Influence of meteorological variability on interannual variations of springtime boundary layer ozone over Japan during 1981–2005

J Kurokawa,I Uno,M Hayasaki,T Ohara,H Tanimoto

doi:10.5194/acp-9-6287-2009

Abstract

Abstract. We investigated the influence of meteorological variability on the interannual variation of springtime boundary layer ozone over Japan during 1981–2005 by multiyear simulations with the Models-3 Community Multiscale Air Quality (CMAQ) modeling system and the Regional Emission Inventory in Asia (REAS). CMAQ/REAS generally reproduced the observed interannual variability of springtime ozone over Japan, showing year-to-year variations larger than the annual rate of increase of the long-term trend. We then analyzed the influence of the interannual variation of meteorology in simulated results by using the fixed emissions for 2000 and meteorological fields for each year. As a reference parameter, we calculated the area-weighted surface pressure anomaly over the Pacific Ocean east of Japan. When the anomaly has a large negative value, polluted air masses from continental Asia tend to be transported directly to Japan by westerly winds. In contrast, when the anomaly has a large positive value, influence of the outflow from continental Asia tends to be small because the westerly components of wind fields around Japan are comparatively weak. Instead, southerly winds are relatively strong and transport clean air masses from the Pacific Ocean to Japan. Consequently, springtime ozone over Japan is higher (lower) than in ordinary years when the anomaly has a large negative (positive) value. In general, the interannual variation of springtime ozone over Japan is sensitive to the outflow from continental Asia. We also found some correlation between springtime ozone over Japan and the El Niño-Southern Oscillation, indicating that higher and lower springtime ozone over Japan are related to La Niña and El Niño, respectively. Differences in the meridional displacement and diversity of cyclone tracks near Japan between El Niño and La Niña years may be responsible for interannual variations in the springtime boundary layer ozone over Japan.

Highlights

Tropospheric ozone (O3) is a key species in atmospheric chemistry
We further evaluate the general performance of our modeling system for springtime O3 over East Asia
Because that region is outside the model domain of Community Multiscale Air Quality (CMAQ) designed for this study, we examined the relationship between the area-weighted surface pressure anomaly (ASPA) and the averaged anomalies in the area of 30–45◦ N, 180– 150◦ W and found a good positive correlation between them (r=0.83)

Summary

Introduction

O3 and its photochemical derivative OH are major oxidants of most natural and anthropogenic compounds and play controlling roles in the oxidation capacity of the atmosphere. In Japan, surface and boundary layer (BL) O3 has increased continuously since the 1980s despite reductions in the concentrations of nitrogen oxides (NOx=NO+NO2) and non-methane volatile organic compounds (NMVOC), which are precursors of O3 (Ohara et al, 2008). Many studies have reported that trans-boundary transport of O3 and its precursors, especially from East Asia, has greatly influenced the recent increase of O3 over Japan (Pochanart et al, 1999; Naja and Akimoto, 2004; Tanimoto et al, 2005; Tanimoto, 2009; Yamaji et al, 2006, 2008). Many studies have reported that trans-boundary transport of O3 and its precursors, especially from East Asia, has greatly influenced the recent increase of O3 over Japan (Pochanart et al, 1999; Naja and Akimoto, 2004; Tanimoto et al, 2005; Tanimoto, 2009; Yamaji et al, 2006, 2008). Tanimoto et al (2005) estimated that the regional build-up of O3 due to anthropogenic emissions in eastern China and Korea accounts for about 10 ppbv in March and April and about 20 ppbv in May over Japan. Ohara et al (2007) reported that emissions of O3 precursors

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