the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Jul 2025
Investigating the Mechanism of Typhoon Tracks on Ozone Pollution Episodes in Guangdong, China
Abstract. Ozone (O3) pollution has emerged as one of the core challenges in atmospheric environmental governance in China, particularly in Guangdong Province. As a crucial weather system during East Asian summers, typhoons exert profound influences on O3 formation, accumulation, and transboundary transport through variations in their tracks and intensities. This study examined 237 historical typhoons occurring in China's coastal waters between 2013–2023, classifying them into three distinct trajectory types using k-means clustering: westward-moving typhoons (Type 1), Distant northward-recurving typhoons (Type2) and Proximal northward-recurving typhoons (Type3). By integrating ground-based observations, reanalysis data, and WRF-CMAQ model simulations to investigate the mechanisms through which typhoon tracks affect ozone pollution in Guangdong Province. The results demonstrate that for Guangdong Province, proximal northward-recurving typhoons induce more extreme meteorological conditions compared to westward-moving and distant northward-moving typhoons. Backward trajectory analysis reveals that northward-moving typhoons significantly enhance vertical downward transport of upper-level ozone, increasing ozone vertical gradients in Guangdong Province, with concentration enhancements of 2.5–11.6 ppbv (Type 2) and 0.3–12.3 ppbv (Type 3). The analysis of consecutive northward-moving typhoons' impact on ozone pollution in Guangdong Province reveals that surface photochemical reactions served as the dominant factor, while vertical downward transport of upper-level ozone acted as a secondary contributor. During this event, vertical transport contributed up to 39.9 ppbv to near-surface ace (100 m) ozone concentrations, with cross-boundary-layer transport accounting for up to 16 % of boundary layer ozone concentrations, demonstrating that typhoon-induced vertical transport significantly enhances boundary layer ozone levels and consequently worsens surface pollution.
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Status: open (until 05 Dec 2025)
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RC1: 'Comment on egusphere-2025-2635', Anonymous Referee #1, 21 Nov 2025
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AC1: 'Reply on RC1', Xuemei Wang, 03 Dec 2025
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Thank you for your comment. Please refer to the supplement for the reply.
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AC1: 'Reply on RC1', Xuemei Wang, 03 Dec 2025
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RC2: 'Comment on egusphere-2025-2635', Anonymous Referee #2, 24 Nov 2025
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This study analyzed the effects of different typhoon tracks on the ozone concentrations through chemical formation, dispersive condition, horizontal and vertical transport using ground-based observations, reanalysis data, and atmospheric chemistry simulation. The analyses and interpretation are sound and reasonable. I only have minor comments.
- I did not find a data availability section. There are many data included in this study. It would be better to list their public availability.
- Line 338-339: when the typhoon is distant from the target area, how can the local ozone concentrations be attributed to distant typhoon instead of local generation?
- Line 368-370: how would the seasonal biases of meteorological data be eliminated for the comparison between typhoon days and non-typhoon days?
- Line 373-374: Why does 14:00 local time be chosen specifically?
- Line 490-491: How can the selection of June to November help to eliminate the seasonal biases? There are still large variations from summer to fall.
- Line 635-636: By the dominance of photochemical reactions, is it dominated by the promoted reaction rates or the promoted precursor concentrations? Generally, how would regional transport of precursor promote the generation of ozone at the target area?
Citation: https://doi.org/10.5194/egusphere-2025-2635-RC2 -
AC2: 'Reply on RC2', Xuemei Wang, 03 Dec 2025
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Thank you for your comment. Please refer to the supplement for the reply.
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Summary
This manuscript systematically investigated the impact of typhoon tracks on ozone pollution in Guangdong, China. It classifies the three type of typhoon paths, quantifies their occurrence frequency and the extent of their impact on ozone, and further elucidates the underlying process mechanisms. Such work is a good supplement to the typhoon–ozone studies. However, some details and explanations need further clarification. I suggest a major revision before the paper can be accepted by Atmospheric Chemistry and Physics. My detailed comments are listed below.
Major comments
In the abstract, L53–56 emphasize the role of vertical transport, L56–60 claim that chemical production is the main contributor, and L60–64 again stress the impact of cross-boundary-layer vertical transport. This presentation is somewhat disjointed. The authors should integrate these findings into a logically coherent narrative, rather than simply listing results from the main text, and should clarify which conclusions are drawn from mean-state analyses and which are based on individual cases.
The second and third paragraphs of the Introduction should be more concise, explicit, and logically organized to clearly summarize the progress of previous studies and highlight the specific research gap or problem that this work aims to address.
L228-229: I am concerned whether setting only 14 vertical layers in the model is sufficient to accurately resolve vertical motions. How many of these layers are within the boundary layer, and how many are in the free troposphere?
L336–340: It is indeed interesting that a typhoon at such a large distance (even as far north as 60°N) could still influence ozone pollution in the PRD. However, attributing this effect to long-range transport requires supporting evidence.
L430–432: Why would upper-tropospheric convergence lead to stratospheric intrusions into the boundary layer? Does the stratospheric intrusion occur over the North China Plain (NCP)? How does it affect ozone pollution in Guangdong? If L497–501 are intended as an explanation for this issue, they should appear earlier on page 20 to clearly elaborate how stratosphere–troposphere exchange and regional transport contribute to ozone pollution in Guangdong.
L494-495: Does “2.5–11.6 ppbv” and “0.3–12.3 ppbv” refer to column-averaged concentrations? This needs to be clearly stated here as well as in the abstract.
L666: This expression is not sufficiently rigorous. You seem to be calculating a contribution rate, but the two terms on the right-hand side have different units, and their ratio therefore cannot yield a dimensionless contribution. 𝐼𝑃𝑅𝑣,𝑝𝑏𝑙 represents a change in concentration, it should be multiplied by the corresponding time interval. Moreover, the left-hand side should not be labeled as a “transport flux,” which denotes mass passing through a unit area per unit time.
Minor comments
L89: "。" --> ".";
L88: "NOx" --> "NOx";
L94: You have already defined the abbreviation of O3 at L85.
L108: "leads to the formation of elevated ozone concentrations"--> " leads to the elevated ozone concentrations";
L115: "ozone formation efficiency.(Wang et al., 2022a)" --> "ozone formation efficiency (Wang et al., 2022a)";
L274: Please check that “degree” or “ ° ” is used consistently throughout the manuscript.
L566：How were the ozone concentration values marked along the trajectories in Figure 7 obtained?
L717: what is the "radiative high-pressure system"?