Dear Jin Ma

Many thanks for your resubmitted manuscript. Unfortunately, the authors’ response does not identify the changes made in the revised manuscript (as required). You only state what you intend to change. The response needs to identify specifically what you have changed. Otherwise, it is not possible to proceed with the peer-review.

I note that you submitted a manuscript with tracked changes, but you need to include the individual changes made in the authors’ response as well, so that it is clear what was changed in response to which reviewer’s comment.

I also wanted to remind you that the issue with the sulfur flux notation (as per email from 9 July 2020) has not been resolved. As I wrote then, the notation "Gg S a-1" means "gigagram siemens per year" (siemens, symbol S, is the unit for electric conductance). The unit shouldn't be used to identify the chemical of interest. This would be like writing "the speed is 40 m distance h-1" or the "acceleration of gravity is 10 m height s-2".

Many units and chemicals share the same symbol and both are written in upright font, which makes them indistinguishable (e.g. N could be nitrogen or newton; C could be carbon or coulomb). Therefore, units and chemical symbols shouldn’t be mixed.

What should happen is that the species of interest is identified by the name of the quantity, e.g. the "COS flux (as S)” or "COS flux (as S equivalents)”. Alternatively, you could use molar quantities, e.g. "mol a-1", which are independent of the mass of the species. Or place the chemical symbol after the unit, which separates them to some extent (i.e. "Gg a–1 S”), but this is still not great because “S” could be part of the unit. Or you could just omit the chemical symbol because in your paper, all COS mass fluxes are presumably expressed as S equivalents.

Regards
Jan Kaiser
Editor ACP

Dear Jin Ma

I am happy to accept your revised manuscript for publication, subject to a couple of technical corrections:

l. 41: NOx should be written with subscript x, with the x in italics.
Figure caption S1: Please replace "mixing ratio" with "mole fraction".

I very much appreciate the effort that has gone into the careful revision of the paper, addressing the reviewers' comments and meticulous editing.

Best regards
Jan Kaiser
Editor ACP