Tropical Composition, Clouds and Climate Coupling Experiment (TC-4)

The Tropical Composition, Cloud and Climate Coupling (TC-4) experiment will take scientists to the extreme environment of the upper troposphere (the lowest layer of the atmosphere), where temperatures fall below minus 115 degrees Fahrenheit. Here they will measure the movement of gases and tiny particles called aerosols. By closely examining the chemical and physical processes that occur in this region, researchers will gain valuable insight on issues involving global climate change, stratospheric ozone depletion, and global tropospheric chemistry.

NASA aircraft, including the ER-2, WB-57, and DC-8, will be loaded with instruments and deployed on numerous flights from Costa Rica across the Western Pacific. The missions will collect data on the atmospheric processes, ozone, clouds, and aerosols in the rarely sampled tropical tropopause layer (the boundary region between the troposphere and stratosphere). In the tropics, this layer usually lies between 7.5 and 11 miles above the surface and plays a crucial role in the "dehydration" of air entering the stratosphere.

TC-4 will also gather data on a variety of atmospheric constituents, including water vapor and methane in the upper troposphere. These are important greenhouse gases that affect global temperature. Measurements will also be made of aerosols, which work to absorb or reflect radiation and play a significant role in both global air quality and the regulation of the Earth's climate.

These airborne measurements of the tropical upper troposphere and lower stratosphere will then be used to validate information taken by instruments on NASA's Aura, CloudSat, CALIPSO, and Aqua satellites.

Contacts:

David Starr
NASA Goddard Space Flight Cente
David.O.Starr@nasa.gov

Brian Toon
University of Colorado at Boulder
btoon@lasp.colorado.edu

Mission Website:

http://cloud1.arc.nasa.gov/tc4/

Science Goals:

• Validate satellite measurements of geophysical parameters and atmospheric constituents, including aerosols, water vapor, ozone, nitric acid, carbon monoxide, and cloud ice
• Determine how cirrus clouds evolve over their life cycle and impact the Earth's radiation budget
• Study the chemical fates of short-lived compounds and ozone transported from near the surface to the tropical tropopause layer
• Evaluate the relative roles of both large-scale and convective transport and how these processes are coupled
• Assess the physical mechanisms that control long-term changes in the humidity of the upper troposphere in the tropics and subtropics
• Gather data to better understand cloud-water vapor feedbacks in the global climate

Partners:

NASA scientists will work closely with researchers from several other agencies and universities, including the University of Colorado, California Institute for Technology, Harvard University and the University of North Dakota.

When:

June - August 2007

Where:

Aircraft flights will originate from Costa Rica and travel across the Western Pacific.

Links:

NASA's ER-2 aircraft:
http://www.nasa.gov/centers/dryden/research/AirSci/ER-2/

NASA's WB-57 aircraft:
http://jsc-aircraft-ops.jsc.nasa.gov/wb57/index.html

NASA's DC-8 aircraft:
http://www.nasa.gov/centers/dryden/news/FactSheets/FS-050-DFRC.html

NASA's Aura satellite:
http://aura.gsfc.nasa.gov/