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Section R R index 1-9 of 589 terms
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R-meter—Analog radar device used in the 1950s to measure the fluctuation rate of the detected target signal from which may be estimated the root-mean-square relative velocity among the scatterers in the pulse volume. This approach was made obsolete when pulsed Doppler radar was introduced to meteorology in the late 1950s.
R-scope—A radar display with coordinates of received signal amplitude versus range but differing from the A-display by starting from a range offset from zero.
rabal—A method of winds-aloft observation; that is, the determination of wind speeds and directions in the atmosphere above a station. It is accomplished by recording the elevation and azimuth angles of the balloon at specified time intervals while visually tracking a radiosonde balloon with a theodolite. A rabal is basically the same as a pilot-balloon observation, except that the height data are derived from the radiosonde observation rather than from an assumed balloon ascension rate.
racoon—A zero-pressure balloon flying high above a very cold tropopause in tropical or summer midlatitudes. When the balloon cools and descends at night, its radiation temperature does not change, but its lift increases as it descends to the colder levels. The lost lift is overcome and the balloon floats at a lower altitude without the need for ballast. The flight altitude of the balloon is radiation- controlled.
radar algorithm—A computer program that automatically detects the presence of desired features or signatures in radar data.
radar altimeter—(Also called radio altimeter.) An onboard radar for determining the altitude of an aircraft above an underlying surface. Pulse-radar techniques measure altitude in terms of the transit time of the radar pulse; continuous-wave radar measures altitude in terms of the phase difference between the transmitted and received signals.
radar altitude—The altitude of an aircraft as determined by radar-type radio altimeter; thus, the actual distance from the nearest terrain feature. For all practical purposes, the radar altitude over oceans is equal to the height above mean sea level.
radar band—1. A radar frequency band. 2. A precipitation band.
radar beam—The focused electromagnetic emissions from a radar antenna. The beam is defined by the main lobe of the antenna pattern.
radar calibration—1. The act of determining the proportionality factor or radar constant that relates the radar reflectivity of a target to the power measured at the output of a radar receiver. 2. The numerical value of the radar constant that associates target reflectivity and measured power. See radar equation.
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