- 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 more or less irregular surface in the ground that marks the upper limit of the permafrost; not to be confused with frost table.
Industry:Weather
A method of testing for instability in which a displacement is made from a steady state under the assumption that only the parcel or parcels displaced are affected, the environment remaining unchanged. Although this method has been applied to various problems (e.g., inertial instability), its most familiar context is with vertical displacements from hydrostatic equilibrium, in which the parcel displaced is assumed to undergo adiabatic temperature changes, and the buoyant force resulting from its contrast with the unchanged environment leads to the criterion for stability, γ < Γ, where γ is the lapse rate of virtual temperature with height and Γ is the dry- or saturation-adiabatic lapse rate, according to the condition of the parcel. Compare slice method.
Industry:Weather
A diffuse, but sometimes fairly bright, illumination of those parts of a thundercloud that surround the path of a lightning flash, particularly a cloud discharge or cloud-to-cloud discharge. Thus, sheet lightning is no unique form of lightning but only one manifestation of ordinary lightning types in the presence of obscuring clouds. Compare heat lightning.
Industry:Weather
Flood that can be expected from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible in a region.
Industry:Weather
Flood that can be expected from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible in a region.
Industry:Weather
That part of an image focused on the region of the retina surrounding the fovea. This region contains a mixture of cones and rods and does not provide as high a resolution as does the fovea. Although rods do not permit color vision, they respond to much lower illuminance. Nighttime vision is performed primarily with the rods. See dark adaptation.
Industry:Weather
That part of an image focused on the region of the retina surrounding the fovea. This region contains a mixture of cones and rods and does not provide as high a resolution as does the fovea. Although rods do not permit color vision, they respond to much lower illuminance. Nighttime vision is performed primarily with the rods. See dark adaptation.
Industry:Weather
A hygrometer that determines the amount of precipitable moisture in a given region of the atmosphere by measuring the attenuation of radiant energy caused by the absorption bands of water vapor. The instrument consists of a collimated energy source, separated by the region under investigation from a detector that is sensitive to those frequencies that correspond to the absorption bands of water vapor. The basis for determining the water vapor concentration is Beer's Law: I/ I<sub>0</sub> = exp(−''kx''), where I is the light intensity after passing through the sample, I<sub>0</sub> is the incident intensity, ''x'' is the pathlength reduced to some absolute standard like STP, and ''k'' is the absorption coefficient. The most useful regions of the electromagnetic spectrum for this purpose lie in the ultraviolet and infrared regions. The most widespread application is the monitoring of very-high- frequency variations in humidity, as the time constant of a spectral hygrometer is typically just a few milliseconds. The use of spectral hygrometers remains mostly restricted to research applications. See Krypton hygrometer, Lyman-alpha hygrometer, differential absorption hygrometer.
Industry:Weather
The ratio between the distance separating two points on a map of the earth's surface at a standard latitude (or latitudes) and the distance between the corresponding points on the earth's surface itself. For most map projections, this factor is a slowly varying function of latitude, and for synoptic- chart base maps it is usually of the order of 10<sup>−6</sup> to 10<sup>−7</sup>. The scale factor is sometimes defined as the reciprocal of the above ratio. Compare conformal map.
Industry:Weather
