Sensitivity of Chemical-Transport Model Simulations of Wildfire Smoke to Fire Emission Inventories
KRUTHIKA KUMAR, Soroush Neyestani, Rawad Saleh, University of Georgia
Abstract Number: 658
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
We investigated the sensitivity of wildfire carbonaceous aerosol (CA) burdens over the U.S. predicted by the Weather and Research Forecasting Model Coupled with Chemistry (WRF-Chem) model to choice of fire emission inventory. We performed simulations for the month of August 2015, which featured extensive wildfires in the Northwestern U.S., and implemented two emission inventories: 1) the Fire INventory from NCAR (FINN) and 2) the National Emission Inventory (NEI).
FINN predicted larger total burned area than NEI (5,280 km2 versus 4,480 km2), as well as higher emissions (in gigatonnes) of CO (49,500 versus 34,700), black carbon (BC) (349 versus 264), organic carbon (OC) (3,231 versus 1,285), and total volatile organic compounds (VOCs) (15,080 versus 6,410). In addition to differences in absolute emissions, FINN and NEI had substantially different emission profiles that led to wide differences in the relative burdens of the CA and gaseous species. For the wildfires included in this study, NEI had OC:BC = 4.87 and VOCs:CO = 0.18, while FINN had OC:BC = 9.25 and VOCs:CO = 0.3. The larger emission factors of VOCs in FINN compared to NEI led to a factor 2.5 higher secondary organic aerosol (SOA) burden predicted by the simulation the FINN simulation compared to NEI. Furthermore, the differences in plume rise treatment between FINN and NEI led to discrepancies in transport and spatial distribution of the emitted species. For example, despite the higher emission rate of BC in FINN compared to NEI, the NEI simulation predicted higher average surface concentration of wildfire BC in the Northwestern U.S. compared to the FINN simulation, whereas the FINN simulation had higher overall BC burden and more prominent long-range transport. Overall, these results highlight the importance of improving the accuracy of emission inventories to better assess the impact of wildfires on atmospheric chemistry and air quality.