Analysis of ENSO Event Intensity Changes and Time–Frequency Characteristic Since 1875

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Following comments may improve the manuscript.

1. Title is no clear, Mention the timeframe 

2. Keywords are need to be reduced.

3. Introduction is short and state of the art is weak. Need to expand with recent studies.

4. Several abbreviations were used give the list for it.

5. Data collection is appropriate. Need language improvement.

6. Correlation table 2. The point of difference need to be highlighted.

7. Figure is not adequately explained.

8. Discussion and conclusion need to be improved. Lack of comparative arguments. Mostly repeating the results without comments or interpretation.

Comments on the Quality of English Language

Need Improvement

Author Response

Dear Reviewer,

Thank you for your comments on our manuscript. We have followed all your suggestions, and the responses are as follows:

1.Comment:Title is no clear, Mention the timeframe.

Reply: Thank you very much for your thoughtful review and valuable comments regarding our manuscript. In response to your comment, I have revised the title from "Analysis of ENSO Event Intensity Changes and Time-Frequency Characteristics Since 1875" to "Analysis of ENSO Event Intensity Changes and Time-Frequency Characteristics from 1875 to 2023" to clearly specify the timeframe of the study.

2. Comment:Keywords are need to be reduced.

Reply: Thank you for your valuable feedback, reducing keywords is a vital suggestion for our manuscript. In response, wehave reduced the number of keywords and retained the most essential ones for this study, including "ENSO","intensity definition", "interannual variability" and "decadal variability". We hope this reduction will provide readers with a clearer and more focused reading experience.

3. Comment:Introduction is short and state of the art is weak. Need to expand with recent studies.

Reply: Thank you very much for your constructive suggestions! We acknowledge that the introduction could be expanded to better reflect the current state of the art. In response, we have revised the section to include a more comprehensive overview of recent studies relevant to the topic.This expansion aims to provide a stronger foundation for the paper and highlight the contribution of our research within the context of the latest advancements in the field.Thank you again for your valuable feedback on our manuscript.

4. Comment:Several abbreviations were used give the list for it.

Reply: Thank you for your insightful suggestion.In response to your concern, I have added a table: “Table A3.List of abbreviations used in the article”, in Appendix A to provide a comprehensive list of all abbreviations used in the article along with their full forms and explanations. This table aims to enhance the readability and clarity of the article for readers who may be unfamiliar with some of the terminology.

5. Comment:Data collection is appropriate. Need language improvement.

Reply: We are glad that the data collection is considered appropriate. In response to your comment, we have carefully reviewed and improved the language throughout the manuscript to enhance clarity, precision, and overall readability.

6. Comment:Correlation table 2. The point of difference need to be highlighted.

Reply: Thank you for your meticulous review and for the insightful suggestion to enhance the readability of the tables in my article.I have taken your advice to heart and have made modifications to Table 2 by assigning different colors based on the correlation coefficients, allowing readers to quickly grasp the strength and direction of the relationships between variables. This color-coding approach should facilitate easier navigation and understanding of the table.

Furthermore, inspired by your feedback, I have also applied similar modifications to Table 1 and Table 3. By incorporating color-coding in these tables, I aim to achieve a more intuitive presentation of the data, making it easier for readers to identify patterns and differences at a glance. I believe that these enhancements will significantly improve the overall clarity and engagement of my article. Once again, thank you for your valuable input. Your suggestions have greatly contributed to the improvement of my work.

7. Comment:Figure is not adequately explained.

Reply: .Thank you for your helpful comment. We acknowledge that the figures in the manuscriptwerenot adequately explained. In response, we have revised the figure legends to provide a more detailed and thorough explanation, ensuring that all elements of the figures are clearly described and properly interpreted. This should improve the clarity and understanding of the figures for the readers.

8. Comment:Discussion and conclusion need to be improved. Lack of comparative arguments. Mostly repeating the results without comments or interpretation.

Reply: Thank you for your valuable feedback. We appreciate your suggestion to enhance the discussion and conclusion sections. In response, we have revised these sections to include more comparative arguments and deeper interpretation of the results. Rather than simply repeating the findings, we have focused on drawing connections to existing literature, discussing the implications of our results in the context of previous studies, and highlighting the significance of our contributions to the field.

 

Thank you once again for your guidance and consideration.

Best regards.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The aim of the work is to comprehensively study the ENSO event on a long-term series of observations using a number of indices.

The authors generally coped with the task.

I found this study is rather interesting and ready for publications with minor recommendations.

My remarks and recommendations are the following:

Line 28: Southern Oscillation (SO)

- Here is the decryption of SO. However, this is often repeated in the text. Perhaps these repetitions are unnecessary. The same applies to some other abbreviations.

Line 58: SOI sequences

- This is the first time that the abbreviation SOI is encountered, so the decryption should also be here, and not in the following text.

In the Section 2. Materials and Methods:

- In here and in the rest of the text, the authors do not use the index Niño 1+2, although it is mentioned in the introduction. It is desirable to indicate why this index was not considered.

In the Section 3.2 Changes in ENSO Event Intensity:

- When describing seasons, their names are used: winter, summer, etc. However, when studying the ENSO phenomenon and the corresponding indices in the equatorial zone, it is not entirely clear to which hemisphere these seasons belong. Maybe it would be better to use combinations of DJF, JJA, etc. instead.

Author Response

Dear Reviewer,

Thank you for your comments on our manuscript. We have followed all your suggestions, and the responses are as follows:

1.Comment:Line 28: Southern Oscillation (SO)  

-Here is the decryption of SO. However, this is often repeated in the text. Perhaps these repetitions are unnecessary. The same applies to some other abbreviations.

Reply: Thank you very much for your suggestion. I apologize for the error.We appreciate your observation regarding the repeated decryption of "SO" and other abbreviations throughout the text. In response, we have streamlined the manuscript by reducing unnecessary repetitions while ensuring that all abbreviations are clearly defined at their first occurrence. This should improve the readability and flow of the paper.

2. Comment:Line 58: SOI sequences

- This is the first time that the abbreviation SOI is encountered, so the decryption should also be here, and not in the following text.

Reply: Thank you for your helpful suggestion. We have made the necessary revision to ensure that the abbreviation "SOI" is properly defined at its first occurrence in the manuscript, as opposed to being introduced later in the text. This should improve clarity for the readers.

3. Comment:In the Section 2. Materials and Methods:

- In here and in the rest of the text, the authors do not use the index Niño 1+2, although it is mentioned in the introduction. It is desirable to indicate why this index was not considered..

Reply: Thank you for your insightful comment. We acknowledge that the Niño 1+2 index is mentioned in the introduction but not used in the analysis. In response, we have added an explanationin the manuscript clarifying that the Niño 1+2 index was not considered in our study, due to [ the Niño 1+2 index is one of Niño indices which is mainly used to monitor the initial changes of ENSO events, reflects the sea surface temperature anomalies in the eastern Pacific, closest to South America. The SST fluctuations in this region are more susceptible to local climatic phenomena(such as tropical storms, monsoons, etc.). Therefore, changes in this index may reflect more local weather patterns rather than the intensity and persistence of ENSO events on a global scale. As a result, we do not consider using this index in our research.] The explanation was added in 1 Data. We hope this addition ensures transparency and addresses the gap you pointed out.

4. Comment:In the Section 3.2 Changes in ENSO Event Intensity:

- When describing seasons, their names are used: winter, summer, etc. However, when studying the ENSO phenomenon and the corresponding indices in the equatorial zone, it is not entirely clear to which hemisphere these seasons belong. Maybe it would be better to use combinations of DJF, JJA, etc. instead.

Reply:Thank you for your thoughtful suggestion. We understand the potential confusion regarding the use of seasonal names, particularly in the context of ENSO studies in the equatorial zone. In response, we have revised the manuscript to replace seasonal names such as winter and summer with the standard abbreviations (DJF, JJA, etc.) to avoid any ambiguity and ensure clarity for readers regarding hemispheric distinctions.

 

Thank you once again for your guidance and consideration.

Best regards.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript by Chen et al. explores the intensity variations of ENSO and its mode of variability since 1875. This research provides a valuable framework for evaluating ENSO events. However, some minor corrections are required before the work can be published in Atmosphere.

The manuscript is well-structured, with an introduction that provides sufficient background references. The methodology is clearly explained, detailing the ENSO indices and wavelet analysis employed in the study.

The discussion section, however, requires revision. The description of ENSO intensity variation should incorporate explanations referencing the ocean-atmosphere intensity and SST intensity plots presented in Figure 2.

 

Line 360: Figure 7. Wavelet energy spectrum at the 3–8a scale. What is 3-8a??

Line 141: Please make the sentence clear.

Additionally, the manuscript would benefit from discussing the practical applications of the study, particularly in relation to ENSO teleconnection patterns (remote impacts). It would also be useful to elaborate on how ENSO intensity variations influences prediction skill for ENSO events.

 

Author Response

Responses to reviews 

1.Comment:The discussion section, however, requires revision. The description of ENSO intensity variation should incorporate explanations referencing the ocean-atmosphere intensity and SST intensity plots presented in Figure 2.

1.Reply: Thank you for your valuable suggestion.We agree that the discussion section can be improved by providing a more detailed explanation of ENSO intensity variation.In response, we have expanded the discussion section (Line 489) to include a more detailed analysis of ENSO event intensity variations, specifically referencing the changes in the SST intensity and ocean-atmosphere intensity curves shown in Figure 2. This addition provides a more comprehensive interpretation of the ENSO event intensity dynamics.

 

2. Comment:Line 360: Figure 7. Wavelet energy spectrum at the 3–8a scale. What is 3-8a??

2. Reply: Thank you for pointing this out. The term "3–8a" is a typographical error, and we apologize for the confusion. It should refer to the "3–8year" scale. The updated version can now be found on line 393. We have corrected this in the manuscript to ensure clarity.

 

3. Comment:Line 141: Please make the sentence clear.

3. Reply:Thank you for your feedback. We have revised the sentence on line 141 to improve its clarity and ensure that the meaning is more easily understood. The revised sentence now reads as follows:[In Equation (1), represents the cumulative value of ONI for warm (cold) events, and  denotes the cumulative value of SOI for warm (cold) events.] The updated version can now be found on line 173. We believe this revision better conveys the intended meaning.

 

4. Comment:Additionally, the manuscript would benefit from discussing the practical applications of the study, particularly in relation to ENSO teleconnection patterns (remote impacts). It would also be useful to elaborate on how ENSO intensity variations influences prediction skill for ENSO events.

4. Reply: Thank you for your valuable suggestion. We agree that discussing the practical applications of the study, particularly with regard to ENSO teleconnection patterns and their remote impacts, would strengthen the manuscript. In response, we extended various methods of ENSO intense definition, including SST indices, principal component analysis with remote correlation and large scale climate models (Line 458). We discussed the advantages and disadvantages of these methods and compared them with the methods we adopted. And based on the analysis of these methods, we discussed some ideas for our future research, We hope these extentions  can help readers expand their understanding of methodologies in related fields and have a clearer understanding of our methods

Author Response File: Author Response.docx