from a higher elevation down a slope under the force of gravity. Such winds are sometimes also called fall winds; the spelling catabatic winds[1] is also used. Katabatic winds can rush down elevated slopes at hurricane speeds, but most are not that intense and many are 10 knots (18 km/h) or less.
Plateau-cooled air falls into the Makhtesh Ramon, traced by radiation fog, just after dawn. Radiative cooling of the desert highlands chills the air, making it more dense than the air over the lowlands. Cooler air can also hold less water vapour; it condenses out as tiny fog droplets, which re-evaporate as the air warms. Here, the falling air is warming adiabatically, and so the fog re-evaporates as it falls.
Katabatic wind in Antarctica
Not all downslope winds are katabatic. For instance, winds such as the föhn and chinook are rain shadow winds where air driven upslope on the windward side of a mountain range drops its moisture and descends leeward drier and warmer. Examples of true katabatic winds include the bora in the Adriatic, the Bohemian Wind or Böhmwind in the Ore Mountains, the Santa Ana in southern California, the piteraq winds of Greenland, and the oroshi in Japan. Another example is "the Barber", an enhanced katabatic wind that blows over the town of Greymouth in New Zealand when there is a southeast flow over the South Island. "The Barber" has a local reputation for its coldness.
Sketch of the generation of katabatic winds in Antarctica
A katabatic wind originates from radiational cooling of air atop a plateau, a mountain, glacier, or even a hill. Since the density of air is inversely proportional to temperature, the air will flow downwards, warming approximately adiabatically as it descends. The temperature of the air depends on the temperature in the source region and the amount of descent. In the case of the Santa Ana, for example, the wind can (but does not always) become hot by the time it reaches sea level. In Antarctica, by contrast, the wind is still intensely cold.
The entire near-surface wind field over Antarctica is largely determined by the katabatic winds, particularly outside the summer season, except in coastal regions when storms may impose their own wind field.
Impacts
Coastal polynyas are produced in the Antarctic by katabatic winds
Katabatic winds are most commonly found blowing out from the large and elevated ice sheets of Antarctica and Greenland. The buildup of high density cold air over the ice sheets and the elevation of the ice sheets brings into play enormous gravitational energy. Where these winds are concentrated into restricted areas in the coastal valleys, the winds blow well over hurricane force,[2] reaching around 300 km/h (190 mph).[3] In Greenland these winds are called piteraq and are most intense whenever a low pressure area approaches the coast.
In a few regions of continental Antarctica the snow is scoured away by the force of the katabatic winds, leading to "dry valleys" (or "Antarctic oases") such as the McMurdo Dry Valleys. Since the katabatic winds are descending, they tend to have a low relative humidity, which desiccates the region. Other regions may have a similar but lesser effect, leading to "blue ice" areas where the snow is removed and the surface ice sublimates, but is replenished by glacier flow from upstream.
In the Fuegian Archipelago (Tierra del Fuego) in South America as well as in Alaska in North America, a wind known as a williwaw is a particular danger to harboring vessels. Williwaws originate in the snow and ice fields of the coastal mountains, and they can be faster than 120 knots (140 mph; 220 km/h).[4]
In California, strong katabatic wind events have been responsible for the explosive growth of many wildfires, including the 2018 Camp Fire and the 2020 North Complex.
^The NASA Scope and Subject Category Guide. NASA SP. Vol. 7603. National Aeronautics and Space Administration, Scientific and Technical Information Office, Center for Aerospace Information. 2000. p. 71. Retrieved 2018-01-17. Katabatic winds (also catabatic)
^Climate: The South Pole 2008-09-18 at the Wayback Machine Stanford Humanities Lab Archived 2006-09-12 at archive.today, Retrieved 2008-10-01
^Trewby, M. (Ed., 2002): Antarctica. An encyclopedia from Abbott Ice Shelf to Zooplankton Firefly Books Ltd. ISBN1-55297-590-8
Giles, Bill. Weather A-Z - Katabatic Winds By Bill Giles OBE, BBC, Retrieved 2008-10-14
McKnight, TL & Hess, Darrel (2000). Katabatic Winds. In Physical Geography: A Landscape Appreciation, pp. 131–2. Upper Saddle River, NJ: Prentice Hall. ISBN0-13-020263-0
Parish, Thomas R.; Bromwich, David H. (1991). "Continental-Scale Simulation of the Antarctic Katabatic Wind Regime". Journal of Climate. 4 (2): 135–46. Bibcode:1991JCli....4..135P. doi:10.1175/1520-0442(1991)004<0135:CSSOTA>2.0.CO;2.
Bromwich, David H. (1989). "Satellite Analyses of Antarctic Katabatic Wind Behavior". Bulletin of the American Meteorological Society. 70 (7): 738–49. Bibcode:1989BAMS...70..738B. doi:10.1175/1520-0477(1989)070<0738:SAOAKW>2.0.CO;2.
Bromwich, David H. (1989). "An Extraordinary Katabatic Wind Regime at Terra Nova Bay, Antarctica". Monthly Weather Review. 117 (3): 688–95. Bibcode:1989MWRv..117..688B. doi:10.1175/1520-0493(1989)117<0688:AEKWRA>2.0.CO;2.
External links
Media related to katabatic wind at Wikimedia Commons
May 17, 2023
katabatic, wind, album, katabatic, wind, katabatic, wind, named, from, ancient, greek, κατάβασις, katábasis, descent, drainage, wind, wind, that, carries, high, density, from, higher, elevation, down, slope, under, force, gravity, such, winds, sometimes, also,. For the album see The Katabatic Wind A katabatic wind named from Ancient Greek katabasis katabasis descent is a drainage wind a wind that carries high density air from a higher elevation down a slope under the force of gravity Such winds are sometimes also called fall winds the spelling catabatic winds 1 is also used Katabatic winds can rush down elevated slopes at hurricane speeds but most are not that intense and many are 10 knots 18 km h or less Plateau cooled air falls into the Makhtesh Ramon traced by radiation fog just after dawn Radiative cooling of the desert highlands chills the air making it more dense than the air over the lowlands Cooler air can also hold less water vapour it condenses out as tiny fog droplets which re evaporate as the air warms Here the falling air is warming adiabatically and so the fog re evaporates as it falls Katabatic wind in Antarctica Not all downslope winds are katabatic For instance winds such as the fohn and chinook are rain shadow winds where air driven upslope on the windward side of a mountain range drops its moisture and descends leeward drier and warmer Examples of true katabatic winds include the bora in the Adriatic the Bohemian Wind or Bohmwind in the Ore Mountains the Santa Ana in southern California the piteraq winds of Greenland and the oroshi in Japan Another example is the Barber an enhanced katabatic wind that blows over the town of Greymouth in New Zealand when there is a southeast flow over the South Island The Barber has a local reputation for its coldness Contents 1 Theory 2 Impacts 3 See also 4 References 5 Further reading 6 External linksTheory Edit Sketch of the generation of katabatic winds in Antarctica A katabatic wind originates from radiational cooling of air atop a plateau a mountain glacier or even a hill Since the density of air is inversely proportional to temperature the air will flow downwards warming approximately adiabatically as it descends The temperature of the air depends on the temperature in the source region and the amount of descent In the case of the Santa Ana for example the wind can but does not always become hot by the time it reaches sea level In Antarctica by contrast the wind is still intensely cold The entire near surface wind field over Antarctica is largely determined by the katabatic winds particularly outside the summer season except in coastal regions when storms may impose their own wind field Impacts Edit Coastal polynyas are produced in the Antarctic by katabatic winds Katabatic winds are most commonly found blowing out from the large and elevated ice sheets of Antarctica and Greenland The buildup of high density cold air over the ice sheets and the elevation of the ice sheets brings into play enormous gravitational energy Where these winds are concentrated into restricted areas in the coastal valleys the winds blow well over hurricane force 2 reaching around 300 km h 190 mph 3 In Greenland these winds are called piteraq and are most intense whenever a low pressure area approaches the coast In a few regions of continental Antarctica the snow is scoured away by the force of the katabatic winds leading to dry valleys or Antarctic oases such as the McMurdo Dry Valleys Since the katabatic winds are descending they tend to have a low relative humidity which desiccates the region Other regions may have a similar but lesser effect leading to blue ice areas where the snow is removed and the surface ice sublimates but is replenished by glacier flow from upstream In the Fuegian Archipelago Tierra del Fuego in South America as well as in Alaska in North America a wind known as a williwaw is a particular danger to harboring vessels Williwaws originate in the snow and ice fields of the coastal mountains and they can be faster than 120 knots 140 mph 220 km h 4 In California strong katabatic wind events have been responsible for the explosive growth of many wildfires including the 2018 Camp Fire and the 2020 North Complex See also EditAnabatic wind Foehn wind Valley exit jet Bora wind PiteraqReferences Edit The NASA Scope and Subject Category Guide NASA SP Vol 7603 National Aeronautics and Space Administration Scientific and Technical Information Office Center for Aerospace Information 2000 p 71 Retrieved 2018 01 17 Katabatic winds also catabatic Climate The South Pole Archived 2008 09 18 at the Wayback Machine Stanford Humanities Lab Archived 2006 09 12 at archive today Retrieved 2008 10 01 Trewby M Ed 2002 Antarctica An encyclopedia from Abbott Ice Shelf to Zooplankton Firefly Books Ltd ISBN 1 55297 590 8 Williwaw weatheronline co uk Accessed 2013 04 29 Further reading EditGiles Bill Weather A Z Katabatic Winds By Bill Giles OBE BBC Retrieved 2008 10 14 McKnight TL amp Hess Darrel 2000 Katabatic Winds In Physical Geography A Landscape Appreciation pp 131 2 Upper Saddle River NJ Prentice Hall ISBN 0 13 020263 0 Parish Thomas R Bromwich David H 1991 Continental Scale Simulation of the Antarctic Katabatic Wind Regime Journal of Climate 4 2 135 46 Bibcode 1991JCli 4 135P doi 10 1175 1520 0442 1991 004 lt 0135 CSSOTA gt 2 0 CO 2 Bromwich David H 1989 Satellite Analyses of Antarctic Katabatic Wind Behavior Bulletin of the American Meteorological Society 70 7 738 49 Bibcode 1989BAMS 70 738B doi 10 1175 1520 0477 1989 070 lt 0738 SAOAKW gt 2 0 CO 2 Bromwich David H 1989 An Extraordinary Katabatic Wind Regime at Terra Nova Bay Antarctica Monthly Weather Review 117 3 688 95 Bibcode 1989MWRv 117 688B doi 10 1175 1520 0493 1989 117 lt 0688 AEKWRA gt 2 0 CO 2 External links Edit Media related to katabatic wind at Wikimedia Commons Retrieved from https en wikipedia org w index php title Katabatic wind amp oldid 1151620042, wikipedia, wiki, book, books, library,
