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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
doi:10.5194/acp-2017-226
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
23 Mar 2017
Review status
This discussion paper is under review for the journal Atmospheric Chemistry and Physics (ACP).
Classification of Arctic, Mid-Latitude and Tropical Clouds in the Mixed-Phase Temperature Regime
Anja Costa1, Jessica Meyer1,a, Armin Afchine1, Anna Luebke1,b, Gebhard Günther1, James R. Dorsey2, Martin W. Gallagher2, André Ehrlich3, Manfred Wendisch3, Darrel Baumgardner4, Heike Wex5, and Martina Krämer1 1Forschungszentrum Jülich GmbH, Jülich, Germany
2Centre for Atmospheric Science, University of Manchester, UK
3Leipziger Institut für Meteorologie, Universität Leipzig, Germany
4DMT, Boulder/Colorado, USA
5Leibniz Institute for Tropospheric Research, Leipzig, Germany
anow at: Bundesanstalt für Arbeitsschutz und Arbeitsmedizin, Dortmund, Germany
bnow at: Max Planck Institute for Meteorology, Atmosphere in the Earth System Department, Hamburg, Germany
Abstract. The degree of glaciation of mixed-phase clouds constitutes one of the largest uncertainties in climate prediction. In order to better understand cloud glaciation, cloud spectrometer observations are presented in this paper that were made in the mixed-phase temperature regime between 0 °C and −38 °C, where cloud particles can either be frozen or liquid. The extensive dataset covers four airborne field campaigns providing a total of 139,000 1 Hz data points (38.6 hours within clouds) over Arctic, mid-latitude and tropical regions. We develop algorithms combining the information on number concentration, size and asphericity of the observed cloud particles to classify four cloud types associated with liquid clouds, clouds where liquid droplets and ice crystals coexist, fully glaciated clouds after the Wegener-Bergeron-Findeisen process, and clouds where secondary ice formation occurred. We quantify the occurrence of these cloud groups depending on the geographical region and temperature and find that liquid clouds dominate in our measurements during the Arctic spring, while clouds dominated by the Wegener-Bergeron-Findeisen process are most common in mid-latitude spring. Coexistence of liquid water and ice crystals is found over the whole mixed-phase temperature range in tropical convective towers in the dry season. Secondary ice is found at mid-latitudes at −5 °C to −10 °C and at higher altitudes, i.e. lower temperatures in the tropics. The distribution of the cloud types with decreasing temperatures is shown to be consistent with the theory of evolution of mixed-phase clouds. With this study, we aim to contribute to a large statistical database on cloud types in the mixed-phase temperature regime.

Citation: Costa, A., Meyer, J., Afchine, A., Luebke, A., Günther, G., Dorsey, J. R., Gallagher, M. W., Ehrlich, A., Wendisch, M., Baumgardner, D., Wex, H., and Krämer, M.: Classification of Arctic, Mid-Latitude and Tropical Clouds in the Mixed-Phase Temperature Regime, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-226, in review, 2017.
Anja Costa et al.
Anja Costa et al.
Anja Costa et al.

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Short summary
The paper presents 38 hours of in-situ cloud spectrometer observations of microphysical cloud properties in the Arctic, mid-latitudes and tropics. The clouds are classified via particle concentrations, size distributions, and – as a novelty – small particle aspherical fractions. Cloud type profiles are given for different temperatures and locations. The results confine regions where different cloud transformation processes occurred, and emphasize the importance of small particle shape detection.
The paper presents 38 hours of in-situ cloud spectrometer observations of microphysical cloud...
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