Atmos. Chem. Phys. Discuss., 8, 20965-21000, 2008
© Author(s) 2008. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Single ice crystal measurements during nucleation experiments with the depolarization detector IODE
M. Nicolet1, O. Stetzer1, U. Lohmann1, and O. Möhler2
1Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
2Institute for Meteorology and Climate Research, Forschungszentrum Karlsruhe, Germany

Abstract. In order to determine the efficiency of aerosol particles of several types to nucleate ice, an Ice Optical DEpolarization detector (IODE) was developed to distinguish between water droplets and ice crystals in ice nucleation chambers. A laser beam polarized linearly (power: 50 mW, wavelength: 407 nm) is directed through the chamber. The scattered light intensity from particles is measured at a scattering angle of Θ=175° in both polarization components (parallel and perpendicular). The ratio between the perpendicular intensity over the total one gives the depolarization ratio δ. Single particle detection is possible, using a peak detection algorithm. For high particle concentrations, a real-time signal averaging method can also be run simultaneously. The IODE detector was used in connection with the Zurich ice nucleation chamber during the ICIS 2007 workshop where ice nucleation experiments were performed with several aerosol types. In presence of ice crystals, peaks were detected in both channels, generating depolarization signals. Mean values of δ ranged from 0.24 to 0.37.

Citation: Nicolet, M., Stetzer, O., Lohmann, U., and Möhler, O.: Single ice crystal measurements during nucleation experiments with the depolarization detector IODE, Atmos. Chem. Phys. Discuss., 8, 20965-21000, doi:10.5194/acpd-8-20965-2008, 2008.
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