Projection of surface ozone over East Asia in 2020

Abstract

To evaluate the impact of emission changes in East Asia on the surface ozone concentration, we conducted 1-year calculations with emission inventories for 2000 and 2020, using a one-way nested global-regional chemical transport model (CTM), consisting of global and regional CTMs. The global CTM was based on the chemical atmospheric general circulation model for the study of the atmospheric environment and radiative forcing (CHASER) model, while the regional part is based on the Weather Research and Forecasting (WRF)/Chem model. The anthropogenic emissions in East Asia were taken from the Regional Emission inventory in ASia (REAS). Comparison of the modeled surface ozone with ground-based observations at Mt. Tai showed that the model generally reproduced the diurnal variations of ozone in the North China Plain. For the horizontal distribution of surface ozone concentration, comparison between 2000 and 2020 revealed an ozone decrease of 1-3 ppbv in the North China Plain, where the increase of ozone precursors was most remarkable. An increase of 3-10 ppbv was also apparent in the outflow region of the North China Plain, over the Sichuan Province, Korea, and Japan. Comparison of the diurnal variations of surface ozone over the North China Plain in 2000 and in the “policy failed case” for 2020 (2020PFC) showed ozone levels peaking at 10% more in the latter, due to enhanced ozone production during the daytime.