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. Measurements of the pollution trace gases ethane (C2H6), ethyne(C2H2), formic acid (HCOOH), and peroxyacetyl nitrate (PAN) wereperformed in the North Atlantic upper troposphere and lowermost stratosphere(UTLS) region with the airborne limb imager GLORIA (Gimballed Limb Observerfor Radiance Imaging of the Atmosphere) with high spatial resolution down tocloud top. Observations were made during flights with the German researchaircraft HALO (High Altitude and LOng Range Research Aircraft) in the frameof the WISE (Wave-driven ISentropic Exchange) campaign, which was carriedout in autumn 2017 from Shannon (Ireland) and Oberpfaffenhofen (Germany).Enhanced volume mixing ratios (VMRs) of up to 2.2 ppbv C2H6, 0.2ppbv C2H2, 0.9 ppbv HCOOH, and 0.4 ppbv PAN were detected duringthe flight on 13 September 2017 in the upper troposphere and around thetropopause above the British Isles. Elevated quantities of PAN were measuredeven in the lowermost stratosphere (locally up to 14 km), likely reflectingthe fact that this molecule has the longest lifetime of the four speciesdiscussed herein. Backward trajectory calculations as well as globalthree-dimensional ChemicalLagrangian Model of the Stratosphere (CLaMS) simulations with artificial tracers of air massorigin have shown that the main sources of the observed pollutant speciesare forest fires in North America and anthropogenic pollution in South Asia andSoutheast Asia uplifted and moved within the Asian monsoon anticyclone (AMA)circulation system. After release from the AMA, these species or theirprecursor substances are transported by strong tropospheric winds over largedistances, depending on their particular atmospheric lifetime of up tomonths. Observations are compared to simulations with the atmospheric modelsEMAC (ECHAM5/MESSy Atmospheric Chemistry) and CAMS (Copernicus AtmosphereMonitoring Service). These models are qualitatively able to reproduce themeasured VMR enhancements but underestimate the absolute amount of theincrease. Increasing the emissions in EMAC by a factor of 2 reduces thedisagreement between simulated and measured results and illustrates theimportance of the quality of emission databases used in chemical models.

atmospheric chemistry and physics

Pollution trace gases C&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;H&amp;lt;sub&amp;gt;6&amp;lt;/sub&amp;gt;, C&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, HCOOH, and PAN in the North Atlantic UTLS: observations and simulations