NASA’s Airborne Tropical Tropopause Experiment (ATTREX) returned to the skies for its fifth and final year of science flights on March 4. The remotely piloted Global Hawk research aircraft took off from its base at NASA’s Armstrong Flight Research Center, Edwards, California, to track the transport of water vapor into the upper atmosphere and help researchers understand how greenhouse gases affect Earth’s climate.
This year, NASA ATTREX is collaborating with United Kingdom (UK) researchers to execute their Coordinated Airborne Studies in the Tropics (CAST) project, funded by their country’s Natural Environment Research Council (NERC). The mission continues to focus on the transport and exchange of greenhouse gases, in particular water vapor, in the tropical tropopause region, the transition layer between the troposphere, the lowest part of the atmosphere, and the stratosphere, the layer above it. The suite of instruments onboard includes a subset of the ATTREX payload previously flown, with a focus on cloud and water vapor measurements. In addition, two new CAST instruments will be included: the Aerosol Ice Interface Transition Spectrometer (AIITS) and the GreenHouse gas Observations in the Stratosphere and Troposphere (GHOST).
“The combination of ATTREX and CAST instruments will provide new information about the formation of tropical tropopause layer cirrus and the shapes of the ice crystals that comprise them,” said Eric Jensen, the ATTREX principal investigator at NASA’s Ames Research Center at Moffett Field, Calif. “The cirrus ice crystal sizes and shapes determine how fast they fall and remove water vapor from air rising into the stratosphere. The measurements made in this flight series will add to the extensive ATTREX dataset that is being used to improve our understanding of tropical tropopause layer transport and cloud processes. The science community is using this dataset to evaluate and improve global models used to predict future climate change.”
Studies show that even slight changes in the amount of water vapor in the stratosphere can warm the surface temperature by absorbing thermal radiation rising from the surface.
Scientists consider the tropical tropopause to be the gateway for transport of water vapor, ozone and other gases into the stratosphere. For this mission, the Global Hawk will fly in the tropical tropopause layer (from altitudes of 45,000 to 60,000 feet) near the equator over the Pacific Ocean, providing measurements in this critical atmospheric layer.
AIITS was jointly developed by UK’s Universities of Hertfordshire and Manchester. It will measure the scattering properties of aerosols and cirrus clouds, providing information about particle shapes and composition. Scientists expect these measurements, combined with those from the ATTREX Hawkeye, a cloud particle probe managed by Stratton Park Engineering (SPEC), Inc., Boulder, Colo., and water vapor instruments, will provide valuable new information about the formation and impact of extensive, thin cirrus clouds in the tropical tropopause layer.
GHOST was jointly developed by the UK Astronomy Technology Centre in Edinburgh and the Universities of Edinburgh and Leicester. It will measure columns of greenhouse gases, such as carbon dioxide, methane, carbon monoxide, and water, below the aircraft’s path. It is a novel, compact Short-Wave InfraRed (SWIR) spectrometer built on similar principles to the instrument aboard the NASA Orbiting Carbon Observatory (OCO)-2 satellite launched in 2014, and will provide high spatial-resolution information about these gases as well as validation for the satellite instrument.
ATTREX will conduct three long-duration science flights totaling 66 hours, averaging more than 22 hours per flight. This year’s flights bring the total hours flown in support of ATTREX to about 390 hours since 2011.
Jensen and Project Manager Dave Jordan of Ames have led the ATTREX mission. Investigators include four NASA facilities: Ames, Langley Research Center in Hampton, Virginia, Goddard Space Flight Center in Greenbelt, Maryland, and the Jet Propulsion Laboratory in Pasadena, California. The team also includes investigators from the National Oceanic and Atmospheric Administration, Boulder, Colorado, the National Center for Atmospheric Research, Boulder, University of Cambridge, United Kingdom, the University of California at Los Angeles, the University of Miami, Florida, the University of Heidelberg, Germany, and private industry. The project is managed by the NASA Ames Earth Science Project Office.
ATTREX is one of the first research missions of NASA’s new Earth Venture project. These targeted science investigations complement NASA’s research satellite missions. The Earth Venture missions are part of NASA’s Earth System Science Pathfinder Program managed by Langley.
For more information about NASA’s Earth science activities in 2015, visit:
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NASA Armstrong Flight Research Center