the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 19 May 2025
Cyclone enhances the contribution of oceanic dimethyl sulfide to the free troposphere over the Southern Ocean
Abstract. Under cold and clean atmospheric conditions, such as in free troposphere, oceanic dimethyl sulfide (DMS) was likely to form new particles. This is likely to happen over the Southern Ocean, where high DMS emissions occur along with frequent cyclones and storm activities which enhance vertical entrainment. Herein, the DMS contribution to free troposphere from the surface ocean was evaluated using the data collected from 34th Chinese Antarctic Research Expedition and Lana DMS emission climatology by running the Lagrangian particle dispersion model FLEXPART. Up to 13.1 % of the DMS was found to be transported to the free troposphere (altitudes above 2 km) from the surface ocean, which was enhanced by the cyclones. High DMS mixing ratios (> 100 pptv) were found surrounding the cyclones even at an altitude of 5 km. These results indicate that the significant DMS-derived new particles have probably occurred in high altitudes of the Southern Ocean.
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RC1: 'Comment on egusphere-2025-1622', Anonymous Referee #1, 09 Jun 2025
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Review of MS egusphere-2025-1622:
The manuscript by Zhang et al entitled “Cyclone enhances the contribution of oceanic dimethyl sulfide to the free troposphere over the Southern Ocean” deals with the measurement of oceanic and atmospheric dimethyl sulfide (DMS) during a cruise to the Southern Ocean which experienced low pressure systems. The authors have used a Lagrangian particle dispersion model (FLEXPART) to the observed data to generate a distribution pattern of DMS over 1, 3 and 5 kms. In addition, they also applied the model to the monthly climatology of DMS flux by Lana et al (2011) to generate similar altitude distribution pattern to compensate for the lack in their data as it was only along the ship track. Using the modelled data the authors want to drive the idea that cyclonic conditions will push oceanic DMS to much higher levels than under normal scenario. While the idea of the authors is commendable, the entire work is based on modelling, which is OK, but in the absence of any ground truthing and/or direct/indirect evidence of DMS or other derived products to higher levels under the influence of cyclone, the plot loses ground. Thus, I do not recommend publication of the manuscript in its present form. Please find below specific comments on the manuscript.
Introduction:
Line 54: The authors mention several cyclones, but in fact there were only 2 instances as shown in Fig. 1c and these seem to be low pressure systems. It is not clear whether they were cyclones. Satellite images as supplementary figures would have been provided.
Materials and methods:
Line 64: Details of underway shipboard measurements both in seawater and atmosphere is missing. What depth was the intake of seawater, similarly what height was the atmospheric air taken? A photo of the automated system as a supplementary figure would prove useul. How was the system calibrated?
Results and discussion:
Line 98: While the text mentions 27.5 µmol m-2 d-1, the scale in Fig. 1a is only up till 10 µmol m-2 d-1.
Line 102: Please give an explanation to why the DMS flux is lower than Lana climatology.
Line 127-128: The atmospheric DMS graph is not shown, thus its difficult to corroborate the sentence.
Citation: https://doi.org/10.5194/egusphere-2025-1622-RC1
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