Atmosphere, along with oceans, the geosphere, and the cryosphere, forms an essential component of the earth's life support system. Changes due to natural phenomena or human activity in any of these components can strongly influence the chemical composition of the atmosphere. These chemical changes control a vast array of processes that impact human health, welfare, and climate. A main goal of our research is to measure and understand how atmospheric composition is changing in response to changes induced by natural and anthropogenic activities, and to develop the capability to predict these changes which may be deleterious to the quality of human life. The overarching questions that motivate our research are:

1. How do changing emissions resulting from natural and man-made activities alter the composition of the atmosphere?
2. How does the chemistry of the atmosphere respond to and affect climate change?
3. What are the effects of regional pollution on the global atmosphere, and the effects of global chemical and climatic changes on regional air quality?

These goals are addressed through a series of efforts that primarily involve development of new instrumentation and their deployment in targeted intensive field studies. Usually these are efforts that focus on the remote troposphere or lower stratosphere, use surface and airborne platforms, and involve international collaborations. These observations are analyzed and interpreted with the help of models both within NASA Ames and through a series of external collaborations. Presently our focus is on understanding the ozone chemistry of the troposphere with special emphasis on the cycles of NO_x, HO_x and ClO_x.

The complexity of the atmospheric system demands collaborative studies. Following is a partial list of our most recent scientific collaborators:

Dr. Frank Arnold, Max Planck Institute für Kernphysik, Heidelberg, Germany.
Prof. Donald Blake, Department of Chemistry, University of California, Irvine. USA.
Dr. Edward Browell, Earth Science Division, NASA Langley Research Center, Hampton, Virginia, USA.
Prof. William Brune, Department of Meteorology, Penn State University, PA. USA.
Prof. Dr. Paul Crutzen, Max Planck Institute for Chemistry, Mainz, Germany.
Prof. Douglas Davis, Dept. of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA.
Prof. Brian Heikes, University of Rhode Island, Narragansett, RI, USA.
Prof. Daniel Jacob, Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA.
Prof. Yutaka Kondo, Solar Terrestrial Environmental Laboratory, Nagoya University, Toyokawa, Japan.
Dr. Hans Schlager, DLR, Oberpfaffenhofen, Wessling, Germany.
Prof. Robert Talbot, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, NH, USA.
Dr. Anne M. Thompson, NASA Goddard Space Flight Center, Greenbelt, MD, USA.