Spatio-Temporal Evolution of a Typical Sandstorm Event in an Arid Area of Northwest China in April 2018 Based on Remote Sensing Data

Round 1

Reviewer 1 Report

I believe the manuscript has been significantly improved and now warrants publication in remote sensing.

Author Response

Reviewer 2 Report

Manuscript ID: Remotesensing-1724841. Title: Spatio-temporal evolution of typical sandstorm events in an arid area of Northwest China based on remote sensing data.   In this work, using ground-based measurements of particulate matter and  remote sensing data such as MODIS, OMI, and CALIPSO data, the sources of  aerosol pollution and aerosol optical properties of the typical sandstorm  event that occurred in Northwest China in 2018 was studied and the  HYSPLIT  model was used to explore the air mass trajectories in order to analyze the sand and dust migration process during the sandstorm event.

Comments:

1. Please check the last keyword. It is very extensive.
2. In this new version submitted the introduction improved significantly.
3. In Figure 1 please indicate what the color scale corresponds to. Apparently it is the elevation in meters above sea level?
4. Please detail the title in Figure 1 better.
5. A suitable description of the study sites was made in this version.
6. I suggest using a more conventional chapter title for section 3. That is, I suggest using the following as a title: 3. Results, 3.1.....
7. Section 4 should also be included in Chapter 3. Results. Please integrate.
8. Apparently, a title needs to be included for chapter 3.
9. Please check in all the references of the article the use of the acronym "at al.", it is necessary to include in some of them the point.
10. In the discussion chapter it is necessary to significantly increase the references used. This to contrast the findings of this study with other researchers.
11. Please move the references included in the conclusions chapter to the discussion chapter. Additionally, avoid discussing the results in the conclusions chapter.
12. At the end of the conclusions please indicate the main limitations of this study. Additionally, include future lines of research.
13. It is suggested to include a final section with all the abbreviations used in the article.
14. I suggest closing the conclusions with a couple of lines where the practical utility of this study in the context of air quality is visualized. Indeed, supported in remote sensing.
15. In this new version the manuscript improved significantly. Most of the suggestions made were addressed correctly. However, minor comments are left to be resolved by the authors.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Review is given in the attached file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

In this new version the manuscript improved significantly. I suggest accepting for publication.

Reviewer 3 Report

This reviewer thanks the authors for addressing all the comments. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and suggestions are provided in the attached file.

Comments for author File: Comments.pdf

Reviewer 2 Report

This paper analyzes two dust storm events originated from the Taklimakan desert, NW China. It uses mostly satellite retrievals of MODIS-AOD, CALIPSO, AAI and ground PM10 concentrations at selected stations in NW China. It also uses HYSPLIT backtrajectories at the receptor sites. In the second part of the manuscript, authors examine some meteorological and topographic parameters that are associated with dust emissions and provide a map of wind erosion sensitivity. However, this is a totally different concept than the previous one and is not clear if that analysis considers only the two dust-storm events or uses long-term data. Of course, such analysis needs longer datasets and similar researches have been performed in arid environments in Iran and central Asia. 

Overall, the literature is really poor for such an important scientific issue, there is no meteorological analysis about the atmospheric circulation and dynamic processes that triggered these dust events, while there are numerous works dealing with dust-storm events in NW China. Overall, due to lack of a real concept and all the above reasons, I do not think that the present paper can be considered as an important contribution to the journal. In the attached pdf file, I have included many comments on specific parts of the text, justifying the low contribution of the current work. Much more analysis is needed, mainly in the meteorological part, while the section "discussions" does not refer to the current results, but to another topic.  

Comments for author File: Comments.pdf

Reviewer 3 Report

Review of "Spatio-temporal evolution of typical sandstorm events in an arid area of northwest China based on remote sensing data" by Wu et al.

Recommendation: Major Revisions

The manuscript mainly studied the spatio-temporal evolution of two typical sandstorm events in northwest China by using ground-based PM measurements and multi-source satellite-based remote sensing data. Furthermore, the wind erosion sensitivity of northwest China and the study area with a high comprehensive wind erosion sensitivity was also analyzed and identified. It is an interesting work for understanding the evolution of sandstorm by combining the measurements and the analysis of wind erosion sensitivity. The findings of this study can provide scientific references for the mitigation of damage caused by sandstorm events. I therefore recommend major revisions to this work to address the following concerns:

Major Comments:

1. The manuscript should be polished in language, in addition to the specific comments listed in the following.
2. As for references, authors should cite relevant satellite data references according to official requirements, and indicate the source of the methods and definitions adopted in this study; In addition, the latest relevant research references need to be updated. Not limited to the references listed in specific comments.
3. In this article, there are many concepts given different names, such as “wind field intensity” and “wind energy intensity”, “aerosol optical thickness” and “aerosol optical depth”, “atmospheric aerosol index” and “AOD”, which will reduce the readability of the article. It is recommended to check the full text.
4. Lines 281-291. Figure 4 shows the surface wind speed, which is mostly easterly at the junction of Xinjiang-Gansu-Qinghai, which is not conducive to the transport of dust aerosol from deserts to the downstream. It is thus inconsistent with the dust backward trajectories in different cities of Northwest China shown in Figure 7. This is because the wind direction at different altitude levels in Taklamakan Desert and surrounding areas is different, resulting in the near surface being not conducive to the eastward transport of dust. Only when the dust rises to more than 3km, dust can be transported to the downstream cities under the action of the west wind. Details please refer to [New insights into the Asian dust cycle derived from CALIPSO lidar measurements, Remote Sensing of Environment, 272, 112906, doi:10.1016/j.rse.2022.112906]. It is suggested that the author rewrite this paragraph based on comprehensive analysis of surface wind speed, 500hpa wind speed (such as reanalysis data, etc.) and backward trajectory (Fig. 7).
5. Lines 318-333, The description and definition of sand cloud in this paragraph is quite confusing. Does it specifically refer to dust, cloud, or a mixture of dust and cloud? As far as I know, it's hard to distinguish dust from clouds using the total attenuation backscattering coefficient at 532nm alone. In general, dust identification requires the use of its observed depolarization ratio. Please rewrite this paragraph.
6. About the sensitivity analysis of wind erosion factors in Section 4.1 and 4.2, authors should give a more detailed description of analysis method and add the related reference. The description at line 407 is too simple.

Specific Comments:

1. Line 24, what is the unit of ‘lg/m³’ for PM10, please check and correct it.
2. Line 33, the same as line 24, the unit of total attenuated backscatter coefficient is not ‘km’, please carefully check all units used in this study.
3. Line 36, there are two cases mentioned in this study, which one is “this sandstorm event”? Please clear it.
4. Lines 46-48, I propose to add references respectively to climate effect, human health, environmental impact, and socio-economic impact. For example, the climate effect of Asian dust has been reviewed by the paper [Sources of Asian dust and role of climate change versus desertification in Asian dust emission, Geophysical Research Letters, doi: 10.1029/2003GL018206], please refer it.
5. Lines 77-91, Please change the order of lines 81-91 and 79-81, because lines 81-91 introduce dust monitoring methods, which can be followed by lines 77-79, while lines 79-81 introduce more large-scale dust transmission.
6. Lines 79-81, In order to facilitate readers to understand the satellite-based large-scale dust transport, it is suggested to refer to the research work of different satellite sensors separately. For example, MODIS: [Dust transport and deposition observed from the Terra-Moderate Resolution Imaging Spectroradiometer (MODIS) spacecraft over the Atlantic ocean. J. Geophys. Res. Atmos. 110. doi:10.1029/2003jd004436], CALIPSO [New insights into the Asian dust cycle derived from CALIPSO lidar measurements, Remote Sensing of Environment, 272, 112906, doi:10.1016/j.rse.2022.112906], and so on.
7. Line 87, about “aerosol optical thickness” or “aerosol optical depth”, please use a uniform name throughout the paper.
8. Line 120, about data sources, please refer to the 2^nd major comments.
9. Line 137, please define the NDVI when it first appears in the paper.
10. Line 140 and Line 144, please refer to the 3^rd major comments
11. Line 150, please add the reference.
12. Section 2.6, please briefly explain the significance of defining the relief amplitude in this study.
13. Lines 242-243, this sentence is a little confusing, at least to me. What’s the atmospheric aerosol index you mentioned? Similar to Line 245. If it refers to AOD, please do not give misleading names. Please refer to the 2^nd major comments.
14. Line 315, the figure title is repeated, please revise it.
15. Line 395, Why separate dust from aerosol here?
16. Line 486, please check the unit.
17. Line 413, what’s the Venturi effect? Please explain it and add the reference.

Reviewer 4 Report

Manuscript ID: remotesensing-1637464. Spatio-temporal evolution of typical sandstorm events in an arid area of northwest China based on remote sensing data.  

In this study, northwest China, which has the most abundant sand sources in China, was selected as the target area. The aerosol transport paths and dust sources of two dust events originating in northwest China were explored with the HYSPLIT model using ground-based measurements of particulate matter as well as MODIS, OMI, and CALIPSO data.

Comments:  

1. Please synthesize the abstract. Currently it is very extensive.
2. Check the nomenclature on all the paper. For example, in L24 it is PM₁₀.
3.  Please include in the description of the study site its main physical and climatic characteristics. For example, annual average precipitation, temperature, wind speed, prevailing wind direction, relative humidity, etc. On the other hand, also include average terrain slope, elevation, soil type, etc.
4. Check the nomenclature on all the paper. For example, in L124 it is PM_2.5.
5. In section 2.2. please include the websites from which the information was collected.
6. A reference is needed in section 2.3 to support the equation used. Please include.
7. A reference is needed in section 2.4 to support the model used. Please include. Additionally, specify the units of each variable.
8. A reference is needed in section 2.5 to support the method used. Please include. Additionally, specify the units of each variable.
9. Throughout the chapter on materials and methods, relevant references are needed to support the methods used.
10. A reference is needed in section 2.6 to support the method used. Please include. Additionally, specify the units of each variable.
11. The title of Chapter 3 should be changed to: Results.
12. Throughout the chapter of results there are technical statements without supporting references. Please include: L187-193.
13. The paragraphs throughout the document should have an integral development. Please review L194-197, L340-343, L371-375, etc.
14. Figure 2 appears not to be previously mentioned in the text. Please check.
15. Please refer well in the text all the standards included in the document. For example, see L205.
16. In section 3.1. the findings of this study should be quantified. For example, check L202-203, L205-207, etc.
17. Please include at the end of the paper a section with all the abbreviations used.
18. Check on all paper that the figures are previously mentioned in the text.
19. In section 3.2. please include a statistical test that shows the possible correlation between AOD and wind speed.
20. Please increase the arrowheads in Figure 7 to better visualize the direction of the dust.
21. In the chapter of results the discussion of these is carried out. This should be in the discussion chapter. Please check. For example, see L385-390.
22. Please include a statistical test to assess the correlation between land coverage and dust.
23. References should be included in the discussion chapter to contrast the results obtained in this study.
24. Please check the PM10 and PM2.5 units of measurement. For example, see L486.