Many thanks for the revision of your manuscript. This has been improved significantly since the initial submission by addressing the comments of the reviewers and I see you have performed a deep linguistic correction, however more effort is needed in this respect. I have a number of points on this revised version that further require to be considered (pages and line refer to the track changes version) and several other minor ones.
Please revise your manuscript accordingly and resubmit the re-revised track changes version together with a point-by-point reply to the comments for final consideration.

Major comments:
1- Page 2, First sentence is misleading. Nitrogen oxides do not react directly with volatile organic compounds to form ozone. To have to rephrase this sentence, for instance to ‘Tropospheric ozone is formed primarily during the oxidation of volatile organic compounds in the presence of nitrogen oxides and sunlight’.
2- Table 1 provides the list of tagged European source regions. However in Figures 6,7, and 8 other source regions and source types are also presented. I suggest to add those in Table 1 (as 2 (?) different categories) clearly mentioning that the contribution of those comes from the boundary conditions (discussed in page6 last paragraph).
3- How this ‘tracking of contribution’ is done for these extra regions and source types requires a bit more explanation than currently provided in page 6. You need also to make clear whether you double count of not between source regions and source types. Double counting should not happen and remains unclear of this is the case.
4- Table 1 and Figures 6 and 8 – please make naming of regions compatible between the Table and the Figure’s titles. Also in Table 1 better explain GEN as Germany, Belgium, Netherland, Luxembourg; ALP as High Alps (West Austria…); SCA as Scandinavia (Finland…). TCA shoud be used in Figures instead of Turkey.
5- Page 11, lines 25-30: The change in this sentence to address the reviewer's comments leads to a misunderstanding, leaving a wrong message to the reader. Stratospheric ozone intrusions to the troposphere vary seasonally with maxima in winter/spring. The summertime increase in photochemical production of ozone is not responsible for the changes in the stratospheric influx, which is driven by atmospheric dynamics. So the fact the stratospheric CONTRIBUTION to surface ozone levels is less during summer is due to two reasons to the decreased stratospheric influx of O3 and the increased photochemical production of ozone during that period. Therefore some rephrasing is needed at this part of the discussion.
6- Figure 8 is impossible to read for the other source types and HTAP regions – some lumping would increase readability.
7- Improve Figure 6,7 and 8 captions to clearly state that contributions from other source types and HTAP regions are also shown
8- Page 19, lines 15-18: rephrase this sentence AOT40 by definition does not account at all for O3 below 20 ppb.

Pages and line to check for English use and rephrasing for clarity:
9- Page 2, lines 25: are  is
10- Line 30: enhances
11- Page3, line5 to make estimations
12- Line 31-32: ugly sentence, rephrase sentence
13- Line 32: information is available
14- Page 5, line 16-20: rephrase
15- Line 18: a long term objective
16- Line 27: ‘briefly describe the details’ ? please rephrase
17- Page 5, line 22: to consider
18- Page 7, lines 2-3: unclear statement –please clarify and justify that there is no double counting (see major points)
19- Line 19: m-3 correct exponents
20- Page8, line 8: is (the contribution)
21- Line 17 (analysis) was determined  was performed
22- Page 9, line 6: set-up used…
23- Line16: data were well reproduced
24- Line 18: temperature was …
25- Page 10, line 7: different O3 sources – rephrase because O3 is secondary anyway i.e. chemically produced in the atmosphere.
26- Line 13: combined contribute
27- Line16: I am not aware of an ocean source of ozone, if you refer to emissions of NOx from shipping please rephrase.
28- Line 21: other source types
29- Line 21: this time of the year better specify months
30- Page 11, line3 explain boundary conditions for stratospheric O3
31- Line 19: noticed the spread
32- Line 34: was contribution
33- Page 12, line 22: peaks
34- Page 13, line 1: have shown
35- Line 25: type to modelled and to observed MDA8 O3 values
36- Line 28: I think ‘occurred’ is not needed.
37- Lines 30-31: the contribution … is (or both in plural)
38- Page 16, line23: natural source account
39- Page 17, line9 remove ‘more’
40- Line 12 remove ‘that’
41- Line 20: Due to the way
42- Line 27: linear regressions
43- Line 29 more highly ? rephrase
44- Lines 28-30: please rephrase, sentence is ugly
45- Page28, line22 have identified …

Thank you for the careful revision of the manuscript. This can be now suitable for publication in ACP. with kind regards, Maria Kanakidou (co-editor)