Quasi-spherical ice in convective clouds

AMS Citation:
Järvinen, E., and Coauthors, 2016: Quasi-spherical ice in convective clouds. Journal of the Atmospheric Sciences, 73, 3885-3910, doi:10.1175/JAS-D-15-0365.1.
Date:2016-10-01
Resource Type:article
Title:Quasi-spherical ice in convective clouds
Abstract: Homogeneous freezing of supercooled droplets occurs in convective systems in low and midlatitudes. This droplet-freezing process leads to the formation of a large amount of small ice particles, so-called frozen droplets, that are transported to the upper parts of anvil outflows, where they can influence the cloud radiative properties. However, the detailed microphysics and, thus, the scattering properties of these small ice particles are highly uncertain. Here, the link between the microphysical and optical properties of frozen droplets is investigated in cloud chamber experiments, where the frozen droplets were formed, grown, and sublimated under controlled conditions. It was found that frozen droplets developed a high degree of small-scale complexity after their initial formation and subsequent growth. During sublimation, the small-scale complexity disappeared, releasing a smooth and near-spherical ice particle. Angular light scattering and depolarization measurements confirmed that these sublimating frozen droplets scattered light similar to spherical particles: that is, they had angular light-scattering properties similar to water droplets. The knowledge gained from this laboratory study was applied to two case studies of aircraft measurements in midlatitude and tropical convective systems. The in situ aircraft measurements confirmed that the microphysics of frozen droplets is dependent on the humidity conditions they are exposed to (growth or sublimation). The existence of optically spherical frozen droplets can be important for the radiative properties of detraining convective outflows.
Peer Review:Refereed
Copyright Information:Copyright 2016 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.
OpenSky citable URL: ark:/85065/d7pn9797
Publisher's Version: 10.1175/JAS-D-15-0365.1
Author(s):
  • Emma Järvinen
  • Martin Schnaiter
  • Guillaume Mioche
  • Olivier Jourdan
  • Valery N. Shcherbakov
  • Anja Costa
  • Armin Afchine
  • Martina Krämer
  • Fabian Heidelberg
  • Tina Jurkat
  • Christiane Voigt
  • Hans Schlager
  • Leonid Nichman
  • Martin Gallagher
  • Edwin Hirst
  • Carl Schmitt - NCAR/UCAR
  • Aaron Bansemer - NCAR/UCAR
  • Andy Heymsfield - NCAR/UCAR
  • Paul Lawson
  • Ugo Tricoli
  • Klaus Pfeilsticker
  • Paul Vochezer
  • Ottmar Möhler
  • Thomas Leisner
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