The BB-FLUX Project: How Much Fuel Goes up in Smoke?

Today's fire season is three times longer, and affects a larger area than 20 years ago. This expansion of the spatial and seasonal "fire niche" is largely due to human caused wildfires. While there is hardly a month without wildfires in the continental U.S., pyrogenic emissions of trace gases and aerosols remain a poorly characterized source of pollution. Predicting pyrogenic carbon emissions remains a major challenge, in part due to the lack of measurement techniques to evaluate wildfire emissions comprehensively and quantitatively. In October 2017, the University of Colorado (CU) demonstrated first measurements of CO mass fluxes on the scale of actual wildfires (the Santa Rosa fires in Northern CA) by means of the CU airborne Solar Occultation Flux (CU SOF) instrument. CU SOF measures the column absorption of a variety of trace gases above the aircraft at mid-infrared wavelengths along the direct solar beam. This presentation discusses the first science deployment of CU SOF as part of the “Biomass burning of trace gases and aerosol” (BB-FLUX) project to exploit remote-sensing and in-situ synergies to quantify mass fluxes of CO₂, CO, aerosols and other trace gases (e.g., NH₃, NO₂, HCHO, CHOCHO, HONO, etc). BB-FLUX deployed CU SOF, DOAS, Lidar, in-situ CO, CO₂, O₃, H₂O, and aerosol volume during 38 research flights, and sampled 125+ plumes, 60+ plume profiles from 18 different fires during the 2018 wildfire season in the northwestern United States. In collaboration with NEON and the USFS the fuel amounts, fuel speciation, and aerial photographs of the Keithly, Miriam, Tepee and Watson Creek fires were characterized. The science objectives of the BB-FLUX project are to advance analytical means to better characterize emissions, evaluate plume injection height, study secondary plume chemistry, and ecosystem impacts from wildfires. This presentation describes new approaches that exploit synergies between remote-sensing and in-situ data to inform two question: how much fuel goes up in smoke? And what are the major uncertainties with predicting pyrogenic carbon emissions?