1. Department of Physics, National and Kapodistrian University of Athens, 15784 Athens, Greece
2. Institute for Environmental Research and Sustainable Development, National Observatory of Athens, 15236 Athens, Greece
3. Research Centre Human Biometeorology, German Meteorological Service (DWD), 79085 Freiburg, Germany
4. Institute of Earth and Environmental Sciences, University of Freiburg, 79104 Freiburg, Germany