Observational analysis of surface ozone variability in China from 2015 to 2020: Insights from consecutive ENSO episodes

Utilizing daily surface ozone (O3) concentration data (MDA8-O3) from nearly 1500 monitoring stations across mainland China, complemented by gridded atmospheric reanalysis data, this study conducts a comprehensive analysis of O3 concentration, anomalies, and oscillations. Employing regression and composite analyses, we investigate the potential linkage between O3 variations and the phase and strength of El Nino-Southern Oscillation (ENSO) across diverse regions and seasons in China. Noteworthy findings include the identification of regions exhibiting peak O3 concentrations in autumn or spring, deviating from the typical seasonal cycle, as well as regions exhibiting varying strengths of seasonal and semi-annual O3 oscillations. Moreover, the study unveils the spatiotemporal patterns of synoptic and intra-seasonal O3 oscillations. The analyses reveal a prevailing inverse association between O3 anomalies and ENSO in most Chinese regions except for the southern and southeastern coastal areas. The potential impacts of ENSO on O3 are elucidated by anomalous atmospheric conditions linked to ENSO, the nature of which strongly depends on the region and season. In northern China, anomalous temperature and solar radiation related to ENSO exert a more pronounced influence on O3 anomalies. On the other hand, in southern China, anomalies in wind speed/direction and precipitation associated with anomalous atmospheric circulations play a more predominant role. These findings contribute valuable insights to the nuanced understanding of O3 variability, paving the way for the development of sophisticated O3 forecasting approaches tailored to different regions and seasons across China.