Problem: Biomass burning, which includes wildfires and prescribed burning, is the largest combustion source of organic aerosol (OA) to the atmosphere and has large impacts on visibility, climate and human health. Biomass burning emits primary organic aerosol (POA) but atmospheric processes (e.g., dilution, photochemistry) can not only perturb the POA mass but also form and process secondary organic aerosol (SOA) via a multitude of reaction pathways. Despite the importance, very little is understood about the atmospheric evolution of biomass burning organic aerosol and how it varies with biomass type and burn conditions. Further, regional and global models are unequipped to simulate the atmospheric processes that eventually control the climate- and health-relevant properties of biomass burning organic aerosol (BBOA).
Rationale: Over the past decade, significant advances have been made in understanding the emissions, formation and evolution of organic aerosol �?? particularly from combustion sources. These advances when combined with data from the Fire Influence on Regional and Global Environments Experiment (FIREX) campaign, will offer a unique opportunity to model and understand the physio-chemical evolution of BBOA.
The three objectives of the proposed research are:
1. Next-Generation Carbon-, Oxygen- and Size-Resolved OA (COSO) Model: We will develop a state-of-the-science OA model that combines the two-dimensional statistical oxidation model (SOM) with a detailed microphysics model (TOMAS) to simulate the physics, chemistry and thermodynamics of BBOA. The model will include recent findings about OA (effects of dilution, photochemistry, aqueous processing and experimental artifacts) and will be constrained using new laboratory data from the FIREX campaign.
2. Lagrangian Parcel Model: We will use the COSO model in a 1-D Lagrangian parcel model to evaluate performance against historical- and FIREX-related field measurements.
3. Condensed COSO for Regional/Global Models: We will develop a computationally-efficient, condensed version of the COSO model to couple with a regional chemical transport model.
Our work will establish the most important precursors and processes that control the size, mass, composition and properties of biomass burning organic aerosol and quantify, during the wildfire season, the regional contribution of biomass burning to atmospheric aerosols.