General Comments:
The authors have addressed the initial comments extensively and I find that the manuscript is greatly improved. In general, I think that the results are clear and the methods used are reliable. The manuscript is well written, especially the introduction, methods, discussion and conclusion sections. In some parts the results section seems to jump from one topic to another, and could be improved somewhat, with some suggested revisions detailed below. I think that the manuscript should be published after the authors consider the relatively minor changes suggested below.
Some general comments are:
1. The beginning of the results section does not make it clear that the computed distributions are being used as an indication of the expected evolution of seasonal albedo, which the observations generally appear to confirm, rather than being compared to the observations directly. Please add a few sentences to make this clear.
2. I am not entirely clear on how melt rates are calculated in the cases where observations of incoming solar radiation are not available. It seems that if values for June are used in the calculations, the amount of melting later in the season would be underestimated. Please clarify how this is done in the methods section.
Specific Comments
1. P. 1, Lines 15-16: Change “melt rate percent difference increase” to “melt rate increase”.
2. P. 1, Line 17: I think “pentad-to-pentad” is unnecessary for the abstract.
3. P. 1, Lines 18-19: Change “In 2012 a more complex multimodal distribution emerges” to “Ablation area albedos in 2012 exhibited a more complex multimodal distribution,”
4. P. 3, Lines 16-17: MAR does not incorporate black carbon concentrations, but RACMO2 does according to van Angelen et al. 2012. Perhaps move the mention of this to the next sentence.
5. P. 5, Line 12: Change “measuring at” to “measuring over a wavelength range of”
6. P. 6, Lines 23-24: Is it necessary to mention the field of view with the bare fiber if the RCR was used?
7. P. 7, Line 13: The mention of “surface roughness effects” here seems to contradict the previous statement about αtop measurements not being accurate because of surface roughness effects. Perhaps the authors can move the sentence on P. 7, Lines 6-7 here, e.g. “Although surface roughness effects were not quantified, analysis of measurements of αtop suggest that they were compromised by surface roughness effects,…(Appendix A).”
8. P. 8, Line 26: “no albedo measurements were made”. This contradicts the discussion of abase in earlier sections. Wasn’t broadband albedo measured at the Base Met Station? I think the authors mean to say that spectral albedos were not measured at Base Met Station. Please clarify in the manuscript. Perhaps αMET_base should be called αASD_base since it is an ASD value used to represent the abledo at the Base Met station. Could αMET_base possibly be corrected using the broadband albedos from the station?
9. P. 10, Line 8: Can a web address be provided for the WorldViewer?
10. P. 10, Line 12: I am confused about how melt rates can be calculated for all the distributions (even the late season simulated distributions) if incoming radiation values are only available in early June.
11. P. 10, Line 22: If the units are ms-1, I believe the Δt is not needed. If Δt were included wouldn’t the resulting units be “m water equivalent”?
12. P. 11, Line 18: “Confirmed and observed”. Perhaps it’s better to say that the changes are “consistent” with each other.
13. P. 11, Lines 21-22: “where the difference…” This part of the sentence seems unconnected to the first part of the sentence. I think the authors are trying to say if the temperature record from the tundra is adjusted 3°C lower, there are likely snowfall events occurring over the ice sheet. Please clarify.
14. P. 11, Line 22: How do the authors know that snowfall events happened with certainty during June, when it is unclear whether events occurred during July. Perhaps these events should be referred to as “likely events”, given that the temperature dipped below zero over the tundra station?
15. P. 12, Line 1: Change “less temporal” to “a lower”
16. P. 12, Line 6: Change “at the first than the last observation” to “at the beginning as compared with the end of the month of June”
17. P. 12, Lines 13-14: Change “αASD above 0.4” to “values of αASD > 0.4”
18. P. 12, Line 17: Perhaps section 4.2.1 should be renamed. As noted in the response to reviewers, the simulated distributions are not being compared directly to the observed distributions, and the computed distributions are for 2012, not for 2013, if I’m not mistaken. Perhaps this should simply read “2012 Computed and 2013 observed albedo distributions.” Or perhaps the simulated distributions should be discussed in a separate section.
19. P. 12, Line 20: Perhaps indicate that this simulation represents how the distribution of albedo is likely to evolve over the course of a melt season in response to different changing surface types.
20. P. 12, Line 30 – P. 13, Line 1: The changing distributions are not really “confirmed” by the αASD measurements. I think it would be better to say that the changes in the ASD distributions are “consistent” with the simulated changes. The ASD results seem to be an example of albedo values from the start of the melt season, but the change in the distribution over the course of the month of June suggests that the ASD results are beginning to show the evolution suggested by the simulation.
21. P. 13, Lines 7-8: Clarify that these results are for 2013.
22. P. 13, Lines 23 and 25: Since Fig. 10 has not really been introduced, perhaps it is better not to refer to it just yet.
23. P. 14, Line 2: Figure 14 is being referred to before Figures 11-13. Please move Figure 14 so that it becomes Fig. 11.
24. P. 14, Line 14: Again, Figure 15 is referred to before Figures 11-13. Please rearrange this figure as well.
25. P. 16, Line 10: Change “computed” to “simulated”.
26. P. 18, Lines 4-5: Is there a reference available that discusses changes in ice crystal size?
27. P. 18, Line 20: Change “findings turn out to be true, these effects” to “changes do occur, their effects”
28. P. 20, Lines 11-14: The authors do suggest that wind-blown dust may have an impact on short timescales, but that the large changes seen in 2012, are likely a result of melting. Can this be made clear here?
29. P. 47, Line 26 – P. 48, Line 6: I think it makes more sense to move these sentences to the next section, since this section is supposed to be about quality control of αASD. In fact, some of the material here is already mentioned in the next section.
30. P. 48, Line 26: What is meant by “close to 1”? Isn’t the slope 0.26?
31. P. 49, Line 11: Can the authors briefly explain how surface roughness can produce the observed hysteresis?
32. Table 2: Perhaps sites A,B,C, and E, should also include values for “clean surfaces”, since I believe each of these locations was considered to consist of “clean surfaces” only?
33. Figure A2: Caption: Suggest moving “(a)” on line 2 to the beginning of the sentence.
Technical Corrections
1. P. 3, Line 26: Change “control of” to “control on”.
2. P. 7, Line 6: Change “suggests that αtop” to “suggests that measurements of αtop”
3. P. 10, Line 5: Change “was examined” to “were examined”.
4. P. 13, Line 14: change “which is” to “which are”
5. P. 14, Line 5: Change “pentad” to “pentad distribution” and “coincides to” to “coincides with”
6. P. 14, Line 15: Change “2012 MODIS is” to “2012 MODIS observations are”
7. P. 15, Line 21: Change “next” to “below”.
8. P. 15, Lines 24-25: This statement seems contradicted by what follows. The authors go on to suggest that few measurements were taken over streams, suggesting that the range of albedo values for streams is in fact larger.
9. P. 15, Lines 26-27: This sentence is unclear. Do the authors mean that “Differences in observed and measured ablation rates for streams are due to a lack of albedo measurements taken over streams.”?
10. P. 16, Line 5: Change “on” to “in”
11. P. 16, Line 13: Change “a shift in” to “shifts in”
12. P. 16, Line 14: Change “is an important driver” to “are important drivers”.
13. P. 17, Line 21: Change “attributes” to “attribute”
14. P. 20, Lines 20-21: Change “ablation area albedos’ contribution to GrIS mass loss” to “the contribution of ablation area albedo to GrIS mass loss”.
15. P. 46, Line 10: Change “sites” to “sites,”
16. P. 46, Line 27: Change “…section 7.2 that all…” to “…section 7.2. All…”
17. P. 47, Line 24: Change “daily range of variability in cloud conditions” to “daily range in cloud fractions” (if it is cloud fraction that is being referred to here”
18. P. 47, Line 25: Change “yet” to “which”
19. P. 47, Line 26: Change “transect times” to “transect measurements”
20. Table 1: Caption: Place “Brd” in quotes.
21. Fig 12 and Fig 13: I think these figures were created using the Matlab function “contourf”. The functions “imagesc” or “pcolor; shading flat” might yield more details regarding spatial variations in albedo, but this is a minor detail. |
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