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 O3 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

This study focused on the trends and meteorological contributions of surface ozone (O-3) pollution in the coastal region of Southeast China. It was found that meteorological conditions, such as relative humidity, boundary layer height, solar radiation, and cloud cover, played important roles in O-3 variability. The weakening southwest winds and increased anti-cyclone systems under climate change were identified as factors that could increase surface O-3 levels. This study provided valuable insights into the meteorological drivers of O-3 pollution in relatively clean areas and highlighted the challenges of mitigating O-3 pollution under global climate change.