- 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, ...
An atmospheric tide due to gravitational attraction of the sun or moon. The semidiurnal solar atmospheric tide is partly gravitational; the semidiurnal lunar atmospheric tide is totally gravitational. See thermal tide, tide-producing force.
Industry:Weather
An approximation to a differential equation that uses a linear combination of basis functions with weights determined by minimizing a globally integrated measure of the error in the solution. The resulting error is orthogonal to each basis function in an integral sense. Finite-element approximations result when piecewise linear basis functions are selected. Spectral approximations are produced when spherical harmonic basis functions are selected over spherical domains. See finite-element model.
Industry:Weather
An arbitrarily fixed and generally accepted gauge height or elevation above which a rise in the water surface elevation is termed a flood. It is commonly fixed as the stage at which overflow of the normal banks or damage to property would begin.
Industry:Weather
An approximation made to solve turbulence equations that assumes turbulent fluxes of a quantity such as moisture flow down the mean gradient of moisture, where the rate of flow is proportional to an eddy diffusivity. The symbol for eddy diffusivity is often K, hence this theory is also known as K-theory. By first order, it is implied that any turbulence statistics of second or higher order (variances, covariances, etc. ) that appear in the governing equations are replaced by approximations that depend only on first-order statistics (i.e., mean values of the dependent variables and of independent variables). Such an approximation reduces the number of unknowns in the governing equations, allowing them to be mathematically closed, thereby allowing them to be solved for the approximate flow state. First-order closure can be applied locally (as in K-theory) or nonlocally (as in transilient turbulence theory). See also closure assumptions, closure problem.
Industry:Weather
An approximate theory of near-forward scattering of electromagnetic waves by objects large compared with the wavelength. This theory is independent of the composition of the objects and the state of polarization of the illumination.
Industry:Weather
An apparent fog in the distance where no fog actually exists. The appearance is sufficiently compelling that one can observe ships, say, vanishing into or emerging from the seeming fog. The fata bromosa seems to be an infrequent partner of the superior mirage. The name translates as “fairy fog. ” Compare fata morgana.
Industry:Weather
An alternative, somewhat inappropriate, name for the atmospheric boundary layer. In the real atmosphere, turbulent drag, rather than molecular friction, is responsible for reducing wind speeds in the boundary layer. Another inappropriate name for the friction layer is the Ekman layer, where turbulence is modeled similar to molecular friction except that an eddy viscosity is used in place of a molecular viscosity.
Industry:Weather
An air layer with its base at the ground surface and in which temperature increases with height. These often form at night over land under clear skies and are statically stable. See inversion, lapse rate.
Industry:Weather
An air velocity sensing instrument usually mounted on the front of an aircraft that resolves turbulent fluctuations in all three components relative to the aircraft. Instruments used for this purpose include differential pressure probes, vanes, and heated wires (hot-wire anemometers). To measure the air velocity relative to the earth, the gust probe measurements must be corrected for the aircraft attitude and velocity.
Industry:Weather
Amount of water held in a soil after drainage of gravitational water. Gravitational water typically drains from a soil within a few days of wetting.
Industry:Weather
