the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 25 Mar 2025
Cloud-radiation interactions amplify ozone pollution in a warming climate
Abstract. Ozone (O3) pollution has recently become the most critical air quality issue in China, yet its underlying drivers related to climate change remain poorly understood. Using a regional atmospheric chemistry model, along with 10-year ground-level O3 measurements and reanalysis data on low cloud cover (LCC) and surface downward shortwave radiation (SSRD), we found that O3 production is strongly modulated by LCC and SSRD. Cloud-radiation interactions (CRI) play significant roles in regulating O3 concentration, i.e., reduced LCC, increased SSRD, and weakened CRI are primarily responsible for the sharp increase in O3 concentration observed during the warm season of 2022 in the Yangtze River Delta, China. Moreover, climate warming is likely to exacerbate future O3 pollution via weakening CRI due to fewer clouds and more SSRD. To mitigate O3 pollution, we thus propose implementing more stringent emission reduction measures on O3 precursors, along with proactive strategies to address climate change.
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RC1: 'Comment on egusphere-2025-682', Anonymous Referee #1, 13 Apr 2025
In this paper, the authors conducted an analysis of the O3 observation and reanalysis data, employing WRF-Chem to quantify the contribution of CRI to O3 generation during the 2022 warm season. Furthermore, potential future O3 pollution risks are assessed based on the CMIP6. The manuscript’s structure and the English expression is good. I would like to review the following major comments.
General Comments
- This study focuses on the effect of CRI on O3 Nevertheless, a paucity of relevant reviews exists regarding the effects of LCC, SSRD and CRI on O3 production in the introduction. This deficiency hinders the comprehension of the significance of the work for readers, and consequently, the recommendation is made that relevant content should be incorporated.
- The authors conducted a comprehensive analysis of various factors leading to the abnormal increase in O3 concentration in July 2022, and emphasized the importance of CRI in them. It is recommended that the authors undertake a comparative analysis of the contribution of CRI to O3 change with that of other influencing factors, and incorporate a discussion on the relevant mechanism to enhance the clarity of the analysis.
- As demonstrated in Section 3, the analysis indicates that CRI has been shown to contribute significantly to the abnormal increase in O3 during the warm season of 2022. As the climate continues to warm in the future, lower LCC and higher SSRD are evident in CMIP6 products; however, the precise contribution of future CRI changes to future O3 trends remains unclear. It is recommended that the authors incorporate a more explicit discussion.
Specific Comments
Page 2, Line 19-31 It is recommended that numerical descriptions be included to facilitate a more profound comprehension of the impact of CRI on O3 among scholars.
Sect.2.2, Page 5, Line 174-175 Tabel S2 is recommended to be placed in the Figures to facilitate the reading process for the reader.
Sect.3.3, Page 10, Line 353-355 In order to enhance the clarity of the data, it is suggested that a greater emphasis be placed on the comparison of LCC and SSRD values.
In Table S2, the authors have devised a series of scenarios with the objective of quantifying the influence of different factors on O3. Given the focus of this paper on the contribution of CRI to O3 generation, it is suggested that CRI should be strengthened in scenario design, for example by numbering scenarios with or without consideration of CRI separately.
Citation: https://doi.org/10.5194/egusphere-2025-682-RC1 -
AC1: 'Reply on RC1', Shuyu Zhao, 20 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-682/egusphere-2025-682-AC1-supplement.pdf
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RC2: 'Comment on egusphere-2025-682', Anonymous Referee #2, 06 May 2025
General comments
The influences of emission changes, particularly the precursors, on ozone formation have drawn much attention in the science community, but few studies have focused on the photochemical condition related to solar radiation. Since the surface ozone is formed in photochemistry, the change in incident solar radiation is vital for ozone formation. The authors examine the crucial role of changing solar radiation, mostly perturbed by the appearance of clouds, in ozone formation in eastern China. Also, future scenarios of solar radiation and clouds are involved to present a projection of ozone pollution. The authors finally highlight that climate change will pose greater challenges for ozone pollution prevention and control in China. The manuscript is well organized with clear structure, and the language reads fluent. I still have some concerns in the introduction and future projections as shown in the major comments. The authors should address these issues soundly before its publication. Besides that, some technical revisions follow.
Major comments
- The introduction on the current knowledge of the impacts of solar radiation on ozone formation is insufficient, although the authors have introduced the meteorological factors that affect ozone formation. More information and references are suggested to be included in the Introduction.
- The comparison between the scenarios in 2021 and 2022 suggests crucial impacts of solar radiation on ozone. This result has a background that the anthropogenic emissions change little for these two years. This is indeed right because the two years are so close that the emissions shall not change much. Yet, for the SSP scenarios in the 21st century, emissions are expected to vary largely during the long term. What will the ozone pollution be considering both the changes in emissions and solar radiation? I suggest the authors to include more discussion on it.
- We know that the SSP scenarios have large uncertainties. In Figure 6, the SSP scenarios are shown from 2025 to 2099 only. As the first quarter of the 21st century has past, are these SSP scenarios consistent with the variations in real-world Tmax, TCC, and SSRD? The ERA5 reanalysis may help.
- The model validation approach should appear in Data and Method.
Minor comments
- L45-48: need references, also for L48-49
- L59: the temperature --> air temperature
- L95: in particular, and --> and, in particular,
- L227-235: The ozone variation during 2013-2021 is totally attributed to the emission changes in ozone precursors by the authors. Not any other contributors?
- L253-254: Revise the citation format
- L289: decimal precision --> decimal fractions
- L293-294: a should be an. I also see this typo in other lines of the text.
- L305: MB = -0.0 --> MB = 0.0
- L365: Noticeably, the correlation between O 3concentration and SSRD is more significant. Compare with what?
- Figure 1, L759: remove ‘map’; L764: the MEGAN --> MEGAN
Citation: https://doi.org/10.5194/egusphere-2025-682-RC2 -
AC2: 'Reply on RC2', Shuyu Zhao, 20 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-682/egusphere-2025-682-AC2-supplement.pdf
Status: closed
-
RC1: 'Comment on egusphere-2025-682', Anonymous Referee #1, 13 Apr 2025
In this paper, the authors conducted an analysis of the O3 observation and reanalysis data, employing WRF-Chem to quantify the contribution of CRI to O3 generation during the 2022 warm season. Furthermore, potential future O3 pollution risks are assessed based on the CMIP6. The manuscript’s structure and the English expression is good. I would like to review the following major comments.
General Comments
- This study focuses on the effect of CRI on O3 Nevertheless, a paucity of relevant reviews exists regarding the effects of LCC, SSRD and CRI on O3 production in the introduction. This deficiency hinders the comprehension of the significance of the work for readers, and consequently, the recommendation is made that relevant content should be incorporated.
- The authors conducted a comprehensive analysis of various factors leading to the abnormal increase in O3 concentration in July 2022, and emphasized the importance of CRI in them. It is recommended that the authors undertake a comparative analysis of the contribution of CRI to O3 change with that of other influencing factors, and incorporate a discussion on the relevant mechanism to enhance the clarity of the analysis.
- As demonstrated in Section 3, the analysis indicates that CRI has been shown to contribute significantly to the abnormal increase in O3 during the warm season of 2022. As the climate continues to warm in the future, lower LCC and higher SSRD are evident in CMIP6 products; however, the precise contribution of future CRI changes to future O3 trends remains unclear. It is recommended that the authors incorporate a more explicit discussion.
Specific Comments
Page 2, Line 19-31 It is recommended that numerical descriptions be included to facilitate a more profound comprehension of the impact of CRI on O3 among scholars.
Sect.2.2, Page 5, Line 174-175 Tabel S2 is recommended to be placed in the Figures to facilitate the reading process for the reader.
Sect.3.3, Page 10, Line 353-355 In order to enhance the clarity of the data, it is suggested that a greater emphasis be placed on the comparison of LCC and SSRD values.
In Table S2, the authors have devised a series of scenarios with the objective of quantifying the influence of different factors on O3. Given the focus of this paper on the contribution of CRI to O3 generation, it is suggested that CRI should be strengthened in scenario design, for example by numbering scenarios with or without consideration of CRI separately.
Citation: https://doi.org/10.5194/egusphere-2025-682-RC1 -
AC1: 'Reply on RC1', Shuyu Zhao, 20 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-682/egusphere-2025-682-AC1-supplement.pdf
-
RC2: 'Comment on egusphere-2025-682', Anonymous Referee #2, 06 May 2025
General comments
The influences of emission changes, particularly the precursors, on ozone formation have drawn much attention in the science community, but few studies have focused on the photochemical condition related to solar radiation. Since the surface ozone is formed in photochemistry, the change in incident solar radiation is vital for ozone formation. The authors examine the crucial role of changing solar radiation, mostly perturbed by the appearance of clouds, in ozone formation in eastern China. Also, future scenarios of solar radiation and clouds are involved to present a projection of ozone pollution. The authors finally highlight that climate change will pose greater challenges for ozone pollution prevention and control in China. The manuscript is well organized with clear structure, and the language reads fluent. I still have some concerns in the introduction and future projections as shown in the major comments. The authors should address these issues soundly before its publication. Besides that, some technical revisions follow.
Major comments
- The introduction on the current knowledge of the impacts of solar radiation on ozone formation is insufficient, although the authors have introduced the meteorological factors that affect ozone formation. More information and references are suggested to be included in the Introduction.
- The comparison between the scenarios in 2021 and 2022 suggests crucial impacts of solar radiation on ozone. This result has a background that the anthropogenic emissions change little for these two years. This is indeed right because the two years are so close that the emissions shall not change much. Yet, for the SSP scenarios in the 21st century, emissions are expected to vary largely during the long term. What will the ozone pollution be considering both the changes in emissions and solar radiation? I suggest the authors to include more discussion on it.
- We know that the SSP scenarios have large uncertainties. In Figure 6, the SSP scenarios are shown from 2025 to 2099 only. As the first quarter of the 21st century has past, are these SSP scenarios consistent with the variations in real-world Tmax, TCC, and SSRD? The ERA5 reanalysis may help.
- The model validation approach should appear in Data and Method.
Minor comments
- L45-48: need references, also for L48-49
- L59: the temperature --> air temperature
- L95: in particular, and --> and, in particular,
- L227-235: The ozone variation during 2013-2021 is totally attributed to the emission changes in ozone precursors by the authors. Not any other contributors?
- L253-254: Revise the citation format
- L289: decimal precision --> decimal fractions
- L293-294: a should be an. I also see this typo in other lines of the text.
- L305: MB = -0.0 --> MB = 0.0
- L365: Noticeably, the correlation between O 3concentration and SSRD is more significant. Compare with what?
- Figure 1, L759: remove ‘map’; L764: the MEGAN --> MEGAN
Citation: https://doi.org/10.5194/egusphere-2025-682-RC2 -
AC2: 'Reply on RC2', Shuyu Zhao, 20 Jun 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-682/egusphere-2025-682-AC2-supplement.pdf
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