- 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, ...
A fluid in which the density varies from point to point. For most purposes, the atmosphere must be treated as heterogeneous, particularly with regard to the decrease of density with height. Compare homogeneous fluid.
Industry:Weather
A fast-moving section of an ice sheet contained within the ice sheet. Motion of an ice stream is dominated by basal sliding.
Industry:Weather
A dome-shaped perennial cover of ice and snow over an extensive portion of the earth's surface. Ice caps are considerably smaller than ice sheets, and it is felt improper to refer to the Greenland and Antarctic Ice Sheets as ice caps. Most ice caps are most probably remnants of the Quaternary Ice Age. The term was first used for the supposedly perennial ice cover at both poles of the earth. However, since it has been found that the ice of arctic waters is largely seasonal, the use of this term to denote arctic polar ice is now considered improper.
Industry:Weather
A discrete block of slow-moving land ice that has been incorporated en masse into either an ice stream or an ice shelf.
Industry:Weather
A direct thermally driven and zonally symmetric circulation under the strong influence of the earth's rotation, first proposed by George Hadley in1735 as an explanation for the trade winds. It consists of the equatorward movement of the trade winds between about latitude 30° and the equator in each hemisphere, with rising wind components near the equator, poleward flow aloft, and, finally, descending components at about latitude 30° again. In a dishpan experiment, a Hadley cell is any direct thermally driven vertical cell of the approximate scale of the dishpan.
Industry:Weather
A diffuse bright region surrounding the shadow an observer's head casts on a irregular surface. It is most apparent when the sun is low in the sky and when the surface is dew-covered. The explanation of the heiligenschein varies depending upon whether it is seen over a dry or a dew- covered surface. When an observer's shadow is cast on a dry, irregular surface (such as gravel or vegetation), each irregularity near the antisolar point covers its own shadow. In other directions, the average brightness results from a mixture of sunlit and shaded surfaces. The lower the sun in the sky, the longer the shadows and so the greater the contrast with the brighter region near the antisolar point. While evident over virtually any irregular surface, the ready appearance of the heiligenschein in sunlit wooded areas when seen from an airplane has spawned the epithet, the “hot spot in the forest. ” Observations of the “hot spot in the forest. ” are undoubtedly all the more striking when the plane is high enough that its own shadow (the umbra portion) has vanished. The presence of dew on some species of grass greatly enhances the heiligenschein. Dewdrops held off the surface of the leaf by small hairs focus sunlight on the leaf where it is diffusely reflected. The drop, acting in a manner similar to the lens in a lighthouse, then collects a large fraction of this diffusely reflected light that would have otherwise gone in other directions and sends it back toward the source and the observer. The heiligenschein is occasionally called Cellini's halo, after Benvenuto Cellini who described its behavior in his memoirs of 1562. He even pointed out that “it appears to the greatest advantage when the grass is moist with dew,” but felt its appearance bespoke “the wondrous ways of (God's) providence toward me. ” Shades of this interpretation are also found in the name heiligenschein: It is German for “the light of the holy one. ”
Industry:Weather
A diagram that shows isopleths of atmospheric variation, such as pressure or thickness, usually averaged over a band of latitude. Time is usually on one axis, longitude the other. This product demonstrates the progression of large-scale atmospheric features over a long period of time.
Industry:Weather
A device used to obtain data on the size distribution and mass of hailstones. A hailpad usually consists of a plastic foam panel covered by aluminum foil or white latex paint and set in a frame that is hammered into the ground. Hail that impinges on the pad leaves dents in it. The dimensions of the dents are analyzed to obtain the hailstone size and mass data.
Industry:Weather
A device designed to measure the rate of infiltration of water into soil.
Industry:Weather
A deposit of interlocking ice crystals (hoar crystals) formed by direct deposition on objects, usually those of small diameter freely exposed to the air, such as tree branches, plant stems and leaf edges, wires, poles, etc. Also, frost may form on the skin of an aircraft when a cold aircraft flies into air that is warm and moist or when it passes through air that is supersaturated with water vapor. The deposition of hoarfrost is similar to the process by which dew is formed, except that the temperature of the befrosted object must be below freezing. It forms when air with a dewpoint below freezing is brought to saturation by cooling. In addition to its formation on freely exposed objects (air hoar), hoarfrost also forms inside unheated buildings and vehicles, in caves, in crevasses (crevasse hoar), on snow surfaces (surface hoar), and in air spaces within snow, especially below a snow crust (depth hoar). Hoarfrost is more fluffy and feathery than rime, which in turn is lighter than glaze. Observationally, hoarfrost is designated light or heavy (frost) depending upon the amount and uniformity of deposition.
Industry:Weather
