the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Jul 2024
Estimating the mass of tephra accumulated on roads to best manage the impact of volcanic eruptions: the example of Mt. Etna, Italy
Abstract. During explosive eruptions a large amount of tephra is dispersed and deposited on the ground with the potential to cause a variety of damage and disruption on public infrastructure, such as road networks, which can require a rapid clean-up. The quantification of the tephra load is, therefore, of significant interest to reduce environmental and socio-economic impact, and for managing crises. Tephra dispersal and deposition is a function of multiple factors, including mass eruption rate, tephra characteristics (size, shape, density), top plume height, grain size distribution and local wind field. In this work we quantified the tephra mass deposited on the main road network on the east-southeast flanks of Mt. Etna (Italy), during lava fountains occurring in 2021. We focused this analysis on road connections of municipalities mostly affected by these events such as Milo, Santa Venerina and Zafferana Etnea. First, we analysed a sequence of 39 short-lasting and intense Etna’s lava fountains detected by the X-band weather radar, applying the volcanic ash radar retrieval approach able to retrieve main eruption source parameters, such as mass eruption rate, top plume height, grain-size distribution of those events. When the radar measurements were unavailable for a specific event, we analysed images acquired both by the SEVIRI radiometer and by the visible and/or thermal infrared camera of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (Catania) to derive some ESPs. Second, we used those eruption source parameters as inputs to run two different numerical models, Tephra2 and Fall3D, and reproduce tephra dispersal and accumulation on the road network. Finally, we produce, for the first time, georeferenced estimates of tephra mass deposited on the whole road network of three municipalities, allowing to identify the main roads which have been mostly impacted by significant tephra accumulation, as well as to estimate the total mass of primary tephra that has been removed from roads and disposed. Such information represents a valuable input for quick planning and management of the short-term tephra load hazard for possible future Etna explosive events.
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RC1: 'Comment on egusphere-2024-2028', Alvaro Aravena, 02 Oct 2024
Dear editor,
in this contribution, Mereu et al. address the problem of estimating the load of tephra accumulated on roads as a consequence of explosive activity at Mt. Etna, Italy. The authors analyze data from 39 explosive events during 2021 in order to obtain a set of inputs to run numerical simulations with the widely used programs Tephra2 and Fall3D. Numerical results are post-processed taking into account the road network in order to quantify the mass of tephra accumulated on critical points around Mt. Etna (from a crisis management perspective). In general, the text is well-written, but some parts are a little bit redundant. On the other hand, a lot of data related to figures (e.g. color scales) are indicated in the main text, and I think they should be restricted to the caption. In addition, some redundant methodological explanations are included in the results section and is not always easy to follow the structure of the text. The state of the art and the addressed problem are introduced in the first section in a clear manner, and this problem is correctly addressed in the manuscript (although a few references are suggested below). The methodology is clear and responses to the introduced problem. Discussion and conclusions are effectively based on results, and presentation of results is accompanied by descriptive figures that effectively display the main results highlighted in the manuscript.
However, I would like to raise the following issues that I think must be addressed before publication:
1. I wonder how efficient is the clean-up of roads due to natural reasons (meteorological phenomena) and effects related to routine human activities (different from cleaning-up activities). The authors describe this point in L348-352 as a limitation of the adopted methodology. This is ok, but it is still critical, in order to understand the validity and significance of results, to have an idea of the order of magnitude of the “natural” clean-up velocity of roads, and thus a larger discussion about this point is needed. For instance, when we analyze the curves presented in Figs. 4 and 5, how are these slopes compared to the expected natural clean-up of roads? Are there differences in the natural clean-up velocity as a function of elevation or vehicles circulation?
2. How comparable are estimates of H_TP derived from XWR, ECV frames and SEVIRI data with respect to those computed from ENT images? Are there examples for which all the methodologies have been applied simultaneously?
3. In general, model limitations should be described better.
4. I identified the following citations issues:
a) In L80, is it Bonadonna et al. 2021a or 2021b?
b) Bonadonna et al. 2023 is not present in the reference list.
c) Guobadia et al. 2021 is not present in the main text.
d) Macedonio and Costa 2012 is not present in the main text.
e) Pardini et al. 2023 is not present in the main text.All in all, I recommend publication of this manuscript in EGUSphere after minor but essential revisions. In the following lines, I include a set of detailed and editorial comments and suggestions. Please note that my mother-tongue is not English.
Alvaro Aravena
Detailed and editorial comments:
L13: I suggest to delete “, which can require a rapid clean-up”.
L14: “reduce” > “evaluate and reduce”.
L16: I suggest to delete “top”.
L18: I suggest to delete “this analysis”.
L18: “mostly” > “significantly”.
L20: “the volcanic ash radar retrieval approach able to retrieve” > “a volcanic ash radar retrieval approach that permits us to compute the”.
L21: I suggest to delete “top”.
L21: “, grain size distribution of those events” > “and grain size distribution”.
L21: “When the” > “When”.
L24: “those” > “the computed”.
L26: “allowing” > “allowing us”.
L27: I suggest to delete “significant”.
L28: I suggest to delete “and disposed”.
L29: “quick planning and management” > “planning and quick management”.
L29: I suggest to delete “possible”.
L31-32: Please rephrase. “Quantification of data” is not a piece of information by itself. I think the phrase “of a specific intensity” is not necessary.
L35: “poor visibility conditions” is not a problem by itself. I suggest to delete it and include the reference in the part related to “dangerous road conditions”.
L48: “, to allow” > “and to allow”
L52: I suggest to delete “try to”.
L53: “Etna that were more affected” > “Etna, which were affected”
L54-55: “hours and sometimes … times a day” > “hours, separated by periods that can last from few hours to few days”
L56: Please delete “generally”. The word “most” is already present.
L58: “accumulation” > “tephra accumulation”.
L61: “only to 39 events which” > “on 39 events that”.
L63: “in” > “to”.
L70: “those” > “these”.
L71-72: Please define MER and HTP in the first mention.
L73: I suggest to move some of the citations to the previous sentence (“… advection dispersion-models”), where you could include references of other diffusion-advection models that consider the same inputs. For instance:
- Tadini, A., Gouhier, M., Donnadieu, F., de’Michieli Vitturi, M., & Pardini, F. (2022). Particle sedimentation in numerical modelling: a case study from the Puyehue-Cordón Caulle 2011 eruption with the PLUME-MoM/HYSPLIT models. Atmosphere, 13(5), 784.
- Takishita, K., Poulidis, A. P., & Iguchi, M. (2021). Tephra4D: a python-based model for high-resolution tephra transport and deposition simulations—applications at Sakurajima volcano, Japan. Atmosphere, 12(3), 331.
And I suggest to keep the specific references associated with the presentation of the codes Tephra2 and Fall3D in the next sentence (“… such as Tephra2 and Fall3D”).
L77: “and to assess uncertainties” > “and assess the associated uncertainties”.
L80: 2021a or 2021b?
L82: I suggest to delete “theoretically”.
L81-90: I think parts of this paragraph are a little bit redundant. L94: “finally,” > “, finally,”.
L94: “are in” > “are included in”.
L101: “, Fig. 1” > “ (Fig. 1)”.
L106: “that is” > “calculated as”.
L108-109: I suggest to delete “integrating the … we retrieve”. Otherwise, the enumeration becomes strange.
L110-112: I suggest to include the following reference (I am sorry for the self-reference):
Aravena, A., Carparelli, G., Cioni, R., Prestifilippo, M., & Scollo, S. (2023). Toward a real-time analysis of column height by visible cameras: an example from mt. Etna, in Italy. Remote Sensing, 15(10), 2595.
L116: “altitude derived” > “altitude, which is derived”.
L124: “specific” > “the following”
L132: “of which three of these under examination and” > “of which three are under examination, and”.
L134: “symbol” > “symbols”.
L138-139: “is derived … previously described” > “is displayed in Table 1”.
L139: I suggest to delete “Usually” if you use the expression “not always” in the same sentence.
L140: “the plume” > “of plume”.
L141: “derive” > “collect”.
L141-143: I suggest to rephrase this part.
L151: “straight” > “straightly”.
L151: “Qm estimates XWR-based” > “XWR-based Qm estimates”.
L152: “time” > “and iii) time”.
L153: I suggest to delete “iii)” and “iv)”.
L156: So are the authors considering a constant wind field at different heights?
L160: I suggest to delete “, as available in literature”.
L162: “in the Table” > “in Table”.
L168: I think the method used in each case to compute H_TP should be indicated.
L176: “2005; Bonadonna et al., 2006;” > “2005, 2006;”
L176: “input” > “inputs”.
L177-180: I suggest to enumerate using ‘;’ instead of ‘,’ because you are also including some descriptions (and I would use ‘,’ to separate variables and their descriptions).
L180: “the plume” > “and the plume”.
L185: “from buoyant” > “from the buoyant”.
L186: “cost in computational time” > “computational cost”.
L190: “assuming a” > “assuming”.
L190-191: I suggest to delete “In particular … respectively”. This should be indicated in the caption.
L192-193: I suggest to delete “Isomass … 5 10^3 kg/m2”. This should be indicated in the caption.
L198: “The tephra” > “Tephra”.
L202-203: “the geo-referenced … on the ground” > “the geo-referenced data of tephra load on the ground in UTM coordinates … resolution of 500 m”.
L218-219: I would end the paragraph after “February 2021”. This should be indicated in the caption.
L230: I am not sure that “validation” is the correct word. I suggest “verification”.
L234: “; Table 2 shows also” > “, as well as the”.
L235: “first” > “the first”.
L239: “These” > “These discrepancies”.
L241: “derived on 14 field data” > “on 14 sites”.
L261: “equals” > “=”.
L261: “greatest” > “their larger”.
L271: I think this parenthesis is not necessary.
L272: “specific” > “discrepancies in the”.
L272: “It is worth noting” again is a little bit redundant.
L272-276: I did not understand this part. Please rephrase.
L280: “in the” > “is presented in the”. L284-286: Please rephrase (or delete). I think it is not needed to explain results and included in the introduction.
L286: “the Sicily” > “Sicily”.
L288: “the east … Etna flanks … at south” > “east (31%), southeast (35%) and nordwest (29%), and only 6% towards south”.
L289: It this consistent with wind data in the Etna zone during the last decades?
L289-293: I think this is a methodological explanation.
L295: “Each … symbol” should be in the caption.
L296: “Obviously” > “Obviously,”.
L300: “contrast with” > “contrast to”.
L314: “is constant” > “stabilizes”.
L317: “to the” > “due to”.
L332-333: Please rephrase.
L341: “lava fountains” > “explosive events”.
L345: “greater” > “larger”.
Table 4: I would combine the cells “39 Etna lava … 2021” and “Location”, and call it “Location”.
L358: I suggest to delete “what is shown in”.
L365: “assuming a” > “assuming”.
L374: “2021 and” > “2021, and”.
L382: “eruptions” > “eruption(s)”
L383: I suggest to delete “the year”.
L387: “; at” > “. At”.
L389-390: This is a very interesting point that should be highlighted in the introduction, for instance.
L393: I suggest to delete “, focusing on the … municipalities”.
L401: “intrinsic” > “different sources of”.
L401: “data to” > “data, and due to”.
L403: “mainly due both” > “related”.
L409: 2021a or 2021b?
L409: Bonadonna et al. 2023 is not present in the reference list.
L432: Different reference formats are present. Please unify them.
L441-442: This reference does not follow alphabetic order.
L498: Guobadia et al. 2021 is not present in the main text.
L542-543: Macedonio and Costa 2012 is not present in the main text.
L544-545: Pardini et al. 2023 is not present in the main text.
L579-580: This reference does not follow alphabetic order.
L581-582: This reference does not follow alphabetic order.
Citation: https://doi.org/10.5194/egusphere-2024-2028-RC1 -
AC1: 'Reply on RC1', Luigi Mereu, 29 Nov 2024
We thank the reviewer for the useful comments and suggestions and believe that now this manuscript has been significantly improved. Please, find hereafter our replies to all your comments highlighted in red, whereas all modifications in the main text are in yellow. Thank you for having considered this manuscript.
Dear editor,
in this contribution, Mereu et al. address the problem of estimating the load of tephra accumulated on roads as a consequence of explosive activity at Mt. Etna, Italy. The authors analyze data from 39 explosive events during 2021 in order to obtain a set of inputs to run numerical simulations with the widely used programs Tephra2 and Fall3D. Numerical results are post-processed taking into account the road network in order to quantify the mass of tephra accumulated on critical points around Mt. Etna (from a crisis management perspective). In general, the text is well-written, but some parts are a little bit redundant. On the other hand, a lot of data related to figures (e.g. color scales) are indicated in the main text, and I think they should be restricted to the caption. In addition, some redundant methodological explanations are included in the results section and is not always easy to follow the structure of the text. The state of the art and the addressed problem are introduced in the first section in a clear manner, and this problem is correctly addressed in the manuscript (although a few references are suggested below). The methodology is clear and responses to the introduced problem. Discussion and conclusions are effectively based on results, and presentation of results is accompanied by descriptive figures that effectively display the main results highlighted in the manuscript.
However, I would like to raise the following issues that I think must be addressed before publication:
1. I wonder how efficient is the clean-up of roads due to natural reasons (meteorological phenomena) and effects related to routine human activities (different from cleaning-up activities). The authors describe this point in L348-352 as a limitation of the adopted methodology. This is ok, but it is still critical, in order to understand the validity and significance of results, to have an idea of the order of magnitude of the “natural” clean-up velocity of roads, and thus a larger discussion about this point is needed. For instance, when we analyze the curves presented in Figs. 4 and 5, how are these slopes compared to the expected natural clean-up of roads? Are there differences in the natural clean-up velocity as a function of elevation or vehicles circulation?
>> We have stressed this point highlighting how a combination of different cleaning methods is necessary to speed up the ash removal from high priority routes used in the management of these crises.
2. How comparable are estimates of H_TP derived from XWR, ECV frames and SEVIRI data with respect to those computed from ENT images? Are there examples for which all the methodologies have been applied simultaneously?
>>The H_TP estimate derived from different sensors (XWR, ECV frames, and SEVIRI) shows a time trend that is quite comparable to those described in previous works (e.g., Freret-Lorgeril et al., 2021; Scollo et al., 2019). The H_TP estimations are derived from the analysis of XWR observations, ECV frames, and SEVIRI data. Generally, the XWR estimates show values slightly lower than those derived from ECV and SEVIRI. This difference is due to the sensitivity limitations of XWR in detecting the finest ash particles at higher altitudes, compared to the other two sensors. In contrast, by analyzing the ENT images, whose field of view is mainly focused on the lower section of the volcanic plume (a few kilometers above the volcano vent) and not on the entire cloud, we identify the Incandescent Jet Region, which is considered a proxy for the lava fountain (Mereu et al., 2020). Hence, this is not a direct measure of the H-TP but only of the mass eruption rate, having consequently higher errors.
3. In general, model limitations should be described better.
>> We have added some texts and references regarding the model limitations. Limitations, in fact, have been already analyzed in literature (Scollo et al. 2008B; Folch et al., 2012, 2016).
4. I identified the following citations issues: a) In L80, is it Bonadonna et al. 2021a or 2021b?>>done b) Bonadonna et al. 2023 is not present in the reference list.→Bonadonna et al., 2021a>>corrected c) Guobadia et al. 2021 is not present in the main text.→Bonadonna et al., 2021a>>corrected d) Macedonio and Costa 2012 is not present in the main text.>>cancelled e) Pardini et al. 2023 is not present in the main text.>>this work is cited in par.3.1
All in all, I recommend publication of this manuscript in EGUSphere after minor but essential revisions. In the following lines, I include a set of detailed and editorial comments and suggestions. Please note that my mother-tongue is not English.
Alvaro Aravena
Detailed and editorial comments:
L13: I suggest to delete “, which can require a rapid clean-up”.>>done
L14: “reduce” > “evaluate and reduce”.>>done
L16: I suggest to delete “top”.>> it’s the definition of acronym Top Plume Height H_TP
L18: I suggest to delete “this analysis”.>>done
L18: “mostly” > “significantly”.>>done
L20: “the volcanic ash radar retrieval approach able to retrieve” > “a volcanic ash radar retrieval approach that permits us to compute the”.>>done
L21: I suggest to delete “top”.>>as before
L21: “, grain size distribution of those events” > “and grain size distribution”.>>done
L21: “When the” > “When”.>>done
L24: “those” > “the computed”.>>done
L26: “allowing” > “allowing us”.>>done
L27: I suggest to delete “significant”.>>done
L28: I suggest to delete “and disposed”.>>done
L29: “quick planning and management” > “planning and quick management”.>>done
L29: I suggest to delete “possible”.>>done
L31-32: Please rephrase. “Quantification of data” is not a piece of information by itself. I think the phrase “of a specific intensity” is not necessary.>>corrected
L35: “poor visibility conditions” is not a problem by itself. I suggest to delete it and include the reference in the part related to “dangerous road conditions”.>>done
L48: “, to allow” > “and to allow”>>done
L52: I suggest to delete “try to”.>>done
L53: “Etna that were more affected” > “Etna, which were affected”>>done
L54-55: “hours and sometimes … times a day” > “hours, separated by periods that can last from few hours to few days”>>done
L56: Please delete “generally”. The word “most” is already present.>>done
L58: “accumulation” > “tephra accumulation”.>>done
L61: “only to 39 events which” > “on 39 events that”.>>done
L63: “in” > “to”.>>done
L70: “those” > “these”.>>done
L71-72: Please define MER and HTP in the first mention.>>done
L73: I suggest moving some of the citations to the previous sentence (“… advection dispersion-models”), where you could include references of other diffusion-advection models that consider the same inputs. For instance:
- Tadini, A., Gouhier, M., Donnadieu, F., de’Michieli Vitturi, M., & Pardini, F. (2022). Particle sedimentation in numerical modelling: a case study from the Puyehue-Cordón Caulle 2011 eruption with the PLUME-MoM/HYSPLIT models. Atmosphere, 13(5), 784.
- Takishita, K., Poulidis, A. P., & Iguchi, M. (2021). Tephra4D: a python-based model for high-resolution tephra transport and deposition simulations—applications at Sakurajima volcano, Japan. Atmosphere, 12(3), 331.
>>We have modified and added the new references
And I suggest to keep the specific references associated with the presentation of the codes Tephra2 and Fall3D in the next sentence (“… such as Tephra2 and Fall3D”).>>done
L77: “and to assess uncertainties” > “and assess the associated uncertainties”.>>done
L80: 2021a or 2021b?>>corrected
L82: I suggest to delete “theoretically”.>>done
L81-90: I think parts of this paragraph are a little bit redundant.>>We simplified this paragraph
>>We have reformulated this paragraph, as highlighted in yellow in the main text
L94: “finally,” > “, finally,”.>>done
L94: “are in” > “are included in”.>>done
L101: “, Fig. 1” > “ (Fig. 1)”.>>done
L106: “that is” > “calculated as”.>>done
L108-109: I suggest to delete “integrating the … we retrieve”. Otherwise, the enumeration becomes strange.>>done
L110-112: I suggest to include the following reference (I am sorry for the self-reference):
Aravena, A., Carparelli, G., Cioni, R., Prestifilippo, M., & Scollo, S. (2023). Toward a real-time analysis of column height by visible cameras: an example from mt. Etna, in Italy. Remote Sensing, 15(10), 2595.>>We have added this reference
L116: “altitude derived” > “altitude, which is derived”.>>done
L124: “specific” > “the following”>>done
L132: “of which three of these under examination and” > “of which three are under examination, and”.>>done
L134: “symbol” > “symbols”.>>done
L138-139: “is derived … previously described” > “is displayed in Table 1”.>>done
L139: I suggest to delete “Usually” if you use the expression “not always” in the same sentence.>>done
L140: “the plume” > “of plume”.>>done
L141: “derive” > “collect”.>>done
L141-143: I suggest to rephrase this part.>>We rephrased this paragraph
>>We have reformulated this part of text (highlighted in yellow) in the paragraph.
L151: “straight” > “straightly”.>>done
L151: “Qm estimates XWR-based” > “XWR-based Qm estimates”.>>done
L152: “time” > “and iii) time”.>>done
L153: I suggest to delete “iii)” and “iv)”.>>done
L156: So are the authors considering a constant wind field at different heights?>>done
L160: I suggest to delete “, as available in literature”.>>done
L162: “in the Table” > “in Table”.>>done
L168: I think the method used in each case to compute H_TP should be indicated. >> This point is described in points a)-i), b) and c) of par. 2.1.1
L176: “2005; Bonadonna et al., 2006;” > “2005, 2006;”>>done
L176: “input” > “inputs”.>>done
L177-180: I suggest to enumerate using ‘;’ instead of ‘,’ because you are also including some descriptions (and I would use ‘,’ to separate variables and their descriptions).>>done
L180: “the plume” > “and the plume”.>>done
L185: “from buoyant” > “from the buoyant”.>>done
L186: “cost in computational time” > “computational cost”.>>done
L190: “assuming a” > “assuming”.>>done
L190-191: I suggest to delete “In particular … respectively”. This should be indicated in the caption.>>done
L192-193: I suggest to delete “Isomass … 5 10^3 kg/m2”. This should be indicated in the caption.>>done
L198: “The tephra” > “Tephra”.>>done
L202-203: “the geo-referenced … on the ground” > “the geo-referenced data of tephra load on the ground in UTM coordinates … resolution of 500 m”.>>done
L218-219: I would end the paragraph after “February 2021”. This should be indicated in the caption.>>modified
L230: I am not sure that “validation” is the correct word. I suggest “verification”.>>modified
L234: “; Table 2 shows also” > “, as well as the”.>>done
L235: “first” > “the first”.>>done
L239: “These” > “These discrepancies”.>>done
L241: “derived on 14 field data” > “on 14 sites”.>>done
L261: “equals” > “=”.>>done
L261: “greatest” > “their larger”.>>done
L271: I think this parenthesis is not necessary.>>done
L272: “specific” > “discrepancies in the”.>>done
L272: “It is worth noting” again is a little bit redundant.>>modified
L272-276: I did not understand this part. Please rephrase.>>modified
L280: “in the” > “is presented in the”. >>done
L284-286: Please rephrase (or delete). I think it is not needed to explain results and included in the introduction.>>This sentence has been modified and moved in the introduction
L286: “the Sicily” > “Sicily”.>>done
L288: “the east … Etna flanks … at south” > “east (31%), southeast (35%) and nordwest (29%), and only 6% towards south”.>>done
L289: It this consistent with wind data in the Etna zone during the last decades?>> We stressed this point in the main text (Scollo et al., 2013; Barsotti et al., 2010). Generally the direction of the wind disperses the volcanic plume towards the east and south. In this analysis we use the data derived from the ECMWF-Ara5 Reanalysis for more reliable information for Etna events.
L289-293: I think this is a methodological explanation.>>We have modified this sentence which is preparatory to Figure 5.
L295: “Each … symbol” should be in the caption.>>modified
L296: “Obviously” > “Obviously,”.>>done
L300: “contrast with” > “contrast to”.>>done
L314: “is constant” > “stabilizes”.>>done
L317: “to the” > “due to”.>>done
L332-333: Please rephrase.>>done
L341: “lava fountains” > “explosive events”.>>done
L345: “greater” > “larger”.>>done
Table 4: I would combine the cells “39 Etna lava … 2021” and “Location”, and call it “Location”.>>modified
L358: I suggest to delete “what is shown in”.>>done
L365: “assuming a” > “assuming”.>>done
L374: “2021 and” > “2021, and”.>>done
L382: “eruptions” > “eruption(s)”>>done
L383: I suggest to delete “the year”.>>done
L387: “; at” > “. At”.>>done
L389-390: This is a very interesting point that should be highlighted in the introduction, for instance.>>We have highlighted this point also in the introduction.
L393: I suggest to delete “, focusing on the … municipalities”.>>done
L401: “intrinsic” > “different sources of”.>>done
L401: “data to” > “data, and due to”.>>done
L403: “mainly due both” > “related”.>>done
L409: 2021a or 2021b?>>done
L409: Bonadonna et al. 2023 is not present in the reference list.>> corrected: Bonadonna et al., 2021a
L432: Different reference formats are present. Please unify them.>>done
L441-442: This reference does not follow alphabetic order.>>done
L498: Guobadia et al. 2021 is not present in the main text.>> corrected: Bonadonna et al., 2021a
L542-543: Macedonio and Costa 2012 is not present in the main text.>>cancelled
L544-545: Pardini et al. 2023 is not present in the main text.>>This work is in par. 3.1
L579-580: This reference does not follow alphabetic order.>>done
L581-582: This reference does not follow alphabetic order.>>done. We have verified all the references and alphabetically ordered.
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AC1: 'Reply on RC1', Luigi Mereu, 29 Nov 2024
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RC2: 'Comment on egusphere-2024-2028', Anonymous Referee #2, 04 Oct 2024
The manuscript presents the results of a modelling study aiming at quantifying tephra deposition from lava fountain events on the Etna volcano road network. Authors use two models (Tephra2 and FALL3D) to model the transport and deposition of the tephra released from the volcano and find that both models give similar results when taking into account the sensitivity tied to volcanic quantities (here a factor of 5).
I find this to be an interesting study looking at an important problem. However, I feel that despite its novelty, at the current stage the study feels a bit too simple. I do believe though that some additional simulations and analysis can lead to a much more impactful publication. To this end I have written down some recommendation and a number of concerns about the methodology employed:
- As the authors’ note, there is no analysis of the impact of the ESP sensitivity. Considering the relative novelty of the work presented, I would emphatically argue that this is a perfect opportunity to look into the sensitivity of the results to the different combinations of ESP values. I feel that including a robust error analysis (see comment 3) and a quantification of the impact, the study will have a much stronger central point.
- I am not sure if Tephra2 is the right model to use here as the study focuses on relatively proximal dispersal of unsteady plumes over very complex topography. From the Scollo et al 2019 study, I understand that this is probably due to the fact that Tephra2 is part of the forecast system employed. Is this correct? I think that objectively, FALL3D is a more appropriate model to use, so I would frame this as cross-examination of the Tehpra2 results (necessitated due to the computational constraints) against a more sophisticated model.
- Even though the eruption studied here are described in Scollo et al 2019, I feel that a section discussing their main characteristics is warranted.
- Despite the presentation of ground observations along the radar-derived values, there is no proper error-based evaluation. This is particularly important for the comparison of the two model results. There’s a number of error metrics commonly used (RMSE, MAPE, bias etc) along with correlation coefficients such as Pearson or Kendall tau. Considering the nature of concentrations and depositions, the use of the logarithm error might offer a better tool as it penalises both over and underestimation in the same way. A proper error analysis can help put the conflicting model results into better context.
- I'm not sure if I missed information regarding plumes, but how is tephra introduced in the model? Is there a plume model employed, or is it a standard profile or single point release? I know that the representation of tephra concentration along unsteady volcanic plumes is very much an open issue with no proper answer and considering the fact that forecasts do need to be carried out we must accept the use of simplifications, but I think that important information are missing.
- Expanding comment 4, in general there's a lot of important model configuration information that seems to be missing from the manuscript.
- The estimation of the road width also needs more information. I have added a relevant comment in the pdf version, but in short, as the results directly scale with the road width chosen further information would help make a more convincing case.
- This is a nit-pick, but the interpolation method seems computationally inefficient. Is the intermediate step of interpolating everything at 5m really necessary? I feel that directly interpolating over the road network would be more efficient.
- Second nit-pick – the word “resolution” is used throughout the manuscript instead of “grid spacing”. The two are not the same, as resolution refers to the scale of phenomena models are able to explicitly resolve. In the case of transport modelling, resolution is mostly tied to the grid spacing of the meteorological data.
Finally, there are some minor points, language errors, typos etc. I’ve highlighted some in the pdf, but the manuscript merits another careful read-through by the authors.
Overall, I think that this is an interesting and novel study that requires some additional simulations to truly reach its potential. My overall recommendation would be publication after major revisions as discussed above. I hope that the authors will find the comments constructive.
Kind regards and best of luck with the revisions.
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AC2: 'Reply on RC2', Luigi Mereu, 29 Nov 2024
We thank the reviewer for the useful comments and suggestions and believe that now this manuscript has been significantly improved. Please, find hereafter our replies to all your comments highlighted in red, whereas all modifications in the main text are in yellow. Thank you for having considered this manuscript.
The manuscript presents the results of a modelling study aiming at quantifying tephra deposition from lava fountain events on the Etna volcano road network. Authors use two models (Tephra2 and FALL3D) to model the transport and deposition of the tephra released from the volcano and find that both models give similar results when taking into account the sensitivity tied to volcanic quantities (here a factor of 5).
I find this to be an interesting study looking at an important problem. However, I feel that despite its novelty, at the current stage the study feels a bit too simple. I do believe though that some additional simulations and analysis can lead to a much more impactful publication. To this end I have written down some recommendation and a number of concerns about the methodology employed:
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As the authors’ note, there is no analysis of the impact of the ESP sensitivity. Considering the relative novelty of the work presented, I would emphatically argue that this is a perfect opportunity to look into the sensitivity of the results to the different combinations of ESP values. I feel that including a robust error analysis (see comment 3) and a quantification of the impact, the study will have a much stronger central point.
>> In paragraph 2 and in the discussionwe have added the reference to paper Scollo et al., 2008b, where it is described the sensitivity analysis of ESP on results of Tephra2 and Fall3D. Following your suggestion we have added an error analysis on results derived from both models, from the radar and field data.
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I am not sure if Tephra2 is the right model to use here as the study focuses on relatively proximal dispersal of unsteady plumes over very complex topography. From the Scollo et al 2019 study, I understand that this is probably due to the fact that Tephra2 is part of the forecast system employed. Is this correct? I think that objectively, FALL3D is a more appropriate model to use, so I would frame this as cross-examination of the Tehpra2 results (necessitated due to the computational constraints) against a more sophisticated model.
>> The reviewer is right. .Tephra2 is the model for the real-time forecast of ash plume dispersion at INGV-OE surveillance system since 2009 but it also includes topography effects. Differently, the Fall3D model is more complex with respect to Tephra2 but due to the computational constraints is less suited for surveillance issues. In this paper, we don’t want to explore what is the best model with respect to another but we wish to estimate the uncertainty due to the different physical assumptions and computational constraints. However, comparisons among the results of the two models and field data of 28 February 2021 were also added to estimate the goodness of both models.
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Even though the eruption studied here are described in Scollo et al 2019, I feel that a section discussing their main characteristics is warranted.
>> We added a section to describe the main features of these Etna events.
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Despite the presentation of ground observations along the radar-derived values, there is no proper error-based evaluation. This is particularly important for the comparison of the two model results. There’s a number of error metrics commonly used (RMSE, MAPE, bias etc) along with correlation coefficients such as Pearson or Kendall tau. Considering the nature of concentrations and depositions, the use of the logarithm error might offer a better tool as it penalises both over and underestimation in the same way. A proper error analysis can help put the conflicting model results into better context.
>> We stressed this point and we added a description of the statistical error analysis on the retrievals of tephra mass such as derived from models and from the XWR, and we have compared them with field data (Pardini et al., 2021); further, we have added a new paragraph 4.5 with some considerations.
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I'm not sure if I missed information regarding plumes, but how is tephra introduced in the model? Is there a plume model employed, or is it a standard profile or single point release? I know that the representation of tephra concentration along unsteady volcanic plumes is very much an open issue with no proper answer and considering the fact that forecasts do need to be carried out we must accept the use of simplifications, but I think that important information are missing.
>> We added in the paragraph the information about the plume model considered and different assumptions (Lines 206-209 and 212-217).
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Expanding comment 4, in general there's a lot of important model configuration information that seems to be missing from the manuscript.
>> We added other references which refer to detailed information about employed models (Lines 216-217 and 223-225).
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The estimation of the road width also needs more information. I have added a relevant comment in the pdf version, but in short, as the results directly scale with the road width chosen further information would help make a more convincing case.
>> We specified in the main text that the roads width have been obtained from both (i) randomly sampling some roads and measuring their width, thus obtaining on average a width of 6 m, and (ii) from the legislation as reported in the text. We also added a width variability of +/- 0.5 m to examine in depth this aspect.
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This is a nit-pick, but the interpolation method seems computationally inefficient. Is the intermediate step of interpolating everything at 5m really necessary? I feel that directly interpolating over the road network would be more efficient.
>>The reviewer is right, but in this work we opted to interpolate the tephra load over the whole map, as it was still computationally easily feasible. We added a paragraph with a description of uncertainties and results variation.
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Second nit-pick – the word “resolution” is used throughout the manuscript instead of “grid spacing”. The two are not the same, as resolution refers to the scale of phenomena models are able to explicitly resolve. In the case of transport modelling, resolution is mostly tied to the grid spacing of the meteorological data.
>>The reviewer is right, we corrected it and replaced it with grid spacing.
Finally, there are some minor points, language errors, typos etc. I’ve highlighted some in the pdf, but the manuscript merits another careful read-through by the authors.
Overall, I think that this is an interesting and novel study that requires some additional simulations to truly reach its potential. My overall recommendation would be publication after major revisions as discussed above. I hope that the authors will find the comments constructive.
Kind regards and best of luck with the revisions.
>>We thank the reviewer for the several corrections and suggestions pointed out in the pdf, that have greatly improved the manuscript quality. We have changed the text according to each recommendation, and the various corrections are shown in the main text highlighted in yellow.
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