Long-term change in the contributions of various source regions to surface ozone over Japan
Tatsuya Nagashima1, Kengo Sudo2,3, Hajime Akimoto1, Junichi Kurokawa4, and Toshimasa Ohara11National Institute for Environmental Studies , Tsukuba, Japan 2Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan 3Frontier Research Center for Global Change, Yokohama, Japan 4Asia Center for Air Pollution Research, Niigata, Japan
Received: 02 Dec 2016 – Accepted for review: 07 Jan 2017 – Discussion started: 19 Jan 2017
Abstract. The relative contributions of various source regions to the long-term (1980–2005) increasing trend in surface ozone (O3) over Japan were estimated by a series of tracer-tagging simulations using a global chemical transport model. The model well simulated the observed increasing trend of surface O3 including its seasonal variation and geographical features in Japan and demonstrated the relative roles of different source regions in forming this trend. Most of the simulated increasing trend of surface O3 over Japan (~ 97 %) was explained as the sum of trends in contributions of different regions to photochemical O3 production. The increasing trend in O3 produced in China accounted for 36 % of the total increasing trend and those in the other northeast Asian regions (the Korean Peninsula, coastal regions in East Asia, and Japan) each accounted for about 12–15 %. Furthermore, the contributions of O3 created in the entire free troposphere and in West, South, and Southeast Asian regions also increased; and their increasing trends accounted for 16 and 7 % of the total trend, respectively. The impact of interannual variations in climate, in methane concentration, and in emission of O3 precursors from different source regions on the relative contributions of O3 created in each region estimated above was also investigated. The variation of climate and the increase in methane concentration together caused the increase of photochemical O3 production in several regions, and represented about 19 % of the total increasing trend of surface O3 over Japan. The increase in emission of O3 precursors in China caused an increase of photochemical O3 production not only in China itself but also in the other northeast Asian regions and accounted for about 46 % of the total increase in surface O3 over Japan. Similarly, the relative impact of O3 precursor emission changes in the Korean Peninsula and Japan were estimated as about 16 and 4 % of the total increasing trend, respectively. The O3 precursor emission change in regions other than northeast Asia caused increases in surface O3 over Japan mainly through increasing photochemical O3 production in West, South, and Southeast Asia and the free troposphere, and accounted for about 16 % of the total.
Nagashima, T., Sudo, K., Akimoto, H., Kurokawa, J., and Ohara, T.: Long-term change in the contributions of various source regions to surface ozone over Japan, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1087, in review, 2017.