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Katabatic wind

Katabatic wind is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Katabatic wind rather than just read about it. In short: A katabatic wind (named from Ancient Greek κατάβασις (katábasis) 'descent') is a downslope wind caused by the flow of an elevated, high-density air mass into a lower-density air mass below. The spelling catabatic is also used.

Katabatic wind — main illustration
Katabatic wind — illustration

Key takeaways

  • Katabatic wind belongs to earth science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Katabatic wind to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Katabatic wind from memory before moving on to harder problems.

Reference excerpt

A katabatic wind (named from Ancient Greek κατάβασις (katábasis) 'descent') is a downslope wind caused by the flow of an elevated, high-density air mass into a lower-density air mass below. The spelling catabatic is also used. Since air density is strongly dependent on temperature, the high-density air mass is usually cooler, and the katabatic winds are relatively cool or cold. Examples of katabatic winds include the downslope valley and mountain breezes, the piteraq winds of Greenland, the Bora in the Adriatic, the Bohemian Wind or Böhmwind in the Ore Mountains, the Santa Ana winds in southern California, the oroshi in Japan, or "the Barber" in New Zealand. 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.

Mechanism

A katabatic wind originates from the difference of density of two air masses located above a slope. This density difference usually comes from temperature difference, though humidity may also play a role. Schematically, katabatic winds can be divided into two types for which the mechanisms are slightly different: the katabatic winds due to radiative cooling (the most common) and the fall winds. In general, colder air becomes denser than warmer air, which allows it to move downslope due to the gravity. In the first case, the slope surface cools down radiatively after sunset through radiative cooling, as ground loss heat, which cools down the air near the slope. This cooler air layer then flows down in the valley, producing the downslope wind that is easily observed at night in mountainous areas. The term katabatic actually often refer to this type of wind. In contrast, fall wind do not come from radiative cooling of the air, but rather from the advection of a relatively cold air mass to the top of a slope. This cold air mass can come from the arrival of a cold front (see Bora), or from the advection of cool marine air by a sea-breeze.

Impacts

Katabatic winds are for example 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, reaching around 160 kn (300 km/h; 180 mph). 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 kn (220 km/h; 140 mph; 62 m/s). 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 Marinada in Catalonia, Spain is a fall wind that eases the summer heat in the Urgell region.

See also Anabatic wind Bora (wind) Foehn wind Piteraq Valley exit jet

References

Further reading 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. Giles, Bill. Weather A-Z - Katabatic Winds By Bill Giles OBE[link removed], 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. 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<0135:CSSOTA>2.0.CO;2.

External links Media related to Katabatic wind at Wikimedia Commons

Illustrations

Katabatic wind: 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.[citation needed]
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.[citation needed]
Katabatic wind: Katabatic wind in Antarctica
Katabatic wind in Antarctica
Katabatic wind: Sketch of the generation of katabatic winds in Antarctica
Sketch of the generation of katabatic winds in Antarctica
Katabatic wind: Coastal polynyas are produced in the Antarctic by katabatic winds
Coastal polynyas are produced in the Antarctic by katabatic winds

Worked examples

Example 1 — a first encounter with Katabatic wind

Start with the simplest possible case. Write down what Katabatic wind claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Katabatic wind before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Katabatic wind ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Katabatic wind

In research
Katabatic wind appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Katabatic wind in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Katabatic wind is common in secondary-school and first-year university syllabi. It links to neighbouring topics Climate of Antarctica, Climate of Greenland, Wind, so understanding it makes those chapters shorter.
In everyday life
Look for Katabatic wind outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Katabatic wind in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Katabatic wind means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Katabatic wind out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Katabatic wind in simple terms?

A katabatic wind (named from Ancient Greek κατάβασις (katábasis) 'descent') is a downslope wind caused by the flow of an elevated, high-density air mass into a lower-density air mass below. The spelling catabatic is also used.

Why does Katabatic wind matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Katabatic wind?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Katabatic wind.

Tags

  • Climate of Antarctica
  • Climate of Greenland
  • Wind

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