the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Climate-driven biogenic emissions alleviate the impact of man-made emission reduction on O3 control in Pearl River Delta region, southern China
Abstract. O3 concentrations in the Pearl River Delta (PRD) during summer are typically low and often overlooked. However, integrated observational data reveal a consistent increase in summer O3 levels over recent decades (+0.96 ppb/year), contradicting China's efforts to reduce anthropogenic emissions. Our dynamically calculated natural emissions show that biogenic volatile organic compound (BVOC) emissions in the region significantly increased between 2001 and 2020, primarily due to climate change and alterations in vegetation cover, with climate-driven BVOC emissions accounting for approximately 80 % of the increase. Furthermore, parallel simulations using the WRF-CMAQ model indicate that climate-driven BVOC emissions, by enhancing atmospheric oxidative capacity and accelerating O3 formation, have weakened or even offset the benefits of anthropogenic emission reductions, contributing 6.2 ppb to O3 formation and leading to an unexpected rise in O3 levels. This study enhances our understanding of the mechanisms behind natural emissions in urban O3 formation under climate change and provides insights for future O3 pollution control strategies.
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RC1: 'Comment on egusphere-2024-3771', Anonymous Referee #1, 11 Feb 2025
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This manuscript analyzes the characteristics of summer BVOC emissions in the Pearl River Delta (PRD) region from 2001 to 2020 and uses WRF-CMAQ simulations to reveal that climate-driven increases in BVOC emissions lead to higher ozone concentrations in the region. The entire study appears technically sound, and the results are well interpreted. Thus, I recommend the publication by addressing the comments below.
- For Figure.1, The labels C and D in the title of Figure 1 should be swapped.
- For lines 179-183, meteorological conditions and vegetation distribution mutually influence each other, so is it reasonable to fix only one of them while keeping the other unchanged?
- For 2.3 section, please list the evaluation metrics for the Random Forest model to verify its accuracy.
- For lines 405-409, the authors reveled the rise of ozone levels from climate-driven BVOC emissions and vegetation-change BVOC emissions, respectively. What about the compound effect of the two effects?
- For Figure 5D, the PRD region shows a pair of symmetrical patterns with opposite effects. According to the author's description, under the influence of climate effects, areas with significant positive effects are mainly driven by heatwave days, while areas with significant negative effects are primarily due to extreme precipitation. Are there any relevant data or materials to further substantiate this claim?
Citation: https://doi.org/10.5194/egusphere-2024-3771-RC1
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