We apply satellite observations, global models, and in situ measurements to improve understanding about the processes controlling air quality, climate, and biogeochemical cycling.

We devote particular attention to emissions and other processes affecting tropospheric ozone and aerosols. Satellite remote sensing is yielding unprecedented insight into global atmospheric composition by observing regions and phenomena that are otherwise difficult to observe. Global chemical transport models offer the three-dimensional perspective needed to analyze the vast amount of information provided by satellite remote sensing. Ground- and aircraft-based observations provide a wealth of additional information, such as on atmospheric constituents that are not observed from satellite.