Extratropical Cyclone Response to Projected Reductions in Snow Extent over the Great Plains

Round 1

Reviewer 1 Report

Firstly, the reviewers were highly appreciative of the research significance of the manuscript. The authors conducted a series of simulations of 15 cool season temperate cyclones over or near the North American Great Plains to measure their trajectories, intensity and associated precipitation dependence on the underlying snowpack.

The results of the study do diverge from available observations, however, these results are less than satisfactory and the reasons for the divergence are not apparent from the conclusions of the manuscript.

Overall, the reviewers consider the manuscript worthy of publication, but there are a number of issues that need improvement.

1. whether the scientific innovation of the manuscript could be highlighted in the introduction. What are the advances over the current state of existing research.

2. The format of Table 1 is not standardised and is laid out according to the three-line table format.

3. Figures 4 - 6 look messy, could the clarity and layout of the images be improved.

4. The reviewers could not see the specific conclusions of the study in the discussion and conclusion sections. Please give a clear conclusion from the authors. Then give an analysis of the possible reasons for the lack of clarity and a follow-up perspective. The current version only shows the reasons and outlook but not the specific study conclusions.

5. Please cite the following literature in the manuscript

Qiang Li, Hongtao Jia, Qing Qiu, Yongzhu Lu, Jun Zhang, Jianghong Mao, Weijie Fan, M. F. Huang. Typhoon-induced fragility analysis of transmission towers in Ningbo area considering the effects of long-term corrosion [J]. Applied Sciences, 2022, 12(9), 4774.

Author Response

Firstly, the reviewers were highly appreciative of the research significance of the manuscript. The authors conducted a series of simulations of 15 cool season temperate cyclones over or near the North American Great Plains to measure their trajectories, intensity and associated precipitation dependence on the underlying snowpack.

The results of the study do diverge from available observations, however, these results are less than satisfactory and the reasons for the divergence are not apparent from the conclusions of the manuscript.

Overall, the reviewers consider the manuscript worthy of publication, but there are a number of issues that need improvement.

Thank you for the positive evaluation. We have made changes to emphasize the results in conclusion and abstract and address the minor comments below.

1. whether the scientific innovation of the manuscript could be highlighted in the introduction. What are the advances over the current state of existing research.

The abstract has been updated to note that this is the first study using realistic retreat of snow cover on mid-latitude cyclone trajectory using a larger than past number of simulations across multiple cases. We added text to the introduction to highlight differences from prior studies. We added text to the conclusion to focus on what new science we have learned from this study.

2. The format of Table 1 is not standardised and is laid out according to the three-line table format.

Table format has been updated following the MDPI journal template

3. Figures 4 - 6 look messy, could the clarity and layout of the images be improved.

These were challenging figures to represent well. We did some editing to improve visual appeal.

4. The reviewers could not see the specific conclusions of the study in the discussion and conclusion sections. Please give a clear conclusion from the authors. Then give an analysis of the possible reasons for the lack of clarity and a follow-up perspective. The current version only shows the reasons and outlook but not the specific study conclusions.

The first paragraph of section 5 outlines the main goal, findings, and novelty of our study. We have added more specifics here and additional conclusion.

5. Please cite the following literature in the manuscript

Qiang Li, Hongtao Jia, Qing Qiu, Yongzhu Lu, Jun Zhang, Jianghong Mao, Weijie Fan, M. F. Huang. Typhoon-induced fragility analysis of transmission towers in Ningbo area considering the effects of long-term corrosion [J]. Applied Sciences, 2022, 12(9), 4774.

While we appreciate the suggestion, it is not immediately clear to us how to cite literature regarding typhoon influence on energy infrastructure in the Western Pacific in our work about snow cover influence of extratropical cyclone development in North America.  We are unable to meaningfully add this research to our own at this time.

Reviewer 2 Report

In this work, the authors present an elegant model for the extratropical cyclone Response to reductions in snow extent. The introduction and backghround setting is comprehansive, along with detailed account of literature works on similar area. The methodlogy needs additional details on the modeling framework, and the conclusion needs to be enriched with in-depth outcomes of the work. The work can be accepted in its current form.

Author Response

In this work, the authors present an elegant model for the extratropical cyclone Response to reductions in snow extent. The introduction and backghround setting is comprehansive, along with detailed account of literature works on similar area. The methodlogy needs additional details on the modeling framework, and the conclusion needs to be enriched with in-depth outcomes of the work. The work can be accepted in its current form.

Thank you for the positive evaluation of our manuscript.

Reviewer 3 Report

Many studies have examined the effect of terrestrial snow cover on atmospheric baroclinicity. However, fewer studies have focused on the modulation of the continental snow cover extent on cyclones’ intensities, trajectories, and precipitation characteristics. it is important to investigate the potential influence of projected future poleward shifts in North American snow extent on extratropical cyclones over the North American Great Plains. The results show that a majority of 15 cold-season extratropical cyclones experienced a small decrease in SLP, consistent increases in precipitation, modest increases in kinetic energy, and limited changes in trajectory under a background of a retreat of snow cover with climate warming in the future. Although the simulated anomalies do not agree with expectations gained from observational studies, several simulation results show the systematic anomalies of cyclones forced by the poleward shifts of snow cover. For example, the mean trajectory deviations (MTDs) of each perturbed simulation cyclone present a significant positive linear relationship with the area of snow removed. Generally speaking, this paper is interesting and well written. Therefore, it should be recommended for publication after a minor revision.

Minor suggestions

(1)   I wonder why several interesting and meaningful results were not shown in the abstract and conclusion. For instance, the linear relationship between the MTDs and the area of snow removed.

(2)   Fifteen cases seem insufficient. As the authors indicated, weaker cyclone cases may be more sensitive to the retreat of the snow line. More robust and reliable results may be obtained through simulating a large number of stronger and weaker cyclone cases. Clearly, this study deserves further investigation using more cases in the future.

Author Response

Many studies have examined the effect of terrestrial snow cover on atmospheric baroclinicity. However, fewer studies have focused on the modulation of the continental snow cover extent on cyclones’ intensities, trajectories, and precipitation characteristics. it is important to investigate the potential influence of projected future poleward shifts in North American snow extent on extratropical cyclones over the North American Great Plains. The results show that a majority of 15 cold-season extratropical cyclones experienced a small decrease in SLP, consistent increases in precipitation, modest increases in kinetic energy, and limited changes in trajectory under a background of a retreat of snow cover with climate warming in the future. Although the simulated anomalies do not agree with expectations gained from observational studies, several simulation results show the systematic anomalies of cyclones forced by the poleward shifts of snow cover. For example, the mean trajectory deviations (MTDs) of each perturbed simulation cyclone present a significant positive linear relationship with the area of snow removed. Generally speaking, this paper is interesting and well written. Therefore, it should be recommended for publication after a minor revision.

Thank you for the positive evaluation. We have made changes to emphasize the results in conclusion and abstract and address the minor comments below.

Minor suggestions

(1)   I wonder why several interesting and meaningful results were not shown in the abstract and conclusion. For instance, the linear relationship between the MTDs and the area of snow removed.

We have revised the abstract and included the statistics on the linear relationship.

(2)   Fifteen cases seem insufficient. As the authors indicated, weaker cyclone cases may be more sensitive to the retreat of the snow line. More robust and reliable results may be obtained through simulating a large number of stronger and weaker cyclone cases. Clearly, this study deserves further investigation using more cases in the future.

Indeed, further investigation will be needed to clarify the relationships observed in this study.  The cyclone cases presented here are the result of extensive work evaluating observational data and modeling hundreds of individual simulations across numerous snow retreat scenarios. We were therefore limited in the amount of cyclones we could investigate in the course of this research. We noted this in the conclusion.

Reviewer 4 Report

This is an interesting study in the interaction between extratropical cyclones and snow extent retreat. The authors use the WRF-ARW to investigate the tracjctories and intensities of 15 extratropical cyclones with the snow extent perturbed. This topic is of great significance since the snow drought and cyclones are two of the most destructive natural hazards in the study area. The manuscript is well-written with appropriate figures.

My major concern is the reliability of results since the authors do not provide any model evaluation experiments. It remains unclear whether the control experiment can well reproduce the observed cyclone trajectories and intensities. This is easy and very important, or the conclusions can be highly questionable.

On the other hand, the role of snow extent retreat can be small, as the authors indicates, but it remains unclear whether the difference in the trajectories and intensities are statistically significant. And the horizontal grid spacing is 30 km in the WRF-ARW experiment, but Figure 7 shows that the trajectory deviation is lower than 30 km for most cases, especially for the 10^th and 50^th percentiles.

I also have several minor comments as follows.

1. Line 168: Why do you select four cyclone cases here? Please explain it.

2. Table 3: It is confusing to use different scenarios in a single percentile. Please clarify it.

Author Response

This is an interesting study in the interaction between extratropical cyclones and snow extent retreat. The authors use the WRF-ARW to investigate the tracjctories and intensities of 15 extratropical cyclones with the snow extent perturbed. This topic is of great significance since the snow drought and cyclones are two of the most destructive natural hazards in the study area. The manuscript is well-written with appropriate figures.

Thank you for your kind comments. We have revised the document to address concerns from all four reviewers and believe it makes for a stronger manuscript that I hope will inspire others to build on and develop new experiments and analyses.

My major concern is the reliability of results since the authors do not provide any model evaluation experiments. It remains unclear whether the control experiment can well reproduce the observed cyclone trajectories and intensities. This is easy and very important, or the conclusions can be highly questionable.

As noted in section 2.1, we started with 20 cases and retained the 15 where control simulations faithfully tracked the observed analyses in terms of location of mid-latitude pressure center. We added text here to note a qualitative tolerance of ~200 km deviation of low pressure center.

On the other hand, the role of snow extent retreat can be small, as the authors indicates, but it remains unclear whether the difference in the trajectories and intensities are statistically significant. And the horizontal grid spacing is 30 km in the WRF-ARW experiment, but Figure 7 shows that the trajectory deviation is lower than 30 km for most cases, especially for the 10th and 50th percentiles.

The difference here is that MTD reflects a mean deviation, which can include time periods with no deviation averaged together with time periods of deviations greater than one or more grid points. We added text in the results noting this.

I also have several minor comments as follows.

1. Line 168: Why do you select four cyclone cases here? Please explain it.

Four per month (20 total) reflected a desire to balance computational availability (each case had four initialization times (T-1 to T-4) and 5 snow cover retreat cases (control, 10th, 50th, 90th, no snow), for 400 simulations) with desire for well distributed set of cases for statistical analysis. We added text here to note that.

2. Table 3: It is confusing to use different scenarios in a single percentile. Please clarify it.

Each scenario and model was evaluated independently.  Though higher and lower RCP scenario values are intended to indicate greater or lesser degrees of warming influence, we find that some simulations with imposed RCP8.5 only resulted in 10th percentile snow line recession.

Round 2

Reviewer 1 Report

The author's response does not show any emphasis on the innovative nature of the article, including the provision of a revised version that does not show signs of extensive revision.

In the revised version, only one or two sentences are added to the abstract and conclusion.

The author's response mentions that this is the first study of mid-latitude cyclone tracks using a realistic snow cover retreat, but to the reviewer's knowledge, this is not the first one. Therefore, the reviewer is sceptical about the author's innovative point. Please rephrase.

Author Response

The author's response does not show any emphasis on the innovative nature of the article, including the provision of a revised version that does not show signs of extensive revision. In the revised version, only one or two sentences are added to the abstract and conclusion.

Thank you for taking another look at this manuscript and we are glad you are in agreement of the innovative nature of our work. We are sorry the revisions didn't meet your bar for extensive revisions that highlight innovations. Here, we include the track changes version to show both that significant prior and additional revisions were made to reorganize the introduction, highlight key novelties and design components, and better discuss mechanisms to the extent we can with our simulations with outlook for future work. This manuscript has now been revised four times, including two prior rounds in another journal, during which extensive additions were made. We believe through these review processes over the past 3 years, we have made the results of this multi-year study, the outcomes of which form the master's thesis of the first author and the primary finding of our National Science Foundation climate and large-scale dynamics award, robust to many prior issues.

The author's response mentions that this is the first study of mid-latitude cyclone tracks using a realistic snow cover retreat, but to the reviewer's knowledge, this is not the first one. Therefore, the reviewer is sceptical about the author's innovative point. Please rephrase.

We have removed any mention of this being the first study of this, and focused instead on differences and consistencies from prior studies. The only prior studies that have looked at this low-level baroclinicity concept with relation to snow cover extent changes were done by researchers related to this study (e.g., Rydzik and Desai, 2014; Breeden et al., 2020). Prior model studies have not done anything remotely similar in terms of alterations to snow cover extent that maintains snow cover within the region of enhanced baroclinicity and have made those findings discoverable and published in a peer-reviewed journal. The reviewer is welcome to mention any citations that we may have missed of these studies and we would be welcome to read and include them. Over the past 5 years since we initiated this project, we have worked assiduously to stay on top of literature, engage with the research community, present our findings at international conferences (AMS, AGU), and incorporate new literature, classic literature, and comments from multiple groups. We hope you find this well reflected in our revision.

Author Response File: Author Response.docx

Reviewer 4 Report

I have no further comments and the manuscript can be published in present form.

Author Response

Thank you the comments that have helped improve our manuscript. We look forward to its publication!