Measurement report: Chemical composition of submicron aerosol and cirrus and contrail ice residuals measured in the UTLS over Germany in winter 2018

Abstract. The knowledge of submicron aerosol composition in the upper troposphere and lower stratosphere (UTLS) and the contribution of aircraft exhaust on the cirrus and contrail formation is still limited due to sparse observations and snapshots not considering the evolution of these clouds. Airborne measurements of the aerosol chemical composition were conducted in the 2018 wintertime UTLS region over Germany. With the help of the hybrid mass spectrometer ERICA (ERC Instrument for the Chemical composition of Aerosols), the composition of background aerosol was analyzed as well as the composition of cloud residuals by applying a counterflow virtual impactor. We found that carbonaceous material plays an important role in the particulate matter in the wintertime UTLS over Germany, among which biomass burning (BB) material is the prevailing species. Complementary simulations of air mass history and synoptical analysis suggest that BB material results from wildfires, in particular the Thomas fire in Northern America. Besides the long-range transport of BB aerosol, the chemical composition of UTLS aerosol is driven by local meteorological conditions. Further, carbonaceous aerosol from aircraft exhaust including soot and engine oil contribute to the aerosol population in the size range below 200 nm. Aging contrails contain signatures of aircraft exhaust such as coated soot and engine oil among other biogenic organic compounds and are consistent with the enhancement of these compounds in aircraft exhaust plumes. Sea spray and mineral dust dominate cirrus residuals, implying the formation at a liquid state.