Definition
A type of radar that measures the frequency shift of returned radio signals to determine the speed and direction of moving targets, such as precipitation particles or wind. In aviation weather use, it detects motion within storms, allowing identification of wind shear, turbulence, rotation, and precipitation intensity.
Plain English
A radar that does not just see where something is, but also tells how fast it is moving toward or away from the radar. In weather use, this lets it detect wind motion inside storms, not just rain.
Context Anchor
Seen in aviation weather reports and radar observation discussions, especially when pilots are looking at areas of precipitation, storms, or changing weather movement.
Derivation
Named after Christian Doppler, the 19th-century Austrian physicist who described how the observed frequency of a wave changes when the source or observer is moving. The radar uses this 'Doppler effect' to measure motion: signals bouncing off objects moving toward the radar return at a slightly higher frequency, and those moving away return at a slightly lower frequency.
Why Pilots Care
It reveals the speed and direction of precipitation, helping detect hazards such as microbursts and wind shear that can affect approach and departure paths.
Analogy
Like the change in pitch you hear when a siren passes by you on the road -- higher as it approaches, lower as it moves away. Doppler radar listens for that same kind of frequency change in its returned radio signals to measure motion.
Grounding Statement
If a storm is moving toward the radar, the returned radio waves change in one way; if it is moving away, they change in the opposite way.
Intuition Check
Doppler radar does not simply mean a sharper radar picture. The key idea is motion: it helps detect movement toward or away from the radar, not just location.
Example Sentence 1
The briefer noted that Doppler radar was showing strong rotation within the thunderstorm cell west of the airport.
Example Sentence 2
Doppler radar showed strong velocity shifts in the precipitation, indicating possible wind shear on final approach.