A new dataset of Mesoscale Convective Complexes (MCC) derived from FY-2G satellite data

Xu, Ke; Zhao, Shuyun; Ma, Xinyu; Shu, Jianchuan; Wang, Wuke; Deng, Qimin; Babar, Zaheer Ahmad

doi:10.5194/essd-2025-652

Preprints

https://doi.org/10.5194/essd-2025-652

Preprints

19 Jan 2026

| 19 Jan 2026

Status: a revised version of this preprint was accepted for the journal ESSD and is expected to appear here in due course.

A new dataset of Mesoscale Convective Complexes (MCC) derived from FY-2G satellite data

Ke Xu, Shuyun Zhao, Xinyu Ma, Jianchuan Shu, Wuke Wang, Qimin Deng, and Zaheer Ahmad Babar

Abstract. Mesoscale Convective Complexes (MCCs) are major convective weather systems occurring in midlatitude regions, typically associated with significant weather phenomena such as heavy rainfall, thunderstorms, strong winds, and hail. Based on the cloud-top temperature (CTT) data of the FY-2G satellite, and through multi-threshold screening combined with morphological analysis, an automated algorithm for MCC identification and tracking was developed. The algorithm is then applied to generate an hourly dataset of MCC variables over mainland China from June 2015 to December 2024. The dataset encompasses variables describing the spatial extent of the cold-core region (CTT < -52 °C) of MCCs, the minimum cloud-top temperature within the cold cloud shields, and the geographic coordinates (longitude and latitude) of the centroids of the cold cloud shields. This work also conducts a preliminary analysis of the spatial and temporal distribution characteristics of MCCs over mainland China based on the dataset. Results indicate that MCCs occur more frequently in Southwest China than in other regions of the country, and over 70 % of MCC events occur in summer both in Southwest China and mainland China. Moreover, MCC frequency in Southwest China exhibits significant interannual variability.

Received: 30 Oct 2025 – Discussion started: 19 Jan 2026

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

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Ke Xu, Shuyun Zhao, Xinyu Ma, Jianchuan Shu, Wuke Wang, Qimin Deng, and Zaheer Ahmad Babar

Status: closed

RC1:
'Comment on essd-2025-652', Anonymous Referee #1, 07 Feb 2026
Main comments:
This work developed an automated algorithm for mesoscale convective complex (MCC) identification and tracking, and then composed a long-term dataset of MCC variables over mainland China, based on the FY-2G cloud-top temperature data. MCC is an important type of convective system, often bringing about persistent heavy rain and secondary geologic disasters. Thus, this work has the potential in promoting the monitoring and research on the occurrence of MCC, and helping in disaster alleviation over the region. In general, the algorithm is described clearly, the manuscript is well-organized, and the dataset can be actually downloaded. However, there are some places (see specific comments) that need to be revised before it can be accepted for publication.
Specific comments:
At line 37, I think the authors mean “their variation” instead of “their formation”, as the Southern Oscillation, the Madden-Julian Oscillation are not short-term signals.

In lines 46-49, the sentence should be re-arranged to make its means more clear.

At line 80, the sentence begins with “Through multispectral sensing in the visible, infrared, and water-vapor bands, “ is not completed. It seems the latter part of the sentence is missed out.

In lines 80-83: “The satellite’s longitude has been relocated twice: initially at 99.5°E prior to June 1, 2015, ...” can be modified to be more concise. And I don’t understand whether the operational scan cycle is 30 or 60 minutes, or somewhere in the between.

Remove the “measurements” in line 85.

At line 89, what does the “nominal” mean?

At line 96, “reveal” -> “reveals”. And in line 104, “where” -> “with”

The sentence in lines 105-108 needs to be re-arranged. For example, what is the link between “ecc criterion is relaxed from ≥0.7 to ≥0.6 when the cold-cloud shield reaches its maximum extent” and “enabling capturing the full MCC lifecycle”?

At line 110, it is described that “all above morphological and area criteria are satisfied continuously for at least 6 hours”. However, in line 107, is seems that ecc ≥0.6 is only required when the cold-cloud shield reaches maximum extent. Can the authors re-check and clarify these two places?

The caption of Table 1, remove the “the”. And in the table, when a criterion is not used in either Maddox (1980) or this study, probably you can just use “~” instead of “null” or “Not specified”.

At line 124, “0.1°grid” -> “0.1°×0.1°grid”, and “optimizing” -> “to optimize”.

At line 150, “lenient parameter” -> “permissive threshold”, “formative stages” -> “early stages”

The caption of Figure 2 (line 162), I think area ≥ 4×10⁴km²is not applied in the subplot of b, or it will be repetitive with the subplot of c. By the way, Figure 2 has not been cited anywhere in the text.

At line 182, “the” -> “The”. And the citation of Fig. 4 should be put here instead of line 188.

The discussions in the two paragraphs of page 9 is a little puzzle for readers. For example, does the seasonally-filtered data mean winter-excluded data; and the unfiltered national data mean data of all seasons? Probably the authors can modify these two paragraphs to make them more clearly. And by the way, please don’t use “green and pink curves” or “black curve” to describe a scientific story.

The caption of Figure 5, “Area Probability Distribution Curve” -> “Probability distribution function of MCC areal extent. And the description of the three lines in the figure can be more concise.

At line 216, what does the “legitimate climatic signals” mean here. I think here is still about MCC, right? Climatic signals are too ambiguous.

At line 217, the “atmospheric divergence” is not precise here to express seasonal variation in weather pattern.

The caption of Figure 6, “cluster area” is not precise. Here each marker represents an MCC event, right? Then the marker size must represent the areal extent of the MCC event at some time point, mustn’t it?

At line 243, “demarcated in Fig. 6” can not been found in the Figure 6.
Citation: https://doi.org/10.5194/essd-2025-652-RC1
- AC1: 'Reply on RC1', ke xu, 13 Mar 2026
  
  Dear Editor and Reviewers,
  We would like to thank the reviewers for their valuable and constructive comments on our manuscript. We have carefully revised the manuscript according to the suggestions.
  Detailed point-by-point responses to reviewer comments are provided in the supplementary document.
  Best regards,
  
  Ke Xu et al.
  
  Citation: https://doi.org/10.5194/essd-2025-652-AC1
RC2:
'Comment on essd-2025-652', Anonymous Referee #2, 08 Feb 2026
This paper developed an automated algorithm for MCC identification and tracking based on the FY-2G satellite data. Such a dataset is valuable for various applications, such as climate change research and disaster risk reduction. The algorithm is proved to be physically sound and can effectively capture MCC occurrence and movement over mainland China. In general, the paper is well written: the method is clearly described, the analysis and discussions are thorough and comprehensible. However, there are some places that either need more clarification or should be revised before it is published. These are listed in the following specific comments and questions.
Question about the method:
In the north China, cases that are “nealy cloud-free or covered by thin cloud” could be miss-identified as MCC (around line 185) . Can this happen for other seasons and in other regions? If so, how can we justify the correctness of the identified MCCs by simply eliminate the winter season?

Specific comments and corrections:
Line 23: “both in South China and mainland China”. People may misunderstand these as two separate regions of China. Maybe it’s better to say “both in South China and mainland China as a whole”.

Line 35: “region of major topographic features” is an ambiguous expression. Do you mean region of large-scale plateau?

Line 39: The hyphens here should be em-dashes.

Lines 96-97 and lines 100-102: These sentences described how manual census reveals the problem of using the original parameters from Maddox (1980) in China. It’s better to conjunct these sentences properly to increase the logic fluency and coherence.

Line 102: please give proper references to the criteria stated here (i.e., CTT<=-52℃with an area >=50000 km2). And does the 40000 km2 criteria brought from previous studies or randomly set in this study?

Table 1: Both TBB and CTT are used in this table. Are they different variables? Or just two different expressions of the same variable? If the latter, it’s better to use the same expression.

Lines 129-130: the hyphen here should be em-dash.

Equation 1: The equation and text are inconsistent. The equation actually calculated the total clutter area Si, rather than “the individual pixel area” as stated in lines 141-142.

Lines 180-181: this sentence is confusing. a better expression may be “comparative analysis was conducted between two typical algorithm-identified cases, one from this region and the other from southern China, with the latter manually confirmed.”

Line 182: “the CTT” should be “The CTT”. Additionally, please refer to the explicit figure on basis of which the discussion is made.

Lines 198-199: Are this statement addressed from figure 5? If so, it's better to move it below to appropriate places, perhaps after line 205.

Line 202: The title could be “Data Output”, to avoid confusion with the title of section 4.

Section 3.4: It is recommended to provide a table here to summarize the key information of the dataset, for instance the variables, dimensions, attributes.

Line 230: The phrase “cumulative MCC” is confusing. Are there other types of MCC?

Line 235: The phrase “extremely large” is ambiguous. Could give a quantitative number?

Line 243: It’s unclear where the southwest China here refers to. Please consider illustrating the area in the figure, or providing an exact depiction of its extension in the text.

Lines 245-248: Please mention figure 7 here when doing description based on the figure.

Line 251: “Zhang, 2025” should be “Zhang et al., 2025”. “in Figs. 7 and 8” should be “in Figure 7”.

Line 260: Perhaps “The coherence of the peak in 2020 across...” can be “The coherence of the peak in 2020, as well as the periodicity, across...”

Line 281: “2015-2014” should be “2015-2024”.

Line 282-283:”where cold surface conditions can lead to ” perhaps is better to be ”where cold surface conditions and thin very high clouds can lead to ”?
Citation: https://doi.org/10.5194/essd-2025-652-RC2
- AC2: 'Reply on RC2', ke xu, 13 Mar 2026
  
  Dear Editor and Reviewers,
  We would like to thank the reviewers for their valuable and constructive comments on our manuscript. We have carefully revised the manuscript according to the suggestions.
  Detailed point-by-point responses to reviewer comments are provided in the supplementary document.
  Best regards,
  
  Ke Xu et al.
  
  Citation: https://doi.org/10.5194/essd-2025-652-AC2

Status: closed

RC1:
'Comment on essd-2025-652', Anonymous Referee #1, 07 Feb 2026
Main comments:
This work developed an automated algorithm for mesoscale convective complex (MCC) identification and tracking, and then composed a long-term dataset of MCC variables over mainland China, based on the FY-2G cloud-top temperature data. MCC is an important type of convective system, often bringing about persistent heavy rain and secondary geologic disasters. Thus, this work has the potential in promoting the monitoring and research on the occurrence of MCC, and helping in disaster alleviation over the region. In general, the algorithm is described clearly, the manuscript is well-organized, and the dataset can be actually downloaded. However, there are some places (see specific comments) that need to be revised before it can be accepted for publication.
Specific comments:
At line 37, I think the authors mean “their variation” instead of “their formation”, as the Southern Oscillation, the Madden-Julian Oscillation are not short-term signals.

In lines 46-49, the sentence should be re-arranged to make its means more clear.

At line 80, the sentence begins with “Through multispectral sensing in the visible, infrared, and water-vapor bands, “ is not completed. It seems the latter part of the sentence is missed out.

In lines 80-83: “The satellite’s longitude has been relocated twice: initially at 99.5°E prior to June 1, 2015, ...” can be modified to be more concise. And I don’t understand whether the operational scan cycle is 30 or 60 minutes, or somewhere in the between.

Remove the “measurements” in line 85.

At line 89, what does the “nominal” mean?

At line 96, “reveal” -> “reveals”. And in line 104, “where” -> “with”

The sentence in lines 105-108 needs to be re-arranged. For example, what is the link between “ecc criterion is relaxed from ≥0.7 to ≥0.6 when the cold-cloud shield reaches its maximum extent” and “enabling capturing the full MCC lifecycle”?

At line 110, it is described that “all above morphological and area criteria are satisfied continuously for at least 6 hours”. However, in line 107, is seems that ecc ≥0.6 is only required when the cold-cloud shield reaches maximum extent. Can the authors re-check and clarify these two places?

The caption of Table 1, remove the “the”. And in the table, when a criterion is not used in either Maddox (1980) or this study, probably you can just use “~” instead of “null” or “Not specified”.

At line 124, “0.1°grid” -> “0.1°×0.1°grid”, and “optimizing” -> “to optimize”.

At line 150, “lenient parameter” -> “permissive threshold”, “formative stages” -> “early stages”

The caption of Figure 2 (line 162), I think area ≥ 4×10⁴km²is not applied in the subplot of b, or it will be repetitive with the subplot of c. By the way, Figure 2 has not been cited anywhere in the text.

At line 182, “the” -> “The”. And the citation of Fig. 4 should be put here instead of line 188.

The discussions in the two paragraphs of page 9 is a little puzzle for readers. For example, does the seasonally-filtered data mean winter-excluded data; and the unfiltered national data mean data of all seasons? Probably the authors can modify these two paragraphs to make them more clearly. And by the way, please don’t use “green and pink curves” or “black curve” to describe a scientific story.

The caption of Figure 5, “Area Probability Distribution Curve” -> “Probability distribution function of MCC areal extent. And the description of the three lines in the figure can be more concise.

At line 216, what does the “legitimate climatic signals” mean here. I think here is still about MCC, right? Climatic signals are too ambiguous.

At line 217, the “atmospheric divergence” is not precise here to express seasonal variation in weather pattern.

The caption of Figure 6, “cluster area” is not precise. Here each marker represents an MCC event, right? Then the marker size must represent the areal extent of the MCC event at some time point, mustn’t it?

At line 243, “demarcated in Fig. 6” can not been found in the Figure 6.
Citation: https://doi.org/10.5194/essd-2025-652-RC1
- AC1: 'Reply on RC1', ke xu, 13 Mar 2026
  
  Dear Editor and Reviewers,
  We would like to thank the reviewers for their valuable and constructive comments on our manuscript. We have carefully revised the manuscript according to the suggestions.
  Detailed point-by-point responses to reviewer comments are provided in the supplementary document.
  Best regards,
  
  Ke Xu et al.
  
  Citation: https://doi.org/10.5194/essd-2025-652-AC1
RC2:
'Comment on essd-2025-652', Anonymous Referee #2, 08 Feb 2026
This paper developed an automated algorithm for MCC identification and tracking based on the FY-2G satellite data. Such a dataset is valuable for various applications, such as climate change research and disaster risk reduction. The algorithm is proved to be physically sound and can effectively capture MCC occurrence and movement over mainland China. In general, the paper is well written: the method is clearly described, the analysis and discussions are thorough and comprehensible. However, there are some places that either need more clarification or should be revised before it is published. These are listed in the following specific comments and questions.
Question about the method:
In the north China, cases that are “nealy cloud-free or covered by thin cloud” could be miss-identified as MCC (around line 185) . Can this happen for other seasons and in other regions? If so, how can we justify the correctness of the identified MCCs by simply eliminate the winter season?

Specific comments and corrections:
Line 23: “both in South China and mainland China”. People may misunderstand these as two separate regions of China. Maybe it’s better to say “both in South China and mainland China as a whole”.

Line 35: “region of major topographic features” is an ambiguous expression. Do you mean region of large-scale plateau?

Line 39: The hyphens here should be em-dashes.

Lines 96-97 and lines 100-102: These sentences described how manual census reveals the problem of using the original parameters from Maddox (1980) in China. It’s better to conjunct these sentences properly to increase the logic fluency and coherence.

Line 102: please give proper references to the criteria stated here (i.e., CTT<=-52℃with an area >=50000 km2). And does the 40000 km2 criteria brought from previous studies or randomly set in this study?

Table 1: Both TBB and CTT are used in this table. Are they different variables? Or just two different expressions of the same variable? If the latter, it’s better to use the same expression.

Lines 129-130: the hyphen here should be em-dash.

Equation 1: The equation and text are inconsistent. The equation actually calculated the total clutter area Si, rather than “the individual pixel area” as stated in lines 141-142.

Lines 180-181: this sentence is confusing. a better expression may be “comparative analysis was conducted between two typical algorithm-identified cases, one from this region and the other from southern China, with the latter manually confirmed.”

Line 182: “the CTT” should be “The CTT”. Additionally, please refer to the explicit figure on basis of which the discussion is made.

Lines 198-199: Are this statement addressed from figure 5? If so, it's better to move it below to appropriate places, perhaps after line 205.

Line 202: The title could be “Data Output”, to avoid confusion with the title of section 4.

Section 3.4: It is recommended to provide a table here to summarize the key information of the dataset, for instance the variables, dimensions, attributes.

Line 230: The phrase “cumulative MCC” is confusing. Are there other types of MCC?

Line 235: The phrase “extremely large” is ambiguous. Could give a quantitative number?

Line 243: It’s unclear where the southwest China here refers to. Please consider illustrating the area in the figure, or providing an exact depiction of its extension in the text.

Lines 245-248: Please mention figure 7 here when doing description based on the figure.

Line 251: “Zhang, 2025” should be “Zhang et al., 2025”. “in Figs. 7 and 8” should be “in Figure 7”.

Line 260: Perhaps “The coherence of the peak in 2020 across...” can be “The coherence of the peak in 2020, as well as the periodicity, across...”

Line 281: “2015-2014” should be “2015-2024”.

Line 282-283:”where cold surface conditions can lead to ” perhaps is better to be ”where cold surface conditions and thin very high clouds can lead to ”?
Citation: https://doi.org/10.5194/essd-2025-652-RC2
- AC2: 'Reply on RC2', ke xu, 13 Mar 2026
  
  Dear Editor and Reviewers,
  We would like to thank the reviewers for their valuable and constructive comments on our manuscript. We have carefully revised the manuscript according to the suggestions.
  Detailed point-by-point responses to reviewer comments are provided in the supplementary document.
  Best regards,
  
  Ke Xu et al.
  
  Citation: https://doi.org/10.5194/essd-2025-652-AC2

Ke Xu, Shuyun Zhao, Xinyu Ma, Jianchuan Shu, Wuke Wang, Qimin Deng, and Zaheer Ahmad Babar

Data sets

A new dataset of MCC derived from FY-2G satellite data Ke Xu https://doi.org/10.5281/zenodo.17349888

Ke Xu, Shuyun Zhao, Xinyu Ma, Jianchuan Shu, Wuke Wang, Qimin Deng, and Zaheer Ahmad Babar

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Short summary

We developed an automated method using satellite data to create a decade-long record of major storm systems over China. Our results identify southwestern China as the country's primary storm hotspot and link year-to-year frequency changes to Pacific Ocean climate patterns. This new dataset is a vital resource for improving weather forecasts and climate research.


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