Speaker: Nathaniel Brockway
Wildfires are the largest source of primary organic aerosols globally and have the potential to produce large amounts of ozone and secondary organic aerosols (SOA). Ozone and particles can be transported to populated areas and affect the air quality of millions of people. As wildfires are expected to worsen in the coming decades, it is important to understand and monitor smoke emission and chemistry to determine its impact on air quality. The production of secondary pollutants in smoke plumes is driven by radical chemistry, and nitrous acid (HONO) is thought to be the primary source of OH early in smoke plumes.
HONO emissions are difficult to determine due to its fast photolytic decay that reduces its concentration by the time in-situ measurement can safely be performed. Airborne and satellite remote sensing offers a unique opportunity to overcome this challenge. In addition, new satellites with high spatial resolution, such as the TROPOMI and GEMS instruments, allow large-scale monitoring of fire plumes. However, trace gas remote sensing in biomass burning plumes is still in its infancy, and recent studies are based on highly simplified assumptions on radiative transfer in plumes.
Here, I use airborne remote sensing observations with UCLA’s mini-DOAS instrument during the FIREX-AQ campaign to develop techniques to retrieve trace gases, such as HONO, HCHO, and SO2, early in biomass burning plumes. Using data from the numerous other instruments on board the aircraft, I discuss how much information can be retrieved from our remote sensing instrument under realistic conditions. The application of these techniques allows the retrieval of trace gas concentrations and the determination of emission factors of the OH radical precursors HONO and HCHO at the fire location.