Impacts of Soot, Ash, Sand, and Haze on Snow Albedo in Sierra Nevada, Spain

Round 1

Reviewer 1 Report

I suggest to accept this paper.

Author Response

We wish to thank the reviewer for his/her appreciation of our work.

Reviewer 2 Report

This study investigated the impacts of soot, ash, sand and haze on snow albedo, it is a good work, the result is interesting. However, there are snow issues need to be considered and addressed.

The abstract of the current manuscript is tedious, please revise and make it more concise and meanful.

I didn't see the significance or aims of this work, please highlight it in the manuscript.

Introduction is not well organized, especially the first paragraph in page 3. Previous studies should be summarized and reorganized according to different subjects. 

Tables in the paper are not well organized, usually three-line-table is reasonable. 

Fig. 6 is not clear, please improve and modify.

Fig. 1 is poor, we can not capture the important information, please improve this figure. 

The albedo reduction caused by sand is negative, in this case, I think it is not so meanful to study the albedo variation impacted by the sand. Please clarify and improve the manuscript from this aspect. 

There are some new papers relevant to this study, such as Niu, HW et al., (2017, 2018, 2020a b, 2022a b), please cite and update the references of this work. I think it is helpful to authors.  

 

Author Response

C: This study investigated the impacts of soot, ash, sand and haze on snow albedo, it is a good work, the result is interesting. However, there are snow issues need to be considered and addressed.

R: We wish to thank the reviewer for his/her appreciation of our work. We hope that the reviewer comments have been satisfactorily addressed.

C: The abstract of the current manuscript is tedious, please revise and make it more concise and meanful.

R: The abstract has been revised and summarized, trying to avoid unnecessary information. Thank you.

C: I didn't see the significance or aims of this work, please highlight it in the manuscript.

R: The main significance of the study was described in the last paragraph of the Introduction section. However, this paragraph has been extended in the modified version for better clarity.

C: Introduction is not well organized, especially the first paragraph in page 3. Previous studies should be summarized and reorganized according to different subjects.

R:  We have modified this paragraph to link the cited studies by their broadband or spectral character, to include some additional studies, and to organize them by contaminating materials (soot, dust and ash, in this order). In any case, the paragraph just intends to show some selected examples about the reduction of snow albedo derived from contaminating particles.

C: Tables in the paper are not well organized, usually three-line-table is reasonable.

R: Table 2 has been organized as a three-line-table. However, Tables 1 and 3 require a few more horizontal lines to be understood.

C: Fig. 6 is not clear, please improve and modify.

R: Figure 6 (Figure 3 in the revised version) has been simplified and improved. Figure caption has been extended to clarify its content.

C: Fig. 1 is poor, we can not capture the important information, please improve this figure.

R: The left panel in Figure 1 has been replaced with another map with more visible background. In addition, the caption has been re-written for more clarity.

C: The albedo reduction caused by sand is negative, in this case, I think it is not so meanful to study the albedo variation impacted by the sand. Please clarify and improve the manuscript from this aspect. 

R: The broadband albedo reduction from sand contamination is almost nil. However, we think that it is interesting to observe that spectral albedo reductions in the UV and visible range are compensated with the increase in the IR range. Detailed radiative balances must be made spectrally, and thus the spectral contribution of each contaminant is very relevant.

C: There are some new papers relevant to this study, such as Niu, HW et al., (2017, 2018, 2020a b, 2022a b), please cite and update the references of this work. I think it is helpful to authors.  

R: Among the papers suggested we have selected Science of the Total Environment 581–582 (2017) 848–856, because this is the one were reductions in snow albedo are more clearly quantified as a consequence of black carbon and dust deposition.

Author Response File: Author Response.docx

Reviewer 3 Report

This modeling of the influence of impurities and polutants on snow albedo is very important to understand the evolution of the snow cover. In this respect, this work is of great importance for the scientific community.

The authors state some facts that are not clear at all. Before being accepted for publication the authors must improve the paper answering the questions below:

1) Regarding the methods:

1.1) In figure 6, they say that they used Raman spectroscopy for the structural characterization of the samples. However, Raman spectroscopy is not mentioned in the manuscript. Did they use Raman spectroscopy? If so, what for? If not, they must delete the use of this technique in Figure 6.

1.2) According to table 1, it seems that albedo measurements were carried out at SZA = 75, 65, 68 and 48.5 degrees. it is well known that albedo measurements for SZA above 70 degrees can be problematic. The results of albedo measurements at SZA = 75 degrees are not reliable. The authors must take these results out or correct them somehow.

2. Regarding the results:

2.1 The results shown in Figure 10 exhibit a very big discrepancy between modelled and experimental spectral albedo for wavelenghts above 1200 nm. The authors do not comment on this on the paper. They must give hints or explanation for this huge faliure of the model at these wavelenghts.

2.2 Figure 11.- the comment provided on lines 293-294 ( "It
can be observed that there is a higher albedo reduction in the visible range rather than on the infrared, as expected"), is not reliable  given the big discrepancy between modelled and calculated albedo in the IR.

2.3 Is the difference in figure 11 calculated from experimental data or from calculated albedo?

2.4 A comparison with results obtained using other softwares to simulate snow albedo must be provided. I think the model proposed by the others fails in the infrared part of the spectrum.

 

3.- The paper needs to be edited. The position of the figures in the manuscript is not correct. Figure 6 is cut on the right hand side.

Author Response

C: This modeling of the influence of impurities and polutants on snow albedo is very important to understand the evolution of the snow cover. In this respect, this work is of great importance for the scientific community.

R: We wish to thank the reviewer for his/her appreciation of our work and his/her useful suggestions.

C: The authors state some facts that are not clear at all. Before being accepted for publication the authors must improve the paper answering the questions below:

1) Regarding the methods:

C: 1.1) In figure 6, they say that they used Raman spectroscopy for the structural characterization of the samples. However, Raman spectroscopy is not mentioned in the manuscript. Did they use Raman spectroscopy? If so, what for? If not, they must delete the use of this technique in Figure 6.

R: No, we did not. Although the refraction index can be estimated based on the degree of graphitization (which can be estimated from Raman spectroscopy), in this case, only XRD was used. Therefore, we have removed Raman from Figure 6, as suggested. Thank you.

C: 1.2) According to table 1, it seems that albedo measurements were carried out at SZA = 75, 65, 68 and 48.5 degrees. it is well known that albedo measurements for SZA above 70 degrees can be problematic. The results of albedo measurements at SZA = 75 degrees are not reliable. The authors must take these results out or correct them somehow.

R: We have modified Table 1 to include the corrected values of solar zenith angle, considering the slope of the snow surface, rather than the real solar zenith angles. This transformation was already explained in the previous version. The maximum corrected SZA is now 70.3 degrees, which is close to the limit indicated by the reviewer. However, some authors have reported reliable measurements of albedo for SZE values up to 80 degrees (see e.g. doi:10.1175/2008JAMC1843.1, although in this article SZA refers to elevation angle).

2. Regarding the results:

C: 2.1 The results shown in Figure 10 exhibit a very big discrepancy between modelled and experimental spectral albedo for wavelenghts above 1200 nm. The authors do not comment on this on the paper. They must give hints or explanation for this huge faliure of the model at these wavelenghts.

R: The highest discrepancy can be observed in the range 1700-2500 nm. In this range, both solar irradiation and snow radiation are very weak (close to zero), and the ratio between them becomes very noisy and erratic, with any minor disturbance (e.g., any minor deviation of the detectors from parallelism) being highly magnified. The contribution of this discrepancy to the broadband albedo is minor because this is obtained as the integral of spectral irradiance divided by the integral of snow radiance (ω=∫I_rad dλ/∫I_irrad dλ), and both are very low from 1700 nm onwards. This explanation has been included in the revised version: “Discrepancies can also be observed in the range 1700-2500 nm, where both solar irradiation and snow radiation are very weak (close to zero), and the ratio between them becomes very noisy and erratic, with any minor disturbance (e.g., any minor deviation of the detectors from parallelism) being highly magnified. However, the contribution of this discrepancy to the broadband albedo is minor because this is obtained as the integral of spectral irradiation divided by the integral of snow radiation [15], and both are very low from 1700 nm onwards.”

C: 2.2 Figure 11.- the comment provided on lines 293-294 ( "It
can be observed that there is a higher albedo reduction in the visible range rather than on the infrared, as expected"), is not reliable  given the big discrepancy between modelled and calculated albedo in the IR.

R: The discrepancy commented in the previous response occurs from 1700 nm onwards, but not in the near IR, and therefore, we think that the statement is reliable enough. However, we have specified that our observation refers to the near IR range.

C: 2.3 Is the difference in figure 11 calculated from experimental data or from calculated albedo?

R: Differences were calculated from the experimental results. This has been clarified in the figure caption.

C: 2.4 A comparison with results obtained using other softwares to simulate snow albedo must be provided. I think the model proposed by the others fails in the infrared part of the spectrum.

R: We have compared results from soot contamination with other softwares such as SNICAR and Tartes in our previous work (ref. [15]), showing some quantitative differences but small qualitative differences with our OptiPar model. However, such comparison is not possible when other contaminating materials are used because they do not have our autochthonous sand, La Palma volcano ash and saharian haze among their materials database, since these materials have been collected and analysed by us.

C: 3.- The paper needs to be edited. The position of the figures in the manuscript is not correct. Figure 6 is cut on the right hand side.

R: The manuscript has been re-edited, taking care of figures being aligned with the text. Also, the figures have been reallocated and renumbered.

Round 2

Reviewer 2 Report

I am pleased to see that the author os this work has addressed all the questions raised in my previous conmments, I suggest accept the article in present form to publication. 

Reviewer 3 Report

The authors have revised the manuscript following the recommendations in the review process. I think the paper can be published in its present form.