- 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 method of winds-aloft observation, that is, the determination of wind speeds and directions in the atmosphere above a station. This is done by reading the elevation and azimuth angles of a theodolite while visually tracking a pilot balloon. The ascension rate of the balloon is approximately determined by careful inflation to a given total lift. After release from the ground, periodic readings (usually at one-minute intervals) of elevation and azimuth angles of the balloon are recorded. These data are transferred to a winds- aloft plotting board, and the wind speed and direction at selected levels are calculated by trigonometric methods. See graphing board, winds-aloft plotting board; Compare rabal, rawin, rawinsonde, double-theodolite observation.
Industry:Weather
A type of aviation weather observation; the most complete of all such observations, usually taken at regularly specified and equal intervals (hourly, usually on the hour). This type of observation has been replaced by the METAR.
Industry:Weather
A front that is stationary or nearly so. Conventionally, a front that is moving at a speed less than about five knots is generally considered to be quasi-stationary. In synoptic chart analysis, a quasi-stationary front is one that has not moved appreciably from its position on the last previous synoptic chart (three or six hours before).
Industry:Weather
A very stable radio frequency local oscillator used in radio and radar for mixing received signals to produce an intermediate frequency signal. See heterodyne.
Industry:Weather
A very stable radio frequency local oscillator used in radio and radar for mixing received signals to produce an intermediate frequency signal. See heterodyne.
Industry:Weather
Sound-wave transmitting and receiving equipment operated on principles analogous to those of radar. Irregularities in atmospheric temperature and wind velocity constitute sources of scattering for acoustic waves. Sodars measure vertical profiles of the mean and turbulent properties of the sound to heights of several hundred meters by transmitting acoustic waves upward and measuring the Doppler shift in the backscattered acoustic signals. Sodar is sometimes inappropriately called acoustic radar.
Industry:Weather
An electronic instrument used for the detection and ranging of distant objects of such composition that they scatter or reflect radio energy. A radar consists of a transmitter, receiver, antenna, display, and associated equipment for control and signal processing. The most common radars are monostatic radars, which use the same antenna for both transmission and reception. These radars depend on backscattering to produce a detectable echo from a target. Bistatic radars have the transmitter and its antenna at one location and the receiver and its antenna at a remote location. These radars depend upon forward scattering to produce a detectable signal. Radio energy emitted by the transmitter and focused by the antenna of a monostatic radar propagates outward through the atmosphere in a narrow beam. Objects lying in the path of the beam reflect, scatter, and absorb the energy. A small portion of the reflected and scattered energy, called the target signal, travels back along the same path through the atmosphere and is intercepted by the receiving antenna. The time delay between the transmitted signal and the target signal is used to determine the distance or slant range of the target from the radar. The direction in which the focused beam is pointing at the instant the target signal is received (i.e., the azimuth and elevation angles of the antenna) determine the direction and height of the target. This information is presented visually as echoes on different types of radar displays. Because hydrometeors scatter radio energy, weather radars, operating in certain radar frequency bands, can detect the presence of precipitation and other weather phenomena at distances up to several hundred kilometers from the radar, depending upon meteorological conditions and the type of radar. MST radars and wind profilers, which operate at longer wavelengths than weather radars, are able to detect echoes from optically clear air that are caused by spatial fluctuations of refractivity. Additional information provided by a radar about a target may include the radial velocity or rate of change of range, as measured by a Doppler radar, or the depolarizing characteristics of the target, as measured by a polarimetric radar.
Industry:Weather
A simple remapping scheme for polar-orbiting satellites designed to remove some of the distortion caused by the increasing sensor field of view towards the extreme limits of a scan swath. In modern processing systems it is more common to just remap the digital imagery to an extreme map projection.
Industry:Weather
Literally “dry wind”; in Russia, a dry, hot, dusty wind in the southern steppes. It blows principally from the east and frequently brings a prolonged drought and crop damage.
Industry:Weather
An electronic instrument used for the detection and ranging of distant objects of such composition that they scatter or reflect radio energy. A radar consists of a transmitter, receiver, antenna, display, and associated equipment for control and signal processing. The most common radars are monostatic radars, which use the same antenna for both transmission and reception. These radars depend on backscattering to produce a detectable echo from a target. Bistatic radars have the transmitter and its antenna at one location and the receiver and its antenna at a remote location. These radars depend upon forward scattering to produce a detectable signal. Radio energy emitted by the transmitter and focused by the antenna of a monostatic radar propagates outward through the atmosphere in a narrow beam. Objects lying in the path of the beam reflect, scatter, and absorb the energy. A small portion of the reflected and scattered energy, called the target signal, travels back along the same path through the atmosphere and is intercepted by the receiving antenna. The time delay between the transmitted signal and the target signal is used to determine the distance or slant range of the target from the radar. The direction in which the focused beam is pointing at the instant the target signal is received (i.e., the azimuth and elevation angles of the antenna) determine the direction and height of the target. This information is presented visually as echoes on different types of radar displays. Because hydrometeors scatter radio energy, weather radars, operating in certain radar frequency bands, can detect the presence of precipitation and other weather phenomena at distances up to several hundred kilometers from the radar, depending upon meteorological conditions and the type of radar. MST radars and wind profilers, which operate at longer wavelengths than weather radars, are able to detect echoes from optically clear air that are caused by spatial fluctuations of refractivity. Additional information provided by a radar about a target may include the radial velocity or rate of change of range, as measured by a Doppler radar, or the depolarizing characteristics of the target, as measured by a polarimetric radar.
Industry:Weather
