随着大气污染防治行动计划的实施，近年来中国颗粒物（PM2.5）污染得到了明显的改善，但重点区域的臭氧污染问题显现，且有加剧的趋势。承接“大气十条”，国家新发布《打赢蓝天保卫战三年行动计划2018-2020》在主要污染物PM2.5的控制目标上，也强调了对臭氧污染的控制。针对“短期减排对臭氧的年际变化趋势有何影响？影响臭氧重污染变化的机制如何？”这些科学问题，本项目拟结合各类臭氧浓度观测与模式的机理研究，分析2012-2018年中国地区臭氧重污染变化特征和影响机制；综合探讨人为及自然排放、气象、气溶胶及对流层-平流层交换等因素对我国（尤其是京津冀、长三角、珠三角和成渝盆地）臭氧浓度变化趋势的分别和共同影响，对认识臭氧浓度长期变化趋势具有重要的科学意义。通过模式敏感性试验评估当前的减排措施能否有效减少臭氧重污染事件的发生，为控制大气复合污染提供科学依据。

With the implementation of air pollution prevention and control actions plan, the haze problem has effective improved but the ozone pollution has not decreased and is seemingly getting worse, especially in city clusters of China. We examine in this proposal the inter-annual changes in surface ozone over China over 2012-2018, by using a global chemical transport model GEOS-Chem. Simulated ozone pollution are evaluated by using the observed ozone concentrations from the National environmental air quality monitoring network. The combined or separated roles of variations in anthropogenic emissions, biogenic emissions, meteorological parameters, aerosols and Strat-Trop exchange on surface ozone concentrations are quantified by the model’s sensitivity studies. We pay special attention to the impacts of short-term emission reduction plans on the ozone pollution and the inter-annual trend of ozone concentration over the four regions including the Beijing-Tianjin-Hebei, Yangtze River Delta, Pearl River Delta, and Sichuan Basin.