Pollution trace gases C<sub>2</sub>H<sub>6</sub>, C<sub>2</sub>H<sub>2</sub>, HCOOH, and PAN in the North Atlantic UTLS: observations and simulations

Abstract. Measurements of the pollution trace gases ethane (C2H6), ethyne (C2H2), formic acid (HCOOH), and peroxyacetyl nitrate (PAN) were performed in North Atlantic upper troposphere lowermost stratosphere (UTLS) region with airborne limb imager GLORIA (Gimballed Limb Observer for Radiance Imaging Atmosphere) high spatial resolution down to cloud top. Observations made during flights German research aircraft HALO (High Altitude LOng Range Research Aircraft) frame WISE (Wave-driven ISentropic Exchange) campaign, which was carried out autumn 2017 from Shannon (Ireland) Oberpfaffenhofen (Germany). Enhanced volume mixing ratios (VMRs) up 2.2 ppbv C2H6, 0.2 C2H2, 0.9 HCOOH, 0.4 PAN detected flight on 13 September around tropopause above British Isles. Elevated quantities measured even (locally 14 km), likely reflecting fact that this molecule has longest lifetime four species discussed herein. Backward trajectory calculations as well global three-dimensional Chemical Lagrangian Model Stratosphere (CLaMS) simulations artificial tracers air mass origin have shown main sources observed pollutant are forest fires America anthropogenic South Asia Southeast uplifted moved within Asian monsoon anticyclone (AMA) circulation system. After release AMA, these or their precursor substances transported by strong tropospheric winds over large distances, depending particular atmospheric months. compared models EMAC (ECHAM5/MESSy Atmospheric Chemistry) CAMS (Copernicus Atmosphere Monitoring Service). These qualitatively able reproduce VMR enhancements but underestimate absolute amount increase. Increasing emissions a factor 2 reduces disagreement between simulated results illustrates importance quality emission databases used chemical models.