EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Climatic Significance of Organic Aerosol in the Boreal Region

Tero Mielonen1, Taina Yli-Juuti2, Liine Heikkinen3, Antti Arola1, Mikael Ehn3, Sini Isokääntä2, Helmi-Marja Keskinen3,4, Markku Kulmala3, Anton Laakso1, Antti Lipponen1, Krista Luoma3, Santtu Mikkonen2,5, Tuomo Nieminen2,3,6, Pauli Paasonen3, Tuukka Petäjä3, Sami Romakkaniemi1, Juha Tonttila1, Harri Kokkola1, and Annele Virtanen2
Tero Mielonen et al.
  • 1Finnish Meteorological Institute, Atmospheric Research Centre of Eastern Finland, Kuopio, Finland (
  • 2University of Eastern Finland, Department of Applied Physics, Kuopio, Finland.
  • 3University of Helsinki, Institute for Atmospheric and Earth System Research / Physics, Faculty of Science, Helsinki, Finland.
  • 4Tampere University, Aerosol Physics Laboratory, Physics Unit, Tampere, Finland.
  • 5University of Eastern Finland, Department of Environmental and Biological Sciences, Kuopio, Finland
  • 6University of Helsinki, Institute for Atmospheric and Earth System Research / Forest Sciences, Faculty of Agriculture and Forestry, Helsinki, Finland

Biogenic secondary organic aerosol (BSOA) constitutes a major fraction of aerosol over boreal forests. As the emissions of BSOA precursors are temperature dependent, changes in temperature have potentially important implications on regional aerosol radiative forcing. Here, we have used long-term aerosol composition and temperature data measurements from a boreal forest site together with remote sensing observations of aerosol and cloud properties to investigate the effect of increasing temperature on organic aerosol mass loadings, and further on aerosol direct and indirect radiative effects. The analysis was based on 7 years of measurements done at Hyytiälä, Southern Finland, and they cover the summer months (July-August) between 2012-2018. We limited the analyses to these summer months to isolate the temperature dependence of the organic mass loadings from the seasonal effects arising from the vegetation growth cycle. Our analysis showed that organic aerosol loadings and cloud condensation nuclei concentrations increased in concert with surface temperature. Furthermore, we found that cloud reflectivity increased when the organic aerosol loadings increased. This research presents the first direct observational evidence on the effect of BSOA on cloud properties and their climatic significance.

How to cite: Mielonen, T., Yli-Juuti, T., Heikkinen, L., Arola, A., Ehn, M., Isokääntä, S., Keskinen, H.-M., Kulmala, M., Laakso, A., Lipponen, A., Luoma, K., Mikkonen, S., Nieminen, T., Paasonen, P., Petäjä, T., Romakkaniemi, S., Tonttila, J., Kokkola, H., and Virtanen, A.: The Climatic Significance of Organic Aerosol in the Boreal Region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8319,, 2021.