Technical note: Adaptably diagnosing O₃-NO_x-VOC sensitivity evolution with routine pollution and meteorological data

Abstract. Elucidating the evolving O₃-NO_x-VOC sensitivity in response to varying precursor emission trends is critical for mitigating the elevating ozone. Due to the complexities and resource constraints inherent in conventional methods, we developed an adaptable methodology addressing this issue through empirical parametric regression of routine data (O₃/NO_x/NO₂). The log-Bragg3 model (Equation 3) performed best in globally characterizing the daytime ozone production (DPO₃)-NO_x (or NO₂) relation, including regions with severe PM_2.5 contamination where ozone formation is additionally influenced by aerosol-inhibited photochemical regime. Over 95 % of these fits achieved statistical significance (p<0.1). This model provides parametric interpretations of ozone formation intensity (d), the associated chemical processes (b), and the O₃-NO_x-VOC sensitivity partition threshold (e). More vigorous photochemical reactions are implicated in the studied Chinese regions by higher values of parameters b (0.87–2.42) and d (34.72–54.78) relative to EU/US (b=0.26–0.57, d=9.97–31.45). Divergent temporal trends in parameter b further indicate fundamentally distinct evolutionary pathways in regional ozone chemistry between China and EU/US. Specific to MDA8-daytime hours, the Chinese city agglomerations were all diagnosed as being in the VOC-limited regime in both 2014 and 2019 on the regional scale, exhibiting significantly higher spatial predominance than the previous satellite-derived HCHO/NO₂ ratio inferences. The DPO₃-NO₂ pseudo-diagnosis constituted major uncertainty in spatiotemporal diagnosis, whereas the DPO₃-NO_x curve showed superior reliability. This methodology helps provide critical insights for formulating spatially differentiated precursor control policies.