Tracer study to estimate the transport of cruise altitude aviation emissions in Northern Hemisphere

Abstract. Given the increasing role of intercontinental and higher altitude emissions influence on surface air quality, it is important to understand the transport characteristics of these emissions both for policy and mitigation strategies. The horizontal and vertical transport of directly emitted upper troposphere anthropogenic cruise altitude aircraft emissions (CAAE) has not been well understood due to limited studies. Therefore, in this study we conducted tracer simulations for key source regions in the Northern hemisphere to understand the transport and influence of CAAE on surface air quality. Our results from Northern hemisphere simulations highlight that < 0.6% of CAAE tracer mass fraction occur near the surface even after 90 days of transport time. 30–40 % of tracers are found in the upper and mid-troposphere with slightly higher downward transport occurring during winter than summer season. The tagged source tracer simulations illustrated the source-receptor relationships and showed that ~ 10–50 % source contributions occur in downwind receptor regions.