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Oh,
a storm is threatening
My very life today
If I don't get some shelter
Oh yeah, I'm gonna fade away … ("Gimme Shelter,"
The Rolling Stones)
April 22, 2009: Imagine a monster tornado is ripping
through a neighboring county and bearing down on yours.
If
you live in north Alabama, your forecasters are well prepared
to tell you when to seek shelter.
The
National Weather Service there shares a building – the National
Space Science and Technology Center – with NASA's Short-term
Prediction Research and Transition, or SPoRT, Center. SPoRT
puts state-of-the-art NASA satellite data directly into forecasters
hands, arming them to recognize weather that threatens your
safety.
Right:
The National Weather Service's Chris Darden (Science Operations
Officer) and Mike Coyne (Meteorologist In Charge) handle communications
during severe weather. [Larger
image]
"It's
not just a matter of them throwing random data sets over the
fence to us and hoping we might be able to use them,"
says Chris Darden from the National Weather Service (NWS).
"They work with us to figure out precisely what we need.
Then they put that data into a format we can read, actually
integrating it with our radar displays. And they train us
to understand and interpret the information they give us."
Dr.
Gary Jedlovec, SPoRT principal investigator, notes, "We're
all in this together in this building, and the public is the
ultimate winner. Adding our data to NWS weather models helps
forecasters give the community accurate advanced warnings."
That
tornado plowing through an adjoining county is a prime example.
SPoRT gives forecasters several tools to help predict a thunderstorm’s
potential for spawning such a beast. One of the best such
tools is the North Alabama Lightning Mapping Array -- an 11-sensor
network that measures lightning around the area.
Think
of how your radio crackles noisily when lightning flashes.
That's because lightning produces a lot of radio frequency
noise. By zeroing in on an unused frequency, the 11 sensors
scattered around on water towers, radio towers, and roof tops,
measure a storm's total amount of lightning.
Above:
Click on the image to launch a 16 megabyte animation of data
from the Lightning Mapping Array. It shows the progress of
lightning activity in Franklin County, Alabama, during a severe
storm in March 2002. [movie]
"The total lightning data can help forecasters predict
whether a storm might generate a tornado," says Rich
Blakeslee, NASA atmospheric scientist. "We've found that
often intercloud lightning – not cloud-to-ground lightning
-- suddenly spikes and then, just as suddenly, diminishes
a very few minutes before a tornado forms."
Darden
adds, "We add the total real-time lightning data to our
radar and wind velocity information to help us make that critical
decision whether to send out a warning."
SPoRT
and other NSSTC programs also have access to another tool
-- a Dual-Polarimetric Doppler Radar -- that actually reveals
the shapes of raindrops. Traditional weather radar sends pulses
of radiation that oscillate in one direction only--horizontally.
Dual polarization radar sends pulses that oscillate in two
directions--horizontally and vertically. By combining the
reflections from both kinds of pulses, scientists can tell
what shape and size a raindrop is.
"Flatter
and wider means bigger raindrops, because the larger the raindrop
is the flatter it gets as it falls," explains Walt Petersen,
NASA physical scientist. "That information helps weather
forecasters better estimate rainfall amounts – and therefore
flash flooding – and storm intensity."
This
radar can also tell the difference between rain and hail because
hail is typically spherical while raindrops tend to flatten.
Adding this information to the strength of the return, forecasters
can tell the size of the hail.
Right:
A slice through a 2.5 inch hail stone collected at the home
of NASA scientist Walt Petersen in Madison, Alabama. "The
layering in the stone illustrates the different growth regimes
that the hail stone went through (sometimes coated with water,
sometimes dry) as it ascended and descended through the storm.
We can detect these types of changes on the hailstone surface
with the dual-polarization radar." [Larger
image]
"Large
hail indicates powerful updraft and downdraft winds within
a thunderstorm," says Petersen. "So it usually means
a strong storm, and sometimes means that a storm may produce
a tornado."
"This
radar tells us a lot about a potentially violent storm,"
says Darden. "It's pretty new, so we still have a lot
to learn."
No
problem. The scientists at the NSSTC train current forecasters
and future meteorologists alike to use these cutting-edge
tools. University of Alabama Huntsville's Atmospheric Science
Department is, like the NWS, collocated with NASA researchers
at NSSTC.
"During
severe weather, day or night, my students gather here to operate
the radar," says Petersen. "You should see 'em.
It's like weather central here sometimes!
"When
there's a fierce storm brewing, or even crashing around us,
the students, UAH and NASA researchers, and forecasters communicate
in real time by instant messaging with the NWS's IEM online
chat tool (NWSChat). They chat about operating the radar and
interpreting the radar data. It's a great hands-on way to
learn."
Right:
Ph.D. student Christopher Schultz operates the dual polarization
radar from his workstation at UAH. [Larger
image]
WHNT-TV,
a local TV station, also uses the data from this radar, and
is in fact the first broadcast meteorology station in the
world to have access to such a tool.
"So
the benefit goes straight to the consumer--the viewing audience,"
says Petersen.
And
the benefits are not just local.
"We've
transferred many of these tools to other forecast offices
across the country," says Darden. "For example,
our office is one of only a few U.S. NWS offices with access
to this kind of radar, but all the offices must convert their
radars to dual pole by the end of next year. We'll be helping
to train them in its use, passing along what we've learned
from SPoRT."
Both
the lightning mapping and dual pole radar are ground-based
now, but in the future will be space-based.
"We're
developing products to work with the Geostationary Lightning
Mapper on GOES-R – NOAA's next-generation weather satellite,"
says Jedlovec. "With the launch of that satellite in
about 2015, lightning could be mapped all across the U.S.
from the vantage point of space."
Again,
thanks to NASA, the NWS forecasters here will be a step ahead
in using a new tool, and ready to help other forecasters learn
the ropes to help their communities.
"This
is an exciting place to work," says Jedlovec. "All
the tornado warnings for Madison County come right out of
this building. We don't just write research papers. With the
help of the National Weather Service, we see our data used
for the good of the public. That makes us feel good about
what we do."
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Author: Dauna Coulter
| Editor: Dr.
Tony Phillips | Credit: Science@NASA
end
notes |
SPoRT
Partners
•
NOAA/NESDIS/STAR - transitional activities, GOES and
AIRS products
• Joint Center for Satellite Data Assimilation (JCSDA)
- transitional activities, computational resources
• National Severe Storms Laboratory (NSSL) - real-time
WRF model forecasts
• NWS Southern Region Headquarters - data dissemination,
WFO interface
• University or Wisconsin / CIMSS - real-time MODIS,
AMSR-E, and AIRS data and products
• Jet Propulsion Laboratory - AIRS data and products
• University of Alabama - Huntsville - radar and atmospheric
electricity applications
• University of South Florida - real-time MODIS data
and products
• Florida State University - data assimilations studies
• University of Oklahoma - data assimilation studies
NASA's
Future: US
Space Exploration Policy |
|