Impact of Changing Climate and Emissions on Surface Ozone Distributions and Evolution

Socio-economic activities are rapidly increasing in many countries of Asia due to a population explosion. It is also suggested that greenhouse gases alter regional climate, causing changes in meteorological factors such as atmospheric circulation, precipitation, heat balance, and monsoon. These factors have potential impact on chemical transformation and long-range transport of air pollutants. To detect current and future changes in air quality, systematic observational networks with wide spatial and temporal coverage are highly required. In this work, ground-based measurement data of ozone and its precursors at ~20 remote sites from multiple monitoring networks including operational programs and collaborative research projects in East Asia are integrated. The idea and basis is that in-situ data are more accurate than satellite and sounding data, though its spatial coverage is limited. The intercomparisons of reference scales in each network make ambient data comparable to each other, and the integration of such traceable data allows us to cover wide latitudinal zones ranging from subtropical to boreal regions in the western Pacific within ~2% uncertainties. The data are further utilized to test multi-year simulations by a regional chemistry transport model (CMAQ). Interestingly, there are sizable interannual variations (and latitudinal dependences), suggesting that changes in regional meteorology (e.g., transport paths, patterns, and efficiency) and/or enhanced precursor emissions from biomass burning may have large contribution. Trends for 7 years are not visible at boundary layer sites, but are substantial at mountainous sites during continental outflow seasons, possibly due to increasing NOx emissions from East Asia. Implications to Meditteranean region are discussed in terms of emissions from biomass burning in present and expanding human activities in future.