the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Sep 2022
Gravity waves generated by the high graupel/hail loading through buoyancy oscillations in an overshooting hailstorm
Abstract. The convectively generated gravity waves (GWs) have important contributions on the stratospheric and mesospheric momentum and energy budget, and chemical composition, however, large uncertainties still remain about wave source properties and the associated wave-generated mechanisms. The formation mechanism and significant impacts of downward propagating GWs generated by a continental overshooting hailstorm occurred on 19 June 2017 in Beijing in the mid-latitude are reported in this study based on radar observations and simulated results from a three-dimensional cloud model with hail-bin microphysics. It is found that the overshooting storm penetrates the tropopause and enters the lower stratosphere in the mature stage. After the mature stage, the continuous descending process of the upper-level high graupel/hail loading causes the breaking of equilibrium between the buoyancy force and hydrometeor loading established in the mature stage and induces a restoring force of buoyancy, as well as buoyancy oscillations that excite downward propagating GWs. The GWs have a duration of about 20 min and the estimated wavelength of about 3–4 km. The downward propagating GWs not only result in the storm updraft splitting quickly, and significantly change the storm morphology and evolution, but also form the upward propagating GWs through surface reflection process, and induce strong vertical fluctuations in temperature and vertical velocity, and significantly change the dynamic and thermodynamic structure in the lower stratosphere.
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Interactive discussion
Status: closed
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RC1: 'Comment on acp-2022-559', Anonymous Referee #1, 11 Oct 2022
General comments:
This paper reproduces the gravity waves generated by graupel/hail loading in a hailstorm, which were captured by radar observations, in a numerical model and examines their generation, propagation, and impact on the storm and stratosphere. The mechanism of gravity wave generation, in which the vertical equilibrium is disrupted by graupel/hail loading, looks new and interesting to the reviewer. Although the paper describes gravity waves based on temperature, pressure, and vertical wind perturbations, it is unclear which variations in the figures are corresponding to gravity waves for the most part, and many of them do not establish phase relationships among temperature, pressure, and vertical wind. In addition, four types of gravity waves (upward-propagating, downward-propagating, reflected, and trapped) are described, but the authors do not specify on what basis they made such judgments. The figures are also difficult to read, which makes it difficult to judge whether the authors' claims are correct or not. For these reasons, we consider it appropriate to reject this paper.
Specific comments:
- 1. Introduction
There is too little information on past studies on convective GWs. For example, it should be described how convective GWs affect the stratosphere and/or the source storms more specifically. It should also be described how graupel/hail, the subject of this study, is or is not addressed in the past studies and what might change by considering graupel/hail. - 2.1 Data
Basic specifications of the radar such as station latitude/longitude, temporal/vertical resolutions, observation range in the vertical and horizontal, etc. are not described. There is no reference. - 2.2 The model
Is the method of giving the thermal bubble, its size and amplitude optimized? Are different values of each parameter tested? - Description of GWs
- L. 291-295, 296-298
Why can you say that the pressure and temperature perturbations are due to downward-propagating GWs? I cannot catch which part of the figure is the downward-propagating GWs. Please show the t-z section.
- L. 299-303
The previous sentences state that pressure perturbation is due to GWs, but is the background pressure perturbations here different from that? If so, what is it due to?
- L. 310-313
As mentioned above, it is impossible to tell if it is downward-propagating without looking at the t-z section.
- L. 320-328
Why can you say that these temperature and vertical wind perturbations were enhanced by GWs?
- L. 334-336
I do not understand which part of the figure you are referring to as upward-propagating GWs.
- L. 344-345
Why do you think that it is due to the effect of upward-propagating GWs?
- L. 347-348
Is the wavelike structure of vertical velocity different from the above-mentioned GWs?
- L. 363-367
Why does continuous descending excite gravity waves, and why do GWs split storms?
- L. 367-369
In which part of the figures are GW amplitudes and wavelengths shown?
- L. 387-389
There does not appear to be any indication that GWs cause storms to split.
- L. 398-408
Pressure and temperature perturbations have different structures. They do not look like due to the same GW.
- L. 434-443
I do not see a gravity wave structure in the figure. If there is also energy and momentum transport, it should be shown in the figure.
- Figures
- Which altitude range is the hodograph in Fig. 1?
- The subscripts in Figs. 2 and 4 are missing.
- What does "composite" mean in Fig. 2? Does it mean integrated in altitude? If not, which altitude is drawn?
- The latitude of xz-section on the right side of Fig. 2 should be given by a line on the left side.
- The longitude ranges shown in Figs. 2a2-e2 should be the same.
- The contour labels in Figs. 3-5 are too small to read.
- How were the environmental positive and negative temperatures obtained? Deviation from initial values?
- Why are the figures arranged differently in Figs. 4 and 5? - L. 175-176, 183-184
No southeastward extension is seen in Figs. 2b1 and 2c1. - L. 178-181
Please cite references that show a relationship between the magnitude of reflectivity and graupel/hail loading. - L. 239-240
“All modeled features are well consistent …” is an exaggeration. It is already split in the observation, but is not seen in Fig. 3c. Should be a correct description of what is consistent and what is not. - L. 285
“Perturbation” is perturbation from what? From the initial value? Explicitly state it. - L. 306-310
Why does a collapse of equilibrium cause a strong restoring force of buoyancy? Does it mean that the drag of the falling particles pulls on the surrounding air and the restoring force acts against it? - L. 433-434
I think that the cooled lower layer stabilize and do not rise.
Technical corrections:
- L. 81 and many places
Please replay “stratospheric atmosphere” by “stratosphere”. - L. 143 and many places
Please add “BST” after the time expression. - L. 273
Are graupel/hail mixing ratio and total hydrometeor mixing ratio the same or different? If they are the same, the same expression should be used. - L. 319
Which of vertical or horizontal does the wavelength mean?
Citation: https://doi.org/10.5194/acp-2022-559-RC1 -
AC1: 'Reply on RC1', Xueliang Guo, 18 Oct 2022
We appreciate your important and detailed comments. The main concerns raised by the reviewer have two aspects: one is that which variations of temperature, pressure, and vertical wind perturbations are corresponding to gravity waves. The other is the basis for the proposed gravity waves (upward-, downward-, reflected and trapped). The reasons that cause such confusions are largely due to that the important properties obtained by this paper are not clearly indicated on the relevant figures and in part due to unclear descriptions in the text. Therefore, we have carefully considered all comments. Some apparent indications added on the figures may help reviewer to catch significant features obtained in this study. More detailed and clearer descriptions are also added. All figures are revised to be clearer based on the comments.
Please find the detailed replies in an attached document in pdf version.
- 1. Introduction
-
RC2: 'Comment on acp-2022-559', Anonymous Referee #2, 20 Oct 2022
This paper presents results from a single mesoscale model simulation of a thunderstorm. In its present form, I do not think the paper sufficiently advances the state-of-the-art to warrant publication. My reasons are as follows.
- The model seems to be over two decades old. In the late ’90s, when many of the referenced articles were written, 3D mesoscale models had 1 to 2 km horizontal grids, 0.5 km vertical grids, 100 to 500 km horizontal domains, and vertical domains reaching the Stratopause. This model seems to belong to that family with a 35km horizontal domain. By comparison, the 2018 Muller et al. paper looks at convection-allowing simulations with a 5000km horizontal domain.
- It is not clear to me how the authors can confidently ascribe the downward propagating gravity waves to the novel process since the “buoyancy restoration force” occurs in the same area where the updraft overshoots the tropopause. I would have expected the authors to conduct a spectral analysis of the downward propagating gravity waves in order to identify clear distinguishing spectral properties (vertical and horizontal wavelengths and frequency) to associate with the length scales of the suggested originating process.
- The authors claim that it is necessary to understand these new waves because of the role they play in tropospheric dynamics. I do not see where the authors make the case for an important role for downward propagating waves. The only argument I discern is that these waves cause storm splitting. But storm splitting by downward propagating waves is argued based on the fact that the split occurs at a given time. This explanation is unsatisfying. Storm splitting is a common phenomenon. Is it always caused by downward propagating waves?
- As far as the upward propagating waves caused by reflection from the surface go, the authors claim that they “significantly change the dynamic and thermodynamic structure in the lower stratosphere”. I do not see that a significant effect was measured or even described. Did the waves break and deposit momentum?
Perhaps the authors could consider extending the physical and temporal domain of the simulation and produce a spectral analysis of the waves they detect in order to support their conclusions that a new generating process is being observed. They should also produce quantitative arguments that downward propagating GWs cause storm splitting, and that ground-reflected GWs have a significant effect on stratospheric dynamics.
Citation: https://doi.org/10.5194/acp-2022-559-RC2 -
AC2: 'Reply on RC2', Xueliang Guo, 21 Oct 2022
Comment on acp-2022-559
Anonymous Referee #2
This paper presents results from a single mesoscale model simulation of a thunderstorm. In its present form, I do not think the paper sufficiently advances the state-of-the-art to warrant publication. My reasons are as follows.Reply: Thank a lot for your important comments. We carefully consider all comments and reply as following.
The model seems to be over two decades old. In the late ’90s, when many of the referenced articles were written, 3D mesoscale models had 1 to 2 km horizontal grids, 0.5 km vertical grids, 100 to 500 km horizontal domains, and vertical domains reaching the Stratopause. This model seems to belong to that family with a 35km horizontal domain. By comparison, the 2018 Muller et al. paper looks at convection-allowing simulations with a 5000 km horizontal domain.
Reply: The main result in our study find that the upper-level high loading of graupel/hail can generate downward propagating gravity waves when descending rather than thermal or mechanical processes. It means that the model used for this purpose must have an ability to simulate hail and hailstorm in details.
Hail and hailstorms simulations are not available in most GCM models or climate models owing to that the inclusion of hail process in models not only require the high resolution but also need relevant physical processes. The very high terminal velocity for hail particles always causes stability problems. In our paper we use a hail-bin microphysics rather than hail parameterization scheme as used in most previous storm-scale models in order to appropriately simulate the hail falling process and associated gravity waves. For this purpose, the storm-scale high-resolution cloud models with detailed hail processes are the best choice for theoretically interpret the observed phenomenon.
Muller et al. (2018) conducted many sensitivity experiments to resolution for convection-allowing simulations, however, cloud water, cloud ice, snow and rainwater processes are included in their models but no hail process (Stevens et al., 2013; Satoh et al., 2014). Therefore, these models can be used for thermally or mechanically induced gravity waves in convection, and cannot be used for gravity waves generated by hailstorms as this study. It is not clear to me how the authors can confidently ascribe the downward propagating gravity waves to the novel process since the “buoyancy restoration force” occurs in the same area where the updraft overshoots the tropopause. I would have expected the authors to conduct a spectral analysis of the downward propagating gravity waves in order to identify clear distinguishing spectral properties (vertical and horizontal wavelengths and frequency) to associate with the length scales of the suggested originating process. The authors claim that it is necessary to understand these new waves because of the role they play in tropospheric dynamics. I do not see where the authors make the case for an important role for downward propagating waves. The only argument I discern is that these waves cause storm splitting. But storm splitting by downward propagating waves is argued based on the fact that the split occurs at a given time. This explanation is unsatisfying. Storm splitting is a common phenomenon. Is it always caused by downward propagating waves?
Reply: The main reason to ascribe the downward propagating gravity waves reported in this study to a novel process is that the downward gravity waves are generated by the hail process rather than thermal or mechanical forcing although the “buoyancy restoration force” induced by the descending of graupel/hail is similar to those induced by thermal and mechanical forcing （Fig.1）.
The upward propagating gravity waves are also generated by the storm top in the development stage for our simulated storm as reported in previous studies (Fig.2), however, the downward gravity waves generated by hail process occurs in the mature and decaying stages and the generation mechanisms are completely different from those found in previous studies.
To date, we found that the important role for the downward propagating gravity waves can cause the storm splitting rapidly (Fig.3), the issue is very important to the storm tracking and forecasting since the severe storms always cause significant damages to the public property. As you said, the storm splitting is a common phenomenon. The mechanisms that cause the storm splitting have been intensively investigated. The main mechanisms can be attributed to two aspects, one is related to interactions among wind shear, pressure perturbation and updraft development. The other is related to the precipitating-induced downdraft. We indicate that downward gravity waves generated by severe overshooting storm can be critical to storm splitting. However, issue relevant to storm splitting is not a main topic of this study.
For your suggestions to conduct spectral analysis in the downward propagating gravity waves, we will consider carefully. This study just physically interprets the generation process for gravity waves induced by a hailstorm and their potential impacts. The wave properties such as wave lengthen, duration and amplitude are estimated and found to be generally consistent with those found by previous studies. As far as the upward propagating waves caused by reflection from the surface go, the authors claim that they “significantly change the dynamic and thermodynamic structure in the lower stratosphere”. I do not see that a significant effect was measured or even described. Did the waves break and deposit momentum?
Reply: This phenomenon can be seen clearly when upward gravity waves reflected by the surface enter the stratosphere and induce strong fluctuations in temperature and vertical velocity (Fig.4-6). As you said, when upward gravity waves enter the stable stratosphere and they will deposit momentum and induce strong perturbations in temperature and vertical velocity, showing horizontal propagating gravity waves in the layer, and then breaking and decaying.
Perhaps the authors could consider extending the physical and temporal domain of the simulation and produce a spectral analysis of the waves they detect in order to support their conclusions that a new generating process is being observed. They should also produce quantitative arguments that downward propagating GWs cause storm splitting, and that ground-reflected GWs have a significant effect on stratospheric dynamics.
Reply: Thanks a lot for this final comment. As stated above, the storm-scale storm model with hail-bin microphysics is an appropriate choice to simulate the gravity waves generated by the upper-level high graupel/hail loading. We will further revise and improve our manuscript based on your important comments.
Please find attached document in pdf version for relevant descriptions and figures.
-
AC3: 'Reply on RC2', Xueliang Guo, 21 Oct 2022
Comment on acp-2022-559
Anonymous Referee #2
This paper presents results from a single mesoscale model simulation of a thunderstorm. In its present form, I do not think the paper sufficiently advances the state-of-the-art to warrant publication. My reasons are as follows.Reply: Thank a lot for your important comments. We carefully consider all comments and reply as following.
The model seems to be over two decades old. In the late ’90s, when many of the referenced articles were written, 3D mesoscale models had 1 to 2 km horizontal grids, 0.5 km vertical grids, 100 to 500 km horizontal domains, and vertical domains reaching the Stratopause. This model seems to belong to that family with a 35km horizontal domain. By comparison, the 2018 Muller et al. paper looks at convection-allowing simulations with a 5000 km horizontal domain.
Reply: The main result in our study find that the upper-level high loading of graupel/hail can generate downward propagating gravity waves when descending rather than thermal or mechanical processes. It means that the model used for this purpose must have an ability to simulate hail and hailstorm in details.
Hail and hailstorms simulations are not available in most GCM models or climate models owing to that the inclusion of hail process in models not only require the high resolution but also need relevant physical processes. The very high terminal velocity for hail particles always causes stability problems. In our paper we use a hail-bin microphysics rather than hail parameterization scheme as used in most previous storm-scale models in order to appropriately simulate the hail falling process and associated gravity waves. For this purpose, the storm-scale high-resolution cloud models with detailed hail processes are the best choice for theoretically interpret the observed phenomenon.
Muller et al. (2018) conducted many sensitivity experiments to resolution for convection-allowing simulations, however, cloud water, cloud ice, snow and rainwater processes are included in their models but no hail process (Stevens et al., 2013; Satoh et al., 2014). Therefore, these models can be used for thermally or mechanically induced gravity waves in convection, and cannot be used for gravity waves generated by hailstorms as this study. It is not clear to me how the authors can confidently ascribe the downward propagating gravity waves to the novel process since the “buoyancy restoration force” occurs in the same area where the updraft overshoots the tropopause. I would have expected the authors to conduct a spectral analysis of the downward propagating gravity waves in order to identify clear distinguishing spectral properties (vertical and horizontal wavelengths and frequency) to associate with the length scales of the suggested originating process. The authors claim that it is necessary to understand these new waves because of the role they play in tropospheric dynamics. I do not see where the authors make the case for an important role for downward propagating waves. The only argument I discern is that these waves cause storm splitting. But storm splitting by downward propagating waves is argued based on the fact that the split occurs at a given time. This explanation is unsatisfying. Storm splitting is a common phenomenon. Is it always caused by downward propagating waves?
Reply: The main reason to ascribe the downward propagating gravity waves reported in this study to a novel process is that the downward gravity waves are generated by the hail process rather than thermal or mechanical forcing although the “buoyancy restoration force” induced by the descending of graupel/hail is similar to those induced by thermal and mechanical forcing （Fig.1）.
The upward propagating gravity waves are also generated by the storm top in the development stage for our simulated storm as reported in previous studies (Fig.2), however, the downward gravity waves generated by hail process occurs in the mature and decaying stages and the generation mechanisms are completely different from those found in previous studies.
To date, we found that the important role for the downward propagating gravity waves can cause the storm splitting rapidly (Fig.3), the issue is very important to the storm tracking and forecasting since the severe storms always cause significant damages to the public property. As you said, the storm splitting is a common phenomenon. The mechanisms that cause the storm splitting have been intensively investigated. The main mechanisms can be attributed to two aspects, one is related to interactions among wind shear, pressure perturbation and updraft development. The other is related to the precipitating-induced downdraft. We indicate that downward gravity waves generated by severe overshooting storm can be critical to storm splitting. However, issue relevant to storm splitting is not a main topic of this study.
For your suggestions to conduct spectral analysis in the downward propagating gravity waves, we will consider carefully. This study just physically interprets the generation process for gravity waves induced by a hailstorm and their potential impacts. The wave properties such as wave lengthen, duration and amplitude are estimated and found to be generally consistent with those found by previous studies. As far as the upward propagating waves caused by reflection from the surface go, the authors claim that they “significantly change the dynamic and thermodynamic structure in the lower stratosphere”. I do not see that a significant effect was measured or even described. Did the waves break and deposit momentum?
Reply: This phenomenon can be seen clearly when upward gravity waves reflected by the surface enter the stratosphere and induce strong fluctuations in temperature and vertical velocity (Fig.4-6). As you said, when upward gravity waves enter the stable stratosphere and they will deposit momentum and induce strong perturbations in temperature and vertical velocity, showing horizontal propagating gravity waves in the layer, and then breaking and decaying.
Perhaps the authors could consider extending the physical and temporal domain of the simulation and produce a spectral analysis of the waves they detect in order to support their conclusions that a new generating process is being observed. They should also produce quantitative arguments that downward propagating GWs cause storm splitting, and that ground-reflected GWs have a significant effect on stratospheric dynamics.
Reply: Thanks a lot for this final comment. As stated above, the storm-scale storm model with hail-bin microphysics is an appropriate choice to simulate the gravity waves generated by the upper-level high graupel/hail loading. We will further revise and improve our manuscript based on your important comments.
Please find attached document in pdf version for relevant descriptions and figures.
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EC1: 'Comment on acp-2022-559', Heini Wernli, 26 Oct 2022
As you have seen, both reviewers are very critical about the quality of your study. They both regard the scientific significance and scientific quality as “low”, they both recommend rejecting the paper for publication, and they both would not be willing to review a potentially revised manuscript. The reviewers, who are both experts on gravity waves and deep convective storms, are in particular critical about the model used, the gravity wave diagnostics, and the general quality of the figures. Both reviewers don’t see the conclusions supported by the analyses shown in the paper. I agree with their serious concerns and, also after reading your short reply documents, I suggest that you don’t upload a revised manuscript. Instead, my suggestion is that you withdraw this paper and invest more time to consider doing higher-resolution simulations and certainly more convincing gravity wave diagnostics. I also invite you to consider submitting your study to a different journal. ACP does not have a strong record on papers about hailstorms. Many papers you referenced were published in the Journal of Atmospheric Science, and maybe this journal would be more appropriate for your work.
Citation: https://doi.org/10.5194/acp-2022-559-EC1 -
AC4: 'Reply on EC1', Xueliang Guo, 27 Oct 2022
Dear Editor, Dr. Heini Wernli
Thank you very much for your comments and suggestions.
By this chance, we like to express our sincere thanks to ACP editorial team for their excellent work. We will accept your suggestions and withdraw our manuscript from ACP. After adding our manuscript in spectral analysis of gravity waves, we like to submit the revised manuscript to other journals which might be more suitable for relevant studies in hailstorms. We also feel that our manuscript is weak in spectral analysis, which should be important to understand the properties of gravity waves found in our study.
Best regards,
Xueliang Guo, on behalf of all authors.
Citation: https://doi.org/10.5194/acp-2022-559-AC4
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AC4: 'Reply on EC1', Xueliang Guo, 27 Oct 2022
Interactive discussion
Status: closed
-
RC1: 'Comment on acp-2022-559', Anonymous Referee #1, 11 Oct 2022
General comments:
This paper reproduces the gravity waves generated by graupel/hail loading in a hailstorm, which were captured by radar observations, in a numerical model and examines their generation, propagation, and impact on the storm and stratosphere. The mechanism of gravity wave generation, in which the vertical equilibrium is disrupted by graupel/hail loading, looks new and interesting to the reviewer. Although the paper describes gravity waves based on temperature, pressure, and vertical wind perturbations, it is unclear which variations in the figures are corresponding to gravity waves for the most part, and many of them do not establish phase relationships among temperature, pressure, and vertical wind. In addition, four types of gravity waves (upward-propagating, downward-propagating, reflected, and trapped) are described, but the authors do not specify on what basis they made such judgments. The figures are also difficult to read, which makes it difficult to judge whether the authors' claims are correct or not. For these reasons, we consider it appropriate to reject this paper.
Specific comments:
- 1. Introduction
There is too little information on past studies on convective GWs. For example, it should be described how convective GWs affect the stratosphere and/or the source storms more specifically. It should also be described how graupel/hail, the subject of this study, is or is not addressed in the past studies and what might change by considering graupel/hail. - 2.1 Data
Basic specifications of the radar such as station latitude/longitude, temporal/vertical resolutions, observation range in the vertical and horizontal, etc. are not described. There is no reference. - 2.2 The model
Is the method of giving the thermal bubble, its size and amplitude optimized? Are different values of each parameter tested? - Description of GWs
- L. 291-295, 296-298
Why can you say that the pressure and temperature perturbations are due to downward-propagating GWs? I cannot catch which part of the figure is the downward-propagating GWs. Please show the t-z section.
- L. 299-303
The previous sentences state that pressure perturbation is due to GWs, but is the background pressure perturbations here different from that? If so, what is it due to?
- L. 310-313
As mentioned above, it is impossible to tell if it is downward-propagating without looking at the t-z section.
- L. 320-328
Why can you say that these temperature and vertical wind perturbations were enhanced by GWs?
- L. 334-336
I do not understand which part of the figure you are referring to as upward-propagating GWs.
- L. 344-345
Why do you think that it is due to the effect of upward-propagating GWs?
- L. 347-348
Is the wavelike structure of vertical velocity different from the above-mentioned GWs?
- L. 363-367
Why does continuous descending excite gravity waves, and why do GWs split storms?
- L. 367-369
In which part of the figures are GW amplitudes and wavelengths shown?
- L. 387-389
There does not appear to be any indication that GWs cause storms to split.
- L. 398-408
Pressure and temperature perturbations have different structures. They do not look like due to the same GW.
- L. 434-443
I do not see a gravity wave structure in the figure. If there is also energy and momentum transport, it should be shown in the figure.
- Figures
- Which altitude range is the hodograph in Fig. 1?
- The subscripts in Figs. 2 and 4 are missing.
- What does "composite" mean in Fig. 2? Does it mean integrated in altitude? If not, which altitude is drawn?
- The latitude of xz-section on the right side of Fig. 2 should be given by a line on the left side.
- The longitude ranges shown in Figs. 2a2-e2 should be the same.
- The contour labels in Figs. 3-5 are too small to read.
- How were the environmental positive and negative temperatures obtained? Deviation from initial values?
- Why are the figures arranged differently in Figs. 4 and 5? - L. 175-176, 183-184
No southeastward extension is seen in Figs. 2b1 and 2c1. - L. 178-181
Please cite references that show a relationship between the magnitude of reflectivity and graupel/hail loading. - L. 239-240
“All modeled features are well consistent …” is an exaggeration. It is already split in the observation, but is not seen in Fig. 3c. Should be a correct description of what is consistent and what is not. - L. 285
“Perturbation” is perturbation from what? From the initial value? Explicitly state it. - L. 306-310
Why does a collapse of equilibrium cause a strong restoring force of buoyancy? Does it mean that the drag of the falling particles pulls on the surrounding air and the restoring force acts against it? - L. 433-434
I think that the cooled lower layer stabilize and do not rise.
Technical corrections:
- L. 81 and many places
Please replay “stratospheric atmosphere” by “stratosphere”. - L. 143 and many places
Please add “BST” after the time expression. - L. 273
Are graupel/hail mixing ratio and total hydrometeor mixing ratio the same or different? If they are the same, the same expression should be used. - L. 319
Which of vertical or horizontal does the wavelength mean?
Citation: https://doi.org/10.5194/acp-2022-559-RC1 -
AC1: 'Reply on RC1', Xueliang Guo, 18 Oct 2022
We appreciate your important and detailed comments. The main concerns raised by the reviewer have two aspects: one is that which variations of temperature, pressure, and vertical wind perturbations are corresponding to gravity waves. The other is the basis for the proposed gravity waves (upward-, downward-, reflected and trapped). The reasons that cause such confusions are largely due to that the important properties obtained by this paper are not clearly indicated on the relevant figures and in part due to unclear descriptions in the text. Therefore, we have carefully considered all comments. Some apparent indications added on the figures may help reviewer to catch significant features obtained in this study. More detailed and clearer descriptions are also added. All figures are revised to be clearer based on the comments.
Please find the detailed replies in an attached document in pdf version.
- 1. Introduction
-
RC2: 'Comment on acp-2022-559', Anonymous Referee #2, 20 Oct 2022
This paper presents results from a single mesoscale model simulation of a thunderstorm. In its present form, I do not think the paper sufficiently advances the state-of-the-art to warrant publication. My reasons are as follows.
- The model seems to be over two decades old. In the late ’90s, when many of the referenced articles were written, 3D mesoscale models had 1 to 2 km horizontal grids, 0.5 km vertical grids, 100 to 500 km horizontal domains, and vertical domains reaching the Stratopause. This model seems to belong to that family with a 35km horizontal domain. By comparison, the 2018 Muller et al. paper looks at convection-allowing simulations with a 5000km horizontal domain.
- It is not clear to me how the authors can confidently ascribe the downward propagating gravity waves to the novel process since the “buoyancy restoration force” occurs in the same area where the updraft overshoots the tropopause. I would have expected the authors to conduct a spectral analysis of the downward propagating gravity waves in order to identify clear distinguishing spectral properties (vertical and horizontal wavelengths and frequency) to associate with the length scales of the suggested originating process.
- The authors claim that it is necessary to understand these new waves because of the role they play in tropospheric dynamics. I do not see where the authors make the case for an important role for downward propagating waves. The only argument I discern is that these waves cause storm splitting. But storm splitting by downward propagating waves is argued based on the fact that the split occurs at a given time. This explanation is unsatisfying. Storm splitting is a common phenomenon. Is it always caused by downward propagating waves?
- As far as the upward propagating waves caused by reflection from the surface go, the authors claim that they “significantly change the dynamic and thermodynamic structure in the lower stratosphere”. I do not see that a significant effect was measured or even described. Did the waves break and deposit momentum?
Perhaps the authors could consider extending the physical and temporal domain of the simulation and produce a spectral analysis of the waves they detect in order to support their conclusions that a new generating process is being observed. They should also produce quantitative arguments that downward propagating GWs cause storm splitting, and that ground-reflected GWs have a significant effect on stratospheric dynamics.
Citation: https://doi.org/10.5194/acp-2022-559-RC2 -
AC2: 'Reply on RC2', Xueliang Guo, 21 Oct 2022
Comment on acp-2022-559
Anonymous Referee #2
This paper presents results from a single mesoscale model simulation of a thunderstorm. In its present form, I do not think the paper sufficiently advances the state-of-the-art to warrant publication. My reasons are as follows.Reply: Thank a lot for your important comments. We carefully consider all comments and reply as following.
The model seems to be over two decades old. In the late ’90s, when many of the referenced articles were written, 3D mesoscale models had 1 to 2 km horizontal grids, 0.5 km vertical grids, 100 to 500 km horizontal domains, and vertical domains reaching the Stratopause. This model seems to belong to that family with a 35km horizontal domain. By comparison, the 2018 Muller et al. paper looks at convection-allowing simulations with a 5000 km horizontal domain.
Reply: The main result in our study find that the upper-level high loading of graupel/hail can generate downward propagating gravity waves when descending rather than thermal or mechanical processes. It means that the model used for this purpose must have an ability to simulate hail and hailstorm in details.
Hail and hailstorms simulations are not available in most GCM models or climate models owing to that the inclusion of hail process in models not only require the high resolution but also need relevant physical processes. The very high terminal velocity for hail particles always causes stability problems. In our paper we use a hail-bin microphysics rather than hail parameterization scheme as used in most previous storm-scale models in order to appropriately simulate the hail falling process and associated gravity waves. For this purpose, the storm-scale high-resolution cloud models with detailed hail processes are the best choice for theoretically interpret the observed phenomenon.
Muller et al. (2018) conducted many sensitivity experiments to resolution for convection-allowing simulations, however, cloud water, cloud ice, snow and rainwater processes are included in their models but no hail process (Stevens et al., 2013; Satoh et al., 2014). Therefore, these models can be used for thermally or mechanically induced gravity waves in convection, and cannot be used for gravity waves generated by hailstorms as this study. It is not clear to me how the authors can confidently ascribe the downward propagating gravity waves to the novel process since the “buoyancy restoration force” occurs in the same area where the updraft overshoots the tropopause. I would have expected the authors to conduct a spectral analysis of the downward propagating gravity waves in order to identify clear distinguishing spectral properties (vertical and horizontal wavelengths and frequency) to associate with the length scales of the suggested originating process. The authors claim that it is necessary to understand these new waves because of the role they play in tropospheric dynamics. I do not see where the authors make the case for an important role for downward propagating waves. The only argument I discern is that these waves cause storm splitting. But storm splitting by downward propagating waves is argued based on the fact that the split occurs at a given time. This explanation is unsatisfying. Storm splitting is a common phenomenon. Is it always caused by downward propagating waves?
Reply: The main reason to ascribe the downward propagating gravity waves reported in this study to a novel process is that the downward gravity waves are generated by the hail process rather than thermal or mechanical forcing although the “buoyancy restoration force” induced by the descending of graupel/hail is similar to those induced by thermal and mechanical forcing （Fig.1）.
The upward propagating gravity waves are also generated by the storm top in the development stage for our simulated storm as reported in previous studies (Fig.2), however, the downward gravity waves generated by hail process occurs in the mature and decaying stages and the generation mechanisms are completely different from those found in previous studies.
To date, we found that the important role for the downward propagating gravity waves can cause the storm splitting rapidly (Fig.3), the issue is very important to the storm tracking and forecasting since the severe storms always cause significant damages to the public property. As you said, the storm splitting is a common phenomenon. The mechanisms that cause the storm splitting have been intensively investigated. The main mechanisms can be attributed to two aspects, one is related to interactions among wind shear, pressure perturbation and updraft development. The other is related to the precipitating-induced downdraft. We indicate that downward gravity waves generated by severe overshooting storm can be critical to storm splitting. However, issue relevant to storm splitting is not a main topic of this study.
For your suggestions to conduct spectral analysis in the downward propagating gravity waves, we will consider carefully. This study just physically interprets the generation process for gravity waves induced by a hailstorm and their potential impacts. The wave properties such as wave lengthen, duration and amplitude are estimated and found to be generally consistent with those found by previous studies. As far as the upward propagating waves caused by reflection from the surface go, the authors claim that they “significantly change the dynamic and thermodynamic structure in the lower stratosphere”. I do not see that a significant effect was measured or even described. Did the waves break and deposit momentum?
Reply: This phenomenon can be seen clearly when upward gravity waves reflected by the surface enter the stratosphere and induce strong fluctuations in temperature and vertical velocity (Fig.4-6). As you said, when upward gravity waves enter the stable stratosphere and they will deposit momentum and induce strong perturbations in temperature and vertical velocity, showing horizontal propagating gravity waves in the layer, and then breaking and decaying.
Perhaps the authors could consider extending the physical and temporal domain of the simulation and produce a spectral analysis of the waves they detect in order to support their conclusions that a new generating process is being observed. They should also produce quantitative arguments that downward propagating GWs cause storm splitting, and that ground-reflected GWs have a significant effect on stratospheric dynamics.
Reply: Thanks a lot for this final comment. As stated above, the storm-scale storm model with hail-bin microphysics is an appropriate choice to simulate the gravity waves generated by the upper-level high graupel/hail loading. We will further revise and improve our manuscript based on your important comments.
Please find attached document in pdf version for relevant descriptions and figures.
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AC3: 'Reply on RC2', Xueliang Guo, 21 Oct 2022
Comment on acp-2022-559
Anonymous Referee #2
This paper presents results from a single mesoscale model simulation of a thunderstorm. In its present form, I do not think the paper sufficiently advances the state-of-the-art to warrant publication. My reasons are as follows.Reply: Thank a lot for your important comments. We carefully consider all comments and reply as following.
The model seems to be over two decades old. In the late ’90s, when many of the referenced articles were written, 3D mesoscale models had 1 to 2 km horizontal grids, 0.5 km vertical grids, 100 to 500 km horizontal domains, and vertical domains reaching the Stratopause. This model seems to belong to that family with a 35km horizontal domain. By comparison, the 2018 Muller et al. paper looks at convection-allowing simulations with a 5000 km horizontal domain.
Reply: The main result in our study find that the upper-level high loading of graupel/hail can generate downward propagating gravity waves when descending rather than thermal or mechanical processes. It means that the model used for this purpose must have an ability to simulate hail and hailstorm in details.
Hail and hailstorms simulations are not available in most GCM models or climate models owing to that the inclusion of hail process in models not only require the high resolution but also need relevant physical processes. The very high terminal velocity for hail particles always causes stability problems. In our paper we use a hail-bin microphysics rather than hail parameterization scheme as used in most previous storm-scale models in order to appropriately simulate the hail falling process and associated gravity waves. For this purpose, the storm-scale high-resolution cloud models with detailed hail processes are the best choice for theoretically interpret the observed phenomenon.
Muller et al. (2018) conducted many sensitivity experiments to resolution for convection-allowing simulations, however, cloud water, cloud ice, snow and rainwater processes are included in their models but no hail process (Stevens et al., 2013; Satoh et al., 2014). Therefore, these models can be used for thermally or mechanically induced gravity waves in convection, and cannot be used for gravity waves generated by hailstorms as this study. It is not clear to me how the authors can confidently ascribe the downward propagating gravity waves to the novel process since the “buoyancy restoration force” occurs in the same area where the updraft overshoots the tropopause. I would have expected the authors to conduct a spectral analysis of the downward propagating gravity waves in order to identify clear distinguishing spectral properties (vertical and horizontal wavelengths and frequency) to associate with the length scales of the suggested originating process. The authors claim that it is necessary to understand these new waves because of the role they play in tropospheric dynamics. I do not see where the authors make the case for an important role for downward propagating waves. The only argument I discern is that these waves cause storm splitting. But storm splitting by downward propagating waves is argued based on the fact that the split occurs at a given time. This explanation is unsatisfying. Storm splitting is a common phenomenon. Is it always caused by downward propagating waves?
Reply: The main reason to ascribe the downward propagating gravity waves reported in this study to a novel process is that the downward gravity waves are generated by the hail process rather than thermal or mechanical forcing although the “buoyancy restoration force” induced by the descending of graupel/hail is similar to those induced by thermal and mechanical forcing （Fig.1）.
The upward propagating gravity waves are also generated by the storm top in the development stage for our simulated storm as reported in previous studies (Fig.2), however, the downward gravity waves generated by hail process occurs in the mature and decaying stages and the generation mechanisms are completely different from those found in previous studies.
To date, we found that the important role for the downward propagating gravity waves can cause the storm splitting rapidly (Fig.3), the issue is very important to the storm tracking and forecasting since the severe storms always cause significant damages to the public property. As you said, the storm splitting is a common phenomenon. The mechanisms that cause the storm splitting have been intensively investigated. The main mechanisms can be attributed to two aspects, one is related to interactions among wind shear, pressure perturbation and updraft development. The other is related to the precipitating-induced downdraft. We indicate that downward gravity waves generated by severe overshooting storm can be critical to storm splitting. However, issue relevant to storm splitting is not a main topic of this study.
For your suggestions to conduct spectral analysis in the downward propagating gravity waves, we will consider carefully. This study just physically interprets the generation process for gravity waves induced by a hailstorm and their potential impacts. The wave properties such as wave lengthen, duration and amplitude are estimated and found to be generally consistent with those found by previous studies. As far as the upward propagating waves caused by reflection from the surface go, the authors claim that they “significantly change the dynamic and thermodynamic structure in the lower stratosphere”. I do not see that a significant effect was measured or even described. Did the waves break and deposit momentum?
Reply: This phenomenon can be seen clearly when upward gravity waves reflected by the surface enter the stratosphere and induce strong fluctuations in temperature and vertical velocity (Fig.4-6). As you said, when upward gravity waves enter the stable stratosphere and they will deposit momentum and induce strong perturbations in temperature and vertical velocity, showing horizontal propagating gravity waves in the layer, and then breaking and decaying.
Perhaps the authors could consider extending the physical and temporal domain of the simulation and produce a spectral analysis of the waves they detect in order to support their conclusions that a new generating process is being observed. They should also produce quantitative arguments that downward propagating GWs cause storm splitting, and that ground-reflected GWs have a significant effect on stratospheric dynamics.
Reply: Thanks a lot for this final comment. As stated above, the storm-scale storm model with hail-bin microphysics is an appropriate choice to simulate the gravity waves generated by the upper-level high graupel/hail loading. We will further revise and improve our manuscript based on your important comments.
Please find attached document in pdf version for relevant descriptions and figures.
-
EC1: 'Comment on acp-2022-559', Heini Wernli, 26 Oct 2022
As you have seen, both reviewers are very critical about the quality of your study. They both regard the scientific significance and scientific quality as “low”, they both recommend rejecting the paper for publication, and they both would not be willing to review a potentially revised manuscript. The reviewers, who are both experts on gravity waves and deep convective storms, are in particular critical about the model used, the gravity wave diagnostics, and the general quality of the figures. Both reviewers don’t see the conclusions supported by the analyses shown in the paper. I agree with their serious concerns and, also after reading your short reply documents, I suggest that you don’t upload a revised manuscript. Instead, my suggestion is that you withdraw this paper and invest more time to consider doing higher-resolution simulations and certainly more convincing gravity wave diagnostics. I also invite you to consider submitting your study to a different journal. ACP does not have a strong record on papers about hailstorms. Many papers you referenced were published in the Journal of Atmospheric Science, and maybe this journal would be more appropriate for your work.
Citation: https://doi.org/10.5194/acp-2022-559-EC1 -
AC4: 'Reply on EC1', Xueliang Guo, 27 Oct 2022
Dear Editor, Dr. Heini Wernli
Thank you very much for your comments and suggestions.
By this chance, we like to express our sincere thanks to ACP editorial team for their excellent work. We will accept your suggestions and withdraw our manuscript from ACP. After adding our manuscript in spectral analysis of gravity waves, we like to submit the revised manuscript to other journals which might be more suitable for relevant studies in hailstorms. We also feel that our manuscript is weak in spectral analysis, which should be important to understand the properties of gravity waves found in our study.
Best regards,
Xueliang Guo, on behalf of all authors.
Citation: https://doi.org/10.5194/acp-2022-559-AC4
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AC4: 'Reply on EC1', Xueliang Guo, 27 Oct 2022
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