Detecting volcanic sulfur dioxide plumes in the Northern Hemisphere using the Brewer spectrophotometers, other networks, and satellite observations

Zerefos, Christos S.; Eleftheratos, Kostas; Kapsomenakis, John; Solomos, Stavros; Inness, Antje; Balis, Dimitris; Redondas, Alberto; Eskes, Henk; Allaart, Marc; Amiridis, Vassilis; Dahlback, Arne; De Bock, Veerle; Diémoz, Henri; Engelmann, Ronny; Eriksen, Paul; Fioletov, Vitali; Gröbner, Julian; Heikkilä, Anu; Petropavlovskikh, Irina; Jarosławski, Janusz; Josefsson, Weine; Karppinen, Tomi; Köhler, Ulf; Meleti, Charoula; Repapis, Christos; Rimmer, John; Savinykh, Vladimir; Shirotov, Vadim; Siani, Anna Maria; Smedley, Andrew R. D.; Stanek, Martin; Stübi, René

doi:https://doi.org/10.5194/acp-17-551-2017

Articles | Volume 17, issue 1

https://doi.org/10.5194/acp-17-551-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-17-551-2017

© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 17, issue 1

Research article

|

11 Jan 2017

Research article |

| 11 Jan 2017

Detecting volcanic sulfur dioxide plumes in the Northern Hemisphere using the Brewer spectrophotometers, other networks, and satellite observations

Christos S. Zerefos, Kostas Eleftheratos, John Kapsomenakis, Stavros Solomos, Antje Inness, Dimitris Balis, Alberto Redondas, Henk Eskes, Marc Allaart, Vassilis Amiridis, Arne Dahlback, Veerle De Bock, Henri Diémoz, Ronny Engelmann, Paul Eriksen, Vitali Fioletov, Julian Gröbner, Anu Heikkilä, Irina Petropavlovskikh, Janusz Jarosławski, Weine Josefsson, Tomi Karppinen, Ulf Köhler, Charoula Meleti, Christos Repapis, John Rimmer, Vladimir Savinykh, Vadim Shirotov, Anna Maria Siani, Andrew R. D. Smedley, Martin Stanek, and René Stübi

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Final revised paper (published on 11 Jan 2017)
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Preprint (discussion started on 04 Jul 2016)
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Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'referee comment', Anonymous Referee #1, 28 Jul 2016
RC2: 'Review of “Detecting volcanic sulfur dioxide plumes in the Northern Hemisphere using the Brewer spectrophotometer, other networks, and satellite observations” by C.S. Zerefos et al.', Anonymous Referee #2, 01 Aug 2016
AC1: 'Reply to the reviewers' comments', Christos S. Zerefos, 11 Oct 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Christos S. Zerefos on behalf of the Authors (11 Oct 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (01 Nov 2016) by Andreas Engel

RR by Anonymous Referee #1 (19 Nov 2016)

Suggestions for revision or reasons for rejection

This paper investigating so2 plumes from volcanic eruptions using the Brewer network has improved considerably. The authors keep their statements in line with the correlations shown between ground based Brewer and space based satellite observations and thus don’t weaken their conclusions with false claims of correlation. They have done a much better job of explaining how the Brewer data was used to identify volcanic so2 plumes in the data. The paper is nearly ready for publication. Here are a few minor comments the authors should consider/fix prior to final acceptance.

1.47-48. Fix this awkward sentence as follows, …significant columnar SO2 increases, exceeding on the average 2 DU relative to an unperturbed pre-volcanic 10-day baseline, with a mean close to zero and σ = 0.46, as calculated...

2.22-23. Suggest … quantities of both ash and SO2 are released which in the case of ash can result in air travel disruptions…

7.39-8.5. The authors need to explain what the ground based measurements are in this statement, “… the columnar SO2 measurements over Europe were also compared with measurements from ground level European stations from the European Environment Agency databases (AirBase) covering…”. I have no idea what “measurement” the columnar so2 measurements are being compared to.

8.21-35. Authors should explain why the STL product is not used, since it seems that would be the correct altitude for explosive volcanic eruptions versus volcanic degassing for TRM. I was surprised when STL was not mentioned further after the explanation of what it was.

Section 3.1 The 2014 Bárðarbunga case – What is difficult to understand about this case is the timing of the ejected material from the volcano. The dispersion modeling is from 18-26 Sept. The back trajectories shown are 5 days from about 20 Sept., so a similar period. In contrast the eruption is indicated to occur at day 0 in figures 4 and 5 with the plume not appearing until 20 days later. How does the reader reconcile this significant time difference? Did the outgassed so2 hang around Iceland for 15 days prior to being dispersed? I doubt it. Was the volcano continuing to outgas for a number of weeks? The authors need to be clear and not mark the eruption as a one day event if that is not the case. If that is the case then the authors need to explain why the so2 was located over Iceland 15 days later.

Figure 9. The positive so2 signal at Taipei on 06/19 is compromised by the equivalent negative excursion on 07/17. Can the authors explain this?

12.38. “The increase in SO2 due to the passage of the Nabro volcano plume over the Canary Islands is significant using both methods, showing an offset between them (Figure 11).” What is meant by “showing an offset between them”? Do the different zeroing methods produce the offset, does the volcanic plume produce the offset, is the offset introduced to separate the lines, …?

Fig. 12 and 13.20. This figure has the same problem as Figs. 4 and 5. The mark indicating the eruption is misleading. First the text states that the eruption first occurred on 14 April. The figure legend claims the time frame is April-May so the reader assumes day 0 corresponds with April 1, but that would make the eruption occurring on 4 April. The text goes further to claim the eruption has three phases so it occurs on a number of days in April/May leaving the figure misleading again since it indicates an eruption on just one day. The authors could make this clear with appropriately labelled ordinates indicating what day 0 is, or better, use the actual dates of the month for simplicity, then add a mark on each day when there was significant effluent from Eyjafjallajökull.

13.36-14.5. It is surprising that back trajectories are not shown for Uccle and DeBilt, in fact no back trajectories are shown for Eyjafjallajökull, whereas a number of such trajectories were shown for Bárðarbunga. It appears that if there is no increase in so2 then the authors don’t bother to calculate a back trajectory. That makes sense in most cases, but not when stations are as close as Uccle and DeBilt. The authors should consider adding back trajectories here to demonstrate that indeed one station was outside and one inside the plume on the same date. It would be a nice confirmation of the reliability of the back trajectories and the localized nature of the volcanic clouds.

14.10-19. The reader cannot compare any of these dates and details to Fig. 12 for the reasons stated concerning the timing of the eruption shown. Without that link then the value of these details are lost on the reader.

Sodankÿla should be Sodankylä everywhere it appears.

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ED: Reconsider after minor revisions (Editor review) (25 Nov 2016) by Andreas Engel

AR by Christos S. Zerefos on behalf of the Authors (01 Dec 2016) Author's response Manuscript

ED: Publish as is (12 Dec 2016) by Andreas Engel

AR by Christos S. Zerefos on behalf of the Authors (14 Dec 2016) Manuscript

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Short summary

The paper makes a convincing case that the Brewer network is capable of detecting enhanced SO₂ columns, as observed, e.g., after volcanic eruptions. For this reason, large volcanic eruptions of the past decade have been used to detect and forecast SO₂ plumes of volcanic origin using the Brewer and other ground-based networks, aided by satellite, trajectory analysis calculations and modelling.