The Nexrad radar operates at S-band frequencies (2.7 to 3 GHz) and is equipped with a 28-foot- (8.5-metre-) diameter antenna. High-speed communication lines integrated with the Nexrad system allow timely weather information to be transmitted for display to various users. The computer automatically identifies severe weather effects and indicates their nature on a display viewed by the observer. The spread in radial speed is an indication of wind turbulence.Īnother improvement in the weather information provided by Nexrad is the digital processing of radar data, a procedure that renders the information in a form that can be interpreted by an observer who is not necessarily a meteorologist. In addition to measuring precipitation (from the intensity of the echo signal) and radial speed (from the Doppler frequency shift), Nexrad also measures the spread in radial speed (difference between the maximum and the minimum speeds) of the precipitation particles within each radar resolution cell. The pulse Doppler weather radars employed by the National Weather Service, which are known as Nexrad, make quantitative measurements of precipitation, warn of potential flooding or dangerous hail, provide wind speed and direction, indicate the presence of wind shear and gust fronts, track storms, predict thunderstorms, and provide other meteorological information. (Rotation is indicated when the measurement of the Doppler frequency shift shows that the wind is coming toward the radar at one angle and away from it at a nearby angle.) Since tornadoes, mesocyclones (which spawn tornadoes), hurricanes, and other hazardous weather phenomena tend to rotate, measurement of the radial wind speed as a function of viewing angle will identify rotating weather patterns.
The Doppler frequency shift is important because it is related to the radial velocity of the precipitation blown by wind (the component of the wind moving either toward or away from the radar installation). A major improvement in the capability of weather radar came about when engineers developed new radars that could measure the Doppler frequency shift in addition to the magnitude of the echo signal reflected from precipitation. This application of radar is well known in the United States from the familiar television weather reports of precipitation observed by the radars of the National Weather Service. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!įor many years radar has been used to provide information about the intensity and extent of rain and other forms of precipitation.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.
BIG WEATHER RADAR HOW TO
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