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Discussion papers | Copyright
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 12 Jun 2018

Research article | 12 Jun 2018

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This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

Additional Global Climate Cooling by Clouds due to Ice Crystal Complexity

Emma Järvinen1, Olivier Jourdan2, David Neubauer3, Bin Yao4, Chao Liu4, Meinrat O. Andreae5,6, Ulrike Lohmann3, Manfred Wendisch7, Greg M. McFarquhar8,9, Thomas Leisner1, and Martin Schnaiter1 Emma Järvinen et al.
  • 1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany
  • 2Laboratoire de Météorologie Physique, Université Clermont Auvergne, OPGC, UMR/CNRS 6016, Clermont-Ferrand, France
  • 3Institute of Atmospheric and Climate Science, ETH Zürich, Zürich, Switzerland
  • 4Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 5Biogeochemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 6Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
  • 7Leipzig Institute for Meteorology, University of Leipzig, Leipzig, Germany
  • 8Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK, USA
  • 9School of Meteorology, University of Oklahoma, Norman, OK, USA

Abstract. Ice crystal submicron structures have a large impact on the optical properties of cirrus clouds and consequently on their radiative effect. Although there is growing evidence that atmospheric ice crystals are rarely pristine, direct in-situ observations of the degree of ice crystal complexity are largely missing. Here we show a comprehensive in-situ dataset of ice crystal complexity coupled with measurements of the cloud asymmetry factor collected at diverse geographical locations. Our results demonstrate that an overwhelming fraction (between 61 and 81%) of atmospheric ice crystals in the different regions sampled contain submicron deformations and, as a consequence, a low asymmetry factor of 0.75 is observed. The measured cloud angular light scattering functions were parameterized in terms of the cloud bulk asymmetry factor and tested in a global climate model. The modelling results suggest that due to ice crystal complexity, ice clouds can induce an additional cooling effect of −1.12Wm−2 on the radiative budget that has not yet been considered.

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Emma Järvinen et al.
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Publications Copernicus
Short summary
Using light diffraction it is possible to detect small features within ice particles, like surface roughness, that have not yet been fully characterised. It was found that majority of all atmospheric ice particles have small features that significantly change the way atmospheric particles interact with solar light. These small features make ice containing clouds more reflective than previously thought, which could have consequences for predicting our climate.
Using light diffraction it is possible to detect small features within ice particles, like...