dust devil
A well-developed
dust whirl; a small but vigorous
whirlwind, usually of short
duration, rendered visible by
dust, sand, and debris picked up from the ground.
Dust devils are occasionally strong enough to cause minor damage (up to EF0 on the
Enhanced Fujita scale). Diameters
range from about 3 m to greater than 30 m; their average height is about 200 m, but a few have been observed as high as 1 km or more. They have been observed to rotate anticyclonically as well as cyclonically. Although the
vertical velocity is predominantly upward, the flow along the axis of large dust devils may be downward. Large dust devils may also contain secondary vortices. Dust devils are best developed on a hot,
calm afternoon with
clear skies, in a dry region when intense surface heating causes a very steep
lapse rate of
temperature in the lowest 100 m of the
atmosphere.
term edited 28 April 2016
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