- 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 measure of the strength of the easterly surface wind between the latitudes of 20° and 35°N. The index is computed from the average sea level pressure difference between these latitudes and is expressed as the east to west component of the corresponding geostrophic wind to the tenth of a meter per second. Compare zonal index, polar-easterlies index, temperate-westerlies index.
Industry:Weather
A measure of the extinction due to scattering of monochromatic radiation as it traverses a medium containing scattering particles. Usually expressed as a volume scattering coefficient with units of reciprocal length (i.e., area per unit volume), but also as a mass scattering coefficient with units of area per unit mass.
Industry:Weather
A measure of the intensity of rainfall by calculating the amount of rain that would fall over a given interval of time if the rainfall intensity were constant over that time period. The rate is typically expressed in terms of length (depth) per unit time, for example, millimeters per hour, or inches per hour.
Industry:Weather
A measure of the state of the Southern Oscillation. A common index used for this purpose is the sea level pressure at Tahiti minus the sea level pressure at Darwin, Australia, divided by the standard deviation of that quantity. It is closely associated with El Niño and is thus often referred to as ENSO (El Niño–Southern Oscillation).
Industry:Weather
A measure of the relative phase between two meteorological variables, segregated by wavelength. It is the phase difference for any frequency between two time series that yields the greatest correlation. The phase spectrum is computed as the arctangent of the ratio of the quadrature spectrum to the cospectrum. For example, turbulence usually consists of vertical velocity and potential temperature either in phase (for daytime convection) or 180° out of phase (for turbulence in a statically stable environment). However, gravity waves usually consist of vertical velocity and potential temperature that are 90° out of phase. Thus, if one were analyzing the cross spectra at night in a stable boundary layer, and found 90° phase shift for the longer wavelengths, but 180° for the shorter wavelengths, then one could infer that long-wavelength gravity waves are propagating through a region of small-eddy turbulence.
Industry:Weather
A measure of the noise power density at the output of a radio or radar receiver due to internally generated noise and passive losses in the receiver. In particular, the receiver temperature ''T<sub>r</sub>'' is the temperature of a resistor having noise power per unit bandwidth equal to that of the receiver output at a given frequency. It is given in terms of the power output ''P'' and bandwidth ''B'' of the receiver by ''T<sub>r</sub>'' = ''P''/''kB'', where ''k'' denotes Boltzmann's constant, 1. 38 × 10<sup>−23</sup>J K<sup>−1</sup>. The receiver temperature is related to the receiver noise factor ''F'' by ''T<sub>r</sub>'' = ''T<sub>o</sub>''(''F'' − 1) with ''T<sub>o</sub>'' = 290 K. See noise temperature, noise figure.
Industry:Weather
A measure of the length of time that molecules will stay in a chamber or region. It can be estimated by dividing the volume of a chamber or region by the volumetric flow rate through it. For example, the residence time of air in clouds is important for aqueous-phase chemical reactions and for the size to which hydrometeors can grow.
Industry:Weather
A knowledge-based system that uses rules as its knowledge representation. See'' also'' expert system.
Industry:Weather
A labeled, directed graph with nodes representing physical or conceptual objects and labeled arcs representing relations between objects. This permits the use of generic rules, inheritance, and object-oriented programming, which in turn allow the development of meteorological expert systems that can be adapted to more than one location.
Industry:Weather
it is defined as the force per unit area that must be exerted in order to extract water from soil.A measure of the amount of work that must be done (suction that would need to be applied) to move water in the soil. Also the energy of retention at the outer edge of the moisture film of the soil particles. Tensions are generally expressed in pascals, bars, or atmospheres. See water potential.
Industry:Weather
