Aerosol-ozone interactions: an example from five coastal provinces in Southeast China

Studying aerosol-ozone interactions provides a better understanding of atmospheric chemical processes and their impact on climate. Aerosols affect ozone concentration by influencing the rate of photolysis and, thus, ozone concentration. However, how ozone varies with the radiative forcing induced by different modes of aerosols is unclear. Here in this study, the surface ozone concentration, aerosol concentration, and optical properties are analyzed based on data from remote sensing satellites and AERONET sites, and the effect of different modes of aerosol radiation on surface ozone is studied using the model of air exposure conveying (SBDART). The results show that (1) temporally, the aerosol optical thickness (AOD) and total ozone column in the five southeastern coastal provinces from 2005 to 2021 showed a downward trend, while the tropospheric ozone and near-surface ozone layer showed an upward trend. Seasonally, high values of AOD occurred from March to August, high values of surface ozone occurred in summer and autumn, and high-value of particulate matter (PM₁₀, PM_2.5) occurred in spring and winter. (2) Surface ozone concentration decreases at higher precursor NO_X and VOC_S concentrations and higher AOD values. At the same time, surface ozone is less diffusible at higher pressures and lower wind speeds, and the concentration further decreases. (3) The SBDART analysis shows that the surface radiative and atmospheric radiative forcing are in good agreement with the change characteristics of AOD. In contrast to the dust effect that decreases surface ozone, when urban pollution is high, fine-mode particulate matter decrease the number of sunbeam arriving the ground by insignificant amounts of radiation, the photosynthetic speed decreases insignificantly, and ground O₃ concentrations increase. Meantime, ground level O₃ affects radiative forcing, reducing negative aerosol radiative forcing (ARF) values at ground level by absorbing ground-level radiation. This study contributes to understanding the relationship between different modes of aerosol radiative forcing and ozone. It may provide an adequate scientific basis for aerosol radiative forcing affecting ozone.