Review of Recent Advances in Understanding Secondary Organic Aerosols for Earth System Modeling
Researchers review recent findings on secondary organic aerosols and the impact on radiative forcing in global models.
This work, led by Department of Energy (DOE) scientists with numerous national and international collaborators from universities and national laboratories, highlights several advances in understanding the processes and properties of secondary organic aerosols (SOA) in the last decade. SOA are complex aerosol systems, formed in the atmosphere through many diverse nonlinear processes. These processes can be synergistic or act to compensate each other, leading to predictive uncertainty. Holistically including them in climate models is important, since SOA aerosols impact both aerosol radiative forcing and current understanding of Earth system sensitivity to greenhouse gases.
This review emphasizes the most influential processes that govern the chemical and dynamic evolution of SOA mass and number concentrations in Earth system models, focusing on those that are not yet incorporated in atmospheric chemistry-climate models. Properly addressing these processes could impact the understanding of aerosol climate forcing.
The manuscript is based on a workshop, “New Strategies for Addressing Anthropogenic-Biogenic Interactions of Organic Aerosol in Climate Models,” supported by DOE’s Office of Biological and Environmental Research Atmospheric System Research program within the Office of Science. The workshop was held at Pacific Northwest National Laboratory on June 8-9, 2015. The researchers summarized some of the important developments during the past decade in understanding of SOA formation. They highlighted the importance of several processes that influence the growth of SOA particles to sizes relevant for clouds and radiative forcing, including (1) formation of extremely low-volatility organics in the gas phase, (2) acid-catalyzed multiphase chemistry of isoprene epoxydiols (IEPOX), (3) particle-phase oligomerization, and (4) physical properties such as volatility and viscosity. Several SOA processes highlighted in this review are complex and interdependent and have nonlinear effects on SOA properties, formation, and evolution. Current global models neglect this complexity and nonlinearity, and thus are less likely to accurately predict Earth system forcing of SOA. The workshop also emphasized the need to rank the most influential processes and nonlinear process-related interactions, so that these processes can be accurately represented in atmospheric chemistry-Earth system models.
Pacific Northwest National Laboratory
This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research, Atmospheric System Research and Earth System Modeling programs. Christopher D. Cappa was supported by the National Science Foundation.
Shrivastava, M., et al. 2017. “Recent Advances in Understanding Secondary Organic Aerosol: Implications for Global Climate Forcing,” Reviews of Geophysics 55(2), 509-59. DOI: 10.1002/2016RG000540.