Abstract Ambient ozone () levels in China have risen in recent years, impacting air quality, atmospheric chemistry, and climate forcing. formation varies regionally due to differences in emissions and meteorology. This study investigates the atmospheric presence and transformation of and its sensitivity to and VOCs across China from 2015 to 2020. Using long‐term measurement data, we clustered the spatial distribution of to evaluate precursor impacts and exposure risks for humans and vegetation. sensitivity in each region was analyzed using the WRF‐Chem model. Seasonal sensitivity shifts show ‐sensitive regimes dominating in summer (>50% probability), while the probabilities of titration is 10%. VOC‐sensitive regimes prevailing in winter (40% chance), with 30% chance of titration, likely driven by emission changes such as wintertime heating. Most regions exceed long‐term exposure limits, with the North China Plain and Northeast Plain facing the highest human and vegetation risks. Furthermore, we analyzed anomalous concentrations during the COVID‐19 pandemic using the established sensitivity regimes, revealing influence of reduced emissions and meteorological conditions. Global sensitivity analysis (GSA) employing a Gaussian Process (GP) emulator demonstrated that transportation‐related emissions are the primary driver of concentrations in China, highlighting that increased precursor emissions do not necessarily raise levels. This study provides valuable insights into the spatiotemporal characteristics and determinants of , enhancing the understanding of its atmospheric behavior and transformation. The findings offer guidance for managing air quality and mitigating pollution in the context of emerging atmospheric tracers.
Ka Lok Chan (Fri,) studied this question.
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