Dear authors,

thanks for the revisions and clarifications. I would like to ask for more efforts from you to clarify the text. Reading the questions from the reviewers I find the following questions adequate to ask to you:

- the new figure 11 shows the budget. But for CHBr3 the ocean contributes 45%. But thats not 60% ? How do these numbers correspond to each other? Can you visualise a budget where the 60% is appearing? I don’t see where you get the 60% from.

- I think that the box model is too complicated and caused confusion by the reviewers. I don’t see why you need to introduce ODR, CLR, ADR . I believe all can be computed as source/loss terms (fluxes) and life times. If you want to explain which part of the flux to the free troposphere is marine, you can simply multiply the marine VMR with the COL flux. Unless proven otherwise, I request to remove all ODR, CLR, ADR from the text and formulate all budgets in terms of OD, CL, COL and AD.

- Reviewer had asked for a diagram showing the magnitude of the fluxes. I don’t see that the new figure 11 shows the magnitude of the fluxes. It shows relative magnitudes. Since COL is the same for all tracers (isnt it?) the figure can be simpler: I suggest to make one graph with absolute magnitudes, unit [% d-1] . The sum = COL in % d-1 could be shown to the right as the counterbalancing flux. Or do I misunderstand? This would go with my above comment.

- please revise the whole new phrase: “a joint pattern of atmospheric mixing ratios along the cruise “ its not clear. And in general: All new text should be checked once more for english and grammar. It doesn’t sound correct in several places.

with kind regards
Michael Schulz

Dear authors,

Thanks for your explanations. They have made clear, where I think the problem lies.

The budget in the MABL is well documented. I would appreciate to indeed use your new figure B with the Daily contributions in %/d indicated on the figure. Although confusing the ODR etc terms are probably a matter of style and could stay.

What I think is not resolved is how you arrive at 60% oceanic contribution to FT bromoform mixing ratios, starting from 45% in the MABL. You do not explain how you get to that number. After several reads I come to the conclusion that there is serious flaw in your vertical mixing computation method.

Air with any given mixing ratio at MABL level can not be transformed to air with a higher mixing ratio when mixed up into the free troposphere. FT-air, which has supposedly smaller background mixing ratios, will dilute more and more. Yet, when looking at figure 11 the mixing ratios for bromoform increase towards the top of the troposphere, relative to the mid level altitudes (actually seen for all three compounds). How can this “accumulation” happen? I think this is a numerical artifact of the rather unorthodox method to compute the vertical mixing, as described in section 2.4.3, esp equation 13. Using a trajectory model and a pressure profile. I think this is an oversimplified paternoster model of vertical mixing. As if MABL air is injected directly, eg into a layer at 12 km height, expands and then the clean FT air is, in compensation, pressed down. There is no entrainment, no turbulent mixing assumed, which in reality will dilute MABL air considerably during transport. Figure 8 shows that 80% of trajectories left the box in 10 days. At the same time the authors state that the steady state of the vmr vertical profile is reached after ca 10 days. I suspect that the profiles reach steady state because after 10 days most of the trajectories left your bounding box. How long are the trajectories actually run? Can the trajectories go higher than 13km? What happens to air if carried out of the Fig 8 box? What would happen to the profiles if the Fig 8 box was twice as big, or spanning the whole northern hemisphere?

By the way: The observations don’t show this enrichment at the top of the troposphere, no surprise for a substance with a surface source and sink in the FT.

Bromoform: 60% oceanic contribution to FT air cannot be kept as a conclusion, to my opinion. 45% as in the MABL air is an upper limit for the FT air. That should be explained.

Please expand on the proper value of your vertical mixing calculations. And its caveats. I consider this a major revision, since I don’t believe this can be done in 1-2 sentences.

As written before, I believe the material is very worth publishing,

With kind regards
Michael Schulz

Dear authors,

as discussed in our separate email discussion and according to your question in the answer to my latest review, you wish to resubmit another revised manuscript. I am calling this a minor revision, since I need to review it again.

kind regards
Michael