High-Altitude Discharges and Whistlers of Volcanic Thunderstorms

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Review of “High-altitude discharges and whistlers of volcanic thunderstorms” by Malkin et al.,

 

I recommend a major revision for this article. The underlying assumptions on volcanic cloud charging mechanisms are incomplete, and as they form the basis for the conclusions of the article, a major revision is required to reassess the data under different assumptions.

 

In the introduction the authors discuss the role of magma fragmentation in the electrification of a cloud but neglect the contributions of water in electrification [lines 28-31]. From this, the authors draw conclusions about the charge structure of the volcanic clouds (that the upper edge of a volcanic cloud is negative), which is a bold and unfounded conclusion to draw – there is no modeling or observations to support this claim as a universal truth. This is used to support the authors observations of so-called “high-altitude discharges.” The authors need to examine the literature on volcanic cloud electrification mechanisms and observations of volcanic lightning. The authors already cite articles that discuss water-based electrification in volcanic plumes, so it is a mystery as to why they ignored the contributions from water.

 

The ordering of references is confusing. The first citation is listed as #26, rather than 1.

 

Would the authors please add a citation (and discuss the mechanism in more detail) for the statement about positive CGs “exposing the negative charge on the upper edge of the cloud” [line 37].

 

Is a “breakdown into the ionosphere” [line 40] the same thing as a discharge like a gigantic jet?

 

The quality of the figures needs to be improved:

 

Figure 2 – What is being plotted here – it says “total daily thunderstorm activity.” What do the purple colors mean? A total number of flashes? Is there a color scale?

 

Figure 3 – The black and white coloring makes this figure very difficult to interpret. Please make this more readable.

 

The format of the bulleted list makes the discussion difficult to follow. Please put this in paragraph form and provide more details on how you draw your conclusions.

Author Response

Comments 1: In the introduction the authors discuss the role of magma fragmentation in the electrification of a cloud but neglect the contributions of water in electrification [lines 28-31]. From this, the authors draw conclusions about the charge structure of the volcanic clouds (that the upper edge of a volcanic cloud is negative), which is a bold and unfounded conclusion to draw – there is no modeling or observations to support this claim as a universal truth. This is used to support the authors observations of so-called “high-altitude discharges.” The authors need to examine the literature on volcanic cloud electrification mechanisms and observations of volcanic lightning. The authors already cite articles that discuss water-based electrification in volcanic plumes, so it is a mystery as to why they ignored the contributions from water.

 

Response 1: Thank you for your note, the introduction has been revised, a picture has been added and a link to the work where eruption scenarios are considered has been inserted.

 

 

Comments 2: The ordering of references is confusing. The first citation is listed as #26, rather than 1.

 

Response 2: It is corrected.

 

Comments 3: Would the authors please add a citation (and discuss the mechanism in more detail) for the statement about positive CGs “exposing the negative charge on the upper edge of the cloud” [line 37].

 

Response 3: A reference to a paper that addresses this issue has been added.

 

Comments 4: Is a “breakdown into the ionosphere” [line 40] the same thing as a discharge like a gigantic jet?

Response 4: This could be either a giant jet or a sprite..

 

Comments 5: Figure 2 – What is being plotted here – it says “total daily thunderstorm activity.” What do the purple colors mean? A total number of flashes? Is there a color scale?

 

Response 5:X- marker of lightning stroke . Explanations have been added to the caption to the picture.

 

Comments 6: Figure 3 – The black and white coloring makes this figure very difficult to interpret. Please make this more readable.

 

Response 6: Other color schemes lead to worse perception; black and white is the most successful.

 

Comments 7: The format of the bulleted list makes the discussion difficult to follow. Please put this in paragraph form and provide more details on how you draw your conclusions.

 

Response 7:The format of the presentation of the results and the discussion has been changed.

 

Thanks for the discussion!

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper presents the analysis of atmospheric and whistlers generated by eruptions of the Bezymyanny and Shiveluch volcanoes, where the authors identified two-hop whistlers and estimated the height of the electrical discharges. The results are interesting and deserve to be published in Atmosphere. However, I think the structure of the paper has to be revised to make it easier for the reader to follow it.

 

Section 2 Materials and Methods is a mixture of many topics: a) Previous studies of whistling and very low frequency (VLF) electromagnetic signals related to volcanic thunderstorms; b) description of Bezymyanny and Shiveluch eruptions; c) Material and Methods used in this study; d) results; e) analysis and interpretation. All these topics should be separated in different sections, or at the very least, in different paragraphs. In particular, the data and methods used in this study should be more clearly and explicitly stated.

 

The introduction section can also be separated into at least 3 different paragraphs to delimitate different topics.

 

Minor comments:

 1)     Line 62: This line was several times. Add was.

2)     Line 65: “and this suggested that the source…” instead of “and this served as an assumption that the source…”

3)     Lines 70-72. This sentence is already a conclusion, while the methods have not been described yet. It should be moved to a different section.

4)     Lines 118-119: Does Storey postulate that these whistlers are generated in Kamchatka and reflected above Australia?

5)     Line 128: Whistlers, with capital W.

6)     Line 143 “soft scenario”, or “weak scenario”, as it is described in the Discussion section?

7)     Line 160: Why the whistlers with K₁ are not shown in Fig. 4 as they are in Fig. 3?

8)     Lines 181 and 182. Use either DL or Dl, but not both.

9)     Discussion section: The order of the points in this section should be presented in a logical order. For instance, point 1 should be after point 4, and point 6 should be after point 7, which defines the strong and weak regimes.

10)  Line 199-202: The height of electrical discharges and the region of whistler generation were only presented for Shiveluch volcanoes, not for Bezymyanny.

Author Response

Comments 1 : Section 2 Materials and Methods is a mixture of many topics: a) Previous studies of whistling and very low frequency (VLF) electromagnetic signals related to volcanic thunderstorms; b) description of Bezymyanny and Shiveluch eruptions; c) Material and Methods used in this study; d) results; e) analysis and interpretation. All these topics should be separated in different sections, or at the very least, in different paragraphs. In particular, the data and methods used in this study should be more clearly and explicitly stated.

Response 1: This section is structured.

Comments 2: The introduction section can also be separated into at least 3 different paragraphs to delimitate different topics.

Response 2: And this section is structured.

Minor comments:

Comments 3: Line 62: This line was several times. Add was.

Response 3: It is corrected.

Comments 4: Line 65: “and this suggested that the source…” instead of “and this served as an assumption that the source…”

 

Response 4: It is corrected. 

Comments 5: Lines 70-72. This sentence is already a conclusion, while the methods have not been described yet. It should be moved to a different section.

Response 5: Moved in conclusion.

Comments 6: Lines 118-119: Does Storey postulate that these whistlers are generated in Kamchatka and reflected above Australia?

Response 6: Storey postulates that whistlers with twice the dispersion coefficient are two-hop whistlers. It is corrected. 

Comments 7: Line 128: Whistlers, with capital W.

Response 7: It is corrected. 

Comments 8: Line 143 “soft scenario”, or “weak scenario”, as it is described in the Discussion section?

Response 8: It is described in the Introduction and Discussions.

Comments 9: Line 160: Why the whistlers with K₁ are not shown in Fig. 4 as they are in Fig. 3?

Response 9: The answer is in the added explanations of the pictures 2 and 4. There were no thunderstorms at the conjugate point, Figure 2, right.

Comments 10: Lines 181 and 182. Use either DL or Dl, but not both.

Response 10: It is corrected. 

Comments 11: Discussion section: The order of the points in this section should be presented in a logical order. For instance, point 1 should be after point 4, and point 6 should be after point 7, which defines the strong and weak regimes.

Response 11: Discussion section is corrected.

Comments 12: Line 199-202: The height of electrical discharges and the region of whistler generation were only presented for Shiveluch volcanoes, not for Bezymyanny.

Response 12: The pattern for the high-altitude discharge during the eruption of the Bezymyanny volcano will be the same, since the atmospheric of the high-altitude discharge in both cases has the same shape, which is determined by the properties of the atmosphere.

Thanks for the discussion!

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript has improved significantly. In particular, it is better structured, which clarifies the analysis and findings presented by the authors. I consider this manuscript almost ready for publication, but there still are some minor issues that should be corrected:

Line 58: "scheme" instead of "shceme"

Line 261: remove the word "also".

Lines 278 and 292: “soft” scenario instead of “weak”.

Line 287: "The direction of the current is indicated here by a sequence of words". This sentence is not clear.

Line 302: change to “…the ionosphere-mast discharge. For its part, Shiveluch raised the charge…”

Line 309: Add a comma after the word “whistler”.

Conclusions section: Volcanic eruptions, which are the subject of this study, should be mentioned in the conclusions section.

 

Author Response

Comments 1: Line 58: "scheme" instead of "shceme"

Response 1: It is corrected.

Comments 2: Line 261: remove the word "also".

Response 2: It is corrected.

Comments 3: Lines 278 and 292: “soft” scenario instead of “weak”.

Response 3: It is corrected.

 

Comments 4: Line 287: "The direction of the current is indicated here by a sequence of words". This sentence is not clear.

Response 4: With this sentence we wanted to say that for the "vortex-earth" discharge the electric current has a direction from the vortex to the earth, and for the "ionosphere-vortex" discharge the current is directed from the ionosphere to the vortex. You are right, this sentence is unnecessary, we deleted it.

 

Comments 5: Line 302: change to “…the ionosphere-mast discharge. For its part, Shiveluch raised the charge…”

Response 5: It is corrected.

Comments 6: Line 309: Add a comma after the word “whistler”.

Response 6: The conclusion has been revised.

Comments 7: Conclusions section: Volcanic eruptions, which are the subject of this study, should be mentioned in the conclusions section.

Response 7: The conclusion has been revised.

Author Response File: Author Response.pdf