Deployed in the early 1990s, the network of Doppler radars run by the National Weather Service now totals 150-plus stations across the country that track storms and serve as the source of many of the radar maps on TV and the Internet. Underlying all this is the Doppler effect, which dictates that when radar energy bounces off a thundercloud and returns, its frequency changes just enough for a computer to determine not only a storm's location (which any radar can do) but also its velocity and intensity. (It's like how your ears process frequency shifts when an ambulance races by.) Then there's Super Doppler, which is ... Doppler with better marketing. Still, truly super Dopplers are coming soon, says Doug Forsyth, chief of radar research and development at the NOAA National Severe Storms Lab, in Norman, Oklahoma: "We'll start deploying dual-polarization upgrades—which can distinguish better between rain and hail—at the end of this year."
Filed To: Science