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Wednesday, October 17, 2018
4:00 PM - 5:00 PM
South Mudd 365

Environmental Science and Engineering Seminar

Light absorption by atmospheric particles: using field and lab studies to understand linkages between sources, chemical processing and impacts
Christopher Cappa, Professor, Department of Civil and Environmental Engineering, UC Davis,

An important process through which atmospheric particles exert an influence on regional and global climate is the absorption of solar radiation. Three classes of particles contribute most of the absorption: black carbon (BC), absorbing organic carbon (aka "brown" carbon, or BrC) and dust. Absorption by BC and BrC can contribute nearly as much to global radiative forcing as CO2. However, the uncertainties in the absolute and relative BC and BrC contributions are substantial. In this seminar, new results from two CA field studies and a laboratory study focused on biomass burning emissions will be used to understand the atmospheric variability in observed BC and BrC properties. The field studies, in wintertime Fresno and summertime Fontana, CA, provide context for understanding seasonal and regional differences in how sources and chemical processing impact the relationship between particle composition and absorptivity. The "FIREX" lab study, at the US Forest Service Fire Lab, provides a comprehensive look at how chemical processing in smoke plumes alters the absorption by biomass burning-derived particles, and how this depends on the fuel burned. Together, these studies provide new constraints for representing the atmospheric variability evolution of BC and BrC in models.