The term "Doppler" often refers to the Doppler Effect, named after the Austrian physicist Christian Doppler. This phenomenon describes the change in frequency or wavelength of a wave relative to an observer who is moving relative to the wave source. You might be most familiar with it in terms of sound: when a vehicle with a siren passes by, the pitch of the siren seems higher as it approaches and lower as it moves away. This effect applies to all types of waves, including light.

In weather forecasting, Doppler radar is used to measure the velocity of objects, like raindrops, within a storm. This helps meteorologists determine the intensity and movement of storms.

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