Observational Evidence of Aerosol Radiation Modifying Photochemical Ozone Profiles in the Lower Troposphere

Aerosol optical effects can trigger complex changes in solar shortwave radiation (SW) in the atmosphere, resulting in significant impacts on the photochemistry and vertical structure of ozone. This paper provides observational evidence of aerosol absorbing and scattering effects on modifying the SW and ozone profiles in the low troposphere. Using field vertical measurements and observation-based model simulations, we demonstrated that absorbing aerosols decreased SW, resulting in substantial inhibition of ozone production throughout the boundary layer (BL). A similar inhibition effect occurred within the lower BL under sufficient scattering aerosols. However, the scattering augmentation effect played an additional role in enhancing the photolysis rate and promoting ozone generation in the upper BL. Hence, the observational evidence as well as our model simulations disentangled the radiative effects of different types of aerosols on the vertical structures of ozone. Plain Language Summary Atmospheric aerosols can modify incident solar radiation by scattering and absorption, resulting in significant impacts on the photolysis rate and photochemical products in the lower troposphere. Such influences could be physically understood, but can only be observed with a detailed vertical measurement system. In this study, through vertical observational data analysis and observational constrained numerical simulations, we found that absorbing aerosols can weaken the shortwave radiation (SW) and photolysis rate in the entire layer, resulting in less ozone formation. In contrast, scattering aerosols enhance the SW and photolysis rate above the aerosol layer and promote ozone formation. Overall, the radiative effects of aerosols lead to an ozone decrease in the low layer and an increase above the boundary layer.