Q: What exactly is “Doppler radar” that the weather folks refer to?
A: It’s the type of radar that uses sound waves to detect strength and movement of severe storms, says Brent McRoberts of Texas A&M University. It’s named after the Austrian scientist Christian Doppler, who in 1842 discovered many of the principles of sound waves that we know today. “Doppler radar allows us to observe the movement of precipitation, such as rainfall or even snowfall and ice crystals, by using sound waves that bounce off these substances,” he says. “Water drops and snow and ice will reflect a sound wave and send it back to a transmitter or receiver and because it’s so precise, Doppler can tell us the movement of storms and how intense they are. It usually does this with the use of a colored monitor or screen showing severe storms as dark green, blue or red.”
Q: Is Doppler radar effective?
A: Very much so, notes McRoberts. “It’s the most advanced weather radar system there is,” he explains. “The unique aspect of Doppler radar is that it allows us to look inside a storm. We can project rainfall amounts and detect the movement of storms, even tornadoes, better than ever, and this gives meteorologists a method to give the public advance warnings, sometimes even up to an hour. Up until the 1980s, many weather stations were using radar technology that was used in the 1940s and 1950s. Doppler radar eventually replaced all of those. Today, there are 160 Doppler sites around the U.S., and about 113 of these are operated by the National Weather Service. The rest are used by the Federal Aviation Administration (FAA) or by the Department of Defense.”
Weather Whys is a service of Texas A&M University’s Department of Atmospheric Sciences.