Annual and Seasonal Variations in Aerosol Optical Characteristics in the Huai River Basin, China from 2007 to 2021
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors Based on the aerosol remote sensing products of MODIS and CALIOP, this paper analyzes the long-term series changes of aerosol optical depth and aerosol type in the Huai River Basin (HRB), which can deepen the understanding of regional aerosol pollution problems in China. Overall, the topic of this paper is suitable for the Remote Sensing journal, but there are still some details that need to be clarified. In addition, the language of this article needs to be polished. Here are the specific comments: 1. Line 108: Why use this 3° × 3° study area instead of the actual HRB area? 2. Lines 142–148: How applicable are the aerosol types obtained by CALIOP? It is recommended to add references reflecting its quantitative accuracy. 3. Line 160: Why use results with CAD less than -20? Is -20 the official recommended value? 4. Lines 184–188: Are the authors using DT or DB products? 5. Lines 238–240: Is there evidence that boundary layer height and relative humidity are significantly different in the morning and afternoon? In addition, the expression of this passage is confusing. 6. Line 259: PD type does have a higher frequency of occurrence, but from Figure 3(a) we can see that its AOD is obviously lower than PC type. I think the expression "PD is the dominant aerosol type" is inappropriate. Or how to define "dominant"? 7. Figure 5: Why are 2014 used as the boundary and divided into two periods for comparison of aerosol types? 8. Lines 321–324: Is there any literature to support this idea? Or do the authors verify the MODIS AOD product? In addition, if this view is correct, then it seems meaningless to use MODIS AOD products in this article, and only CALIOP aerosol products can be used for analysis. 9. Figure 9: Legend is missing wind speed units (m /s). Additionally, this figure is not cited in the text.
Comments on the Quality of English Language
The English expression is not good and I cannot follow many sentences. It is recommended that authors find native English speakers to polish their language.
Author Response
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsI have carefully reviewed your paper titled " Annual and Seasonal Variations in Aerosol Optical Characteristics in the Huai River Basin, China from 2007 to 2021." Overall, I find the study deepens the understanding of the Annual and Seasonal Variations in AOD.
However, I have identified some issues that require attention before the paper can be considered for publication. I recommend minor revisions to address this concern adequately. I believe the paper would greatly benefit from further clarification on the following points presented below.
1. Fig.3: “(a) The long-term AOD Trends in the Shou County region from 2005 to 2021”, The period in the picture is only 2007-2021, a clerical error?
2. In Figure 4 we can clearly see the high-value year/low-value year, and in Figure 7 we can also see the obvious high-value month/low-value month, these changes do not seem to have much to do with the season, can you explain the reason for the change?
3. Fig.8: Adjust the subgraph size and line thickness to clarify the results. It might make more sense to put the seasonal labeling in the top right corner.
4. Why did you only analyze the “Surface Wind Variations from 2015-2021”, and what is the difference between the Surface Wind Variations from 2005-2014?
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors use CALIPSO and MODIS data to study geometrical and optical aerosol properties above Huai River Basin in eastern China.
It is a comprehensive study using longterm dataset of satellite remote sensing instruments and at least some ground-based measurements.
Furthermore, the used data is thoroughly explained, again except the used ground-based measurements.
Most interestingly are the presented trends in aerosol optical depths and how and how differently they are captured by the multiple instruments.
Therefore, the manuscript is suitable for publication in Remote Sensing after some minor revisions.
Main comments:
Fig 1. has unneccessary large white spaces , blue text "CALIPSO Overpasses" and also "Shouxian" in yellow are almost not readable, and also a), b), c) are almost not readable. Enlarge, and maybe use white font.
Line 147-148: "Then, aerosol type dependent lidar 147 ratios are used to improve aerosol extinction coefficient retrievals[30,31]." Rephrase. Lidar ratios are not used to improve. The extinction can ONLY be retrieved using lidar ratios (Klett retrieval).
Line111/189. In Fig. 2, you show a ground-based lidar temporal development plot, but you do not discuss the used lidar (only mentioned it in Line 111). Add at least a sentence or two to this lidar in this section, and add a reference to the used lidar system, if existing.
Fig 2. The colorbars and labels are too small, hardly readable. TAB is not explained.
Line 267 ff. Are these heights above ground or above sea level? State it. In line 339/341, the same. Please, state if a.g.l. or a.s.l. The same in Figure 7 and respective text.
Fig. 6. The y-axis label have to be corrected. Especially, micrograms per cubicmeter.
Fig. 6. Please, state in the text, how you retrieve extinction coefficient from visibility. Koschmieder formula? Which minimum identifiable contrast is used?
Fig. 9. The colorbar labels are hardly readable. They are always the same, you could increase its size and show it only once, valid for all subplots.
Some further, minor comments and suggestions concerning textual changes can be found in the attached, annotated pdf. Especially the references and figures need to be checked.
Comments for author File: 
Comments.pdf
Quality of English is remarkably good, as far as I can judge.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
