How Does Doppler Radar Work?
Doppler radar uses the “Doppler effect” to determine the movement of the particles (rain drops, hail, ice crystals) that are reflecting the radar’s signal back to the radar. Movement either toward or away from the radar along the radar beam, or radial, is all that can be detected, hence the term radial velocity. This movement is detectable because the frequency of the reflected signal is shifted, due to the movement of the rain or ice particles as they are blown around by the wind. This frequency shift is termed the Doppler effect after the Austrian physicist Christian Doppler, who discovered it. We experience this frequency shift in our lives every day. Picture yourself at a railroad crossing, waiting for the train to pass so you can drive on. The train in blowing its whistle as it approaches, and you can hear the pitch of the sound changing as the train nears. The pitch increases as the train approaches and then decreases as the train leads. You are standing still and the train, the
