Why is Doppler radar an improvement over previous technologies?

Answer 1

It only returns echoes from moving objects.

Standard radar would return an echo from a mountain when you point it in the direction of the mountain. If you wanted to see what was in the sky in that direction you would have a problem since you would need to block out the strong returns coming from the radar when it was turned toward the mountain. Or think of a radar watching planes at an airport that could not see a plane that was on the same azimuth as the airport's control tower - that is useless.

Doppler processes the echoes to show only those from moving objects and has more practical value in most regions where stationary targets are common.

Answer 2

It provides new information. Any radar will reflect from a metal surface, whether it's moving or not. Older radar just measured the distance, by measuring the time delay between sending the pulse and receiving the reflection. If you make two measurements a few seconds apart, you can estimate speed by seeing the difference in distance and knowing how much time passed. Uncertainty about the two distance measurements limits the accuracy of the speed estimate.

Doppler radar detects not only the presence, but also the exact frequency of the returning echo. The Doppler effect says that something moving toward you will shift frequencies up, and something moving away shifts frequencies down. Faster movement toward or away from you shifts the frequency more. The frequency shift can be measured very accurately, so Doppler radar can give a better speed measurement, and with only one pulse.

If there are multiple targets, each can return an echo with a different Doppler shift. Police speed enforcement radar picks out the highest frequency shift as the one of interest.

Answer 3

Because... it isn't?

Doppler Radar is only one of many radar technologies that all have different applications. Just because we have Doppler radar does not mean we are not using anything else.

I think whoever thought of that question might have had a certain application in mind. It might be useful to know what that application was before speculating about the right answer to the question.

Answer 4

Looking at the first radars all you would see would be a large blob on the radar screen that showed the extent of a storm and maybe it's direction of travel.

Intensity, tornadoes, etc were only detected by observers on the ground.

Doppler Radar measures the speed and direction of movement in the storm which identifies likely tornadoes and other intense activities, like wind shear (which has caused planes to crash on take-off and landing).

Bu identifying the "signature" of a tornado they can give warnings far enough in advance for people to react.