WASHINGTON — Scientists planning NASA’s largest Earth science expedition of the year will hold a media teleconference on Wednesday, June 27, at 2 p.m. EDT to discuss the upcoming Tropical Composition, Cloud and Climate Coupling (TC4) field campaign.

The TC4 study will tackle challenging questions about Earth’s ozone layer and climate using coordinated observations from satellites and high-flying NASA airplanes. Researchers will study how chemical compounds in the air are transported to the stratosphere, the area of the atmosphere that contains most of Earth’s ozone. They will investigate how this vertical transport of water and chemicals affects climate-influencing cirrus clouds, and the chemistry of the upper atmosphere, of which ozone is an important component. The campaign will be based out of San Jose, Costa Rica, starting in mid-July.

Briefing participants are:

— Michael Kurylo, TC4 program scientist, NASA Headquarters, Washington

— Hal Maring, TC4 program scientist, NASA Headquarters

— David Starr, TC4 mission scientist, NASA Goddard Space Flight Center, Greenbelt, Md.

— Brian Toon, TC4 mission scientist, University of Colorado, Boulder

Media interested in participating in the teleconference should call 888 664-9853. The international toll number is 210 234-0004. The passcode is “TC4.” At the time of the teleconference, streaming audio will be available at:

http://www.nasa.gov/newsaudio

Images and supporting data will be available during the teleconference at:

http://www.nasa.gov/formedia