Aviation-induced aerosol particles within the UTLS: Properties and processing observed from the IAGOS-CARIBIC Flying Laboratory

The influence of aviation on atmospheric aerosol, its processing, and its implications for climate are still areas associated with significant uncertainties. We carried out an in-depth examination of the characteristics of atmospheric aerosols linked to aviation by analysing aircraft emissions observed during missions of the IAGOS-CARIBIC Flying Laboratory.

Equipped with a wide variety of aerosol and trace gas instrumentation, the IAGOS-CARIBIC Flying Laboratory conducted 42 operational flights on a Lufthansa Airbus A340-600 passenger aircraft from July 2018 to March 2020. These flights included routes from Munich, Germany, to various destinations in North America, South Africa, and East Asia. We developed and implemented a method to automatically identify aircraft exhaust plumes based on the 1 Hz resolved NOy and aerosol data sets. Between 2018 and 2020, this method identified over 1100 distinct aircraft plumes, offering a robust statistical foundation and global perspectives on aviation's influence on aerosol and trace gas characteristics. For each plume, the measured parameters were further divided into their respective background and plume excess values.

The analysis of the plume excess properties, such as the non-volatile aerosol fraction, shows similar characteristics independent of the emission altitude. Notably, the emitted aerosol predominantly existed as an external mixture in contrast to the mostly internally mixed background aerosol, even at a mean plume age of 1 to 3 hours. For the large accumulation mode particles (diameter > 250 nm) no enhancement above the background variability could be detected in the aircraft plume. Furthermore, we discuss the particle emission indices (EI's) derived from our aircraft plume analysis in comparison to the particle EI's used in global models and those reported from aircraft engine certification measurements.