Publication
Aerosol particles play a fundamental role in the Earth system because of their impact on climate and human health. The climate impact stems from their effect on Earth's energy balance through the scattering and absorption of incoming solar radiation and the seeding of droplets and ice crystals in clouds. The climate impacts of aerosol-radiation interactions and aerosol-cloud interactions remain however the largest uncertainty in climate projections to this day, which is mainly attributable to a lack of observations during the pre-industrial era and nowadays, particularily in the vertical dimension. The impact of aerosols on health is related to their toxicity and ability to enter the respiratory tract, potentially causing a wide range of diseases and even death. Because aerosols exhibit large variability in space and time, their accurate representation in models is still challenging today. The vertical distribution of aerosols is essential for assessing their impacts but the quantification of the latter is limited by the lack of vertical in situ observations. This is especially the case in high-latitude regions characterized by the frequent occurrence of a stable boundary layer. To bridge this gap, the Modular Multiplatform Compatible Air Measurement System (MoMuCAMS) was developed during this thesis. MoMuCAMS is a platform of miniaturized aerosol and trace gas instruments designed for deployment under a tethered-balloon to carry out lower-atmospheric vertical measurements in extreme environments. In January and February 2022, MoMuCAMS was deployed in Fairbanks, Alaska for the Alaskan Layered Pollution and Chemical Analysis (ALPACA) campaign to study the vertical layering of anthropogenic emissions in the stable boundary layer. The very stable boundary layer observed during winter in high-latitude continental regions like Fairbanks is characterized by a strong reduction of turbulence, which drastically limits the dispersion of anthropogenic emissions and leads to high pollution levels. These situations are typically challenging to model. Our measurements provide a quantitative assessment of the vertical extent of the surface pollution layer and how synoptic and local meteorological conditions can affect pollution mixing. Furthermore, direct measurements of power plant plumes above ground have contributed to validating a plume dispersion model in a related study and provide a reference for future research on the impact of power plant emissions on local and regional air pollution. In 2023, MoMuCAMS was deployed from an icebreaker in the Fram Strait for the Atmospheric Rivers and the Onset of Sea Ice Melt (ARTofMELT) campaign to observe the aerosol size distribution in relation to Arctic low-level clouds (LLC). Our observations have shown distinct aerosol populations directly above LLCs with increased cloud condensation nuclei compared to below. A comparison with cloud droplet number concentrations suggests the need for entrainment of aerosols from