1. Laboratory of Atmospheric Physics, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
2. Research Centre for Atmospheric Physics and Climatology, Academy of Athens, Solonos 84, 10680 Athens, Greece
3. Department of Meteorology and Climatology, School of Geology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
4. Atmospheric Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany