please see the attached document

General comments

This manuscript provides a thorough description about retrieving snow grain sizes from airborne LiDAR and investigating their impact on penetration biases in ICESat-2 elevation data. It is very impressive to see the recovery of new information from datasets that were collected in the past (that were not necessarily customized to retrieve this information). The data and methods are dense but described in detail. The authors make this research immediately applicable by linking recovered snow grain sizes with elevation bias corrections for ICESat-2.

Most of my concerns can be addressed by improving the writing style (see specific comments). My major gripe is the use of “Figure X shows” at the start of paragraphs. It’s OK once or twice but it becomes tiresome when every paragraph of the results starts with these words. I recommend that the authors revise some of the first sentences of these paragraphs.

I was also a little underwhelmed by the correlations between ATM/AVIRIS grain sizes with satellite-derived grain sizes. But the authors provide some ideas for the differences which I think this is sufficient for the current scope of the paper.

Specific comments

L33: There are a lot of “efficients” in the first paragraph. It would be useful to clarify why these detectors are so “efficient”. Are they sensitive? Low SNR? Energy efficient?

L32-25: Long, wordy sentence, consider splitting.

L36: Just glaciers? Or ice sheets as well? It seems like these two terms are being used interchangeably which is at odds with the first couple of sentences.

L41-49: Even though this is a well-known phenomenon, it might be useful to add some references here which describe this in more detail.

L56-59: I would need access to these manuscripts to judge overlap and novelty of this paper.

L84: Define acronym on first use of term “ATM” (L75) rather than here.

L88: Diameter?

L103: Instruments? Surely there is only one LiDAR or were LVIS and SIMPL also onboard? It may be useful to name the lidar sensor given that ATM is defined as a suite of instruments (or revise L84).

L110-112: Might be useful to clarify the difference in swath widths here or L96 when it is first mentioned. Or are these two different sensors? Either way I think some general tightening of terminology is needed in this section.

L114: “Verify” seems a bit strong. Validate or evaluate might be better.

L123: This raises the question about how many data files were excluded from the analysis. Are all 26 data files from the same five-day period in 2019 when ATM was followed by AVIRIS-NG?

L134: Consider revising because the way it’s written makes it sound like Gallet et al. (2009) validated snow-grain sizes from OLCI which was launched in 2016.

L143: What was the threshold for removing data points that have not been recently updated?

L213: It would be useful to briefly remind readers how the IRF was measured here.

L280: Is the satellite not named “ICESat-2”?

Fig. 5: AVIRIS is misspelled in Panel E

L361: It would be useful to name the two ATM sensors since this is the first sentence of the paragraph

L398: Please could you clarify if this is all coincident grain sizes from Summer 2019 or just a sample.

L401: “comes about” is clumsy, consider revising.

Fig. 9: What is the justification for the position of the dashed lines? It would be useful to clarify that here.

Fig. 10: Same comment about the dashed lines as above.

L411: Which years?

Fig. 11: I think the satellite grain size should be on the y-axis to be consistent with Fig. 10.

Fig. 12: It took me a minute to figure out what this figure was showing and I think it is because the word “satellite” is being used to refer to both Sentinel-3 grain size and ICESat-2 range bias. Please modify the axes labels to clarify. Also if the black lines show the modeled range bias as a function of grain size then the x-axis label should just be “grain size” and the legend should provide information about where the grain sizes came from.

L440-449: Be specific about which satellite.

L485-489: I think the first half of this paragraph should be removed (or placed later in the discussion) because, as it is written, it seems like the main takeaway is the consistency of the different snow grain size estimates. However, there are substantial biases between the estimates (Figs. 9-11) which the authors are up front about later in the discussion and should be the focus.

L532: Again, which satellite measurements?

L542-543: This statement seems at odds with L584-585 which states that elevation biases could be decimeter scale. Consider revising.