Our work focuses on using observations of the atmosphere from all scales (in situ to satellite) with global models (GEOS-Chem, the Community Earth System Model) to understand the composition and chemistry of the troposphere. Research in our group is supported by NSF, NOAA, NASA, DOE, and the EPA.


Check out this 2012 video in which Colette talks about what motivates our research and the tools we use.


Here are the main research themes in our group:

Aerosol Sources, Composition, Chemistry, and Impacts

View of a high-PM day in Hong Kong from the Star Ferry (C.L. Heald)


Aerosols (or particulate matter, PM) degrade visibility and air quality in both the developed and developing world. Exposure to particulate matter is the most significant environmental cause of premature mortality, responsible for > 4 million deaths per year. Atmospheric aerosols are also the leading source of uncertainty in global climate forcing. These particles have both natural (e.g. dust) and anthropogenic (e.g. vehicles) sources. Understanding the sources, transformations, properties, and long range transport of aerosols in the troposphere is key to characterizing their role in climate and air pollution.


Work in our group focuses on understanding the global lifecycle of aerosols in the atmosphere: What are their sources? How are they processed in the atmosphere? And what impact do they have? Recent projects include: investigating the effects of black carbon aging on radiative forcing and exploring the role of brown carbon; investigating the sources and impacts of bioaerosol; exploring the sources and sinks of organic aerosol and the total organic carbon budget; investigating the sources and trends of dust from North Africa; and investigating the role of ammonia in aerosol formation and air quality.

Biosphere-Chemistry-Climate Interactions

Looking up in Muir Woods (C.L. Heald)

Our climate is influenced by the combination of natural and human-induced changes, including feedbacks within the climate system. For example, volatile organic compounds (VOCs) emitted from vegetation participate in the formation of ozone and also of organic aerosol, both of which are sensitive to anthropogenic emissions of nitrogen oxides and VOCs as well. These same particles and gases may damage ecosystem health or be a source of nutrients to the biosphere. The latest generation of models can be used to investigate these chemistry-climate interactions and project how the composition of the atmosphere may change.

Work in our group focuses on developing a better understanding of biosphere-atmosphere interactions. Specific topics of interest are understanding the role of land use change on atmospheric composition (e.g. in Southeast Asia due to palm plantation expansion, or due to agricultural expansion); how crop productivity is affected by both climate change and air pollution; how ozone is taken up by plants; the prediction of air quality extremes in a future climate; and investigating the role of wildfires on air quality.