Preprints
https://doi.org/10.5194/acp-2022-57
https://doi.org/10.5194/acp-2022-57
 
22 Feb 2022
22 Feb 2022
Status: this preprint is currently under review for the journal ACP.

The ice-nucleating activity of African mineral dust in the Caribbean boundary layer

Alexander D. Harrison1, Daniel O’Sullivan1, Michael P. Adams1, Grace C. E. Porter1, Edmund Blades2, Cherise Brathwaite3, Rebecca Chewitt-Lucas3, Cassandra Gaston4, Rachel Hawker1, Ovid O. Krüger5, Leslie Neve1, Mira L. Pöhlker5,6,7, Christopher Pöhlker5, Ulrich Pöschl5, Alberto Sanchez-Marroquin1, Andrea Sealy3, Peter Sealy8, Mark D. Tarn1, Shanice Whitehall3, James B. McQuaid1, Kenneth S. Carslaw1, Joseph M. Prospero4, and Benjamin J. Murray1 Alexander D. Harrison et al.
  • 1School of Earth and Environment, University of Leeds, Woodhouse Lane, Leeds, England
  • 2Queen Elizabeth Hospital, Martindales Road, St. Michael, Barbados
  • 3Caribbean Institute for Meteorology and Hydrology, Bridgetown, Barbados
  • 4Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, U.S.A.
  • 5Multiphase Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
  • 6Leibniz Institute for Tropospheric Research (TROPOS), Leipzig, Germany
  • 7Institute for Meteorology, University of Leipzig, Stephanstraße, Leipzig, Germany
  • 8AEROCE Research Facility, Ragged Point, St Philip, Barbados

Abstract. African mineral dust is transported many thousands of kilometres from its source regions and, because of its ability to nucleate ice, it plays a major role in cloud glaciation around the globe. The ice-nucleating activity of desert dust is influenced by its mineralogy, which varies substantially between source regions and across particle sizes. However, in models it is often assumed that the activity (expressed as active sites per unit surface area as a function of temperature) of atmospheric mineral dust is the same everywhere on the globe. Here, we find that the ice-nucleating activity of African desert dust sampled in the summertime marine boundary layer of Barbados (July and August, 2017) is substantially lower than parameterizations based on soil from specific locations in the Saharan desert or dust sedimented from dust storms. We conclude that the activity of dust in Barbados’ boundary layer is primarily defined by the low K-feldspar content of the dust, which is around 1 %. We propose that the dust we sampled in the Caribbean was from a region in West Africa (in and around the Sahel in Mauritania and Mali), which has a much lower feldspar content than other African sources across the Sahara and Sahel.

Alexander D. Harrison et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-57', Anonymous Referee #1, 07 Mar 2022
  • RC2: 'Comment on acp-2022-57', Anonymous Referee #2, 21 Mar 2022

Alexander D. Harrison et al.

Alexander D. Harrison et al.

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Short summary
The formation of ice in clouds fundamentally alters cloud properties, hence it is important we understand the special aerosol particles that can nucleate ice when immersed in supercooled cloud droplets. In this paper we show that African desert dust that has travelled across the Atlantic to the Caribbean nucleates ice much less well than we might have expected.
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