Climatic characteristics of the Jianghuai cyclone and its linkage with precipitation during the Meiyu period from 1961 to 2020

Zhu, Ran; Chen, Lei

doi:https://doi.org/10.5194/egusphere-2023-2008

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https://doi.org/10.5194/egusphere-2023-2008

Preprints

27 Oct 2023

| 27 Oct 2023

Climatic characteristics of the Jianghuai cyclone and its linkage with precipitation during the Meiyu period from 1961 to 2020

Ran Zhu and Lei Chen

Abstract. This study examines the climatic characteristics of 202 Jianghuai cyclones and their linkage with precipitation during the Meiyu period from 1961 to 2020. The results show that cyclones mainly originate from eastern Hubei Province and south-central Anhui Province. The frequency of Jianghuai cyclone occurrences shows an increasing trend in 1965–1970, 1990–2000, and after 2020. A decreasing trend is observed for 1970–1990 and 2000–2010. There is a positive correlation coefficient of 0.769 between the frequency of cyclone activity and precipitation in the Meiyu period. The percentage of precipitation affected by cyclone activities can reach up to 47 %. The anomalous increase in precipitation caused by cyclones above 27° N can reach a maximum of 7 mm/day. In contrast, precipitation is decreased in southern China because of the strengthening positive geopotential height in the Western Pacific subtropical high (WPSH). Precursor negative geopotential height anomalies for these cyclones emerge over the Mongolian region. The abnormal signal of the negative geopotential height can be traced to day -4 at the 500 hPa level. The WPSH and southwest jet are the dominant factors causing abnormal precipitation during Jianghuai cyclones. The significant water vapor convergence anomalies in the middle and lower reaches of the Yangtze River and the southwestward water vapor transport anomalies provide sufficient water vapor for cyclone development.

Received: 01 Sep 2023 – Discussion started: 27 Oct 2023

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Ran Zhu and Lei Chen

Status: final response (author comments only)

RC1:
'Comment on egusphere-2023-2008', Anonymous Referee #1, 13 Dec 2023

This manuscript analyses Jianghuai cyclones during the Meiyu period using ERA5 reanalysis data. It explores cyclone characteristics, genesis locations, and tracks, establishing a positive correlation between intensity, radius, and interdecadal variations. The study emphasizes the link between cyclone activity and Yangtze River precipitation. Spatially, abnormal precipitation patterns are identified, tracing the evolution of geopotential height anomalies and water vapor flux.
The results presented in this paper are both interesting and significant, as the study delves into understanding the complex dynamics of Jianghuai cyclones and their impact on regional precipitation. While the methodology employed by the authors appears sound, there are a few areas that require revision. For example, I think it is advisable to provide more details on the parameters and statistical analyses to enhance a deeper understanding of how the results are obtained and the derived conclusions. Also, the manuscript mentions the positive correlation between cyclone activity and precipitation but does not delve into the causal mechanisms. These considerations, and the ones below, are important for a more compelling paper, and while they currently prevent me from giving my full endorsement for publication in its current state, I eagerly anticipate reviewing a revised version.
Below, I am giving an account of more specific comments and suggestions.
Abstract: The current abstract resembles a list of outcomes instead of a storyline, so it might benefit from a stronger overarching structure that seamlessly connects the climatological characteristics of Jianghuai cyclones, their correlation with precipitation in the Yangtze River region, and the atmospheric anomalies associated with their activity.
Section 1: Please provide a more extensive description of the Meiyu front and period as they represent specific manifestations of the East Asian monsoon that may not be widely recognized worldwide.
Adding a map to illustrate the location of Yangtze River, Jianghuai, and its surrounding provinces/regions would enhance the reader's understanding of the geographical context. It could also include the Meiyu front location. This visual aid would be valuable for situating the study area and providing context for readers who may not be familiar with the region.
L.39. I think there might be a typo: floors -> floods?
L.117. Please specify that the “National Meteorological Information Center” is part of the “China Meteorological Administration” to avoid confusions with similar institutions from other countries.
Section 2.2: The description of tracking methods is presented at a technical level without a comparative analysis of their strengths and weaknesses. A more descriptive approach would offer insights into why the chosen method is ideal for this study, providing a more comprehensive methodological evaluation.
L.154. It could be interesting to add a rectangle that illustrates this region, possibly incorporating it into the new figure.
L. 165. When referring to the frequency of occurrence, what are the units? From the numbers, I would say that it refers to the total number of cyclones during the Meiyu period from 1961 to 2020. Please specify in the text, here and hereafter, and add to figures and/or figure captions as well.
L.245. Please add the definition of “Meiyu intensity index” as it is not defined in the text. It is important to know how this index is defined to be able to fully follow and understand the discussions where it is used.
L.225, and so on. The term “anomaly/anomalies” is used throughout the text without explicitly defining it. I guess it takes the whole Meiyu period from 1961 to 2020 as the base state; however, it is not defined in the text. Please do.
L. 334 -344. Are these results from the present study and backed up by the references provided or are the results of the references? Please clarify.
Section 4: It is advisable to briefly mention potential directions for future research, identifying unexplored questions and areas for further study to build upon the presented findings. For example, the specific mechanism of the southwest jet's influence could be further analyzed and researched.
Fig. 1: It would be beneficial to have the same size in both subfigures. In the caption, I think the parentheses containing two sentences should be integrated as part of the text.
Fig. 2: I would change the y-labels to "Number of cyclones" for easier interpretation at first glance. Additionally, the units of intensity are hard to read in the figures. Consider enlarging the figures or adjusting their layout to improve visibility.
Fig. 3: I don’t understand what “Point” in figure b means. Please clarify or correct.
Fig. 4, 6: I think “Number” in the y-labels refers to the “number of cyclones per year”. Please add and specify both in the caption and the text.
Fig. 7 and 8: Again, consider enlarging the figures or adjusting their layout to improve visibility.
Also, please consider relocating the "T test" specification to the main text when discussing confidence levels, rather than including it in the figure captions. Include it the first time it is mentioned and subsequent times if you deemed necessary or use the hereafter expression.
Please, review the text and figure captions to explicitly specify the units of the magnitudes.

Citation: https://doi.org/10.5194/egusphere-2023-2008-RC1
- AC1:
  'Reply on RC1', Ran Zhu, 26 Dec 2023
  
  Response:
  
  We would like to express our sincere gratitude for your help and supports. The most of your suggestions have been accepted and the manuscript is revised accordingly. Our responses to the comments are listed in a one-by-one manner as follows in the pdf.
  
  Citation: https://doi.org/10.5194/egusphere-2023-2008-AC1
  - RC2: 'Reply on AC1', Anonymous Referee #1, 28 Dec 2023
    
    From the comments document, the authors seem to have addressed my previous concerns regarding the manuscript. However, I cannot see the revised manuscript document, so I cannot properly review it as a whole. If the authors could attach the revised manuscript to the next reply, I would be able to finish my review. Thank you very much, and Happy New Year!
    
    Citation: https://doi.org/10.5194/egusphere-2023-2008-RC2
    
    AC2: 'Reply on RC2', Ran Zhu, 29 Dec 2023
    
    We appreciate your approval of the revised part. We have attached the revised manuscript to the back. Thank you so much, and Happy New Year too.
    
    Citation: https://doi.org/10.5194/egusphere-2023-2008-AC2
    
    RC3: 'Reply on AC2', Anonymous Referee #1, 30 Dec 2023
    
    Thanks for attaching the new version of the manuscript so quickly. After reviewing it, I have some minor comments regarding the Meiyu intensity index. I am wondering about the values of L_0 and R_0, as well as the years over which the average is measured. Additionally, for the study period, it could be interesting to specify the values for L and R so that the reader can compare them. Best regards!
    
    Citation: https://doi.org/10.5194/egusphere-2023-2008-RC3
    
    AC3: 'Reply on RC3', Ran Zhu, 06 Jan 2024
    
    We appreciate your suggestions and comments on the article. The values of Meiyu intensity are from the National Climate Center of China. We regret that it is not convenient for us to give you the specific value. Taking 2020 as an example, L_0 is the average value of the observations from 1961 to 2019, and R_0 is the same as above. The L, R values are the observed values for the current year. I hope this example can help you solve this problem. Best regards!
    
    Citation: https://doi.org/10.5194/egusphere-2023-2008-AC3
    
    RC4: 'Reply on AC3', Anonymous Referee #1, 08 Jan 2024
    
    Thank you for providing clarification on the Meiyu intensity values. I understand the constraints on sharing specific values. To enhance transparency, it would be beneficial to explicitly state in the manuscript that these data originate from the repositories of the National Climate Center of China.
    
    Moreover, for better clarity, could you consistently specify the average period in the manuscript? For example, you mentioned that L_0 and R_0 values for 2020 are the averages from 1961 to 2019. It might be helpful to explicitly state this in the methodology section, specifying the average period as from 1961 to the previous year of the study (2019 for the current study).
    
    Regarding the statement "The L, R values are the observed values for the current year," does this mean you calculate the average based on individual observed values for the current year? If possible, including this detail in the manuscript would be valuable.
    
    Please attach the revised manuscript in the next comment. Thank you again for all the work and the fluid communication. Best regards!
    
    Citation: https://doi.org/10.5194/egusphere-2023-2008-RC4
    
    AC4: 'Reply on RC4', Ran Zhu, 09 Jan 2024
    
    Thank you very much for your valuable suggestions. We have revised the relevant description of Meiyu intensity index in L.132-L.145.
    We are very sorry that there is a mistake in the description of the average value of L_0 before, and we have checked it again. The average period is from 1961 to the current year. For example, L_0 and R_0 values for 2000 are the averages from 1961 to 2000.L_0 and R_0 values for 2001 are the averages from 1961 to 2001. We have redescribed this and have changed it in the manuscript.
    Thank you again for your support to our work. Best regards!
    
    Citation: https://doi.org/10.5194/egusphere-2023-2008-AC4
RC5:
'Comment on egusphere-2023-2008', Anonymous Referee #1, 09 Jan 2024

The authors have addressed all my previous concerns regarding the manuscript and have done a commendable job with its revision. Consequently, I am recommending the paper for publication. Best regards!

Citation: https://doi.org/10.5194/egusphere-2023-2008-RC5
- AC5: 'Reply on RC5', Ran Zhu, 10 Jan 2024
  
  Thank you very much for your review work and valuable suggestions during this time. These will also be of great help to our future work. Thank you again for your recognition and support of our work. Best regards!
  
  Citation: https://doi.org/10.5194/egusphere-2023-2008-AC5
RC6:
'Comment on egusphere-2023-2008', Anonymous Referee #2, 08 Mar 2024
Comments
General Comments:
The authors employed the relative vorticity method to track Jianghuai cyclones and subsequently investigated their climatological characteristics, including frequency, intensity, and radius, in relation to Meiyu precipitation. This study holds significant value and serves as a crucial foundation for further research on the dynamics of Jianghuai cyclones and their impact on both mean and extreme precipitation. However, the current study requires substantial revisions. The key strength of this research lies in the association between Jianghuai cyclones and Meiyu precipitation; however, the analysis in this aspect is relatively limited. Therefore, I recommend that the authors devote more attention to this particular area. For instance, they could explore the differences in circulation patterns and underlying mechanisms between cyclone precipitation days and non-cyclone precipitation days, or investigate the connection with extreme precipitation events.
Detailed Comments:
Line 116: CN05.1 data need a citation.

Section 2.2 Methods:

I would suggest the authors giving a briefly introduction of the rationale of the vorticity tracking method proposed by Hodges firstly, and then the details would be more readable. Besides, the method (Hodges, 1994, 1995) introduction still left too much attention to detail and seems tedious. And the advantages of the method used in this study over other methods should be stressed. That is, the last two paragraphs in this section could be rewritten to improve readability.
Line 155-156: “genesis location” is the repetition of “the first occurrence”. I would suggest changing to be: The brown dots represent the genesis locations, i.e., the first place meeting the criterion, of the Jianghuai cyclone.

Lines 157-161: The authors have pointed out that the tracks of the cyclone can be categorized into two group, the easterly and the northeasterly. However, since there are no further discussions for the two groups respectively. Indeed, both the easterly or northeasterly paths are related to the locations of the WPSH.

Line 165-166: Two centers with high values, i.e., southwestern Hubei and eastern Hubei. The original sentences is puzzling, and I suggest the authors revising it.

1: “(The brown dots represent the genesis locations. The yellow lines indicate the tracks).” The bracket is no need.

Line 176: “. The larger the relative vorticity intensity is, the stronger the cyclone intensity is.” seems redundant.

Line 178: It is confusing to see a “0×10^-5 s ^-1” in the relative vorticity for the Jianghuai cyclone.

Line 186: “radii” to “radius”?

Line 187: “time” to “time span”? This is different from the caption of Fig. 2, in which the “time” is the “lifetime”? Which is right? The description in the main text or the figure caption of Fig. 2?

Lines 193-197: Several places in the manuscript are repetitive. I suggest the authors revised them carefully. Below is an example. “Figure 3a shows a positive correlation between the maximum intensity and the maximum radius of cyclone development. The stronger the intensity of a cyclone is, the larger its radius. Therefore, the horizontal scale of most strong cyclones is larger than that of weak cyclones, the precipitation is greater, and the precipitation range is larger.”

Line 215: Indian Ocean dipole (IOP) to “Indian Ocean Dipole (IOD)”?

Line 219: “Southwestern rapids” to “Southwesterly low-level jet”?

Lines 228-230: The alternatively increase and decrease of the numbers of Jianghuai cyclones is indeed the “decadal variation of Jianghuai cylone”, with positive anomaly in 1965-1970, 1990-2000, and 2000-after, and negative anomaly in 1970-1990 and 2000-2010.

Line 230-232: I would suggest the authors illustrating the relationship between the decadal variation of Jianghuai cyclone and that of Meiyu precipitation.

Line 242: I would suggest removing “gales” since there is no further discussion.

Line 245: “Meiyu intensity index” should be defined explicitly.

Lines 250 and Lines 252: “0.769” and “0.760” to be “0.77” and “0.76”.

Line 259: “annual average” to “annual total”?

Line 267-269: The definition of non-cyclone precipitation days should be explicitly stated.

Lin 387: The colored region passed the 95% confidence interval according to a test. Student’s t-test?
Citation: https://doi.org/10.5194/egusphere-2023-2008-RC6
- AC6: 'Reply on RC6', Ran Zhu, 21 Mar 2024
  
  We would like to express our sincere gratitude for your help and supports. The most of your suggestions have been accepted and the manuscript is revised accordingly. Our responses to the comments are listed in a one-by-one manner as follows in the pdf.
  
  Citation: https://doi.org/10.5194/egusphere-2023-2008-AC6

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Short summary

There is a positive correlation between the frequency of cyclone activity and precipitation in the Meiyu period.The frequency of Jianghuai cyclone activity is high in the years with strong Meiyu rainfall. Its occurrence frequency has obvious interdecadal variation, which has a good correspondence with the periodic and interdecadal variation in precipitation in the Meiyu period.This study provides a reference for the long-term and short-term forecasting of precipitation in the Meiyu period.


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