Sources, spatio-temporal variation and co-variability of cloud condensation nuclei and black carbon

Aerosol-cloud and aerosol-radiation interactions depend on several factors such as the physico-chemical properties, geographical and temporal variability, and vertical distribution of atmospheric aerosols. Of particular importance are cloud condensation nuclei (CCN) and black carbon (BC) particles as a subset of the atmospheric aerosol population. CCN are a prerequisite for cloud droplet formation, and variations in CCN loading can modify cloud properties. BC can efficiently absorb solar radiation, induce local heating and inhibit cloud formation. In order to determine the effects of CCN and BC on clouds, precipitation, radiation and the Earth’s energy budget, atmospheric loading and spatio-temporal distribution of aerosols are highly relevant. Thus this dissertation addresses and helps to elucidate the spatio-temporal variation and co-variability of CCN and BC with extensive field measurement data from aircraft and ground-based measurements. The data analyses focus on anthropogenic pollution, wildfire emissions and volcanic aerosols. In the Anthropocene, the distribution and abundance of atmospheric aerosols have changed drastically. Major sources of anthropogenic particulate pollution are the combustion of fossil fuels and biofuels as well as emissions from open biomass burning. The ubiquitous presence of anthropogenic air pollution, especially over continental regions in the Northern Hemisphere, hampers the assessment of anthropogenic influence on aerosol and climate due to a lack of unperturbed reference measurements. The abrupt reduction in human activities during the first COVID-19 lockdown created unprecedented atmospheric conditions that allowed us to investigate and quantify changes in the tropospheric composition in response to changes in anthropogenic emissions. The results reflect a strong and immediate influence of human activities on air quality, the role of BC as a major air pollutant in the Anthropocene, and close links between the atmospher