A Three-Regime Transition of Ozone Control Driven by Northward-Moving Tropical Cyclones: From Local Chemistry to Transport-Supported Replenishment

Tropical cyclones (TCs) profoundly reshape ozone (O 3 ) pollution in coastal regions, yet their mechanistic impacts across the full life cycle remain insufficiently understood. By integrating a decadal (2014–2023) observational data set with multiscale numerical simulations, this study resolves the phase-dependent response mechanisms under northward-moving TCs over the Yangtze River Delta (YRD). The study characterizes a systematic transition among three fundamentally distinct control regimes. Before landfall, large-scale subsidence and stagnant, high-temperature conditions catalyze intense in situ photochemical production under a VOC-limited regime, elevating O 3 to ∼91 ppb. During landfall, VOC-based O 3 formation potential decreases by 66.5% relative to P1, as cloud- and rainfall-related radiation reduction, enhanced ventilation, and deposition-related losses suppress photochemical O 3 formation. Following TC passage, surface O 3 rebounds, with nonlocal source contributions increasing from 41.3% to 63.3%. This rebound is not attributable solely to direct near-surface O 3 advection. Instead, it is consistent with the combined effects of enhanced nonlocal influence, elevated-layer photochemical production, and subsequent vertical redistribution toward the surface. These findings establish TCs as active modulators that sequentially restructure the relative importance of chemistry, transport, and deposition. Our results underscore the necessity of vertically explicit diagnostics and coordinated regional precursor controls to mitigate extremes in a warming climate where TC characteristics are rapidly evolving.