the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 Feb 2026
Air–Sea Interactions and Biogeochemical Responses to Medicane Daniel
Abstract. Medicane Daniel, formed on 4–12 September 2023, has stood out as the deadliest recorded storm in Mediterranean history. In this study, we investigate the role of sea features as contributors to the intensification of the Medicane Daniel. Our findings reveal the presence of a warm core eddy (WCE), high ocean heat content, and a moderate marine heat wave (MHW) at the location where Medicane Daniel intensified. These features were situated near the coastal region, facilitating the Medicane's intensification close to the coast. Consequently, the Medicane did not weaken significantly after landfall, leading to severe damage along the coast of Libya. These conditions favoured the Medicane's intensification and, due to high moisture convergence, contributed to significant precipitation at the eddy and MHW position. Importantly, observations from the high-resolution Surface Water and Ocean Topography (SWOT) satellite captured the WCE more accurately or in finer detail. This allowed for attribution of changes in biogeochemical properties –namely, chlorophyll, phytoplankton, nutrients, and dissolved oxygen concentrations due to eddy-induced vertical mixing and upwelling. The biogeochemical properties tend to increase over the WCE and MHW locations due to mixing and upwelling induced by the presence of the WCE and MHW. Our case-study analysis suggests that, under atmospheric cyclone conditions, subsurface mixing may be more influential within CCEs than upwelling driven by Ekman pumping, which, by contrast, may play a more prominent role within WCEs.
Competing interests: The contact author has declared that neither of the authors has any competing interests.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-6375', Anonymous Referee #1, 03 Feb 2026
This manuscript presents an observational analysis of Medicane Daniel and its evolution in relation to contemporaneous upper-ocean conditions, including the presence of a warm-core eddy (WCE) and a moderate marine heatwave (MHW), using satellite observations and reanalysis products. While the dataset assembled is extensive, the manuscript currently advances causal interpretations that are not fully supported by the analysis presented. I therefore recommend extra diagnostics and suggest reconsidered subjected to major revisions.
The paper claims that Daniel rapidly intensified because it passed over a Warm Core Eddy and a Marine Heat Wave. However, that doesn't clearly explain the intensification happening at some point. The intensification point must satisfy a higher OHC/SST/enthalpy flux than other points along the track with a moderate/low wind shear over that region. The authors indeed show local warmth at the point of intensification, but not relative uniqueness. If the authors can provide an along-track comparison or outlier analysis in the manuscript, it would definitely make a good paper.
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AC1: 'Reply on RC1', Babita Jangir, 21 Apr 2026
We sincerely thank the reviewer for their valuable time and effort in reviewing our manuscript. The comments and suggestions provided are very helpful and have significantly improved the quality of the manuscript. The responses to the reviewer's comments are given in the attached file.
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AC1: 'Reply on RC1', Babita Jangir, 21 Apr 2026
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RC2: 'Comment on egusphere-2025-6375', Anonymous Referee #2, 04 Mar 2026
1. Caption Figure 1: The red dot is not visible, and the yellow star mark is not visible on the white background, so it is difficult to visualise.
2. Line 345-350: What are the dates?
3. Line 351: Significance
4. Line 365: Is it the total water column for the precipitation?
5. Line 368-372: Did the meso-scale eddy and MHW coincide?
6. Line 392 for Figure 3: The dates on panels a, b, c, and d may not be correct. The date fr the chlorophyll difference is not mentioned. Ekman pumping is positive in (f), which is associated with the downwelling at the chlorophyll location. So it is not clear to me how Ekman pumping is associated with the high chlorophyll concentration. It would be more meaningful if the Ekman pumping showed as a difference, like chlorophyll.
7. Line 410-412: It is confusing without mentioning the dates used here. I suggest that the authors must mention the dates. Figure 4 is not clear to me; the caption does not show what the variables are in panels a-g in terms of physical and biogeochemical. Also, if these variables a-g are computed as a difference of two days before and after, then how are they represented on dates in the x-axis? The figure caption is not detailed enough to understand the analysis. The signature of MHW and WCE is not visible in the temperature (4a). It would also be informative if the authors had shown the MLD in all the variables from Fig. 4a-g.
Line 413: It is also not clear to me why the salinity decreases in the top 50 m. Is it related to the increased frehening, possibly?
Line 413-418: It is difficult to anticipate. I suggest that the author take the difference between 2 days after and 2 days before, and plot the anomalies of the variables from 2 days before the genesis to 2 days after the landfall, which will be more informative.
Line 421: "DCM." I strongly suggest that the authors avoid using jargon and acronyms; e.g., DCM is a term they use without explaining it. This manuscript uses excessive jargon and acronyms, making it difficult to read and understand. Hence, I strongly recommend that the authors address this to improve readability. This should also be followed in the figure panel titles and figure captions.
Line 428-430: It is not clear to me what the authors want to convey. It would be informative if the Brunt-Vaisala frequency were shown here, or at least supported by a reference citation.
Line 432-442: Adding MLD to the plot (b-g) will provide the necessary understanding, as well as the change in MLD for h-k.
Figure 7: The schematic shown here is confusing, and it is difficult to draw a conclusion from the schematic, e.g. drop vs sudden drop, etc. Also, the author must avoid using acronyms and jargon. I guess the WS in the schematic is wind speed. I strongly encourage the authors to remove all jargon and acronyms to improve readability for the broad scientific community.Citation: https://doi.org/10.5194/egusphere-2025-6375-RC2 -
AC2: 'Reply on RC2', Babita Jangir, 21 Apr 2026
We would like to sincerely thank the reviewer for their valuable time and effort in reviewing our manuscript and considering it after the ‘minor revision’. The comments and suggestions provided are very helpful and have significantly contributed to improving the quality of the manuscript. The response to the reviewer's comment is given in the attached file.
-
AC2: 'Reply on RC2', Babita Jangir, 21 Apr 2026
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RC3: 'Comment on egusphere-2025-6375', Anonymous Referee #3, 16 Mar 2026
The manuscript, “Air–Sea Interactions and Biogeochemical Responses to Medicane Daniel” by B. Jangir and E. Strobach, investigates air-sea interactions during Medicane Daniel and examines the role of warm- and cold-core eddies, marine heat waves, and ocean heat content in influencing the storm’s intensity. The study also analyzes how the ocean responds to the storm, focusing on both physical and biogeochemical changes.
Using multiple satellite and reanalysis datasets, the authors examine atmospheric and oceanic parameters relevant for cyclone dynamics, as well as pre-storm, during-storm, and post-storm changes in chlorophyll. They show that the presence of a warm-core eddy and the marine heatwave in the path of the storm contributed to the intensification, primarily through enhanced moisture convergence. The study also uses high-resolution SWOT data to detect mesoscale ocean structures that may influence cyclone intensity, providing a better understanding of the relationship between Mediterranean cyclones and underlying ocean features. Finally, the manuscript investigates the response of ocean biogeochemical parameters to the passage of the storm, including enhanced chlorophyll concentrations associated with cyclone-induced mixing and upwelling.
The manuscript contains interesting scientific analyses which are relevant to the community, especially it uses SWOT data for highlighting finer eddy structure and better heterogeneity on biogeochemical parameters. However, in my opinion, the manuscript requires substantial revisions in terms of structure and overall presentation to improve readability and clarity. In addition, it requires further discussion to put the findings in a better context; for example, the methodology and rationale behind each section should be described more clearly. The study should also discuss the potential limitations of the data used and interpretation, such as causation vs association. My comments are following:
General Comment:
In its present form, the manuscript attributes cyclone intensification primarily to the presence of warm-core eddies and marine heat waves along the storm track. However, the analysis is, right now, showing an association, rather than causation. Though showing such an association is important and scientifically justified, as this study is mainly observation-based, probable limitations or other factors that may support or contradict these findings must be discussed.
The manuscript requires clear separation between two components: how existing oceanic conditions influence the storm, and then how the storm influences the ocean, which could be done with a better presentation and restrructing if the write-up. In its current form, many important finding lost or require multiple readings of the manuscript. Also, how authors own previously published articles as cited show similar findings, it would benefit how this case study contributes to existing literature over would significantly improve the impact of the work.
The reported increase in chlorophyll and nutrient concentrations following the cyclone is interesting; however, the mechanisms responsible for these changes remain unclear. In some sections the manuscript attributes the increase in chlorophyll to enhanced Ekman pumping and cyclone-induced upwelling, while later the discussion indicates that Ekman pumping is negative (i.e., downwelling) at the same location and instead suggests subsurface mixing as the dominant mechanism. These differing explanations create ambiguity regarding the physical processes responsible for the observed biological response. Clarifying the dominant mechanism and ensuring consistent terminology throughout the manuscript would strengthen the interpretation.
The abstract contains too much information, which is relevant and important, but not structured properly, and which could be structured better. Currently, it sounds a bit incoherent.
Minor Comments
L47: “positioned” ?
L51: “Phenomenon” to “Events” in this context
L63-64: phrasing feels a bit odd “under-researched and often inadequately communicated,”
L168: “originated” to “developed”
L198: recheck (‘Total Column Water’)
L217: I think this warrants a section of its own, which includes a high-level summary of retrievals, gridding and averaging procedure, any potential limitations and uncertainty bound
L221: Better phrasing of what aspects of Medicane and also this should be a place where you summarize what each subsection will describe, and what relevance they have in your interpretation of results.
L291: It should have one paragraph, what are the major results that you further divided into subheadings
L292-293: “The presence of ocean features, i.e., Eddies, Marine Heat Wave, and Ocean Heat Content along the cyclone track and their Impact on cyclone intensity.” This subheading should be shortened
L312-314: rephrase the sentence for better clarity
L338-340: Calculation of MSLP is not clear, mentioning the Cressman technique without describing details, for example, search radius, etc.
L339: warm-core eddy, which region in the plot 2a (I think it would be better to mention the green line), also associated with figure 2, seems distorted.
L337-344: This paragraph mentions at least three eddies; however, in Fig. 2a not shown where they are on the timeline. I think it will be needed for a coherent interpretation. Also, my suggestion would explain systematically and follow the chronological evolution of the storm.
Fig 2b-g: From the caption, these plots are not anomalies; thus, it would be better to show them with some sequential colormap. Also, line contours are not legible
L362: Only Eddy supplied moisture? Or is it a positive association, while other factors may also be influencing moisture convergence?
L383: This section, as claimed, is the major focus of the study; however, the discussion does not justify it. It should clearly convey and highlight the contrast of what was not adequately represented in the low-resolution data. Also, it will improve the clarity if you separate the physical and biogeochemical parameters.
L409: One sentence is required to show what those parameters are, as a follow-up to the previous sentence ending “profiles of key variables along the cyclone’s.”
L413: mention the exact box with colors shown in the plot, for example, WCE (red lines) in Fig 4a
L414: No discussion on salinity, while it is included in plots Fig. 4b? .
L421: what is “DCM”? It is not defined in the throughput the manuscript, including any of the figure? My suggestion would be to reduce the number of such abbreviations.
L436: (panels b-d and h-i). of which figure ?
L438: “circulation motion starting.” The word “motion” is redundant.
L446: WCE should be panel (a) of Fig 6 if you are discussing this first
L448-455: Needs careful revision, as it is not clear in its current form.
L478: Sentence seems incomplete.
Citation: https://doi.org/10.5194/egusphere-2025-6375-RC3 - AC3: 'Reply on RC3', Babita Jangir, 21 Apr 2026
Peer review completion
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2025-6375', Anonymous Referee #1, 03 Feb 2026
This manuscript presents an observational analysis of Medicane Daniel and its evolution in relation to contemporaneous upper-ocean conditions, including the presence of a warm-core eddy (WCE) and a moderate marine heatwave (MHW), using satellite observations and reanalysis products. While the dataset assembled is extensive, the manuscript currently advances causal interpretations that are not fully supported by the analysis presented. I therefore recommend extra diagnostics and suggest reconsidered subjected to major revisions.
The paper claims that Daniel rapidly intensified because it passed over a Warm Core Eddy and a Marine Heat Wave. However, that doesn't clearly explain the intensification happening at some point. The intensification point must satisfy a higher OHC/SST/enthalpy flux than other points along the track with a moderate/low wind shear over that region. The authors indeed show local warmth at the point of intensification, but not relative uniqueness. If the authors can provide an along-track comparison or outlier analysis in the manuscript, it would definitely make a good paper.
-
AC1: 'Reply on RC1', Babita Jangir, 21 Apr 2026
We sincerely thank the reviewer for their valuable time and effort in reviewing our manuscript. The comments and suggestions provided are very helpful and have significantly improved the quality of the manuscript. The responses to the reviewer's comments are given in the attached file.
-
AC1: 'Reply on RC1', Babita Jangir, 21 Apr 2026
-
RC2: 'Comment on egusphere-2025-6375', Anonymous Referee #2, 04 Mar 2026
1. Caption Figure 1: The red dot is not visible, and the yellow star mark is not visible on the white background, so it is difficult to visualise.
2. Line 345-350: What are the dates?
3. Line 351: Significance
4. Line 365: Is it the total water column for the precipitation?
5. Line 368-372: Did the meso-scale eddy and MHW coincide?
6. Line 392 for Figure 3: The dates on panels a, b, c, and d may not be correct. The date fr the chlorophyll difference is not mentioned. Ekman pumping is positive in (f), which is associated with the downwelling at the chlorophyll location. So it is not clear to me how Ekman pumping is associated with the high chlorophyll concentration. It would be more meaningful if the Ekman pumping showed as a difference, like chlorophyll.
7. Line 410-412: It is confusing without mentioning the dates used here. I suggest that the authors must mention the dates. Figure 4 is not clear to me; the caption does not show what the variables are in panels a-g in terms of physical and biogeochemical. Also, if these variables a-g are computed as a difference of two days before and after, then how are they represented on dates in the x-axis? The figure caption is not detailed enough to understand the analysis. The signature of MHW and WCE is not visible in the temperature (4a). It would also be informative if the authors had shown the MLD in all the variables from Fig. 4a-g.
Line 413: It is also not clear to me why the salinity decreases in the top 50 m. Is it related to the increased frehening, possibly?
Line 413-418: It is difficult to anticipate. I suggest that the author take the difference between 2 days after and 2 days before, and plot the anomalies of the variables from 2 days before the genesis to 2 days after the landfall, which will be more informative.
Line 421: "DCM." I strongly suggest that the authors avoid using jargon and acronyms; e.g., DCM is a term they use without explaining it. This manuscript uses excessive jargon and acronyms, making it difficult to read and understand. Hence, I strongly recommend that the authors address this to improve readability. This should also be followed in the figure panel titles and figure captions.
Line 428-430: It is not clear to me what the authors want to convey. It would be informative if the Brunt-Vaisala frequency were shown here, or at least supported by a reference citation.
Line 432-442: Adding MLD to the plot (b-g) will provide the necessary understanding, as well as the change in MLD for h-k.
Figure 7: The schematic shown here is confusing, and it is difficult to draw a conclusion from the schematic, e.g. drop vs sudden drop, etc. Also, the author must avoid using acronyms and jargon. I guess the WS in the schematic is wind speed. I strongly encourage the authors to remove all jargon and acronyms to improve readability for the broad scientific community.Citation: https://doi.org/10.5194/egusphere-2025-6375-RC2 -
AC2: 'Reply on RC2', Babita Jangir, 21 Apr 2026
We would like to sincerely thank the reviewer for their valuable time and effort in reviewing our manuscript and considering it after the ‘minor revision’. The comments and suggestions provided are very helpful and have significantly contributed to improving the quality of the manuscript. The response to the reviewer's comment is given in the attached file.
-
AC2: 'Reply on RC2', Babita Jangir, 21 Apr 2026
-
RC3: 'Comment on egusphere-2025-6375', Anonymous Referee #3, 16 Mar 2026
The manuscript, “Air–Sea Interactions and Biogeochemical Responses to Medicane Daniel” by B. Jangir and E. Strobach, investigates air-sea interactions during Medicane Daniel and examines the role of warm- and cold-core eddies, marine heat waves, and ocean heat content in influencing the storm’s intensity. The study also analyzes how the ocean responds to the storm, focusing on both physical and biogeochemical changes.
Using multiple satellite and reanalysis datasets, the authors examine atmospheric and oceanic parameters relevant for cyclone dynamics, as well as pre-storm, during-storm, and post-storm changes in chlorophyll. They show that the presence of a warm-core eddy and the marine heatwave in the path of the storm contributed to the intensification, primarily through enhanced moisture convergence. The study also uses high-resolution SWOT data to detect mesoscale ocean structures that may influence cyclone intensity, providing a better understanding of the relationship between Mediterranean cyclones and underlying ocean features. Finally, the manuscript investigates the response of ocean biogeochemical parameters to the passage of the storm, including enhanced chlorophyll concentrations associated with cyclone-induced mixing and upwelling.
The manuscript contains interesting scientific analyses which are relevant to the community, especially it uses SWOT data for highlighting finer eddy structure and better heterogeneity on biogeochemical parameters. However, in my opinion, the manuscript requires substantial revisions in terms of structure and overall presentation to improve readability and clarity. In addition, it requires further discussion to put the findings in a better context; for example, the methodology and rationale behind each section should be described more clearly. The study should also discuss the potential limitations of the data used and interpretation, such as causation vs association. My comments are following:
General Comment:
In its present form, the manuscript attributes cyclone intensification primarily to the presence of warm-core eddies and marine heat waves along the storm track. However, the analysis is, right now, showing an association, rather than causation. Though showing such an association is important and scientifically justified, as this study is mainly observation-based, probable limitations or other factors that may support or contradict these findings must be discussed.
The manuscript requires clear separation between two components: how existing oceanic conditions influence the storm, and then how the storm influences the ocean, which could be done with a better presentation and restrructing if the write-up. In its current form, many important finding lost or require multiple readings of the manuscript. Also, how authors own previously published articles as cited show similar findings, it would benefit how this case study contributes to existing literature over would significantly improve the impact of the work.
The reported increase in chlorophyll and nutrient concentrations following the cyclone is interesting; however, the mechanisms responsible for these changes remain unclear. In some sections the manuscript attributes the increase in chlorophyll to enhanced Ekman pumping and cyclone-induced upwelling, while later the discussion indicates that Ekman pumping is negative (i.e., downwelling) at the same location and instead suggests subsurface mixing as the dominant mechanism. These differing explanations create ambiguity regarding the physical processes responsible for the observed biological response. Clarifying the dominant mechanism and ensuring consistent terminology throughout the manuscript would strengthen the interpretation.
The abstract contains too much information, which is relevant and important, but not structured properly, and which could be structured better. Currently, it sounds a bit incoherent.
Minor Comments
L47: “positioned” ?
L51: “Phenomenon” to “Events” in this context
L63-64: phrasing feels a bit odd “under-researched and often inadequately communicated,”
L168: “originated” to “developed”
L198: recheck (‘Total Column Water’)
L217: I think this warrants a section of its own, which includes a high-level summary of retrievals, gridding and averaging procedure, any potential limitations and uncertainty bound
L221: Better phrasing of what aspects of Medicane and also this should be a place where you summarize what each subsection will describe, and what relevance they have in your interpretation of results.
L291: It should have one paragraph, what are the major results that you further divided into subheadings
L292-293: “The presence of ocean features, i.e., Eddies, Marine Heat Wave, and Ocean Heat Content along the cyclone track and their Impact on cyclone intensity.” This subheading should be shortened
L312-314: rephrase the sentence for better clarity
L338-340: Calculation of MSLP is not clear, mentioning the Cressman technique without describing details, for example, search radius, etc.
L339: warm-core eddy, which region in the plot 2a (I think it would be better to mention the green line), also associated with figure 2, seems distorted.
L337-344: This paragraph mentions at least three eddies; however, in Fig. 2a not shown where they are on the timeline. I think it will be needed for a coherent interpretation. Also, my suggestion would explain systematically and follow the chronological evolution of the storm.
Fig 2b-g: From the caption, these plots are not anomalies; thus, it would be better to show them with some sequential colormap. Also, line contours are not legible
L362: Only Eddy supplied moisture? Or is it a positive association, while other factors may also be influencing moisture convergence?
L383: This section, as claimed, is the major focus of the study; however, the discussion does not justify it. It should clearly convey and highlight the contrast of what was not adequately represented in the low-resolution data. Also, it will improve the clarity if you separate the physical and biogeochemical parameters.
L409: One sentence is required to show what those parameters are, as a follow-up to the previous sentence ending “profiles of key variables along the cyclone’s.”
L413: mention the exact box with colors shown in the plot, for example, WCE (red lines) in Fig 4a
L414: No discussion on salinity, while it is included in plots Fig. 4b? .
L421: what is “DCM”? It is not defined in the throughput the manuscript, including any of the figure? My suggestion would be to reduce the number of such abbreviations.
L436: (panels b-d and h-i). of which figure ?
L438: “circulation motion starting.” The word “motion” is redundant.
L446: WCE should be panel (a) of Fig 6 if you are discussing this first
L448-455: Needs careful revision, as it is not clear in its current form.
L478: Sentence seems incomplete.
Citation: https://doi.org/10.5194/egusphere-2025-6375-RC3 - AC3: 'Reply on RC3', Babita Jangir, 21 Apr 2026
Peer review completion
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Ehud Strobach
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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