Small Ice Particles at Slightly Supercooled Temperatures in Tropical Maritime Convection

Gary Lloyd, Thomas Choularton, Keith Bower, Jonathan Crosier, Martin Gallagher, Michael Flynn, James Dorsey, Dantong Liu, Jonathan Taylor, Oliver Schlenczek, Jacob Fugal, Stephan Borrmann, Richard Cotton, Paul Field, Alan Blyth

Research output: Contribution to journalArticlepeer-review

Abstract

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

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