All three referees have provided reports on the revised version of your paper. All referees take the view that the paper has been improved in revision, but nonetheless all identify specific ways in which the paper could be improved further. (Two referees provide long and detailed comments, the third makes briefer comments but is nonetheless quite specific about where s/he believes significant improvements should be made -- with respect to the discussion of Sprenger et al. (2003) and with respect to comparison between January and April on the basis of one year only.

Please consider these latest referees' comments carefully, revise the paper appropriately and provide a detailed set of responses to the comments. I will then be pleased to consider the paper further. My hope that is if you are thorough in your revision and in your comments then I will be able to accept the paper without consulting the referees further -- but I cannot guarantee that.

Your replies and revision in response to the latest round of referees' comments are thorough and I feel that the most productive way forward is to accept the paper for publication in ACP after one final round of minor revisions that I will consider myself.

I do feel that some of the previous criticism of the referees remains valid and I request that you consider making changes in response to the comments below prior to submitting a final version. I am not demanding these changes -- it is up to you whether you make them or not. But my view is that your paper will have most impact if it is as clear as possible, both in detail and in emphasising what is new about the work.

General comment: To me the natural major question motivated by your study is — is there strong overall relationship between times of high Be7 concentration and evidence from trajectory calculations of transport from the tropopause region. (That might be a useful quality control on trajectory calculations.) I still find it quite difficult to decide whether you have answered that question and if you have, what the answer is. Any extra summary sentence you can provide to make that clearer — if only to confirm that you are not intending to address that question would be helpful.

Title: One referee requests strongly that you include Be7 in the title — because that is an important aspect of your study that distinguishes it from previous studies. I don’t insist on a change — but have you considered:

‘Fast descent from the stratosphere to the surface at Fukuoka studied using Be7 measurements and trajectory calculations.

l15: 'Because parcels descend, pushing low isentropic surfaces, their potential temperature decreases upon mixing with parcels having low potential temperature in the lower layers.' -- I found it very difficult to understand the meaning of or the logic of this sentence. The idea of 'descending parcels pushing isentropic surfaces' does not really make any sense. I recommend that you omit the second two sentences of the paragraph and retain only the first, perhaps adding 'e.g. through mixing' -- i.e. 'potential temperature decreases along trajectories, e.g. through mixing'.

l23: Again I found it difficult to identify the precise meaning of this sentence, particularly 'cannot descend in the stratosphere when moving from high to mid-latitudes' -- are you saying that there are no isentropic surfaces that intersect the surface at mid latitudes that are in the stratosphere at high latitudes? Again I think that saying less is probably better. Perhaps the whole final sentence could be omitted.

l57: 'Because the deepest area of the troposphere is above the Earth's surface ...' -- this is very confusing. Surely all the the troposphere is above the Earth's surface. A change is needed.

l90-99: You are making the point here that following trajectories to the surface is difficult -- notwithstanding that several previous papers, e.g. Wernli and Bourqui (2002) have studied aspects of 'deep exchange' and I think that important point is the difference between a chosen surface such as 700hPa and the Earth's surface -- i.e. many calculated trajectories starting in the upper troposphere/lower stratosphere reach 700hPa but very few reach the Earth's surface itself. It might be helpful to say that explicit. Otherwise readers may remain confused about what the difficultly actually is.

l118: 'the ratio is still small in rapid descent' -- it might be clearer to say 'small values of this ratio indicate rapid descent'.

l230-241: Calculations of trajectories is now fairly routine and some of the details here -- e.g. how you deal with the pole -- are perhaps not needed. But, on balance, it is good to have all details provided. For me the question is -- do you have any confidence in the trajectories within the atmospheric boundary layer? Do JRA-55 velocities contain any parametrisation of boundary layer turbulence, for example? Note that some standard trajectory codes such as FLEXPART include a ‘boundary-layer parametrization’ — i.e. a stochastic addition to the velocity field. If you cannot point to previous evidence that JRA-55 velocities + your trajectory code provide a good representation then you should clearly note this as an uncertainty and something that might be improved in a future study.

l266: Like one of the referees, I remain confused about where ‘267 times’ comes from. Which of the various numbers that appear in the text or in the tables do I add together to give 267? You might not consider this sort of detail important, but if the reader is not sure about how exactly you have defined your various calculations then their confidence in the whole paper will be reduced.

This paper has been through several iterations and I think this a good point to end the process. I am pleased to accept the current version of the paper for publication in ACP.