Biomass burning pollution in the South Atlantic upper troposphere: GLORIA trace gas observations and evaluation of the CAMS model

Abstract. In this study, we present simultaneous airborne measurements of peroxyacetyl nitrate (PAN), ethane (C2H6), formic acid (HCOOH), methanol (CH3OH), and ethylene (C2H4) above the South Atlantic in September October 2019. Observations were obtained from Gimballed Limb Observer for Radiance Imaging Atmosphere (GLORIA), as two-dimensional altitude cross sections along flight path. The flights part SouthTRAC (Transport Composition Southern Hemisphere Upper Troposphere/Lower Stratosphere) campaign with German High Altitude Long Range Research Aircraft (HALO). On two (8 2019 7 2019), large enhancements all these substances found between 14 km maximum volume mixing ratios (VMRs) 1000 pptv PAN, 1400 C2H6, 800 HCOOH, 4500 CH3OH, 200 C2H4. One showed a common filamentary structure trace gas distributions, while second is characterized by one plume. Using backward trajectories, show that measured pollutants likely reached upper troposphere lower stratosphere (UTLS) altitudes America central Africa, where elevated PAN VMRs are visible at surface layer Copernicus Monitoring Service (CAMS) model during weeks before both measurements. comparison to results CAMS reanalysis interpolated onto GLORIA measurement geolocations, able reproduce overall pollution distributions. For absolute agreement However, C2H6 HCOOH generally underestimated model, CH3OH C2H4, species shortest atmospheric lifetimes gases discussed, overestimated CAMS. good observations suggests general transport pathways emissions locations well captured model. poorer other therefore most linked deficiencies representation loss processes emission strength.