- 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, ...
In a porous medium, the advance of one fluid into the pore space occupied by another fluid when the two fluids fully dissolve into each other. Compare immiscible displacement.
Industry:Weather
A horizontal vortex with a width of between 40 m and 4 km. It is often used to refer to 1) a vortex within a convective storm with a horizontal scale of less than 4 km, and 2) a near-surface vortex with a horizontal scale of less than 4 km along a convergence line.
Industry:Weather
A nephoscope in which the motion of the cloud is observed by its reflection in a mirror. A representative instrument consists of a black mirror disk, engraved with special concentric circles calibrated in degrees, and mounted on a tripod stand fitted with leveling screws. An eyepiece is arranged so that it can be rotated about the center of the mirror and adjusted to various distances above the mirror surface. The observer orients the mirror so that its zero corresponds to true north, and then adjusts the eyepiece until the cloud is observed at the center of the mirror. The cloud's direction of motion is indicated by the azimuth at which the image leaves the mirror.
Industry:Weather
1. A suspension in the air consisting of an aggregate of microscopic water droplets or wet hygroscopic particles (of diameter not less than 0. 5 mm or 0. 02 in. ), reducing the visibility at the earth's surface to not less than 1 km or 5/8 mi. The term mist is used in weather reports when there is such obscurity and the associated visibility is 1000 m or more, and the corresponding relative humidity is 95% or more, but is generally lower than 100%. These hydrometeors form a thin greyish veil that covers the landscape. It also reduces visibility, but to a lesser extent than fog. 2. In popular usage in the United States, same as drizzle.
Industry:Weather
An image formed when the atmosphere behaves as a lens. Mirages have a very small angular extent compared with that of the sky: They are normally seen near the horizon and involve image displacements and distortions of less than half a degree. Consequently, even though visible with the naked eye, they are easiest to see with the aid of binoculars or when photographed with a telephoto lens. The name applied to a particular type of mirage is dependent upon the way in which the appearance of the image differs from that of the object. The simplest distinction for the observer is that between a mirage that exhibits but a single image and one showing multiple images. If there is only a single image, and if that image is displaced down from the position of the object, it is said that there is sinking; if up, looming. If the image appears vertically enlarged, there is towering; if vertically shrunken, there is stooping. Recognition of these states depends critically on one's knowledge or memory of the appearance of the scene in the absence of a mirage, because all that is seen is the image. However, the change is often so striking as to make classification fairly easy. Mirages are explained by the refraction of light through an atmosphere with a gradient of refractive index. The refractive index of air depends mainly on the molecular number density of air, but as the layer through which the majority of the refractive bending occurs is often fairly thin, this density variation is primarily dependent upon temperature. Indeed, it a simple matter to associate a particular type of mirage with the shape of a temperature profile. Because the observer is located inside this atmospheric lens, the mirage can change its appearance markedly as a result of slight changes in position, say changing the height of the observer above a surface. See fata bromosa, fata morgana.
Industry:Weather
A cold southwesterly wind blowing in the winter (June through September) in the coastal region of southern Brazil, the country of the Minuano Indians. It is a weak pampero. Compare reboyo.
Industry:Weather
Highest temperature, for a particular pressure, at which a condensation trail can form.
Industry:Weather
A pressure trough of smaller scale than a long-wave trough. It ordinarily moves rapidly and is associated with a migratory cyclonic disturbance in the lower troposphere. See short wave.
Industry:Weather
A ridge of smaller scale than a long-wave ridge. It ordinarily moves rapidly and is associated with a migratory anticyclonic disturbance in the lower troposphere. See short wave.
Industry:Weather
