The project, called ATTREX (Airborne Tropical TRopopause EXperiment), will provide measurements of moisture and chemical composition, radiation levels, meteorological conditions, and trace gas levels in the high atmosphere. A slew of climate specialists hope to collect unprecedented amounts of data from the tropopause, the boundary between the troposhere (where most weather phenomenon take place) and the stratosphere. The ultimate goal, according to principal investigator Eric Jensen, is to improve the mathematical models scientists use to predict climate change.
"It turns out that even the smallest changes in the humidity of the stratosphere are important to climate," he says. "As we put more greenhouse gasses in the atmosphere, there are going to be changes in the tropopause that will affect the air going into the stratosphere. This will have a feedback effect on climate change. It could dampen or magnify it." With more data from this vital region, he says, climate-change models can give us a better sense of what?s coming.
Climate researchers first realized the importance of this region more than a decade ago. Greenhouse gases seem to cause the stratosphere to cool, allowing a greater number of clouds to form. This in turn causes a faster depletion of ozone in the stratosphere, as the clouds destroy ozone faster than dry air. Since the composition of the stratosphere affects climate, and the tropopause is the gateway to the stratosphere, understanding how water vapor circulates in this layer is vital to understanding climate change. Without good data on how the air circulates, climate models won?t produce accurate predictions.
The trick to studying the tropical tropopause is finding an aircraft that can withstand the temperatures (as low as minus 115 degrees F) and long-duration flight time required. Traditional manned aircraft can?t breach the altitude the scientists are interested in studying. That?s because in the tropics the troposphere is higher than it is in many parts of the globe, where commercial jets can soar into the stratosphere with ease.
Instead, NASA will use drones. With the two Global Hawks the agency has acquired for the project, Jensen and his colleagues will complete 24-hour missions, during which they can watch and control the craft using a high-speed satellite. "It?s very interactive," he says. "We?re changing parameters in real time. In a way, it?s like we?re in the aircraft . . . even though we?re all sitting in a comfy control room."
The Global Hawk, which can fly about 20,000 feet higher than commercial airliners, has been used for climate research before. In September, the Hurricane and Severe Storm Sentinel began a five-year project flying into and around hurricanes. These five-year campaigns, of which ATTREX is one of the first, are part of NASA?s Earth Ventures project. Low- to moderate-cost missions can get preapproval for five years of research, something that makes it possible to plan for data collection across the globe during different seasons.
Eventually, ATTREX will be moving to Guam and Australia to collect more data. While in Guam, researchers will collaborate with scientists from the U.K. and the National Science Foundation, who will fly their aircraft at different altitudes. Jensen says he hopes the data from three aircraft will provide a more complete picture of what?s happening from the surface to the stratosphere.
The first science flight is scheduled to leave on Jan. 17 or 18 from the Dryden Flight Research Center in California. It can?t come soon enough for Jensen and his team. "It?s going to be exhausting," Jensen says, "Because the flights last for 24 hours, and you just want to stay up for the whole thing."
It could take years before the data collected by ATTREX has any effect on climate-change models, but it could change our picture of the planet?s future.
