the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 07 May 2024
The crucial representation of deep convection for the cyclogenesis of medicane Ianos
Abstract. The paper presents a model intercomparison study to improve the prediction and understanding of Mediterranean cyclone dynamics. It is based on a collective effort with five mesoscale models to look for a robust response among ten numerical frameworks used in the community involved in the networking activity of the EU COST Action "MedCyclones". The obtained multi-model, multi-physics ensemble is applied to the high-impact medicane Ianos of September 2020 with focus on the cyclogenesis phase, which was poorly forecast by numerical weather prediction systems. Models systematically perform better when initialised from operational IFS analysis data compared to the widely used ERA5 reanalysis. Reducing horizontal grid spacing from 10 km with parameterised convection to convection-permitting 2 km further improves the cyclone track and intensity. This highlights the critical role of deep convection during the early development stage. Higher resolution enhances convective activity, which improves the phasing of the cyclone with an upper-level jet and its subsequent intensification and evolution. This upscale impact of convection matches a conceptual model of upscale error growth in the midlatitudes, while it emphasises the crucial interplay between convective and baroclinic processes during medicane cyclogenesis. The ten numerical frameworks show robust agreement but also reveal model specifics that should be taken into consideration, such as the need for a parameterization of deep convection even at 2 km horizontal grid spacing in some models. While they require generalisation to other cases of Mediterranean cyclones, the results provide guidance for the next generation of global convection-permitting models in weather and climate.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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- Final revised paper
Journal article(s) based on this preprint
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2024-1105', Anonymous Referee #1, 25 May 2024
The present manuscript provides a comprehensive overview of the intensification and convection formation of Medicane Ianos using different limited area models. While there are many articles related to Medicane Ianos, the reviewer recognizes that this manuscript represents a thorough investigation of the most important factors that could affect the formation and intensification of the medicane, including initial data, resolution, and initial time, with significant scientific collaboration.
The manuscript is very well written. Despite the complexity of the research, which involves numerous models and sensitivity experiments, the authors have managed to condense the information in the figures and text in a way that flows smoothly and is easy for readers to follow.
I believe the document should be published, with only a few minor comments that the authors should review or clarify. Otherwise, the document is excellent in its current state.
MINOR COMMENTS:
- Line 190 (page 7): In the sentence "Additional simulations were initialized at 00 UTC on 14 September but are not shown, because they generally did not develop a cyclone," you use the word "generally," which does not imply "all." Does this mean that at least one model configuration developed a cyclone at 00 UTC on the 14th? If so, it would be good to be more specific, because if at least one model did develop a cyclone at that time, it would be worth describing here, as I don´t know any previous scientific paper that showed that in the past.
- Line 200 (page 7): Is there any database with estimated intensity based on different types of observations?
- Lines 323 - 325 (page 11): Here, you might consider discussing that explicit convection with deep convection parametrization switched OFF may result in overly strong cyclones and excessive precipitation in some cases. Additionally, you could mention that the ocean-atmosphere interaction in the model could help mitigate this negative effect.
- Figure 4: The legends in the figure captions should be described more thoroughly. While they are clear when reading the article, they are not immediately clear just from the figure caption.
Citation: https://doi.org/10.5194/egusphere-2024-1105-RC1 -
AC1: 'Reply on RC1', Florian Pantillon, 31 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1105/egusphere-2024-1105-AC1-supplement.pdf
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RC2: 'Comment on egusphere-2024-1105', Anonymous Referee #2, 09 Jul 2024
Summary: This manuscript investigates the sensitivity of medicane Ianos to several model configurations. The analysis is based on several ensembles of simulations using 10 different models and different initial conditions, initialization times, and model grid spacing. Results show that relatively high resolution (~2 km), accurate initial conditions, and a relatively short lead time are necessary to produce simulations with relatively small track and intensity error. Conversely, using relatively high resolution (~10 km) with a cumulus parameterization or initializing the models too early results in relatively large track and intensity errors. The authors attribute this behavior to the phasing between a surface cyclone, its deep convection, and a nearby upper-tropospheric jet. This result leads to the conclusion that the representation of deep convection is important for the accurate representation of medicanes in numerical models, at least based on this case study.
Evaluation: This study is the product of a major undertaking – at least 10 models were integrated with multiple configurations. This is not an easy task, and I commend the authors for doing a nice job at synthesizing the data from all those model simulations. I found the manuscript generally well written and well organized. I only found several areas where the writing could be improved (listed below). The manuscript’s conclusions would have been even stronger with cyclone-relative composites that more clearly showed the deep convection and its phasing with the upper-tropospheric dynamics. Also, the manuscript could benefit from references to the ample body of work (outside the medicanes subdiscipline) that demonstrates the benefits of convection-permitting resolution for the representation of atmospheric phenomena.
Minor/editorial comments:
Lines 140–145: This may be a stylistic preference, but I wonder if you would consider narrating the evolution of Ianos in past tense since it was an observed event.
L150: I believe that “and surface low” should be “and a surface low”
Figures: it would be helpful to your readers to have labels next to the color bars.
L155–160: I’m not sure how to see the “baroclinic interaction” from Figure 2d. I know what you mean, but your readers may benefit from a more explicit description.
L169: “are affected by large differences” is a confusing phrase. Would it be possible to rephrase for clarity?
L171: “shallower MSLP” do you mean “stronger MSLP”? The word “shallower” is not appropriate here.
Figures 4, 5, 6, & 11: The dashed lines in the panels with only two colors (panels b, c, & d) are unnecessary. These plots merge all models together and, as far as I understand it, they do not intend to highlight intermodal differences but sensitivities to initialization time, resolution, etc. Would you consider using only solid lines since it is difficult to differentiate between models anyway due to the single color for each sensitivity test?
L180–185: Can the authors comment on the different WRF configurations and how they may have led to such wide spread?
L200–210: Your readers need more information about your ASCAT analysis. Did you average the ASCAT data within the same domain as in the models? Did you interpolate the ASCAT data to a similar grid as in your model for a clean comparison?
L206: I don’t understand what “measured values” refers to. Please modify.
L207: “As for the MSLP” Did you mean “As in the MSLP”? I am confused…
L220–230: These statements would be more convincing if you could show cyclone-relative maps that would remove the non-trivial sensitivity to the different cyclone positions.
L245: I don’t understand this sentence. Please rewrite.
Fraction skill score analysis and Fig. 10: The description of this analysis is insufficient to understand how you obtained your results. I am unsure how interpret Fig. 10 and even less confident on your readers’ ability to replicate your analysis. Would it be possible to add more details about this analysis? Why do you obtain a PDF for each scale? Are you comparison on a grid point by grid point basis? On a model-by-model basis? More information would be very helpful here. Also, is it fair to start at a scale of 10 km when your coarsest model grid spacing is 10 km (i.e., you are considering a single grid point)? Why not a scale that is more representative of the effective model resolution (~6*dx)?
L260-265: It looks like you used the 3-hourly IMERG product. Did you use the level 3 (research) product? I don’t believe you mentioned this earlier. For a robust comparison, I would recommend interpolating the model output to the IMERG grid before averaging over a domain.
Figure 11: This figure needs a label for “IMERG” corresponding to the black line.
L215: The attribution of wind overestimation to “an inaccurate representation of the air-sea interactions” is speculative; i.e., this manuscript does not show anywhere that the air-sea interactions are not properly represented in the model.
L275: This statement is purely speculative (i.e., you haven’t shown sufficient proof): “Thus, intense convection during the second burst around 00 UTC on 16 September is crucial for the phasing between Ianos and the large-scale dynamics, which pilots the cyclone track and intensity via steering and baroclinic interaction.”
L291: What is that “alternative scenario”? I admittedly don’t know what this is referring to. Please be more explicit.
L290–295 & L340: It is true that MESONH performs relatively well. Coincidentally, this model has the highest number of vertical levels. I realize that testing the sensitivity to vertical grid spacing is beyond the scope of this study, but this needs to be acknowledged. One could argue that vertical resolution is equally or even more important than horizontal resolution when resolving deep convection and its turbulent processes.
L330–335: I do not understand how the “sensitivity to both initial conditions and model physics suggests a balanced contribution of baroclinic and diabatic processes.” Please be more specific.
Citation: https://doi.org/10.5194/egusphere-2024-1105-RC2 -
AC2: 'Reply on RC2', Florian Pantillon, 31 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1105/egusphere-2024-1105-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Florian Pantillon, 31 Jul 2024
Interactive discussion
Status: closed
-
RC1: 'Comment on egusphere-2024-1105', Anonymous Referee #1, 25 May 2024
The present manuscript provides a comprehensive overview of the intensification and convection formation of Medicane Ianos using different limited area models. While there are many articles related to Medicane Ianos, the reviewer recognizes that this manuscript represents a thorough investigation of the most important factors that could affect the formation and intensification of the medicane, including initial data, resolution, and initial time, with significant scientific collaboration.
The manuscript is very well written. Despite the complexity of the research, which involves numerous models and sensitivity experiments, the authors have managed to condense the information in the figures and text in a way that flows smoothly and is easy for readers to follow.
I believe the document should be published, with only a few minor comments that the authors should review or clarify. Otherwise, the document is excellent in its current state.
MINOR COMMENTS:
- Line 190 (page 7): In the sentence "Additional simulations were initialized at 00 UTC on 14 September but are not shown, because they generally did not develop a cyclone," you use the word "generally," which does not imply "all." Does this mean that at least one model configuration developed a cyclone at 00 UTC on the 14th? If so, it would be good to be more specific, because if at least one model did develop a cyclone at that time, it would be worth describing here, as I don´t know any previous scientific paper that showed that in the past.
- Line 200 (page 7): Is there any database with estimated intensity based on different types of observations?
- Lines 323 - 325 (page 11): Here, you might consider discussing that explicit convection with deep convection parametrization switched OFF may result in overly strong cyclones and excessive precipitation in some cases. Additionally, you could mention that the ocean-atmosphere interaction in the model could help mitigate this negative effect.
- Figure 4: The legends in the figure captions should be described more thoroughly. While they are clear when reading the article, they are not immediately clear just from the figure caption.
Citation: https://doi.org/10.5194/egusphere-2024-1105-RC1 -
AC1: 'Reply on RC1', Florian Pantillon, 31 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1105/egusphere-2024-1105-AC1-supplement.pdf
-
RC2: 'Comment on egusphere-2024-1105', Anonymous Referee #2, 09 Jul 2024
Summary: This manuscript investigates the sensitivity of medicane Ianos to several model configurations. The analysis is based on several ensembles of simulations using 10 different models and different initial conditions, initialization times, and model grid spacing. Results show that relatively high resolution (~2 km), accurate initial conditions, and a relatively short lead time are necessary to produce simulations with relatively small track and intensity error. Conversely, using relatively high resolution (~10 km) with a cumulus parameterization or initializing the models too early results in relatively large track and intensity errors. The authors attribute this behavior to the phasing between a surface cyclone, its deep convection, and a nearby upper-tropospheric jet. This result leads to the conclusion that the representation of deep convection is important for the accurate representation of medicanes in numerical models, at least based on this case study.
Evaluation: This study is the product of a major undertaking – at least 10 models were integrated with multiple configurations. This is not an easy task, and I commend the authors for doing a nice job at synthesizing the data from all those model simulations. I found the manuscript generally well written and well organized. I only found several areas where the writing could be improved (listed below). The manuscript’s conclusions would have been even stronger with cyclone-relative composites that more clearly showed the deep convection and its phasing with the upper-tropospheric dynamics. Also, the manuscript could benefit from references to the ample body of work (outside the medicanes subdiscipline) that demonstrates the benefits of convection-permitting resolution for the representation of atmospheric phenomena.
Minor/editorial comments:
Lines 140–145: This may be a stylistic preference, but I wonder if you would consider narrating the evolution of Ianos in past tense since it was an observed event.
L150: I believe that “and surface low” should be “and a surface low”
Figures: it would be helpful to your readers to have labels next to the color bars.
L155–160: I’m not sure how to see the “baroclinic interaction” from Figure 2d. I know what you mean, but your readers may benefit from a more explicit description.
L169: “are affected by large differences” is a confusing phrase. Would it be possible to rephrase for clarity?
L171: “shallower MSLP” do you mean “stronger MSLP”? The word “shallower” is not appropriate here.
Figures 4, 5, 6, & 11: The dashed lines in the panels with only two colors (panels b, c, & d) are unnecessary. These plots merge all models together and, as far as I understand it, they do not intend to highlight intermodal differences but sensitivities to initialization time, resolution, etc. Would you consider using only solid lines since it is difficult to differentiate between models anyway due to the single color for each sensitivity test?
L180–185: Can the authors comment on the different WRF configurations and how they may have led to such wide spread?
L200–210: Your readers need more information about your ASCAT analysis. Did you average the ASCAT data within the same domain as in the models? Did you interpolate the ASCAT data to a similar grid as in your model for a clean comparison?
L206: I don’t understand what “measured values” refers to. Please modify.
L207: “As for the MSLP” Did you mean “As in the MSLP”? I am confused…
L220–230: These statements would be more convincing if you could show cyclone-relative maps that would remove the non-trivial sensitivity to the different cyclone positions.
L245: I don’t understand this sentence. Please rewrite.
Fraction skill score analysis and Fig. 10: The description of this analysis is insufficient to understand how you obtained your results. I am unsure how interpret Fig. 10 and even less confident on your readers’ ability to replicate your analysis. Would it be possible to add more details about this analysis? Why do you obtain a PDF for each scale? Are you comparison on a grid point by grid point basis? On a model-by-model basis? More information would be very helpful here. Also, is it fair to start at a scale of 10 km when your coarsest model grid spacing is 10 km (i.e., you are considering a single grid point)? Why not a scale that is more representative of the effective model resolution (~6*dx)?
L260-265: It looks like you used the 3-hourly IMERG product. Did you use the level 3 (research) product? I don’t believe you mentioned this earlier. For a robust comparison, I would recommend interpolating the model output to the IMERG grid before averaging over a domain.
Figure 11: This figure needs a label for “IMERG” corresponding to the black line.
L215: The attribution of wind overestimation to “an inaccurate representation of the air-sea interactions” is speculative; i.e., this manuscript does not show anywhere that the air-sea interactions are not properly represented in the model.
L275: This statement is purely speculative (i.e., you haven’t shown sufficient proof): “Thus, intense convection during the second burst around 00 UTC on 16 September is crucial for the phasing between Ianos and the large-scale dynamics, which pilots the cyclone track and intensity via steering and baroclinic interaction.”
L291: What is that “alternative scenario”? I admittedly don’t know what this is referring to. Please be more explicit.
L290–295 & L340: It is true that MESONH performs relatively well. Coincidentally, this model has the highest number of vertical levels. I realize that testing the sensitivity to vertical grid spacing is beyond the scope of this study, but this needs to be acknowledged. One could argue that vertical resolution is equally or even more important than horizontal resolution when resolving deep convection and its turbulent processes.
L330–335: I do not understand how the “sensitivity to both initial conditions and model physics suggests a balanced contribution of baroclinic and diabatic processes.” Please be more specific.
Citation: https://doi.org/10.5194/egusphere-2024-1105-RC2 -
AC2: 'Reply on RC2', Florian Pantillon, 31 Jul 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-1105/egusphere-2024-1105-AC2-supplement.pdf
-
AC2: 'Reply on RC2', Florian Pantillon, 31 Jul 2024
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Journal article(s) based on this preprint
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- 1
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Florian Pantillon
Silvio Davolio
Elenio Avolio
Carlos Calvo-Sancho
Diego S. Carrió
Stavros Dafis
Emmanouil Flaounas
Emanuele Silvio Gentile
Juan Jesus Gonzalez-Aleman
Suzanne Gray
Mario Marcello Miglietta
Platon Patlakas
Ioannis Pytharoulis
Didier Ricard
Antonio Ricchi
Claudio Sanchez
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
- Preprint
(10869 KB) - Metadata XML
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Supplement
(83 KB) - BibTeX
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- Final revised paper