- 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 radio or radar, the signal at the transmitted or received frequency, as opposed to a signal translated to a different frequency (IF signal) or a detected signal (video signal).
Industry:Weather
An imager designed to observe the sun's x-ray emissions providing earth detection and location of flares, loops, coronal holes and coronal mass ejections from the sun that are important for forecasting space weather. The SXI instrument captures a full disk solar image every minute. First flown on the GOES-12 satellite, this device will be included on the GOES-R series of satellites.
Industry:Weather
A phrase used in physics to indicate a temperature of 0°C and a pressure of one standard atmosphere.
Industry:Weather
Organic compound formed in the atmosphere from the addition of nitrogen dioxide, NO<sub>2</sub>, to the peroxyacyl radical formed in the oxidation of acetaldehyde. PAN and its larger homologs are irritants to the eyes and breathing system. They are formed in dangerous levels in photochemical smogs. The PANs are thermally quite stable “reservoir” species and can transport active nitrogen from polluted to pristine regions.
Industry:Weather
The term, now somewhat obsolete, used to denote the procedure of reducing the sensitivity of a radar receiver at close ranges to compensate for the limited dynamic range of the receiver and avoid saturation. The primary disadvantage of STC is that weak echoes at close range may be undetected because of the lowered sensitivity. The term is sometimes used erroneously to denote range correction of the received power to compensate for the inverse-square falloff of the power from distributed targets with range. See radar equation.
Industry:Weather
A principal cloud type (cloud genus) in the form of a gray layer with a rather uniform base. Stratus does not usually produce precipitation, but when it does occur it is in the form of minute particles, such as drizzle, ice crystals, or snow grains. Stratus often occurs in the form of ragged patches, or cloud fragments (stratus fractus), in which case rapid transformation is a common characteristic. Stratus clouds have characteristically low vertical velocities, usually less than 1 m s<sup>−1</sup>. When the sun is seen through the cloud, its outline is clearly discernible, and it may be accompanied by corona phenomena. In the immediate area of the solar disk, stratus may appear very white. Away from the sun, and at times when the cloud is sufficiently thick to obscure it, stratus gives off a weak, uniform luminance. The particulate composition of stratus is quite uniform, usually of fairly widely dispersed water droplets and, at lower temperatures, of ice crystals (although this is much less common). Halo phenomena may occur with this latter composition. Dense stratus often contains particles of precipitation. The prior existence of any other cloud in the low or middle levels is seldom required for the formation of stratus. A common mode of stratus development is the transformation of fog, the lower part of which evaporates while the upper part may rise (St nebulomutatus). As can be expected by its close relationship to fog, stratus follows a diurnal cycle with a maximum (over land) in the night and early morning. Insolation tends to dissipate this cloud rapidly, and often brings about the transformation of stratus fragments to cumulus clouds. Fog arriving from the sea frequently becomes stratus over the adjacent land. Coastal regions also provide the low-level moisture and frequently the lapse-rate stability conducive to its formation, and therefore these areas have the greatest stratus status. Stratus also develops from stratocumulus when the undersurface of the latter descends or for any reason loses its relief or apparent subdivisions (St stratocumulomutatus). Nimbostratus and cumulonimbus often produce stratus fractus, as precipitation from these clouds causes low-level condensation (St fractusnimbostratogenitus or St fractus cumulonimbogenitus). Stratus fractus in this form constitutes the accessory feature pannus of these mother-clouds. Stratocumulus and nimbostratus are the clouds most difficult to distinguish from stratus. Stratus is lower and lacks the uniform undulations or relief of stratocumulus. More difficulty is encountered when differentiating it from nimbostratus. Their modes of formation are different, nimbostratus usually having been formed from a preexisting mid- or low-level cloud; nimbostratus is more dense and has a wetter aspect, and its precipitation is of the ordinary varieties. As a final distinction, the wind accompanying nimbostratus is usually stronger than that with stratus. See cloud classification.
Industry:Weather
The microwave temperature and water vapor sounders on the DMSP polar-orbiting satellites. SSM/T is a temperature sounder, while SSM/T2 is a water vapor profiler. Many of the capabilities of the SSM/T and SSM/T2 instruments will be duplicated on the AMSU.
Industry:Weather
A three-channel infrared sounder on operational NOAA polar-orbiting satellites. The three channels are used to determine profiles of temperature in the stratosphere.
Industry:Weather
A passive conical-scanning multichannel microwave radiometer on DMSP satellites that is used to derive parameters such as land and sea surface temperature, ocean surface wind speed, precipitable water, rainfall rate, and snow/ ice cover.
Industry:Weather
A measure of the streamwise vorticity within the inflow environment of a convective storm. It is calculated by multiplying the storm-relative inflow velocity vector by the streamwise vorticity and integrating this quantity over the inflow depth. Geometrically, the storm-relative environmental helicity is represented by the area on a hodograph swept out by the storm-relative wind vectors between specified levels (typically the surface and 3 km to represent the primary storm inflow). It is thought to be a measure of the tendency of a supercell to rotate.
Industry:Weather
