Our ability to understand natural forces is only as good as the tools we have to study them. One highlight in this regard is Doppler radar, developed in the mid-1970s with the help of NSF funds. Since the 1960s, meteorologists' ability to predict violent weather patterns has depended largely on two kinds of technology: an array of orbiting space satellites that observe Earth's environment on a scale not previously possible, and ground-based radar technology. Radar peers inside clouds for clues about their potential for severe weather by sending out electromagnetic pulses that bounce off particles and return with valuable information about the location and intensity of precipitation. Most weather radars send out signals with relatively short wavelengths that, while offering a precise picture of a cloud's interior, can be absorbed by the very particles they're supposed to measure. On the other hand, Doppler radar uses longer wavelengths, so that even distant weather systems will appear on the radar screen with accurately rendered intensity. What's more, Doppler radar provides additional information (such as the velocity at which precipitation is moving) that is critical to short-term forecasting.
In the last decade, the National Weather Service has installed Doppler radar systems at fixed locations across the country, improving meteorologists' ability to issue timely flash flood and severe thunderstorm warnings and cutting by more than 60 percent the number of tornadoes that strike without public notice. Recently NSF-funded scientists have also begun experimenting with more advanced mobile Doppler instruments mounted on flat-bed trucks, which allow the hardier breed of researcher to chase down storms for even more precise readings.
With Doppler radar, NCAR scientists helped a University of Chicago wind expert, the late T. Theodore Fujita, to confirm in the 1980s a whole new atmospheric hazardthe microburst. Microbursts are concentrated blasts of downdrafts from thunderstorms that have been responsible for airplane crashes killing more than five hundred people in the United States. And in 1999, NCAR researchers began testing whether Doppler radar systems installed on airplanes can detect so-called convective turbulence, associated with storms and clouds, which can rip sections off small planes and injure crew and passengers.
Another significant new observing technology developed at NCAR is a probe employed by hurricane-hunting aircraft. The probes are dropped from government planes into offshore hurricanes to profile previously hard-to-measure factors such as low-level winds, pressures, and temperatures around the storm's eye. Data from these probes have greatly improved the National Weather Service's ability to predict the course and intensity of hurricanes. Hurricanes develop over the warm tropical oceans and have sustained winds in excess of 75 miles per hour. One hundred years ago, coastal residents generally had less than a day's warning before a hurricane struck. Today, thanks to satellites and radar, these same residents know days in advance that a hurricane is maturing and moving their way.