the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 24 Jun 2025
The impact of tropical cyclones on regional ozone pollution and its future trend in the Yangtze River Delta of China
Abstract. Tropical cyclones (TCs) have a significant impact on ozone (O3) in coastal regions by affecting atmospheric circulation and meteorological conditions. This paper investigates the impact and its future changing trends in the Yangtze River Delta (YRD) region. It was found that regional O3 pollution usually occurred before TCs made landfall and after they dissipated in 2018–2022. Using rotation principal component analysis in T-mode (PTT) method, five main synoptic weather patterns (SWPs) are identified. The TC weather pattern (SWP5) is a high-frequency weather pattern in summer (72.22 %). Subsequently, with the aid of the data reconstruction of O3 concentrations, how SWPs, especially TCs, affect O3 is quantified. It is found that the intensity of SWPs is the dominant factor for the annual variation sequence of O3, contributing 81.39 %. Finally, based on future climate scenario data, the changes in TCs and their impact on the trend of O3 are discussed. Under the SSP2-4.5 scenario, the O3 in the warm seasons of the YRD is expected to increase by 8.3 μg/m3 compared with the historical period, and the SWP5 is expected to contribute the most to the estimated O3 concentration in 2030 (15.14 %). Under the SSP5-8.5 scenario, the O3 will increase by 10.9 μg/m3. The SWP5 is expected to contribute the most to the estimated O3 in 2060 (20.66 %). This shows that the intensification of climate change will intensify the impact of TCs on O3 in the YRD, and monitoring and early warning need to be strengthened.
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RC1: 'Comment on egusphere-2025-2466', Anonymous Referee #1, 11 Jul 2025
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I have carefully reviewed the manuscript entitled “The impact of tropical cyclones on regional ozone pollution and its future trend in the Yangtze River Delta of China”. While the topic is of potential interest and relevance, particularly in the context of climate change and regional air quality, I cannot recommend publication in its current form. The manuscript suffers from multiple major flaws in methodology, presentation, data interpretation, and referencing, which severely undermine its scientific credibility. I therefore recommend rejection, although a substantially revised version may be reconsidered as a new submission. My major and specific concerns are listed below.
Major concerns:
1. The authors identify five synoptic weather patterns (SWPs) using a rotated principal component analysis (PTT method), but they do not provide adequate information on the physical characteristics of these SWPs or justify the use of different meteorological parameters and domains in defining their intensities (Lines 167–171, 259–264).
Furthermore, Table 1 suggests that some SWPs primarily occur in winter, spring, and autumn, while SWP2 and SWP5 dominate in summer. This implies a strong seasonal signal embedded in the classification. However, the authors proceed to analyse O₃ pollution impacts without removing seasonal cycles, which is inappropriate given the strong seasonal variability in both O₃ precursors and photochemistry. Weather pattern classification should be conducted on seasonally detrended data to avoid conflating synoptic and seasonal influences.2. Many key numerical conclusions lack both graphical support and proper referencing (e.g., Lines 394–404, 436–438). For instance, the stated contributions of SWP5 to O₃ concentration changes—15.14% in 2030 and 20.66% in 2060—are not clearly contextualised. These values appear to indicate that SWP5 is the most influential within those respective years compared to other years, rather than compared to other weather patterns. However, the manuscript does not clearly define the comparison baseline, which may mislead readers into interpreting these percentages as reflecting the dominance of SWP5 over other synoptic types. Clarification is essential to avoid misinterpretation.
Several critical results, such as the contribution index and the role of TC-generated meteorological conditions (e.g., "low humidity and strong solar radiation"), lack quantitative evidence (Lines 309–311). This weakens the entire discussion on the role of TCs in driving O₃ changes.3. Throughout the manuscript—particularly in the introduction—numerous claims are either incorrectly cited, misrepresented, or not supported by the referenced sources. This significantly undermines the scientific credibility and rigour of the work.
Here are some examples, lines 38–40: The statement that O₃ accounted for over 50% of polluted days is not substantiated by the referenced China Ecological Environment Bulletin. The authors should provide the correct citation, improve the clarity of the English, and revise the conclusion to reflect the actual content of the report.
Lines 77–80: Assertions regarding the low-frequency modulation of tropical cyclones (TCs) by climate change are made without any credible or peer-reviewed references.
Lines 86–88: The claim that TC frequency in the Northwest Pacific has decreased, while intensity and duration have increased, is not convincingly supported by the cited literature. In fact, some references appear to be news media or secondary summaries rather than original peer-reviewed scientific studies.
Specific Comments
1. Line 50: Please spell out "TC" at first mention.
2. Lines 190–192: Claims on O₃ variation lack data or plots. Add evidence.
3. Lines 213–217: The description of two TC-O₃ response types is unsupported. Provide composite analysis and classify examples accordingly.
4. Lines 217–218: No references for TC genesis location or influence radius. Clarify language: “generation” implies early-stage oceanic development, likely too far from YRD to affect local O₃.
5. Lines 227–229: Claims not supported by figures. Add case studies or remove.
6. Lines 309–311: The link between TC conditions and “low humidity, strong solar radiation” is unsubstantiated. TCs often increase regional moisture. Provide observational support.
7. Line 348: The 500 hPa ridge discussion (Fig. 5g–i) is unclear. Differences between panels are not visually apparent. Consider replotting with clearer contrasts.
8. Lines 368–372: The “contribution index” needs a mathematical definition and justification. The interpretation lacks physical meaning without context.
9. Lines 393–394: Contradiction between SWP1's role here and in Table 1, where it corresponds to low O₃ levels. This undermines the credibility of classification.
10. Figure 1 caption: Missing units and variable definitions.
11. Figures 3 & 4: The presentation of SWPs is unclear. Color bars and annotations should be enhanced for readability. Distinctions among SWPs are not evident visually.
12. Materials and Methods: Define the "daily 8h average O₃" precisely, including time windows.
Citation: https://doi.org/10.5194/egusphere-2025-2466-RC1
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