- Doppler weather radar
The Doppler weather radar is named after the Austrian physicist J.C. Doppler who hypothesized that the frequency of acoustic or sound waves from a moving source -- such as a train -- would increase as they approached a listener and decrease as they moved away. He was right.
As a train comes towards the listener, the whistle's pitch climbs as the motion of the train compresses the sound wave. When the train speeds away, the pitch drops because the sound wave is no longer being compressed by the motion. This process is called a frequency shift and is known as the Doppler effect.
Doppler weather radar uses the same principle to track the size, concentration, and relative motion of precipitation in storm systems. This helps meteorologists identify tornadoes in the early stages of development
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