- 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, ...
In radar, a device for supporting and positioning the antenna. Typically, the pedestal allows the azimuth and elevation angles of the antenna to be controlled separately or in a coordinated way to permit different methods of scanning.
Industry:Weather
In radar terminology, the decrease of power density with range in accordance with the inverse-square law as a result of the divergence of the beam. For one-way transmission, this attenuation is proportional to 1/''r''<sup>2</sup> where ''r'' is the range from the antenna. For a monostatic radar and a point target, the range attenuation is proportional to 1/''r''<sup>4</sup> because the beam diverges on the outward path and the return path. For monostatic radar and a distributed target, the range attenuation varies between these two limits, depending on the extent to which the pulse volume is filled with precipitation or other scatterers. Range attenuation only arises from the spreading of the attenuation with distance and should not be confused with attenuation caused by scattering and absorption. See radar equation, beam filling, range normalization.
Industry:Weather
In radar and lidar, adjustment of the received power to compensate for the divergence of radiant flux density with range. The received power is multiplied by (''r''/''r''<sub>0</sub>)<sup>2</sup>, where ''r'' is the range and ''r''<sub>0</sub> is an arbitrary reference range (e.g., 1 km). This normalization assumes that a distributed target fills the pulse volume at range ''r'' (See beam filling) so that the size of the scattering volume increases with ''r''<sup>2</sup> even as the incident flux density decreases with ''r''<sup>2</sup>. The normalization in effect corrects for the flux divergence on the return trip from the scattering volume to the receiver. See lidar equation, radar equation.
Industry:Weather
In physics, usually the density of water at the ice point (0°C), 0. 99984 g cm<sup>−3</sup>; or the maximum density of water (at 4°C), 0. 99997 g cm<sup>−3</sup>. In the U. S. Standard Atmosphere–1976, the density of air at a standard temperature of 15°C and a standard pressure of 1013. 25 mb is 1225. 00 g cm<sup>−3</sup>.
Industry:Weather
In radar meteorology, the motion of the radar antenna during data collection. Scanning usually follows a systematic pattern involving one of the following: 1) In horizontal scanning, used to generate PPI displays, the antenna is continuously rotated in azimuth around the horizon or is rotated back and forth in a sector (sector scanning); at the completion of each 360° or sector scan, the elevation angle of the scan typically is increased; 2) Vertical scanning, used to generate RHI displays, is accomplished by holding the azimuth constant while continuously varying the elevation angle of the antenna; at the completion of each vertical scan, the azimuth typically is incremented and the vertical scan proceeds in the opposite direction. See'' also'' volume scan.
Industry:Weather
In radar meteorology, the looping flight path described by an aircraft's track during storm investigation.
Industry:Weather
In radar meteorology, a characteristic pattern observed on RHI or THI displays caused by snow falling from an isolated region in space or a generating cell. The shape of the trajectory depends on the wind speed at the altitude of origin of the snow, the fall speed of the snow, and the vertical profile of the ambient wind through which the snow falls.
Industry:Weather
In pulsed radar, an echo from a given pulse that is not received until after the transmission of the next pulse. See maximum unambiguous range.
Industry:Weather
In physics, usually the ice point (0°C); less frequently, the temperature of maximum water density (4°C). In meteorology, this has no generally accepted meaning, except that it may refer to the temperature at zero pressure altitude in the standard atmosphere (15°C).
Industry:Weather
