Anthropogenic emissions dominate long-term trends of ozone production sensitivity in southeastern China derived from the ozone monitoring instrument.

This study analyzes the spatiotemporal evolution of ozone (O3) production sensitivity in Fujian province, from 2005 to 2020 using satellite-derived formaldehyde to nitrogen dioxide ratios (FNR). The monthly 16-year analysis reveals a shift towards a more frequent NOx-limited regime and a less frequent VOC-limited regime, with non-coastal cities showing greater seasonal FNR variability. Long-term trends, isolated by kolmogorov-zurbenko adaptive (KZA) filter, indicate a consistent annual FNR increase, suggesting a shift towards transitional/NOx-limited conditions, particularly in non-coastal areas, while coastal regions transition more slowly from VOC-limited. Spatial FNR distributions highlight VOC-limited regimes in developed coastal areas and transitional/NOx-limited regimes non-coastal areas. While meteorological factors drive the monthly variation of FNR (51 % to 70 %), anthropogenic emissions dominate long-term trends (63 % to 84 %), as determined by XGBoost and SHAP analysis. This indicates that, from a long-term perspective, emission reductions simultaneously alter O3 sensitivity. Therefore, to more effectively mitigate O3, our emission control strategies must also account for the changes in O3 sensitivity that reductions of NOx and VOCs bring about.