Enhancement of Arctic surface ozone during the 2020–2021 winter associated with the sudden stratospheric warming

Surface ozone is an important pollutant causing damage to human health and ecosystems. Here, we find that the Arctic surface ozone during the 2020–2021 winter was evidently enhanced after the sudden stratospheric warming (SSW) onset based on reanalysis data and simulations of a state-of-the-art chemistry-climate model. Further analysis suggests that this enhancement of Arctic surface ozone is primarily a result of the strengthening of the stratosphere-to-troposphere transport associated with the SSW. It is found that the SSW leads to more ozone in the Arctic stratosphere and enhanced downward transport with SSW-related downdraft. The 2021 SSW may also lead to positive anomalies in surface ozone in the northern midlatitudes, which are associated with cold air outbreaks. Our results indicate that the SSW not only affects the weather and climate in the troposphere but may also affect the surface air quality.