Dear Dr. Baumgartner

Per ACP guidelines: Before submitting a revised version of their manuscript for publication in ACP, the authors should have answered the referee comments and relevant short comments cumulatively or individually in one or more author comments. The author comments should be structured in a clear and easy-to-follow sequence: (1) comments from referees/public, (2) author's response, and (3) author's changes in manuscript. Regarding author's changes,  a marked-up manuscript version (track changes in Word, latexdiff in LaTeX) converted into a *.pdf must be submitted, uploaded as a supplement to the author comment.

It is point (3) that is currently missing from the author response file. I look forward to further considering manuscript on completion of this point that I find substantially smooths the review process.

Regards,

Tim Garrett

Dear Dr. Baumgartner,

I would first like to acknowledge the thorough examination of your work by both reviewers. Both reviewers are recommending the paper for publication. My personal assessment, and I suspect the reviewers would agree, is to congratulate you and your co-authors on such an investigation, for giving the fundamentals of atmospheric sciences a second close look.

However reviewer 1 raises a couple of minor points that should be addressed. Most concerning is perhaps the argument that the extreme values of the specific heat referred to unnecessarily "blacken the picture". As part of a revised manuscript, I would like to see this issue addressed. In general, it is difficult for any reader to appreciate how such a fundamental parameter as C_p could be substantially in error, so a convincing, very sober assessment is especially important.

If the final comments of Reviewer 1 can be addressed satisfactorily, I will forward the paper for publication in ACP.

Dear Dr. Baumgartner

I am pleased to accept your article for publication in ACP. I see the paper as a particularly imaginative exploration of the sensitivity of key atmospheric calculations, such as heating rates, to one of the most fundamental "constants" in the atmospheric sciences: the specific heat capacity of air. The article starts from the ground up, tying together a wide range of published experimental results with carefully described thermodynamics and perturbation studies. The appendices alone are worthy of publication. A possible concern is that the variability in potential temperature and ensuing calculations that is described has magnitudes that are sufficiently small so as to be swamped by errors associated with other diabatic factors such as uncertainties in turbulent mixing rates. Hopefully future numerical model error calculations will address this issue.

Pascal Marquet and an anonymous reviewer gave particularly thoughtful reviews that led to substantial clarifications and improvements. Their efforts are much appreciated.

Regards,

Tim Garrett