- 行业: Weather
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The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
The leading edge of a duststorm, which looks like a knobby vertical or convex wall when viewed from the clear air ahead of the storm. Sharply defined dust walls are caused by gust fronts at the leading edge of thunderstorm straight-line outflow winds along the surface. Sometimes surface friction will slow the air immediately touching the surface resulting in a dust wall that curves back at the bottom. See also haboob.
Industry:Weather
The top of a dust layer confined by a low-level temperature inversion with the appearance of the horizon when viewed from above against the sky. In such instances the true horizon is usually obscured by the dust layer. Similarly defined are fog horizon and smoke horizon.
Industry:Weather
The electrification of dust by frictional effects produced by the movement of the dust over surfaces.
Industry:Weather
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 occasionally are strong enough to cause minor damage (up to F1 on the 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.
Industry:Weather
General term for an instrument that measures the size and number of dust particles in a known volume of air. See Aitken dust counter, cascade impactor, Owens dust recorder, nucleus counter, konimeter.
Industry:Weather
A name given, early in 1935, to the region in the south-central United States affected by drought and duststorms at that time. It included parts of five states: Colorado, Kansas, New Mexico, Texas, and Oklahoma. It resulted from a long period of deficient rainfall combined with loosening of the soil by destruction of the natural vegetation. The name has since been extended to similar regions in other parts of the world.
Industry:Weather
Solid materials suspended in the atmosphere in the form of small irregular particles, many of which are microscopic in size. It imparts a tannish or grayish hue to distant objects. The sun's disk is pale or colorless or has a yellowish tinge at all periods of the day. Dust cannot be a stable component of the atmosphere because it must eventually fall back to the earth's surface when winds and turbulence become too weak to bear it aloft. Dust is due to many natural and artificial sources, for example, volcanic eruptions, salt spray from the seas, blowing solid particles, plant pollen, bacteria, and smoke and ashes from forest fires and industrial combustion processes. It was once thought that dust particles were a main source of condensation nuclei; this is no longer regarded as probable as most dusts are not sufficiently hygroscopic. Compare smoke, haze; see duststorm, dust devil.
Industry:Weather
The part of morning or evening twilight between complete darkness and civil twilight (i.e., the combined nautical and astronomical twilights). In nontechnical usage, dusk is the evening counterpart of dawn. In technical usage, morning dusk is the first part of dawn.
Industry:Weather
The mountain-gap wind of the Dardenelles; a strong east-northeast wind that blows out of the Dardanelles into the Aegean Sea, penetrating as far as the island of Lemnos. It is caused by a ridge of high pressure over the Black Sea. See jet-effect wind.
Industry:Weather
