Long-range transport, characteristics, and scattering effects of atmospheric Saharan dust

Magnetic minerals and giant particles in atmospheric dust are strong absorbers of solar energy. Recent studies have shown that the giant particles can travel long distances, from Sahara to Iceland, due to strong winds (Varga et al. 2021). The absorption effects of magnetic (nano)particles can be comparable to black carbon (Moteki et al. 2017), they promote ice nucleation and play a role in cloud formation, therefore contributing to global warming (e.g. Maher, 2011). However, the properties and sources of these particles remain often poorly described (e.g. Moteki et al. 2017; Adebiyi & Kok, 2020). Our project aims to investigate the influence of giant particles and magnetic minerals on the atmosphere and on climate, by characterizing their properties. The research material consists of Saharan dust that was deposited in Finland in 2021 and collected by citizens.

The citizen science initiative resulted with samples from 525 locations, including one or more samples from each location. The first results regarding some of the dust samples were published by Meinander et al. (2023). The multidisciplinary study showed that the Saharan dust deposited in Finland originated from the Sahel desert (south of Sahara), based on the magnetic properties of the particles, and the SILAM model.

This study begins by using mineralogical, geochemical, and magnetic methods to identify and characterize the particles in the Saharan dust samples. This information enables geological classification of the material, as well as prediction of the transport mechanisms and deposition modes of the dust.

The research then focuses on the scattering and absorption of light by these particles, both experimentally and theoretically. The scattering matrix measurements will be conducted to analyze their physical and chemical characteristics, such as shape and composition. The experimentally obtained information will then be used for developing the theoretical modeling of the particles, using numerical methods. This is the first time when the scattering studies will culminate in an analysis of radiative effects of both the giant and magnetic particles in the Earth’s atmosphere.

Our project combines experimental and theoretical approaches to enhance our understanding of giant and magnetic particles in atmospheric dust, utilizing methods from both geosciences and physics. Ultimately, our work aims to contribute to characterizing the particles and their source areas, long-range transport, and scattering effects, to be utilized in emission, transport, and deposition modeling, and in climate models.

Adebiyi, A.A., & Kok, J.F. (2020). Science Advances 6, 15.
Maher, B. A. (2011). Aeolian Research 3(2), 87-144.
Meinander, O., Kouznetsov, R., Uppstu, A. et al (2023). Sci.Rep. 13, 21379.
Moteki N. et al. (2017). Nature Communications 8, 15329.
Varga, G., Dagsson-Waldhauserová, P., Gresina, F. et al. (2021). Sci.Rep. 11, 11891.