Dear Authors,

Thanks for your detailed response to reviewers comments. You have addressed the major comments. Reviewer 2 has a few further comments, please see below. Once these are addressed, the manuscript will be suitable for publication in ACP.

Best,
Sally


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It is clear that the authors have done a thorough job with their revisions, and what they have done is much clearer now. It is, however, unfortunate that their conclusions now become much less solid w.r.t. the biogenic SOA case, in particular. In essence, for biogenic SOA they either conclude that it is always well mixed (one limit) or often not well-mixed (the other limit). This speaks more to the constraints on the available data, and the inconsistencies in the literature, than it does to the specific work here.

As such, I suggest that the authors update their abstract to more directly point out what they now state in their revised manuscript, namely that "Considering these caveats, we are unable to make strong conclusions about how often mixing times of organic molecules are < 1 h within a-pinene SOA generated at low mass concentrations." But, I actually think it goes beyond this because what the goal is (presumably) is not to assess global variability in mixing times at very high and moderate OA concentrations, but to assess what the real atmosphere does. Thus, I suggest the authors more directly say that the difference between the parameterizations means that they also cannot make "strong conclusions" regarding the mixing timescales of biogenic SOA under ambient concentrations. This should be stated in the main text and in the abstract in some manner.

Also, I suggest that they change "low mass concentrations" on P7/L7 to "low, atmospherically relevant mass concentrations".