Impact of Vehicle Soot Agglomerates on Snow Albedo

Round 1

Reviewer 1 Report

The paper is aimed to estimate the impact of BC emission from vehicles on snow albedo. Both measurements from field experiments and results from a set of radiation transfer models(RTM) are used to achieve this purpose. The experiment design is very detailed and includes many aspects of the considered problem, for example measuring of numerous parameters used in the RTM. It is  shown a general agreement between estimates obtained by these two approaches, which is especially accurate for the OptiPar RTM.

1) The surface albedo of the contaminated snow depends on concentration profiles of LAPs (light absorbing particles) in the snow. If BC particles have been deposited on the surface in a short time, as in the case in your experiment, probably BC concentration profile will have a sharp vertical gradient. Have you measured the vertical profile of the BC concentration in the snow or study sensitivity of model results to this parameter? For BC deposition in the natural conditions, as it is shown in the (Dang et al., JGR,2017), one can use for albedo calculation a uniform BC profile with average concentration obtained from top 5 cm of snow layer.

2) Another point concerns non-BC LAPs in the snow, f.e. dust, organic carbon. The albedo calculation will depends on its concentrations in the snow. Have your taken this factor into account in your experiments?

3) A comparison of the obtained estimate for albedo reduction per unit mass of BC in snow with previous results (f. e. Dang et al, 2017, Beres et al., 2020) is not presented. What are the possible reasons for the difference between your and previous estimates of this parameter, if it is any?

Line 31. It seems to me that melting temperature of the snow should not change after soot deposition at the snow surface, but soot particles can serve as heating centres to more efficiently heat the snow layer.

Author Response

See attached file

Author Response File: Author Response.doc

Reviewer 2 Report

This is an interesting study and the authors have collected a unique dataset using cutting edge methodology. The paper is generally well written and structured. However, I believe that the title should be revised. It should say vehicle soot agglomerates instead of local contamination.

Line 106: aforementioned

Line 151: if surrounding roads have traffic/vehicle numbers around snow fields, please provide further information.

Line 170: a reference is required.

Line 204: a full stop is needed, i.e.

The manuscript requires minor modifications as a result of these flaws.

Author Response

See attached file

Author Response File: Author Response.doc