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December
11, 2006
NASA
Aircraft Captures Windy Details in
Hurricane's Ups and Downs
Hurricanes not only threaten lives and
property, they also
often behave erratically, with seemingly endless shifts in intensity
and
movement that have long challenged forecasters. But new research using
sophisticated weather research tools is shedding new light on the
nature of
these fickle storms.
Flying over Hurricane Dennis in July
2005 - a category 4
hurricane - with NASA's ER-2 aircraft and the National Oceanic and
Atmospheric
Administration's (NOAA) P-3 aircraft, scientists took measurements of
the
storm's internal structure. The information is giving clues about the
evolution
of a hurricane's warm inner core and the factors related to its
formation.
Joe Turk, Steve Miller, and Jeff Hawkins of the Naval Research
Laboratory, Monterey,
Calif., and
Steve Guimond of Florida
State University,
Tallahassee, Fla.,
will present their findings today at the American Geophysical Union's
2006 Fall
Meeting in San
Francisco.
The research flights were conducted as part of the Tropical Cloud
Systems and
Processes (TCSP) mission in Costa Rica,
a NASA field experiment with
cooperative participation from NOAA and several universities. This
experiment
was aimed at studying the birthing conditions for tropical storms and
hurricanes and identifying the factors that cause them to strengthen or
weaken.
"This campaign was particularly unique because two types of aircraft
provided measurements on different atmospheric variables," said Turk.
"The information is also being used to determine how accurately
satellites
capture storm details." While a few satellites can now look through
clouds, the aircraft data provide a level of detail far superior to
satellites.
Dennis reached hurricane strength on
July 7, 2005, in the
eastern Caribbean Sea, and rapidly strengthened into a category 4 storm
before
making landfall in Cuba
on July 8. After weakening over land, Dennis quickly re-intensified
over the
Gulf of Mexico before weakening again prior to its second landfall in Florida.
As the storm fluctuated in intensity, flights into the storm continued,
taking
critical measurements of wind, rainfall, temperature, and moisture.
"The
erratic nature of the storm and the timing of the research mission
allowed
scientists to pierce through the core of the hurricane at many stages
of its
life cycle and for the first time map a hurricane's entire evolution,"
said Guimond.
NASA's ER-2 Doppler radar measured
wind speed along the
track of the aircraft including measurements indicative of the size and
concentration of raindrops and ice particles, while another ER-2
instrument,
the Advanced Microwave Precipitation Radiometer, gathered microwave
imagery of
the internal structure of rain clouds. By analyzing when and where
strong winds
are occurring, researchers can better determine when intensity changes
may
occur. Data on the storm's vertical temperature structure - indirectly
related
to wind speed and rainfall - was also examined from overpasses of NOAA
satellites.
Previous research has suggested that rapid hurricane intensification,
like that
seen in Dennis, is linked to hot towers, rain clouds that reach at
least the
top of troposphere - the lowest layer of the atmosphere - and about
nine miles
high in the tropics. They are called "hot" because of the large
amount of latent heat they release, fuel for strong winds and heavy
rainfall.
"With Dennis, it appears the hot towers played a major role in the
rapid
intensification of the storm, giving clues on how energy is
concentrated and
winds evolve at various stages of development," said Guimond. "The
observations also helped place the storm's behavior in greater context
and
matched well with computer model simulations, suggesting that we are
making
progress in replicating hurricane development."
While meteorologists have made
considerable strides in
forecasting a hurricane's track, intensity predictions have remained a
more
significant challenge. Part of the difficulty is that the many factors
that
control intensity, particularly the speed, direction and spin of air
throughout
the atmosphere, are constantly changing and difficult to measure.
For
more information and images, visit:
http://www.nasa.gov/mission_pages/hurricanes/archives/2006/hurricane_life.html
For more
information
about the NASA ER-2 research aircraft, visit:
http://www.nasa.gov/centers/dryden/research/AirSci/ER-2/index.html
For a feature
story about "hot towers," visit:
http://www.nasa.gov/centers/goddard/news/topstory/2004/0112towerclouds.html
For
a feature story about the NOAA P-3, visit:
http://www.noaanews.noaa.gov/stories/s672.htm
Writer: Mike Bettwy, NASA
Goddard Space Flight Center
##
Contact:
Rob Gutro
NASA Goddard Space Flight Center
301-286-4044
Robert.J.Gutro@nasa.gov
This text is
derived from:
http://www.nasa.gov/mission_pages/hurricanes/archives/2006/hurricane_life.html
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