Aerosol Physical–Optical Properties under Different Stages of Continuous Wet Weather over the Guangdong–Hong Kong–Macao Greater Bay Area, China
Round 1
Reviewer 1 Report
Aerosol is one of the most import atmospheric component as its contributions to climate system and human’s health, more attention has been paid to its direct forcing on earth modeling system. While its physical properties and loading in the atmosphere under extreme weather condition not yet discussed, in this paper, the aerosol and its physical optical properties under CWW weather was discussed, including its transporting effects and local originating reasons. This paper is sure suitable to be published in this journal, my major concerns are:
1. The language here is not easier for the readers, either in English language and logistic structures, the author should ask an english-native person to improve this draft.
2. The connection between AOD and CWW weather process are discussed through reanalysis data such as ERA5 and MERRA2, its physics behind the phenomena should be discussed, e.g. the growth of aerosol as atmospheric humidity, and the size of aerosol under CWW etc.
3. Introduction: GBA including nine-a definite number used here, but “etc”, at end of this sentences.
4. Line 77 and 84, Xu et al. ….., Yang et al……should be followed an reference, many other places need references.
5. A lot of sentences are not necessary, please make the paper easier to read.
Author Response
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Reviewer 2 Report
The paper entitled “Aerosol Physical-Optical Properties Under Different Stages of Continuous Wet Weather over the Guangdong-Hong Kong-Macao Greater Bay Area, China” by Zhao et al. discuss the characteristics of meteorology and aerosol parameters under 3 humidity levels during continues wet season. The manuscript is well-written. However, some problems should be addressed before publication of the paper:
The major problem I concern is the paper is weak in remote sensing data. The only remote sensing data is the aerosol data from CALIPSO, and only takes up small spaces of the manuscript. I am afraid that the paper is not within the scope of Remote Sensing. However, the paper still has scientific value.
Other comments:
Section 2.1, are there any specific criteria for the recognized CWW processes? Besides, it is better to define the term “absolute humidity” earlier in the text. Why not use specific humidity or water vapor mixing ratio which are commonly used in meteorology? If the absolute humidity is still used, please explain the meaning of the parameter specifically.
Relative humidity is also an important factor. The hygroscopic behavior of aerosols is influenced by relative humidity, so size distributions and optical properties are correlated with relative humidity. Besides, relative humidity can also influence chemical reactions of secondary particle formation. Therefore, relative humidity rather than absolute humidity should be discussed in terms of aerosol study. Line 345-356 mentioned relative humidity several times, but readers cannot see any information about the relative humidity.
Also, authors should make it clear whether the angstrom exponents and surface mass concentrations discussed in the paper are under dry conditions or under ambient relative humidity?
Figure 3, is the parameters displayed in the figure represent the mean values, median values, or some other values? Please clarify.
Table 2, are the values showed in the table represent “daily average” values of the parameters or it should be the averaged value of all days? As for the BLH, BLHs in daytime and night time differ a lot. Maximum BLH during daytime is better than daily averaged BLH.
Authors need to give specific information about the CALIPSO data to explain data of which days are missing. It is important to tell readers the spatial distribution of aerosols from MERRA-2 and the vertical distribution of aerosols from CALIPSO do not represent the same days.
Some correlation studies should be made between aerosol and meteorology parameters.
Technical:
Line 36, “GBA” should be explained.
Line 39, “CWW” should be explained.
Line 207, a comma is missing after “humidity”
Author Response
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Reviewer 3 Report
Line 77: Add reference number
Line 84: Add reference number
Line 110: Typo “methods”
Line 157: Reference to the dataset should be placed in a phrase
Line 158: What is the aerosol surface mass concentration? For which aerosol fraction (PM1, PM2.5, PM10 etc.) Explain the source of these values and briefly how they are determined.
Line 161: Typo “ERA5”
Line 179: Phrase is not complete or needs to be connected to the previous one
Line 255: Table 2: Where are the BLH values coming from?
Line 289: Is the mean AOD over the whole considered surface (maps in Figure 5)?
Line 289: Correction “for which the AOD is 0.61”
Line 327: Figure 6: put units for surface mass concentration
Line 333: How can you have such a precision (36.7 m) for the BLH? Where do these values come from?
Line 341: Put reference number for Man and Shih
Line 371: Why does the percentage of sulfate decrease in the wet-stage? Could you please comment on the sources of sulfate and smoke in the area?
Line 415: Put reference number
Line 432: Figure 10: Put title on X-axis of the plot
Line 537: Use micrometer symbol
Author Response
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Reviewer 4 Report
The manuscript explored the variations of meteorological quantities and physical properties of aerosols within Greater Bay Area when there was CWW, then validated the ideas and principles via a case study in Zhuhai (during 2021). The topic itself is interesting (but not new), however some parts have to be structured in a better manner before its publication.
Major Modifications
1. In Introduction (Lines 64-73), the authors should relate AOD with ground-based PM2.5 retrieval and associated environmental assessment, especially some of its applications in developing countries / cities, and include a some descriptions of its recent applications. Some references are as follows:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8172751/
https://www.sciencedirect.com/science/article/abs/pii/S1352231020301497
https://www.sciencedirect.com/science/article/pii/S2352938522000246
2. Figure 1(c): The figure has not much use and significance within this study, please convert the relevant information onto bar / line graph. Further, the caption should be "The probability density function (PDF)..."
3. Please add acronym of all meteorological parameters / quantities in Table 2.
4. In Lines 275-276: For "movement in the atmosphere and various weather conditions", please be more specific.
5. Line 297: How's the set-up of the experiment in [49]?
6. In Section 3.3: Please explain clearly how do you calculate and account for averaged AOD? Also, please explain why dust and sea salt has least contribution towards AOD, from chemical perspectives.
7. For Section 3.4: Please explain the significance of selecting Zhuhai as the case study? Why not other parts of the Greater Bay Area?
8. Lines 418-419: "The AOD retrieved by MERRA-2 is higher than the corresponding observation, this overestimation has been confirmed...". Since overestimation is observed, is this "overestimation" a systematic bias / random bias? How is the adjustment being applied and conducted?
9. Figure 11 shows the respective contribution of each component of aerosols towards AOD levels. Explain it in words within the manuscript.
10. Conclusion: The scientific impacts of this study is rather vague, and the conclusion may not be applicable for other places / case studies, i.e., may have weakness in generalization. Please discuss why the obtained results are critical and useful in this discipline.
Minor Edits / Modifications
Line 93: PM2.5 should be sub-scripted, similar for all chemicals appeared in this manuscript.
Line 95: Define SIA.
Line 100: So --> Therefore
Line 136: defined as an excellent condition.
Table 1: Unit of absolute humidity should be g/m3, similar as the AH in Table 2, as well as other parts of the manuscript.
Line 192: layer that may be caused...
Line 308: concentration has reduced by...
Line 446: northeastern
Line 473: What do you mean by "east road cold high pressure"?
Author Response
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Reviewer 5 Report
Please see the attached file.
Comments for author File: 
Comments.pdf
Author Response
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Round 2
Reviewer 2 Report
The authors have addressed all my questions.
Author Response
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Reviewer 4 Report
The authors have addressed majority of my comments, and I think the manuscript is quite clear now, except the following 3 points
(1) The y-axis and x-axis labelling, title etc. of all figures should be of larger font size.
(2) Referring to review report major point 8: there is still error even MERRA-2 datasets were adopted. By what percentages? Have these discrepancies been well justified and have the reasons been discussed in literature?
(3) Referring to review report major point 10: The scientific breakthrough and novelty of this project and study should be discussed and highlighted in both Introduction and Conclusion of this manuscript.
Further, a proper round of English editing might be needed. Afterwards, I think the manuscript is good to be published.
Author Response
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