ARB Research Seminar

This page updated July 9, 2019

Characterizing the Climate Impacts of Brown Carbon

Photo of Lynn Russell, Ph.D

Lynn Russell, Ph.D

Photo of Christopher Cappa, Ph.D

Christopher Cappa, Ph.D

Photo of Michael Kleeman, Ph.D

Michael Kleeman, Ph.D

Lynn Russell , Ph.D, Christopher Cappa, Ph.D., Michael Kleeman Ph.D

August 19, 2019
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Brown carbon (BrC) emissions from residential, agricultural, and wildfire burning activities are a highly seasonal, episodic, and poorly characterized fraction of fine particulate matter (PM2.5) in California. In addition, secondary formation of additional carbonaceous particle mass in urban areas may contribute even more light-absorbing BrC year round. These types of BrC may have substantial impacts on climate in California and worldwide. Through a multi-institution collaboration, this study identified and characterized the contribution of BrC to climate forcing in California by (1) providing PM1 and PM2.5 physical measurements and chemical analyses of fine particles that constrain the chemical concentrations and optical properties of burning emissions, (2) quantifying the BrC organic components and the multi-wavelength absorption from burning emissions and from atmospheric formation of secondary components at two California locations, and (3) examining the globally and regionally-averaged climate response of BrC. We looked at areas with significant residential burning in the San Joaquin Valley (Fresno) and with photochemical aerosol formation in the South Coast Air Basin (Fontana) to characterize their different mixes of emission sources and seasonality. The advanced cavity ring-down/photoacoustic and mass spectrometric instrumentation used for these measurements provided unprecedented chemical composition and optical property (e.g. multi wavelength absorption and extinction) characterization of BrC. The quantitative analysis of these results separated and characterized BrC, providing important quantification of emissions-specific particle absorption properties for modeling climate forcing. These results were used to evaluate column measurements of absorption partitioning, showing good agreement when surface conditions were representative of the boundary layer and column. Global and regional models were then used with the realistic quantification of organic particles and their absorption. The results, averaged over one year (2014-2015), of the global through regional nested simulations indicate that absorption by BrC in aerosol particles and clouds increased domain-averaged near surface air temperatures by ~0.018 degree Kelvin (K), whereas absorption by organic matter plus black carbon (BC) increased it by ~0.17 K, suggesting a warming by BC of ~0.15 K. The combination of the source-oriented regional modeling and global plus regional modeling showed that diesel engines make a larger contribution than biomass burning to total-column absorption in California.

Speaker Biography

Lynn M. Russell is Professor at Scripps Institution of Oceanography on the faculty of University of California at San Diego. Her research is in the area of aerosol particle chemistry, including the behavior of particles from both biogenic and combustion processes. Her research group pursues both modeling and measurement studies of atmospheric aerosols, using the combination of these approaches to advance our understanding of fundamental processes that affect atmospheric aerosols. She completed her undergraduate work at Stanford University, and received her Ph.D. in Chemical Engineering from the California Institute of Technology for her studies of marine aerosols. Her postdoctoral work as part of the National Center for Atmospheric Research Advanced Studies Program investigated aerosol and trace gas flux and entrainment in the marine boundary layer. She was named a fellow of AAAR in 2013 and of AGU in 2017.

Christopher D. Cappa is the Ray B. Krone Professor of Environmental Engineering and Vice Chair at the University of California, Davis in the department of Civil and Environmental Engineering. He received his B.S. in Chemistry with a minor in Environmental Science from Hope College in Holland, MI in 2000 and his Ph.D. in physical chemistry from the University of California, Berkeley, in 2005, after which he was a postdoc at the National Oceanic and Atmospheric Administration in Boulder, CO. His work encompasses both laboratory and field measurements in pursuit of improving our understanding of the chemical, physical and optical properties of atmospheric aerosols.

Michael Kleeman is a Professor of Civil and Environmental Engineering at the University of California at Davis. He received his Ph.D. in Environmental Engineering Science from California Institute of Technology. His research is focused on measurements and modeling of urban and regional air pollution problems. Dr. Kleeman has published over 130 peer-reviewed research articles on topics ranging from ozone production from agricultural sources to interactions between climate-energy-air quality to characterization & source apportionment of atmospheric ultrafine particles.

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