Doppler Radar Facts
Meteorologists use a device called Doppler radar to predict the weather. Without Doppler radar, we probably wouldn't be able to receive severe storm warnings and tornado warnings in advance. Thanks to modern technology, Doppler radar is capable of measuring precipitation patterns and determining whether a storm will be severe.
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What is Doppler Radar?
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Doppler radar measures Doppler shift in a radar beam. The beam is reflected based on an object's motion. The "Doppler effect" is used in radars in order to detect thunderstorms or tornadoes. Based on the extent of the red and blue shifts, angular velocity can be calculated. This measures precipitation patterns and is also capable of determining the severity of storms and whether a tornado is likely to develop in the general area.
Doppler Effect
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Christian Doppler, an Austrian physicist, proposed the "Doppler effect" in 1842. The Doppler effect is the apparent change in frequency of a wave for the person observing the moving source of the wave. For example, if an ambulance is coming toward you while it's far away, it sounds quiet. As it approaches, it gets louder. Once it passes by, the frequency is identical to the emitted frequency, and as it leaves, the frequency gets lower.
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Invention and History
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Dr. A. Hoyt Taylor at the Naval Research Laboratory in Washington, D.C., investigated radar in the 1920s. In 1935, Robert Wilson-Watt created the first pulsed radio wave system. After World War II, radar technology developed rapidly. During the 1950s, the weather service radar came out specifically for the study of tornadoes. NASA's Wind Shear Program worked to invent a sensor to warn pilots about microbursts so that winds could be avoided in order to prevent airplane crashes due to wind shears during landing and takeoff. This led to Doppler radar, complete with color animation.
Locations
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In the United States, the National Weather Service has Doppler radar locations in all 50 states. There are also Doppler radar sites in Guam and Puerto Rico, which are U.S. territories. A radar site in Cuba is run by the Department of Defense. Users with Internet can access and monitor any of the National Weather Service's Doppler radars online.
Doppler Radar Uses
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Doppler radar is used in more than just meteorology. In addition to aviation, Doppler radar is also employed in sounding satellites, police speed guns and radiology. A police radar gun is a small Doppler radar unit that is used in order to determine the speed of a moving object. Radar guns rely on the Doppler effect in order to measure the speed of objects. In radiology, color-flow Doppler ultrasounds are used to measure the stage of peripheral vascular disease in cardiology. Doppler technology is also used to allow a mother to listen to her unborn child's heartbeat.
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References
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- Photo Credit radar image by alain baron from Fotolia.com
