NASA will send a remotely piloted research aircraft 65,000 feet over
the tropical Pacific Ocean this month to probe unexplored regions of the
upper atmosphere and detect how a warming climate is changing Earth.
The first flights of the Airborne Tropical Tropopause Experiment
(ATTREX), a multi-year airborne science campaign with a heavily
instrumented Global Hawk aircraft, will take off from and be operated by
NASA's Dryden Flight Research Center at Edwards Air Force Base in
California.
The Global Hawk is able to make 30-hour flights, NASA said in a statement.
Water vapour and ozone in the stratosphere can have a large
impact on Earth's climate. The processes that drive the rise and fall of
these compounds, especially water vapour, are not well understood.
This limits scientists' ability to predict how these changes will influence global climate in the future.
ATTREX will study moisture and chemical composition in the upper
regions of the troposphere, the lowest layer of Earth's atmosphere.
The tropopause layer between the troposphere and stratosphere, 12
km to 17 km above Earth's surface, is the point where water vapour,
ozone and other gases enter the stratosphere.
Studies have shown even small changes in stratospheric humidity
may have significant climate impacts. Predictions of stratospheric
humidity changes are uncertain because of gaps in the understanding of
the physical processes occurring in the tropical tropopause layer.
ATTREX will use the Global Hawk to carry instruments to sample this layer near the equator off the coast of Central America.
"The ATTREX payload will provide unprecedented measurements of
the tropical tropopause," said Eric Jensen, ATTREX principal
investigator at NASA's Ames Research Center in Moffett Field,
California.
"This is our first opportunity to sample the tropopause region during
winter in the northern hemisphere when it is coldest and extremely dry
air enters the stratosphere," Jensen said.
The 11 instruments installed in the Global Hawk include remote
sensors for measuring clouds, trace gases and temperatures above and
below the aircraft, as well as instruments to measure water vapour,
cloud properties, meteorological conditions, radiation fields and
numerous trace gases around the aircraft.
Engineering test flights conducted in 2011 ensured the aircraft
and instruments operated well at the very cold temperatures encountered
at high altitudes in the tropics, which can reach minus 115 degrees
Fahrenheit.
Six science flights are planned between January 16 and March 15.
The ATTREX team also is planning remote deployments to Guam and
Australia in 2014.
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