Future prediction of surface ozone over east Asia using Models‐3 Community Multiscale Air Quality Modeling System and Regional Emission Inventory in Asia

Abstract

Present and future tropospheric ozone (O3) concentrations over east Asia have been simulated by the Models‐3 Community Multiscale Air Quality Modeling System (CMAQ) coupled with the Regional Emission Inventory in Asia (REAS) to predict surface O3 variations caused by future anthropogenic emissions changes. For future prediction, REAS provides three emission scenarios for China (the reference (REF), the policy succeed case (PSC), and the policy failure case (PFC) scenarios) and one emission scenario (the REF scenario) for the other countries. Simulated O3 concentration in summer was relatively high (70–80 ppbv in June and 65–75 ppbv in August) over the North China Plain in 2000. The projected REF emissions for 2020 (2020REF) enhance the monthly averaged O3 to 75–90 ppbv in June and 75–85 ppbv in August. The projected PSC emissions for 2020 (2020PFC), including a slight NOx reduction of –0.2 Tg (–2%) and a large NMVOC increase of 14.3 Tg (97%) for total Chinese emissions during 2000–2020, cause the monthly and annually averaged O3 concentrations to decrease by less than 2 ppbv in northeastern and central China. Over the North China Plain, the projected PFC emissions for 2020 (2020PFC) cause significant increases, more than 20 ppbv in the monthly averaged O3, and the O3 will be 85–105 ppbv in June and 80–95 ppbv in August for 2020. The 2020PFC also affect O3 increases in early summer in South Korea (14–18 ppbv increase for monthly average) and Japan (2–14 ppbv increase for monthly average) during 2000–2020 despite the slight NOx increase of 0.4 Tg (25%) in South Korea and the slight NOx reduction of –0.2 Tg (–10%) in Japan during 2000–2020. The pollutant in these regions seems to be transport from upwind source regions. These experiments show that over central eastern China at midday in June, the O3 concentration is largely affected by NOx emission increases but is insensitive to NMVOC emission increases.