the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 10 Oct 2024
Investigating the response of China’s surface ozone concentration to the future changes of multiple factors
Abstract. Climate change and associated human response are supposed to greatly alter surface ozone (O3), an air pollutant generated through photochemical reactions involving both anthropogenic and biogenic precursors. However, a comprehensive evaluation of China’s O3 response to these multiple changes has been lacking. We present a modelling framework under Shared Socioeconomic Pathways (SSP2-45), incorporating future changes in local and foreign anthropogenic emissions, meteorological conditions, and BVOCs emissions. From the 2020s to 2060s, daily maximum 8-hour average (MDA8) O3 concentration is simulated to decline by 7.7 ppb in the warm season (April–September) and 1.1 ppb in non-warm season (October–March) over the country, with a substantial reduction in exceedances of national O3 standards. Notably, O3 decreases are more pronounced in developed regions such as BTH, YRD, and PRD during warm season, with reductions of 9.7, 14.8, and 12.5 ppb, respectively. Conversely, in non-warm season, the MDA8 O3 in BTH and YRD will increase by 5.4 and 3.4 ppb, partly attributed to reduced NOx emissions and thereby weakened titration effect. O3 pollution will thus expand into the non-warm season in the future. Sensitivity analyses reveal that local emission change will predominantly influence future O3 distribution and magnitude, with contributions from other factors within ±25 %. Furthermore, the joint impact of multiple factors on O3 reduction will be larger than the sum of individual factors, due to changes in the O3 formation regime. This study highlights the necessity of region-specific emission control strategies to mitigate potential O3 increases during non-warm season and under climate penalty.
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RC1: 'Comment on egusphere-2024-2713', Anonymous Referee #1, 18 Oct 2024
The authors presented a comprehensive and detailed analysis of the response of surface O3 concentrations in China to future changes including factors of anthropogenic and biogenic emissions, meteorology, and transboundary transport. The topic is interesting, and the analysis is important for a better understanding of surface O3 evolution in the future. I recommend this manuscript for publication, after consideration of the points below:
Lines 40-43: here the authors emphasized the threat of O3 pollution to human health, crop yield, and short-lived climate change. However, the references mainly focused on crop yield and there is only one reference (Jerrett et al. 2009) for human health. It is suggested to cite a few more recent studies about human health.
Lines 114-118: recent studies (Hou et al. 2023; Liu et al. 2023) analyzed the effects of emission reduction on surface O3 evolution in China in warm and non-warm seasons, which may be worth citing. Furthermore, as discussed in Lines 123-128: Hou et al. (2023) analyzed the effect of global emission reduction on surface O3 evolution in China. Its conclusion seems consistent with this work.
Hou, X., Wild, O., Zhu, B., and Lee, J.: Future tropospheric ozone budget and distribution over east Asia under a net-zero scenario, Atmos. Chem. Phys., 23, 15395-15411, 10.5194/acp-23-15395-2023, 2023.
Liu, Z., Wild, O., Doherty, R. M., O'Connor, F. M., and Turnock, S. T.: Benefits of net-zero policies for future ozone pollution in China, Atmos. Chem. Phys., 23, 13755-13768, 10.5194/acp-23-13755-2023, 2023.
Lines 202-205: Here the description of the emission changes outside of the Chinese mainland seems inconsistent: “Emissions outside Chinese mainland are obtained from CMIP6 dataset under SSP2-45 scenario”; “emissions outside Chinese mainland are assumed the same as those in MIX Asian emission inventory”.
Figure 3: The increase in O3 concentration over the BTH in the non-warm season is interesting. I found it is consistent with the modeled results of Hou et al. 2023 and Liu et al. 2023. It is suggested to cite these studies to support the simulation in this work.
Figure 7: The modeled O3 chemical regime evolution in the 2020s is very interesting. It seems consistent with recent observation-based analysis (Chen et al. 2023; Kong et al. 2024). However, it is surprising that the O3 chemical regime is still around the turning point in BTH in the 2060s. Considering the rapid cross of the turning point in the US in 1990-2010, what policy suggestions can the authors give?
Chen, X., Wang, M., He, T. L., Jiang, Z., Zhang, Y., Zhou, L., Liu, J., Liao, H., Worden, H., Jones, D., Chen, D., Tan, Q., and Shen, Y.: Data‐ and Model‐Based Urban O3 Responses to NOx Changes in China and the United States, J. Geophys. Res.-Atmos., 128, e2022JD038228, 10.1029/2022jd038228, 2023.
Kong, L., Song, M., Li, X., Liu, Y., Lu, S., Zeng, L., and Zhang, Y.: Analysis of China's PM(2.5) and ozone coordinated control strategy based on the observation data from 2015 to 2020, J Environ Sci (China), 138, 385-394, 10.1016/j.jes.2023.03.030, 2024.
Lines 421-422: It may not be good to have a paragraph with only one sentence.
Table S1: the values of simulated O3 concentrations seem incorrect.
Citation: https://doi.org/10.5194/egusphere-2024-2713-RC1 -
RC2: 'Comment on egusphere-2024-2713', Anonymous Referee #3, 05 Dec 2024
This study explores the response of surface ozone concentration in China to the future changes of multiple factors (domestic and foreign anthropogenic emissions, biogenic emissions, and meteorological conditions) under SSP2-45 scenario, based on a series of sensitivity experiments with WRF-MEGAN-CMAQ simulations. The combined and individual effects are quantified and discussed with informative figures. In general, this study is well-structured, with the results well supported by the analyses, and is well written. The manuscript can be improved by addressing the following comments.
Section 2.3: Using the five-year mean to represent present and future scenarios is commendable. Have the authors noted any significant interannual variability within these five-year simulations that should be discussed?
Line 229: Could you please specify which surrounding areas are considered in the analysis?
Figure 2: What causes the difference in wind speed between the warm season and non-warm season?
Table S4: Can you explain what the colors represent?
Conclusions and discussions: Some studies have indicated that soil NOx emissions from agricultural activities will become increasingly important in ozone formation, especially as NOx emissions from fuel combustion decrease. It is unclear how soil NOx emissions are addressed in this study. How might these emissions influence the ozone projections conducted here?
Citation: https://doi.org/10.5194/egusphere-2024-2713-RC2
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