1. Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, 11810 Athens, Greece
2. Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
3. Laboratory of Meteorology & Climatology, Department of Physics, University of Ioannina, 45110 Ioannina, Greece
4. Laboratory of Climatology and Atmospheric Environment, Department of Geology and Environment, National and Kapodistrian University of Athens (LACAE/NKUA), 10679 Athens, Greece
5. Research Centre for Atmospheric Physics and Climatology, Academy of Athens, 10679 Athens, Greece
6. Physicalisch Meteorologisches Observatorium, 7260 Davos, Switzerland