the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Halogen chemistry in volcanic plumes: a 1D framework based on MOCAGE-1D (version R1.18.1) preparing 3D global chemistry modelling
Virginie Marécal
Ronan Voisin-Plessis
Tjarda Jane Roberts
Alessandro Aiuppa
Herizo Narivelo
Paul David Hamer
Béatrice Josse
Jonathan Guth
Luke Surl
Lisa Grellier
Abstract. Volcanoes are a known source of halogens to the atmosphere. HBr volcanic emissions lead rapidly to the formation of BrO within volcanic plumes. BrO, having a longer residence time in the atmosphere than HBr, is expected to have an impact on tropospheric chemistry, at least at the local and regional scales. The objective of this paper is to prepare a framework for further 3-D modelling of volcanic halogen emissions in order to determine their fate within the volcanic plume and then in the atmosphere at the regional and global scales. This work is based on a 1-D configuration of the global chemistry transport model MOCAGE whose low computational cost allows us to perform a large set of sensitivity simulations. This paper studies the Mount Etna eruption on 10 May, 2008. Several reactions are added to MOCAGE to represent the halogen chemistry occurring within the volcanic plume. A simple sub-grid scale parameterization of the volcanic plume is also implemented and tested. The use of this parameterization tends to limit slightly the efficiency of BrO net production. Both simulations with and without the parameterization give similar results for the partitioning of the bromine species, ozone depletion and of the BrO / SO2 ratio that are consistent with previous studies and with the BrO / SO2 ratio in the volcanic plume estimated from GOME-2 spaceborne observations.
A series of test experiments were performed to evaluate the sensitivity of the results to the composition of the emissions, and, in particular, primary sulphate aerosols, the Br radical, and NO. Simulations show that the plume chemistry is sensitive to these assumptions. Another series of tests on the effective radius assumed for the volcanic sulphate aerosols shows that BrO net production is sensitive to this parameter with lower BrO concentrations reached when larger aerosols (smaller total surface area) are assumed. We also find that the maximum altitude of the eruption changes the BrO production, which is linked to the vertical variability of the concentrations of oxidants. These sensitivity tests display changes in the bromine chemistry cycles that are generally at least as important as the subgrid scale plume parameterization.
Overall, the version of the MOCAGE chemistry developed for this study is suitable to produce the expected halogen chemistry in volcanic plumes during daytime and night. These results will be used to guide the implementation of volcanic halogen emissions in the 3-D configuration of MOCAGE for regional and global simulations.
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Virginie Marécal et al.
Status: final response (author comments only)
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CEC1: 'Comment on gmd-2022-180', David Ham, 29 Sep 2022
I've taken a look at the code and data availability sections of this manuscript and they're currently far from satisfactory.
This manuscript documents a proprietary code that the authors do not have the licence to distribute publicly. Nonetheless, GMD policy requires that the authors have archived (privately) the code used in the paper, and given the editor and reviewers access. The purpose of this is so that the editor and reviewers can satisfy themselves that the authors would be able to reproduce the work presented.
In this case, it appears that the authors have only archived the newly developed code, and not the whole model. It seems the archived code might not even be fully compilable, let alone sufficient to demonstrate the reproducibility of the work presented. In order for this manuscript to be properly reviewed, the authors need to ensure that the exact version of all the code necessary to reproduce the work presented has been archived, and access given to the editor and reviewers.
The data archive is also, regretably, unsatisfactory. It appears to be a fileshare site with no assurances of persistence or non-revokability. No persistent identifier (e.g. DOI) is provided for the data. Further, the data is very small (2.6Mb) so there does not seem to be any reason why a suitable archive, such as Zenodo, could not be employed. As with the code availability, this issue needs to be remedied so that the reviewers and editor can satisfy themselves that the work presented is reproducible and will remain so into the future.
Citation: https://doi.org/10.5194/gmd-2022-180-CEC1 - AC1: 'Reply on CEC1', Virginie Marécal, 09 Nov 2022
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RC1: 'Comment on gmd-2022-180', Anonymous Referee #1, 04 Oct 2022
Rev of gmd-2022-180
Marecal et al., MOCAGE-1D (version R1.18.1) preparing 3D global chemistry modelling
First, my abject apologies for letting my review slide past the deadline. The authors deserved a more timely review than I provided. I began several weeks ago, reading from the beginning, and making typical, small-correction notes for the authors to improve the manuscript's readability. Then at L326, I "hit the wall" in terms of what the model was doing. I did not know how to continue with the review when I was unsure as to the physical representation of this new model.
The intervention by the Editor Ham regarding the paper's suitability pushed me to quickly finish this review so that it may still be useful. I would like to see this work published, but it does need some more clarity for the science, and documentation of the model as noted by the Editor.
First, this appears to be a 0-D box-in-box model since there is no interaction in the vertical? Is there not interaction between the overhead plume and the photolysis rates? There appears to be no other 1D connection.
Second, from the three bullets (L344-349) it is not clear that any chemistry is calculated within the P box. I presume it is – Yes it is so stated in Figure 1.
Third, is the plume constantly injected over multiple time steps? That would seem odd as the upper layers are moving across the volcano, not hovering. From Figure 1, the P-box stays exactly over the emission plume for the whole time of the eruption. That makes no sense given normal atmospheric winds.
at time T1 you have a volcanic plume (size = P-box) going into the M-box, OK
at time T2, you have done chemistry on both boxes and then mixed at some rate
in your step 3 (not T3) you state that you mix unidirectionally from P-box to M-box, does not the P-box shrink? but then in step 4, you mix M-box air back into P-box. OK
but at step 5 you add more fresh volcanic emissions to the P-box does that not include new air mass?
does the P-to-M mixing rate control the rate of new emission flux into P-box?
This model implies that the outflow of chemically processed P-box air keeps going into the same M-box air. Possible, but sounds difficult. If so, then the original P-box should become more dilute.
Fourth, the mixing between P box and M-P box should be based on a mixing frequency defined by the inverse time to mix the P box (e.g., 4 /hour for 15min). Presumably you conserve air mass and mix equal parts air mass of the M-P and P boxes and then put it back into both boxes? I cannot tell if that was done. YES, after reading the Fig 1 caption, it is clear stated. You need to be more precise in the sentences describing this in the text and not rely on the Figure caption.
Fifth, you should really show that your results converge as you reduce the time step. That shows you are reasonably modeling a continuous process. That is why mixing rates need to be in per hour.
Basically the model looks sort like a smokestack model, but even there the exhaust is constantly encountering new background (M-box) air. Putting emissions of trace gases into the P-box is maybe convenient, but in reality these emissions come with an air mass that must be incorporated into the P-box. Is this the way you would model a standard smokestack plume?
So, overall, I am not sure what kind of plume you are modeling. The physics of injection and mixing seem not to be realistic for volcanic plumes. I am readily willing to be convinced otherwise if the authors can make a clear case.
Comments below may be helpful for language use when revising this paper.
Title: awkward, try maybe: Halogen chemistry in volcanic plumes: a 1D framework based on MOCAGE-1D (version R1.18.1) preparing 3D global chemistry modelling
L20 – maybe "a 1-D single-column configuration…."
L28 – how about also to the background atmospheric conditions?
Abstract – Overall, it is too long, can you shorten?
L42 – Iodine clearly eats O3, does CL do much in the troposphere? (not sure)
L104 – 'no possibility' is too strong, how about 'no direct way to '
L122 – I am confused, a 1D single-column model really has not horizontal resolution, yet here you talk about it grid size and a sub-grid parameterization.
L123 – 'also' not needed.
L135 – Make its shorter and easier to see the 3 things:
There are three reasons behind the choice of this volcanic eruption: (1) Mount Etna is one of the largest known emission sources of halogens (Aiuppa et al., 2005); (2) the Etna volcano is also continuously and extensively monitored by INGV (Istituto Nazionale di Geofisica e Vulcanologia) including gas composition needed for the model; and (3) satellite observations above the Mediterranean region are available.
L146 – 'passive' = 'non-eruptive'
L150 – "The composition of Mount Etna plumes has extensively been characterised before this case study by both in situ (e.g.,….
L152 – drop the "as"
L153- 'location' instead of 'space' ??
L155 – ' … more distal, safe locations, are…'
L158 – 'such' instead of 'similar'
L161 – eruptions are available, and none for 10 May
L169 – I would drop the clause: 'being representative of Etna emissions'
L176 - 'al., 2021). MOCAGE is developed"
L177 – drop ' Due to the low computational cost', just say simply that: "This 1-D configuration of MOCAGE allows us to make a large set of sensitivity tests on the…"
L179 – very confusing ("It does not…"), do you mean: "MOCAGE 1D does not focus on the very early stages…. " then stop and delete "but to …." this is already said or implied.
L182 – "corresponds here to the vertical column" I do not agree with this. You need to make it clear that the 1-D column model does not connect across vertical layer with transport or photolysis (? does it). It starts as a 1-D column, but the layers shear out an separate as they would in 3D. Right? OK OK, I see this in L187, so maybe combine this information.
L190 – the problem is the entrainment mixing on the way up. You should consider doing LES models or other models to find the entrainment factor as a function of altitude
L195 – do not keep mentioning 'future' – "The 1-D configuration of MOCAGE is designed so that the chemistry model developed for volcanic emissions can be seamlessly inserted into MOCAGE-3D.
L201 – " MOCAGE-1D start with those in MOCAGE-3D,
L233 – I am looking forward to a plot of chemistry vs time showing this Br explosion
L245-256 – All this makes sense and seems logical.
L255 – 'of volcanically derived sulphate' The volcano emits sulphate or SO2? if both (below) then make this clear
L262 – "The RELATIVE TRACE GAS composition in the plume is …Table 1.
[What is unclear here is the absolute concentration in the plume at each level?]
L266 – the high temperature (magma?) chemistry should be already taken into account in Table 1.
L276 – 'given in Table 2' – this really needs to be combined with Table 1.
L302 "THAT PARTICULAR eruption…"
L307 – the aerosol mass, diam and surface area should be in Table 1+2. Do not scatter critical input parameters.
L321 – (resp. 'D.BGD)' (spelling)
Citation: https://doi.org/10.5194/gmd-2022-180-RC1 -
RC2: 'Comment on gmd-2022-180', Anonymous Referee #2, 11 Nov 2022
Marecal et al. evaluate volcanic plumes in the 1D-version of the model
MOCAGE. They also test a sub-grid scale parameterization. The
sensitivity studies are very interesting, and the chemistry scheme is
adequate to describe bromine explosions.General comments:
My main criticism is that I do not find the comparison to the Etna
eruption of 10 May 2008 very convincing because there seem to be hardly
any useful observations for this comparison:- I didn't see any observational BrO data mentioned with one
exception: a single data point from GOME-2 (2.3E14).- Bromine is systematically below the detection threshold of FTIR (page
5, lines 158-159).- No reports of near-downwind volcanic BrO are available for 10 May
2008 (lines 159-162).- It is said (lines 730-731) that the bromine partition is realistic
during the night. I did not see any nighttime measurements mentioned
that can support this statement.If any additional experimental data are available, I suggest to show
them in the Figures for comparison. If not, it may be better to make a
general comparison between volcanic observations and the model instead
of focusing on a case study for a specific Etna eruption.Specific comments:
- Page 4, line 112: It is unclear what is meant by the "explicit
representation of Br2 species". There is only one Br2 species:
molecular bromine. Did you mean "Bry" species instead of Br2?- Why do you say on page 7 that there is "no mixing with background air"
even though it is included when setting the X value to 0.1 or 0.3?- The caption of Table 3 does not explain the meaning of the X value,
and when the table is mentioned in the text for the first time, X
hasn't been mentioned yet.- I first had the impression that the N.Ref simulation is identical to a
simulation with X=0. Why, however, is the X value for N.Ref in Table 3
listed as "N/A" and not as "0"? Does this mean that a simulation with
X=0 would be different from N.Ref? I checked "XFP" in the model code
which seems to be the same as "1-X". As far as I can see, there is no
difference between setting XFP=1 and PLUME2=.TRUE.- The caption of Fig. 1 says that the Model-P Box is defined as the
shaded blue square minus the big blue square. This would be a negative
number. Is this correct?- A vertical 1D model has no horizontal resolution. What do you mean on
page 31 with "The 1D simulations were run with resolution of 0.5°
longitude x 0.5° latitude"?- Page 3, line 89 and page 30, lines 717-719: The chemical lifetime of
BrO is on the order of minutes. Therefore, it will not undergo
long-range transport.- The plots of BrO and BrO/SO2 in Fig. 2 are very similar. This means
that SO2 is nearly constant, which makes sense for N.Ref. However,
shouldn't SO2 decrease a lot via plume dilution during the model runs
N.Plume.0.1 and N.Plume.0.3? Can you add SO2 to the plots in Fig. 2?
This would help to compare the dilution rates of SO2.- In Fig. 2 it can be seen that BrO starts to decrease even before the
volcanic eruption emissions stop (i.e., inside the green zone). It
would be interesting to explain this behaviour.Citation: https://doi.org/10.5194/gmd-2022-180-RC2
Virginie Marécal et al.
Virginie Marécal et al.
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