Design, Decisions, and Critical Data for FIREX

Biomass burning (BB) is a globally-distributed year-round phenomenon that is highly variable and complex in chemical composition and intensity. BB is the second largest global producer of CO₂ (the main climate forcer), total greenhouse gases, and non-methane organic gases (NMOG), which are precursors for ozone (O₃) and organic aerosol (OA). BB is the largest global source of fine primary OA, black carbon (BC, the second largest global climate forcer) and brown carbon (BrC). BB is historically understudied and field sampling of wildfires even in the US just began in 2013, but without comprehensive NMOG measurements. Many mysteries remain about smoke. A large percent of the NMOG emitted are unidentified. Post-emission, a net increase of inorganic aerosol is always measured. OA always evolves, but the net effect can be an increase or small decrease in OA and the factors deciding the outcome are unknown. The accuracy of BC measurements and the effect of organic coatings on BC properties are controversial. It’s now more widely recognized that OA – often previously treated as purely scattering – may absorb light enough to tip the net global effect of BB from cooling to warming. Absorbing OA (i.e. BrC) is produced almost entirely by BB. Few studies have measured BrC emissions and just one measured the BrC lifetime in the field. BrC formation in nighttime smoke due (e.g.) to NO₃ chemistry is likely significant, but unstudied, as is nighttime smoke chemistry in general. Smoke impacts on cloud properties are significant, but cloud impacts on smoke thru e.g. enhanced photochemistry, lightning NO_X, scavenging, and “in-droplet growth” are almost unstudied.

To address these critical unknowns we will provide both a suite of measurements and assistance with the design and execution of the NOAA FIREX program. We will quantify a critical, foundational suite of ~20-30 trace gases in the Fire Lab stack and night-time smoke using advanced artifact-free optical remote sensing. This includes the major organic and inorganic emissions of both flaming and smoldering and C, H, N, S, O, and Cl species. We will quantify BC and BrC using advanced photoacoustic spectroscopy, which avoids filter-based artifacts, in the fire lab stack and also measure how these species evolve in well-characterized context in smog chambers and nighttime smoke. Our BC and BrC instruments will be part of the first intercomparison of BC measurement techniques carried out in BB aerosol. Yokelson will provide service and timely intelligence to enhance the design and execution of all FIREX components, including the aircraft campaigns. Yokelson’s last 22 years of research includes leading and assisting projects at all scales that: (1) measured BB emissions at the Fire Lab and globally from the ground, air, and space; (2) measured interactions of BB emissions with urban sources, clouds, and biogenics; (3) synthesized lab and field emissions data; (4) advanced photochemical modeling of smoke; (5) developed/deployed new advanced instrumental techniques for smoke characterization, etc. This experience will inform his steering committee service and assistance with all aspects of FIREX.