Characterizing the Variations of Total Column, Profile, and Surface Ozone in the Huaihai Economic Zone of China

The Huaihai Economic Zone (HEZ) of China is an important industrial region experiencing substantial surface ozone (O3) pollution. To characterize the long-term spatiotemporal and vertical variability of ozone over the HEZ, we integrated satellite-derived total column ozone (TCO), Ozone Monitoring Instrument (OMI) ozone profiles, and the ChinaHighO3 surface ozone product. OMI data for 2005–2022 showed a pronounced seasonal cycle in TCO, with daily mean values ranging from approximately 248 to 385 DU. Empirical orthogonal function (EOF) analysis indicated that the dominant TCO variability was characterized by a spatially coherent regional mode. The Pettitt test detected no statistically significant change point in the dominant TCO principal component (PC1; p = 0.197), indicating that its temporal evolution should be interpreted as variability in PC behaviour rather than a regime shift. Layer-by-layer trend analysis of OMI ozone profiles during 2005–2020 identified statistically significant trends in 15 of the 18 vertical layers, ranging from −1.24 to 2.67 DU decade−1. The strongest positive trend occurred near 14 hPa (2.67 DU decade−1, p < 0.001), demonstrating pronounced vertical heterogeneity in long-term ozone changes. ChinaHighO3 surface ozone showed an overall increasing tendency during 2005–2023, with a more pronounced increase after 2018. EOF analysis of the detrended and deseasonalized ChinaHighO3 fields showed that the dominant surface-ozone mode underwent a statistically significant change in temporal behaviour around 2016–2017, as confirmed by the Pettitt test (p < 0.001). Multiple linear regression (MLR) explained 86.8% of the monthly ChinaHighO3 surface O3 variability (R2 = 0.868), with temperature showing the highest relative importance (44.7%), followed by NO2 (28.0%), relative humidity (15.9%), and surface solar radiation (11.4%). Overall, TCO, vertically resolved ozone, and surface ozone exhibit distinct temporal and vertical characteristics over the HEZ, highlighting the importance of considering atmospheric-layer-specific processes and meteorological and precursor-related variability when interpreting regional ozone changes and managing surface ozone pollution.