Dipole pattern of summer ozone pollution in the east of China and its connection with climate variability

Abstract

Surface O3 pollution has become one of the most severe air pollution problems in China, which makes it of practical importance to understand O3 variability. A south–north dipole pattern of summer-mean O3 concentration in the east of China (DP-O3), which was centered in North China (NC) and the Pearl River Delta (PRD), has been identified from the simulation of a global 3-D chemical transport model for the period 1980–2019. Large-scale anticyclonic (cyclonic) and cyclonic (anticyclonic) anomalies over NC and the PRD resulted in a sharp contrast of meteorological conditions between the above two regions. The enhanced (restrained) photochemistry in NC and restrained (enhanced) O3 production in the PRD contributed to the DP-O3. Decreased sea ice anomalies near Franz Josef Land and associated warm sea surface in May enhanced the Rossby wave source over northern Europe and West Siberia, which eventually induced an anomalous Eurasia-like pattern to influence the formation of the DP-O3. The thermodynamic signals of the southern Indian Ocean dipole were stored in the subsurface and influenced the spatial pattern of O3 pollution in the east of China mainly through the Hadley circulation. The physical mechanisms behind the modulation of the atmospheric circulations and related DP-O3 by these two climate anomalies at different latitudes were evidently verified by large-scale ensemble simulations of the Earth system model.