Ehrlich, A., Bierwirth, E., Wendisch, M., Gayet, J.-F., Mioche, G., Lampert, A., and Heintzenberg, J.: Cloud phase identification of Arctic boundary–layer clouds from airborne spectral reflection measurements: Test of three approaches, Atmos. Chem. Phys., 8, 7493–7505, www.atmos-chem-phys.net/8/7493/2008/, 2008b.