Irene Trombini^1,2, Valerio Lembo², Eveline van der Linden³, André Jüling³, Federico Fabiano², Paolo Ruggieri¹ and Susanna Corti², (1)University of Bologna, Department of Physics and Astronomy, Bologna, Italy, (2)CNR, Institute of Atmospheric Sciences and Climate, Bologna, Italy, (3)Royal Netherlands Meteorological Institute, De Bilt, Netherlands