|The main point of the paper is to demonstrate that a significant fraction air pollution observed in France and Europe is of volcanic origin. It is an important topic. I took the liberty to have a look at the previous reviews. I think the authors took on board most of the suggestions which were very valuable. However, the wording of the paper could be a bit more cautious. For example, ‘demonstrate’ means to show/prove that something is true, that is a bit beyond doubt. In addition, the presentation of the results is sometimes questionable, it does not always follow a logical development/methodology and end with the conclusion. |
To illustrate those points, let’s consider the beginning of the ‘results and discussion’ section; it is stated: line17-19, p11: “…we study several volcanogenic events of air pollution observed in France in September 2014 at two locations nearby (Dunkirk) and distant (SIRTA) from industrial activities”.
The reader is told that these air pollution events are of volcanic origin right from the start whereas this should be the conclusion of the analysis.
Then, the authors explain Figure 1 and conclude:
l25, p12: “To conclude, this set of simultaneous observations, from the ground at a regional scale and
from space, allows to demonstrate the volcanogenic origin of the two peak values in ground-level SO4 concentration recorded in Dunkirk on 7 Sept”
The term ‘demonstrate’ is too strong here. For example, the top plots of Figure 1 show two OMPS SO2 maps at two different times (A, B). According to the first OMPS plot, the SO2 volcanic cloud has not yet reached Dunkirk at time A with the SO2 cloud edge still being about 100 km away from Dunkirk. Therefore, time A should not be in the vertical grey area labelled ‘volcanic event 1’ in the plot. Note that the authors do not explain how these grey areas are defined and why they are already labelled ‘volcanic events’ at this stage. Furthermore, the sharp peaks in SO2 and SO4 (bottom plot) in the broad ‘volcanic event 1’ occur a couple of hours before time A (when the SO2 cloud had anyway not reached the French coast). Clearly, there is a doubt about the origin of these SO2 and SO4 peaks, before time A. I think that the authors should be cautious with ‘visual’ evidence, a quantitative analysis is always more convincing. They should also discuss things in a more balanced way, even when they don’t fit their story/thesis (see the example discussed above). Once they have accumulated enough indications/evidence during the discussion of the results, they can claim to have demonstrated the point of the paper in the conclusion. Overall, I would suggest to adjust the wording in the text and tone down some of the early claims.