What Is Doppler Radar?

Doppler radar sends microwave pulses that bounce off precipitation or particles. If the target moves toward the radar, the reflected signal returns at a higher frequency; if away, a lower frequency. This Doppler shift reveals the radial velocity. The U.S. NEXRAD network (159 stations) can detect wind speeds inside storms, identify tornado rotation signatures up to 30 minutes before a tornado forms, and estimate rainfall rates. Dual-polarisation Doppler radar distinguishes rain from hail, snow, and debris. Police speed guns also use Doppler radar.