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Peer-Review Record

Passive Earth Observations of Volcanic Clouds in the Atmosphere

Reviewer 1: Anonymous
Reviewer 2: Anonymous
Atmosphere 2019, 10(4), 199; https://doi.org/10.3390/atmos10040199
Received: 6 March 2019 / Revised: 2 April 2019 / Accepted: 3 April 2019 / Published: 12 April 2019
(This article belongs to the Special Issue Volcanic Emissions in the Atmosphere)

Round 1

Reviewer 1 Report

Review of `Earth Observations of Volcanic Clouds in the Atmosphere' by Fred Prata and Mervyn Lynch


General comments

This new paper by Prata and Lynch provides an excellent overview and review of various methods for detection of volcanic clouds in remote sensing observations. The particular focus of this study is on the analysis of geostationary and polar orbiting infrared instruments. A class of `volcanic ice clouds' (referring to ice-coated ash particles) is introduced based and discussed based on two case studies of volcanic eruptions.

Overall, the paper is very well written, clear, and concise. I recommend it for publication subject to few minor comments and fixes as listed below.


Specific comments

p3, l6: Perhaps clarify that the orbits are _nearly_ polar in most cases?

Table 1: The MetOp satellites (IASI) might be added here?

p12, l19: Another infrared radiative transfer model for the analysis of limb sounding measurements of volcanic ash was introduced and applied by Griessbach et al. (2013, 2014).

Griessbach, S., Hoffmann, L., Höpfner, M., Riese, M., & Spang, R. (2013). Scattering in infrared radiative transfer: A comparison between the spectrally averaging model JURASSIC and the line-by-line model KOPRA. Journal of Quantitative Spectroscopy and Radiative Transfer, 127, 102-118.

Griessbach, S., Hoffmann, L., Spang, R., and Riese, M.: Volcanic ash detection with infrared limb sounding: MIPAS observations and radiative transfer simulations, Atmos. Meas. Tech., 7, 1487-1507, https://doi.org/10.5194/amt-7-1487-2014, 2014.

p16, l19-36: Another approach to set detection thresholds might be to conduct a statistical analysis of a long-term record of observations, considering the ash detections as "outliers" in the record?

p23, l17: I got a bit confused about this notation "T_11 - - T_12". Does this mean "T_11 + T_12"?

Fig. 13: The stereoscopic view is quite difficult to get. I didn't manage, I am afraid. However, I like the idea of presenting it.

p24, l28: Does the discrimination between volcanic ash and desert dust also pose a challenge for this scheme?

p29, l30: It seems there is a quite a lot of potential for applying Lagrangian transport simulations in order to investigate the formation/conversion from ash to `volcanic ice'? Perhaps this could be pointed out more clearly?

p32, l27: Wu et al. (2017) performed a comprehensive analyses of the atmospheric transport processes associated with the Sarychev eruption using satellite observations and Lagrangian transport simulations.

Wu, X., Griessbach, S., and Hoffmann, L.: Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009, Atmos. Chem. Phys., 17, 13439-13455, https://doi.org/10.5194/acp-17-13439-2017, 2017.

p37, l5: Although the focus of this review is on nadir sounding observations, it might be good to refer also to the potential of limb sounding observations (e.g., Griessbach et al., 2013, 2014) for completeness.


Technical corrections

p5, l26-27: fix sentence "Suffice to say..."

p7, l33: fix reference to Rodgers (2000)

p15, l6: < 63 µ_m_

p17, l29: views of a point__

p21, l44: fix "the the"

p23, l11: fix "slghtly"

p24, l39: isolated subsection title 5.5.1 maybe not needed?

p28, l21: multiple tests __ failed

p30, l16: moist environment _and_ was (?)

p34, l7: fix "SO2_2"

p35, l40: was also discussed _and_ the cloud identification

p35, l43: fix "setereoscopic"

Author Response

Reviewer 2

 

General comments

 

This new paper by Prata and Lynch provides an excellent overview and

review of various methods for detection of volcanic clouds in remote

sensing observations. The particular focus of this study is on the

analysis of geostationary and polar orbiting infrared instruments. A

class of `volcanic ice clouds' (referring to ice-coated ash particles)

is introduced based and discussed based on two case studies of volcanic

eruptions.

 

Overall, the paper is very well written, clear, and concise. I recommend

it for publication subject to few minor comments and fixes as listed

below.

 

 

Specific comments

 

p3, l6: Perhaps clarify that the orbits are _nearly_ polar in most

cases?

 

Yes.  We have added the word “near” in the caption to the Table.

 

Table 1: The MetOp satellites (IASI) might be added here?

 

Yes.  An entry with the MetOp satellites has been added to the Table.

 

p12, l19: Another infrared radiative transfer model for the analysis of

limb sounding measurements of volcanic ash was introduced and applied by

Griessbach et al. (2013, 2014).

 

Thanks.  We have added both references.

 

Griessbach, S., Hoffmann, L., Höpfner, M., Riese, M., & Spang, R.

(2013). Scattering in infrared radiative transfer: A comparison between

the spectrally averaging model JURASSIC and the line-by-line model

KOPRA. Journal of Quantitative Spectroscopy and Radiative Transfer, 127,

102-118.

 

Griessbach, S., Hoffmann, L., Spang, R., and Riese, M.: Volcanic ash

detection with infrared limb sounding: MIPAS observations and radiative

transfer simulations, Atmos. Meas. Tech., 7, 1487-1507,

https://doi.org/10.5194/amt-7-1487-2014, 2014.

 

p16, l19-36: Another approach to set detection thresholds might be to

conduct a statistical analysis of a long-term record of observations,

considering the ash detections as "outliers" in the record?

 

This is a very good point and we have added a sentence and included a new reference.

p23, l17: I got a bit confused about this notation "T_11 - - T_12". Does

this mean "T_11 + T_12"?

 

Corrected.  This was supposed to be a minus sign.

 

Fig. 13: The stereoscopic view is quite difficult to get. I didn't

manage, I am afraid. However, I like the idea of presenting it.

 

It is not always possible to get the stereoscopic effect but our study and the papers quoted show some promise.

 

p24, l28: Does the discrimination between volcanic ash and desert dust

also pose a challenge for this scheme?

 

No.  Dust is still a problem.  We have added a sentence to indicate this.

 

p29, l30: It seems there is a quite a lot of potential for applying

Lagrangian transport simulations in order to investigate the

formation/conversion from ash to `volcanic ice'? Perhaps this could be

pointed out more clearly?

 

Thanks.  We have added a new sentence and several references, including the reference suggested.

 

p32, l27: Wu et al. (2017) performed a comprehensive analyses of the

atmospheric transport processes associated with the Sarychev eruption

using satellite observations and Lagrangian transport simulations.

 

Paper now cited and a short sentence added.

 

Wu, X., Griessbach, S., and Hoffmann, L.: Equatorward dispersion of a

high-latitude volcanic plume and its relation to the Asian summer

monsoon: a case study of the Sarychev eruption in 2009, Atmos. Chem.

Phys., 17, 13439-13455, https://doi.org/10.5194/acp-17-13439-2017, 2017.

 

p37, l5: Although the focus of this review is on nadir sounding

observations, it might be good to refer also to the potential of limb

sounding observations (e.g., Griessbach et al., 2013, 2014) for

completeness.

 

This is true and we should have included something on this.  To rectify the omission we have added a paragraph in the Conclusions and also referred to active sensing.  It is not possible to do justice to these topics without greatly expanding the paper.

 

 

 

 

 

Technical corrections

 

p5, l26-27: fix sentence "Suffice to say..."

 

Fixed.

 

p7, l33: fix reference to Rodgers (2000)

 

Proper citation used.

 

p15, l6: < 63 µ_m_

 

Change to µm.

 

p17, l29: views of a point__

 

Changed to “points”

 

p21, l44: fix "the the"

 

Deleted “the”.

 

p23, l11: fix "slghtly"

 

Spelling corrected.

 

p24, l39: isolated subsection title 5.5.1 maybe not needed?

 

Removed.

 

p28, l21: multiple tests __ failed

 

Corrected.

 

p30, l16: moist environment _and_ was (?)

 

Grammar corrected.

 

p34, l7: fix "SO2_2"

 

Deleted first “2”

 

p35, l40: was also discussed _and_ the cloud identification

 

Grammar corrected.

 

p35, l43: fix "setereoscopic"

 

Spelling changed to “stereoscopic”

 

---------------------------------------------------------------------------------------------------

 

Dr Fred Prata and Prof. Mervyn Lynch

 

24 March 2019.


Reviewer 2 Report

This is an excellent review paper, that is a model of clarity. It presents an accessible and critical account of the approaches used for Earth Observation of volcanic clouds (in the most general sense), and does an excellent job of both explaining the current state of the art, and identifying knowledge gaps and new opportunities for research. It is written economically, and is in very good shape. The only suggestion, for completeness, that I would encourage the authors to consider would be to cite data sources in the captions to tables and figures (it may well be that the data sources are already cited elsewhere in the text, in most cases). 

Author Response

This is an excellent review paper, that is a model of clarity. It

presents an accessible and critical account of the approaches used for

Earth Observation of volcanic clouds (in the most general sense), and

does an excellent job of both explaining the current state of the art,

and identifying knowledge gaps and new opportunities for research. It is

written economically, and is in very good shape. The only suggestion,

for completeness, that I would encourage the authors to consider would

be to cite data sources in the captions to tables and figures (it may

well be that the data sources are already cited elsewhere in the text,

in most cases).

 

 

Thank you for the comments.  It was remiss of us not to cite the data sources.  Rather than add these to every Figure and Table (where needed) we have included an acknowledgement to all of the relevant data providers.  We have also acknowledged the HYSPLIT model provider and the two anonymous referees.


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