Impacts of Synoptic Patterns and Meteorological Factors on Distribution Trends of Ozone in Southeast China During 2015-2020

Surface ozone (O-3) pollution under global climate change has become one of the top environmental issues. In this study, we focused on the coastal region in Southeast China with relatively low O-3 precursor's emissions and complicated synoptic conditions, where the O-3 trends and meteorological contributions remain unclear. An increasing trend of O-3 concentrations in the cities (0.3-4.6 mu g m(-3) yr(-1)) from 2015 to 2020 was observed. Twenty-three synoptic patterns were clustered based on weather typing method, in which cyclone-related types and southwesterly type were generally associated with low O-3 concentrations, and high O-3 levels occurred with anticyclone-related types. Considering both frequency and intensity of synoptic patterns, reconstructed O-3 series captured 46.0%-58.3% of the observed variability. Using Kolmogorov-Zurbenko filter, an increasing trend of long-term O-3 was found. By implementing the multiple linear regression model between O-3 concentrations and meteorological factors, the meteorological contributions to O-3 variabilities (44.7%-66.1%) were quantified. The results indicated the meteorological conditions were particularly important in O-3 pollution with the reductions of O-3 precursor's emissions, among which relative humidity, boundary layer height, solar radiation along with low cloud cover were proved to play important roles. The weakening southwest winds along with more anti-cyclone systems under climate change could increase surface O-3. This study elucidated the crucial meteorological drivers on the O-3 variability in relatively clean areas and implied the challenges for local governments to mitigate O-3 pollution under global climate change. Plain Language Summary Ozone (O-3) pollution has become one of the top environmental issues in recent years and can be affected not only by O-3 precursors (volatile organic compounds and nitrogen oxides) but also meteorological condition. Under global climate change, there is a need to deeply understand the impact of meteorological factors on surface O-3 concentrations with the decrease of O-3 precursors. In this study, we focus on the coast area of Southeast China with relatively low O-3 precursors emissions and influenced by the East Asia monsoon. Temporal and spatial variations of O-3 concentrations along with the meteorological impacts on O-3 variabilities from 2015 to 2020 were analyzed. The results show that the relative meteorological contributions on O-3 trends were 44.7%-66.1%. The higher temperature, lower relative humidity, more solar radiation, weakening southwest winds along with more anti-cyclone systems under climate change could increase surface O-3. This study is beneficial to understand different mechanisms of meteorological impacts on O-3 variations in the relatively clean areas, and find out the key drivers to cause O-3 pollution with the decrease of O-3 precursors emissions and climate change.

Automated summary

Surface ozone pollution in Southeast China is a pressing environmental issue under global climate change. This study investigated the trends and meteorological contributions of ozone concentrations in the region from 2015 to 2020. It was found that ozone concentrations showed an increasing trend in cities, and various meteorological factors were identified as important drivers of ozone pollution. The study highlights the importance of understanding the impact of meteorological conditions on ozone concentrations in relatively clean areas.