Improving the treatment of secondary organic aerosols: Bridging the gap between measurements, high resolution regional models and the global climate models.
Authors
Manishkumar Shrivastava — Pacific Northwest National Laboratory
Xiaohong Liu — Texas A&M University
Dick C Easter — Pacific Northwest National Laboratory
Alla Zelenyuk-Imre — Pacific Northwest National Laboratory
Po-Lun Ma — Pacific Northwest National Laboratory
Kai Zhang — Pacific Northwest National Laboratory
Balwinder Singh — Pacific Northwest National Laboratory
Jerome D Fast — Pacific Northwest National Laboratory
Jose-Luis Jimenez — University of Colorado
Qi Zhang — University of California, Davis
Steven J. Ghan — Pacific Northwest National Laboratory
Category
Secondary Organic Aerosol
Description
Secondary organic aerosol (SOA) is a major submicron aerosol species and has important implications on climate. Recent measurements have shown that the processes governing the lifecycle of SOA particles, and their properties (such as evaporation behavior, phase, and viscosity) are not represented accurately in regional and global climate models. As part of the ASR program, we have used laboratory and field measurements of SOA and a high-resolution regional community model (WRF-Chem) to understand the implications of low effective volatility of SOA due to particle phase processes (e.g. oligomerization) and the gas-phase fragmentation (breaking carbon-carbon bonds during aging) reactions. We recently implemented this new modeling framework using the modified volatility basis set approach coupled with the modal aerosol treatment within the atmospheric component of CESM (Community Atmospheric Model CAM5) as part of a SciDAC project. This new framework replaces the previous crude treatment of SOA in CAM5 with a new advanced parameterization that represents multi-generational gas-phase chemistry of organic precursors in each of the three source categories: anthropogenic, biomass burning and biogenic. The multi-generational chemistry parameterization includes both functionalization and fragmentation reactions and also implements our simplified approach to treat the semi-solid (glassy) nearly non-volatile nature of SOA. Preliminary results show large changes in the horizontal and vertical distribution of SOA with implications for changes in direct and indirect climate forcing. This new framework is an essential tool to improve SOA representation and better understand aerosols and their interactions with clouds and global climate change. This work also demonstrates the value of testing the newly-developed measurement-based modeling paradigms for SOA using the high-resolution regional model, and then leveraging these findings to improve predictions of global climate models.Lead PI
Manishkumar Shrivastava — Pacific Northwest National Laboratory