Electrical and computer engineers from the Microwave Remote Sensing Laboratory (MIRSL) are currently spending 15 hours per day scouring Oklahoma and the Great Plains in their two truck-mounted mobile Doppler radar systems as part of the largest, most ambitious study ever launched to figure out how tornadoes form and predict them more accurately. Overall goals of the national project, known as the Verification of the Origins of Rotation in Tornadoes Experiment 2, or VORTEX2, include giving people earlier warning of severe weather and reducing the number of false positive warnings issued.
VORTEX2 involves more than 50 scientists and 10 mobile radars, which sample the wind, temperature, and moisture environments in tornado-spawning storms in great detail.
One of the UMass Amherst truck-mounted Doppler radars brings the highest spatial resolution of any mobile Doppler radar in the nation to the study. It is able to see behind rain and hail in supercell thunderstorms at ground level. “Our millimeter-wave radar is the finest resolution radar available for tornado detection, far finer than conventional stationary radars,” says Electrical and Computer Engineering Professor Stephen Frasier, team leader and director of MIRSL.
The $11.9 million national tornado study lasts from early May to mid-June when severe storms are most common. The two UMass Amherst graduate students on the team are Vijay Venkatesh and Krzysztof Orzel. They are spending many hours a day chasing promising storm cells and, with any luck, they’ll capture data from a handful of actual tornadoes as they form. Another overall VORTEX2 goal is to build a complete observation network around and under a supercell storm.
An exciting aspect of VORTEX2 is that the UMass Amherst W-band radar must be deployed within a few miles of tornadoes embedded in monster storms that can be tens of miles wide. Peril is reduced by approaching storms from the side, Frasier says. Inside the truck, the engineers use radar to measure wind speed, density of raindrops, wind shear, and other variables. Frasier says this radar is important to VORTEX2 because “it provides the best possible opportunity to map the wind field at the lowest levels of tornadoes. It also has the best chance to document the structure of multiple, sub-tornado-scale vortices, which are thought to cause much of the localized, extreme damage in some tornadoes.”
The other MIRSL truck, carrying what is known as X-band polarimetric radar, beams a 9.4 GHz signal at thunderheads from many miles away to see the whole storm at once. Wind data from the X-band radar will also be used in conjunction with data from the other X-band radars in the field to do multiple-Doppler analysis.
The initial VORTEX study in 1994-95 allowed scientists to document the entire life-cycle of a tornado for the first time in history, according to the National Oceanic and Atmospheric Administration (NOAA). An important finding from that original experiment is that the factors responsible for causing tornadoes happen on smaller time and space scales than scientists had thought.
VORTEX2 is supported by NOAA, the National Science Foundation, 10 universities, and three nonprofits to provide forecasters with more tools to improve tornado warning times and short-term severe weather alerts. (May 2010)