Multi-Temporal Scale Response Analysis of Ozone Pollution over Eastern and Central China

Ozone (O3) pollution exhibits complex, scale-dependent variability across short-term (ST), seasonal (SN), and long-term (LT) temporal scales. However, most existing studies examine individual scales separately and focus on static within-scale relationships, leaving cross-scale response relationships insufficiently understood. This study focuses on eastern and central China (105° to 125° E, 20° to 42.5° N) and combines daily gridded fields of O3, NO2, HCHO, and isoprene from the ECMWF EAC4 reanalysis with ERA5 meteorological data for 2017–2025. Treating O3 and its major precursors as a coupled system, a dual-layer Gaussian low-pass filter was applied to standardized pollutant fields to separate ST, SN, and LT components. Joint Empirical Orthogonal Function (EOF) decomposition was then used to identify spatial modes and principal component time series characterizing the co-evolution of ozone and its precursors at each scale. A Physics-Informed Neural Network (PINN) was incorporated to explore potential physical drivers underlying each mode, while rolling multivariate Ordinary Least Squares (OLS) regression and a Convolutional Neural Network–Bidirectional Long Short-Term Memory (CNN–BiLSTM) model were combined to quantify cross-scale response intensity (β) and its temporal variability. Results indicate that (1) modal coupling relationships across temporal scales are continuously evolving. When primary modes (M1) serve as targets, responses generally weaken (→: slope = −0.053 yr−1, →: slope = −2.82 yr−1). When secondary modes (M2) serve as targets, responses strengthen (→: slope = +4.285 yr−1, →: slope = +0.252 yr−1). (2) Even if the long-term upward trend in concentrations is curbed, the continued strengthening of the negative modulation of (−0.053 yr−1) may still cause short-term extreme event risks to increase rather than decrease. (3) Only a marginally significant upward trend is shown (Theil-Sen slope = +10.23 yr−1, p = 0.048).