Harry Vereecken, Agrosphere Institute (IBG-3), Forschungszentrum Juelich GmbH, Julich, GERMANY, Heye Bogena, Agrosphere Institute, IBG-3, Forschungszentrum Juelich GmbH, Juelich, GERMANY, Steffen Zacharias, Helmholtz Centre for Environmental Research, UFZ, Leipzig, Germany, Knut Kaiser, German Research Centre for Geosciences, GFZ, Potsdam, Germany, Hans Papen, IMK-IFU, KIT-Atmospheric Environmental Research Division, Garmisch-Partenkirchen, Germany, Eckart Priesack, Helmholtz Zentrum München, Neuherberg, Germany and Irena Hanjsek, Microwaves and Radar Institute, DLR, 82234 Weßling, Germany