Interpreting satelllite observations of tropospheric composition to improve understanding of climate and air quality

Pressing scientific questions in climate and air quality will be addressed using a combination of satellite observations, aircraft and ground-based measurements, as well as a global three-dimensional model of atmospheric composition. Emphasis will be placed on quantitative interpretation of satellite observations of ozone, aerosols, and their precursors in the troposphere (lowest 12-17 km of the atmosphere). Tropospheric ozone is a major greenhouse gas, is a major pollutant, and largely controls the breakdown of other pollutants. Aerosols degrade health and visibility, and have a highly uncertain effect on climate. Both tropospheric ozone and aerosols can be produced locally and can be transported from afar. Ozone and aerosol precursors include pollutants such as nitrogen oxides and sulfur dioxide which are emitted from combustion. Specific tasks include 1) evaluate and improve satellite observations of ozone and aerosol precursors through comparison with aircraft and ground-based measurements, 2) provide top-down constraints on emissions of ozone and aerosol precursors through inverse modeling of satellite observations, and 3) evaluate and improve the representation of aerosol processes in global models. Achieving these objectives would reduce uncertainty in critical atmospheric processes that impair current efforts to improve air quality and respond to climate change.