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NASA
TECHNOLOGY EYES BETTER HURRICANE FORECASTS Two
NASA scientists have for the first time taken simultaneous high-altitude radar,
temperature, and wind measurements that reveal the anatomy of hurricanes and shed
light on what makes them intensify. The results could lead to better forecasting
in the future.
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1 - NCAR GPS Dropsonde | | |
The
activities were part of CAMEX-4 (The Convection And Moisture EXperiment), a joint
effort between NASA, the National Oceanic and Atmospheric Administration (NOAA)
and a number of universities, that ended on September 24. "We
had three flights over Hurricane Humberto in the last three days," NASA Goddard
Space Flight Center researcher and a mission scientist for Camex-4, Gerry Heymsfield
said. "These were the most comprehensive measurements of the structure of
the hurricane ever recorded."
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2 - Hurricane Humberto | | |
As
Hurricane Humberto raged over the Atlantic Ocean, Heymsfield fitted NASA's high
altitude ER-2 aircraft with a downward-looking radar, called an ER-2 Doppler Radar
(EDOP). From the ER-2's vantage of 12 miles (20 km) up, the EDOP uses the Doppler
shift of rain and ice particles within clouds to measure rain intensity, air speed
and velocity within the storm. NASA's ER-2 aircraft provides a unique perspective
over the top of the storm and flies so high the pilot needs to wear a spacesuit. Earlier,
on September 10, another Goddard scientist, Jeff Halverson, made use of ER-2 to
drop temperature and wind sensors into the eye of Hurricane Erin. The sensors,
called dropsondes, were automatically released from the plane by a computer-operated
system.
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of dropsonde NOTE:
1.3 MB | | | As
they fell, the dropsondes tallied air temperatures and winds through the storm's
eye, from the top of the hurricane to the ocean surface. By taking these readings
at eight different locations in the hurricane, "It's as though we obtained
a topographical temperature map of the storm," says Halverson, who maintains
a dual appointment between Goddard and the University of Maryland-Baltimore County's
Joint Center for Earth Systems Technology. He adds that Erin had a classic hurricane
structure with a well-defined eye, and the new data will provide excellent baselines
for figuring out how these storms intensify. When
hurricanes occur, heat gets generated inside the center of thunderstorms that
eventually make up a hurricane. The heat, created largely by condensation in clouds,
causes the air to expand and rise and that lowers air pressure near surface of
the water. When the surface pressure lowers, air accelerates from areas of higher
pressure surrounding the storm toward the lower pressure area near the sea surface.
As it flows, the air picks up some of the spin of the Earth and starts to move
counterclockwise in a vortex. The winds begin blowing faster towards the center
and the storm intensifies into a hurricane. By
using dropsonde measurements of winds, temperature, surface pressure and moisture,
and then combining those readings with EDOP data of air motions and precipitation
levels in those clouds, the researchers now have necessary data for assessing
a hurricane's structure. That's because the EDOP provides information about the
clouds that create heat and warm the hurricane's spinning vortex, and in turn,
the dropsondes measure the high altitude temperatures that drive the vortex and
in turn create more clouds. "It
is significant to understand the temperature inside the eye of the storm at high
altitudes because that is something that is not very well known," Halverson
said. "To understand whether the storm is intensifying or not you have to
know whether the temperature is increasing." Halverson's
temperature readings and Heymsfield's results "work best together to answer
fundamental questions about the physics that drive a hurricane," said Halverson. Scott
Braun, another NASA Goddard Space Flight Center researcher, will now use the new
data to create detailed computer simulations of hurricanes. These models may help
to better predict future hurricanes. The
dropsonde system was developed by the National Center for Atmospheric Research
(NCAR), and installed onto NASA's ER-2 aircraft. The
Convection And Moisture EXperiment (CAMEX) was the fourth in a series of field
research investigations sponsored by the Earth Science Enterprise at NASA Headquarters,
Washington, DC. The mission united researchers from 10 universities, five NASA
centers and the National Oceanic and Atmospheric Administration (NOAA). Based
out of the Naval Air Station at Jacksonville, Fla., this year's mission ran from
Aug. 16 through Sept. 24 - traditionally the most active part of the hurricane
season. Back
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