Water vapour variability in the high-latitude upper troposphere – Part  2: Impact  of volcanic eruptions

Sioris, Christopher E.; Zou, Jason; McElroy, C. Thomas; Boone, Chris D.; Sheese, Patrick E.; Bernath, Peter F.

doi:https://doi.org/10.5194/acp-16-2207-2016

Articles | Volume 16, issue 4

https://doi.org/10.5194/acp-16-2207-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-16-2207-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 16, issue 4

Research article

|

25 Feb 2016

Research article |

| 25 Feb 2016

Water vapour variability in the high-latitude upper troposphere – Part 2: Impact of volcanic eruptions

Christopher E. Sioris, Jason Zou, C. Thomas McElroy, Chris D. Boone, Patrick E. Sheese, and Peter F. Bernath

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Final revised paper (published on 25 Feb 2016)
Preprint (discussion started on 24 Sep 2015)
Companion paper

Interactive discussion

Status: closed

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

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RC C8262: 'review of "Water vapour variability in the high-latitude upper troposphere: 2. Impact of volcanic emissions"', Anonymous Referee #1, 21 Oct 2015
- AC C10066: 'response to reviewer 1', Chris Sioris, 03 Dec 2015
RC C8264: 'correction to review of Water vapour variability in the high-latitude upper troposphere: 2. Impact of volcanic emissions', Anonymous Referee #1, 21 Oct 2015
RC C8617: 'review of paper by Sioris et al.', Anonymous Referee #3, 28 Oct 2015
- AC C10067: 'response to reviewer 3', Chris Sioris, 03 Dec 2015
SC C9072: 'Comments on "Water vapour variability in the high-latitude upper troposphere: 2. Impact of volcanic emissions"', Michael Fromm, 09 Nov 2015
- AC C10065: 'reply to Mr. Fromm', Chris Sioris, 03 Dec 2015

Peer-review completion

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

AR by Chris Sioris on behalf of the Authors (03 Dec 2015) Author's response Manuscript

ED: Referee Nomination & Report Request started (04 Dec 2015) by Thomas von Clarmann (deceased)

RR by Anonymous Referee #1 (22 Dec 2015)

RR by Anonymous Referee #4 (22 Dec 2015)

Suggestions for revision or reasons for rejection

This papers describes apparent upper tropospheric water vapour anomalies observed in satellite data that may be associated with certain volcanic eruptions that may potentially inject water vapour into the atmosphere. I have been brought in as a referee at the revision stage of this paper, as I was for the companion paper Part I.

I wouldn’t count myself as an expert on water emissions by of volcanic eruptions, so an immediate question, which I don’t see addressed anywhere in this paper, is whether or not the amount of water vapour (e.g. in terms of mass) reaching the upper troposphere could conceivably account for the anomalies in the observations. Are there any previous papers that consider this point?

A second question that occurs to me as a referee is whether the observation of a large-scale water vapour anomaly of possible volcanic is by itself significant enough to justify publication. If the authors believe this to be the case then they need to argue it more strongly. If it is not then my view is that the other material in the paper, be it introductory material, meteorological/dynamical support for the persistence of the injected water vapour in the atmosphere, accompanying model studies, is very slight or non-existent. So I find it difficult to recommend anything other than rejection of the paper in its current form.

My view is that to bring the paper to a form that is suitable for publication then either there has to be convincing argument for the novelty of the observations, or the observations have to form part of a more comprehensive study, e.g. with modelling (off-the-shelf trajectory models could be used) that make the arguments re transport, retention in the atmosphere, etc plausible. The referees have noted that there were other eruptions during the observing period — another aspect that would make the arguments in this paper more plausible would be if modelling could establish why some eruptions give water vapour anomalies that are observable in satellite data and others do not.

Other comments follow below.

p5 l2-5: You state here that temperatures are not relatively warmer, therefore the anomaly in the water vapour cannot be explained on the basis of constant relative humidity. My initial reaction was that if is a core part of the argument in the paper then information on temperatures should be shown explicitly. In fact you have later shown relative humidity in Fig. 7 - it might be helpful to refer ahead to this figure at this point, or else postpone the remark on temperatures until later.

p6 l25: As noted by another referee, this one sentence remark on surface cooling rates is very odd. Also ‘does not significantly change’ conveys the minimum amount of useful information. If you are considering seriously that the upper tropospheric water vapour anomalies associated with volcanic eruptions can have significant effects on surface heating/cooling (presumably prompted by the Solomon et al 2010 and its precursors), then you need to provide preparatory discussion. Note for example that Solomon et al 2010 are at least in part concerned with tropical conditions — is the mid/high latitude effect likely to be as large. Perhaps a better place for this sentence would be in the discussion section — introduced by ‘Bearing in mind previous work that considered the effect of upper tropospheric water vapour on the overall radiation balance of the troposphere … ‘

p8 l2: ‘because of the low background VMR of water vapour in this region, owing to the lack of deep convection’ — this is an example of the generally rather superficial supporting text in this paper. Isn’t the background low VMR due at least as much to the low temperatures and hence low saturation mixing ratio as to the lack of deep convection. Also in the midlatitudes there is a large contribution to water vapour transport in the vertical from ‘conveyor belt’ type flows associated with synoptic systems.

p8 l9: ‘With the rise in altitude …’ — again these two sentences, about ice crystal formation and implications for water vapour, seem completely speculative and superficial. A more serious paper would be referring to previous literature on upper tropospheric cloud formation, etc.

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ED: Reconsider after major revisions (23 Dec 2015) by Thomas von Clarmann (deceased)

AR by Chris Sioris on behalf of the Authors (31 Jan 2016) Author's response Manuscript

ED: Publish subject to technical corrections (05 Feb 2016) by Thomas von Clarmann (deceased)

AR by Chris Sioris on behalf of the Authors (05 Feb 2016) Manuscript

Short summary

This paper shows that volcanic eruptions occurring at higher latitudes in windy environments can lead to significant perturbations to upper tropospheric (UT) humidity mostly due to entrainment of lower tropospheric moisture by wind-blown plumes. This research was performed for the purpose of determining long-term trends in high-latitude UT water vapour. The steps involve building a monthly climatology and using it to deseasonalize the time series. Large observed anomalies are then studied.