- 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, ...
1. That property of an object that enables it to float on the surface of a liquid, or ascend through and remain freely suspended in a compressible fluid such as the atmosphere.
Quantitatively, it may be expressed as the ratio of the specific weight of the fluid to the specific weight of the object; or, in another manner, by the weight of the fluid displaced minus the weight of the object. 2. (Or buoyant force, buoyancy force; also called Archimedean buoyant force.) The upward force exerted upon a parcel of fluid (or an object within the fluid) in a gravitational field by virtue of the density difference between the parcel (or object) and that of the surrounding fluid.
The magnitude of the buoyancy force F per unit mass may be determined by Archimedes's principle as
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Industry:Weather
The abrasive action of wind-borne material, especially sand, dust, and ice crystals; a form of weathering. Compare corrosion, erosion.
Industry:Weather
With the sun; hence anticyclonic; the opposite of contra solem. See also deasil.
Industry:Weather
Winds parallel to the main (longitudinal) axis of a mountain valley, resulting from the diversion of momentum from larger-scale winds above ridgetops into the valley. Most commonly, direct transfer of momentum into the valley by mixing or by an impressed large-scale pressure gradient produces a flow along the valley axis that represents a component of the larger-scale flow, that is, in the same direction as the flow aloft. Occasionally, however, the perpendicular geostrophic wind relationship between the pressure gradient and the large-scale wind can lead to situations where the impressed pressure gradient produces a flow in the valley in the opposite direction to the along-valley component of the large-scale flow above the ridgetops.
Industry:Weather
Winds from the four cardinal points of the compass; that is, north, east, south, and west winds.
Industry:Weather
Wind estimates based on the observed movements of identifiable cloud elements over short time intervals.
Industry:Weather
When a tropical cyclone exhibits concentric eyewalls, the outer eyewall often contracts and replaces the inner one. A cycle typically takes about one day to complete and is accompanied by significant fluctuations in central surface pressure and maximum wind speed, with maximum winds exceeding 50 m s−1 (96 knots). The cycle may repeat indefinitely.
Industry:Weather
When a photographic emulsion is given a very brief exposure to light of high intensity, it is desensitized toward a subsequent longer exposure to light of moderate intensity. That is, the second exposure produces a fainter image than if the preexposure had not been given. This phenomenon was observed originally by Clayden when photographing lightning flashes, but it can be produced equally well by any type of light source, provided the intensity is sufficiently high and the duration short enough. See dark lightning.
Industry:Weather
