This radar is called Doppler radar. This radar is a very specialized radar that uses the doppler effect to produce data about objects. Remember that the Doppler effect is an increase or a decrease of the frequency of sound, light or other types of waves. It causes the sudden change of pitch: As an example, If you are waiting for a bus and then you see an ambulance with the sirens on then you can experience how the sound of the sirens increase as it gets closer to you and how decreases when is going far from you. Most modern radars use the doppler technique to examine the motion precipitation.