NSF PR 99-37 - May 7, 1999
Media contact: |
Cheryl Dybas |
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cdybas@nsf.gov |
Program contact: |
Steve Nelson |
(703) 306-1526 |
snelson@nsf.gov |
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Mobile Doppler Radar Instruments Edge Closer to Swirling
Funnel Clouds
This Week's Oklahoma Tornadoes
Provide Highest-Resolution-Ever Data
Mobile Doppler radar instruments funded by the National
Science Foundation (NSF) and deployed by scientists
Howard Bluestein and Joshua Wurman of the University
of Oklahoma and Andrew Pazmany of the University of
Massachusetts are edging ever closer to the funnel
clouds of tornadoes -- including this week's devastating
storms in Oklahoma. One of these storms passed within
a half-mile of the mobile units.
NSF supports the two complementary projects with the
goal of understanding how tornadoes form and “decay,”
and the damage that might be expected from them. The
first project supports the “Doppler on Wheels,” which
has been jointly developed by the University of Oklahoma
and the NSF-sponsored National Center for Atmospheric
Research in Boulder, Colorado. These two mobile radars
-- one painted pink and yellow, the other blue and
green -- are mounted on two flat-bed trucks. Sporting
the radar instruments, the trucks become odd-looking
configurations of generators, equipment and operator
cabins. According to Wurman, who directs this project,
these radars are ideally suited to provide detailed
information on the three-dimensional wind and precipitation
distribution in the near vicinity of the tornado vortex.
The Doppler on Wheels team collected extensive data
on the genesis of the tornado that struck Moore, Oklahoma.
For many years, meteorologists have used Doppler radar
at fixed locations to monitor weather patterns, as
seen in weather forecasts on television. Due to advances
in technology, Doppler radar has evolved to the point
where it can be mounted to mobile platforms.
"The biggest advantage of the mobile Doppler radars
is that scientists can collect more data with better
precision," says Steve Nelson, program manager in
NSF's atmospheric sciences division, which funds the
mobile Doppler research. "Storms like tornadoes and
hurricanes rarely move in the path of ideally spaced
Doppler systems. Since we can't move the storm, it's
pretty convenient that we can move the radars."
The second radar system is managed by Bluestein and
Pazmany and transmits at a higher radio frequency.
In practical terms, this means that while this radar
can not cover as much area as the Doppler on Wheels,
it does provide finer details of the tornado. In the
storms that struck Oklahoma City, Bluestein and Pazmany
estimate that the radar resolution ranged between
6 and 15 meters. Due to the close proximity of the
radar to the vortex, unprecedented data was collected
at the contact point of the vortex with the ground.
The airflow in this lowest level is believed by scientists
to hold the key to many questions on tornado structure
and life cycle.
"On Monday, May 3rd," Bluestein relates, "which was
my first day out with the new system, we collected
data from a tornado a little more than an hour before
it moved through Oklahoma City, wreaking devastation
as it went." The monster storm tracked by the scientists
exhibited what is called "multivortex structure" --
several funnels - which within minutes turned into
a large single tornado. "Luckily," says a relieved
Bluestein, "when we were probing this storm, it was
out over open country. It did, however, remove a house
from its foundation a little under a mile away.”
Bluestein, Pazmany and Wurman hope to compare data
from this week's efforts with those of other colleagues
also tracking the storms. Notes Bluestein, "We should
soon have a much better picture of the inner workings
of a tornado."
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