- 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 variation of multiple linear regression analysis for prediction of the occurrence or nonoccurrence of an event. To account for the nonnumerical nature of the predictand, a discriminant function is used as a type of regression function usually derived in such a way that positive values of the function correspond to “occurrence” and negative values to “nonoccurrence. ” In meteorology, for example, the occurrence of precipitation (the predictand) can be related to measures of vertical velocity, dewpoint temperature, pressure change, and other variables (the predictors) through a discriminant function. Values of the function above or below a threshold value (typically, zero) can be used to predict precipitation occurrence.
Industry:Weather
Approximating the solution of a continuous problem by representing it in terms of a discrete set of elements. Examples include representing a continuous fluid field at a set of grid points or in terms of a sum of basis functions.
Industry:Weather
A spectrum in which the component wavelengths (and wavenumbers and frequencies) constitute a discrete sequence of values (finite or infinite in number) rather than a continuum of values. A Fourier analysis of a function will yield a discrete spectrum only if the function is periodic, or is assumed to be so, or if the function is represented by a finite sample of its values. Fourier series may be used for the analysis. See continuous spectrum.
Industry:Weather
A situation that occurs in statically stable regions of the atmospheric boundary layer where turbulence is not contiguous, either vertically or horizontally. For example, in the nighttime stable boundary layer one or more layers of turbulence can form that are separated by nonturbulent (laminar) layers. This situation is very difficult to model because the turbulence in each layer does not interact with the surface and thus can evolve separately. During daytime at the top of a convective mixed layer, there is usually a statically stable capping inversion or entrainment zone where turbulent thermals penetrating the layer are separated by regions of laminar air from the free atmosphere. Aircraft flying horizontally through this region would experience intermittent turbulence.
Industry:Weather
Used in fluid mechanics; the ratio of the actual to the theoretical discharge through an orifice, nozzle, weir, or any other opening or passage.
Industry:Weather
The abrupt variation or jump of a variable at a line or surface. Discontinuities are said to be of zero order when an undifferentiated quantity is discontinuous, or of first order when a first derivative of the quantity is discontinuous, etc. See interface, front, surface of discontinuity.
Industry:Weather
Section of a river that is at a right angle with the line connecting the deepest points of the river bed.
Industry:Weather
1. In subsurface hydrology, the area of an aquifer from which water is discharged by evapotranspiration, springs, seepage to streams, and leakage to other aquifers. 2. In surface hydrology, the area of a stream or a pipeline perpendicular to the velocity vector used for the calculation of the rate of flow.
Industry:Weather
1. See electric discharge. 2. The volumetric rate of flow or volume flux.
Industry:Weather
The class of nephoscope in which the observer notes the motion of the cloud by looking directly at it through the instrument. These instruments consist of some form of rectangular gridwork supported on a column and free to rotate about the vertical axis. The observer aligns the gridwork so that the cloud appears to move parallel to its major axis. See comb nephoscope, grid nephoscope.
Industry:Weather
