Sensitivity Analysis of Tropospheric Ozone Concentration to Domestic Anthropogenic Emission of Nitrogen Oxides (NOx) and Volatile Organic Compounds (VOC) in Japan: Comparison Between 2015 and 2050

Tropospheric ozone (O3) is a harmful air pollutant and a short-lived greenhouse gas. To find effective O3 reduction strategies, it is essential to understand the sensitivity of O3 concentrations to its precursors, nitrogen oxides (NOx), and volatile organic compounds (VOC). This study applied the Community Multi-Scale Air Quality model (CMAQ) to assess the effects of domestic anthropogenic emissions in 2015 and 2050. The emission scenarios were based on Japan’s CO2 reduction targets, assuming an 80% decrease by 2050. Sensitivity analysis was performed by adjusting NOx and VOC emissions by ±10% and ±20%, respectively, and examining seasonal and regional variations in the O3 response. The results show that O3 levels will decrease notably in spring and summer by 2050, although concentrations will still exceed the standards in some areas. NOx reductions lead to significant O3 decreases, while VOC reductions show limited benefits, except in urban regions such as Kanto and Kansai. In winter, NOx reductions may even increase O3 levels due to weakened titration. Overall, the findings highlight the importance of prioritizing NOx control measures for effective O3 mitigation in Japan’s future energy transition.