Optimizing Ozone Control Strategies for Chinese Megacity Clusters Under the Influence of Stratospheric Intrusion

Abstract

Stratosphere intrusion (stratospheric intrusion (SI)), the largest natural source of ozone (O₃), poses a significant challenge for policymakers in developing effective O₃ control strategies. Understanding the emission reduction pathway under SI influence is crucial for achieving long-term O₃ attainment. However, the role of SI in tropospheric O₃ pollution in China remains poorly understood. To develop effective O₃ control strategies, we employed a localized comprehensive air quality model and the Whole Atmosphere Community Climate Model. We found that SI contributions vary seasonally, peaking in spring at lower latitudes and then delays northward progressively as latitude increases, with peak SI contributions at higher latitudes occur in June. Spatially, SI impacts surface O₃ most in high-latitude regions, decreasing with lower latitudes. As O₃-laden air reaches the surface, O₃ control strategies become less effective, necessitating additional emission reductions. As SI contributions increase, the optimal emission reduction pathway shifts: for the Beijing-Tianjin-Hebei and Pearl River Delta regions during the spring seasons from 2020 to 2023, it changes from “VOC only” to “NO_x only” at thresholds of 13.57 and 8.39 ppb, respectively. For Yangtze River Delta, Fenwei Plain, and Chengyu, the “VOC only” path remains optimal. This study provides valuable insights for policymakers to develop effective strategies to mitigate SI's negative effects.