Rapid increase in spring ozone in the Pearl River Delta, China during 2013-2022

Surface ozone pollution is a severe air pollution problem and typically occurs in the warm season since it is driven by photochemistry. Recent studies showed a tendency for ozone pollution to spread into the cold season. Yet, less attention was paid to its evolution and causes. Here, we show general uptrends in surface ozone of 1.15 ppbv a-1 during the spring (March to May) over the past decade (2013-2022) in the Pearl River Delta, China. The meteorological shift, primarily the increase in northerly airflow at the 850hPa level and the rise in net surface solar radiation flux (SSR), accounted for 77% of the ozone growth, as determined by the multiple linear regression model. The change in three meteorological factors, namely SSR, U10, and V850, especially in the stagnant weather conditions, are critical in driving spring ozone increase, and their relative importance differs between inland and coastal regions. These results show that the meteorological-induced springtime ozone pollution warrants vigilance, as spring ozone pollution control in climate-sensitive areas, will be more challenging towards climate change.