|The authors put effort into a better interpretation of the MAX-DOAS data concerning the horizontal distribution of BrO. They added the new figure 5 including the results for some radiation transfer calculations and a comparison between observed BrO slant columns as a function of the viewing angle of the instrument and simulated slant columns for different layers of enhanced BRO also as a function of the viewing angle. This corresponds to the additional information requested by both reviewers. Unfortunately, the presentation of these results and the derived conclusions are rather confusing and in my opinion counteract the conclusion of a local ozone depletion event:|
The authors present the observed BrO slant columns with at least three different color codes, but refer in the title two only two categories (4 hours before or after midnight). Why is that? Why not using only two colors?
What is the reason for using 4-hr averages, although according to figure 13 the entire depletion happened within less than 6 hours with potentially highly variable Br and BrO concentrations?
With the current figure it is difficult to identify, however, it seems to me that the observations before and after midnight are rather different. Why do the authors then claim that one profile with BrO in the 0-1 km range can explain all observations? Why don’t the authors use the highest temporal resolution possible for the observations, which is probably below 30 min for a full scan of all viewing angles?
Why do the authors only show results for this specific period? It would be interesting to see the results also for low BrO slant columns.
The authors claim that the observations shown in figure 5 are best reproduced by the BrO profile with a homogeneous layer between 0 and 1 km altitude. Why is that? Fig. 5b actually shows only two simulations with slant columns at 2° outside the observed range: BrO in a layer from 0 to 0.5 km and BrO in a layer from 0 to 1 km. The authors do not provide any quantitative information regarding the comparison of the simulations and the results. I find that the best agreement for the period before midnight (blue points) is obtained with the profile with BrO in the layer from 0 to 2 km and for the period after midnight with the profile with BrO in the layer from 0.5 to 1 km. However, this is only based on the visual inspection of the figure.
In my opinion, the comparison does not support the claim of the authors that the observed event corresponds to a local BrO formation caused by processes at the surface since the simulated slant columns for a BrO layer from 0 to 0.5 km are far from all observations at low elevation angles.
In summary, the analysis of the presented simulations and observations are to superficial to support the claim of the authors that (1) the simulation with BrO confined to 0 to 1 km corresponds best to the observations and (2) that the BrO increase is a local event. In my opinion, many other scenarios seem equally possible or correspond even better to the presented data.
Regarding the other points raised in my previous report (trajectory analysis, analysis of the mesoscale situation, transport of BrO from the Arctic Ocean, analysis of the boundary layer and impact on the observations, timing of the increase in BrO and decrease of ozone and mercury, sea ice conditions, impact of temperature, significance of calcium carbonate precipitation, measured BrO versus estimated Br) the revised manuscript does not provide a lot of additional information. The authors provide some arguments in the “Author’s Response”, but most of them are not included in the revised manuscript. Overall, the tone of the manuscript is still the same of the original version, since the authors claim throughout the manuscript that the depletion was a local process without providing a balanced analysis of other possibilities.