Validation and Analysis of MISR and POLDER Aerosol Products over China

Round 1

Reviewer 1 Report

This manuscript is of good importance to the user community of polarization aerosol products. However, it should take additional necessary major revisions before the publication in the journal.

Major concerns:

1) the result and discussion sections lack of necessary solidarity. Many statements are inaccurate and missing supportive references, e.g., L304-306.  

2) the manuscript needs additional English proofreading. 

3) the figures are too blur.

Author Response

The authors greatly appreciate the time of you to review this paper (remotesensing-1738235). Following these suggestions and comments from you, we have made all corresponding changes, as addressed in the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

General comments:

 

Article is dedicated to validation of aerosol retrieval from multi-angular satellite observation over China. Such theme is within the scope of the Remote Sensing journal. Being one of very scarce articles that addresses advanced aerosol properties, such as angstrom exponent and absorption it should be of some interest to the community.

 

Generally, article is well illustrated and written, although language would need some minor revision, since sometimes it is not exactly clear what authors want to express. Article has more or less clear structure, although some of the authors’ decisions on its organization would need additional clarifications. It is properly referenced, although I would add several references to support some of the statements.

 

I’ll list my concerns in details below.

 

In overall I’d recommend to accept this article for publication with major review.

 

Major comments:

 

One of my concerns that article focuses on a smaller part of the globe -China without good references to similar global validation papers of the corresponding products, I’d like to see a  comparison how results over China are compared to global ones.

 

Lines 154-155: I’m not sure AE could be used to interpolate AAOD. Strictly speaking AE is not equal to AAE for all the aerosol types, and doing so may introduce significant errors in comparison. Generally I’d like to see some explanation in text, why the interpolation was used in the first place.

 

Lines 217–218: I find it quite hard to accept that using 21 points are significant to withdraw reliable statistics and conclusions.

 

Table 6. To me it is a bit illogical where this Table is placed, why not put it next to all other similar comparison in section 4. Secondly, why EE are so different? I understand that they come from different papers, but for the sake of comparison I’d like to see GRASP and MISR to be estimated for the same 0.05±0.2*AOD, this shouldn’t be a big issue for the authors, I believe.

Lines 538–539: Please make sure that reader will understand that AHI and H8 in the Table 6 is the same product.

 

Lines 593–595: This is quite strong statement, that is not supported by anything, either reformulate either provide a paper that discusses issues of PODLER calibration. Also authors discuss a lot about improvements that multi-angular observations introduce into the AEROSOL retrieval (I’d suggest to put some review papers to support this statement, e.g. Dubovike t al., 2019) but do not pay any significance to the retrieval methodologies, that has to be adapted to maximise profits from such complex observations.

 

 

Table 3.

 

Why some sites are level 2 and some are level1.5? AERONET does’t guarantee quality retrievals of AAOD below level 2.0. It is unclear was this data excluded from the comparison or not.

 

Section 4.3 It is a bit unclear why MISR data is missing in this section. It breaks the inter-comparison structure one would expect from such a paper. At least provide some explanations why you decided to focus on only one product in this section. Also MISR can provide a wider temporal coverage up to the modern days…

 

In general, the whole AAOD study, at least as it presented doesn’t look very solid to me, among the issue I could mention is questionable spectral interpolation, very low number of pairs and totally disregarded fact by authors that AAOD even for AERONET is quality assured under quite strict limitations (for e.g. level2.0 only and, among others AOD higher than 0.4), I do believe that such particularities should be discussed in the text, or at least some attention should be drawn to it.

 

Minor comments:

 

Table 1 and Table 2.

I’d like to see similar tables but for the PRODUCTS used, i.e. their brief characteristics, what values are provided and at which wavelengths, and resolution. This will make some of the comparison methodology decisions more obvious 9e.g. decision to interpolate using AE).

 

Lines 87-92. I do believe Chen et al., 2020 deserves to be mentioned here.

 

Lines 134–138. Please provide level and version of the data used. Some of the levels provided by the link are quality assured, some are not, this is important.

Lines 155-156: I do not exactly get what “closest wavelength” means in terms of AE. Is this the closest pair, please provide values in text.

Lines 268–269 and 217–218: “the number of matched pairs 268 is much smaller than that of AOD ” please provide explanation why.

Figure 4 and 6. It would be easier to compare the figures if AOD and AE scales will be same. Also the AE scale on figure 4 is exaggerating the variability which is not that high to be frank, taking that ae changes in the range ~0–2

Lines 449–454. I’d like to see some references here at least for meteorological effects discussed.

 

Table 3:

It seems that most of Beijing sites are within the 0.1 degree proximity, i.e. there’s a chance they all be in one POLDER product pixel, not mentioning the 50km averaging.

 

Table 3. It would be nice to see here which surface type each site is.

 

Section 4.3. please indicate wavelengths for AOD and AAOD.

 

Technical comments:

Line 273: I believe “AAODPOLDER,565 ” should have POLDER,565 in the subscript.

 

 

 

 

 

 

 

Author Response

The authors greatly appreciate the time of you to review this paper (remotesensing-1738235). Following these suggestions and comments from you, we have made all corresponding changes, as addressed in the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have addressed my concerns.

Author Response

  Thank you for your comments. We sincerely appreciate your valuable reviews which are helpful for improving this manuscipt.

Reviewer 2 Report

All of my major and minor concerns were corrected, i do believe the paper is improved in overall and know clearer and more easy to understand.