Extensive spatiotemporal analyses of surface ozone and related meteorological variables in South Korea for the period 1999-2010

Spatiotemporal characteristics of surface ozone (O-3) variations over South Korea are investigated with consideration of meteorological factors and timescales based on the Kolmogorov-Zurbenko filter (KZ filter), using measurement data at 124 air quality monitoring sites and 72 weather stations for the 12 yr period of 1999-2010. In general, O-3 levels at coastal cities are high due to dynamic effects of the sea breeze while those at the inland and Seoul Metropolitan Area (SMA) cities are low due to the NOx titration by local precursor emissions. We examine the meteorological influences on O-3 using a combined analysis of the KZ filter and linear regressions between O-3 and meteorological variables. We decomposed O-3 time series at each site into short-term, seasonal, and long-term components by the KZ filter and regressed on meteorological variables. Impact of temperature on the O-3 levels is significantly high in the highly populated SMA and inland region, but low in the coastal region. In particular, the probability of high O-3 occurrence doubles with 4 A degrees C of temperature increase in the SMA during high O-3 months (May-October). This implies that those regions will experience frequent high O-3 events in a future warming climate. In terms of short-term variation, the distribution of high O-3 probability classified by wind direction shows the effect of both local precursor emissions and long-range transport from China. In terms of long-term variation, the O-3 concentrations have increased by +0.26 ppbv yr(-1) (parts per billion by volume) on nationwide average, but their trends show large spatial variability. Singular value decomposition analyses further reveal that the long-term temporal evolution of O-3 is similar to that of nitrogen dioxide, although the spatial distribution of their trends is different. This study will be helpful as a reference for diagnostics and evaluation of regional- and local-scale O-3 and climate simulations, and as a guide to appropriate O-3 control policy in South Korea.