July 1, 2007 A high-flying NASA mission over Costa Rica and Panama in July and August should help scientists better understand how tropical storms influence global warming and stratospheric ozone depletion, says a University of Colorado at Boulder professor who is one of two mission scientists for the massive field campaign.
Brian Toon, chair of CU-Boulder's atmospheric and oceanic sciences department, said the $12 million effort will mobilize in San Jose, Costa Rica, and involve about 400 scientists, students and support staff operating three NASA aircraft, seven satellites and a suite of other instruments. The team is targeting the gases and particles that flow out of the top of the vigorous storm systems that form over the warm tropical ocean, said Toon.
The warm summer waters of the Pacific Ocean in Central and South America are a breeding ground for heat-driven convective storms targeted by the mission, said NASA officials. Such tropical systems are the major mechanism for Earth's system to loft air into the upper troposphere and stratosphere and are characterized primarily by cumulus clouds with large dense anvils and wispy cirrus clouds.
Known as the Tropical Composition, Cloud and Climate Coupling mission, or TC4, The expedition runs from July 16 through Aug. 8 and is NASA's largest field campaign in several years. The tropical storm systems under study pump air more than 40,000 feet above the surface, where they can influence the make-up of the stratosphere, home of Earth's protective ozone layer.
"This is a very little-studied region of the atmosphere, but it is crucial to understanding global climate change and changes in stratospheric ozone," Toon said.
One mission goal is to understand how transport of chemical compounds - both natural and man-made - occurs from the surface to the lower stratosphere, which is roughly 10 miles in altitude. Another goal is to understand the properties of high-altitude clouds and how they impact Earth' s radiation budget, Toon said.
As a TC4 mission scientist, Toon will be coordinating daily flights of three NASA aircraft filled with scientific instruments that will collect data in concert with NASA satellites. The aircraft include the ER-2 -- NASA's modern version of the Air Force U2-S reconnaissance aircraft -- which can reach an altitude of 70,000 feet and which will fly above the clouds and act as a "surrogate satellite," he said.
The mission also includes a broad-winged WB-57 research plane that will fly into the cirrus clouds at 60,000 feet and sample cloud particles and the make-up of chemicals flowing from massive tropical storm systems. The third plane, a converted DC-8, will fly at about 35,000 feet to probe the region between Earth' s troposphere and stratosphere and sample cloud particles and air chemistry.
"The critical lever in greenhouse warming is water in the upper troposphere," said Toon. "Added water, or more extensive clouds as a result of global warming, would significantly amplify the greenhouse effect from human made pollutants such as carbon dioxide." Conversely, more extensive convection due to rising sea-surface temperatures could lead to more precipitation and less cloud cover, acting to "retard" greenhouse warming, he said.
Toon and his graduate students will be studying the size and role of ice particles in clouds to better understand how Earth might respond to warming temperatures. "We'd really like to understand the processes that control water as it is going into the stratosphere, which should help improve climate models," he said.
Toon, who spent several years helping to design the NASA mission and chaired the committee that organized the effort, also will be working with CU-Boulder graduate student Charles Bardeen in San Jose on daily weather forecasts, which will help dictate when planes can safely sample in targeted atmospheric regions.
Other participants from CU's oceanic and atmospheric sciences department, or ATOC, include Associate Professor Linnea Avallone, who will work with graduate students to sample water condensed in clouds. Associate Professor Peter Pilewskie and his students will study reflected sunlight from bright clouds to better understand Earth's energy budget in relation to climate change, while Research Associate Frank Evans will study ice cloud properties using radiometry.
Scientists from CU-Boulder's Cooperative Institute for Research in Environmental Sciences -- a joint venture of CU-Boulder and the National Oceanic and Atmospheric Administration -- also will participate in the mission. CIRES and NOAA have 14 researchers involved in the TC4 mission from Boulder.
Observations from a suite of NASA satellites flying in formation, known as the "A-Train," will complement the aircraft measurements. The satellites will measure ozone, water vapor, carbon monoxide and map clouds, charting the aerosol particles inside that affect their formation.
"The potential economic repercussions of global warming are almost unimaginable," said Toon. "We could lose large fractions of entire states over the next century or so if there are significant increases in sea level. "This mission will help us understand Earth's systems and what happens when we modify the planet."
Toon said NASA has a made a huge investment in its satellite fleet over the years and in finally implementing the TC4 mission. "NASA has a commitment to better understand these complex issues," he said. "And our graduate students will probably be writing theses on data from the TC4 mission for the next decade."
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