Assessment of the Representativeness and Uncertainties of CTD Temperature Profiles

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors,

after second reading of your manuscript I must say I share a concern on the evidence of the contribution of your work. It can be conducted partially from the fact temperature sensors and techology are not my primary area of interest apart from vertical temperature profile features in surface and ground water intepretation, but also can be a fact theat the identification of the contribution is missed from the manuscript. 

Unless introduction seems well relevant, Discussion and Conclusion sections I see without clear and unique definition of the manuscripts contribution. 

Hereby, I want to kindly emphasize the need for clarification in the contribution. Whether it is novel observation product, framework either novel interpretation of the T profiles. 

Author Response

After second reading of your manuscript I must say I share a concern on the evidence of the contribution of your work. It can be conducted partially from the fact temperature sensors and technology are not my primary area of interest apart from vertical temperature profile features in surface and ground water interpretation, but also can be a fact that the identification of the contribution is missed from the manuscript. 

Unless introduction seems well relevant, Discussion and Conclusion sections I see without clear and unique definition of the manuscripts contribution. 

Hereby, I want to kindly emphasize the need for clarification in the contribution. Whether it is novel observation product, framework either novel interpretation of the T profiles. 

Thank you for pointing this out. In order to respond as well as possible to your remark, some sentences have been added lines 39 and following of the manuscript new version:

“…but no methodology exists to quantify the uncertainties obtained during in situ measurement profiles. In 2018 Raiteri et al. [6] applied the formula of uncertainties propagations to salinity data acquired during profiles made in the Gulf of La Spezzia, but the temperature profiles were not evaluated and the errors in relation with the dynamic effects were excludes. In 2022, Waldmann et al. [7] proposed a methodology to assess uncertainties of CDT used on mooring, but this configuration excludes the uncertainties in relation with the dynamic effects. In 2023, Wong et al. [8] published an article to describe the Argo delayed-mode process and to validate it to quantify residual errors and regional variations in uncertainty, but this procedure can’t be applied to ship-based CTD profiles. The goal of this publication is to propose a methodology to assess temperature profiles measurement uncertainties that include static and dynamic effects.”

And line 68:

“It is another goal of this publication.”

The conclusion has been also improved to clarify the contribution of the elements demonstrated in this publication.

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

The authors cleverly fixed a dual C-T sensor, the SBE 9 sonde, to the bottom of a rotating water sampler and mounted a second C-T sensor on top of the sampler to compare the temperature measurements in the descending and ascending profiles. This unique configuration not only allows the assessment of natural fluctuations in temperature, but also may increase system complexity and cost. To present the data more accurately, the figures in this article suggest optimized processing at higher resolution.

 

Overall, this article not only proposes an innovative method to evaluate the representativeness and uncertainty of CTD temperature measurements, but also provides valuable insights for improving the accuracy of the data assimilation process.

Author Response

The authors cleverly fixed a dual C-T sensor, the SBE 9 sonde, to the bottom of a rotating water sampler and mounted a second C-T sensor on top of the sampler to compare the temperature measurements in the descending and ascending profiles. This unique configuration not only allows the assessment of natural fluctuations in temperature, but also may increase system complexity and cost. To present the data more accurately, the figures in this article suggest optimized processing at higher resolution.

Overall, this article not only proposes an innovative method to evaluate the representativeness and uncertainty of CTD temperature measurements, but also provides valuable insights for improving the accuracy of the data assimilation process.

 Thank you for this comment. We agree with your remark. The size of figures has been increased in order to improve their understanding.

 

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presents an innovative use of a dual-sensor CTD configuration to evaluate the representativeness of temperature profiles during sea campaigns. The overall experimental design and data presentation are clear and detailed. However, a few areas need clarification before the work can be considered for publication:

 

The authors should better explain how their approach differs from previous methods and clearly highlight its unique contributions. Additionally, the findings on natural variability exceeding instrumental uncertainty in shallow layers should be more explicitly connected to existing literature and their broader implications.

 

The need for pressure characterization of SBE 3 sensors for deep-water measurements is mentioned but not explained in detail. Providing more context on why this has not been addressed and offering specific recommendations for future work would add value to the study.

 

Lastly, figure notation and labeling, as well as table formatting, are inconsistent and should be corrected for clarity and professionalism.

Author Response

The manuscript presents an innovative use of a dual-sensor CTD configuration to evaluate the representativeness of temperature profiles during sea campaigns. The overall experimental design and data presentation are clear and detailed. However, a few areas need clarification before the work can be considered for publication:

The authors should better explain how their approach differs from previous methods and clearly highlight its unique contributions. Additionally, the findings on natural variability exceeding instrumental uncertainty in shallow layers should be more explicitly connected to existing literature and their broader implications.

The need for pressure characterization of SBE 3 sensors for deep-water measurements is mentioned but not explained in detail. Providing more context on why this has not been addressed and offering specific recommendations for future work would add value to the study.

Lastly, figure notation and labelling, as well as table formatting, are inconsistent and should be corrected for clarity and professionalism.

Thank you for these comments and remarks.

Comment 1: The authors should better explain how their approach differs from previous methods and clearly highlight its unique contributions.

Thank you for pointing this out. In order to respond as well as possible to your remark, some sentences have been added lines 39 and following of the manuscript's new version:

“…but no methodology exists to quantify the uncertainties obtained during in situ measurement profiles. In 2018 Raiteri et al. [6] applied the formula of uncertainties propagations to salinity data acquired during profiles made in the Gulf of La Spezzia, but the temperature profiles were not evaluated and the errors in relation with the dynamic effects were excludes. In 2022, Waldmann et al. [7] proposed a methodology to assess uncertainties of CDT used on mooring, but this configuration excludes the uncertainties in relation with the dynamic effects. In 2023, Wong et al. [8] published an article to describe the Argo delayed-mode process and to validate it to quantify residual errors and regional variations in uncertainty, but this procedure can’t be applied to ship-based CTD profiles. The goal of this publication is to propose a methodology to assess temperature profiles measurement uncertainties that include static and dynamic effects.”

And line 68:

“It is another goal of this publication.”

The conclusion has been also improved to clarify the contribution of the elements demonstrated in this publication.

Comment 2: Additionally, the findings on natural variability exceeding instrumental uncertainty in shallow layers should be more explicitly connected to existing literature and their broader implications.

Thank you for pointing this out. As we are the first to point this out, there is no literature on the subject. The variability of shallow waters is in relation with tides, currents, internal waves, sun and clouds activity… This variability is known, but it was hardly quantified. This sentence has been added line 385 of the manuscript’s new version.

Ship-based CTD profiles are generally considered as perfect or without uncertainties in data assimilation and in the qualification per comparison of the other instruments (XBT, ARGO profiles…). Our findings imply that this hypothesis will have to be reconsidered. This sentence has been added in the conclusion of the manuscript’s new version.

Comment 3: The need for pressure characterization of SBE 3 sensors for deep-water measurements is mentioned but not explained in detail. Providing more context on why this has not been addressed and offering specific recommendations for future work would add value to the study.

Thank you for pointing this out. Oceanographers have always been confident in Sea-Bird Scientific instruments. Until Uchida’s publication in 2007, this effect was not known. The sentence “This effect was ignored until several assessments were carried out.” has been add line 168.

About specific recommendations, the conclusion contains the sentence line 628: “A pressure characterisation of each sensor is recommended to reduce this uncertainty to one and a half mK, as shown in the budget set out in Table 2.”

Comment 4: Lastly, figure notation and labelling, as well as table formatting, are inconsistent and should be corrected for clarity and professionalism.

The size of figures has been increased. The format and the police of tables has been adapted to the template of JMSE. Some legends have been corrected. 

Reviewer 4 Report

Comments and Suggestions for Authors

Review of Manuscript: "Assessment of the representativeness and uncertainties of CTD temperature profiles"

 

The paper is well-structured, with a clear delineation of sections for methodology, results, discussion, and conclusions. This organization aids readability and ensures the logical flow of the research. The study demonstrates a rigorous approach to assessing the representativeness and uncertainties of CTD temperature profiles. The use of dual sensors and detailed uncertainty calculations enhances credibility. However, some division needs to be modified and addressed below.

 

Abstract

The abstract is concise but could benefit from emphasizing the practical applications of the findings, such as their relevance to data assimilation processes or improving oceanographic models.

Introduction

The introduction effectively contextualizes the problem but could elaborate on how this study addresses existing gaps in the literature. Adding a brief comparison with similar studies would strengthen the narrative.

Results

The results are detailed and supported by robust data. However: Some figures (e.g., on pages 10–12) include multiple overlapping elements, which can be challenging to interpret. Consider simplifying or breaking these into separate figures for clarity. The error signals discussed in Figures 3 and 4 could be better contextualized regarding their implications for oceanographic studies.

 

 

Author Response

The paper is well-structured, with a clear delineation of sections for methodology, results, discussion, and conclusions. This organization aids readability and ensures the logical flow of the research. The study demonstrates a rigorous approach to assessing the representativeness and uncertainties of CTD temperature profiles. The use of dual sensors and detailed uncertainty calculations enhances credibility. However, some division needs to be modified and addressed below.

Abstract

The abstract is concise but could benefit from emphasizing the practical applications of the findings, such as their relevance to data assimilation processes or improving oceanographic models.

Introduction

The introduction effectively contextualizes the problem but could elaborate on how this study addresses existing gaps in the literature. Adding a brief comparison with similar studies would strengthen the narrative.

Results

The results are detailed and supported by robust data. However: Some figures (e.g., on pages 10–12) include multiple overlapping elements, which can be challenging to interpret. Consider simplifying or breaking these into separate figures for clarity. The error signals discussed in Figures 3 and 4 could be better contextualized regarding their implications for oceanographic studies.

 Thank you very much for these positive comments.

Comment 1: Abstract

The abstract is concise but could benefit from emphasizing the practical applications of the findings, such as their relevance to data assimilation processes or improving oceanographic models.

The following sentence has been added at the end of the abstract:

“Ship-based CTD profiles are generally considered as perfect or without uncertainty in data assimilation and in the qualification per comparison of other instruments (XBT, ARGO profiles…). Our findings imply that this hypothesis will have to be reconsidered.”

Comment 2: Introduction

The introduction effectively contextualizes the problem but could elaborate on how this study addresses existing gaps in the literature. Adding a brief comparison with similar studies would strengthen the narrative.

Thank you for pointing this out. In order to respond as well as possible to your remark, some sentences have been added lines 39 and following of the manuscript new version:

“…but no methodology exists to quantify the uncertainties obtained during in situ measurement profiles. In 2018 Raiteri et al. [6] applied the formula of uncertainties propagations to salinity data acquired during profiles made in the Gulf of La Spezzia, but the temperature profiles were not evaluated and the errors in relation with the dynamic effects were excludes. In 2022, Waldmann et al. [7] proposed a methodology to assess uncertainties of CDT used on mooring, but this configuration excludes the uncertainties in relation with the dynamic effects. In 2023, Wong et al. [8] published an article to describe the Argo delayed-mode process and to validate it to quantify residual errors and regional variations in uncertainty, but this procedure can’t be applied to ship-based CTD profiles. The goal of this publication is to propose a methodology to assess temperature profiles measurement uncertainties that include static and dynamic effects.”

Comment 3: Results

The results are detailed and supported by robust data. However: Some figures (e.g., on pages 10–12) include multiple overlapping elements, which can be challenging to interpret. Consider simplifying or breaking these into separate figures for clarity. The error signals discussed in Figures 3 and 4 could be better contextualized regarding their implications for oceanographic studies.

The size of figures has been increased to improve their interpretation. We didn’t want to multiply the figures, it is why we overlapped several information on the same graph. On figures a), we overlapped the measured temperature and the deviations between the downcast and the upcast with two different temperature scales. We think that it allows to better visualize the correspondences between the profile, the amplitude of deviations and the corresponding expanded uncertainties.

On figures b), the model is perfectly superimposed on the measured profile. Visualizing the differences would require to zoom on some parts with a scale of a better resolution. It is why we created the graphs c) with again two temperature scales: one for the deviations and one for the measured profile. The overlap allows again to see immediately where are deviations on the different phases of the profile.

In order to contextualize the error signals, the following sentence has been added line 394: “If this profile was used as a reference in data assimilation, its uncertainty or representativity would be 0.3 °C at this depth, so that the model error is 0.065 °C at the same depth.”

Reviewer 5 Report

Comments and Suggestions for Authors

The manuscript describes a more precise CTD data collection with respect to operational procedures due to limitations of the temperature sensors, rate of vertical deployment, water column variability, vertical displacement due to sea state and the additional of an additional sensor set at the top of the instrument cage.  The detailed examinations of the duel sensor responses while being lowered from surface to near bottom depths in various oceanic regions allowed an examination of probable deviations from actual temperatures.  The discussion was especially important with regard to ARGO profiling floats with regard to their accuracy of measurement.  In general, the manuscript was well written and organized.  The English was good but it is recommended that line 245 be revised to read "before being lowered the carousel remains under the surface"

The figures and tables are appropriate and easy to read. 

Author Response

The manuscript describes a more precise CTD data collection with respect to operational procedures due to limitations of the temperature sensors, rate of vertical deployment, water column variability, vertical displacement due to sea state and the additional of an additional sensor set at the top of the instrument cage.  The detailed examinations of the duel sensor responses while being lowered from surface to near bottom depths in various oceanic regions allowed an examination of probable deviations from actual temperatures.  The discussion was especially important with regard to ARGO profiling floats with regard to their accuracy of measurement.  In general, the manuscript was well written and organized.  The English was good but it is recommended that line 245 be revised to read "before being lowered the carousel remains under the surface"

Thank you very much for these positive comments. The correction recommended for the line 245 has been made.