Changes in stratospheric aerosol extinction  coefficient after the 2018 Ambae eruption as  seen by OMPS-LP and MAECHAM5-HAM

Malinina, Elizaveta; Rozanov, Alexei; Niemeier, Ulrike; Wallis, Sandra; Arosio, Carlo; Wrana, Felix; Timmreck, Claudia; von Savigny, Christian; Burrows, John P.

doi:https://doi.org/10.5194/acp-21-14871-2021

Articles | Volume 21, issue 19

https://doi.org/10.5194/acp-21-14871-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/acp-21-14871-2021

© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 21, issue 19

Research article

|

07 Oct 2021

Research article |

| 07 Oct 2021

Changes in stratospheric aerosol extinction coefficient after the 2018 Ambae eruption as seen by OMPS-LP and MAECHAM5-HAM

Elizaveta Malinina, Alexei Rozanov, Ulrike Niemeier, Sandra Wallis, Carlo Arosio, Felix Wrana, Claudia Timmreck, Christian von Savigny, and John P. Burrows

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Final revised paper (published on 07 Oct 2021)
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Preprint (discussion started on 05 Aug 2020)

Interactive discussion

Status: closed

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

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RC1: 'Review of Malinina et al.', Daniele Visioni, 11 Aug 2020
- AC1: 'Reply on RC1', Elizaveta Malinina, 08 Jun 2021
SC1: 'Comparison with the stratospheric aerosol extinction coefficient and radiative forcing estimations of Kloss et al., 2020', Pasquale Sellitto, 16 Sep 2020
- AC2: 'Reply on SC1', Elizaveta Malinina, 08 Jun 2021
RC2: 'Review ``Changes in stratospheric aerosol extinction coefficient after the 2018 Ambae eruption as seen by OMPS-LP and ECHAM5-HAM''', Anonymous Referee #2, 11 Nov 2020
- AC3: 'Reply on RC2', Elizaveta Malinina, 08 Jun 2021

Peer-review completion

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

AR by Elizaveta Malinina on behalf of the Authors (18 Jun 2021) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (25 Jun 2021) by Manvendra Krishna Dubey

RR by Anonymous Referee #2 (14 Jul 2021)

Suggestions for revision or reasons for rejection

Dear authors,

thank you for the detailed answers. You did a very good job with revising the manuscript and clarifying open questions. In particular, I very much appreciate the high level of detail concerning technical aspects. I think this makes your study sound, comprehensible, and reproducible. Please find below 5 minor comments for consideration before publication.

Minor comments:

l478, l523 (revised manuscript): Tropopause
Indeed the tropopause definition is a crucial aspect. But, not only the tropopause definition, but also the algorithm to calculate the tropopause is important as different interpretations/implementations of the WMO lapse rate tropopause may lead to different results e.g. see Maddox and Mullendore (2018) WMO tropopause vs. simplified WMO. Please provide information on your implementation.

l350-354 (revised manuscript): QBO pattern
I cannot identify any of the described QBO patterns between 25 and 30\,km in Fig 3a and b. In Fig. 3b the most prominent feature I see is the annually (NH winter) reoccurring increase in extinction (Ext869). In Fig. 3a this pattern is also visible, but weaker and shifted to the middle of the year (NH summer). The dark blue bands mentioned in the reply I would identify in the years 2014, 2016, and 2019, which is different to the years listed in the reply and paper: "2013, 2015, 2017". Please clarify.

Fig. B1 (revised manuscript) and reply to comment l248-250: OMI/OMPS SO2
Thank you for also deriving the SO2 mass from OMI/OMPS for the second eruption. In my opinion this is an important figure, as it a) supports the finding that the second eruption injected more SO2 than the first one and subsequently this cannot be considered an artifact due to better sampling by TROPOMI, and b) makes the transition from OMI/OMPS to TROPOMI more transparent, as it gives an indication of the uncertainty of SO2 mass due to different instruments. It seems that OMI/OMPS data is more noisy, but averaging the 4 data points after the maximum (red circle) yields about 0.36Tg, which is pretty close to 0.39Tg (0.26Tg) for TROPOMI with mass centered at 7km (15km) (Fig. B1). Please consider adding Fig. 3b from the reply to Fig. B1 in the manuscript.

Reply to comment l125/126:
Thanks a lot for the very detailed answer that explains the reasons why you have chosen this cloud filter threshold. Actually, I think, these thoughts are worth publishing. Please consider adding a condensed paragraph of your reply to the manuscript, e.g.:
"The highest retrieved extinction is 4.0978×1013 km−1. ... This value occurs on the 28th of June 2017 at 08:40UTC at 26.8°N, 66.7°E at 10.5 km, which is most likely to be in a thick convective cloud.
The threshold to reject clouds is selected empirically to keep as much as possible of the aerosol extinction and reject as many clouds as possible. The trade-off is determined by the potential application of the data set. For applications, where it is more important to get rid of as many clouds as possible and single high aerosol peaks are not that important, a rather conservative value of 0.002 km−1 is used. This value is based on the results from Bourassa et al. (2010), where the Ext750 after the Kasatochi eruption were not exceeding 0.0015 km−1. We used this threshold when we previously showed our OMPS-LP data (e.g., Malinina, 2019). For the investigation of an isolated volcanic eruption, as, for example, the Raikoke eruption 2019 (Mauser et al, 2020) or in this study, a higher threshold is necessary as we are interested in preserving all increased aerosol values. As we investigated the plume propagation at rather high altitudes we do not rate a possible contamination by clouds as a crucial issue. Thus, for the Raikoke case the threshold was set to avoid loosing any increased extinction value above the tropopause, which resulted in the value of 0.1 km−1. We also used this threshold for Ambae."

One comment on plume height derived from MLS SO2 data versus CALIOP and OMPS-LP. Yes, the latter two do not measure SO2, but since conversion to sulfate aerosol starts immediately (e.g. see von Glasow et al., 2009 and references therein) I consider measured sulfate aerosol heights in the first few days after the eruption as a good indicator of injection height.

Technical comments:

Please add comma before "which" in l28, 50, 53, 175, 405 and more

l 405 boarders -> borders

References:
Maddox, E. M. and G. L. Mullendore, 2018: Determination of Best Tropopause Definition for Convective Transport Studies. J. Atmos. Sci., 75, 3433–3446, https://doi.org/10.1175/JAS-D-18-0032.1

von Glasow R., Bobrowski N., Kern C. (2009) The effects of volcanic eruptions on atmospheric chemistry. Chem Geol 263:131–142.

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ED: Publish subject to minor revisions (review by editor) (11 Aug 2021) by Manvendra Krishna Dubey

AR by Elizaveta Malinina on behalf of the Authors (04 Sep 2021) Author's response Author's tracked changes Manuscript

ED: Publish as is (07 Sep 2021) by Manvendra Krishna Dubey

AR by Elizaveta Malinina on behalf of the Authors (07 Sep 2021) Manuscript

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Short summary

In the paper, changes in the stratospheric aerosol loading after the 2018 Ambae eruption were analyzed using OMPS-LP observations. The eruption was also simulated with the MAECHAM5-HAM global climate model. Generally, the model and observations agree very well. We attribute the good consistency of the results to a precisely determined altitude and mass of the volcanic injection, as well as nudging of the meteorological data. The radiative forcing from the eruption was estimated to be −0.13 W m⁻².