[Impact of Summer Tropospheric Ozone Radiative Forcing on Meteorology and Air Quality in North China]

With the vigorous implementation of the Clean Air Action since 2013, the atmospheric particle pollution in China has been substantially reduced, but ozone concentrations have been increasing. Moreover, tropospheric ozone can make a difference in meteorology and air quality through its radiative forcing as an important greenhouse gas. A coupled regional meteorology-chemistry model (WRF-Chem) was used to reproduce an ozone pollution event that occurred in North China in June 2017. The impact of tropospheric ozone radiative forcing on local meteorological fields and its feedback effect on ozone air quality were analyzed through sensitivity experiments. The results revealed the excellent performance of the WRF-Chem model for meteorological parameters and ozone pollutant concentrations. Tropospheric ozone radiative forcing (TORF) increased the average near-surface temperature by 0.23 K in the Beijing-Tianjin-Hebei-Shandong Region (the maximum temperature increase could reach 0.8 K), reduced the relative humidity by 1.84%, and elevated the height of the boundary layer by 27.73 m. TORF had a weaker effect on wind speed (-0.02 m·s^-1), but the generated anomalous southwestern wind was more liable to transport ozone and its precursors from upstream polluted areas to North China. Under the impacts of ozone radiation feedback, the ozone volume fraction in the study area increased by an average of 1.7% (1.23×10^-9), whereas in the heavily polluted Beijing and Tianjin areas, the increase reached up to 5×10^-9. Furthermore, the enhanced gas phase chemical reactions were identified as the dominant cause worsening near-surface ozone pollution by progress diagnostic analysis.