Dear authors,

You have substantially modified your manuscript in response to reviewer comments. I recommend three additional minor changes as outlined below (all following up on comments made by A. Neuman) and then I will be happy to accept your manuscript for publication.

Anne

1. With regard to instrumental details, I think it would be appropriate to include mention of the times when data are discarded due to rapid baseline shifts from pressure fluctuations even if there aren’t many and to briefly state that zeroes were always below ambient sampling in this campaign specifically (even if that was the case reported in the experimental paper the reader can’t necessarily assume that is always the case).

2. The wording with regards to the DOAS comparison is confusing unless the reader is already familiar with the literature. Please rephrase to make clear that the techniques have been compared during a previous study and not in the present work.

3. The wording with regard to the Kaser study is similarly confusing (as to whether this finding is for the PBL in general or for this study specifically). I suggest rewording to something like “the OH radical whose average concentration was found to be 3 ×10^6 mole cm-3 in the PBL during NOMADDS.”