the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Assessing the coastal hazard of medicane Ianos through ensemble modelling
Christian Ferrarin
Florian Pantillon
Silvio Davolio
Marco Bajo
Mario Marcello Miglietta
Elenio Avolio
Diego S. Carrió
Ioannis Pytharoulis
Claudio Sanchez
Platon Patlakas
Juan Jesús González-Alemán
Emmanouil Flaounas
Abstract. On 18 September 2020, medicane Ianos hit the western coast of Greece resulting in flooding and severe damage at several coastal locations. In this work, we aim at evaluating its impact on sea conditions and the associated uncertainty through the use of an ensemble of numerical simulations. We applied a coupled wave-current model to an unstructured mesh representing the whole Mediterranean Sea, with a grid resolution increasing in the Ionian Sea along the cyclone path and the landfall area. To investigate the uncertainty of modelling sea levels and waves for such an intense event, we performed a multimodel ensemble of ocean simulations using several coarse (10 km) and high-resolution (2 km) meteorological forcings from different mesoscale models. The performance of the ocean and wave models was evaluated against observations retrieved from fixed monitoring stations and satellites. All model runs emphasized the occurrence of severe sea conditions along the cyclone path and at the coast. Due to the rugged and complex coastline, extreme sea levels are localised at specific coastal sites. However, numerical results show a large spread of the simulated sea conditions for both the sea level and waves highlighting the large uncertainty in simulating this kind of extreme event. The multi-model / multi-physics approach allows us to assess how the uncertainty propagates from meteorological to ocean variables and the subsequent coastal impact. The ensemble mean and standard deviation were combined to prove the hazard scenarios of the potential impact of such an extreme event to be used in a flood risk management plan.
Christian Ferrarin et al.
Status: closed
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RC1: 'Comment on egusphere-2022-990', Anonymous Referee #1, 19 Jan 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-990/egusphere-2022-990-RC1-supplement.pdf
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RC2: 'Reply on RC1', Anonymous Referee #1, 19 Jan 2023
Dear colleagues, in the pdf, next to last remark page14, L237 should read:
"page14, L237: yes, mean+stdev could provide a conservative estimate of risk – but they could also lead to so many false positives that the product would cease to be taken seriously by downstream stakeholders. Perhaps this could be mentioned as a downside of such conservative estimates. Figure 11 would be a dramatic false positive if this conservative approach were to be used. There is an compromise to be found between model precision ()how many predicted floods occurred) and its recall (how many occurred floods were predicted). It is not obvious to me that simply adding mean+stdev leads to a good compromise."Citation: https://doi.org/10.5194/egusphere-2022-990-RC2 -
AC3: 'Reply on RC2', Christian Ferrarin, 26 Apr 2023
Thanks for the correction.
Citation: https://doi.org/10.5194/egusphere-2022-990-AC3
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AC3: 'Reply on RC2', Christian Ferrarin, 26 Apr 2023
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AC1: 'Reply on RC1', Christian Ferrarin, 31 Jan 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-990/egusphere-2022-990-AC1-supplement.pdf
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RC2: 'Reply on RC1', Anonymous Referee #1, 19 Jan 2023
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RC3: 'Comment on egusphere-2022-990', Anonymous Referee #2, 15 Apr 2023
The authors compare the prediction of wave and sea level conditions during the impact of the Medicane Ianos simulated by a coupled hydrodynamic-wave model. The model is forced by a set of atmospheric conditions simulated by different atmospheric models with different spatial resolution. Authors propose to use the ensemble mean and deviation to predict induced hazards in the coast as a conservative way of approaching to hazard/risk mapping.
The paper is well written, it is well structured and results are clearly presented, with figures and tables being all of them relevant.
Despite this, the manuscript presents some points that need to be addressed before being considered for publication. In what follows, some comments and suggestions are given.
[1] Lines 55-59. Which is the objective of the paper? Is the objective to present/propose a methodological approach? Is to identify which model performs better? To identify the best resolution? To quantify model uncertainty? To avoid confusion, authors can include a sentence such as “The main aim of this work is …”.
[2] Line 64. Which was the criteria to select the used atmospheric models?
[3] Line 67. Which was the criteria to select these two resolutions.
[4] Line 89. Is the objective to make a fair comparison or, to look for the best results? Thus, would it not be better to use the best set of initial/boundary conditions for different model resolutions.
[5] Lines 92-95. Why did you use this set of models? Will the results be similar for a different set or will they depend on the models used? If so, a warning about this should be included in the discussion of results and conclusions.
[6] General meteorological conditions
6.1 Would it be relevant to cite in this section results obtained by Comellas Prat et al (2021) doi.org/10.3390/rs13244984?
6.2 Fig 3. Are you using ECMWF IFS as the measured conditions during the Medicane propagation? Is this referring to ERA-5 reanalysis? If yes, please mention it for readers not familiar with it.
6.3 Lines 125-127. Even if your objective was not to simulate atmospheric conditions, a large deviation from the simulated conditions will have a significant impact on marine variables.
[7] Open sea conditions
7.1 When did you compare measured and modelled wave fields? At what time of the cyclone path? Is there any difference throughout the duration of the event?
7.2 Lines 176-178. This may imply that you are using an ocean model that cannot reproduce the effects captured by the only data source available to validate/compare model results. Do you have any idea of the potential magnitude of this effect under the conditions studied to compare with the measured sea level profile?
[8] Sea conditions at the coast
8.1 Line 211. “…reducing the uncertainty…”. If we use the same criteria you use here to state that 2 km reduces the uncertainty, 10 km will do so for the sea level and wave maximum value. However, you mentioned earlier that there was no clear indication that one of the simulation sets would provide a more accurate reproduction of the observed maximum sea levels and waves.
[9] Assessing the potential coastal hazard
9.1 Line 219. “…probabilistic approach”. Do you refer here to the number of models used to produce the ensemble? It would be enough to say the ensemble method. Probabilistic seems to suggest a large number of simulations which is not the case.
9.2 Line 221. See comments 2, 3, 4, 6.1 and 6.3. This can be the result of your previous choices.
9.3. Lines 234-235. The ensemble mean may be considered as the most probable hazard scenario in the case you are using proper models fed with proper initial/boundary conditions. If not, it is only representing the most probable scenario according to the used conditions and models (see comment 7.2).
9.4 Using the sum of the mean and deviation as the final hazard assessment is a conservative approach that is, of course, on the safe side. However, it can generate a number of false warnings that may affect the population's future response to real warnings.
10. Conclusions
10.1 Adapt conclusions accordingly to any change resulting from the above comments.
10.2 Lines 284-286. Are you referring to the proposed ensemble or are you talking in generic terms? I would say that you need to be very careful in the selection of models to be used, resolutions and boundary conditions.
Citation: https://doi.org/10.5194/egusphere-2022-990-RC3 -
AC2: 'Reply on RC3', Christian Ferrarin, 26 Apr 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-990/egusphere-2022-990-AC2-supplement.pdf
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AC2: 'Reply on RC3', Christian Ferrarin, 26 Apr 2023
Status: closed
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RC1: 'Comment on egusphere-2022-990', Anonymous Referee #1, 19 Jan 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-990/egusphere-2022-990-RC1-supplement.pdf
-
RC2: 'Reply on RC1', Anonymous Referee #1, 19 Jan 2023
Dear colleagues, in the pdf, next to last remark page14, L237 should read:
"page14, L237: yes, mean+stdev could provide a conservative estimate of risk – but they could also lead to so many false positives that the product would cease to be taken seriously by downstream stakeholders. Perhaps this could be mentioned as a downside of such conservative estimates. Figure 11 would be a dramatic false positive if this conservative approach were to be used. There is an compromise to be found between model precision ()how many predicted floods occurred) and its recall (how many occurred floods were predicted). It is not obvious to me that simply adding mean+stdev leads to a good compromise."Citation: https://doi.org/10.5194/egusphere-2022-990-RC2 -
AC3: 'Reply on RC2', Christian Ferrarin, 26 Apr 2023
Thanks for the correction.
Citation: https://doi.org/10.5194/egusphere-2022-990-AC3
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AC3: 'Reply on RC2', Christian Ferrarin, 26 Apr 2023
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AC1: 'Reply on RC1', Christian Ferrarin, 31 Jan 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-990/egusphere-2022-990-AC1-supplement.pdf
-
RC2: 'Reply on RC1', Anonymous Referee #1, 19 Jan 2023
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RC3: 'Comment on egusphere-2022-990', Anonymous Referee #2, 15 Apr 2023
The authors compare the prediction of wave and sea level conditions during the impact of the Medicane Ianos simulated by a coupled hydrodynamic-wave model. The model is forced by a set of atmospheric conditions simulated by different atmospheric models with different spatial resolution. Authors propose to use the ensemble mean and deviation to predict induced hazards in the coast as a conservative way of approaching to hazard/risk mapping.
The paper is well written, it is well structured and results are clearly presented, with figures and tables being all of them relevant.
Despite this, the manuscript presents some points that need to be addressed before being considered for publication. In what follows, some comments and suggestions are given.
[1] Lines 55-59. Which is the objective of the paper? Is the objective to present/propose a methodological approach? Is to identify which model performs better? To identify the best resolution? To quantify model uncertainty? To avoid confusion, authors can include a sentence such as “The main aim of this work is …”.
[2] Line 64. Which was the criteria to select the used atmospheric models?
[3] Line 67. Which was the criteria to select these two resolutions.
[4] Line 89. Is the objective to make a fair comparison or, to look for the best results? Thus, would it not be better to use the best set of initial/boundary conditions for different model resolutions.
[5] Lines 92-95. Why did you use this set of models? Will the results be similar for a different set or will they depend on the models used? If so, a warning about this should be included in the discussion of results and conclusions.
[6] General meteorological conditions
6.1 Would it be relevant to cite in this section results obtained by Comellas Prat et al (2021) doi.org/10.3390/rs13244984?
6.2 Fig 3. Are you using ECMWF IFS as the measured conditions during the Medicane propagation? Is this referring to ERA-5 reanalysis? If yes, please mention it for readers not familiar with it.
6.3 Lines 125-127. Even if your objective was not to simulate atmospheric conditions, a large deviation from the simulated conditions will have a significant impact on marine variables.
[7] Open sea conditions
7.1 When did you compare measured and modelled wave fields? At what time of the cyclone path? Is there any difference throughout the duration of the event?
7.2 Lines 176-178. This may imply that you are using an ocean model that cannot reproduce the effects captured by the only data source available to validate/compare model results. Do you have any idea of the potential magnitude of this effect under the conditions studied to compare with the measured sea level profile?
[8] Sea conditions at the coast
8.1 Line 211. “…reducing the uncertainty…”. If we use the same criteria you use here to state that 2 km reduces the uncertainty, 10 km will do so for the sea level and wave maximum value. However, you mentioned earlier that there was no clear indication that one of the simulation sets would provide a more accurate reproduction of the observed maximum sea levels and waves.
[9] Assessing the potential coastal hazard
9.1 Line 219. “…probabilistic approach”. Do you refer here to the number of models used to produce the ensemble? It would be enough to say the ensemble method. Probabilistic seems to suggest a large number of simulations which is not the case.
9.2 Line 221. See comments 2, 3, 4, 6.1 and 6.3. This can be the result of your previous choices.
9.3. Lines 234-235. The ensemble mean may be considered as the most probable hazard scenario in the case you are using proper models fed with proper initial/boundary conditions. If not, it is only representing the most probable scenario according to the used conditions and models (see comment 7.2).
9.4 Using the sum of the mean and deviation as the final hazard assessment is a conservative approach that is, of course, on the safe side. However, it can generate a number of false warnings that may affect the population's future response to real warnings.
10. Conclusions
10.1 Adapt conclusions accordingly to any change resulting from the above comments.
10.2 Lines 284-286. Are you referring to the proposed ensemble or are you talking in generic terms? I would say that you need to be very careful in the selection of models to be used, resolutions and boundary conditions.
Citation: https://doi.org/10.5194/egusphere-2022-990-RC3 -
AC2: 'Reply on RC3', Christian Ferrarin, 26 Apr 2023
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2023/egusphere-2022-990/egusphere-2022-990-AC2-supplement.pdf
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AC2: 'Reply on RC3', Christian Ferrarin, 26 Apr 2023
Christian Ferrarin et al.
Christian Ferrarin et al.
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