Aerosol chemistry and physics in and around clouds

Our ability to understand and predict climate change is limited due to uncertainties in how humans have modified aerosols (atmospheric particles) and clouds. This is the most uncertain factor in recent climate change quantified by the Intergovernmental Panel on Climate Change. This uncertainty is both from the impact that aerosols have on clouds and the impact of clouds on aerosol size, concentration and chemical composition. In this research program, we will investigate the interactions of aerosols and clouds while paying specific attention to the impact of these interactions on climate. To help understand and reduce these uncertainties, we will develop a novel computer modelling framework for predicting aerosol and cloud droplet number, size and chemical composition. This framework will be coupled with cloud models that resolve the large-scale structure and properties of the clouds. We will use these cloud models to answer questions about (1) how clouds affect the number, size and chemical composition of aerosols and (2) how changes in these aerosol properties feed back on the clouds. Specific attention will be paid to the affect of organic carbonaceous aerosol, which may affect cloud droplet formation and growth, on the overall cloud properties. Finally, the information learned from these studies will be used to improve the physics of aerosols and clouds in climate models that generally represent aerosols and clouds poorly.