1. Department of Physics, Lund University, Professorsgatan 1, Lund SE-22363, Sweden
2. Swedish Meteorological and Hydrological Institute (SMHI), Norrköping SE-60176, Sweden
3. Department of Chemistry, Aarhus University, Langelandsgade 140, Aarhus DK-8000, Denmark
4. Finnish Meteorological Institute, Kuopio FI-70211, Finland
5. Department of Chemistry, Nanoscience Center, University of Jyväskylä, Jyväskylä FI-40014, Finland
6. Department of Physical Geography and Ecosystem Science, Lund University, Lund SE-22362, Sweden
7. Institute for Atmospheric and Earth System Research/Physics, Faculty of Science, University of Helsinki, Helsinki FI-00014, Finland
8. Joint International Research Laboratory of Atmospheric and Earth System Sciences, School of Atmospheric Sciences, Nanjing University, Nanjing CN-210023, China
9. Swedish Environmental Research Institute IVL, Malmö SE-21119, Sweden