Dear authors,

Thank you for your response to reviewers' comments. I have received additional comments from Reviewer 2. Please see below. Once these comments are addressed, the manuscript can be accepted for publication in ACP.

Best,
Sally
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Reviewer 2 comments

Kollner et al have made useful revisions to their manuscript overview of Arctic single-particle composition during NETCARE flights. In particular, the addition of the sub-potassium particle type (22% of the total) and application of their data analysis approach to these particles was a critical addition. Also, it is important that the composition of another 24% of the particles (ammonium, MSA, and sulfate) is acknowledged, leaving only 16% unclassified. This is an acceptable fraction of unclassified particles. Overall, the many revisions made to the manuscript have significantly improved the work, and these revisions have sufficiently addressed my previous comments and concerns. I only have a few remaining comments, mostly with respect to added text.

Lines 41-42: This new sentence is lacking a reference and is confusing as written, as it states that “the presence of aerosol in Arctic tropospheric layers leading to cooling of the surface beneath by absorbing incoming solar radiation and by reflecting radiation back to space.” Certainly reflection would lead to cooling, but absorption should lead to warming. Please clarify sentence and add an appropriate reference.

Lines 53-55: Please add references for these new sentences.

Lines 504-506: This new sentence states here that “the enhanced abundance of the sub-K particle type…with anthropogenic influence shows that potassium does need not necessarily be linked to a biomass burning source”. This is in section 3.3.2 “Vegetation fire and anthropogenic influences on particle composition”. While a subset of the sub-K particles were associated with anthropogenic influence rather than wildfires, this does not rule out biomass combustion as the source, rather it only rules out the satellite-detected wildfires as the source. Note that biomass burning particles are the most dominant particle type in the FT outside of the Arctic (see Schill et al. 2020, Nature Geosc.; Pratt and Prather 2010, JGR; Hudson et al. 2004, JGR). I suggest revising the current statement and linking to these previous papers.

If possible, I encourage moving the highly useful Fig S11 to the main text. In my opinion, Figures 2 and 4 could be moved to the SI.