Chemical drivers of ozone change in extreme temperatures in eastern China

Surface ozone pollution has become the biggest issue in China's air pollution since particulate matters have been im-proved in the atmosphere. Compared with normal winter/summer, extremely cold/hot weather sustained several days and nights by unfavorable meteorology is more impactful in this regard. However, ozone changes in extreme tem-peratures and their driving processes remain rarely understood. Here, we combine comprehensive observational data analysis and 0-D box models to quantify the contributions of different chemical processes and precursors to ozone change in these unique environments. Analyses of radical cycling indicate that temperature accelerates OH-HO2- RO2, optimizing ozone production efficiency in higher temperatures. The HO2 + NO -OH + NO2 reaction was the most influenced by temperature change, followed by OH + VOCs -HO2/RO2. Although most reactions in ozone formation increased with temperature, the increase in ozone production rates was greater than the rate of ozone loss, leading to a fast net ozone accumulation in heat waves. Our results also show that the ozone sensitivity re-gime is VOC-limited in extreme temperatures, highlighting the significance of volatile organic compound (VOC) con-trol (particularly the control of alkenes and aromatics). In the context of global warming and climate change, this study helps us deeply understand ozone formation in extreme environments and design abatement policies for ozone pollu-tion in such conditions.

Automated summary

Surface ozone pollution has emerged as the major concern in China due to the improvement in particulate matters in the atmosphere. Unfavorable meteorology conditions, such as prolonged extremely cold or hot weather, have a significant impact on ozone formation. However, the mechanisms behind ozone changes in extreme temperatures remain poorly understood.