Long-term change in the source contribution to surface ozone over Japan

Tatsuya Nagashima,Hajime Akimoto,Kengo Sudo,Junichi Kurokawa,Toshimasa Ohara

doi:10.5194/acp-17-8231-2017

Abstract

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 simulated the observed increasing trend in surface O3, including its seasonal variation and geographical features, in Japan well and demonstrated the relative roles of different source regions in forming this trend. Most of the increasing trend in surface O3 over Japan ( ∼ 97 %) that was simulated 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 western, southern, and southeastern 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 in 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 western, southern, and southeast Asia and the free troposphere and accounted for about 16 % of the total.

Highlights

Tropospheric ozone (O3) is an oxidant and photodissociates to generate the hydroxyl radical that strongly oxidizes many atmospheric compounds, including various air pollutants, and removes them from the atmosphere
Nagashima et al (2010) validated how well CHASER can reproduce the observed features of surface O3 concentrations by comparing the simulated surface O3 concentrations with observations taken during 2000–2005 at several sites mainly in rural areas in the Northern Hemisphere, and CHASER successfully simulated the annual variation in surface O3 in a variety of regions
We demonstrated the relative importance of the regions of photochemical O3 production in the global atmosphere in the long-term increasing trend in surface O3 over Japan reported in recent decades by conducting a series of tracer-tagging simulations using the global chemical transport model (CTM) CHASER

Summary

Introduction

Tropospheric ozone (O3) is an oxidant and photodissociates to generate the hydroxyl radical that strongly oxidizes many atmospheric compounds, including various air pollutants, and removes them from the atmosphere. High levels of O3 are a major air pollutant and cause adverse effects on human health, natural vegetation, and agricultural produce (Wang and Mauzerall, 2004; Mauzerall et al, 2005; US EPA, 2006; Silva et al, 2013). Tropospheric O3 is a major greenhouse gas in the atmosphere, and reduction of its amount was recently recognized as an effective measure to mitigate near-term climate change (UNEP and WMO, 2011; Shindell et al, 2012). The spatial and temporal variations in tropospheric O3 have always been a matter of scientific and public concern.

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Conclusion