CO Editor

Suggestions for revision or reasons for rejection

Thanks for the opportunity to read the revised version of this manuscript. I am satisfied that the authors have addressed the majority of my concerns, and recommend that the paper be published once the following technical corrections have been made:

Page 3, line 13: 'de' should be corrected to 'the'
Page 5, line 31, and throughout: you have used data as singular here (i.e. 'data was', rather than 'data were'), but as a plural elsewhere. Please check the manuscrip one last time to make sure you are consistent
Page 9, line 30: swap 'varies' and 'clearly'
Page 9, line 32: 'personnel at the airports ARE'
Page 10, line 5: 'but barely occur', rather than 'but do barely occur'
Page 10, line 7: 'hence this issue is largely absent'
Page 10, line 27: 'on a monthly and daily scale' (remove the 'a' before daily)
Page 11, line 25: 'approach' not 'approache'
Page 11, line 28: 'detected on average'
Page 12, line 8: 'reference stations', rather than 'references'
Page 17, line 32: what do you mean by 'cannot take UDQI into account'? I think you mean that UDQI must be considered and ideally removed, but it is not clear in this statement
Table 1 caption: I would refer to Figure 1 here when mentioning the different regions, and also add a sentence at the end pointing readers to Hunziker et al 2017 for extra information on the tests.

RC1: 'Review', Anonymous Referee #1, 09 Jun 2017

AC1: 'Response to Anonymous Referee #1', Stefan Hunziker, 09 Aug 2017

RC2: 'Review of Hunziker et al.', Anonymous Referee #2, 14 Jun 2017

AC2: 'Response to Anonymous Referee #2', Stefan Hunziker, 09 Aug 2017

EC1: 'Editor comment', Volker Rath, 14 Jul 2017

Interactive discussion

Peer-review completion