Preprints
https://doi.org/10.5194/egusphere-2024-3747
https://doi.org/10.5194/egusphere-2024-3747
08 Jan 2025
 | 08 Jan 2025

Origin, size distribution and hygroscopic properties of marine aerosols in the south-western Indian Ocean: report of 6 campaigns of shipborne observations

Meredith Dournaux, Pierre Tulet, Joris Pianezze, Jérome Brioude, Jean-Marc Metzger, and Melilotus Thyssen

Abstract. Marine aerosol observations from 6 shipborne campaigns carried out in 2021 and 2023 in the southwest Indian Ocean are presented. A set of aerosol instruments is used to study the spatial and temporal variability of the aerosol size distribution, cloud condensation nuclei (CCN), activation diameters, and hygroscopicity (κ). Total number of aerosols (Na) shows concentration above 1500 cm-3 in polluted areas, and between 100–1500 cm-3 in the open ocean. CCN measurements (0.2 %, 0.4 % supersaturation) range from 40 to 500 cm-3. At 0.2 % (0.4 %) supersaturation, the average activation diameter is 104 (76) nm and κ is 0.36 (0.25). Using a back-trajectory model, the aerosol data were classified into three source regions. Aerosols are hydrophobic in the continental group (κ from 0.1 to 0.13), hydrophilic in the Subtropical Indian Ocean group (κ from 0.24 to 0.4), and intermediate values are found in the Southern Indian Ocean group (κ from 0.17 to 0.22). Subtropical Indian Ocean κ increases with stronger wind speeds. Southern Indian Ocean κ decreases significantly (between 0.2 % and 0.4 % supersaturation) with stronger wind speeds, probably due to a higher concentration of organic species on the smallest particle surface. High aerosol concentration events are presented. Pollution related to air masses passing through a well-developed continental boundary layer. Nucleation triggered by clear skies between two cloudy periods. Arrival of air masses at the ship’s location after a precipitation event.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
Share

Journal article(s) based on this preprint

10 Sep 2025
Origin, size distribution, and hygroscopic properties of marine aerosols in the southwestern Indian Ocean: results of six campaigns of shipborne observations
Meredith Dournaux, Pierre Tulet, Joris Pianezze, Jérome Brioude, Jean-Marc Metzger, Melilotus Thyssen, and Gilles Athier
Atmos. Chem. Phys., 25, 10315–10335, https://doi.org/10.5194/acp-25-10315-2025,https://doi.org/10.5194/acp-25-10315-2025, 2025
Short summary
Meredith Dournaux, Pierre Tulet, Joris Pianezze, Jérome Brioude, Jean-Marc Metzger, and Melilotus Thyssen

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3747', Anonymous Referee #1, 25 Feb 2025
    • AC1: 'Reply on RC1', Meredith Dournaux, 13 May 2025
  • RC2: 'Comment on egusphere-2024-3747', Anonymous Referee #2, 25 Mar 2025
    • AC2: 'Reply on RC2', Meredith Dournaux, 13 May 2025

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-3747', Anonymous Referee #1, 25 Feb 2025
    • AC1: 'Reply on RC1', Meredith Dournaux, 13 May 2025
  • RC2: 'Comment on egusphere-2024-3747', Anonymous Referee #2, 25 Mar 2025
    • AC2: 'Reply on RC2', Meredith Dournaux, 13 May 2025

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
AR by Meredith Dournaux on behalf of the Authors (13 May 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Referee Nomination & Report Request started (30 May 2025) by Tuukka Petäjä
RR by Anonymous Referee #1 (15 Jun 2025)
ED: Publish subject to minor revisions (review by editor) (24 Jun 2025) by Tuukka Petäjä
AR by Meredith Dournaux on behalf of the Authors (25 Jun 2025)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (30 Jun 2025) by Tuukka Petäjä
AR by Meredith Dournaux on behalf of the Authors (02 Jul 2025)

Journal article(s) based on this preprint

10 Sep 2025
Origin, size distribution, and hygroscopic properties of marine aerosols in the southwestern Indian Ocean: results of six campaigns of shipborne observations
Meredith Dournaux, Pierre Tulet, Joris Pianezze, Jérome Brioude, Jean-Marc Metzger, Melilotus Thyssen, and Gilles Athier
Atmos. Chem. Phys., 25, 10315–10335, https://doi.org/10.5194/acp-25-10315-2025,https://doi.org/10.5194/acp-25-10315-2025, 2025
Short summary
Meredith Dournaux, Pierre Tulet, Joris Pianezze, Jérome Brioude, Jean-Marc Metzger, and Melilotus Thyssen
Meredith Dournaux, Pierre Tulet, Joris Pianezze, Jérome Brioude, Jean-Marc Metzger, and Melilotus Thyssen

Viewed

Total article views: 685 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
514 143 28 685 19 40
  • HTML: 514
  • PDF: 143
  • XML: 28
  • Total: 685
  • BibTeX: 19
  • EndNote: 40
Views and downloads (calculated since 08 Jan 2025)
Cumulative views and downloads (calculated since 08 Jan 2025)

Viewed (geographical distribution)

Total article views: 660 (including HTML, PDF, and XML) Thereof 660 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 10 Sep 2025
Download

The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Short summary
Aerosol measurements collected during six oceanographic campaigns carried out in 2021 and 2023 in the southwest Indian Ocean are presented and analyzed in this paper. The results highlight a large variability in the aerosol concentration, size and water vapor affinity depending on in-situ conditions and air mass transport over the ocean. Marine aerosol chemical composition is highly variable over this region, and should be considered to better study their impacts on regional weather and climate.
Share