Variations in Cloud Concentration Nuclei Related to Continental Air Pollution Control and Maritime Fuel Regulation over the Northwest Pacific Ocean

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

 

Review for “Variations in cloud concentration nuclei related to continental air pollution control and maritime fuel regulation over the northwest Pacific Ocean”

This manuscript address source apportionment of aerosols in the marine environment from ship measurements made during deployments during two different years.  Each deployments spans across two seasons with some overlap in the specific days of the year for the deployments.  The paper considers many measurements to diagnose source apportionment of the different aerosols, in this case particle size distributions, that were measured. The paper does need some revisions to ensure clarity for publication.

 Major Comments:

1)  From the title of the paper, I thought that the authors were going to provide some insight to the implications of the impact of air pollution control and marine fuel regulations.  However, in the implications, I found few implications that circle back around to this.  Rather I found additional results from satellites that aid in confirming their source apportionments that they identified. I can see where this hints at the implications, but it is not very direct. The Introduction is also limited in why this title is important but rather this is found really only in the abstract. If this is the title, then please describe these controls and regulations in the introduction and how they might impact aerosol (CCN). Then, circle back to how your results such as the apportionment, provide insight into these impacts and the implication on clouds/climate.

2) The manuscript talks much about the apportionment of CCN but the process actually uses particle size distributions. These are not necessarily CCN as PSDs can include particles that would not activate and at 0.4 and 0.2%, the CCN are not likely to include the smaller sizes of PSDs. Perhaps this just requires rewording.

 

Specific comments:

Lines 47-51: The authors should really add some citations of Twomey in this discussion. Twomey (1991) described the sensitivity of cloud albedo to the CCN concentrations. [Twomey, S. (1991). Aerosols Clouds and Radiation. Atmospheric Environment, 25A (11), 2435-2442.]

Line 92: This figure should be moved from the supplement to the regular manuscript. It provides a better perspective of the area of the measurements.

Lines 115-119: If data from this instrument is not used, there is no need to include it here.

Lines 137-144:  The authors need to be careful with the use of MODIS LWP and CER. There are inherent biases in the algorithms that are more pronounced in drizzling stratus clouds.  Additionally, from the supplement, the authors are using the non-physical factor of 5/9 in attempt to reduce the biases. While not necessarily a problem, the authors should be aware that it is an empirically derived adjustment to the LWP.

Line 152 & 159: What supersaturation were used for this CCN concentrations?

Line 181: What are you using to define Ncn? You did not state what instrument is measuring this. I am guessing it is from the condensation particle counter, but this is not clear.

Figure 1: Panels e-h should be a separate figure. The discussion of this occurs much later and these are too little to truly see the data.

Figure 2 & 3: The particle size distributions in both these figures are shows with different ranges on the x-axis. They should be shown on the same scale for a true comparison between the two years.

Line 337: Should be “non-precipitating”.

 

Author Response

This manuscript address source apportionment of aerosols in the marine environment from ship measurements made during deployments during two different years. Each deployments spans across two seasons with some overlap in the specific days of the year for the deployments. The paper considers many measurements to diagnose source apportionment of the different aerosols, in this case particle size distributions that were measured. The paper does need some revisions to ensure clarity for publication.

 

Response: Thank you very much for reviewing and providing valuable feedback on our manuscript. Your insights have significantly contributed to the improvement of the paper. We have addressed your concerns and made the necessary revisions in the corresponding sections of the manuscript. The detailed changes can be found in the Major Comments and Specific Comments sections. Thank you again for your assistance and guidance.

 

Major Comments:

1. From the title of the paper, I thought that the authors were going to provide some insight to the implications of the impact of air pollution control and marine fuel regulations. However, in the implications, I found few implications that circle back around to this. Rather I found additional results from satellites that aid in confirming their source apportionments that they identified. I can see where this hints at the implications, but it is not very direct. The Introduction is also limited in why this title is important but rather this is found really only in the abstract. If this is the title, then please describe these controls and regulations in the introduction and how they might impact aerosol (CCN). Then, circle back to how your results such as the apportionment, provide insight into these impacts and the implication on clouds/climate.

 

Response: In the background section, we further refined the statement. While emission reductions may significantly decrease particle number concentrations in the NWPO, this does not necessarily lead to a proportional reduction in CCN concentrations. In lines 65-66, we added “The same can be said to the possible impact from the changes on clouds over the NWPO [23]. ”; lines 71-76, we added “two important questions were raised: (1) how to quantify the decease of PNCs and N_ccn over the NWPO with the reduction from observations? (2) does the reduction increase the susceptibility of cloud droplet numbers to N_ccn over the NWPO? To investigate the issues, i.e., the reduction-derived decease of PNCs and N_ccn and the possible impact on cloud properties over the NWPO,  ”

In the conclusion section, we emphasized that (1) CCN concentrations respond differently to FSC policies and continental emission reductions. The observations showed a pronounced downward trend in both N_cn and N_ccn, amounting to an overall decrease of approximately 80%, from the marginal seas of China to the NWPO in 2021 and 2014 with reducing anthropogenic inputs from the continental sources; and (2) the reduction likely led to a PMF-resolved factor, characterized by a dominant nucleation mode, disappearing in 2021 compared to that resolved in 2014.

 

2. The manuscript talks much about the apportionment of CCN but the process actually uses particle size distributions. These are not necessarily CCN as PSDs can include particles that would not activate and at 0.4 and 0.2%, the CCN are not likely to include the smaller sizes of PSDs. Perhaps this just requires rewording.

 

Response: The authors are sorry that the reviewer might misunderstand the PMF modeling. In the literature, specific gaseous concentrations, meteorological conditions, etc., were also frequently included in PMF modeling while the variables just serviced tracers to identify specific sources. Here, we use these aerosols with specific particle size distributions as tracers for certain sources to analyze their potential contributions to the CCN number concentration. The issue has been clarified in the revision. We agree with the reviewer that particles of small diameters could not activate into cloud droplets under 0.2% and 0.4% SS.

 

Specific comments:

1. Lines 47-51: The authors should really add some citations of Twomey in this discussion. Twomey (1991) described the sensitivity of cloud albedo to the CCN concentrations. [Twomey, S. (1991). Aerosols Clouds and Radiation. Atmospheric Environment, 25A (11), 2435-2442.]

 

Response: Agree. The references have been added at Line 48 of the manuscript and Line 644 of the references.

 

2. Line 92: This figure should be moved from the supplement to the regular manuscript. It provides a better perspective of the area of the measurements.

 

Response: Agree. We have modified the position of the images and adjusted the numbering of the images in the manuscript, accordingly.

 

3. Lines 115-119: If data from this instrument is not used, there is no need to include it here.

 

4. Lines 137-144: The authors need to be careful with the use of MODIS LWP and CER. There are inherent biases in the algorithms that are more pronounced in drizzling stratus clouds. Additionally, from the supplement, the authors are using the non-physical factor of 5/9 in attempt to reduce the biases. While not necessarily a problem, the authors should be aware that it is an empirically derived adjustment to the LWP.

 

Response: Agree, MODIS satellite data may contain errors. Therefore, we added the sentence "However, the products suffered from uncertainties in LWP and CER, particularly those data associated with drizzling stratus clouds" in Lines 150-151 to clarify the potential inaccuracies when using satellite data.

 

5. Line 152 & 159: What supersaturation were used for this CCN concentrations?

 

Response: We used cloud condensation nuclei concentrations at 0.2% and 0.4% SS and have added explanations at the corresponding sections.

 

6. Line 181: What are you using to define Ncn? You did not state what instrument is measuring this. I am guessing it is from the condensation particle counter, but this is not clear.

 

Response: N_cn represents the number concentration of particles, which was continuously monitored using a condensation particle counter (CPC, TSI Model 3775). We have refined this description at Lines 192 and 194.

 

7. Figure 1: Panels e-h should be a separate figure. The discussion of this occurs much later and these are too little to truly see the data.

 

Response: Agree. The corresponding figures in the article have been modified as per your request at Line 289.

 

 

8. Figure 2 & 3: The particle size distributions in both these figures are shows with different ranges on the x-axis. They should be shown on the same scale for a true comparison between the two years.

 

Response: Agree. The corresponding figures in the article have been modified accordingly.

 

9. Line 337: Should be “non-precipitating”

 

Response: Done.

Reviewer 2 Report

Comments and Suggestions for Authors

Te subject addressed in this article is worthy of investigation. The paper is  not an original contribution to the field. The research method is solid and proven partly. References are upadated and related to the topic of the manuscript.

 There are some drawbacks that the authors should address them to improve this study.

1.  Lack of a specific purpose of work. The text on lines 71 to 86 is a summary that is unnecessary.

2. The manuscript is missing a Conclusions chapter.

3. The authors did not indicate any limitations of their work.

4. The quality of Figures is poor, making them unreadable.

5. Lack of emphasized novelty of the research and simulations performed.

Comments on the Quality of English Language

minor editing recommended

Author Response

There are some drawbacks that the authors should address them to improve this study.

 

Response: Thank you very much for your assistance during the paper review process. We have revised the paper according to your suggestions.

 

1. Lack of a specific purpose of work. The text on lines 71 to 86 is a summary that is unnecessary.

 

Response: Thank you for your suggestion, but we believe this summary is necessary and cannot be omitted. Here, we clarified the scientific question 'The specific quantification of the impact of FSC policy and upwind continental emission reductions on aerosols over the NWPO is unclear and needs to be determined whether this impact is significant' in line 70. Therefore, this summary roughly outlines the work we have done to address this issue, the tools we used, and the analyses we conducted. We believe this makes the logic more coherent.

 

2. The manuscript is missing a Conclusions chapter.

 

Response: Agree. We have followed your suggestion and changed the original "4. Implications and future study" to the current "4. Conclusion and implications." At the beginning of this section, we provided a summary of the article's content, emphasizing the conclusions of the current research. Additionally, in the paragraph after Line 563, we discussed the issues that further research can address and the potential challenges that may arise.

 

3. The authors did not indicate any limitations of their work.

 

Response: We described the potential issues in our study from the following perspectives:

1. Source apportionment of CCN concentrations using the PMF model. PMF does not require a detailed list of pollutants for source apportionment, which makes the factors (Factor) derived from the model more dependent on individual judgment. This is an inherent limitation of PMF. Therefore, we combined specific element data from ion chromatography with the regression of CCN contributions from PMF-derived factors to further ensure the reasonableness of factor definitions. For example, the contributions of Factor 2 and Factor 3 to CCN both show a good match with the spatiotemporal variations in Na⁺ concentrations in PM_2.5.
2. The seasonal correction factors were derived from CDNC data in the MODIS satellite. We should acknowledge that using CDNC data can lead to significant errors in satellite data in drizzling stratus clouds. However, currently, we do not have a better method to address this requirement.

 

4. The quality of Figures is poor, making them unreadable.

 

Response: We have modified and refined the figures according to the journal's requirements and the suggestions of other reviewers. The information that needs to be conveyed is now clearly presented, and the figures are readable.

 

5. Lack of emphasized novelty of the research and simulations performed.

 

Response: The primary innovation in this study is our use of an improved PMF model for source apportionment. First, to reduce the impact of zero values on the model and maintain the original peak shape of the particle size distribution, we replaced the spectral information for sizes larger than 400 nm with 1/100 CCN. Second, we reduced the particle size characteristic information to fewer than 30 bins to minimize the homogeneity of the input sources, thereby preventing a single source from being decomposed into multiple factors. Finally, we used the mode pattern of PNSDs associated with each PMF-derived source profile as a tracer for N_ccn. These aspects are emphasized in “section 2.3 PMF analysis”. The novelty is related to the quantitative estimation of CCN concentrations respond differently to FSC policies and continental emission reductions, which has been added in the revised conclusion.

The authors have much concerns on the 3-D simulation on N_ccn based on a series of our recent papers published on simulating N_ccn and N_cn in upwind continental atmosphere. The major challenges include two aspects: 1) PNSDs associated with various sources were deputy database, and whether the deputy PNSDs can truly reflect the values in East-Asian continent is entirely unknown; 2) 3-D poorly reproduce the growth of pre-existing particles in the atmosphere.

 

Minor editing recommended

 

Response: The language has been polished using the AI tool.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

I appreciate the effort the authors have put into the revision of the paper.  With the addition to the conclusions and introductions, the paper fits much better to the title and provides more scientific perspective to the study. I do have a minor comment.

The authors stated in the response that they had updated now Figures 4 and 5 to have the particle size distributions have the same x-axis, but in the version that I received, I do not see this.  I will try to clarify what I meant.  In order to easily compare 2021 with 2014, the x-axis range of panels c to h should be the same range.  Currently, Figure 4 panels appear to have a scale from 20 to 250 nm while Figure 5 panels have a scale from 10 to 800 nm.  For a fast comparison, these should be the same scale.

 

Comments on the Quality of English Language

Editing: Line 71 and 73: "decease" should be "decrease".

Please read through and find any other spelling errors from the 

Author Response

Comments and Suggestions for Authors

1. I appreciate the effort the authors have put into the revision of the paper. With the addition to the conclusions and introductions, the paper fits much better to the title and provides more scientific perspective to the study. I do have a minor comment.

 

Response：Thank you very much for your efforts in improving the article. We will make critical revisions according to your suggestions to enhance the readability and scientific quality of the paper.

 

2. The authors stated in the response that they had updated now Figures 4 and 5 to have the particle size distributions have the same x-axis, but in the version that I received, I do not see this. I will try to clarify what I meant. In order to easily compare 2021 with 2014, the x-axis range of panels c to h should be the same range. Currently, Figure 4 panels appear to have a scale from 20 to 250 nm while Figure 5 panels have a scale from 10 to 800 nm. For a fast comparison, these should be the same scale.

 

Response：We apologize for any misunderstanding regarding your previous suggestion. The corresponding figures in the article have been modified accordingly.

 

Comments on the Quality of English Language

1. Editing: Line 71 and 73: "decease" should be "decrease".

 

Response：Agree.

 

 

2. Please read through and find any other spelling errors from the paper

 

Response：We have reviewed the entire text to avoid any spelling errors.

Reviewer 2 Report

Comments and Suggestions for Authors

I have read the authors' responses. They have only minimally implemented the suggested changes. The quality of the presented content from a scientific perspective has not improved. I have no further comments.

Author Response

Comments and Suggestions for Authors

1. I have read the authors' responses. They have only minimally implemented the suggested changes. The quality of the presented content from a scientific perspective has not improved. I have no further comments.

 

Response：Thank you very much for your suggestions during the review process. They make us realize that there is considerable room for improving the readability and scientific quality of the article and illustrations. We have made minimal revisions to the article according to the detailed comments from all reviewers and the editor, hoping not to compromise the authenticity of the article with extensive changes. The authors believe that we have fully addressed the comments. The authors also have no idea what the reviewer concerns because of no further comments.