x) Investigation of atmospheric transport of aerosols into the Arctic: The proposed work will mainly use the Lagrangian atmospheric transport model FLEXPART (Pisso et al., 2019; Bakels et al., 2024) to investigate the atmospheric transport of aerosols into and within the Arctic and corresponding trends on a decadal/climatological time scale. An accurate quantification of the Arctic atmospheric aerosol burden will help to address open questions about the contribution of aerosols to Arctic amplification and its future evolution, and provide emission constraints that can be used to test and improve aerosol schemes in Earth system models, thereby reducing uncertainties in effective radiative forcing and climate sensitivity. The aim is to explain observed Arctic aerosol trends, evaluating the importance of local versus remote emission sources, and changing emissions versus changing meteorology. Different Arctic observation stations are sensitive to different emission regions, it is therefore important to understand observed trends at various stations to get a comprehensive picture of aerosol emissions and atmospheric changes which affect these trends. Due to it’s Lagrangian nature, FLEXPART needs to be run specifically for several Arctic observation stations independently. Also, due to the fact that different aerosols are scavenging differently in the atmosphere, aerosol-species specific simulations are necessary. x) Transport simulations of Arctic Warm-Air intrusions: In addition to the study of Arctic aerosol transport on a climatological time scale, I will also investigate short term events, so-called Arctic Warm-Air Intrusions. These type of events potentially account for almost 30% of the total wintertime poleward transport of moisture (Woods et al., 2013). Warm-air intrusions can also be favourable for an enhanced transport of aerosols (e.g., Dada et al., 2022; Lapere et al., 2024). Since climate models show large biases in moisture flux during these events (Woods et al., 2017), there is a need to better quantify the transport of moisture, energy, and aerosols during warm-air intrusions. This will also help to provide better forcing for climate simulations. Bakels et al. (2024): 10.5194/gmd-17-7595-2024; Dada et al. (2022): 10.1038/s41467-022-32872-2; Lapere et al. (2024): 10.1029/2023JD039606; Pisso et al. (2019): 10.5194/gmd-12-4955-2019; Woods et al. (2013): 10.1002/grl.50912; Woods et al. (2017): 10.1175/JCLI-D-16-0710.1