Weather radar highlights of NSSL's first 40 years

The Weather Bureau's first experimental Doppler Radar unit

The Weather Bureau's first experimental Doppler Radar unit. This radar was a 3-cm continuous wave Doppler unit obtained from the Navy and modified for meteorological purposes.

Don Burgess points out details in Doppler reflectivity, velocigy and spectrum width data.

NSSL engineers developed real-time color displays in the late 1970's; here, Don Burgess points out details in Doppler reflectivity, velocigy and spectrum width data.

Doppler Radar

In 1964, scientists were working to acquire additional radar technology. A 3-cm wavelength research Doppler radar was added to NSSL's list of assets — a move that would revolutionize weather observation. This new radar allowed scientists to delve into and measure motion inside the storm for the very first time — providing valuable clues into the development of severe weather. A change in frequency occurred when a radar signal was reflected from a moving target, such as a cluster of raindrops — similar to the shift in frequency experienced with a passing sound (e.g., when a train blowing its whistle passes by). When they measured this shift in frequency, scientists could tell if particles were moving towards or away from the radar. It is this ability to discern internal air circulation that makes Doppler radar such a powerful weather-monitoring tool.

Scientists and engineers soon discovered the 3-cm radar was not powerful enough for a large-scale storm surveillance network, and NSSL embarked on a program to develop a much stronger 10-cm Doppler radar. In 1969, NSSL was able to obtain and upgrade a surplus 10-cm radar that had been used by the U.S. Air Force.

The 10-cm Doppler radar in Norman became operational during the 1971 spring tornado season. Data were collected on magnetic tapes and processed on a NASA computer weeks or even months later because there was no real-time capability.

Scientists made many significant discoveries using these data, but one of the most important was the discovery of the tornadic vortex signature. When a circulation begins to form, its winds blow raindrops in a signature pattern on the radar screen. In May of 1973, a devastating tornado tore through Union City, Okla., a town just west of Oklahoma City. For the first time, Doppler radar and storm intercept teams documented the entire life cycle of the tornado. In reviewing the data, researchers discovered that a small-scale Doppler velocity circulation appeared aloft even before the tornado descended to the ground — a feature that would allow forecasters to better warn the public of the impending danger.

Additional research on thunderstorms led to the Joint Doppler Operational Project, which tested the warning potential of the Doppler radar. JDOP conclusively showed that Doppler radar had the potential to assist in issuing more accurate warnings, and more importantly, warnings with enough lead time for the public to find safe shelter.


Further advances...