Evaluation of hygroscopic cloud seeding in warm rain process by a hybrid microphysics scheme on WRF model: a real case study

Lin, Kai-I; Chung, Kao-Shen; Wang, Sheng-Hsiang; Chen, Li-Hsin; Liou, Yu-Chieng; Lin, Pay-Liam; Chang, Wei-Yu; Chiu, Hsien-Jung; Chang, Yi-Hui

doi:https://doi.org/10.5194/egusphere-2023-573

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https://doi.org/10.5194/egusphere-2023-573

Preprints

20 Apr 2023

| 20 Apr 2023

Evaluation of hygroscopic cloud seeding in warm rain process by a hybrid microphysics scheme on WRF model: a real case study

Kai-I Lin, Kao-Shen Chung, Sheng-Hsiang Wang, Li-Hsin Chen, Yu-Chieng Liou, Pay-Liam Lin, Wei-Yu Chang, Hsien-Jung Chiu, and Yi-Hui Chang

Abstract. To evaluate the hygroscopic cloud seeding in reality, this study develops a hybrid microphysics scheme on WRF model, WDM6–NCU, which involves 43 bins of seeded cloud condensation nuclei (CCN) in the WDM6 bulk method scheme. This scheme can describe the size distribution of seeded CCNs and explain the process of the CCN imbedding, cloud and raindrop formation in detail. Furthermore, based on the observational CCN size distribution applied in the modelling, a series of tests on cloud seeding was conducted during the seeding periods of 21–22 October, 2020 with stratocumulus clouds. The model simulation results reveal that seeding at in-cloud regions with an appropriate CCN size distribution can yield greater rainfall and that spreading the seeding agents over an area of 40–60 km² is the most efficient strategy to create a sufficient precipitation rate. With regard to the microphysical processes, the main process that causes the enhancement of precipitation is the strengthening of the accretion process of raindrops. In addition, hygroscopic particles larger than 0.4 μm primarily contribute to cloud-seeding effects. The study results could be used as references for model development and warm cloud seeding operations.

Received: 25 Mar 2023 – Discussion started: 20 Apr 2023

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Journal article(s) based on this preprint

20 Sep 2023

Evaluation of hygroscopic cloud seeding in warm-rain processes by a hybrid microphysics scheme using a Weather Research and Forecasting (WRF) model: a real case study

Kai-I Lin, Kao-Shen Chung, Sheng-Hsiang Wang, Li-Hsin Chen, Yu-Chieng Liou, Pay-Liam Lin, Wei-Yu Chang, Hsien-Jung Chiu, and Yi-Hui Chang

Atmos. Chem. Phys., 23, 10423–10438, https://doi.org/10.5194/acp-23-10423-2023,https://doi.org/10.5194/acp-23-10423-2023, 2023

Short summary

Kai-I Lin et al.

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-573', Anonymous Referee #1, 05 May 2023
This research incorporates a bin method into a bulk microphysical scheme (WDM) to calculate the warm rain process and uses this scheme to investigate the warm rain seeding effect through several sensitivity experiments. I suggest that the authors should provide more information about this new scheme.
Line 625: “The WRF model employs … the third-order Runger-Kutta numerical method for solving the time split integration of the governing equation”. In fact, the third Ruger-Kutta method is just an option in the namelist. input, you can also choose the fifth-order one, so it is not “The WRF model employs”, but you choose this third-order method. Please reword.

Line 98: “the bins of CCNs whose size extends the critical radius will be able to activate the corresponding liquid bins”, How to understand “corresponding liquid bins”? I feel that the WDM-NCU scheme has not been introduced in detail in this manuscript. What is the size range of the 43 bins? Which microphysics processes are calculated in this bin scheme? Can this scheme reflect the fact that large CCN becomes large cloud droplets? How does the scheme deal with the coupling of the bin part and bulk part?

Line 102: “After the number concentration and mixing ratio of the liquid bins is calculated, they are used in the calculation of the mixing ratio and number concentration of cloud and rain, and the microphysics processes continue as is the case in the original WDM6”. Do you mean that the bin part of the WDM-NCU scheme only calculates the nucleation process? How do you separate the cloud and rain categories from the liquid bins? The authors have to provide more information.

Fig. 5 The simulated accumulated precipitation comes from which domain? Is the horizontal space resolution close to the observed data?

Fig. 6 What is RCWF and RCSL? They have not been explained in the manuscript. And which are observed data and which are simulated results?

Fig. 7, I suggest to depict the simulated results using dashed lines and put them over the observed data. So that only three 3 subplots are needed. And the Dongyan Mountain site should be plotted in Fig. 3 (or 5, 6).

Fig. 8: Observation or simulation?

Where are the seeding points or areas when you seed in 1km², 10km², and 100km²? These seeding points should be plotted. The seeding effects should also be shown in horizontal shadow figures, not just be plotted in lines as in Figs 9 and 10. And how much sea salt is seeded?

Line 240: Why do you say seeding in such large area (100 km²) at 500 m is “impractical and ineffective” but at the same time seeding in 100 km2 at 1300 m is “more suitable”? I think both of them are impractical.

Fig. 13, Why Praut increases in seed_500(100 km2) but Qr does not increase as shown in Fig.11 g, h.

Fig. 15, Why the units of dN/dlog(D) is %？

Line 261: Why do you think when the seeding area is larger than 64km2, the Shihmen region no longer has plenty of cloud water to transform to precipitation？ Is there any evidence supporting your conclusion？ Didn’t you say that seeding leads to an increase in Qc in 10 min?
Citation: https://doi.org/10.5194/egusphere-2023-573-RC1
- AC1: 'Reply on RC1', Kao-Shen Chung, 19 May 2023
  
  We greatly appreciate the care taken by the reviewer in evaluating the manuscript. We believe the actions we have taken to address the comments have substantially strengthened the revision of the manuscript. Our bolded responses appear below the reviewer comments.
  
  Citation: https://doi.org/10.5194/egusphere-2023-573-AC1
CC1:
'Comment on egusphere-2023-573', Tian Xian, 26 Jun 2023
The manuscript “ Evaluation of hygroscopic cloud seeding in warm rain process by a hybrid microphysics scheme on WRF model: a real case study” develops a hybrid cloud-seeding microphysics scheme and selects a case with optimal model performance and a typical weather condition in northern Taiwan to conduct a series of cloud-seeding sensitivity tests. The results show that seeding at in-cloud regions with an appropriate CCN size distribution can yield greater rainfall and that spreading the seeding agents over an area of 40–60 km² is the most efficient strategy to create a sufficient 15 precipitation rate. Overall, this is an interesting study that has the potential to advance our understanding of the evaluation of hygroscopic cloud seeding and may be of interest to ACP readers.
However, there are several issues to address before the paper is suitable to publication in ACP. Thus, I suggest minor revision before publication.
Major comments:
It is suggested that the horizontal resolution of Large eddy simulation should be below 100m, and the horizontal and vertical resolution below the PBLH should be nearly equal. Therefore, the LES resolution of this manuscript needs to be reconsidered, unless it is well justified.

As mentioned in the manuscript, the environment is crucial for cloud seeding. However, this manuscript only discusses saturation and does not delve into the discussion of the environment. Meanwhile, it only simulates a real case, so whether this conclusion has universality remains to be discussed.

Minor comments:
Lack of discussion and comparison with existing relevant research, some comparisons can be added in the introduction or discussion section to highlight the findings of this manuscript

L30: consider whether there are recent references supporting this phenomenon

L70: Suggest not adding references in the title

It is recommended to merge Figures 7a and b for comparison purposes

Figure 7: The horizontal axis does not appear to be a font

Figure 8: “Lontitude”“Longitude”

Figure 14: maintaining a unified time zone for the entire manuscript
Citation: https://doi.org/10.5194/egusphere-2023-573-CC1
RC2:
'Comment on egusphere-2023-573', Anonymous Referee #3, 06 Jul 2023
The manuscript “ Evaluation of hygroscopic cloud seeding in warm rain process by a hybrid microphysics scheme on WRF model: a real case study” develops a hybrid cloud-seeding microphysics scheme and selects a case with optimal model performance and a typical weather condition in northern Taiwan to conduct a series of cloud-seeding sensitivity tests. The results show that seeding at in-cloud regions with an appropriate CCN size distribution can yield greater rainfall and that spreading the seeding agents over an area of 40–60 km² is the most efficient strategy to create a sufficient 15 precipitation rate. Overall, this is an interesting study that has the potential to advance our understanding of the evaluation of hygroscopic cloud seeding and may be of interest to ACP readers.
However, there are several issues to address before the paper is suitable to publication in ACP. Thus, I suggest minor revision before publication.
Major comments:
It is suggested that the horizontal resolution of Large eddy simulation should be below 100m, and the horizontal and vertical resolution below the PBLH should be nearly equal. Therefore, the LES resolution of this manuscript needs to be reconsidered, unless it is well justified.

As mentioned in the manuscript, the environment is crucial for cloud seeding. However, this manuscript only discusses saturation and does not delve into the discussion of the environment. Meanwhile, it only simulates a real case, so whether this conclusion has universality remains to be discussed.

Minor comments:
Lack of discussion and comparison with existing relevant research, some comparisons can be added in the introduction or discussion section to highlight the findings of this manuscript

L30: consider whether there are recent references supporting this phenomenon

L70: Suggest not adding references in the title

It is recommended to merge Figures 7a and b for comparison purposes

Figure 7: The horizontal axis does not appear to be a font

Figure 8: “Lontitude”“Longitude”

Figure 14: maintaining a unified time zone for the entire manuscript
Citation: https://doi.org/10.5194/egusphere-2023-573-RC2

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-573', Anonymous Referee #1, 05 May 2023
This research incorporates a bin method into a bulk microphysical scheme (WDM) to calculate the warm rain process and uses this scheme to investigate the warm rain seeding effect through several sensitivity experiments. I suggest that the authors should provide more information about this new scheme.
Line 625: “The WRF model employs … the third-order Runger-Kutta numerical method for solving the time split integration of the governing equation”. In fact, the third Ruger-Kutta method is just an option in the namelist. input, you can also choose the fifth-order one, so it is not “The WRF model employs”, but you choose this third-order method. Please reword.

Line 98: “the bins of CCNs whose size extends the critical radius will be able to activate the corresponding liquid bins”, How to understand “corresponding liquid bins”? I feel that the WDM-NCU scheme has not been introduced in detail in this manuscript. What is the size range of the 43 bins? Which microphysics processes are calculated in this bin scheme? Can this scheme reflect the fact that large CCN becomes large cloud droplets? How does the scheme deal with the coupling of the bin part and bulk part?

Line 102: “After the number concentration and mixing ratio of the liquid bins is calculated, they are used in the calculation of the mixing ratio and number concentration of cloud and rain, and the microphysics processes continue as is the case in the original WDM6”. Do you mean that the bin part of the WDM-NCU scheme only calculates the nucleation process? How do you separate the cloud and rain categories from the liquid bins? The authors have to provide more information.

Fig. 5 The simulated accumulated precipitation comes from which domain? Is the horizontal space resolution close to the observed data?

Fig. 6 What is RCWF and RCSL? They have not been explained in the manuscript. And which are observed data and which are simulated results?

Fig. 7, I suggest to depict the simulated results using dashed lines and put them over the observed data. So that only three 3 subplots are needed. And the Dongyan Mountain site should be plotted in Fig. 3 (or 5, 6).

Fig. 8: Observation or simulation?

Where are the seeding points or areas when you seed in 1km², 10km², and 100km²? These seeding points should be plotted. The seeding effects should also be shown in horizontal shadow figures, not just be plotted in lines as in Figs 9 and 10. And how much sea salt is seeded?

Line 240: Why do you say seeding in such large area (100 km²) at 500 m is “impractical and ineffective” but at the same time seeding in 100 km2 at 1300 m is “more suitable”? I think both of them are impractical.

Fig. 13, Why Praut increases in seed_500(100 km2) but Qr does not increase as shown in Fig.11 g, h.

Fig. 15, Why the units of dN/dlog(D) is %？

Line 261: Why do you think when the seeding area is larger than 64km2, the Shihmen region no longer has plenty of cloud water to transform to precipitation？ Is there any evidence supporting your conclusion？ Didn’t you say that seeding leads to an increase in Qc in 10 min?
Citation: https://doi.org/10.5194/egusphere-2023-573-RC1
- AC1: 'Reply on RC1', Kao-Shen Chung, 19 May 2023
  
  We greatly appreciate the care taken by the reviewer in evaluating the manuscript. We believe the actions we have taken to address the comments have substantially strengthened the revision of the manuscript. Our bolded responses appear below the reviewer comments.
  
  Citation: https://doi.org/10.5194/egusphere-2023-573-AC1
CC1:
'Comment on egusphere-2023-573', Tian Xian, 26 Jun 2023
The manuscript “ Evaluation of hygroscopic cloud seeding in warm rain process by a hybrid microphysics scheme on WRF model: a real case study” develops a hybrid cloud-seeding microphysics scheme and selects a case with optimal model performance and a typical weather condition in northern Taiwan to conduct a series of cloud-seeding sensitivity tests. The results show that seeding at in-cloud regions with an appropriate CCN size distribution can yield greater rainfall and that spreading the seeding agents over an area of 40–60 km² is the most efficient strategy to create a sufficient 15 precipitation rate. Overall, this is an interesting study that has the potential to advance our understanding of the evaluation of hygroscopic cloud seeding and may be of interest to ACP readers.
However, there are several issues to address before the paper is suitable to publication in ACP. Thus, I suggest minor revision before publication.
Major comments:
It is suggested that the horizontal resolution of Large eddy simulation should be below 100m, and the horizontal and vertical resolution below the PBLH should be nearly equal. Therefore, the LES resolution of this manuscript needs to be reconsidered, unless it is well justified.

As mentioned in the manuscript, the environment is crucial for cloud seeding. However, this manuscript only discusses saturation and does not delve into the discussion of the environment. Meanwhile, it only simulates a real case, so whether this conclusion has universality remains to be discussed.

Minor comments:
Lack of discussion and comparison with existing relevant research, some comparisons can be added in the introduction or discussion section to highlight the findings of this manuscript

L30: consider whether there are recent references supporting this phenomenon

L70: Suggest not adding references in the title

It is recommended to merge Figures 7a and b for comparison purposes

Figure 7: The horizontal axis does not appear to be a font

Figure 8: “Lontitude”“Longitude”

Figure 14: maintaining a unified time zone for the entire manuscript
Citation: https://doi.org/10.5194/egusphere-2023-573-CC1
RC2:
'Comment on egusphere-2023-573', Anonymous Referee #3, 06 Jul 2023
The manuscript “ Evaluation of hygroscopic cloud seeding in warm rain process by a hybrid microphysics scheme on WRF model: a real case study” develops a hybrid cloud-seeding microphysics scheme and selects a case with optimal model performance and a typical weather condition in northern Taiwan to conduct a series of cloud-seeding sensitivity tests. The results show that seeding at in-cloud regions with an appropriate CCN size distribution can yield greater rainfall and that spreading the seeding agents over an area of 40–60 km² is the most efficient strategy to create a sufficient 15 precipitation rate. Overall, this is an interesting study that has the potential to advance our understanding of the evaluation of hygroscopic cloud seeding and may be of interest to ACP readers.
However, there are several issues to address before the paper is suitable to publication in ACP. Thus, I suggest minor revision before publication.
Major comments:
It is suggested that the horizontal resolution of Large eddy simulation should be below 100m, and the horizontal and vertical resolution below the PBLH should be nearly equal. Therefore, the LES resolution of this manuscript needs to be reconsidered, unless it is well justified.

As mentioned in the manuscript, the environment is crucial for cloud seeding. However, this manuscript only discusses saturation and does not delve into the discussion of the environment. Meanwhile, it only simulates a real case, so whether this conclusion has universality remains to be discussed.

Minor comments:
Lack of discussion and comparison with existing relevant research, some comparisons can be added in the introduction or discussion section to highlight the findings of this manuscript

L30: consider whether there are recent references supporting this phenomenon

L70: Suggest not adding references in the title

It is recommended to merge Figures 7a and b for comparison purposes

Figure 7: The horizontal axis does not appear to be a font

Figure 8: “Lontitude”“Longitude”

Figure 14: maintaining a unified time zone for the entire manuscript
Citation: https://doi.org/10.5194/egusphere-2023-573-RC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Kao-Shen Chung on behalf of the Authors (21 Jul 2023) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (23 Jul 2023) by Zhanqing Li

RR by Anonymous Referee #3 (29 Jul 2023)

RR by Anonymous Referee #1 (05 Aug 2023)

Suggestions for revision or reasons for rejection

The authors carefully respond to my comments and revise the manuscript. In the revised manuscript, the WDM-NCU scheme is introduced in more detail. We appreciate the efforts made by the authors, although we still have some new questions:
1. If I understand correctly, when nucleating, a CCN particle will become a liquid droplet whose radius is five times larger than the CCN particle. As the radius of CCN particles ranges from 0.001 to 20 um, it means a CCN particle with the radius of 20 um will become a liquid particle with the radius of 100 um. That is to say, a large CCN particle will directly become a rain drop immediately after nucleation! It is impossible! There must be an upper limit on the radius that the newly nucleated particles will be.
2. Based on your description in the revised manuscript, it seems that only the nucleation process is calculated using the BIN part of the scheme, the mass and number concentration of the newly nucleated particles are added to the BULK part of this scheme and all the other warm rain processes are calculated in the BULK part. In the BIN part, it is true that “large CCN becomes larger liquid particle”. But as you only add the mass and number concentration of the newly nucleated particles to the BULK part, it (“large CCN becomes larger liquid particle”) may not be true, since the particle size distribution (PSD) of liquid water in the bulk part may deviate from the that in the bin part. You should compare the PSDs in these two parts after nucleation to see whether the parameterized PSDs in the BULK part are close to that in the BIN part.
3. Line 21. "Taiwanese government" is not a globally accepted term, and I don't see the necessity of using "Taiwanese government" here, please reword.

Referee Report: PDF

Hide

ED: Publish subject to minor revisions (review by editor) (05 Aug 2023) by Zhanqing Li

AR by Kao-Shen Chung on behalf of the Authors (11 Aug 2023) Author's response Author's tracked changes Manuscript

ED: Publish as is (12 Aug 2023) by Zhanqing Li

AR by Kao-Shen Chung on behalf of the Authors (14 Aug 2023) Manuscript

Journal article(s) based on this preprint

20 Sep 2023

Evaluation of hygroscopic cloud seeding in warm-rain processes by a hybrid microphysics scheme using a Weather Research and Forecasting (WRF) model: a real case study

Kai-I Lin, Kao-Shen Chung, Sheng-Hsiang Wang, Li-Hsin Chen, Yu-Chieng Liou, Pay-Liam Lin, Wei-Yu Chang, Hsien-Jung Chiu, and Yi-Hui Chang

Atmos. Chem. Phys., 23, 10423–10438, https://doi.org/10.5194/acp-23-10423-2023,https://doi.org/10.5194/acp-23-10423-2023, 2023

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This study develops a hybrid microphysics scheme to enable the complex model simulation of cloud seeding based on the observational CCN size distribution. Our result illustrates more precipitation can be developed in the scenarios seeding at the in-cloud region and seeding over an area of tens km² is the most efficient strategy, due to the strengthening of the accretion process. Moreover, particles bigger than 0.4 μm are the main factor contributing to cloud-seeding effects.


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