A small, rapidly rotating column of air made visible by the dust, sand or debris it lifts from the ground, forming on hot, calm days when intense surface heating causes a pocket of hot air to rise quickly through cooler air above it. Unlike a tornado, a dust devil forms from the ground up rather than descending from a storm cloud, and is usually weak and short-lived. They are especially common in deserts, including Mars, where orbital imagery has captured similar dust devils on the Martian surface.
Facts
PeriodicityTypically forms under sunny conditions during fair weather rather than storm systems; not tied to a fixed season, and rarely approaches tornado intensity. 1 ScaleMost are small and weak, under 0.9 meters (3 feet) across with average peak winds near 72 km/h (45 mph), dissipating within a minute; rare large ones reach up to 90 meters (300 feet) across, exceed 97 km/h (60 mph), and can last upward of 20 minutes. 1 Open Questions
First DescribedNo single first scientific description found in the source consulted.
No source found naming who first scientifically described or classified dust devils; the Wikipedia article records regional folk names (willy willy in Australia, si gaoithe in Ireland) but no formal first description, checked this pass. Identification
Distinguishing AppearanceA fully formed dust devil appears as a funnel-like chimney through which hot air rises while rotating, usually made visible by the dust, sand or debris it lifts from the ground. 1 Connections
Demonstrated By
Desert, Biomes Source National Oceanic and Atmospheric Administration
Sources
1. Dust Devil (Wikipedia)
Wikipedialead section (formation-conditions sentence)
While they are comparable to tornadoes in that both are a weather phenomenon involving a vertically oriented rotating column of wind, dust devils typically form under sunny conditions during fair weather, rarely coming close to the intensity of a tornado.
Intensity and duration section
Dust devils are usually small and weak, often less than 0.9 m (3 feet) in diameter with maximum winds averaging about 72 km/h (45 mph), and they often dissipate less than a minute after forming. On rare occasions, a dust devil can grow very large and intense, sometimes reaching a diameter of up to 90 m (300 feet) with winds in excess of 97 km/h (60 mph) and can last for upwards of 20 minutes before dissipating.
Formation section (funnel sentence)
A fully-formed dust devil is a funnel-like chimney through which hot air moves upwards and in a circle.
View the Source National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric AdministrationDemonstrated By: DesertView the Source Reader Challenges (0)
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