[Impact of Climate Change on Summer Ozone in China]

Meteorological conditions have important impacts on surface ozone (O₃) formation. To evaluate the influence of future climate change on O₃ concentrations in different regions of China, this study employed the climate data from the community earth system model provided by the CMIP5 under the RCP4.5, RCP6.0, and RCP8.5 scenarios to generate the initial and boundary conditions for the WRF model. Then, the dynamic downscaling WRF results were fed into a CMAQ model as meteorological fields with fixed emission data. Two 10-year periods (2006-2015 and 2046-2055) were selected in this study to discuss the impacts of climate change on O₃. The results showed that climate change increased boundary layer height, mean temperature, and heatwave days in China during summer. Relative humidity decreased and wind speed near the surface showed no obvious change in the future. O₃ concentration showed an increasing trend in Beijing-Tianjin-Hebei, Sichuan Basin, and South China. The extreme value of O₃ maximum daily 8-hour moving average (MDA8) showed an increasing trend, following the order of RCP8.5 (0.7 μg·m^-3)>RCP6.0 (0.3 μg·m^-3)>RCP4.5 (0.2 μg·m^-3). The number of days exceeding the standard for summer O₃ had a similar spatial distribution with the heatwave days in China. The increase in heatwave days led to the increase in O₃ extreme pollution events, and the possibility of a long-lasting O₃ pollution event will increase in China in the future.