The Earth’s atmosphere is a highly oxidizing medium. The tropospheric abundance of oxidants such as the hydroxyl radical (OH) and ozone (O3) determines the lifetime, and thus the concentration, of most reduced trace gases important to climate (e.g. CH4) and human health (e.g. CO). In addition, atmospheric oxidant abundances can influence the formation pathway of aerosols with implications for their climate effects and for air pollution. Our research examines how tropospheric aerosol and oxidant chemistry varies over time and space. The time scales we consider range from seasonal to glacial-interglacial variability on the global scale. We aim to answer two fundamental questions in atmospheric chemistry:
1) How do the formation pathways of sulfate and nitrate aerosols vary over space and time, and what are the implications for atmospheric chemistry and climate?
2) How has the oxidation capacity of the atmosphere changed in response to both anthropogenic and climate forcing, and what are the implications for climate feedback processes via the impact on the concentration of reduced trace gases (e.g. CH4) that affect the distribution of energy in the climate system?
The main approaches that we use to answer the above questions are:
1) Measuring the isotopic composition of sulfate and nitrate from aerosol, water, snow, and ice core samples (see our laboratory facilities)
2) Modeling using global three-dimensional models of atmospheric chemistry and climate (mostly GEOS-Chem)
Please see our publications page for examples of past and on-going projects.