The CU Airborne SOF Instrument: Spectral Retrieval and Data Validation for the 2018 BB-FLUX Campaign

Biomass burning emissions are a significant but poorly characterized source of atmospheric trace gases. Part of the reason why biomass burning emissions are so poorly characterized is because smoke plumes from biomass burning events often operate on spatial scales too large to comprehensively sample solely using in situ techniques. The University of Colorado mobile Solar Occultation Flux instrument (CU SOF), which is capable of directly measuring entire trace gas columns via the direct solar beam, can be used in conjunction with in situ sensors to better characterize biomass burning emissions. Most recently, the CU SOF was deployed onboard the University of Wyoming King Air during the 2018 Biomass Burning Flux (BB-FLUX) campaign, which aimed to quantify emission fluxes from smoke plumes during the 2018 wildfire season in the northwestern United States. Infrared spectra obtained by the CU SOF were used to calculate vertical columns of CO, NH₃, C₂H₄, C₂H₆, and other trace gases. During a number of coordinated comparison flights with the Western Wildfire Experiment for Cloud Chemistry, Aerosol, Absorption, and Nitrogen (WE-CAN) team, vertical columns obtained by the CU SOF were evaluated against data from in situ instruments onboard the NSF C-130. Following the end of the BB-FLUX campaign, collocation experiments were performed alongside the high-resolution FTS at NCAR. Additionally, vertical columns from the CU SOF were validated using output from the NASA GEOS5 model.