Long-range transport of volcanic aerosol from the 2010 Merapi tropical eruption to Antarctica

Wu, Xue; Griessbach, Sabine; Hoffmann, Lars

doi:https://doi.org/10.5194/acp-18-15859-2018

Articles | Volume 18, issue 21

https://doi.org/10.5194/acp-18-15859-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-18-15859-2018

© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 18, issue 21

Research article

|

06 Nov 2018

Research article |

| 06 Nov 2018

Long-range transport of volcanic aerosol from the 2010 Merapi tropical eruption to Antarctica

Xue Wu, Sabine Griessbach, and Lars Hoffmann

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Final revised paper (published on 06 Nov 2018)
Preprint (discussion started on 22 May 2018)

Interactive discussion

Status: closed

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

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RC1: 'Reviewer comment', Anonymous Referee #1, 01 Jun 2018
RC2: 'Review', Anonymous Referee #2, 25 Jun 2018
RC3: 'Aerosol Cloud Index problematic for model validation', Anonymous Referee #3, 05 Jul 2018
AC1: 'Authors' final response', Xue Wu, 29 Aug 2018

Peer-review completion

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

AR by Xue Wu on behalf of the Authors (29 Aug 2018) Author's response Manuscript

ED: Referee Nomination & Report Request started (10 Sep 2018) by Kostas Tsigaridis

RR by Anonymous Referee #3 (21 Sep 2018)

Suggestions for revision or reasons for rejection

General comments
The manuscript contains now important improvements like the removal of the QBO-discussion and a more detailed description of the aerosol cloud index (ACI). However, it is still difficult to interpret the results because several figure captions are too short or inconsistent with the text, and because ACI depends on too many parameters if you try to find missing information in the references. It would be very helpful to include more information provided in the author's response into the manuscript, but also to include a frame with H_2SO_4-observations from Günther et al. (2018) in Figure 9. There are still distracting sentences in the text. The discussion of uncertainties is too short.

Specific comments
In the abstract and at other places in the text it is always claimed that Merapi erupted in October, however the most important explosive eruption occured in early November as in the references. This is misleading concerning a possible impact on the ozone hole of the same year.

Page 2, line 46: This should hold also for Merapi.

Page 2, line 48: Better write: strongly enhanced heterogeneous ozone depletion at the vortex edge. 'Penetration' is also in contradiction to the figures presented.

Page 3: Höpfner et al (2015) on MIPAS SO_2 should be cited here or in the AIRS-section.

Section 2.2 and line 177: The SO_2 index indicates that a volcanic plume is there and how it moves, but provides only poor information on the amount of injected SO_2 and its altitude distribution. Here it would help also to include other satellite data or to derive a real L2 product.

Line 205: Misleading, in November/December the winter hemisphere is the Northern hemisphere. Section 3.1 contains some material not relevant for the study, please shorten.

Line 240ff: This 'puff' in October is quite controversial. Maybe some CALIOP observations should be provided in a supplement.

Line 261: This mass estimate is the upper end available in the literature. What is the stratospheric fraction?

Line 364: Which transport barrier?

Section 4: Isn't it too late (December) for heterogeneous ozone depletion? Possible effect on next ozone hole season?

Captions of Figure 6 and Figure 9: Please include the odd definition of the difference in the text (lines 313 and 390) to avoid confusion on the sign of ACI changes which is not following standard conventions.

Figure 8 and page 13: Is this equivalent or geographic latitude? Please clarify.

References
Höpfer, M. et al., 2015: Sulfur dioxide (SO_2) from MIPAS in the upper troposphere and lower stratosphere 2002–2012. Atmos. Chem. Phys., 15, 7017–7037.

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RR by Anonymous Referee #2 (05 Oct 2018)

Suggestions for revision or reasons for rejection

The manuscript is much improved from its initial version. I my opinion, only a few relatively minor issues remain to be addressed before publication.

L51: I don’t think it’s true that “Most of the sulfate found in ice cores can be attributed to volcanic eruptions”. Marine biogenic sources contribute a significant amount of sulfate to (some) ice cores, which is usually subtracted first wen estimating sulfate of volcanic origin. This sentence should be rephrased.

L52: Anyhow, the point to be made here I think is that ice cores contain sulfate from tropical eruptions.

L61: The logical connection implied by “Thus” is not clear.

L133: volcanic aerosol?

L170: Can you provide justification (and references) for these chosen values of Dx and Dz? It’s surprising to me that the value of Dx is 0 in the stratosphere but non-zero in the troposphere.

L174: Can you provide justification for the value of 7-days? This seems rather fast compared to the usual 30-day timescale of SO2 decay inferred from satellite observations.

L221: Does this statement about the correlation between temperature and eddy heat flux come from your work, or prior studies? Perhaps reference should be made to works like that of Newman et al. (2001).

Newman, P. A., Nash, E. R., and Rosenfield, J. E.: What controls the temperature of the Arctic stratosphere during the spring?, J. Geophys. Res., 106, 19999, doi:10.1029/2000JD000061, 2001.

L286: There seems to be transport below the jet as well, why is the one above "most significant"?

L325: “confirming” seems too strong, “consistent with” would fit better.

L396: The colorbars of Fig. 9 are confusing, since the same colors are used in panel a to show only positive values but also negative numbers in panel b. better would be to use a different color for negative values in panel b.

L454: The Summary and conclusion section repeats a lot from the discussion. These two sections could be edited dow, or merged into a single section.

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ED: Publish subject to minor revisions (review by editor) (13 Oct 2018) by Kostas Tsigaridis

AR by Xue Wu on behalf of the Authors (23 Oct 2018) Author's response Manuscript

ED: Publish subject to minor revisions (review by editor) (25 Oct 2018) by Kostas Tsigaridis

AR by Xue Wu on behalf of the Authors (25 Oct 2018) Author's response Manuscript

ED: Publish as is (26 Oct 2018) by Kostas Tsigaridis

AR by Xue Wu on behalf of the Authors (26 Oct 2018) Manuscript

Short summary

Volcanic aerosol is an important source of sulfur for Antarctica, where local sources of sulfur are rare. Midlatitude and high-latitude volcanism can directly influence the aerosol budget of the polar stratosphere, but tropical volcanic eruptions can also enhance polar aerosols by transport. Our study investigates pathway and transport processes of volcanic aerosol from the tropics to the lower stratosphere over Antarctica by combining Lagrangian transport simulation and satellite observations.