Dear authors,

I have received the reports from the two referees. One referee thinks that the manuscript needs further revisions before being accepted for publication. Please consider the comments and suggestions from this referee carefully, on the radiative transfer effects in particular, and make necessary revisions and/or responses.

Best regards,

Jianzhong Ma

Dear authors,

I have received a new report from Referee #2, who gave additional comments on your manuscript while thinking that it deserves to be published. Please give an appropriate response to these comments and, if necessary, make minor changes of your manuscript accordingly.

Best regards,

Jianzhong Ma

Dear Jonas Gliß,

Your manuscript has improved a lot, thanks to the several rounds of substantial discussions, especially helpful comments and suggestions from the referees. The manuscript can be accepted for publican in ACP subject to some technical corrections as described below.

It seems that the instrument was not inside the plume all the way during the experiment. Therefore, the two sentences in Line 2-4 and Line 43-44 might be rewritten, respectively, as
“Spatial and temporal profiles of chlorine dioxide (OClO), bromine monoxide (BrO) and sulfur dioxide (SO2) in the volcanic plume were investigated at Mt. Etna, Italy, in September 2012 using Multi-Axis-Differential-Optical-Absorption-Spectroscopy (MAX-DOAS)”;
“In this study we present MAX-DOAS measurements (e.g. Hönninger et al., 2004) of the volcanic plumes performed at Mt. Etna on Sicily, Italy”.

Please check if the serial numbers of the reaction coefficients are written correctly. For example,
Line 151: k8 => k7;
Line 373: k1 => k7;
Lines 679-680 and Eqs. (5)-(9) in Page 28: k10 => k9, k11 => k10?

Typos? Lines 481, 579 and 855: were => where ?

Best regards,
Jianzhong Ma