This award will allow a postdoctoral researcher the opportunity to study the sources and composition of atmospheric ice nuclei. Ice nuclei are small particles that are especially efficient at forming ice crystals in clouds. Very few particles in the atmosphere have this property, but their effect on clouds and precipitation is large. The main aspect of this award will be the measurement of ice nuclei that originates from combustion sources, such as agricultural burning, wildfires, and vehicle pollution. The number of ice nuclei and the ability of the particles to form ice crystals will be studied. The end result of the project will be a better understanding of the role of particles from combustion sources in the cloud system, and an improved tool that will be incorporated into numerical models from the cloud scale to the global scale. The researcher will also promote cross-disciplinary research between the atmospheric and biological sciences, as well as mentor a summer intern in order to enhance undergraduate training and learning.
The ice nucleation activity of carbonaceous combustion aerosol is poorly constrained, with conflicting results from both field and laboratory studies. This work will address this shortcoming through the direct sampling of combustion aerosols in the field, and associated laboratory work. The main instruments to be used are the Colorado State University (CSU) continuous flow diffusion chamber (CFDC) to determine the number concentration of ice nuclei and the single particle soot photometer (SP2) to selectively remove refractory black carbon. Biosamplers will also be used to determine the contribution of biological particles and organic materials. Select particles will be further assessed using Scanning Electron Microscopy coupled to Energy Dispersive Spectroscopy (SEM-EDS). The specific objectives of the project are to: 1) conduct laboratory experiments to test the technique of coupling the SP2 instrument to the CFDC, 2) measure ice nuclei from controlled winter wheat burns in Oklahoma, 3) conduct sampling of ice nuclei from wildfires in Colorado, 4) perform sampling of fossil fuel combustion near highways in Colorado, and 5) modify or create new parameterizations for cloud to global scale models.
