Small Ice Particles at Slightly Supercooled Temperatures in Tropical Maritime Convection

Research output: Contribution to journalArticlepeer-review

  • External authors:
  • Gary Lloyd
  • Michael Flynn
  • James Dorsey
  • Dantong Liu
  • Oliver Schlenczek
  • Jacob Fugal
  • Stephan Borrmann
  • Richard Cotton
  • Paul Field
  • Alan Blyth


In this paper we show that the origin of the ice phase in tropical cumulus clouds over the sea may occur by primary ice nucleation of small crystals at temperatures just between 0 and − 5 ◦C. This was made possible through use of a holographic instrument able to image cloud particles at very high resolution and small size (6 μm). The environment in which the observations were conducted was notable for the presence of desert dust advected over the ocean from the Sahara. However, there is no laboratory evidence to suggest that these dust particles can act as ice nuclei at temperatures warmer than about −10 ◦ C, the zone in which the first ice was observed in these clouds. The small ice particles were observed to grow rapidly by vapour diffusion, riming, and possibly through collisions with supercooled raindrops, causing these to freeze and potentially shatter. This in turn leads to the further production of secondary ice in these clouds. Hence, although the numbers of primary ice particles are small, they are very effective in initiating the rapid glaciation of the cloud, altering the dynamics and precipitation produc- tion processes.

Bibliographical metadata

Original languageEnglish
Pages (from-to)3895–3904
Number of pages20
JournalAtmospheric Chemistry and Physics
Early online date8 Jul 2019
Publication statusPublished - 31 Mar 2020