Variability of the Suspended Particle Cross-Sectional Area in the Bohai Sea and Yellow Sea
Round 1
Reviewer 1 Report
The results presented in this manuscript are new and interesting, although they have a significant regional focus. In general, the manuscript is written very well, all its sections are consistent with each other, details of field measurement and data processing techniques are described in details. However, I had some questions and suggestions:
1) Line 42-45 “relationship between bbp(λ) and diameter is expressed as follows [9, 10]: … ”. But Equation (1) doesn’t consist diameter. This becomes clear only from Equation (2), which is given below. Therefore, I would suggest to reformulate the sentence before Equation (1) or to combine these two Equations.
2) Authors use the names of bays, rivers, etc. But these objects are not shown on the map. Therefore, for a person who is not familiar with these two seas, it is difficult to understand described results when looking at Figures 2, 4, ... I would suggest to add names of main objects on the map. (by the way, in a previous study [14], I found a well understandable map of study water area).
3) Figures 2,4,6 are too small.
4) It is necessary to replace Fig on Figure in all manuscript.
5) It is not clear where the start and finish of sections A, B, C. They need to be specified in order to be clear where the distance starts in Figures 3, 7.
6) In Figure 3 along X-axis, the distance is plotted for sections A and B while the geographical coordinates is plotted for the section C. I would recommend to use one style for all Figures. The same comment applies to Figure 7.
7) Line 175 “Meanwhile, in transect C, due to the shallow water in the nearshore, the water column was mixed uniformly and the depth of the mixed layer reached 20m (Fig.3i).” But the average depth is also equal to 20-25 m along 200 km at section A (Figure 3a). Despite this, according to the presented data, there is stratification in section A, but there isn’t for shallow water in section C. In this regard, the statement in Line 175 is not obvious.
8) If I understood correctly, the described measurements were carried out only once per season (winter, spring, summer, autumn). Why the results of one seasonal expedition are considered as results for the whole season? The authors do not provide a description of meteorological conditions at the time of field measurements and before it. Were these conditions typical for the seasons or not? In addition, it would be useful to indicate how long the field measurements took and how weather conditions changed during this time interval.
9) The absolute values of the wind speed are not presented in Figure 9. For what time interval are these distributions built?
10) In this manuscript, there are often statements that are obviously related to the hydrology of the mentioned seas and meteorological conditions. For example:
Line 280 “At the same time, the summer wind speed was too weak to stir the water column ”.
Line 405 “The stratification in summer was strong enough to block the vertical mixing.”
Line … .
What are these statements based on? Their validity is not obvious due to the lack of data from field measurements of currents, wind waves, precipitation, or their modeling.
Author Response
Dear Reviewer,
We deeply appreciate your comments and suggestions towards improving our manuscript (remotesensing-486809). We have accounted for your constructive comments and carefully revised our manuscript accordingly. For the revision, please kindly refer to the point-to-point responses as followings and the revised manuscript. The changes we made have been noted in the yellow color for highlighting.
Response to Reviewer 1
Comments and Suggestions for Authors
The results presented in this manuscript are new and interesting, although they have a significant regional focus. In general, the manuscript is written very well, all its sections are consistent with each other, details of field measurement and data processing techniques are described in details. However, I had some questions and suggestions:
1) Line 42-45 “relationship between bbp(λ) and diameter is expressed as follows [9, 10]: … ”. But Equation (1) doesn’t consist diameter. This becomes clear only from Equation (2), which is given below. Therefore, I would suggest to reformulate the sentence before Equation (1) or to combine these two Equations.
Response: Thank you for your comments. According to your comments and suggestions, we have revised the Equation (1).
2) Authors use the names of bays, rivers, etc. But these objects are not shown on the map. Therefore, for a person who is not familiar with these two seas, it is difficult to understand described results when looking at Figures 2, 4, ... I would suggest to add names of main objects on the map. (by the way, in a previous study [14], I found a well understandable map of study water area).
Response: Thank you for your comments. We have revised according to your comments and suggestions. For the details, please kindly refer to the revised Figure 1.
3) Figures 2, 4, 6 are too small.
Response: Thank you for your comment. We have revised accordingly.
4) It is necessary to replace Fig on Figure in all manuscript.
Response: Thank you for your comment. It has been clarified accordingly for the entire manuscript.
5) It is not clear where the start and finish of sections A, B, C. They need to be specified in order to be clear where the distance starts in Figures 3, 7.
Response: Thank you for your suggestion. We have clarified this issue in the revised manuscript.
6) In Figure 3 along X-axis, the distance is plotted for sections A and B while the geographical coordinates is plotted for the section C. I would recommend to use one style for all Figures. The same comment applies to Figure 7.
Response: We greatly appreciate your valuable comment. These issues have been clarified accordingly in the Figure 3 and Figure 7.
7) Line 175 “Meanwhile, in transect C, due to the shallow water in the nearshore, the water column was mixed uniformly and the depth of the mixed layer reached 20m (Fig.3i).” But the average depth is also equal to 20-25 m along 200 km at section A (Figure 3a). Despite this, according to the presented data, there is stratification in section A, but there isn’t for shallow water in section C. In this regard, the statement in Line 175 is not obvious.
Response: Thank you for your suggestion. In the revised manuscript, we have clarified this issue accordingly.
8) If I understood correctly, the described measurements were carried out only once per season (winter, spring, summer, autumn). Why the results of one seasonal expedition are considered as results for the whole season? The authors do not provide a description of meteorological conditions at the time of field measurements and before it. Were these conditions typical for the seasons or not? In addition, it would be useful to indicate how long the field measurements took and how weather conditions changed during this time interval.
Response: Thank you for your comments. We agree with you about this point. Indeed, the data collected once per season can’t totally reflect the situation in each season. However, due to the constraints of the cruise observations, it is quite difficult to carry out observations within each month in our study region which covers a large geographic range. Therefore, we used the data collected during in four cruises in each season to examine the seasonal variability of CSA. To some extent, these data could represent the information in four seasons since there were collected during around one month in each season. Actually, we are planning to build fixed stations and maritime buoys at sea to make continuous long-term observation of CSA at the surface layer in the future, which should be suitable for studying the temporal changes (monthly, seasonal, and so on) of CSA as you expected. The weathers and the durations of the cruises have been added in the section 2.1.
9) The absolute values of the wind speed are not presented in Figure 9. For what time interval are these distributions built?
Response: Thank you for your suggestion. The time resolution of wind data was one day interval. The corresponding modifications have been done in the revised manuscript.
10) In this manuscript, there are often statements that are obviously related to the hydrology of the mentioned seas and meteorological conditions. For example:
Line 280 “At the same time, the summer wind speed was too weak to stir the water column ”.
Line 405 “The stratification in summer was strong enough to block the vertical mixing.”
Line … .
What are these statements based on? Their validity is not obvious due to the lack of data from field measurements of currents, wind waves, precipitation, or their modeling.
Response: Thank you for your comments. According to the previous study, the wind influences the CSA in two ways, that is (1) in the shallow sea area, the bottom shear stress associated with wind waves stirs the seabed sediment into the water column and (2) the vertical shear of the wind-driven currents transports the bottom layer suspended sediment upwards to the sea surface [1], which may influence the CSA distribution. In the revised, we have added discussions and related references to support these statements.
References used in this response:
1. Bian C.; Jiang W.; Quan Q.; Wang T.; Greatbatch R.J.; Li W. Distributions of suspended sediment concentration in the Yellow Sea and the East China Sea based on field surveys during the four seasons of 2011. Journal of Marine Systems 2013, 121, 24-35.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Abstract
Specific comments:
L10 – AC is usually used as an acronym for “atmospheric correction”, is it possible to change the acronym here?
L16 – What is the highest value? What is the lowest value? You need to add some quantitative values here.
L20 – How important? You need to add some quantitative values here.
Introduction
General comment:
Overall, this introduction was adequate for the manuscript, however, wording needs improvement. It would be good if authors could highlight the importance of a better bb estimation as well as the uncertainties about the measurement of bb especially in inland and coastal waters (waters with high concentrations of particles) using an equipment like LISST. Additionally, authors could present the results for the work from Wang [14] once it was just quickly described and did not presented how this new algorithm performed.
Specific comments:
L55 – “growing body of researcher” is a strange term.
L70-72 – need a reference for this statement
Materials and Methods
General comment:
The main concern here is the lack of the analysis methodology. Authors only described data collection material and methods, however, they fail to deliver the methodology for analysis, especially statistical analysis. Therefore, I would recommend authors to add another sub-section to describe the analysis conducted in this research.
Specific comments:
L95 – Why these months were selected? Are they related to climate? What is the climate over the region in each of these months?
L131 – Figure 1 – This figure is too busy, especially with the lines crossing some of the sampling locations. Additionally, there are some cartography features missing in this figure such as: north arrow and scale.
Results
General comments:
My main concern about this section is the lack of mixing and stratification indicators. Authors based their classification of mixing and stratification on temperature measurements while other indicators like “Richardson number”, density stratification, Wedderburn Number and others. Another concern is the low quality of the figures which should be improved to be readable.
Specific Comments:
L146-158 – All these sentences are not results, they are part of water column stability concepts. I do not think it should be here in this section.
L148 – need a reference for this statement.
L164 – How did you analyze if this variation is significant different for your study site?
L175 – there is no letter to indicate which plot you are referring to on Figure 3.
L192 – How can you classify the intensity of the mixing? Did you compute any mixing or stratification index like Richardson number?
L196 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
L199 – This figure has many problems. Starting with axis titles that are not uniform, and some plots do not even have axis titles. Please try to keep axis titles constant in the same Figure. Values on the axis as well as in the color bar are too small, it is not readable. On the first plot on Transect A it is clearly cutting half of the axis title.
L231 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
L234 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
L237 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
Discussion
General Comments:
My main concern with this section is because authors did not explore the relationship of their results to remote sensing applications. Overall, their discussion only on the aquatic sciences aspects while since this is a remote sensing journal, the relationship to remote sensing application should be more explored. Another concern is related to the use of LIIST without showing a calibration to check if the equipment is working well for the study sites.
Specific Comments:
L298 - – this figure needs better quality, it is very hard to read the axis. Please, add an image with at least 300 dpi.
L310 - this figure needs better quality. Please, add an image with at least 300 dpi. Figure needs a scale and north arrow.
L316 – Chl-a concentration measurements are not described in the methods section.
L354 – What are the open circles in the first plot?
L387 – “AS” should be “As”
Conclusions
General Comments:
You should conclude how your results would affect the remote sensing of suspended matter as well as what are the implications for bio-optical modeling.
Author Response
Dear Reviewer,
We deeply appreciate your comments and suggestions towards improving our manuscript (remotesensing-486809). We have accounted for your constructive comments and carefully revised our manuscript accordingly. For the revision, please kindly refer to the point-to-point responses as followings and the revised manuscript. The changes we made have been noted in the yellow color for highlighting.
Response to Reviewer 2
Abstract
Specific comments:
L10 – AC is usually used as an acronym for “atmospheric correction”, is it possible to change the acronym here?
Response: We greatly appreciate your valuable comment. We have replaced AC using CSA in all manuscript.
L16 – What is the highest value? What is the lowest value? You need to add some quantitative values here.
Response: Thank you for your comments. We have added the quantitative values in the revised Abstract.
L20 – How important? You need to add some quantitative values here.
Response: Thank you for your comments. We have added some quantitative values as you suggested.
Introduction
General comment:
Overall, this introduction was adequate for the manuscript, however, wording needs improvement. It would be good if authors could highlight the importance of a better bb estimation as well as the uncertainties about the measurement of bb especially in inland and coastal waters (waters with high concentrations of particles) using an equipment like LISST. Additionally, authors could present the results for the work from Wang [14] once it was just quickly described and did not presented how this new algorithm performed.
Response: We greatly appreciate these valuable comments. We have taken great care to revise all of your comments and suggestions in the revised manuscript. The English in the revised manuscript has been checked by at least one native speaker of English. We believe the quality of the paper has been significantly improved. The bbp has great importance in the remote-sensing retrieval accuracy of total suspended matters (TSM) and Chl-a [1]. The uncertainties of observed bbp and the application of CSA in deriving bbp have been added in the section 4.2. As you suggested, more detailed information has been added in the revised manuscript. And the performance of the new algorithm has been added in the Introduction.
Specific comments:
L55 – “growing body of researcher” is a strange term.
Response: We greatly appreciate this valuable comment. It has been revised accordingly.
L70-72 – need a reference for this statement
Response: Thank you for your comments. As you suggested, we have added references to support our statement in the revised manuscript.
Materials and Methods
General comment:
The main concern here is the lack of the analysis methodology. Authors only described data collection material and methods, however, they fail to deliver the methodology for analysis, especially statistical analysis. Therefore, I would recommend authors to add another sub-section to describe the analysis conducted in this research.
Response: We greatly appreciate this valuable comment. Standard statistical measure, such as coefficient of determination (R2), has been added in the revised manuscript accordingly.
Specific comments:
L95 – Why these months were selected? Are they related to climate? What is the climate over the region in each of these months?
Response: Thank you for your comments. The data collected once per season can’t totally reflect the situation in each season. However, due to the constraints of the cruise observations, it is quite difficult to carry out observations within each month in our study region which covers a large geographic range. According to the previous study, spring is from March to May, June to August is summer, September to November is autumn, and December to next February stands for winter [2]. Therefore, we used the data collected during in four cruises in each season to examine the seasonal variability of CSA. To some extent, these data could represent the information in four seasons since there were collected during around one month in each season. Actually, we are planning to build fixed stations and maritime buoys at sea to make continuous long-term observation of CSA at the surface layer in the future, which should be suitable for studying the temporal changes (monthly, seasonal, and so on) of CSA. And the weather and the duration of the voyage have been added in the section 2.1.
L131 – Figure 1 – This figure is too busy, especially with the lines crossing some of the sampling locations. Additionally, there are some cartography features missing in this figure such as: north arrow and scale.
Response: Thank you for your positive comments. Corresponding modifications have been done.
Results
General comments:
My main concern about this section is the lack of mixing and stratification indicators. Authors based their classification of mixing and stratification on temperature measurements while other indicators like “Richardson number”, density stratification, Wedderburn Number and others. Another concern is the low quality of the figures which should be improved to be readable.
Response: We greatly appreciate your valuable comments. As you suggested, the density was calculated, and the density difference between the surface and bottom was added as the mixing and stratification indicator. The smaller temperature difference between the surface and bottom indicates weaker stratification stability, which is opposite to the salinity and density. Meanwhile, the quality of the figures has been improved in the revised manuscript.
Specific Comments:
L146-158 – All these sentences are not results, they are part of water column stability concepts. I do not think it should be here in this section.
Response: Thank you for your comment. We have revised accordingly and this section has been removed.
L148 – need a reference for this statement.
Response: Thank you for your suggestion. We have added references as you suggested in the revised manuscript.
L164 – How did you analyze if this variation is significant different for your study site?
Response: Thank you for your question. Actually, in our study area, this significant difference did not exist in most area. When this happens, the density stratification is as a standard to determine the degree of mixing.
L175 – there is no letter to indicate which plot you are referring to on Figure 3.
Response: Thank you for your comment. It has been clarified accordingly.
L192 – How can you classify the intensity of the mixing? Did you compute any mixing or stratification index like Richardson number?
Response: Thank you for your comments. According to the definition of MLD and the thermocline, in this paper, the gradients of temperature and salinity between the surface and bottom were used to indicate the strength of vertical turbulence mixing. The smaller temperature difference between the surface and bottom indicates weaker stratification stability, which is opposite to the salinity. As you suggested, in this section, the density was calculated based on the temperature and salinity. The density difference between the surface and bottom, together with the temperature and salinity difference, was used as the mixing and stratification indicator. The smaller density difference is, the weaker stratification stability is.
L196 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
Response: Thank you for your comment. It has been clarified accordingly.
L199 – This figure has many problems. Starting with axis titles that are not uniform, and some plots do not even have axis titles. Please try to keep axis titles constant in the same Figure. Values on the axis as well as in the color bar are too small, it is not readable. On the first plot on Transect A it is clearly cutting half of the axis title.
Response: Thank you for your comment. It has been clarified accordingly.
L231 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
Response: Thank you for your comment. It has been clarified accordingly.
L234 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
Response: Thank you for your comment. It has been clarified accordingly.
L237 – this figure needs better quality, it is very hard to read the legend. Please, add an image with at least 300 dpi. Also, it is the caption of the Figure is confusing, please re-write the caption of this figure. Figure needs a scale and north arrow.
Response: Thank you for your comment. It has been clarified accordingly.
Discussion
General Comments:
My main concern with this section is because authors did not explore the relationship of their results to remote sensing applications. Overall, their discussion only on the aquatic sciences aspects while since this is a remote sensing journal, the relationship to remote sensing application should be more explored. Another concern is related to the use of LIIST without showing a calibration to check if the equipment is working well for the study sites.
Response: We are grateful for your concerns about these points. As you suggested, more detailed information about the applications of CSA has been added in revised manuscript. Because of the strong relationship between the CSA and inherent optical properties, the CSA may be a better indicator to describe the values of beam attenuation and backscattering coefficients. Recently, most remote sensing algorithms are empirical, and the understanding of CSA is essential for deepening the understanding of the inherent optical properties and improving the semi-analytical ocean color inversion algorithms. The backscattering efficiency (Qbbe) is bound up with the particle composition [3, 4], the CSA can be derived from the satellite using the model established by Wang et al. [5], and together with the inherent optical properties algorithm [6], the backscattering coefficient can be calculated via satellite Rrs(λ), which imply that the pattern of particles composition can be mapped based on the Qbbe derived from satellite. Based on the relationship between TSM, CSA, ρ and DA, we may provide a new an alternative approach to estimate TSM, which can avoid introducing errors in TSM estimations.
Meanwhile, the LISST was calibrated with Milli-Q ultrapure water before each cruise. We have added this information in the section 2.2 of the revised manuscript.
Specific Comments:
L298 - – this figure needs better quality, it is very hard to read the axis. Please, add an image with at least 300 dpi.
Response: Thank you for your comment. It has been clarified accordingly.
L310 - this figure needs better quality. Please, add an image with at least 300 dpi. Figure needs a scale and north arrow.
Response: Thank you for your comment. It has been clarified accordingly.
L316 – Chl-a concentration measurements are not described in the methods section.
Response: We greatly appreciate this valuable comment. As you suggested, more detailed information about Chl-a concentration measurements has been added in the revised manuscript.
L354 – What are the open circles in the first plot?
Response: Thank you for your comment. The open circles represented sampling stations located near the coast.
L387 – “AS” should be “As”
Response: Thank you for your comment. We are very sorry for this mistake. We have carefully checked and corrected wording for the entire manuscript.
Conclusions
General Comments:
You should conclude how your results would affect the remote sensing of suspended matter as well as what are the implications for bio-optical modeling.
Response: We greatly appreciate these valuable comments. The knowledge of CSA has a great potential to deepen the understanding of inherent optical properties, and improve the remote sensing algorithms. Meanwhile, due to the strong relationship between the CSA and inherent optical properties, the CSA may be a better indicator to describe the values beam attenuation and backscattering coefficients. As you suggested, the results about the applications of CSA has been added in the Conclusion.
References used in this response:
1. Brown C.A.; Huot Y.; Werdell P.J.; Gentili B.; Claustre H. The origin and global distribution of second order variability in satellite ocean color and its potential applications to algorithm development. Remote Sensing of Environment 2008, 112(12), 4186-203.
2. Maghrabi A.H.; Dajani H.M.A. Time distribution of the precipitable water vapor in central Saudi Arabia and its relationship to solar activity. Advances in Space Research 2014, 53(8), 1169-79.
3. Wang S.; Qiu Z.; Sun D.; Shen X.; Zhang H. Light beam attenuation and backscattering properties of particles in the Bohai Sea and Yellow Sea with relation to biogeochemical properties. Journal of Geophysical Research: Oceans 2016, 121(6), 3955-69.
4. Bowers D.; Hill P.; Braithwaite K. The effect of particulate organic content on the remote sensing of marine suspended sediments. Remote sensing of environment 2014, 144, 172-8.
5. Wang S.; Huan Y.; Qiu Z.; Sun D.; Zhang H.; Zheng L., et al. Remote sensing of particle cross-sectional area in the Bohai Sea and Yellow Sea: algorithm development and application implications. Remote Sensing 2016, 8(10), 841.
6. Lee Z.; Carder K.L.; Arnone R.A. Deriving inherent optical properties from water color: a multiband quasi-analytical algorithm for optically deep waters. Applied optics 2002, 41(27), 5755-72.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Dear Authors,
Thank you so much for revising the article and providing a response for each comment from my previous report.
This new version is really improved from the previous one and I believe it will be an interesting contribution for the development of the field, especially when considering IOPs.
Here is a list of some minor comments:
- Line 51 - it is not only important for marine environments but for aquatic environments in general (marine, coastal and inland).
- Line 74 - is it necessary to start the sentence with "specifically"?
- Line 81 - a reference is needed to support that this leads to particles resuspension.
- Line 118 - can you please provide a reference for this protocol? Maybe from IOCCG Protocol Documents?
- Line 142 - Maybe Figure 1 could be placed after subsection 2.1 - Study site.
- Line 161 - Why only R2 was selected as an statistical estimator?
- Line 207 - 209 - Was this based on your measurements or in the literature? It is not clear.
- Line 234 - the numbers inside the figures (for each line) are still too small, can you please increase it?
- Line 316 - the numbers inside the figures (for each line) are still too small, can you please increase it?
- Line 351 - Why not explore the relationship between CSA and TSM?
- Line 370 - the legend should be CSA not AC.
- Line 384 - a reference is needed to support that this statement.
- Line 440 - The work would provide more results if authors use this relationship and validate it. Since authors have TSM data and CSA data, they could validate this relationship.
Author Response
Dear Reviewer,
We deeply appreciate your comments and suggestions towards improving our manuscript. We have accounted for your constructive comments and carefully revised our manuscript to reflect your suggestions. For the revision, please kindly refer to the point-to-point responses as followings and the revised manuscript. The changes we made have been noted in the blue color for highlighting.
Response to Reviewer 2:
- Line 51 - it is not only important for marine environments but for aquatic environments in general (marine, coastal and inland).
Response: Thank you for your comment. Corresponding modifications have been done.
- Line 74 - is it necessary to start the sentence with "specifically"?
Response: Thank you for your suggestion. It has been revised accordingly.
- Line 81 - a reference is needed to support that this leads to particles resuspension.
Response: Thank you for your comment. As you suggested, we have added references to support our statement in the revised manuscript.
- Line 118 - can you please provide a reference for this protocol? Maybe from IOCCG Protocol Documents?
Response: Thank you for your comment. The reference has been added to support our statement in the revised manuscript.
- Line 142 - Maybe Figure 1 could be placed after subsection 2.1 - Study site.
Response: Thank you for your suggestion. Figure 1 has been placed after the section 2.1.
- Line 161 - Why only R2 was selected as a statistical estimator?
Response: Thank you for your comment. In this paper, we just want to explore the relationship between CSA and Chl-a, thus, the R2 was selected as a statistical estimator.
- Line 207 - 209 - Was this based on your measurements or in the literature? It is not clear.
Response: Thank you for your comment. Field data revealed the degree of vertical mixing in summer and winter. Due to the lack of CTD data in spring and autumn, the strength of ocean stratification has been discussed based on the previous study. We have added the references in the revised manuscript.
- Line 234 - the numbers inside the figures (for each line) are still too small, can you please increase it?
Response: Thank you for your suggestion. We have clarified this issue in the revised manuscript.
- Line 316 - the numbers inside the figures (for each line) are still too small, can you please increase it?
Response: Thank you for your suggestion. We have clarified this issue in the revised manuscript.
- Line 351 - Why not explore the relationship between CSA and TSM?
Response: Thank you for your comment. In order to explore the influencing factors on CSA, the influence of the particle composition was considered. The TSM can be divided into the OSM and ISM. Therefore, in this paper, the influences of OSM and ISM on CSA were explored, respectively. In one hand, due to the vertical mixing, the ISM, such as sediment, was transported to the surface, and increased the CSA. In the other hand, as the phytoplankton bloom began and progressed, the organic particles increased, and detrital particles gradually aggregated to form loose flocs, which increased the CSA. The Chl-a concentration may be used as the representative of the phytoplankton contribution to CSA, therefore, the relationship between CSA and Chl-a was explored. This has been clarified accordingly in the revised manuscript.
- Line 370 - the legend should be CSA not AC.
Response: Thank you for your comment. We are very sorry for this mistake. We have carefully checked and corrected wording for the entire manuscript.
- Line 384 - a reference is needed to support that this statement.
Response: Thank you for your suggestion. We have added references to support our statement in the revised manuscript.
- Line 440 - The work would provide more results if authors use this relationship and validate it. Since authors have TSM data and CSA data, they could validate this relationship.
Response: Thank you for your suggestion. The relationship between TSM and CSA was shown in Figure 1. In winter, the phytoplankton concentration was too low to form flocs, and the inorganic particles became dominant, so the correlation between CSA and TSM was high (Figure 1b). However, the relationship between TSM and CSA in summer is poor (R2=0.29), which is corresponded with the previous study [1]. This is due to the fact that particles in seawater do not appear as single particles, but as aggregates (flocs), thus, TSM varies as a function of CSA, density and particle diameter [1]. Therefore, estimating TSM from CSA also requires additional information on density and particle diameter, and this algorithm still needs to be further evaluated.
Please find Figure 1 in the attached file.
Figure 1. The relationship between CSA and TSM, (a) summer, (b) winter; the red lines represent the fitting curve.
References used in this response:
1. Mikkelsen O.A. Variation in the projected surface area of suspended particles: Implications for remote sensing assessment of TSM. Remote Sensing of Environment 2002, 79(1), 23-9.
Author Response File: 
Author Response.pdf
