Towards Quantifying Smoke Emissions from Wildfires: The BB-Flux Project

Wildfire impacts on ecosystem and the atmosphere are difficult to quantify because of uncertain amounts of fuel on the ground, and their uncertain combustion efficiency to produce emissions of trace gases and aerosols (smoke). Past studies have primarily characterized emission ratios (ER = the excess mixing ratio inside wildfire plumes over background, divided by the excess of CO or CO2). Models use ERs in combination with information about fuel amounts, types, and burn conditions, to calculate emission fluxes. However, there is a lack of measurement techniques to evaluate the modelled emissions quantitatively. The University of Colorado airborne Solar Occultation Flux (CU airborne SOF) prototype instrument is a quantum leap technology that provides more direct quantitative assessments of wildfire smoke. CU airborne SOF was first deployed on research aircraft downwind of the wildfires near Sta Rosa, CA in Oct 2017, which eventually caused $9B in economic damage. The BB-FLUX project (Biomass Burning Fluxes of Trace Gases and Aerosols) deployed CU SOF together with other remote sensing (DOAS, Lidar) and in-situ measurements (CO, CO2, H2O, O3, particle size distributions) aboard the University of Wyoming King Air research aircraft during the 2018 wildfire season in the Pacific Northwest. A subset of flights were also coordinated with the NSF/NCAR C130 aircraft (WE-CAN project). In partnership with the National Ecology Observation Network fuel amounts and fuel types were characterized for a subset of the wildfires probed during the BB-FLUX project.