- 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 medium within which harmonic waves move at wave speeds that are functions of their wavelengths. See dispersion.
Industry:Weather
The mass transfer (mass/unit time/unit area) that occurs because of dispersion. It is equal to the dispersion coefficient multiplied by the gradient of the concentration with respect to distance.
Industry:Weather
A theoretical relationship between the frequency and wavelength of a wave that shows that waves of different frequencies travel at different (phase) velocities. See dispersion diagram, wave dispersion.
Industry:Weather
1. The variation of the complex index of refraction with frequency (or, equivalently, wavelength in free space), sometimes classified as normal (if n increases with increasing frequency) or anomalous (if n decreases with increasing frequency). But there is nothing anomalous about anomalous dispersion: Every material substance exhibits anomalous dispersion at some frequencies. Dispersion is a consequence of the inherent frequency- dependent response of individual atoms and molecules to excitation by a time-harmonic field. By means of dispersion a beam of light composed of many frequencies can be spatially separated (angular dispersion) into its components as, for example, with a prism. Rainbows and halos owe their colors to angular dispersion. 2. The spreading of atmospheric constituents, such as air pollutants. Dispersion can be the result of molecular diffusion, turbulent mixing, and mean wind shear. The displacement or advection of polluted air by the mean wind is usually called transport rather than dispersion. The amount of dispersion is usually described statistically by the standard deviation (σx, σy and σz) of pollutant particle locations (x, y, z) from the pollutant puff center-of- mass for isolated short releases such as explosions, or from the plume centerline for continuous emissions such as from a smokestack. For a plume, the local Cartesian coordinate system can be aligned with the x axis pointing in the mean wind direction at plume centerline height, allowing the crosswind and vertical dispersion to be described by σy and σz, respectively. 3. In statistics, the scattering (or degree thereof) of the values of a frequency distribution from their average.
Industry:Weather
“An instrument for measuring snow hardness in terms of the resistance of snow to the pressure exerted by a disk attached to a spring-loaded rod; a gauge calibrated in pounds per square inch registers the amount of resistance” (Glossary of Arctic and Subarctic Terms, 1955). Compare Canadian hardness gauge.
Industry:Weather
Model experiments carried out by differential heating of a fluid in a flat rotating pan. Such experiments, by establishing similarity with the atmosphere through such nondimensional parameters as the Rossby number, Taylor number, etc. , have reproduced many important features of the general circulation and of smaller scales of atmospheric motion. See Rossby regime.
Industry:Weather
An instrument that measures and records the sizes of raindrops. A common type of disdrometer consists of a sensitive transponder that measures the momentum of individual drops as they fall onto an exposed horizontal surface. Size is determined from momentum through calibration, and the drop-size distribution is obtained by keeping a tally of the number of drops in different size categories that fall onto the surface in a given period of time.
Industry:Weather
A parabolic reflector type of radio or radar antenna. The term is occasionally used incorrectly in referring to any type of radar antenna.
Industry:Weather
