The CU Airborne Solar Occultation Flux instrument: Performance evaluation during BB-FLUX

The Biomass Burning Flux Measurements of Trace Gases and Aerosols (BB-FLUX) field campaign deployed the University of Colorado Airborne Solar Occultation Flux (CU AirSOF) instrument aboard the University of Wyoming King Air research aircraft during the 2018 Pacific Northwest wildfire season (July- September).

CU AirSOF tracks the sun even through thick smoke plumes using short-wave infrared wavelengths to minimize scattering from smoke partides, and uses Fourier transform infrared spectroscopy (FTS) to measure the column absorption of multiple trace gases at mid-infrared wavelengths. The instrument is described, characterized, and evaluated using colocated ground-based remote sensing and airborne in situ data sets. Vertical column density (VCD) measurements agree well with a colocated stationary high-resolution FTS for carbon monoxide (CO, slope within 2%), formaldehyde (HCHO, 3%), formic acid (HCOOH, 18%), ethane (C2H6, 4%), ammonia (NH3, 4%), hydrogen cyanide (HCN, 10%), and peroxyacyl nitrate (PAN(FTs), 1%; we distinguish the molecule PAN from PAN(FTs), which includes similar molecules and is measured as a sum by FTS).