the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Exploring hail and lightning diagnostics over the Alpine-Adriatic region in a km-scale climate model
Nikolina Ban
Marie-Estelle Demory
Christoph Schär
Abstract. The north and south of the Alps, as well as the eastern shores of the Adriatic Sea, are hot spots of severe weather events, including hail and lightning associated with deep convection. With advancements in computing power, it has become feasible to simulate deep convection explicitly in climate models by decreasing the horizontal grid spacing to less than 4 km. These so-called kilometer-scale or convection-resolving models improve the representation of orography and reduce uncertainties associated with the use of deep convection parameterizations.
In this study, we perform convection-resolving simulations for eight observed cases of severe convective events (seven with and one without observed hail) over the Alpine-Adriatic region. The simulations are performed with COSMO-crCLIM, a climate version of the Consortium for Small-scale Modeling (COSMO) regional model that runs on Graphics Processing Units (GPUs) at a horizontal grid spacing of 2.2 km. For analyzing hail and lightning, we have explored the hail growth model (HAILCAST) and lightning potential index (LPI) diagnostics integrated with the COSMO-crCLIM model.
Comparison with available high-resolution observations reveals good performance of the model in simulating heavy precipitation, hail, and lightning. By performing a detailed analysis of three of the case studies, we identified the importance of significant meteorological factors for heavy thunderstorms that were reproduced by the model. Among these are the moist unstable boundary layer and dry mid-level air, the topographic barrier, as well as an approaching upper-level trough and cold front. Although COSMO HAILCAST tends to underestimate the hail size on the ground, the results indicate that both HAILCAST and LPI are promising candidates for future climate research.
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Ruoyi Cui et al.
Status: closed
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RC1: 'Comment on wcd-2023-11', Olivia Martius, 31 May 2023
Exploring hail and lighting diagnostics over the Alpine-Adriatic region in a km-scale climate model
The study presents simulations of severe thunderstorms in the Alpine and Adriatic areas. The eight case studies are run with ERA-5 boundary conditions and initiated at 12 UTC of the previous day to allow for spin-up. The model simulations include, for the first time Hailcast and LPI diagnostics to identify and characterize hail and lightning over the study areas in Europe. The simulations are compared in detail to observations.
The paper is well-written, it is very well structured, and the figures are very clear and well-readable. The results are highly relevant, and the detailed process discussions are instructive and illustrate the diversity of thunderstorm environments in the complex topography. The paper is ready for publication after some minor revisions.
Kind regards
Olivia
Major point
L312ff I think that there is an issue with this comparison. If you compare two relative frequency distributions that both sum up to 1 for a variable that is expected to have an exponential distribution and one distribution starts at 0mm and one at 20mm, then by construction you will always find relatively fewer large values in the distribution that starts at 0mm. To check if this is true, you can artificially cut the model data at 20mm. Since the issue is not present in the comparison with the crowd-sourced reports, I suspect that your comparison improves a lot if you use only hailcast data of >=20mm.
Minor points:
L 20 e.g. Punge and Kunz …
L30 averaged --> average
L31 is located between
L33 A transition sentence is needed before the sentence “It remains ….”
L35 local-scale
L39 With this --> Radar provides
L45 due to multiple
L49 The statement “has been used … “ is very vague, maybe be a bit more specific.
L59 troughs
L119 Please specify in more detail the variable that hailcast stores at hourly intervals. Is it the mean, max or instantaneous hailstone size?
L131 is epsilon a function of height?
L150 Maybe add a sentence on the ability of RhighresD to capture convective precipitation? Local maxima could be missed due to too coarse station density.
L153 in-situ observations and remote radar-based observations
L167 crowd-sourced reports --> insurance loss reports
L169 delete “on the other side” since there is no matching on the one side
L169 in units of cm starting at 20mm :-)
L172 2009 -->2002
L186 we use data from
L200ff Please explain the calculation of tau in a bit more detail. Is dCAPE/dt a daily mean or daily max value?
L223 heavy --> severe
L255 near the mountainous region of central Europe --> a bit more specific?
L265 Please explain in a bit more detail how you compare across the different spatial resolutions and how sensitive the method is to the interpolation in space. I suggest adding 1 – 2 sentences of discussion.
L298 Note that the black forest is already quite far away from the radar, and the data quality may become an issue because the radar gates become very big and the lowest beam height is quite high. If you compare only within a 140km area around the radars, the radar quality should be very good.
L303 Please mention that both radar-based hail products only see hail in the air and not on the ground
L371 Please mention the time of the hailfall at the beginning of the case study description.
L380ff I do not yet fully get my head around the timing of the individual steps and the position of the cold front. You mention the advection of cold air; this would happen behind the cold front. But then you mention the increased dew point ahead of the cold front. It would be great to know where the front is, at which altitude, and at which time to get the full (complex) 4-D picture of the event.
L409 becomes warmer --> I do not see this; to me, the temperature near the surface looks colder at 00 UTC than at 12 UTC.
L418 Given the southeasterly flow --> this implies causality; please explain in more detail
L432 Please explain in a bit more detail why the stable was eroded by the upper-level westerly flow
L439 add not shown
L461 It is unclear to what “this” refers and what is meant by these kind of events (I think there is some grammatical confusion as to whether you mean the synoptically driven cases or not)
L471 three cases that were selected
L485 In this context … this statement is not very clear to me yet
Figure 1, caption four --> three
Figure 11 text says the sounding is at Payerne, but the figure title suggests the sounding is at Stuttgart.
Figure 11f Please add the borders of Switzerland.
Citation: https://doi.org/10.5194/wcd-2023-11-RC1 -
RC2: 'Comment on wcd-2023-11', Anonymous Referee #2, 07 Jun 2023
The comment was uploaded in the form of a supplement: https://wcd.copernicus.org/preprints/wcd-2023-11/wcd-2023-11-RC2-supplement.pdf
-
AC1: 'Comment on wcd-2023-11', Ruoyi Cui, 13 Aug 2023
The comment was uploaded in the form of a supplement: https://wcd.copernicus.org/preprints/wcd-2023-11/wcd-2023-11-AC1-supplement.pdf
Status: closed
-
RC1: 'Comment on wcd-2023-11', Olivia Martius, 31 May 2023
Exploring hail and lighting diagnostics over the Alpine-Adriatic region in a km-scale climate model
The study presents simulations of severe thunderstorms in the Alpine and Adriatic areas. The eight case studies are run with ERA-5 boundary conditions and initiated at 12 UTC of the previous day to allow for spin-up. The model simulations include, for the first time Hailcast and LPI diagnostics to identify and characterize hail and lightning over the study areas in Europe. The simulations are compared in detail to observations.
The paper is well-written, it is very well structured, and the figures are very clear and well-readable. The results are highly relevant, and the detailed process discussions are instructive and illustrate the diversity of thunderstorm environments in the complex topography. The paper is ready for publication after some minor revisions.
Kind regards
Olivia
Major point
L312ff I think that there is an issue with this comparison. If you compare two relative frequency distributions that both sum up to 1 for a variable that is expected to have an exponential distribution and one distribution starts at 0mm and one at 20mm, then by construction you will always find relatively fewer large values in the distribution that starts at 0mm. To check if this is true, you can artificially cut the model data at 20mm. Since the issue is not present in the comparison with the crowd-sourced reports, I suspect that your comparison improves a lot if you use only hailcast data of >=20mm.
Minor points:
L 20 e.g. Punge and Kunz …
L30 averaged --> average
L31 is located between
L33 A transition sentence is needed before the sentence “It remains ….”
L35 local-scale
L39 With this --> Radar provides
L45 due to multiple
L49 The statement “has been used … “ is very vague, maybe be a bit more specific.
L59 troughs
L119 Please specify in more detail the variable that hailcast stores at hourly intervals. Is it the mean, max or instantaneous hailstone size?
L131 is epsilon a function of height?
L150 Maybe add a sentence on the ability of RhighresD to capture convective precipitation? Local maxima could be missed due to too coarse station density.
L153 in-situ observations and remote radar-based observations
L167 crowd-sourced reports --> insurance loss reports
L169 delete “on the other side” since there is no matching on the one side
L169 in units of cm starting at 20mm :-)
L172 2009 -->2002
L186 we use data from
L200ff Please explain the calculation of tau in a bit more detail. Is dCAPE/dt a daily mean or daily max value?
L223 heavy --> severe
L255 near the mountainous region of central Europe --> a bit more specific?
L265 Please explain in a bit more detail how you compare across the different spatial resolutions and how sensitive the method is to the interpolation in space. I suggest adding 1 – 2 sentences of discussion.
L298 Note that the black forest is already quite far away from the radar, and the data quality may become an issue because the radar gates become very big and the lowest beam height is quite high. If you compare only within a 140km area around the radars, the radar quality should be very good.
L303 Please mention that both radar-based hail products only see hail in the air and not on the ground
L371 Please mention the time of the hailfall at the beginning of the case study description.
L380ff I do not yet fully get my head around the timing of the individual steps and the position of the cold front. You mention the advection of cold air; this would happen behind the cold front. But then you mention the increased dew point ahead of the cold front. It would be great to know where the front is, at which altitude, and at which time to get the full (complex) 4-D picture of the event.
L409 becomes warmer --> I do not see this; to me, the temperature near the surface looks colder at 00 UTC than at 12 UTC.
L418 Given the southeasterly flow --> this implies causality; please explain in more detail
L432 Please explain in a bit more detail why the stable was eroded by the upper-level westerly flow
L439 add not shown
L461 It is unclear to what “this” refers and what is meant by these kind of events (I think there is some grammatical confusion as to whether you mean the synoptically driven cases or not)
L471 three cases that were selected
L485 In this context … this statement is not very clear to me yet
Figure 1, caption four --> three
Figure 11 text says the sounding is at Payerne, but the figure title suggests the sounding is at Stuttgart.
Figure 11f Please add the borders of Switzerland.
Citation: https://doi.org/10.5194/wcd-2023-11-RC1 -
RC2: 'Comment on wcd-2023-11', Anonymous Referee #2, 07 Jun 2023
The comment was uploaded in the form of a supplement: https://wcd.copernicus.org/preprints/wcd-2023-11/wcd-2023-11-RC2-supplement.pdf
-
AC1: 'Comment on wcd-2023-11', Ruoyi Cui, 13 Aug 2023
The comment was uploaded in the form of a supplement: https://wcd.copernicus.org/preprints/wcd-2023-11/wcd-2023-11-AC1-supplement.pdf
Ruoyi Cui et al.
Ruoyi Cui et al.
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