Ground solar absorption observations of total column CO, CO2, CH4, and aerosol optical depth from California's Sequoia Lightning Complex Fire: emission factors and modified combustion efficiency at regional scales

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Frausto-Vicencio, Isis, Heerah, Sajjan, Meyer, Aaron G., Parker, Harrison A., Dubey, Manvendra, Hopkins, Francesca M.
• Format: Text
• Language: English
• Published: 2023
• Subjects: Aerosol Robotic Network
• Online Access: https://doi.org/10.5194/acp-23-4521-2023; https://acp.copernicus.org/articles/23/4521/2023/

With global wildfires becoming more widespread and severe, tracking their emissions of greenhouse gases and air pollutants is becoming increasingly important. Wildfire emissions have primarily been characterized by in situ laboratory and field observations at fine scales. While this approach captures the mechanisms relating emissions to combustion phase and fuel properties, their evaluation on regional-scale plumes has been limited. In this study, we report remote observations of total column trace gases and aerosols during the 2020 wildfire season from smoke plumes in the Sierra Nevada of California with an EM27/SUN solar Fourier transform infrared (FTIR) spectrometer. We derive total column aerosol optical depth (AOD), emission factors (EFs) and modified combustion efficiency (MCE) for these fires and evaluate relationships between them, based on combustion phase at regional scales. We demonstrate that the EM27/SUN effectively detects changes in CO, CO 2 , and CH 4 in the atmospheric column at ∼10 km horizontal scales that are attributed to wildfire emissions. These observations are used to derive total column EF CO of 120.5±12.2 and EF CH 4 <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="17pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="32fcb9b06949ba990243bb7a696d298c"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-23-4521-2023-ie00001.svg" width="17pt" height="10pt" src="acp-23-4521-2023-ie00001.png"/></svg:svg> of 4.3±0.8 for a regional smoke plume event in mixed combustion phases. These values are consistent with in situ relationships measured in similar temperate coniferous forest wildfires. FTIR-derived AOD was compared to a nearby AERONET (AErosol RObotic NETwork) station and observed ratios of X CO to AOD were consistent with those previously observed from satellites. We also show that co-located X CO observations from the TROPOspheric Monitoring Instrument (TROPOMI) satellite-based instrument are 9.7±1.3 % higher than our EM27/SUN ...