Doppler Radar

A Doppler Radar uses the Doppler effect of returned echoes from certain objects to measure their radial velocity. They are used for various things including air traffic control, police speed guns, and air defense. Here is a photograph from a Doppler Radar of Hurricane Andrew that hit Miami and caused extreme damage. This is a Doppler Radar picture of Hurricane Charley. Doppler radar picks up the precipitation (and may also pick up fog, smoke, etc.). The green and blue shades are the lighter precipitation. The yellow, orange and red (and sometimes purple) are where the heavier precipitation is.

http://www.weatherusa.net/blog/images/doppler-orlando-1943.gif