NASA scientists have successfully completed flight tests in preparation for deployment of a multi-year airborne science campaign to study the humidity and chemical composition of air entering the tropical tropopause layer of the atmosphere. NASA's Airborne Tropical TRopopause EXperiment (ATTREX) will conduct the science campaign over the Pacific Ocean from three locations in 2013 and 2014.

Studies have shown that even small changes in stratospheric humidity may have climate impacts that are significant compared to those of decadal increases in greenhouse gases. Predictions of stratospheric humidity changes are uncertain, due to gaps in the understanding of the physical processes occurring in the tropical tropopause layer, which ranges from about eight to 11 miles above the ground.

"These were test flights, although we did get science-quality data, including samples from tropical thin cirrus clouds at about 55,000 feet altitude," said Leonhard Pfister, ATTREX deputy principal investigator at NASA’s Ames Research Center in Moffett Field, Calif. "These clouds regulate water vapor in the lower tropical stratosphere, which is important for Earth's radiation balance."

Pfister will discuss the ATTREX mission goals, objectives and planned research flights at the Monday, Dec. 5, afternoon poster session at the American Geophysical Union Fall meeting held at the Moscone Center, San Francisco, Calif.

Led by principal investigator Eric Jensen and project manager Dave Jordan of NASA Ames, scientists integrated instruments onto one of NASA's Global Hawk unmanned aircraft and verified their operation during four checkout flights from NASA's Dryden Flight Research Center at Edwards, Calif.

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http://www.nasa.gov/centers/dryden/news/NewsReleases/2011/11-37.html